Effects of Progesterone and Other Gonadal Hormones on Glutamatergic Circuits in the Retina

BACKGROUND

Gonadal hormones function in the retina; however, their targets have not yet been identified. Therefore, the present study examined the effects of progesterone and other gonadal hormones on glutamatergic circuits in the retina.

METHODS

Extracellular glutamate concentrations, which correspond to the amount of glutamate released, were examined using an enzyme-linked fluorescent assay system. The activity of glutamatergic synapses between bipolar cells and ganglion cells was investigated using a patch clamp technique. Changes in retinal thickness during pregnancy were assessed using optical coherence tomography (OCT) images.

RESULTS

Progesterone and pregnenolone sulfate increased extracellular glutamate concentrations, whereas estrogen and testosterone did not. Progesterone increased the activity of glutamatergic synapses between bipolar cells and ganglion cells. A temporal decrease in the thickness of the peripheral retina was observed in the 1st trimester.

CONCLUSIONS

Progesterone, but not estrogen or testosterone, activated glutamate release in the mouse retina. Increases in the concentration of progesterone during pregnancy did not induce any detectable change in retinal thickness.

Girl Power in Glaucoma: The Role of Estrogen in Primary Open Angle Glaucoma

Estrogen is essential in maintaining various physiological features in women, and a decline in estrogen levels are known to give rise to numerous unfortunate symptoms associated with menopause. To alleviate these symptoms hormone replacement therapy with estrogen is often used, and has been shown to be fruitful in improving quality of life in women suffering from postmenopausal discomforts. An often forgotten condition associated with menopause is the optic nerve disorder, glaucoma. Thus, estrogen may also have an impact in maintaining the retinal ganglion cells (RGCs), which make up the optic nerve, thereby preventing glaucomatous neurodegeneration. This review aims to provide an overview of possible associations of estrogen and the glaucoma subtype, primary open-angle glaucoma (POAG), by evaluating the current literature through a PubMed-based literature search. Multiple in vitro and in vivo studies of RGC protection, as well as clinical and epidemiological data concerning the well-defined retinal neurodegenerative disorder POAG have been reviewed. Over all, deficiencies in retinal estrogen may potentially instigate RGC loss, visual disability, and eventual blindness. Estrogen replacement therapy may therefore be a beneficial future treatment. However, more studies are needed to confirm the relevance of estrogen in glaucoma prevention.

Menopause exacerbates visual dysfunction in experimental glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Recently, estrogen deficiencies caused by early menopause, alterations in estrogen signaling via mutations in estrogen receptors, and polymorphisms along estrogen metabolic pathways have all been linked to an increased risk of developing glaucoma. Here, we examined how menopause and age impact visual function and retinal structure in an experimental model of glaucoma. Young (3-4 months) and aged (9-10 months) female Brown Norway rats were divided into pre- and post-menopausal cohorts by surgically inducing menopause via ovariectomy (OVX). After six weeks, ocular hypertension (OHT) was induced unilaterally for a period of eight weeks. Four cohorts were successfully followed to eight weeks: young sham (n = 8), young OVX (n = 9), aged sham (n = 10), and aged OVX (n = 11) animals. Intraocular pressure (IOP) was monitored weekly in all groups. Prior to inducing OHT (baseline) and at four and eight weeks after inducing OHT, we assessed visual acuity via the optomotor response (OMR) and retinal structure using optical coherence tomography (OCT). OHT decreased the OMR in all cohorts. We found that spatial frequency thresholds decreased by 54% in OVX animals after OHT compared to sham animals after OHT, regardless of age (p < 0.001). We also found thinning of the retinal nerve fiber layer (RNFL) and loss of total retinal thickness after induction of OHT. Aged animals had more thinning of the RNFL and loss of total retinal thickness compared to young animals (p < 0.001). Overall, OHT caused significant changes in visual function and retinal structure. Observing that OVX in young and aged animals further decreased spatial frequency thresholds after OHT suggests that an estrogen deficiency may intensify visual impairment after OHT.

