G-protein coupled estrogen receptor-mediated non-genomic facilitatory effect of estrogen on cooling-induced reduction of skin blood flow in mice

GPER Acts Through the cAMP/Epac/JNK/AP-1 Pathway to Induce Transcription of Alpha 2C Adrenoceptor in Human Microvascular Smooth Muscle Cells

ABSTRACT

Raynaud's phenomenon, which results from exaggerated cold-induced vasoconstriction, is more prevalent in females than males. We previously showed that estrogen increases the expression of alpha 2C-adrenoceptors (α 2C -AR), the sole mediator of cold-induced vasoconstriction. This effect of estrogen is reproduced by the cell-impermeable form of the hormone (E 2 :bovine serum albumin [BSA]), suggesting a role of the membrane estrogen receptor, G-protein-coupled estrogen receptor [GPER], in E 2 -induced α 2C -AR expression. We also previously reported that E 2 upregulates α 2C -AR in microvascular smooth muscle cells (VSMCs) via the cAMP/Epac/Rap/JNK/AP-1 pathway, and that E 2 :BSA elevates cAMP levels. We, therefore, hypothesized that E 2 uses GPER to upregulate α 2C -AR through the cAMP/Epac/JNK/AP-1 pathway. Our results show that G15, a selective GPER antagonist, attenuates the E 2 -induced increase in α 2C -AR transcription. G-1, a selective GPER agonist, induced α 2C -AR transcription, which was concomitant with elevated cAMP levels and JNK activation. Pretreatment with ESI09, an Epac inhibitor, abolished G-1-induced α 2C -AR upregulation and JNK activation. Moreover, pretreatment with SP600125, a JNK-specific inhibitor, but not H89, a PKA-specific inhibitor, abolished G-1-induced α 2C -AR upregulation. In addition, transient transfection of an Epac dominant negative mutant (Epac-DN) attenuated G-1-induced activation of the α 2C -AR promoter. This inhibitory effect of Epac-DN on the α 2C -AR promoter was overridden by the cotransfection of constitutively active JNK mutant. Furthermore, mutation of AP-1 site in the α 2C -AR promoter abrogated G1-induced expression. Collectively, these results indicate that GPER upregulates α 2C -AR through the cAMP/EPAC/JNK/AP-1 pathway. These findings unravel GPER as a new mediator of cold-induced vasoconstriction, and present it as a potential target for treating Raynaud's phenomenon in estrogen-replete females.

Targeting estrogen signaling and biosynthesis for aged skin repair

Non-healing skin wounds are disproportionally prevalent in older adults. Current treatments do not account for the particularities of aged skin and result in inadequate outcomes. Overall, healing chronic wounds in the elderly remains a major unmet clinical need. Estrogens play a critical role in reproduction but also have important actions in non-reproductive organs. Estrogen biosynthesis and signaling pathways are locally activated during physiological wound healing, processes that are inhibited in elderly estrogen-deprived skin. Estrogen deprivation has been shown to be a critical mediator of impaired wound healing in both postmenopausal women and aged men, and topical estrogen application reverses age-associated delayed wound healing in both elderly men and women. These data indicate that adequate estrogen biosynthesis and properly regulated estrogen signaling pathways are essential for normal wound healing and can be targeted to optimize tissue repair in the elderly. However, due to fundamental questions regarding how to safely restore estrogen signaling locally in skin wounds, there are currently no therapeutic strategies addressing estrogen deficiency in elderly chronic wounds. This review discusses established and recent literature in this area and proposes the hypothesis that estrogen plays a pleiotropic role in skin aging and that targeting estrogen signaling and biosynthesis could promote skin repair in older adults.

Nonfreezing Cold Injury and Cold Intolerance in Paddlesport

INTRODUCTION

Nonfreezing cold injury (NFCI) occurs when tissues are subjected to prolonged cooling that causes tissue damage, but not freezing. Long-term effects include cold intolerance, with allodynia, pain, or numbness of the affected limb. Those who participate in outdoor paddlesports are at particular risk.

