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Amritlal Mandal, Mohammad Shahidullah, Nicholas A Delamere; Evidence of Transient Receptor Potential Vanilloid 1 (TRPV1) Channel-mediated Signaling in Lens Epithelium. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3638. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recently we determined that the Transient Receptor Potential Vanilloid 4 ion channel (TRPV4) in the lens epithelium plays crucial signaling role in a pathway that regulates lens Na,K-ATPase-mediated transport activity. Here we show expression of different TRP channel, TRPV1, linked to signaling pathways in the lens epithelium.
Western blot analysis was used to probe expression of TRPV1 protein in porcine lens epithelium as well as ERK1/2 and p38 activation. Cytoplasmic calcium was measured by ratiometric imaging of cultured lens epithelial cells loaded with Fura-2 AM. Results (mean ± SE) were analyzed by t-test or 1-way ANOVA (p <0.05 considered significant).
TRPV1 protein was detected in the lens epithelium, equatorial and cortical fibers as well as in cultured lens epithelium. A transient increase in cytoplasmic calcium (Control 157.69±5.79 nM, vs capsaicin 233.45±21.69 nM, p=0.028, n=3) was observed when cultured lens epithelial cells were exposed to a selective TRPV1 agonist, capsaicin (100 nM). Intact lenses exposed to 100 nM capsaicin responded with a rapid (<2 min), robust transient increase in ERK1/2 phosphorylation (38.92±7.56 fold, p=0.0011, n=3) and p38 MAPK phosphorylation (5.93±0.56 fold, p<0.0001, n=3) in the epithelium. Lenses challenged with hyperosmotic solution (350 mOsm) also showed transient activation of ERK1/2 (8.54±2.76 fold, p=0.012, n=3) and p38 (4.74±0.83 fold, p=0.003, n=3) in the epithelium. Interestingly, the magnitude of ERK1/2 and p38 MAPK activation was significantly reduced by 49.11±3.98% (p=0.005, n=3) and by 34.73±1.24% (p=0.0001, n=3), respectively when lenses were exposed to hyperosmotic solution in the presence of a selective TRPV1 antagonist, A889425 (1.0 µM).
Lens cells express functional TRPV1 channels and their stimulation causes ERK1/2 and p38 MAPK activation in lens epithelium. The evidence points to TRPV1 stimulation in response to hyperosmotic solution, or the shrinkage it causes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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