SIRT1 regulates mitochondrial fission to alleviate high altitude hypoxia inducedcardiac dysfunction in rats via the PGC-1α-DRP1/FIS1/MFF pathway.

High-altitude exposure has been linked to cardiac dysfunction. Silent information regulator factor 2-related enzyme 1 (sirtuin 1, SIRT1), a nicotinamide adenine dinucleotide-dependent deacetylase, plays a crucial role in regulating numerous cardiovascular diseases. However, the relationship between SIRT1 and cardiac dysfunction induced by hypobaric hypoxia (HH) remains unexplored. This study aims to assess the impact of SIRT1 on HH-induced cardiac dysfunction and delve into the underlying mechanisms, both in vivo and in vitro. In this study, we have demonstrated that exposure to HH results in cardiomyocyte injury, along with the downregulation of SIRT1 and mitochondrial dysfunction. Upregulating SIRT1 significantly inhibits mitochondrial fission, improves mitochondrial function, reduces cardiomyocyte injury, and consequently enhances cardiac function in HH-exposed rats. Additionally, HH exposure triggers aberrant expression of mitochondrial fission-regulated proteins, with a decrease in PPARγ coactivator 1 alpha (PGC-1α) and mitochondrial fission factor (MFF) and an increase in mitochondrial fission 1 (FIS1) and dynamin-related protein 1 (DRP1), all of which are mitigated by SIRT1 upregulation. Furthermore, inhibiting PGC-1α diminishes the positive effects of SIRT1 regulation on the expression of DRP1, MFF, and FIS1, as well as mitochondrial fission. These findings demonstrate that SIRT1 alleviates HHinduced cardiac dysfunction by preventing mitochondrial fission through the PGC-1α-DRP1/FIS1/MFF pathway.

Intermittent high altitude hypoxia induced liver and kidney injury leading to hyperuricemia.

About 140 million people worldwide live at an altitude above 2500 m. Studies have showed an increase of the incidence of hyperuricemia among plateau populations, but little is known about the possible mechanisms. This study aims to assess the effects of high altitude on hyperuricemia and explore the corresponding mechanisms at the histological, inflammatory and molecular levels. This study finds that intermittent hypobaric hypoxia (IHH) exposure results in an increase of serum uric acid level and a decrease of uric acid clearance rate. Compared with the control group, the IHH group shows significant increases in hemoglobin concentration (HGB) and red blood cell counts (RBC), indicating that high altitude hyperuricemia is associated with polycythemia. This study also shows that IHH exposure induces oxidative stress, which causes the injury of liver and renal structures and functions. Additionally, altered expressions of organic anion transporter 1 (OAT1) and organic cation transporter 1 (OCT1) of kidney have been detected in the IHH exposed rats. The adenosine deaminase (ADA) expression levels and the xanthione oxidase (XOD) and ADA activity of liver of the IHH exposure group have significantly increased compared with those of the control group. Furthermore, the spleen coefficients, IL-2, IL-1ß and IL-8, have seen significant increases among the IHH exposure group. TLR/MyD88/NF-κB pathway is activated in the process of IHH induced inflammatory response in joints. Importantly, these results jointly show that IHH exposure causes hyperuricemia. IHH induced oxidative stress along with liver and kidney injury, unusual expression of the uric acid synthesis/excretion regulator and inflammatory response, thus suggesting a potential mechanism underlying IHH-induced hyperuricemia.

Expression and significance of SOX B1 genes in glioblastoma multiforme patients.

