Glucocorticoid induction of occludin expression and endothelial barrier requires transcription factor p54 NONO

Stabilizing the neural barrier - A novel approach in pain therapy

Chronic and neuropathic pain are a widespread burden. Incomplete understanding of underlying pathomechanisms is one crucial factor for insufficient treatment. Recently, impairment of the blood nerve barrier (BNB) has emerged as one key aspect of pain initiation and maintenance. In this narrative review, we discuss several mechanisms and putative targets for novel treatment strategies. Cells such as pericytes, local mediators like netrin-1 and specialized proresolving mediators (SPMs), will be covered as well as circulating factors including the hormones cortisol and oestrogen and microRNAs. They are crucial in either the BNB or similar barriers and associated with pain. While clinical studies are still scarce, these findings might provide valuable insight into mechanisms and nurture development of therapeutic approaches.

Non-coding RNAs in the regulation of blood–brain barrier functions in central nervous system disorders

The blood–brain barrier (BBB) is an essential component of the neurovascular unit that controls the exchanges of various biological substances between the blood and the brain. BBB damage is a common feature of different central nervous systems (CNS) disorders and plays a vital role in the pathogenesis of the diseases. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNA (lncRNAs), and circular RNAs (circRNAs), are important regulatory RNA molecules that are involved in almost all cellular processes in normal development and various diseases, including CNS diseases. Cumulative evidences have demonstrated ncRNA regulation of BBB functions in different CNS diseases. In this review, we have summarized the miRNAs, lncRNAs, and circRNAs that can be served as diagnostic and prognostic biomarkers for BBB injuries, and demonstrated the involvement and underlying mechanisms of ncRNAs in modulating BBB structure and function in various CNS diseases, including ischemic stroke, hemorrhagic stroke, traumatic brain injury (TBI), spinal cord injury (SCI), multiple sclerosis (MS), Alzheimer's disease (AD), vascular cognitive impairment and dementia (VCID), brain tumors, brain infections, diabetes, sepsis-associated encephalopathy (SAE), and others. We have also discussed the pharmaceutical drugs that can regulate BBB functions via ncRNAs-related signaling cascades in CNS disorders, along with the challenges, perspective, and therapeutic potential of ncRNA regulation of BBB functions in CNS diseases.

LncRNA NEAT1 Recruits SFPQ to Regulate MITF Splicing and Control RPE Cell Proliferation

Purpose

Retinal pigment epithelium (RPE) cell proliferation is precisely regulated to maintain retinal homoeostasis. Microphthalmia-associated transcription factor (MITF), a critical transcription factor in RPE cells, has two alternatively spliced isoforms: (+)MITF and (-)MITF. Previous work has shown that (-)MITF but not (+)MITF inhibits RPE cell proliferation. This study aims to investigate the role of long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) in regulating MITF splicing and hence proliferation of RPE cells.

Methods

Mouse RPE, primary cultured mouse RPE cells, and different proliferative human embryonic stem cell (hESC)-RPE cells were used to evaluate the expression of (+)MITF, (-)MITF, and NEAT1 by reverse-transcription PCR (RT-PCR) or quantitative RT-PCR. NEAT1 was knocked down using specific small interfering RNAs (siRNAs). Splicing factor proline- and glutamine-rich (SFPQ) was overexpressed with the use of lentivirus infection. Cell proliferation was analyzed by cell number counting and Ki67 immunostaining. RNA immunoprecipitation (RIP) was used to analyze the co-binding between the SFPQ and MITF or NEAT1.

Results

NEAT1 was highly expressed in proliferative RPE cells, which had low expression of (-)MITF. Knockdown of NEAT1 in RPE cells switched the MITF splicing pattern to produce higher levels of (-)MITF and inhibited cell proliferation. Mechanistically, NEAT1 recruited SFPQ to bind directly with MITF mRNA to regulate its alternative splicing. Overexpression of SFPQ in ARPE-19 cells enhanced the binding enrichment of SFPQ to MITF and increased the splicing efficiency of (+)MITF. The binding affinity between SFPQ and MITF was decreased after NEAT1 knockdown.

Conclusions

NEAT1 acts as a scaffold to recruit SFPQ to MITF mRNA and promote its binding affinity, which plays an important role in regulating the alternative splicing of MITF and RPE cell proliferation.

