Related Experiment Videos
Distribution of nitric oxide synthase in normal and cirrhotic human liver
Lance McNaughton1, Lakshmi Puttagunta, Maria Angeles Martinez-Cuesta
1Departments of Pharmacology, Laboratory Medicine and Pathology, Surgery, and Medicine, University of Alberta, Edmonton, AB, Canada T6G 2H7.
Insights
Chronic liver disorders are a major health concern. This study reveals altered expression of nitric oxide synthase (NOS) proteins, specifically inducible NOS (iNOS) and endothelial NOS (eNOS), in diseased human livers.
Area of Science:
- Hepatology
- Molecular Biology
- Biochemistry
Background:
- Chronic liver disorders pose a significant global health burden.
- Nitric oxide synthase (NOS) plays a role in hepatic vasculature, but its expression in healthy and diseased human livers is not well understood.
Purpose of the Study:
- To investigate the expression patterns and activity of endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS) in healthy and diseased human liver tissues.
- To determine how NOS protein expression is altered in various chronic liver conditions.
Main Methods:
- Analysis of human liver sections (n=42 diseased, n=14 control) using citrulline assay, Western immunoblot, immunohistochemistry, and in situ hybridization.
- Measurement of plasma nitric oxide (NO) metabolites via HPLC.
- Inclusion of diverse liver pathologies: alcoholic cirrhosis, viral hepatitis, cholestasis, acute necrosis, and alpha(1)-anti-trypsin disorder.
Main Results:
- In healthy livers, eNOS was uniformly distributed in hepatocytes and vasculature, while iNOS was localized to the periportal zone.
- Diseased livers, particularly cirrhotic ones, showed a significant increase in Ca(2+)-independent NOS activity and iNOS expression.
- eNOS was observed to translocate to hepatocyte nuclei in diseased liver samples.
Conclusions:
- Endothelial NOS (eNOS) and inducible NOS (iNOS) are differentially expressed in healthy human liver.
- Liver disease, especially cirrhosis, significantly alters the expression and localization of eNOS and iNOS proteins.
Abstract:
Chronic liver disorders represent a serious health problem, considering that 300 million people worldwide are hepatitis B virus carriers, and 8,000-10,000 patients per year, in the U.S. alone, die as a result of liver failure caused by hepatitis C infection. Nitric oxide synthase (NOS) regulates hepatic vasculature; however, the patterns of expression and activity of NOS proteins in healthy and diseased human livers are unknown. Sections of diseased (n = 42) and control livers (n = 14) were collected during orthotopic liver transplants and partial hepatectomy. The diseased sections included alcoholic cirrhosis, viral hepatitis, cholestasis, acute necrosis, and uncommon pathologies including alpha(1)-anti-trypsin disorder. The endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS) were studied by using the citrulline assay, Western immunoblot, immunohistochemistry, and in situ hybridization. The systemic generation of plasma NO metabolites was measured by HPLC. In control livers, Ca(2+)-dependent and -independent NOS activities were identified by Western analysis as eNOS and iNOS, respectively. The eNOS was uniformly distributed in the hepatocytes and also detected in the endothelium of hepatic arteries, terminal hepatic venules, sinusoids, and in biliary epithelium. The iNOS was detected in hepatocytes and localized mainly in the periportal zone of the liver acinus. This pattern of distribution of eNOS and iNOS in normal liver was confirmed by in situ hybridization. In diseased livers, there was a significant increase in Ca(2+)-independent NOS with the corresponding strong appearance of iNOS in the cirrhotic areas. The eNOS was translocated to hepatocyte nuclei. Thus, eNOS and iNOS proteins are differentially expressed in healthy human liver, and this expression is significantly altered in cirrhotic liver disorders.