Redox Regulation of Sarcoidosis Granulomas and Fibrosis

PROJECT SUMMARY Sarcoidosis is a pulmonary and systemic granulomatous disease of unknown cause. To better understand disease mechanisms, we have recently established a novel ex vivo human granuloma model that shares many structural and molecular features of the disease in human tissues, yielding novel insights into mechanisms

regulating early granuloma formation. In keeping with prior investigations and clinical experience linking sarcoidosis to elevated levels of angiotensin converting enzyme (ACE) in sarcoidosis tissues, molecular characterization of the sarcoidosis granuloma model indicates that macrophages participating in sarcoidosis

granuloma formation are regulated by the renin-angiotensin-aldosterone system (RAAS). Our strong preliminary data shows that sarcoidosis macrophages produce aldosterone, a hormone that promotes inflammation through the activation of mineralocorticoid receptors (MRs); and we further show that inhibition of

MRs attenuates granuloma formation. We hypothesize that RAAS promotes pathological granuloma formation and fibrosis in patients with sarcoidosis through activation of MRs and related production of reactive oxidant species (ROS). In the spirit of the R21 funding mechanisms, this project is highly innovative and has important

beneficial implications for advancing our understanding of sarcoidosis disease mechanisms and for providing novel therapeutic targets and disease biomarkers. Aim 1 will determine if RAAS/MR activation promotes sarcoidosis granuloma formation through redox signaling to promote NRF2/heme oxygenase-1 (HO-1)

pathway activation. We posit that MR activation promotes mitochondrial ROS production to trigger NRF2/HO-1 signaling resulting in alternative macrophage (M2) polarization favoring granuloma formation. Aim 2 will determine if RAAS/MR activation promotes collagen and pro-fibrotic molecule formation by

sarcoidosis granulomas through induction of TGFβ and inflammasome signaling. These studies will determine if sustained MR activation (by RAAS) promotes pro-fibrotic induction through pathways independent from NRF2/HO-1; dependent on direct ROS-dependent activation of TGFβ and induction of inflammasome

mediated IL-33 release. The short-term goals of this project are to advance basic understanding of sarcoidosis disease mechanisms regulating distinct disease manifestations of (1) granuloma formation induced by MR induced ROS production and downstream pathways regulating granuloma formation (NRF2/HO-1) and (2)

tissue fibrosis relating to TGFβ and inflammasome/IL-33 regulated pro-fibrotic responses. Long-term aspirations of this project are to address current deficiencies in the field of sarcoidosis as relates to identifying novel disease-specific therapies targeting granuloma formation and tissue fibrosis, including

repurposing of safe, widely available RAAS modulating drugs (e.g., ACE and MR inhibitors) or antioxidants, and emerging therapies targeting NRF2, HO-1 and IL-33.