Abstract Background Pulmonary arterial hypertension (PAH) is characterized by vascular remodeling and right ventricular pressure overload. Elevated oxidized lipid metabolites, particularly hydroxyeicosatetraenoic acids (HETEs), are consistently observed in PAH patients and animal models. Although HETEs are lipoxygenase (LOX) derived oxylipins, the tissue origin of these lipids and their mechanistic role in PH pathogenesis remain incompletely understood. We previously demonstrated that dietary 15-HETE alone is sufficient to induce pulmonary hypertension (PH) in wild type mice accompanied by systemic oxylipin elevation. However, the molecular mechanisms remain poorly understood. During our investigations, we discovered that dietary 15-HETE increases systemic oxylipin levels of not only 15HETE but also other HETEs (including 5-, 12-), like PAH patients. To determine whether the intestine is a key source of LOX dependent oxylipin amplification driving PH, we investigated the role of 12/15-lipoxygenase (12/15-LOX). Methods C57BL/6J wild-type mice, total 12/15-LOX knockout (12/15-LOX KO), were fed control or 15-HETE supplemented diets (5 µg/mouse/day) for three weeks. Pulmonary hypertension was assessed by right ventricular systolic pressure (RVSP) and pulmonary artery acceleration time (PAAT). Plasma lipid profiles were analyzed by targeted mass spectrometry, and pharmacologic inhibition of 5-LOX with zileuton was used to examine pathway crosstalk. Cytokine levels were measured by multiplex immunoassay. Flow cytometry was used to evaluate gut immune populations. Results Dietary 15-HETE increased RVSP and decreased PAAT in wild-type mice, confirming PH induction, whereas total 12/15-LOX deletion prevented PH and reduced 5-, 12-, and 15-HETE levels in the intestine and 12- and 15-HETE in the lung. Further analyses revealed an elevation in plasma inflammatory cytokines (including eotaxin, G-CSF, IL-15, and MCP-1) and shifts in gut immune cells (increased Type 1 macrophages and decreased neutrophils) in 15-HETE treated mice, suggesting an inflammatory response initiated in the gut. Lipidomic profiling revealed increases in plasma triacylglycerols, cholesterol esters, hexosylceramides, free fatty acids, linoleic acid and arachidonic acid in 15-HETE treated mice. These findings demonstrate that 12/15-LOX drives systemic oxylipin amplification, gut metabolic remodeling, and pulmonary vascular dysfunction in 15-HETE induced PH, highlighting a gut-LOX-lung axis as a novel mechanistic link between diet, lipid metabolism, and pulmonary hypertension. Collectively, our results identify the intestine as a critical regulator of LOX-dependent lipid oxidation and highlight 12/15-LOX as a novel therapeutic target in PAH This abstract is funded by: NIH
Emamimeybodi et al. (Fri,) studied this question.