Altered Antioxidant and Inflammatory Signaling by Fibroblasts in the Hypertensive Heart

Abstract

In response to hypertensive stimuli, like angiotensin II (AngII), cardiac fibroblasts (CFs) transform into an activated phenotype, which triggers increased collagen deposition and pro‐inflammatory signals. Transforming growth factor beta 1 (TGF‐β1) and reactive oxygen species are important modulators of AngII‐induced cardiac fibrosis and CF activation. The extent to which the AngII‐induced changes in CF phenotype persist in the absence of ongoing stimulation is not known. The objective of the present study was to determine the persistent impact of chronic AngII infusion on CF phenotype. Specifically, we performed an in vitro characterization of CFs isolated from rats chronically treated with AngII (in vivo) or saline (vehicle) and investigated acute (in vitro) responses to AngII thereafter. Adult male SD rats were administered AngII (200 ng/kg/min) or saline for 4 weeks. In half of the rats in each group, we measured mean arterial pressure (MAP), weighed the left ventricle (LV), and fixed a section of LV for assessment of collagen deposition (Sirius Red). In remaining rats, CFs were isolated and passaged to P1. CFs were treated in vitro with AngII (1uM) or vehicle for 72 hr. TGF‐β1 and monocyte chemoattractant protein 1 (MCP‐1) were assessed in culture media. Expression of pro‐/anti‐oxidant proteins NADPH oxidase 2 (Nox2), catalase and superoxide dismutase 1 (SOD1) were determined by western blot. Ang II increased MAP (43%, p<0.05), LV/BW (30%, p<0.05), and LV collagen deposition. TGF‐β1 release was not different from CFs isolated from saline vs. AngII infused rats. However, in vitro incubation with AngII significantly increased TGF‐β1 secretion in all CFs. CFs isolated from AngII‐infused rats secreted elevated levels of MCP‐1 (p<0.05), when compared to control CFs. MCP‐1 levels were not further modified by acute AngII treatment. Basal expression of Nox2, SOD1, and catalase was similar between CFs isolated from control vs. AngII‐infused rats. Acute AngII tended to increase Nox2 expression in CFs isolated from vehicle and AngII‐treated rats, whereas AngII only increased SOD1 expression (46%, p<0.05) in CFs from AngII‐infused rats. In vitro stimulation with AngII tended to increase catalase in CFs isolated from control rats, but reduced (20%, p<0.05) expression in CFs isolated from AngII infused rats. Taken together, these data demonstrate that CFs isolated from an actively remodeling myocardium continue to secrete elevated levels of MCP‐1, but not TGF‐β1, in vitro. Moreover, CFs from AngII‐infused rats displayed altered expression of antioxidant enzymes following AngII in vitro, which may play a role in worsened inflammatory signaling and resultant pro‐fibrotic activity. Future studies will further elucidate the fibrotic and inflammatory characteristics of CFs from the remodeling myocardium and determine the extent to which this persistent phenotype alters the future responsiveness to a pathogenic stimulus.Support or Funding InformationSpringboard Grant, UA College of Medicine – PhoenixThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.