[An experimental study on the reverse mechanism of PPAR-gamma agonist rosiglitazone in rats with non-alcoholic steatohepatitis].

OBJECTIVE: To investigate the influence and significance of peroxisome proliferator- activated receptor-gamma (PPAR-gamma) agonist rosiglitazone on the expression of I kappa B kinase-beta(IKK-beta) mRNA and protein induced by LPS in Kupffer cells (KCs) cultured in vitro and to investigate the activity of nuclear factor-kappa B (NF-kappa B) together with the expression of cyclooxygenase-2 (COX-2) in livers of rats with non-alcoholic steatohepatitis (NASH).

METHODS: (1) KCs from healthy Wistar rats were isolated and purified with IV collagenase digestion and gradient centrifugalization, and then were incubated in the presence or absence of LPS (1 microg/ml) together with two different concentrations of rosiglitazone (10 nmol/L and 50 nmol/L). (2) Thirty-eight healthy Wistar rats were randomly divided into a normal blank control group (10 rats) fed with a normal diet and a NASH model group (28 rats) fed with a fat-rich diet (10% lard + 2% cholesterol + 5% corn oil). After the NASH model was established successfully and confirmed by pathological examination of the livers of 4 rats, 24 rats that continued with the high fat-rich diet, were divided into three groups (8 rats in each group): a control group fed normal saline (NS), a lower dose rosiglitazone group (1 mg.kg(-1).d(-1)) and a higher dose rosiglitazone group (4 mg.kg(-1).d(-1)) for 12 weeks. The mRNA expression of IKK-beta in KCs and COX-2 in livers were measured using reverse transcription-polymerase chain reaction (RT-PCR). The IKK-beta protein in KCs and the NF-kappa B activity of hepatic tissues were determined respectively by Western blot and electrophoretic mobility shift assay (EMSA). The concentration of tumor necrosis factor alpha (TNF alpha) in the supernatant of KCs cultures and serum of the rats was quantified by enzyme linked immunosorbent assay (ELISA).

RESULTS: LPS significantly increased the expression of IKK-beta mRNA and protein in the KCs and the concentration of TNF alpha in the supernatant of the KCs cultures. The expressions of COX-2 mRNA and protein were more obvious in rats with NASH than those in the normal control group, and the binding activity of NF-kB correlated positively with the expression of COX-2 in the livers and the level of serum TNF alpha of model rats as well. Rosiglitazone blocked the expression of IKK-beta mRNA and protein induced by LPS in KCs, and also inhibited NF-kappa B activation and reduced COX-2 expression in the rats.

CONCLUSIONS: PPAR-gamma specific agonist rosiglitazone can play an anti-inflammatory role by IKK-beta/I kappa B/NF-kappa B/TNF alpha signal ways, and minimize inflammatory reaction at cellular and molecular levels. This may help to provide a new idea for treating NASH effectively.