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Results for “FOLIC ACID ANTAGONISTS”

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PubMed1988

Specific in vitro anti-tumour activity of methotrexate-monoclonal antibody conjugates prepared using human serum albumin as an intermediary.

Methotrexate (MTX) is a folic acid antagonist widely used in the treatment of cancer but, like other such agents, has non-specific toxic side effects. With the aim of reducing these toxic effects, MTX was coupled to monoclonal antibodies (MoAb) in one of two ways; either (a) directly using an active ester derivative or (b) via human serum albumin (HSA), to act as an intermediary and so increase the amount of MTX bound. The MTX coupled directly to anti-Ly-2.1 antibody had approximately 10 molecules of MTX per antibody molecule, whereas the HSA coupled material had 24 molecules of MTX per antibody molecule. After coupling MTX directly to antibody there was a loss of potency of the MTX, and MTX-MoAb conjugates were 30-fold less potent than free MTX, although the antibody-coupled material was more specific than free MTX and bound only to the antibody-reactive target cells. By contrast, the MTX-HSA-MoAb conjugates were 3.5 times less potent than free MTX and were 8.5 times more potent than MTX-MoAb conjugates. Thus, by increasing the amount of drug bound to antibody, more toxic conjugates were made--an important principle for the use of such conjugates for the treatment of cancer in man.

Animals↗

PubMed1968

Pyruvate metabolism by aminopterin-inhibited Aerobacter aerogenes.

1. The synthesis and utilization of both alanine (by reductive amination, oxidative deamination and transamination) and valine (by transamination only) in Aerobacter aerogenes are unaffected by aminopterin. These amino acids, which accumulate in aminopterin-treated cultures of this organism, are therefore considered to be formed as secondary products from the excess of pyruvate that also accumulates. 2. Oxidative metabolism of pyruvate and the synthesis of acetylmethylcarbinol by A. aerogenes cells are unaltered by growth in the presence of aminopterin. 3. Cells from static and anaerobic cultures that have been treated with the folic acid antagonist in the early exponential phase have a decreased ability to cleave pyruvate to acetate and formate, and to effect the exchange of formate with the carboxyl group of pyruvate. 4. 3-Methyl-2-oxobutanoate, the keto acid precursor of valine, cannot replace pyruvate as substrate in either the phosphoroclastic or the exchange reaction.

Alanine↗

PubMed1989

[Pancytopenia during low-dose oral methotrexate therapy of psoriatic arthritis].

Pancytopenia and interstitial pneumonia occurred in a 70-year-old woman with psoriatic arthritis and compensated renal insufficiency while she was being treated with low doses of the folic-acid antagonist methotrexate (5 mg weekly). Despite the administration of platelets, red blood cells, antibiotics, acyclovir and folinic acid (100 mg daily), the pneumonia progressed, and the patient died of global respiratory failure.

Administration, Oral↗

PubMed2005

Methotrexate causes oxidative stress in rat kidney tissues.

AIM: Methotrexate (MTX), a folic acid antagonist, is one of the chemotherapeutic agents widely used in the treatment of some types of cancers. Nephrotoxicity is one of the complications of MTX treatment. The aim of this study was to investigate possible effects of MTX treatment on the oxidant/antioxidant status in rat kidney tissues and enzymatic mechanisms leading to nephrotoxicity. METHODS: For this aim, 10 Sprague-Dawley type female rats of 4 weeks old were used in the study. The animals were divided into two groups randomly. Five of them were used as control, and the others were treated with MTX intravenously (60 mg/m2 of body surface area per week) for 7 weeks. At the end of this period, they were sacrificed, and kidney tissues were removed to be used in the analyses of malondialdehyde (MDA) levels, antioxidant potential (AOP) values, and superoxide dismutase, catalase, glutathione peroxidase, xanthine oxidase, adenosine deaminase, and 5' nucleotidase enzyme activities. RESULTS: There was significant increase in the MDA level in the MTX group compared with the control group (1.74+/-0.23 nmol/mg vs. 1.04+/-0.30 nmol/mg; p<0.05, respectively). There were however no meaningful differences between enzyme activities and AOP values of the groups. CONCLUSION: It has been suggested that MTX leads to oxidative stress in rat kidney tissues, which might be one of the reasons for MTX-induced nephrotoxicity.

