Members of the claudin protein family are the major constituents of tight junction strands and determine the permeability properties of the paracellular pathway. In the kidney, each nephron segment expresses a distinct subset of claudins that form either barriers against paracellular solute transport or charge- and size-selective paracellular channels. It was the aim of the present study to determine and compare the permeation properties of these renal paracellular ion channel-forming claudins.
Methods
MDCK II cells, in which the five major claudins had been knocked out (claudin quintupleKO), were stably transfected with individual mouse Cldn2, -4, -8, -10a, -10b, or -15, or with dog Cldn16 or -19, or with a combination of mouse Cldn4 and Cldn8, or dog Cldn16 and Cldn19. Permeation properties were investigated in the Ussing chamber and claudin interactions by FRET assays.
Results
Claudin-4 and -19 formed barriers against solute permeation. However, at low pH values and in the absence of HCO3−, claudin-4 conveyed a weak chloride and nitrate permeability. Claudin-8 needed claudin-4 for assembly into TJ strands and abolished this anion preference. Claudin-2, -10a, -10b, -15, -16+19 formed highly permeable channels with distinctive permeation profiles for different monovalent and divalent anions or cations, but barriers against the permeation of ions of opposite charge and of the paracellular tracer fluorescein.
Conclusion
Paracellular ion permeabilities along the nephron are strictly determined by claudin expression patterns. Paracellular channel-forming claudins are specific for certain ions and thus lower transepithelial resistance, yet form barriers against the transport of other solutes.
{"title":"Ion permeability profiles of renal paracellular channel-forming claudins","authors":"Ioanna Pouyiourou, Anja Fromm, Jörg Piontek, Rita Rosenthal, Mikio Furuse, Dorothee Günzel","doi":"10.1111/apha.14264","DOIUrl":"10.1111/apha.14264","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Aim</h3>\u0000 \u0000 <p>Members of the claudin protein family are the major constituents of tight junction strands and determine the permeability properties of the paracellular pathway. In the kidney, each nephron segment expresses a distinct subset of claudins that form either barriers against paracellular solute transport or charge- and size-selective paracellular channels. It was the aim of the present study to determine and compare the permeation properties of these renal paracellular ion channel-forming claudins.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>MDCK II cells, in which the five major claudins had been knocked out (claudin quintupleKO), were stably transfected with individual mouse Cldn2, -4, -8, -10a, -10b, or -15, or with dog Cldn16 or -19, or with a combination of mouse Cldn4 and Cldn8, or dog Cldn16 and Cldn19. Permeation properties were investigated in the Ussing chamber and claudin interactions by FRET assays.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Claudin-4 and -19 formed barriers against solute permeation. However, at low pH values and in the absence of HCO<sub>3</sub><sup>−</sup>, claudin-4 conveyed a weak chloride and nitrate permeability. Claudin-8 needed claudin-4 for assembly into TJ strands and abolished this anion preference. Claudin-2, -10a, -10b, -15, -16+19 formed highly permeable channels with distinctive permeation profiles for different monovalent and divalent anions or cations, but barriers against the permeation of ions of opposite charge and of the paracellular tracer fluorescein.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>Paracellular ion permeabilities along the nephron are strictly determined by claudin expression patterns. Paracellular channel-forming claudins are specific for certain ions and thus lower transepithelial resistance, yet form barriers against the transport of other solutes.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11740656/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nitika Gupta, Ella M. B. Richards, Vanessa S. Morris, Rachael Morris, Kirsty Wadmore, Marie Held, Liam McCormick, Ohm Prakash, Caroline Dart, Nordine Helassa
Aim
Long QT syndrome (LQTS) and catecholaminergic polymorphism ventricular tachycardia (CPVT) are inherited cardiac disorders often caused by mutations in ion channels. These arrhythmia syndromes have recently been associated with calmodulin (CaM) variants. Here, we investigate the impact of the arrhythmogenic variants D131E and Q135P on CaM's structure–function relationship. Our study focuses on the L-type calcium channel Cav1.2, a crucial component of the ventricular action potential and excitation–contraction coupling.
Methods
We used circular dichroism (CD), 1H-15N HSQC NMR, and trypsin digestion to determine the structural and stability properties of CaM variants. The affinity of CaM for Ca2+ and interaction of Ca2+/CaM with Cav1.2 (IQ and NSCaTE domains) were investigated using intrinsic tyrosine fluorescence and isothermal titration calorimetry (ITC), respectively. The effect of CaM variants of Cav1.2 activity was determined using HEK293-Cav1.2 cells (B'SYS) and whole-cell patch-clamp electrophysiology.
