Mechano- and Glucocorticoid-Sensitive TREK-1 Channels Regulate Conventional Outflow and Intraocular Pressure

The purpose of this study was twofold: to determine the molecular link between corticosteroid exposure and mechanosensation and to establish the role of mechanosensitive TWIK-related potassium channel-1 (TREK-1) in the regulation of aqueous humor outflow and corticosteroid-induced ocular hypertension (OHT).

Real-time PCR was used to determine the corticosteroid dexamethasone (DEX) dependence of expression of tandem-pore potassium (K2P), transient receptor potential vanilloid (TRPV), Piezo channel, extracellular matrix (ECM), and fibrotic marker genes in mouse trabecular meshwork (mTM) cells. Immunohistochemistry was employed to assess TREK-1 localization, iPerfusion to determine the TREK-1 dependence of conventional outflow, and tonometry to track intraocular pressure (IOP) in mouse eyes. Telemetry additionally tested TREK-1 dependence of OHT in rat. Steroid-induced transcriptional suppression of mTM Kcnk2 was validated by whole-cell recording in primary human trabecular meshwork (TM) cells.

The tandem pore K+ channel transcriptome in mTM cells was dominated by Trek-1 (Kcnk2) mRNA; with residual levels of Traak and Thik-2 transcripts; and low levels of Trek-2, Twik3, and Task1 expression. DEX upregulated Fsp1 and suppressed Kcnk2 expression without affecting Trpv4, Piezo1, or Trpc1 mRNA content. The TREK-1 agonist ML-402 doubled outflow facility in mouse eyes and reduced IOP in the mouse model of DEX-induced OHT and in rat eyes with spontaneously elevated IOP. Chronic DEX exposure depolarized human primary TM (pTM) cells and reduced the amplitude of the ML-402-evoked current.

Ocular overexposure to corticosteroids may compromise IOP homeostasis by impairing TM expression and function of TREK-1. Pharmacological activation of TREK-1 facilitates conventional outflow and could help lower IOP in eyes with steroid-induced ocular hypertension.