Animals↗

PubMed1985

Ultrastructural analysis of the effect of trimethoprim and sulphamethoxazole on the development of Chlamydia trachomatis in cell culture.

Folic acid antagonists have been demonstrated to cause gross changes in the morphology of chlamydial inclusions in cell culture. The ultrastructural changes were examined by electron microscopy in cultures of Chlamydia trachomatis treated with trimethoprim and sulphamethoxazole. Examination of these cultures demonstrated a failure of the reticulate bodies to develop into normal elementary bodies. These changes were seen in cultures treated with either compound, although sulphamethoxazole was more active by weight, and suggest that both drugs ultimately interfere with nucleic acid synthesis.

Chlamydia trachomatis↗

PubMed1976

Cytokinetics and chemotherapy of psoriasis.

The successful treatment of psoriasis with folic acid antagonists during the past 25 years has led to extensive research in the areas of cytokinetics and chemotherapy. In this paper we shall review selected aspects of these topics relevant to the treatment of psoriasis. The effectiveness of methotrexate treatment of psoriasis can be related to both the hyperproliferative cytokinetics of psoriasis and an increased biochemical sensitivity of psoriatic epidermal cells to this drug. Future research goals in chemotherapy of psoriasis include (a) optimizing drug schedules for available drugs; (b) identifying other susceptible biochemical points of selective drug attack; (c) identifying secondary advantages in order to facilitate selective drug action in psoriasis, such as ultraviolet light therapy in combination with a systemic drug; and (d) developing topically effective chemotherapeutic agents. Approaches to research on topical therapy are reviewed with specific reference to animal testing models for psoriasis and percutaneous penetration of topically applied agents.

Administration, Topical↗

PubMed2005

Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethylpyrimidine) induces apoptosis of freshly isolated human T lymphocytes, bypassing CD95/Fas molecule but involving its intrinsic pathway.

Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethyl-pyrimidine), a folic acid antagonist, may exert, in addition to antiprotozoan effects, immunomodulating activities, including induction of peripheral blood lymphocyte apoptosis. However, the molecular mechanisms underlying this proapoptotic activity remain to be elucidated. Here we show that pyrimethamine, used at a pharmacologically relevant concentration, induced per se apoptosis of activated lymphocytes via the activation of the caspase-8- and caspase-10-dependent cascade and subsequent mitochondrial depolarization. Importantly, this seems to occur independently from CD95/Fas engagement. The proapoptotic activity of pyrimethamine was further confirmed in a patient with autoimmune lymphoproliferative syndrome, an immune disorder associated with a defect of Fas-induced apoptosis. In this patient, pyrimethamine treatment resulted in a "normalization" of lymphocyte apoptosis with a significant amelioration of laboratory parameters. Altogether, these results suggest a mechanism for pyrimethamine-mediated apoptosis that seems to bypass CD95/Fas engagement but fully overlaps CD95/Fas-induced subcellular pathway. On these bases, a reappraisal of the use of pyrimethamine in immune lymphoproliferative disorders characterized by defects in CD95/Fas-mediated apoptosis should be taken into account.

Annexin A5↗

PubMed1995

A general method for the consecutive integration of single copies of a heterologous gene at multiple locations in the Bacillus subtilis chromosome by replacement recombination.

We have devised a two-step procedure by which multiple copies of a heterologous gene can be consecutively integrated into the Bacillus subtilis 168 chromosome without the simultaneous integration of markers (antibiotic resistance). The procedure employs the high level of transformability of B. subtilis 168 strains and makes use of the observation that thymine-auxotrophic mutants of B. subtilis are resistant to the folic acid antagonist trimethoprim (Tmpr), whereas thymine prototrophs are sensitive. First, a thymine-auxotrophic B. subtilis mutant is transformed to prototrophy by integration of a thymidylate synthetase-encoding gene at the desired chromosomal locus. In a second step, the mutant strain is transformed with a DNA fragment carrying the heterologous gene and Tmpr colonies are selected. Approximately 5% of these appear to be thymine auxotrophic and contain a single copy of the heterologous gene at the chromosomal locus previously carrying the thymidylate synthetase-encoding gene. Repetition of the procedure at different locations on the bacterial chromosome allows the isolation of strains carrying multiple copies of the heterologous gene. The method was used to construct B. subtilis strains carrying one, two, and three copies of the Bacillus stearothermophilus branching enzyme gene (glgB) in their genomes.

