Activation of TRPV1 channels leads to stimulation of NKCC1 cotransport in the lens

• Published in: American Journal of Physiology: Cell Physiology 2018-12, Vol.315 (6), p.C793-C802
• Main Authors: Shahidullah, Mohammad, Mandal, Amritlal, Delamere, Nicholas A
• Format: Article
• Language: English
• Subjects: Animals; Bumetanide; Bumetanide - antagonists & inhibitors; Bumetanide - pharmacology; Butadienes - pharmacology; Calcium signalling; Capsaicin; Capsaicin - pharmacology; Capsaicin receptors; Chloride transport; Enzyme inhibitors; Epithelium; Epithelium - drug effects; Epithelium - metabolism; Extracellular signal-regulated kinase; Giant Cells - drug effects; Giant Cells - metabolism; Homeostasis; Humans; Imidazoles - pharmacology; Inhibitor drugs; Ion channels; Ions; Kinases; Lens, Crystalline - drug effects; Lens, Crystalline - metabolism; Lysine; MAP Kinase Signaling System - drug effects; Nitriles - pharmacology; Osmotic Pressure; Phosphorylation; Phosphorylation - drug effects; Protein kinase C; Pyrrolidines - pharmacology; Rubidium; Solute Carrier Family 12, Member 2 - genetics; Swine; Transient receptor potential proteins; TRPV Cation Channels - genetics; Water content
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00252.2018

Lens ion homeostasis is crucial in maintaining water content and, in turn, refractive index and transparency of the multicellular syncytium-like structure. New information is emerging on the regulation of ion transport in the lens by mechanisms that rely on transient receptor potential vanilloid (TRPV) ion channels. We found recently that TRPV1 activation leads to Ca /PKC-dependent ERK1/2 signaling. Here, we show that the TRPV1 agonist capsaicin (100 nM) and hyperosmotic solution (350 vs. 300 mosM) each caused an increase of bumetanide-inhibitable Rb uptake by intact porcine lenses and Na-K-2Cl cotransporter 1 (NKCC1) phosphorylation in the lens epithelium. The TRPV1 antagonist A889425 (1 µM) abolished the increases of Rb uptake and NKCC1 phosphorylation in response to hyperosmotic solution. Exposing lenses to hyperosmotic solution in the presence of MEK/ERK inhibitor U0126 (10 µM) or the with-no-lysine kinase (WNK) inhibitor WNK463 (1 µM) also prevented NKCC1 phosphorylation and the Rb uptake responses to hyperosmotic solution. WNK463 did not prevent the increase in ERK1/2 phosphorylation that occurs in response to capsaicin or hyperosmotic solution, suggesting that ERK1/2 activation occurs before WNK activation in the sequence of signaling events. Taken together, the evidence indicates that activation of TRPV1 is a critical early step in a signaling mechanism that responds to a hyperosmotic stimulus, possibly lens shrinkage. By activating ERK1/2 and WNK, TRPV1 activation leads to NKCC1 phosphorylation and stimulation of NKCC1-mediated ion transport.