Thrombolytic tPA-induced hemorrhagic transformation of ischemic stroke is mediated by PKCß phosphorylation of occludin.

The current standard of care for moderate to severe ischemic stroke is thrombolytic therapy with tissue plasminogen activator (tPA). Treatment with tPA can significantly improve neurologic outcomes; however, thrombolytic therapy is associated with an increased risk of intracerebral hemorrhage (ICH). The risk of hemorrhage significantly limits the use of thrombolytic therapy, and identifying pathways induced by tPA that increase this risk could provide new therapeutic options to extend thrombolytic therapy to a wider patient population. Here, we investigate the role of protein kinase Cß (PKCß) phosphorylation of the tight junction protein occludin during ischemic stroke and its role in cerebrovascular permeability. We show that activation of this pathway by tPA is associated with an increased risk of ICH. Middle cerebral artery occlusion (MCAO) increased phosphorylation of occludin serine 490 (S490) in the ischemic penumbra in a tPA-dependent manner, as tPA-/- mice were significantly protected from MCAO-induced occludin phosphorylation. Intraventricular injection of tPA in the absence of ischemia was sufficient to induce occludin phosphorylation and vascular permeability in a PKCß-dependent manner. Blocking occludin phosphorylation, either by targeted expression of a non-phosphorylatable form of occludin (S490A) or by pharmacologic inhibition of PKCß, reduced MCAO-induced permeability and improved functional outcome. Furthermore, inhibiting PKCß after MCAO prevented ICH associated with delayed thrombolysis. These results show that PKCß phosphorylation of occludin is a downstream mediator of tPA-induced cerebrovascular permeability and suggest that PKCß inhibitors could improve stroke outcome and prevent ICH associated with delayed thrombolysis, potentially extending the window for thrombolytic therapy in stroke.

Inflammatory resolution and vascular barrier restoration after retinal ischemia reperfusion injury.

BACKGROUND: Several retinal pathologies exhibit both inflammation and breakdown of the inner blood-retinal barrier (iBRB) resulting in vascular permeability, suggesting that treatments that trigger resolution of inflammation may also promote iBRB restoration. METHODS: Using the mouse retinal ischemia-reperfusion (IR) injury model, we followed the time course of neurodegeneration, inflammation, and iBRB disruption and repair to examine the relationship between resolution of inflammation and iBRB restoration and to determine if minocycline, a tetracycline derivative shown to reverse microglial activation, can hasten these processes. RESULTS: A 90-min ischemic insult followed by reperfusion in the retina induced cell apoptosis and inner retina thinning that progressed for approximately 2 weeks. IR increased vascular permeability within hours, which resolved between 3 and 4 weeks after injury. Increased vascular permeability coincided with alteration and loss of endothelial cell tight junction (TJ) protein content and disorganization of TJ protein complexes. Shunting of blood flow away from leaky vessels and dropout of leaky capillaries were eliminated as possible mechanisms for restoring the iBRB. Repletion of TJ protein contents occurred within 2 days after injury, long before restoration of the iBRB. In contrast, the eventual re-organization of TJ complexes at the cell border coincided with restoration of the barrier. A robust inflammatory response was evident a 1 day after IR and progressed to resolution over the 4-week time course. The inflammatory response included a rapid and transient infiltration of granulocytes and Ly6C+ classical inflammatory monocytes, a slow accumulation of Ly6Cneg monocyte/macrophages, and activation, proliferation, and mobilization of resident microglia. Extravasation of the majority of CD45+ leukocytes occurred from the superficial plexus. The presence of monocyte/macrophages and increased numbers of microglia were sustained until the iBRB was eventually restored. Intervention with minocycline to reverse microglial activation at 1 week after injury promoted early restoration of the iBRB coinciding with decreased expression of mRNAs for the microglial M1 markers TNF-α, IL-1ß, and Ptgs2 (Cox-2) and increased expression of secreted serine protease inhibitor Serpina3n mRNA. CONCLUSIONS: These results suggest that iBRB restoration occurs as TJ complexes are reorganized and that resolution of inflammation and restoration of the iBRB following retinal IR injury are functionally linked.

Associations between VEGF isoforms and impending retinopathy of prematurity.

