A Green and Blue Monochromatic Light Combination Therapy Reduces Oxidative Stress and Enhances B-Lymphocyte Proliferation through Promoting Melatonin Secretion.

Artificial illumination may interfere with biological rhythms and distort physiological homeostasis in avian. Our previous study demonstrated that 660 nm red light exacerbates oxidative stress, but a combination of green and blue lights (G→B) can improve the antibody titer in chickens compared with single monochromatic light. Melatonin acts as an antioxidant which is a critical signaling to the coordination between external light stimulation and the cellular response from the body. This study further clarifies the potential role of melatonin in monochromatic light combination-induced bursa B-lymphocyte proliferation in chickens. A total of 192 chicks were exposed to a single monochromatic light (red (R), green (G), blue (B), or white (W) lights) or various monochromatic light combinations (B→G, G→B, and R→B) from P0 to P42. We used qRT-PCR, MTT, western blotting, immunohistochemistry, and Elisa to explore the effect of a combination of monochromatic light on bursa B-lymphocytes and its intracellular signal pathways. With consistency in the upregulation in melatonin level of plasma and antioxidant enzyme ability, we observed increases in organ index, follicle area, lymphocyte density, B-lymphocyte proliferation, PCNA-positive cells, and cyclin D1 expression in bursa of the G→B group compared with other light-treated groups. Melatonin bound to Mel1a and Mel1c and upregulated p-AKT, p-PKC, and p-ERK expression, thereby activating PI3K/AKT and PKC/ERK signaling and inducing B-lymphocyte proliferation. Overall, these findings suggested that melatonin modulates a combination of green and blue light-induced B-lymphocyte proliferation in chickens by reducing oxidative stress and activating the Mel1a/PI3K/AKT and Mel1c/PKC/ERK pathways.