The recent CANTOS Trial has proved that anti-infammation therapy targeting the interleukin-1? lowers the incidence of cardiovascular events. However, we lack therapies that can limit the inflammatory injury triggered by acute ischemia, even though it clearly links to worse clinical outcomes. A critical gap of knowledge in understanding danger recognition, especially intracellular danger recognition, plays a significant role, because detecting danger dictates the scope of inflammation. Our long-term goal is to develop immune modulators that modify danger recognition to contain inflammation-mediated injury. The overall objective of this proposal is to determine how DNA and its cytosolic receptor the cyclic GAMP synthase (cGAS) propagate injury triggered by ischemia. The damaged myocardium is enriched with both mitochondrial (thousands of copies per cardiomyocyte) and nuclear DNA. The large amount of DNA poses a serious threat to myocardial repair when macrophages, the professional phagocytes, detect it and respond with the robust inflammatory responses intended to get rid of pathogens from the evolutionary standpoint. The central hypothesis of this project is that recognition of DNA by cGAS sustains the inflammatory macrophages via activation of the type I interferon (IFN) pathway that promotes AIM2 (absent in melanoma 2) inflammasone; as a result, cGAS is crucial in ischemia-induced remodeling. This hypothesis has been formulated on the preliminary data and the recently published work from the applicants? laboratory. The rationale for the proposed research is that understanding the intracellular immunity in ischemic-triggered inflammation has the potential to discover effective ways of limiting inflammation-related injury. Guided by strong preliminary data, this hypothesis will be tested by pursuing the following specific aims: 1) Determine that cGAS activation in macrophages drives pathological remodeling and HF; 2) Determine that cGAS-mediated signaling activates the AIM2 inflammasome pathway. cGAS activates type 1 interferon- mediated signaling that governs the expression of the guanylate binding proteins (GBPs). GBPs destabilize the phagosome and cause the release of DNA into the cytosol and triggers AIM2 inflammasome activation; 3) Identify effective approaches for inhibition of the cGAS pathway to reduce remodeling and HF after ischemic injury.
Aim 1 will be addressed using a cGASf/f mouse line to determine macrophage as the responsible cell type. Under the second aim, the cGAS-dependent AIM2 inflammasone activation and the essential roles of GBPs will be examined using loss or gain of function experiments with in vitro and in vivo models.
Aim 3 will test potential protection from immune modulators that inhibit the cGAS-mediated signaling, including two clinically available agents. The study is conceptually novel by targeting DNA and its cytosolic sensing system, traditionally viewed as a viral response pathway, in the setting of myocardial ischemia. Knowledge acquired will vertically advance our understanding of the critical role of intracellular immunity in ischemic injury. As ischemic heart disease is an enormous burden and often a devastating condition to our veterans, the proposed study moves the field forward by finding novel strategies alleviating the burden and improve care.
Myocardial infarction is the major cause of heart failure that is projected to increase 46% by the year of 2030. My proposed studies aim to understand how macrophages, the key immune cells recruited to carry out tissue repair after ischemic injury, control this crucial process through sensing and responding to DNA presented in the cytosol. My studies will also delineate if two immune modulators that have the potential to disrupt the DNA sensing and responding and are readily available clinically, modulate the behavior of macrophages and promote repair. This research will have the potential to reveal novel therapeutic targets to limit remodeling and heart failure after myocardial infarction.