Epigenetics in blood-brain barrier disruption

The vessels of the central nervous system (CNS) have unique barrier properties. The endothelial cells (ECs) which comprise the CNS vessels contribute to the barrier via strong tight junctions, specific transporters, and limited endocytosis which combine to protect the brain from toxins and maintains brain homeostasis. Blood-brain barrier (BBB) leakage is a serious secondary injury in various CNS disorders like stroke, brain tumors, and neurodegenerative disorders. Currently, there are no drugs or therapeutics available to treat specifically BBB damage after a brain injury. Growing knowledge in the field of epigenetics can enhance the understanding of gene level of the BBB and has great potential for the development of novel therapeutic strategies or targets to repair a disrupted BBB. In this brief review, we summarize the epigenetic mechanisms or regulators that have a protective or disruptive role for components of BBB, along with the promising approaches to regain the integrity of BBB.

NONO Is a Negative Regulator of SOX2 Promoter

BACKGROUND/AIM

Sex determining region Y (SRY)-box 2 (SOX2) is a transcription factor essential for the maintenance of proliferation and self-renewal of cancer stem cells and is associated with breast cancer initiation. Regulation of cancer stem cell plasticity by SOX2 requires both positive and negative SOX2 transcription factors, but the negative regulator is still largely unknown.

MATERIALS AND METHODS

SOX2 promoter-binding proteins were identified by liquid chromatography-mass spectrometry/mass spectrometry, luciferase assay, and chromatin immunoprecipitation. The effects of one such transcription factor on SOX2 expression was investigated by knockdown and overexpression experiments.

RESULTS

Non-POU domain-containing octamer-binding protein (NONO) (also known as 54-kDa nuclear RNA-binding protein, P54NRB) was identified as a SOX2 promoter-binding protein and a negative regulator of SOX2 expression. Its activity was controlled by its coiled-coil domain and the C-terminal domain.

CONCLUSION

These results suggest that NONO acts as a key regulator of SOX2 transcription through the repression of SOX2 promoter activity in breast cancer cells.

Title: efficacy of intravitreal dexamethasone implant on hard exudate in diabetic macular edema

Background

To investigate the effect of intravitreal dexamethasone implant (DEX implant) on hard exudate (HE) accompanying diabetic macular edema (DME).

Methods

This study was a non-comparative non-randomized 1-year prospective interventional study. Patients with DME and HE were treated using DEX implant two or three times. Color fundus photography and optical coherence tomography (OCT) were performed at every visit. HE area was measured semi-automatically from the fundus photographs.

Results

Thirty-five patients completed the study. Eleven patients (31.4%) received two injections, while the remaining received three times. HE area (primary outcome) significantly decreased from 1.404±2.094 mm2 (baseline) to 0.212±0.592 mm2 (last visit), which was 24% of the baseline HE area (P<0.001). HE1500 (HE within 1500 μm from the fovea) area also decreased significantly from 0.382±0.467 mm2 to 0.066±0.126 mm2 (P<0.001). Furthermore, anaverage best corrected visual acuity (BCVA) improvement of 4.4 Early Treatment Diabetic Retinopathy Study (ETDRS) letters was observed (from 49.9±18.3 to 54.3±20.4 letters) (P= 0.008). Central macular thickness (CMT) decreased from 455.8±23.6 μm to 366.8±31.1 μm (P=0.009). Repetitive measurements for entire study duration was analyzed using generalized estimating equations (GEE), where BCVA was related to age, CMT, and HE1500 area in multivariate analyses.

Conclusion

DEX implant could reduce and suppress HE in DME for one year with two or three injections. And centrally located HE area (HE1500 area) is related to vision.

Trial registration

ClinicalTrials.gov, NCT02399657, Registered 26 March 2015. 

Endothelial Barrier Integrity Is Disrupted In Vitro by Heme and by Serum From Sickle Cell Disease Patients

Free extracellular heme has been shown to activate several compartments of innate immunity, acting as a danger-associated molecular pattern (DAMP) in hemolytic diseases. Although localized endothelial barrier (EB) disruption is an important part of inflammation that allows circulating leukocytes to reach inflamed tissues, non-localized/deregulated disruption of the EB can lead to widespread microvascular hyperpermeability and secondary tissue damage. In mouse models of sickle cell disease (SCD), EB disruption has been associated with the development of a form of acute lung injury that closely resembles acute chest syndrome (ACS), and that can be elicited by acute heme infusion. Here we explored the effect of heme on EB integrity using human endothelial cell monolayers, in experimental conditions that include elements that more closely resemble in vivo conditions. EB integrity was assessed by electric cell-substrate impedance sensing in the presence of varying concentrations of heme and sera from SCD patients or healthy volunteers. Heme caused a dose-dependent decrease of the electrical resistance of cell monolayers, consistent with EB disruption, which was confirmed by staining of junction protein VE-cadherin. In addition, sera from SCD patients, but not from healthy volunteers, were also capable to induce EB disruption. Interestingly, these effects were not associated with total heme levels in serum. However, when heme was added to sera from SCD patients, but not from healthy volunteers, EB disruption could be elicited, and this effect was associated with hemopexin serum levels. Together our in vitro studies provide additional support to the concept of heme as a DAMP in hemolytic conditions.

