Activation of Piezo1 Increases Na,K-ATPase-Mediated Ion Transport in Mouse Lens

Abstract

Lens ion homeostasis depends on Na,K-ATPase and NKCC1. TRPV4 and TRPV1 channels, which are mechanosensitive, play important roles in mechanisms that regulate the activity of these transporters. Here, we examined another mechanosensitive channel, piezo1, which is also expressed in the lens. The purpose of the study was to examine piezo1 function. Recognizing that activation of TRPV4 and TRPV1 causes changes in lens ion transport mechanisms, we carried out studies to determine whether piezo1 activation changes either Na,K-ATPase-mediated or NKCC1-mediated ion transport. We also examined channel function of piezo1 by measuring calcium entry. Rb uptake was measured as an index of inwardly directed potassium transport by intact mouse lenses. Intracellular calcium concentration was measured in Fura-2 loaded cells by a ratiometric imaging technique. Piezo1 immunolocalization was most evident in the lens epithelium. Potassium (Rb) uptake was increased in intact lenses as well as in cultured lens epithelium exposed to Yoda1, a piezo1 agonist. The majority of Rb uptake is Na,K-ATPase-dependent, although there also is a significant NKCC-dependent component. In the presence of ouabain, an Na,K-ATPase inhibitor, Yoda1 did not increase Rb uptake. In contrast, Yoda1 increased Rb uptake to a similar degree in the presence or absence of 1 µM bumetanide, an NKCC inhibitor. The Rb uptake response to Yoda1 was inhibited by the selective piezo1 antagonist GsMTx4, and also by the nonselective antagonists ruthenium red and gadolinium. In parallel studies, Yoda1 was observed to increase cytoplasmic calcium concentration in cells loaded with Fura-2. The calcium response to Yoda1 was abolished by gadolinium or ruthenium red. The calcium and Rb uptake responses to Yoda1 were absent in calcium-free bathing solution, consistent with calcium entry when piezo1 is activated. Taken together, these findings point to stimulation of Na,K-ATPase, but not NKCC, when piezo1 is activated. Na,K-ATPase is the principal mechanism responsible for ion and water homeostasis in the lens. The functional role of lens piezo1 is a topic for further study.

Mechanotransductive receptor Piezo1 as a promising target in the treatment of fibrosis diseases

“…Piezo1 can also activate the protein kinase pathway and further regulate the activity of multiple cell signaling pathways (Blythe et al, 2019;Chen S. et al, 2022;Wang et al, 2022). In addition, Piezo1 can also regulate the activity of Na, and K-ATPase, further affecting intracellular ion balance and cell membrane stability (Shahidullah et al, 2022;Hirata et al, 2023). Recently, Shahidullah M and his colleagues studied the relationship between Piezo1 and Na, K-ATPase-mediated ion transport in mouse crystals.…”

“…Recently, Shahidullah M and his colleagues studied the relationship between Piezo1 and Na, K-ATPase-mediated ion transport in mouse crystals. They found that after activation of Piezo1, Na, K-ATPase in cells will be affected (Shahidullah et al, 2022).…”

Mechanical Stretch Activates TRPV4 and Hemichannel Responses in the Nonpigmented Ciliary Epithelium

“…Immunolocalization studies were carried out on intact ciliary body (CB) of porcine eye paraffin sections using an approach described earlier [ 34 , 35 ]. Porcine CBs were fixed in 10% neutral buffered formalin (NBF) for 24 h at 2–4 °C.…”

Matrix stiffness affects tumor-associated macrophage functional polarization and its potential in tumor therapy

“…For example, Piezo1 activates integrin-FAK signaling, regulates ECM and reinforces tissue stiffness to promote glioma aggression, while deleting Piezo1 inhibits tumor aggression and prolongs survival [ 153 ]. At present, only a few Piezo1 inhibitors (GsMTx4, ruthenium red, Dooku1, gadolinium) have been reported in preclinical studies and no agents are engaged in clinical trials [ 56 , 154 – 156 ]. The role of Piezo1 inhibitors in tumors is still in the initial stage, and with more in-depth research in the future, the development of drugs targeting Piezo1 may be of great value.…”