A New IL6 Isoform in Chinese Soft-Shelled Turtle (Pelodiscus sinesis) Discovered: Its Regulation during Cold Stress and Infection

Abstract

The Chinese soft-shelled turtle (Pelodiscus sinesis) is a widely cultured commercial species in East and Southeast Asian countries. The turtles frequently suffer from acute cold stress during farming in China. Stress-induced factor such as Interleukin-6 (IL6) is a multifunctional molecule that plays important roles in innate and adaptive immune response. In the present study, we found that the turtle possessed two IL6 transcripts, where one IL6 transcript contained a signal peptide sequence (psIL6), while the other IL6 transcript (psIL6ns) possessed no such signal peptide gene. To test any differential expression of the two isoforms during temperature and microbial stress, turtles were adapted to optimal environmental water temperature (25 °C), stressed by acute cooling for 24 h, followed with the challenge of Aeromonas hydrophila (1.8 × 108 CFU) or Staphylococcus aureus (5.8 × 108 CFU). Gene characterization revealed that psIL6ns, a splicer without codons encoding a signal peptide and identical to the one predicted from genomic sequence, and psIL6, a splicer with codons encoding a signal peptide, were both present. Inducible expression was documented in primary spleen cells stimulated with ConA and poly I: C. The splenic and intestinal expression of psIL6ns and psIL6 was increased in response to temperature stress and bacterial infection.

Sympathetic nerve-adipocyte interactions in response to acute stress

“…Canonical IL-6 signaling is essential in the chemoresistance of ovarian cancer [60], autoimmune diseases [61], colitis [62], and hepatic inflammation [63], while non-canonical IL-6 signaling influences rheumatoid arthritis, Castleman disease [64], osteoclastogenesis [65], and type 2 diabetes [66]. Increased IL-6 levels have been related to a series of stressors such as cold, infection, restraint, fatigue, sleep deprivation, and psychosocial stressors [67][68][69][70][71]. Thus, IL-6 increase may affect different tissues differently during psychological stress [72].…”

“…A spliced isoform of IL-6 was also detected in renal cell carcinoma which acts as IL-6 inhibitor [74]. Recently, there were also reported two IL-6 isoforms in turtles subjected to stress homologous to the mammalian IL-6 [67]. The two IL-6 transcripts were named psIL6 and psIL6ns.…”

Comparative Transcriptome Analysis Reveals the Molecular Immunopathogenesis of Chinese Soft-Shelled Turtle (Trionyx sinensis) Infected with Aeromonas hydrophila

“…Although the research of turtle immunology lags behind that of mammals and fish, the unique evolutionary status as secondary aquatic reptiles has recently aroused wide concern on the distinct immune response mechanism against pathogens in turtles [ 17 , 18 , 19 , 20 ]. Fifteen candidate TLR family genes have been identified in T. sinensis [ 21 ].…”