Modulation of the p75 neurotrophin receptor using LM11A-31 prevents diabetes-induced retinal vascular permeability in mice via inhibition of inflammation and the RhoA kinase pathway

AIMS/HYPOTHESIS

Breakdown of the inner blood-retinal barrier (BRB) is an early event in the pathogenesis of diabetic macular oedema, that eventually leads to vision loss. We have previously shown that diabetes causes an imbalance of nerve growth factor (NGF) isoforms resulting in accumulation of its precursor proNGF and upregulation of the p75 neurotrophin receptor (p75^NTR), with consequent increases in the activation of Ras homologue gene family, member A (RhoA). We also showed that genetic deletion of p75^NTR in diabetes preserved the BRB and prevented inflammatory mediators in retinas. This study aims to examine the therapeutic potential of LM11A-31, a small-molecule p75^NTR modulator and proNGF antagonist, in preventing diabetes-induced BRB breakdown. The study also examined the role of p75^NTR/RhoA downstream signalling in mediating cell permeability.

METHODS

Male C57BL/6 J mice were rendered diabetic using streptozotocin injection. After 2 weeks of diabetes, mice received oral gavage of LM11A-31 (50 mg kg^-1 day^-1) or saline (NaCl 154 mmol/l) for an additional 4 weeks. BRB breakdown was assessed by extravasation of BSA-AlexaFluor-488. Direct effects of proNGF were examined in human retinal endothelial (HRE) cells in the presence or absence of LM11A-31 or the Rho kinase inhibitor Y-27632.

RESULTS

Diabetes triggered BRB breakdown and caused significant increases in circulatory and retinal TNF-α and IL-1β levels. These effects coincided with significant decreases in retinal NGF and increases in vascular endothelial growth factor and proNGF expression, as well as activation of RhoA. Interventional modulation of p75^NTR activity through treatment of mouse models of diabetes with LM11A-31 significantly mitigated proNGF accumulation and preserved BRB integrity. In HRE cells, treatment with mutant proNGF (10 ng/ml) triggered increased cell permeability with marked reduction of expression of tight junction proteins, zona occludens-1 (ZO-1) and claudin-5, compared with control, independent of inflammatory mediators or cell death. Modulating p75^NTR significantly inhibited proNGF-mediated RhoA activation, occludin phosphorylation (at serine 490) and cell permeability. ProNGF induced redistribution of ZO-1 in the cell wall and formation of F-actin stress fibres; these effects were mitigated by LM11A-31.

CONCLUSIONS/INTERPRETATION

Targeting p75^NTR signalling using LM11A-31, an orally bioavailable receptor modulator, may offer an effective, safe and non-invasive therapeutic strategy for treating macular oedema, a major cause of blindness in diabetes.

Characterization of mouse ocular response to a 35-day spaceflight mission: Evidence of blood-retinal barrier disruption and ocular adaptations

The health risks associated with spaceflight-induced ocular structural and functional damage has become a recent concern for NASA. The goal of the present study was to characterize the effects of spaceflight and reentry to 1 g on the structure and integrity of the retina and blood-retinal barrier (BRB) in the eye. To investigate possible mechanisms, changes in protein expression profiles were examined in mouse ocular tissue after spaceflight. Ten week old male C57BL/6 mice were launched to the International Space Station (ISS) on Space-X 12 at the Kennedy Space Center (KSC) on August, 2017. After a 35-day mission, mice were returned to Earth alive. Within 38 +/− 4 hours of splashdown, mice were euthanized and ocular tissues were collected for analysis. Ground control (GC) and vivarium control mice were maintained on Earth in flight hardware or normal vivarium cages respectively. Repeated intraocular pressure (IOP) measurements were performed before the flight launch and re-measured before the mice were euthanized after splashdown. IOP was significantly lower in post-flight measurements compared to that of pre-flight (14.4–19.3 mmHg vs 16.3–20.3 mmHg) (p < 0.05) for the left eye. Flight group had significant apoptosis in the retina and retinal vascular endothelial cells compared to control groups (p < 0.05). Immunohistochemical analysis of the retina revealed that an increased expression of aquaporin-4 (AQP-4) in the flight mice compared to controls gave strong indication of disturbance of BRB integrity. There were also a significant increase in the expression of platelet endothelial cell adhesion molecule-1 (PECAM-1) and a decrease in the expression of the BRB-related tight junction protein, Zonula occludens-1 (ZO-1). Proteomic analysis showed that many key proteins and pathways responsible for cell death, cell cycle, immune response, mitochondrial function and metabolic stress were significantly altered in the flight mice compared to ground control animals. These data indicate a complex cellular response that may alter retina structure and BRB integrity following long-term spaceflight.

