American journal of physiology. Cell physiology最新文献

Uterine contractility is regulated by the interaction of myogenic, neurogenic, and hormonal mechanisms. The hormonal peptide somatostatin (SST) is significantly increased in human plasma during late pregnancy and term labor (TL). SST mediates its effects by a family of G-protein-coupled receptors (SSTR1-5). Activation of somatostatin receptor type 2 (SSTR2) facilitates the contractility of smooth muscles, including the human gut and nonpregnant pig uterus. We hypothesized that SST/SSTR2 play a role in labor contractions, both term and preterm. The expression and localization of SST/SSTR2 were studied in human, rat, and mouse pregnant and laboring uterine tissues. Rodents' uteri were collected throughout gestation, TL, and preterm labor (PTL). Human myometrial biopsies were collected from TL and PTL women undergoing cesarean section. Human and rodent uterine tissues were fixed in formalin for immunohistochemistry (n = 4-7/group). Immunostaining of human and rodent' myometrium revealed stronger SSTR2 protein expression by myocytes and tissue macrophages during TL and PTL, as compared with not-in-labor patients or rodents. To examine the SST/SSTR2 mechanism, human monocytes were isolated from maternal peripheral blood and differentiated into macrophages. Primary human myocytes were isolated from the myometrium, cultured, and subjected to static mechanical stretch in vitro. Proteins were extracted and analyzed by immunoblotting, and the results indicate stretch-induced upregulation of SSTR2 in myocytes. Cell-conditioned media were analyzed by SST enzyme-linked immunosorbent assay (ELISA), indicating that human myocytes are a source of SST. When treated with exogenous SST, human myocytes induced contraction of a collagen gel. We conclude that SST/SSTR2 signaling may play a role in the process of labor in humans.NEW & NOTEWORTHY We show for the first time that somatostatin receptor type 2 (SSTR2) expression is upregulated in human and rodent myometrium during term and preterm labor. SSTR2 is expressed by myocytes and resident macrophages and is induced by mechanical stretch and inflammatory conditions. Human myocytes secrete somatostatin (SST), and its binding to SSTR2 enhances myocyte contractility in collagen gels, revealing a stretch- and inflammation-responsive SST-SSTR2 axis that promotes uterine contraction.

Obesity is associated with an elevated risk of pathological cardiac hypertrophy, whereas exercise confers cardioprotective effects; however, the cellular mechanisms underlying these opposing influences remain incompletely defined, particularly in females. We investigated how obesity and exercise affect cardiomyocyte ultrastructure, Ca²⁺ release, and contractility in female Zucker diabetic fatty rats and their lean littermates. Animals were assigned at 12 wk to sedentary or aerobic exercise-trained groups and maintained on a standard diet. By 18 wk, obese rats exhibited increased body mass and myocardial hypertrophy in the absence of diabetes. Sedentary obese animals showed a reduced fraction of compact dyads and diminished stimulated and caffeine-induced Ca²⁺ release, whereas contractility remained preserved. In lean rats, exercise increased dyad density but reduced Ca²⁺ release, whereas in obese rats, exercise enhanced both dyad compactness and Ca²⁺ release. Across all groups, global cardiomyocyte ultrastructure and contractile function were similar. Type III ANOVA revealed a significant obesity × exercise interaction for dyadic structure and Ca²⁺ release. These findings demonstrate that obesity itself, independent of diabetes, triggers early dyadic remodeling and altered Ca²⁺ handling in female myocardium before detectable impairment of global cardiomyocyte structure or contractile function. Furthermore, exercise exerts beneficial effects on dyadic ultrastructure and Ca²⁺ signaling in obese animals.NEW & NOTEWORTHY Using a female rat model of obesity without diabetes, we demonstrate that obesity induces early remodeling of the dyadic system and impairs Ca²⁺ release in cardiac myocytes. We further show that the effects of aerobic exercise on dyadic structure and function are obesity-dependent, improving both dyad organization and Ca²⁺ signaling. These findings identify the dyadic microdomain as a vulnerable cellular site in obesity and a potential target for exercise-induced recovery.

