Physiological Reports最新文献

Cardiovascular disease is exacerbated by diabetes through hyperglycemia-induced endothelial dysfunction, which arises from oxidative stress. Glutamine is postulated to decrease oxidative stress; however, its effect on endothelial dysfunction in hyperglycemia is unknown. Therefore, we investigated how glutamine affects endothelial function in normal and high glucose. Human coronary artery endothelial cells were treated with 0, 0.5, or 2 mM glutamine in 5.5 or 15 mM glucose for 24 h. We then assessed cell proliferation, oxidative stress, cell survival, and endothelial nitric oxide synthase (eNOS) activity. Our data showed that independent of glucose concentration, glutamine increased proliferation by up to 3.5-fold. Furthermore, glutamine metabolism through glutaminase-1 reduced oxidative stress and cell death by up to 70% and 94%, respectively, by doubling glutathione and NADPH. Glutamine also increased ex vivo vasodilation in isolated murine carotid arteries without altering eNOS activity or nitric oxide in vitro, suggesting that the enhanced vasodilation results from reduced oxidative stress. These findings indicate that glutamine mitigates endothelial cell oxidative stress by enhancing reducing capacity, which may protect against diabetic cardiovascular disease.

Intraflagellar transport protein 88 (IFT88) is essential for primary and motile cilia formation. In murine models and humans, Ift88 mutations contribute to renal cysts, epithelial proliferation and impaired immune responses. In mice, Ift88 knockout (KO) reduces airway cilia, increases airway epithelial proliferation and hyperreactivity, elevates IL-22 and decreases lung T regulatory cells. Pulmonary hypertension (PH) is a deadly disease marked by aberrant metabolism and immunoinflammatory mediators causing vasoconstriction and vascular remodeling. Endothelial-to-mesenchymal transition (EndMT) contributes to PH, and endothelial-specific Ift88 KO promotes endothelial proliferation and EndMT. We hypothesized that global loss of Ift88 causes PH. We assessed PH indices at 2 and 14 weeks postdeletion in tamoxifen-inducible Ift88 KO mice. These mice showed signs of PH, including increased right ventricular systolic pressure, cell proliferation in the walls of resistance arteries, and arterial wall thickening. At the early time point examined, we did not detect evidence of lung inflammation or EndMT. Because this is a tamoxifen-induced global Ift88 KO model, we cannot attribute the PH features to gene deletion in specific vascular cells, nor can we rule out the possibility that tamoxifen administration, global Ift88 deletion, the associated weight gain and food restriction may have influenced cardiovascular physiology in these mice.

Heat acclimation refers to the physiological adaptations that occur during repeated heat exposures, ultimately reducing thermal and cardiovascular strain in the heat. It is unknown whether body mass index (BMI) influences an individual's ability to adapt during heat acclimation, which was tested in the present analysis. Forty-two healthy adults (16F; age: 23 ± 5 years) underwent 8 days of treadmill walking (5 km·h^-1) in the heat (40°C, 40% RH). Groups were compared based on BMI (<25 and >25). We measured core temperature (T_C), heart rate (HR) and whole-body sweating rate (WBSR) on days 1, 4 and 8. The BMI <25 group showed decreases in peak T_C (D1: 38.62°C ± 0.58°C, D4: 38.27 ± 0.38, D8: 38.10 ± 0.32; p ≤ 0.018). The BMI >25 group showed a reduction in peak T_C only on Day 8 (38.35 ± 0.45) compared to Day 1 (38.54 ± 0.53, p = 0.019). Peak T_C was lower in the BMI <25 group compared to the BMI > 25 group on Day 8 only (p = 0.042). HR decreased and WBSR increased over time, with no difference between groups (p > 0.05). The BMI <25 group showed greater reductions in peak T_C from D1 to D8 than the BMI >25 group (p = 0.010). These data suggest that individuals with BMI >25 may have attenuated T_C adaptations to heat acclimation compared to individuals with BMI <25.

