Quercetin protects against diabetic encephalopathy via SIRT1/NLRP3 pathway in db/db mice

Epidemiological studies have found that diabetes and cognitive dysfunction are closely related. Quercetin has been certified with the effect on improving diabetes mellitus (DM) and cognitive impairment. However, the effect and related mechanism of quercetin on diabetic encephalopathy (DE) are still ambiguous. In this study, we used the db/db mice (diabetic model) to discover whether quercetin could improve DE through the Sirtuin1/NLRP3 (NOD-, LRR- and pyrin domain-containing 3) pathway. Behavioural results (Morris water maze and new object recognition tests) showed that quercetin (70 mg/kg) improved the learning and memory. Furthermore, quercetin alleviated insulin resistance and the level of fasting blood glucose. Besides, Western blot analysis also showed that quercetin increased the protein expressions of nerve- and synapse-related protein, including postsynapticdensity 93 (PSD93), postsynapticdensity 95 (PSD95), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the brain of db/db mice. Quercetin also increased the protein expression of SIRT1 and decreased the expression of NLRP3 inflammation-related proteins, including NLRP3, the adaptor protein ASC and cleaved Caspase-1, the pro-inflammatory cytokines IL-1β and IL-18. In conclusion, the present results indicate that the SIRT1/NLRP3 pathway may be a crucial mechanism for the neuroprotective effect of quercetin against DE.     

Corynoline protects against zearalenone-induced liver injury by activating the SIRT1/Nrf2 signaling pathway

Corynoline has been reported to have anti-inflammatory and antioxidative effects. In the present study, the potential protective effects of corynoline against zearalenone (ZEA)-induced liver injury were investigated. ZEA was administered daily for 5 days. Then, liver tissues were used for subsequent experiments. Corynoline attenuated liver histopathological changes induced by ZEA. The production of tumor necrosis factor-α and interleukin-1β in liver tissues, as well as aspartate aminotransferase and alanine aminotransferase in serum, was also inhibited by corynoline. Meanwhile, ZEA-induced MPO activity and MDA content were both attenuated by corynoline. ZEA-induced NF-κB p65 and IκBα phosphorylation were inhibited by corynoline. Furthermore, SIRT1, Nrf2, and HO-1 expression were increased by corynoline. In addition, the protective effects of corynoline against liver injury were reversed by the SIRT1 inhibitor EX-527. Taken together, corynoline protected against ZEA-induced liver injury by activating the SIRT1/Nrf2 signaling pathway.     

Quercetin attenuates oxidative stress-induced apoptosis via SIRT1/AMPK-mediated inhibition of ER stress in rat chondrocytes and prevents the progression of osteoarthritis in a rat model

Apoptosis of chondrocytes are the main initiator of osteoarthritis (OA) and can be explained by oxidative stress and endoplasmic reticulum (ER) stress, thus the pharmacological interventions aimed at inhibiting of these pathways may be a promising approach for the management of OA. Quercetin is a member of the flavonoid family and has antioxidant and anti-inflammatory properties in degenerative diseases. However, its effects and potential mechanisms on the pathological process of OA are not very clear. The present study aimed to investigate the protective effects of quercetin on OA and the underlying mechanisms. The tert-butyl hydroperoxide (TBHP)-stimulated rat chondrocytes and destabilization of the medial meniscus OA rat model was used to explore the protective effects of quercetin. Our results showed that quercetin treatment can attenuate oxidative stress, ER stress, and associated apoptosis. Moreover, quercetin inhibited ER stress through activating the sirtuin1/adenosine monophosphate-activated protein kinase (SIRT1/AMPK) signaling pathway. The protective effects of quercetin were also observed in OA rat model which is evidenced by abolished cartilage degeneration and decreased chondrocytes apoptosis in the knee joints. Our results suggested that quercetin is a promising treatment for OA.     

HMGB1 mediates hyperglycaemia‐induced cardiomyocyte apoptosis via ERK/Ets‐1 signalling pathway

