American journal of physiology. Cell physiology最新文献

Sepsis survivors face a heightened risk of secondary infections following discharge, yet the underlying mechanisms remain poorly defined. Our study identifies a novel mechanism of endothelial inflammatory memory, wherein inflammatory exposure induces durable chromatin remodeling in endothelial cells (ECs), priming them for exaggerated responses to a subsequent infection. Utilizing a clinically relevant two-hit mouse model, cecal ligation and puncture (CLP) followed by mild Streptococcus pneumoniae (Sp) infection in CLP survivors, we reveal transcriptional activation in endothelial cells (ECs) following secondary infection, marked by significantly elevated expression of proinflammatory cytokines, adhesion molecules, complement factors, and interferon-stimulated genes. Genome-wide ATAC-seq revealed that a subset of inflammatory gene loci retained increased chromatin accessibility even after cytokine withdrawal, demonstrating stable epigenetic remodeling consistent with transcriptional priming and inflammatory memory. In vitro, we uncovered a critical role for the activator protein-1 transcription factor JunB in mediating this epigenetic remodeling. JunB knockdown attenuated chromatin accessibility after an initial IL-6 challenge and subsequent transcriptional amplification upon a secondary LPS challenge, pinpointing JunB-driven chromatin modifications as central to endothelial reprogramming. Our findings offer mechanistic insights into how transient inflammation creates lasting epigenetic states within the endothelium, highlighting JunB as a potential therapeutic target to mitigate chronic endothelial dysfunction and increased susceptibility to secondary infections postsepsis.NEW & NOTEWORTHY We uncover that endothelial cells retain a form of inflammatory memory, driven by chromatin remodeling and sustained JunB activity. Using two-hit models in mice and human endothelial cells, we show that an initial inflammatory exposure primes the endothelium for exaggerated responses to future inflammation. This discovery reveals a new mechanism of chronic endothelial dysfunction and identifies JunB as a potential therapeutic target in postsepsis care.

Cancer cachexia causes skeletal muscle wasting and metabolic dysfunction, worsening clinical outcomes in colorectal cancer (CRC). This study examines microscopic and macroscopic skeletal muscle fiber characteristics, and muscle volume in patients with CRC-associated cachexia and without cachexia compared with healthy controls (HCs), and explores how these factors relate to physical performance. In total, 12 patients with CRC-associated cachexia, 25 CRC patients without cachexia, and 25 HCs were included. Cachexia was determined by weight loss and Cachexia Staging Score. Biopsies from the vastus lateralis and erector spinae muscles were analyzed using immunohistochemistry for muscle fiber type cross-sectional area (CSA) and distribution, myonuclear content, and capillary density. Muscle volume was assessed using three-dimensional ultrasound, and CSA and density by computerized tomography scans. Physical function was evaluated with the Short Physical Performance Battery test, handgrip strength, and the Physical Activity Scale for Individuals with Physical Disabilities. Quality of life was assessed using the 36-item Short Form Survey. Patients with CRC-associated cachexia showed reduced type II muscle fiber CSA in the vastus lateralis compared with HCs and CRC patients without cachexia. CRC Patients without cachexia exhibited a slow-to-fast muscle fiber shift compared with HCs. Myonuclear content was lower in both cancer groups. Muscle volume and density were reduced in patients with CRC-associated cachexia. Positive correlations were found between microscopic and macroscopic skeletal muscle characteristics, muscle strength, physical performance, and quality of life, respectively. CRC Patients, especially those with cachexia, showed type II muscle fiber atrophy, reduced myonuclear content, and impaired physical function, emphasizing the need for targeted prehabilitation interventions.NEW & NOTEWORTHY This study reveals skeletal muscle alterations in colorectal cancer patients with cachexia, at microscopic (fiber-type specific atrophy, myonuclear content, and capillarization) and macroscopic levels (muscle volume and quality). These alterations were associated with clinically important measures of physical functioning and quality of life. Collectively, these findings establish clinically relevant links between structural muscle alterations and physical outcomes, highlighting the potential value of targeted (p)rehabilitation interventions in these patient populations.

