CB2 cannabinoid receptors in trabecular meshwork cells mediate JWH015-induced enhancement of aqueous humor outflow facility.

PURPOSE To study the effects of JWH015, a CB2-selective agonist, on aqueous humor outflow facility, to investigate whether functional CB2 cannabinoid receptors are expressed in trabecular meshwork cells, and to study whether these receptors are involved in the enhancement of outflow facility induced by JWH015. METHODS A porcine anterior segment perfused organ culture model was used to measure the effects of JWH015 on aqueous humor outflow facility. Immunofluorescence microscopy, Western blot analysis, and mitogen-activated protein (MAP) kinase activity assays were used to study the expression of CB2 cannabinoid receptors on cultured porcine trabecular meshwork cells and the coupling of these receptors to p42/44 MAP kinase. RESULTS The outflow facility was increased dose dependently within 1 hour after adding 10, 30, and 100 nM of JWH015, a CB2 agonist. In addition, the effect of 100 nM of JWH015 was completely blocked by SR144528, a selective CB2 antagonist. Furthermore, the outflow-enhancing effect of JWH015 was blocked by pretreatment with PD98059, an inhibitor of the p42/44 MAP kinase pathway. In immunofluorescence microscopy and Western blot studies, positive signals were detected on cultured porcine trabecular meshwork cells with an anti-CB2 antibody. In MAP kinase assays, treatment of porcine trabecular meshwork cells with 100 nM of JWH015 activated p42/44 MAP kinase activity. Pretreatment with SR144528 blocked the effect of JWH015 on p42/44 MAP kinase activity. CONCLUSIONS The data from this study demonstrate that the CB2-selective cannabinoid agonist JWH015 increases aqueous humor outflow facility. The results also indicate that functional CB2 cannabinoid receptors are expressed in trabecular meshwork cells, and these receptors are involved in the enhancement of outflow facility induced by JWH015.