Carbon monoxide rescues ischemic lungs by interrupting MAPK-driven expression of early growth response 1 gene and its downstream target genes

Abstract

Carbon monoxide (CO), an endogenous cytoprotective product of heme oxygenase type-1 regulates target thrombotic and inflammatory genes in ischemic stress. Regulation of the gene encoding early growth response 1 (Egr-1), a potent transcriptional activator of deleterious thrombotic and inflammatory cascades, may govern CO-mediated ischemic lung protection. The exact signaling mechanisms underlying CO-mediated cytoprotection are not well understood. In this study we tested the hypothesis that inhibition of mitogen-activated protein kinase-dependent Egr-1 expression may be pivotal in CO-mediated ischemic protection. In an in vivo isogeneic rat lung ischemic injury model, inhaled CO not only diminished fibrin accumulation and leukostasis and improved gas exchange and survival but also suppressed extracellular signalregulated kinase (ERK) activation, Egr-1 expression, and Erg DNAbinding activity in lung tissue. Additionally, CO-mediated inhibition of Egr-1 reduced expression of target genes, such as tissue factor, serpine-1, interleukin-1, and TNF-␣. However, CO failed to inhibit serpine-1 expression after unilateral lung ischemia in mice null for the Egr-1 gene. In RAW macrophages in vitro, hypoxiainduced Egr-1 mRNA expression was ERK-dependent, and COmediated suppression of ERK activation resulted in Egr-1 inhibition. Furthermore, CO suppression of ERK phosphorylation was reversed by the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one but was insensitive to cAMP-dependent protein kinase A inhibition with H89 and NO synthase inhibition with L-nitroarginine methyl ester. This finding indicates that CO suppresses ERK in a cGMP-dependent but cAMP͞protein kinase A-and NO-independent manner. Together, these data identify a unifying molecular mechanism by which CO interrupts proinflammatory and prothrombotic mediators of ischemic injury.

GGPPS, a New EGR-1 Target Gene, Reactivates ERK 1/2 Signaling through Increasing Ras Prenylation

“…It has been reported that ERK 1/2 also regulates the activation of EGR-1. 33 Here we found that EGR-1 could also provide positive feedback to regulate Ras activation through its target gene GGPPS under CSE . The cells were then lysed and separated into membrane (P100) and cytosolic (S100) portions and subjected to immunoprecipitation and Western blotting against K-Ras and glyceraldehydes-3-phosphate dehydrogenase (GADPH), which was used to show that the separation of membrane and cytosol was successful.…”

“…[33][34][35][36][37][38] We have suggested that EGR-1 can also stimulate HSP70 elevation in an ERK 1/2-dependent manner, which is thought to regulate cigarette smoke-induced inflammatory processes. 18 Here we provide the first evidence that EGR-1 could activate MAPK ERK 1/2 in a positive feedback manner through increasing Ras prenylation by promoting GGPPS transcription in lung epithelial cells during CSE challenge (Figure 6).…”

Does activation of the blood coagulation cascade have a role in malaria pathogenesis?

“…; it has also been reported that carbon monoxide (CO) suppresses the pathogenesis of experimental cerebral malaria 45 . While pleiotropic mechanisms may explain the action of these gazes 45 47 48, it is documented that NO negatively modulates endothelium activation and platelet function 52 whereas CO inhibits the expression of pro-inflammatory genes (e.g., TF and TNF-α) and prevents inflammatory events in vivo 53 . Finally, the finding that TF is potentially a crucial mediator of malaria pathogenesis suggests that therapeutics targeting TF and/or EC 54 could be useful in the treatment of malaria and/or its complications 4,55 .…”

Dissecting the Factors Involved in the Locomotion Mode of Neuronal Migration in the Developing Cerebral Cortex

“…The concentrations of inhibitors were determined by referring to previous in vitro studies that used cultured cells (27)(28)(29)(30)(31)(32)(33)(34).…”