Cytochrome P450 1B1 (CYP1B1) Knockout Mice are Less Susceptible to Hyperoxic Pulmonary Injury: A Novel Pro‐Oxidant Role for CYP1B1 in Vivo
Authors: Veith Alex , Jiang Weiwu , Wang Lihua , Zhou Guodong , Couroucli Xanthi , Lingappan Krithika , Moorthy Bhagavatula 
Published: November 2023

Supplemental oxygen is a life‐saving intervention provided to individuals suffering from respiratory distress, including adults with acute respiratory distress syndrome (ARDS) as well as premature newborns with respiratory distress syndrome. However, experimental evidence has shown that supplemental oxygen can create a hyperoxic environment which can lead to and exacerbate existing pulmonary injury due to increases in pathogenic reactive oxygen species (ROS) and oxidative stress. Many molecular and biochemical mechanisms are known to regulate ROS levels and oxidative stress, but previous studies have shown the importance of cytochrome P450 1A1 and 1A2 (CYP1A1/1A2) as well as the aryl hydrocarbon receptor (AHR) in the protection against hyperoxic lung injury. Further, there is evidence suggesting that cytochrome P450 1B1 (CYP1B1) may contribute to hyperoxic toxicity in human epithelial cells. The objective of this study was to test the hypothesis that CYP1B1 mechanistically contributes to hyperoxia‐induced toxicity. Ten‐week‐old C57BL/6 (WT) and Cyp1b1−/− male mice were exposed to hyperoxia (>95% oxygen) for 24–72 hours or maintained in room air as a control group. Lung weight changes were used to quantify lung injury. Mass spectrometry and 32P‐postlabeling were used to quantify lipid peroxidation and oxidative DNA damage, respectively, as markers of oxidative stress. Western blot and qPCR were used to quantify CYP1 protein and RNA expression. We found that Cyp1b1−/− mice had significantly decreased normalized lung weights after 48 (P=0.04) and 72 hours (P=0.017) of hyperoxia exposure, indicating reduced pulmonary edema and lung injury. We also found that Cyp1b1−/− mice have lower pulmonary isofurans (P=0.0331) and oxidative DNA adducts (P=0.0157) after 24 hours of hyperoxia. Gene expression studies showed that Cyp1b1−/− mice had increased CYP1A1 (P=2.9×10‐05) RNA expression during hyperoxia exposure and increased CYP1A2 (P=0.016) RNA expression after 48 hours of hyperoxia. Our results support the hypothesis that CYP1B1 contributes to hyperoxic lung injury, possibly by increasing ROS levels and oxidative stress. Our results also suggest that Cyp1b1−/− mice display lesser lung injury in part via increased transcriptional activation of Cyp1a1/1a2 genes. The goal of future studies will be to determine if CYP1B1 directly contributes to injury by creating a pro‐oxidant environment or indirectly contributes to injury by negatively feeding back on protective AHR‐dependent transcription. Elucidating the mechanism underlying these observations will help determine the viability of CYP1B1‐directed therapeutics and treatment strategies to treat and/or prevent hyperoxia toxicity and improve care for ARDS patients.Support or Funding InformationResearch reported in this publication was supported by the National Institutes of Health under award number R01ES019689, R01ES009132, R01HL12516, R01HL129794, and R01HL087174 to B.M., R01HL088343 to X.I.C., and T32GM088129 to A.C.V. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.