Inflammatory cytokine-specific alterations in retinal endothelial cell function

Inhibition of Extracellular Signal-Regulated Kinase Activity Improves Cognitive Function in Mice Subjected to Myocardial Infarction

Cognitive impairment is a commonly observed complication following myocardial infarction; however, the underlying mechanisms are still not well understood. The most recent research suggests that extracellular signal-regulated kinase (ERK) plays a critical role in the development and occurrence of cognitive dysfunction-related diseases. This study aims to explore whether the ERK inhibitor U0126 targets the ERK/Signal Transducer and Activator of Transcription 1 (STAT1) pathway to ameliorate cognitive impairment after myocardial infarction. To establish a mouse model of myocardial infarction, we utilized various techniques including Echocardiography, Hematoxylin-eosin (HE) staining, Elisa, Open field test, Elevated plus maze test, and Western blot analysis to assess mouse cardiac function, cognitive function, and signal transduction pathways. For further investigation into the mechanisms of cognitive function and signal transduction, we administered the ERK inhibitor U0126 via intraperitoneal injection. Reduced total distance and activity range were observed in mice subjected to myocardial infarction during the open field test, along with decreased exploration of the open arms in the elevated plus maze test. However, U0126 treatment exhibited a significant improvement in cognitive decline, indicating a protective effect through the inhibition of the ERK/STAT1 signaling pathway. Hence, this study highlights the involvement of the ERK/STAT1 pathway in regulating cognitive dysfunction following myocardial infarction and establishes U0126 as a promising therapeutic target.

Investigating the impact of empagliflozin on the retina of diabetic mice

BACKGROUND

Diabetic retinopathy (DR) frequently results in compromised visual function, with hyperglycemia-induced disruption of the blood-retinal barrier (BRB) through various pathways as a critical mechanism. Existing DR treatments fail to address early and potentially reversible microvascular alterations. This study examined the effects of empagliflozin (EMPA), a selective Sodium-glucose transporter 2 (SGLT2) inhibitor, on the retina of db/db mice. The objective of this study is to investigate the potential role of EMPA in the prevention and delay of DR.

METHODS

db/db mice were randomly assigned to either the EMPA treatment group (db/db + Emp) or the model group (db/db), while C57 mice served as the normal control group (C57). Mice in the db/db + Emp group received EMPA for eight weeks. Body weight, fasting blood glucose (FBG), and blood VEGF were subsequently measured in all mice, along with the detection of specific inflammatory factors and BRB proteins in the retina. Retinal SGLT2 protein expression was compared using immunohistochemical analysis, and BRB structural changes were observed via electron microscopy.

RESULTS

EMPA reduced FBG, blood VEGF, and retinal inflammatory factors TNF-α, IL-6, and VEGF levels in the eye tissues of db/db mice. EMPA also increased Claudin-1, Occludin-1, and ZO-1 levels while decreasing ICAM-1 and Fibronectin, thereby preserving BRB function in db/db mice. Immunohistochemistry revealed that EMPA reduced SGLT2 expression in the retina of diabetic mice, and electron microscopy demonstrated that EMPA diminished tight junction damage between retinal vascular endothelial cells and prevented retinal vascular basement membrane thickening in diabetic mice.

CONCLUSION

EMPA mitigates inflammation and preserves BRB structure and function, suggesting that it may prevent DR or serve as an effective early treatment for DR.

Mechanisms of blood-retinal barrier disruption related to intraocular inflammation and malignancy

Blood-retinal barrier (BRB) disruption is a common accompaniment of intermediate, posterior and panuveitis causing leakage into the retina and macular oedema resulting in vision loss. It is much less common in anterior uveitis or in patients with intraocular lymphoma who may have marked signs of intraocular inflammation. New drugs used for chemotherapy (cytarabine, immune checkpoint inhibitors, BRAF inhibitors, EGFR inhibitors, bispecific anti-EGFR inhibitors, MET receptor inhibitors and Bruton tyrosine kinase inhibitors) can also cause different types of uveitis and BRB disruption. As malignant disease itself can cause uveitis, particularly from breast, lung and gastrointestinal tract cancers, it can be clinically difficult to sort out the cause of BRB disruption. Immunosuppression due to malignant disease and/or chemotherapy can lead to infection which can also cause BRB disruption and intraocular infection. In this paper we address the pathophysiology of BRB disruption related to intraocular inflammation and malignancy, methods for estimating the extent and effect of the disruption and examine why some types of intraocular inflammation and malignancy cause BRB disruption and others do not. Understanding this may help sort and manage these patients, as well as devise future therapeutic approaches.

Effects of tumor necrosis factor-α and interleukin-1β on human retinal endothelial cells

Uveitis, or intraocular inflammation, is a potentially blinding condition that mostly affects the working-age population. The cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-1β, play a role in the pathogenesis of non-infectious uveitis and have been linked to the breakdown of the inner blood-retinal barrier, composed mainly of retinal endothelial cells, leading to macular oedema and vascular leakage. However, the effects of TNF-α and IL-1β on human retinal endothelial function are not fully understood. In this work, we investigated the impact of TNF-α and IL-1β on several aspects of human retinal endothelial cell biology. Through a real-time biosensor, the impact of TNF-α and IL-1β on formation of a retinal endothelial cell barrier was analyzed. Changes in junctional components were assessed via RT-qPCR and immunolabelling. Cell survival, necrosis and apoptosis were appraised via cell proliferation and flow cytometric studies. Tumor necrosis factor-α and IL-1β impaired the electrical resistance of the retinal endothelial cell barrier, while the addition of a potentially barrier-impairing cytokine, IL-6, did not enhance the effect of TNF-α and IL-1β. Level of the gene transcript encoding zonula occludens (ZO)-1 was diminished, while ZO-1 protein configuration was changed by TNF-α and IL-1β. Both cytokines affected human retinal endothelial cell proliferation and viability, while only TNF-α increased rates of necrosis. These results indicate that TNF-α and IL-1β are important drivers of retinal endothelial dysfunction in non-infectious uveitis, suggesting that targeting these cytokines is critical when treating complications of uveitis, such as macular oedema and vascular leakage.

Inflammatory cytokines as mediators of retinal endothelial barrier dysfunction in non-infectious uveitis

Characterised by intraocular inflammation, non-infectious uveitis includes a large group of autoimmune and autoinflammatory diseases that either involve the eye alone or have both ocular and systemic manifestations. When non-infectious uveitis involves the posterior segment of the eye, specifically the retina, there is substantial risk of vision loss, often linked to breakdown of the inner blood-retinal barrier. This barrier is formed by non-fenestrated retinal vascular endothelial cells, reinforced by supporting cells that include pericytes, Müller cells and astrocytes. Across the published literature, a group of inflammatory cytokines stand out as prominent mediators of intraocular inflammation, with effects on the retinal endothelium that may contribute to breakdown of the inner blood-retinal barrier, namely tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL-17 and chemokine C-C motif ligand (CCL)2. This article reviews the function of each cytokine and discusses the evidence for their involvement in retinal endothelial barrier dysfunction in non-infectious uveitis, including basic laboratory investigations, studies of ocular fluids collected from patients with non-infectious uveitis, and results of clinical treatment trials. The review also outlines gaps in knowledge in this area. Understanding the disease processes at a molecular level can suggest treatment alternatives that are directed against appropriate biological targets to protect the posterior segment of eye and preserve vision in non-infectious uveitis.

Azilsartan suppresses the antiapoptotic biomarker and pro-inflammatory cytokines in rat model of cisplatin-induced retinal and optic nerve toxicity

BACKGROUND

The local renin-angiotensin system has been discovered in the eyes; thus, this study evaluates the Azilsartan effect in the retina and optic nerve toxicity induced by Cisplatin in vivo.

