Cultured AIDS-related kaposi's sarcoma (AIDS-KS) cells demonstrate impaired bioenergetic adaptation to oxidant challenge: Implication for oxidant stress in AIDS-KS pathogenesis

Despite its recognition as the most prevalent HIV associated cancer, speculation still abounds regarding the pathogenesis of AIDS-related Kaposi's sarcoma (AIDS-KS). However, it has been established that both cytokines, e.g. IL-6, and HIV-associated products, e.g., Tat, are integral in AIDS-KS cellular proliferation. Further, both experimental and clinical evidence is accumulating to link reactive oxygen intermediates (ROI) with both cytokine induction (primarily via nuclear factor-κB [NF-κB] dependent routes) as well as the subsequent cytokine, tumor necrosis factor α (TNFα) stimulation of HIV replication. Features of AIDS-KS patients, such as retention of phagocytes, presence of sustained immunostimulation, and a frequent history of KS lesions arising at traumatized sites, make oxidant stress a viable clinical factor in AIDS-KS development. Time course nucleotide profile analyses show that AIDS-KS cells have an inherent, statistically significant, biochemical deficit, even prior to oxidant stress, due to (1) a more glycolytic bioenergetic profile, resulting in lower levels of high energy phosphates (impairing capacity for glutathione [GSH] synthesis and DNA repair); (2) lower levels of NADPH (compromising the activities of GSSG reductase and peroxidase function of catalase); and (3) reduced levels of GSH (impeding both GSH peroxidase and GSH-S-transferases). Following exposure to physiologically relevant levels of H₂O₂ only the human microvascular endothelial cells (a putative AIDS-KS progenitor cell) responded with bioenergetic adaptations that reflected co-ordination of energy generating and cytoprotective pathways, e.g., retention of the cellular energy charge, increased NAD⁺, and an accentuation of the ATP, NADPH, and total adenine nucleotide differences relative to AIDS-KS cells. Also, some of the AIDS-KS strains retained intracellular GSSG subsequent to oxidant challenge, inviting the formation of deleterious protein mixed disulfides. While the results of our study address some AIDS-KS issues, they also raise an etiological question, i.e., Does the inability to tolerate oxidant stress arise in conjunction with AIDS-KS neoplastic development, or is it pre-existing in the population at risk? Regardless, use of antioxidant therapy (low risk/potentially high benefit) in both the “at risk” population as well as in those individuals with active disease may prove a useful preventative and/or treatment modality. © 1995 Wiley-Liss, Inc.     

Hormone-induced preimplantation Lyt 2+ murine uterine suppressor cells persist after implantation and may reduce the spontaneous abortion rate in CBA/J mice

Immunoregulatory cells in the maternal uterine endometrium and decidua are thought to play an important role in ensuring the success of the semiallogeneic conceptus. Two phases of suppression have been described in pregnant mice. Prior to implantation, the hormonal changes triggered by mating activate or recruit a population of nonspecific Lyt 2+ suppressor cells that inhibit cytotoxic T lymphocyte generation: this suppression appears to wane at the time or implantation and 4-5 days after implantation, a non-T suppressor cell population activated or recruited by fetal trophoblast cells develops. In this paper we confirm the non-major histocompatibility complex specificity of the hormone-regulated preimplantation suppressor cell. We show that this activity persists in the uterus during the early postimplantation period where its suppressive activity is masked by an Fc-receptor-positive cell population recruited by the implanting embryo. The potential importance of the persisting suppressor cells is suggested by an increase in the rate of spontaneous abortion of DBA2-mated CBA/J mice following injection of monoclonal anti-Lyt 2+ antibody in the early postimplantation period.     

