GDF3 Protects Mice against Sepsis-Induced Cardiac Dysfunction and Mortality by Suppression of Macrophage Pro-Inflammatory Phenotype.

Lu Wang,Yigang Wang,Tianqing Peng,Xingjiang Mu,Xiaohong Wang,Guo-Chang Fan,Yutian Li,Wei Huang,Zhenling Liu,Kobina Essandoh,Shunan Cui,Peng Wang

doi:10.3390/cells9010120

Abstract

Macrophages are critical for regulation of inflammatory response during endotoxemia and septic shock. However, the mediators underlying their regulatory function remain obscure. Growth differentiation factor 3 (GDF3), a member of transforming growth factor beta (TGF-β) superfamily, has been implicated in inflammatory response. Nonetheless, the role of GDF3 in macrophage-regulated endotoxemia/sepsis is unknown. Here, we show that serum GDF3 levels in septic patients are elevated and strongly correlate with severity of sepsis and 28-day mortality. Interestingly, macrophages treated with recombinant GDF3 protein (rGDF3) exhibit greatly reduced production of pro-inflammatory cytokines, comparing to controls upon endotoxin challenge. Moreover, acute administration of rGDF3 to endotoxin-treated mice suppresses macrophage infiltration to the heart, attenuates systemic and cardiac inflammation with less pro-inflammatory macrophages (M1) and more anti-inflammatory macrophages (M2), as well as prolongs mouse survival. Mechanistically, GDF3 is able to activate Smad2/Smad3 phosphorylation, and consequently inhibits the expression of nod-like receptor protein-3 (NLRP3) in macrophages. Accordingly, blockade of Smad2/Smad3 phosphorylation with SB431542 significantly offsets rGDF3-mediated anti-inflammatory effects. Taken together, this study uncovers that GDF3, as a novel sepsis-associated factor, may have a dual role in the pathophysiology of sepsis. Acute administration of rGDF3 into endotoxic shock mice could increase survival outcome and improve cardiac function through anti-inflammatory response by suppression of M1 macrophage phenotype. However, constitutive high levels of GDF3 in human sepsis patients are associated with lethality, suggesting that GDF3 may promote macrophage polarization toward M2 phenotype which could lead to immunosuppression.

Highlights

Sepsis is a life-threatening syndrome following a dysregulated host response to infection with an increasing incidence and nearly 40% of mortality, as defined by the Sepsis-3 definition [1,2]
Receiver operating characteristic (ROC) curves were generated for Growth differentiation factor 3 (GDF3) to discriminate sepsis from healthy donors (Figure 1B)
The area under the curve (AUC) of GDF3 was 0.825 with 95% confidence interval (CI, 0.697–0.953, p = 0.001), and optimal cut-off level was 90.23pg/mL (Figure 1B)

Summary

Introduction

Sepsis is a life-threatening syndrome following a dysregulated host response to infection with an increasing incidence and nearly 40% of mortality, as defined by the Sepsis-3 definition [1,2]. M1 macrophages are antigen-presenting cells that can be induced by LPS or IFN-γ They are mainly responsible for producing pro-inflammatory mediators like tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin 1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and iNOS [6,7]. M2 macrophages could be induced by IL-4, they are recognized by anti-inflammatory and tissue-repairing characteristics at later stage of sepsis [6]. These macrophages express high levels of markers, i.e., transforming growth factor β (TGF-β), Arg-1, CD206 and IL-10 [6]

Methods

Results

Conclusion