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Physiological crosstalk between the Mel1a and Mel1c pathways modulates melatonin-mediated, monochromatic light combination-induced bursa B-lymphocyte proliferation in chickens


 Background: Our previous study demonstrated that a combination of green and blue light (G→B or B→G) can improve the antibody titer in chickens compared with single monochromatic light, and melatonin is a critical signaling in the coordination between external light stimulation and the cellular response in the body. This study further clarifies the role of melatonin receptors in monochromatic lights combinations-induced bursa B-lymphocyte proliferation in chickens. Results: A total of 192 chickens were exposed to single monochromatic light (red [R], green [G], blue [B] or white [W] lights) or various monochromatic light combinations (B→G, G→B, R→B) from post-hatching day (P) 0 to P42. With consistency in the upregulation in melatonin level of plasma and melatonin receptors Mel1a, Mel1b and Mel1c expression of bursa, 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 and B→G group compared with other light-treated groups. Melatonin bound to Mel1a and Mel1c and upregulated p-PKC, p-ERK and p-AKT expression, thereby activating PI3K/AKT and PKC/ERK signaling and inducing B-lymphocyte proliferation in vitro and in vivo. Conclusion: These findings suggested that melatonin modulates a combination of green and blue light-induced B-lymphocyte proliferation in chickens via the Mel1a/PI3K/AKT and Mel1c/PKC/ERK pathways.