Study Of The Role And Mechanisms Of BDNF Mediates IL-1?-induced F-actin Remodeling In Hippocampal Neurons

Background:Major depressive disorder (MDD) is a debilitating, life-threatening disease that is increasing in prevalence. At present, it is widely recognized that a loss of hippocampal volume is a major risk factor for the development of MDD. At the cellular level, MDD is characterized by decreased F-actin. Although the multiple signaling mechanisms that control the program of MDD have been extensively studied, the molecular mechanisms that mediate the development of MDD are not completely understood.The avalilable evidence suggests that immune system plays an important role in regulating psychiatric disorders. The expression level of Interleukin-1beta (IL-1?), which is known as one of the proinflammatory cytokine, is widely changed in various situations in brain. In our group studys, we identify IL-1? as a critical regulator of hippocampus neuron by stimulating F-actin. However, our understanding of this pathogenesis at the molecular level remains extremely limited.Brain-derived neurotrophic factor (BDNF) was discovered in1982by the German chemist Y.A.Barde, who was the first to isolate and purify BDNF from the porcine brain. The monomer BDNF molecule is composed of119amino acid residues and is a mature polypeptide-secreted protein. BDNF, which has a molecular weight of13.15Kd, is mainly composed of a ? sheet and a random N-stage structure with three disulfide bonds. The BDNF protein is synthesized in the brain and widely distributed throughout the central nervous system. BDNF plays important roles in the central nervous system during development by contributing to neuronal survival, differentiation and growth. It also can prevent the death of injured neurons, improve neuropathological conditions and promote the regeneration of injured neurons. Thus, BDNF is necessary for neuronal survival in the mature central and peripheral nervous systems.Therefore, BDNF may be an attractive target for therapeutic intervention to prevent MDD.Objective:The current study included the following objectives:1) to determine whether BDNF is altered in a cell culture model of MDD and2) to identify the mechanisms underlying any observed effects. Methods:(1) Primary hippocampal neuron culture, The hippocampal neurons were used in experiments after a culturing period of7to9days;(2) Experimental groups:IL-1? was administered at a final concentration of0(PBS was added to control neurons at a concentration of0.1%),0.01,0.1,1,10,20,50or100ng/ml. After12h of treatment, the neurons were harvested for use in other experiments.(3) Immunocytochemistry:the neuronal identity and morphology of the cultures were confirmed by immunocytoc-hemical labeling for neuron-specific enolase (NSE)(4)A Cell Counting Kit-8were used to assay the neuron viability (5) Enzyme-linked immunoassay (ELISA) technique were used to measure the level of BDNF (6) Western blot were used to measure the level of protein for BDNF and F-actin and NF-kB.Results:(1)we successfully culteured the primary hippocampal. Viability was markedly increased in cell cultures from five to nine days, and the highest viability was observed at9days.(2) IL-1? increases neuronal survival and the expression fo F-actin in a dose-dependent manner at low doses and is less effective in increasing neuronal survival in a dose-dependent manner at high doses. The increase in neural survival and F-actin was significant at0.1ng/ml.(3) The ELISA test and Western blot results showed that the BDNF content was higher in the0.01ng/ml group compared to the control group. Similarly, the BDNF content was higher in the0.1ng/ml and1ng/ml groups than in the control group but lower than in the0.01ng/ml group. However, these increases were severely blunted at higher concentrations.(4) With elevated concentrations of IL-1?, NF-?B protein expression exhibited a dose-dependent increase. In particular, the level of NF-?B was the highest at50ng/ml.Conclusion:Taken together, our findings indicate that BDNF acts as an F-actin-protective regulator during stimulation by IL-1? and that this function largely occurs via the regulation of NF-?B signaling. These results suggest that interventions targeting the BDNF signaling system may be of therapeutic value against major depressive disorder.