ALDH2 attenuates ischemia and reperfusion injury through regulation of mitochondrial fusion and fission by PI3K/AKT/mTOR pathway in diabetic cardiomyopathy

The function of mitochondrial fusion and fission is one of the important factors causing ischemia-reperfusion (I/R) injury in diabetic myocardium. Aldehyde dehydrogenase 2 (ALDH2) is abundantly expressed in heart, which involved in the regulation of cellular energy metabolism and stress response. However, the mechanism of ALDH2 regulating mitochondrial fusion and fission in diabetic myocardial I/R injury has not been elucidated. In the present study, we found that the expression of ALDH2 was downregulated in rat diabetic myocardial I/R model. Functionally, the activation of ALDH2 resulted in the improvement of cardiac hemodynamic parameters and myocardial injury, which were abolished by the treatment of Daidzin, a specific inhibitor of ALDH2. In H9C2 cardiomyocyte hypoxia-reoxygenation model, ALDH2 regulated the dynamic balance of mitochondrial fusion and fission and maintained mitochondrial morphology stability. Meanwhile, ALDH2 reduced mitochondrial ROS levels, and apoptotic protein expression in cardiomyocytes, which was associated with the upregulation of phosphorylation (p-PI3K_Tyr458, p-AKT_Ser473, p-mTOR). Moreover, ALDH2 suppressed the mitoPTP opening through reducing 4-HNE. Therefore, our results demonstrated that ALDH2 alleviated the ischemia and reperfusion injury in diabetic cardiomyopathy through inhibition of mitoPTP opening and activation of PI3K/AKT/mTOR pathway.

Docosahexaenoic acid inhibits Ca2+ influx and downregulates CaSR by upregulating microRNA-16 in pulmonary artery smooth muscle cells

Docosahexaenoic acid (DHA) is reported to have the potential to ameliorate pulmonary arterial hypertension (PAH), while the specific mechanism is still obscure. This study aims to investigate the function of DHA in pulmonary artery smooth muscle cells (PASMCs) and explore the underlying mechanism. In our study, DHA was used to incubate PASMCs. Cytosolic-free Ca²⁺ concentration ([Ca²⁺ ]cyt) was measured using Fluo-3 AM method. Real-time polymerase chain reaction was used to detect microRNA-16 (miR-16) and calcium-sensing receptor (CaSR) messenger RNA expression levels. CCK-8 assay, BrdU assay, and Transwell assay were employed to detect the effects of DHA on proliferation and migration of PASMCs. CaSR was confirmed as a direct target of miR-16 using dual-luciferase assay, polymerase chain reaction, and Western blot analysis. It was found that DHA significantly inhibited PASMC proliferation and migration and decreased [Ca²⁺ ]cyt. After transfection of miR-16 mimics, proliferation and migration ability of PASMCs were significantly inhibited, whereas opposite effects were observed after miR-16 inhibition. [Ca²⁺ ]cyt was also inhibited by miR-16 transfection. DHA then promoted the expression of miR-16, and the effects of DHA on PASMCs were annulled when miR-16 was inhibited. CaSR was identified as a direct target of miR-16. CaSR was inhibited directly by miR-16 and indirectly by DHA. In conclusion, DHA inhibits the proliferation and migration of PASMCs, and probably ameliorates PAH via regulating miR-16/CaSR axis.

MicroRNA-143-5p modulates pulmonary artery smooth muscle cells functions in hypoxic pulmonary hypertension through targeting HIF-1α

This paper explores the potential mechanism of microRNA-143-5p regulation effects on pulmonary artery smooth muscle cells (PASMCs) functions in hypoxic pulmonary hypertension (HPH) via targeting HIF-1a, which may offer a new idea for HPH therapy. PASMCs were transfected with mimics control/miR-143-5p mimics or inhibitor control/miR-143-5p inhibitor. We used Western blotting and RT-qPCR to detect the protein and mRNA expressions, CCK-8 assay to detect cellular viability, Annexin V-FITC/PI staining and caspase- 3/cleaved caspase-3 protein to evaluate cellular apoptosis, transwell migration experiment for cellular migration measurement and Dual luciferase reporter gene assay to prove the target of miR-143-5p. Cells under hypoxic condition presented the decreased protein and mRNA expressions of α-smooth muscle actin (SM-α-actin), Myocardin, smooth muscle myosin heavy chain (SMMHC), and smooth muscle-22α (SM22α), Calponin1 and Hypoxia-inducible factor-1α(HIF-1α), the increased cell viability and miR-143-5p level; Overexpression of miR-143-5p obviously reduced vascular smooth muscle-specific contraction marker protein levels and cellular apoptosis, increased cellular migration of PASMCs with hypoxia stimulation; Low-expression of miR-143-5p caused the opposite changes, while co-transfected with Si HIF-1 α blocked the beneficial effects of miR-143-5p inhibition on PASMCs under hypoxia. MicroRNA-143-5p can promote the phenotype conversion, proliferation and migration of pulmonary artery smooth muscle cells under hypoxic condition through direct targeting of HIF-1α.