The aim of the present study was to investigate the secretory responses elicited by inositol 1,4,5-trisphosphate (IP₃) and their regulation by Ca²⁺ from different sources. Fura-2, carbon fiber amperometry, and plasma membrane capacitance recordings were performed in mouse chromaffin cells to evaluate cytosolic Ca²⁺ changes, catecholamine release, and exocytosis, respectively. Amperometric recordings revealed that IP₃ triggered the continuous release of catecholamines to the cytosol with a plateau shape, either applied independently or in combination with the V-ATPase blocker bafilomycin A1, without exhibiting additive effects, which suggests that V-ATPase blockade might be a potential mechanism of action. The catecholamine release elicited by IP₃ can take place in the absence of cytosolic Ca²⁺; however, it may be also regulated by it through a bell-shaped mechanism, with the contribution of Ca²⁺ stored in intracellular organelles. Furthermore, plasma membrane capacitance recordings showed that IP₃ could also elicit exocytosis of secretory vesicles with the participation of intracellular organelle Ca²⁺ stores. This exocytosis could be regulated by vesicular or cytosolic Ca²⁺, as shown in experiments with bafilomycin A1 or the Ca²⁺ chelator BAPTA-AM, respectively, and by kaempferol, an activator of the mitochondrial Ca²⁺ uniporter, suggesting that mitochondria may exert physiologically this Ca²⁺ regulatory mechanism. Therefore, in the IP₃-mediated secretion, Ca²⁺ from different sources control the different steps of catecholamine release from the secretory vesicle to the cytosol and then finally to the extracellular space.NEW & NOTEWORTHY Inositol 1,4,5-trisphosphate (IP₃) triggers the release of catecholamines from secretory vesicles to the cytosol through a process that may occur in the absence of cytosolic Ca²⁺, it is biphasically regulated by it and is dependent on Ca²⁺ from intracellular organelles. Additionally, IP₃ triggers the exocytosis of secretory vesicles through a cytosolic and vesicular Ca²⁺ regulatory mechanism that may be physiologically modulated by mitochondria.

Preeclampsia (PE) is a complex gestational disorder marked by vascular abnormalities and elevated blood pressure yet remains without widely effective treatments. This study investigates the efficacy of ferulic acid (FA) in alleviating PE symptoms by targeting the signal transducer and activator of transcription 3 (STAT3)/vascular endothelial growth factor (VEGF) signaling axis to enhance endothelial integrity and reduce inflammation. An N^G-nitro-l-arginine methyl ester hydrochloride (l-NAME)-induced PE mouse model was used, with FA administration to pregnant mice to assess therapeutic effects on key outcomes such as blood pressure, proteinuria, and placental function. Single-cell RNA sequencing (scRNA-seq) and molecular assays were conducted to examine FA's impact on endothelial cell balance, inflammation, and pathway-specific activity. The results showed that FA treatment significantly reduced hypertension, proteinuria, and inflammation, while improving endothelial cell balance in PE mice. In addition, inhibition of STAT3 phosphorylation by FA enhanced endothelial barrier function, stabilized vascular integrity, and supported improved fetal development outcomes. Overall, these findings demonstrate the protective effects of FA in PE by alleviating endothelial impairment and dampening inflammatory activity, offering a promising strategy to improve maternal and fetal health in PE, with implications for managing pregnancy-related vascular dysfunctions.NEW & NOTEWORTHY Our study investigates ferulic acid (FA) as a potential therapeutic intervention for preeclampsia (PE), a severe pregnancy complication with limited treatment options. By targeting the STAT3/VEGF signaling pathway, FA demonstrated significant reductions in hypertension, inflammation, and improved endothelial cell balance in PE mice. These results highlight FA's promise in enhancing maternal and fetal health by addressing endothelial dysfunction, suggesting its potential for broader applications in managing pregnancy-related vascular dysfunctions.

Amino acids (AAs) play structural and metabolic roles in muscle, heart, and liver-tissues impacted by cancer and chemotherapy. Changes in AA profiles within these tissues have not been evaluated in response to tumor growth and chemotherapy. This study investigated how tumor growth with or without doxorubicin altered tissue-level amino acids. Female C57bl/6 mice (n = 7-10/group) were randomly assigned to groups: control, doxorubicin control at 3 and 7 days, 21-day tumor, 24-day tumor, 28-day tumor, 24-day tumor + doxorubicin, 28-day tumor + doxorubicin. Tumor groups were injected with E0771 cells in the right flank on day 0. Doxorubicin was administered once (intraperitoneally) at 10 mg/kg in doxorubicin control and tumor + doxorubicin groups on day 21, with endpoints at day 24 and 28. Muscle glutamate and aspartate were significantly depleted by day 28 in both tumor and tumor + doxorubicin groups (P < 0.05), whereas proline, arginine, leucine, and isoleucine increased (P < 0.05). Hepatic aspartate was elevated by 21 days, and lysine by 24 days (P < 0.05). Cardiac glutamate was depleted at days 21, 24, and 28 (P < 0.05). Notably, doxorubicin did not add to tumor-induced changes in muscle or heart. Tumor AAs remained largely stable. Tumor growth induced profound changes to skeletal muscle AA pools, reflecting impaired handling of AAs that could serve structural roles, or expand the substrate pool for ATP synthesis. Despite this, most tumor AAs remained stable over tumor growth. These results suggest a link between muscle wasting and skeletal muscle-derived AAs for tumor growth. Further work is needed to characterize the mechanisms mediating the observed changes in AA profiles.NEW & NOTEWORTHY This study demonstrates significantly perturbed amino acid pools within muscle as a result of tumor growth, with marginal additive effects of doxorubicin administration. Notably, tumor amino acid pools remain primarily unchanged despite muscle suggesting significant changes, which may be indicative of structural damage or reduced ability to produce energy.