Neonatal hyperoxia is a key contributor to bronchopulmonary dysplasia (BPD) which is characterized by airway hyperreactivity due to increased contraction and impaired relaxation of airway smooth muscle (ASM). This study investigated whether inhibition of the Rho/Rho-kinase signaling pathway restored tracheal smooth muscle (TSM) relaxation and reactivated the nitric oxide-guanosine 3',5'-cyclic monophosphate (NO-cGMP) pathway in neonatal rats exposed to hyperoxia. Newborn rats (P4) were exposed to either ambient air (AA; n = 61) or hyperoxia (FiO₂ >95%; n = 58) for 7 days. The effects of Rho-kinase inhibitors (Y-27632 or fasudil) in vitro (10 μM) or in vivo (10 mg kg^-1 day^-1) on electric field stimulation-induced TSM relaxation were assessed. In subsets of the experiment, tissues were pre-incubated in a nitric oxide synthase (NOS) inhibitor-N^ω-nitro-L-arginine methyl ester (L-NAME; 100 μM) or a Rho activator-lysophosphatidic acid (LPA; 30 μM). Rho-kinase inhibitors, both in vitro and in vivo, restored hyperoxia-impaired TSM relaxation to levels comparable to those of ambient air TSM. The relaxant responses in tissues supplemented with Y-27632 or fasudil were significantly increased compared to hyperoxia control (p < 0.01 and p < 0.001), and the maximal values at 20 V were 77.90 ± 3.80%; 81.20 ± 6.10% and 40.20 ± 3.60%, respectively. These Rho-kinase inhibitor effects in TSM were attenuated by L-NAME, indicating mechanistic action through the NO-cGMP pathway. Activation of Rho reduced relaxation in the AA group, an effect that was reversed by Rho-kinase inhibition. Hyperoxia impairs ASM in neonatal rats via upregulation of Rho-kinase activity and suppression of NO-cGMP signaling. Pharmacological inhibition of Rho-kinase restores relaxation, highlighting its therapeutic potential for airway dysfunction in BPD.

Physical performance can be improved in aerobic athletes and breath-hold divers (BHD) by limb exposure to repetitive ischemia: remote ischemic conditioning (RIC). RIC protects against cardiac ischemia, and its blood-borne transferable substrate could be lactate. Accordingly, lactate added to whale blood increases oxygen unloading and adult seals possess higher cardiac lactate dehydrogenase activity (LDHa) than terrestrial mammals. Because BHD and adult diving mammals share adaptations to hypoxia, including lactate metabolization during apnea, we hypothesized that BHD compared to BMI/VO₂max-matched aerobic controls have higher LDHa and lactate added to blood from BHD unloads oxygen more efficiently. Six BHD and six matched aerobic controls underwent RIC: three cycles of 5-min inflation and 4-min deflation of a blood pressure cuff on the dominant arm, maximum apnea after three submaximal apneas (BHD only), and a VO₂max-test. Blood-samples were collected from the nondominant radial artery and the vena basilica of the dominant arm at rest, before termination of the three interventions, and for LDHa. Blood gases were compared to samples added lactate or placebo suspension. BHD had ⁓30% higher cardiac/erythrocyte LDHa compared to controls (p < 0.05). Lactate added to arterial blood from BHD after RIC increased oxygen unloading (p < 0.05). PaO₂ decreased ⁓66% during apnea (375+/-49 s; p < 0.001; BHD only). We conclude that 1 (erythrocyte- and cardiac-LDHa is higher in BHD compared to matched controls, and 2) lactate facilitates oxygen-unloading in blood from BHD after RIC, similar to diving mammals.

Mitochondrial subcellular area influences function. Muscle disuse reduces mitochondrial content; however, its effect on mitochondrial subcellular location is unclear. Omega-3 fatty acid (n-3) attenuates declines in muscle mass and mitochondrial function during disuse; however, whether n-3 supplementation prevents the decline in mitochondrial content has not been examined. We investigated the effects of 2 weeks of leg immobilization followed by 2 weeks of remobilization on skeletal muscle mitochondrial content and subcellular localization with and without n-3 supplementation. Twenty healthy females supplemented with n-3 (2.97 g EPA and 2.03 g DHA) or control (isoenergetic sunflower oil) during 2 weeks of unilateral leg immobilization and 2 weeks of remobilization. Vastus lateralis biopsies were taken for electron microscopic analysis of mitochondrial content. Subsarcolemmal (SS) mitochondrial content decreased during immobilization (control: -9%, n-3: -66%, p = 0.009) and remained lower following recovery (control: -41%, n-3: -42%, p = 0.005). This effect was driven by the n-3 group (p < 0.02). Intermyofibrillar (IMF) mitochondrial content did not decline during immobilization, but was lower than baseline following recovery in the central (p = 0.01) IMF. The effects of leg immobilization on mitochondrial content differ by location, are not reversed with short-term recovery, and are influenced by n-3 supplementation.