Results
Using a combination of protein biophysics and structural biology, we show that the disease-associated mutations D131E and Q135P mutations alter apo/CaM structure and stability. In the Ca2+-bound state, D131E and Q135P exhibited reduced Ca2+ binding affinity, significant structural changes, and altered interaction with Cav1.2 domains (increased affinity for Cav1.2-IQ and decreased affinity for Cav1.2-NSCaTE). We show that the mutations dramatically impair Ca2+-dependent inactivation (CDI) of Cav1.2, which would contribute to abnormal Ca2+ influx, leading to disrupted Ca2+ handling, characteristic of cardiac arrhythmia syndromes.
Conclusions
These findings provide insights into the molecular mechanisms behind arrhythmia caused by calmodulin mutations, contributing to our understanding of cardiac syndromes at a molecular and cellular level.
{"title":"Arrhythmogenic calmodulin variants D131E and Q135P disrupt interaction with the L-type voltage-gated Ca2+ channel (Cav1.2) and reduce Ca2+-dependent inactivation","authors":"Nitika Gupta, Ella M. B. Richards, Vanessa S. Morris, Rachael Morris, Kirsty Wadmore, Marie Held, Liam McCormick, Ohm Prakash, Caroline Dart, Nordine Helassa","doi":"10.1111/apha.14276","DOIUrl":"10.1111/apha.14276","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Aim</h3>\u0000 \u0000 <p>Long QT syndrome (LQTS) and catecholaminergic polymorphism ventricular tachycardia (CPVT) are inherited cardiac disorders often caused by mutations in ion channels. These arrhythmia syndromes have recently been associated with calmodulin (CaM) variants. Here, we investigate the impact of the arrhythmogenic variants D131E and Q135P on CaM's structure–function relationship. Our study focuses on the L-type calcium channel Ca<sub>v</sub>1.2, a crucial component of the ventricular action potential and excitation–contraction coupling.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We used circular dichroism (CD), <sup>1</sup>H-<sup>15</sup>N HSQC NMR, and trypsin digestion to determine the structural and stability properties of CaM variants. The affinity of CaM for Ca<sup>2+</sup> and interaction of Ca<sup>2+</sup>/CaM with Ca<sub>v</sub>1.2 (IQ and NSCaTE domains) were investigated using intrinsic tyrosine fluorescence and isothermal titration calorimetry (ITC), respectively. The effect of CaM variants of Ca<sub>v</sub>1.2 activity was determined using HEK293-Ca<sub>v</sub>1.2 cells (B'SYS) and whole-cell patch-clamp electrophysiology.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Using a combination of protein biophysics and structural biology, we show that the disease-associated mutations D131E and Q135P mutations alter apo/CaM structure and stability. In the Ca<sup>2+</sup>-bound state, D131E and Q135P exhibited reduced Ca<sup>2+</sup> binding affinity, significant structural changes, and altered interaction with Ca<sub>v</sub>1.2 domains (increased affinity for Ca<sub>v</sub>1.2-IQ and decreased affinity for Ca<sub>v</sub>1.2-NSCaTE). We show that the mutations dramatically impair Ca<sup>2+</sup>-dependent inactivation (CDI) of Ca<sub>v</sub>1.2, which would contribute to abnormal Ca<sup>2+</sup> influx, leading to disrupted Ca<sup>2+</sup> handling, characteristic of cardiac arrhythmia syndromes.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>These findings provide insights into the molecular mechanisms behind arrhythmia caused by calmodulin mutations, contributing to our understanding of cardiac syndromes at a molecular and cellular level.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11742489/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
John P. Salvas, Thomas Moore-Morris, Craig J. Goergen, Pierre Sicard
Aim
Left atrial (LA) strain is emerging as a valuable metric for evaluating cardiac function, particularly under pathological conditions such as pressure overload. This preclinical study investigates the predictive utility of LA strain on cardiac function in a murine model subjected to pressure overload, mimicking pathologies such as hypertension and aortic stenosis.
Methods
High-resolution ultrasound was performed in a cohort of mice (n = 16) to evaluate left atrial and left ventricular function at baseline and 2 and 4 weeks after transverse aortic constriction (TAC). Acute adaptations in cardiac function were assessed in a subgroup of mice (n = 10) with 3 days post-TAC imaging.
