25 research outputs found
Estudio del efecto protector de la melatonina en el cristalino, análisis de su acción hipotensora y modulación de su secreción usando un filtro amarillo
Get PDFTesis inédita de la Universidad Complutense de Madrid, Facultad de Óptica y Optometría, leída el 21-04-2022El cristalino es una lente biconvexa, avascular y transparente situada en el polo anterior del ojo por detrás del iris. Su función principal es enfocar la luz a la retina. La opacificación o pérdida de transparencia del cristalino genera cataratas, la principal causa de ceguera reversible en el mundo, siendo el estrés oxidativo un mecanismo patológico clave en su desarrollo. La melatonina es una neurohormona secretada principalmente por la glándula pineal, también es producida a nivel ocular en estructuras como el cuerpo ciliar, la retina y el cristalino. La síntesis y liberación de melatonina sigue un ritmo circadiano, siendo suprimida su liberación mediante la luz por la activación del fotopigmento melanopsina. Recientes estudios han evidenciado la presencia de este fotopigmento en el cristalino y como su activación mediante luz azul disminuye la expresión de enzimas biosintéticas de la melatonina así como su producción, sugiriendo que la modificación de la luz, por ejemplo mediante el uso de filtros, podría regular la liberación de melatonina ocular. La melatonina actúa como agente antioxidante, adquiriendo así un potencial anticataratogénico. Se desconoce si los niveles de melatonina ocular presentan alguna alteración en la patología de cataratas, repercutiendo en la progresión de la enfermedad...The lens is an avascular and transparent structure located in the anterior pole of the eyeball behind the iris. Its main function is to focus light on the retina. The opacification or loss of transparency of the lens generates cataracts, which are the main cause of reversible blindness in the world. Oxidative stress is a key pathological mechanism in cataract progress.Melatonin is a neurohormone mainly secreted by the pineal gland and also produced at eye structures such as the ciliary body, the retina and the lens. The synthesis and release of melatonin follows a circadian rhythm. Melatonin release is suppressed by the activation of the photopigment melanopsin by light. Recent studies have shown the presence of melanopsin in the lens and how its activation by blue light exposure decreases the expression of enzymes involved in melatonin biosynthesis as well as neurohormone production, suggesting that light modulation, for example with filters, could regulate melatonin in the eye. Among the functions of melatonin in the eye highlights its possible role as an antioxidant agent. Taking into account the relationship of cataracts with oxidative stress, the anticataratogenic potential of melatonin has been suggested. It is unknown whether ocular melatonin levels are altered in cataracts, which could affect the disease progression...Fac. de Óptica y OptometríaTRUEunpu
Mecanismos de regulación de la síntesis de la melatonina para el control de la presión intraocular
Get PDFTesis de la Universidad Complutense de Madrid, Facultad de Óptica y Optometría, Departamento de Bioquímica y Biología Molecular IV, leída el 10/11/2017Ocular hypertension, although not considered a disease itself, it leads to glaucoma which eventually cause irreversible vision loss. Consequently, glaucoma therapeutic approach is to lower intraocular pressure (IOP). Nonetheless, anti-glaucoma drugs come often with several side effects that can lead to treatment withdrawal in some cases. In this context, melatonin and its analogs emerges as potential complimentary/alternative treatment, offering the advantage of hypotensive and antioxidant properties. The present PhD thesis aim to investigate endogenous melatonin content in the aqueous humor and describes mechanisms involved in detecting increased IOP, along with a focus on the possibility of melatonin receptors to interact with different receptors with the intention to find a more effective combined therapeutical approach. Finally, to study the attribution of the crystalline lens to the aqueous humor melatonin content and to discover the regulation of its synthesis in this ocular structure. Results showed a correlation between melatonin levels in the aqueous humor and IOP. Melatonin levels were found higher in patients with elevated IOP. Using a glaucomatous animal model (DBA/2J) it was possible to corroborate our findings. In vitro assays pointed to the participation of the TRPV4 channel, which is sensitive to pressure, among other stimuli. Activation of the mentioned channel in human immortalised nonpigmented ciliary body epithelial cells resulted in an increment of melatonin secretion through the increase of aralkylamine N-acetyltransferase (AANAT) expression, the first enzyme in melatonin synthesis. In addition, short term assays showed that the TRPV4 activation leaded to AANAT phosphorylation through a cascade of intracellular events that involves the participation of calmodulin and calcium-calmodulin dependent protein kinase II. This