METHODOLOGY

Forty-eight male rats were randomly assigned into six groups of 8 animals. Group 1 was healthy control that received 0.5 mL/day of 0.5% carboxymethyl cellulose (CMC) orally (PO). Group 2 received a single dose of the 7.0 mg/kg CIS intraperitoneally with 0.5 mL/day of 0.5% CMC-PO. Groups 3 and 4 received 3.5 and 7.0 mg/kg/day of AZIL-PO, respectively. Groups 5 and 6 received 3.5 and 7.0 mg/kg/day of AZIL-PO, respectively together with a single dose of 7.0 mg/kg of CIS-IP. The ocular tissue and serum estimated the TNF-α, NF-kβ, and Casp-3. A complete blood count was also measured, and the eye was sent for histological examination.

RESULTS

The administration of the 3.5 mg/kg AZIL significantly (p < 0.05) reduced the ocular tissue and serum TNF-α, NF-kB, and Casp-3 levels, when given to CIS treated group, while the 7.0 mg/kg AZIL does not. Additionally, azilsartan shows no negative impact on the CBC in rats. Finally, the eye histological examination showed a significant (p < 0.05) drop in the signs of inflammation and cellular degeneration, particularly after administration of the 3.5 mg/kg AZIL to the CIS-treated group.

CONCLUSION

A low dose of AZIL exerts an anti-inflammation and an anti-apoptotic effect through significant suppression of the pro-inflammatory mediators and an apoptotic biomarker by blocking the local angiotensin II type.

Mechanisms of macular edema

Macular edema is the pathological accumulation of fluid in the central retina. It is a complication of many retinal diseases, including diabetic retinopathy, retinal vascular occlusions and uveitis, among others. Macular edema causes decreased visual acuity and, when chronic or refractory, can cause severe and permanent visual impairment and blindness. In most instances, it develops due to dysregulation of the blood-retinal barrier which permits infiltration of the retinal tissue by proteins and other solutes that are normally retained in the blood. The increase in osmotic pressure in the tissue drives fluid accumulation. Current treatments include vascular endothelial growth factor blockers, corticosteroids, and non-steroidal anti-inflammatory drugs. These treatments target vasoactive and inflammatory mediators that cause disruption to the blood-retinal barrier. In this review, a clinical overview of macular edema is provided, mechanisms of disease are discussed, highlighting processes targeted by current treatments, and areas of opportunity for future research are identified.

The extracellular microenvironment in immune dysregulation and inflammation in retinal disorders

Inherited retinal dystrophies (IRDs) as well as genetically complex retinal phenotypes represent a heterogenous group of ocular diseases, both on account of their phenotypic and genotypic characteristics. Therefore, overlaps in clinical features often complicate or even impede their correct clinical diagnosis. Deciphering the molecular basis of retinal diseases has not only aided in their disease classification but also helped in our understanding of how different molecular pathologies may share common pathomechanisms. In particular, these relate to dysregulation of two key processes that contribute to cellular integrity, namely extracellular matrix (ECM) homeostasis and inflammation. Pathological changes in the ECM of Bruch's membrane have been described in both monogenic IRDs, such as Sorsby fundus dystrophy (SFD) and Doyne honeycomb retinal dystrophy (DHRD), as well as in the genetically complex age-related macular degeneration (AMD) or diabetic retinopathy (DR). Additionally, complement system dysfunction and distorted immune regulation may also represent a common connection between some IRDs and complex retinal degenerations. Through highlighting such overlaps in molecular pathology, this review aims to illuminate how inflammatory processes and ECM homeostasis are linked in the healthy retina and how their interplay may be disturbed in aging as well as in disease.

Effect of cytokine-induced alterations in extracellular matrix composition on diabetic retinopathy-relevant endothelial cell behaviors

Retinal vascular basement membrane (BM) thickening is an early structural abnormality of diabetic retinopathy (DR). Recent studies suggest that BM thickening contributes to the DR pathological cascade; however, much remains to be elucidated about the exact mechanisms by which BM thickening develops and subsequently drives other pathogenic events in DR. Therefore, we undertook a systematic analysis to understand how human retinal microvascular endothelial cells (hRMEC) and human retinal pericytes (hRP) change their expression of key extracellular matrix (ECM) constituents when treated with diabetes-relevant stimuli designed to model the three major insults of the diabetic environment: hyperglycemia, dyslipidemia, and inflammation. TNFα and IL-1β caused the most potent and consistent changes in ECM expression in both hRMEC and hRP. We also demonstrate that conditioned media from IL-1β-treated human Müller cells caused dose-dependent, significant increases in collagen IV and agrin expression in hRMEC. After narrowing our focus to inflammation-induced changes, we sought to understand how ECM deposited by hRMEC and hRP under inflammatory conditions affects the behavior of naïve hRMEC. Our data demonstrated that diabetes-relevant alterations in ECM composition alone cause both increased adhesion molecule expression by and increased peripheral blood mononuclear cell (PBMC) adhesion to naïve hRMEC. Taken together, these data demonstrate novel roles for inflammation and pericytes in driving BM pathology and suggest that inflammation-induced ECM alterations may advance other pathogenic behaviors in DR, including leukostasis.

Inhibitory effects of Humulus japonicus extract against hepatic injury in a diabetic rat model

Chronic diabetes mellitus (DM) can cause liver dysfunction and other complications. As Humulus japonicus is known to have anti-inflammatory and antioxidative effects, we sought to evaluate the hepatoprotective effect of H. japonicus extract (HJE) on a DM model. HJE reduced aspartate aminotransferase, alanine aminotransferase, and direct bilirubin levels and restored albumin activities relative to those found in the DM model. The abnormal levels of triglyceride, total cholesterol, high-density lipoprotein, and low-density lipoprotein in DM returned to normal levels after HJE treatment. DM-induced inflammation of the liver was ameliorated by HJE through reduction of tumor necrosis factor-α, interleukin-1β, and cyclooxygenase-2 levels. HJE treatment downregulated malondialdehyde levels that were increased by DM. However, the downregulated superoxide dismutase and glutathione levels in DM were increased by HJE. Histological studies showed that HJE improves the liver tissue damage caused by DM. Collectively, our findings suggest that HJE may improve liver damage in DM and exhibit an inhibitory effect on hepatic injury through its anti-inflammatory and antioxidative actions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00924-w.

Regulation of blood-retinal barrier cell-junctions in diabetic retinopathy

Loss of the blood-retinal barrier (BRB) integrity and subsequent damage to the neurovascular unit in the retina are the underlying reasons for diabetic retinopathy (DR). Damage to BRB eventually leads to severe visual impairment in the absence of prompt intervention. Diabetic macular edema and proliferative DR are the advanced stages of the disease where BRB integrity is altered. Primary mechanisms contributing to BRB dysfunction include loss of cell-cell barrier junctions, vascular endothelial growth factor, advanced glycation end products-induced damage, and oxidative stress. Although much is known about the involvement of adherens and tight-junction proteins in the regulation of vascular permeability in various diseases, there is a significant gap in our knowledge on the junctional proteins expressed in the BRB and how BRB function is modulated in the diabetic retina. In this review article, we present our current understanding of the molecular composition of BRB, the changes in the BRB junctional protein turnover in DR, and how BRB functional modulation affects vascular permeability and macular edema in the diabetic retina.

The role of reactive oxygen species in the pathogenesis and treatment of retinal diseases

Reactive oxygen species (ROS) normally play an important physiological role in health regulating cellular processes and signal transduction. The amount of ROS is usually kept in fine balance with the generation of ROS largely being offset by the body's antioxidants. A tipping of this balance has increasingly been recognised as a contributor to human disease. The retina, as a result of its cellular anatomy and physical location, is a potent generator of ROS that has been linked to several major retinal diseases. This review will provide a summary of the role of oxidative stress in the pathogenesis of diabetic retinopathy, age-related macular degeneration, myopia, retinal vein occlusion, retinitis pigmentosa and retinopathy of prematurity. Therapies aimed at controlling oxidative stress in these diseases are also examined.

