Ibuprofen reduces inflammation, necroptosis and protects photoreceptors from light-induced retinal degeneration
Ping‐Wu Zhang, Zi-He Wan, Weifeng Li, Kavita Vats, Kunal Mehta, Laura Fan, Lingli Zhou, Xi Li, Gloria Li, Casey Keuthan, Cynthia Berlinicke, Cheng Qian, Noriko Esumi, Elia J. Duh, Donald J. Zack
Abstract
BACKGROUND: The retinal degenerative diseases retinitis pigmentosa (RP) and atrophic age- related macular degeneration (AMD) are characterized by vision loss from photoreceptor (PR) degeneration. Unfortunately, current treatments for these diseases are limited at best. Genetic and other preclinical evidence suggest a relationship between retinal degeneration and inflammation. To further explore this relationship, we tested whether Ibuprofen (IBU), an FDA-approved non-steroidal anti-inflammatory drug (NSAID), could promote PR survival and function in a mouse model of light damage (LD)-induced PR degeneration. METHODS: LD was induced by exposing mice to 4000 lx of light for 2-4 hours (h). IBU (100 or 200 mg/kg) or vehicle was administered by daily intraperitoneal injection. Retinal structure and function were evaluated by spectral-domain optical coherence tomography (SD-OCT) and electroretinography (ERG). Cell death genes were analyzed at 24 and 72 h after LD using the Mouse Pan-Cell Death Pathway PCR Array (88 genes). The cellular location and protein expression of key necroptosis genes were assessed by immunohistochemistry. RESULTS: Retinal outer nuclear layer (ONL) thickness in vehicle-injected LD animals was 8.7 ± 0.6% of retinas without LD (p < 0.0001). In IBU 200 mg/kg treated mice, central ONL thickness was 74.9 ± 7.7% of untreated retinas (p < 0.001). A-wave and b-wave ERG amplitudes were significantly preserved in IBU-treated animals. IBU significantly inhibited retinal inflammation. Twenty-four hour after LD, retinal mRNA expression for the inflammatory-factors tumor necrosis factor (Tnf), interleukin-1 beta (Il1B), and C-C motif chemokine ligand 2 (Ccl2) increased by 10-, 17-, and 533-fold, respectively; in IBU-treated animals, the expression levels of these inflammatory factors were not significantly different from no-LD controls. Expression of key necroptosis genes, including Ripk3 and Mlkl, were upregulated in LD vehicle-treated mice, but dramatically reduced to near no LD levels in LD IBU-treated mice. Microglia activation and MLKL protein upregulation were observed primarily in photoreceptors 12 h after LD, as assessed by immunohistochemistry. IBU reduced the upregulation of MLKL protein and microglia migration in the ONL and outer plexiform layer (OPL) of treated retinas. CONCLUSIONS: Systemic administration of the anti-inflammatory drug IBU partially protected mouse retinas from light-induced photochemical damage and inhibited both inflammation and the necroptosis cell death pathways. Our results suggest that NSAIDs may provide a promising therapeutic approach for treatment of the human retinal degenerative diseases.