T-02 (Cheetah Cell Therapeutics)

We have previously demonstrated that triiodothyronine (T(3)) stimulates hepatic IGFBP-4 expression in rats. Since there is evidence that some of the genes whose expression is regulated by T(3) are also sensitive to 3,5-diiodothyronine (T(2)), we used the adult rat hepatocyte model in primary cultures directly exposed to T(2) to evaluate insulin-like growth factor binding protein-4 (IGFBP-4) expression by Northern and Ligand blot analyses in this study. Our results demonstrate that T(2), like T(3), is able to enhance IGFBP-4 mRNA and protein after 12-24 h of incubation. The potency of the two iodothyronines is comparable as judged by dose-dependence experiments. The T(2)-induced IGFBP-4 increase is independent from ongoing protein synthesis but dependent on active transcription. Since T(3) and T(2) do not affect IGF-I production, it appears that the iodothyronines affect the hepatic IGF system at the IGFBP level. Our data, demonstrating that T(2) mimics the stimulatory effect of T(3) on IGFBP-4 expression by rat hepatocytes, allow us to include IGFBP-4 gene among the genes regulated by the two iodothyronines.

Both diabetes mellitus and exposure to environmental contaminants are becoming health hazards to many indigenous populations in the world. In earlier work, we established the embryopathy of the chlorinated pesticide, toxaphene technical mixture (TOX) and its two physiologically most important congeners, T(2) (2-exo,3-endo,5-exo,6-endo,8,8,10,10-octachlorobornane) and T(12) (2-exo,3-endo,5-exo,6-endo,8,8,9,10,10-nonachlorobornane). In this study, the combined effects of toxaphene or its two congeners and high glucose concentrations were studied using rat embryo culture in order to investigate the potential interactions between hyperglycemia and toxaphene exposure. Whole rat embryos (0-2 somite) were explanted and cultured into a normal (8 mM) or hyperglycemic 12.5 mM (12.5 G) or 18.75 mM (18.75 G) culture medium containing TOX, T(2), or T(12) at various concentrations (0, 100, 1000, 5000 ng/ml) for 48 h at 37 degrees C. All treatments, except mild hyperglycemic exposure (12.5 G), had significant adverse effects on the total morphological score, head and crown-rump length, yolk sac diameter and yolk sac circulation. Embryos exposed to 18.75 G did not show malformations but when hyperglycemia at 18.75 G was combined with higher doses of TOX or T(2) synergistic effects on the incidence of neural tube defects were observed. The embryos cultured with T(12) under severe hyperglycemic conditions of 18.75 G showed an inhibition of T(12)-induced neural tube defects, but there was a concurrent underdevelopment of forelimbs or hindlimbs at the highest T(12) dose. The results suggest that there is a site-specific and dose-related interactive dysmorphogenesis elicited by TOX or its congeners with high levels of glucose on rat embryonic development. Because of the relatively high TOX doses used in this study, the drastic growth retardation and malformation observed are unlikely to be observed in human populations. More subtle effects, however, may not be ruled out.