Increased arginase activity and endothelial dysfunction in human inflammatory bowel disease.
Nitric oxide (.NO) generation from conversion of l-arginine to citrulline by nitric oxide synthase isoforms plays a critical role in vascular homeostasis. Loss of .NO is linked to vascular pathophysiology and is decreased in chronically inflamed gut blood vessels in inflammatory bowel disease (IBD; Crohn's disease and ulcerative colitis). Mechanisms underlying decreased .NO production in IBD gut microvessels are not fully characterized. Loss of .NO generation may result from increased arginase (AR) activity, which enzymatically competes with nitric oxide synthase for the common substrate l-arginine. We characterized AR expression in IBD microvessels and endothelial cells and its contribution to decreased .NO production. AR expression was assessed in resected gut tissues and human intestinal microvascular endothelial cells (HIMEC). AR expression significantly increased in both ulcerative colitis and Crohn's disease microvessels and submucosal tissues compared with normal. TNF-alpha/lipopolysaccharide increased AR activity, mRNA and protein expression in HIMEC in a time-dependent fashion. RhoA/ROCK pathway, a negative regulator of .NO generation in endothelial cells, was examined. The RhoA inhibitor C3 exoenzyme and the ROCK inhibitor Y-27632 both attenuated TNF-alpha/lipopolysaccharide-induced MAPK activation and blocked AR expression in HIMEC. A significantly higher AR activity and increased RhoA activity were observed in IBD submucosal tissues surrounding microvessels compared with normal control gut tissue. Functionally, inhibition of AR activity decreased leukocyte binding to HIMEC in an adhesion assay. Loss of .NO production in IBD microvessels is linked to enhanced levels of AR in intestinal endothelial cells exposed to chronic inflammation in vivo.
Horowitz
Scott
S
Dept. of Medicine, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA.
Binion
David G
DG
Nelson
Victoria M
VM
Kanaa
Yasmin
Y
Javadi
Pooria
P
Lazarova
Zelmira
Z
Andrekopoulos
Christopher
C
Kalyanaraman
Balaraman
B
Otterson
Mary F
MF
Rafiee
Parvaneh
P
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D001119:Arginase / Q000378:metabolism*; D001120:Arginine / Q000494:pharmacology; D001905:Botulinum Toxins / Q000494:pharmacology; D015815:Cell Adhesion Molecules / Q000502:physiology; D003424:Crohn Disease / Q000503:physiopathology; D004727:Endothelium / Q000503:physiopathology*; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000503:physiopathology*; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology; D009569:Nitric Oxide / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014633:Valine / Q000494:pharmacology; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000502:physiology
D000577:Amides; D015815:Cell Adhesion Molecules; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D011725:Pyridines; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C108830:Y 27632; D009569:Nitric Oxide; D001120:Arginine; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D001905:Botulinum Toxins; D001119:Arginase; D020742:rhoA GTP-Binding Protein; D014633:Valine