Stress-inducible phosphoprotein 1 (STIP1) is a co-chaperone involved in neuronal proteostasis and stress resilience. Although expressed in the heart, its role remains undefined. We assessed whether STIP1 deficiency impacts cardiac physiology and stress responses. STIP1 expression was analyzed in cardiac tissue from patients with heart failure. Haploinsufficient STIP1 mice (STIP1^+/-) received 7 days of isoproterenol (ISO) to induce cardiac injury, followed by proteomic, histological, and cardiomyocyte analyses. In vitro, neonatal rat cardiomyocytes (NRCMs) underwent STIP1 silencing and were evaluated using immunofluorescence, puromycin incorporation, and Western blotting. STIP1 levels were reduced in cardiac tissue from patients with heart failure, a pattern mirrored in STIP1^+/- mice. Although STIP1^+/- hearts developed normally, ISO exposure led to increased inflammation and fibrosis compared with wild-type. Despite elevated injury markers, STIP1^+/- cardiomyocytes failed to undergo hypertrophy in response to ISO. Proteomic profiling identified impaired protein synthesis as the dominant signature in STIP1^+/-/ISO hearts, explaining the blunted hypertrophic response. To determine STIP1's role in cardiomyocyte hypertrophy and establish causality, we silenced STIP1 in NRCMs. Recapitulating in vivo findings, STIP1 silencing blocked ISO-induced hypertrophy and similarly inhibited the hypertrophic responses to angiotensin II (Ang II) and phenylephrine in NRCMs. Consistent with proteomics, ISO failed to increase protein synthesis or eukaryotic translation initiation factor 4E (eIF4E) expression in STIP1-deficient NRCMs. STIP1 loss impairs the protein synthesis required for pathological cardiomyocyte hypertrophy, highlighting its essential role in cardiac adaptation to injury.NEW & NOTEWORTHY Although STIP1 is expressed in the heart and known for neuroprotection, its cardiac role remains undefined. We show that STIP1 is reduced in failing human hearts and that its deficiency in mice impairs resilience to adrenergic overload. Mechanistically, STIP1 loss disrupts the protein synthesis required for cardiomyocyte hypertrophy, positioning this co-chaperone as a hub of the heart's adaptive response to injury. Clinically, reduced STIP1 in heart failure may worsen dysfunction, underscoring its relevance to disease.

Type VI collagen (COL6) is a key extracellular matrix protein that supports matrix organization and cell-matrix interactions, yet its regulation in idiopathic pulmonary fibrosis (IPF) remains poorly understood. Here, we characterize COL6 gene expression, spatial localization, remodeling, and functional effects of COL6-derived fragments. Analysis of publicly available single-cell RNA sequencing data from 30 control subjects and 32 pulmonary fibrosis patients revealed higher expression of COL6A1-A6 in fibrotic lungs, predominantly in mesenchymal cells (A1: P = 0.0002, A2: P = 0.0005, A3: P = 2.5 × 10^-5, A5: P = 0.016, A6: P = 0.007). Immunohistochemical analysis of lung tissue from never-smoker (n = 9) and ex-smoker (n = 9) control subjects and IPF patients (n = 12) showed extensive COL6 localization across parenchyma, airways, and vessels. The proportion of COL6α1 and COL6α2 was lower around IPF vessels (α1: P < 0.001, α2: P = 0.012), and COL6α2 was lower around IPF airways (P = 0.033) compared with never-smokers. Quantification of COL6 remodeling fragments in lung tissue from never-smoker (n = 3) and ex-smoker (n = 5) control subjects and IPF patients (n = 10) revealed that COL6 production (PRO-C6) localized around airways and vessels but was proportionally lower in IPF airways (never-smokers: P = 0.0075). In contrast, COL6 degradation (C6M) was widely distributed throughout the tissue, with lower levels in IPF (never-smokers: P = 0.0008). Functionally, COL6 and PRO-C6 increased fibroblast viability (COL6: P = 0.002, PRO-C6: P = 0.0021), whereas apoptosis was unaffected. Similar trends were observed in epithelial and endothelial cells. In summary, despite increased COL6 gene expression, IPF lungs exhibited lower proportions of COL6 protein and synthesis around airways and vessels, suggesting disrupted matrix organization, altered remodeling, and prosurvival effects that may contribute to fibroblast persistence and fibrosis progression.NEW & NOTEWORTHY In this study, we revealed that idiopathic pulmonary fibrosis (IPF) lungs are characterized by increased type VI collagen (COL6) gene expression but lower COL6 protein and turnover proportions around airways and blood vessels compared with controls. COL6 and a fragment associated with its production (PRO-C6) increased lung fibroblast viability. These findings highlight that pulmonary fibrotic tissue is characterized by disrupted extracellular matrix and altered tissue remodeling and suggest that COL6 may contribute to fibroblast persistence and fibrosis progression.

