Professor Volker Rudolph

Organisation / Institute
Department III of Internal Medicine
Cologne University Heart Center

Address

PD Dr. Volker Rudolph
Department III of Internal Medicine,
Cologne University Heart Center
Kerpener Str. 62
50937 Köln, Germany

volker.rudolph[at]uk-koeln.de  

G. Effect of nitrated fatty acids on the nitric oxide-response in heart failure with preserved ejection fraction

Professor Volker Rudolph

Rationale and aims

Vascular inflammation and depletion of nitric oxide (NO) with ensuing microvascular dysfunction is critical in HF with preserved ejection fraction (HFPEF). Nitrated fatty acids (NO2-FA) are endogenously occurring termination products of inflammatory, oxidant-induced nitration reactions. By reversible electrophilic adduction to biological targets via their NO2-group, these molecules increase vascular NO, and resolve inflammation. Previously, our group has demonstrated protective effects of NO2-FA in myocardial ischemia/reperfusion and angiotensin II-(ang II) induced atrial fibrotic remodeling. Given the central role of vascular inflammation and impaired NO signaling in HFPEF, we aim to unravel the role of NO2-FA in this disorder.

Current state of research and own preliminary work

Figure 1: OA-NO2 treatment attenuates elevated hypertrophy and fibrosis in AngII+NaCl (AS) treated mice. (A-E) Represen-tative picrosirius stainings and histomorphometric hypertrophy and fibrosis quantification of isolated left ventricles (n=4/6/4). (F) Ratio of ventricular weight to body weight. (G-I) Representative echocardiographic evaluation of LV hypertrophy and quantification of LV posterior wall thickness and LV mass. Data are expressed as means ± SEM. *P<0.05; **P<0.01.

In preliminary studies, the effects of NO2-FA on C57BL/6J mice exposed to a continuous subcutaneous infusion of Ang II (1000 mg/kg/min) in addition to a salt diet (1% NaCl) for a period of 28 days (AS-treatment) were investigated. Compared to untreated animals, AS-treated mice revealed a significant increase in normalized heart weight, as well as pronounced evidence of cardiomyocyte hypertrophy and interstitial fibrosis. Additional treatment with OA-NO2 (1nmol/(g*h)) via subcutaneous osmotic mini-pumps lead to the suppression of left ventricular hypertrophy and diastolic dysfunction upon echocardiographic examination (Figure 1).

Experimental approach and work program

To further characterize diastolic dysfunction, mice will be investigated by in vivo conductance-catheter-based pressure-volume loop analyses. Apart from pertinent parameters of diastolic function, special attention will be paid to effective arterial elastance (Ea) and arterial-ventricular coupling (EES/Ea) to determine the contributions of systemic vascular effects of OA-NO2 on the observed ventricular changes. In addition, systemic endothelial dysfunction will be investigated by determination of systemic vascular resistance as well as acetylcholine-dependent relaxation of aortic rings. eNOS expression, phosphorylation, dimerization, and uncoupling will be assessed in cardiac and aortic tissues along with protein nitro-tyrosination and quantification of NO metabolites. As coronary endothelial dysfunction has been described as a contributor to the pathophysiology of diastolic dysfunction [1] cardiac endothelial dysfunction will be assessed by measurement of acetylcholine-dependent coronary perfusion pressure in Langendorff hearts after in vivo pretreatment as described above. In addition, since recent data have demonstrated highly efficient in vivo synthesis of NO2-FA upon dietary supplementation with conjugated linoleic acid (cLA), mice exposed to ang II and salt loading will be kept on a diet high in a racemic mixture of (9Z,11E)-cLA and (10E,12Z)-cLA and nitrite, which have been identified as the most efficient naturally substrate for in vivo NO2-FA formation[5]. Vascular function as well cardiac reverse remodeling will be assessed in relation to plasma levels of nitrated conjugated linoleic acids as determined by liquid chromatography/mass spectrometry.

Potential future therapeutic implications

Given the potent anti-inflammatory and anti-fibrotic effects of nitroalkenes, administration of the purified compound as well as dietary supplementation might evolve as attractive therapeutic options for cardiovascular disorders like HFpEF. Of note is that nitrated conjugated linoleic acid is currently being tested in phase 1 clinical studies.

Added value through collaborations within the CCRC

Given the potent anti-inflammatory properties of these molecules, further characterization of additional 'pleiotropic' effects with regard to macrophage polarization (Brüning, Pasparakis, Baldus), NFkB activation (Benzing), or pulmonary vascular remodeling (Rosenkranz) will facilitate close interaction with other groups from this consortium. Moreover, the fact that both NO2-FA and ceramides (Brüning) are membrane-derived lipids with potent effects on vascular signaling pathways offers exciting perspectives for characterizing these molecules in states of vascular stress. This project will be linked to core facilities histopathology (A. Quaas / R. Büttner) and molecular imaging (B. Neumaier).