Changes in endocannabinoid and palmitoylethanolamide levels in eye tissues of patients with diabetic retinopathy and age-related macular degeneration

Cannabinoid receptors and the endocannabinoids (anandamide (N-arachidonoylethanolamine-AEA) and 2-arachidonoylglycerol (2-AG)), as well as the AEA congener, palmitoylethanolamide (PEA), are involved in ocular physiology. We measured endocannabinoid and PEA levels by isotope-dilution liquid chromatography-mass spectrometric analysis in post-mortem eye tissues of patients with diabetic retinopathy (DR) or age-related macular degeneration (AMD). In eyes with DR, significantly enhanced levels of AEA were found in the retina (similar to 1.8-fold), ciliary body (similar to 1.5-fold) and, to a lesser extent, cornea (similar to 1.3-fold). Surprisingly, 2-AG levels were significantly higher (similar to 3-fold) only in the iris, whereas PEA levels only slightly increased (similar to 1.3-fold) in the ciliary body. In eyes with AMD, significantly enhanced levels of AEA were found in the choroid (similar to 1.3-fold), ciliary body (similar to 1.4-fold) and cornea (similar to 1.4-fold), whereas in the retina only a trend towards an increase (similar to 1.5-fold) was observed. The tissue- and disease-selective nature of the changes observed suggests that the compounds analyzed here may play different roles in the control of eye function under different pathological conditions. (c) 2006 Elsevier Ltd. All rights reserved.