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.

摘要

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-fold (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.