Possible involvement of galectin-3 in microglial activation in the hippocampus with trimethyltin treatment

Trimethyltin (TMT) is an organotin neurotoxicant with effects that are selectively localized to the limbic system (especially the hippocampus), which produces memory deficits and temporal lobe seizures. Galectin-3 (Gal-3) is a beta-galactoside-binding lectin that is important in cell proliferation and regulation of apoptosis. The present study evaluated the temporal expression of Gal-3 in the hippocampus of adult BALB/c mice after TMT treatment (i.p., 2.5 mg/kg). Western blotting analyses showed that Gal-3 immunoreactivity began to increase 2 days after treatment; the immunoreactivity peaked significantly within 4 days after treatment but significantly declined between days 4 and 8. Immunohistochemical analysis indicated that Gal-3 expression was very rare in the hippocampi of vehicle-treated controls. However, Gal-3 immunoreactivity appeared between 2 and 8 days after TMT treatment and was primarily localized to the hippocampal dentate gyrus (DG), in which neuronal degeneration occurred. The immunoreactivity was detected predominantly in most of the Iba1-positive microglia and in some GFAP-positive astrocytes of the hippocampal DG. Furthermore, Gal-3 expression co-localized with the pro-inflammatory enzymes cyclooxygenase-2 and inducible nitric oxide synthase in the hippocampal DG. Therefore, we suggest that Gal-3 is involved in the inflammatory process of neurodegenerative disorder induced by organotin intoxication.