Stanniocalcin-1 (STC-1), a downstream effector molecule in latanoprost signaling, acts independent of the FP receptor for intraocular pressure reduction

Abstract

Prostaglandin F2 alpha (PGF2α) analogues such as latanoprost are common first-line intraocular pressure (IOP) lowering medications. However, their clinical use is limited in some patient populations due to minimal or no IOP lowering response or side effects. In searching for a more targeted approach for IOP reduction, our lab recently identified Stanniocalcin-1 (STC-1) as a molecule that was required for latanoprost-mediated IOP reduction and also acted as a stand-alone IOP lowering agent. In order to determine whether latanoprost and STC-1 were equivalent and/or additive for IOP reduction, we treated C57BL/6J mice with one or a combination of these agents and measured IOP. Importance of the FP receptor for latanoprost-and STC-1-mediated IOP reduction was examined in C57BL/6J mice utilizing the pharmacologic FP receptor inhibitor AL-8810 as well as FP receptor knockout mice generated in our laboratory. Latanoprost-free acid (LFA) and STC-1 reduced IOP to a similar degree and were non-additive in C57BL/6J mice. As expected, the IOP lowering effects of LFA were abrogated by pharmacologic inhibition of the FP receptor with AL-8810 and in FP receptor knockout mice. In contrast, STC-1 maintained IOP-lowering effects in the presence of AL-8810 and also in FP receptor knockout mice. These results suggest that LFA and STC-1 show equivalent and non-additive IOP reduction in C57BL/6J mice and that unlike LFA, STC-1-mediated IOP reduction occurs independent of the FP receptor.

Transgene expression of Stanniocalcin-1 provides sustained intraocular pressure reduction by increasing outflow facility

“…The ability of latanoprost to lower IOP depends on its binding to the FP receptor and activation of downstream signaling cascades [ 45 ]. We had previously shown that STC-1 was necessary for latanoprost-mediated IOP reduction [ 38 ] and when applied topically as an eye drop, could lower IOP through an FP receptor independent mechanism [ 39 ] To determine whether sustained IOP reduction following ssAAV2-STC-1-FLAG injection also did not require the FP receptor, we performed intracameral injections of ssAAV2-STC-1-FLAG in one eye and ssAAV2-GFP in the fellow eye of FP receptor knockout mice previously generated by our laboratory [ 28 ]. There was no difference in baseline IOP measurements between fellow eyes (16.3 ± 0.8 vs 16.3 ± 0.9 mmHg, n = 6, P = 0.8, Fig 6A ).…”

“…Three-month-old C57BL/6J wild-type or FP receptor knockout mice previously generated by our laboratory [ 39 ] were anesthetized with an intraperitoneal injection of ketamine/xylazine/acepromazine (80/6/1 mg/kg body weight) for intracameral injections. Mice were subsequently placed on a dissecting microscope to visualize the anterior chamber.…”

“…To determine the effects of ssAAV2-STC-1-FLAG on parameters of aqueous outflow, 3-month-old C57BL/6J mice were separately treated with the following: 1) intracameral ssAAV-STC-1-FLAG (n = 5), 2) intracameral ssAAV2-GFP (n = 5), 3) topical recombinant human STC-1-FLAG (n = 4; Biovender Research and Diagnostic Products, Czech Republic) [ 38 , 39 ], 4) topical LFA (n = 5; Cayman Chemical, Ann Arbor, MI), or 5) untreated mice (n = 4). Mice that received topical treatments were treated with once daily topical doses of STC-1 (5 μl of a 0.5 μg/μl solution) or LFA (10 −4 M) for 5 days prior to aqueous outflow experiments.…”

“…STC-1 was one of the most consistently upregulated molecules following LFA treatment, and later studies revealed that unlike wild-type controls, STC-1 knockout mice were unresponsive to IOP reduction when treated with LFA. Furthermore, topical application of recombinant STC-1 protein lowered IOP in normotensive [ 38 , 39 ] and ocular hypertensive [ 40 ] mice. Finally, topically administered STC-1 showed equivalent IOP reduction as topically administered LFA, but STC-1 did not require the FP receptor for IOP reduction [ 39 ].…”

“…Furthermore, topical application of recombinant STC-1 protein lowered IOP in normotensive [ 38 , 39 ] and ocular hypertensive [ 40 ] mice. Finally, topically administered STC-1 showed equivalent IOP reduction as topically administered LFA, but STC-1 did not require the FP receptor for IOP reduction [ 39 ]. Given these unique features, we hypothesized that transgene expression of STC-1 in the anterior chamber of the mouse eye would provide sustained IOP reduction.…”