Buxing Chen

A soluble receptor for advanced glycation end-products inhibits myocardial apoptosis induced by ischemia/reperfusion via the JAK2/STAT3 pathway

AbstractsRAGE can protect cardiomyocytes from apoptosis induced by ischemia/reperfusion (I/R). However, the signaling mechanisms in cardioprotection by sRAGE are currently unknown. We investigated the cardioprotective effect and potential molecular mechanisms of sRAGE inhibition on apoptosis in the mouse myocardial I/R as an in vivo model and neonatal rat cardiomyocyte subjected to ischemic buffer as an in vitro model. Cardiac function and myocardial infarct size following by I/R were evaluated with echocardiography and Evans blue/2,3,5-triphenyltetrazolium chloride. Apoptosis was detected by TUNEL staining and caspase-3 activity. Expression of the apoptosis-related proteins p53, Bax, Bcl-2, JAK2/p-JAK2, STAT3/p-STAT3, AKT/p-AKT, ERK/p-ERK, STAT5A/p-STAT5A and STAT6/p-STAT6 were detected by western blot analysis in the presence and absence of the JAK2 inhibitor AG 490. sRAGE (100xa0µg/day) improved the heart function in mice with I/R: the left ventricular ejection fraction and fractional shortening were increased by 42 and 57xa0%, respectively; the infarct size was decreased by 52xa0%, the TUNEL-positive myocytes by 66xa0%, and activity of caspase-3 by 24xa0%, the protein expression of p53 and ratio of Bax to Bcl-2 by 29 and 88xa0%, respectively; protein expression of the p-JAK2, p-STAT3 and p-AKT were increased by 92, 280 and 31xa0%, respectively. sRAGE have no effect on protein expression of p-ERK1/2, p-STAT5A and p-STAT6 following by I/R. sRAGE (900xa0nmol/L) exhibited anti-apoptotic effects in cardiomyocytes by decreasing TUNEL-positive myocytes by 67xa0% and caspase-3 activity by 20xa0%, p53 protein level and the Bax/Bcl-2 ratio by 58 and 86xa0%, respectively; increasing protein expression of the p-JAK2 and p-STAT3 by 26 and 156xa0%, respectively, p-AKT protein level by 33xa0%. The anti-apoptotic effects of sRAGE following I/R were blocked by JAK2 inhibitor AG 490. The effect of sRAGE reduction on TUNEL-positive myocytes and caspase-3 activity were abolished by PI3K inhibitor LY294002, but not ERK 1/2 inhibitor PD98059. These results suggest that sRAGE protects cardiomyocytes from apoptosis induced by I/R in vitro and in vivo by activating the JAK2/STAT3 signaling pathway.

A soluble receptor for advanced glycation end-products inhibits hypoxia/reoxygenation-induced apoptosis in rat cardiomyocytes via the mitochondrial pathway.

Severe myocardial dysfunction and tissue damage resulting from ischemia/reperfusion (I/R) is a common clinical scenario in patients with certain types of heart diseases and therapies such as thrombolysis, percutaneous coronary intervention, coronary artery bypass grafting, and cardiac transplantation. The underlining mechanism of endogenous cardiac protection after I/R injury has been a focus of current research. Growing evidences suggests that soluble receptor for advanced glycation end-products (sRAGE) has a cardioprotective effect; however, its role in I/R injury remains unclear. We hypothesized that exogenous administration of sRAGE during hypoxia/reoxygenation (H/R) induces cardioprotection by inhibiting cardiomyocyte apoptosis via multiple signals, involving mitochondrial membrane potential (MMP), the mitochondrial permeability transition pore (mPTP), mitochondrial cytochrome c, caspase-3, Bcl-2 and Bax. Neonatal rat cardiomyocytes underwent hypoxia for 3-h followed by 2-h reoxygenation or were treated with sRAGE for 10 min before H/R. Compared with H/R alone, sRAGE pretreatment reduced H/R-induced cardiomyocyte apoptosis from 27.9% ± 5.9% to 9.4% ± 0.7% (p < 0.05). In addition, sRAGE treatment significantly inhibited H/R-induced mitochondrial depolarization and mPTP opening, reduced mitochondrial cytochrome c leakage, caspase-3 and caspase-9 activity, and decreased the ratio of Bax to Bcl-2. Therefore, we conclude that the exogenous administration of sRAGE during H/R is involved in cardioprotection by inhibiting apoptosis via the mitochondrial pathway, which, if further confirmed in vivo, may have important clinical implications during H/R.

