Macrophage-Stimulated Cardiac Fibroblast Production of IL-6 Is Essential for TGF β/Smad Activation and Cardiac Fibrosis Induced by Angiotensin II

Abstract

Interleukin-6 (IL-6) is an important cytokine participating in multiple biologic activities in immune regulation and inflammation. IL-6 has been associated with cardiovascular remodeling. However, the mechanism of IL-6 in hypertensive cardiac fibrosis is still unclear. Angiotensin II (Ang II) infusion in mice increased IL-6 expression in the heart. IL-6 knockout (IL-6-/-) reduced Ang II-induced cardiac fibrosis: 1) Masson trichrome staining showed that Ang II infusion significantly increased fibrotic areas of the wild-type mouse heart, which was greatly suppressed in IL-6-/- mice and 2) immunohistochemistry staining showed decreased expression of α-smooth muscle actin (α-SMA), transforming growth factor β1 (TGF-β1) and collagen I in IL-6-/- mouse heart. The baseline mRNA expression of IL-6 in cardiac fibroblasts was low and was absent in cardiomyocytes or macrophages; however, co-culture of cardiac fibroblasts with macrophages significantly increased IL-6 production and expression of α-SMA and collagen I in fibroblasts. Moreover, TGF-β1 expression and phosphorylation of TGF-β downstream signal Smad3 was stimulated by co-culture of macrophages with cardiac fibroblasts, while IL-6 neutralizing antibody decreased TGF-β1 expression and Smad3 phosphorylation in co-culture of macrophage and fibroblast. Taken together, our results indicate that macrophages stimulate cardiac fibroblasts to produce IL-6, which leads to TGF-β1 production and Smad3 phosphorylation in cardiac fibroblasts and thus stimulates cardiac fibrosis.

Tenascin-C May Accelerate Cardiac Fibrosis by Activating Macrophages via the Integrin αVβ3/Nuclear Factor–κB/Interleukin-6 Axis

“…18,29 We also confirmed that recombinant IL-6 upregulated collagen I mRNA expression of cardiac fibroblasts in culture. Increased level of IL-6 was detected in the mouse heart undergoing fibrosis.…”

“…18 We confirmed that treatment with IL-6 significantly accelerated mRNA expression of collagen type I at 6 h in cardiac fibroblasts isolated from a mouse heart. (P<0.01; Figure S5).…”

γδT Cell–Derived Interleukin-17A via an Interleukin-1β–Dependent Mechanism Mediates Cardiac Injury and Fibrosis in Hypertension

“…Recent studies have suggested that Th17 cellpolarizing cytokines (IL-1β, TGF-β, IL-6, and IL-23) regulate selective retinoic acid receptor-related orphan nuclear receptor γ expression and IL-17A production in γδT cells, [21][22][23] and production of TGF-β and IL-6 was increased after Ang II infusion. 26 We found that activated DCs significantly enhanced IL-6 production by CF. Stromal cells, such as fibroblasts or epithelial cells, may support the expansion of IL-17A-producing T cells by influencing the cytokine milieu within the microenvironment.…”

Vascular Endothelial Growth Factor-A in <i>Lactobacillus Casei </i>Cell Wall Extract-Induced Coronary Arteritis of a Murine Model

“…IL-6 is a pro-fibrotic regulatory factor, mediating cardiac fibrosis in response to angiotensin II infusion. 41 Therefore, we speculate that an early increase in VEGF-A expression occurs during the process of acute inflammation, and that the later decrease in VEGF-A expression and the associated imbalance between pro-angiogenic VEGF-A and pro-fibrotic IL-6 contribute to subsequent fibrotic changes in CALs. Taken together, these findings suggest that, in addition to systemic and local aortic TNF-α and IL-6, other factors also play a crucial role in mediating local VEGF-A regulation in LCWE-induced CALs.…”