Reciprocal induction of tumor necrosis factor-alpha and interleukin-1 beta activity mediates fibronectin synthesis in coronary artery smooth muscle cells

Abstract

We previously demonstrated an immune-inflammatory response associated with increased expression of interleukin (IL)-1 beta and fibronectin in graft coronary arteriopathy in piglets following heterotopic heart transplant. Further studies showed that increased endogenously produced IL-1 beta was upregulating fibronectin production by donor coronary artery (CA) smooth muscle cells (SMC). Since co-induction of IL-1 beta and tumor necrosis factor (TNF)-alpha has been shown in other systems, we investigated the possible interaction between these cytokines in regulating fibronectin production in CA SMC. First, we documented increased TNF-alpha expression in vivo in donor compared to host CA. Next, synthesis of fibronectin was measured in host and donor CA SMC following [35S]-methionine radiolabeling and gelatin-sepharose extraction. As previously shown with IL-1 beta, increased donor CA SMC fibronectin synthesis was reduced to host levels in the presence of TNF-alpha antibodies, and exogenous TNF-alpha upregulated fibronectin synthesis in host CA SMC to levels in donor cells. In normal CA SMC, TNF-alpha-stimulated fibronectin production was downregulated to or below control levels in the presence of IL-1 beta antibodies. Likewise, IL-1 beta-stimulated fibronectin synthesis was downregulated to control levels when TNF-alpha neutralizing antibodies were added. Combining TNF-alpha and IL-1 beta enhanced fibronectin production over that observed with either cytokine alone, but was not additive. Thus, our studies suggest that vascular SMC fibronectin synthesis is regulated by reciprocal induction of IL-1 beta and TNF-alpha activity and provide the first demonstration of a 'cytokine loop' modulating matrix production.