VASCULAR SOMATOSTATIN RECEPTORS IN SYNOVIUM FROM PATIENTS WITH RHEUMATOID-ARTHRITIS

The peripheral nervous system and its neuropeptidergic pathways may pl ay an important role in the pathogenesis and development of rheumatoid arthritis. In the present study, the role of the neuropeptide somatos tatin (SRIF), which was recently shown to be implicated in inflammator y diseases of the gastrointestinal tract, was evaluated by measuring t he expression of somatostatin receptors in synovium from patients with rheumatoid arthritis. Somatostatin receptors were detected using in v itro receptor autoradiography in the synovium from five patients with active disease. No receptors were found in one case, a successfully tr eated patient with quiescent disease. The receptors were of high affin ity and specific for biologically active somatostatin analogs. Displac ement by nanomolar concentrations of somatostatin-14, somatostatin-28, and octreotide was observed, suggesting that most of the receptors id entified belong to the SRIF(1A) subtype. The somatostatin receptors we re preferentially located in blood vessels, with specific labeling of the veins but not of the arteries. The whole vessel wall was homogeneo usly labeled including the smooth muscle cells and probably the endoth elium. These data suggest that the synovium in active rheumatoid arthr itis expresses a high density of somatostatin receptors. Somatostatin may act through these venous receptors to influence the inflammatory p rocess by induction of vasoconstriction, inhibition of plasma extravas ation and cell migration, or inhibition of neovascularization.