H+-dependent efflux of Ca2+ from heart mitochondria

A rapid loss of accumulated Ca²⁺ is produced by addition of H⁺ to isolated heart mitochondria. The H⁺-dependent Ca⁺ efflux requires that either (a) the NAD(P)H pool of the mitochondrion be oxidized, or (b) the endogenous adenine nucleotides be depleted. The loss of Ca²⁺ is accompanied by swelling and loss of endogenous Mg^2–. The rate of H⁺-dependent Ca²⁺ efflux depends on the amount of Ca²⁺ and P_i taken up and the extent of the pH drop imposed. In the absence of ruthenium red the H⁺-induced Ca²⁺-efflux is partially offset by a spontaneous re-accumulation of released Ca²⁺. The H⁺-induced Ca²⁺ efflux is inhibited when the P_i transporter is blocked withN-ethylmaleimide, is strongly opposed by oligomycin and exogenous adenine nucleotides (particularly ADP), and inhibited by nupercaine. The H⁺-dependent Ca²⁺ efflux is decreased markedly when Na⁺ replaces the K⁺ of the suspending medium or when the exogenous K⁺/H⁺ exchanger nigericin is present. These results suggest that the H⁺-dependent loss of accumulated Ca²⁺ results from relatively nonspecific changes in membrane permeability and is not a reflection of a Ca²⁺/H⁺ exchange reaction.     

Ion transport by heart mitochondria: XXVII. The relation of mercurial-dependent adenosine triphosphatase activity to ion movements

The properties of a mercurial-dependent adenosine triphosphatase activity have been examined in isolated beef heart mitochondria. The reaction differs from that induced by uncouplers in that it is associated with extensive ion uptake and osmotic swelling, is highly specific for K⁺ over Na⁺, and is enhanced by respiration. Evidence is presented which suggests that the following events can account for the observations: (1) The mercurial blocks the phosphate transporter so that phosphate hydrolyzed from ATP is trapped in the matrix. (2) This interior negative potential causes cations to move inward and swelling results. (3) Permeability to K⁺ but not to Na⁺ is enhanced greatly by the reaction of the mercurial with the membrane. The inward movement of K⁺ closely resembles that produced by valinomycin, in that it is accompanied by proton ejection into the medium and it rapidly establishes a condition in which ion gradients cannot be maintained. This marked increase in permeability may be related to the pH gradient and is manifest as additional passive swelling in the absence of sucrose and passive contraction when sucrose is present. A comparison of the kinetics of swelling and of ATP hydrolysis shows that the elevated rates of ATPase are correlated with this condition of high permeability. When a corresponding condition of high permeability to Na⁺ is established by treatment with gramicidin or EDTA, the mercurial-dependent ATPase is nearly as rapid in Na⁺ as in the K⁺ medium. It appears, therefore, that the K⁺ specificity resides at the level of membrane permeability and is not a feature of the ATPase reaction per se. (4) Respiration appears to affect the ATPase reaction by virtue of its ability to extrude ions from the matrix in the presence of the mercurial. p-Chloromercuriphenyl sulfonate causes a switch from respiration-dependent ion accumulation to respiration-dependent ion extrusion to occur. A model to explain these reactions is presented.     

Effects of ionic strength and sulfhydryl reagents on the binding of creatine phosphokinase to heart mitochondrial inner membranes

The concept that creatine phosphokinase is bound to the outer surface of the heart mitochondrial inner membrane originated from observations that the enzyme is retained by water-swollen heart mitochondria and by digitonintreated heart mitochondria suspended in isotonic sucrose. The present study establishes that digitonin-treated mitochondria release creatine phosphokinase in isotonic KCl, and other investigators have reported an identical response for the water-swollen organelles. These observations suggest that mitochondrial creatine phosphokinase is not bound to the outer surface of the inner membrane at a site adjacent to the adenine nucleotide translocase under physiologic conditions.     

Energy-dependent contraction of swollen mitochondria: activation by nigericin.

The rate, extent, and efficiency of the energy-dependent contraction of heart mitochondria swollen in Na+ or K+ nitrate are all strongly activated by nigericin, an antibiotic which is known to support cation/H+ exchange in natural and model membranes. In the absence of nigericin, the cation selectivity sequence of energy-dependent contraction (Na+>Li+>K+>choline+) is identical to that of passive swelling in acetate salts, a reaction which is presumed to be dependent on an endogenous cation/H+ exchanger. These results strongly favor an osmotic mechanism for energy-dependent contraction which depends on electrogenic H+ ejection, H+/cation exchange, and electrophoretic anion efflux.