Effects of LPS injection on Pc-astakine expression in the gastropod Pomacea canaliculata

Astakine-1 is a prokineticin-containing factor and the first hematopoietic cytokine described in invertebrates. Astakine-1 was firstly retrieved in the freshwater crayfish Pacifastacus leniusculus, and recent experiments have demonstrated the presence of astakine-like molecules also in insects and molluscs, including the freshwater snail, Pomacea canaliculata. In control conditions Pcastakine is expressed in several organs, especially in the ampulla (reservoir of hemocytes and potential district of hemocyte maturation) and in the pericardial fluid (i.e. the hematopoietic tissue). By mean of qPCR experiments, we have analyzed the effects of the injection of 50 µg LPS on the expression of the gene Pc-astakine. Our observations indicate that 24 h after the injection, the major modification of the Pc-astakine expression was evident in the anterior kidney, a potential hemocyte reservoir, in which the expression of the gene decreased to almost undetectable level. In the pericardial fluid, ampulla and circulating hemocytes, the expression of Pc-astakine dropped to less than 50 % with respect to the sham-injected control snails. The drop in the amount of mRNA detected by qPCR could reflect an increased rate of translation and consequent degradation of the available mRNA, rather than a decrease of the transcription rate. Similarly, in the bivalve Crassostrea gigas, it has been suggested that accumulated Cg-astakine transcripts are largely translated under some environment stress, including immune stimuli. On the whole, our results indicate that the expression of Pc-astakine and the translation rate of its mRNA may be influenced by immune stimuli, and support the hypothesis that PcAstakine may be involved in Pomacea hematopoiesis and/or may have immune-related functions, as well.