Comparative Analysis of Multiplex Platforms for Detecting Vitreous Biomarkers in Diabetic Retinopathy

Purpose

To evaluate the feasibility of using the Proximity Extension Assay (PEA) platform to detect biomarkers in vitreous and to compare the findings with results obtained with an electrochemiluminescent (ECL) sandwich immunoassay.

Methods

Vitreous samples from patients with proliferative diabetic retinopathy (PDR) and non-diabetic controls were tested using two different proteomics platforms. Forty-one assays were completed with the ECL platform and 459 with the PEA platform. Spearman's rank correlation coefficient (r_s) was used to determine the direction and strength of the relationship between protein levels detected by both platforms.

Results

Three hundred sixty-six PEA assays detected the tested protein in at least 25% of samples, and the difference in protein abundance between PDR and controls was statistically significant for 262 assays. Seventeen ECL assays yielded a detection rate ≥ 25%, and the difference in protein concentration between PDR and controls was statistically significant for 13 proteins. There was a subset of proteins that were detected by both platforms, and for those the Spearman's correlation coefficient was higher than 0.8.

Conclusions

PEA is suitable for the analysis of vitreous samples, showing a strong correlation with the ECL platform. The detection rate of PEA panels was higher than the panels tested with ECL. The levels of several proinflammatory and angiogenic cytokines were significantly higher in PDR vitreous compared to controls.

Translational Relevance

This study provides new information on the yields of small-volume assays that can detect proteins of interest in ocular specimens, and it identifies patterns of cytokine dysregulation in PDR.

The hepato-protective effect of eupatilin on an alcoholic liver disease model of rats

ABSTRACT Eupatilin is known to possess anti-apoptotic, anti-oxidative, and anti-inflammatory properties. We report here that eupatilin has a protective effect on the ethanol-induced injury in rats. Sprague–Dawley rats were divided into 6 groups: control, vehicle, silymarin, eupatilin 10 mg/kg, eupatilin 30 mg/kg, and eupatilin 100 mg/kg. Plasma levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were analyzed to determine the extent of liver damage. Total cholesterol (TC) and triglycerides (TG) were analyzed to determine the level of liver steatosis. Malondialdehyde level, superoxide dismutase (SOD) activity, and glutathione (GSH) level were analyzed to determine the extent of oxidative stress. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β were quantified to verify the degree of inflammation. Based on our findings, chronic alcohol treatment significantly changed the serum indexes and liver indicators of the model rats, which were significantly improved by eupatilin treatment. Rats in the eupatilin-treatment group showed reduced levels of AST, ALT, TG, TC, TNF-α, and IL-1β, increased SOD activity and GSH levels, and improved overall physiology compared to the alcoholic liver disease model rats. H&E staining also verified the eupatilin-mediated improvement in liver injury. In conclusion, eupatilin inhibits alcohol-induced liver injury via its antioxidant and anti-inflammatory effects.

Long-term lutein administration attenuates retinal inflammation and functional deficits in early diabetic retinopathy using the Ins2Akita/+ mice

INTRODUCTION

Lutein is a carotenoid whose protective effects in the retina have been reported in various studies. The effect of lutein has not been reported in the retina of the Ins2^Akita/+ mouse, a well-characterized genetic model for diabetic retinopathy (DR) in which the etiology of diabetes is better defined than the chemically induced diabetes. The objective of the present study is to investigate the effect of long-term administration of lutein in early stages of DR using the Ins2^Akita/+ mouse.

RESEARCH DESIGN AND METHODS

Heterozygous male Ins2^Akita/+ and age-matched wild-type mice were used. Lutein was administered to the mice in drinking water starting 6 weeks old daily until analysis at 4.5, 6.5 or 9 months of age. Plain water served as non-treatment control. Microglia were immunostained with ionized calcium-binding adapter molecule 1 (Iba-1) and cluster of differentiation 68 (CD68) in retinal flat-mounts. Vascular endothelial growth factor (VEGF) level in the retina was assessed by enzyme-linked immunosorbent assay (ELISA). Vascular permeability was analyzed in retinal flat-mounts after fluorescein isothiocyanate (FITC)-dextran perfusion. Retinal occludin expression was assessed via Western blots. Retinal function was examined by electroretinography (ERG).

RESULTS

Increased microglial reactivity was detected in the Ins2^Akita/+ mouse retina and was suppressed by lutein. Lutein administration also reduced the upregulation of VEGF in the Ins2^Akita/+ mouse retina. Increased vascular leakage and decreased occludin expression were observed in the Ins2^Akita/+ mouse retina, and these alterations were attenuated by lutein treatment. ERG recordings showed reduced a-wave and b-wave amplitudes in the Ins2^Akita/+ mice. With lutein treatment, the ERG deficits were significantly alleviated.

CONCLUSIONS

We showed beneficial effects of long-term lutein administration in the Ins2^Akita/+ mouse retina, including suppression of retinal inflammation, protection of retinal vasculature and preservation of retinal function. These results point to lutein's potential as a long-term therapeutic intervention for prevention of inflammation and retinal degeneration in patients with early DR.

Tunicamycin-induced photoreceptor atrophy precedes degeneration of retinal capillaries with minimal effects on retinal ganglion and pigment epithelium cells

Endoplasmic reticulum (ER) stress is recognized as a contributing factor to various ocular neurovascular pathologies including retinitis pigmentosa, glaucoma, and diabetic retinopathy (DR). ER stress in particular is implicated in the development of DR, which is significantly influenced by inflammation driven retinal vascular degeneration and dysfunction. Ultimately, loss of vision occurs if left untreated. However, the identity of the target cells and their temporal involvement in diabetes-mediated dysfunction need further investigation. Early diabetes-induced stress in photoreceptor cells is proposed as the driver of inflammatory mediated neurovascular changes during diabetes. Although tunicamycin induced ER stress results in photoreceptor loss, its consequences for retinal vascular degeneration and retinal ganglion (RGC) and pigment epithelium (RPE) cell loss remains unclear. Here we show intravitreal delivery of tunicamycin primarily induced ER stress in photoreceptor cells resulting in their loss by apoptosis. This was concomitant with induced expression of the unfolded protein response marker CHOP in these cells. We also demonstrated significant degeneration of retinal capillaries following the loss of photoreceptor cells with minimal impact on loss of RGC and RPE cells. However, activation of retinal microglial and Muller cells were noticeable. Thus, our data support the notion that ER stress mediated dysfunction and/or loss of photoreceptor cells in response to inflammation and oxidative stress could precede retinal vascular and neuronal dysfunction and degeneration.

Cyp1b1 expression impacts the angiogenic and inflammatory properties of liver sinusoidal endothelial cells

Cytochrome P450 1B1 (CYP1B1) is a member of the cytochrome p450 family of enzymes that catalyze mono-oxygenase reactions. Although constitutive Cyp1b1 expression is limited in hepatocytes, its expression and function in liver sinusoidal endothelial cells (LSEC) remains unknown. Here we determined the impact of Cyp1b1 expression on LSEC properties prepared from Cyp1b1+/+ and Cyp1b1-/- mice. LSEC expressed PECAM-1, VE-cadherin, and B4 lectin similar to EC from other mouse tissues. Cyp1b1 +/+ LSEC constitutively expressed significant levels of Cyp1b1, while Cyp1b1-/- LSEC lacked Cyp1b1 expression. LSEC also expressed VEGFR3, PROX-1, and LYVE-1, VEGFR1 and VEGFR2, as well as other cell adhesion molecules including ICAM-1, ICAM-2, VCAM-1, and thrombospondin-1 (TSP1) receptors, CD36 and CD47. However, the expression of PV-1 and stabilin (fenestration markers), and endoglin were limited in these cells. The Cyp1b1-/- LSEC showed limited fenestration, and decreased levels of VEGF and BMP6. Cyp1b1-/- LSEC also showed a decrease in the levels of VE-cadherin and ZO-1 impacting adherens and gap junction formation. Cyp1b1-/- LSEC were significantly more apoptotic, proliferated at a faster rate, and were less adherent and more migratory. These changes were attributed, in part, to decreased amounts of TSP1 and increased AKT and ERK activation. The expressions of integrins were also altered by the lack of Cyp1b1, but the ability of these cells to undergo capillary morphogenesis was minimally affected. Furthermore, Cyp1b1-/- LSEC expressed lower levels of inflammatory mediators MCP-1 and TNF-α. Thus, Cyp1b1 expression has a significant impact on LSEC angiogenic and inflammatory functions.

The dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin ameliorates retinal endothelial cell dysfunction triggered by inflammation

Diabetic retinopathy is considered a low-grade chronic inflammatory disease and several inflammatory molecules, including tumor necrosis factor (TNF)-α, are known to play a major role in the degeneration of retinal capillaries. Previous studies have reported that sitagliptin, a DPP-4 inhibitor, prevents the increase in blood-retinal barrier (BRB) permeability and inhibits the tight junction disassembly induced by diabetes.

AIM

Our goal was to investigate whether sitagliptin is able to prevent retinal endothelial cells (EC) dysfunction triggered by the pro-inflammatory cytokine TNF-α.

MAIN METHODS

The effects of TNF-α and/or sitagliptin on primary cultures of bovine retinal EC were tested. The EC monolayer permeability was analyzed by using 70 kDa rhodamine isothiocyanate (RITC) dextran. The cellular distribution profile of claudin-5 was examined by immunofluorescence staining, and DPP-4 activity was evaluated by using a fluorogenic substrate. Cell viability was assessed by MTT assay, and cell proliferation by the BrdU incorporation assay. Retinal EC migration and angiogenesis were evaluated by a scratch assay and a capillary tube formation in matrigel assay, respectively.

KEY FINDINGS

TNF-α increased the permeability of EC monolayer and induced the loss of claudin-5 immunostaining at the cell borders. This impairment was associated with decreased migration and capillary morphogenesis of retinal EC. Sitagliptin was unable to prevent the effect of TNF-α on EC permeability. However, it decreased DPP-4 activity in bovine retinal EC exposed to TNF-α, without affecting cell viability. Moreover, sitagliptin enhanced the migration and capillary morphogenesis in bovine retinal EC challenged with TNF-α.

SIGNIFICANCE

These results suggest that sitagliptin is able to positively modulate vascular EC function under conditions of retinal inflammation.

Neuroprotection by (endo)Cannabinoids in Glaucoma and Retinal Neurodegenerative Diseases

BACKGROUND

Emerging neuroprotective strategies are being explored to preserve the retina from degeneration, that occurs in eye pathologies like glaucoma, diabetic retinopathy, age-related macular degeneration, and retinitis pigmentosa. Incidentally, neuroprotection of retina is a defending mechanism designed to prevent or delay neuronal cell death, and to maintain neural function following an initial insult, thus avoiding loss of vision.

METHODS

Numerous studies have investigated potential neuroprotective properties of plant-derived phytocannabinoids, as well as of their endogenous counterparts collectively termed endocannabinoids (eCBs), in several degenerative diseases of the retina. eCBs are a group of neuromodulators that, mainly by activating G protein-coupled type-1 and type-2 cannabinoid (CB1 and CB2) receptors, trigger multiple signal transduction cascades that modulate central and peripheral cell functions. A fine balance between biosynthetic and degrading enzymes that control the right concentration of eCBs has been shown to provide neuroprotection in traumatic, ischemic, inflammatory and neurotoxic damage of the brain.

RESULTS

Since the existence of eCBs and their binding receptors was documented in the retina of numerous species (from fishes to primates), their involvement in the visual processing has been demonstrated, more recently with a focus on retinal neurodegeneration and neuroprotection.

CONCLUSION

The aim of this review is to present a modern view of the endocannabinoid system, in order to discuss in a better perspective available data from preclinical studies on the use of eCBs as new neuroprotective agents, potentially useful to prevent glaucoma and retinal neurodegenerative diseases.

A function-blocking CD47 antibody modulates extracellular vesicle-mediated intercellular signaling between breast carcinoma cells and endothelial cells

Tumor cells release extracellular vesicles (EVs) into the tumor microenvironment that may facilitate malignant progression and metastasis. Breast carcinoma EVs express high levels of the thrombospondin-1 and signal regulatory protein-α receptor CD47, which is the target of several experimental therapeutics currently in clinical trials. We analyzed changes in gene expression and function in human umbilical vein endothelial cells (HUVEC) induced by treatment with EVs derived from breast carcinoma cells and the effects of the function-blocking CD47 antibody B6H12 on the resulting intercellular communication. CD47⁺ EVs exhibited greater uptake by HUVEC compared to CD47^- EVs, but the CD47 antibody did not inhibit their uptake. Global and targeted analyses of transcripts demonstrated that treatment of HUVEC with EVs derived from MDA-MB-231 breast carcinomas cells altered pathways associated with tumor necrosis factor-α signaling, angiogenesis, lymphangiogenesis, endothelial-mesenchymal transition, and extracellular matrix. EVs from triple-negative MDA-MB-231 cells were more active than EVs from less metastatic breast carcinoma cell lines. Treatment with MDA-MB-231 EVs down-regulated VEGFR2 mRNA expression and tyrosine phosphorylation while enhancing phosphorylation of the tyrosine phosphatase SHP2. VEGFR2 expression and phosphorylation in HUVEC was further inhibited by the CD47 antibody. Consistent with the observed changes in endothelial-mesenchymal transition genes and SHP2, treatment with MDA-MB-231-derived EVs decreased Zeb1 protein levels in HUVEC, whereas the CD47 antibody increased Zeb1 levels. The induction of E-selectin and other known targets of tumor necrosis factor-α signaling by EVs was also enhanced by the CD47 antibody, and E-selectin was the most up-regulated transcript following CD47 antibody treatment alone. These studies reveal several mechanisms by which therapeutics targeting CD47 could modulate tumor growth by altering the cross talk between cancer-derived EVs and nonmalignant cells in the tumor stroma.

Tenascins in Retinal and Optic Nerve Neurodegeneration

Tenascins represent key constituents of the extracellular matrix (ECM) with major impact on central nervous system (CNS) development. In this regard, several studies indicate that they play a crucial role in axonal growth and guidance, synaptogenesis and boundary formation. These functions are not only important during development, but also for regeneration under several pathological conditions. Additionally, tenascin-C (Tnc) represents a key modulator of the immune system and inflammatory processes. In the present review article, we focus on the function of Tnc and tenascin-R (Tnr) in the diseased CNS, specifically after retinal and optic nerve damage and degeneration. We summarize the current view on both tenascins in diseases such as glaucoma, retinal ischemia, age-related macular degeneration (AMD) or diabetic retinopathy. In this context, we discuss their expression profile, possible functional relevance, remodeling of the interacting matrisome and tenascin receptors, especially under pathological conditions.

