Bothrops jararaca and Bothrops erythromelas Snake Venoms Promote Cell Cycle Arrest and Induce Apoptosis via the Mitochondrial Depolarization of Cervical Cancer Cells.

Emanuelly Bernardes-Oliveira,Dayanne Lopes Gomes,Matheus de Freitas Fernandes-Pedrosa,Hugo Alexandre Oliveira Rocha,Kleber Juvenal Silva Farias,Ana Katherine Gonçalves,Janaina Cristiana de Oliveira Crispim,Wilmar Dias da Silva,Gustavo Martelli Palomino

doi:10.1155/2016/1574971

Abstract

Bothrops jararaca (BJ) and Bothrops erythromelas (BE) are viper snakes found in South-Southeast and Northeast regions of Brazil, respectively. Snake venoms are bioactive neurotoxic substances synthesized and stored by venom glands, with different physiological and pharmacological effects, recently suggesting a possible preference for targets in cancer cells; however, mechanisms of snakes have been little studied. Here, we investigated the mechanism responsible for snake crude venoms toxicity in cultured cervical cancer cells SiHa and HeLa. We show that BJ and BE snake crude venoms exert cytotoxic effects to these cells. The percentage of apoptotic cells and cell cycle analysis and cell proliferation were assessed by flow cytometry and MTT assay. Detection of mitochondrial membrane potential (Rhodamine-123), nuclei morphological change, and DNA fragmentation were examined by staining with DAPI. The results showed that both the BJ and BE venoms were capable of inhibiting tumor cell proliferation, promoting cytotoxicity and death by apoptosis of target SiHa and HeLa cells when treated with BJ and BE venoms. Furthermore, data revealed that both BJ venoms in SiHa cell promoted nuclear condensation, fragmentation, and formation of apoptotic bodies by DAPI assay, mitochondrial damage by Rhodamine-123, and cell cycle block in the G1-G0 phase. BJ and BE venoms present anticancer potential, suggesting that both Bothrops venoms could be used as prototypes for the development of new therapies.

Highlights

Cervical cancer is the third most common cancer in women worldwide [1, 2] and the fourth major cause of cancer death in women in developing countries, remaining a critical public health problem [3, 4]
This study showed that the death of SiHa cells presented 84.95% and 90.02%, respectively, when treated with Bothrops jararaca (BJ) and Bothrops erythromelas (BE)
The results suggest that venoms may reduce the mitochondrial membrane potential of SiHa cells by depolarization inducing death by apoptosis via the mitochondrial pathway (Figure 5)

Summary

Introduction

Cervical cancer is the third most common cancer in women worldwide [1, 2] and the fourth major cause of cancer death in women in developing countries, remaining a critical public health problem [3, 4]. In Brazil, it is estimated that there are 16,340 new cases of cervical cancer in 2016 [5]. High-risk human papilloma viruses (HPVs) such as HPVs 16, 18, 31, and 33 have been attributed to being the major risk factors for cervical cancer, out of which HPVs 16 and 18 account for almost 70% of the cancers [6, 7]. The method currently used in clinical medicine against different types of cancers, including cervical cancer, is surgical removal of the tumor followed by radiotherapy and chemotherapy [8]. New treatments for various types of cancers, including cervical cancer [9, 10], are considered one of the greatest challenges to medicine today because of the resistance to the effects due to repeated exposure [11]. Interventions with the use of chemotherapy are far from satisfactory, because of side effects, destruction of healthy cells, and above all acquired resistance by tumors [12,13,14]

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