Background
We have recently shown that the proinflammatory cytokine IL-32 is associated with arterial stiffness and cardiovascular disease in people with HIV (PWH). We also demonstrated that IL-32 induces coronary artery endothelial cell (CAEC) inflammation and dysfunction and that IL-32 alterations in PWH with subclinical atherosclerosis are associated with a deficit in the short-chain fatty acid (SCFA) caproic acid. In this study, we investigated the beneficial effect of the intestinal microbiota-driven SCFAs acetic, butyric, propionic, valeric and caproic to alleviate the IL-32-mediated CAEC dysfunction.
Methods
Human primary CAEC from Creative Bioarray are isolated from human coronary artery and used between passage 3 to passage 12. CAEC were conditioned with the different SCFAs at similar concentrations (1mM) before being stimulated with IL-32γ (the longest and most inflammatory IL-32 isoform) at 500ng/ml. The impact of SCFAs on upregulation of the CAEC typical dysfunction markers IL-6, CCL-2, ICAM-I and VCAM-I was measured in cell supernatants by ELISA. Differences in the potential of SCFAs to protect against the upregulation of the dysfunction markers were calculated with one-way ANOVA test. Cell viability of SCFA-treated cells was carried by measuring the cell release of the Lactate dehydrogenase LDH enzyme by ELISA.
Results
Caproic acid was the only SCFA that diminished the impact of IL-32γ on coronary artery endothelial cells dysfunction by simultaneously downregulating the expressions of IL-6, CCL-2, ICAM-I and VCAM-I (2.4±0.6, 1.2±0.1, 2±0.5, and 2.5±0.9 fold, p=0.0003, p=0.02, p=0.03, and p<0.0001, respectively) without impacting cell viability. In contrast, acetic acid inhibited CCL-2 (p=0.02) and VCAM-I (p=0.015) while propionic, butyric, and valeric acids only inhibited V-CAM-I (p=0.0003, p<0.0001 and p<0.0001, respectively) but not IL-6, CCL-2 or ICAM-I. These results suggest that caproic acid has a dominant positive effect in restoring endothelial cell functions, which are dysregulated by the inflammatory cytokine IL-32.
Conclusions
Our results uncover the potential benefits of caproic acid (a short chain fatty acid that we recently shown to be diminished in stool samples collected from PWH with subclinical atherosclerosis) in reversion of the endothelial cell dysfunction mediated by the inflammatory cytokine IL-32. These results warrant further investigations to the therapeutic potential of caproic acid in PWH with risk of cardiovascular disease.
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