p38-Regulated/activated protein kinase plays a pivotal role in protecting heart against ischemia-reperfusion injury and preserving cardiac performance

Deletion of PRAK Mitigates the Mitochondria Function and Suppresses Insulin Signaling in C2C12 Myoblasts Exposed to High Glucose

Background: p38 regulated/activated protein kinase (PRAK) plays a crucial role in modulating cell death and survival. However, the role of PRAK in the regulation of metabolic stress remains unclear. We examined the effects of PRAK on cell survival and mitochondrial function in C2C12 myoblasts in response to high glucose stresses.

Methods: PRAK of C2C12 myoblasts was knocked out by using CRISPR/Cas-9 genome editing technology. Both wild type and PRAK^−/− C2C12 cells were exposed to high glucose at the concentration of 30 mmol/L to induce metabolic stress. The effect of irisin, an adipomyokine, on both wild type and PRAK^−/− cells was determined to explore its relationship with RPAK. Cell viability, ATP product, glucose uptake, mitochondrial damage, and insulin signaling were assessed.

Results: PRAK knockout decreased C2C12 viability in response to high glucose stress as evident by MTT assay in association with the reduction of ATP and glucose uptake. PRAK knockout enhanced apoptosis of C2C12 myoblasts in response to high glucose, consistent with an impairment in mitochondrial function, by decreasing mitochondrial membrane potential. PRAK knockout induced impairment of mitochondrial and cell damage were rescued by irisin. PRAK knockout caused decrease in phosphorylated PI3 kinase at Tyr 485, IRS-1 and AMPKα and but did not affect non-phosphorylated PI3 kinase, IRS-1 and AMPKα signaling. High glucose caused the further reduction of phosphorylated PI3 kinase, IRS-1 and AMPKα. Irisin treatment preserved phosphorylated PI3 kinase, IRS-1by rescuing PRAK in high glucose treatment.

Conclusion: Our finding indicates a pivotal role of PRAK in preserving cellular survival, mitochondrial function, and high glucose stress.

The Essential Role of PRAK in Preserving Cardiac Function and Insulin Resistance in High-Fat Diet-Induced Diabetes

Regulated/activated protein kinase (PRAK) plays a crucial role in modulating biological function. However, the role of PRAK in mediating cardiac dysfunction and metabolic disorders remains unclear. We examined the effects of deletion of PRAK on modulating cardiac function and insulin resistance in mice exposed to a high-fat diet (HFD). Wild-type and PRAK^-/- mice at 8 weeks old were exposed to either chow food or HFD for a consecutive 16 weeks. Glucose tolerance tests and insulin tolerance tests were employed to assess insulin resistance. Echocardiography was employed to assess myocardial function. Western blot was used to determine the molecular signaling involved in phosphorylation of IRS-1, AMPKα, ERK-44/42, and irisin. Real time-PCR was used to assess the hypertrophic genes of the myocardium. Histological analysis was employed to assess the hypertrophic response, interstitial myocardial fibrosis, and apoptosis in the heart. Western blot was employed to determine cellular signaling pathway. HFD-induced metabolic stress is indicated by glucose intolerance and insulin intolerance. PRAK knockout aggravated insulin resistance, as indicated by glucose intolerance and insulin intolerance testing as compared with wild-type littermates. As compared with wild-type mice, hyperglycemia and hypercholesterolemia were manifested in PRAK-knockout mice following high-fat diet intervention. High-fat diet intervention displayed a decline in fractional shortening and ejection fraction. However, deletion of PRAK exacerbated the decline in cardiac function as compared with wild-type mice following HFD treatment. In addition, PRAK knockout mice enhanced the expression of myocardial hypertrophic genes including ANP, BNP, and βMHC in HFD treatment, which was also associated with an increase in cardiomyocyte size and interstitial fibrosis. Western blot indicated that deletion of PRAK induces decreases in phosphorylation of IRS-1, AMPKα, and ERK44/42 as compared with wild-type controls. Our finding indicates that deletion of PRAK promoted myocardial dysfunction, cardiac remodeling, and metabolic disorders in response to HFD.

CircANXA2 Promotes Myocardial Apoptosis in Myocardial Ischemia-Reperfusion Injury via Inhibiting miRNA-133 Expression

OBJECTIVE

This project is aimed at investigating whether CircANXA2 can promote the apoptosis of myocardial cells by inhibiting miR-133 expression and thereby participate in the development of myocardial ischemia-reperfusion injury. Materials and Method. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression level of CircANXA2 in H9c2 cells after hypoxia/reoxygenation (H/R) treatment. Evaluation of myocardial injury markers in H9c2 cells was performed using commercial kits, including lactate dehydrogenase (LDH), malonaldehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidation (GSH-PX). MTT analysis and flow cytometry were used to detect myocardial cell proliferation and apoptosis, respectively. Western blot was used to detect the protein expression of apoptosis-related genes.

RESULT

qRT-PCR results showed that compared with the control, the expression of CircANXA2 was upregulated and the expression level of miR-133 was significantly decreased in H/R-treated H9c2 cells. CircANXA2 overexpression increased LDH, MDA, SOD, and GSH-PX activity in H/R-treated H9c2 cells. At the same time, CircANXA2 overexpression inhibited the proliferation of H/R-treated cells, and CircANXA2 was able to induce cardiomyocyte apoptosis. Western blot results showed that after overexpression of CircANXA2, the proapoptotic genes Bax and cytochrome C was upregulated, while the antiapoptotic gene Bcl-2 was downregulated. In H9c2 cells, upregulating miR-133 can reverse the inhibition of proliferation induced by CircANXA2 overexpression and increase apoptosis.

CONCLUSIONS

CircANXA2 promotes cardiomyocyte apoptosis in myocardial ischemia-reperfusion injury by inhibiting the expression of miR-133. CircANXA2 may be a potential target for myocardial ischemia-reperfusion injury.