Carbon monoxide rescues ischemic lungs by interrupting MAPK-driven expression of early growth response 1 gene and its downstream target genes.
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 signal-regulated kinase (ERK) activation, Egr-1 expression, and Erg DNA-binding 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-alpha. 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, hypoxia-induced Egr-1 mRNA expression was ERK-dependent, and CO-mediated 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 cAMP/protein 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.
Department of Internal Medicine, University of Michigan, 3119N Taubman Center, 1500 East Medical Center Drive, Ann Arbor, MI 48109, USA.
Snigdha
S
Mishra
Tomoyuki
T
Fujita
Vibha N
VN
Lama
Douglas
D
Nam
Hui
H
Liao
Morihito
M
Okada
Kanji
K
Minamoto
Yasushi
Y
Yoshikawa
Hiroaki
H
Harada
David J
DJ
Pinsky
D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006085:Graft Survival; D000860:Hypoxia / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007511:Ischemia / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008171:Lung Diseases / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016040:Lung Transplantation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D051381:Rats
D051766:Early Growth Response Protein 1; D009569:Nitric Oxide; D002248:Carbon Monoxide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D006152:Cyclic GMP