Heart failure (HF) is a chronic disease with increasing global incidence, requiring the development of personalized therapeutic strategies. Despite remarkable progress in the treatment of acute myocardial infarction (MI), MI remains the most common cause of HF. Many animal models have been developed to attempt to recreate the chronic HF phenotype after MI. Still, few characterize the consequences of ischemia-reperfusion (I/R) injury on the progression of MI to HF according to sex. To this end, we aimed to develop a preclinical model capable of reproducing post-MI clinical symptoms and to compare, after constitutive infarction, the progression of post-I/R remodeling. Twelve- to sixteen-weeks-old female and male C57BL/6J mice underwent 90 min of ischemia followed by 16 wk of reperfusion. Mortality, cardiac structural and functional characteristics were assessed on day 2 and at 4, 8, 12, and 16 wk after reperfusion. Our results showed that 90-min I/R injury induces comparable acute contractile dysfunction, cardiac remodeling, and interstitial fibrosis during the first 8 wk of reperfusion in females and males. Although fractional area change was significantly decreased at week 8, leading males to congestive and chronic HF from week 12, females exhibited a 4-wk delay in developing similar post-I/R HF symptoms. Mechanically, at week 16, failing cardiomyocytes exhibited reduced contractility with a decrease in Ca²⁺ transients that was more pronounced in males. In conclusion, our 90-min I/R mouse model mimicked clinical post-MI HF and could be used to elucidate the sex-dependent pathophysiology of post-I/R HF further to identify novel targets against HF with reduced ejection fraction (HFrEF).NEW & NOTEWORTHY This study provides researchers and clinicians with a relevant preclinical mouse model, reproducing the clinical reality of ischemia-reperfusion (I/R) injury progression to congestive and worsening heart failure, and highlighting sex-specific differences in disease progression. This model is therefore important for understanding sex-specific mechanisms of post-I/R heart failure and identifying future targeted therapies.

Interleukin-6 (IL-6), produced by skeletal muscle and extramuscular tissues, regulates skeletal muscle function through the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. However, the interaction between intrinsic (locally produced) IL-6 and extrinsic (circulating) IL-6 in skeletal muscle remains unclear. We investigated whether and how intrinsic expression of IL-6 in cultured primary human myoblasts influences their response to extrinsic stimulation with recombinant human IL-6 (rhIL-6). Using gene silencing, we found that suppression of intrinsic IL-6 enhanced rhIL-6-induced phosphorylation of STAT1 and STAT3. Silencing STAT3 also increased rhIL-6-induced STAT1 phosphorylation, but silencing STAT1 had no effect on STAT3 phosphorylation. Pretreatment of myoblasts with neutralizing anti-IL-6 antibodies increased phosphorylation of STAT1 and STAT3 induced by 50 ng/mL rhIL-6, whereas pretreatment with 5 ng/mL rhIL-6 reduced this response. Despite increased JAK/STAT signaling, IL-6 silencing decreased glucose and oleic acid uptake and oxidation under both basal and rhIL-6-stimulated conditions. Collectively, our results imply that intrinsic IL-6 restrains activation of the JAK/STAT pathway by extrinsic IL-6, but acts synergistically with it to promote myoblast energy metabolism.

Urothelial ATP release during bladder filling modulates afferent nerve activity and detrusor contractility to regulate the micturition reflex, yet the upstream mechanosensory mechanism linking distension to ATP release remains unclear. Here we investigated the role of Piezo1 in regulating mechanosensitive ATP release in human urothelial TRT-HU1 cells and in a rat model of bladder outlet obstruction (BOO). In TRT-HU1 cells, mechanical stress increased ATP release 60% above baseline. Bath-applied Yoda1 (1-10 µM) suppressed mechanically stimulated ATP release in a dose-dependent manner, an effect abolished by PIEZO1 knockdown and reproduced across three mechanically distinct stimuli. PIEZO1 knockdown alone, however, did not reduce mechanically stimulated ATP release. PANX1 knockdown reduced baseline but not mechanically stimulated ATP release, whereas carbenoxolone suppressed it, implicating a carbenoxolone-sensitive, PANX1-independent pathway in which connexin hemichannels are the most likely mediator. Removal of extracellular calcium markedly elevated ATP release, and Yoda1 partially suppressed this elevation even in calcium-free conditions, indicating both Ca²⁺-dependent and Ca²⁺-independent inhibitory mechanisms. A 1-min application of Yoda1 evoked a sustained intracellular Ca²⁺ rise that was abolished in calcium-free medium and in PIEZO1 knockdown cells. In BOO rats, intravesical ATP was significantly elevated compared to sham animals. Intravesical Yoda1 instillation significantly reduced ATP levels in BOO rats and decreased non-voiding contractions by 40% (p < 0.01) without altering voiding parameters. These findings identify pharmacological activation of Piezo1 as a brake on mechanosensitive purinergic signaling in the bladder and suggest that it warrants further evaluation as a therapeutic approach to BOO-induced lower urinary tract dysfunction.

