Carbonic Anhydrase Inhibitor Modulation of Intraocular Pressure Is Independent of Soluble Adenylyl Cyclase

Abstract

Purpose: We investigated whether a clinically used carbonic anhydrase inhibitor (CAIs) can modulate intraocular pressure (IOP) through soluble adenylyl cyclase (sAC) signaling. Methods: IOP was measured 1 h after topical treatment with brinzolamide, a topically applied and clinically used CAIs, using direct cannulation of the anterior chamber in sAC knockout (KO) mice or C57BL/6J mice in the presence or absence of the sAC inhibitor (TDI-10229). Results: Mice treated with the sAC inhibitor TDI-10229 had elevated IOP. CAIs treatment significantly decreased increased intraocular pressure (IOP) in wild-type, sAC KO mice, as well as TDI-10229-treated mice. Conclusions: Inhibiting carbonic anhydrase reduces IOP independently from sAC in mice. Our studies suggest that the signaling cascade by which brinzolamide regulates IOP does not involve sAC.

Keywords: IOP; cAMP; carbonic anhydrase; intraocular pressure; pharmacological inhibitors; soluble adenylyl cyclase.

FIG. 1.

The concentration of cAMP in sAC-overexpressing 4-4 cells. Cellular accumulation of cAMP was measured in cells pretreated with inhibitors for 10 min followed by treatment with 500 μM IBMX and 30 μM DP (IBMX+DP) for 10 min, mean ± SEM (n = 3). DP, dipyridamole; cAMP, cyclic 3′, 5′ adenosine monophosphate; sAC, soluble adenylyl cyclase; SEM, standard error of the mean.

FIG. 2.

The concentration-response of TDI-10229, a potent and selective sAC inhibitor, acetazolamide (green) and brinzolamide (orange) on purified recombinant human sAC protein in the presence of 1 mM ATP, 2 mM Ca²⁺, 4 mM Mg²⁺, and 40 mM HCO₃⁻, normalized to the respective DMSO-treated control; mean ± SEM (n = 3). ATP, adenosine triphosphate; DMSO, dimethylsulfoxide.

FIG. 3.

Brinzolamide decreases IOP in both WT and sAC KO mice. IOP was measured in WT (sAC^+/+, C57BL/6J) or KO (sAC^−/−) mice after 1 h treatment with topical brinzolamide (1 drop (15 μL) of 10 mg/mL). The line indicates mean. n = 101 sAC^+/+, n = 26 sAC^+/+ with brinzolamide, n = 27 sAC^−/−, n = 12 sAC^−/− with brinzolamide. *P < 0.05, **P < 0.01. IOP, increased intraocular pressure; KO, knockout; WT, wild-type.

FIG. 4.

Administration of brinzolamide decreases IOP in both vehicle and TDI-10229-treated wild-type mice (sAC^+/+, C57BL/6J). IOP was measured in mice IP injected with vehicle (DMSO) or TDI-10229 (20 mg/kg) and treated topically with vehicle or brinzolamide [1 drop (15 μL) of 10 mg/mL]. The line indicates mean. n = 52 sAC^+/+ with DMSO, n = 30 sAC^+/+ with DMSO + brinzolamide, n = 29 TDI-10229 sAC^+/+, n = 15 sAC^+/+ with TDI-10229 + brinzolamide. **P < 0.01, ***P < 0.001, and ****P < 0.0001. IP, intraperitoneally.