Increased ethanol‐inducible cytochrome P450‐2E1 and cytochrome P450 isoforms in exosomes of alcohol‐exposed rodents and patients with alcoholism through oxidative and endoplasmic reticulum stress

This study investigated the role of ethanol‐inducible cytochrome P450‐2E1 (CYP2E1) in enhancing CYP2E1 and other P450 proteins in extracellular vesicles (EVs) from alcohol‐exposed rodents and human patients with alcoholism and their effects on oxidative hepatocyte injury. Female Fischer rats and wild‐type or Cyp2e1‐null mice were exposed to three oral doses of binge ethanol or dextrose control at 12‐hour intervals. Plasma EV and hepatic proteins from alcohol‐exposed rodents, patients with alcoholism, and their respective controls were isolated and characterized. The number of EVs and the amounts of EV CYP2E1, CYP2A, CYP1A1/2, and CYP4B proteins were markedly elevated in both patients with alcoholism and alcohol‐exposed rats and mice. The number of EVs and EV P450 proteins were significantly reduced in ethanol‐exposed rats fed a diet containing polyunsaturated fatty acids. The increased number of EVs and EV CYP2E1 and other P450 isoforms in alcohol‐exposed wild types were significantly reduced in the corresponding Cyp2e1‐null mice. EV CYP2E1 amounts depended on increased oxidative and endoplasmic reticulum (ER) stress because their levels were decreased by cotreatment with the antioxidant N‐acetylcysteine or the CYP2E1 inhibitor chlormethiazole but increased by ER stress‐inducer thapsigargin, which was blocked by 4‐phenylbutyric acid. Furthermore, cell death rates were elevated when primary hepatocytes or human hepatoma cells were exposed to EVs from alcohol‐exposed rodents and patients with alcoholism, demonstrating that EVs from alcohol‐exposed rats and patients with alcoholism are functional and can promote cell death by activating the apoptosis signaling pathway, including phospho‐c‐Jun N‐terminal kinase, proapoptotic Bax, and activated caspase‐3. Conclusion: CYP2E1 has an important role in elevating EV CYP2E1 and other P450 isoforms through increased oxidative and ER stress. Elevated EV‐CYP2E1 detected after withdrawal from alcohol or exposure to the CYP2E1 inducer pyrazole can be a potential biomarker for liver injury. (Hepatology Communications 2017;1:675–690)