HIV-1 Tat induces microvascular endothelial apoptosis through caspase activation.
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.
Park
I W
IW
Division of Experimental Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA.
Ullrich
C K
CK
Schoenberger
E
E
Ganju
R K
RK
Groopman
J E
JE
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D016207:Cytokines / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000201:enzymology* / Q000473:pathology*; D004789:Enzyme Activation / Q000187:drug effects; D015696:Gene Products, tat / Q000235:genetics / Q000276:immunology / Q000633:toxicity*; D015497:HIV-1 / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D019014:fas Receptor / Q000096:biosynthesis; D054322:tat Gene Products, Human Immunodeficiency Virus
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D016207:Cytokines; D015696:Gene Products, tat; D009842:Oligopeptides; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; C108637:aspartyl-glutamyl-valyl-aspartal; D019014:fas Receptor; D054322:tat Gene Products, Human Immunodeficiency Virus; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases