The in-vitro effect of human CRP isoforms containing azide and oxLDL on U937 derived macrophages production of cytokines involved in atherosclerosis

Abstract

Background: Atherosclerosis is an inflammatory chronic disease affecting walls of the arteries and caused by white blood cells mainly the macrophages. C-reactive protein (CRP) and oxidized low density lipoprotein (oxLDL) seem to deeply affect the atherosclerotic plaque formation and progression. The monomeric (m) CRP and pentameric (p) CRP play with oxLDL either a pro or anti-inflammatory role on macrophages. Azide, the commercial preservative of CRP, is judged to influence its action in in-vitro experiments. Aim: Our project aims to determine the effect of both isoforms of azide-containing CRP (mCRP and pCRP) with and without oxLDL, on cytokines production by U937 derivedmacrophages. Methods: U937 monocytes were cultured in-vitro and differentiated into macrophages, then treated with mCRP, pCRP and oxLDL in single, double and triple combination. ELISA assays for IFN-, IL-4, IL-6, IL-10 and TNF- cytokines were performed to assess their levels in the supernatant under different treatments. Results: Macrophages respond differently for the different cytokine. The levels of IFN- and IL-6 were decreased while those of IL-4 and IL-10 were increased under the different treatments. On the other hand, the level of TNF- was lowered by the mixture of mCRP and oxLDL. According to azide, a significant effect was detected with IL-6 and TNF- release. Conclusion: In general, mCRP, pCRP and oxLDL single or together have different effects on down-regulating pro-atherogenic cytokines such as IFN- IL-6 and TNF-and up-regulating athero-protective ones as IL-4 and IL-10. We conclude that the miroenvironment of the intima, and those substances themselves, plays a crucial role in atherogenesis.