Study On The Mechanism Of Kynurenic Acid In HIV-1 Associated Neurocognitive Disorder Through Inhibition Of α7nAChR Mediated Astrocyte Phenotypic Transformation

Human immunodeficiency virus-1(HIV-1)-associated neurocognitive disorder(HAND)as the presenting manifestation of HIV-infected end-organ injury,of which clinical symptoms include motor and attention deficits,impaired learning and memory,and even dementia in severe cases.Thanks to the significant therapeutic effect of highly active antiretroviral therapy(HAART),the life expectancy of patients with AIDS is prolonged greatly,even approaching the general population.This,in turn,led indirectly to a sharp increase in the incidence of HAND.Astrocytes,the most abundant cell type in the central nervous system(CNS),dynamically adjust those functional status according to disease state.It will be a hot spot for future research on whether astrocytes undergo a phenotypic transformation and accurate identification of different phenotypes.However,further investigation is necessary to elaborate on the regulation of host immune response and mechanism of phenotypic transformation in pathological processes of HAND,which explore the possibilities as a biomarker for diagnosis and monitoring of the progression of HAND.This study focused mainly on certain biological characteristics of A1/A2 phenotypes and predictions based on the contribution of α7 nicotinic ACh receptors(α7nAChR)to pathological processes.Tryptophan neuroactive tryptophan metabolites,kynurenic acid(KYNA)were screened preliminarily as a potential neuroprotective agent,we then further explored the neuroprotective effect and mechanism of KYNA associated with phenotypic transformation under the persistent activation of α7nAChR induced by gp120.Firstly,the temporal model,constructed by gp120 transgenic mice(gp120 tgm)simulated lesions in HAND was observed kinetically.The detection of phenotypic markers at transcript and protein level,combined with the behavioral indicators might contribute significantly to assessing the relevance of phenotypic transformation and cognitive dysfunction.Additionally,to simulate abnormal reactivity with accompanying inflammatory response in vivo environment,we carried out to construct the nerve injury model by using primary astrocytes under the stimulation of gp120.Alternatively,to fully verify the regulation mechanisms of the phenotypic transformation in astrocytes,we performed the rescue experiment to be consistent with the double genetically modified mice model,and to investigate the therapeutic potential of KYNA targeted to α7nAChR.Based on high tolerance of tryptophan,we carried out a preliminary exploration that increased endogenous KYNA secretion to regulate brain function with a high-tryptophan diet,which attempted to alter disease progression or neuropathologic outcomes in HAND.Experimental results indicated that concentration gradient gp120 concentrations induced a decrease in cell vitality,apoptosis,senescence,and activation of inflammatory responses.Nevertheless,KYNA showed greater resistance to gp120induced damage,characterized by reversing these above processes.Additionally,Western blot,RT-qPCR,and immunofluorescence staining were independently performed to confirm the role of α7nAChR mediated JAK2/STAT3 pathway in astrocyte phenotypic transformation in response to induction of gp120,we then observed that this signal transduction was accompanied with the changes in the expression of phenotypic markers and upregulation of pro-inflammatory cytokines.KYNA bound specifically to α7nAChR,which blocked activation of the A1 phenotype from the quiescent state,and drove the conversion to the A2 phenotype to some extent.However,subsequent research including the rescue experiments and double genetically modified mice model successively verified the significant correlation between the phenotypic regulation and immune protection of KYNA with α7nAChR.The temporal HAND model also demonstrated age-dependent associations with sustained activation of astrocytes,which represented as dynamic upregulation of A1 phenotypic markers,better sensitivity to pathological changes,and higher accordance with behavioral indicators.Neuronal damage and inflammatory responses showed significant improvement in gp120 tgm with high-tryptophan feeding,which manifested as improvement of cognitive function and inhibition of A1 phenotype astrocytes activation.Given all of that,we have discovered that astrocytes and α7nAChR might represent the potential therapeutic targets,then KYNA was screened preliminarily as a potential neuroprotective agent.These advances had implications for knowledge about the underlying pathogenic mechanisms and the development of new therapies for HAND.