Pathophysiological roles of adrenomedullin in experimental autoimmune uveitis

Abstract

Purpose : Adrenomedullin is a peptide produced by various cells and has diverse physiological effects, including anti-inflammatory, anti-apoptotic, and anti-oxidative stress effects. Experimental autoimmune uveitis (EAU) is a well-established model of human autoimmune uveitis. In this study, we investigated the pathophysiological roles of AM in uveitis using EAU model in mice.

Methods : 8 to 10-week-old female wild-type (WT) mice and AM knockout (AMKO) mice were used. To induce EAU, N-terminal peptide fragment of human interphotoreceptor retinoid-binding protein (hIRBP(1-20)) emulsified with complete Freund’s adjuvant containing Mycobacterium tuberculosis H37Ra was subcutaneously injected at the base of tails, followed by intraperitoneal injection of pertussis toxin. The expression of inflammation-related genes in the retina and T cell markers in the spleen was evaluated by real-time PCR on day 7 after immunization. Next, in WT mice, human recombinant AM or vehicle was administered subcutaneously using an osmotic pump for 14 days. On day 14, clinical and histological scores were evaluated according to the severity of inflammatory findings. The number of CD3-positive T cells was also counted.

Results : The retinas of AMKO mice showed higher expression of inflammatory cytokines, while their spleens showed significantly lower expression of CD3 (p=0.0002, n=7~8), compared to those of WT mice. The expression of CD3 in the spleens of WT EAU mice was suppressed to the equivalent level of AMKO mice. Furthermore, significant differences were found in the clinical score (p<0.05, n=5) and the number of T cells in the retinas (p<0.0001, n=5) between AM-treated and vehicle-treated groups.

Conclusions : AM is suggested to improve the pathogenesis of uveitis by regulating T cell recruitment and inflammation. Additional flow cytometry analysis would be necessary to elucidate the precise mechanism of AM's therapeutic effect on uveitis.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.