Cytosolic DNA sensing instructs resident macrophage vitality and organismal longevity

Tufts University Boston, Boston MA

Investigators

Abstract

Project Summary Age-associated chronic inflammation is thought to be directly linked to the cellular processes termed senescence and senescence associated secretory phenotype (SASP). Recent studies suggest that the sensing of cytosolic chromatin or damaged DNA in senescent cells by the cyclic-di-GMP-AMP-synthase (cGAS) and Stimulator of Interferon Genes (STING) regulate the SASP. Based on these reports, it is presumed that cGAS/STING signaling drives age-associated pathology. However, these studies primarily focused on understanding the role of the cGAS/STING dependent senescence in fibroblasts. As fibroblasts represent only a small sliver of the cells found in tissues, we sought to extend these studies by exploring the contribution of cGAS/STING-signaling to changes in multiple tissues during chronological and physiological aging. Using single-cell RNA-sequencing, we note predominant signatures of senescence in all tissues tested (kidneys, lungs, heart, liver and brain). These signatures extend to fibroblasts and non-fibroblast stromal cells like endothelial and epithelial cells, but also to tissue-resident macrophages (TRMs). TRMs are critical for optimal organ function and repair. The loss of cGAS or STING impacts TRM viability in vivo and ex vivo, predisposing them to cell-death. Furthermore, we show that endogenous retroelements (EREs), a proven ligand for cGAS/STING activation, are expressed in TRMs and critical for normal tissue-centric functions of TRMs. Finally, contrary to expectations based on previous studies, the loss of cGAS or STING leads to significantly shorter lifespans and greater peripheral inflammatory signature. Based on these paradigm shifting findings, we propose that cGAS/STING signaling balances the protective effects of senescence with its pathological effects through cell-specific roles. Our broad objective is thus, to understand the cell-specific contribution of cGAS/STING signaling to organismal aging. Our specific aims will methodically tackle this objective by focusing on TRMs. Given the critical role DNA-sensing plays in discriminating endpoints like senescence induction or cell-survival, the unique nature of ligands may play a role in cell-fate decisions. Thus, we will first ascertain the role EREs play in shaping TRM survival and function and how their engagement of the cGAS/STING pathway factors into their role (Aim1). We then aim to clarify how cGAS/STING deficiency impacts the vitality of TRMs, predisposing them to cell-death (Aim2). Finally, we will determine if a TRM-intrinsic deficiency of cGAS/STING signaling can recapitulate the tissue dysfunction and compromised lifespans seen in mice with global cGAS/STING deficiency (Aim3). These aims will utilize cutting-edge and innovative tools like single-cell spatial multi-omics (a spatially oriented simultaneous profiling of proteomics and transcriptomics in whole tissues), multi-modal CITE-seq (phenotypic profiling and transcriptomics with single-cell resolution) and powerful genetic tools. Given the massive therapeutic push to target this pathway in cancer, several autoimmune diseases and now aging, our proposed studies are urgently needed to fully comprehend the impact of modifying this pathway long-term.