ATP-sensitive potassium (KATP) channel openers diazoxide and nicorandil lower intraocular pressure by activating the Erk1/2 signaling pathway

Abstract

Elevated intraocular pressure is the most prevalent and only treatable risk factor for glaucoma, a degenerative disease of the optic nerve. While treatment options to slow disease progression are available, all current therapeutic and surgical treatments have unwanted side effects or limited efficacy, resulting in the need to identify new options. Previous reports from our laboratory have established a novel ocular hypotensive effect of ATP-sensitive potassium channel (KATP) openers including diazoxide (DZ) and nicorandil (NCD). In the current study, we evaluated the role of Erk1/2 signaling pathway in KATP channel opener mediated reduction of intraocular pressure (IOP). Western blot analysis of DZ and NCD treated primary normal trabecular meshwork (NTM) cells, human TM (isolated from perfusion cultures of human anterior segments) and mouse eyes showed increased phosphorylation of Erk1/2 when compared to vehicle treated controls. DZ and NCD mediated pressure reduction (p<0.02) in human anterior segments (n = 7 for DZ, n = 4 for NCD) was abrogated by U0126 (DZ + U0126: -9.7 ± 11.5%, p = 0.11; NCD + U0126: -0.1 ± 11.5%, p = 1.0). In contrast, U0126 had no effect on latanoprostfree acid-induced pressure reduction (-52.5 ± 6.8%, n = 4, p = 0.001). In mice, DZ and NCD reduced IOP (DZ, 14.9 ± 3.8%, NCD, 16.9 ± 2.5%, n = 10, p<0.001), but the pressure reduction was inhibited by U0126 (DZ + U0126, 0.7 ± 3.0%; NCD + U0126, 0.9 ± 2.2%, n = 10, p>0.1). Histologic evaluation of transmission electron micrographs from DZ + U0126 and NCD + U0126 treated eyes revealed no observable morphological changes in the ultrastructure of the conventional outflow pathway. Taken together, the results indicate that the Erk1/2 pathway is necessary for IOP reduction by KATP channel openers DZ and NCD.

Effect of Cromakalim Prodrug 1 (CKLP1) on Aqueous Humor Dynamics and Feasibility of Combination Therapy With Existing Ocular Hypotensive Agents

“…Work from our laboratory indicates that the Erk1/2 signaling pathway is activated in the cells of the conventional outflow pathway following treatment with K ATP channel openers. 83 However, it remains to be seen if similar pathways are involved in episcleral venous cells in response to treatment with CKLP1.…”

Effect of Nicorandil Administration on Preventing Contrast-Induced Nephropathy: A Meta-Analysis

“…Nicorandil is a hybrid antianginal and potassium (K) channel (K-ATP channel) opener 6 that reduces myocardial injury and improves coronary hemodynamic parameters. 7 Currently, the European Society of Cardiology guidelines recommend the use of nicorandil for the management of stable coronary artery disease. 8 There are conflicting results as to whether nicorandil can prevent CIN.…”

Isolation and characterization of novel primary cells from the human distal outflow pathway

“…After analyzing total protein content using Bradford’s assay, cell lysates were mixed with 5X reducing sample buffer (Thermo Scientific, Waltham, MA) containing 15% β-mercaptoethanol (Sigma-Aldrich). Equal amounts of total protein (15–20 µg) was loaded in each well of a 4–15% gradient SDS-PAGE gel (Bio-Rad, Hercules, CA), transferred to polyvinylidene difluoride membranes (Millipore, Billerica, MA) and blocked in 2% non-fat dried milk, as described previously 43 , 47 . Once protein transfer was complete, blots were probed with primary antibodies against rabbit anti-human polyclonal myocilin (developed in our laboratory against the peptide sequence ARPQETQEGLQRELGTLRRERDQLC) 48 overnight.…”