The overall survival of glioblastoma multiforme (GBM) patients remains poor. To improve patient outcomes, effective diagnostic and prognostic biomarkers for GBM are needed. In this study, we first applied bioinformatic analyses to identify biomarkers for GBM, focusing on SOX (sex-determining region on the Y chromosome (SRY)-related high mobility group (HMG) box) B1 family members. The ONCOMINE, GEPIA, LinkedOmics and CCLE databases were used to assess mRNA expression levels of the SOX B1 family members in different cancers and normal tissue. Further bioinformatic analysis was performed using the ONCOMINE database in combination with the LinkedOmics data set to identify the prognostic value of SOX B1 family members for GBM. We found mRNA expression levels of all tested SOX B1 genes were significantly increased in GBM. In the LinkedOmics database, increased expression of SOX3 indicated a better overall survival. In GEPIA databases, increased expression of all SOX B1 family members suggested an improved overall survival, but none of them were statistically different. Then, Transwell assays and wound healing were employed to evaluate the motility and invasive captivity of U251 cells when silencing SOX2 and SOX3. We found exogenous inhibition of SOX2 appeared to reduce the migration and invasion of U251 cells in vitro. Collectively, our research suggested that SOX2 might serve as a cancer-promoting gene to identify high-risk GBM patients, and SOX3 had the potential to be a prognostic biomarker for GBM patients.

Resveratrol Ameliorates High Altitude Hypoxia-Induced Osteoporosis by Suppressing the ROS/HIF Signaling Pathway.

Hypoxia at high-altitude leads to osteoporosis. Resveratrol (RES), as an antioxidant, has been reported to promote osteoblastogenesis and suppress osteoclastogenesis. However, the therapeutic effect of RES against osteoporosis induced by high-altitude hypoxia remains unclear. Thus, this study was intended to investigate the potential effects of RES on high-altitude hypoxia-induced osteoporosis both in vivo and in vitro. Male Wistar rats were given RES (400 mg/kg) once daily for nine weeks under hypoxia, while the control was allowed to grow under normoxia. Bone mineral density (BMD), the levels of bone metabolism-related markers, and the changes on a histological level were measured. Bone marrow-derived mesenchymal stem cells (BMSCs) and RAW264.7 were incubated with RES under hypoxia, with a control growing under normoxia, followed by the evaluation of proliferation and differentiation. The results showed that RES inhibited high-altitude hypoxia-induced reduction in BMD, enhanced alkaline phosphatase (ALP), osteocalcin (OCN), calcitonin (CT) and runt-related transcription factor 2 (RUNX2) levels, whereas it reduced cross-linked carboxy-terminal telopeptide of type I collagen (CTX-I) levels and tartrate-resistant acid phosphatase (TRAP) activity in vivo. In addition, RES attenuated histological deteriorations in the femurs. In vitro, RES promoted osteoblastogenesis and mineralization in hypoxia-exposed BMSCs, along with promotion in RUNX2, ALP, OCN and osteopontin (OPN) levels, and inhibited the proliferation and osteoclastogenesis of RAW264.7. The promotion effects of RES on osteoblastogenesis were accompanied by the down-regulation of reactive oxygen species (ROS) and hypoxia inducible factor-1α (HIF-1α) induced by hypoxia. These results demonstrate that RES can alleviate high-altitude hypoxia-induced osteoporosis via promoting osteoblastogenesis by suppressing the ROS/HIF-1α signaling pathway. Thus, we suggest that RES might be a potential treatment with minimal side effects to protect against high-altitude hypoxia-induced osteoporosis.

Quantitative Proteomics Reveals the Effects of Resveratrol on High-Altitude Polycythemia Treatment.

High-altitude polycythemia (HAPC) is a common plateau chronic disease in which red blood cells are compensatory hyperproliferative due to high altitude hypoxic environment. HAPC severely affects the physical and mental health of populations on the plateau. However, the pathogenesis and treatment of HAPC has been rarely investigated. Here, the hypoxia-induced HAPC model of rat is established, in which hemoglobin concentration significantly increases and platelets clearly decrease. The effect of resveratrol upon hypoxia enables HAPC remission and makes hemoglobin and platelet tend to a normal level. Furthermore, quantitative proteomics is applied to investigate the plasma proteome variation and the underlying molecular regulation during HAPC occurrence and treatment with resveratrol. Hypoxia promotes erythrocyte developing and differentiating and disrupts cytoskeleton organization. Notably, the resveratrol administration reverses the proteome change pattern due to hypoxia and contributes to plateau adaption. Quantitative verification of differentially expressed proteins confirms the roles of resveratrol in HAPC. Resveratrol is expected to be useful for HAPC treatment.

