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TRPV1, TRPA1, and TRPM8 are expressed in axon terminals in the cornea: TRPV1 axons contain CGRP and secretogranin II; TRPA1 axons contain secretogranin 3.
Mol Vis. 2020; 26:576-587.MV

Abstract

Purpose

The cornea is highly enriched in sensory neurons expressing the thermal TRP channels TRPV1, TRPA1, and TRPM8, and is an accessible tissue for study and experimental manipulation. The aim of this work was to provide a concise characterization of the expression patterns of various TRP channels and vesicular proteins in the mammalian cornea.

Methods

Immunohistochemistry (IHC) was performed using wholemount and cryostat tissue preparations of mouse and monkey corneas. The expression patterns of TRPV1 and TRPA1 were determined using specific antisera, and further colocalization was performed with antibodies directed against calcitonin-related gene protein (CGRP), neurofilament protein NF200, and the secretogranins ScgII and SCG3. The expression of TRPM8 was determined using corneas from mice expressing EGFP under the direction of a TRPM8 promoter (TRPM8EGFP mice). Laser scanning confocal microscopy and image analysis were performed.

Results

In the mouse cornea, TRPV1 and TRPM8 were expressed in distinct populations of small diameter C fibers extending to the corneal surface and ending either as simple or ramifying terminals, or in the case of TRPM8, as complex terminals. TRPA1 was expressed in large-diameter NF200-positive Aδ axons. TRPV1 and TRPA1 appeared to localize to separate intracellular vesicular structures and were primarily found in axons containing components of large dense vesicles with TRPV1 colocalizing with CGRP and ScgII, and TRPA1 colocalizing with SCG3. Monkey corneas showed similar colocalization of CGRP and TRPV1 on small-diameter axons extending to the epithelial surface.

Conclusions

The mouse cornea is abundant in sensory neurons expressing TRPV1, TRPM8, and TRPA1, and provides an accessible tissue source for implementing a live tissue preparation useful for further exploration of the molecular mechanisms of hyperalgesia. This study showed that surprisingly, these TRP channels localize to separate neurons in the mouse cornea and likely have unique physiological functions. The similar TRPV1 expression pattern we observed in the mouse and monkey corneas suggests that mice provide a reasonable initial model for understanding the role of these ion channels in higher mammalian corneal physiology.

Authors+Show Affiliations

Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA.Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA.Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA.Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA.Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle, WA.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

32863706

Citation

Schecterson, Leslayann C., et al. "TRPV1, TRPA1, and TRPM8 Are Expressed in Axon Terminals in the Cornea: TRPV1 Axons Contain CGRP and Secretogranin II; TRPA1 Axons Contain Secretogranin 3." Molecular Vision, vol. 26, 2020, pp. 576-587.
Schecterson LC, Pazevic AA, Yang R, et al. TRPV1, TRPA1, and TRPM8 are expressed in axon terminals in the cornea: TRPV1 axons contain CGRP and secretogranin II; TRPA1 axons contain secretogranin 3. Mol Vis. 2020;26:576-587.
Schecterson, L. C., Pazevic, A. A., Yang, R., Matulef, K., & Gordon, S. E. (2020). TRPV1, TRPA1, and TRPM8 are expressed in axon terminals in the cornea: TRPV1 axons contain CGRP and secretogranin II; TRPA1 axons contain secretogranin 3. Molecular Vision, 26, 576-587.
Schecterson LC, et al. TRPV1, TRPA1, and TRPM8 Are Expressed in Axon Terminals in the Cornea: TRPV1 Axons Contain CGRP and Secretogranin II; TRPA1 Axons Contain Secretogranin 3. Mol Vis. 2020;26:576-587. PubMed PMID: 32863706.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - TRPV1, TRPA1, and TRPM8 are expressed in axon terminals in the cornea: TRPV1 axons contain CGRP and secretogranin II; TRPA1 axons contain secretogranin 3. AU - Schecterson,Leslayann C, AU - Pazevic,Alexander A, AU - Yang,Ruian, AU - Matulef,Kimberly, AU - Gordon,Sharona E, Y1 - 2020/08/13/ PY - 2016/03/28/received PY - 2020/08/11/accepted PY - 2020/9/1/entrez PY - 2020/8/31/pubmed PY - 2021/7/3/medline SP - 576 EP - 587 JF - Molecular vision JO - Mol Vis VL - 26 N2 - Purpose: The cornea is highly enriched in sensory neurons expressing the thermal TRP channels TRPV1, TRPA1, and TRPM8, and is an accessible tissue for study and experimental manipulation. The aim of this work was to provide a concise characterization of the expression patterns of various TRP channels and vesicular proteins in the mammalian cornea. Methods: Immunohistochemistry (IHC) was performed using wholemount and cryostat tissue preparations of mouse and monkey corneas. The expression patterns of TRPV1 and TRPA1 were determined using specific antisera, and further colocalization was performed with antibodies directed against calcitonin-related gene protein (CGRP), neurofilament protein NF200, and the secretogranins ScgII and SCG3. The expression of TRPM8 was determined using corneas from mice expressing EGFP under the direction of a TRPM8 promoter (TRPM8EGFP mice). Laser scanning confocal microscopy and image analysis were performed. Results: In the mouse cornea, TRPV1 and TRPM8 were expressed in distinct populations of small diameter C fibers extending to the corneal surface and ending either as simple or ramifying terminals, or in the case of TRPM8, as complex terminals. TRPA1 was expressed in large-diameter NF200-positive Aδ axons. TRPV1 and TRPA1 appeared to localize to separate intracellular vesicular structures and were primarily found in axons containing components of large dense vesicles with TRPV1 colocalizing with CGRP and ScgII, and TRPA1 colocalizing with SCG3. Monkey corneas showed similar colocalization of CGRP and TRPV1 on small-diameter axons extending to the epithelial surface. Conclusions: The mouse cornea is abundant in sensory neurons expressing TRPV1, TRPM8, and TRPA1, and provides an accessible tissue source for implementing a live tissue preparation useful for further exploration of the molecular mechanisms of hyperalgesia. This study showed that surprisingly, these TRP channels localize to separate neurons in the mouse cornea and likely have unique physiological functions. The similar TRPV1 expression pattern we observed in the mouse and monkey corneas suggests that mice provide a reasonable initial model for understanding the role of these ion channels in higher mammalian corneal physiology. SN - 1090-0535 UR - https://www.unboundmedicine.com/medline/citation/32863706/TRPV1_TRPA1_and_TRPM8_are_expressed_in_axon_terminals_in_the_cornea:_TRPV1_axons_contain_CGRP_and_secretogranin_II L2 - http://www.molvis.org/molvis/v26/576/ DB - PRIME DP - Unbound Medicine ER -