Heme oxygenase 1, nuclear factor E2-related factor 2, and nuclear factor kappaB are involved in hemin inhibition of type 2 cationic amino acid transporter expression and L-Arginine transport in stimulated macrophages.
BACKGROUND
L-Arginine transport mediated by type 2 cationic amino acid transporter (CAT-2) is one crucial mechanism that regulates nitric oxide production mediated by inducible nitric oxide synthase. Heme oxygenase (HO)-1 induction has been reported to significantly attenuate inducible nitric oxide synthase expression and nitric oxide production. The authors sought to explore the effects of HO-1 induction on CAT-2 expression and L-arginine transport. The effects of HO-1 induction on nuclear factor E2-related factor 2 (Nrf2) and nuclear factor kappaB (NF-kappaB) were also investigated.


METHODS
Murine macrophages (RAW264.7 cells) were randomized to receive lipopolysaccharide, lipopolysaccharide plus hemin (an HO-1 inducer; 5, 50, or 500 microm), lipopolysaccharide plus hemin (5, 50, or 500 microm) plus tin protoporphyrin (an HO-1 inhibitor), or lipopolysaccharide plus hemin (5, 50, or 500 microm) plus hemoglobin (a carbon monoxide scavenger). Then, cell cultures were harvested and analyzed.


RESULTS
Lipopolysaccharide significantly induced Nrf2 activation and HO-1 expression. Lipopolysaccharide also significantly induced NF-kappaB activation, CAT-2 expression, and L-arginine transport. In a dose-dependent manner, hemin enhanced the lipopolysaccharide-induced Nrf2 activation and HO-1 expression. In contrast, hemin, also in a dose-dependent manner, significantly attenuated the lipopolysaccharide-induced NF-kappaB activation, CAT-2 expression, and L-arginine transport. Furthermore, the effects of hemin were significantly reversed by both tin protoporphyrin and hemoglobin.


CONCLUSIONS
HO-1 induction significantly inhibited CAT-2 expression and L-arginine transport in lipopolysaccharide-stimulated macrophages, possibly through mechanisms involved activation of Nrf2 and inhibition of NF-kappaB. In addition, carbon monoxide mediated, at least in part, the effects of HO-1 induction on CAT-2 expression and L-arginine transport.
Tsai
Pei-Shan
PS
Department of Anesthesiology, Mackay Memorial Hospital, Nursing and Management College, Taipei, Taiwan, Republic of China.
Chen
Chien-Chuan
CC
Tsai
Pei-Shan
PS
Yang
Lin-Cheng
LC
Huang
Wan-Yu
WY
Huang
Chun-Jen
CJ
D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D002248:Carbon Monoxide / Q000378:metabolism; D027202:Cationic Amino Acid Transporter 2 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D003600:Cytosol / Q000737:chemistry; D051547:Heme Oxygenase-1 / Q000502:physiology*; D006427:Hemin / Q000494:pharmacology*; D006454:Hemoglobins / Q000494:pharmacology; D015151:Immunoblotting; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008665:Metalloporphyrins / Q000494:pharmacology; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D016328:NF-kappa B / Q000502:physiology*; D011524:Protoporphyrins / Q000494:pharmacology
D027202:Cationic Amino Acid Transporter 2; D006454:Hemoglobins; D008070:Lipopolysaccharides; D008665:Metalloporphyrins; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; D011524:Protoporphyrins; D006427:Hemin; D002248:Carbon Monoxide; D001120:Arginine; C032628:tin protoporphyrin IX; D051547:Heme Oxygenase-1