AICAR decreases acute lung injury by phosphorylating AMPK and upregulating heme oxygenase-1
Israr Ahmad, Adam Molyvdas, Ming‐Yuan Jian, Ting Zhou, Amie Traylor, Huachun Cui, Gang Liu, Weifeng Song, Anupam Agarwal, Tamás Jilling, Saurabh Aggarwal, Sadis Matalon
Abstract
Aim We investigated the mechanisms by which N1-(β-d-ribofuranosyl)-5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an activator of AMP-activated protein kinase (AMPK), decreases lung injury and mortality when administered to mice post exposure to bromine gas (Br 2 ). Methods We exposed male C57BL/6 mice and heme oxygenase-1 (HO-1)-deficient (HO-1 −/− ) and corresponding wild-type (WT) littermate mice to Br 2 (600 ppm for 45 or 30 min, respectively) in environmental chambers and returned them to room air. AICAR was administered 6 h post exposure (10 mg·kg −1 , intraperitoneal). We assessed survival, indices of lung injury, high mobility group box 1 (HMGB1) in the plasma, HO-1 levels in lung tissues and phosphorylation of AMPK and its upstream liver kinase B1 (LKB1). Rat alveolar type II epithelial (L2) cells and human club-like epithelial (H441) cells were also exposed to Br 2 (100 ppm for 10 min). After 24 h we measured apoptosis and necrosis, AMPK and LKB1 phosphorylation, and HO-1 expression. Results There was a marked downregulation of phosphorylated AMPK and LKB1 in lung tissues and in L2 and H441 cells post exposure. AICAR increased survival in C57BL/6 but not in HO-1 −/− mice. In WT mice, AICAR decreased lung injury and restored phosphorylated AMPK and phosphorylated LKB1 to control levels and increased HO-1 levels in both lung tissues and cells exposed to Br 2 . Treatment of L2 and H441 cells with small interfering RNAs against nuclear factor erythroid 2-related factor 2 or HO-1 abrogated the protective effects of AICAR. Conclusions Our data indicate that the primary mechanism for the protective action of AICAR in toxic gas injury is the upregulation of lung HO-1 levels.