Administration Of Azidothymidine Research Articles

Evaluation of the PIGRET assay in rats by single oral dosing with azidothymidine

In vivo phosphatidylinositol glycan, class A (Pig-a) gene mutation assay using peripheral blood is known to be a novel and useful tool to evaluate the mutagenicity of compounds. Recently, the rat PIGRET assay which is an improved method for measuring Pig-a mutant cells in reticulocytes with magnetic enrichment of CD71 positive cells has been developed. Several reports showed that the PIGRET assay could detect the increase of Pig-a mutant frequency earlier than the Pig-a assay in total red blood cells (RBC Pig-a assay). Therefore, as part of a collaborative study by the Mammalian Mutagenicity Study (MMS) Group of the Japanese Environmental Mutagen Society, the usefulness of the PIGRET assay in comparison to the RBC Pig-a assay has been assessed for 24 compounds with various mechanisms of action. In the present study, we performed the PIGRET assay and RBC Pig-a assay with a nucleoside analogue, azidothymidine (AZT), and compared the results in these assays. We administered a single dose of AZT to rats by oral gavage up to 2000mg/kg and examined Pig-a mutant frequencies at days 7, 14 and 28 by PIGRET and RBC Pig-a assays. No significant increases in mutant frequency were observed after administration of AZT in both the RBC Pig-a and PIGRET assays and comparable to the previous results of the International Workshop on Genotoxicity Testing (IWGT) workgroup. AZT has been thought to induce not only DNA chain termination as a pharmacological effect but also a large deletion on the genome DNA. The Pig-a assays may be less sensitive to compounds such as AZT which induce large deletions on the genome DNA.

Modulation of efflux proteins by electromagnetic field for delivering azidothymidine and saquinavir into the brain

An exposure to an electromagnetic field (EMF) has been shown to enhance the membrane permeability of endothelial cells. This study investigates the effect of EMF on the modulation of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) for delivering saquinavir (SQV) and azidothymidine (AZT). To assess the transport of SQV and AZT, an EMF and P-gp/MRP (transport protein) inhibitors were employed to stimulate confluent human brain-microvascular endothelial cells (HBMECs) with the regulation of human astrocytes. SQV at 40 μM and AZT at 300 μM were acceptable dosages for the viability of HBMECs. Under an EMF, verapamil showed a higher ability to elevate the permeation across the blood–brain barrier (BBB) than probenecid during treating with SQV. The reverse was true during treating with AZT. After an exposure to an EMF and administration of SQV and AZT, P-gp and MRP1 localized on the luminal side of HBMECs, exhibiting polar characteristics of the cell membranes. The synergetic effect of an EMF exposure and efflux protein inhibition can be promising in delivering antiretroviral drugs across the BBB.

New drug combinations for the treatment of murine AIDS and macrophage protection.

The failure of highly active antiretroviral therapies (HAART) is mainly due to the existence of latent infected reservoirs, such as macrophages and resting CD4+ T cells. In this paper, we report the results that we obtained in a murine model of AIDS by alternating the administration of the lympholitic drug 2-Fluoro-ara-AMP (Fludarabine) to eliminate the infected cells, with that of Azidothymidine (AZT) plus reduced glutathione (GSH) encapsulated in erythrocytes, to protect lymphocytes and macrophages not yet infected, respectively. Two groups of infected mice were treated as follows: one group was treated by alternating the administration of Fludarabine and AZT (treatment A), while the other group received the same treatment plus GSH-loaded erythrocytes given with AZT (treatment A + L-RBC). Fludarabine was administered intraperitoneally, AZT in the drinking water and GSH was encapsulated in erythrocytes by a procedure of hypotonic dialysis and isotonic resealing. The results obtained show that GSH-loaded erythrocytes provide additive effects in all the parameters examined. Alternation of a lympholitic drug and antiretroviral drug is effective in reducing the progression of murine AIDS. Addition of a system to protect macrophages provides additive effects in almost all the parameters considered, confirming that combination therapies aimed at protecting different infectable cell compartments are better than treatments protecting mainly lymphocytes.

Inhibition of murine AIDS by alternate administration of azidothymidine and fludarabine monophosphate.

