Drp1/p53 interaction mediates p53 mitochondrial localization and dysfunction in septic cardiomyopathy.

BACKGROUND: Previous studies have implicated p53-dependent mitochondrial dysfunction in sepsis induced end organ injury, including sepsis-induced myocardial dysfunction (SIMD). However, the mechanisms behind p53 localization to the mitochondria have not been well established. Dynamin-related protein 1 (Drp1), a mediator of mitochondrial fission, may play a role in p53 mitochondrial localization. Here we examined the role of Drp1/p53 interaction in SIMD using in vitro and murine models of sepsis. METHODS: H9c2 cardiomyoblasts and BALB/c mice were exposed to lipopolysaccharide (LPS) to model sepsis phenotype. Pharmacologic inhibitors of Drp1 activation (ψDrp1) and of p53 mitochondrial binding (pifithrin µ, PFTµ) were utilized to assess interaction between Drp1 and p53, and the subsequent downstream impact on mitochondrial morphology and function, cardiomyocyte function, and sepsis phenotype. RESULTS: Both in vitro and murine models demonstrated an increase in physical Drp1/p53 interaction following LPS treatment, which was associated with increased p53 mitochondrial localization, and mitochondrial dysfunction. This Drp1/p53 interaction was inhibited by ΨDrp1, suggesting that this interaction is dependent on Drp1 activation. Treatment of H9c2 cells with either ΨDrp1 or PFTµ inhibited the LPS mediated localization of Drp1/p53 to the mitochondria, decreased oxidative stress, improved cellular respiration and ATP production. Similarly, treatment of BALB/c mice with either ΨDrp1 or PFTµ decreased LPS-mediated mitochondrial localization of p53, mitochondrial ROS in cardiac tissue, and subsequently improved cardiomyocyte contractile function and survival. CONCLUSION: Drp1/p53 interaction and mitochondrial localization is a key prodrome to mitochondrial damage in SIMD and inhibiting this interaction may serve as a therapeutic target.

The impact of DRP1 on myocardial fibrosis in the obese minipig.

BACKGROUND: The heart is a highly oxidative tissue, thus mitochondria play a major role in maintaining optimal cardiac function. Our previous study established a dietary-induced obese minipig with cardiac fibrosis. The aim of this study was to elucidate the role of mitochondrial dynamics in cardiac fibrosis of obese minipigs. DESIGN: Four-month-old Lee-Sung minipigs were randomly divided into two groups: a control group (C) and an obese group (O) by feeding a control diet or a high-fat diet (HFD) for 6 months. Exposure of H9c2 cardiomyoblasts to palmitate was used to explore the effects of high-fat on induction of myocardial injury in vitro. RESULTS: The O pigs displayed greater heart weight and cardiac collagen accumulation. Obese pigs exhibited a lower antioxidant capacity, ATP concentration, and higher oxidative stress in the left ventricle (LV). The HFD caused downregulation in protein expression of PGC-1α and OPA1, and upregulation of DRP1, FIS1, and PINK1 in the LV of O compared to C pigs. Furthermore, palmitate induced apoptosis and decreased ATP content in H9c2 cells. Palmitate elevated the protein expression of DRP1 and PINK1 in these cells. Inhibition of DRP1 protein expression by siDRP1 in H9c2 cells resulted in enhanced ATP and decreased palmitate-induced apoptosis. CONCLUSIONS: These results suggest that mitochondrial dynamics were linked to the progression of obesity-related cardiac injury. Inhibition of DRP1 after palmitate exposure in H9c2 cells resulted in improved ATP level and decreased apoptosis in vitro suggesting that mitochondrial fission serves a key role in progression of obesity-induced cardiac fibrosis.

A nutritional nonalcoholic steatohepatitis minipig model.

BACKGROUND AND AIMS: The objective of this study was to elucidate whether a Western diet was associated with nonalcoholic steatohepatitis (NASH), and the relationship between NASH, autophagy and endoplasmic reticulum (ER) stress. METHODS: Four-month-old Lee-Sung minipigs were randomly assigned to two groups: control diet (C) and Western diet (W), for a 5-month experimental period. RESULTS: Feeding a Western diet produced a body composition with more fat, less lean and a greater liver weight. Compared with C pigs, W pigs also exhibited an elevated level of plasma insulin and free fatty acid. The W pigs displayed glucose intolerance, lower circulation antioxidant capacity and greater hepatic oxidative stress. Furthermore, pig fed the W diets had increased collagen accumulation in the liver and elevated systemic inflammation [tumor necrosis factor α and interleukin (IL)-6]. Compared with C pigs, W pigs had higher hepatic ER stress-related protein expression of GRP94, CHOP and caspase-12. The W pigs also had greater hepatic autophagy-related protein expression of p62 and LC3II. In an obesity antibody array analysis, W pigs had higher type 2 diabetes mellitus- (insulin-like growth factor 1, osteoprotegerin and resistin), atherosclerosis- (vascular endothelial growth factor, platelet-derived growth factor-AA and plasminogen activator inhibitor-I) and inflammation- [IL-1, macrophage-stimulating protein alpha, X-linked ectodermal dysplasia receptor and serum amyloid A (SAA)] related protein expressions. In addition, W pigs had greater plasma SAA concentration than C pigs and plasma SAA level was highly associated with IL-6. CONCLUSIONS: We successfully established a NASH pig model, and our findings suggested an association of NASH with ER stress and autophagy. The SAA has potential as a novel plasma biomarker for nonalcoholic fatty liver disease pigs.