Soluble receptor for advanced glycation end-products protects against ischemia/reperfusion-induced myocardial apoptosis via regulating the ubiquitin proteasome system.

AIMnApoptosis participated in the pathological process of myocardial ischemia/reperfusion (I/R) injury. Previous studies have reported that endogenous substance sRAGE protect against I/R injury through inhibiting myocardial apoptosis. But the mechanisms are currently unknown. Prior work has demonstrated that ubiquitin proteasome system (UPS) dysfunction is closely related to apoptosis. We explored the potential role of UPS in the effect of sRAGE inhibition on I/R-induced myocardial apoptosis.nnnMETHODS AND RESULTSnAdult male C57BL mice treated with sRAGE (100μg/day, i.p.) or saline were performed to ligate left anterior descending coronary artery (LAD) as an in vivo model. As an in vitro model, primary murine cardiomyocytes pretreated with sRAGE or sRAGE-containing adenovirus were simulated I/R by ischemia buffer. The TUNEL and caspase-3 activity were assessed. Also the activity and expression of proteasome were detected. sRAGE decreased the number of TUNEL-positive cardiomyocytes and caspase-3 activity, however, the inhibition of sRAGE on I/R-induced apoptosis was abolished by proteasome inhibitor Bortezimb (BTZ). sRAGE inhibited the decreased proteasome activity, also the reduction in protein and gene levels of β1i and β5i following I/R. Suppression of STAT3 blocked the inhibition of sRAGE on apoptosis induced by I/R. The chromatin immunoprecipitation (CHIP) results confirmed that sRAGE promoted activating STAT3 binding to β1i and β5i promoter.nnnCONCLUSIONSnOur data suggest that the inhibition of sRAGE on I/R-induced apoptosis is associated with activation and expression of proteasome, including improved proteasome activity and elevated β1i and β5i expression mediated by STAT3 activation. We predict that sRAGE is a novel intervention to target UPS activation for preventing and treating myocardial apoptosis.

Effect of Blood Pressure Variability on Cardiovascular Outcome in Diabetic and Nondiabetic Patients with Stroke

BACKGROUNDnThe association between blood pressure (BP) variability and stroke outcome is controversial, and there are few studies that have focused on the impact of BP variability in diabetic patients with stroke. Therefore, we aimed to examine the impact of BP variability on cardiovascular outcome in diabetic and nondiabetic patients with stroke.nnnMETHODSnA total of 373 ischemic stroke patients with large artery atherosclerosis were recruited and followed up. Ambulatory BP monitoring was performed in all patients and divided according to the 25th and 75th percentiles interval of SD of daytime systolic BP (SBP). Kaplan-Meier analysis and Cox regression were used to assess the relationship between BP variability and cardiovascular outcomes including stroke recurrence, vascular events and cardiovascular death.nnnRESULTSnThe 339 patients were included in the final analysis. During an average follow-up of 19.0 ± 5.1 months (.6-26.8 months), 69 (20.4%) cardiovascular events occurred in all patients. Kaplan-Meier analysis found that there were no differences in cardiovascular events-free survival among the different BP variability groups in diabetic patients (P = .995); however, nondiabetic patients with greater BP variability showed a lesser cardiovascular events-free survival (P = .039). Through Cox regression we found the SD of daytime SBP (hazard ratio 1.103; 95% CI 1.011-1.203) was associated with cardiovascular outcomes in nondiabetic patients with stroke.nnnCONCLUSIONSnWe show that SBP variability is associated with cardiovascular outcomes in stroke patients without diabetes, but we didnt find a correlation between SBP variability and cardiovascular outcomes in stroke patients with diabetes.

