Pre-B cell colony-enhancing factor in lower vertebrates: First evidence of this cytokine being involved in antioxidant activity by reconstruction of a novel NAD salvage pathway in E. coli

The pre-B cell colony-enhancing factor identified in mammals is an important cytokine involved in multiple functions, such as immunoregulation, cellular proliferation and differentiation. However, little is known about its existence and function in lower vertebrates; therefore, we investigated the characterization, expression and especially the biofunction of this factor in Tetraodon nigroviridis, a model organism of lower vertebrates. We focus on the question of whether the pre-B cell colony-enhancing factor of lower vertebrates contributes to the NAD mediated antioxidant activity by its involvement in the biosynthesis of NAD through pyridine nucleotide cycles. Experimental data demonstrated that by transforming fish pre-B cell colony-enhancing factor into Escherichia coli cells, the amounts of NAD and NADP significantly increased, and cellular antioxidant activity greatly improved. This is the first report about vertebrate pre-B cell colony-enhancing factor acting as a nicotinamide phosphoribosyltransferase to reconstruct a pyridine nucleotide cycle III pathway in E. coli and playing an important role in antioxidant stress by up-regulation of NAD biosynthesis. We hope that our observations may enrich the study of pre-B cell colony-enhancing factor, and contribute to a better understanding of the molecular and functional evolution of the pre-B cell colony-enhancing factor family in both lower vertebrates and mammals as a whole.