Modulation of calcium entry and glutamate release in cultured cerebellar granule cells by palytoxin

Abstract

A channel open on the membrane can be formed by palytoxin (PTX). Ten nanomolar PTX caused an irreversible increase in the cytosolic calcium concentration ([Ca(2+)](c)), which was abolished in the absence of external calcium. The increase was eliminated by saxitoxin (STX) and nifedipine (NIF). Calcium rise is secondary to the membrane depolarization. PTX effect on calcium was dependent on extracellular Na(+). Li(+) decreased the PTX-evoked rise in [Ca(2+)](c); replacement of Na(+) by N-methyl-D-glucamine (NMDG) abolished PTX-induced calcium increase. [Ca(2+)](c) increase by PTX was strongly reduced after inhibition of the reverse operation of the Na(+)/Ca(2+) exchanger, in the presence of antagonists of excitatory amino acid (EAA) receptors, and by inhibition of neurotransmitter release. PTX did not modify calcium extrusion by the plasma membrane Ca(2+)-ATPase (PMCA), because blockade of the calcium pump increased rather than decreased the PTX-induced calcium influx. Extracellular levels of glutamate and aspartate were measured by HPLC and exocytotic neurotransmitter release by determination of synaptic vesicle exocytosis using total internal reflection fluorescence microscopy (TIRFM). PTX caused a concentration-dependent increase in EAA release to the culture medium. Ten nanomolar PTX decreased cell viability by 30% within 5 min. PTX-induced calcium influx involves three pathways: Na(+)-dependent activation of voltage-dependent sodium channels (VDSC) and voltage-dependent calcium channels (VDCC), reverse operation of the Na(+)/Ca(2+) exchanger, and indirect activation of EAA receptors through glutamate release. The neuronal injury produced by the toxin could be partially mediated by the PTX-induced overactivation of EAA receptors, VDSC, VDCC and the glutamate efflux into the extracellular space.

Activation of Mas Oncogene-Related G Protein–Coupled Receptors Inhibits Neurochemical Alterations in the Spinal Dorsal Horn and Dorsal Root Ganglia Associated with Inflammatory Pain in Rats

“…The levels of aspartate and glutamate were measured by high-performance liquid chromatography using a fluorescence detector (Vale et al, 2006). Derivatization was performed by adding 70 ml of AccQ Tag Fluor borate buffer and 20 ml of AccQ Tag derivative reagent to 10 ml of sample or standard solution, shaking the mixture, and then allowing it to react for 10 minutes at 55°C.…”

Scientific Opinion on marine biotoxins in shellfish - Palytoxin group

“…In addition to Na + , K + -ATPase, other plasma membrane components involved in transport of other ions have been proposed to contribute to molecular responses induced by PlTX (Muramatsu et al, 1984;Ikeda et al, 1988;Sauviat, 1989;Frelin and Van Renterghem, 1995;Vale et al, 2006), but the existence of PlTX targets other than the Na + , K + -ATPase is uncertain (Tosteson, 2000).…”

“…For instance, the intracellular sodium accumulation induces sodium-dependent transport of calcium ions into the cells by Na + /Ca 2+ exchangers (Ikeda et al, 1988;Frelin and Van Renterghem, 1995;Kockskämper et al, 2004;Vale et al, 2006). Similarly, intracellular sodium is exchanged for extracellular protons by Na + /H + exchangers, leading to the lowering of intracellular pH (Frelin et al, 1990;Yoshizumi et al, 1991;Monroe and Tashjan, 1996).…”

A roadmap for hazard monitoring and risk assessment of marine biotoxins on the basis of chemical and biological test systems

“…Intracellular Na + accumulation induces the transport of Ca 2+ into the cells via Na + /Ca 2+ exchangers (Frelin and Van Renterghem, 1995;Ikeda et al, 1988;Kockskamper et al, 2004;Vale et al, 2006). the latter increased intracellular Ca 2+ concentration affects skeletal, heart and smooth muscle cells (Frelin and Van Renterghem, 1995;Ito et al, 1977;Karaki et al, 1988;Kockskamper et al, 2004;Nagase and Karaki, 1987;Vale et al, 2006).…”

“…the latter increased intracellular Ca 2+ concentration affects skeletal, heart and smooth muscle cells (Frelin and Van Renterghem, 1995;Ito et al, 1977;Karaki et al, 1988;Kockskamper et al, 2004;Nagase and Karaki, 1987;Vale et al, 2006).…”