Prevention of streptozotocin­induced Neuro­2a cell death by C8­B4 microglia transformed with repetitive low­dose lipopolysaccharide.

Diabetes­associated neuronal dysfunction (DAND) is one of the serious complications of diabetes, but there is currently no remedy for it. Streptozotocin [2­deoxy­2­(3­methy1­3­nitrosoureido) D­glucopyranose; STZ] is one of the most well­established diabetes inducers and has been used in vivo and in vitro DAND models. The aim of the present study was to demonstrate that C8­B4 microglia transformed by the stimulus of repetitive low­dose lipopolysaccharide (LPSx3­microglia) prevent STZ­induced Neuro­2a neuronal cell death in vitro. The ELISA results showed that neurotrophin­4/5 (NT­4/5) secretion was promoted in LPSx3­microglia and the cell viability assay with trypan blue staining revealed that the culture supernatant of LPSx3­microglia prevented STZ­induced neuronal cell death. In addition, reverse transcription­quantitative PCR showed that neurons treated with the culture supernatant of LPSx3­microglia promoted the gene expression of B­cell lymphoma­extra large and glucose­dependent insulinotropic polypeptide receptor. Furthermore, the inhibition of tyrosine kinase receptor B, a receptor of NT­4/5, suppressed the neuroprotective effect of LPSx3­microglia. Taken together, the present study demonstrated that LPSx3­microglia prevent STZ­induced neuronal death and that NT­4/5 may be involved in the neuroprotective mechanism of LPSx3­microglia.