Results
We report an increase in LA max volume from 11.0 ± 4.3 μL at baseline to 26.7 ± 16.7 μL at 4 weeks (p = 0.002) and a decrease in LA reservoir strain from 20.8 ± 5.4% at baseline to 10.2 ± 6.9% at 4 weeks (p = 0.001). In the acute phase, LA strain dysfunction was present at 3 days (p < 0.001), prior to alterations in LA volume (p = 0.856) or left ventricular (LV) ejection fraction (p = 0.120). LA reservoir strain correlated with key indicators of cardiac performance including left ventricular (LV) ejection fraction (r = 0.541, p < 0.001), longitudinal strain (r = −0.637, p < 0.001), and strain rate (r = 0.378, p = 0.007). Furthermore, markers of atrial structure and function including LA max volume (AUC = 0.813, p = 0.003), ejection fraction (AUC = 0.853, p = 0.001), and strain (AUC = 0.884, p < 0.001) all predicted LV dysfunction.
Conclusion
LA strain and function assessments provide a reliable, non-invasive method for the early detection and prediction of cardiac dysfunction in a model of pressure overload.
{"title":"Left atrial reservoir strain as a predictor of cardiac dysfunction in a murine model of pressure overload","authors":"John P. Salvas, Thomas Moore-Morris, Craig J. Goergen, Pierre Sicard","doi":"10.1111/apha.14277","DOIUrl":"10.1111/apha.14277","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Aim</h3>\u0000 \u0000 <p>Left atrial (LA) strain is emerging as a valuable metric for evaluating cardiac function, particularly under pathological conditions such as pressure overload. This preclinical study investigates the predictive utility of LA strain on cardiac function in a murine model subjected to pressure overload, mimicking pathologies such as hypertension and aortic stenosis.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>High-resolution ultrasound was performed in a cohort of mice (<i>n</i> = 16) to evaluate left atrial and left ventricular function at baseline and 2 and 4 weeks after transverse aortic constriction (TAC). Acute adaptations in cardiac function were assessed in a subgroup of mice (<i>n</i> = 10) with 3 days post-TAC imaging.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>We report an increase in LA max volume from 11.0 ± 4.3 μL at baseline to 26.7 ± 16.7 μL at 4 weeks (<i>p</i> = 0.002) and a decrease in LA reservoir strain from 20.8 ± 5.4% at baseline to 10.2 ± 6.9% at 4 weeks (<i>p</i> = 0.001). In the acute phase, LA strain dysfunction was present at 3 days (<i>p</i> < 0.001), prior to alterations in LA volume (<i>p</i> = 0.856) or left ventricular (LV) ejection fraction (<i>p</i> = 0.120). LA reservoir strain correlated with key indicators of cardiac performance including left ventricular (LV) ejection fraction (<i>r</i> = 0.541, <i>p</i> < 0.001), longitudinal strain (<i>r</i> = −0.637, <i>p</i> < 0.001), and strain rate (<i>r</i> = 0.378, <i>p</i> = 0.007). Furthermore, markers of atrial structure and function including LA max volume (AUC = 0.813, <i>p =</i> 0.003), ejection fraction (AUC = 0.853, <i>p</i> = 0.001), and strain (AUC = 0.884, <i>p</i> < 0.001) all predicted LV dysfunction.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>LA strain and function assessments provide a reliable, non-invasive method for the early detection and prediction of cardiac dysfunction in a model of pressure overload.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11737473/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Igor Maciel Souza-Silva, Victor Corasolla Carregari, U. Muscha Steckelings, Thiago Verano-Braga
The Renin-Angiotensin System (RAS) is a complex neuroendocrine system consisting of a single precursor protein, angiotensinogen (AGT), which is processed into various peptide hormones, including the angiotensins [Ang I, Ang II, Ang III, Ang IV, Ang-(1–9), Ang-(1–7), Ang-(1–5), etc] and Alamandine-related peptides [Ang A, Alamandine, Ala-(1–5)], through intricate enzymatic pathways. Functionally, the RAS is divided into two axes with opposing effects: the classical axis, primarily consisting of Ang II acting through the AT1 receptor (AT1R), and in contrast the protective axis, which includes the receptors Mas, AT2R and MrgD and their respective ligands. A key area of RAS research is to gain a better understanding how signaling cascades elicited by these receptors lead to either “classical” or “protective” effects, as imbalances between the two axes can contribute to disease. On the other hand, therapeutic benefits can be achieved by selectively activating protective receptors and their associated signaling pathways. Traditionally, robust “hypothesis-driven” methods like Western blotting have built a solid knowledge foundation on RAS signaling. In this review, we introduce untargeted mass spectrometry-based phosphoproteomics, a “hypothesis-generating approach”, to explore RAS signaling pathways. This technology enables the unbiased discovery of phosphorylation events, offering insights into previously unknown signaling mechanisms. We review the existing studies which used phosphoproteomics to study RAS signaling and discuss potential future applications of phosphoproteomics in RAS research including advantages and limitations. Ultimately, phosphoproteomics represents a so far underused tool for deepening our understanding of RAS signaling and unveiling novel therapeutic targets.
