Down-regulated RPS-30 in Angiostrongylus cantonensis L5 plays a defensive role against damage due to oxidative stress

Background: Eosinophilic meningitis, caused by Angiostrongylus cantonensis L5, is mainly attributed to the Eosinophils, which contribute to tissue inflammatory responses in helminthic infections. Eosinophils are associated with helminthic killing, using the peroxidative oxidation and hydrogen peroxide (H2O2) generated by dismutation of superoxide produced during respiratory burst. In contrast, residing in the host with high level of eosinophils, helminthic worms have evolved to attenuate eosinophil-mediated tissue inflammatory responses for their survival in hosts. Our previous study demonstrated that the expression of Acan-rps-30 was significantly down-regulated in A. cantonensis L5 worms, which reside in the cerebrospinal fluid with high level of Eosinophils. Acan-RPS-30, a homologous protein of human Fau, which plays a pro-apoptotic regulatory role, may function in protecting worms from oxidative stress.Methods: RACE, genome Walking, bioinformatics were used to isolate and analyse the structural characterisation of Acan-RPS-30; qRT-PCR and microinjection was performed to detect the expression patterns of Acan-rps-30; feeding RNAi was used to ced-3 knock-down; microinjection was performed to construct transgenic worms; oxidative stress assay was used to determine the functions of Acan-RPS-30.Results: Our results showed that Acan-RPS-30 consisted of 130 amino acids, and was grouped into Clade V with C. elegans in phylogenetic analysis. It was expressed ubiquitously in worms and was down-regulated in both L5 and adult A. cantonensis. Worms expressing pCe-rps30::Acan-rps-30::rfp, with the refractile “button-like” apoptotic corpses, were susceptible to oxidative stress. Apoptosis genes ced-3 and ced-4 were both up-regulated in the transgenic worms. And the phenotype susceptible to oxidative stress could be converted with ced-3 defective mutation and RNAi. rps-30–/– mutant worms were resistant to oxidative stress, with ced-3 and ced-4 were both down-regulated. And the oxidative stress resistance phenotype could be rescued and inhibited by expressing pCe-rps30::Acan-rps-30::rfp in rps-30–/– mutant worms.Conclusion: In C. elegans worms, down-regulated RPS-30 plays a defensive role against damage due to oxidative stress for worm survival by regulating ced-3 down-regulated. And this might indicate the mechanism of A. cantonensis L5 worms, with Acan-RPS-30 down-regulated, surviving in the central nervous system of human from immune attack of Eosinophil.