METHODS

This is an epidemiological study that aimed to determine the risk factors for paddlesport athletes developing NFCI and chronic cold intolerance in their hands. Secondary outcomes were to correlate cumulative cold exposure with the development of cold intolerance and to identify risk factors for developing NFCI or cold intolerance. Six hundred nine athletes responded to a survey distributed by their national governing body obtaining demographic and activity details, symptoms of NFCI, and a cold intolerance severity score (CISS).

RESULTS

Twenty-three percent reported symptoms consistent with acute NFCI. The median CISS was 31 y (interquartile range 25-43), and 15% had a pathological CISS defined as >50. Females and individuals with Raynaud's phenomenon or migraines had a significantly higher CISS (P<0.05). Regression analysis found that females, smokers, and those with Raynaud's phenomenon or a previous nerve injury had a significantly higher risk of developing pathological cold intolerance (CISS >50). There was no correlation between cumulative cold exposure and CISS.

CONCLUSIONS

A large proportion of paddlesport athletes undertaking activity in cold conditions have a pathological CISS or episodes consistent with NFCI. Cumulative cold exposure was not associated with a pathologically high CISS. The risk factors were female sex, smokers, and those suffering from either Raynaud's phenomenon or nerve injury.

G-Protein-Coupled Estrogen Receptor Expression in Rat Uterine Artery Is Increased by Pregnancy and Induces Dilation in a Ca2+ and ERK1/2 Dependent Manner

Increasing levels of estrogens across gestation are partly responsible for the physiological adaptations of the maternal vasculature to pregnancy. The G protein-coupled estrogen receptor (GPER) mediates acute vasorelaxing effects in the uterine vasculature, which may contribute to the regulation of uteroplacental blood flow. The aim of this study was to investigate whether GPER expression and vasorelaxation may occur following pregnancy. Elucidation of the functional signalling involved was also investigated. Radial uterine and third-order mesenteric arteries were isolated from non-pregnant (NP) and pregnant rats (P). GPER mRNA levels were determined and—concentration–response curve to the GPER-specific agonist, G1 (10−10–10−6 M), was assessed in arteries pre-constricted with phenylephrine. In uterine arteries, GPER mRNA expression was significantly increased and vasorelaxation to G1 was significantly enhanced in P compared with NP rats. Meanwhile, in mesenteric arteries, there was a similar order of magnitude in NP and P rats. Inhibition of L-type calcium channels and extracellular signal-regulated kinases 1/2 significantly reduced vasorelaxation triggered by G1 in uterine arteries. Increased GPER expression and GPER-mediated vasorelaxation are associated with the advancement of gestation in uterine arteries. The modulation of GPER is exclusive to uterine arteries, thus suggesting a physiological contribution of GPER toward the regulation of uteroplacental blood flow during pregnancy.

Prevalence of Raynaud's Phenomenon in Saudi Arabia

Purpose

Raynaud’s phenomenon (RP) is defined as frequent ischaemic attacks in the fingers and toes due to vascular vasospasm. Studies have been conducted in many countries worldwide to determine the prevalence of RP. The aim of the current study was to assess the prevalence of RP in the Saudi Arabian population.

Patients and Methods

An online survey based on international consensus criteria used to diagnose RP was conducted to collect data from individuals from the Saudi population. Participants were considered positive if they had triphasic or biphasic colours of the extremities with cold-related sensitivity. Awareness of RP was also assessed.

Results

A total of 1025 responses were collected and included in the final analysis. The prevalence of RP was 4.29%, including 22% men and 77% women. The most common age group among women was 26–40 years (36.3%). Familiarity with RP was low, with 56.82% of participants lacking adequate awareness regarding RP. Only 32% of patients with RP reported attending doctor visits regarding symptoms of the disease.

Conclusion

The RP prevalence in Saudi Arabia is comparable to that reported in the international literature. Public awareness activities should be conducted to increase knowledge about RP.

Trial Registration

Not applicable.

Non-genomic actions of sex hormones on pregnant uterine contractility in rats: An in vitro study at term

AIMS

The non-genomic (prompt) actions of sex steroids on pregnant uterine contractility are not fully explored yet, the aim of our study was to clarify such effects of 17-β estradiol (E2), progesterone (P4) and testosterone (T) on late (22-day) pregnant uterine contractions together with the signaling pathways in rats in vitro.

