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Summary: T helper type 17 lymphocytes (Th17 cells) infiltrate the central nervous system (CNS), induce inflammation and demyelination and play a pivotal role in the pathogenesis of multiple sclerosis. Sialomucin CD43 is highly expressed in Th17 cells and mediates adhesion to endothelial selectin (E‐selectin), an initiating step in Th17 cell recruitment to sites of inflammation. CD43−/− mice have impaired Th17 cell recruitment to the CNS and are protected from experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis. However, E‐selectin is dispensable for the development of EAE, in contrast to intercellular and vascular cell adhesion molecules (ICAM‐1 and VCAM‐1). We report that CD43−/− mice have decreased demyelination and T‐cell infiltration, but similar up‐regulation of ICAM‐1 and VCAM‐1 in the spinal cord, compared with wild‐type (WT) mice, at the initiation of EAE. CD43−/− Th17 cells have impaired adhesion to ICAM‐1 under flow conditions in vitro, despite having similar expression of LFA‐1, the main T‐cell ligand for ICAM‐1, as WT Th17 cells. Regardless of the route of integrin activation, CD43−/− Th17 cell firm arrest on ICAM‐1 was comparable to that of WT Th17 cells, but CD43−/− Th17 cells failed to optimally apically migrate on immobilized ICAM‐1‐coated coverslips and endothelial cells, and to transmigrate under shear flow conditions in an ICAM‐1‐dependent manner. Collectively, these findings unveil novel roles for CD43, facilitating adhesion of Th17 cells to ICAM‐1 and modulating apical and transendothelial migration, as mechanisms potentially responsible for Th17 cell recruitment to sites of inflammation such as the CNS. [ABSTRACT FROM AUTHOR]

R1616 --> Percutaneous coronary interventions (PCI) are commonly used to improve blood flow in Peripheral Artery Disease. Complications of PCI are delayed re‐endothelialization and endothelial cell (EC) dysfunction leading to adverse clinical outcomes. Stimulator of Interferon Genes (STING), canonically activated downstream of the cGAS enzyme, is a signaling hub molecule modulating immune responses triggered by self‐derived and/or foreign DNA. We hypothesized that EC‐intrinsic STING regulates re‐endothelialization in response to vascular injury. We modeled PCI in WT, STING‐/‐, and in a newly generated inducible vascular EC‐ specific mouse (VECad5Cre‐ERT2STINGfl/fl mice: EC‐STING‐/‐) using the wire induced carotid injury model. We used Evans Blue Dye injection post injury to identify the areas denuded of EC and quantified the % of non‐blue (re‐endothelialized) area. We found that WT mice had complete re‐endothelialization five days post injury (95.16 ± 2.77 %). In contrast, injured carotid arteries in STING‐/‐ mice exhibited a decrease in re‐endothelialization at the same timepoint (43.57 ± 9.79%). Moreover, EC‐STING‐/‐ mice recapitulated the delayed re‐endothelialization (10.45 ± 1.56% in Tamoxifen treated mice to induce excision of STING in EC, compared to 40 ± 1.28% observed in vehicle treated VECad5Cre‐ERT2STINGfl/fl control mice 5 days post scratch) in the injured arteries, supporting a role of EC STING in re‐endothelialization post injury. To further investigate this EC‐specific effect of STING mechanistically in vitro, we performed scratch assays on WT and STING mouse heart EC (MHEC) monolayers, as well as on human EC monolayers lacking STING after CRISPR knock down and imaged wound healing in real time by IncuCyte. WT MHEC and HUVEC completely covered the scratch area within 24 hours, and 4 hours, respectively, whereas both EC lacking STING were delayed healing the scratch. Additionally, we found that the healing response was independent of cGAS, since cGAS KD HUVEC had similar post‐ scratch recovery time as control HUVEC. Ongoing experiments investigate the mechanisms involved in this novel STING dependent, cGAS‐independent pathway of EC response to injury, as well as the consequences of EC‐STING in adverse chronic vascular remodeling. [ABSTRACT FROM AUTHOR]

