Increased levels of erythrocyte glutathione in acute myocardial infarction: an antioxidant defence

Glutathione [GSH] has a central role in the defence against oxidative damage. This study was carried out to investigate any change in erythrocyte GSH levels in a population of patients with acute myocardial infarction [AMI] and compare them with levels in normal healthy subjects. Method: GSH levels were determined in erythrocytes of one hundred and seventy six patients with AMI [age: 30-70 years; 131 males and 45 females] admitted to the National Institute of Cardiovascular Diseases, Karachi. These levels were compared with eryrocyte GSH levels obtained from 95 normal healthy subjects [controls]. Mean ' SD erythrocyte GSH levels in AMI patients and controls were found to be 2.34 ' 0.62 micro mol/ml of packed cells and 2.08' 0.62 micro mol/ml of packed cells, respectively. The two values when compared with one way ANOVA were found to be significantly different [p=0.001]. Age had little effect on erythrocyte GSH levels in both AMI patients and normal healthy subjects. Increased production of reactive oxygen species is a feature of cardiovascular disease, such as AMI and cells can respond to mild oxidative stress by upregulating antioxidant defence in terms of increased production of GSH

Induction of white cell proliferation due to haematopoietic growth factors is associated with an increase in multiple forms of dihydrofolate reductase in non-neutropenic cancer patients

OBJECTIVE: Granulocyte-colony stimulating factor [G-CSF] and granulocyte macrophage-colony stimulating factor [GM-CSF] are frequently used in cancer patients to overcome the granulocytopenic effects of chemotherapy, and also to mobilize the stem cells. The mobilized stem cells are collected from the peripheral blood and used for transplantation following high doses of chemotherapy. However, the molecular mechanism by which these colony stimulating factors [CSFs] bring about proliferation of myeloid precursor cells is not clearly known. Dihydrofolate reductase [DHFR], which has an established role in DNA synthesis, could be a link between administration of CSF and stem cell proliferation. The purpose of this study was to investigate whether CSFs induce white cell proliferation by producing multiple forms of DHFR. METHODS: Twelve patients with non-haematological malignancies were treated with either G-CSF or GM-CSF to mobilize stem cells. Nine healthy subjects were treated with placebo as controls. Blood samples were obtained before and after stimulation with CSFs or placebo. White blood cells were separated and concentrations of both active DHFR and immunoreactive nonfunctional form of DHFR were determined in their cytoplasm using methotrexate-binding assay and enzyme-linked immunosorbent assay, respectively. Total leucocytes count [TLC] was also monitored before and after stimulation with CSFs or placebo. There was a significant [P < 0.05] increase in concentration of immunoreactive nonfunctional form of DHFR and TLC following stimulation with CSFs. There was an increase in concentration of active DHFR as well, however, this did not reach statistical significance. In the placebo-treated subjects, no significant increase in active DHFR, immunoreactive nonfunctional form of enzyme or TLC was observed. However, it was noticed that the base-line values of active DHFR and immunoreactive nonfunctional form of enzyme in leucocytes of cancer patients were higher than the base-line values in leukocytes of normal healthy subjects. Our data suggest that colony stimulating factors induce white cell proliferation by increasing levels of multiple forms of DHFR

Role of methotrexate as an anti-inflammatory drug

Methotrexate has been known so far as an anticancer drug with a wide application in numerous neoplastic diseases, such as acute lymphocytic Ieukemia, osteogenic sarcoma, adenocarcinoma of head and neck, breast and ovary, and certain lymphomas. However, for the past few years it has been used in low doses in the management of rheumatoid arthritis and severe asthma indicating its anti-inflammatory role. On the basis of a number of clinical trials carried out on rheumatoid arthritis patients, the American Health and Public Policy Committee has put forward certain guidelines regarding the efficacy and safety of methotrexate therapy in this particular disease. The therapy also appears to have a definite steroid- sparing effect in the management of severe asthma. The success so far achieved with methotrexate as an anti-inflammatory agent in the treatment of rheumatoid arthritis and severe asthma is suggestive that the therapy would gain more ground not only in the management of these diseases but other inflammatory diseases as well

new form of dihydrofolate reductase in cancer cells

By using ligand-binding radioassay for the enzyme dihydrofolate reductase [DHFR], a new form of this enzyme has been identified in L1210 leukemia cells. This form of DHFR displays very low affinity for the anticancer drug, methotrexate [MTX]. Further enzyme kinetic studies using a sensitive radioenzymatic assay for DHFR revealed that this form of DHFR had catalytic activity for the reduction of dihydrofolic acid to tetrahydrofolic acid. Studies using gel filtration chromatography with Sephadex G-75 at pH 5.0 and pH 7.2 on crude L1210 leukemia cell lysate and purified L1210 DHFR, both complexed with radiolabelled MTX, provided additional evidence that the MTX binding results were not due to some experimental artifacts. This low affinity form of enzyme was also found in two human colon tumor tissues. We suggest that, presence of a low affinity form of the enzyme in certain cancer cells may be one of the underlying causes of resistance to MTX therapy in these cells