| First Author | Shahidullah M | Year | 2020 |
| Journal | Am J Physiol Cell Physiol | Volume | 318 |
| Issue | 5 | Pages | C969-C980 |
| PubMed ID | 32293931 | Mgi Jnum | J:292811 |
| Mgi Id | MGI:6450368 | Doi | 10.1152/ajpcell.00391.2019 |
| Citation | Shahidullah M, et al. (2020) TRPV1 activation stimulates NKCC1 and increases hydrostatic pressure in the mouse lens. Am J Physiol Cell Physiol 318(5):C969-C980 |
| abstractText | The porcine lens response to a hyperosmotic stimulus involves an increase in the activity of an ion cotransporter sodium-potassium/two-chloride cotransporter 1 (NKCC1). Recent studies with agonists and antagonists pointed to a mechanism that appears to depend on activation of transient receptor potential vanilloid 1 (TRPV1) ion channels. Here, we compare responses in lenses and cultured lens epithelium obtained from TRPV1(-/-) and wild type (WT) mice. Hydrostatic pressure (HP) in lens surface cells was determined using a manometer-coupled microelectrode approach. The TRPV1 agonist capsaicin (100 nM) caused a transient HP increase in WT lenses that peaked after approximately 30 min and then returned toward baseline. Capsaicin did not cause a detectable change of HP in TRPV1(-/-) lenses. The NKCC inhibitor bumetanide prevented the HP response to capsaicin in WT lenses. Potassium transport was examined by measuring Rb(+) uptake. Capsaicin increased Rb(+) uptake in cultured WT lens epithelial cells but not in TRPV1(-/-) cells. Bumetanide, A889425, and the Akt inhibitor Akti prevented the Rb(+) uptake response to capsaicin. The bumetanide-sensitive (NKCC-dependent) component of Rb(+) uptake more than doubled in response to capsaicin. Capsaicin also elicited rapid (<2 min) NKCC1 phosphorylation in WT but not TRPV1(-/-) cells. HP recovery was shown to be absent in TRPV1(-/-) lenses exposed to hyperosmotic solution. Bumetanide and Akti prevented HP recovery in WT lenses exposed to hyperosmotic solution. Taken together, responses to capsaicin and hyperosmotic solution point to a functional role for TRPV1 channels in mouse lens. Lack of NKCC1 phosphorylation and Rb(+) uptake responses in TRPV1(-/-) mouse epithelium reinforces the notion that a hyperosmotic challenge causes TRPV1-dependent NKCC1 activation. The results are consistent with a role for the TRPV1-activated signaling pathway leading to NKCC1 stimulation in lens osmotic homeostasis. |
