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Jing Yuan, Fan Zhang, Hua Yang, Peter Reinach; CB1 Receptor Activation Elicits Human Corneal Epithelial Layer Barrier Function Restoration During Exposure To A Hypertonic Stress. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4393.
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© ARVO (1962-2015); The Authors (2016-present)
The effects of CB1 stimulation on (HCEC) tight junctional permeability have not been determined. We characterized the effects of CB1 activation on translayer electrical resistance during exposure to a hypertonic stress described in some types of dry eye disease.
SV40-immortalized HCEC were seeded on 0.4 µm pore size Transwell® inserts. They were air lifted and reached confluence after about 5 days. Transepithelial layer electrical resistance (TEER) assessed tight junctional integrity.
After 5 h exposure to a 300 mOsm isotonic medium, TEER slightly declined to reach 200 ± 3.7 (n=3) ohm*cm2 and remained stable during the subsequent 15 h. On the other hand, replacement at 5 h with a 375 mOsm medium caused TEER to initially fall by 31% with partial restoration to a level at 20 h that was still 16 % below the isotonic control. However, inclusion of the mixed CB1/TRPV1 agonist, anandamide (AEA), at concentrations ranging from 1 to 10 µM, in the 375 mOsm medium, hastened complete TEER restoration to its isotonic control level. It occurred as early as 5 h after imposition of this stress. Under isotonic conditions, 1 µM AEA blocked the initial 31% decline in the baseline TEER. In 375 mOsm medium, the TEER decreased from 20% to 25% despite the presence of either 10 or 20 µM AEA if HCEC were instead preexposed for 30 min to either 5µM or 10 µM AM 251, a selective CB1 antagonist. Furthermore, in isotonic medium, AM251 prevented TEER recovery from its 5 h suppressed level to its baseline levels. The TEER in isotonic medium was unchanged with either 5 or 10 µM AM251.
During exposure of HCEC to a hypertonic stress simulating tear film osmolarity in some types of dry eye disease, TEER initially declined and failed to fully recover with time. However, CB1 activation by AEA instead caused the TEER to fully recover more rapidly to its isotonic level. These AEA effects were solely due to CB1 activation since AM 251 fully inhibited both of them. Taken together, endocannabinoids may have therapeutic potential in reducing declines in epithelial barrier function occurring in some types of dry eye disease.
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