Transcription factor SP1 mediates hyperglycemia-induced upregulation of roundabout4 in retinal microvascular endothelial cells

Roundabout4 (Robo4) is a gene that is expressed specifically in vasculature and is involved in the angiogenesis and integrity of blood vessels. The expression level of Robo4 increases gradually along with the development of diabetic retinopathy (DR). In this study, we explored the mechanism of transcriptional regulation of Robo4 in retinal endothelial cells, and investigated the effects of this regulation on cellular functions under hyperglycemic conditions. Human retinal endothelial cells (HREC) exposed to hyperglycemia were used to detect the expression levels of specificity protein 1 (SP1) and Robo4 by RT-qPCR and western blotting. Small interfering RNA (SiRNA) transfection technology was used to analyze the regulatory relationship between SP1 and Robo4. The effect of transcription factor SP1 on Robo4 promoter activity and the location of SP1 binding sites were investigated using chromatin immunoprecipitation (ChIP) and luciferase assay. Cell migration, monolayer permeability and tube formation assays were performed to demonstrate the role of SP1/Robo4 in regulating HREC functions in hyperglycemic conditions. The results showed that hyperglycemia upregulated the mRNA and protein levels of SP1 and Robo4 in HREC. Depletion of SP1 by siRNA transfection inhibited the hyperglycemia induced overexpression of Robo4. ChIP combined with luciferase assay showed that under hyperglycemic conditions, SP1 significantly increased the transcriptional level of Robo4 via an additional SP1 binding site at -1912/-1908 in the Robo4 promoter. Repressing the SP1/Robo4 pathway effectively mitigated the abnormity in HREC migration, permeability and angiogenesis induced by hyperglycemia. All these findings indicate that hyperglycemia-induced upregulation of Robo4 is mediated by enhanced transcription of SP1. The SP1/Robo4 signaling pathway can regulate the migratory ability, monolayer permeability and angiogenesis of HREC under hyperglycemic conditions, suggesting that it may play an important role in microvascular dysfunction during DR.

Expression and Function of Interleukin-1β-Induced Neutrophil Gelatinase-Associated Lipocalin in Renal Tubular Cells

Acute kidney injury (AKI) is characterized by a sudden loss of renal function. Early recognition of AKI, especially in critically ill patients, is essential for adequate therapy. Currently, neutrophil gelatinase-associated lipocalin (NGAL) is considered to be an effective biomarker of AKI; however, the regulation of its expression and function in renal tubular cells remains unclear. In this study, we investigated the regulation of the expression and function of NGAL in IL-1β-treated Madin–Darby canine kidney (MDCK) cells as a model of renal tubular cells. IL-1β induced a disturbance in the localization of E-cadherin and zonaoccludin-1 (ZO-1). The transepithelial electrical resistance (TER) also decreased 5 days after IL-1β treatment. IL-1β induced NGAL mRNA expression and protein secretion in a time- and dose-dependent manner, which occurred faster than the decrease in TER. In the presence of ERK1/2 and p38 inhibitors, IL-1β-induced NGAL mRNA expression and protein secretion were significantly attenuated. In the presence of recombinant NGAL, IL-1β-induced disturbance in the localization of E-cadherin and ZO-1 was attenuated, and the decrease in TER was partially maintained. These results suggest that NGAL can be used as a biomarker for AKI and that it functions as a protector from AKI.

LRP-1 Pathway Targeted Inhibition of Vascular Abnormalities in the Retina of Diabetic Mice

PURPOSE

The cell surface LDL (low-density lipoprotein) receptor-related protein-1 (LRP-1) is important for lipid transport and several cell signaling processes. Human apolipoprotein E (apoE) is a ligand of LRP-1. We previously reported that a short peptide (apoEdp) mimicking the LRP-1 binding region of apoE prevents hyperglycemia-induced retinal endothelial cell dysfunction in vitro. The in-vivo outcome of apoE-based peptidomimetic inhibition of LRP-1 in the treatment of diabetic retinopathy is unknown.

METHODS

Six months after streptozotocin induction of diabetes, male C57Bl/6 mice were intravitreally inoculated with apoEdp in a controlled release formulation. On the 15th day post-apoEdp treatment, mouse retinas were harvested to examine (1) blood-retinal-barrier (BRB) permeability by Evans blue dye, inflammatory leukostasis by concanavalin staining of leukocytes and LRP-1 pathway-related protein expression by Western blot analysis and gelatin zymography.

RESULTS

Intravitreal apoEdp treatment of diabetic mice significantly reduced Evans blue extravasation and the number of adherent leukocytes in the diabetic mouse retinas. ApoEdp treatment inhibited the expression of extracellular matrix (ECM) degrading proteases heparanase and MMP-2, and restores the BRB tight junction proteins occludin and ZO-1. ApoEdp treatment also inhibited Wnt/β-catenin-related expression of pro-inflammatory molecules ICAM-1, HIF-1α, and VEGF through negative regulation by LRP-1.

CONCLUSION

Intravitreal apoEdp treatment of diabetic mice resulted a significant decrease in retinal vascular abnormalities through downregulation of LRP-1-related ECM protein degradation and Wnt/β-catenin-related pro-angiogenic molecules.

Transplantation of IL-10-transfected endothelial progenitor cells improves retinal vascular repair via suppressing inflammation in diabetic rats

PURPOSE

We aimed to evaluate the effect of IL-10 gene transfection on endothelial progenitor cells (EPCs) under inflammatory conditions, and explore the therapeutic potential of IL-10-transfected EPC transplantation on nonproliferative diabetic retinopathy (NPDR).

METHODS

Lentivirus vectors encoding IL-10 were constructed and introduced into EPCs isolated from rat bone marrow. After exposure to recombinant rat TNF-α, abilities of nontransfected EPCs (non-EPCs) and EPCs transfected with normal control lentivirus (EPCs-GFP) or IL-10 expressing lentivirus (EPCs-IL-10-GFP) were assessed, including migration, adhesion, and tube formation. IL-10 production by EPCs-IL-10-GFP was determined by ELISA. Following 12 weeks after establishment of diabetes, diabetic rats were randomly injected with non-EPCs, EPCs-GFP, or EPCs-IL-10-GFP via tail vein. Expression of inflammatory factors and factors associated with nuclear factor-kappa B (NF-kB) signal pathway, retinal histological analysis, and retinal vascular permeability were assessed 2 weeks after transplantation.

RESULTS

The detrimental effects of TNF-ɑ on the abilities of EPCs were significantly attenuated in EPCs-IL-10-GFP compared with non-EPCs and EPCs-GFP. The concentration of IL-10 in the EPCs-IL-10-GFP group was significantly higher than the non-EPCs and EPCs-GFP groups. Additionally, transplantation of EPCs-IL-10-GFP significantly inhibited inflammatory factors expression and activation of NF-kB signal pathway, improved retinal histological changes, and attenuated retinal vascular permeability.

CONCLUSION

In conclusion, transplantation of IL-10-transfected EPCs significantly improved EPCs-mediated retinal vascular repair and subsequently suppressed NPDR progression. This was associated with inflammation suppression, at least partly via inhibiting the NF-kB signal pathway. Transplantation of IL-10-transfected EPCs may be a new strategy for treatment of NPDR.

Early remodelling of the extracellular matrix proteins tenascin-C and phosphacan in retina and optic nerve of an experimental autoimmune glaucoma model

Glaucoma is characterized by the loss of retinal ganglion cells (RGCs) and optic nerve fibres. Previous studies noted fewer RGCs after immunization with ocular antigens at 28 days. It is known that changes in extracellular matrix (ECM) components conduct retina and optic nerve degeneration. Here, we focused on the remodelling of tenascin‐C and phosphacan/receptor protein tyrosine phosphatase β/ζ in an autoimmune glaucoma model. Rats were immunized with optic nerve homogenate (ONA) or S100B protein (S100). Controls received sodium chloride (Co). After 14 days, no changes in RGC number were noted in all groups. An increase in GFAPmRNA expression was observed in the S100 group, whereas no alterations were noted via immunohistochemistry in both groups. Extracellular matrix remodelling was analyzed after 3, 7, 14 and 28 days. Tenascin‐C and 473HD immunoreactivity in retinae and optic nerves was unaltered in both immunized groups at 3 days. At 7 days, tenascin‐C staining increased in both tissues in the ONA group. Also, in the optic nerves of the S100 group, an intense tenascin‐C staining could be shown. In the retina, an increased tenascin‐C expression was also observed in ONA animals via Western blot. 473HD immunoreactivity was elevated in the ONA group in both tissues and in the S100 optic nerves at 7 days. At 14 days, tenascin‐C and 473HD immunoreactivity was up‐regulated in the ONA retinae, whereas phosphacan expression was up‐regulated in both groups. We conclude that remodelling of tenascin‐C and phosphacan occurred shortly after immunization, already before RGC loss. We assume that both ECM molecules represent early indicators of neurodegeneration.

