The Effect Of Endoplasmic Reticulum Sterss Involved In Manganese-Induced Neurotoxicity In Rats

Objective:The research is to discuss the possible mechanism of apoptosis induced by ERS in rat striatum neurotoxicity exposed to manganese and the change of ER stress response under the 4-PBA, the inhibitor of ERS. And to provide biochemistry evidence for early prevention and treatment of Subacute manganese poisoning and Parkinsonism caused by manganese.Methods:Method:Select 60 3-4 months old SD rats (body weight range:200-220g)and randomly allocate to control group (n=15), low-dose group (n=15), high-dose group (n=15) and high-dose +4-PBA (200mg/kg) group (n=15). Intraperitoneal injection was performed on 4 group rats:saline to control group, MnCI2 solution (6mg/kg) to low-dose group (n=15), MnCI2 solution (15mg/kg) to high-dose group (n=15), 4-PBA solution (200mg/kg) to high-dose +4-PBA (200mg/kg) group (n=15) first and then high-dose manganese solution (15mg/kg) was injected half an hour later. Six days a week for four weeks, rats were killed,and detected the content of manganese in the stratum by Inductively Coupled Plasma -Atomic Emission Spectrometry (ICP-AES).Observed pathologic change using rat striatum tissue paraffin section and HE staining. TUNEL method was used to detect neuronal apoptosis of rat striatum while morphologic change of striatum cellular structure and endoplasmic reticulum was observed under electron microscope. Extracted protein through rat striatum tissue homogenate to detect the expression quantity change of protein GRP78, CHOP, JNK and caspase-12 relating to endoplasmic reticulum stress and apoptosis by Western blot test.Result:1. Compared with the control group, the concentration of manganese in stratum in manganese exposed group were significantly increased(P<0.01). But 4-PBA can not decrease the concentration of manganese in high-does group.2.By comparing pathologic change of striatum tissue after manganese exposure and HE staining with control ones, striatum neuron cell structure of manganese exposure group was found dim along with varying degree of shrinking necrosis, cell deformation and shrinkage and cytoplasm staining. A part of neuronal cytoplasm swelled obviously and showed vacuolar degeneration, while cell destruction was more evident in high-dose group. The degree of neuronal cell destruction of 4-PBA+high-dose group was lesser than that of high-dose group.3.Cell apoptosis by TUNEL test showed that rat striatum neuronal apoptosis rate of manganese exposure group was much higher than that of control group, higher dose, more neuronal cell apoptosis (P<0.05). Striatum neuronal apoptosis rate of high-dose group was obviously lower when compared with 4-PBA+high-dose group (P <0.05).4. Observation of striatum neuronal ultrastructure using electron microscope showed that neuronal organelle structure of control group was clear and complete, while manganese exposure group to varying degree developed endoplasmic reticulum swelling, vacuolization. More abnormal cell structure was found in high-dose group & low-dose group. The degree of endoplasmic reticulum swelling and vacuolization of 4-PBA+high-dose group was lesser than that of high-dose group.5. Western blot test was used to detect the expression level of striatum protein GRP78、CHOP、JNK、Caspase12. It showed that manganese exposure group expressed at higher level with significant difference (P<0.05) and showed higher manganese concentration when compared with control group.4-PBA+high-dose group expressed less protein level in comparison but it was still higher than that of control group (P<0.05).Conclusion:1.The apoptosis mechanism induced by neuronal endoplasmic reticulum stress of striatum maybe involved in the neuronal damage of manganese exposure rats. The higher dose of manganese, the severer damage is.2.4-PBA inhibition of endoplasmic reticulum stress can significantly reduce the damage and apoptosis of manganese neurons induced by manganese exposure.Inhibition of endoplasmic reticulum stress provides new research direction for treatment of neurotoxicity induced by manganese exposure.