Studies On The Effect Of S100B In The Development Of Parkinson’s Disease

Background:Parkinson’s disease is a neurodegenerative disorder characterized by degeneration of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies (LBs). Resting tremor, rigidity, bradykinesia and postural instability are the main clinical features of Parkinson’s disease. S100B is an acidic calcium binding protein. As a specific protein in the brain, S100B is expressed and secreted by astrocytes and plays a widely biological effect through the mediation of signal conduction. S100B can promote neuronal development and damage-repair in physiological concentration. But, in brain injury caused by various reasons, the proliferation and activation of reactive astrocytes result in the overproduction of S100B, high-concentration of S100B induces central neurons apoptosis by calcium overload, increasing the level of NO, the formation of neurofibrillary tangles, etc. Researches showed that the expression of S100B was increased in cerebrovascular diseases,. brain trauma, central nervous system inflammation, Down’s syndrome, Alzheimer’s disease and was proportional to the severity of neural symptoms. But, the relationship between S100B and Parkinson’s disease is rarely reported. So, we established the brain specific S100B gene transgenic mice and investigated the effects of S100B on the development of Parkinson’s disease in two aspects:①The effects of S100B on the expression of dopamine receptors and the levels of monoamine neurotransmitters in the basal ganglia neural circuit.②Studies on the relationship between S100B and a-synuclein with A53T mutation. The researches make us explore the more potential function of S100B in Parkinson’s disease.Methods:The transgenic vector was constructed by inserting the human S100B gene into the down stream of PDGD promoter. The transgenic mice were produced by microinjection and the genotyping was detected by PCR. The expression levels of the transgenic gene were detected with Western blot and the location of human S100B in mouse brain was detected by immunohistochemical staining. Motor coordination; the expressions of D1DR, D2DR, GRK2, GRK5, TH, phosphorylated TH at serl9, Ser31, Ser40; the levels of Tyr, DOPA, DA, HVA, Trp,5-HT,5-HIAA were measured by Rota-rod test, RT-PCR, Western blot and HPLC-FLD respectively in S100B transgenic mice, S100B knockout mice and the negative control group. Motor coordination and the expression of S100B protein in the brain were measured by Rota-rod test, ELISA and double-labeled immunostaining respectively inα-synuclein A53T transgenic mice and the negative control group. Then, we established S100B×α-synuclein A53T double transgenic mice by crossbreeding the S100B andα-synuclein A53T transgenic mice. The formation of Lewy body, the aggregation of ubiquitinated a-synuclein and the expressions of iNOS, nitratedα-synuclein, Cox-2, TH protein in the brain of S100B×α-synuclein A53T double transgenic mice,α-synuclein A53T transgenic mice and wild type mice were detected by HE staining, double immunofluorescent staining and Western blot respectively.Results:①Five founders of brain specific PDGF-hS100B transgenic mice were established and two high-level expression lines were identified. The location of S100B was detected in the cytoplasms and nucleus of astrocytes and oligodendrocytes in cerebral, hippocampus and mesencephalon.②Compared with negative control group, the motor coordination ability of S100B transgenic mice were down 39.1% and 48.2% respectively at the age of 3 and 6 month old, showed progressive decline. The expressions of D2DR, GRK2 mRNA and protein were decreased and phosphorylated TH at Ser19 and Ser40 were increased, the levels of DOPA, DA and its metabolite HVA were elevated, the levels of 5-HT was reduced in the brain of S100B transgenic mice at the age of 6 month old. The high ratios of HVA/DA and 5-HIAA/5-HT in the brain of S100B transgenic mice suggested active metabolism of DA and 5-HT. No obvious change of detection indexes was observed in S100B knockout mice compared with negative group.③Compared with negative group, the motor coordination ability ofα-synuclein A53T transgenic mice were down 20.8%,43.3%,50.7% and 63.3% respectively at the age of 3,6,9 and 12 month old, showed progressive decline. The expression level of S100B was elevated in the brain ofα-synuclein A53T transgenic mice accompanied with the increase of S100B (+) astrocytes in the striatum at the age of 9 and 12 month old.④No typical Lewy body was observed in the brain of S100B×α-synuclein A53T double transgenic,α-synuclein A53T transgenic and wild type mice. But, in the nigral dopaminergic neurons’ cytoplasm, ubiquitinatedα-synuclein distributed uniformly in wild type mice and accumulated granularly in S100B×α-synuclein A53T andα-synuclein A53T transgenic mice. Compared withα-syriuclein A53T transgenic and wild type mice, the amount of accumulated ubiquitinatedα-synuclein and the expressions of iNOS, nitratedα-synuclein, Cox-2 protein were increased. Conclusions:The motor coordination ability of S100B transgenic mice showed progressive decline which is the main behavior change in mice model of Parkinson’s disease. Overexpression of S100B promoted the development of Parkinson’s disease by reducing the expressions D2DR and GRK2, influencing the synthesis, metabolism of neurotransmitters DA and 5-HT, enhancing oxidative stress. a-synuclein with A53T mutation resulted in the overexpression of S100B protein in the brain by inducing the proliferation and activation of astrocytes. Furthermore, high level of S100B could exacerbate the abnormal aggregation of ubiquitinated a-synuclein in the dopaminergic neurons’ cytoplasm of a-synuclein A53T transgenic. S100B play an important role in the development of Parkinson’s disease and the suppression of its overpression maybe a new strategy to treat Parkinson’s disease.