MITOCHONDRIAL DYSFUNCTIONS IN CIRCULATING T-LYMPHOCYTES FROM HUMAN IMMUNODEFICIENCY VIRUS-1 CARRIERS

In several models of lymphocyte apoptosis, two alterations of mitochon drial function precede advanced DNA fragmentation: (1) a reduction of mitochondrial transmembrane potential (Delta Psi(m)) and (2) an increa se in mitochondrial generation of superoxide anion. Here we show that two fluorochromes allow for the identification of analogous mitochondr ial perturbations in circulating T lymphocytes from human immunodefici ency virus (HIV)-1(+) donors. The first among these fluorochromes, the cationic lipophilic dye DiOC(6)(3), measures Delta Psi(m); the second marker, hydroethidine (HE), is nonfluorescent, unless it is oxidized by superoxide anions to the product ethidium (Eth). CD4(+) or CD8(+) c ells from clinically asymptomatic HIV-1 carriers contain a significant ly elevated percentage of cells endowed with enhanced HE --> Eth conve rsion and/or reduced DiOC(6)(3) uptake as compared with normal control s. Phenotypic characterization of (HE --> Eth)(high) cells from HIV+ d onors shows that these cells possess a low Delta Psi(m), thus demonstr ating a functional alteration of mitochondria. In addition, (HE --> Et h)(high) cells display a reduced incorporation of the cardiolipin-spec ific dye nonyl-acridine orange (NAO), showing a structural defect of t he cardiolipin-containing inner mitochondrial membrane. Control experi ments involving rotenone, an inhibitor of the respiratory chain comple x I, indicate that the reactive oxygen species responsible for HE --> Eth conversion is generated during mitochondrial electron transport. I n synthesis, it appears that mitochondrial alterations occur in a sign ificant percentage of circulating T lymphocytes from HIV-1 carriers. T he extent of Delta Psi(m) reduction, as determined ex vivo, correlates with the frequency of cells undergoing DNA fragmentation after overni ght in vitro culture. These observations may be important for the unde rstanding and for the direct ex vivo quantitation of HIV-triggered lym phocyte destruction. (C) 1995 by The American Society of Hematology.