{"title":"Phosphoproteomics for studying signaling pathways evoked by hormones of the renin-angiotensin system: A source of untapped potential","authors":"Igor Maciel Souza-Silva, Victor Corasolla Carregari, U. Muscha Steckelings, Thiago Verano-Braga","doi":"10.1111/apha.14280","DOIUrl":"10.1111/apha.14280","url":null,"abstract":"<p>The Renin-Angiotensin System (RAS) is a complex neuroendocrine system consisting of a single precursor protein, angiotensinogen (AGT), which is processed into various peptide hormones, including the angiotensins [Ang I, Ang II, Ang III, Ang IV, Ang-(1–9), Ang-(1–7), Ang-(1–5), etc] and Alamandine-related peptides [Ang A, Alamandine, Ala-(1–5)], through intricate enzymatic pathways. Functionally, the RAS is divided into two axes with opposing effects: the classical axis, primarily consisting of Ang II acting through the AT<sub>1</sub> receptor (AT<sub>1</sub>R), and in contrast the protective axis, which includes the receptors Mas, AT<sub>2</sub>R and MrgD and their respective ligands. A key area of RAS research is to gain a better understanding how signaling cascades elicited by these receptors lead to either “classical” or “protective” effects, as imbalances between the two axes can contribute to disease. On the other hand, therapeutic benefits can be achieved by selectively activating protective receptors and their associated signaling pathways. Traditionally, robust “hypothesis-driven” methods like Western blotting have built a solid knowledge foundation on RAS signaling. In this review, we introduce untargeted mass spectrometry-based phosphoproteomics, a “hypothesis-generating approach”, to explore RAS signaling pathways. This technology enables the unbiased discovery of phosphorylation events, offering insights into previously unknown signaling mechanisms. We review the existing studies which used phosphoproteomics to study RAS signaling and discuss potential future applications of phosphoproteomics in RAS research including advantages and limitations. Ultimately, phosphoproteomics represents a so far underused tool for deepening our understanding of RAS signaling and unveiling novel therapeutic targets.</p>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11737475/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The blood–brain barrier (BBB) is a highly selective, semipermeable barrier critical for maintaining brain homeostasis. The BBB regulates the transport of essential nutrients, hormones, and signaling molecules between the bloodstream and the central nervous system (CNS), while simultaneously protecting the brain from potentially harmful substances and pathogens. This selective permeability ensures that the brain is nourished and shielded from toxins. An exception to this are brain regions, such as the hypothalamus and circumventricular organs, which are irrigated by fenestrated capillaries, allowing rapid and direct response to various blood components. We overview the metabolic functions of the BBB, with an emphasis on the impact of altered glucose metabolism and insulin signaling on BBB in the pathogenesis of neurodegenerative diseases. Notably, endothelial cells constituting the BBB exhibit distinct metabolic characteristics, primarily generating ATP through aerobic glycolysis. This occurs despite their direct exposure to the abundant oxygen in the bloodstream, which typically supports oxidative phosphorylation. The effects of insulin on astrocytes, which form the glial limitans component of the BBB, show a marked sexual dimorphism. BBB nutrient sensing in the hypothalamus, along with insulin signaling, regulates systemic metabolism. Insulin modifies BBB permeability by regulating the expression of tight junction proteins, angiogenesis, and vascular remodeling, as well as modulating blood flow in the brain. The disruptions in glucose and insulin signaling are particularly evident in neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, where BBB breakdown accelerates cognitive decline. This review highlights the critical role of normal glucose metabolism and insulin signaling in maintaining BBB functionality and investigates how disruptions in these pathways contribute to the onset and progression of neurodegenerative diseases.