Glucocorticoids exert differential effects on the endothelium in an in vitro model of the blood-retinal barrier

PURPOSE

Glucocorticoids (GCs) are used as treatment in diabetic macular oedema, a condition caused by blood-retinal barrier (BRB) disruption. The proposed mechanisms by which GCs reduce macular oedema are indirect anti-inflammatory effects and inhibition of VEGF production, but direct effects on the BRB endothelium may be equally important. Here, we investigated direct effects of GCs on the endothelium to understand the specific pathways of GC action, to enable development of novel therapeutics lacking the adverse side-effects of the presently used GCs.

METHODS

Primary bovine retinal endothelial cells (BRECs) were grown on Transwell inserts and treated with hydrocortisone (HC), dexamethasone (Dex) or triamcinolone acetonide (TA). Molecular barrier integrity of the BRB was determined by mRNA and protein expression, and barrier function was assessed using permeability assays. In addition, we investigated whether TA was able to prevent barrier disruption after stimulation with VEGF or cytokines.

RESULTS

Treatment of BRECs with GCs resulted in upregulation of tight junction mRNA (claudin-5, occludin, ZO-1) and protein (claudin-5 and ZO-1). In functional assays, only TA strengthened the barrier function by reducing endothelial permeability. Moreover, TA was able to prevent cytokine-induced permeability in human retinal endothelial cells and VEGF-induced expression of plasmalemma vesicle-associated protein (PLVAP), a key player in VEGF-induced retinal vascular leakage.

CONCLUSION

Glucocorticoids have differential effects in an experimental in vitro BRB model. TA is the most potent in improving barrier function, both at the molecular and functional levels, and TA prevents VEGF-induced expression of PLVAP.

Pharmacology of Corticosteroids for Diabetic Macular Edema

Purpose

Corticosteroids remain the mainstay of treatment for inflammatory diseases almost 80 years after their first clinical use. Topical ophthalmic formulations of corticosteroids have been available to treat disease of the anterior segment of the eye, but the approval of corticosteroids to treat vitreoretinal diseases, including vein occlusion, diabetic macular edema, and uveitis, has occurred only recently. Although most diseases respond to corticosteroid therapy, some patients are resistant to this therapy and side effects, including cataract and elevated intraocular pressure, can limit their use. The purpose of this review is to detail the basic science of corticosteroids focusing on differences in potency, drug delivery, pharmacokinetics, and gene activation, and how these differences affect safety and efficacy in the treatment of diabetic macular edema.

Methods

A review was conducted of basic science and pharmacology of the corticosteroids used to treat diabetic macular edema.

Results

Clinically available corticosteroids not only have differing potency and pharmacokinetics, but also activate different genes in different target tissues. These differences are associated with distinct efficacy, pharmacokinetic, and safety profiles. It is important to understand these differences in selecting corticosteroids to treat diabetic macular edema.

Conclusions

Recent advances in our understanding of the basic science of corticosteroids can explain clinical differences in these agents regarding efficacy and safety. Importantly, this understanding should allow the future discovery of additional novel corticosteroids to treat diabetic macular edema.

The role of tight junction proteins in ovarian follicular development and ovarian cancer

Tight junctions (TJ) are protein structures that control the transport of water, ions and macromolecules across cell layers. Functions of the transmembrane TJ protein, occluding (OCLN) and the cytoplasmic TJ proteins, tight junction protein 1 (TJP1; also known as zona occludens protein-1), cingulin (CGN) and claudins (CLDN) are reviewed, and current evidence of their role in the ovarian function is reviewed. Abundance of OCLN, CLDNs and TJP1 mRNA changed during follicular growth. In vitro treatment with various growth factors known to affect ovarian folliculogenesis indicated that CGN, OCLN and TJP1 are hormonally regulated. The summarized studies indicate that expression of TJ proteins (i.e., OCLN, CLDN, TJP1 and CGN) changes with follicle size in a variety of vertebrate species but whether these changes in TJ proteins are increased or decreased depends on species and cell type. Evidence indicates that autocrine, paracrine and endocrine regulators, such as fibroblast growth factor-9, epidermal growth factor, androgens, tumor necrosis factor-α and glucocorticoids may modulate these TJ proteins. Additional evidence presented indicates that TJ proteins may be involved in ovarian cancer development in addition to normal follicular and luteal development. A model is proposed suggesting that hormonal downregulation of TJ proteins during ovarian follicular development could reduce barrier function (i.e., selective permeability of molecules between theca and granulosa cells) and allow for an increase in the volume of follicular fluid as well as allow additional serum factors into the follicle that may directly impact granulosa cell functions.

