JAK/STAT pathway in HIV-1–induced endothelial dysfunction. (A) Effect of FLUD on monocyte migration across in vitro BBB models in response to HIV-1 and IL-6. HIV-1 infection and IL-6 increased monocyte migration across the BBB and the STAT1 inhibitor (FLUD) significantly diminished HIV-1- and IL-6-induced monocyte migration (*P < .05). NI represent migration of noninfected macrophages. (B,C) HIV-1 phosphorylates STAT1 and STAT3 at serine-727, and the JAK-3 inhibitor WHI-P154 diminished HIV-1–induced phosphorylation of STAT1 and STAT3. HIV-1 induced phosphorylation of STAT-3 at S-727 but did not phosphorylate STAT-5 or STAT-3 at tyrosine residues. FLUD had no effect on HIV-1–induced STAT-3 phosphorylation (panel B). The JAK-3 inhibitor (WHI-P154) significantly diminished HIV-induced serine phosphorylation of STAT1 and STAT3, while the JAK-2 inhibitor (AG490) had no effect (C). No activation of STAT3 at tyrosine residues was detected. HIV-1 did not activate STAT-2, STAT-5 or STAT-6.