Isoquercitrin attenuates the osteoclast-mediated bone loss in rheumatoid arthritis via the Nrf2/ROS/NF-κB pathway.

An excess of osteoclastogenesis significantly contributes to the development of rheumatoid arthritis (RA). Activation of the nuclear factor erythroid-2 related factor 2 (Nrf2) and nuclear factor kappa B (NF-κB) ligand (RANKL)-induced reactive oxygen species (ROS)-to-NF-κB signaling cascade are important mechanisms regulating osteoclastogenesis; however, whether Nrf2 is involved in RANKL-induced NF-κB activation is controversial. Isoquercitrin, a natural flavonoid compound, has been shown to have Nrf2-dependent antioxidant effects inprevious studies. We sought to verify whether isoquercitrin could modulate RANKL-induced NF-κB activation by activating Nrf2, thereby affecting osteoclastogenesis. Tartrate-resistant acid phosphatase staining, F-actin ring staining and resorption pit assay suggested that isoquercitrin significantly inhibited osteoclastogenesis and osteolytic function. Mitosox staining showed that RANKL-induced ROS generation was significantly inhibited by isoquercitrin from day 3 of the osteoclast differentiation cycle. Quantitative real-time PCR, Western blot, and immunofluorescence indicated that isoquercitrin activated the Nrf2 signaling pathway and inhibited NF-κB expression. And when we used the Nrf2-specific inhibitor ML385, the inhibition of NF-κB by isoquercitrin disappeared. Moreover, we found that Nrf2 is not uninvolved in RANKL-induced NF-κB activation and may be related to the timing of ROS regulation. When we limited isoquercitrin administration to 2 days, Nrf2 remained activated and the inhibition of NF-κB disappeared. In vivo experiments suggested that isoquercitrin attenuated RA modeling-induced bone loss. Overall, isoquercitrin-activated Nrf2 blocked the RANKL-induced ROS-to-NF-κB signaling cascade response, thereby inhibiting osteoclastogenesis and bone loss. These findings provide new ideas for the treatment of RA.

Corrigendum: Sestrin2 protects against hypoxic nerve injury by regulating mitophagy through SESN2/AMPK pathway.

[This corrects the article DOI: 10.3389/fmolb.2023.1266243.].

Saikosaponin A attenuates osteoclastogenesis and bone loss by inducing ferroptosis.

To alleviate bone loss, most current drugs target osteoclasts. Saikosaponin A (Ssa), a triterpene saponin derived from Bupleurum falcatum (also known as Radix bupleuri), has immunoregulatory, neuromodulatory, antiviral, anticancer, anti-convulsant, anti-inflammatory, and anti-proliferative effects. Recently, modulation of bone homeostasis was shown to involve ferroptosis. Herein, we aimed to determine Ssa's inhibitory effects on osteoclastogenesis and differentiation, whether ferroptosis is involved, and the underlying mechanisms. Tartrate-resistant acid phosphatase (TRAP) staining, F-actin staining, and pit formation assays were conducted to confirm Ssa-mediated inhibition of RANKL-induced osteoclastogenesis in vitro. Ssa could promote osteoclast ferroptosis and increase mitochondrial damage by promoting lipid peroxidation, as measured by iron quantification, FerroOrange staining, Dichloro-dihydro-fluorescein diacetate, MitoSOX, malondialdehyde, glutathione, and boron-dipyrromethene 581/591 C11 assays. Pathway analysis showed that Ssa can promote osteoclasts ferroptosis by inhibiting the Nrf2/SCL7A11/GPX4 axis. Notably, we found that the ferroptosis inhibitor ferrostatin-1 and the Nrf2 activator tert-Butylhydroquinone reversed the inhibitory effects of Ssa on RANKL-induced osteoclastogenesis. In vivo, micro-computed tomography, hematoxylin and eosin staining, TRAP staining, enzyme-linked immunosorbent assays, and immunofluorescence confirmed that in rats with periodontitis induced by lipopolysaccharide, treatment with Ssa reduced alveolar bone resorption dose-dependently. The results suggested Ssa as a promising drug to treat osteolytic diseases.

Sestrin2 protects against hypoxic nerve injury by regulating mitophagy through SESN2/AMPK pathway.