Interferon-γ mediates the protective effects of soluble receptor for advanced glycation end-product in myocardial ischemia/reperfusion

The ubiquitin–proteasome system (UPS) is essential for protein degradation and plays critical roles in myocardial ischemia/reperfusion (MI/R) injuries. Previous studies have demonstrated that the soluble receptor for advanced glycation end-product (sRAGE) inhibited MI/R-induced apoptosis by upregulating proteasome subunits. However, the mechanism remains unknown. An MI/R model was established by left anterior descending (LAD) coronary artery ligation in mice. Recombinant sRAGE protein or saline was injected intramyocardially with or without neutralizing interferon-γ (IFN-γ) antibody injected intraperitoneally before ligation. In cardiomyocytes, ischemia was simulated with “ischemia buffer” and sRAGE was overexpressed by adenovirus. Adenovirus expressing the interference RNA of β5i was used to knockdown β5i in cardiomyocytes. IFN-γ was induced by sRAGE both in sham and MI/R mice. Blockade of IFN-γ using IFN-γ antibody abolished the rescue effects of sRAGE for cardiac dysfunction, infarct size and apoptosis provoked by MI/R. Blockade of IFN-γ reversed the upregulation of β1i and β5i expression induced by sRAGE during MI/R in heart, accompanied by decreasing chymotrypsin-like proteasome activity. In addition, IFN-γ antibody abolished the suppressing effect of sRAGE on MI/R-induced p38 and c-Jun N-terminal kinase (JNK) activation, as well as p53 expression, both in vivo and in vitro. However, knockdown of β5i abolished the antiapoptosis effect of sRAGE during hypoxia/reoxygenation (H/R) in vitro, accompanied by decreased degradation of p53. Our data suggest a novel mechanism for sRAGE in preventing MI/R-induced apoptosis in heart: sRAGE inhibits MI/R-induced apoptosis in cardiomyocytes by degrading p53 by β5i subunit that is increased via upregulation of IFN-γ.In this study, the authors found that interferon-γ mediates the protective effects of soluble receptor for advanced glycation end-product (SRAGE) on myocardial ischemia/reperfusion (MI/R) injuries in heart, which might be associated with the increasing expression of proteasome β5i. In addition, the increased β5i in cardiomyocytes promoted the p53 degradation which contributed to the anti-apoptosis effects of sRAGE in MI/R injuries.

Soluble receptor for advance glycation end-products inhibits ischemia/reperfusion-induced myocardial autophagy via the STAT3 pathway

ABSTRACT The pathogenesis of myocardial ischemia/reperfusion (I/R) is poorly understood, but recent evidence suggests that autophagy plays crucial roles in I/R injuries. Soluble receptor for advanced glycation end‐products (sRAGE) exerts protective effects during I/R by decreasing cardiac apoptosis, which is mediated via increasing the ubiquitin proteasome system (UPS) and signal transducer and activator of transcription 3 (STAT3). The present study examined the effects and mechanisms of sRAGE on I/R‐triggered cardiac autophagy. I/R was performed in mice or primary neonatal cardiomyocytes with or without sRAGE administration or overexpression. Cardiac function and infarct size were detected in mouse hearts. Apoptosis, autophagy and autophagy‐related signaling pathways were detected in mouse hearts and cardiomyocytes. The results demonstrated that sRAGE significantly improved cardiac function and reduced infarct size during I/R in mice. sRAGE inhibited I/R‐induced apoptosis, which correlated with a reduction in autophagy‐associated proteins, including ATG7, Beclin‐1 and microtubule‐associated protein 1 light chain 3 (LC3). sRAGE reduced autophagosome formation during I/R in vivo and in vitro. sRAGE significantly activated STAT3, but not mammalian target of rapamycin (mTOR), during I/R in vivo and in vitro, and suppression of STAT3 abolished the sRAGE inhibition of autophagy during I/R in vitro. Activation of autophagy using ATG7 overexpression with an adenovirus significantly abolished the sRAGE‐induced reduction of cardiac apoptosis during I/R. These results suggest that sRAGE inhibits I/R injuries in the heart via a decrease in autophagy, a process that is dependent on STAT3 activation. Graphical abstract Figure. No Caption available. HighlightsIt was reported sRAGE inhibited autophagy during I/R for the first time.sRAGE inhibited I/R‐triggered autophagy via an mTOR‐independent pathway.The protecting effect of sRAGE was dependent on inhibition of autophagy during I/R.