{"title":"Understanding glucose metabolism and insulin action at the blood–brain barrier: Implications for brain health and neurodegenerative diseases","authors":"Yiyi Zhu, Alexei Verkhratsky, Hui Chen, Chenju Yi","doi":"10.1111/apha.14283","DOIUrl":"10.1111/apha.14283","url":null,"abstract":"<p>The blood–brain barrier (BBB) is a highly selective, semipermeable barrier critical for maintaining brain homeostasis. The BBB regulates the transport of essential nutrients, hormones, and signaling molecules between the bloodstream and the central nervous system (CNS), while simultaneously protecting the brain from potentially harmful substances and pathogens. This selective permeability ensures that the brain is nourished and shielded from toxins. An exception to this are brain regions, such as the hypothalamus and circumventricular organs, which are irrigated by fenestrated capillaries, allowing rapid and direct response to various blood components. We overview the metabolic functions of the BBB, with an emphasis on the impact of altered glucose metabolism and insulin signaling on BBB in the pathogenesis of neurodegenerative diseases. Notably, endothelial cells constituting the BBB exhibit distinct metabolic characteristics, primarily generating ATP through aerobic glycolysis. This occurs despite their direct exposure to the abundant oxygen in the bloodstream, which typically supports oxidative phosphorylation. The effects of insulin on astrocytes, which form the glial limitans component of the BBB, show a marked sexual dimorphism. BBB nutrient sensing in the hypothalamus, along with insulin signaling, regulates systemic metabolism. Insulin modifies BBB permeability by regulating the expression of tight junction proteins, angiogenesis, and vascular remodeling, as well as modulating blood flow in the brain. The disruptions in glucose and insulin signaling are particularly evident in neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, where BBB breakdown accelerates cognitive decline. This review highlights the critical role of normal glucose metabolism and insulin signaling in maintaining BBB functionality and investigates how disruptions in these pathways contribute to the onset and progression of neurodegenerative diseases.</p>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11737474/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ashley Zubkowski, Amanda N. Sferruzzi-Perri, David S. Wishart
Purpose
Homoarginine (hArg) is an arginine metabolite that has been known for years, but its physiological role in the body remains poorly understood. For instance, it is well known that high hArg concentrations in the blood are protective against several disease states, yet the mechanisms behind these health benefits are unclear. This review compiles what is known about hArg, namely its synthetic pathways, its role in different diseases and conditions, and its proposed mechanisms of action in humans and experimental animals.
Findings
Previous work has identified multiple pathways that control hArg synthesis and degradation in the body. Furthermore, endogenous hArg can modulate the cardiovascular system, with decreased hArg being associated with cardiovascular complications and increased mortality. Studies also suggest that hArg could serve as a diagnostic biomarker for a variety of immune, pancreatic, renal, and hepatic dysfunctions. Finally, in women, hArg concentrations rapidly increase throughout pregnancy and there are suggestions that alterations in hArg could indicate pregnancy complications like pre-eclampsia.
Summary
Homoarginine is an under-appreciated amino acid with potential wide-ranging roles in systemic health, pregnancy, and pathophysiology. Although recent research has focused on its health or disease associations, there is a need for more investigations into understanding the mechanistic pathways by which hArg may operate. This could be aided using metabolomics, which provides a comprehensive approach to correlating multiple metabolites and metabolic pathways with physiological effects. Increasing our knowledge of hArg's roles in the body could pave the way for its routine use as both a diagnostic and therapeutic molecule.