Apoptosis is a key event involved in diabetic cardiomyopathy. The expression of high mobility group box 1 protein (HMGB1) is up‐regulated in diabetic mice. However, the molecular mechanism of high glucose (HG)‐induced cardiomyocyte apoptosis remains obscure. We aimed to determine the role of HMGB1 in HG‐induced apoptosis of cardiomyocytes. Treating neonatal primary cardiomyocytes with HG increased cell apoptosis, which was accompanied by elevated levels of HMGB1. Inhibition of HMGB1 by short‐hairpin RNA significantly decreased HG‐induced cell apoptosis by reducing caspase‐3 activation and ratio of Bcl2‐associated X protein to B‐cell lymphoma/leukemia‐2 (bax/bcl‐2). Furthermore, HG activated E26 transformation‐specific sequence‐1 (Ets‐1), and HMGB1 inhibition attenuated HG‐induced activation of Ets‐1 via extracellular signal‐regulated kinase 1/2 (ERK1/2) signalling. In addition, inhibition of Ets‐1 significantly decreased HG‐induced cardiomyocyte apoptosis. Similar results were observed in streptozotocin‐treated diabetic mice. Inhibition of HMGB1 by short‐hairpin RNA markedly decreased myocardial cell apoptosis and activation of ERK and Ets‐1 in diabetic mice. In conclusion, inhibition of HMGB1 may protect against hyperglycaemia‐induced cardiomyocyte apoptosis by down‐regulating ERK‐dependent activation of Ets‐1.     

Heme oxygenase 1 regulates apoptosis induced by heat stress in bovine ovarian granulosa cells via the ERK1/2 pathway

Heat stress can inhibit follicular development in dairy cows, and thus can affect their reproductive performance. Follicular granulosa cells can synthesize estrogen, that affects the development and differentiation of follicles by apoptosis. Heme oxygenase 1 (HO-1/heat shock protein 32) plays an antiapoptotic and cytoprotective role in various cells during stress-induced apoptosis, but little is known about its definitive function in bovine (ovarian) granulosa cells (bGCs). In our study, the roles and mechanism of HO-1 on the heat stress-induced apoptosis of bGCs were studied. Our results show that the expression of HO-1 was significantly increased under heat stress. Moreover, HO-1 silencing increased apoptosis, whereas its overexpression dampened apoptosis by regulating the expression of Bax/Bcl-2 and the levels of cleaved caspase-3. In addition, HO-1 can also play a cytoprotective role by affecting estrogen levels and decomposing heme to produce biologically active metabolite carbon monoxide (CO). Meanwhile, CO significantly increased the level of HO-1, decreased Bax/Bcl-2 levels, and inhibited the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. The apoptosis of ovarian GCs can affect the secretion of estrogen and lead to disorder of the ovarian microenvironment, thus affecting the normal function of the ovary. Our results indicate that HO-1 acts as a cytoprotective enzyme and plays a protective role in heat-induced apoptosis of bGCs. In conclusion, HO-1 and its metabolite CO inhibit the apoptosis of bGCs induced by heat stress through the ERK1/2 pathway. The results of this study provide a valuable clue for improving the fertility of heat stressed cows in summer.     

MEK/ERK pathway mediates cytoprotection of salvianolic acid B against oxidative stress‐induced apoptosis in rat bone marrow stem cells

To improve the survival and/or differentiation of grafted BMSCs (bone marrow stem cells) represents one of the challenges for the promising cell‐based therapy. Considerable reports have implicated Sal B (salvianolic acid B), a potent aqueous extract of Salvia miltiorrhiza, in enhancing the survival of cells under various conditions. In this study, we investigated the effect of Sal B on H₂O₂‐induced apoptosis in rat BMSCs, focusing on the survival signalling pathways. Results indicated that the MEK [MAPK (mitogen‐activated protein kinase)/ERK (extracellular‐signal‐regulated kinase) kinase] inhibitor (PD98059) and 10 μM Sal B remarkably prevented BMSCs from H₂O₂‐induced apoptosis through attenuating caspase‐3 activation, which is accompanied by the significant up‐regulation of Bcl‐2. In addition, the ROS (reactive oxygen species) accumulation was also reduced after Sal B treatment. Furthermore, Sal B inhibited the ERK1/2 phosphorylations stimulated by H₂O₂. Taken together, our results showed that H₂O₂‐induced apoptosis in BMSCs via the ROS/MEK/ERK1/2 pathway and Sal B may exert its cytoprotection through mediating the pathway.     

EV71 infection induces cell apoptosis through ROS generation and SIRT1 activation