BACKGROUND/OBJECTIVE: Vascular Endothelial Growth Factor (VEGF) is the main driver of angiogenesis during neurodevelopment (i.e., brain and retina). VEGF165 and VEGF121 are the two most prevalent human VEGF isoforms. Although retinopathy of prematurity (ROP), a neuroretinal disorder, is associated with VEGF dysregulation, little is known about the interaction of VEGF isoforms on neuroretinal angiogenesis. We hypothesized that: (a) A specific VEGF165/VEGF121 correlation, at a given time point, is associated with normal retinal development (no ROP) and (b) An altered correlation, of such, is associated with aberrant retinal development (ROP). Utilizing pre-collected dried blood spots (DBS) from <1-week-old preterm infants, we aimed to determine whether correlations between VEGF165 and VEGF121 precede the diagnosis of early stage, non-proliferative ROP (NP-ROP). METHODOLOGY: We conducted a case/control study, utilizing DBS from 65 preterm infants. We measured DBS levels of VEGF165 on the Mesoscale Discovery Platform and VEGF121 via Cloud Clone Elisa Assay. RESULTS: In infants with NP-ROP, VEGF165 is significantly higher in males (than females). In infants without ROP, there is a significant correlation between VEGF165 and VEGF121 in females (but not males). In infants with NP-ROP, the opposite is so; there is a significant correlation between VEGF165 and VEGF121 in males (but not females). CONCLUSIONS: This pilot study, utilizing de-identified data, suggests the potential importance of examining interactions between VEGF isoforms, at <1 week after birth, to better understand ROP development. Our study also suggests that retinal angiogenesis may not be a sex-neutral process. A prospective study is needed to confirm our novel findings.

The association between high levels of luteinizing hormone and proliferative retinopathy of prematurity in female preterm infants.

BACKGROUND: Luteinizing hormone (LH) and human chorionic gonadotropin (hCG), generally considered reproductive hormones, have potent proangiogenic properties. Both of these hormones and their joint receptor (CG/LH receptor) are found in the human eye. We hypothesized that an excess of these hormones is associated with proliferative retinopathy of prematurity (P-ROP). METHODS: Dried blood spots (DBS) were used to perform a cross-sectional study of infants (gestational age of <26 weeks) with and without P-ROP, born in Michigan between August 1, 2012, and March 15, 2015. The DBS were collected at 1 week and 4 weeks of age from 45 preterm infants (27 no-ROP and 18 P-ROP). The DBS were linked to hospital records and then deidentified. ICD-9 codes were used to identify P-ROP cases. Hormones levels were measured via electrochemiluminescence assays on the Meso Scale Discovery platform. Associations between hormone levels at 1 and 4 weeks of age and the presence or absence of P-ROP were assessed. RESULTS: In female infants, we noted a trend toward higher LH levels in ROP cases at week 1 (P = 0.11) and significantly higher LH levels in cases at week 4 (P = 0.03). In male infants, no ROP-related differences in LH levels were found at either time point. For hCG levels, no associations with P-ROP were found in either sex at either time point. CONCLUSIONS: The association of high LH with P-ROP in female but not male infants raises the possibility that there are sex-specific hormonal determinants of aberrant retinal angiogenesis.

Feasibility of neonatal haemoglobin A1C as a biomarker for retinopathy of prematurity.

INTRODUCTION: Retinopathy of prematurity (ROP) is a potentially serious eye disorder affecting very preterm infants. Non-proliferative ROP (NP-ROP), also known as Early Stage ROP, is characterized by deficient retinal angiogenesis. Proliferative ROP (P-ROP), also known as Late Stage ROP, is characterized by pathologic angiogenesis. The use of neonatal haemoglobin A1C as a biomarker for ROP has not yet been evaluated. MATERIALS AND METHODS: We modified the Haemoglobin A1C assay for use with neonatal dried blood spots (DBS) and then assessed A1C levels via Elisa immunoassay on DBS from 43 preterm infants (with gestational ages 26-28 weeks). We measured A1C on DBS collected at <1 week and 4 weeks of chronological age. RESULTS: Compared to matched counterparts without ROP, there is significantly lower HbA1c in infants who develop NP-ROP, this occurs at Week 4 (p=0.004), but is not seen at Week 1; there is significantly higher HbA1c in infants with P-ROP, this occurs both at Week 1 (p<0.05) and Week 4 (p=0.005). CONCLUSIONS: The A1C test, modified for use with DBS, is a feasible biomarker for ROP; low A1C is a potential biomarker for non-proliferative ROP and high A1C is for proliferative ROP.

