Inhibition of ERK downregulates autophagy via mitigating mitochondrial fragmentation to protect SH-SY5Y cells from OGD/R injury.

BACKGROUND: Cerebral ischemia-reperfusion injury (CIRI) is the main cause leading to high mortality and neurological disability in patients with cardiac arrest/cardiopulmonary resuscitation (CA/CPR). Our previous study found that extracellular signal-regulated kinase (ERK) activation, dynamin-related protein1 (Drp1)/Mitofusin2 (Mfn2)-dependent mitochondrial dynamics imbalance, and excessive autophagy were involved in the mechanism of nerve injury after CA/CPR. However, the specific pathological signaling pathway is still unknown. This study aimed to explore the molecular function changes of ERK-Drp1/Mfn2-autophagy signaling pathway in SH-SY5Y cell oxygen-glucose deprivation/reoxygenation (OGD/R) model, to further clarify the pathophysiological mechanism of CIRI, and to provide a new strategy for cerebral protection after CIRI. METHODS: SH-SY5Y cells were pretreated with drugs 24 h before OGD/R. The Drp1 and Mfn2 knockdown were adopted small interfering RNAs. The overexpression of p-Drp1S616 and Mfn2 were used recombinant plasmids. The expression levels of mitochondrial dynamics proteins (p-Drp1, Drp1, Mfn2, Mfn1 and Opa1) and autophagy markers (LC3, Beclin1 and p62) were measured with the Western blotting. The mRNA levels after transfection were determined by PCR. Cell injury and viability were evaluated with released LDH activity and CCK8 assay kits. Mitochondria morphology and autophagosome were observed under transmission electron microscopy. Mitochondrial function was detected by the mitochondrial permeability transition pore assay kit. The co-expression of p-ERK, p-Drp1 and LC3 was assessed with multiple immunofluorescences. One-way analysis of variance followed by least significance difference post hoc analysis (for equal homogeneity) or Dunnett's T3 test (for unequal homogeneity) were used for statistical tests. RESULTS: ERK inhibitor-PD98059 (PD) protects SH-SY5Y cells from OGD/R-induced injury; while ERK activator-TPA had the opposite effect. Similar to autophagy inhibitor 3-MA, PD downregulated autophagy to improve cell viability; while autophagy activator-rapamycin further aggravated cell death. PD and Drp1-knockdown synergistically attenuated OGD/R-induced Drp1 activation, mPTP opening and cell injury; overexpression of Drp1S616E or ablating Mfn2 partly abolished the protective effects of PD. Multiple immunofluorescences showed that p-ERK, p-Drp1 and LC3 were co-expressed. CONCLUSION: Inhibition of ERK downregulates autophagy via reducing Drp1/Mfn2-dependent mitochondrial fragmentation to antagonize mitochondrial dysfunction and promotes cell survival in the SH-SY5Y cells OGD/R model. Video Abstract.

The effect of high-intensity interval training on exercise capacity in post-myocardial infarction patients: a systematic review and meta-analysis.

AIMS: Exercise-based cardiac rehabilitation has been recommended a treatment for patients with cardiovascular disease. Nevertheless, it remains controversial which exercise characteristics are most beneficial for post-myocardial infarction (MI) patients. We performed a systematic review and meta-analysis to investigate the effects of high-intensity interval training (HIIT) in these patients. METHODS AND RESULTS: We searched PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Periodical Database (VIP), and Wanfang Dataset (from the earliest date available to February 2021) for randomized controlled trials and cohort studies that evaluated the effects of HIIT on post-MI patients. Studies were selected according to inclusion and exclusion criteria. Data synthesis was performed with R software version 4.0.1. Eight studies met the study criteria, including 387 patients. Compared to the control group [moderate-intensity continuous training (MICT) and/or routine physical activity], HIIT significantly improved peak oxygen uptake (peak VO2) [mean difference = 3.83 mL/kg/min, 95% confidence interval (CI) (3.25, 4.41), P < 0.01]. No significant difference in systolic and diastolic blood pressures, peak and resting heart rate, left ventricular ejection fraction, left ventricular end-diastolic volume, and the quality of life was found between HIIT group and control group. The duration of follow-up ranged from 6 to 12 weeks. The incidence of adverse events was similar between groups [risk difference = 0.01, 95% CI (-0.02, 0.04), P = 0.53]. CONCLUSION: Compared with MICT and routine physical activity, HIIT could significantly improve exercise capacity in post-MI patients, and appears to be safe.