American journal of physiology. Cell physiology最新文献

Glioblastoma (GBM) remains one of the most aggressive and treatment-resistant brain malignancies in adults. Standard approaches, including surgical resection followed by adjuvant radio- and chemotherapy with temozolomide (TMZ), provide only transient control, as GBM frequently recurs due to its infiltrative nature and the presence of therapy-resistant subpopulations such as glioma stem cells (GSCs). GSCs, with their quiescent state and robust resistance mechanisms, evade conventional therapies, contributing significantly to relapse. Consequently, current treatment methods for GBM face significant limitations in effectively targeting GSCs. In this review, we emphasize the relationship between GBM recurrence and GSCs, discuss the current limitations, and provide future perspectives to overwhelm the challenges associated with targeting GSCs. Eliminating GSCs may suppress recurrence, achieve durable responses, and improve therapeutic outcomes for patients with GBM.

High-load resistance exercise (>60% of 1-repetition maximum) is a well-known stimulus to enhance skeletal muscle hypertrophy with chronic training. However, studies have intriguingly shown that low-load resistance exercise training (RET) (≤60% of 1-repetition maximum) can lead to similar increases in skeletal muscle hypertrophy as compared with high-load RET. This has raised questions about the underlying mechanisms for eliciting the hypertrophic response with low-load RET. A key characteristic of low-load RET is performing resistance exercise to, or close to, task failure, thereby inducing muscle fatigue. The primary aim of this evidence-based narrative review is to explore whether muscle fatigue may act as an indirect or direct mechanism contributing to skeletal muscle hypertrophy during low-load RET. It has been proposed that muscle fatigue could indirectly stimulate muscle hypertrophy through increased muscle fiber recruitment, mechanical tension, ultrastructural muscle damage, the secretion of anabolic hormones, and/or alterations in the expression of specific proteins involved in muscle mass regulation (e.g., myostatin). Alternatively, it has been proposed that fatigue could directly stimulate muscle hypertrophy through the accumulation of metabolic by-products (e.g., lactate), and/or inflammation and oxidative stress. This review summarizes the existing literature eluding to the role of muscle fatigue as a stimulus for low-load RET-induced muscle hypertrophy and provides suggested avenues for future research to elucidate how muscle fatigue could mediate skeletal muscle hypertrophy.

Cancer cachexia is a multifaceted metabolic syndrome characterized by muscle wasting, fat redistribution, and metabolic dysregulation, commonly associated with advanced cancer but sometimes also evident in early-stage disease. More subtle body composition changes have also been reported in association with cancer, including sarcopenia, myosteatosis, and increased fat radiodensity. Emerging evidence reveals that body composition changes including sarcopenia, myosteatosis, and increased fat radiodensity, arise from distinct biological mechanisms and significantly impact survival outcomes. Importantly, these features often occur independently, with their combined presence exacerbating poor prognoses. Tumor plays a pivotal role in driving these host changes, either by acting as a metabolic parasite or by releasing mediators that disrupt normal tissue function. This review explores the diversity of tumor metabolism. It highlights the potential for tumor-specific metabolic phenotypes to influence systemic effects, including fat redistribution and sarcopenia. Addressing this tumor-host metabolic interplay requires personalized approaches that disrupt tumor metabolism while preserving host health. Promising strategies include targeted pharmacological interventions and anticachexia agents like growth differentiation factor 15 (GDF-15) inhibitors. Nutritional modifications such as ketogenic diets and omega-3 fatty acid supplementation also merit further investigation. In addition to preserving muscle, these therapies will need to be evaluated for their capability to improve survival and quality of life. This review underscores the need for further research into tumor-driven metabolic effects on the host and the development of integrative treatment strategies to address the interconnected challenges of cancer progression and cachexia.

Inflammation is a significant risk factor for preterm birth. Inflammation enhances glycolytic processes in various cell types and contributes to the development of myometrial contractions. However, the potential of inflammation to activate glycolysis in pregnant murine uterine smooth muscle cells (mUSMCs) and its role in promoting inflammatory preterm birth remain unexplored. In this study, lipopolysaccharide was employed to establish both cell and animal inflammation models. We found that inflammation of mUSMCs during late pregnancy could initiate glycolysis and promote cell contraction. Subsequently, the inhibition of glycolysis using the glycolysis inhibitor 2-deoxyglucose can reverse inflammation-induced cell contraction. The expression of 6-phosphofructokinase 2 kinase (PFKFB3) was significantly upregulated in mUSMCs following lipopolysaccharide stimulation. In addition, lactate accumulation and enhanced contraction were observed. Inhibition of PFKFB3 reversed the lactate accumulation and enhanced contraction induced by inflammation. We also found that inflammation activated the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of the rapamycin (mTOR) pathway, leading to the upregulation of PFKFB3 expression. The PI3K-Akt pathway inhibitor LY294002 and the mTOR pathway inhibitor rapamycin effectively inhibited the upregulation of PFKFB3 protein expression, lactate production, and the enhancement of cell contraction induced by lipopolysaccharide. This study indicates that inflammation regulates PFKFB3 through the PI3K-Akt-mTOR pathway, which enhances the glycolytic process in pregnant mUSMCs, ultimately leading to myometrial contraction.NEW & NOTEWORTHY Expression of PFKFB3, a key enzyme in glycolysis, was significantly upregulated both in the mUSMCs and myometrium of mice during late pregnancy after lipopolysaccharide stimulation. Activation of the PI3K-Akt-mTOR pathway enhanced PFKFB3 expression, which is involved in the initiation of glycolysis. Inflammation-activated PFKFB3 via the PI3K-Akt-mTOR pathway, which enhances the cellular glycolytic process and thus promotes myometrium contraction in pregnancy.

