Mechanistic role of cytochrome P450 (CYP)1B1 in oxygen-mediated toxicity in pulmonary cells: A novel target for prevention of hyperoxic lung injury

Abstract

Supplemental oxygen, which is routinely administered to preterm infants with pulmonary insufficiency, contributes to bronchopulmonary dysplasia (BPD) in these infants. Hyperoxia also contributes to the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) in adults. The mechanisms of oxygen-mediated pulmonary toxicity are not completely understood. Recent studies have suggested an important role for cytochrome P450 (CYP)1A1/1A2 in the protection against hyperoxic lung injury. The role of CYP1B1 in oxygen-mediated pulmonary toxicity has not been studied. In this investigation, we tested the hypothesis that CYP1B1 plays a mechanistic role in oxygen toxicity in pulmonary cells in vitro. In human bronchial epithelial cell line BEAS-2B, hyperoxic treatment for 1–3 days led to decreased cell viability by about 50–80%. Hyperoxic cytotoxicity was accompanied by an increase in levels of reactive oxygen species (ROS) by up to 110%, and an increase of TUNEL-positive cells by up to 4.8-fold. Western blot analysis showed hyperoxia to significantly down-regulated CYP1B1 protein level. Also, there was a decrease of CYP1B1 mRNA by up to 38% and Cyp1b1 promoter activity by up to 65%. On the other hand, CYP1B1 siRNA appeared to rescue the cell viability under hyperoxia stress, and overexpression of CYP1B1 significantly attenuated hyperoxic cytotoxicity after 48 h of incubation. In immortalized lung endothelial cells derived from Cyp1b1-null and wild-type mice, hyperoxia increased caspase 3/7 activities in a time-dependent manner, but endothelial cells lacking the Cyp1b1 gene showed significantly decreased caspase 3/7 activities after 48 and 72 h of incubation, implying that CYP1B1 might promote apoptosis in wild type lung endothelial cells under hyperoxic stress. In conclusion, our results support the hypothesis that CYP1B1 plays a mechanistic role in pulmonary oxygen toxicity, and CYP1B1-mediated apoptosis could be one of the mechanisms of oxygen toxicity. Thus, CYP1B1 could be a novel target for preventative and/or therapeutic interventions against BPD in infants and ALI/ARDS in adults.

Role of cytochrome P450s in the generation and metabolism of reactive oxygen species

“…Our initial study found that CYP1B1 may in fact contribute to hyperoxic toxicity. Cells overexpressing CYP1B1 showed increased hyperoxic toxicity in an MTT assay and cells in which CYP1B1 was knocked down showed decreased caspase 3/7 activity, a marker of apoptosis [56]. We have also found that Cyp1b1 −/− mice are less susceptible to hyperoxic lung injury, suggesting that CYP1B1, unlike CYP1A, contributes to hyperoxic toxicity (Veith et al, unpublished data).…”

New Perspectives of CYP1B1 Inhibitors in the Light of Molecular Studies

“…Human cells overexpressing CYP1B1 were more susceptible to oxygen toxicity, while the use of CYP1B1-siRNA attenuated the toxic effect of hyperoxia. In immortalized lung endothelial cells derived from Cyp1b1-null and wild-type mice, Cyp1b1 expression promoted apoptosis induced by oxidative stress, while in cells derived from Cyp1b1-null mice, hyperoxia cytotoxicity was significantly diminished [31]. In studies in vivo, Cyp1b1−/− mice lacking the cytochrome P450 1B1 gene were less susceptible to hyperoxic lung injury than C57BL/6 wild type mice [32].…”

“…The role of CYP1B1 in hyperoxia cytotoxicity in human lung endothelial cells in vitro was studied [31]. Human cells overexpressing CYP1B1 were more susceptible to oxygen toxicity, while the use of CYP1B1-siRNA attenuated the toxic effect of hyperoxia.…”

Role of reactive oxygen species and iron in host defense against infection

“…As the level of oxidation reactions controls ROS production, changes in the activity of these enzymes as a result of various conditions can result in ROSmediated damage. As an example, enzyme CYP1B1 in pulmonary cells is associated with oxygenmediated pulmonary toxicity in cases of hyperoxia where its activity increases and ROS production rises (14). Enzyme CYP2E1, found in hepatocytes, shows an increase in activity after heavy alcohol consumption, leading to enhanced ROS production (15).…”