Demonstrating a Linear Relationship Between Vascular Endothelial Growth Factor and Luteinizing Hormone in Kidney Cortex Extracts.

Vascular endothelial growth factor (VEGF) helps to control angiogenesis and vascular permeability in the kidney. Renal disorders, such as diabetic nephropathy, are associated with VEGF dysregulation in the kidney. The factors that govern VEGF under physiologic conditions in the kidney are not well-understood. Luteinizing hormone (LH), a pro-angiogenic hormone, helps regulate physiologic VEGF expression in reproductive organs. Given that LH receptors are found in the kidney, we, at Zietchick Research Institute, hypothesized here that LH also helps regulate VEGF expression in the kidney as well. To provide evidence, we aimed to show that LH levels are able to predict VEGF levels in the mammalian kidney. Most VEGF-related investigations involving the kidney have used lower order mammals as models (i.e., rodents and rabbits). To translate this work to the human body, it was decided to examine the relationship between VEGF and LH in higher order mammals (i.e., bovine and porcine models). This protocol uses the total protein lysate from the kidney cortex. Keys to this method's success include procurement of kidneys from slaughterhouse animals immediately after death as well as normalization of analyte levels (in the kidney extract) by total protein. This study successfully demonstrates a significant linear relationship between LH and VEGF in both bovine and porcine kidneys. The results are reproducible in two different species. The study provides supporting evidence that the use of kidney extracts from cows and pigs are an excellent, economical, and abundant resource for the study of renal physiology, particularly for examining the correlation between VEGF and other analytes.

The postnatal presence of human chorionic gonadotropin in preterm infants and its potential inverse association with retinopathy of prematurity.

BACKGROUND: Human chorionic gonadotropin (hCG) and luteinizing hormone (LH) are pro-angiogenic gonadotropic hormones, which classically target the reproductive organs. However, hCG, LH, and their shared CG/LH receptor are also present in the human eye. The possibility that a deficiency of these hormones may be involved in the pathogenesis of retinopathy of prematurity (ROP) during its early non-proliferative phase has not been explored. METHODS: We conducted a cross-sectional study of Michigan-born preterm infants utilizing dried blood spots. We analyzed hCG and LH blood levels at 1 week and 4 weeks of age from 113 study participants (60 without ROP; 53 with non-proliferative ROP). We utilized electrochemiluminescence assays on the Mesoscale Discovery platform. RESULTS: Similar levels of hCG are found in preterm infants at both 1 week and 4 weeks after birth. Preterm infants with non-proliferative ROP, after adjusting for sex and gestational age, have 2.42 [95% CI: 1.08-5.40] times the odds of having low hCG at fourth week of age. CONCLUSIONS: We found that hCG is present postnatally in preterm infants and that a deficiency of hCG at 4 weeks of age is potentially associated with non-proliferative ROP. This provides novel evidence to suggest that hCG may participate in human retinal angiogenesis.

The potential effect of human chorionic gonadotropin on vasoproliferative disorders of the immature retina.

Human chorionic gonadotropin (hCG) is known to be a powerful vascular endothelial growth factor (VEGF)-regulating hormone. It stimulates vascularization of the gravid uterus by upregulating VEGF expression. In the body, hCG activates the same receptor as luteinizing hormone (LH). Like hCG, LH is also strongly proangiogenic. Recently, it has been shown that LH/hCG receptors are present in the retina and that both LH and hCG are found in the eye. In fact, the human eye can synthesize its own hCG. We have previously shown that LH and VEGF are significantly correlated in mammalian eyes, potentially implicating LH-receptor/hCG-receptor activation in intraocular VEGF regulation. Given that elevated VEGF is associated with progression of two vasoproliferative pediatric retinal disorders, retinopathy of prematurity and retinoblastoma, our objective was to determine whether hCG may potentially affect VEGF production and pathologic retinal vascularization in vasoproliferative disorders affecting the immature retina. In this study, we used (a) oxygen-induced retinopathy mouse model (standard model for retinopathy of prematurity) and (b) Y79 retinoblastoma cells (a human cell line derived from immature retinal cells). In the oxygen-induced retinopathy model, number of preretinal nuclei (representing pathologic retinal neovascularization) significantly increases by 57% (P<0.05) in hCG-treated mice. In Y79 cells, VEGF production significantly increases by 37% (P<0.05) in hCG-treated cells. These findings suggest that hCG is potentially able to influence retinal vascularization and VEGF production and thus, the hCG receptor may potentially represent a therapeutic target for vasoproliferative retinal disorders affecting the young eye.

