Nitro-Oleic Acid (NO₂-OA) Improves Systolic Function in Dilated Cardiomyopathy by Attenuating Myocardial Fibrosis

Nitro-oleic acid (NO₂-OA), a nitric oxide (NO)- and nitrite (NO₂^-)-derived electrophilic fatty acid metabolite, displays anti-inflammatory and anti-fibrotic signaling actions and therapeutic benefit in murine models of ischemia-reperfusion, atrial fibrillation, and pulmonary hypertension. Muscle LIM protein-deficient mice (Mlp) develop dilated cardiomyopathy (DCM), characterized by impaired left ventricular function and increased ventricular fibrosis at the age of 8 weeks. This study investigated the effects of NO₂-OA on cardiac function in Mlp mice both in vivo and in vitro. Mlp mice were treated with NO₂-OA or vehicle for 4 weeks via subcutaneous osmotic minipumps. Wildtype (WT) littermates treated with vehicle served as controls. Mlp mice exhibited enhanced TGFβ signalling, fibrosis and severely reduced left ventricular systolic function. NO₂-OA treatment attenuated interstitial myocardial fibrosis and substantially improved left ventricular systolic function in Mlp mice. In vitro studies of TGFβ-stimulated primary cardiac fibroblasts further revealed that the anti-fibrotic effects of NO₂-OA rely on its capability to attenuate fibroblast to myofibroblast transdifferentiation by inhibiting phosphorylation of TGFβ downstream targets. In conclusion, we demonstrate a substantial therapeutic benefit of NO₂-OA in a murine model of DCM, mediated by interfering with endogenously activated TGFβ signaling.