Surya Bali Prasad

Genotoxic effects of malathion: an organophosphorus insecticide, using three mammalian bioassays in vivo

The genotoxic effects of malathion was evaluated using chromosome aberration, sister chromatid exchange (SCE) and sperm abnormality assays in mice. All the three acute doses (2.5, 5 and 10mg/kg) of malathion tested in the present study, induced significant dose-dependent increase in the frequency of chromosome aberrations and sperm abnormalities, but did not affect the total sperm count. The highest acute dose induced a >12-fold increase in the frequency of chromosome aberrations, two-fold increase in the frequency of SCEs and four-fold increase in the frequency of sperms with abnormal head morphology following intraperitoneal (i.p.) exposure. Further, a significant increase in the frequency of SCEs was observed, but the increase was not dose-dependent. At higher doses, malathion induced a moderate delay in cell cycle as evident from the increase in average generation time (AGT). The present findings suggest that technical grade malathion is a potent genotoxic agent and may be regarded as a potential germ cell mutagen also.

Vitamin C mediated protection on cisplatin induced mutagenicity in mice.

In present studies the development of chromosomal aberrations, micronuclei in bone marrow cells and sperm head abnormalities were used as mutagenic bioassay in Swiss albino mice treated with cisplatin alone or ascorbic plus cisplatin. It was noted that in the combined treated hosts the frequency of all the mutagenic parameters were always significantly less than that treated with cisplatin alone. These findings suggest a protective role of ascorbic acid against cisplatin induced mutagenic potentials. Interestingly, in combined treated hosts glutathione (GSH) level in bone marrow cells increased significantly which may suggest a possible mechanism of ascorbic acid mediated protection against cisplatin induced mutagenic potentials in the hosts.

Mutagenic effects of carbosulfan, a carbamate pesticide

The genotoxic effects of carbosulfan were evaluated using chromosome aberration (CA), bone marrow micronucleus (MN) and sperm abnormality assays in mice. All the three acute doses (1.25, 2.5 and 5mg/kg) of carbosulfan induced significant dose-dependent increase in the frequency of CA (P<0.02), micronucleated polychromatic erythrocytes (PCEs) (P<0.05) and sperm head abnormalities (P<0.05) but did not affect the total sperm count. The highest acute dose of carbosulfan induced >7-fold increase in the frequency of CA, >3.5-fold increase in the frequency of micronucleated PCEs and >4.6-fold increase in the frequency of sperms with abnormal head morphology following intraperitoneal exposure as compared to the untreated controls. The present findings suggest that carbosulfan is a potent genotoxic agent and may be regarded as a potential germ cell mutagen also.

Effect of cisplatin on mitochondrial protein, glutathione, and succinate dehydrogenase in Dalton lymphoma-bearing mice

Cisplatin treatment of tumor-bearing mice resulted a significant decrease of protein in the tissues studied (liver, kidney, and Dalton lymphoma) and also in their mitochondrial fractions. As compared to respective tissues, the protein decrease was noted to be more conspicuous in their mitochondrial fractions. Similarly, mitochondrial glutathione also decreased significantly in the tissues. However, succinate dehydrogenase activity was selectively decreased in the kidney and Dalton lymphoma cells, whereas in liver it remained almost unchanged. An increase in serum urea concentration and kidney mitochondrial lipid peroxidation was also observed after cisplatin treatment. It is suggested that the cisplatin-induced biochemical changes in mitochondria involving mitochondrial protein, glutathione, and succinate dehydrogenase could be the important potent cellular sites contributing to toxicity/cytotoxicity after cisplatin treatment.