METHODS

The uterine effects of sex steroids on KCl-stimulated contractions were examined in the presence of genomic pathway blocker actinomycin D and cycloheximide, sex hormone receptor antagonists (flutamide, fulvestrant, mifepristone) and also after removing the endometrium. The modifications in uterine G-protein activation and cAMP levels were also detected.

RESULTS

T and E2 both relaxed the uterine contractions in the concentration range of 10^-8-10^-3 M with an increase in the activated G-protein and cAMP levels of the uterus, while P4 was ineffective. Cycloheximide, actinomycin D, antagonist for T and E2 were not able to modify the responses along with the endothelium removal. Mifepristone blocked the relaxing effects of T and E2 and reduced the activation of G-protein and the formation of cAMP.

SIGNIFICANCE

T and E2 can inhibit KCl-stimulated contractions in the late pregnant uterus in high concentrations and in a non-genomic manner. Their actions are mediated by a G-protein coupled receptor that can be blocked by mifepristone. A single and high dose of T or E2 might be considered in premature contractions, however, further preclinical and clinical studies are required for the approval of such a therapeutic intervention.

Differential contribution of calcium channels to α1-adrenoceptor-mediated contraction is responsible for diverse responses to cooling between rat tail and iliac arteries

Our previous studies have shown that α₁-adrenoceptors, in addition to α₂-adrenoceptors, are involved in enhanced contraction of cutaneous blood vessels during cooling. The present study aimed to elucidate the mechanism underlying it. In tail and iliac arteries isolated from rats, isometric contraction was measured using a myograph and the phosphorylation level of myosin phosphatase target subunit 1 (MYPT1) was quantified by western blotting. The phenylephrine-induced contraction was enhanced by cooling to 24 °C in tail arteries, but was suppressed in iliac arteries. Endothelium denudation or treatment with iberiotoxin enhanced the phenylephrine-induced contraction in tail arteries at 37 °C; however, neither affected the contraction at 24 °C. The phenylephrine-induced contraction at 37 °C was largely suppressed by nifedipine in iliac arteries, but only slightly in tail arteries. The Rho kinase inhibitor H-1152 largely suppressed the phenylephrine-induced contraction at 24 °C, but only slightly at 37 °C, in both arteries. The phosphorylation level of MYPT1 at Thr855 in tail arteries was increased by the cooling. Taken together, these results suggest the following mechanism in regard to cooling-induced enhancement of α₁-adrenoceptor-mediated contraction in tail arteries: Cooling enhances the contraction of tail arteries via α₁-adrenoceptor stimulation by reducing endothelium-dependent, large-conductance Ca²⁺-activated K⁺ channel-mediated relaxation and by inducing Rho kinase-mediated Ca²⁺ sensitization, although the latter occurs even in iliac arteries. A smaller contribution of voltage-dependent Ca²⁺ channels, which are largely suppressed by cooling, to α₁-adrenoceptor-mediated contraction in tail arteries seems to be more crucially involved in the appearance of the enhanced contractile response to cooling.

Tumor necrosis factor alfa and interleukin 1 alfa induced phosphorylation and degradation of inhibitory kappa B alpha are regulated by estradiol in endometrial cells

Objective:

When bound to the inhibitory kappa B (IкB) protein, the transcription factor nuclear factor kappa B (NF-кB) remains inactively in the cytoplasm. Activated NF-кB upregulates the gene expression of many chemokines including monocyte chemoattractant protein-1 and interleukin (IL)-8. We hypothesized that estrogen may regulate IкB phosphorylation and degradation thus influencing NF-кB-dependent gene expression. Regulation of chemokines by estrogen is different in uterine endometrial cells when compared to ectopic endometrial cells of endometriosis.

Materials and Methods:

We investigated the in vivo expression of IкB in normal endometrium and in eutopic and ectopic endometrium of women with endometriosis. We then studied in cultured endometrial cells to assess the effects of estradiol on IкB and NF-кB function.

Results:

Normal endometrium from mid-late proliferative phase revealed the strongest IкB immunoreactivity throughout the cycle (p<0.05). When compared to paired homologous eutopic endometrium, ectopic endometrium revealed significantly less immunoreactivity for IкB (p<0.05). Moreover, estradiol induced a decrease in tumor necrosis factor-and IL-1-induced IкB phosphorylation, and also decreased the levels of active-NF-кB (p<0.05).