Anti-HIV-1 combination therapies, including protease and reverse transcriptase inhibitors, can reduce plasma viremia to undetectable levels within the first 2 weeks of treatment. This reduction is followed by a slower decline that primarily results from the presence of viral reservoirs such as CD4+ memory cells, dendritic cells, and macrophages. For this reason, we evaluated a new drug combination therapy that includes a lympholytic drug: (2-fluoro-ara-AMP, fludarabine) to eliminate cells already infected and an antiviral drug (azidothymidine [AZT]) to protect cells not yet infected. We used C57BL/6 mice infected with the retroviral complex LP-BM5, which developed severe immunodeficiency (i.e., murine AIDS), to select the most effective fludarabine regimen to inhibit disease progression, and then to evaluate the efficacy and toxicity of the fludarabine and AZT combinations. The results obtained show that intraperitoneal administration of fludarabine at 3 mg/mouse twice a day for 4 weeks is the most effective regimen in reducing splenomegaly, lymphadenopathy, hypergammaglobulinemia, and proviral DNA content in spleen and lymph nodes and in restoring the architecture of lymph nodes. Subsequently, we evaluated the combined or sequential administration of fludarabine and AZT. The data reported in this paper show that the sequential administration of the two drugs provides additive antiviral effects that reduce spleen and lymph node weights to normal values and proviral DNA content by approximately 95% in all infected organs; the phenotypes of blood T and B cells moved toward control values, although the number of B cells was significantly reduced by fludarabine treatment. Finally, we evaluated the outcome of the disease after suspension or continuation of different treatment regimens. In all treatment groups, the disease progressed and increased proviral DNA content was found in infected organs, but animals receiving the sequential administration of fludarabine and AZT were less affected than those receiving only fludarabine or the simultaneous administration of both. The results obtained suggest that fludarabine could be part of a new therapeutic approach aiming at eradicating HIV from those cells that have been already infected and that are not protected by highly active antiretroviral therapy (HAART).

Inhibition of Murine AIDS by Alternate Administration of Azidothymidine and Fludarabine Monophosphate

Inhibition of Murine AIDS by Alternate Administration of Azidothymidine and Fludarabine Monophosphate

PS-48-12 A pathologic post traumatic gait pattern normalized with an applied weight loading

As typical mitochondrial myopathy has been reported to be expressed among many patients with AIDS treated with long-term azidothymidine (AZT) therapy, we examined changes in mouse liver mitochondrial DNA (mtDNA) after 4-week administration of AZT. Even below 110th the dose given to the patients (AZT, 1 mg/kg/day), 25% of the total deoxyguanosine (dG) was converted to be 8-hydroxy-deoxyguanosine (8-OH-dG). 38% of the total dG was converted to 8-OH-dG with AZT 5 mg/kg/day. In vitro, the conversion of dG to 8-OH-dG was demonstrated by incubating mtDNA in the oxygen radical producing system containing NADH and KCN treated mitochondrial inner membrane. Thus it is concluded that, by lack of repairing system, damaged mtDNA with AZT results in impaired mitochondrial respiratory chain causing oxygen radicals which are responsible for 8-OH-dG formation. These results suggest that the oxygen damage of mtDNA is the primary cause of mitochondrial myopathy with AZT therapy.

Effects of azidothymidine on type C hepatitis

Abstract Interferon (IFN) is now commonly used for the treatment of type C hepatitis; however, the effects of IFN are variable. In patients with the Kl genotype of hepatitis C virus (HCV), a complete response following IFN treatment was observed in only a limited number of patients (less than 25%). These results indicate that a combination therapy of IFN with virucidal drugs may be essential, especially in patients with the KI genotype. In the present study, the effects of azidothymidine (AZT), a virucidal drug, on type C hepatitis were analyzed. In three patients with chronic hepatitis and one patient with cirrhosis, 500 mg of AZT per day were given for 4–8 weeks. HCV RNA encoding the NS5 region became negative in all patients at the end of AZT administration. The titer of HCV decreased clearly in all patients, and serum transaminase (ALT) activity also decreased clearly in all patients, except for one, as a result of AZT administration. In two patients, a combination therapy with IFN and AZT was used. In one of these patients, serum ALT decreased quickly and HCVRNA disappeared from the blood within 3 months. In the other patient, serum ALT levels decreased by the combined administration of AZT with IFN and increased when AZT administration ceases. Serum ALT activity decreased again when AZT was readministered. These results suggest the possibility that a combination therapy may be effective for type C hepatitis, even in patients with the Kl genotype, and indicate the necessity of more extensive studies.