Elimination of Signaling by the Luteinizing Hormone Receptor Reduces Ocular VEGF and Retinal Vascularization during Mouse Eye Development.

Purpose/Aim: Vascular endothelial growth factor (VEGF) dysregulation is implicated in the pathogenesis of retinopathy of prematurity (ROP). Identifying the factors that contribute to VEGF regulation during normal retinal vascularization is the key to ROP prevention. Currently, physiologic hypoxia is thought to be responsible for retinal VEGF regulation in utero. However, a potential hormonal contribution to VEGF regulation during eye development has not been fully investigated. The placental hormone, human chorionic gonadotropin and the pituitary hormone, and luteinizing hormone (LH) induce VEGF expression in several tissue types. Both of these gonadotropins activate the same LH receptor (LHR) in the human body; LHRs are expressed in the retina. In this study, we aimed to show that LHR signaling participates in VEGF regulation in the developing eye. METHODS: When offspring from breeding pairs of LHR knockout mice (lhrkos) reached 21 days old, eyes and serum were extracted from homozygote lhrkos and wildtype (WT) siblings. VEGF levels were measured using Mouse VEGF Quantikine immunoassay kit. Retinas were incubated with isolectin for endothelial cell staining, flat mounted and imaged by confocal microscopy. Retinal vascular density was quantified using Imaris software. Some eyes were sectioned and stained for histopathologic review. RESULTS: Ocular VEGF and retinal vascular volumes were significantly reduced by ~ 15% in lhrko eyes. Serum VEGF was not changed. The lhrko retinas did not display any anomalies. CONCLUSIONS: We provide evidence that LHR signaling plays a role in VEGF regulation and vascularization in the developing eye. Given that human preterm infants may have altered LHR-activity, the effect of gonadotropins on eye development should be further studied to identify novel strategies for ROP prevention.

Confirmation of Luteinizing Hormone (LH) in Living Human Vitreous and the Effect of LH Receptor Reduction on Murine Electroretinogram.

Luteinizing hormone (LH), produced in the anterior pituitary, has been detected in cadaver eyes and LH receptors (LHRs) have been identified in the retina, with the highest density in cone photoreceptors. Our aim was to confirm the presence of LH in the living, human eye as well as to examine the potential impact of a reduction in LHR signaling on visual processing. Vitreous samples were collected from 40 patients (23 diabetics, 17 non-diabetics) who were undergoing vitrectomies for various indications. LH concentration was quantified in each sample via an electro-chemiluminescence immunoassay and Meso Scale Discovery platform and normalized to total protein. In addition, full-field electroretinography (ERG) was performed on 11 adult LHR knockout heterozygous mice (B6;129X1-Lhcgrtm1Zmlei/J) and 11 wild types using the Celeris-Diagnosys system. The median LH values (pg/mg total protein) for non-diabetics, diabetics without proliferative diabetic retinopathy (PDR) and diabetics with PDR were 40.7, 41.9 and 167.8 respectively. LH levels were significantly higher in diabetics with PDR. In our ERG investigation, heterozygous LHRKOs were found to have significantly reduced amplitudes of a-wave and b-waves at high stimulus intensities with no significant change in a-wave or b-wave amplitudes at lower intensities; this is consistent with a selective impairment of cone-mediated responses. Our findings confirm LH is present in the adult human eye. Our findings also suggest that a reduction in LH receptor signaling negatively impacts visual processing of the cone photoreceptors. Overall, our study results support the theory that LH likely plays a physiologic role in the eye.

Vitreous Levels of Luteinizing Hormone and VEGF are Strongly Correlated in Healthy Mammalian Eyes.

