Indian propolis ameliorates the mitomycin C-induced testicular toxicity by reducing DNA damage and elevating the antioxidant activity

Abstract

Development of excellent curative therapy for most of the malignancies has resulted in a growing population of cancer survivors who are at increased risk for a variety of health problems including infertility. Therefore, fertility preservation has become an important issue during cancer treatment in recent years. Combination therapy with natural agents such as vitamins, antioxidants, dietary supplements, and plant products are considered as an attractive option to mitigate normal tissue toxicity imparted by chemotherapy. The aim of the present study was to explore the beneficial effect of hydroethanolic extract of Indian propolis (HEIP) on mitigating mitomycin C (MMC)-induced testicular damage and its mechanism of action. Healthy adult male mice were injected intraperitoneally with saline, MMC, HEIP and HEIP followed by MMC after 1 h. The animals were dissected at 35 days after various treatments to analyze testicular function. MMC administration resulted in significant reduction in testicular function in a dose-dependent manner at 35 days after treatment which significantly improved by HEIP pre-treatment. At 24 h after treatment, MMC induced significant increase in oxidative stress, γ-H2AX foci and expression of RAD51 and KU80 in testicular cells. Prior treatment with HEIP decreased the oxidative stress, reduced DNA damage and restored the testicular testosterone and inhibin B level. In conclusion, co-administration of Indian propolis extract may play a promising beneficial role in fertility preservation of males undergoing chemotherapy.

Introduction

For more than seven decades, chemotherapy still stands as the first line of therapy for all types of cancers [1]. Chemotherapeutic agents activate the cell death pathways in the cancer cells, and in rapidly proliferating somatic cells. Apart from causing cell death, they induce debilitating mutations and long-term DNA/cellular damages in the germ cells and somatic cells [2].

Mitomycin C (MMC) is a potent DNA alkylating agent, used as first line of drug in treatment of pancreatic, gastric, breast, prostate, and bladder cancers [3]. MMC induces cell death by forming DNA adducts, DNA cross links, RNA adducts and its cross links [3], [4], [5]. Once the adducts and cross links are formed, in the subsequent replications it creates mutations and thus resulting in DNA damage. MMC in its original form is not cytotoxic; it needs to be activated by enzymatic reduction in the biological system. It forms bis-electrophile byproduct which leads to alkylation of DNA, RNA and proteins [6], [7]. A previous study has shown that a reactive byproduct of MMC formed after enzymatic reduction can inhibit rRNA by reacting with the selenothiol moiety of thioredoxin reductase [7]. These highly reactive bis-electrophiles are responsible for the damages incurred to the cells. Earlier studies have shown that bone marrow, cardiac system, neurological, nephrological and gonadal systems are acutely and chronically affected by the chemotherapy [8]. Several studies have shown that naturally or/and chemically derived adjuvants can effectively protect the reproductive systems from the chemical insults caused by chemotherapy. These chemo-protective adjuvants not only provide protection against the damages caused by chemo agents, but also help in good quality life during and after the chemotherapy [9], [10], [11].

Propolis is a complex resinous mixture containing more than 300 compounds collected by honey bees from various flora to construct the hive. The composition in the propolis varies between the geographical locations due to the plant diversity. The compositions of propolis which are having biological activity include flavonoids, phenolics, and aromatic compounds, they also constitute bee wax, terpenes and volatile oils [12]. Human beings have used propolis since ancient times for treating variety of diseases [13] which is supported by in vivo and in vitro studies suggesting them to have a plethora of biological activities [13], [14]. In our previous study, we have reported that propolis mitigates MMC-induced bone marrow toxicity [15]. The present study was taken up to further explore whether hydroethanolic extract of Indian propolis (HEIP) can help in recovery of testicular function following MMC administration and augment testicular toxicity in mice.