Dexamethasone suppresses JMJD3 gene activation via a putative negative glucocorticoid response element and maintains integrity of tight junctions in brain microvascular endothelial cells

The blood-brain barrier (BBB) exhibits a highly selective permeability to support the homeostasis of the central nervous system (CNS). The tight junctions in the BBB microvascular endothelial cells seal the paracellular space to prevent diffusion. Thus, disruption of tight junctions results in harmful effects in CNS diseases and injuries. It has recently been demonstrated that glucocorticoids have beneficial effects on maintaining tight junctions in both in vitro cell and in vivo animal models. In the present study, we found that dexamethasone suppresses the expression of JMJD3, a histone H3K27 demethylase, via the recruitment of glucocorticoid receptor α (GRα) and nuclear receptor co-repressor (N-CoR) to the negative glucocorticoid response element (nGRE) in the upstream region of JMJD3 gene in brain microvascular endothelial cells subjected to TNFα treatment. The decreased JMJD3 gene expression resulted in the suppression of MMP-2, MMP-3, and MMP-9 gene activation. Dexamethasone also activated the expression of the claudin 5 and occludin genes. Collectively, dexamethasone attenuated the disruption of the tight junctions in the brain microvascular endothelial cells subjected to TNFα treatment. Therefore, glucocorticoids may help to preserve the integrity of the tight junctions in the BBB via transcriptional and post-translational regulation following CNS diseases and injuries.

Dexamethasone ameliorates H2S-induced acute lung injury by increasing claudin-5 expression via the PI3K pathway

Acute lung injury (ALI) is a major outcome of exposure to high levels of hydrogen sulfide (H₂S). Dexamethasone (DXM) has been used to treat ALI. However, the mechanisms involved in H₂S-induced ALI and the protective mechanisms of DXM in treating ALI are still nebulous. To explore the mechanisms involved, we evaluated the role of claudin-5 in the protective effect of DXM against H₂S-induced ALI. Sprague-Dawley rats were exposed to H₂S to establish the ALI model. In parallel with the animal model, a cell model was also established by incubating human umbilical vein endothelial cells (HUVECs) with NaHS. Lung hematoxylin-eosin staining, electron microscope assay, and wet/dry ratio were used to identify whether the ALI was successfully induced by H₂S, and changes in claudin-5 expression were detected in both rats and HUVECs. Our results revealed that claudin-5 was markedly decreased after H₂S exposure and that DXM significantly attenuated the H₂S-induced downregulation of claudin-5 in both rats and HUVECs. In the animal experiment, p-Akt and p-FoxO₁ presented a similar tendency as claudin-5, but their levels decreased 6 h prior to the levels of claudin-5. In a further investigation, the DXM-induced protective effect on ALI and rescue effect on downregulation of claudin-5 were both blocked by LY294002. The current study demonstrated that claudin-5 was involved in the development of H₂S-induced ALI and that DXM exerted protective effects through increasing claudin-5 expression by activating the phosphatidylinositol 3-kinase pathway. Therefore, claudin-5 might represent a novel pharmacological target for treating ALI induced by H₂S and other hazardous gases.

ECIS technology reveals that monocytes isolated by CD14+ve selection mediate greater loss of BBB integrity than untouched monocytes, which occurs to a greater extent with IL-1β activated endothelium in comparison to TNFα

Background

We have previously shown that TNFα and IL-1β differentially regulate the inflammatory phenotype of human brain endothelial cells (hCMVECs). In this regard, IL-1β treatment was considerably more potent than TNFα at increasing expression of inflammatory chemokines and leukocyte adhesion molecules. We therefore hypothesised that interaction of the hCMVECs with human monocytes would also be dependent on the activation status of the endothelium. Therefore, the primary aim of this study was to assess whether brain endothelial cells activated by IL-1β or TNFα differed in their interaction with monocytes.

Methods

Monocyte interaction was measured using the real time, label-free impedance based ECIS technology, to evaluate endothelial barrier integrity during monocyte attachment and transendothelial migration.

