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Dual contribution of TRPV4 antagonism in the regulatory effect of vasoinhibins on blood-retinal barrier permeability: diabetic milieu makes a difference.

ABSTRACT: Breakdown of the blood-retinal barrier (BRB), as occurs in diabetic retinopathy and other chronic retinal diseases, results in vasogenic edema and neural tissue damage, causing vision loss. Vasoinhibins are N-terminal fragments of prolactin that prevent BRB breakdown during diabetes. They modulate the expression of some transient receptor potential (TRP) family members, yet their role in regulating the TRP vanilloid subtype 4 (TRPV4) remains unknown. TRPV4 is a calcium-permeable channel involved in barrier permeability, which blockade has been shown to prevent and resolve pulmonary edema. We found TRPV4 expression in the endothelium and retinal pigment epithelium (RPE) components of the BRB, and that TRPV4-selective antagonists (RN-1734 and GSK2193874) resolve BRB breakdown in diabetic rats. Using human RPE (ARPE-19) cell monolayers and endothelial cell systems, we further observed that (i) GSK2193874 does not seem to contribute to the regulation of BRB and RPE permeability by vasoinhibins under diabetic or hyperglycemic-mimicking conditions, but that (ii) vasoinhibins can block TRPV4 to maintain BRB and endothelial permeability. Our results provide important insights into the pathogenesis of diabetic retinopathy that will further guide us toward rationally-guided new therapies: synergistic combination of selective TRPV4 blockers and vasoinhibins can be proposed to mitigate diabetes-evoked BRB breakdown.

SUBMITTER: Arredondo Zamarripa D

PROVIDER: S-EPMC5638810 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Dual contribution of TRPV4 antagonism in the regulatory effect of vasoinhibins on blood-retinal barrier permeability: diabetic milieu makes a difference.

Arredondo Zamarripa David D Noguez Imm Ramsés R Bautista Cortés Ana María AM Vázquez Ruíz Osvaldo O Bernardini Michela M Fiorio Pla Alessandra A Gkika Dimitra D Prevarskaya Natalia N López-Casillas Fernando F Liedtke Wolfgang W Clapp Carmen C Thébault Stéphanie S

Scientific reports 20171012 1

Breakdown of the blood-retinal barrier (BRB), as occurs in diabetic retinopathy and other chronic retinal diseases, results in vasogenic edema and neural tissue damage, causing vision loss. Vasoinhibins are N-terminal fragments of prolactin that prevent BRB breakdown during diabetes. They modulate the expression of some transient receptor potential (TRP) family members, yet their role in regulating the TRP vanilloid subtype 4 (TRPV4) remains unknown. TRPV4 is a calcium-permeable channel involved ...[more]

PMID: 29026201

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Project description:BackgroundSupraventricular tachycardia is a group of rhythm disturbances that affect 1 in 300-1200 Australian children annually. The differentiation of supraventricular tachycardia (SVT) symptoms and age of onset according to their subtype is not well understood in the pediatric population. Most studies rely on ECG criteria only to characterize the subtype of the SVT, which is not applicable to all subtypes. The purpose of this study was to identify the symptoms and ages of onset of SVT subtypes, and to analyze whether ethnicity or severity correlated with the SVT subtype confirmed in an invasive Electrophysiology (EP) study.MethodsA retrospective analysis and prospective survey evaluated 364 patients who underwent an EP study at The Royal Children's Hospital, Melbourne between 2009 and 2015. Age of onset, symptoms, and ethnicity were collected by phone survey or medical records in addition to EP study diagnostic data, medication status, and follow-up information about their symptom status following EP procedure. Patients were grouped according to their SVT subtype. Data analysis was performed using chi-squared, Fisher's exact, and ANOVA statistical tests to determine associations between SVT substrates.ResultsTwo hundred and thirty-three suitable cases of SVT were identified (131 men, 102 women) aged between 0 and 18 years. Atrioventricular Reentrant Tachycardia (AVRT) (n = 153) was the most common SVT subtype, followed by Atrioventricular Nodal Reentrant Tachycardia (AVNRT) (n = 55), Atrial Tachycardia (AT) (n = 17), and other SVT subtypes (n = 8) which included Atrial Fibrillation, Atrial Flutter, and Junctional Tachycardia. There was a male predominance in all subtypes, except for AVNRT. AVNRT patients had palpitations, dyspnoea, dizziness, and anxiety more than any other group, AVRT patients complained of vomiting most and patients with AT had the most fatigue. The mean age of symptom onset varied among groups, being earlier in AVRT, later in AVNRT with a significant difference between AVRT with unidirectional retrograde accessory pathway (URAP) and AVNRT subtypes (P < 0.01).ConclusionSome specific symptoms were strong discriminators between different SVT subtypes. Ethnicity did not have strong correlations with SVT subtype incidence. This study was able to show clinical differences among children with SVT due to AVRT (URAP) compared to AVNRT, allowing the prognosis and intended management of pediatric SVT to be anticipated by less invasive means.

