Nitro-oleic acid reduces thoracic aortic aneurysm progression in a mouse model of Marfan syndrome.

AIMS: Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the Fibrillin-1 gene. It is associated with formation of thoracic aortic aneurysms that can potentially be a life-threatening condition due to aortic rupture or dissection. Excessive non-canonical transforming growth factor beta signalling, mediated by activation of extracellular signal-regulated kinases 1/2 (ERK1/2), as well as inducible nitric oxide synthase (NOS2)-dependent nitric oxide production, have been identified to drive aortic pathology in MFS through induction of elastin fragmentation and smooth muscle cell apoptosis. Despite promising results in animal studies, specific pharmacological interventions approved for clinical use in patients with MFS-related aortic disease are rare. Nitro-oleic acid (NO2-OA) is an endogenously generated signalling modulator, which is available as an oral compound and has been shown to inhibit ERK1/2 activation and NOS2 expression in different disease models, thereby exerting promising therapeutic effects. In this study, we investigated whether NO2-OA decreases aortic dilation in MFS. METHODS AND RESULTS: Eight-week-old MFS (Fbn1C1041G/+) mice were treated with NO2-OA or vehicle for 4 weeks via subcutaneously implanted osmotic minipumps. Echocardiography indicated progressive ascending aortic dilation and wall stiffening in MFS mice, which was significantly attenuated by NO2-OA treatment. This protective effect was mediated by inhibition of aortic ERK1/2, Smad2 as well as nuclear factor kappa B overactivation and consequent attenuation of elastin fragmentation by matrix metalloproteinase 2, apoptosis, and collagen deposition. Critically, the therapeutic efficacy of NO2-OA in MFS was further emphasized by demonstrating its capability to reduce lethal aortic complications in Fbn1C1041G/+ mice challenged with Angiotensin II. CONCLUSION: NO2-OA distinctly attenuates progression of aortic dilation in MFS via modulation of well-established disease-mediating pathways, thereby meriting further investigation into its application as a therapeutic agent for the treatment of this condition.

Stamp2 Protects From Maladaptive Structural Remodeling and Systolic Dysfunction in Post-Ischemic Hearts by Attenuating Neutrophil Activation.

The six-transmembrane protein of prostate 2 (Stamp2) acts as an anti-inflammatory protein in macrophages by protecting from overt inflammatory signaling and Stamp2 deficiency accelerates atherosclerosis in mice. Herein, we describe an unexpected role of Stamp2 in polymorphonuclear neutrophils (PMN) and characterize Stamp2's protective effects in myocardial ischemic injury. In a murine model of ischemia and reperfusion (I/R), echocardiography and histological analyses revealed a pronounced impairment of cardiac function in hearts of Stamp2-deficient- (Stamp2-/- ) mice as compared to wild-type (WT) animals. This difference was driven by aggravated cardiac fibrosis, as augmented fibroblast-to-myofibroblast transdifferentiation was observed which was mediated by activation of the redox-sensitive p38 mitogen-activated protein kinase (p38 MAPK). Furthermore, we observed increased production of reactive oxygen species (ROS) in Stamp2-/- hearts after I/R, which is the likely cause for p38 MAPK activation. Although myocardial macrophage numbers were not affected by Stamp2 deficiency after I/R, augmented myocardial infiltration by polymorphonuclear neutrophils (PMN) was observed, which coincided with enhanced myeloperoxidase (MPO) plasma levels. Primary PMN isolated from Stamp2-/- animals exhibited a proinflammatory phenotype characterized by enhanced nuclear factor (NF)-κB activity and MPO secretion. To prove the critical role of PMN for the observed phenotype after I/R, antibody-mediated PMN depletion was performed in Stamp2-/- mice which reduced deterioration of LV function and adverse structural remodeling to WT levels. These data indicate a novel role of Stamp2 as an anti-inflammatory regulator of PMN and fibroblast-to-myofibroblast transdifferentiation in myocardial I/R injury.

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 TGFß 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 TGFß-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 TGFß 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 TGFß signaling.