Role of Acanthopagrus schlegelii MyD88 and IκBα in Inflammation Regulation Against Vibrio parahaemolyticus Infection

MyD88 and I kappa B alpha are inflammation-related genes involved in various immune responses in vertebrate, but their function in Acanthopagrus schlegelii was not clear. In this article, the open reading frame (ORF) of A. schlegelii MyD88 (AsMyD88) is 867 bp, encoding 288 amino acids, and containing a death domain and a TIR domain. The ORF of A. schlegelii kappa B alpha (AsI kappa B alpha) is 951 bp, encoding 324 amino acids and containing multiple ANK domains. The results of qRT-PCR showed that AsMyD88 was most distributed in the liver, followed by the gill, while AsI kappa B alpha was highly distributed in the kidney and muscle. After infection with Vibrio parahaemolyticus, the transcription of AsMyD88 in the liver and kidney was significantly increased, and the transcription of AsI kappa B alpha in the liver and kidney was inhibited. After the successful overexpression in RAW264.7 cells, it was found that the overexpressed AsMyD88 was distributed in both the nucleus and cytoplasm, while the I kappa B alpha was mainly located in the cytoplasm. The expression of p65 was increased, while the expression of I kappa B alpha was decreased after AsMyD88 overexpression. Meanwhile, the transcription of inflammatory factors was significantly increased after overexpression of AsMyD88, while the transcription of inflammatory factors was inhibited after overexpression of AsI kappa B alpha. The result showed that NF-kappa B pathway was activated by AsMyD88. Meanwhile, the phosphorylation of JNK, ERK, and p38 was significantly changed after overexpression of AsMyD88 and AsI kappa B alpha, respectively. In conclusion, AsMyD88 and AsI kappa B alpha could regulate cellular inflammatory response to participate in the immune response of fish.