The Role of Subterminal Hydroxyeicosatetraenoic Acids in the Pathogenesis of Cardiac Hypertrophy

Cardiac hypertrophy is a complex condition which is characterized by increased mass of the heart muscle. If untreated, cardiac hypertrophy can ultimately lead to heart failure (HF), arrhythmia and sudden death. Accumulating evidence suggest that pathological cardiac hypertrophy is strongly correlated with aberrations in cytochrome P450 (CYP)-mediated arachidonic acid (AA) metabolism in the cardiac tissue. In the heart, AA is metabolized by the recently recognized CYP pathway, forming several biologically-active epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs). HETEs could be further classified as mid-chain, subterminal and terminal HETEs. Subterminal HETEs are group of lipid mediators that are implicated in a spacious array of physiological and pathophysiological processes. However, their role in the heart has yet to be investigated. Another important group of AA metabolites in the heart are mid-chain HETEs. Several experimental studies have demonstrated a role of CYP1B1 and its associated mid-chain HETEs metabolites in the development of cardiovascular diseases. Characterization of the role of subterminal HETEs in the heart and modulating the CYP1B1/mid-chain HETEs pathway will help to identify novel points of intervention that could help in the development of new therapeutic agents for cardiac hypertrophy and heart failure. Therefore, the objectives of the current work were to test whether R- and S-enantiomers of 19-HETE have differential role in the cardioprotective mechanism against cardiac hypertrophy, examine the inhibitory effect of both enantiomers of 19-HETE on human recombinant CYP1B1 enzyme, test the capability of synthetic analogues of 19-HETE to exert an inhibitory effect on some human recombinant CYP enzymes and test the cardioprotective effects of CYP modulators such as resveratrol and fluconazole on experimental models of cardiac hypertrophy and HF. The results demonstrated that both enantiomers of 19-HETE protected against angiotensin II (Ang II)-induced cardiac hypertrophy via decreasing the level of cardiotoxic mid-chain HETEs, inhibiting the catalytic activity of CYP1B1 and decreasing the protein expression level of LOX and COX-2 enzymes, with the S-enantiomer having more protection than the R-enantiomer. In addition, both enantiomers of 19-HETE noncompetitively inhibited human recombinant CYP1B1 enzymatic activity with higher potency of the S-enantiomer. Also, we have tested the potential inhibitory effect of synthetic 19-HETE analogs on different CYP enzymes. We showed that the synthetic analogues of 19(R)-HETE and 19(S)-HETE noncompetitively inhibited CYP1A1 and CYP1B1 enzymatic activity with preferential selectivity of the S-analogue. Interestingly, we demonstrated that resveratrol attenuated Ang II-induced cardiac hypertrophy and caused a significant decrease of CYP1B1 protein expression and mid-chain HETEs. Furthermore, in vivo studies showed that low dose resveratrol reduces the severity of myocardial infarction (MI)-induced HF, at least in part, through the inhibition of CYP1B1 and cardiotoxic mid-chain HETE metabolites. Lastly, the results showed that the protective role of fluconazole against pressure overload-induced cardiac hypertrophy is associated with a significant inhibition of CYP1B1 at the gene and protein levels and a reduction in the formation rate of mid-chain HETEs. In conclusion, the findings of the current work highlight the role of subterminal HETEs in the development of cardiac hypertrophy and indicate that their synthetic analogues could serve as a novel target for the treatment of heart diseases. Also, the findings of this work point out the potential repurposing of available clinically-approved drugs including resveratrol and fluconazole as a CYP1B1 inhibitors for the treatment of cardiovascular diseases.