Abstract 328: Vascular Smooth Muscle Cell Mechanotransduction Through Serum And Glucocorticoid Inducible Kinase -1 Promotes Interleukin-6 Production And Macrophage Accumulation In Murine Hypertension

Abstract

Objective: Signaling through the serum and glucocorticoid inducible kinase-1 (SGK-1) can be mechanically activated. The objective of this investigation was to demonstrate that in vitro cyclic stretch of aortic VSMCs and in vivo induction of hypertension (HTN) can cause SGK-1-dependent production of cytokines to promote macrophage accumulation in the murine abdominal aorta. Methods: HTN was induced in C57Bl/6 mice with AngiotensinII (AngII) infusion (1.46mg/kg/day x 21 days) and a subset of animals had systemic infusion of EMD638683 (2.5mg/kg/day x 21 days), a selective SGK-1 inhibitor. Aortas were digested and analyzed by flow cytometry for abundance of CD11b + /F4-80 + cells (macrophages) and serum was analyzed by ELISA to quantify IL-6 and MCP-1. Aortic VSMCs from wild-type (WT) and SGK-1 flox-induced knockout mice (FloxSGK-1KO) were subjected to 12% biaxial cyclic stretch for 12 hours +/- EMD638683 (10υM). Media was analyzed by ELISA. Statistical analysis included two-way ANOVA with significance at p<0.05. Results: Having previously demonstrated that AngII infusion induced HTN and upregulated SGK-1 activity in the abdominal aorta, this experimentation indicated a concurrent trend for increased CD11b + /F4-80 + cells in the HTN group and marked reduction with EMD638683 infusion. Serum IL-6 levels were elevated in AngII-induced HTN (p<0.05 vs Control), and reduced to baseline with concurrent EMD638683 treatment. This mirrored the increased abundance of IL-6 in media from Stretch WT VSMCs (p<0.05 vs Static), and attenuation of the effect with EMD638683. Interestingly, MCP-1 was not detectable in the serum samples but was increased in media from Stretch WT VMSCs (p<0.05 vs Static), suggesting potential paracrine or autocrine function of this cytokine within the vessel wall to support macrophage accumulation. Further supporting the integral role of mechanical signaling through SGK-1, media from Stretch FloxSGK-1KO VSMCs had no change in IL-6 or MCP-1 compared to Static. Conclusion: Mechanotransduction through SGK-1 is instrumental in pro-inflammatory cytokine production and aortic macrophage accumulation, therefore further investigation into targeting this kinase may present opportunities to modulate hypertensive vascular remodeling.