phosphorylation activates AANAT and therefore melatonin synthesis is stimulated...La hipertensión ocular, aunque no se considera una enfermedad en sí, es un factor de riesgo para desarrollar glaucoma, que eventualmente causa pérdida irreversible de la visión. En consecuencia, el enfoque terapéutico más habitual en el glaucoma es reducir la presión intraocular (PIO). No obstante, los fármacos anti-glaucomatosos presentan varios efectos secundarios que pueden conducir a la retirada del tratamiento en algunos casos. En este contexto, la melatonina y sus análogos emergen como un tratamiento complementario/ alternativo, ofreciendo la ventaja de poseer propiedades hipotensoras y antioxidantes. La presente tesis doctoral tiene como objetivo investigar el contenido de la melatonina endógena en el humor acuoso y describir los mecanismos implicados en la detección de los cambios en la IOP. Igualmente se estudia la capacidad de los receptores de melatonina para interactuar con otros receptores con la intención de encontrar un enfoque terapéutico combinado más eficaz. Finalmente, esta tesis también estudia la contribución del cristalinoen su aporte de melatonina al humor acuoso. Los resultados han mostrado una correlación entre los niveles de melatonina en el humor acuoso y la PIO. Los niveles de melatonina se encontraron más altos en pacientes con PIO elevada. El uso de modelo animal glaucomatoso (DBA/2J) corroboró nuestros hallazgos de una manera consistente. Por otro lado, los ensayos in vitro señalaron la participación del canal TRPV4, proteína que es sensible a la presión,como principal activador de la sintesis de la melatonina. De este modo, la estimulación de este canal en células epiteliales del cuerpo ciliar no pigmentadas inmortalizadas humanas dio como resultado un incremento de la secreción de melatonina a través de un aumento de la expresion de la Aralquilamina N-acetiltransferasa(AANAT), la primera enzima en la síntesis de melatonina. Además, los ensayos a corto plazo mostraron que la activación de TRPV4 induce a la fosforilación de AANAT, y su activación, a través de una cascada de eventos intracelulares implica la participación de la calmodulina y la calmodulina quinasa II dependiente de calcio-calmodulina...Unidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEunpu
TRPV4 activation triggers the release of melatonin from human non-pigmented ciliary epithelial cells
No full textReceived 11 December 2014; received in revised form 10 March 2015; accepted in revised form 27 April 2015; available online 29 April 2015.Melatonin is a neurohormone mainly produced in the pineal gland; nevertheless, various ocular structures such as the ciliary body, lens and the retina produce it. One of the roles of melatonin in the eye is the modulation of intraocular pressure, although little is known about the mechanisms that causes its presence in the aqueous humour. TRPV4 is a membrane channel which is activated by both physical and chemical stimuli. Therefore, this channel is sensitive to osmotic and hydrostatic pressure. As a consequence, TRPV4 results as an interesting candidate to study the relation between the activation of the TRPV4 channel and the production of melatonin. In this sense we have studied the role of the TRPV4 agonist GSK1016790A to modulate the production of melatonin in a cell line derived from human non-pigmented ciliary epithelial cells. The stimulation of the TRPV4 produced an increase in the extracellular melatonin levels changing from 8.5 ± 0.6 nM/well/30 min (control) to 23.3 ± 2.1 nM/well/30 min after 10 nM GSK1016790A application, this action being blocked by the selective antagonist RN 1734. The activation of the TRPV4 by GSK1016790A permitted to observe a melatonin increase which was concentration-dependent, and provided a pD2 value of −8.5 ± 0.1 (EC50 of 3.0 nM). In conclusion, the activation of the TRPV4 present in human non-pigmented ciliary epithelial cells can modulate the presence of extracellular melatonin, this being of relevance since this substance controls the dynamics of the aqueous humour.Universidad Complutense de MadridUnidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEpu
Improving Melatonin Delivery Within the Eye
Get PDFMelatonin is a neurohormone synthesized in the pineal gland as well as in other organs and it plays an important role in many ocular functions, as it is synthesized in numerous eye structures. Melatonin can reduce the intraocular pressure and to serves as an antioxidant preventing against free radicals, hence cataract formation as well as retinal damage due to glaucoma, among other functions. Ocular pharmacology is a challenging field giving the difficulties of drug delivery inside the eye due to its low bioavailability. In this sense, the present brief commentary is summarizing the latest advances in non-invasive ocular drug delivery focused on the effect of melatonin in different ocular diseases.Ministerio de Economía y Competitividad (MINECO)Ministerio de Sanidad de EspañaRETICS (Redes temáticas de investigación cooperativa en salud) (España)Unidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEpu
Epigenetics in the Eye: An Overview of the Most Relevant Ocular Diseases
Get PDFThis Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.Sight for mammals is one of the most appreciated senses. In humans there are several factors that contribute to the increment in all kind of eye diseases. This mini-review will focus on some diseases whose prevalence is steadily increasing year after year for non-genetic reasons, namely cataracts, dry eye, and glaucoma. Aging, diet, inflammation, drugs, oxidative stress, seasonal and circadian style-of-live changes are impacting on disease prevalence by epigenetics factors, defined as stable heritable traits that are not explained by changes in DNA sequence. The mini-review will concisely show the data showing epigenetics marks in these diseases and on how knowledge on the epigenetic alterations may guide therapeutic approaches to have a healthy eye.Ministerio de Economía, Comercio y Empresa (España)Ministerio de Sanidad (España)Redes Temáticas de Investigación Cooperativa en Salud (España)Unidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEpu
Recent developments on dry eye disease treatment compounds
Get PDFAbstractDry eye syndrome is a common tears and ocular surface multifactorial disease, described by changes in the ocular surface epithelia related to reduced tears quantity and ocular surface sensitivity, leading to inflammatory reaction. Managing the eye inflammation proved helpful to patients with dry eye disease and current treatment is based on the use of topically applied artificial tear products/lubricants, tear retention management, stimulation of tear secretion and using anti-inflammatory drugs. In this article we revise the corresponding literature and patents assembling the new treatment approaches of novel and future pharmaceutical compounds destined for the dry eye disease treatment. The most frequent categories of compounds presented are secretagogues and anti-inflammatory drugs. These compounds are the research outcome of novel therapeutic strategies designed to reduce key inflammatory pathways and restore healthy tear film
Melatonin synthesis in the human ciliary body triggered by TRPV4 activation: Involvement of AANAT phosphorylation
No full textReceived 26 January 2017, Revised 23 June 2017, Accepted 23 June 2017, Available online 24 June 2017.Melatonin is a substance synthesized in the pineal gland as well as in other organs. This substance is involved in many ocular functions, giving its synthesis in numerous eye structures. Melatonin is synthesized from serotonin through two enzymes, the first limiting step into the synthesis of melatonin being aralkylamine N-acetyltransferase (AANAT). In this current study, AANAT phosphorylation after the activation of TRPV4 was studied using human non-pigmented epithelial ciliary body cells. Firstly, it was necessary to determine the adequate time and dose of the TRPV4 agonist GSK1016790A to reach the maximal phosphorylation of AANAT. An increase of 72% was observed after 5 min incubation with 10 nM GSK (**p < 0.05, n = 6) with a concomitant rise in N-acetyl serotonin and melatonin synthesis. The involvement of a TRPV4 channel in melatonin synthesis was verified by antagonist and siRNA studies as a previous step to studying intracellular signalling. Studies performed on the second messengers involved in GSK induced AANAT phosphorylation were carried out by inhibiting several pathways. In conclusion, the activation of calmodulin and calmodulin-dependent protein kinase II was confirmed, as shown by the cascade seen in AANAT phosphorylation (***p < 0.001, n = 4). This mechanism was also established by measuring N-acetyl serotonin and melatonin levels. In conclusion, the activation of a TRPV4 present in human ciliary body epithelial cells produced an increase in AANAT phosphorylation and a further melatonin increase by a mechanism in which Ca-calmodulin and the calmodulin-dependent protein kinase II are involved.Ministerio de Economía y Competitividad (MINECO)Ministerio de SanidadUnidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEpu
Adreno–melatonin receptor complexes control ion homeostasis and intraocular pressure ‐ their disruption contributes to hypertensive glaucoma
Get PDFThis is the peer reviewed version of the following article: Alkozi, HA, Navarro, G, Aguinaga, D, et al. Adreno–melatonin receptor complexes control ion homeostasis and intraocular pressure ‐ their disruption contributes to hypertensive glaucoma. Br J Pharmacol. 2020; 1– 16, which has been published in final form at https://doi.org/10.1111/bph.14971. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Background and Purpose: Often, glaucoma courses with elevated eye hydrostatic pression, which is regulated by endogenous melatonin. Via α1‐adrenoceptor activation, phenylephrine increases cytoplasmic [Ca2+] that is detrimental in glaucoma. The aims of the paper were i) elucidating the role of melatonin receptors in humour production and intraocular pressure (IOP) maintenance and ii) identifying glaucoma relevant melatonin‐adrenergic interactions.
