Heme oxygenase-1 mediates cytoprotection against nitric oxide-induced cytotoxicity via the cGMP pathway in human pulp cells.
OBJECTIVE
This study examined the effects of exogenous nitric oxide (NO) on human pulp cells and the involvement of cyclic 3',5'-monophosphate (cGMP) in pulpal protection induced by heme oxygenase-1 (HO-1) against NO-induced cytotoxicity.


METHODS
This study investigated cytotoxicity and HO-1 induction in pulp cells induced by the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP), by using Western blotting and a cell viability assay. It also investigated whether HO-1 contributes to the cytoprotective effect against the cytotoxicity caused by NO and the relationship between HO-1 and cGMP in the signaling pathway.


RESULTS
S-nitroso-N-acetyl-D,L-penicillamine decreased cell viability, but increased HO-1 expression in a concentration- and time-dependent manner in human pulp cells. NO-induced cytotoxicity was inhibited in the presence of hemin (inducer of HO-1), whereas it was enhanced in the presence of zinc protoporphyrin IX (ZnPP IX, HO-1 inhibitor); therefore, the NO-induced cytotoxicity was correlated with HO-1 expression. Pretreatment with a membrane-permeable cGMP analog, 8-bromo-cGMP, restored cell death and enhanced the HO-1 protein expression induced by SNAP. By contrast, 1 mM SNAP inhibited guanylate cyclase in pulp cells pretreated with 1H-[1,2,4]oxadiazole[4,3-alpha]quinoxalin-1-one (ODQ), resulting in marked cytotoxicity.


CONCLUSIONS
These findings of a link between HO-1, regulated via the cGMP system and NO-induced cytotoxicity in human pulp cells, suggest a protective role for HO-1 in pulpal inflammation.
Min
Kyung-San
KS
Department of Conservative Dentistry, College of Dentistry, Wonkwang University, Iksan, South Korea.
Hwang
Young-Hee
YH
Ju
Hyun-Jin
HJ
Chang
Hoon-Sang
HS
Kang
Kyung-Hwa
KH
Pi
Sung-Hee
SH
Lee
Sun-Kyung
SK
Lee
Suk-Keun
SK
Kim
Eun-Cheol
EC
D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism*; D019610:Cytoprotection / Q000502:physiology; D003782:Dental Pulp / Q000166:cytology / Q000201:enzymology*; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D051547:Heme Oxygenase-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000633:toxicity*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D011524:Protoporphyrins; D011810:Quinoxalines; C110881:S-nitro-N-acetylpenicillamine; C017803:zinc protoporphyrin; D009569:Nitric Oxide; D006427:Hemin; D051547:Heme Oxygenase-1; D006162:Guanylate Cyclase; D010396:Penicillamine; D006152:Cyclic GMP