Hydrogen peroxide attenuates store-operated calcium entry and enhances calcium extrusion in thyroid FRTL-5 cells

• Published in: Biochemical journal Vol. 351; no. Pt 1; pp. 47 - 56
• Main Authors: Törnquist, K, Vainio, P J, Björklund, S, Titievsky, A, Dugué, B, Tuominen, R K
• Format: Journal Article
• Language: English
• Published: England 01-10-2000
• Subjects: Adenosine Triphosphate - metabolism; Animals; Barium - metabolism; Calcium - metabolism; Calcium Channels - metabolism; Calcium-Transporting ATPases - metabolism; Cell Line; Down-Regulation - drug effects; Enzyme Activation - drug effects; Hydrogen Peroxide - pharmacology; Isoenzymes - metabolism; Manganese - metabolism; Membrane Potentials - drug effects; Mercaptoethanol - pharmacology; Naphthalenes - pharmacology; Oxidation-Reduction - drug effects; Phorbol 12,13-Dibutyrate - metabolism; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Protein Transport - drug effects; Rats; Sodium - pharmacology; Staurosporine - pharmacology; Thapsigargin - pharmacology; Thyroid Gland - cytology; Thyroid Gland - drug effects; Thyroid Gland - metabolism
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/0264-6021:3510047

Redox modulation participates in the regulation of intracellular free calcium concentration ([Ca(2+)](i)) in several cell types. In thyroid cells, including FRTL-5 cells, changes in [Ca(2+)](i) regulate several important functions, including the production of H(2)O(2) (hydrogen peroxide). As H(2)O(2) is of crucial importance for the production of thyroid hormones, we investigated the effects of H(2)O(2) on [Ca(2+)](i) in thyroid FRTL-5 cells. H(2)O(2) itself did not modulate basal [Ca(2+)](i). However, H(2)O(2) attenuated store-operated calcium entry evoked by thapsigargin, both in a sodium-containing buffer and in a sodium-free buffer. The effect of H(2)O(2) was abrogated by the reducing agent beta-mercaptoethanol. H(2)O(2) also attenuated the thapsigargin-evoked entry of barium and manganese. The effect of H(2)O(2) was, at least in part, mediated by activation of protein kinase C (PKC), as H(2)O(2) enhanced the binding of [(3)H]phorbol 12,13-dibutyrate. H(2)O(2) also stimulated the translocation of the isoenzyme PKCepsilon from the cytosolic fraction to the particulate fraction. Furthermore, H(2)O(2) did not attenuate store-operated calcium entry in cells treated with staurosporine or calphostin C, or in cells with down-regulated PKC. H(2)O(2) depolarized the membrane potential in bisoxonol-loaded cells and when patch-clamp in the whole-cell mode was used. The depolarization was attenuated in cells with down-regulated PKC. This depolarization, at least in part, explained the H(2)O(2)-evoked inhibition of calcium entry. In addition, H(2)O(2) enhanced the extrusion of calcium from cells stimulated with thapsigargin and this effect was abolished in cells with down-regulated PKC and after treatment of the cells with the reducing agent beta-mercaptoethanol. In conclusion H(2)O(2) attenuates an increase in [Ca(2+)](i). As H(2)O(2) is produced in thyroid cells in a calcium-dependent manner, our results suggest that H(2)O(2) may participate in the regulation of [Ca(2+)](i) in these cells via a negative-feedback mechanism involving activation of PKC.