Photoprotective and cryoprotective effect of the carotenoid bacterioruberin on peripheral blood mononuclear cells.

Carotenoids are known for their antioxidant and antiapoptotic properties, which make them effective in reducing cellular damage caused by UV radiation and improving cryopreservation outcomes in various cell types. Among them, bacterioruberin (BR) stands out as a potent antioxidant carotenoid produced by Haloarchaea, such as Haloferax mediterranei. This study evaluates the effects of a bacterioruberin-rich carotenoid extract (BRCE) on peripheral blood mononuclear cells (PBMCs) under these conditions. Fluorescence microscopy and flow cytometry revealed that pre-incubation with BRCE at concentrations of 1-2.7 µg/mL significantly increased PBMC viability after UV irradiation, reducing apoptosis and cell death. Higher BRCE concentrations (≥ 25 µg/mL) diminished these protective effects, with 75 µg/mL further increasing apoptosis and cell death rates. For cryopreserved PBMCs, BRCE concentrations of 1-2.7 µg/mL improved cell viability, reduced apoptosis, and minimized cell death, with similar adverse effects observed at higher concentrations. These findings underscore BRCE's dual role in mitigating UV-induced cellular damage and enhancing cryopreservation efficiency, with optimal concentrations identified for both processes. This highlights BR's potential in biomedical applications requiring immune cell preservation and protection. KEY POINTS: • BRCE enhances PBMC viability after UV exposure and cryopreservation. • Low BRCE doses (1-2.7 µg/mL) are protective; high doses increase cell death. • BRCE shows biomedical potential as an antioxidant and natural UV filter.