Cold Shock Induced Oxidative Stress, Apoptosis and Genome-wide Gene Expression Perturbation in the Eyes of Zebrafish and the Mitigation of Blue Wavelength Light

Abstract

As global climate changes, severely temperature variations have significant impacts on survival and development of fish. While the potential effects of light wavelength on cold shock and associated mechanisms remain largely unknown in fish. Here, zebrafish were pre-exposed to white LEDs (an irradiance of 0.9 W/m2) and blue LEDs (LDB, peak at 450 nm, 0.9 W/m2) for 2 weeks, and then exposed to 26℃ or 11℃ for 48 hours, respectively. Cold shock led to low survival rate. Cold shock altered retinal structure, increased the number of apoptotic cells and Caspase-3 activity, inhibited superoxide dismutase (SOD) and catalase (CAT) activities, up-regulated mRNA expression of (NF-E2-related factor 2) nrf2, p53, casp3 and casp9, and down-regulated cat expression in fish eyes. These results demonstrated that acute cold exposure induced oxidative stress and apoptosis in zebrafish eyes, which may lead to mortality. However, cold shock in combination with LDB apparently mitigated these negative effects, which might be involved in the up-regulation of antioxidant response and down-regulation of apoptotic responses at transcriptional and translational levels. Furthermore, cold shock also caused dysregulation of genome-wide gene expression involved in circadian rhythm, phototransduction and il-17 signaling pathway, indicating that cold shock disturbed phototransduction cascade and circadian rhythm signals and caused inflammatory responses. Ten key genes involved in circadian rhythm, phototransduction, cell cycle arrest, RNA processing or inflammatory responses were identified, including muc5d, rnps1, si:dkey-243i1.1, opn1mw1, gadd45ba, cebpd, btg2, si:dkey-242g16.2, nr1d1 and zgc:122979, which may play an important role in the protection of LDB against cold shock. Finally, our study suggested the relationship between spectrum and cold stress and demonstrated LDB could protect fish against the negative effect of cold stress in the eyes.