Comparative immune profiling in HFpEF: cross-species insights into inflammation and mitochondrial dysfunction

Abstract The development and progression of chronic heart failure (HF) are closely linked to inflammation. While HF with reduced ejection fraction (HFrEF) involves monocyte-driven immune activation, the composition and activation patterns of immune cells—particularly peripheral blood mononuclear cells (PBMCs)—in HF with preserved ejection fraction (HFpEF) remain less well understood. Obesity is a key risk factor for HFpEF, though lean individuals are also affected. Single-cell RNA sequencing of PBMCs from HFpEF (n=6) and HFrEF (n=8) patients, as well as healthy controls (n=7) was performed. Participants were classified as lean (BMI30) or obese (BMI30). Additionally, PBMCs from a murine HFpEF model (HFD+L-NAME, n=5) were examined, with a subgroup receiving nitro-oleic acid (NO2-OA), a compound known to improve diastolic function. HFpEF mice exhibited an increased left atrium-area, reduced again by NO2-OA. LVEF did not differ significantly between the groups, consistent with the HFpEF phenotype. The study aimed to assess immune cell-specific activation, identify conserved immune response genes across species, and examine their regulation in relation to LVEF and obesity. Distinct immune cell profiles emerged: HFrEF showed fewer T-cells and an elevated monocyte-to-T-cell-ratio, whereas HFpEF lacked these changes. NK-cells and T-cells displayed an activated transcriptional state in both HF phenotypes. Focusing on inflammatory signatures, each disease showed a specific regulatory profile. HFpEF exhibited a lesser inflammatory response with obesity playing a critical role (e.g. no increase in IL1B) and a metabolic shift, particularly affecting mitochondrial activity (↑ ATP5ME, ATP5F1E, UQCRQ, NDUFB1). Cross-species analysis in the murine HFpEF model demonstrated an upregulation of inflammatory cytokines (Il1a, Il6, Il1b, Mcp1 (Ccl2), Tnf). NO2-OA treatment partially normalized immune cell composition and attenuated inflammatory signaling, suggesting a potential therapeutic avenue for HFpEF. Orthologous gene analysis identified potentially shared regulatory mechanisms between humans and mice, with mitochondrial metabolism emerging as a critical pathway involved in HFpEF pathophysiology. In conclusion, this study provides novel insights into the immune and metabolic dysregulation in HFpEF. Unlike the monocyte-driven inflammation observed in immune cells of HFrEF, immune cells of HFpEF are characterized by an NK- and T-cell-driven immune response, alongside with significant metabolic dysregulation, particularly in mitochondrial pathways. While obesity plays a crucial role in modulating these inflammatory responses in HFpEF, it is not the sole factor contributing to the condition. NO2-OA treatment effectively mitigates these pathological changes, suggesting potential therapeutic benefits. The identification of conserved immune response genes across species highlights promising targets for future therapies aimed at modulating inflammation and metabolism in HFpEF.