Omega-3 fatty acids protect retinal neurons in the DBA/2J hereditary glaucoma mouse model

The purpose of this study was to evaluate the neuroprotective effects of omega-3 polyunsaturated fatty acid (omega 3-PUFA) supplementation, alone or in combination with timolol eye drops, in a mouse model of hereditary glaucoma. DBA/2J mice (8.5-month-old) were assigned to an omega 3-PUFAs + timolol, omega 3-PUFAs only, timolol only, or an untreated group. Treated mice received a daily gavage administration of eicosapentaenoic acid (EPA) and docosahexaenoic acid and/or topical instillation of timolol (0.5%) once a day for 3 months. Blood was analysed regularly to determine omega 3-PUFA levels and retinas were histologically analysed. Real-time PCR and Western blot were performed for retinal pro-inflammatory cytokines and macrophages. Blood arachidonic acid/EPA ratio gradually decreased and reached the desired therapeutic range (1-1.5) after 4 weeks of daily gavage with (omega 3-PUFAs in the omega 3-PUFAs + timolol and omega 3-PUFAs only groups. Retinal ganglion cell densities were significantly higher in the omega 3-PUFAs + timolol (1303.77 +/- 139.62/mm(2)), omega 3-PUFAs only (768.40 +/- 52.44/mm(2)) and timolol only (910.57 +/- 57.28/mm(2)) groups than in the untreated group (323.39 +/- 95.18/mm(2)). omega 3-PUFA supplementation alone or timolol alone, significantly increased protein expression levels of M1 macrophage-secreted inducible nitric oxide synthase and M2 macrophage-secreted arginase-1 in the retina, which led to significant decreases in the expression levels of tumour necrosis factor-alpha (TNF-alpha). omega 3-PUFA supplementation alone also resulted in significantly reduced expression of interleukin-18 (IL-18). omega 3-PUFA + timolol treatment had no effect on the expression level of any of the aforementioned mediators in the retina. Supplementation with omega 3-PUFAs has neuroprotective effect in the retinas of DBA/2J mice that is enhanced when combined with timolol eye drops. The continued inflammation following omega 3-PUFAs + timolol treatment suggests that downregulation of IL-18 and TNF-alpha may not be the only factors involved in omega 3-PUFA-mediated neuroprotection in the retina.