Proinflammatory cytokines but not acute phase serum amyloid A or C-reactive protein, downregulate paraoxonase 1 (PON1) expression by HepG2 cells

The expression of paraoxonase(1) (PON1) during inflammation has been investigated in vitro. The alteration of steady state PON1 mRNA in HepG2 cells by interleukin-1,8 (IL-1) and tumor necrosis factor-alpha (TNF-alpha), was investigated relative to acute-phase serum amyloid A (A-SAA) mRNA. PON1 mRNA expression by HepG2 cells was decreased within three hours of stimulation by IL-1beta or TNFalpha. Relative to PON1 mRNA expression, the pattern of steady state A-SAA mRNA expression was altered reciprocally and inversely by IL- 1beta. These findings suggested that the decrease in serum PON activity after abdominal surgery in our previous clinical study may he ascribed to a decrease in steady state PON1 mRNA expression by liver with proinflammatory cytokines.