Abstract Body: Introduction: Combined obesity and hypertension alter the endoplasmic reticulum (ER) stress response by downregulating X-box binding protein 1 (Xbp1) in T cells, which heightens T cell inflammatory potential and persistence in Heart Failure with Preserved Ejection Fraction (HFpEF), a prevalent syndrome with no cure. The ER protein Stimulator of Interferon Genes (STING), in concert with Xbp1, coordinates T cell inflammation and death in other contexts, yet its role in the T cell inflammatory response in cardiometabolic HFpEF is unknown.
Hypothesis: STING activation and dysregulated ER stress responses drive T cell inflammation in HFpEF by balancing T cell activation and persistence in response to combined comorbidities.
Methods: C67BL/6J (wild type, WT) mice were fed high-fat diet/L-NAME (H/L) or standard chow (STD) for 5 weeks, and STING activation was measured in splenic CD4⁺ T cells by Western blotting. Splenic CD4⁺ T cells from WT or STING-deficient mice (STING^-/-) were activated with αCD3/αCD28 for 3 days in vitro, then treated with complete media (CM) or CM with 0.2 mM palmitate (abundant in dietary fat)/0.2 mM L-NAME (PALNA) for up to 48 hours. T cell gene expression, activation, and death were assessed using qPCR, flow cytometry, Western blotting, and Lionheart live-cell microscopy.
Results: Mice fed H/L had significantly increased splenic T cell expression of phospho-STING, alongside decreased T cell Xbp1 expression and increased cardiac inflammation, compared to STD-fed mice. Ex vivo incubation of CD4⁺ T cells with PALNA significantly decreased Xbp1 gene expression and increased apoptosis, indicated by cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP) expression, compared to cells in CM. However, the remaining live PALNA-treated cells showed higher expression of the activation protein CD69, and this was sustained over time, compared to cells in CM. Strikingly, live cell imaging revealed that STING^-/- T cells had improved survival and decreased CD69 expression in response to PALNA compared to WT PALNA-treated cells.
Conclusions: STING contributes to T cell inflammation in experimental cardiometabolic HFpEF by synergizing with dysregulated ER stress responses to promote the emergence of hyperactivated T cells.