Expression Response Profiles of Toll-Like Receptor Family Members in Cyprinus Carpio after Lipopolysaccharide Stimulation, and Implication for Disease Control in Aquaculture

Abstract

In this study, response profiles of 17 Toll-like receptors (TLRs) to lipopolysaccharide (LPS) stimulation were studied at mRNA levels in the liver of the common carp Cyprinus carpio. Three types of gene response profiles were observed in TLR family. The first pattern was that the expressions of some TLRs were initially up-regulated and then decreased with time. This finding indicated that the responses of these TLRs were sensitive to LPS stimulation, and it was suggested that these TLRs were involved in responding and coping with LPS, implying that these TLRs were important in immune defense from Gram-negative bacteria. The second pattern was that some TLR expressions showed no obvious change after LPS stimulation, demonstrating that they were not sensitive to LPS and probably did not recognize LPS, implying that these TLRs should not be regarded as the major receptors to be regulated to prevent disease caused by Gram-negative bacteria. The third pattern was that gene expressions of partial TLRs were significantly downregulated after a period of LPS stimulation, indicating that their gene expressions were inhibited by LPS action, and implying that these TLRs did not initiate the signal pathway for inflammation reaction to clear Gramnegative bacteria. This study is based on the different response patterns of TLRs to LPS, that imply that the sensitive response TLR genes to LPS might be selected as target genes regulated by drugs that control inflammation reaction of diseased fish in aquaculture.