Purpose/Aim: Luteinizing hormone (LH) is known to function as a key regulator of vascular endothelial growth factor (VEGF) expression in reproductive organs. In recent years, LH has also been detected in human vitreous and LH receptors have been identified in human retina. This study was aimed to investigate a potential correlation between LH and VEGF levels in healthy mammalian eyes to provide supporting evidence of LH's potential involvement in intraocular VEGF regulation. METHODS: 18 bovine and 30 porcine eyes were procured from an abattoir and VEGF and LH levels were measured in the vitreous extracted from these eyes by commercially available bovine & porcine ELISA assay kits. Total protein of the vitreous was measured by using Micro BSA protein assay kit. RESULTS: After total protein normalization, the Pearson Correlation Coefficients (PCC) showed a strong and significant correlation between LH and VEGF levels. (Bovine LH/VEGF PCC: 0.89, p < 0.001; Porcine LH/VEGF PCC: 0.80, p < 0.001). Linear regression analyses, adjusted for gender, showed significant linear relationships between LH and VEGF levels in both bovine and porcine vitreous. (Bovine: t-value = 7.69, p < 0.0001, adjusted r2 = .79; Porcine: t-value = 6.71, p < 0.001, adjusted r2 = .62) Conclusions: We show that VEGF and LH are strongly correlated in healthy, adult mammalian eyes. The robustness of the correlation is shown both by its strength of association and reproducibility in two species. Given that LH is well known to regulate VEGF levels in several tissue types, the LH/VEGF linear relationship in vitreous potentially implicates LH in homeostatic VEGF regulation of the eye. Because we also found that the correlation between LH and VEGF only became manifest when our targeted analytes were normalized by total amount of protein, preclinical and clinical investigators should consider normalizing analytes in vitreous by total protein when assessing potential correlations among them.

Protective Effect of a GLP-1 Analog on Ischemia-Reperfusion Induced Blood-Retinal Barrier Breakdown and Inflammation.

PURPOSE: Inflammation associated with blood-retinal barrier (BRB) breakdown is a common feature of several retinal diseases. Therefore, the development of novel nonsteroidal anti-inflammatory approaches may provide important therapeutic options. Previous studies demonstrated that inhibition of dipeptidyl peptidase-IV, the enzyme responsible for the degradation of glucagon-like peptide-1 (GLP-1), led to insulin-independent prevention of diabetes-induced increases in BRB permeability, suggesting that incretin-based drugs may have beneficial pleiotropic effects in the retina. In the current study, the barrier protective and anti-inflammatory properties of exendin-4 (Ex-4), an analog of GLP-1, after ischemia-reperfusion (IR) injury were examined. METHODS: Ischemia-reperfusion injury was induced in rat retinas by increasing the intraocular pressure for 45 minutes followed by 48 hours of reperfusion. Rats were treated with Ex-4 prior to and following IR. Blood-retinal barrier permeability was assessed by Evans blue dye leakage. Retinal inflammatory gene expression and leukocytic infiltration were measured by qRT-PCR and immunofluorescence, respectively. A microglial cell line was used to determine the effects of Ex-4 on lipopolysaccharide (LPS)-induced inflammatory response. RESULTS: Exendin-4 dramatically reduced the BRB permeability induced by IR injury, which was associated with suppression of inflammatory gene expression. Moreover, in vitro studies showed that Ex-4 also reduced the inflammatory response to LPS and inhibited NF-κB activation. CONCLUSIONS: The present work suggests that Ex-4 can prevent IR injury-induced BRB breakdown and inflammation through inhibition of inflammatory cytokine production by activated microglia and may provide a novel option for therapeutic intervention in diseases involving retinal inflammation.

Retinylamine Benefits Early Diabetic Retinopathy in Mice.

Recent evidence suggests an important role for outer retinal cells in the pathogenesis of diabetic retinopathy (DR). Here we investigated the effect of the visual cycle inhibitor retinylamine (Ret-NH2) on the development of early DR lesions. Wild-type (WT) C57BL/6J mice (male, 2 months old when diabetes was induced) were made diabetic with streptozotocin, and some were given Ret-NH2 once per week. Lecithin-retinol acyltransferase (LRAT)-deficient mice and P23H mutant mice were similarly studied. Mice were euthanized after 2 (WT and Lrat(-/-)) and 8 months (WT) of study to assess vascular histopathology, accumulation of albumin, visual function, and biochemical and physiological abnormalities in the retina. Non-retinal effects of Ret-NH2 were examined in leukocytes treated in vivo. Superoxide generation and expression of inflammatory proteins were significantly increased in retinas of mice diabetic for 2 or 8 months, and the number of degenerate retinal capillaries and accumulation of albumin in neural retina were significantly increased in mice diabetic for 8 months compared with nondiabetic controls. Administration of Ret-NH2 once per week inhibited capillary degeneration and accumulation of albumin in the neural retina, significantly reducing diabetes-induced retinal superoxide and expression of inflammatory proteins. Superoxide generation also was suppressed in Lrat(-/-) diabetic mice. Leukocytes isolated from diabetic mice treated with Ret-NH2 caused significantly less cytotoxicity to retinal endothelial cells ex vivo than did leukocytes from control diabetics. Administration of Ret-NH2 once per week significantly inhibited the pathogenesis of lesions characteristic of early DR in diabetic mice. The visual cycle constitutes a novel target for inhibition of DR.