Several studies have substantiated the correlation between reactive oxygen species (ROS) and Sirtuin 1 (SIRT1). Normally, enterovirus 71 (EV71) is associated with severe clinical manifestations and death. However, the effect of EV71 on the induction of cellular death and the interplay between ROS/SIRT1 in cell death has not been confirmed yet. In the current study, an increase in the number of apoptotic cells was observed as soon as the EV71 infection was initiated in cells and mice. Furthermore, EV71 infection also promoted a rise in the levels of three commonly known proinflammatory cytokines, interleukin 1β (IL-1β), IL-6, and tumor necrosis factor-α. During EV71-induced apoptosis in the different cell lines, ROS generation and SIRT1 downregulation were observed. Further investigations showed that the administration of ROS inhibitor, N-acetyl- l -cysteine (NAC), reduced the level of apoptosis and inflammation, reduced EV71 propagation, and increased SIRT1 expression in EV71-infected cells. In addition, combined administration of NAC and EX527 (SIRT1 inhibitor) restored apoptosis in the EV71-infected cells, which was reduced due to NAC. This data demonstrated that ROS generation is positively associated with EV71-induced apoptosis and inflammation, while this effect could be reversed by SIRT1 inhibition. Collectively, we have shown that EV71 induces apoptosis and inflammation by promoting ROS generation and reducing SIRT1 expression.     

Astragaloside IV improves pulmonary arterial hypertension by increasing the expression of CCN1 and activating the ERK1/2 pathway

The aim of the present study was to investigate the underlying mechanism of AS-IV and CCN1 in PAH and to evaluate whether the protective effect of AS-IV against PAH is associated with CCN1 and its related signalling pathway. In vivo, male SD rats were intraperitoneally injected with monocrotaline (MCT, 60 mg/kg) or exposed to hypoxia (10% oxygen) and gavaged with AS-IV (20, 40 and 80 mg/kg/day) to create a PAH model. In vitro, human pulmonary artery endothelial cells (hPAECs) were exposed to hypoxia (3% oxygen) or monocrotaline pyrrole (MCTP, 60 μg/mL) and treated with AS-IV (10, 20 and 40 μM), EGF (10 nM, ERK agonist), small interfering CCN1 (CCN1 siRNA) and recombinant CCN1 protein (rCCN1, 100 ng/mL). We identified the differences in the expression of genes in the lung tissues of PAH rats by proteomics. At the same time, we dynamically detected the expression of CCN1 by Western blot both in vivo and in vitro. The Western blot experimental results showed that the expression of CCN1 increased in the early stage of PAH and decreased in the advanced stage of PAH. The results showed that compared with the control group, MCT- and hypoxia-induced increased the hemodynamic parameters and apoptosis. AS-IV can improve PAH, as characterized by decreased hemodynamic parameters, vascular wall area ratio (WA%), vascular wall thickness ratio (WT%) and α-SMA expression and inhibition of cell apoptosis. Moreover, the improvement of PAH by AS-IV was accompanied by increased CCN1 expression, which activated the ERK1/2 signalling pathway. Meanwhile, CCN1 and p-ERK1/2 were inhibited by siCCN1 and promoted by rCCN1. EGF not only activated the ERK1/2 signalling pathway but also induced the expression of CCN1. In conclusion, AS-IV improves PAH by increasing the expression of CCN1 and activating the ERK1/2 signalling pathway. The results of our study provide a theoretical basis for additional study on the protective effect of AS-IV against PAH.     

Neferine protected cardiomyocytes against hypoxia/oxygenation injury through SIRT1/Nrf2/HO-1 signaling

Acute myocardial infarction is regarded as myocardial necrosis resulting from myocardial ischemia/reperfusion (I/R) damage and retains a major cause of mortality. Neferine, which was extracted from the green embryos of mature seeds of Nelumbo nucifera Gaertn., has been reported to possess a broad range of biological activities. However, its underlying mechanism on the protective effect of I/R has not been fully clarified. A hypoxia/reoxygenation (H/R) model with H9c2 cells closely simulating myocardial I/R injury was used as a cellular model. This study intended to research the effects and mechanism underlying neferine on H9c2 cells in response to H/R stimulation. Cell Counting Kit-8 and lactate dehydrogenase (LDH) release assays were employed to measure cell viability and LDH, respectively. Apoptosis and reactive oxygen species (ROS) were determined by flow cytometry analysis. Oxidative stress was evaluated by detecting malondialdehyde, superoxide dismutase, and catalase. Mitochondrial function was assessed by mitochondrial membrane potential, ATP content, and mitochondrial ROS. Western blot analysis was performed to examine the expression of related proteins. The results showed that hypoxia/reoxygenation (H/R)-induced cell damage, all of which were distinctly reversed by neferine. Moreover, we observed that neferine inhibited oxidative stress and mitochondrial dysfunction induced by H/R in H9c2 that were concomitant with increased sirtuin-1 (SITR1), nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 expression. On the contrary, silencing the SIRT1 gene with its small interferingRNA eliminated the beneficial effects of neferine. It is concluded that neferine preconditioning attenuated H/R-induced cardiac damage via suppressing apoptosis, oxidative stress, and mitochondrial dysfunction, which may be partially ascribed to the activation of SIRT1/Nrf2 signaling pathway.     