Results

ECIS technology revealed that there was a greater loss of barrier integrity with IL-1β activation and this loss lasted for longer. This was expected and consistent with our hypothesis. However, more striking and concerning was the observation that the method of monocyte enrichment greatly influenced the extent of endothelial barrier compromise. Importantly, we observed that positively isolated monocytes (CD14^+ve) caused greater reduction in barrier resistance, than the negatively selected monocytes (untouched). Analysis of the isolated monocyte populations revealed that the CD14^+ve isolation consistently yields highly pure monocytes (>92%), whereas the untouched isolation was much more variable, yielding ~70% enrichment on average. These two enrichment methods were compared as it was thought that the presence of non-classical CD16^hi monocytes in the untouched enrichment may mediate greater compromise than the classical CD14^hi monocytes. This however, was not the case and these observations raise a number of important considerations pertaining to the enrichment strategy, which are essential for generating reliable and consistent data.

Conclusions

We conclude that IL-1β and TNFα differentially influence monocyte interaction with brain endothelial cells and moreover, the enrichment method also influences the monocyte response as revealed using ECIS technology.

Retinal vascular calibre changes after intravitreal bevacizumab or dexamethasone implant treatment for diabetic macular oedema

PURPOSE

To compare changes in retinal vascular calibre after 2 years of treatment with intravitreal bevacizumab (BVZ) or dexamethasone implant (DEX) in patients with centre-involving diabetic macular oedema (DMO).

METHODS

At baseline, 88 eyes of 61 patients with DMO were recruited in a prospective, multicentre, randomised, single-masked clinical trial. Of these subjects, 22 BVZ-treated (52%) and 22 DEX-treated (48%) eyes of 34 patients (56%) had gradable retinal photographs at both the baseline and 24-month visits. Retinal vascular calibre was measured from digital fundus photographs and summarised as central retinal artery (CRAE) and vein (CRVE) equivalents in all gradable eyes at baseline and 24 months.

RESULTS

At 24 months, 40.9% of BVZ and 45.5% of DEX eyes gained 10 or more letters (p=0.77). There was concurrent reduction in mean central macular thickness, -157.7 μm in BVZ and -192.5 μm in DEX-treated eyes (p=0.40). DEX-treated eyes showed a statistically significant reduction in CRVE compared with BVZ-treated eyes, with a mean change from baseline of -31.78 to +4.34 µm, respectively (p<0.001). CRAE showed a non-statistically significant trend towards reduction over time in DEX-treated eyes compared with BVZ-treated eyes, with a mean change from baseline of -6.09 and +1.66, respectively (p=0.077).

CONCLUSIONS

DEX had a significant narrowing effect on venular diameter in eyes with DMO not seen with BVZ. The changes in retinal vascular calibre suggest that these agents have a differing actions effects retinal vasculature and thereby suggest a potentially different mechanism of action on reducing DMO.

TRIAL REGISTRATION NUMBER

NCT01298076.

Glucocorticoids in the management of peritumoral brain edema: a review of molecular mechanisms

Peritumoral brain edema (PTBE) is mediated by blood-brain barrier breakdown. PTBE results from interstitial vasogenic brain edema due to vascular endothelial growth factor and other inflammatory products of brain tumors. Glucocorticoids (GCs) are the mainstay for treatment of PTBE despite significant systemic side effects. GCs are thought to affect multiple cell types in the edematous brain. Here, we review preclinical studies of GC effects on edematous brain and review mechanisms underlying GC action on tumor cells, endothelial cells, and astrocytes. GCs may reduce tumor cell viability and suppress vascular endothelial growth factor (VEGF) production in tumor cells. Modulation of expression and distribution of tight junction proteins occludin, claudin-5, and ZO-1 in endothelial cells likely plays a central role in GC action on endothelial cells. GCs may also have an effect on astrocyte angiopoietin production and limited effect on astrocyte aquaporin. A better understanding of these molecular mechanisms may lead to the development of novel therapeutics for management of PTBE with a better side effect profile.

