• Ping Jia, Xiaoli Wu, Yan Dai, Jie Teng, Yi Fang, Jiachang Hu, Jianzhou Zou, Mingyu Liang, and Xiaoqiang Ding.
• 1Division of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.2Traditional Chinese Medicine Pharmacology Laboratory, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.3Department of Physiology, Medical College of Wisconsin, Milwaukee, WI.4Kidney and Dialysis Institute of Shanghai, Shanghai, China.5Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China.
• Crit. Care Med. 2017 Jul 1; 45 (7): e703-e710.

ObjectiveSepsis, triggered by microbial infection, is a common and life-threatening systemic illness, often leads to impaired function of vital organs. Ischemic preconditioning induced by transient brief episodes of ischemia is a powerful innate mechanism of organ protection. We have reported that a 15-minute renal ischemic preconditioning substantially attenuated subsequent renal ischemia-reperfusion injury. Here, we investigate whether a brief ischemia and reperfusion in kidney can provide protection at local and remote sites against sepsis-induced organ injury, and whether this protection is microRNA-21 dependent.DesignLaboratory study.SettingUniversity laboratory.SubjectsMouse renal tubular epithelial cells, C57BL/6 J wildtype (Animal Center of Fudan University, Shanghai, China) and microRNA-21-/- mice (B6.129-Mir21atm1Smoc, Shanghai Biomodel Organism Science & Technology Development Co. Shanghai, China).InterventionsMouse renal tubular epithelial cells were treated with hypoxia (2% oxygen). Renal ischemic preconditioning was induced by bilateral renal pedicle clamping for 15 minutes, and sepsis was induced by a single intraperitoneal injection of lipopolysaccharide at a dose of 20 mg/kg or cecal ligation and puncture in mice.Measurements And Main ResultsMice treated with renal ischemic preconditioning were protected from endotoxemia or polymicrobial sepsis-induced multiple organ injury, including kidneys, heart, liver, and lungs. Renal ischemic preconditioning induced activation of hypoxia-inducible factor-1α in kidneys, which up-regulated microRNA-21 at transcriptional level, subsequently, leading to increased expression of microRNA-21 in serum exosomes and remote organs, resulting in decreased apoptosis and reduced proinflammatory cytokines production in these organs. In vivo knockdown of microRNA-21 or genetic deletion of microRNA-21 abrogated the organoprotective effects conferred by renal ischemic preconditioning. Mechanistically, we discovered that knockdown of microRNA-21 increased programmed cell death protein 4 expression and nuclear factor-kappa B activity, decreased expression of anti-apoptotic B-cell lymphoma-2.ConclusionMicroRNA-21 is required for local and remote ischemic preconditioning in multiple organ protection against sepsis, and up-regulation of miR-21 may be a potential therapy for sepsis.

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