Pagán Melvin, Camila A.
Laura D. McGee
Abigail S. Hackam

Universidad Central del Caribe School of Medicine, Bayamón, Puerto Rico
University of Miami Miller School of Medicine, Bascom Palmer Eye Institute

Introduction

Retinitis pigmentosa (RP) is a progressive retinal degenerative disease characterized by photoreceptor loss and chronic inflammation, with no current curative therapies. IL-27, an immunomodulatory cytokine, has shown potential neuroprotective effects in retinal degenerative models. This study investigates the effect of IL-27 intravitreal injections on JNK pathway activation (P-SAPK/JNK), C-JUN expression, STAT1 signaling, and cytokine secretion in rd10 mice, a model of autosomal recessive RP.

Methods

Rd10 mice received intravitreal injections of IL-27 (10 ng, 20 ng, or 40 ng), while the contralateral eye served as a no-treatment control. Additional groups received saline injections. For P-SAPK/JNK and C-JUN immunohistochemistry, group sizes were: no treatment (n=2), saline (n=2), 10 ng IL-27 (n=1), 20 ng IL-27 (n=3), and 40 ng IL-27 (n=2). STAT1 immunohistochemistry and cytokine analysis were performed with n=4 per group. Retinal sections were analyzed via immunohistochemistry for P-SAPK/JNK, C-JUN, and STAT1 expression, with a focus on the inner plexiform, outer plexiform, and inner nuclear layers. Cytokine levels (IL-18, IL-23, IL-27, IL-33, IL-10, Ccl2, Ccl22) were assessed using multiplex immunoassay from retinal lysates. Signal intensity was evaluated through immunofluorescence microscopy and quantitative image analysis.

Results

IL-27 treatment resulted in dose-dependent modulation of the JNK pathway, with the 20 ng dose demonstrating optimal P-SAPK/JNK and C-JUN activation within the inner plexiform, outer plexiform, and inner nuclear layers. IL-27 also significantly increased activated STAT1 levels compared to saline controls, suggesting restoration of STAT1 signaling towards wild-type levels. Cytokine analysis revealed alterations in pro- and anti-inflammatory mediators, with IL-27 reducing IL-10 and Ccl2 levels while decreasing IL-23 and increasing IL-33 compared to saline-treated eyes.

Conclusions

Our findings suggest that IL-27 modulates key molecular pathways involved in retinal degeneration, including JNK activation, C-JUN expression, STAT1 signaling, and cytokine secretion. These results provide mechanistic insight into IL-27’s protective effects in RP and support further investigation into its potential as a therapeutic strategy for retinal degenerative diseases.

IACUC Protocol Number

22-046