Cellular damage and altered carbohydrate expression in P815 tumor cells induced by direct electric current: An in vitro analysis

Abstract

Treatment with direct electric current (DC) can inhibit tumor growth in several systems. To evaluate the cellular reactions generated by this treatment, we stimulated mouse mastocytoma P815 cells with DC and examined their viability and ultrastructural characteristics, as well as the effect of DC on surface carbohydrate expression. DC treatment affected cell viability and caused marked alterations in vital structures of P815 cells. Alterations varied depending on the duration of stimulation and polarity of electrode. Anodic and cathodic treatments caused decrease in cell viability, although the latter was more effective in generating cell lysis. DC stimulation also induced changes such as membrane damage, alterations in cell shape and chromatin organization, mitochondrial swelling and condensation, cytoplasmic swelling, and matrix rarefaction. Stimulation of P815 cells without contact with electrodes produced no alterations, suggesting that this contact might be essential for the occurrence of the cellular modifications. DC treatment also altered the membrane distribution of anionic sites of P815 cells, as well as the surface carbohydrate exposition, involving a diminished binding of Concanavalin A to the cell surface after cathodic stimulation, and an increased binding of sialic acid- and fucose-specific lectins after anodic treatment. In this work we describe important cellular targets for the action of DC, which may contribute to the understanding of the mechanisms by which DC supresses several kinds of tumors.

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“…21 Our research group has detected the effects of pH acidification and alkalinization induced by AF and CF on different tumor cell lines. [28][29][30]38 However, in these studies, tumor death was not only attributed exclusively to the electrolysis damage, but also to the oxidant species generated by the AF. 29,30 In fact, the acidification of the AFtreated medium could not be held responsible for the cell killing, as the pH variation induced by anodic reactions is not significant (6.5 after 10 min of stimulation).…”

“…[28][29][30]38 However, in these studies, tumor death was not only attributed exclusively to the electrolysis damage, but also to the oxidant species generated by the AF. 29,30 In fact, the acidification of the AFtreated medium could not be held responsible for the cell killing, as the pH variation induced by anodic reactions is not significant (6.5 after 10 min of stimulation). 30 Besides, when the pH was artificially mimetized by the addition of HCl drops, cell viability was not diminished at equivalent rates as detected by AF generated by DC source, suggesting the role of other electrolysis products, such as reactive chlorine and oxygen species, in tumor killing.…”

“…pH was controlled by the addition of 3 g/L N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid, 0.2 g/L NaHCO 3 , streptomycin (100 µg/mL), and penicillin (100 UI/mL) as previously described. 28,37 The initial inoculum was 5 × 10 4 cells/mL, which was subcultured every 2 days as described elsewhere 28,29 and maintained in a log-phase growth. Cell detachment was performed with 2 mL of trypsin 0.05% (w/v) for 2 min.…”

“…26,27 An important milestone for the study of EChT was the development of an in vitro experimental model for investigation of DC effects on culture cell lines. [28][29][30] Using this model, Veiga et al showed that DC can destroy tumor cells via two distinct mechanisms: apoptosis and necrosis. 30 Both aforementioned mechanisms appear to be associated with the DC polarity: cells exposed to anodic flow (AF) undergo mostly apoptosis, whereas those exposed to cathodic flow (CF) die almost entirely as a result of necrosis.…”

“…The distance between the electrodes was 8 cm, and an electric field of approximately 2.5 V/cm was generated as a result. Cell suspensions were treated at room temperature with DC of 2 mA, for 0 (control), 2, 4, 6, 8, and 10 min, similar to the conditions previously used [28][29][30]38 to assess cell viability. In all subsequent experiments, cells were treated for 6 min, an intermediate period that was representative of the alterations in morphology and viability.…”