The Association between Female Reproductive Factors and Open-Angle Glaucoma in Korean Women: The Korean National Health and Nutrition Examination Survey V

Purpose

We investigated associations between female reproductive factors and open-angle glaucoma (OAG) in Korean females using the Korea National Health and Nutrition Examination Survey (KNHANES).

Methods

A nationwide, population-based, cross-sectional study was conducted. We enrolled 23,376 participants from the KNHANES who had undergone ophthalmologic exams from 2010 through 2012. Associations between undiagnosed OAG and female reproductive factors such as age at menarche and menopause, parity, history of lactation, and administration of oral contraceptives (OC) or hormone replacement therapy (HRT) were determined using stepwise logistic regression analyses.

Results

Of the enrolled participants, 6,860 participants (397 with OAG and 6,463 without OAG) met our study criteria and were included in the analyses. In the multivariate logistic regression analysis after adjusting for all potential confounding factors, only early menopause (younger than 45 years) was significantly associated with OAG in participants with natural menopause (OR 2.28, 95% CI 1.17–4.46). Age at menarche, parity, history of lactation, and administration of OC or HRT were not significantly associated with OAG.

Conclusions

Only early menopause was associated with an increased risk of OAG in our study, in contrast to previous Western studies reporting both early menopause and late menarche as associated factors.

Oestrogen, ocular function and low-level vision: a review

Over the past 10 years, a literature has emerged concerning the sex steroid hormone oestrogen and its role in human vision. Herein, we review evidence that oestrogen (oestradiol) levels may significantly affect ocular function and low-level vision, particularly in older females. In doing so, we have examined a number of vision-related disorders including dry eye, cataract, increased intraocular pressure, glaucoma, age-related macular degeneration and Leber's hereditary optic neuropathy. In each case, we have found oestrogen, or lack thereof, to have a role. We have also included discussion of how oestrogen-related pharmacological treatments for menopause and breast cancer can impact the pathology of the eye and a number of psychophysical aspects of vision. Finally, we have reviewed oestrogen's pharmacology and suggest potential mechanisms underlying its beneficial effects, with particular emphasis on anti-apoptotic and vascular effects.

Evaluation of the macula, retinal nerve fiber layer and choroid thickness in postmenopausal women and reproductive-age women using spectral-domain optical coherence tomography

Objective

Menopause is a physiological life period that potentially affects various organs and systems. Therefore, a wide spectrum of signs and symptoms of eyes may be clinically observed in the postmenopausal period.

Aim of the study

To evaluate the macular, retinal nerve fiber layer (RNFL) and choroidal thickness alterations by using spectral-domain optical coherence tomography (SD-OCT) in postmenopausal women and compare with healthy reproductive-age women controls.

Material and methods

The study population included a healthy reproductive-age control group (n = 72) and postmenopausal study group (n = 72). Retinal thickness parameters were measured by SD-OCT. Peripapillary RNFL thickness parameters, macular thickness and choroidal thickness were evaluated.

Results

Superior inner macula, temporal inner macula, inferior inner macula, nasal inner macula, inferior outer macula and choroid thickness were significantly thinner in the postmenopausal study group than the healthy reproductive-age control group (p = 0.007, p = 0.037, p = 0.027, p = 0.006, p = 0.016, p < 0.001, respectively). After adjusting for age, only choroid thickness was significantly thinner in the postmenopausal study group than controls (p^† = 0.005).

Conclusions

This study revealed that choroidal thickness measured by SD-OCT was significantly thinner in postmenopausal women than healthy reproductive-age women. We can speculate that the decrease in choroidal thickness in postmenopausal women may indicate a reduced estrogen-dependent vasodilatory effect in ophthalmic artery secondary to menopausal estrogen deficiency.

Ophthalmic artery vasodilation after intranasal estradiol use in postmenopausal women

AIM

The study aim was to evaluate the acute hemodynamic effects of intranasal 17-beta-estradiol on ophthalmic arterial circulation in postmenopausal women.

