Protective Role of Galanin during Chemically Induced Inflammation in Zebrafish Larvae

SIMPLE SUMMARY: The neuropeptide galanin is known for its protective role in the central nervous system, but not much is reported about its involvement in innate immunity. Our studies showed that galanin expression became upregulated after incubation in copper sulfate, which caused neuromast damage on the lateral line of the fish. Galanin presence protected the cells from the degenerative effects of the copper sulfate incubation compared to the galanin knockout larvae. Moreover, galanin treatment resulted in a higher expression of some inflammatory markers such as irg1l, il1b and tnfa, which indicated its possible role in immune responses and inflammatory processes. On the other side, galanin knockout caused more severe damage to the neuromasts, as well as downregulation in expression of the studied genes. Taken together, our results showed that galanin’s function was not only limited to the central nervous system as it was involved in other processes in the organism. ABSTRACT: During a pathological condition, many different systems are involved in the response of an affected organism. Galanin is considered to be a neuropeptide that plays an important role in the central nervous system; however, it is involved in many other biological processes, including the immune response. During our studies, we showed that galanin became upregulated in zebrafish larvae when exposed to copper sulfate. Moreover, the presence of normal levels of galanin, administration of a galanin analog NAX 5055 or galanin overexpression led to lowered lateral line damage and enhanced expression of inflammatory markers compared to the knockout larvae. The results showed that the neuroendocrine system acts multifunctionally and should be considered as a part of the complex neuro–immune–endocrine axis.