As a gas molecule, hydrogen sulfide (H₂S) exerts neuroprotective effects. Despite its recognized importance, there remains a need for a deeper understanding of H₂S's impact on vascular smooth muscle cells and its role in ischemic brain injury. This study employs encompassing cultured primary cerebral vascular smooth muscle cells, oxygen-glucose deprivation/reoxygenation model, in vitro vascular tone assessments, in vivo middle cerebral artery occlusion and reperfusion experimentation in male rats, and the utilization of Rho-associated coiled-coil containing protein kinase 2 (ROCK₂) knockout, to unravel the intricate relationship between H₂S and cerebrovascular diastolic function. Our findings show that RhoA activation induces heightened vascular smooth muscle cell (VSMC) contraction, whereas the introduction of exogenous H₂S mitigates the relaxant effect of the middle cerebral artery in rats through the downregulation of both ROCK₁ and ROCK₂, with ROCK₂ exhibiting a more pronounced effect. Correspondingly, the attenuation of ROCK₂ expression yields a more substantial reduction in the protective impact of H₂S on cerebral blood flow, as well as learning and memory ability in ischemic injury, compared with the decrease in ROCK₁ expression. Moreover, we demonstrate that H₂S effectively mitigates the damage induced by oxygen-glucose deprivation/reoxygenation in male mouse primary vascular smooth muscle cells. This effect is characterized by enhanced cell proliferation, reduced lactate dehydrogenase leakage, elevated superoxide dismutase activity, and inhibited apoptosis. Notably, this protective effect is markedly diminished in cells derived from ROCK₂ knockout mice. Our study reveals that H₂S can relax cerebral vascular smooth muscle and ameliorate ischemic stroke injury by inhibiting the ROCK, with a particular emphasis on the role of ROCK₂.NEW & NOTEWORTHY This study employs a diverse array of methods; our collective findings indicate that H₂S safeguards against ischemic brain injury by inhibiting ROCK activity, thereby promoting relaxation of cerebral smooth muscle and mitigating the impairment of cerebral smooth muscle cell function caused by oxygen-glucose deprivation/reoxygenation. In addition, our data underscore the critical role of ROCK₂ in mediating the cerebral protective effects of H₂S, surpassing that of ROCK₁.

Chronic low-level inflammation or "inflammaging" is hypothesized to contribute to sarcopenia and frailty. Resident microbiota are thought to promote inflammaging, frailty, and loss of skeletal muscle mass. We tested immunity and frailty in male C57BL6/N germ-free (GF), specific pathogen-free (SPF) mice, and mice that were born germ-free and colonized (COL) with an SPF microbiota. Male and female GF mice had lower systemic cellular inflammation indicated by lower blood Ly6C^high monocytes across their lifespan. Male GF mice had lower body mass, but relative to body mass, GF mice had smaller hindlimb muscles and smaller muscle fibers compared with SPF mice across the lifespan. Male and female GF mice had increased frailty at 18 mo or older. Colonization of female GF mice increased blood Ly6C^high monocytes but did not affect frailty at 18 mo or older. Colonization of male GF mice increased blood Ly6C^high monocytes, skeletal muscle size, myofiber fiber size, and decreased frailty at 18 mo or older. Transcriptomic analysis of the tibialis anterior muscle revealed a microbiota-muscle axis with over 550 differentially expressed genes in COL male mice at 18 mo or older. Colonized male mice had transcripts indicative of lower tumor necrosis factor (TNF)-α signaling via nuclear factor κB (NF-κB). Our findings show that microbiota can increase systemic cellular immunity while decreasing muscle inflammation, thereby protecting against muscle loss and frailty. We also found sex differences in the role of microbiota regulating frailty. We propose that microbiota components protect against lower muscle mass and frailty across the lifespan in mice.NEW & NOTEWORTHY Germ-free mice had increased frailty, lower muscle mass, and lower circulating inflammatory monocytes. Therefore, lower systemic inflammation coincided with worse frailty and muscle loss. Microbial colonization decreased frailty, restored muscle mass, and increased circulating inflammatory monocytes while lowering transcripts in inflammatory TNF and NF-κB pathways within muscle. Hence, microbiota can increase circulating inflammation but decrease muscle inflammation to protect against frailty. This microbiota-muscle axis should be investigated for therapeutic potential in muscle wasting and sarcopenia.

