Background and purpose: Trabecular meshwork (TM) is an ocular tissue involved in the regulation of aqueous humour outflow and intraocular pressure (IOP). CB 1 receptors (CB 1 ) are present in TM and cannabinoid administration decreases IOP. CB 1 signalling was investigated in a cell line derived from human TM (hTM). Experimental approach: CB 1 signalling was investigated using ratiometric Ca 2 þ imaging, western blotting and infrared In-Cell Western analysis. Key results: WIN55212-2, a synthetic aminoalkylindole cannabinoid receptor agonist (10-100 mM) increased intracellular Ca 2 þ in hTM cells. WIN55,212-2-mediated Ca 2 þ increases were blocked by AM251, a CB 1 antagonist, but were unaffected by the CB 2 antagonist, AM630. The WIN55,212-2-mediated increase in [Ca 2 þ ] i was pertussis toxin (PTX)-insensitive, therefore, independent of G i/o coupling, but was attenuated by a dominant negative Ga q/11 subunit, implicating a G q/11 signalling pathway. The increase in [Ca 2 þ ] i was dependent upon PLC activation and mobilization of intracellular Ca 2 þ stores. A PTXsensitive increase in extracellular signal-regulated kinase (ERK1/2) phosphorylation was also observed in response to WIN55,212-2, indicative of a G i/o signalling pathway. CB 1 -G q/11 coupling to activate PLC-dependent increases in Ca 2 þ appeared to be specific to WIN55,212-2 and were not observed with other CB 1 agonists, including CP55,940 and methanandamide. CP55940 produced PTX-sensitive increases in [Ca 2 þ ] i at concentrations Z15 mM, and PTX-sensitive increases in ERK1/2 phosphorylation. Conclusions and implications: This study demonstrates that endogenous CB 1 couples to both G q/11 and G i/o in hTM cells in an agonist-dependent manner. Cannabinoid activation of multiple CB 1 signalling pathways in TM tissue could lead to differential changes in aqueous humour outflow and IOP.

The upregulation of Trx1 in HLE B3 cells under oxidative stress and the presence of Trx1 in the lens suggest that the thioredoxin system may be an effective defense system that protects the lens against oxidative stress.

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