Anti-Inflammatory Effects of Gamma-Linolenic Acid and Eicosapentaenoic Acid on a Scopolamine-Induced Dry Eye Rat Model

Abstract

Purpose:: The aim of this study was to evaluate the potential anti-inflammatory effects of dietary γ-linolenic acid (GLA) and eicosapentaenoic acid (EPA) in a scopolamine-induced dry eye rat model.

Methods:: Female Lewis rats were fed with 5%-lipid diets containing 10% of either GLA or EPA. After two months of feeding, we induced dry eye syndrome using scopolamine continuously delivered via osmotic pumps for 2, 10 and 28 days. At the end of the treatment period, we performed fluorescein staining on the cornea. We sacrificed the animals and excised the ocular tissues and the exorbital lacrimal glands. We immunostained MHCII and mucin MUC5AC on ocular sphere cryosections. We extracted lipids from the lacrimal glands for fatty acid analysis.

Results:: After 28 days of treatment, the prevalence of keratitis was significantly reduced in the dry eye GLA-diet (DE-GLA) and EPA-diet (DE-EPA) groups as compared to the dry eye control diet (DE-CD) group (38% and 50%, respectively, versus 100%). The decrease in MUC5AC immunostaining observed after 10 days of treatment on the palpebral conjunctival epithelium in the DE-CD group was partially prevented by GLA or EPA supplementations, at the same level in both groups. After 2 and 10 days of treatment, the expression of MHCII on the conjunctival epithelium was reduced in the DE-GLA and DE-EPA groups as compared to the DE-CD group. The decrease of staining was higher in the DE-GLA group in comparison with the DE-EPA group after 2 days of treatment. In lacrimal gland phospholipids, GLA (0.17% in DE-CD group) and EPA (0.30% in DE-CD group) and their longer-chain metabolites were significantly increased in DE-GLA and DE-EPA groups (+59% and +3700%, respectively, after 10 days of treatment). The Δ5-desaturase index (arachidonic acid / dihomo GLA ratio) was increased in DE-CD group as compared to control group (+8% after 10 days of treatment), and decreased in DE-GLA and DE-EPA groups as compared to DE-CD group (-25% and -10%, respectively).

Conclusions:: Altogether these results showed that dietary GLA and EPA can be incorporated in lacrimal glands and may have a protective effect on experimentally induced dry eye model. A GLA-enriched diet was more efficient than an EPA-enriched diet.

Keywords: inflammation • lipids • keratitis