Myeloid Cell Derived IL1ß Contributes to Pulmonary Hypertension in HFpEF.

BACKGROUND: Pulmonary hypertension (PH) in heart failure with preserved ejection fraction (HFpEF) is a common and highly morbid syndrome, but mechanisms driving PH-HFpEF are poorly understood. We sought to determine whether a well-accepted murine model of HFpEF also displays features of PH, and we sought to identify pathways that might drive early remodeling of the pulmonary vasculature in HFpEF. METHODS: Eight-week-old male and female C57BL/6J mice received either Nγ-nitro-L-arginine methyl ester and high-fat diet or control water and diet for 2, 5, and 12 weeks. The db/db mice were studied as a second model of HFpEF. Early pathways regulating PH were identified by bulk and single-cell RNA sequencing. Findings were confirmed by immunostain in lungs of mice or lung slides from clinically performed autopsies of patients with PH-HFpEF. ELISA was used to verify IL-1ß (interleukin-1 beta) in mouse lung, mouse plasma, and also human plasma from patients with PH-HFpEF obtained at the time of right heart catheterization. Clodronate liposomes and an anti-IL-1ß antibody were utilized to deplete macrophages and IL-1ß, respectively, to assess their impact on pulmonary vascular remodeling in HFpEF in mouse models. RESULTS: Nγ-nitro-L-arginine methyl ester/high-fat diet-treated mice developed PH, small vessel muscularization, and right heart dysfunction. Inflammation-related gene ontologies were overrepresented in bulk RNA sequencing analysis of whole lungs, with an increase in CD68+ cells in both murine and human PH-HFpEF lungs. Cytokine profiling showed an increase in IL-1ß in mouse and human plasma. Finally, clodronate liposome treatment in mice prevented PH in Nγ-nitro-L-arginine methyl ester/high-fat diet-treated mice, and IL-1ß depletion also attenuated PH in Nγ-nitro-L-arginine methyl ester/high-fat diet-treated mice. CONCLUSIONS: We report a novel model for the study of PH and right heart remodeling in HFpEF, and we identify myeloid cell-derived IL-1ß as an important contributor to PH in HFpEF.

MALDI Imaging Mass Spectrometry as a Lipidomic Approach to Heart Valve Research.

BACKGROUND: Valvular disease is characterized in part by lipid deposition, but systematic analysis of the patterns of global lipid expression in healthy and diseased valve tissues are unknown. This is due in part to tissue limitations for lipidomic preparations and technologies for evaluating lipid distribution in tissues. The study aim was to examine the application of matrixassisted laser desorption ionization imaging mass spectrometry (MALDI IMS) to the aortic valve during development and disease, as an approach to detect and map lipids and ultimately better understand valve structure and function. METHODS: Established MALDI IMS strategies were applied to thin tissue sections of heart valves to map lipids to corresponding morphological features. Healthy prenatal and adult ovine aortic valve tissues were evaluated using the developed techniques. Lipid expression levels were compared between prenatal and adult valves using Wilcoxon rank sum testing and area under the receiver operating curves. A classification algorithm was used to determine distinct lipid signatures in adult extracellular matrix (ECM) substructures, including fibrosa and spongiosa layers. Lipid patterns were examined in heart valve tissue from pediatric patients with congenital aortic valve stenosis (CAVS). RESULTS: Lipid levels were decreased in adult ovine aortic valves when compared with prenatal valves. Classification algorithms applied to lipid signatures reported distinct lipid signatures mapping to ECM substructures in the adult aortic valve, but could not distinguish amorphous structures at pre-natal day 5. In CAVS, the in-situ lipid aggregation of distinct lipid species showed unique patterning both concurrent and divergent with ECM disarray. Fatty acid content varied between normal and diseased human aortic valves. CONCLUSIONS: MALDI IMS provides a new and useful approach to evaluate lipid biology in heart valve tissue. These findings define a role for lipid regulation in aortic valve development and demonstrate patterns of lipid deregulation in congenital disease.

Quantitative and qualitative differences in proatherogenic NKT cells in apolipoprotein E-deficient mice.

BACKGROUND: Atherosclerosis is a disease marked by lipid accumulation and inflammation. Recently, atherosclerosis has gained recognition as an autoimmune-type syndrome characterized by increased activation of the innate and acquired immune systems. Natural killer T (NKT) cells have characteristics of both conventional T cells and NK cells and recognize glycolipid antigens presented in association with CD1d molecules on antigen-presenting cells. The capacity of NKT cells to respond to lipid antigens and modulate innate and acquired immunity suggests that they may play a role in atherogenesis. METHODS AND RESULTS: We examined the role of NKT cells in atherogenesis and how the atherosclerotic environment affects the NKT cell population itself. The data show that CD1d-deficiency in male apolipoprotein E-deficient (apoE(0)) mice results in reduction in atherosclerosis, and treatment of apoE(0) mice with alpha-galactosylceramide, a potent and specific NKT cell activator, results in a 2-fold increase in atherosclerosis. Interestingly, we demonstrate that alpha-galactosylceramide-induced interferon-gamma responses and numbers of NKT cells in apoE(0) mice show age-dependent qualitative and quantitative differences as compared with age-matched wild-type mice. CONCLUSIONS: Collectively, these findings reveal that hyperlipidemia and atherosclerosis have significant effects on NKT cell responses and that these cells are proatherogenic.