Adrenaline restores Bmal1 transcriptional rhythms dampened by SARS-CoV-2 infection in Cthrc1-positive pulmonary fibroblasts derived from the Nile grass rat

Disturbances in sleep and circadian rhythms are observed as sequelae of COVID-19 syndrome. However, the pathogenetic mechanisms remain largely unknown. Here, we established a fibroblast cell line (GrLBmal1-luc) from the lungs of diurnal Nile grass rats stably expressing the Bmal1-luciferase reporter gene to investigate peripheral clock regulation. First, endogenous receptor expression was screened with quantitative RT-PCR, immunohistochemistry, Ca2+ imaging, and Bmal1-luciferase reporter in GrLBmal1-luc cells. Through these, the present study discovered phase-shifting effects of adrenaline via β2-adrenoceptor. Interestingly, GrLBmal1-luc cells expressed collagen triple helix repeat containing-1 (Cthrc1) and exhibited a morphology typical of fibroblasts that accumulate in the fibrotic lungs of severe COVID-19 patients. Therefore, human angiotensin-converting enzyme-2 (ACE2) receptors were overexpressed in GrLBmal1-luc cells, and the effects of SARS-CoV-2 (Omicron, XBB.1) infection were analyzed. Following SARS-CoV-2 infection, Bmal1 transcriptions were significantly reduced, while IL-6 and Ciart transcriptions were upregulated. Rev-erbα and Per1 transcriptions were not substantially impacted. The flattened Bmal1-luciferase rhythms gradually recovered 4 days after infection, and adrenaline stimulation amplified and recovered the rhythms faster compared with unstimulated controls. These results provide insight into the molecular mechanisms underlying circadian rhythm disturbances during SARS-CoV-2 infection, and they suggest that adrenergic agents may have therapeutic potential in COVID-19 patients.