Reciprocal Interaction between Macrophages and T cells Stimulates IFN-γ and MCP-1 Production in Ang II-induced Cardiac Inflammation and Fibrosis

BackgroundThe inflammatory response plays a critical role in hypertension-induced cardiac remodeling. We aimed to study how interaction among inflammatory cells causes inflammatory responses in the process of hypertensive cardiac fibrosis. Methodology/Principal FindingsInfusion of angiotensin II (Ang II, 1500 ng/kg/min) in mice rapidly induced the expression of interferon γ (IFN-γ) and leukocytes infiltration into the heart. To determine the role of IFN-γ on cardiac inflammation and remodeling, both wild-type (WT) and IFN-γ-knockout (KO) mice were infused Ang II for 7 days, and were found an equal blood pressure increase. However, knockout of IFN-γ prevented Ang II-induced: 1) infiltration of macrophages and T cells into cardiac tissue; 2) expression of tumor necrosis factor α and monocyte chemoattractant protein 1 (MCP-1), and 3) cardiac fibrosis, including the expression of α-smooth muscle actin and collagen I (all p Conclusions/SignificanceReciprocal interaction between macrophages and T cells in heart stimulates IFN-γ expression, leading to increased MCP-1 expression in macrophages, which results a forward-feed recruitment of macrophages, thus contributing to Ang II-induced cardiac inflammation and fibrosis.