Yanhua Luo, Jiajia Liu, Songgao Huang, Hongmei Li, Yunsheng Li
PPM1H was upregulated during intestinal I/R injury and might exacerbate damage by regulating excessive mitophagy through mediating the dephosphorylation of FUNDC1 at Ser13, which subsequently regulates apoptosis. Thus, our findings revealed PPM1H as a closely associated regulator in intestinal I/R injury.
INTRODUCTION: Intestinal ischemia/reperfusion (I/R) injury causes severe mucosal damage via mitochondrial dysfunction. While mitophagy regulates mitochondrial quality, its specific modulation by protein phosphatase magnesium-dependent 1H (PPM1H) remains unclear. We investigated PPM1H's role and its mechanism involving FUN14 domain-containing 1 (FUNDC1)-mediated mitophagy.
METHODS: Intestinal I/R injury was modeled in C57BL/6 mice by occluding the superior mesenteric artery for 60 min followed by 120 min of reperfusion. In vitro, mouse intestinal mucosa epithelial (MIME) cells were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R). In MIME cells, PPM1H expression was knocked down using specific siRNA prior to OGD/R challenge. Histological evaluation, cell viability, diamine oxidase (DAO) activity, mitochondrial autophagosome formation, apoptotic index, and the expression levels of key proteins were assessed.
RESULTS: Both in vivo and in vitro models showed that PPM1H and total FUNDC1 were upregulated, while the relative phosphorylation level of FUNDC1 at Ser13 (p-FUNDC1-Ser13) was downregulated following I/R or OGD/R injury. Concurrently, mitophagy was activated, as evidenced by an increased LC3-II/LC3-I ratio and decreased p62 levels. These changes were accompanied by significant intestinal damage, elevated DAO levels, and increased apoptosis. Conversely, knockdown of PPM1H in MIME cells reversed these effects: it increased p-FUNDC1-Ser13/total FUNDC1 ratio, suppressed mitophagy, improved cell survival, reduced DAO release, and attenuated apoptosis.
CONCLUSIONS: PPM1H was upregulated during intestinal I/R injury and might exacerbate damage by regulating excessive mitophagy through mediating the dephosphorylation of FUNDC1 at Ser13, which subsequently regulates apoptosis. Thus, our findings revealed PPM1H as a closely associated regulator in intestinal I/R injury.