Cor pulmonale, indicative of right heart failure (RHF), is precipitated by pulmonary conditions that escalate pulmonary arterial pressure. This complication is notably prevalent in patients with chronic obstructive pulmonary disease (COPD), and is recognized as an independent predictor of adverse outcomes. Despite its significance, the lack of appropriate animal models has hindered the development of therapies for cor pulmonale in COPD patients. Therefore, we aimed to establish a mouse model that mimics the essential pathological features of COPD-cor pulmonale. All mice underwent thoracic surgery, including left pulmonary artery ligation (LPAL) or sham surgery (artery exposed without ligation). Following a 2-week recuperation, the mice were exposed to cigarette smoke or room air for 28 weeks. At the end of the exposure, pulmonary function, right ventricular hemodynamics, and histological alterations were determined. CD31, α-SMA, and CD68 were detected by immunofluorescence and immunohistochemistry to show vascular and macrophage changes. Mice subjected to LPAL and cigarette smoke exposure exhibited COPD-like features, including impaired lung function, emphysematous alterations, pulmonary inflammatory cell infiltration, and airway remodeling, accompanied by the increase in right ventricular systolic pressure, right ventricular hypertrophy, fibrosis, macrophage aggregation, and reduced capillary density. This model, integrating cigarette smoke exposure with LPAL, effectively replicates the critical pathological features of COPD-cor pulmonale.

Regular exercise benefits cardiovascular and cardiorespiratory health. Passive heating also induces cardiovascular responses, but its effect on cardiorespiratory fitness remains unclear. Given the overlapping physiological mechanisms between passive heating and exercise, hot-water immersion may serve as an alternative strategy to prevent decline in cardiovascular function and fitness. This systematic review and meta-analysis investigated the effects of hot-water immersion (HWI) on cardiovascular health markers and cardiorespiratory fitness in healthy populations. A comprehensive search of six databases identified 20 studies. The meta-analysis found that a single HWI session significantly increased heart rate (N = 10; mean difference [MD]: 28 bpm, 95% confidence interval [CI]: 19-36.2, p < 0.0001) and decreased diastolic (N = 6; MD: -5 mmHg, 95% CI: -9 to -1, p = 0.015) and mean arterial blood pressure (N = 4; MD: -7 mmHg, 95% CI: -12 to -1, p = 0.03). Repeated immersion reduced resting heart rate (N = 5; MD: -3 bpm, 95% CI: -6 to -1 p = 0.01). No significant effects were observed for other cardiovascular markers, and only one study reported data on cardiorespiratory fitness. Overall, our findings indicate inconclusive beneficial effects of HWI on cardiovascular health markers and further research is needed, especially on cardiorespiratory fitness.

Cultures of primary mouse bile duct epithelial cells are a valuable tool to study cholangiocyte secretion and bile formation. However, freshly isolated cells have a limited ability to expand in culture. Here we report a novel isolation and culture technique for normal mouse cholangiocytes (NMC) that enables long-term growth without compromising function. Mouse cholangiocytes were isolated and cultured in conditioned medium (CM) that was subsequently supplemented with ROCK inhibitor Y-27632. Expression of cholangiocyte markers was assessed by qPCR, immunofluorescence, and Western blotting. Patch clamp techniques were used to measure cAMP-activated Cl- current, Ca2+-activated Cl- current, and volume-stimulated Cl- current. We obtained NMC cultures that were polarized and maintained a cholangiocyte phenotype for over 50 passages. Functional studies show that ion channel activity is maintained in NMC regardless of the number of passages and despite removal of CM. NMC also perform other physiological functions such as ATP release and intracellular Ca2+ changes in response to stimulation with bile acids. Thus, our isolation procedure produces viable NMC that maintain biophysical properties in long-term culture. We also demonstrate the utility of NMC in studies investigating the cellular mechanisms responsible for cholangiocyte secretion and bile formation.

The thoracic duct (TD) is the largest vessel of the lymphatic system, transporting interstitial fluid, macromolecules, and immune cells into the venous circulation via the lymphovenous junction. Respiratory and circulatory forces have been proposed as key drivers of TD lymph propulsion; however, the literature reports inconsistent findings. This study systematically reviews the effects of respiration and circulation on TD lymph flow and pressure in humans and non-human mammals. A systematic review was conducted in accordance with PRISMA guidelines using MEDLINE, Embase, and Google Scholar databases. Studies published up to August 2025 were included with no language or past date restrictions. Twenty-three human and animal studies met the inclusion criteria. Respiratory activity influenced TD flow and/or pressure in 5/6 human and 12/17 animal studies. Circulatory influences were reported in 3/6 human and 8/17 animal studies. Intrinsic TD contractility was described in 3/6 human and 6/17 animal studies and was identified as an independent contributor to lymph propulsion. Overall, reported effects ranged from absent to highly synchronous physiological coupling. Evidence regarding respiratory and circulatory influences on TD lymphodynamics remains inconsistent, reflecting methodological heterogeneity. Findings should be considered hypothesis-generating and highlight the need for modern imaging and standardized physiological protocols.