Glucagon-like peptide 1 receptor agonists (GLP1Ra) are widely used for the management of obesity and cardiometabolic disease. While causing robust weight loss, GLP1Ra also result in reductions in lean tissue, including skeletal muscle and bone. The purpose of the current review is to discuss key findings demonstrating the effects of GLP1Ra treatment on skeletal muscle and bone, approaches that have been implemented to mitigate these changes, and to highlight important areas of future research.

Exercise induces diverse adaptations in skeletal muscle, and extracellular matrix remodeling plays a key role in these adaptations. Capillaries, which are essential for transporting oxygen and other molecules to maintain skeletal muscle function, are crucial for exercise adaptation. Perlecan, a heparan sulfate proteoglycan and a major basement membrane molecule in skeletal muscle, has been implicated in capillary formation and maintenance. However, its role in exercise adaptation remains unclear. Herein, we used male mice lacking perlecan expression outside of cartilage (Hspg2^-/--Tg) as well as Hspg2 wild-type transgenic control mice to examine the regulatory relationship between perlecan and PGC-1α isoforms, which are key mediators of exercise-induced metabolic and angiogenic responses. Following acute treadmill exercise, Hspg2^-/--Tg mice showed a significant increase in the mRNA expression of alternative promoter-driven PGC-1α isoforms (ex1b and ex1b') 3 h after exercise, whereas proximal promoter-driven isoforms showed little response. This isoform-specific response was accompanied by enhanced expression of angiogenesis-related genes, including Vegfa, Angpt1, Angpt2, and Hif1a, which peaked 3 h after exercise in perlecan-deficient muscle. In parallel with these transcriptional changes, immunofluorescent analysis revealed significantly higher baseline capillary density in Hspg2^-/--Tg quadriceps muscle, a difference that became even more pronounced after 2 wk of exercise training. These findings demonstrate that perlecan deficiency enhances baseline vascular remodeling features and the angiogenic transcriptional response to exercise, suggesting that the composition of the basement membrane extracellular matrix critically regulates exercise-induced PGC-1α isoform expression and muscle-vascular crosstalk during skeletal muscle adaptation.

Silymarin, a flavonolignan complex from Silybum marianum, and its principal constituent silybin have long been used as hepatoprotective and antifibrotic agents. In the liver, silymarin suppresses tissue inhibitor of metalloproteinases 1 (TIMP-1), a central regulator of matrix turnover in fibrogenesis. This effect is reproducible across several models of hepatic fibrosis, but its magnitude is inconsistent. Some studies report no or only a nonsignificant reduction in hepatic TIMP-1 with free silymarin, while others report a substantial decline. Much of this inconsistency tracks with formulation and route. The clinical use of silymarin is limited by low aqueous solubility, low bioavailability, and rapid clearance. Conjugating flavonolignans to β-cyclodextrin or phospholipids, or preparing a nanoparticle formulation, could address these limitations. Across the mRNA-based studies compiled here, complexed or nanoparticle-encapsulated preparations achieved significantly greater recovery of hepatic Timp1 toward baseline than free compound. Among nanocarrier formulations, gold nanoparticles are an attractive platform. Independent of any drug coating, they themselves exhibit hepatoprotective and antifibrotic activity in models of liver injury, although this intrinsic activity has not been shown to extend to TIMP-1 itself. Conjugating milk thistle flavonolignans, the actual source of TIMP-1 suppression, to this platform could therefore combine two complementary benefits, though this specific combination remains untested.