Abstract Rationale Cigarette smoke (CS) exposure increases both the incidence and severity of influenza A virus (IAV) infections in humans and increases mortality in murine models. We have demonstrated that deletion of Cytochrome P450 family 1 subfamily B member 1 (CYP1B1) in mice confers protection against CS-induced susceptibility to IAV infection. Notably, several approved drugs possess CYP1B1 inhibitory activity and exhibit low toxicity. These drugs also have well-characterized pharmacokinetics and dosing regimens. Therefore, repurposing these pharmaceuticals to target CYP1B1 presents a promising translational strategy for improving influenza outcomes in smokers. Methods To test the hypothesis that pharmacological inhibition of CYP1B1 alters survival outcomes during IAV infection, we employed an in vivo mouse model. Therapeutic doses of CYP1B1 inhibitors—ticagrelor (5 mg/kg), chlorprothixene (1.3 mg/kg), and TMS (1.5 mg/kg)—were administered intraperitoneally once daily for 9 days post-infection (p.i.) in CS-exposed, IAV-infected mice. To evaluate the efficacy of CYP1B1 inhibition in mitigating CS-enhanced disease severity, we compared survival rates, lung-to-body weight ratios, and host immune responses between treated and untreated groups following IAV challenge, with or without prior CS exposure. Results CS-exposure increased mortality during IAV infection as compared with nonsmoking (NS) controls, with survival rates of 36% for CS and 80% for NS, respectively. Treatment with the CYP1B1 inhibitors ticagrelor (43%) and TMS (36%) did not improve survival in CS-exposed mice at the tested doses. In contrast, chlorprothixene treatment at 1.3 mg/kg increased survival to 64% in CS-exposed mice. Notably, chlorprothixene did not confer survival benefits in NS mice (67%), and TMS treatment worsened outcomes in NS mice (40% survival), suggesting that chlorprothixene selectively benefits CS-exposed, IAV-infected mice. To optimize dosing, we evaluated higher (5.2 mg/kg) and lower (0.26 mg/kg) concentrations of chlorprothixene in CS-exposed mice. Both doses yielded lower survival rates (50% and 40%, respectively) compared to the 1.3 mg/kg dose. CS exposure suppressed total immune cell counts in bronchoalveolar lavage fluid (BALF) following IAV infection. Importantly, chlorprothixene treatment significantly restored immune cell recruitment in BALF and attenuated lung injury, further supporting its therapeutic potential in CS-exposed mice with influenza. Conclusions Our findings in mice demonstrate that treatment with the CYP1B1 inhibitor chlorprothixene significantly improved survival in IAV infection, and restored total immune cell counts that are otherwise suppressed by CS exposure. These results confirm the translational potential of this strategy to improve outcomes of influenza infections in people who smoke, or are exposed to, combustible tobacco smoke. This abstract is funded by: Veterans Affairs, Grant Number I01 BX001937
Metcalf et al. (Fri,) studied this question.