Basement membrane stiffening promotes retinal endothelial activation associated with diabetes

Endothelial activation is a hallmark of the high-glucose (HG)-induced retinal inflammation associated with diabetic retinopathy (DR). However, precisely how HG induces retinal endothelial activation is not fully understood. We hypothesized that HG-induced up-regulation of lysyl oxidase (LOX), a collagen-cross-linking enzyme, in retinal capillary endothelial cells (ECs) enhances subendothelial basement membrane (BM) stiffness, which, in turn, promotes retinal EC activation. Diabetic C57BL/6 mice exhibiting a 70 and 50% increase in retinal intercellular adhesion molecule (ICAM)-1 expression and leukocyte accumulation, respectively, demonstrated a 2-fold increase in the levels of BM collagen IV and LOX, key determinants of capillary BM stiffness. Using atomic force microscopy, we confirmed that HG significantly enhances LOX-dependent subendothelial matrix stiffness in vitro, which correlated with an ∼2.5-fold increase in endothelial ICAM-1 expression, a 4-fold greater monocyte-EC adhesion, and an ∼2-fold alteration in endothelial NO (decrease) and NF-κB activation (increase). Inhibition of LOX-dependent subendothelial matrix stiffening alone suppressed HG-induced retinal EC activation. Finally, using synthetic matrices of tunable stiffness, we demonstrated that subendothelial matrix stiffening is necessary and sufficient to promote EC activation. These findings implicate BM stiffening as a critical determinant of HG-induced retinal EC activation and provide a rationale for examining BM stiffness and underlying mechanotransduction pathways as therapeutic targets for diabetic retinopathy.

Deletion of Src family kinase Lyn aggravates endotoxin-induced lung inflammation

Overwhelming acute inflammation often leads to tissue damage during endotoxemia. In the present study, we investigated the role of Lyn, a member of the Src family tyrosine kinases, in modulating inflammatory responses in a murine model of endotoxemia. We examined lung inflammatory signaling in Lyn knockout (Lyn−/−) mice and wild-type littermates (Lyn+/+) during endotoxemia. Our data indicate that Lyn deletion aggravates endotoxin-induced pulmonary inflammation and proinflammatory signaling. We found increased activation of proinflammatory transcription factor NF-κB in the lung tissues of Lyn−/− mice after endotoxin challenge. Furthermore, during endotoxemia, the lung tissues of Lyn−/− mice showed increased inflammasome activation indicated by augmented caspase-1 and IL-1β cleavage and activation. The aggravated lung inflammatory signaling in Lyn−/− mice was associated with increased production of proinflammatory mediators and elevated matrix metallopeptidase 9 and reduced VE-cadherin levels. Our results suggest that Lyn kinase modulates inhibitory signaling to suppress endotoxin-induced lung inflammation.

Palmitoylethanolamide treatment reduces retinal inflammation in streptozotocin-induced diabetic rats

Although the pathogenesis of diabetic retinopathy (DR) is still insufficiently understood, new evidences indicate 'retinal inflammation' as an important player in the pathogenesis of the complication. Accordingly, common sets of upregulated inflammatory cytokines are found in serum, vitreous and aqueous samples obtained from subjects with DR, and these cytokines can have multiple interactions to impact the pathogenesis of the disease. Thus, based on previously published data, we investigated the effects of Palmitoylethanolamide (PEA), an endogenous lipid amide that belongs to the N-acyl-ethanolamines family, on DR in streptozotocin (STZ)-induced diabetic rats. PEA (10mg/kg) was administered orally daily starting 3 days after the iv administration of STZ. The rats were killed 15 and 60day later and eyes were enucleated to evaluate, through immunohistochemical analysis, the key inflammatory events involved in the breakdown of blood retinal barrier (BRB). Immunohistochemical analysis confirmed the presence of VEGF, ICAM-1, nitrotyrosine (a marker of peroxynitrite), and tight junctions in the retina of STZ-treated rats. Of interest, the extent of injury was significantly reduced after treatment with PEA. Altogether, this study provides the first evidence that PEA attenuates the degree of inflammation while preserving the blood-retinal barrier in rats with experimental DR.

IL-1 beta but not the NALP3 inflammasome is an important determinant of endothelial cell responses to necrotic/dangerous trophoblastic debris

INTRODUCTION

Necrotic but not apoptotic trophoblastic debris can induce endothelial cell activation but the mechanism by which endothelial cells distinguish apoptotic from necrotic debris is unclear. The NALP3 inflammasome is a pattern recognition receptor that macrophages employ to recognise "danger signals" in necrotic cell corpses. In this study, we hypothesized that endothelial cells can identify and respond to necrotic trophoblastic debris via the NALP3 inflammasome.

METHODS

The effect of trophoblastic debris on endothelial expression of NALP3 inflammasome components was investigated using qRT-PCR, immunoassays and fluorescent caspase 1 activity assay. IL-1β in was quantified by ELISA. Endothelial cell activation was measured by cell surface ICAM expression and monocytes adhesion assay.

RESULTS

The NALP3 inflammasome was expressed in resting vascular endothelial cells and is involved in endothelial response to danger signals. However, exposure to necrotic trophoblastic debris did not significantly alter the expression of any of the three components of the NALP3 inflammasome at the mRNA level, nor was caspase-1 activation increased. Conditioned media from endothelial cells exposed to necrotic trophoblastic debris contained elevated levels of IL-1β which was derived from the necrotic debris and which contributed to endothelial cell activation.

DISCUSSION

Necrotic trophoblastic debris induced endothelial cell activation through the IL-1β/IL-1R pathway. However, the NALP3 inflammasome in endothelial cells was not involved in this process.

Effect of Musca domestic maggot polypeptide extract on HUVEC dysfunction induced by early-activated macrophages

CONTEXT

Musca domestica Linn. maggot is a traditional Chinese medicine. In our previous studies, Musca domestica maggot protein-enriched fraction and polypeptide extract (molecular weight <30 kD) were found to reverse endothelial cell dysfunction in atherosclerotic lesions.

OBJECTIVE

This study determines whether and how M. domestica maggot polypeptide extract affects the dysfunction of human umbilical vein endothelial cells (HUVEC) induced by macrophages (Mϕ).

MATERIALS AND METHODS

HUVEC and early-activated THP-1 Mϕ (incubated with LPS of 1 μg/ml for 2 h) were co-cultured in a Transwell system. The effects of Musca domestica maggot polypeptide extract (with increasing concentrations, i.e., 1.0, 2.5, 5.0, 10.0, 20.0, and 40.0 µg/ml) on the proliferation and migration HUVEC and their secretion of vascular endothelial growth factor (VEGF) were determined by flow cytometry, modified Boyden chamber assay, and enzyme-linked immunosorbent assay (ELISA) after incubation for 24 h.

RESULTS

Musca domestica maggot polypeptide extract decreased the proliferation of HUVEC in a concentration-dependent manner, with a 50% effective concentration (EC50) of 22.16 ± 1.48 µg/ml, and effectively inhibited HUVEC migration (EC50 = 35.15 ± 2.03 µg/ml) and VEGF secretion (EC50 = 28.64 ± 1.29 µg/ml).

