Study On The Mechanism Of Dopamine Inhibiting Neuroinflammation Through DRD2

Neuroinflammation is a crucial defense system utilized by the body to safeguard the brain against foreign pathogens or toxic substances.Within the brain,dopamine serves as a key neurotransmitter and immune regulator,controlling neuroinflammatory responses,as well as regulating human behaviors such as movement,reward,and cognition.Among the five human dopamine receptors(DRD1,DRD2,DRD3,DRD4,and DRD5),DRD1,DRD2,and DRD3 are closely associated with neuroinflammation.However,the precise molecular mechanism underlying dopamine’s role in the improvement of neuroinflammation remains unclear,warranting further investigation.In this study,it was discovered that DA had the ability to suppress the expression of inflammatory factors such as NO,TNF-α protein,and IL-1β,which were induced by LPS,in primary microglia,primary astrocytes,and BV-2 microglia.However,DA and its endogenous analogues,including p-tyramine,3-methoxytyramine,and L-DOPA,were unable to inhibit NO production in LPS-induced BV-2 cells.The viability of the cells remained unaffected by the presence of DA.Furthermore,the findings indicated that DA could not inhibit the expression of the transcription factor NF-kappa B in BV-2 cells induced by LPS,and had no impact on the phosphorylation of p38,ERK,JNK of the mitogen-activated protein kinase family(MAPKs),or interferon regulatory factor 3(IRF3).However,DA was found to exert a significant inhibitory effect on the phosphorylation of the transcription factor STAT3 in BV-2 cells induced by LPS,and it was confirmed that DA can inhibit BV-2 cells from producing inflammatory factor NO through DRD2 receptor.To further investigate the role of DRD2 in the inhibition of neuroinflammation by DA,lentivirus interference plasmids were used to knock down DRD2 expression in BV-2 cells.The results showed that DA had no effect on the production of NO,TNF-α,and phosphorylation of STAT3 induced by LPS in BV-2 cells when DRD2 was knocked down.These findings suggest that DA inhibits LPS-induced neuroinflammation in BV-2 cells by regulating the downstream transcription factor STAT3 through DRD2.Moreover,the study demonstrated that inhibiting the phosphorylation of STAT3 protein could also effectively inhibit neuroinflammation.In addition,this study utilized molecular dynamics simulation to investigate the interaction between DA and DRD2.The DRD2 protein’s crystal structure was obtained from the PDB database,and Autodock Vina 1.1.2 software was used to dock DA with DRD2.The screened and established structure of DA docking DRD2 was simulated.Using VMD software,the RMSD and RMSF in apo-DRD2 system and DA-DRD2 system,and the intermolecular force in the DA-DRD2 system were analyzed.Results showed that the binding of DA and DRD2 could alter the conformation of the DRD2 protein while generating a stable hydrogen bond with the ASP114,THR119,and SER197 residues on DRD2,thus confirming the specific and stable binding between DA and DRD2 through hydrogen bonding.The MM-PBSA method was used to calculate the binding energy of DA to DRD2 protein,which confirmed that the binding between DA and DRD2 had excellent affinity.In summary,this research has provided evidence that DA has the ability to inhibit LPSinduced neuroinflammation by regulating the expression of proinflammatory cytokines such as NO,TNF-α,and IL-1β in neuroglias.Furthermore,it was discovered that DA exerts its role in regulating the inflammatory response through the inhibition of STAT3 phosphorylation via the DRD2.Results from molecular dynamics simulations have confirmed the stable and specific binding between DA and DRD2,whereby hydrogen bonds play a significant role in the binding.Through clarifying the molecular mechanism by which DA-DRD2 signaling inhibits LPS-induced inflammation in BV-2 cells,this study has provided a theoretical foundation for the development of anti-inflammatory drugs.