BACKGROUNDHIV-1 infected and immune-activated macrophages and microglia secrete neurotoxins, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), which play major role in the neuronal death. It has been shown that different HIV-1 variants have varying abilities to elicit secretion of TNF-α by peripheral blood mononuclear cell (PBMC); however, whether the difference of gp120 gene could affect the secretion of TNF-α and IL-1β by glial cells is unknown. The aim of this study was to explore the association between gene diversity and induction of neurotoxic cytokines.

METHODSIn this study, we constructed retroviral vectors MSCV-IRES-GFP/gp120 using HIV-1 gp120 genes isolated from four different tissues of one patient who died of AIDS dementia complex (ADC). Recombinant retroviruses produced by cotransfection of MSCV-IRES-GFP/gp120, pCMV-VSV-G and pUMVC into 293T cells were collected and added into U87 glial cells. Concentrations of TNF-α and IL-1β secreted by transduced U87 cells were assayed with ELISA separately.

RESULTSThe four HIV-1 gp120 were in the different branch of the neighbor-joining tree. Compared to the pMIG retrovirus (gp120-negative) or U87 cells, all the gp120-positive recombinant retroviruses induced more TNF-α (P < 0.01) and IL-1β (P < 0.01). In addition, compared with the L/MIG retrovirus, all the three brain gp120-positive recombinant retroviruses induced less TNF-α (P < 0.01) and IL-1β (P < 0.01).

CONCLUSIONSHIV-1 gp120 could induce U87 cells secret more TNF-α and IL-1β again. The more important is that difference of HIV-1 gp120, especially cell-tropism may account for the different ability in eliciting secretion of TNF-α and IL-1β, which might supply a novel idea helping understand the pathogenesis of ADC.

AIDS Dementia Complex ; metabolism ; virology ; Cell Line ; Cell Line, Tumor ; Enzyme-Linked Immunosorbent Assay ; HIV Envelope Protein gp120 ; genetics ; metabolism ; Humans ; Interleukin-1beta ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism

The infiltration of monocytes into the CNS represents one of the early steps to inflammatory events in AIDS-related encephalitis and dementia. Increased activity of selected matrix metalloproteinases (MMPs) such as MMP-9 impairs the integrity of blood-brain barrier leading to enhanced monocyte infiltration into the CNS. In this study, we examined the effect of HIV-1 Tat on the expression of MMP-9 in CRT-MG human astroglioma cells. Treatment of CRT-MG cells with HIV-1 Tat protein significantly increased protein levels of MMP-9, as measured by Western blot analysis, zymography and an ELISA. Treatment of CRT-MG cells with HIV-1 Tat protein markedly increased mRNA levels of MMP-9, as analyzed by RT-PCR. Pretreatment of CRT-MG cells with NF-kappaB inhibitors led to decrease in Tat-induced protein and mRNA expression of MMP-9. Pretreatment of CRT-MG cells with MAPK inhibitors suppressed Tat-induced MMP-9 expression. Furthermore, HIV-1 Tat-induced expression of MMP-9 was significantly inhibited by neutralization of TNF-alpha, but not IL-1beta and IL-6. Taken together, our results indicate that HIV-1 Tat can up-regulate expression of MMP-9 via MAPK-NF-kappaB-dependent mechanisms as well as Tat-induced TNF-alpha production in astrocytes.
AIDS Dementia Complex/*metabolism ; Astrocytes/*drug effects/enzymology ; HIV Infections/*complications ; *HIV-1 ; Humans ; Matrix Metalloproteinase 9/*genetics/immunology ; Mitogen-Activated Protein Kinase Kinases/*metabolism ; NF-kappa B/*metabolism ; Tumor Cells, Cultured ; Tumor Necrosis Factor-alpha/immunology/metabolism ; Up-Regulation/drug effects ; tat Gene Products, Human Immunodeficiency Virus/*metabolism

Inflammation, a self-defensive reaction against various pathogenic stimuli, may become harmful self-damaging process. Increasing evidence has linked chronic inflammation to a number of neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis. In the central nervous system, microglia, the resident innate immune cells play major role in the inflammatory process. Although they form the first line of defense for the neural parenchyma, uncontrolled activation of microglia may directly toxic to neurons by releasing various substances such as inflammatory cytokines (IL-1beta, TNF-alpha, IL-6), NO, PGE
alpha-Synuclein/physiology ; Signal Transduction ; Parkinson Disease/*etiology/immunology ; Multiple Sclerosis/etiology ; Models, Biological ; Microglia/immunology/metabolism/*physiology ; Metalloproteases/physiology ; Melanins/physiology ; Matrix Metalloproteinase 3 ; Inflammation Mediators/metabolism ; Humans ; Encephalitis/*etiology/immunology ; Cytokines/secretion ; Animals ; Alzheimer Disease/etiology ; AIDS Dementia Complex/etiology

OBJECTIVETo explore the role of HIV-1 tat gene variations in AIDS dementia complex (ADC) pathogenesis.

METHODSHIV-1 tat genes derived from peripheral spleen and central basal ganglia of an AIDS patient with ADC and an AIDS patient without ADC were cloned for sequence analysis. HIV-1 tat gene sequence alignment was performed by using CLUSTAL W and the phylogentic analysis was conducted by using Neighbor-joining with MEGA4 software. All tat genes were used to construct recombinant retroviral expressing vector MSCV-IRES-GFP/tat. The MSCV-IRES-GFP/tat was cotransfected into 293T cells with pCMV-VSV-G and pUMVC vectors to assemble the recombinant retrovirus. After infection of gliomas U87 cells with equal amount of the recombinant retrovirus, TNF-α, and IL-1β concentrations in the supernatant of U87 cells were determined with ELISA.

RESULTSHIV-1 tat genes derived from peripheral spleen and central basal ganglia of the AIDS patient with ADC and the other one without ADC exhibited genetic variations. Tat variations and amino acid mutation sites existed mainly at Tat protein core functional area (38-47aa). All Tat proteins could induce U87 cells to produce TNF-α and IL-1β, but the level of IL-1β production was different among Tat proteins derived from the ADC patient's spleen, basal ganglia, and the non-ADC patient's spleen. The level of Tat proteins derived from the ADC patient's spleen, basal ganglia, and the non-ADC patient's spleen were obviously higher than that from the non-ADC patient's basal ganglia.

CONCLUSIONTat protein core functional area (38-47aa) may serve as the key area of enhancing the secretion of IL-1β. This may be related with the neurotoxicity of HIV-1 Tat.

AIDS Dementia Complex ; metabolism ; pathology ; virology ; Adult ; Amino Acid Sequence ; Basal Ganglia ; virology ; Cell Line, Tumor ; Gene Expression Regulation, Viral ; Genes, tat ; HIV-1 ; genetics ; pathogenicity ; Humans ; Interleukin-1beta ; biosynthesis ; genetics ; secretion ; Middle Aged ; Molecular Sequence Data ; Neuroglia ; pathology ; secretion ; Spleen ; virology ; Tumor Necrosis Factor-alpha ; biosynthesis ; genetics ; secretion ; tat Gene Products, Human Immunodeficiency Virus ; genetics ; physiology