The transmembrane-electrostatically localized protons/cations charges (TELPs/TELCs) theory can serve as a theoretical framework to better explain cell electrophysiology and elucidate bioenergetic systems, including both delocalized and localized protonic coupling. According to the TELCs model, the excess positive charges of TELCs at one side of the membrane are balanced by the excess negative charges of transmembrane-electrostatically localized hydroxide anions (TELAs) at the other side of the membrane. Through the TELCs-membrane-TELAs capacitor model, the energetics of oxidative phosphorylation have recently been better elucidated in mitochondria and alkalophilic bacteria, leading to the identification of a novel Type-B energetic process. Both the TELCs model studies and experimental demonstration results showed that the putative "potential well/barrier" model is not needed to explain TELPs formation. Application of the TELCs model to neural cells has recently resulted in novel neural transmembrane potential integral equations. In this review article, we will visit the TELCs-membrane-TELAs model and its applications, including its features and predictions that may help better understand cell energetics. Meanwhile, we will also discuss some of the recent critiques and point out the opportunities and directions for future research. The TELCs model can be well predictive and provide new opportunities as a theoretical tool for further research to better understand cell physiology, bioenergetics, and neurosciences. This Landmark Review article timely provides the latest discoveries, breakthrough advances with new developments and knowledge, directions and opportunities for future research in a major emerging and exciting scientific area of protonic capacitor cell energetics: transmembrane-electrostatically localized protons/cations.

Eye disease-associated K⁺ channel Kir7.1 is highly expressed together with the Na⁺-K⁺ pump at the apical membrane of retinal pigment epithelial cells (RPEs) that line the subretinal space (SRS). SRS K⁺ concentration ([K⁺]_SRS) decreases from ∼5 to 2 mM upon light stimulation. Kir7.1 is crucial in its buffering, with failure thought to be causal in visual disease mutations of its gene. The unusual inverse relation to [K⁺]_o of its conductance, deemed essential for [K⁺]_SRS buffering, relies on nonconserved outer pore methionine-125. We now probe the role of Kir7.1 in the visual process by generating Kir7.1-M125R mutant mice with the channel predicted to lack [K⁺]_SRS buffering ability. RPE cell electrical properties and mouse electroretinograms (ERG) are assessed. Membrane potential of RPE cells was found to be dominated by K⁺, but while conductance decreased with increasing [K⁺]_o in control cells, the reverse was true for cells of Kir7.1-M125R-expressing mice. ERG of mutant animals revealed a larger c-wave than in controls, consistent with the relative K⁺ permeabilities of the RPE. In contrast, there was no difference between the a- and b-waves of Kir7.1-M125R and control mice, suggesting normal functioning of photoreceptors and bipolar cells, and therefore retinal processing of the light signal. If, as predicted, [K⁺]_SRS buffering is altered in mutant animals, this does not affect the retinal processing of the light signal. Other consequences of Kir7.1 malfunction, such as proposed function in photoreceptor outer segment recycling, must be involved in originating the disease phenotype associated with mutations in its gene.NEW & NOTEWORTHY Retinal pigment epithelium apical membrane K⁺ channel Kir7.1 is crucial in the buffering of changes in subretinal K⁺ concentration occurring upon light stimulation, this thanks to its unusual inverse conductance relation to extracellular K⁺. We demonstrate that inactivating this property by mutation Kir7.1-M125R in mice did not affect retinal response to light stimulus, suggesting that a different channel function must be affected in eye disease caused by mutations of the Kir7.1 gene.

