Effects of aminoguanidine on nitric oxide production induced by inflammatory cytokines and endotoxin in cultured rat hepatocytes.
OBJECTIVE
To study the effects of aminoguanidine (AG) and two L-arginine analogues N(omega)-nitro-L-arginine methyl ester (L-NAME) and N(omega)-nitro-L-arginine (L-NNA) on nitric oxide (NO) production induced by cytokines (TNF-alpha, IL-1 beta, and IFN-gamma) and bacterial lipopolysaccharide (LPS) mixture (CM) in the cultured rat hepatocytes, and examine their mechanisms action.


METHODS
Rat hepatocytes were incubated with AG, L-NAME, L-NNA, Actinomycin D (ActD) and dexamethasone in a medium containing CM (LPS plus TNF-alpha, IL-1 beta, and IFN-gamma) for 24h. NO production in the cultured supernatant was measured with the Griess reaction. Intracellular cGMP level was detected with radioimmunoassy.


RESULTS
NO production was markedly blocked by AG and L-NAME in a dose-dependent manner under inflammatory stimuli condition triggered by CM in vitro. The rate of the maximum inhibitory effects of L-NAME (38.9%) was less potent than that obtained with AG(53.7%, P < 0.05). There was no significant difference between the inhibitory effects of AG and two L-arginine analogues on intracellular cGMP accumulation in rat cultured hepatocytes. Non-specific NOS expression inhibitor dexamethasone (DEX)and iNOS mRNA transcriptional inhibitor ActD also significantly inhibited CM-induced NO production. AG(0.1 mmol x L(-1)) and ActD (0.2 ng x L(-1)) were equipotent in decreasing NO production induced by inflammatory stimuli in vitro, and both effects were more potent than that induced by non-selectivity NOS activity inhibitor L-NAME (0.1 mmol x L(-1)) under similar stimuli conditions (P<0.01).


CONCLUSIONS
AG is a potent selective inhibitor of inducible isoform of NOS,and the mechanism of action may be not only competitive inhibition in the substrate level, but also the gene expression level in rat hepatocytes.
Zhang
G L
GL
Department of Pharmacology, School of Basic Medical Sciences, Beijing University, Beijing 100083, China. yuankui@public.bta.net.cn
Wang
Y H
YH
Teng
H L
HL
Lin
Z B
ZB
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology*; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005938:Glucocorticoids / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000970:Antineoplastic Agents; D016207:Cytokines; D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D006146:Guanidines; D007375:Interleukin-1; D008070:Lipopolysaccharides; D011500:Protein Synthesis Inhibitors; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; D019335:Nitroarginine; D009569:Nitric Oxide; D003907:Dexamethasone; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; C004479:pimagedine; D019331:NG-Nitroarginine Methyl Ester