Differential Mechanisms of Inflammation and Endothelial Dysfunction by HIV-1 Subtype-B and Recombinant CRF02_AG Tat Proteins on Human Brain Microvascular Endothelial Cells: Implications for Viral Neuropathogenesis
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The recombinant HIV-1 CRF02_AG is prevalent in West-Central Africa but its effects on the blood-brain barrier (BBB) and HIV-associated neurocognitive disorders (HAND) are not known. We analyzed the effects of Tat from HIV-1 subtype-B (Tat.B) and CRF02_AG (Tat.AG) on primary human brain microvascular endothelial cells (HBMEC), the major BBB component. Exposure of HBMEC to Tat.B increased IL-6 expression and transcription by 9- (P < 0.001) and 113-fold (P < 0.001), respectively, whereas Tat.AG increased IL-6 expression and transcription by 2.7–3.8-fold and 35.7-fold (P < 0.001), respectively. Tat.B induced IL-6 through the interleukin-1 receptor-associated kinase (IRAK)-1/4/mitogen-activated protein kinase kinase(MKK)/C-jun N-terminal kinase(JNK) pathways, in an activator protein-1(AP1)- and nuclear factor-kappaB (NFκB)-independent manner, whereas Tat.AG effects occurred via MKK/JNK/AP1/NFκB pathways. Tat-induced effects were associated with activation of c-jun (serine-63) and SAPK/JNK (Thr183/Tyr185). We demonstrated increased expression of transcription factors associated with these pathways (Jun, RELB, CEBPA), with higher levels in Tat.B-treated cells compared to Tat.AG. Functional studies showed that Tat.B and Tat.AG decreased the expression of tight junction proteins claudin-5 and ZO-1 and decreased the trans-endothelial electric resistance (TEER); Tat.B induced greater reduction in TEER, claudin-5, and ZO-1, compared to Tat.AG. Overall, our data showed increased inflammation and BBB dysfunction with Tat.B, compared to Tat.AG. This suggests these two HIV-1 subtypes differentially affect the BBB and central nervous system; our data provides novel insights into the molecular basis of these differential Tat-mediated effects.
KeywordsHIV-1 Tat subtypes CRF02_AG Blood-brain barrier IL-6 JNK/NFκB signaling
This work was supported by grant from the National Institute of Health, National Institute of Mental Health R01 MH094160.
B.B. carried out immunoassays, real-time PCR, Western blot, TEER, adhesion and migration assays and participated in the making of the figures and tables, data analysis, and writing the methods and results. G.D.K. conceived and designed the study, participated in the making of the figures and tables, data analysis, and wrote the manuscript.
Compliance with Ethical Standards
The authors declare that they have no conflict of interest.
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