Chlorophyllin attenuates IFN-gamma expression in lipopolysaccharide-stimulated murine splenic mononuclear cells via suppressing IL-12 production

Abstract

Chlorophyllin (CHL) is a chlorophyll derivative with anticarcinogen and antioxidant activities. Despite clinical importance of CHL as a potential therapeutics for treating cancer patients, little is known about the immunological properties of CHL. In the present study, we investigated the effect of CHL on the activation of murine splenocytes stimulated with lipopolysaccharide (LPS). RT-PCR analysis showed that LPS-activated IFN-gamma expression gradually declined by CHL treatment in a dose dependent manner while mRNA production of TNF-alpha, IL-2, and FasL was not changed. CHL also suppressed IL-12 production (p70, a heterodimer of p40 and p35) and the mRNA expression of IL-12 p40 and IL-12 receptors (both IL-12Rbeta1 and IL-12Rbeta2), which are involved in the induction of IFN-gamma expression. Furthermore, an electrophoretic mobility shift assay showed that CHL inhibited DNA binding activity of NF-kappaB, STAT-3, and STAT-4 to their cognate DNA recognition motifs, all of which contribute to the IL-12-induced IFN-gamma transcription. Exogenous addition of recombinant IL-12 abrogated the inhibitory effect of CHL on IFN-gamma and its mRNA expression in LPS-activated splenocytes. Collectively, these results show that CHL inhibits IFN-gamma production by LPS-stimulated splenic mononuclear cells due to down-regulation of IL-12 production.