Toll-like receptors (TLRs) respond to tributyltin chloride (TBT-Cl) exposure in the river pufferfish (Takifugu obscurus): Evidences for its toxic injury function.

Tributyltin chloride (TBT-Cl) residual in water body had become a noticeable ecological problem for aquatic ecosystems. Toll-like receptors (TLRs) are an ancient family of pattern recognition receptors that play key roles in detecting nonself antigens and immune system activation. In this study, we explored the effect of TBT-Cl exposure on four TLRs expression in river pufferfish, Takifugu obscurus. The four T. obscurus Toll-like receptors (To-TLRs) contained different types of domains such as leucine-rich repeats (LRRs), leucine-rich repeats, typical subfamily (LRR_TYP) and other special domains. The To-TLRs mRNA transcripts expressed in all tissues, also To-TLR2 was investigated with higher level in kidney, as well as To-TLR3 in kidney, while To-TLR18 in liver and To-TLR22 in intestine. After the acute and chronic exposure of TBT-Cl, To-TLR2 and To-TLR3 mRNA transcripts were significantly down-regulated in gill. However, To-TLR18 and To-TLR22 were significantly up-regulated in gill and liver. Moreover, the histology and immunohistochemistry (IHC) results showed the different injury degrees of TBT-Cl in liver and gill and implied the cytoplasm reorganization after TBT-Cl stress and the function of immunoregulation for To-TLRs to TBT-Cl exposure. All the results indicated that To-TLRs might involve in sensing and mediating innate immune responses caused by TBT-Cl for keeping detoxification homeostasis.

Toxic function of CD28 involving in the TLR/MyD88 signal pathway in the river pufferfish (Takifugu obscurus) after exposed to tributyltin chloride (TBT-Cl).

Cluster of differentiation 28 (CD28) is a co-stimulatory receptor found on the surface of T cells. Takifugu obscurus is a kind of anadromous fish species. In this study, the full-length sequence of To-CD28 was obtained, including a 672-bp open reading frame that encodes a peptide chain of 223 amino acids. The phylogenetic analysis showed that To-CD28 is similar to the CD28 protein in Takifugu rubripes. The total hematocyte count distinctly decreased after TBT-Cl exposure, showing the adverse effects of TBT-Cl invasion and self-adjusting ability upon To-CD28 accumulation. The production of reactive oxygen species increased, demonstrating the oxidation resistance of T. obscurus when exposed to TBT-Cl. The tissue expression patterns indicated To-CD28 is a widely distributed receptor in T. obscurus. Its high expression in the liver and gill suggests that To-CD28 could be potentially functioned in TBT-Cl toxic process. The mRNA levels of To-CD28 and relative genes in the TLR-MyD88 signal pathway were significantly up-regulated under TBT-Cl exposure. The immunohistochemistry also showed that the To-CD28 protein signal was enhanced under TBT-Cl exposure, which proved that the positive protection of To-CD28 for maintaining homeostasis. Our study indicated that To-CD28 might participate in the toxicity mechanism upon TBT-Cl exposure and regulate homeostasis stability of T. obscurus.

Effect of tributyltin chloride (TBT-Cl) exposure on expression of HSP90ß1 in the river pufferfish (Takifugu obscurus): Evidences for its immunologic function involving in exploring process.

HSP90ß1 (known as glyco-protein 96, GP96) is a vital endoplasmic reticulum (ER) depended chaperonin among the HSPs (heat shock proteins) family. Furthermore, it always processes and presents antigen of the tumor and keeps balance for the intracellular environment. In the present study, we explored the effect of tributyltin chloride (TBT-Cl) exposure on HSP90ß1 expression in river pufferfish, Takifugu obscurus. The full length of To-HSP90ß1 was gained with 2775 bp in length, with an ORF (open reading frame) encoding an 803 aa polypeptide. A phylogenetic tree was constructed and showed the close relationship to other fish species. The HSP90ß1 mRNA transcript was expressed in all tissues investigated with higher level in the gill and liver. After the acute and chronic exposure of TBT-Cl, the To-HSP90ß1 mRNA transcript significantly was up-regulated in gills. Moreover, the histology study indicated the different injury degree of TBT-Cl in liver and gill. Immunohistochemistry (IHC) staining results implied the cytoplasm reorganization after TBT-Cl stress and the function of immunoregulation for To-HSP90ß1 to TBT-Cl exposure. All the results indicated that HSP90ß1 may be involved in the resistance to the invasion of TBT-Cl for keeping autoimmune homeostasis.

Biotransformation of Tributyltin chloride by Pseudomonas stutzeri strain DN2

A bacterial isolate capable of utilizing tributyltin chloride (TBTCl) as sole carbon source was isolated from estuarine sediments of west coast of India and identified as Pseudomonas stutzeri based on biochemical tests and Fatty acid methyl ester (FAME) analysis. This isolate was designated as strain DN2. Although this bacterial isolate could resist up to 3 mM TBTCl level, it showed maximum growth at 2 mM TBTCl in mineral salt medium (MSM). Pseudomonas stutzeri DN2 exposed to 2 mM TBTCl revealed significant alteration in cell morphology as elongation and shrinkage in cell size along with roughness of cell surface. FTIR and NMR analysis of TBTCl degradation product extracted using chloroform and purified using column chromatography clearly revealed biotransformation of TBTCl into Dibutyltin dichloride (DBTCl2) through debutylation process. Therefore, Pseudomonas stutzeri strain DN2 may be used as a potential bacterial strain for bioremediation of TBTCl contaminated aquatic environmental sites.

Biotransformation of Tributyltin chloride by Pseudomonas stutzeri strain DN2.

A bacterial isolate capable of utilizing tributyltin chloride (TBTCl) as sole carbon source was isolated from estuarine sediments of west coast of India and identified as Pseudomonas stutzeri based on biochemical tests and Fatty acid methyl ester (FAME) analysis. This isolate was designated as strain DN2. Although this bacterial isolate could resist up to 3 mM TBTCl level, it showed maximum growth at 2 mM TBTCl in mineral salt medium (MSM). Pseudomonas stutzeri DN2 exposed to 2 mM TBTCl revealed significant alteration in cell morphology as elongation and shrinkage in cell size along with roughness of cell surface. FTIR and NMR analysis of TBTCl degradation product extracted using chloroform and purified using column chromatography clearly revealed biotransformation of TBTCl into Dibutyltin dichloride (DBTCl2) through debutylation process. Therefore, Pseudomonas stutzeri strain DN2 may be used as a potential bacterial strain for bioremediation of TBTCl contaminated aquatic environmental sites.