Semen analysis in human immunodeficiency virus infection

To examine the effect of human immunodeficiency virus (HIV) infection on semen quality and to investigate the role of clinical stage of infection, mode of virus acquisition, and azidothymidine (AZT) treatment. DESIGN, PATIENTS, MAIN OUTCOME MEASURES: Ejaculates from 39 HIV-seropositive men and 51 seronegative controls were compared using conventional semen analysis parameters. Centers for Disease Control (Atlanta, GA) classification and peripheral blood CD4 lymphocyte count of seropositive men were recorded at the time of semen analysis. Five patients provided semen before and after AZT treatment.Semen from seropositive men contained significantly fewer motile sperm (48.8% versus 58.8%, P = 0.001), more round cells (62% versus 28% subjects with density greater than 1 x 10(6)/mL, P = 0.003), and was more viscous (1.3 versus 0.5 cm, P less than 0.05) than semen from seronegative controls. The proportion of motile sperm was correlated with absolute number (r = 0.49, P = 0.004) and percentage (r = 0.37, P = 0.03) of CD4-positive lymphocytes in peripheral blood. Total sperm output, however, was preserved and was not correlated with lymphocyte count or symptomatic disease. Administration of AZT had no deleterious effect on sperm output or other semen variables.Human immunodeficiency virus infection per se does not significantly reduce sperm production, regardless of clinical stage or mode of acquisition; however, HIV-seropositive men produce more viscous semen containing fewer motile sperm and more round cells.

Semen analysis in human immunodeficiency virus infection

To examine the effect of human immunodeficiency virus (HIV) infection on semen quality and to investigate the role of clinical stage of infection, mode of virus acquisition, and azidothymidine (AZT) treatment. DESIGN, PATIENTS, MAIN OUTCOME MEASURES: Ejaculates from 39 HIV-seropositive men and 51 seronegative controls were compared using conventional semen analysis parameters. Centers for Disease Control (Atlanta, GA) classification and peripheral blood CD4 lymphocyte count of seropositive men were recorded at the time of semen analysis. Five patients provided semen before and after AZT treatment. Semen from seropositive men contained significantly fewer motile sperm (48.8% versus 58.8%, P = 0.001), more round cells (62% versus 28% subjects with density greater than 1 x 10(6)/mL, P = 0.003), and was more viscous (1.3 versus 0.5 cm, P less than 0.05) than semen from seronegative controls. The proportion of motile sperm was correlated with absolute number (r = 0.49, P = 0.004) and percentage (r = 0.37, P = 0.03) of CD4-positive lymphocytes in peripheral blood. Total sperm output, however, was preserved and was not correlated with lymphocyte count or symptomatic disease. Administration of AZT had no deleterious effect on sperm output or other semen variables. Human immunodeficiency virus infection per se does not significantly reduce sperm production, regardless of clinical stage or mode of acquisition; however, HIV-seropositive men produce more viscous semen containing fewer motile sperm and more round cells.

Massive conversion of guanosine to 8-hydroxy-guanosine in mouse liver mitochondrial DNA by administration of azidothymidine

As typical mitochondrial myopathy has been reported to be expressed among many patients with AIDS treated with long-term azidothymidine (AZT) therapy, we examined changes in mouse liver mitochondrial DNA (mtDNA) after 4-week administration of AZT. Even below 1 10 th the dose given to the patients (AZT, 1 mg/kg/day), 25% of the total deoxyguanosine (dG) was converted to be 8-hydroxy-deoxyguanosine (8-OH-dG). 38% of the total dG was converted to 8-OH-dG with AZT 5 mg/kg/day. In vitro, the conversion of dG to 8-OH-dG was demonstrated by incubating mtDNA in the oxygen radical producing system containing NADH and KCN treated mitochondrial inner membrane. Thus it is concluded that, by lack of repairing system, damaged mtDNA with AZT results in impaired mitochondrial respiratory chain causing oxygen radicals which are responsible for 8-OH-dG formation. These results suggest that the oxygen damage of mtDNA is the primary cause of mitochondrial myopathy with AZT therapy.

Programmed activation of T-lymphocytes. A theoretical basis for short term treatment of AIDS with azidothymidine

When its T-lymphocyte host cell is activated, the latent (DNA) form of human immunodeficiency virus (HIV) is activated to produce RNA copies which are liberated as virus particles from the cell. In this process the cell is destroyed together with the latent virus. If administered at this time, 3′-azidothymidine (AZT) would specifically prevent the liberated RNA copies replicating and establishing latency in new host cells. The RNA copies would then be degraded by viral or host ribonucleases. Thus, one DNA copy of HIV and its RNA progeny would be eliminated from the body. However, many DNA copies of HIV would remain in other cells. The main problem of therapy with AZT is that activation of host cells to become permissive for production of virus is random in time. Activation depends on chance encounters of an infected person with the particular foreign antigens to which individual T-cells bearing latent HIV can specifically respond. It is primarily for this reason that AZT must be administered continuously. If all T-cells could be polyclonally stimulated at one time, all HIV-bearing T-cells would be destroyed and concomitant administration of AZT for a short term would prevent the replication of all liberated viruses. Unlike most renewable ‘end’ cells in the body, the maturation of T cells involves processes of positive and negative selection. To preserve the ‘educated’ T-cell population, T-cell renewal occurs at the end cell, rather than at the stem cell level. It is possible that normal physiological signals concerned with this homeostatic regulation of T-lymphocyte population size could be harnessed to produce synchronous activation of all T-lymphocytes. Tumor necrosis factor-α has some of the properties expected of a postulated polyclonal activator needed for this programmed activation of T-lymphocytes.