Pharmaceutical research has undergone significant transformation over time, particularly in the development of potent compounds that target specific physiological mechanisms. The need to demonstrate clinical benefit posed challenges. These challenges led to the rise of translational physiology and precision medicine aided by the development of the chemical biology platform. The chemical biology platform is an organizational approach to optimize drug target identification and validation and improve safety and efficacy of biopharmaceuticals. The platform achieves this goal through emphasis on understanding the underlying biological processes and leveraging knowledge gained from the action of similar molecules on these biological processes. The platform connects a series of strategic steps to determine whether a newly developed compound could translate into clinical benefit using translational physiology. Translational physiology examines biological functions across multiple levels, from molecular interactions to population-wide effects, and has been deeply influenced by the advancement of the chemical biology platform. Unlike traditional trial-and-error methods, by leveraging systems biology techniques, such as proteomics, metabolomics, and transcriptomics, chemical biology prioritizes targeted selection to enhance drug discovery. This historical review explores the evolution of the chemical biology platform and its role in precision medicine, highlighting its continued influence in both academic research and pharmaceutical innovation. By fostering a mechanism-based approach to clinical advancement, chemical biology remains a critical component in modern drug development. In addition, understanding the history and integrative nature of this platform is essential for training the next generation of researchers in the design of experimental studies that effectively incorporate translational physiology.

Lysosomes are membrane-bound organelles responsible for the degradation of damaged or dysfunctional cellular components, including mitochondria. Their acidic internal environment and the presence of an array of hydrolytic enzymes facilitate the efficient breakdown of macromolecules such as proteins, lipids, and nucleic acids. Mitochondria play a critical role in maintaining skeletal muscle homeostasis to meet the energy demands under physiological and pathological conditions. Mitochondrial quality control within skeletal muscle during processes such as exercise, disuse, and injury is regulated by mitophagy, where dysfunctional mitochondria are targeted for lysosomal degradation. The limited understanding of quality control mechanisms in skeletal muscle necessitates the need for isolating intact lysosomes to assess organelle integrity and the degradative functions of hydrolytic enzymes. Although several methods exist for lysosome isolation, the complex structure of skeletal muscle makes it challenging to obtain relatively pure and functional lysosomes due to the high abundance of contractile proteins. Here, we describe a method to isolate functional lysosomes from small amounts of mouse skeletal muscle tissue, preserving membrane integrity. We also describe functional assays that allow direct evaluation of lysosomal enzymatic activity, and we provide data indicating reduced lysosomal degradative activity in lysosomes from aging muscle. We hope that this protocol provides a valuable tool to advance our understanding of lysosomal biology in skeletal muscle, supporting investigations into lysosome-related dysfunction in aging, disease, and exercise adaptations.NEW & NOTEWORTHY Lysosomes within skeletal muscle function to degrade dysfunctional debris and initiate retrograde signaling pathways. We developed a method to isolate purified lysosomal fractions using small portion of skeletal muscle, eliminating the need for density gradients or lysosome-modifying agents, ensuring high lysosomal purity without compromising structure or function. By enabling functional analysis via acid phosphatase, cathepsin-B activity, and calcium release, this approach offers a powerful tool to study lysosomal roles in muscle physiology, disease, and exercise.

Cardiac fibrosis is the activation of cardiac fibroblasts (CFs) and deposition of extracellular matrix caused by various injurious factors, which affects cardiac function and structure and ultimately leads to the development of heart failure. Studies have shown that the Sonic Hedgehog (Shh) signaling pathway is reactivated after myocardial ischemia and regulates cardiac tissue repair. However, the effect of Shh signaling pathway on the biological function of CFs and the mechanism of its regulation have not been clarified, so we explored it through a series of in vivo and in vitro experiments. Our results demonstrated that activation of Smoothened (Smo), a key molecule in the Shh signaling pathway, inhibits CFs G1/S phase transition and proliferation. Adenoviral knockdown of Gli1, a downstream transcription factor of the Shh signaling pathway, largely reversed the functional inhibition of CFs caused by activation of Smo, and conversely, overexpression of Gli1 was consistent with Smo activation effects. Further results indicated that the effects of Smo/Gli1 pathway may be mediated by AKT. In addition, in a cardiac remodeling model, early activation of Smo for intervention was observed to not only improve the extent of fibrosis, but also to have a protective effect on cardiac function and structure. These results suggest that activation of Smo may inhibit the proliferation of CFs and have an antifibrotic effect in vivo. This suggests that the Shh signaling pathway may be a potential therapeutic target for cardiac fibrosis.NEW & NOTEWORTHY The Sonic Hedgehog (Shh) signaling pathway is reactivated after myocardial ischemia and regulates cardiac tissue repair. However, the effect of Shh signaling pathway on the biological function of CFs and the mechanism of its regulation have not been clarified. Our results demonstrated that activation of Smo may inhibit the proliferation of CFs and have an antifibrotic effect in vivo. This suggests that the Shh signaling pathway may be a potential therapeutic target for cardiac fibrosis.