All-trans retinoic acid- and N-(4-hydroxyphenil)-retinamide-induced growth arrest and apoptosis in orbital fibroblasts in Graves' disease.

In this study, we evaluated by reverse transcription-polymerase chain reaction (RT-PCR) the expression pattern of retinoic acid receptors (RAR) alpha, beta, and gamma and cellular retinoic acid binding protein-I (CRBP-I) genes in 12 primary cultures of fibroblasts (F) from orbital tissue of Graves' ophthalmopathy (GO) patients. We also studied the in vitro effects of all-trans retinoic acid (RA) and N-(4-hydroxyphenil)-retinamide (4HPR), a less toxic and better tolerated synthetic derivative of RA, on cell morphology, growth, apoptosis, and cyclic adenosine monophosphate (cAMP) accumulation. All primary cultures expressed RAR alpha, beta, gamma, and CRBP-I. FGO treated with RA and 4HPR (10(-7) mol/L) presented morphologic changes and significantly inhibited cell growth after 72 hours. At 96 hours of drug exposure, apoptosis was detected in 15% and 50% of RA- and 4HPR (10(-7) mol/L)-treated cells, and p53 protein increased in cell lysates. 4HPR induced a 70% decrease of Bcl-2 protein. After 30 minutes of RA and 4HPR (10(-7) mol/L) exposure, a 20% decrease of basal cAMP accumulation was seen, and forskolin cAMP-induced increase was abolished. The expression of RAR alpha, beta, gamma, and CRBP-I in primary cultures of FGO indicates that they are targets for retinoids. Moreover, we show that RA and 4HPR are able to induce morphologic changes, inhibition of cell growth, and apoptosis in FGO exerting their effects through RAR-modulated pathways. The rapid inhibition of cAMP accumulation indicates that a novel nonclassic retinoid pathway may also be involved. Finally, the potent in vitro effects of 4HPR, a retinoid derivative with fewer adverse reactions in vivo, could justify further investigations on a clinical application of retinoids in GO.

Somatostatin receptor genes are expressed in lymphocytes from retroorbital tissues in Graves' disease.

The radiolabeled somatostatin (SST) analog octreotide accumulates within the orbits of active Graves' ophthalmopathy (GO), and octreotide and lanreotide have been proposed to treat this disorder. It is still unclear which retroorbital cells the SST analogs target. Lymphocytic infiltration of retroorbital tissues is a peculiarity of GO, and labeled octreotide could accumulate at specific sites on retroorbital-activated lymphocytes. The accumulation of radiolabeled analogs is due to the interaction with specific cell surface SST receptors. Five subtypes of somatostatin receptors (SST1-5), member of the G protein-coupled, seven-transmembrane superfamily, are described. It still unknown which SST subtype is expressed in retroorbital activated lymphocytes. The aim of this study was to evaluate the expression of SST1-5 genes in lymphocytes recovered from retroorbital tissues obtained from patients with GO undergoing orbital decompression. Cultured phytohemagglutinin-stimulated lymphocytes from retroorbital blood samples, drawn during orbital surgery in five patients with GO and in two control patients without autoimmune or thyroid diseases and without orbital inflammatory conditions, were also studied. RT-PCR of total RNA extracted from lymphocytes was performed using primers for SST1-5 and, as internal control, for glyceraldehyde-3-phosphate dehydrogenase. All SSTs transcripts were found in lymphocytes both from GO retroorbital tissues and blood samples. The levels of expression of SST1, -2, and -4 mRNA were higher than those of the SST3 and -5 transcripts. In the lymphocytes from control subjects, the SST subtypes with high affinity for octreotide were barely found. The presence, even if at different concentrations, of all SST1-5 receptors in retroorbital lymphocytes from GO shows that they are targeted by SST analogs and could explain the effects described in GO patients treated with SST analogs.