Benzylacyclouridine reverses azidothymidine-induced marrow suppression without impairment of anti-human immunodeficiency virus activity

Increased extracellular concentrations of uridine (Urd) have been reported to reduce, in vitro, azidothymidine (AZT)-induced inhibition of human granulocyte-macrophage progenitor cells without impairment of its antihuman immunodeficiency virus (HIV) activity. Because of the clinical toxicities associated with chronic Urd administration, the ability of benzylacyclouridine (BAU) to effect, in vivo, AZT-induced anemia and leukopenia was assessed. This agent inhibits Urd catabolism and, in vivo, increases the plasma concentration of Urd in a dose- dependent manner, without Urd-related toxicity. In mice rendered anemic and leukopenic by the administration of AZT for 28 days in drinking water (1.5 mg/mL), the continued administration of AZT plus daily BAU (300 mg/kg, orally) partially reversed AZT-induced anemia and leukopenia (P less than .05), increased peripheral reticulocytes (to 4.9%, P less than .01), increased cellularity in the marrow, and improved megaloblastosis. When coadministered with AZT from the onset of drug administration, BAU reduced AZT-induced marrow toxicity. In vitro, at a concentration of 100 mumol/L, BAU possesses minimal anti- HIV activity and has no effect on the ability of AZT to reverse the HIV- induced cytopathic effect in MT4 cells. The clinical and biochemical implications of these findings are discussed.

Benzylacyclouridine Reverses Azidothymidine-Induced Marrow Suppression Without Impairment of Anti-Human Immunodeficiency Virus Activity

Increased extracellular concentrations of uridine (Urd) have been reported to reduce, in vitro, azidothymidine (AZT)-induced inhibition of human granulocyte-macrophage progenitor cells without impairment of its antihuman immunodeficiency virus (HIV) activity. Because of the clinical toxicities associated with chronic Urd administration, the ability of benzylacyclouridine (BAU) to effect, in vivo, AZT-induced anemia and leukopenia was assessed. This agent inhibits Urd catabolism and, in vivo, increases the plasma concentration of Urd in a dose-dependent manner, without Urd-related toxicity. In mice rendered anemic and leukopenic by the administration of AZT for 28 days in drinking water (1.5 mg/mL), the continued administration of AZT plus daily BAU (300 mg/kg, orally) partially reversed AZT-induced anemia and leukopenia (P less than .05), increased peripheral reticulocytes (to 4.9%, P less than .01), increased cellularity in the marrow, and improved megaloblastosis. When coadministered with AZT from the onset of drug administration, BAU reduced AZT-induced marrow toxicity. In vitro, at a concentration of 100 mumol/L, BAU possesses minimal anti-HIV activity and has no effect on the ability of AZT to reverse the HIV-induced cytopathic effect in MT4 cells. The clinical and biochemical implications of these findings are discussed.

Pharmacokinetics of subcutaneous azidothymidine in rhesus monkeys.

The pharmacokinetics of subcutaneous bolus and continuous infusion azidothymidine (AZT) was studied in rhesus monkeys. Three animals received 100 mg/m2 as a bolus injection both intravenously and subcutaneously, with the order of administration randomly determined. Two animals received a continuous subcutaneous infusion of 25 mg/m2 per h for 12 or 24 h. AZT was measured in plasma by a reverse-phase high-pressure liquid chromatographic assay. Following intravenous bolus administration, AZT elimination was rapid, with a mean half-life of 1.2 h and a mean clearance of 318 ml/min per m2 (range, 200 to 441 ml/min per m2). The bolus subcutaneous dose was rapidly (time to peak concentration, 15 to 30 min) and nearly completely (fraction absorbed, 92%) absorbed without evidence of local tissue toxicity. With continuous subcutaneous infusion of AZT, the steady state was attained within 4 h and steady-state concentrations in plasma in the two animals exceeded 3.0 mumol/liter. No local tissue toxicity was observed at the infusion site. The subcutaneous route may be a practical alternative to intravenous administration of AZT and deserves further clinical study.