• Author / Creator
    El-Sherbeni, Ahmed Abd El-Hakeem
  • Arachidonic acid (AA) metabolism has long been a very appealing target for drug discovery and development efforts. Beside cyclooxygenase and lipoxygenase pathways, AA is also metabolized by the recently recognized cytochrome P450 (P450) pathway, forming several biologically-active epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs). Already, drugs that are targeting cyclooxygenase- and lipoxygenase-mediated AA metabolism are remarkably successful medicines. For P450-derived AA metabolites, recent data demonstrated their potent and multifaceted roles in cardiovascular pathophysiology, albeit no drug was clinically approved to target these metabolites. Our focus was on cardiac hypertrophy, which is a prelude for heart failure estimated to affect 2.2% of US population. Once heart failure develops from cardiac hypertrophy, the condition is irreversible and is associated with a high death rate. Accordingly, our aims were; 1) to characterize AA metabolism by microsomes separated from different rat organs and by individual recombinant rat P450 enzymes, 2) to determine the alterations in P450-mediated AA metabolism in the heart during cardiac hypertrophy,, 3) to identify novel drug targets in the P450-mediated AA metabolic cascade, and 4) to extrapolated animal and human in vitro data to identify an effective and safe modulator of P450-mediated AA metabolism Our results showed that microsomes from different rat organs can mediate the formation of their own P450-derived AA metabolites with organ-distinct metabolic and kinetic profiles. In addition, our data suggest that the major P450-epoxygenases are CYP2C11, CYP2Bs, CYP2C23 and CYP2C11/ CYP2C23 for the heart, lungs, kidneys and liver, respectively, while CYP4As may be the major ω-hydroxylase in the heart and kidneys, and CYP4As and/or CYP4Fs may be the major hydroxylases in the lungs and liver. Cardiac P450 enzymes that were altered and significantly impacted P450-mediated AA metabolism during cardiac hypertrophy were identified in SD rats to be, CYP1B1, CYP2B2, CYP2J3 and CYP4As, which may have a role in the development and progression of pressure overload-induced cardiac hypertrophy, by mediating the formation and degradation of 12-, 19- and 20-HETEs and EETs. Furthermore, our results showed that certain rat P450 enzymes could be exceptionally good candidates for drug targeting based on their high activity, narrow regioselectivity and high inducibility, most importantly CYP1As, CYP2C11, and CYP2E1, that may be useful for several diseases, such as heart and renal diseases. Finally, our data suggest that P450 modulation by clinically-approved drugs could be employed to effectively and selectively modulate P450-mediated AA metabolism in humans, comparable to investigational drugs, of which resveratrol and fluconazole could be good candidates to be repurposed as new P450-based treatments. In conclusion, we identified several potentially critical drug targets in the cascade of AA metabolism that could be used to counterbalance the alterations of P450-mediated AA metabolism in the heart during cardiac hypertrophy. These drug targets may be effectively and selectively modulated by agents that are already approved for clinical use, and therefore, they are readily available to clinical trials.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.