Hypoxia induced by high altitude can lead to severe neurological dysfunction. Mitophagy is known to play a crucial role in hypoxic nerve injury. However, the regulatory mechanism of mitophagy during this injury remains unclear. Recent studies have highlighted the role of Sestrin2 (SESN2), an evolutionarily conserved stress-inducible protein against acute hypoxia. Our study demonstrated that hypoxia treatment increased SESN2 expression and activated mitophagy in PC12 cells. Furthermore, the knock-out of Sesn2 gene led to a significant increase in mitochondrial membrane potential and ATP concentrations, which protected the PC12 cells from hypoxic injury. Although the AMPK/mTOR pathway was significantly altered under hypoxia, it does not seem to participate in mitophagy regulation. Instead, our data suggest that the mitophagy receptor FUNDC1 plays a vital role in hypoxia-induced mitophagy. Moreover, SESN2 may function through synergistic regulation with other pathways, such as SESN2/AMPK, to mediate cellular adaptation to hypoxia, including the regulation of mitophagy in neuron cells. Therefore, SESN2 plays a critical role in regulating neural cell response to hypoxia. These findings offer valuable insights into the underlying molecular mechanisms governing the regulation of mitophagy under hypoxia and further highlight the potential of SESN2 as a promising therapeutic target for hypoxic nerve injury.

LAMC2 regulates proliferation, migration, and invasion mediated by the Pl3K/AKT/mTOR pathway in oral.

Background: Oral squamous cell carcinoma (OSCC) is a common malignant tumor. Recently, Laminin Gamma 2 (LAMC2) has been shown to be abnormally expressed in OSCC; however, how LAMC2 signaling contributes to the occurrence and development of OSCC and the role of autophagy in OSCC has not been fully explored. This study aimed to analyze the role and mechanism of LAMC2 signaling in OSCC and the involvement of autophagy in OSCC. Methods: To explore the mechanism by which LAMC2 is highly expressed in OSCC, we used small interfering RNA (siRNA) to knock down LAMC2 to further observe the changes in the signaling pathway. Furthermore, we used cell proliferation assays, Transwell invasion assays, and wound-healing assays to observe the changes in OSCC proliferation, invasion, and metastasis. RFP-LC3 was used to detect the level of autophagy intensity. A cell line-derived xenograft (CDX) model was used to detect the effect of LAMC2 on tumor growth in vivo. Results: This study found that the level of autophagy was correlated with the biological behavior of OSCC. The downregulation of LAMC2 activated autophagy and inhibited OSCC proliferation, invasion, and metastasis via inhibiting the PI3K/AKT/mTOR pathway. Moreover, autophagy has a dual effect on OSCC, and the synergistic downregulation of LAMC2 and autophagy can inhibit OSCC metastasis, invasion, and proliferation via the PI3K/AKT/mTOR pathway. Conclusions: LAMC2 interacts with autophagy to regulate OSCC metastasis, invasion, and proliferation via the PI3K/AKT/mTOR pathway. LAMC2 down-regulation can synergistically modulate autophagy to inhibit OSCC migration, invasion, and proliferation.

[Resveratrol attenuates cardiac function impairment in plateau hypobaric hypoxia rats].

