Hepatic ischemia/reperfusion injury (IRI) is a common cause of morbidity and mortality in liver transplantation settings and involves severe cell death and inflammatory responses. MicroRNA-191 has recently been reported to be abnormally expressed in hepatocellular carcinoma and other liver diseases in the regulation of important cellular processes. However, little is known about its function and molecular mechanism in IRI. Here, we demonstrate that miR-191 is significantly upregulated in a cultured cell line during hypoxia/reperfusion (H/R) and in liver tissue during IRI in mice. The activation of miR-191 under hypoxic conditions is mediated by hypoxia-inducible factor-1α (HIF1α) binding to its promoter region. Global miR-191 KO mice were constructed by CRISPR/Cas9 system, and we found that miR-191 deficiency markedly reduces liver tissue damage, cell inflammatory responses and cell death in a mouse hepatic IRI model. Under the H/R condition, miR-191 overexpression promotes G0/G1 cell cycle arrest and cell apoptosis, but inhibition of miR-191 facilitates cell cycle progression and decreases cell death. Mechanistically, upon induction by hypoxia or ischemia, miR-191 suppresses expression of ZO-1-associated Y-box factor (ZONAB) and its downstream factor Cyclin D1, consequently resulting in cell death and tissue injury. Moreover, the effects of miR-191 on cell cycle arrest and cell apoptosis are abrogated by ZONAB overexpression, and vice versa. Taken together, our results indicate an important role of the HIF1α/miR-191/ZONAB signaling pathway in hepatic IRI and suggest miR-191 as a novel therapeutic target for the treatment of liver IRI.

Traumatic hemorrhagic shock (THS) is a major cause of mortality and morbidity worldwide in severely injured patients. Mesenchymal stem cells (MSCs) possess immunomodulatory properties and tissue repair potential mainly through a paracrine pathway mediated by MSC-derived extracellular vesicles (MSC-EVs). Interleukin 10 (IL-10) is a potent anti-inflammatory cytokine that plays a crucial role during the inflammatory response, with a broad range of effects on innate and adaptive immunity, preventing damage to the host and maintaining normal tissue homeostasis. However, the function and mechanism of IL-10 in MSC-mediated protective effect in THS remain obscure. Here, we show that MSCs significantly attenuate hepatic injury and inflammation from THS in mice. Notably, these beneficial effects of MSCs disappeared when IL-10 was knocked out in EVs or when recombinant IL-10 was administered to mice. Mechanistically, MSC-EVs function to carry and deliver IL-10 as cargo. WT MSC-EVs restored the function of IL-10 KO MSCs during THS injury. We further demonstrated that EVs containing IL-10 mainly accumulated in the liver during THS, where they were captured by Kupffer cells and induced the expression of PTPN22. These effects subsequently shifted Kupffer cells to an anti-inflammatory phenotype and mitigated liver inflammation and injury. Therefore, our study indicates that MSC-EVs containing IL-10 alleviate THS-induced hepatic injury and may serve as a cell-free therapeutic approach for THS.

Background and Aims Hepatic ischemia‐reperfusion (IR) injury is a major complication of liver transplantation, resection, and hemorrhagic shock. Hypoxia is a key pathological event associated with IR injury. MicroRNA‐210 (miR‐210) has been characterized as a micromanager of hypoxia pathway. However, its function and mechanism in hepatic IR injury is unknown. Approach and Results In this study, we found miR‐210 was induced in liver tissues from patients subjected to IR‐related surgeries. In a murine model of hepatic IR, the level of miR‐210 was increased in hepatocytes but not in nonparenchymal cells. miR‐210 deficiency remarkably alleviated liver injury, cell inflammatory responses, and cell death in a mouse hepatic IR model. In vitro, inhibition of miR‐210 decreased hypoxia/reoxygenation (HR)–induced cell apoptosis of primary hepatocytes and LO2 cells, whereas overexpression of miR‐210 increased cells apoptosis during HR. Mechanistically, miR‐210 directly suppressed mothers against decapentaplegic homolog 4 (SMAD4) expression under normoxia and hypoxia condition by directly binding to the 3′ UTR of SMAD4. The pro‐apoptotic effect of miR‐210 was alleviated by SMAD4, whereas short hairpin SMAD4 abrogated the anti‐apoptotic role of miR‐210 inhibition in primary hepatocytes. Further studies demonstrated that hypoxia‐induced SMAD4 transported into nucleus, in which SMAD4 directly bound to the promoter of miR‐210 and transcriptionally induced miR‐210, thus forming a negative feedback loop with miR‐210. Conclusions Our study implicates a crucial role of miR‐210‐SMAD4 interaction in hepatic IR‐induced cell death and provides a promising therapeutic approach for liver IR injury.