Molecular role of cytochrome P4501A enzymes inoxidative stress

Cytochrome P4501A (CYP1A) enzymes play important roles in xenobiotic and endobiotic metabolism. Due to uncoupling reactions during the enzymatic cycle, CYP1A enzymes can release reactive oxidative species (ROS) in the form of superoxide radical, hydrogen peroxide, hydroxyl radical etc. An imbalance between production of free radicals and the ability of antioxidants to detoxify the free radicals can lead to accumulation of ROS, which in turn can lead to oxidative stress. Oxidative stress can lead to inflammation and toxicity, which in turn can cause human diseases such as bronchopulmonary disease (BPD), ARDS, renal hypertension, etc. CYP1A enzymes, depending on the organ system, they either contribute or protect against oxidative injury. Thus, they have dual roles in regard to oxidative stress. This review presents an overview of the mechanistic relationship between CYP1A enzymes and oxidative stress in relation to various diseases in different organs (e.g., liver, lungs, heart, kidneys, and reproductive organs).

Epoxide hydrolase 1 (EPHX1) hydrolyzes epoxyeicosanoids and impairs cardiac recovery after ischemia

Stimuli such as inflammation or hypoxia induce cytochrome P450 epoxygenase-mediated production of arachidonic acid-derived epoxyeicosatrienoic acids (EETs). EETs have cardioprotective, vasodilatory, angiogenic, anti-inflammatory, and analgesic effects, which are diminished by EET hydrolysis yielding biologically less active dihydroxyeicosatrienoic acids (DHETs). Previous in vitro assays have suggested that epoxide hydrolase 2 (EPHX2) is responsible for nearly all EET hydrolysis. EPHX1, which exhibits slow EET hydrolysis in vitro, is thought to contribute only marginally to EET hydrolysis. Using Ephx1^-/-, Ephx2^-/-, and Ephx1^-/-Ephx2^-/- mice, we show here that EPHX1 significantly contributes to EET hydrolysis in vivo Disruption of Ephx1 and/or Ephx2 genes did not induce compensatory changes in expression of other Ephx genes or CYP2 family epoxygenases. Plasma levels of 8,9-, 11,12-, and 14,15-DHET were reduced by 38, 44, and 67% in Ephx2^-/- mice compared with wildtype (WT) mice, respectively; however, plasma from Ephx1^-/-Ephx2^-/- mice exhibited significantly greater reduction (100, 99, and 96%) of those respective DHETs. Kinetic assays and FRET experiments indicated that EPHX1 is a slow EET scavenger, but hydrolyzes EETs in a coupled reaction with cytochrome P450 to limit basal EET levels. Moreover, we also found that EPHX1 activities are biologically relevant, as Ephx1^-/-Ephx2^-/- hearts had significantly better postischemic functional recovery (71%) than both WT (31%) and Ephx2^-/- (51%) hearts. These findings indicate that Ephx1^-/-Ephx2^-/- mice are a valuable model for assessing EET-mediated effects, uncover a new paradigm for EET metabolism, and suggest that dual EPHX1 and EPHX2 inhibition may represent a therapeutic approach to manage human pathologies such as myocardial infarction.