Interleukin-35 Promotes Macrophage Survival and Improves Wound Healing After Myocardial Infarction in Mice

Rationale: Targeting inflammation has been shown to provide clinical benefit in the field of cardiovascular diseases. Although manipulating regulatory T-cell function is an important goal of immunotherapy, the molecules that mediate their suppressive activity remain largely unknown. IL (interleukin)-35, an immunosuppressive cytokine mainly produced by regulatory T cells, is a novel member of the IL-12 family and is composed of an EBI3 (Epstein-Barr virus-induced gene 3) subunit and a p35 subunit. However, the role of IL-35 in infarct healing remains elusive. Objective: This study aimed to determine whether IL-35 signaling is involved in healing and cardiac remodeling after myocardial infarction (MI) and, if so, to elucidate the underlying molecular mechanisms. Methods and Results: IL-35 subunits (EBI3 and p35), which are mainly expressed in regulatory T cells, were upregulated in mice after MI. After IL-35 inhibition, mice showed impaired infarct healing and aggravated cardiac remodeling, as demonstrated by a significant increase in mortality because of cardiac rupture, decreased wall thickness, and worse cardiac function compared with wild-type MI mice. IL-35 inhibition also led to decreased expression of alpha-SMA (alpha-smooth muscle actin) and collagen I/III in the hearts of mice after MI. Pharmacological inhibition of IL-35 suppressed the accumulation of Ly6C(low) and major histocompatibility complex IIlow/C-C motif chemokine receptor type 2-(MHC IIlow CCR2(-)) macrophages in infarcted hearts. IL-35 activated transcription of CX3CR1 (C-X3-C motif chemokine receptor 1) and TGF (transforming growth factor) beta 1 in macrophages by inducing GP130 signaling, via IL12R beta 2 and phosphorylation of STAT1 (signal transducer and activator of transcription family) and STAT4 and subsequently promoted Ly6C(low) macrophage survival and extracellular matrix deposition. Moreover, compared with control MI mice, IL-35-treated MI mice showed increased expression of alpha-SMA and collagen within scars, correlating with decreased left ventricular rupture rates. Conclusions: IL-35 reduces cardiac rupture, improves wound healing, and attenuates cardiac remodeling after MI by promoting reparative CX3CR1(+) Ly6C(low) macrophage survival.