Adrenergic and serotonin receptors affect retinal superoxide generation in diabetic mice: relationship to capillary degeneration and permeability.

Reactive oxygen species play an important role in the pathogenesis of diabetic retinopathy. We studied the role of adrenergic and serotonin receptors in the generation of superoxide by retina and 661W retinal cells in high glucose and of the α1-adrenergic receptor (AR) on vascular lesions of the retinopathy in experimentally diabetic C57Bl/6J mice (and controls) after 2 and 8 months. Compared with 5 mM glucose, incubating cells or retinal explants in 30 mM glucose induced superoxide generation. This response was reduced or ablated by pharmacologic inhibition of the α1-AR (a Gq-coupled receptor) or Gs-coupled serotonin (5-HT2, 5-HT4, 5-HT6, and 5-HT7) receptors or by activation of the Gi-coupled α2-AR. In elevated glucose, the α1-AR produced superoxide via phospholipase C, inositol triphosphate-induced Ca(2+) release, and NADPH oxidase, and pharmacologic inhibition of these reactions prevented the superoxide increase. Generation of retinal superoxide, expression of proinflammatory proteins, and degeneration of retinal capillaries in diabetes all were significantly inhibited with daily doxazosin or apocynin (inhibitors of α1-AR and NADPH oxidase, respectively), but increased vascular permeability was not significantly affected. Adrenergic receptors, and perhaps other GPCRs, represent novel targets for inhibiting the development of important features of diabetic retinopathy.

Targeted disruption of a ring-infected erythrocyte surface antigen (RESA)-like export protein gene in Plasmodium falciparum confers stable chondroitin 4-sulfate cytoadherence capacity.

The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family proteins mediate the adherence of infected erythrocytes to microvascular endothelia of various organs, including the placenta, thereby contributing to cerebral, placental, and other severe malaria pathogenesis. Several parasite proteins, including KAHRP and PfEMP3, play important roles in the cytoadherence by mediating the clustering of PfEMP1 in rigid knoblike structures on the infected erythrocyte surface. The lack of a subtelomeric region of chromosome 2 that contains kahrp and pfemp3 causes reduced cytoadherence. In this study, microarray transcriptome analysis showed that the absence of a gene cluster, comprising kahrp, pfemp3, and four other genes, results in the loss of parasitized erythrocytes adhering to chondroitin 4-sulfate (C4S). The role of one of these genes, PF3D7_0201600/PFB0080c, which encodes PHISTb (Plasmodium helical interspersed subtelomeric b) domain-containing RESA-like protein 1 expressed on the infected erythrocyte surface, was investigated. Disruption of PFB0080c resulted in increased var2csa transcription and VAR2CSA surface expression, leading to higher C4S-binding capacity of infected erythrocytes. Further, PFB0080c-knock-out parasites stably maintained the C4S adherence through many generations of growth. Although the majority of PFB0080c-knock-out parasites bound to C4S even after culturing for 6 months, a minor population bound to both C4S and CD36. These results strongly suggest that the loss of PFB0080c markedly compromises the var gene switching process, leading to a marked reduction in the switching rate and additional PfEMP1 expression by a minor population of parasites. PFB0080c interacts with VAR2CSA and modulates knob-associated Hsp40 expression. Thus, PFB0080c may regulate VAR2CSA expression through these processes. Overall, we conclude that PFB0080c regulates PfEMP1 expression and the parasite's cytoadherence.