Regulation of PCGEM1 by p54/nrb in prostate cancer

PCGEM1 is a long non-coding RNA (lncRNA) that is often upregulated in prostate cancer. However, little is known how PCGEM1 is regulated. In the present study, we show transcriptional regulation of PCGEM1 in response to androgen deprivation by p54/nrb. While ectopic expression of p54/nrb increases, suppression of p54/nrb by RNAi or knockout (KO) reduces PCGEM1. Moreover, rescue experiments indicate that re-expression of p54/nrb in KO cells restores the ability to induce PCGEM1, leading to upregulation of the androgen receptor splice variant AR3 which has been shown to play a role in castration resistance. Finally, 3,3′-Diindolylmethane (DIM), a known chemoprevention agent, is capable of suppressing PCGEM1 expression by preventing the interaction of p54/nrb with the PCGEM1 promoter. In particular, DIM reduces tumor growth by suppression of PCGEM1 and promoting apoptosis in the castrated xenograft mouse model. Together, these results demonstrate a novel mechanism of p54/nrb-mediated expression of PCGEM1 and AR3, contributing to castration resistance in prostate cancer.

Tight Junctions and the Tumor Microenvironment

PURPOSE OF REVIEW

Tight junctions (TJs) are specialized differentiations of epithelial and endothelial cell membranes. TJs play an important role in the adhesion of cells and their interaction with each other. Most cancers originate from epithelial cells. Thus, it is of significance to examine the role of TJs in the tumor microenvironment (TME) and how they affect cancer metastasis.

RECENT FINDINGS

In epithelium-derived cancers, intactness of the primary tumor mass is influenced by intercellular structures as well as cell-to-cell adhesion. Irregularities of these factors may lead to tumor dissociation and subsequent metastasis. Low expression of TJs is observed among highly metastatic cancer cells.

SUMMARY

In this review, we summarized findings from current literature in consideration of the role of TJs in relation to the TME and cancer. Deeper understanding of the mechanisms leading to TJ dysregulation is needed to facilitate the design and conceptualization of new and better therapeutic strategies for cancer.

Pharmacologic Treatment of Noninfectious Uveitis

Uveitis encompasses a spectrum of diseases whose common feature is intraocular inflammation, which may be infectious or noninfectious in etiology (Nussenblatt and Whitcup 2010). Infectious causes of uveitis are typically treated with appropriate antimicrobial therapy and will not be discussed in this chapter. Noninfectious uveitides are thought have an autoimmune component to their etiology and are thus treated with anti-inflammatory agents.

Sustained-release steroids for the treatment of diabetic macular edema

Glucocorticoids have been used for decades in the treatment of ocular disorders via topical, periocular, and more recently intravitreal routes. However, their exact mechanisms of action on ocular tissues remain imperfectly understood. Fortunately, two recently approved intravitreal sustained-release drug delivery systems have opened new perspectives for these very potent drugs. To date, among other retinal conditions, their label includes diabetic macular edema, for which a long-lasting therapeutic effect has been demonstrated both morphologically and functionally in several randomized clinical trials. The rate of ocular complications of intravitreal sustained-release steroids, mainly cataract formation and intraocular pressure elevation, is higher than with anti-vascular endothelial growth factor agents. Yet, a better understanding of the mechanisms underlying these adverse effects and the search for the minimal efficient dose should help optimize their therapeutic window.

Identification of genes and transcription factors associated with glucocorticoid response in lens epithelial cells

Prolonged glucocorticoids (GCs) treatment may lead to the formation of posterior subcapsular cataracts. The present study aimed to investigate differential gene expression in lens epithelial cells (LECs) in response to GCs using DNA microarray profiling. The gene expression profile of GSE13040 was downloaded from the Gene Expression Omnibus database, which includes 12 human LECs treated with vehicle or dexamethasone (Dex) for 4 or 16 h with six samples at each time period, of which three samples were treated with vehicle (control group) and three samples were treated with Dex (Dex group) at each time point. The differentially expressed genes (DEGs) were identified between the control group and the Dex group at each time period with the thresholds of P<0.05 and |logFC|>1. The DEGs were further analyzed using bioinformatics methods. Firstly, DEGs were subject to a hierarchical cluster analysis. Subsequently, the functional enrichment analysis was performed for the common DEGs between the two time periods. Finally, the transcription factors and binding sites of DEGs associated with response to GC stimulus were analyzed. A total of 696 and 949 DEGs were identified at 4 h and 16 h, respectively. Hierarchical cluster analysis revealed that DEG expression was higher in the Dex group than in the control group (P<0.05). A total of 13 significant functions were enriched for the 72 common DEGs at the two time periods. Chemokine (C-C motif) ligand 2 (CCL2), dual-specificity phosphatase-1 (DUSP1) and FAS were associated with the response to GC stimulus and the transcription factor c-Jun bound to promoter regulation regions of CCL2, DUSP1 and FAS. In conclusion, the transcription factors and binding sites of DEGs associated with the response of LECs to GCs may provide potential gene targets for designing and developing drugs to protect against GC-induced cataract formation.

