B. Pasquis

Time course of ocular surface and lacrimal gland changes in a new scopolamine-induced dry eye model.

BackgroundThe aim of this study was to set up an animal model of dry eye showing disturbance in several components of the lacrimal functional unit, and to describe the time course of the appearance of clinical signs and inflammatory markers.MethodsDry eye was induced in 6-week-old female Lewis rats by a systemic and continuous delivery of scopolamine via osmotic pumps implanted subcutaneously. We first determined the appropriate dose of scopolamine (6, 12.5, or 25xa0mg/day) for 28xa0days. In a second set of experiments, we determined markers after 1, 2, 3, 7, 10, 17, or 28xa0days of a 12.5-mg/day dose. Clinical signs of corneal dryness were evaluated in vivo using fluorescein staining. MHC II expression and mucin Muc5AC production were detected on the conjunctival epithelium using immunostaining. The level of IL-1β, IL-6, TNF-α, and IFN-γ mRNA was evaluated by real-time polymerase chain reaction in conjunctiva and exorbital lacrimal gland (LG). Lipids were extracted from the exorbital LG for fatty acid analysis.ResultsDaily scopolamine doses of 12.5xa0mg and 25xa0mg applied for a 28-day period induced keratitis, a decrease in Muc5AC immunostaining density in the conjunctival epithelium, and modifications in the fatty acid composition of the exorbital LG. Animals treated with a 12.5-mg/day dose of scopolamine exhibited an increase in corneal fluorescein staining after 2, 10, and 28xa0days. All animals exhibited unilateral or bilateral keratitis after 17xa0days. In the conjunctival epithelium, a significant decrease in Muc5AC immunostaining density was observed at early and late time points, and MHC II expression tended to be increased after 1, 7, 10, and 28xa0days, without reaching statistical significance. The levels of TNF-α, IL-1β and IL-6xa0mRNA were increased with scopolamine treatment in both conjunctiva and exorbital LG. Arachidonic acid and the Δ5 desaturase index were significantly increased in the exorbital LG of dry eye animals at each time point.ConclusionsThis systemic and continuous scopolamine-induced model of dry eye in the rat may represent a helpful tool to investigate moderate dry eye, and makes a contribution in the field of dry eye study.

No consequences of dietary n-3 polyunsaturated fatty acid deficiency on the severity of scopolamine-induced dry eye

PurposeEpidemiological studies suggest that dietary n-3 polyunsaturated fatty acids (PUFAs) may protect against dry eye. This study aimed to evaluate whether a dietary deficiency in n-3 PUFAs may increase the severity of the pathology in a scopolamine-induced model of dry eye in the rat.MethodsLewis rats of three consecutive generations were bred under a balanced diet or a diet deprived of n-3 PUFAs. Dry eye was experimentally induced by continuous scopolamine delivery in female animals from the third generation of both groups. After 10xa0days of treatment, the clinical signs of ocular dryness were evaluated in vivo using fluorescein staining. MHC II and the rat mucin rMuc5AC were immunostained on ocular sphere cryosections. The transcript levels of the pro-inflammatory cytokines interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and interferon (IFN)-γ were quantified in the exorbital lacrimal glands (LG) and in the conjunctiva using reverse transcription followed by polymerase chain reaction. Lipids were extracted from the exorbital LG for fatty acid analysis of the phospholipids using gas chromatography.ResultsWhen compared to control animals, the scopolamine treatment induced an increase in the cornea fluorescein staining score (from 0.5u2009±u20090.0 to 2.5u2009±u20091.0 arbitrary units (AU) for the balanced diet and from 1.2u2009±u20090.8 to 2.6u2009±u20090.5xa0AU for the n-3 PUFA-deficient diet); a decrease in rMuc5AC immunostaining in the conjunctival epithelium (−34% for the balanced diet and −23% for the n-3 PUFA-deficient diet); an increase in the LG transcript levels of TNF-α for the balanced diet and of TNF-α and IFN-γ for the deficient diet; an increase in the conjunctival transcript levels of IL-1β and IL-6 for the deficient diet; an increase in arachidonic acid (AA) and in the ∆5-desaturase index (ratio of AA to dihomo-gamma-linolenic acid) in the exorbital LG for both diets. When compared to the balanced diet, the n-3 PUFA-deficient diet induced an increase in the LG transcript levels of IL-6 for the control animals and of TNF-α for the control and dry eye animals as well as an increase in the conjunctival transcript levels of IL-6 for the dry eye animals. There was no significant diet difference in fluorescein staining, rMuc5AC, and MHC II immunostaining scores.ConclusionsOur data suggest that an n-3 PUFA deficiency does not increase the severity of dry eye in a rat model of dry eye.

Dietary polyunsaturated fatty acids reduce retinal stress induced by an elevation of intraocular pressure in rats

N-6 and n-3 polyunsaturated fatty acids (PUFAs) have been shown to prevent tissue release of inflammatory molecules. We have shown that a combination of n-6 and n-3 PUFAs is more efficient than single supplementations on the long-term consequences of intraocular pressure elevation. We hypothesized that such an association is also more effective during early retinal stress by modifying retinal proinflammatory prostaglandin and cytokine productions. Rats were supplemented for 3 months with n-6 PUFAs, n-3 PUFAs, or both n-6 and n-3 PUFAs. After 3 months, a surgical elevation of intraocular pressure was induced. Retinal morphometry and glial cell activation were evaluated 24 hours after laser treatment. The retinal levels of prostaglandin E(1) (PGE(1)) and prostaglandin E(2) (PGE(2)) and the messenger RNA levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α were measured. Retinal glial cell activation after laser treatment was partly prevented by dietary n-6, n-3, and n-6 and n-3 PUFAs. Retinal PGE(1) was unaffected by the laser treatment or by the diet. Dietary n-6 and/or n-3 PUFAs prevented the increase in PGE(2) levels observed in laser-treated retinas without affecting the induction of interleukin-1β, interleukin-6, and tumor necrosis factor-α messenger RNAs. This study shows that not only a combination of n-6 and n-3 PUFAs but also single supplementations can preserve the retina from early glial cell activation and PGE(2) release. The protective effect is not mediated by changes in cytokine expression but may be related to modifications in retinal prostaglandin metabolism.