Nitric oxide modulates hypoxic pulmonary smooth muscle cell proliferation and apoptosis by regulating carbon monoxide pathway.
OBJECTIVE
To explore the role of carbon monoxide (CO) in the regulation of hypoxic pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis by nitric oxide (NO).


METHODS
PASMC of Wistar rats was cultured in vitro in the presence of a NO donor, sodium nitroprusside, or an inhibitor of heme oxygenase (HO), zinc protoporphyrin-IX, or under both normoxic and hypoxic conditions. Nitrite and carboxyhemoglobin in PASMC medium were detected with spectrophotometry. The proliferating and apoptotic percentage of PASMC was measured by flow cytometry. The expression of HO-1 mRNA in PASMC was analyzed by fluorescent real-time quantitative PCR, and the proliferating cell nuclear antigen and caspase-3 were examined by immunocytochemical analysis.


RESULTS
The results showed that hypoxia suppressed NO generation from PASMC, which promoted hypoxic PASMC proliferation and induced apoptosis. Meanwhile, hypoxia induced HO-1 expression in PASMC and promoted CO production from PASMC, which inhibited PASMC proliferation and regulated PASMC apoptosis. NO upregulated the expression of HO-1 mRNA in hypoxic PASMC; NO also inhibited proliferation and promoted apoptosis of hypoxic PASMC, possibly by regulating the production of CO.


CONCLUSIONS
The results indicated that CO could inhibit proliferation and regulate apoptosis of PASMC, and NO inhibited proliferation and promoted apoptosis of hypoxic PASMC, possibly by regulating the production of CO.
Wang
Yan-Fei
YF
Department of Pediatrics, Peking University First Hospital, Beijing 100034, China.
Tian
Hong
H
Tang
Chao-Shu
CS
Jin
Hong-Fang
HF
Du
Jun-Bao
JB
D000818:Animals; D017209:Apoptosis; D002248:Carbon Monoxide / Q000378:metabolism / Q000502:physiology*; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002478:Cells, Cultured; D005434:Flow Cytometry; D051547:Heme Oxygenase-1 / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology; D011651:Pulmonary Artery / Q000166:cytology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
D020030:Nitric Oxide Donors; D011524:Protoporphyrins; D012333:RNA, Messenger; C017803:zinc protoporphyrin; D009599:Nitroprusside; D009569:Nitric Oxide; D002248:Carbon Monoxide; D051547:Heme Oxygenase-1