Light-mediated interaction of methotrexate with transition metal Cu(II)

Physiological serum copper concentrations found in malignancies cause unfolding induced aggregation of human serum albumin in vitro

Malignancies are characterized by several drastic metabolic changes, one of which is a progressive rise in the levels of serum copper. This rise in serum copper is documented across all malignancies and across malignancies in several species. This study aims to explore in vitro the effect of increased copper levels on the structure of the blood protein human serum albumin. Exposure of human serum albumin to physiologically relevant copper concentrations for 21 days resulted in structural modifications in the protein which were evident by changes in the intrinsic florescence. A loss of the predominantly alpha helical structure of human serum albumin was recorded along with a tendency to form protein aggregates. This aggregation was characterized by Thioflavin T and Congo Red assays. Rayleigh light scattering and turbidity assays confirmed aggregation. The aggregates were visually confirmed using transmission electron microscopy. This is the first report implicating increased copper levels as a cause of aggregation of blood proteins in malignancies. The physiological and biochemical implications of this phenomenon are discussed.

The impact of methotrexate on lung inflammatory and apoptotic pathway biomarkers-The role of gallic acid

BACKGROUNDS

The aim of this study was to investigate the effects of methotrexate (MTX) on the lung via inflammatory and apoptotic pathway biomarkers and the role of gallic acid (GA).

METHODS

In this study, twenty four male Wistar-Albino rats weighing 300-350g were divided into 3 groups as follows; Control group (0.1ml/oral saline, for 7 days+2nd day i.p.). MTX group (20mg/kg, single dose, on 2nd day). MTX+GA group (15mg/kg, orally, for 7 days). Comet analysis, oxidant-antioxidant status, IMA were conducted. Histopathological analyses were evaluated.

RESULTS

Comet assay on the blood, TOS and OSI values in the lung were increased in the group II compared with the control group (p<0.05). GA significantly reduced the comet score and IMA levels in the blood, TOS and OSI values in the lung tissue in group III compared with group II (p<0.05). Immunohistochemically PGE₂, TNF-α, CRP, serum SAA, Caspase 3 and Caspase 9 expressions significantly increased in group II compared with the control group (p<0.001) and GA treatment ameliorated these parameters significantly in group III compared with group II (p<0.001).

CONCLUSIONS

MTX caused oxidative stress and DNA damage in the blood tissue and caused oxidative damage, inflammation and apoptosis in the lung tissue.

Cu(II)-coumestrol interaction leads to ROS-mediated DNA damage and cell death: a putative mechanism for anticancer activity

Phytoestrogens have attracted considerable interest as natural alternatives to hormone replacement therapy and their potential as cancer therapeutic agents. Among phytoestrogens, coumestrol has shown multipharmacological properties such as antiinflammatory, neuroprotective, osteoblastic differentiation and anticancer. Though several studies have described anticancer effects of coumestrol, a clear underlying molecular mechanism has not been elucidated. Unlike normal cells, cancer cells contain elevated copper levels that play an integral role in angiogenesis. Copper is an important metal ion associated with the chromatin DNA, particularly with guanine. Thus, targeting copper in cancer cells can serve as effective anticancer strategy. Using human peripheral lymphocytes, we assessed lipid peroxidation, protein carbonylation, reactive oxygen species (ROS) generation, DNA damage and apoptosis by coumestrol in the presence of exogenously added Cu(II) in cells to simulate malignancy-like condition. Results showed that Cu(II)-coumestrol interaction leads to lipid peroxidation and protein carbonylation (markers of oxidative stress), DNA fragmentation and apoptosis in treated lymphocytes. Further, incubation of lymphocytes with ROS scavengers and membrane-permeant copper chelator, neocuproine, resulted in inhibition of DNA damage and apoptosis. This suggests that coumestrol engages in redox cycling of Cu(II) to generate ROS that leads to DNA fragmentation and apoptosis. In conclusion, this is the first report showing that coumestrol targets cellular copper to induce prooxidant death in malignant cells. We believe that such a prooxidant cytotoxic mechanism better explains the anticancer activity of coumestrol. These findings will provide significant insights into the development of new chemical molecules with better copper-chelating and prooxidant properties against cancer cells.

Interaction of methotrexate, an anticancer agent, with copper(II) ions: coordination pattern, DNA-cleaving properties and cytotoxic studies

The acid-base properties and the Cu(II) binding processes of methotrexate (MTX) were characterized by selected spectroscopic techniques and potentiometric measurements. The pH titration data showed that MTX behaves as a triprotic ligand. The deprotonation constants were determined for α-COOH and γ-COOH groups and (N1)H⁺ from the pteridine ring. Taking all the obtained results into consideration, a coordination pattern was proposed. The DNA-cleaving activity and reactive oxygen species (ROS) generation were investigated for both MTX and the Cu(II)-MTX system. The complex displayed a promising nuclease activity toward plasmid DNA in the presence of hydrogen peroxide. Interestingly, the induction of ROS, such as hydroxyl radicals, superoxide anions or singlet oxygen, was excluded and a different mechanism of DNA degradation was proposed. As MTX is now commonly used in anticancer therapy i.e. against lung cancer, basic cell-based studies were carried out to establish if its Cu(II) complex exhibits higher cytotoxic properties than the ligand alone. Activities of both compounds were also tested against colon carcinoma. Moreover, the determined values of IC₅₀ were confronted with the cytotoxic activity of cisplatin.

Cu(II)-vitamin D interaction leads to free radical-mediated cellular DNA damage: a novel putative mechanism for its selective cytotoxic action against malignant cells

Vitamin D (vit D) is a known anticancer molecule, and cancer cells are reported to have elevated levels of Cu(II) ions. In this study, we show that interaction of vit D and Cu(II) leads to the formation of hydroxyl free radicals, superoxide anion and hydrogen peroxide, which causes severe oxidative stress, selectively in malignant cells. We show that the production of these reactive oxygen species causes cellular DNA fragmentation which may cause cell death. A novel putative chemical mechanism explaining how vit D causes cell death by DNA damage, selectively in malignant cells, is proposed.