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

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.

Cytotoxic mechanism of Bothrops jararaca venom mediated by mitochondrial depolarization

“…Results showed that crude snake venom induces depolarization of the mitochondrial membrane in a dose-dependent manner ( Figure 3A). This result was very interesting since the evaluations were performed using sub-lethal doses and acute treatment time, indicating that accumulated mitochondrial damage could be the cause of cell death, mainly intrinsic apoptosis pathway, as evidenced by another research [23].…”

“…Nevertheless, this outcome was not observed in the crude venom from B. jararaca, neither in 24h nor in 48h of treatment ( Figure 2). Recently it was described that crude venom from B. jararaca and B. erythromelas exhibited a cytotoxic effect promoting cell cycle arrest and inducing apoptosis through mitochondrial depolarization in cervical cancer cells [23]. Mitochondrial damage is related to intrinsic apoptosis pathway activation by cytochrome c release and caspase cascade, mediated production of hydrogen peroxide [13].…”

Cytotoxic effect of Montivipera bornmuelleri’s venom on cancer cell lines: in vitro and in vivo studies

“…Whether venom compounds affect the cell cycle is also possible. For example, it was reported that snake venom (Bernardes-Oliveira et al, 2016), and more precisely Phospholipases A2 (Prinholato da Silva et al, 2015), can lead to cell cycle arrest at the G0/G1 phase. M. bornumelleri's venom is known to contain Phospholipases A2 (Accary et al, 2015); therefore, it will not be surprising if the venom affects the cell cycle in a similar way to what was reported previously (Bernardes-Oliveira et al, 2016;Prinholato da Silva et al, 2015).…”

Tityus serrulatusScorpion Venom Induces Apoptosis in Cervical Cancer Cell Lines

“…SiHa and HeLa cells were cultivated in a 96-well plate at an initial density of 5 × 10 3 cells/well and after 24 h were treated with 200 μ L/well of different concentrations of TsV venom (50, 125, 250, and 500 μ g/mL) and CDDP 33 μ g/mL [16] [Cisplatin, citoplax, 50 mg from Bergamo Taboão da Serra, SP, Brazil, drug control]. During the procedures we used as negative control (NC) cells with only culture medium.…”

“…Moreover, chemotherapy has been shown in some cases to have a limited effect on the cure and survival of patients, particularly in patients with cervical cancer, and especially when the disease is advanced; what is more it may promote chemoresistance or even relapse, which limits the success [13–15]. Therefore, an urgent goal in medicine is the search for new biomarkers with lower cytotoxicity, with less side effects, and, at the same time, selective with normal cells, or at least presenting minimal effects [16, 17].…”