Protective effect of dietary selenium supplementation on delayed cardiotoxicity of adriamycin in rat: is PHGPX but not GPX involved?

Evaluation of nephroprotective and immunomodulatory activities of antioxidants in combination with cisplatin against murine visceral leishmaniasis

Background

Most available drugs against visceral leishmaniasis are toxic, and growing limitations in available chemotherapeutic strategies due to emerging resistant strains and lack of an effective vaccine against visceral leishmaniasis deepens the crisis. Antineoplastic drugs like miltefosine have in the past been effective against the parasitic infections. An antineoplastic drug, cisplatin (cis-diamminedichloroplatinum II; CDDP), is recognized as a DNA-damaging drug which also induces alteration of cell-cycle in both promastigotes and amastigotes leading to cell death. First in vivo reports from our laboratory revealed the leishmanicidal potential of cisplatin. However, high doses of cisplatin produce impairment of kidney, which can be reduced by the administration of antioxidants.

Methodology/Principal Findings

The present study was designed to evaluate the antileishmanial effect of cisplatin at higher doses (5 mg and 2.5 mg/kg body weight) and its combination with different antioxidants (vitamin C, vitamin E and silibinin) so as to eliminate the parasite completely and reduce the toxicity. In addition, various immunological, hematological and biochemical changes induced by it in uninfected and Leishmania donovani infected BALB/c mice were investigated.

Conclusion/Significance

A significant reduction in parasite load, higher IgG2a and lower IgG1 levels, enhanced DTH responses, and greater concentration of Th1 cytokines (IFN-γ, IL-2) with a concomitant down regulation of IL-10 and IL-4 pointed towards the generation of the protective Th1 type of immune response. A combination of cisplatin with antioxidants resulted in successful reduction of nephrotoxicity by normalizing the enzymatic levels of various liver and kidney function tests. Reduction in parasite load, increase in Th1 type of immune responses, and normalization of various biochemical parameters occurred in animals treated with cisplatin in combination with various antioxidants as compared to those treated with the drug only. The above results are promising as antioxidants reduced the potential toxicity of high doses of cisplatin, making the combination a potential anti-leishmanial therapy, especially in resistant cases.

Leishmaniasis, a neglected tropical disease (NTD) caused by Leishmania, has been put on the World Health Organization agenda for eradication as a part of their Special Programme for Tropical Diseases Research. Visceral leishmaniasis (VL) is a life-threatening disease when no treatment is given. Most of the drugs still used to treat VL are often expensive, difficult to administer, have serious side effects, and several are becoming ineffective because of increasing parasite resistance. Cisplatin is a first-generation platinum-containing drug, used in the treatment of various solid tumors. We have for the first time characterized the in vivo effect of cisplatin in murine experimental visceral leishmaniasis, but at higher doses it is nephrotoxic. Considering the above findings, the present study was designed to evaluate the protective efficacy of the drug in combination with various antioxidants to reduce or prevent cisplatin-induced nephrotoxicity. Drug treatment induces a higher secretion of Th1 cytokines, diminution in parasite burden, and the supplementation of antioxidants which are antagonists of the toxicity helps in reducing the nephrotoxicity.

Anthracycline-induced phospholipase A2 inhibition

The purpose of this essay is to overview our findings that membrane-associated calcium-independent phospholipase A2 is markedly inhibited by low, clinically relevant concentrations of anthracyclines. Our studies suggest that due to the essential role of this enzyme in membrane homeostasis, its inhibition can be one of the early culprits leading to anthracycline-induced cardiac dysfunction. The clinical importance and potential pharmaceutical use of this new phenomenon await further studies.