{"title":"Mechanisms of Homoarginine: Looking Beyond Clinical Outcomes","authors":"Ashley Zubkowski, Amanda N. Sferruzzi-Perri, David S. Wishart","doi":"10.1111/apha.14273","DOIUrl":"10.1111/apha.14273","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>Homoarginine (hArg) is an arginine metabolite that has been known for years, but its physiological role in the body remains poorly understood. For instance, it is well known that high hArg concentrations in the blood are protective against several disease states, yet the mechanisms behind these health benefits are unclear. This review compiles what is known about hArg, namely its synthetic pathways, its role in different diseases and conditions, and its proposed mechanisms of action in humans and experimental animals.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Findings</h3>\u0000 \u0000 <p>Previous work has identified multiple pathways that control hArg synthesis and degradation in the body. Furthermore, endogenous hArg can modulate the cardiovascular system, with decreased hArg being associated with cardiovascular complications and increased mortality. Studies also suggest that hArg could serve as a diagnostic biomarker for a variety of immune, pancreatic, renal, and hepatic dysfunctions. Finally, in women, hArg concentrations rapidly increase throughout pregnancy and there are suggestions that alterations in hArg could indicate pregnancy complications like pre-eclampsia.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Summary</h3>\u0000 \u0000 <p>Homoarginine is an under-appreciated amino acid with potential wide-ranging roles in systemic health, pregnancy, and pathophysiology. Although recent research has focused on its health or disease associations, there is a need for more investigations into understanding the mechanistic pathways by which hArg may operate. This could be aided using metabolomics, which provides a comprehensive approach to correlating multiple metabolites and metabolic pathways with physiological effects. Increasing our knowledge of hArg's roles in the body could pave the way for its routine use as both a diagnostic and therapeutic molecule.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11737358/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Oliver Kitzerow, Samuel Christensen, Juan Hong, Ryan J. Adam, Irving H. Zucker, Heather Jensen-Smith, Han-Jun Wang
Aim
Tissue clearance is a rapidly evolving technology that allows for the three-dimensional imaging of intact biological tissues. Preexisting tissue-clearing techniques, such as Passive Clarity Technique (PACT) and Clear Unobstructed Brain Imaging Cocktails and Computational Analysis (CUBIC), clear tissues adequately but have distinct disadvantages, such as taking extensive time to clear tissues and degradation of endogenous tissue fluorescence. We developed a new tissue-clearing technique combining PACT and CUBIC protocols to map the neural lineages expressing the transient receptor potential vanilloid type 1 (TRPV1) receptor.
Methods
To test the effectiveness of this modified protocol, a TdTomato reporter mouse line was crossed with a separate mouse line containing Cre recombinase under the control of the TRPV1 promoter, which would result in TRPV1 cell lineages expressing green fluorescence protein (GFP).
Results
Compared to the PACT protocol that requires several weeks to months for tissue clearance, our approach reached a satisfactory clearance within 3 days in all neural tissues as well as several non-neural tissues such as colon, duodenum, and pancreas. Compared to the CUBIC approach, all tissues reserved strong GFP fluorescence. Robust GFP fluorescence was visualized in sensory neuronal soma but not in sympathetic ganglia neuronal soma. On the other hand, GFP fluorescence in the TRPV1 cells appeared to be expressed throughout the epithelium of the duodenum and colon and the arteriole smooth muscle in all non-neuronal tissues.
Conclusion
This study shows that our combined PACT and CUBIC (CPC) protocol can clear tissues in significantly less time while preserving tissue integrity and fluorescence.
{"title":"Anatomical mapping of neural lineages expressing the transient receptor potential vanilloid type 1 receptor using a modified and combined PACT and CUBIC protocol for rapid tissue clearance","authors":"Oliver Kitzerow, Samuel Christensen, Juan Hong, Ryan J. Adam, Irving H. Zucker, Heather Jensen-Smith, Han-Jun Wang","doi":"10.1111/apha.14275","DOIUrl":"10.1111/apha.14275","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Aim</h3>\u0000 \u0000 <p>Tissue clearance is a rapidly evolving technology that allows for the three-dimensional imaging of intact biological tissues. Preexisting tissue-clearing techniques, such as Passive Clarity Technique (PACT) and Clear Unobstructed Brain Imaging Cocktails and Computational Analysis (CUBIC), clear tissues adequately but have distinct disadvantages, such as taking extensive time to clear tissues and degradation of endogenous tissue fluorescence. We developed a new tissue-clearing technique combining PACT and CUBIC protocols to map the neural lineages expressing the transient receptor potential vanilloid type 1 (TRPV1) receptor.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>To test the effectiveness of this modified protocol, a TdTomato reporter mouse line was crossed with a separate mouse line containing Cre recombinase under the control of the TRPV1 promoter, which would result in TRPV1 cell lineages expressing green fluorescence protein (GFP).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Compared to the PACT protocol that requires several weeks to months for tissue clearance, our approach reached a satisfactory clearance within 3 days in all neural tissues as well as several non-neural tissues such as colon, duodenum, and pancreas. Compared to the CUBIC approach, all tissues reserved strong GFP fluorescence. Robust GFP fluorescence was visualized in sensory neuronal soma but not in sympathetic ganglia neuronal soma. On the other hand, GFP fluorescence in the TRPV1 cells appeared to be expressed throughout the epithelium of the duodenum and colon and the arteriole smooth muscle in all non-neuronal tissues.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>This study shows that our combined PACT and CUBIC (CPC) protocol can clear tissues in significantly less time while preserving tissue integrity and fluorescence.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11737471/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Urška Černe, Anemari Horvat, Ena Sanjković, Nika Kozoderc, Marko Kreft, Robert Zorec, Nicole Scholz, Nina Vardjan
Aim
Octopamine in the Drosophila brain has a neuromodulatory role similar to that of noradrenaline in mammals. After release from Tdc2 neurons, octopamine/tyramine may trigger intracellular Ca2+ signaling via adrenoceptor-like receptors on neural cells, modulating neurotransmission. Octopamine/tyramine receptors are expressed in neurons and glia, but how each of these cell types responds to octopamine remains elusive. This study aimed to characterize Ca2+ responses of neurons and astrocytes to neuromodulatory octopamine signals.
