Arginase blockade protects against hepatic damage in warm ischemia-reperfusion.
BACKGROUND
Liver ischemia reperfusion (I/R) injury is associated with profound arginine depletion due to arginase release from injured hepatocytes. Nitric oxide (NO), shown to have protective effects in I/R, is produced by nitric oxide synthase (NOS) from the substrate arginine. The purpose of this study was to determine if nor-NOHA, a novel arginase inhibitor, would be able to increase circulating arginine levels and decrease hepatic damage following warm I/R.


METHODS
C57BL/6 mice underwent partial liver warm I/R and were treated intraperitoneally with either nor-NOHA (100mg/kg) or saline. Serum and tissue samples were collected to measure liver enzyme levels, amino acids, and inflammatory mediators. The agent nor-NOHA (100mg/kg) was administered 15 min before ischemia and immediately after reperfusion. Serum amino acid analysis was performed using HPLC.


RESULTS
Arginase activity after hepatic I/R peaked at 3-6h after reperfusion and resulted in a 10-fold drop in circulating arginine levels. Treatment with nor-NOHA inhibited arginase activity and reversed the arginine depletion after I/R while simultaneously increasing serum nitric oxide. In addition, circulating citrulline, a product of NOS activity, was increased in nor-NOHA-treated animals compared to controls. Inhibition of arginase also resulted in protection from hepatic I/R-induced damage in association with markedly lower hepatic TNF, IL-6, and inducible NOS mRNA levels compared to controls.


CONCLUSIONS
Arginase blockade represents a potentially novel strategy to combat liver injury under conditions of arginine deficiency. This protection may be mediated through the arginine-NO pathway.
Jeyabalan
Geetha
G
Department of Surgery, University of Pittsburgh, Starzl Transplantation Institute, 3459 Fifth Avenue, MUH 7 South, Pittsburgh, PA 15213, USA.
Klune
John R
JR
Nakao
Atsunori
A
Martik
Nicole
N
Wu
Guoyao
G
Tsung
Allan
A
Geller
David A
DA
D000596:Amino Acids / Q000097:blood; D000818:Animals; D001119:Arginase / Q000494:pharmacology / Q000627:therapeutic use*; D001120:Arginine / Q000031:analogs & derivatives; D002851:Chromatography, High Pressure Liquid; D015850:Interleukin-6 / Q000378:metabolism; D008107:Liver Diseases / Q000188:drug therapy* / Q000473:pathology / Q000517:prevention & control*; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015427:Reperfusion Injury / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D048069:Tumor Necrosis Factors / Q000378:metabolism; D052096:Warm Ischemia
D000596:Amino Acids; D015850:Interleukin-6; C404735:N(omega)-hydroxynorarginine; D012333:RNA, Messenger; D048069:Tumor Necrosis Factors; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D001119:Arginase