METHODS

Twenty-one healthy women in natural menopause for at least 6 months (mean age: 53.2± 2.9 years) were investigated. Each patient received 300 µg intranasal 17-beta-estradiol. We evaluated the heart rate, systolic and diastolic blood pressure, ophthalmic artery velocity at systolic and diastolic peak and its flow curve integral (FCI) before and 30, 60 and 180 minutes after the administration of the drug.

RESULTS

At all time points, the ophthalmic artery FCI showed statistically significant variations (p<0.001) of velocity (cm/sec) compared to T0 (speed recorded at baseline before drug administration). Moreover, systolic blood pressure, diastolic blood pressure and heart rate did not significantly differ each other after drug administration.

CONCLUSIONS

Administration of a single dose of intranasal 17-beta-estradiol to healthy postmenopausal women increases ophthalmic artery perfusion.

Should Men and Women be Managed Differently in Glaucoma?

Introduction

To assess differences in associations of ocular perfusion pressure (OPP) as well as retinal and retrobulbar blood flow between men and women with primary open angle glaucoma (OAG).

Methods

A total of 116 patients with OAG (age 66.9 ± 10.9 years, 70 females) participating in the Indianapolis Glaucoma Progression Study were assessed for OPP, retinal microcirculation, and retrobulbar blood flow. Confocal scanning laser Doppler flowmetry measured peripapillary retinal capillary blood flow. Color Doppler imaging measured peak systolic (PSV) and diastolic blood flow velocities and vascular resistance in the ophthalmic (OA), central retinal (CRA), and nasal and temporal short posterior ciliary arteries (N/T PCA). Bivariate Spearman correlation and multivariate linear regression analyses were performed.

Results

In female patients with OAG, inferior retinal capillary flow was associated with OPP (r = 0.246, P = 0.044). In men, superior and inferior sector retinal blood flow was associated with OPP (r = −0.402, P = 0.006 and r = −0.357, P = 0.016, respectively). There was no statistically significant association between OPP and retrobulbar blood vessel flow velocities in male patients with OAG but there was an association between OA and TPCA PSV and OPP in female patients with OAG (r = 0.290, P = 0.015 and r = 0.357, P = 0.002, respectively). In female patients with OAG, multivariate regression showed no statistically significant effect of any variable on the superior retinal capillary blood flow, with CRA PSV as a sole predictor to the inferior retinal sector (partial rho = 0.302, P = 0.015) and in male patients with OAG, superior sector retinal capillary blood flow was independently associated with intraocular pressure (partial rho = −0.371, P = 0.016) and OPP (partial rho = −0.456, P = 0.002) with a trend of association with OPP in the inferior retina (partial rho = −0.301, P = 0.053).

Conclusions

There was a positive linear association between retinal microcirculation and OPP in females and a negative association in males. Male and female patients with OAG may differ in their vascular autoregulation in response to changes in OPP.

The effects of age on the spatial and temporal integration of global motion

The purpose of this study was to determine the relative contributions of local element speed and/or spatial displacement to age-related deficits in global motion processing. Motion coherence thresholds (79% correct) were measured for discriminating the direction of translational random dot kinematograms (RDKs) as a function of dot speed and spatial displacement across the adult lifespan (20-79 years). Age-related impairments in global motion processing were only apparent in observers 70-79 years of age. In agreement with previous studies, we found an age-related impairment at low (0.625 deg/s) and high speeds (10 deg/s). However, these effects were heavily mediated by dot spatial displacement. Motion coherence thresholds were also most markedly elevated in women aged over 70 years. These findings suggest a prominent role of spatial integration in global motion processing. Moreover, global motion perception appears to be relatively well preserved until around 70 years of age.

Contrast sensitivity, ocular blood flow and their potential role in assessing ischaemic retinal disease

PURPOSE

To examine the definition, evaluation methodology, association to ocular blood flow and potential clinical value of contrast sensitivity (CS) testing in clinical and research settings, focusing in patients with ischemic retinal disease.