R1600 --> Heart Failure with Preserved Ejection Fraction (HFpEF) is a prevalent and heterogenous cardiovascular syndrome characterized by impaired cardiac relaxation (diastolic function) with preserved contractility (systolic function), generally as a result of the presentation of several comorbidities. Despite its high and increasing prevalence, there are no therapies available to directly treat or cure HFpEF. Obesity and hypertension, the two dominant risk factors of HFpEF, have been independently associated with T cell inflammation, however, the inflammatory mechanisms driving HFpEF by these two comorbidities together, and T cell contributions, remain elusive. We hypothesized that T cell immune responses and cardiotropism promote diastolic dysfunction and HFpEF. C57/BL6 (wild‐type, WT) and T cell receptor alpha‐deficient (Tcra‐/‐) male mice were fed a high fat diet (HFD) with L‐NAME‐treated water (0.5 g/L) for 5 weeks to mimic obesity and hypertension, respectively, a recently established model of HFpEF. Age‐ and sex‐matched mice were fed standard chow (STD) as controls. Cardiac function was assessed using hemodynamic analyses, and plasma was collected to evaluate systemic levels of pro‐ and anti‐inflammatory cytokines. The heart, mediastinal lymph nodes, inguinal lymph nodes, and spleen were harvested to characterize cardiac and systemic immune cell populations by flow cytometry. Cardiac tissue was also collected for gene expression analysis by qPCR of markers of adverse cardiac remodeling and HFpEF. WT mice fed HFD/L‐NAME had increased cardiac CD11b+ cell abundance and increased CD4+ T cell infiltration compared to controls. Furthermore, in contrast to control mice, HFD/L‐NAME‐treated mice had an increased abundance of CD44hi/CD62Llo effector T cells in the mediastinal lymph nodes and spleen. This was associated with increased passive chamber stiffness (end‐diastolic pressure volume relationship, EDPVR) and decreased expression of the unfolded protein response (UPR) proteins spliced form of X‐box binding protein 1 and binding immunoglobulin protein (XBP1s and BIP), hallmarks of HFpEF. Additionally, HFD/L‐NAME induced a 2.5‐fold increase in plasma levels of IL‐17, without altering the levels of interferon‐gamma or IL‐2. Strikingly, Tcra‐/‐ mice did not develop diastolic dysfunction when fed HFD/L‐NAME, supporting a causal role of T cells in HFpEF pathology. We conclude that T cell activation and recruitment to the heart contribute to diastolic dysfunction in HFpEF. Further studies will interrogate the mechanisms by which combined risk factors prime T cells for cardiac infiltration and effector function in the heart to induce and drive HFpEF. [ABSTRACT FROM AUTHOR]

R3672 --> Gut dysbiosis has recently been associated with the severity of the complex syndrome of heart failure (HF) in patients. The mechanisms of action involving gut microbes and immune responses are starting to be characterized in experimental models of HF. More than 50% of HF patients present with HF with preserved ejection fraction (HFpEF), characterized by impaired relaxation (diastolic function) and preserved contractility (systolic function), which do not respond to any of the available treatments for HF. Obesity and hypertension are major risk factors for HFpEF, and have been independently associated with gut dysbiosis, and modulation of the microbiota in experimental models of these risk factors has revealed mechanistic insights. However, whether and how the microbiota contributes to HFpEF is unknown. Recently, a novel mouse model of HFpEF induced by a combination of high‐fat diet (HFD) and L‐NAME, to mimic obesity and hypertension, respectively. We hypothesize that specific microbiota and derived metabolites, are altered in HFpEF and contribute to systemic inflammation and diastolic dysfunction. C57/BL6 WT mice were fed HFD and L‐NAME (H/L) to induce HFpEF. We used invasive hemodynamics to determine diastolic and systolic function, and 16S rRNA sequencing in fecal samples to characterize gut bacteria and perform metabolic pathway analysis. The heart, the intestine and plasma were collected and evaluated for indicators of cardiac remodeling and gut permeability using flow cytometry and qPCR. As expected, H/L triggered diastolic dysfunction at 5 weeks. At this time, H/L intestinal epithelial cells (iECs) showed downregulation in gene expression of the junctional markers cadherin‐1, ZO‐1 and