Pflugers Archiv : European journal of physiology最新文献

The brain employs a sophisticated and multi-layered system to maintain its delicate acid-base balance, ensuring optimal conditions for neuronal and glial function. This intricate regulation involves a combination of chemical buffering, active transport mechanisms, and systemic controls. The balance of pH in mammalian cells is vital for the control of metabolism, as hydrogen and hydroxyl ions are essential. It is important for the nervous system to keep its pH in a neutral range (7.2-7.6) for proper function. Even small pH changes can impact neuron activity, synaptic transmission, and communication between cells. Many membrane proteins sensitive to pH changes play vital roles in neurotransmission. Recent research has identified pH-sensitive proteins that respond to acidic (pH 5) and alkaline (pH 9) conditions, influencing various cellular activities. This review discusses these pH-sensitive proteins in neurons.

Obesity, a prevalent metabolic disease characterized by chronic systemic inflammation and dysregulated energy homeostasis, contributes to comorbidities such as type 2 diabetes and non-alcoholic fatty liver disease. Despite advancements in lifestyle interventions, pharmacotherapy and bariatric surgery, limitations in efficacy and safety emphasize the necessity for alternative therapeutic interventions. Electroacupuncture (EA), a contemporary form of traditional acupuncture, has emerged as a promising non-invasive intervention for obesity. This review synthesizes current evidence on the neuroendocrine, immunomodulatory, and metabolic mechanisms through which EA modulates hypothalamic nuclei, gut-liver axis signaling, white adipose tissue browning, and sympathetic-immune interactions. Preclinical studies have highlighted the potential of EA to enhance satiety signals, restore gut microbiota balance, suppress inflammasome activity, and promote white adipose tissue browning. Future research needs to prioritize human studies, elucidate neural circuitry, and optimize treatment protocols to translate preclinical findings into clinical practice.

The complement component C3, factor B (FB) and factor D (FD) belong to the alternative complement pathway and have been identified in urine samples from nephrotic mice. However, it is not yet known whether these factors are involved in mediating sodium retention in nephrotic syndrome (NS). Here we used a genetic mouse model of NS based on an inducible podocin deletion (Nphs2^Δipod). These mice were intercrossed with mice deficient for FB, FD or C3, yielding Nphs2^Δipod*Cfb^-/-, Nphs2^Δipod*Cfd^-/- or Nphs2^Δipod*C3^-/- mice, respectively. NS was induced after oral doxycycline treatment for 14 days. C3, FB and FD were detected in the nephrotic urine of Nphs2^Δipod mice as well as fragments of C3 and FB, indicating intrarenal activation of the alternative complement pathway. Lack of FB and FD had no impact on the activation of C3. Immunohistochemistry demonstrated positive C3 staining in protein casts and within the proximal tubule. Nephrotic mice of all genotypes experienced similar proteolytic activation of the epithelial sodium channel ENaC, developed sodium retention (urinary sodium concentration < 20 mM) and body weight gain. This was associated with a stimulation of proteolytic processing of epithelial sodium channel ENaC in all genotypes. In conclusion, components of the alternative complement pathway are detectable and activated in nephrotic syndrome. Mice with deletion of C3, FB or FD are not protected from proteolytic ENaC activation and sodium retention in NS.

Modern cardiac electrophysiology is largely focused on global electrical properties of tissue, frequently assessed by extracellular electrical recordings or optical mapping, whereas studies on the microscopic nature of action potential conduction are more rare, though fundamental to understand the whole-heart behavior. The electrophysiological dynamics of two ventricular myocytes electrically connected via gap junctions is the simplest conceivable model to study the laws governing the conduction of the electrical impulse within the heart ventricles. Since the enzymatic dispersion of cardiac cells has made it possible to isolate and investigate cardiac cell pairs directly, additional techniques have been introduced to investigate the problem, including coupling clamp, dynamic clamp, and numerical simulations. The physiology of a ventricular cell pair allows to define the basic laws governing the electrotonic interaction between cardiac cells in the absence of factors, like fiber orientation, heterogeneous spatial dispersion of electrophysiological properties, complex interaction with vessels and fibrotic tissue, that play a significant role in multicellular tissue studies. However, these laws remain at the base of our understanding of cardiac electrical functioning and should be bear in mind when dealing with the complexity of the whole organ level. This review will face both the technical issues encountered with the studies of ventricular cell pairs as well as the results found by the different authors concerning the physiological electrical coupling between cells, their physiological and pharmacological modulation, and the complex interactions between the conducted action potentials in the two cells.