Cisplatin-induced genotoxic effects and endogenous glutathione levels in mice bearing ascites Dalton’s lymphoma

cis-Diaminedichloroplatinum(II), commonly known as cisplatin, treatment of mice for 24-96, 30 h and 10 days caused the development of chromosomal aberrations in bone marrow cells as well as in Daltons lymphoma (DL) cells, micronuclei (MN) in bone marrow cells and abnormalities in sperm heads, and it indicates the genotoxic potential of cisplatin in the host. Cisplatin exerts differential effects on the chromosomes of the bone marrow and tumor cells. Combination treatment of cisplatin with L-buthionine(S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, enhanced these cisplatin-induced genotoxic effects, but supplementing glutathione level with cysteine, its precursor, reduced the cisplatin-induced genotoxicity. The reduction in cellular glutathione level may facilitate increased intracellular accumulation and binding of drug to DNA to enhance the frequency of genotoxicity parameters. These findings support the possible involvement of glutathione as an important intracellular protective agent and suggest that differences in its levels may be one of the factors in the varying sensitivity of cells to cisplatin-induced genotoxic effects in the mice bearing ascites Daltons lymphoma.

Fenvalerate-induced chromosome aberrations and sister chromatid exchanges in the bone marrow cells of mice in vivo

Fenvalerate, a synthetic pyrethroid insecticide, is commonly used in agriculture and other domestic applications due to its high insecticidal activity and low mammalian-, avian- and phyto-toxicities. However, the genotoxic effect of fenvalerate is highly equivocal. In the present study the genotoxic effects of fenvalerate was evaluated using structural chromosome aberration (CA) and sister chromatid exchange (SCE) assays in mice. Out of the three doses (5, 10 and 20 mg/kg) tested, statistically significant increase in CA was found following intra peritoneal (i.p.) treatment of 2 0 mg/kg of fenvalerate for 24 h (P<0.01) and 48 h (P<0.05) only. Neither the acute doses of 5 and 10 mg/kg, nor the sub-acute dose (5x4 mg/kg) of fenvalerate could induce any significant effect. All the three acute doses induced significant increase in the frequency of SCEs (P<0.01) in the bone marrow cells, which showed a significant dose-response correlation (r=0.9541, P<0.05). With certain reservations to possible impurities, from the present findings technical grade fenvalerate may be considered as a weak clastogen and a potent inducer of SCEs in mice.

Hematotoxicity and blood glutathione levels after cisplatin treatment of tumor-bearing mice.

The involvement of glutathione, a major cellular antioxidant, in cisplatin-mediated development of various hematological changes in mice bearing ascites Dalton lymphoma tumor was investigated. With tumor growth, glutathione levels decreased in blood but increased in tumor cells. Cisplatin treatment of tumor-bearing mice caused a decrease in glutathione levels in blood, ascites supernatant, and tumor cells. Blood hemoglobin, erythrocytes, packed cell volume and leukocytes (eosinophils, basophils, and lymphocytes) were also decreased along with the development of various morphological abnormalities in erythrocytes (microcytes, macrocytes, echinocytes, acanthocytes, etc.) after cisplatin treatment. All these hematotoxic features were noted to be increased more when buthionine sulfoximine (a specific glutathione-depleting agent) was also given prior to cisplatin treatment. However, combination treatment of cysteine (precursor for glutathione synthesis) plus cisplatin resulted in an improvement in the glutathione levels and decrease in hematological toxicities. It is noted that the glutathione levels in blood and abnormalities in erythrocytes and other hematological parameters are inversely related in cisplatin-mediated cancer chemotherapy. It is suggested that blood glutathione may play an important role in the development of cisplatin-mediated hematological toxicity in the host.

Changes in glutathione-related enzymes in tumor-bearing mice after cisplatin treatment