DISCUSSION AND CONCLUSION

Musca domestica maggot polypeptide extract can inhibit the dysfunction of HUVEC induced by early-activated THP-1 Mϕ.

Extracellular matrix, gap junctions, and retinal vascular homeostasis in diabetic retinopathy

The vascular basement membrane (BM) contains extracellular matrix (ECM) proteins that assemble in a highly organized manner to form a supportive substratum for cell attachment facilitating myriad functions that are vital to cell survival and overall retinal homeostasis. The BM provides a microenvironment in which bidirectional signaling through integrins regulates cell attachment, turnover, and functionality. In diabetic retinopathy, the BM undergoes profound structural and functional changes, and recent studies have brought to light the implications of such changes. Thickened vascular BM in the retinal capillaries actively participate in the development and progression of characteristic changes associated with diabetic retinopathy. High glucose (HG)-induced compromised cell-cell communication via gap junctions (GJ) in retinal vascular cells may disrupt homeostasis in the retinal microenvironment. In this review, the role of altered ECM synthesis, compromised GJ activity, and disturbed retinal homeostasis in the development of retinal vascular lesions in diabetic retinopathy are discussed.

Cytochrome P450 1B1 and Primary Congenital Glaucoma

Cytochrome P450 1B1 (Cyp1b1) belongs to the CYP450 superfamily of heme-binding mono-oxygenases which catalyze oxidation of various endogenous and exogenous substrates. The expression of Cyp1b1 plays an important role in the modulation of development and functions of the trabecular meshwork (TM). Mutations in Cyp1b1 have been reported in patients with primary congenital glaucoma (PCG). Mice lacking Cyp1b1 also exhibit developmental defects in the TM similar to those reported in congenital glaucoma patients. However, how Cyp1b1 deficiency contributes to TM dysgenesis remains unknown. In the present review, we will address the significance of Cyp1b1 expression and/or its function in anterior segment development. Cyp1b1-deficient (Cyp1b1^−/−) mice are discussed as a promising model for an oxidative stress-induced model of PCG, in which Cyp1b1 activity is revealed as an important modulator of oxidative homeostasis contributing to the development and structural function of the TM. This conclusion suggests a possible clinical intervention for individuals who are genetically at high risk of developing PCG.

Interactions between osteopontin and vascular endothelial growth factor: Implications for cancer

For this comprehensive review, 257 publications with the keywords "osteopontin" or "OPN" and "vascular endothelial growth factor" or "VEGF" in PubMed were screened (time frame from year 1996 to year 2014). 37 articles were excluded because they were not focused on the interactions between these molecules, and papers relevant for transformation-related phenomena were selected. Osteopontin (OPN) and vascular endothelial growth factor (VEGF) are characterized by a convergence in function for regulating cell motility and angiogenesis, the response to hypoxia, and apoptosis. Often, they are co-expressed or one molecule induces the other, however, in some settings OPN-associated pathways and VEGF-associated pathways are distinct. Their relationships affect the pathogenesis in cancer, where they contribute to progression and angiogenesis and serve as markers for poor prognosis. The inhibition of OPN may reduce VEGF levels and suppress tumor progression. In vascular pathologies, these two cytokines mediate remodeling, but may also perpetuate inflammation and narrowing of the arteries. OPN and VEGF are elevated and contribute to vascularization in inflammatory diseases.

Sirt1 restrains lung inflammasome activation in a murine model of sepsis

Excessive inflammation is a major cause of organ damage during sepsis. The elderly are highly susceptible to sepsis-induced organ injury. Sirt1 expression is reduced during aging. In the present study, we investigated the role of Sirt1, a histone deacetylase, in controlling inflammatory responses in a murine sepsis model induced by cecal ligation and puncture (CLP). We examined lung inflammatory signaling in inducible Sirt1 knockout (Sirt1(-/-)) mice and wild-type littermates (Sirt1(+/+)) after CLP. Our results demonstrated that Sirt1 deficiency led to severe lung inflammatory injury. To further investigate molecular mechanisms of Sirt1 regulation of lung inflammatory responses in sepsis, we conducted a series of experiments to assess lung inflammasome activation after CLP. We detected increased lung inflammatory signaling including NF-κB, signal transducer and activator of transcription 3, and ERK1/2 activation in Sirt1(-/-) mice after CLP. Furthermore, inflammasome activity was increased in Sirt1(-/-) mice after CLP, as demonstrated by increased IL-1β and caspase-7 cleavage and activation. Aggravated inflammasome activation in Sirt1(-/-) mice was associated with the increased production of lung proinflammatory mediators, including ICAM-1 and high-mobility group box 1, and further disruption of tight junctions and adherens junctions, as demonstrated by dramatic reduction of lung claudin-1 and vascular endothelial-cadherin expression, which was associated with the upregulation of matrix metallopeptidase 9 expression. In summary, our results suggest that Sirt1 suppresses acute lung inflammation during sepsis by controlling inflammasome activation pathway.

Aberrant phenotype in human endothelial cells of diabetic origin: implications for saphenous vein graft failure?

Type 2 diabetes (T2DM) confers increased risk of endothelial dysfunction, coronary heart disease, and vulnerability to vein graft failure after bypass grafting, despite glycaemic control. This study explored the concept that endothelial cells (EC) cultured from T2DM and nondiabetic (ND) patients are phenotypically and functionally distinct. Cultured human saphenous vein- (SV-) EC were compared between T2DM and ND patients in parallel. Proliferation, migration, and in vitro angiogenesis assays were performed; western blotting was used to quantify phosphorylation of Akt, ERK, and eNOS. The ability of diabetic stimuli (hyperglycaemia, TNF-α, and palmitate) to modulate angiogenic potential of ND-EC was also explored. T2DM-EC displayed reduced migration (~30%) and angiogenesis (~40%) compared with ND-EC and a modest, nonsignificant trend to reduced proliferation. Significant inhibition of Akt and eNOS, but not ERK phosphorylation, was observed in T2DM cells. Hyperglycaemia did not modify ND-EC function, but TNF-α and palmitate significantly reduced angiogenic capacity (by 27% and 43%, resp.), effects mimicked by Akt inhibition. Aberrancies of EC function may help to explain the increased risk of SV graft failure in T2DM patients. This study highlights the importance of other potentially contributing factors in addition to hyperglycaemia that may inflict injury and long-term dysfunction to the homeostatic capacity of the endothelium.

Interleukin-10 overexpression improves the function of endothelial progenitor cells stimulated with TNF-α through the activation of the STAT3 signaling pathway

Lentivirus vector-interleukin-10 green fluorescent protein (LV-IL-10-GFP) was transfected into endothelial progenitor cells (EPCs) in the present study. The aim was to detect the function of IL‑10‑modified EPCs and analyze the molecular mechanism. EPCs were cultured and identified by fluorescent labeling with the von Willebrand factor antibody, vascular endothelial growth factor (VEGF) receptor, Ulex europaeus agglutinin-1 and acetylated low‑density lipoprotein. Subsequently, EPCs were transfected with LV-IL-10-GFP and lentivirus vector‑noncontain‑GFP as the control group. Enzyme‑linked immunosorbent assay (ELISA) was used to detect the concentrations of cytokines in the supernatant with or without tumor necrosis factor‑α (TNF‑α). All types of cells were assessed by a tube formation assay, adhesion assay and migration assay induced with or without TNF‑α. Cell cycle was assessed by flow cytometry. Western blot analysis was applied to detect the expression of proteins in the cells. ELISA analysis showed that the levels of TNF‑α and IL‑8 in the supernatant without TNF‑α significantly decreased in EPC‑LV‑IL‑10‑GFP (P<0.05 for all). By contrast, the levels of IL‑10 and VEGF were contrasting in association with these. The concentrations of cytokines in the supernatant with TNF‑α were consistent to the supernatant without TNF‑α. There was no statistically significant difference in the average number of EPCs undergoing migration, adhesion, total length and cell growth among the EPC, EPC‑LV‑IL‑10‑GFP and EPC‑LV‑NC‑GFP groups without TNF‑α. Further study showed that EPC‑LV‑IL‑10‑GFP with TNF‑α significantly enhanced EPC migration, adhesion and promoted tube formation (P<0.05 for all). Western blot analysis revealed that the expression of VEGF, matrix metallopeptidase‑9 and phosphorylated‑signal transducer and activator of transcription 3 (p‑STAT3) significantly increased in the EPC‑LV‑IL‑10‑GFP group. Conversely, STAT‑3 expression decreased in the EPC‑LV‑IL‑10‑GFP group. The present study suggested that overexpression of IL‑10 had no effect on migration, adhesion, tubule formation and cell growth of EPCs without TNF‑α. Furthermore, in EPCs stimulated with TNF‑α, the overexpression of IL‑10 improved EPC function, including migration, adhesion and tubule formation by activating the STAT3 signal pathway.