Ischemia-reperfusion injury induces occludin phosphorylation/ubiquitination and retinal vascular permeability in a VEGFR-2-dependent manner.

Retinal ischemia-reperfusion (IR) induces neurodegenaration as well as blood-retinal barrier (BRB) breakdown causing vascular permeability. Whereas the neuronal death has been extensively studied, the molecular mechanisms related to BRB breakdown in IR injury remain poorly understood. In this study, we investigated the early changes in tight junctional (TJ) proteins in response to IR injury. Ischemia-reperfusion injury was induced in male rat retinas by increasing the intraocular pressure for 45 minutes followed by natural reperfusion. The results demonstrate that IR injury induced occludin Ser490 phosphorylation and ubiquitination within 15 minutes of reperfusion with subsequent vascular permeability. Immunohistochemical analysis revealed a rapid increase in occludin Ser490 phosphorylation and loss of Zonula occludens-1 (ZO-1) protein, particularly in arterioles. Ischemia-reperfusion injury also rapidly induced the activation and phosphorylation of vascular endothelial growth factor receptor-2 (VEGFR-2) at tyrosine 1175. Blocking vascular endothelial growth factor (VEGF) function by intravitreal injection of bevacizumab prevented VEGFR-2 activation, occludin phosphorylation, and vascular permeability. These studies suggest a novel mechanism of occludin Ser490 phosphorylation and ubiquitination downstream of VEGFR2 activation associated with early IR-induced vascular permeability.

Minocycline prevents retinal inflammation and vascular permeability following ischemia-reperfusion injury.

BACKGROUND: Many retinal diseases are associated with vascular dysfunction accompanied by neuroinflammation. We examined the ability of minocycline (Mino), a tetracycline derivative with anti-inflammatory and neuroprotective properties, to prevent vascular permeability and inflammation following retinal ischemia-reperfusion (IR) injury, a model of retinal neurodegeneration with breakdown of the blood-retinal barrier (BRB). METHODS: Male Sprague-Dawley rats were subjected to 45 min of pressure-induced retinal ischemia, with the contralateral eye serving as control. Rats were treated with Mino prior to and following IR. At 48 h after reperfusion, retinal gene expression, cellular inflammation, Evan's blue dye leakage, tight junction protein organization, caspase-3 activation, and DNA fragmentation were measured. Cellular inflammation was quantified by flow-cytometric evaluation of retinal tissue using the myeloid marker CD11b and leukocyte common antigen CD45 to differentiate and quantify CD11b+/CD45low microglia, CD11b+/CD45hi myeloid leukocytes and CD11bneg/CD45hi lymphocytes. Major histocompatibility complex class II (MHCII) immunoreactivity was used to determine the inflammatory state of these cells. RESULTS: Mino treatment significantly inhibited IR-induced retinal vascular permeability and disruption of tight junction organization. Retinal IR injury significantly altered mRNA expression for 21 of 25 inflammation- and gliosis-related genes examined. Of these, Mino treatment effectively attenuated IR-induced expression of lipocalin 2 (LCN2), serpin peptidase inhibitor clade A member 3 N (SERPINA3N), TNF receptor superfamily member 12A (TNFRSF12A), monocyte chemoattractant-1 (MCP-1, CCL2) and intercellular adhesion molecule-1 (ICAM-1). A marked increase in leukostasis of both myeloid leukocytes and lymphocytes was observed following IR. Mino treatment significantly reduced retinal leukocyte numbers following IR and was particularly effective in decreasing the appearance of MHCII+ inflammatory leukocytes. Surprisingly, Mino did not significantly inhibit retinal cell death in this model. CONCLUSIONS: IR induces a retinal neuroinflammation within hours of reperfusion characterized by inflammatory gene expression, leukocyte adhesion and invasion, and vascular permeability. Despite Mino significantly inhibiting these responses, it failed to block neurodegeneration.

An improved lectin-based method for the detection of mucin-type O-glycans in biological samples.