Conclusion:

Our results support the conclusion that one pathway for estradiol-mediated NF-кB inhibition occurs through the down-regulation of IкB phosphorylation. We propose that the estradiol-induced regulation of IкB and consequent reduction in active-NF-кB may affect inflammatory responses in human endometrial cells.

Effects of black cohosh and estrogen on core body and tail-skin temperatures in ovariectomized rats by telemetric monitoring with dual thermistor probes

OBJECTIVES

To investigate the effects of black cohosh and estrogen on the temperature in ovariectomized rats, the core body temperature (CBT) and tail-skin temperature (TST) were simultaneously monitored and the relationship between these two temperatures was explored.

METHODS

Twenty-four female Sprague-Dawley rats aged 8 weeks were randomly divided into four groups: sham-operated (SHAM), ovariectomized (OVX), OVX treated with estradiol valerate (OVX + E), and OVX treated with isopropanolic black cohosh extract (OVX + ICR). Rats were sham-operated or ovariectomized and were implanted with telemetry transmitters with dual thermistor probes. Two weeks after surgery, the animals were treated with drugs for 4 weeks. During the last week of the treatments, the dynamic temperature profiles of the CBT and TST were collected.

RESULTS

The average CBT and TST, TST fluctuation frequency, and the average amplitude fluctuation were significantly higher in OVX than in SHAM rats. In addition, dramatic fluctuations of TST in OVX rats occurred at the time points of the day when the CBTs were lower in OVX rats than in SHAM rats. Treatment of OVX rats with estradiol valerate or isopropanolic black cohosh extract markedly decreased the average CBT and TST, TST fluctuation frequency, and the average amplitude fluctuation. Moreover, CBT was found to be significantly higher, while TST was lower in OVX + E than in OVX + ICR rats.

CONCLUSIONS

Both black cohosh and estradiol treatments ameliorated the abnormal thermoregulation in OVX rats. In particular, black cohosh reduced CBT better than estradiol and estradiol reduced TST better than black cohosh.

Activation of G protein-coupled oestrogen receptor 1 at the onset of reperfusion protects the myocardium against ischemia/reperfusion injury by reducing mitochondrial dysfunction and mitophagy

Background and Purpose

Recent evidence indicates that GPER (G protein‐coupled oestrogen receptor 1) mediates acute pre‐ischaemic oestrogen‐induced protection of the myocardium from ischaemia/reperfusion injury via a signalling cascade that includes PKC translocation, ERK1/2/ GSK‐3β phosphorylation and inhibition of the mitochondrial permeability transition pore (mPTP) opening. Here, we investigated the impact and mechanism involved in post‐ischaemic GPER activation in ischaemia/reperfusion injury. We determined whether GPER activation at the onset of reperfusion confers cardioprotective effects by protecting against mitochondrial impairment and mitophagy.

Experimental Approach

In vivo rat hearts were subjected to ischaemia followed by reperfusion with oestrogen (17β‐oestradiol, E2), E2 + G15, a GPER antagonist, or vehicle. Myocardial infarct size, the threshold for the opening of mPTP, mitophagy, mitochondrial membrane potential, ROS production, proteins ubiquitinated including cyclophilin D, and phosphorylation levels of ERK and GSK‐3β were measured.

Results

We found that post‐ischaemic E2 administration to both male and female ovariectomized‐rats reduced myocardial infarct size. Post‐ischaemic E2 administration preserved mitochondrial structural integrity and this was associated with a decrease in ROS production and increased mitochondrial membrane potential, as well as an increase in the mitochondrial Ca²⁺ load required to induce mPTP opening via activation of the MEK/ERK/GSK‐3β axis. Moreover, E2 reduced mitophagy via the PINK1/Parkin pathway involving LC3I, LC3II and p62 proteins. All these post‐ischaemic effects of E2 were abolished by G15 suggesting a GPER‐dependent mechanism.

Conclusion

These results indicate that post‐ischaemic GPER activation induces cardioprotective effects against ischaemia/reperfusion injury in males and females by protecting mitochondrial structural integrity and function and reducing mitophagy.