Adrenomedullin Regulates Cellular Glutathione Content via Modulation of γ-Glutamate-Cysteine Ligase Catalytic Subunit Expression

Abstract

Adrenomedullin (AM) participates in a wide range of physiological and pathological processes including vasorelaxation, angiogenesis, cancer promotion, and apoptosis. Recently, it has been reported that AM protects a variety of cells against oxidative stress induced by stressors such as hypoxia, ischemia/reperfusion, and hydrogen peroxide through the phosphatidylinositol 3-kinase (PI3K)-dependent pathway. However, the molecular mechanisms underlying the pathway of cell survival against hypoxic injury are largely unknown. In an effort to investigate the survival mechanism against hypoxic injury, we studied the effects of AM on cellular levels of reactive oxygen species, well-known mediators of cell death after oxidative stress, and the mechanism involved in the regulation of reactive oxygen species levels. Here, we show that AM increases gamma-glutamate-cysteine ligase (gamma-GCL) activity under both hypoxic and normoxic conditions, resulting in an up-regulation of cellular glutathione levels to more than 2-fold higher than basal expression. In addition, we demonstrate that AM induces concentration-dependent expression of the catalytic subunit of gamma-GCL (gamma-GCLC) at the mRNA and protein levels through the activation of the gamma-GCLC promoter fragment sequence from -597 to -320. However, when treated with the PI3K inhibitors, the effects of AM on gamma-GCLC expression were completely abrogated, suggesting that a PI3K pathway linked AM with the transcriptional activation of the gamma-GCLC promoter. Taken together, our data suggests that AM participates in the regulation of cellular redox status via glutathione synthesis. These results may explain, in part, the mechanism by which AM protects cells against oxidative stress.

Quercetin‐induced upregulation of human GCLC gene is mediated by cis‐regulatory element for early growth response protein‐1 (EGR1) in INS‐1 beta‐cells

“…In consistent with our study, others' studies also indicated importance of the GC rich region to be necessary for transcriptional activity [Tomonari et al, 1997]. Although this study did not assessed the ARE and its binding factor Nrf1/2 which have been demonstrated in the induction of GCLC gene by a wide range of stimuli including quercetin [Myhrstad et al, 2002;Dickinson et al, 2003], it is unlikely that the only interaction of ARE sites with Nrf1/2 is sufficient to drive full activation of the gene promoter because GCLC promoter without ARE motifs still significantly responded to various stimuli [Kim et al, 2006b;Kimura et al, 2009]. In addition, cells deficient in Nrf1 or Nrf2 still retained ability to activate GCLC promoter by tert-butylhyroquinone [Yang et al, 2005].…”

Attenuation of Hyperoxia-induced Lung Injury in Rats by Adrenomedullin

“…AM-deficient mice exhibiting a more severe organ injury in multiple systems that were caused by enhanced oxidative stress [15]. AM treatment can increase cellular glutathione levels via upregulation of gamma-glutamate-cysteine ligase (γ-GCL) catalytic subunit expression [16], and attenuate cardiac oxidative stress by inhibiting NADPH oxidase activity [17]. However, the effect of AM on pulmonary oxidative stress and inflammation that could occur during the development of hyperoxia-induced ALI has so far been unclear.…”

Adrenomedullin Deficiency Increases the Susceptibility of Liver Fibrosis Induced by CCl₄

“…The ROS level was greatly increased in the AM HT mice and the AM WT CCl4 group. Previous reports have shown that AM plays a role as an antioxidant in two ways: suppressing ROS production [1,3,8] and promoting the ROS scavenging system [10]. Consequently, the increased ROS might be due to the down-regulated AM.…”

“…GSH is a key regulator of cellular redox and is involved in the maintenance of interior cellular redox balance in mammals [10,23].…”