• brain macrophages;
  • free radicals;
  • interleukin-1β;
  • isoprostane;
  • nitric oxide;
  • tumour necrosis factor-α

We have extended our previous findings and shown that human immunodeficiency virus Tat protein, in addition to nitric oxide (NO), stimulated rat microglial cultures to release pro-inflammatory cytokine interleukin-1β and tumour necrosis factor-α in a nuclear factor (NF)-κB-dependent manner. At the same time, Tat stimulated the accumulation of free radicals, as indicated by the increased levels of isoprostane 8-epi-prostaglandin F (8-epi-PGF), a reliable marker of lipid peroxidation and oxidative stress, by a mechanism unrelated to NF-κB activation. The presence of free radical scavengers abrogated Tat-induced 8-epi-PGF accumulation without affecting NO and cytokine production. Consistently, Tat-induced IκBα degradation – an index of NF-κB activation – was not affected by free radical scavengers, but was prevented by an NF-κB-specific inhibitor. Our observations indicate that NF-κB plays a key role in Tat-dependent microglial activation, and that oxidative stress and NF-κB activation induced by Tat occur by independent mechanisms.