MicroRNA‑138 promotes proliferation and suppresses mitochondrial depolarization in human pulmonary artery smooth muscle cells through targeting TASK‑1

MicroRNA (miR)‑138 serves an important role in the proliferation, differentiation and apoptosis of human pulmonary artery smooth muscle cells (HPASMCs), indi-cating the involvement of miR‑138 in the development and progression of pulmonary artery hypertension (PAH). Potassium channel subfamily K member 3 (TASK‑1), a two‑pore domain K+ channel, is expressed in HPASMCs and is associated with hypoxic PAH. However, whether miR‑138 mediates PAH through targeting TASK‑1 is not known. In the present study, HPASMCs were transfected with miR‑138 mimic to establish a PAH model in vitro, and the effects of a miR‑138 inhibitor and a TASK‑1 inhibitor (A293) were examined. Cell proliferation and mitochondrial membrane potential (MMP) were measured by CCK‑8 assay and flow cytometry, respectively. Reverse transcription-quantitative polymerase chain reaction and western blotting were performed to examine the expression of miR‑138, TASK‑1, Bcl‑2, caspase‑3 and activation of extracellular signal‑regulated kinase 1/2 (ERK1/2). A dual‑luciferase reporter assay was also used to analyse the expression level of TASK‑1 in HPASMCs. The results of the present study demonstrated that the miR‑138 mimic promoted proliferation and MMP level, which was similar to the effect of A293 treatment on HPASMCs. However, the miR‑138 inhibitor inhibited the effects induced by miR‑138 mimic or A293 treatment, as demonstrated by a decrease in proliferation and MMP level in HPASMCs, accompanied by a decrease of Bcl‑2 and an increase of caspase‑3 expression levels, as well as ERK1/2 activation. The dual‑luciferase reporter assay indicated that TASK‑1 expression was negatively regulated by miR‑138. The results of the present study suggested that miR‑138 promoted proliferation and suppressed mitochondrial depolarization of HPASMCs by targeting TASK‑1.

[Effects of activation of ALDH2 by ethanol on the expression of JNK in kidney of diabetic rats]

OBJECTIVE

To observe the effect of activation of aldehyde dehydrogenase 2 (ALDH2) by ethanol on the expression of c-Jun N-terminal kinase (JNK) in the kidney of diabetic rats.

METHODS

Eightheen healthy male SD rats were randomly divided into 3 groups (n = 6): normal control group, diabetes group and ethanol + diabetes group. After 8 weeks, 24 h urine samples from rats were collected to detect urinary protein content. The kidney was isolated and the ratio of kidney weight/body weight (index of kidney weight) was detected. The levels of fasting blood glucose, glycosylated hemoglobin serum urea nitrogen and serum creatinine were measured. Morphological changes of renal tissue were observed by optical microscope. The protein expressions of ALDH2 and JNK in renal tissue were detected by Western blot.

RESULTS

Compared with the normal control rats, the levels of fasting blood glucose, glycosylated hemoglobin, serum urea nitrogen, serum creatinine and the index of kidney weight were increased markedly in diabetic rats. The expression of ALDH2 protein was decreased, while p-JNK, JNK protein expressions and the ratio of p-JNK/JNK were increased. The morphological observation was shown that the amount of glomerular mesangial matrix were increased, basement membrane were thickened and capillary lumen were narrowed. However,in ethanol + diabetes group, renal function was improved and the damage of renal structure was attenuated. The expression of ALDH2 protein was increased, while p-JNK, JNK and the ratio of p-JNK/JNK were decreased.

CONCLUSION

Enhanced ALDH2 expression can protect kidney in diabetic rats, which may be relevant with inhibitting the activity of JNK pathway.

Ethanol at low concentration attenuates diabetes induced lung injury in rats model

To observe the changes of lung injury when diabetic rats were treated with low concentration of ethanol (EtOH) and analyze the related mechanisms, male Sprague-Dawley (SD) rats were divided into control, diabetic (DM), and EtOH+DM groups. Diabetic rat was mimicked by injection of streptozotocin intraperitoneally. Fasting blood glucose (FBG) level, lung weight (LW), body weight (BW), and LW/BW were measured. The changes of lung tissue and Type II alveolar cell were detected. Pulmonary malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were measured; meanwhile, ALDH2 mRNA and protein expressions were detected by RT-PCR and western blotting, respectively. Compared with control group, in DM group, SOD activity was decreased; FBG level, LW/BW, MDA content, ALDH2 mRNA, and protein expressions were decreased. Compared with DM group, in EtOH+DM group, SOD activity, ALDH2 mRNA, and protein expressions were increased; LW/BW and MDA content were decreased. The structures of lung tissue and lamellar bodies were collapsed in DM group; the injury was attenuated in EtOH+DM group. Our findings suggested that, in diabetic rat, pulmonary ALDH2 expression was decreased accompanying lung injury. EtOH at low concentration decreased diabetes induced lung injury through activating ALDH2 expression.