Bacillus subtilis↗

PubMed2005

Genetic requirements for potassium ion-dependent colony spreading in Bacillus subtilis.

Undomesticated strains of Bacillus subtilis exhibit extensive colony spreading on certain soft agarose media: first the formation of dendritic clusters of cells, followed by spreading (pellicle-like) growth to cover the entire surface. These phases of colonization are dependent on the level of potassium ion (K(+)) but independent of flagella, as verified with a mutant with a hag gene replacement; this latter finding highlights the importance of sliding motility in colony spreading. Exploring the K(+) requirement, directed mutagenesis of the higher-affinity K(+) transporter KtrAB, but not the lower-affinity transporter KtrCD, was found to inhibit surface colonization unless sufficient KCl was added. To identify other genes involved in K(+)-dependent colony spreading, transposon insertion mutants in wild-type strain 3610 were screened. Disruption of genes for pyrimidine (pyrB) or purine (purD, purF, purH, purL, purM) biosynthetic pathways abolished the K(+)-dependent spreading phase. Consistent with a requirement for functional nucleic acid biosynthesis, disruption of purine synthesis with the folic acid antagonist sulfamethoxazole also inhibited spreading. Other transposon insertions disrupted acetoin biosynthesis (the alsS gene), acidifying the growth medium, glutamine synthetase (the glnA gene), and two surfactin biosynthetic genes (srfAA, srfAB). This work identified four classes of surface colonization mutants with defective (i) potassium transport, (ii) surfactin formation, (iii) growth rate or yield, or (iv) pH control. Overall, the ability of B. subtilis to colonize surfaces by spreading is highly dependent on balanced nucleotide biosynthesis and nutrient assimilation, which require sufficient K(+) ions, as well as growth conditions that promote sliding motility.

Acetoin↗

PubMed2000

Potassium-sparing renal effects of trimethoprim and structural analogues.

BACKGROUND/AIMS: The antibiotic antagonists of folic acid trimethoprim, tetroxoprim, pyrimethamine and their antineoplastic analogue methotrexate have structural characteristics in common with the potassium-sparing diuretic triamterene. They may, therefore, share with triamterne potassium-sparing renal effects. METHODS: Clearance studies were performed on anesthetized male Sprague-Dawley rats, and the drug effects on glomerular filtration rate and on urinary excretion of sodium, chloride, and potassium were studied. RESULTS: Trimethoprim and tetroxoprim, injected intravenously at doses ranging from 0.3 to 30 mg/kg, induced dose-dependent natriuretic and antikaliuretic renal effects, whereas pyrimethamine at doses ranging from 1 to 10 mg/kg and methotrexate at doses ranging from 10 to 50 mg/kg did not affect urinary sodium and potassium excretion. An antikaliuretic effect was also observed after application of the structurally related antiprotozoal compound pentamidine at doses ranging from 3 to 10 mg/kg. In contrast to trimethoprim and tetroxoprim, the antikaliuresis was accompanied by a marked decrease of urinary sodium and chloride excretion at all of the doses tested. At 10 mg/kg, pentamidine induced a pronounced fall of the glomerular filtration rate (by 43.5%). CONCLUSIONS: Trimethoprim and tetroxoprim share with potassium-sparing diuretics natriuretic and antikaliuretic renal effects which may be caused by similar mechanisms in the distal nephron, whereas pyrimthamine and methotrexate do not. A depression of renal hemodynamics is an important factor involved in the antikaliuretic effect of pentamidine.

Animals↗

PubMed1985

The use of methotrexate in rheumatoid arthritis.

The use of methotrexate in rheumatoid arthritis is reviewed. Methotrexate, a folic acid antagonist, is sometimes employed in an attempt to symptomatically control patients whose disease does not respond adequately to conventional therapies. Systemic administration of 7.5-15 mg/wk in a "pulse" fashion appears to be effective without precipitating severe adverse effects. However, concern over potentially serious side effects and a lack of well-controlled clinical trials have limited its use to severe, refractory disease. Further studies are needed before its role in rheumatoid arthritis can justifiably be expanded.

