FOXC1 Regulates Expression of Prostaglandin Receptors Leading to an Attenuated Response to Latanoprost

Abstract

PURPOSE. This study examines the effect of FOXC1 on the prostaglandin pathway in order to explore FOXC1's role in the prostaglandin-resistant glaucoma phenotype commonly seen in Axenfeld-Rieger syndrome.METHODS. Binding and transcriptional activity of FOXC1 to the gene coding for the EP3 prostaglandin receptor (PTGER3) were evaluated through ChIP-qPCR and luciferase-based assays. Immortalized trabecular meshwork cells (TM1) and HeLa cells had FOXC1 mRNA reduced via siRNA interference. qPCR and Western blot experiments were conducted to examine the changes in prostaglandin receptor expression brought about by lowered FOXC1. TM1 cells were then treated with 10 lM latanoprost acid and/or an siRNA for FOXC1. The expression of fibronectin and matrix metalloproteinase 9 were evaluated via qPCR in each treatment condition.RESULTS. ChIP-qPCR and luciferase experiments confirmed that FOXC1 binds to and activates transcription of the EP3 gene prostaglandin receptor. qPCR and Western experiments in HeLa and TM1 cells showed that FOXC1 siRNA knockdown results in significantly lowered EP3 levels (protein and RNA). In addition, RNA levels of the other prostaglandin receptor genes EP1 (PTGER1), EP2 (PTGER2), EP4 (PTGER4), and FP (PTGFR) were altered when FOXC1 was knocked down in TM1 and HeLa cells. Analysis of fibronectin expression in TM1 cells after treatment with 10 lM latanoprost acid showed a statistically significant increase in expression; this increase was abrogated by cotreatment with a siRNA for FOXC1. CONCLUSIONS.We show the abrogation of latanoprost signalling when FOXC1 is knocked down via siRNA in a trabecular meshwork cell line. We propose that the lower levels of active FOXC1 in Axenfeld-Rieger syndrome patients with glaucoma account for the lack of response to prostaglandin-based medications.Keywords: prostaglandins, Glaucoma, latanoprost, Axenfeld-Rieger, FOXC1 G laucoma is a leading cause of blindness in developed nations and is caused by the death of retinal ganglion cells within the retina. It has been predicted that 79.6 million people will be affected by glaucoma by the year 2020, 10% of whom will be bilaterally blind.1 Risk factors for the development of glaucoma include corticosteroid use, smoking, age, and ethnicity.2 However, the major risk factor for glaucoma is an increase in intraocular pressure (IOP). Generation and maintenance of IOP occurs through aqueous humor (AH) flow. Outflow of AH occurs through two outflow facilities, conventional and uveoscleral, generating this IOP, which maintains the globular structure of the eye. As increased IOP is the major risk factor for developing glaucoma, it is also the primary target for medical intervention. To manage IOP, surgical or pharmaceutical interventions are employed to either increase AH outflow or to decrease the amount of AH produced. The most common treatment for glaucoma is the administration of prostaglandinbased medications to lower IOP through increasing flow via the uveoscleral outflow facility. This outflow occurs through the supraciliary...

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

“…It remains to be seen whether the 20% of patients with reduced or no response to topical PGF2α that has been associated with SNPs in the FP receptor [7][8][9][10][11][12] may have benefit from topical STC-1. Additionally, it has been proposed that the poor IOPlowering with latanoprost treatment observed in patients with Axenfeld-Rieger malformation is due to abnormal signaling in the FOXC1-FP receptor signaling axis [32,33]. Therefore patients with variants in FP receptor signaling or the FP receptor itself may benefit from a therapy such as STC-1.…”