Chemotherapy-induced chromosomal damage in peripheral blood lymphocytes of cancer patients supplemented with antioxidants or placebo

A total of 27 patients with various types of cancer were treated with cisplatin-based combination chemotherapy. Out of these, 13 patients were randomized to receive supplementation treatment with a beverage containing the antioxidants vitamins C and E, plus selenium, during chemotherapy. The antioxidant mixture was administered to investigate whether it could reduce the potential genotoxic and nephrotoxic effect of the applied chemotherapy. A placebo group of 14 cancer patients received a beverage without selenium or antioxidants. Micronuclei (MN) in cytochalasin B-blocked binucleate (BN) peripheral blood lymphocytes (PBLs) and hypoxanthine phosphoribosyl transferase (HPRT) mutants in PBLs were studied before, during and after chemotherapy as a measure for chemotherapy-induced genotoxic effects. Before chemotherapy, patients mean frequencies of MN and HPRT mutants did not differ from those in a group of 10 healthy subjects. The mean frequency of MN in patients increased significantly after one cycle of chemotherapy (P=0.002). This frequency was still elevated at 2 months after the completion of chemotherapy (not significantly). There was no significant difference in micronuclei frequency (MNF) between the antioxidant and placebo group of patients. Chemotherapy-induced frequencies of MN after three cycles of chemotherapy correlated significantly with the cumulative dose of cisplatin (r=0.58, P=0.012) and the cisplatin-mediated loss of renal function (r=0.53, P=0.03). No consistent change in HPRT mutant frequency following chemotherapy was observed in the placebo and antioxidant group of patients. In conclusion, cisplatin-combination chemotherapy resulted in a cisplatin dose-related increase of the frequency of chromosomal damage. Supplementation with antioxidants did not prevent or reduce this effect.

Doxorubicin toxicity to the skin: possibility of protection with antioxidants enriched yeast

The possibility of skin protection against doxorubicin toxicity was examined after oral antioxidative pretreatment of the rats with yeast supplemented with selenium and vitamins E, C and A for 15 days. The activity and level of antioxidative defense components were monitored in the skin and blood 48 h after i.v. applied doxorubicin. In the blood, increased glutathione peroxidase activity in the erythrocytes, and amounts of vitamin E and glutathione in the plasma were found after the antioxidative treatment. It also led to an increase of the reductive capacity in the skin (increased thioredoxin reductase activity and reduced glutathione level). Doxorubicin alone, depleted reductive capacity, i.e. decreased the activity of thioredoxin reductase in the skin, as well as the content of reduced glutathione both in the skin and blood plasma. Depletion of reductive capacity represents one of the first harmful doxorubicin effects to the skin at the time when the changes of other antioxidative enzyme activities were not detectable. Reductive capacity in the skin of animals given antioxidative pretreatment was maintained elevated upon doxorubicin application in comparison with the corresponding control. Oral supplementation with antioxidants thus prevents toxic effects of doxorubicin in the skin and may contribute to the alleviation of its secondary cytotoxicity during the chemotherapy.

Cisplatin combination chemotherapy induces a fall in plasma antioxidants of cancer patients

BACKGROUND

Antioxidants protect the body against cellular oxidative damage and thus some of the adverse effects induced by cisplatin and other cytostatic drugs.

PATIENTS AND METHODS

The effect of cisplatin-combination chemotherapy on concentrations of plasma antioxidants was studied in 36 cancer patients, including osteosarcoma and testicular carcinoma patients.

RESULTS

Eight to 15 days after the start of each cytostatic drug infusion concentrations of various plasma antioxidants were measured and compared to pretreatment values: vitamin C and E, uric acid and ceruloplasmin levels fell significantly (P < 0.01-0.005) and returned to baseline levels before the start of the next chemotherapy cycle. Levels of the antioxidants bilirubin albumin and the ratio vitamin E/cholesterol + triglycerides measured three weeks after the start of chemotherapy significantly decreased compared to pretreatment levels and remained low thereafter (P < 0.001-0.002). Dietary intake of antioxidants and anthropometric measurements, evaluated in 14 patients did not change during the whole treatment period.

CONCLUSIONS

Cisplatin-combination chemotherapy induces a fall in plasma antioxidant levels, that may reflect a failure of the antioxidant defense mechanism against oxidative damage induced by commonly used anticancer drugs. This probably results from consumption of antioxidants caused by chemotherapy induced-oxidative stress as well as renal loss of water-soluble, small molecular weight antioxidants such as uric acid.