The Effects Of Lead Exposure On Adult Rat Retina Neurons BACE-1 Expression And Downstream Products Aβ In The Early Period

Objective:To study the effects of lead exposure on rat retina BACE-1 expression and downstream product Aβ, and investigate the possible molecular mechanisms in overproduction of A(3 induced by lead exposure in the early period.Methods:Fifty-six adult SD rats were randomly divided into several groups, including experimental groups, PBS vehicle control group and normal control group. To be more precise, experimental groups were randomly selected according to single intravitreal injection of different lead dosage (10μmol/L,100μmol/L,1 mmol/L,10 mmol/L and 100 mmol/L) by lead acetate (dissolved in PBS) for 48h. Thus, every group had 8 rats after animals survived for 48h.4 rats from every group were randomly selected to remove retina after breaking the neck to death. Retina lead level was tested with the way of graphite furnace atomic absorption spectrophotometry. BACE-1 and (3-CTF expression were detected by Western blot and Aβ1-40 expression was determined by ELISA. Another 4 rats in each group were sacrificed to take conventional retinal perfusion for immunofluorescence staining of BACE-1 and GFAP.Results:1. Forty-eight hours after injecting different concentration lead acetate to vitreous body, retina lead level all increased (except 10μmol group) in a dosage dependent manner.2. Immunofluorescence staining showed that normal retina BACE-1 positive production was mainly distributed in ganglion cell layer, inner plexiform layer and outer plexiform layer without distinct cell body stained. With increased concentration of injecting lead acetate into vitreous body, retina BACE-1 distribution did not show significant alternate. However, the BACE-1 expression was up-regulated step by step. It should be mentioned that BACE-1 staining appeared in ganglion cell body in 100 mmol/L group. Western blot showed that BACE-1 band was becoming broader and stronger with increased concentration of injecting lead acetate to vitreous body, which revealed a dosage dependent manner.3. Western blot showed that theβ-CTF band was becoming thicker and bigger with increasing injecting lead acetate concentration to vitreous body (except 10μmol/L group).4. ELISA assay showed concentration of retina tissue all increased in a dosage dependent manner with the exception of 10μmol/L.5.The result of immunofluorescence revealed that GFAP expression in normal rat retina was located in GCL, IPL, INL and OPL, the expression was no significant change in different concentration of lead acetate treatment groups.Conclusions:Lead exposure can lead to up-regulation of BACE-1 expression in rat retina neurons in the early period and excessive its downstream production of retinaβ-CTF and Aβ1-40, but retina microglia did not be obviously activated. The results indicate that regulation of neuronal BACE-1 may be one of main mechanisms in overproduction of A(3 (a key molecule occurred in AD) induced by lead exposure in the early period.