Methods
We expressed Ca2+ indicator jGCaMP7b in specific cell type in adult Drosophila brains and performed intracellular Ca2+ imaging in the brain optic lobes upon bath application of octopamine by confocal microscopy.
Results
Octopamine-stimulated Ca2+ responses in neurons were different from those of glial cells. The amplitude of octopamine-mediated Ca2+ signals in neurons was 3.4-fold greater than in astrocytes. However, astrocytes were more sensitive to octopamine; the median effective concentration that triggered Ca2+ responses was nearly 6-fold lower in astrocytes than in neurons. In both cell types, Ca2+ transients are shaped by Gq and Gs protein-coupled octopamine/tyramine receptors. Our snRNA-seq database screening uncovered differential expression patterns of these receptors between brain cell types, which may explain the difference in Ca2+ signaling.
Conclusion
In the brain optic lobes, astrocytes, not neurons, appear to be the sole responders to low concentration octopamine signals, and therefore likely drive synaptic plasticity and visual processing. Given the interconnectivity of the optic lobes with other brain regions, octopaminergic signals acting through the optic lobe astrocytes may also influence higher-order brain functions including learning and memory.
{"title":"Ca2+ excitability of glia to neuromodulator octopamine in Drosophila living brain is greater than that of neurons","authors":"Urška Černe, Anemari Horvat, Ena Sanjković, Nika Kozoderc, Marko Kreft, Robert Zorec, Nicole Scholz, Nina Vardjan","doi":"10.1111/apha.14270","DOIUrl":"10.1111/apha.14270","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Aim</h3>\u0000 \u0000 <p>Octopamine in the <i>Drosophila</i> brain has a neuromodulatory role similar to that of noradrenaline in mammals. After release from Tdc2 neurons, octopamine/tyramine may trigger intracellular Ca<sup>2+</sup> signaling via adrenoceptor-like receptors on neural cells, modulating neurotransmission. Octopamine/tyramine receptors are expressed in neurons and glia, but how each of these cell types responds to octopamine remains elusive. This study aimed to characterize Ca<sup>2+</sup> responses of neurons and astrocytes to neuromodulatory octopamine signals.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We expressed Ca<sup>2+</sup> indicator jGCaMP7b in specific cell type in adult <i>Drosophila</i> brains and performed intracellular Ca<sup>2+</sup> imaging in the brain optic lobes upon bath application of octopamine by confocal microscopy.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Octopamine-stimulated Ca<sup>2+</sup> responses in neurons were different from those of glial cells. The amplitude of octopamine-mediated Ca<sup>2+</sup> signals in neurons was 3.4-fold greater than in astrocytes. However, astrocytes were more sensitive to octopamine; the median effective concentration that triggered Ca<sup>2+</sup> responses was nearly 6-fold lower in astrocytes than in neurons. In both cell types, Ca<sup>2+</sup> transients are shaped by G<sub>q</sub> and G<sub>s</sub> protein-coupled octopamine/tyramine receptors. Our snRNA-seq database screening uncovered differential expression patterns of these receptors between brain cell types, which may explain the difference in Ca<sup>2+</sup> signaling.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>In the brain optic lobes, astrocytes, not neurons, appear to be the sole responders to low concentration octopamine signals, and therefore likely drive synaptic plasticity and visual processing. Given the interconnectivity of the optic lobes with other brain regions, octopaminergic signals acting through the optic lobe astrocytes may also influence higher-order brain functions including learning and memory.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11726276/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
7th CONGRESS OF PHYSIOLOGY AND INTEGRATIVE BIOLOGY, 91st Congress of French Physiological Society, Tours, France, 5–7 June, 2024
www.societedephysiologie.org
NATIONAL ORGANIZING COMMITTEE
Ruddy RICHARD (President), Bruno Chenuel (Vice President), Dominique SIGAUDO-ROUSSEL (President of the Scientific committee), Emmanuelle Vidal Petiot (General Secretary)
RESPONSIBLE OF THE EDITION
Naim KHAN, Secretary, International Affairs
