Endothelial PINK1 Mediates the Protective Effects of NLRP3 Deficiency during Lethal Oxidant Injury

Abstract

High levels of inspired oxygen, hyperoxia, are frequently used in patients with acute respiratory failure. Hyperoxia can exacerbate acute respiratory failure, which has high mortality and no specific therapies. We identified a novel roles for PINK1 (PTEN-induced putative kinase 1), a mitochondrial protein, and the cytosolic innate immune protein, NLRP3, in the lung and endothelium. We generated double knockouts (PINK1−/−/NLRP3−/−) as well as cell-targeted PINK1 silencing and lung-targeted overexpression constructs to specifically show that PINK1 mediates cytoprotection in wild type (WT) and NLRP3−/− mice. The ability to resist hyperoxia is proportional to PINK1 expression – PINK1−/− mice were the most susceptible, WT mice, which induced PINK1 after hyperoxia, had intermediate susceptibility and NLRP3−/− mice, which had high basal and hyperoxia-induced PINK1, were the least susceptible. Genetic deletion of PINK1 or PINK1 silencing in the lung endothelium increased susceptibility to hyperoxia via alterations in autophagy/mitophagy, proteasome activation, apoptosis and oxidant generation.

Endothelial CD74 mediates macrophage migration inhibitory factor protection in hyperoxic lung injury

“…We then investigated lung injury at 72 hours, a time point that we have previously shown to be associated with maximal lung injury (2). At 72 hours, Mif 2/2 mice demonstrated significantly increased lung injury as evidenced by increased BAL protein and LDH, increased apoptosis as evidenced by TUNEL staining, increased reactive oxygen species (ROS) production as suggested by measurements of BAL H 2 O 2 , and increased inflammation as suggested by measurements of IL-6 content (Fig.…”

“…Others have described that CD74 is induced on lung endothelial cells in response to stimuli (41). In the lung, CD74 has been demonstrated in type II cells, macrophages, and lymphocyte populations (2,3,42). Most recently, CD74 has been demonstrated in endothelial cells of patients with pulmonary HTN (43,44).…”

“…elevated partial pressures of oxygen can result in oxidative stress, cellular damage, and respiratory impairment (1,2). Optimal treatment of individuals with severe respiratory distress therefore will rely on elucidating protective mechanisms against hyperoxic lung injury.…”

Inflammasome and Autophagy Regulation: A Two-way Street

“…Following group A Streptococcus infection, NLRP4 transiently dissociates from beclin1, allowing it to interact with other autophagy proteins to initiate beclin1-mediated autophagy in macrophages (42). Inflammasome-forming NLRP3 has also been shown to negatively regulate autophagy through downregulation of phosphatase and tensin homolog-induced putative kinase 1 expression, an initiator of mitophagy (43). Zhang et al demonstrated that NL-RP3-deficient mice were protected from hyperoxia exposure, and this protection was driven by increased phosphatase and tensin homolog-induced putative kinase 1 expression and preservation of mitophagy in lung endothelial cells of these mice (43).…”

“…Inflammasome-forming NLRP3 has also been shown to negatively regulate autophagy through downregulation of phosphatase and tensin homolog-induced putative kinase 1 expression, an initiator of mitophagy (43). Zhang et al demonstrated that NL-RP3-deficient mice were protected from hyperoxia exposure, and this protection was driven by increased phosphatase and tensin homolog-induced putative kinase 1 expression and preservation of mitophagy in lung endothelial cells of these mice (43). In addition to NLRP3, NLRC4 can also inhibit autophagy in infection (44).…”