Usi innovativi di farmaci antichi L'attuale rivalutazione medica della Cannabis e dei cannabinoidi Cannabis e glaucoma Dott.ssa Anna Porcella Istituto di Neurogenetica e Neurofarmacologia Consiglio Nazionale delle Ricerche, Cagliari Roma 6 ottobre 2001 UNIVERSITÀ "LA SAPIENZA" Glaucoma A condition of the eye where the intraocular pressure is elevated beyond the limit that will permit normal function of the optic nerve. Almost 100 million people affected world wide 7 million totally blind due to the progression of their glaucomas PRIMARY OPEN ANGLE GLAUCOMA (POAG) Open anterior chamber The obstruction of the trabecular meshwork – Schlemm’s canal system blocks the outflow of aqueous humor OUTFLOW OF AQUEOUS HUMOR Marijuana smoking was first reported to reduce intraocular pressure (IOP) in 1971 (Hepler and Frank, 1971) Cloning of CB1 and CB2 receptors and the discovery of Endocannabinoids has opened the field for research into their physiological roles Distribution studies in both the brain and the periphery have shown that in some tissues these receptors are colocalized DIAGRAMMATIC CROSS SECTION OF THE ANTERIOR CHAMBER ANTERIOR CHAMBER CORNEA SCHLEMM’S CANAL SYSTEM IRIS SCLERA CILIARY MUSCLE LENS CILIARY BODY CB1 mRNA IN THE RAT EYE Porcella et al. Mol. Br. Res, 1998 CB1 mRNA IN THE HUMAN EYE Porcella et al. Eur. J. Neurosci, 2000 CB1 PROTEIN IN THE HUMAN EYE Porcella et al. Eur. J. Neurosci, 2000 ARMAMENTARIUM OF DRUGS IN USE TO TREAT GLAUCOMA a2 Adrenoreceptor agonists b2 Adrenoreceptor antagonists Prostaglandin Agonist Dopamninergic agonist Cholinergic Agonist Carbonic Anhydrase Inhibitors Guanylate Cyclase Activators Adenosine agonist NMDA Antagonist Cannabinoids ? Natural cannabinoids 9-THC Cannabinol 8-tetrahydrocannabinol Cannabidiol Endogenous cannabinoids Anandamide 2-AG Synthetic cannabinoids Nabilone WIN 55,212-2 CP 55,940 HU 210 LY320135 SR141716A Palmitoyl-EA (CB2 only) SR144528 DRUG AEA WIN-55,212-2 ANIMAL MODEL ROUTE OF ADMIN EFFECT ON IOP Normotensive rabbits EYE DROPS Normotensive rabbits I.V. REFERENCE Pate et al, 1996 NONE Hodges et al, 1997 CP-55,940 Normotensive EYE DROPS rabbits Pate et al, 1998 WIN-55,212-2 Normotensive EYE DROPS rabbits Song, 2000 8-THC Normotensive 9-THC rabbits CANNABINOL NABILONE I.V. Elsohly, 1981 EFFECT OF TOPIC WIN55212-2 ON IOP OF GLAUCOMATOUS PATIENTS Porcella et al. Eur. J. Neurosci, 2001 SUMMARY (1) THE HIGH LEVEL OF CB1 mRNA AND PROTEIN IN THE CILIARY BODY SUGGEST A LOCALIZED VASODILATION BY CANNABINOIDS IN ADDITION INHIBITION OF PRESYNAPTIC Ca++ CHANNELS BY CANNABINOIDS MAY REDUCE NORADRENALINE RELEASE IN THE EYE AND THE PRODUCTION OF AQUEOUS HUMOR SR141716A ANTAGONIZES IOP LOWERING EFFECTS OF CANNABINOIDS IN RABBITS SUGGESTING A DIRECT CB1 INVOLVEMENT IN THIS MECHANISM HOWEVER THE MECHANISM BY WHICH CANNABINOIDS ARE ABLE TO DECREASE IOP REMAINS TO BE FURTHER ELUCIDATED SUMMARY (2) IOP LOWERING EFFECTS OF TOPIC WIN55212-2 IN GLAUCOMATOUS PATIENTS ARE TIME AND DOSE DEPENDENT SYNTHETIC CB1 AGONISTS SHOULD DESERVE FURTHER RESEARCH AND CLINICAL DEVELOPMENT