Dissociation of the cytotoxicity of cocaine from its local anaesthetic effect: A comparison with lidocaine

Morphological, biochemical and molecular effects of cocaine on mouse neuroblastoma cells culture in vitro

In order to compare the effects of cocaine at morphological, basal cytotoxicity, biochemical and molecular levels, cultured mouse neuroblastoma cells (Neuro-2a) were exposed to a range of concentrations of cocaine hydrochloride. Neuroblastoma cell proliferation, evaluated by quantification of total protein content, was very sensitive to cocaine, being increasingly inhibited from 12 to 72 hr of exposure (EC(50) = 3.1 mm at 24 hr). Cytoplasmic membrane permeability to lactate dehydrogenase was not particularly increased and lysosomal function was stimulated from 0.05 to 1.5 mm, and inhibited from 2.5 mm. A shift to anaerobiosis was detected as intracellular lactate dehydrogenase (LDH) activity was increased and mitochondrial succinate dehydrogenase (SDH) activity decreased. Hexosaminidase (HEX), a lysosomal enzyme involved in sphingolipid degradation, was stimulated only at 1 mm and neural acetylcholinesterase (AChE) activity was stimulated from 2.5 mm. Morphological examination of exposed cultures revealed that most cells became bipolar and multipolar neurons by extension of neurites, but also suffered cytoplasmic vacuolization, hydropic degeneration and nuclear pyknosis. Although cells developing apoptosis were observed, no DNA oligonucleosomal fragmentation was detected by agarose gel electrophoresis of DNA from cells exposed to cocaine. In conclusion, in addition to predominance of anaerobiosis, little disruption of membranes and severe morphologic injury, biochemical and morphological differentiation-like effects were the most prominent alterations produced by cocaine on mouse neuroblastoma cells.

Detection of heavy metal toxicity using cardiac cell-based biosensor

Biosensors incorporating mammalian cells have a distinct advantage of responding in a manner which offers insight into the physiological effect of an analyte. To investigate the potential applications of cell-based biosensors on heavy metal toxicity detection, a novel biosensor for monitoring electrophysiological activity was developed by light-addressable potentiometric sensor (LAPS). Extracellular field potentials of spontaneously beating cardiomyocytes could be recorded by LAPS in the range of 20 microV to nearly 40 microV with frequency of 0.5-3 Hz. After exposed to different heavy metal ions (Hg(2+), Pb(2+), Cd(2+), Fe(3+), Cu(2+), Zn(2+); in concentration of 10 microM), cardiomyocytes demonstrated characteristic changes in terms of beating frequency, amplitude and duration under the different toxic effects of ions in less than 15 min. This study suggests that, with the physiological monitoring, it is possible to use the cardiac cell-based biosensor to study acute and eventually chronic toxicities induced by heavy metal ions in a long-term and no-invasive way.