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York N, Halbach P, Chiu MA, Bird IM, Pillers DAM, Pattnaik BR. Oxytocin (OXT)-stimulated inhibition of Kir7.1 activity is through PIP 2-dependent Ca 2+ response of the oxytocin receptor in the retinal pigment epithelium in vitro. Cell Signal 2017; 37:93-102. [PMID: 28603013 DOI: 10.1016/j.cellsig.2017.06.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 05/28/2017] [Accepted: 06/05/2017] [Indexed: 01/26/2023]
Abstract
Oxytocin (OXT) is a neuropeptide that activates the oxytocin receptor (OXTR), a rhodopsin family G-protein coupled receptor. Our localization of OXTR to the retinal pigment epithelium (RPE), in close proximity to OXT in the adjacent photoreceptor neurons, leads us to propose that OXT plays an important role in RPE-retinal communication. An increase of RPE [Ca2+]i in response to OXT stimulation implies that the RPE may utilize oxytocinergic signaling as a mechanism by which it accomplishes some of its many roles. In this study, we used an established human RPE cell line, a HEK293 heterologous OXTR expression system, and pharmacological inhibitors of Ca2+ signaling to demonstrate that OXTR utilizes capacitative Ca2+ entry (CCE) mechanisms to sustain an increase in cytoplasmic Ca2+. These findings demonstrate how multiple functional outcomes of OXT-OXTR signaling could be integrated via a single pathway. In addition, the activated OXTR was able to inhibit the Kir7.1 channel, an important mediator of sub retinal waste transport and K+ homeostasis.
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Affiliation(s)
- Nathaniel York
- Endocrinology-Reproductive Physiology Program, The University of Wisconsin, Madison, WI 53715, United States; Division of Neonatology& Newborn Nursery, The University of Wisconsin, Madison, WI 53715, United States; Departments of Pediatrics, The University of Wisconsin, Madison, WI 53715, United States; The McPherson Eye Research Institute, The University of Wisconsin, Madison, WI 53715, United States
| | - Patrick Halbach
- Endocrinology-Reproductive Physiology Program, The University of Wisconsin, Madison, WI 53715, United States; Division of Neonatology& Newborn Nursery, The University of Wisconsin, Madison, WI 53715, United States; Departments of Pediatrics, The University of Wisconsin, Madison, WI 53715, United States; The McPherson Eye Research Institute, The University of Wisconsin, Madison, WI 53715, United States
| | - Michelle A Chiu
- Division of Neonatology& Newborn Nursery, The University of Wisconsin, Madison, WI 53715, United States; Departments of Pediatrics, The University of Wisconsin, Madison, WI 53715, United States; The McPherson Eye Research Institute, The University of Wisconsin, Madison, WI 53715, United States
| | - Ian M Bird
- Endocrinology-Reproductive Physiology Program, The University of Wisconsin, Madison, WI 53715, United States; Obstetrics & Gynecology, The University of Wisconsin, Madison, WI 53715, United States
| | - De-Ann M Pillers
- Division of Neonatology& Newborn Nursery, The University of Wisconsin, Madison, WI 53715, United States; Departments of Pediatrics, The University of Wisconsin, Madison, WI 53715, United States; Medical Genetics, The University of Wisconsin, Madison, WI 53715, United States; The McPherson Eye Research Institute, The University of Wisconsin, Madison, WI 53715, United States
| | - Bikash R Pattnaik
- Endocrinology-Reproductive Physiology Program, The University of Wisconsin, Madison, WI 53715, United States; Division of Neonatology& Newborn Nursery, The University of Wisconsin, Madison, WI 53715, United States; Departments of Pediatrics, The University of Wisconsin, Madison, WI 53715, United States; Ophthalmology &Visual Sciences, The University of Wisconsin, Madison, WI 53715, United States; The McPherson Eye Research Institute, The University of Wisconsin, Madison, WI 53715, United States.
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Halbach P, Pillers DAM, York N, Asuma MP, Chiu MA, Luo W, Tokarz S, Bird IM, Pattnaik BR. Oxytocin expression and function in the posterior retina: a novel signaling pathway. Invest Ophthalmol Vis Sci 2015; 56:751-60. [PMID: 25593022 DOI: 10.1167/iovs.14-15646] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Oxytocin (OXT) is recognized as an ubiquitously acting nonapeptide hormone that is involved in processes ranging from parturition to neural development. Its effects are mediated by cell signaling that occurs as a result of oxytocin receptor (OXTR) activation. We sought to determine whether the OXT-OXTR signaling pathway is also expressed within the retina. METHODS Immunohistochemistry using cell-specific markers was used to localize OXT within the rhesus retina. Reverse transcriptase PCR and immunohistochemistry were used to assess the expression of OXTR in both human and rhesus retina. Single-cell RT-PCR and Western blot analyses were used to determine the expression of OXTR in cultured human fetal RPE (hfRPE) cells. Human fetal RPE cells loaded with FURA-2 AM were studied by ratiometric Ca(2+) imaging to assess transient mobilization of intracellular Ca(2+) ([Ca(2+)]i). RESULTS Oxytocin was expressed in the cone photoreceptor extracellular matrix of the rhesus retina. Oxytocin mRNA and protein were expressed in the human and rhesus RPE. Oxytocin mRNA and protein expression were observed in cultured hfRPE cells, and exposure of these cells to 100 nM OXT induced a transient 79 ± 1.5 nM increase of [Ca(2+)]i. CONCLUSIONS Oxytocin and OXTR are present in the posterior retina, and OXT induces an increase in hfRPE [Ca(2+)]i. These results suggest that the OXT-OXTR signaling pathway is active in the retina. We propose that OXT activation of the OXTR occurs in the posterior retina and that this may serve as a paracrine signaling pathway that contributes to communication between the cone photoreceptor and the RPE.
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Affiliation(s)
- Patrick Halbach
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States The Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin, United States
| | - De-Ann M Pillers
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, United States
| | - Nathaniel York
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States The Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin, United States
| | - Matti P Asuma
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States
| | - Michelle A Chiu
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States
| | - Wenxiang Luo
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States
| | - Sara Tokarz
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States
| | - Ian M Bird
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States The Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin, United States Departments of Obstetrics/Gynecology, University of Wisconsin, Madison, Wisconsin, United States
| | - Bikash R Pattnaik
- Division of Neonatology, Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, United States Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, United States
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