Resveratrol protects cardiomyocytes from hypoxia-induced apoptosis through the SIRT1-FoxO1 pathway

Loss of cardiomyocytes through apoptosis has been proposed as a cause of ventricular remodeling and heart failure. Ischemia- and hypoxia-induced apoptosis of cardiomyocytes reportedly plays an important role in many cardiac pathologies. We investigated whether resveratrol (Res) has direct cytoprotective effects against ischemia/hypoxia for cardiomyocytes. Exposure of H9c2 embryonic rat heart-derived cells to hypoxia for 24 h caused a significant increase in apoptosis, as evaluated by TUNEL and flow cytometry, while treatment with 20 μM Res greatly decreased hypoxia-induced apoptosis in these cells. Exposure of the cells to Res (20 μM) caused rapid activation of SIRT1, which had a dual effect on FoxO1 function: SIRT1 increased FoxO1’s ability to induce cell cycle arrest, but inhibited FoxO1’s ability to induce cell death. This effect could be reversed by SIRT1 inhibition. Results of our study indicate that Res inhibits hypoxia-induced apoptosis via the SIRT1-FoxO1 pathway in H9c2 cells. This polyphenol may have potential in preventing cardiovascular disease, especially in coronary artery disease (CAD) patients.     

Protein Kinase D3 promotes the cell proliferation by activating the ERK1/c‐MYC axis in breast cancer

Breast cancer is the second leading death cause of cancer death for all women. Previous study suggested that Protein Kinase D3 (PRKD3) was involved in breast cancer progression. In addition, the protein level of PRKD3 in triple‐negative breast adenocarcinoma was higher than that in normal breast tissue. However, the oncogenic mechanisms of PRKD3 in breast cancer is not fully investigated. Multi‐omic data showed that ERK1/c‐MYC axis was identified as a major pivot in PRKD3‐mediated downstream pathways. Our study provided the evidence to support that the PRKD3/ERK1/c‐MYC pathway play an important role in breast cancer progression. We found that knocking out PRKD3 by performing CRISPR/Cas9 genome engineering technology suppressed phosphorylation of both ERK1 and c‐MYC but did not down‐regulate ERK1/2 expression or phosphorylation of ERK2. The inhibition of ERK1 and c‐MYC phosphorylation further led to the lower protein level of c‐MYC and then reduced the expression of the c‐MYC target genes in breast cancer cells. We also found that loss of PRKD3 reduced the rate of the cell proliferation in vitro and tumour growth in vivo, whereas ectopic (over)expression of PRKD3, ERK1 or c‐MYC in the PRKD3‐knockout breast cells reverse the suppression of the cell proliferation and tumour growth. Collectively, our data strongly suggested that PRKD3 likely promote the cell proliferation in the breast cancer cells by activating ERK1‐c‐MYC axis.     

Artemisinin attenuated ischemic stroke induced cell apoptosis through activation of ERK1/2/CREB/BCL-2 signaling pathway in vitro and in vivo

Ischemic stroke is characterized by the presence of both brain ischemic and reperfusion-induced injuries in the brain, leading to neuronal dysfunction and death. Artemisinin, an FDA-approved antimalarial drug, has been reported to have neuroprotective properties. However, the effect of artemisinin on ischemic stroke is not known. In the present study, we investigated the effect of artemisinin on ischemic stroke using an oxygen-glucose deprivation/reperfusion (OGD/RP) cellular model and a mouse middle cerebral artery occlusion (MCAO) animal model and examined the underlying mechanisms. The obtained results revealed that a subclinical antimalarial concentration of artemisinin increased cell viability and decreased LDH release and cell apoptosis. Artemisinin also attenuated the production of reactive oxygen species (ROS) and the loss of mitochondrial membrane potential (Δψm). Importantly, artemisinin attenuated the infarction volume and the brain water content in the MCAO animal model. Artemisinin also improved neurological and behavioural outcomes and restored grasp strength and the recovery of motor function in MCAO animals. Furthermore, artemisinin treatment significantly inhibited the molecular indices of apoptosis, oxidative stress and neuroinflammation and activated the ERK1/2/CREB/BCL-2 signaling pathway. Further validation of the involved signaling pathway by the ERK1/2 inhibitor PD98059 revealed that inhibiting the ERK1/2 signaling pathway or silencing ERK1/2 reversed the neuroprotective effects of artemisinin. These results indicate that artemisinin provides neuroprotection against ischemic stroke via the ERK1/2/CREB/BCL-2 signaling pathway. Our study suggests that artemisinin may play an important role in the prevention and treatment of stroke.     