Arthritis, Rheumatoid↗

PubMed1994

Trimetrexate in malignant mesothelioma: A Cancer and Leukemia Group B Phase II study.

PURPOSE: Folic acid antagonists are reported to have activity against mesothelioma. The Cancer and Leukemia Group B (CALGB) undertook this phase II study of the new antifolate, trimetrexate (TMTX), to evaluate its response rate and toxicity in chemotherapy-naive patients with malignant mesothelioma. PATIENTS AND METHODS: Fifty-two patients were accrued to this protocol. Because of concerns about TMTX toxicity in patients with malignant effusions and/or hypoalbuminemia, the first 17 patients were treated at a dose of 6 mg/m2 daily for 5 days every 21 days. Because minimal toxicity was observed, the subsequent 35 patients were treated at a dose of 10 mg/m2. RESULTS: Two of 17 patients (12%) in the 6-mg/m2 treatment group had a partial response (PR) and four of 34 eligible patients (12%) in the 10-mg/m2 treatment group had a PR or regression (R) of assessable disease. No patient achieved a complete response (CR). Median survival durations were 5.0 and 8.9 months in the 6- and 10-mg/m2 treatment groups, respectively, while the 2-year survival rates were identical at 18%. At the 10-mg/m2 dose, toxicity was tolerable, with one toxic death from sepsis and a 12% rate of grade 4 thrombocytopenia and granulocytopenia. CONCLUSION: In this large trial, TMTX showed minor activity in the treatment of malignant mesothelioma. Myelosuppression was mild and dose-related. Future studies of higher doses of TMTX should be considered.

Adult↗

PubMed1977

Leukoencephalopathy in childhood leukemia.

A 14-year-old boy survived for 7 years after the initial diagnosis and treatment of acute lymphocytic leukemia. Neurologic deterioration occured repeatedly throughout his complicated clinical course but it was most severe and only partially reversible following orally administered pyrimethamine. The neuropathologic lesions were distinctive and included a diffuse reactive astrocytosis, axonal degeneration, status spongiosis, circumscribed foci of demyelination and coagulative necrosis, and mural thickening with luminal narrowing of microcirculatory vessels. This collection of findings represents the leukoencephalopathy of childhood leukemia that we and others believe results in large part from the combined effects of cranial irradiation and chemotherapy. The role of folic acid antagonists, namely methotrexate and pyrimethamine, are particularly noteworthy in this regard.

Adolescent↗

PubMed1978

The current role of cancer chemotherapy.

Cancer chemotherapy has developed rapidly over the last twenty years. The majority of patients with cancer die from metastatic disease, so the major therapeutic advance now must be better systemic therapy. From its early beginning in the 1940's with oestrogen therapy for prostatic cancer, nitrogen mustards in the lymphomas, and folic acid antagonists in childhood leukaemia, there are now between thirty and forty active anti-cancer agents in clinical use. The main clinical pharmacological points of the major agents are briefly reviewed, together with their main dose-limiting toxic effects and their activity as single agents. Clinical chemotherapy has developed by the introduction of newer agents from the drug screening programmes and a better understanding of the scheduling to avoid serious toxicity. Although drug-resistance is still a major problem, by combining different active agents there has been a dramatic improvement in survival of patients with selected tumours. More recently, treatment of patients early, before they have gross clinical recurrence, has already shown some benefit in pre-menopausal patients with carcinoma of the breast and in patients with osteosarcoma. The limitations of clinical measurements in monitoring therapy are clear, and a major improvement could well be realised if therapy could be monitored on the basis of quantitative markers. The clinical impact of cancer chemotherapy has already been dramatic in drug-sensitive tumours, but these only contribute a small proportion of the total. Some of the common tumours fall into the group that are relatively drug sensitive where the lives of patients can be prolonged, but there is still a significant fraction of tumours which are insensitive to existing drugs and which will probably require the development of newer agents before chemotherapy can make any impact on the survival of patients with these tumours.

Alkylating Agents↗

PubMed2005

Methotrexate prevents renal injury in experimental diabetic rats via anti-inflammatory actions.