High glucose alters retinal astrocytes phenotype through increased production of inflammatory cytokines and oxidative stress

Astrocytes are macroglial cells that have a crucial role in development of the retinal vasculature and maintenance of the blood-retina-barrier (BRB). Diabetes affects the physiology and function of retinal vascular cells including astrocytes (AC) leading to breakdown of BRB. However, the detailed cellular mechanisms leading to retinal AC dysfunction under high glucose conditions remain unclear. Here we show that high glucose conditions did not induce the apoptosis of retinal AC, but instead increased their rate of DNA synthesis and adhesion to extracellular matrix proteins. These alterations were associated with changes in intracellular signaling pathways involved in cell survival, migration and proliferation. High glucose conditions also affected the expression of inflammatory cytokines in retinal AC, activated NF-κB, and prevented their network formation on Matrigel. In addition, we showed that the attenuation of retinal AC migration under high glucose conditions, and capillary morphogenesis of retinal endothelial cells on Matrigel, was mediated through increased oxidative stress. Antioxidant proteins including heme oxygenase-1 and peroxiredoxin-2 levels were also increased in retinal AC under high glucose conditions through nuclear localization of transcription factor nuclear factor-erythroid 2-related factor-2. Together our results demonstrated that high glucose conditions alter the function of retinal AC by increased production of inflammatory cytokines and oxidative stress with significant impact on their proliferation, adhesion, and migration.

Environmental enrichment protects the retina from early diabetic damage in adult rats

Diabetic retinopathy is a leading cause of reduced visual acuity and acquired blindness. Available treatments are not completely effective. We analyzed the effect of environmental enrichment on retinal damage induced by experimental diabetes in adult Wistar rats. Diabetes was induced by an intraperitoneal injection of streptozotocin. Three days after vehicle or streptozotocin injection, animals were housed in enriched environment or remained in a standard environment. Retinal function (electroretinogram, and oscillatory potentials), retinal morphology, blood-retinal barrier integrity, synaptophysin, astrocyte and Müller cell glial fibrillary acidic protein, vascular endothelial growth factor, tumor necrosis factor-α, and brain-derived neurotrophic factor levels, as well as lipid peroxidation were assessed in retina from diabetic animals housed in standard or enriched environment. Environmental enrichment preserved scotopic electroretinogram a-wave, b-wave and oscillatory potential amplitude, avoided albumin-Evan's blue leakage, prevented the decrease in retinal synaptophysin and astrocyte glial fibrillary acidic protein levels, the increase in Müller cell glial fibrillary acidic protein, vascular endothelial growth factor and tumor necrosis factor-α levels, as well as oxidative stress induced by diabetes. In addition, enriched environment prevented the decrease in retinal brain-derived neurotrophic factor levels induced by experimental diabetes. When environmental enrichment started 7 weeks after diabetes onset, retinal function was significantly preserved. These results indicate that enriched environment could attenuate the early diabetic damage in the retina from adult rats.

Matricellular proteins in the trabecular meshwork: review and update

Abstract Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide, and intraocular pressure (IOP) is an important modifiable risk factor. IOP is a function of aqueous humor production and aqueous humor outflow, and it is thought that prolonged IOP elevation leads to optic nerve damage over time. Within the trabecular meshwork (TM), the eye's primary drainage system for aqueous humor, matricellular proteins generally allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). It is now well established that ECM turnover in the TM affects outflow facility, and matricellular proteins are emerging as significant players in IOP regulation. The formalized study of matricellular proteins in TM has gained increased attention. Secreted protein acidic and rich in cysteine (SPARC), myocilin, connective tissue growth factor (CTGF), and thrombospondin-1 and -2 (TSP-1 and -2) have been localized to the TM, and a growing body of evidence suggests that these matricellular proteins play an important role in IOP regulation and possibly the pathophysiology of POAG. As evidence continues to emerge, these proteins are now seen as potential therapeutic targets. Further study is warranted to assess their utility in treating glaucoma in humans.

Current trends in the monitoring and treatment of diabetic retinopathy in young adults

The diagnosis and treatment of diabetic retinopathy (DR) in young adults have significantly improved in recent years. Research methods have widened significantly, for example, by introducing spectral optical tomography of the eye. Invasive diagnostics, for example, fluorescein angiography, are done less frequently. The early introduction of an insulin pump to improve the administration of insulin is likely to delay the development of diabetic retinopathy, which is particularly important for young patients with type 1 diabetes mellitus (T1DM). The first years of diabetes occurring during childhood and youth are the most appropriate to introduce proper therapeutic intervention before any irreversible changes in the eyes appear. The treatment of DR includes increased metabolic control, laserotherapy, pharmacological treatment (antiangiogenic and anti-inflammatory treatment, enzymatic vitreolysis, and intravitreal injections), and surgery. This paper summarizes the up-to-date developments in the diagnostics and treatment of DR. In the literature search, authors used online databases, PubMed, and clinitrials.gov and browsed through individual ophthalmology journals, books, and leading pharmaceutical company websites.

STAT1-mediated Bim expression promotes the apoptosis of retinal pericytes under high glucose conditions

Hyperglycemia impacts different vascular cell functions and promotes the development and progression of various vasculopathies including diabetic retinopathy. Although the increased rate of apoptosis in pericytes (PCs) has been linked to increased oxidative stress and activation of protein kinase C-δ (PKC-δ) and SHP-1 (Src homology region 2 domain-containing phosphatase-1) tyrosine phosphatase during diabetes, the detailed mechanisms require further elucidation. Here we show that the rate of apoptosis and expression of proapoptotic protein Bim were increased in the retinal PCs of diabetic Akita/+ mice and mouse retinal PCs cultured under high glucose conditions. Increased Bim expression in retinal PCs under high glucose conditions required the sustained activation of signal transducer and activator of transcription 1 (STAT1) through production of inflammatory cytokines. PCs cultured under high glucose conditions also exhibited increased oxidative stress and diminished migration. Inhibition of oxidative stress, PKC-δ or Rho-associated protein kinase I/II was sufficient to protect PCs against apoptosis under high glucose conditions. Furthermore, PCs deficient in Bim expression were protected from high glucose-mediated increased oxidative stress and apoptosis. However, only inhibition of PKC-δ lowered Bim levels. N-acetylcysteine did not affect STAT1 levels, suggesting that oxidative stress is downstream of Bim. PCs cultured under high glucose conditions disrupted capillary morphogenesis of retinal endothelial cells (ECs) in coculture experiments. In addition, conditioned medium prepared from PCs under high glucose conditions attenuated EC migration. Taken together, our results indicate that Bim has a pivotal role in the dysfunction of retinal PCs under high glucose conditions by increasing oxidative stress and death of PCs.