METHODS

A review of the medical literature focusing on CS and ocular blood flow in ischemic retinal disease.

RESULTS

CS may be more sensitive than other methods at detecting subtle defects or improvements in primarily central retinal ganglion cell function early on in a disease process. CS testing attempts to provide spatial detection differences which are not directly assessed with standard visual acuity chart testing. Analyzing all studies that have assessed both CS change and ocular blood flow, it is apparent that both choroidal circulation and retinal circulation may have an important role in influencing CS.

CONCLUSION

The concept that CS is directly influenced by ocular blood flow is supported by reviewing the studies involving both. Although the studies in the literature have not established a direct cause and effect relationship per se, the literature review makes it logical to assume that changes in retinal and choroidal blood flow influence CS. This raises the possibility that a subjective visual characteristic, specifically CS, may be able to be evaluated more objectively by studying blood flow. It appears appropriate to study the relationship between blood flow and CS more extensively to develop improved ways of measuring various aspects of blood flow to the eye and to best quantify early changes in visual function.

Dysfunctional regulation of ocular blood flow: A risk factor for glaucoma?

Primary open angle glaucoma (OAG) is a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and associated visual field loss. OAG is an emerging disease with increasing costs and negative outcomes, yet its fundamental pathophysiology remains largely undetermined. A major treatable risk factor for glaucoma is elevated intraocular pressure (IOP). Despite the medical lowering of IOP, however, some glaucoma patients continue to experience disease progression and subsequent irreversible vision loss. The scientific community continues to accrue evidence suggesting that alterations in ocular blood flow play a prominent role in OAG disease processes. This article develops the thesis that dysfunctional regulation of ocular blood flow may contribute to glaucomatous optic neuropathy. Evidence suggests that impaired vascular autoregulation renders the optic nerve head susceptible to decreases in ocular perfusion pressure, increases in IOP, and/or increased local metabolic demands. Ischemic damage, which likely contributes to further impairment in autoregulation, results in changes to the optic nerve head consistent with glaucoma. Included in this review are discussions of conditions thought to contribute to vascular regulatory dysfunction in OAG, including atherosclerosis, vasospasm, and endothelial dysfunction.

The role of estrogen deficiency in skin ageing and wound healing

The links between hormonal signalling and lifespan have been well documented in a range of model organisms. For example, in C. elegans or D. melanogaster, lifespan can be modulated by ablating germline cells, or manipulating reproductive history or pregnenolone signalling. In mammalian systems, however, hormonal contribution to longevity is less well understood. With increasing age human steroid hormone profiles change substantially, particularly following menopause in women. This article reviews recent links between steroid sex hormones and ageing, with special emphasis on the skin and wound repair. Estrogen, which substantially decreases with advancing age in both males and females, protects against multiple aspects of cellular ageing in rodent models, including oxidative damage, telomere shortening and cellular senescence. Estrogen's effects are particularly pronounced in the skin where cutaneous changes post-menopause are well documented, and can be partially reversed by classical Hormone Replacement Therapy (HRT). Our research shows that while chronological ageing has clear effects on skin wound healing, falling estrogen levels are the principle mediator of these effects. Thus, both HRT and topical estrogen replacement substantially accelerate healing in elderly humans, but are associated with unwanted deleterious effects, particularly cancer promotion. In fact, much current research effort is being invested in exploring the therapeutic potential of estrogen signalling manipulation to reverse age-associated pathology in peripheral tissues. In the case of the skin the differential targeting of estrogen receptors to promote healing in aged subjects is a real therapeutic possibility.

Influence of gender and menopausal status on peripheral and choroidal circulation

PURPOSE

To evaluate the influence of menopausal status and age on peripheral and ocular circulation assessed by means of continuous laser Doppler flowmetry (LDF).

METHODS

Fifty-three healthy participants were recruited randomly. Twenty-six men and 27 women were divided into two age groups. Choroidal blood flow was measured by LDF and peripheral circulation was measured at the fingertips (digit IV) using the Perimed PeriFlux (Järfälla, Sweden) laser Doppler System 5000. Independent t-test and two-way analysis of variance (anova) were performed.

