HO-1 overexpression attenuates endotoxin effects on CAT-2 isozymes expression.
BACKGROUND
l-arginine transport mediated by type-2 cationic amino acid transporter (CAT-2) isozymes is one crucial mechanism that regulates nitric oxide (NO) production via inducible nitric oxide synthase (iNOS). We sought to investigate the effects of heme oxygenase-1 (HO-1) overexpression on CAT-2 isozymes, e.g., CAT-2, CAT-2A, and CAT-2B.


METHODS
Adult male Sprague Dawley rats were allocated to receive lipopolysaccharide (LPS), normal saline, hemin (a HO-1 inducer), tin protoporphyrin (SnPP, a HO-1 inhibitor), LPS plus hemin, or LPS plus hemin plus SnPP. After maintaining for 6 h, rats were sacrificed and the expression and activity of individual enzyme was evaluated.


RESULTS
LPS increased HO activity, HO-1 concentration, NO production, l-arginine transport, and concentrations of iNOS, CAT-2, and CAT-2B in rat lungs and kidney. LPS also increased HO activity, HO-1 concentration, NO production, l-arginine transport, and iNOS concentration but decreased CAT-2 and CAT-2B concentrations in rat liver. LPS increased CAT-2A concentration in rat liver but did not affect CAT-2A concentration in rat lungs and kidney. Hemin further increased HO activity and induced HO-1 overexpression in the lungs, kidney, and liver from LPS-treated rats. In addition, the effects of LPS on NO production, l-arginine transport, and concentrations of iNOS and CAT-2 isozymes were significantly attenuated by hemin. SnPP, on the other hand, reversed the effects of hemin.


CONCLUSIONS
HO-1 overexpression significantly attenuates endotoxin-induced increases in NO production and l-arginine transport. Induction of HO-1 overexpression also significantly attenuates the effects of endotoxin on the expression of iNOS and CAT-2 isozymes in septic rats.
Huang
Te-Yang
TY
Department of Orthopedics, Mackay Memorial Hospital, Taipei, Taiwan.
Tsai
Pei-Shan
PS
Huang
Chun-Jen
CJ
D000818:Animals; D001120:Arginine / Q000378:metabolism; D027202:Cationic Amino Acid Transporter 2 / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004731:Endotoxins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006427:Hemin / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008168:Lung / Q000187:drug effects / Q000201:enzymology; D008297:Male; D008665:Metalloporphyrins / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011524:Protoporphyrins / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018805:Sepsis / Q000378:metabolism*
D027202:Cationic Amino Acid Transporter 2; D004731:Endotoxins; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008070:Lipopolysaccharides; D008665:Metalloporphyrins; D011524:Protoporphyrins; D009569:Nitric Oxide; D006427:Hemin; D001120:Arginine; C032628:tin protoporphyrin IX; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1