Hepatitis C virus infection down-regulates the expression of peroxisome proliferator-activated receptor α and carnitine palmitoyl acyl-CoA transferase 1A

AIM: To elucidate the role of the peroxisome proliferator-activated receptor alpha (PPAR alpha) and its target gene carnitine palmitoyl acyl-CoA transferase 1A (CPT1A) in the pathogenesis of hepatitis C virus (HCV) infection. METHODS: Liver samples were collected from the patients with chronic HCV infection and controls. HepG2 cells were transfected with vector pEF352neo carrying. Two independent clones (clone N3 and N4) stably expressing HCV core protein were analyzed. Total RNA was extracted from cells and liver tissues. PPAR alpha and CPT1A mRNAs were quantified by real-time polymerase chain reaction (PCR) using SYBR Green Master. Total extracted proteins were separated by polyacrylamide gel electrophoresis, and electroblotted. Membranes were incubated with the anti-PPAR alpha antibody, then with a swine anti-rabbit IgG conjugated to horseradish peroxidase for PPAR alpha. Protein bands were revealed by an enhanced chemiluminescence reaction for PPAR alpha. For immunohistochemical staining of PPAR alpha, sections were incubated with the primary goat polyclonal antibody directed against PPAR alpha at room temperature. RESULTS: Real-time PCR indicated that the PPAR alpha level and expression level of CPT1A gene in hepatitis C patients lowered significantly as compared with the controls (1.8 +/- 2.8 vs 13 +/- 3.4, P = 0.0002; 1.1 +/- 1.5 vs 7.4 +/- 1, P = 0.004). Western blot results showed that the level of PPAR alpha protein in the livers of hepatitis C patients was lower than that in controls (2.3 +/- 0.3 vs 3.6 +/- 0.2, P = 0.009). The immunohistochemical staining results in chronic hepatitis C patients indicated a decrease in PPAR alpha staining in hepatocytes compared with those in the control livers. The in vitro studies found that in the N3 and N4 colon stably expressing HCV core protein, the PPAR alpha mRNA levels were significantly lower than that in the controls. CONCLUSION: The impaired intrahepatic PPAR alpha expression is associated with the pathogenic mechanism in hepatic injury during chronic HCV infection. HCV infection reduced the expression of PPAR alpha and CPT1A at the level of not only mRNAs but also proteins. PPAR alpha plays an important role in the pathogenesis of chronic HCV infection, but the impaired function of this nuclear receptor in HCV infection needs further studies. (C) 2005 The WJG Press and Elsevier Inc. All rights reserved.