C-Phycocyanin: an effective protective agent against thymic atrophy by tributyltin

Spirulina platensis, used worldwide as a food supplement, is a natural source of protein, vitamins, carbohydrates and polyunsaturated fatty acids. C-Phycocyanin (C-Pc), its major biliprotein, is known to possess anti-oxidant, anti-inflammatory and radical scavenging properties. Our present study showed that treatment with C-Pc protects the rats from Tributyltin (TBT) induced thymic atrophy. The results reveal TBT-induced oxidative stress mediated apoptosis in rat thymocytes in vivo and its attenuation by C-Pc. This ameliorative effect could be attributed to antioxidant activity of the biliprotein. C-Pc also increased TBTC reduced thymic weight and cellularity as well. TBTC-induced ROS generation and lowered GSH levels were restored by C-Pc, suggesting its radical scavenging properties. The various apoptotic determinants such as mitochondrial membrane potential, Bax/Bcl-2 ratio, caspase-3 activity and apoptotic cell population were effectively modulated by C-Pc treatment. We make this first observation to illustrate the effectiveness of C-Pc in reducing TBTC-induced thymic atrophy. The morphology of thymic tissue was restored to near normal by this biliprotein. The present study, therefore, suggests that C-Pc could serve as an effective natural antioxidant for efficient management of TBTC induced oxidative damage.     

Biodiversity of organotin resistant <Emphasis Type="Italic">Pseudomonas</Emphasis> from west coast of India

Five bacterial isolates were screened for resistance to organotin compound, i.e. tributyltin chloride (TBTC) up to 2 mM. The optimum pH, temperature and salinity for the growth of the isolates were found to be 7, 28°C and 2.5%, respectively. The isolates were tested for survival tolerance to heavy metals (mercury, cadmium and zinc) and co-resistance to antibiotics viz. ampicillin, kanamycin, rifampicin, streptomycin, penicillin, chloramphenicol, tetracycline, nalidixic acid and neomycin. Although our earlier study reported that these five bacterial strains are of different species of Pseudomonas, our present 16S rRNA gene sequence analysis revealed that all the strains are Pseudomonas aeruginosa. One of five isolates P. aeruginosa strain 25W could grow in mineral salt medium with 2 mM of TBTC as a sole source of carbon and survive up to 5 mM of TBTC. In presence of 2 mM of TBTC there was comparable up-regulation of 45 kDa protein in the cell extract of the 25W isolate was found indicating involvement of certain enzymes in TBTC resistance.     

Selective inhibition of B lymphocytes in TBTC-treated human bone marrow long-term culture

Tributyltin chloride (TBTC) is well known for its immunotoxic effect, in particular towards immature thymocytes. TBTC is also known to induce adipocyte differentiation in primary human bone marrow cultures, which is reflected in the decrease in a number of adipocyte-derived cytokines, chemokines and the adipocyte-linked hormone leptin. Since adipocytes influence haematopoiesis and lymphopoiesis for instance by these cytokines and hormones, we here investigated whether TBTC has an effect on specific lymphocyte subsets in human bone marrow primary cultures.     

Tributyltin chloride-induced immunotoxicity and thymocyte apoptosis are related to abnormal Fas expression

Tributyltin chloride (TBTC), a characteristic organotin compound, is widely used as an agricultural pesticide, as a stabiliser for polyvinyl-chloride plastics and in antifouling paints for ship hulls. Organotin compounds are known to produce toxicity in the immune system, but the mechanism underlying this immunotoxicity remains unclear. In this study, we evaluated the immunotoxic effect of TBTC on the acquired immune response, and we investigated the involvement of thymocyte apoptosis and Fas expression in the observed immunotoxicity of TBTC. Mice were randomly assigned to four groups (10 mice per group) and treated with TBTC at doses of 0, 0.5, 4 and 20 mg/kg by oral gavage for 28 days. Following TBTC administration, animals were sacrificed, and morphologic changes in the thymus and spleen were assessed. Atrophy in both the thymus and spleen was observed in all groups treated with TBTC, and the relative organ weight in the highest TBTC group (20 mg/kg) was significantly lower than that observed in the control group. We also conducted assays to assess the cellular and humoral functional responses such as plaque-forming cell assay (PFC), lymphocyte proliferation test and delayed-type hypersensitivity (DTH) response to SRBC. Our results indicate that at doses of 4 mg/kg and 20 mg/kg, TBTC could significantly suppress both the humoral and cellular immune responses when compared to the control group (p<0.05). In addition, immunohistochemical staining and flow cytometry analysis were carried out to measure the expression of Fas and thymocyte apoptosis, respectively. We observed a dose-dependent increase in thymocyte apoptosis and that Fas expression in the TBTC-treated groups (4 mg/kg and 20 mg/kg) was significantly enhanced when compared to the control group. Correlation analysis demonstrated a positive linear correlation between apoptosis and Fas expression, indicating that TBTC-induced thymocyte apoptosis may be mediated by Fas expression. Taken together, our data clearly demonstrate that TBTC-induced immunotoxicity is associated with thymocyte apoptosis and that this process is mediated by the Fas pathway.