Project description:A better understanding of the molecular and cellular mechanisms involved in retinal hydro-mineral homeostasis imbalance during diabetic macular edema (DME) is needed to gain insights into retinal (patho-)physiology that will help elaborate innovative therapies with lower health care costs. Transient receptor potential cation channel subfamily vanilloid member 4 (TRPV4) plays an intricate role in homeostatic processes that needs to be deciphered in normal and diabetic retina. Based on previous findings showing that TRPV4 antagonists resolve blood-retina barrier (BRB) breakdown in diabetic rats, we evaluated whether TRPV4 channel inhibition prevents and reverts retinal edema in streptozotocin(STZ)-induced diabetic mice. We assessed retinal edema using common metrics, including retinal morphology/thickness (histology) and BRB integrity (albumin-associated tracer), and also by quantifying water mobility through apparent diffusion coefficient (ADC) measures. ADC was measured by diffusion-weighted magnetic resonance imaging (DW-MRI), acquired ex vivo at 4 weeks after STZ injection in diabetes and control groups. DWI images were also used to assess retinal thickness. TRPV4 was genetically ablated or pharmacologically inhibited as follows: left eyes were used as vehicle control and right eyes were intravitreally injected with TRPV4-selective antagonist GSK2193874, 24 h before the end of the 4 weeks of diabetes. Histological data show that retinal thickness was similar in nondiabetic and diabetic wt groups but increased in diabetic Trpv4-/- mice. In contrast, DWI shows retinal thinning in diabetic wt mice that was absent in diabetic Trpv4-/- mice. Disorganized outer nuclear layer was observed in diabetic wt but not in diabetic Trpv4-/- retinas. We further demonstrate increased water diffusion, increased distances between photoreceptor nuclei, reduced nuclear area in all nuclear layers, and BRB hyperpermeability, in diabetic wt mice, effects that were absent in diabetic Trpv4-/- mice. Retinas of diabetic mice treated with PBS showed increased water diffusion that was not normalized by GSK2193874. ADC maps in nondiabetic Trpv4-/- mouse retinas showed restricted diffusion. Our data provide evidence that water diffusion is increased in diabetic mouse retinas and that TRPV4 function contributes to retinal hydro-mineral homeostasis and structure under control conditions, and to the development of BRB breakdown and increased water diffusion in the retina under diabetes conditions. A single intravitreous injection of TRPV4 antagonist is however not sufficient to revert these alterations in diabetic mouse retinas.

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Dual contribution of TRPV4 antagonism in the regulatory effect of vasoinhibins on blood-retinal barrier permeability: diabetic milieu makes a difference.

Publications

Dual contribution of TRPV4 antagonism in the regulatory effect of vasoinhibins on blood-retinal barrier permeability: diabetic milieu makes a difference.

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