The activation of cannabinoid receptor type II (CB2r) has been demonstrated to provide cardioprotective benefits against heart diseases. Nevertheless, the physiological effects of CB2r activation in healthy myocardial tissue remain poorly understood. Given the current gap in knowledge, particularly relevant in light of the growing therapeutic use of cannabinoids, this study aimed to investigate the effects of a single intraperitoneal injection of the selective synthetic CB2r agonist HU-308 on ventricular contractility, the expression of Ca²⁺-handling proteins, cyclic adenosine monophosphate (cAMP) levels, and redox biomarkers in male Wistar rats. Isolated left ventricular strips from HU-308-treated animals exhibited significant improvements in force of contraction (Fc), cardiac pumping capacity (CPC), and the rates of contraction (+ dF/dt) and relaxation (-dF/dt). Treatment with the CB2r agonist increased myocardial cAMP levels and upregulated the expression of sarcoplasmic reticulum (SR) Ca²⁺-ATPase (SERCA2a), phospholamban (PLB), and Na⁺/Ca²⁺ exchanger (NCX1). Additionally, HU-308 administration increased the glutathione (GSH)/oxidized glutathione (GSSG) ratio and the activity of antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR). Enhancement of the antioxidant defense system contributed to the maintenance of redox balance, as evidenced by decreased levels of lipid peroxidation (LPO), protein carbonyl (PC), and DNA strand breaks (DNA-sb). This study provides the first evidence that CB2r activation exerts antioxidative effects while enhancing both inotropy and lusitropy in the healthy rat myocardium, highlighting CB2r as a potential therapeutic target for preserving cardiac function.

Diet is a key physiological factor shaping brain function and gut microbiota, which together form the dynamic gut-brain axis. This bidirectional communication system plays a pivotal role in regulating behavioural outcomes. Therefore, it is worth investigating various behavioural aspects and connecting them with gut microbial dynamics shaped by differential dietary composition. Using zebrafish, we examined the effects of monotypic and combined diets of live feed and commercial feed on behavioural outcomes, morphometry, and gut microbiota. After chronic dietary intervention, fish receiving a mixed diet (Artemia, pellet, and spirulina) showed behavioural profile with enhanced exploration, reduced anxiety-like behaviour, and moderate aggression, alongside a balanced gut microbial composition. In contrast, monotypic diets produced distinct effects: Artemia-only fish displayed reduced boldness, heightened anxiety, and pathogenic microbial enrichment, while pellet-only fish showed greater growth but increased aggression. These findings highlight the importance of mixed feeding regimens for maintaining healthy gut-brain-behaviour interactions and support zebrafish as a model for studying diet-microbiota-behaviour relationships.

Recent kinetic studies show that the interstitial space contains two functional fluid compartments. This study explores the prerequisites for accumulation of infused crystalloid fluid in the remote slow-exchange space ("third fluid space¨, V_t2). Volume kinetic analysis based on log likelihood mathematics was applied to retrospective data from 132 intravenous infusions in 85 healthy volunteers who received 0.6-2.5 L of crystalloid fluid over 30 min. Frequent measurements of the blood hemoglobin concentration during and after these infusions, together with the measured urine output, served as calculation inputs. Three substudies were set up to illustrate key issues regarding V_t2 filling. In the first of them, infusions were preceded by blood withdrawal, which is known to decrease the interstitial pressure (P_if). Blood withdrawal resulted in smaller volumes entering V_t2, confirming that V_t2 filling is dependent on P_if. In the second substudy, modeled and measured urine outputs were compared after varying the inclusion of V_t2 in kinetic analyses in which the infused volume was gradually increased. Consideration of V_t2 was deemed appropriate when > 1.2 L of fluid was administered. In the third substudy, assessment of V_t2 filling during 7 time periods just before and after the 30 min infusions confirmed that uptake of fluid to V_t2 was initiated between 30 and 35 min. In conclusion, accumulation of fluid in V_t2 is dependent on P_if and occurs following infusion of > 1.2 L of crystalloid fluid. Uptake is not gradual but is initiated at a specific point in time.

Obesity is a leading global health issue, closely associated with a chronic low-grade inflammation termed metaflammation. Metaflammation is driven by immune cell reprogramming, particularly of macrophages. In white adipose tissue (WAT), obesity induces a shift from anti-inflammatory to pro-inflammatory macrophage phenotypes, contributing to insulin resistance and tissue fibrosis. Recent studies have also illuminated the role of macrophages in brown and beige adipose tissue (BAT and scWAT), where they influence thermogenic capacity. Beyond the adipose tissue, the liver is the other main metabolic organ impacted by obesity. Liver macrophages play a critical role in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) by promoting inflammation, lipid accumulation, and fibrosis. This review highlights the role of macrophages in the development and regulation of metaflammation in metabolic organs.