MICAL1 facilitates breast cancer cell proliferation via ROS‐sensitive ERK/cyclin D pathway

Molecule interacting with CasL 1 (MICAL1) is a multidomain flavoprotein mono‐oxygenase that strongly involves in cytoskeleton dynamics and cell oxidoreduction metabolism. Recently, results from our laboratory have shown that MICAL1 modulates reactive oxygen species (ROS) production, and the latter then activates phosphatidyl inositol 3‐kinase (PI3K)/protein kinase B (Akt) signalling pathway which regulates breast cancer cell invasion. Herein, we performed this study to assess the involvement of MICAL1 in breast cancer cell proliferation and to explore the potential molecular mechanism. We noticed that depletion of MICAL1 markedly reduced cell proliferation in breast cancer cell line MCF‐7 and T47D. This effect of MICAL1 on proliferation was independent of wnt/β‐catenin and NF‐κB pathways. Interestingly, depletion of MICAL1 significantly inhibited ROS production, decreased p‐ERK expression and unfavourable for proliferative phenotype of breast cancer cells. Likewise, MICAL1 overexpression increased p‐ERK level as well as p‐ERK nucleus translocation. Moreover, we investigated the effect of MICAL1 on cell cycle‐related proteins. MICAL1 positively regulated CDK4 and cyclin D expression, but not CDK2, CDK6, cyclin A and cyclin E. In addition, more expression of CDK4 and cyclin D by MICAL1 overexpression was blocked by PI3K/Akt inhibitor LY294002. LY294002 treatment also attenuated the increase in the p‐ERK level in MICAL1‐overexpressed breast cancer cells. Together, our results suggest that MICAL1 exhibits its effect on proliferation via maintaining cyclin D expression through ROS‐sensitive PI3K/Akt/ERK signalling in breast cancer cells.     

Quercetin alleviated H2O2‐induced apoptosis and steroidogenic impairment in goat luteinized granulosa cells

Quercetin (Que) is a natural flavonoid in most plants. Luteinized granulosa cell (LGC) culture is necessary for the study of follicle growth/differentiation. In the present study, we analyzed the role of Que in steroid production and apoptosis in hydrogen peroxide (H₂O₂)‐treated goat LGCs. The results showed that treatment with H₂O₂ induced apoptosis in goat LGCs, and treatment with Que decreased LGC apoptosis induced by H₂O₂ (P < .05), accompanied with the different expressions of BAX, BCL‐2, Caspase 3, and Cleaved caspase 3. Meanwhile, the messenger RNA expressions of nuclear factor erythroid 2 like 2 (Nrf2) and its downstream genes were upregulated with H₂O₂ +Que treatment, accompanied by the increased cellular viability (P < .05). Furthermore, Que alleviated H₂O₂‐induced reduction in the secretion of progesterone (P₄) (P < .05); however, it had no effect on the secretion of estrogen (E₂). Simultaneously, the expressions of StAR and P450scc were increased when treated with Que +H₂O₂, compared with the group treated with only H₂O₂ (P < .05). In conclusion, it is observed that Que could alleviate the H₂O₂‐induced apoptosis and steroidogenic impairment in goat LGCs, which might be mediated by the Nrf2 pathway.     

Insulin‐like growth factor‐1 regulates the SIRT1‐p53 pathway in cellular senescence

Cellular senescence, which is known to halt proliferation of aged and stressed cells, plays a key role against cancer development and is also closely associated with organismal aging. While increased insulin‐like growth factor (IGF) signaling induces cell proliferation, survival and cancer progression, disrupted IGF signaling is known to enhance longevity concomitantly with delay in aging processes. The molecular mechanisms involved in the regulation of aging by IGF signaling and whether IGF regulates cellular senescence are still poorly understood. In this study, we demonstrate that IGF‐1 exerts a dual function in promoting cell proliferation as well as cellular senescence. While acute IGF‐1 exposure promotes cell proliferation and is opposed by p53, prolonged IGF‐1 treatment induces premature cellular senescence in a p53‐dependent manner. We show that prolonged IGF‐1 treatment inhibits SIRT1 deacetylase activity, resulting in increased p53 acetylation as well as p53 stabilization and activation, thus leading to premature cellular senescence. In addition, either expression of SIRT1 or inhibition of p53 prevented IGF‐1‐induced premature cellular senescence. Together, these findings suggest that p53 acts as a molecular switch in monitoring IGF‐1‐induced proliferation and premature senescence, and suggest a possible molecular connection involving IGF‐1‐SIRT1‐p53 signaling in cellular senescence and aging.