Decreased serum melatonin levels in rats with experimental autoimmune uveitis/pinealitis and in patients with uveitis

Abstract

The authors measured serum levels of the pineal hormone melatonin to investigate the possibility of pineal dysfunction in both rats with experimental autoimmune uveitis/pinealitis (EAU/EAP) and uveitis patients. The serum melatonin concentrations of EAU/EAP rats were measured by radioimmunoassay over a 24-hour (h) period, and in uveitis patients at night (0200 h). Melatonin concentrations were assayed in six patients with Behçet's disease, four with Vogt-Koyanagi-Harada (VKH) disease, three with sarcoidosis, three with Kirisawa-type uveitis, and one with tubulointerstitial nephritis and uveitis syndrome. Nocturnal serum melatonin levels were significantly lower in Lewis rats with EAU/EAP (2200 h: 33.6±20.4 pg/ml, 0200 h: 43.2±13.9 pg/ml) than in the controls (2200 h: 117.5±25.3 pg/ml, 0200 h: 132.4±20.2 pg/ml) (p>0.01, at 2200 h and 0200 h). Melatonin levels were significantly lower in VKH disease (20.7±10.5 pg/ml) (p>0.01) and Behçet's disease (42.1±42.5 pg/ml) (p>0.05) than in the controls (79.4±36.7 pg/ml). These results suggest that there is a decrease in pineal gland function due to pinealitis in EAU/EAP rats. The markedly decreased nocturnal serum melatonin levels may also be related to the presence of retinal uveitogenic antigens in uveitis patients.