Objective: To study the protective effects of resveratrol (RSV) on cardiac function in rats with high altitude hypobaric hypoxia and its mechanisms. Methods: Thirty-six rats were randomly divided into control group, hypobaric hypoxia group (HH) and hypobaric hypoxia + RSV group (HH+RSV) according to the random number, 12 rats in each group. Rats in the HH and HH+RSV groups were subjected to chronic long-term high altitude hypobaric hypoxia intervention for 8 weeks in a hypobaric chamber at a simulated altitude of 6 000 m for 20 h / d. The rats of HH + RSV were fed with RSV at a dose of 400 mg/(kg·d). The rats were tested once a week for body weight and twice a week for food intake. Before execution, the rats were tested by blood cell analyzer for routine blood parameters and echocardiogram for cardiac function parameters in each group. The routine blood indexes of each group were measured by blood cell analyzer, the cardiac function indexes of each group were measured by echocardiography, myocardial hypertrophy was evaluated by HE staining, myocardial tissue reactive oxygen levels were evaluated by dihydroethidium (DHE) staining. Oxidative stress was evaluated by serum and myocardial tissue total antioxidant capacity (T-AOC), superoxide dismutase activity (SOD) and malondialdehyde (MDA) content. Results: Compared with the C group, the body mass and food intake of rats were decreased significantly (P＜0.05) in HH group, while compared with the C group, RSV had no significant effects on the body mass and food intake of rats in the HH+RSV group (P＞0.05). Compared with the C group, the levels of erythrocytes and hemoglobin of rats in the HH group were increased significantly (P＜0.05), while the platelet concentration was decreased significantly(P＜0.05); compared with the HH group, the erythrocyte and hemoglobin levels were decreased significantly (P＜0.05) and platelet concentration was increased significantly(P＜0.05) in rats of the HH+RSV group. Compared with the C group, the cardiac coefficient, myocardial fiber diameter and thickness were significantly increased in the HH group (P＜0.05); compared with the HH group, the cardiac coefficient and myocardial fiber thickness were significantly decreased in the HH+RSV group (P＜0.05). Echocardiographic analysis showed a significant increase in ventricular wall thickness (P＜0.05) and a significant decrease in ejection fraction and cardiac output (P＜0.05) in the HH group compared with the C group, and a significant decrease in ventricular wall thickness and a significant improvement in cardiac function (P＜0.05) in the HH+RSV group compared with the HH group. The results of DHE staining showed that myocardial tissue reactive oxygen levels were increased significantly in the HH group compared with the C group (P＜0.05); myocardial tissue reactive oxygen levels were significantly restored in the HH+RSV group compared with the HH group (P＜0.05). The oxidative/antioxidant results showed that the serum and myocardial T-AOC and SOD activities were decreased significantly (P＜0.05) and the MDA level was increased significantly (P＜0.05) in the HH group compared with the C group; the serum and myocardial T-AOC and SOD activities were increased significantly (P＜0.05) and the MDA level was decreased significantly(P＜0.05) in the HH+RSV group compared with the HH group. Conclusion: Long-term plateau hypobaric hypoxia exposure leads to myocardial hypertrophy and reduced cardiac function in rats. Resveratrol intervention significantly improves myocardial hypertrophy and cardiac function in rats caused by altitude hypobaric hypoxia exposure, which is closely related to reducing of reactive oxygen species and improving myocardial oxidative stress levels.

Intermittent hypobaric hypoxia causes deleterious effects on the reproductive system in female rats.

BACKGROUNDS: Numerous studies have revealed that hypobaric hypoxia exposure elicited imbalance of homeostasis. However, the effects of intermittent hypobaric hypoxia (IHH) exposure on the female reproductive system have been rarely reported. This study aims to assess the effects of IHH on rat female reproductive system and explore the corresponding mechanism at the histological, endocrine and molecular levels. METHODS: The female rats were randomly divided into control and IHH groups. Multiple pathophysiological parameters, including body weight gain, organ coefficients, estrus cycle, and health signs were measured. Also, the reproductive hormones, hormone receptor mRNA expression and oxidant/antioxidant level were evaluated. RESULTS: Significant increases of the heart, liver and lung coefficients were observed after IHH exposure. There were no statistically significant differences in ovarian and uterine coefficients, but changes were found in the morphology of the ovary and uterus. Additionally, the diestrus phase duration was significantly increased during IHH exposure. Furthermore, estrogen increased and the Luteinizing hormone and progesterone decreased after IHH exposure. Altered expression of ER, PR and LHR were also found in the IHH exposed rats. Importantly, IHH exposure significantly repressed the activities of GSH-Px and T-SOD and improved the contents of MDA. CONCLUSIONS: Our results evince that IHH exposure caused estrus cycle irregularity. IHH induced oxidative stress along with ovarian and uterine structure damages, reproductive hormone disturbances and unusual expression of hormone receptors, thus suggesting a potential mechanism underlying IHH-induced reproductive system dysfunction.