Transient receptor potential vanilloid 4 (TRPV4) is a mechanosensitive ion channel highly expressed in chondrocytes that supports cartilage development and homeostasis. Mutations in the channel can cause skeletal dysplasias, including the gain-of-function mutations V620I and T89I that lead to brachyolmia and metatropic dysplasia, respectively. These mutations suppress hypertrophic differentiation, but the mechanisms by which they alter chondrocyte response to mechanical load remain to be elucidated. To determine the effect of these mutations on chondrocyte mechanotransduction, tissue-engineered cartilage was derived from differentiated CRISPR-edited human induced pluripotent stem cells (hiPSCs) harboring the moderate V620I or severe T89I TRPV4 mutations. Wildtype and mutant tissue-engineered hiPSC-derived cartilage was subjected to compressive mechanical loading at physiological levels, and transcriptomic signatures were assessed by RNA-sequencing. Our results demonstrate that the V620I and T89I mutations diminish the mechanoresponsiveness of chondrocytes, as evidenced by reduced gene expression downstream of TRPV4 activation, including those involved in endochondral ossification. Changes in genes involved in extracellular matrix production and organization were found to contribute towards the phenotype in V620I chondrocytes, whereas dysregulated retinoic acid signaling was linked to T89I, and disrupted proliferation was common to both. Our findings suggest that dysfunctional mechanotransduction due to V620I and T89I mutations in TRPV4 contribute to the developmental phenotypes, supporting TRPV4 modulation as a potential pharmacologic target.

Skeletal muscle microtissues are engineered to develop therapies for restoring muscle function in patients. However, optimal electrical field stimulation (EFS) parameters to evaluate the function of muscle microtissues remain unestablished. This study reports a protocol to optimize EFS parameters for eliciting contractile force of muscle microtissues cultured in micropost platforms. Muscle microtissues were produced across an opposing pair of microposts in polydimethylsiloxane and polymethyl methacrylate culture platforms using primary, immortalized, and induced pluripotent stem cell-derived myoblasts. In response to EFS between needle electrodes, contraction deflects microposts proportional to developed force. At 5 V, pulse durations used for native muscle (0.1-1 ms) failed to elicit contraction of microtissues; durations reported for engineered muscle (5-10 ms) failed to elicit peak force. Instead, pulse durations of 20-80 ms were required to elicit peak twitch force across microtissues derived from 5 myoblast lines. Similarly, while peak tetanic force occurs at 20-50 Hz for native human muscles, it varied across microtissues depending on the cell line type, ranging from 7-60 Hz. A new parameter, the dynamic oscillation of force, captured trends during rhythmic contractions, while quantifying the duration-at-peak force provides an extended kinetics parameter. Our findings indicate that muscle microtissues have cell line type-specific contractile properties, yet all contract and relax more slowly than native muscle, implicating underdeveloped excitation-contraction coupling. Failure to optimize EFS parameters can mask the functional potential of muscle microtissues by underestimating force production. Optimizing and reporting EFS parameters and metrics is necessary to leverage muscle microtissues for advancing skeletal muscle therapies.

This study investigates the mechanisms of poly ADP-ribose polymerase inhibitor (PARPi) resistance in epithelial ovarian cancer (EOC). It also explores strategies to overcome this resistance by combining PARPi with cyclin-dependent kinase 4/6 inhibitors (CDK4/6i). EOC cell lines A2780 and SKOV-3 were treated with PARPi to develop stable drug-resistant cell lines, A2780-ola-r and SKOV-3-ola-r. Low-dose treatments with Olaparib, Palbociclib, and their combination significantly reduced tumor proliferation in these resistant cells. Bioinformatics analysis identified potential therapeutic targets, KNSTRN and TRPC4AP. The combination treatment induced G1 phase cell cycle arrest at low drug concentrations. Immunofluorescence studies demonstrated reduced nuclear RAD51 and increased p-γH2AX levels following combination or Palbociclib treatment, compared to DMSO. Western blot analysis revealed elevated expression of homologous recombination repair (HRR) pathway-related proteins in the resistant cell lines. Post-treatment analysis indicated a negative correlation between KNSTRN levels and the efficacy of CDK4/6i or combination therapy, whereas TRPC4AP levels positively correlated with treatment response. These findings offer critical insights into the mechanisms of PARPi resistance in EOC and suggest that combining PARPi with CDK4/6i is a promising therapeutic strategy to overcome this resistance and improve outcomes for patients with EOC.