Recent studies suggested the involvement of inflammatory processes in the pathogenesis of diabetic nephropathy. Methotrexate (MTX), a folic acid antagonist, is widely used for the treatment of inflammatory diseases. Recently, it has been shown that treatment with low-dose MTX reduces the cardiovascular mortality in patients with rheumatoid arthritis, suggesting that MTX has anti-atherosclerotic effects via its anti-inflammatory actions. This study was designed to determine the anti-inflammatory effects of this agent on diabetic nephropathy. Diabetes was induced in Sprague-Dawley rats with streptozotocin, and MTX (0.5 or 1.0 mg/kg) was administered once a week for 8 wk. Treatment with MTX reduced urinary albumin excretion, mesangial matrix expansion, macrophage infiltration, expression of TGF-beta and type IV collagen, and intercellular adhesion molecule-1 in glomeruli. MTX also reduced the high glucose-induced NF-kappaB activation in vitro and in vivo. The results indicate that intermittent administration of MTX prevented renal injuries without changes in blood glucose level and BP in experimental diabetic rats. The protective effects of MTX are suggested to be mediated by its anti-inflammatory actions through inhibition of NF-kappaB activation and consequent reduction of intercellular adhesion molecule-1 expression and macrophage infiltration. The results suggest that anti-inflammatory agents might be beneficial for the treatment of diabetic nephropathy.

Albuminuria↗

PubMed2005

A novel single nucleotide polymorphism of the human methylenetetrahydrofolate reductase gene in Japanese individuals.

The genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR) have been associated with increased toxicity of methotrexate (MTX), a folic acid antagonist that is widely used to treat cancer and immunosuppressive disorders such as rheumatoid arthritis. In this study, we analyzed all the exons and exon/intron junctions of the MTHFR gene from 200 Japanese individuals. We detected a novel single nucleotide polymorphism (SNP) 148C>T (Arg46Trp) in exon 1. The allele frequency of this polymorphism in the Japanese population appears to be extremely low (0.25%).

Base Sequence↗

PubMed1976

Clinical use of immunosuppressive drugs: part I.

While immunosuppressive drugs are principally used in the treatment of malignant disease, their use in non-malignant disease and transplantation has become commonplace. The mechanisms of action of immunosuppressive agents differ. Alkylating agents react with nucleophilic centres of D, and rna. Folic acid antagonists prevnt the conversion of dihydrofolic acid to tetrahydrofolic acid. Antibiotics act in a variety of different ways; the alkaloids cause metaphase arrest. Cytarabine (cytosine arabinoside), methotrexate, hydroxyurea and thioguanine act during mitosis and the latter also acts during replication is not known...

Arthritis, Reactive↗

PubMed1989

Current recommendations and future prospects in the treatment of toxoplasmosis.

Toxoplasma infection is highly prevalent throughout the world and causes disease in diverse populations. Effective treatment regimens are available for each clinical entity of toxoplasma, but problems of incomplete clinical efficacy, drug potency, drug safety, and length of treatment remain. No well-controlled clinical trials in humans have been performed to evaluate the efficacy and safety of treatment. Primary treatment of toxoplasmosis is with the synergistic combination of pyrimethamine and sulphonamide. This is considered the treatment of choice for severe disease, disease in immunocompromised patients, and congenital toxoplasmosis. Spiramycin, a macrolide antibiotic, is frequently used alone or alternately with pyrimethamine and sulphonamide for pregnant women with the acute acquired infection to prevent congenital toxoplasmosis. Clindamycin is used frequently to treat acute flares of toxoplasmic chorioretinitis and as second-line therapy for toxoplasmic encephalitis in patients with the acquired immunodeficiency syndrome (AIDS). Inadequacies in the treatment of toxoplasmosis in immunosuppressed patients, exemplified by experience with AIDS patients, should provide the impetus for well-designed trials to find and evaluate more potent and better-tolerated agents. Classes of new drugs that have been investigated and show some promise include: (a) macrolides (roxithromycin, azithromycin); (b) folic acid antagonists (piritrexim and trimetrexate), and (c) purine analogues (arprinocid). Immunomodulators have attracted interest, and interferon-gamma alone and in combination with roxithromycin is effective in murine models. Interleukin-2 is also effective in the murine model.

Animals↗