Protective effects of systemic treatment with methylprednisolone in a rodent model of non-arteritic anterior ischemic optic neuropathy (rAION)

This study investigated the protective effects of the administration of steroids on optic nerves (ON) and retinal ganglion cells (RGCs) in a rodent model of non-arteritic anterior ischemic optic neuropathy (rAION). We induced rAION using rose bengal and argon laser irradiation in a photodynamic procedure on the optic discs of rats. The treated groups received methylprednisolone (MP) via peritoneal injection for 2 weeks. The control group received intraperitoneal injections of phosphate-buffered saline (PBS) post-rAION. At the 4th week post-infarct, MP treatments significantly rescued the RGCs (mm(2)) in the central retinas (1920 ± 210, p < 0.001) and mid-peripheral retinas (950 ± 240, respectively, p = 0.018) compared with those of the PBS-treated rats (central: 900 ± 210 and mid-peripheral: 440 ± 180). Functional assessment with flash visual-evoked potentials demonstrated that P1 latency (ms) was shortened in the MP group compared to the PBS group (108 ± 14 and 147 ± 9, respectively, p < 0.001). In addition, the P1 amplitude (uV) was enhanced in the MP group compared to the PBS group (55 ± 12 and 41 ± 13, respectively, p < 0.05). TUNEL assays showed a decrease in the number of apoptotic cells in the RGC layers of MP-treated retinas compared to the PBS-treated group (p < 0.05). ED1 positive cells (/HPF) were significantly decreased in the ONs of the MP group compared to the PBS group (p < 0.001). In conclusion, systemic administration of MP had neuroprotective effects on RGC survival and ON function in the rAION animal model.

Minireview: Steroid/nuclear receptor-regulated dynamics of occluding and anchoring junctions

A diverse set of physiological signals control intercellular interactions by regulating the structure and function of occluding junctions (tight junctions) and anchoring junctions (adherens junctions and desmosomes). These plasma membrane junctions are comprised of multiprotein complexes of transmembrane and cytoplasmic peripheral plasma membrane proteins. Evidence from many hormone-responsive tissues has shown that expression, modification, molecular interactions, stability, and localization of junctional complex-associated proteins can be targeted by nuclear hormone receptors and their ligands through transcriptional and nontranscriptional mechanisms. The focus of this minireview is to discuss molecular, cellular, and physiological studies that directly link nuclear receptor- and ligand-triggered signaling pathways to the regulation of occluding and anchoring junction dynamics.

Steroids and the blood-brain barrier: therapeutic implications

Steroids have a wide spectrum of impact, serving as fundamental regulators of nearly every physiological process within the human body. Therapeutic applications of steroids are equally broad, with a diverse range of medications and targets. Within the central nervous system (CNS), steroids influence development, memory, behavior, and disease outcomes. Moreover, steroids are well recognized as to their impact on the vascular endothelium. The blood-brain barrier (BBB) at the level of the brain microvascular endothelium serves as the principle interface between the peripheral circulation and the brain. Steroids have been identified to impact several critical properties of the BBB, including cellular efflux mechanisms, nutrient uptake, and tight junction integrity. Such actions not only influence brain homeostasis but also the delivery of CNS-targeted therapeutics. A greater understanding of the respective steroid-BBB interactions may shed further light on the differential treatment outcomes observed across CNS pathologies. In this chapter, we examine the current therapeutic implications of steroids respective to BBB structure and function, with emphasis on glucocorticoids and estrogens.

Diabetic macular edema: new concepts in patho-physiology and treatment

Diabetic macular edema (DME), a serious eye complication caused primarily by hyperglycemia, is one of the major causes of blindness. DME, which is characterized by cystic retinal thickening or lipid deposition, is prone to relapse after successful treatment. DME is a complex pathological process caused by multiple factors, including breakdown of the inner and outer blood-retinal barriers, oxidative stress, and elevated levels of vascular endothelial growth factor which have been demonstrated in both preclinical and clinical studies. Starling's law theory explains many of the features of DME. Early detection and treatment of DME can prevent vision loss. Current effective interventions for DME include treatment of systemic risk factors, such as elevated blood glucose, blood pressure and dyslipidemia. Ophthalmic treatments include laser photocoagulation, surgery and intraocular pharmacotherapy. New drugs, which are given by intraocular injection, have emerged in recent years to become first line treatment for DME that affects the central macula with loss of vision. Laser photocoagulation is still the gold standard of treatment for DME which does not involve the central macular. This review outlines these new treatments with particular emphasis on the optimal timing of how they are given.