RESULTS

Group distribution was: male/female = 14/16 for the younger group and 12/11 for the older group. Average age across groups was 31.3 ± 6.8/28.4 ± 7.0 years and 66.3 ± 8.3/61.5 ± 3.6 years, respectively. Finger and choroidal LDF flow values were significantly different between the two female age groups (p < 0.001 and p = 0.03, respectively). In men this was not the case (p = 0.85 and p = 0.56, respectively). anova interaction p-value for the factors 'age group' and 'gender' for finger LDF flow was p = 0.012, and for choroidal LDF flow p = 0.049, demonstrating significant gender differences with ageing.

CONCLUSION

  Menopausal status in women has significant influence on both choroidal and peripheral blood flow; the opposite behaviour occurs with ageing.

Estrogen receptor beta gene polymorphism and intraocular pressure elevation in female patients with primary open-angle glaucoma

PURPOSE

To assess whether the genetic polymorphisms of estrogen receptor beta (ESR2) are associated with primary open-angle glaucoma (POAG).

DESIGN

Case-control study.

METHODS

Four hundred and twenty-five Japanese patients with POAG, including normal-tension glaucoma (NTG, n = 213) and high-tension glaucoma (HTG, n = 212), and 191 control subjects without glaucoma were analyzed for polymorphisms of rs1256031 and rs4986938 in the ESR2 gene. The genotypic and allelic frequencies were compared between NTG or HTG patients and control subjects. The phenotypic features of patients with POAG were compared between each genotype.

RESULTS

There were significant differences in the genotype frequencies of rs1256031 and rs4986938 between the HTG patients and control subjects in women (P = .033 and P = .043 respectively). The frequencies of the C allele of rs1256031 and G allele of rs4986938 were significantly higher in patients with HTG in comparison to the control subjects in women (rs1256031: 53.6% vs 43.4%, P = .044; rs4986938: 89.2% vs 80.6%, P = .027). The maximum intraocular pressures in female POAG patients with the CC or TC genotypes of rs1256031 were significantly higher than that in female POAG patients with the TT genotype (P = .039, analysis of variance, P = .018 and P = .026 respectively).

CONCLUSION

The ESR2 gene polymorphism is therefore considered to be associated with an intraocular pressure elevation in female patients with POAG.

Experimental use of estriol for visualizing the vitreous body in the anterior chamber after posterior capsule rupture in animal models

PURPOSE

To compare the efficacy and safety of estriol and triamcinolone acetonide suspensions in visualizing the prolapsed vitreous body in the anterior chamber after posterior capsule rupture in animal models.

SETTING

Tsukuba University Institute of Clinical Medicine, Ibaraki, Japan.

METHODS

To evaluate efficacy, triamcinolone acetonide or estriol suspension was injected into the anterior chambers of porcine eyes after intentional posterior capsule rupture. To evaluate safety, triamcinolone acetonide 5.0 mg or estriol in 0.1 mL suspension was injected into the anterior chamber of New Zealand white rabbits. Slitlamp examinations, intraocular pressure (IOP), corneal endothelial cell density (ECD) measurements, and histologic examinations were performed up to 28 days after the injection.

RESULTS

Triamcinolone acetonide and estriol were equally effective in allowing visualization of the prolapsed vitreous body in the anterior chamber. The granules of triamcinolone acetonide or estriol disappeared 1 day after the injection and did not affect the IOP or corneal ECD. No statistically significant histological changes were observed in the eyes 28 days after the injection of triamcinolone acetonide or estriol.

CONCLUSIONS

Estriol was effective for the visualization of the prolapsed vitreous body in the anterior chamber after posterior capsule rupture. In experimental models, no significant side effects were observed after the injection of estriol in the anterior chamber. Results suggest that estriol is an alternative reagent for visualizing the vitreous body, especially in steroid responders, because it has no glucocorticoid or mineralocorticoid activity.