{"title":"Conference details","authors":"","doi":"10.1111/apha.14252","DOIUrl":"10.1111/apha.14252","url":null,"abstract":"<p>\u0000 <b>7<sup>th</sup> CONGRESS OF PHYSIOLOGY AND INTEGRATIVE BIOLOGY, 91<sup>st</sup> Congress of French Physiological Society, Tours, France, 5–7 June, 2024</b>\u0000 </p><p>\u0000 www.societedephysiologie.org\u0000 </p><p>NATIONAL ORGANIZING COMMITTEE</p><p>Ruddy RICHARD (President), Bruno Chenuel (Vice President), Dominique SIGAUDO-ROUSSEL (President of the Scientific committee), Emmanuelle Vidal Petiot (General Secretary)</p><p>RESPONSIBLE OF THE EDITION</p><p>Naim KHAN, Secretary, International Affairs</p>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 S732","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/apha.14252","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142976736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. L. Bothe, A. Patzak, O. S. Opatz, V. Heinz, N. Pilz
Objective
Accurate blood pressure (BP) measurement is crucial for the diagnosis, risk assessment, treatment decision-making, and monitoring of cardiovascular diseases. Unfortunately, cuff-based BP measurements suffer from inaccuracies and discomfort. This study is the first to access the feasibility of machine learning-based BP estimation using impedance cardiography (ICG) data.
Methods
We analyzed ICG data from 71 young and healthy adults. Nine different machine learning algorithms were evaluated for their BP estimation performance against quality controlled, oscillometric (cuff-based), arterial BP measurements during mental (Trier social stress test), and physical exercise (bike ergometer). Models were optimized to minimize the root mean squared error and their performance was evaluated against accuracy and regression metrics.
Results
The multi-linear regression model demonstrated the highest measurement accuracy for systolic BP with a mean difference of −0.01 mmHg, a standard deviation (SD) of 10.79 mmHg, a mean absolute error (MAE) of 8.20 mmHg, and a correlation coefficient of r = 0.82. In contrast, the support vector regression model achieved the highest accuracy for diastolic BP with a mean difference of 0.15 mmHg, SD = 7.79 mmHg, MEA = 6.05 mmHg, and a correlation coefficient of r = 0.51.
Conclusion
The study demonstrates the feasibility of ICG-based machine learning algorithms for estimating cuff-based reference BP. However, further research into limiting biases, improving performance, and standardized validation is needed before clinical use.
{"title":"Machine learning-based blood pressure estimation using impedance cardiography data","authors":"T. L. Bothe, A. Patzak, O. S. Opatz, V. Heinz, N. Pilz","doi":"10.1111/apha.14269","DOIUrl":"10.1111/apha.14269","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Objective</h3>\u0000 \u0000 <p>Accurate blood pressure (BP) measurement is crucial for the diagnosis, risk assessment, treatment decision-making, and monitoring of cardiovascular diseases. Unfortunately, cuff-based BP measurements suffer from inaccuracies and discomfort. This study is the first to access the feasibility of machine learning-based BP estimation using impedance cardiography (ICG) data.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We analyzed ICG data from 71 young and healthy adults. Nine different machine learning algorithms were evaluated for their BP estimation performance against quality controlled, oscillometric (cuff-based), arterial BP measurements during mental (Trier social stress test), and physical exercise (bike ergometer). Models were optimized to minimize the root mean squared error and their performance was evaluated against accuracy and regression metrics.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The multi-linear regression model demonstrated the highest measurement accuracy for systolic BP with a mean difference of −0.01 mmHg, a standard deviation (SD) of 10.79 mmHg, a mean absolute error (MAE) of 8.20 mmHg, and a correlation coefficient of <i>r</i> = 0.82. In contrast, the support vector regression model achieved the highest accuracy for diastolic BP with a mean difference of 0.15 mmHg, SD = 7.79 mmHg, MEA = 6.05 mmHg, and a correlation coefficient of <i>r</i> = 0.51.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>The study demonstrates the feasibility of ICG-based machine learning algorithms for estimating cuff-based reference BP. However, further research into limiting biases, improving performance, and standardized validation is needed before clinical use.</p>\u0000 </section>\u0000 </div>","PeriodicalId":107,"journal":{"name":"Acta Physiologica","volume":"241 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11726408/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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