RESUMEN
HIV-1 Tat, in addition to its critical role in viral transcription, is secreted from infected cells and can act as a proto-cytokine. We studied the effects of HIV-1 Tat in primary human microvascular endothelial cells of lung origin and found that it caused apoptosis. This apoptosis occurred without induction of either Fas or TNF, known mediators of programmed cell death. Tat, like Fas ligand, induced cleavage of chromatin structure, as evidenced by changes in DNA laddering, incorporation of fluorescein into the nicked chromosomal DNA (TUNEL assay), and mono- or oligonucleosomes. Furthermore, Tat treatment caused cleavage of poly(A/DP)-ribose polymerase, a substrate of caspases. Caspase-3, but not caspase-9, was activated following treatment of primary human microvascular endothelial cells of lung origin with either Tat or anti-Fas agonist Ab (anti-Fas). Inhibition of caspase-3 activity markedly reduced apoptosis. Although Fas-mediated apoptosis involved changes in Bcl-2, Bax, and Bad regulatory proteins, such alterations were not observed with Tat. Taken together, these data demonstrate that HIV-1 Tat is able to activate apoptosis in microvascular endothelium by a mechanism distinct from TNF secretion or the Fas pathway.
Asunto(s)
Apoptosis/efectos de los fármacos , Caspasas/metabolismo , Endotelio Vascular/enzimología , Endotelio Vascular/patología , Productos del Gen tat/toxicidad , VIH-1/patogenicidad , Secuencia de Aminoácidos , Apoptosis/fisiología , Caspasa 3 , Inhibidores de Caspasas , Células Cultivadas , Inhibidores de Cisteína Proteinasa/farmacología , Citocinas/farmacología , Activación Enzimática/efectos de los fármacos , Productos del Gen tat/genética , Productos del Gen tat/inmunología , VIH-1/genética , VIH-1/inmunología , Humanos , Datos de Secuencia Molecular , Oligopéptidos/farmacología , Poli(ADP-Ribosa) Polimerasas/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Factor de Necrosis Tumoral alfa/biosíntesis , Receptor fas/biosíntesis , Productos del Gen tat del Virus de la Inmunodeficiencia HumanaRESUMEN
The immune dysfunction and cell destruction that occur in the human immunodeficiency virus (HIV)-infected host appear to result from the direct cytopathic effects of viral infection and the effects of viral proteins on uninfected bystander cells. Recently, the alpha-chemokine receptor CXCR4 has been reported to mediate apoptosis in neuronal cells and in CD4(+) and CD8(+) T cells after its binding to HIV-1 envelope proteins. In the current study, it was observed that human umbilical vein endothelial cells (HUVEC) undergo apoptosis after their treatment with the HIV-1 envelope proteins gp120/160. Anti-CXCR4 monoclonal antibody decreased HIV-1 gp120/160-induced apoptosis, suggesting that the CXCR4 chemokine receptor mediates the apoptotic effects of these HIV envelope glycoproteins. Further studies revealed that caspases play an important role in this process because the pretreatment of cells with a general caspase enzyme inhibitor decreased the extent of HUVEC apoptosis induced by gp120/160. In addition, it was found that caspase-3 was activated on HIV-1 gp120/160 treatment of these cells. It was also observed that gp120/160 treatment slightly increased the expression of the pro-apoptotic molecule Bax. These results suggest that HIV-1 envelope glycoproteins can disrupt endothelial integrity through the interaction with CXCR4, thereby facilitating virus transit out of the bloodstream and contributing to the vascular injury syndromes seen in acquired immunodeficiency syndrome. (Blood. 2000;96:1438-1442)