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Kovács I, Luna C, Quirce S, Mizerska K, Callejo G, Riestra A, Fernández-Sánchez L, Meseguer VM, Cuenca N, Merayo-Lloves J, Acosta MC, Gasull X, Belmonte C, Gallar J. Abnormal activity of corneal cold thermoreceptors underlies the unpleasant sensations in dry eye disease. Pain 2016; 157:399-417. [PMID: 26675826 PMCID: PMC4733818 DOI: 10.1097/j.pain.0000000000000455] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/09/2015] [Accepted: 10/28/2015] [Indexed: 12/23/2022]
Abstract
Dry eye disease (DED) affects >10% of the population worldwide, and it provokes an unpleasant sensation of ocular dryness, whose underlying neural mechanisms remain unknown. Removal of the main lachrymal gland in guinea pigs caused long-term reduction of basal tearing accompanied by changes in the architecture and density of subbasal corneal nerves and epithelial terminals. After 4 weeks, ongoing impulse activity and responses to cooling of corneal cold thermoreceptor endings were enhanced. Menthol (200 μM) first excited and then inactivated this augmented spontaneous and cold-evoked activity. Comparatively, corneal polymodal nociceptors of tear-deficient eyes remained silent and exhibited only a mild sensitization to acidic stimulation, whereas mechanonociceptors were not affected. Dryness-induced changes in peripheral cold thermoreceptor responsiveness developed in parallel with a progressive excitability enhancement of corneal cold trigeminal ganglion neurons, primarily due to an increase of sodium currents and a decrease of potassium currents. In corneal polymodal nociceptor neurons, sodium currents were enhanced whereas potassium currents remain unaltered. In healthy humans, exposure of the eye surface to menthol vapors or to cold air currents evoked unpleasant sensations accompanied by increased blinking frequency that we attributed to cold thermoreceptor stimulation. Notably, stimulation with menthol reduced the ongoing background discomfort of patients with DED, conceivably due to use-dependent inactivation of cold thermoreceptors. Together, these data indicate that cold thermoreceptors contribute importantly to the detection and signaling of ocular surface wetness, and develop under chronic eye dryness conditions an injury-evoked neuropathic firing that seems to underlie the unpleasant sensations experienced by patients with DED.
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Affiliation(s)
- Illés Kovács
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
- Department of Ophthalmology, Semmelweis University, Budapest, Hungary
| | - Carolina Luna
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
| | - Susana Quirce
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
| | - Kamila Mizerska
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
| | - Gerard Callejo
- Laboratory of Neurophysiology, Department of Biomedicine, School of Medicine, University of Barcelona, Barcelona, Spain
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Ana Riestra
- Instituto Universitario Fernández-Vega, Universidad de Oviedo and Fundación de Investigación Oftalmológica, Oviedo, Spain
| | - Laura Fernández-Sánchez
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, San Vicente del Raspeig, Spain
| | - Victor M. Meseguer
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
| | - Nicolás Cuenca
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, San Vicente del Raspeig, Spain
| | - Jesús Merayo-Lloves
- Instituto Universitario Fernández-Vega, Universidad de Oviedo and Fundación de Investigación Oftalmológica, Oviedo, Spain
| | - M. Carmen Acosta
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
| | - Xavier Gasull
- Laboratory of Neurophysiology, Department of Biomedicine, School of Medicine, University of Barcelona, Barcelona, Spain
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Carlos Belmonte
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
- Instituto Universitario Fernández-Vega, Universidad de Oviedo and Fundación de Investigación Oftalmológica, Oviedo, Spain
| | - Juana Gallar
- Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, San Juan de Alicante, Spain
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