Phenothiazine-induced increase in thyroid autoantigens and costimulatory molecules on thyroid cells: a pathophysiological mechanism for drug-induced autoimmunity?

We have previously demonstrated (J Immunol 1995; 154:3593) that MHC class II antigens can be induced on thyroid epithelial cells (TEC) by alimemazine, a member of the phenothiazine group. Although this expression of MHC class II antigens on TEC confers the theoretical ability to behave as antigen-presenting cells (APC), the simultaneous expression of self antigens and co-receptor(s) must also occur for efficient presentation of self antigens. Therefore, we investigated whether alimemazine applied at pharmacologic doses would modify the expression of thyroid antigens, and simultaneously, the expression of intercellular adhesion molecule-1 (ICAM-1), B7, and LFA-1 co-receptors in human TEC in culture. Using polymerase chain reaction (PCR) amplification and Northern blot analysis, we showed that alimemazine induces increases in thyroglobulin (Tg) and thyroid-stimulating hormone receptor (TSH-R) cDNA, within the first 2 h following its addition. This phenomenon is followed 48 h later by an increase of Tg and TSH-R protein expression on the surface of TEC. Furthermore, increases in the expression of ICAM-1 and B7 co-receptors were concomitantly observed. These results suggest that alimemazine, a drug currently used in paediatrics, could play a role in the induction and perpetuation of thyroid autoimmune disorders by transforming TEC into functional APC.

Phenothiazine induces de novo MHC class II antigen expression on thyroid epithelial cells. A new mechanism for drug-induced autoimmunity.

Autoimmune responses are initiated by MHC class II-restricted T cell responses directed against tissue-specific autoantigens. Furthermore, HLA-DR expression in thyroid epithelial cells is a prominent feature of autoimmune thyroid disease. In the present work, we were particularly interested in a phenothiazine, a neuroleptic and anti-depressant drug of pharmacologic importance named alimemazine. Our interest in this compound stems from previous findings of immune effects of this and other phenothiazines. We demonstrate that MHC class II Ags can be experimentally induced on thyroid cells by pharmacologic concentrations of alimemazine, a drug commonly used in psychiatry. In contrast, MHC class II Ags were not induced on the lymphoid cell lines Raji and Jurkat. Expression of MHC class II Ag on the surface of the cloned human thyroid cell hybridoma, GEJ, was demonstrated by flow cytometry. Moreover, by using Northern blot and Southern blot analyses, this finding was confirmed at the molecular level in GEJ and in murine thyroid epithelial cell cultures, respectively. The functional role of phenothiazine-, de novo-induced MHC class II Ags on thyroid cells was assessed by both syngeneic murine thyroglobulin-specific and allogeneic proliferative T cell responses. These results suggest that antidepressant drugs of the phenothiazine type could play a role in the induction and the perpetuation of thyroid autoimmune disorders, through induction of class II restriction elements on normally class II-negative thyroid epithelial cells.

Effects of calmodulin antagonists on radiation-induced lipid peroxidation in microsomes.

Rat liver microsomes were irradiated with gamma-rays at a dose rate of 1.31 Gys-1. The extent of lipid peroxidation, measured in terms of malondialdehyde (MDA) formed, increased with radiation dose. The presence of calmodulin antagonists during irradiation decreased lipid peroxidation. The order of their protective efficiency was: chlorpromazine (CPZ) greater than promethazine (PMZ) greater than trimeprazine (TMZ). Their protective effect was diminished in the presence of ferrous (Fe2+) ions and was restored on addition of EDTA. However, calmodulin antagonists considerably inhibited radiation-induced lipid peroxidation in the presence of ferric (Fe3+) ions. Calmodulin antagonists also decreased the cytochrome P-450 content of microsomes. These results are discussed with respect to their applicability to radiotherapy. A possible mechanism for the inhibition of radiation-induced lipid peroxidation is suggested.

Modification of radiation induced lipid peroxidation by calmodulin antagonists.

It has been shown that calmodulin antagonists provide radio-protection in euoxic and sensitization in hypoxic conditions. This differential protection in euoxic conditions might have arisen from the interaction of calmodulin antagonists with oxygen free radicals. This possibility has been tested in the present communication. Radiation induced lipid peroxidation process in liposomes has been used for this purpose. Liposomes prepared from L-alpha-lecithin were irradiated with or without calmodulin antagonists. Calmodulin antagonists inhibited lipid peroxidation significantly. The inhibition was found to increase with increase in concentration of the drugs. These observations suggest that calmodulin antagonists have a capacity to scavenge oxygen free radicals involved in initiation and/or propagation of lipid peroxidation process. This may be the reason for their differential radioprotection in euoxic conditions in biological systems.

Modification of radiation response of E. coli B/r cells by phenothiazines.

Promethazine and trimeprazine sensitized anoxic E. coli B/r cells to 60Co gamma-rays, but both drugs showed a radioprotective effect under euoxic conditions. Their radiosensitizing effect was found to be due to the reaction of radiolytically induced hydroxyl radicals with the sensitizers. The radioprotective effect of these drugs is attributed to changes in the membrane structure conducive with chemical repair of the damaged sites in the gel region of the cellular membrane by intracellular sulphydryl compounds. Pre-irradiation depletion of sulphydryls from E. coli B/r by treatment with N-ethyl maleimide abolished the radio-protective effect of these drugs under euoxic conditions.

Lorazepam in children. A double-blind trial comparing lorazepam, diazepam, trimeprazine and placebo.

One hundred patients aged 5-13 yr were randomly allocated to four groups in a double-blind study of premedication. Drugs studied were lorazepam, diazepam and trimeprazine. A placebo group was included. All the drugs appeared satisfactory as premedicants. Lorazepam induced the most sedation immediately after surgery, but by 4 h lorazepam and diazepam appeared similar. Lorazepam produced better amnesia than the other drugs. There were no untoward side-effects and no cardiorespiratory depression in any group. Lorazepam appears a suitable premedicant for children.

Comparative study of lorazepam and trimeprazine for oral premedication in paediatric anaesthesia.

One hundred and ninety-nine children received lorazepam 0.05 mg kg-1 or trimeprazine 3 mg kg-1 as oral premedication in a double-blind trial. Lorazepam proved more palatable and produced a cheerful demeanour, but possessed no significant advantages on overall assessment before surgery. Following operation, restlessness with vomiting, and evidence of retrograde amnesia occurred more frequently with lorazepam.