occludin, suggesting the induction of leaky gut. We also found increased concentration of proinflammatory molecules in serum (e.g. IL‐6, IL‐17 and CXCL1). Strikingly, H/L treatment resulted in gut dysbiosis in H/L mice compared to those that received standard diet (STD). The main phyla analysis showed a higher Firmicutes/Bacteroidetes ratio in H/L, which has been associated with obesity, compared to STD. At the family level, Ruminococcaceae, also linked to obesity in humans, showed elevated relative abundance in H/L group compared to STD, and Rikenellaceae and Christensenellaceae significantly decreased their numbers. Interestingly, gut bacteria from H/L‐treated mice revealed an enrichment of metabolic pathways related to synthesis and degradation of fatty acids. We studied the gene expression of the main short‐chain fatty acid (SCFA) receptors, associated with improvement in cardiovascular health. FFAR2 (GPR43) expression did not change in the heart neither the gut, but strikingly, FFAR3 (GPR41) expression was significantly upregulated in the heart in the H/L group compared to STD, but not in iECs. In conclusion, we demonstrated that a novel mouse model of HFpEF induced gut dysbiosis and alterations in gut permeability, and identified a dysregulation of fatty acid synthesis and degradation metabolic pathways. Mechanistic studies are needed to see the role of fatty acids and its receptors in cardiac inflammation during diastolic dysfunction. [ABSTRACT FROM AUTHOR]

R2804 --> 10.3 --> Introduction: Heart Failure with Preserved Ejection Fraction (HFpEF) is an uncurable widespread syndrome characterized by impaired cardiac relaxation (diastolic function), preserved cardiac contractility (systolic function), and the concordance of several comorbidities, such as obesity and hypertension. While T cell inflammation is known to contribute to HF with reduced cardiac contractility (HF with reduced EF), whether T cell inflammation occurs in HFpEF remains elusive. Recently, downregulation of the unfolded protein response (UPR) in cardiomyocytes was identified as a cardiometabolic HFpEF‐unique molecular signature. Interestingly, downregulation of the UPR has been reported to improve T cell anti‐tumor inflammatory responses. We hypothesized T cells contribute to diastolic dysfunction in HFpEF following T cell UPR downregulation in response to metabolic and nitrosative stress. Methods: We modeled cardiometabolic HFpEF in male C57/Bl6 (WT), Nur77‐GFP mice, reporter mice for T cell antigen engagement, and T cell receptor‐a (Tcra−/−) mice using high‐fat diet (HFD) and L‐NAME‐supplemented drinking water to mimic obesity and hypertension, respectively. Mice fed standard chow (STD) were used as controls. Invasive hemodynamic analyses were used to measure cardiac function. Immune populations in the heart, mediastinal lymph nodes (MdLN), and spleen were characterized using flow cytometry. CD4+ T cells from MdLN and spleen were isolated using magnetic‐assisted cell sorting, and UPR gene expression was assessed using qPCR. Results: We observed significant increases in cardiac CD4+ T cells in WT mice fed HFD/L‐NAME, concordant with diastolic dysfunction and preserved EF, compared to STD mice. We found increased effector CD4+CD62LloCD44hiIFNγ+ T cells in spleens and MdLN isolated from WT HFD/L‐NAME mice compared to STD controls. Nur77‐GFP mice revealed no antigen recognition by CD4+ T cells in the heart following HFD/L‐NAME. Tcra−/−mice fed HFD/L‐NAME did not develop diastolic dysfunction or cardiomyocyte hypertrophy. Strikingly, qPCR analysis of splenic T cells of WT HFD/L‐NAME mice revealed significantly decreased expression of spliced X box‐binding protein 1 (XBP1s), compared to controls, with no significant changes in unspliced XBP1 or activating transcription factor 4 (ATF4). ATF6 and C/EBP homologous protein (CHOP) gene expression was also reduced compared to T cells from control mice. Conclusion: Our data demonstrate that diastolic dysfunction and cardiomyocyte hypertrophy are T cell dependent in preclinical cardiometabolic HFpEF and reveal downregulation of two branches of the T cell UPR as a potential novel mechanism that contributes to T cell inflammation in HFpEF. [ABSTRACT FROM AUTHOR]