Mucins and mucin-type glycoproteins, collectively referred to as mucin-type O-glycans, are implicated in many important biological functions and pathological conditions, including malignancy. Presently, there is no reliable method to measure the total mucin-type O-glycans of a sample, which may contain one or more of these macromolecules of unknown structures. We report the development of an improved microassay that is based on the binding of lectins to the unique and constant GalNAc-Ser/Thr structural feature of mucin-type O-glycans. Since the sugar-amino acid linkage in the mucin-type O-glycans is invariably cryptic, we first chemically removed the heterogeneous peripheral and core saccharides of model glycoconjugates before examining for their interactions using an enzyme-linked lectin assay (ELLA). Desialylation of the model glycoconjugates led to maximal binding of the lectins but additional treatments such as Smith degradation did not result in increased binding. Of the lectins tested for their ability to probe the desialylated O-glycans, jacalin showed the highest sensitivity followed by champedak galactose binding (CGB) lectin and Vicia villosa agglutinin. Further improvement in the sensitivity of ELLA was achieved by using microtiter plates that were pre-coated with the CGB lectin, which increased the specificity of the assay to mucin-type O-glycans. Finally, the applicability of the developed sandwich ELLA to crude samples was demonstrated by estimating trace quantities of the mucin-type O-glycans in the human serum.

Soluble perlecan domain I enhances vascular endothelial growth factor-165 activity and receptor phosphorylation in human bone marrow endothelial cells.

BACKGROUND: Immobilized recombinant perlecan domain I (PlnDI) binds and modulates the activity of heparin-binding growth factors, in vitro. However, activities for PlnDI, in solution, have not been reported. In this study, we assessed the ability of soluble forms to modulate vascular endothelial growth factor-165 (VEGF165) enhanced capillary tube-like formation, and VEGF receptor-2 phosphorylation of human bone marrow endothelial cells, in vitro. RESULTS: In solution, PlnDI binds VEGF165 in a heparan sulfate and pH dependent manner. Capillary tube-like formation is enhanced by exogenous PlnDI; however, PlnDI/VEGF165 mixtures combine to enhance formation beyond that stimulated by either PlnDI or VEGF165 alone. PlnDI also stimulates VEGF receptor-2 phosphorylation, and mixtures of PlnDI/VEGF165 reduce the time required for peak VEGF receptor-2 phosphorylation (Tyr-951), and increase Akt phosphorylation. PlnDI binds both immobilized neuropilin-1 and VEGF receptor-2, but has a greater affinity for neuropilin-1. PlnDI binding to neuropilin-1, but not to VEGF receptor-2 is dependent upon the heparan sulfate chains adorning PlnDI. Interestingly, the presence of VEGF165 but not VEGF121 significantly enhances PlnDI binding to Neuropilin-1 and VEGF receptor-2. CONCLUSIONS: Our observations suggest soluble forms of PlnDI are biologically active. Moreover, PlnDI heparan sulfate chains alone or together with VEGF165 can enhance VEGFR-2 signaling and angiogenic events, in vitro. We propose PlnDI liberated during basement membrane or extracellular matrix turnover may have similar activities, in vivo.

Short-term intermittent PTH 1-34 administration enhances bone formation in SCID/Beige mice.

The anabolic effect of intermittent PTH on bone is variable depending on the species studied, duration/mode of administration, and location of skeletal response investigated. We tested the hypothesis low dose, short term, intermittent PTH 1-34 administration is sufficient to enhance bone formation without altering bone resorption. To test our hypothesis, mice were treated intermittently with one of three concentrations of PTH 1-34 (1 microg/kg; low, 10 microg/kg, or 20 microg/kg; high) for three weeks. The skeletal response was identified by quantifying: serum markers of bone turnover, cancellous bone parameters in distal femur, proximal tibia, and lumbar vertebrae by microCT, and number of osteoblasts and osteoclasts in distal femur. Mice receiving 20 microg/kg of PTH 1-34 demonstrated a 30% increase in serum osteocalcin, but no differences in serum calcium, type I collagen teleopeptides, or TRACP 5b. For all bones, microCT analysis suggested mice receiving 20 microg/kg of PTH 1-34 had increased cancellous bone mineral density, trabecular thickness and spacing, but decreased trabecular number. A 60% increase in the number of alkaline phosphatase positive osteoblasts in the distal femur was also observed in tissue sections; however, the number of TRAP positive osteoclasts was not different between test and control groups. While animals administered 10 microg/kg demonstrated similar trends for all bone turnover indices, such alterations were not observed in animals administered PTH 1-34 at 1 microg/kg per day. Thus, PTH 1-34, administered intermittently for three weeks at 20 microg/kg is sufficient to enhance bone formation without enhancing resorption.