| Summary: | Many disorders of aging, including blinding-diseases, are associated with deficiency of brain and muscle arnt-like protein 1 (Bmal1) and, thereby, dysregulation of antioxidant-defense pathway. However, knowledge is limited regarding the role of Bmal1 regulation of antioxidant-pathway in the eye lens/lens epithelial cells (LECs) at the molecular level. We found that, in aging human (h)LECs, a progressive decline of nuclear factor erythroid 2-related factor 2 (Nrf2)/ARE (antioxidant response element)-mediated antioxidant genes was connected to Bmal1-deficiency, leading to accumulation of reactive oxygen species (ROS) and cell-death. <i>Bmal1</i>-depletion disrupted Nrf2 and expression of its target antioxidant genes, like <i>Peroxiredoxin 6 (Prdx6)</i>. DNA binding and transcription assays showed that Bmal1 controlled expression by direct binding to E-Box in <i>Prdx6</i> promoter to regulate its transcription. Mutation at E-Box or ARE reduced promoter activity, while disruption of both sites diminished the activity, suggesting that both sites were required for peak <i>Prdx6</i>-transcription. As in aging hLECs, ROS accumulation was increased in <i>Bmal1</i>-deficient cells and the cells were vulnerable to death. Intriguingly, Bmal1/Nrf2/Prdx6 and PhaseII antioxidants showed rhythmic expression in mouse lenses <i>in vivo</i> and were reciprocally linked to ROS levels. We propose that Bmal1 is pivotal for regulating oxidative responses. Findings also reveal a circadian control of antioxidant-pathway, which is important in combating lens/LECs damage induced by aging or oxidative stress.
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