Abstract
Purpose :
Aberrant Innate Immune cell response and chronic inflammation lead to RPEC and photoreceptor cell damage and death. We have recently discovered pro-homeostatic lipid mediators termed “Elovanoids” (ELV) that act in a autocrine/paracrine manner to sustain photoreceptor integrity. ELV are derived as a stress response from VLC-PUFAs (34-6 and 32-6), which are made by the elongase ELOVL4. ELV are neuro-protective against NMDA toxicity and oxygen/ glucose deprivation, at the same time display potent activation of anti-apoptotic and pro-homeostatic signaling in RPEC. We hypothesized that ELV are capable of reducing the deleterious effects of chronic inflammation and tissue injury by modulating the inflammatory response.
Methods :
Human RPEC were either pretreated with IL-1α (24 hs) followed by H2O2 (1200μM for 6 hs) or incubated with ox-LDL (oxidized LDL, 150ug/ml) for 24hs. In both experiments RPEC were pre-treated with 300nM ELV for 30 minutes. Extracted RNA samples were analyzed using a custom-made Prime PCR Panel for human inflammasome and innate immunity markers.
Results :
Both noxious triggers increased the expression of pro-inflammatory signaling including NOD-2, IL-1b, IL-8, IL-6, CCL5 (RANTES) as well as NLRP3. IL-6 and IL-1β responded to IL-1α stimulation only. ELV suppress the expression of IL-1b, IL-6, IL-8 and NOD-2 by 80%, 90%, 65% and 60% respectively (IL-1α activation) and 80% and 65% (ox-LDL) for IL-8 and NOD-2 respectively. ELV reduce the expression of NLPR3 to both ox-LDL and IL-1α stimuli by more than 2 fold in each case. 34-6 ELV pre-incubation before adding IL-1α suppressed CCL5 expression over 3 fold.
Conclusions :
NOD-2/RIP2/BIRC3 complex signaling results in the degradation of IkB dimers and transcriptional activation of IL-1β, IL-6 and IL-8. RPE cells avidly produce IL-6 and IL-8, which contributes to angiogenesis and inflammation in retina. NLRP3 is an important regulator of innate response and contributes to activation of IL-1β in response to inflammasome complex formation. RPEC secrete CCL5 which induces microglial chemotaxis. Reducing the overt pro-inflammatory signal can be beneficial to prevent ocular damage and reduce progression of chronic inflammatory diseases such as AMD. The novel bioactive lipid mediators (ELV) can potentially open innovative prospects for development of therapeutics targeting these NLR family proteins.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.