Changes in the expression of cardiac mitofusin-2 in different stages of diabetes in rats

The aim of this study was to investigate the role of mitofusin-2 (Mfn2) in different stages of diabetes in rats and to analyze the related mechanism(s). A diabetic model in SD rats was induced by a single intraperitoneal injection of 55 mg/kg streptozoticin (STZ). The hearts were isolated from diabetes mellitus (DM) rats at the fourth week (DM4W), eighth week (DM8W) and twelfth week (DM12W) and fasting blood glucose (FBG) levels and the ratio of heart weight to body weight (HW/BW) were measured. Malondialdehyde (MDA) content, superoxide dismutase (SOD) and caspase 3 activities were measured. The expression of Mfn2 of the left anterior myocardium at the mRNA level was detected using RT‑PCR. In contrast to the normal group, in the DM4W, DM8W and DM12W groups, there was a significant increase in the FBG levels, but no difference among the DM4W, DM8W and DM12W groups. The HW/BW ratio as well as the MDA content were increased, while SOD activity was reduced. Caspase‑3 activity was increased, while the expression of Mfn-2 mRNA levels was reduced. In addition, with the development of diabetic cardiomyopathy, the contents of MDA and caspase 3 were increased, whereas SOD activity and Mfn-2 mRNA levels were further reduced. In conclusion, our results indicated that with the development of diabetes, the expression of cardiac Mfn2 has showed a decrease, which may be associated with the decrease of antioxidant ability and progression of apoptosis.

[Effect of ALDH2 activation against myocardial ischemia/reperfusion injury in diabetic rat]

OBJECTIVE

To observe the role of activation of aldehyde dehydrogenase 2 (ALDH2) on myocardial ischemia/reperfusion (I/ R) injury in diabetic rats.

METHODS

Diabetic rat model was simulated by intraperitoneal injection 55 mg/kg streptozotocin (STZ) and divided into diabetes and ethanol + diabetes groups (n = 8). After 8 weeks, myocardial ischemia/reperfusion model was mimicked in vitro. The ventricular dynamical parameters and lactate dehydrogenase (LDH) content in coronary flow were determined. The fasting blood glucose and glycosylated hemoglobin (HbA1c) level were determined by automatic biochemistry analyzer. The ALDH2 mRNA and protein expressions of left anterior myocardium were evaluated by RT-PCR and Western blot.

RESULTS

In contrast to I/R in normal rat, in diabetic rat, left ventricular development pressure (LVDP), maximal rise/fall rate of left ventricular pressure (+/- dp/dtmax) and left ventricular work (RPP) were decreased, left ventricular end diastolic pressure (LVEDP) and LDH release were increased, and ALDH2 mRNA and protein expressions were decreased; compared with I/R in diabetic rat, ALDH2 agonist ethanol significantly promoted the recovery of LVDP, +/- dp/dtmax, RPP, reduced HbA1c level, LVEDP and LDH released, ALDH2 mRNA and protein expressions were increased.

CONCLUSION

In diabetic rat, the expression of ALDH2 was decreased when heart was subjected to I/R. Enhanced mitochondrial ALDH2 expression in diabetic rat could play cardiac protective role.

[Anti-apoptotic role of mitochondrial aldehyde dehydrogenase 2 in myocardial ischemia/reperfusion injury in diabetic rats]

OBJECTIVE

To evaluate the anti-apoptotic effect of aldehyde dehydrogenase 2 (ALDH2) on myocardial ischemia/reperfusion (I/R) injury in diabetic rats.

METHODS

Normal male SD rats were divided into normal, diabetes and ethanol (the agonist of ALDH2) + diabetes groups. In the latter two groups, diabetes was induced by an intraperitoneal injection of 55 mg/kg STZ. Four weeks after the modeling, myocardial I/R was mimicked ex vivo, and lactate dehydrogenase (LDH) content in the coronary flow was determined. The activities of caspase-3 and ALDH2 were evaluated, and the expressions of Bcl-2 and Bax mRNA in the left anterior myocardium were detected using RT-PCR.

RESULTS

In diabetic group, LDH release and caspase-3 activity were increased, while ALDH2 activity and Bcl-2/Bax mRNA expression were decreased as compared to those in normal control group. Compared with the diabetic group, ALDH2 agonist ethanol significantly reduced LDH release and caspase-3 activity, increased ALDH2 activity and Bcl-2/Bax mRNA expression.

CONCLUSION

In diabetic rats, enhanced ALDH2 expression can offer mycardial protection possibly in relation to suppress cell apoptosis.