Experimental approach: Biophysical and proximity ligation assays were performed to identify interactions in heterologous systems, in cell lines and in human eyes. Gs/Gi/Gq signaling was investigated in heterologous systems and cells producing the aqueous humour. IOP was determined in a mice model of glaucoma. Retinography and topically pharmacological treatment were performed in control and in glaucomatous mice.
Key Results: α1‐adrenergic and melatonin receptors form functional complexes in which the C‐terminal tail of the adrenergic receptor play a relevant role. Remarkably, activation of α1‐adrenoceptors in the complex did not lead to cytosolic Ca2+ increases, suggesting Gs instead of Gq coupling. The number of complexes significantly decreased in models of glaucoma and, more importantly, in human samples of glaucoma patients. The results led to hypothesize that melatonin, a hypotensive agent, plus blockade of α1‐adrenergic receptors could normalize pressure in glaucoma. Remarkably, co‐instillation of melatonin and prazosin, an α1‐adrenergic receptor antagonist, resulted in long‐term decreases in IOP in a well‐established animal model of glaucoma.
Conclusions & Implications: The findings are instrumental to understand the physiological function of melatonin in the eye and its potential to address eye pathologies by targeting melatonin receptors and their complexes.Ministerio de Economía, Comercio y Empresa (España)Ministerio de Sanidad (España)Unidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEpu
Epigenetics in the eye: an overview of the most relevant ocular diseases
Get PDFSight for mammals is one of the most appreciated senses. In humans there are several factors that contribute to the increment in all kind of eye diseases. This mini-review will focus on some diseases whose prevalence is steadily increasing year after year for non-genetic reasons, namely cataracts, dry eye, and glaucoma. Aging, diet, inflammation, drugs, oxidative stress, seasonal and circadian style-of-live changes are impacting on disease prevalence by epigenetics factors, defined as stable heritable traits that are not explained by changes in DNA sequence. The mini-review will concisely show the data showing epigenetics marks in these diseases and on how knowledge on the epigenetic alterations may guide therapeutic approaches to have a healthy eye
Yellow Filter Effect on Melatonin Secretion in the Eye: Role in IOP Regulation
Get PDFThis is an Accepted Manuscript of an article published by Taylor & Francis in Journal Current Eye Research on 24-01-2019, available online: https://doi.org/10.1080/02713683.2019.1570276Purpose: Melatonin is a neurohormone mainly synthesized in the pineal gland; however, it is also present in the aqueous humor. One of melatonins’ functions in the eye is the regulation of intraocular pressure (IOP). Melatonin is known to be sensitive to light. Recently, the photopigment which controls melatonin synthesis, melanopsin, was found in the crystalline lens. Therefore, light conditions are an interesting possible way of regulating melatonin levels in the aqueous humor. The current study used yellow filters, since melanopsin is activated by short wavelength (blue light).
Methods: New Zealand white rabbits were used, divided in two groups, one under controlled 12 h light/dark cycles, while the rest had their cages encased with a yellow filter (λ 465–480). IOP measurements were taken every week at the same time before they were anesthetized for aqueous humor extraction.
Results: Keeping the rabbits under the yellow filter resulted in a decrease in IOP up to 43.8 ± 7.8% after 3 weeks. This effect was reversed after the topical application of selective and nonselective melatonin receptors antagonists, 4PPDOT and luzindole. Also, blocking melanopsin by its antagonist AA92593 under white light condition decreased IOP. Finally, melatonin levels were found significantly higher in the aqueous humor of rabbits developed under yellow filter compared to controls (37.4 ± 4.2 and 15.3 ± 3.1 ng/ml, respectively).
Conclusion: Yellow filters modulate melatonin levels in the aqueous humor due to deactivating melanopsin activity. This effect leads to a decrease in IOP mediated by melatonin receptors.Ministerio de Economía, Comercio y Empresa (España)Ministerio de Sanidad (España)Unidad Docente de Bioquímica y Biología MolecularFac. de Óptica y OptometríaTRUEinpres