The effect of cisplatin on five glutathione-related enzymes was studied in liver, kidney, and Dalton lymphoma cells of tumor-bearing mice. In liver, the activities of glutathione S-transferase, glutathione peroxidase, catalase, and superoxide dismutase decreased approximately 30–40%, 60–67%, 35–50% and 70–80% respectively, while glutathione reductase increased about 36–45% after cisplatin treatment. In kidney, catalase activity decreased by 47–82% at all time points (24–96 h) of cisplatin treatment, while glutathione S-transferase activity decreased significantly (~24%) mainly at 72 h of treatment. An increase in glutathione reductase (~1.5–2.5 times), glutathione peroxidase (significant at 24 h, 47%), and superoxide dismutase (~15–60%) was noted in kidney after the treatment. In Dalton lymphoma cells, the activities of glutathione S-transferase, glutathione peroxidase, and catalase decreased very distinctly (~2–5, 2–5 and 5–11 times, respectively) at all time points, but glutathione reductase decreased significantly only at 72 h of cisplatin treatment. Interestingly, the superoxide dismutase activity in Dalton lymphoma cells increased initially at 24–48 h and then decreased (~60%) during later periods (72–96 h) of treatment. Cisplatin treatment caused a decrease in glutathione level in Dalton lymphoma cells (~14–20%) and kidney (~18–28%) but no change in liver. In view of the results, a definite correlation with the changes in glutathione concentrations and enzymatic activities in a tissue could not be firmly derived. It is suggested that the changes in various glutathione-related enzymes and glutathione levels in the tissues of the host during cisplatin-mediated chemotherapy could affect cellular antioxidant defense potential, which may play an important contributory role in cisplatin-mediated toxicity, particularly nephrotoxicity, and anticancer activity in the host.

Structural and biochemical changes in mitochondria after cisplatin treatment of Dalton's lymphoma-bearing mice.

Cisplatin treatment of tumor-bearing mice and analysis of ultrastructural features of mitochondria in the kidney and Daltons lymphoma cells showed the appearance of more roundish mitochondria with thickened membranes. It also caused the reduction in the number and irregularity in the shape of cristae and formation of vacuoles in the mitochondria. After cisplatin treatment, decreased level of protein, succinate dehydrogenase activity, and increased level of lipid peroxidation were noted in Daltons lymphoma tumor cells and kidney. Cisplatin-mediated decrease in SDH activity, GSH level and an increase in LPO in the mitochondria of kidney could play an important role to produce nephrotoxicity. However, in DL cells, decrease in cellular GSH could be noteworthy than mt-GSH, along with decrease in SDH activity and increase in LPO in the cisplatin-mediated anticancer activity. These changes could play an important role to produce both the cisplatin-mediated effects i.e. anticancer activity and nephrotoxicity. Cisplatin-induced biochemical and ultrastructural changes in mitochondria after cisplatin treatment should be an important factor in the development of biochemical injury in mitochondria and affecting the overall metabolism in the cells. The findings from the present studies indicate multilevel effect of cisplatin in the cells and do support the earlier view that mitochondria could be a critical target in cisplatin-mediated anticancer activity and toxicity in the hosts.

Cyclophosphamide and ascorbic acid-mediated ultrastructural and biochemical changes in Dalton's lymphoma cells in vivo.

Cyclophosphamide, an antineoplastic drug effective against a wide variety of cancers is cytotoxic to normal cells also. Ascorbic acid (vitamin C) at higher concentrations possesses cytotoxic effects and it can also enhance the cytotoxicity of 5-fluorouracil in a dose-dependent manner in mouse lymphoma. In the present study, effect of cyclophosphamide treatment alone and in combination with ascorbic acid in vivo on the ultrastructure and some biochemical changes in Daltons lymphoma tumor cells were investigated. Cyclophosphamide treatment causes disappearance of cell membrane processes, thickening and reduction in the number of mitochondrial cristae as well as the manifestation of rounded shape of mitochondria. The combination treatment with ascorbic acid plus cyclophosphamide caused further changes in tumor cells showing disintegration in the cell surface membrane, disruption in the nuclear membrane and roundish mitochondria with reduction and disruption in the mitochondrial cristae. The observed ascorbic acid plus cyclophosphamide-mediated decrease in reduced glutathione (GSH) in tumor cells may play an important role in the antitumor activity of cyclophosphamide by weakening cellular antioxidant-mediated defense mechanism, thereby increasing tumor cells susceptibility to cell death. The cyclophosphamide-mediated decrease in lactate dehydrogenase activity in tumor cells and simultaneous increase in ascites supernatant may possibly indicate alteration in the membrane permeability of tumor cells for lactate dehydrogenase as well as tumor cell injury. Further investigation should determine detailed mechanism(s) involved in cyclophosphamide-induced ultrastructural and biochemical changes in tumor cells.