Alkaline phosphatase expression in cultured endothelial cells of aorta and brain microvessels: induction by interleukin-6-type cytokines and suppression by transforming growth factor betas

Extracellular Purine Metabolism-Potential Target in Multiple Sclerosis

The purinergic signaling system comprises a complex network of extracellular purines and purine-metabolizing ectoenzymes, nucleotide and nucleoside receptors, ATP release channels, and nucleoside transporters. Because of its immunomodulatory function, this system is critically involved in the pathogenesis of multiple sclerosis (MS) and its best-characterized animal model, experimental autoimmune encephalomyelitis (EAE). MS is a chronic neuroinflammatory demyelinating and neurodegenerative disease with autoimmune etiology and great heterogeneity, mostly affecting young adults and leading to permanent disability. In MS/EAE, alterations were detected in almost all components of the purinergic signaling system in both peripheral immune cells and central nervous system (CNS) glial cells, which play an important role in the pathogenesis of the disease. A decrease in extracellular ATP levels and an increase in its downstream metabolites, particularly adenosine and inosine, were frequently observed at MS, indicating a shift in metabolism toward an anti-inflammatory environment. Accordingly, upregulation of the major ectonucleotidase tandem CD39/CD73 was detected in the blood cells and CNS of relapsing-remitting MS patients. Based on the postulated role of A2A receptors in the transition from acute to chronic neuroinflammation, the association of variants of the adenosine deaminase gene with the severity of MS, and the beneficial effects of inosine treatment in EAE, the adenosinergic system emerged as a promising target in neuroinflammation. More recently, several publications have identified ADP-dependent P2Y12 receptors and the major extracellular ADP producing enzyme nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) as novel potential targets in MS.

Distinctive Properties of Endothelial Cells from Tumor and Normal Tissue in Human Breast Cancer

Tumor microenvironments shape aggressiveness and are largely maintained by the conditions of angiogenesis formation. Thus, endothelial cells’ (ECs) biological reactions are crucial to understand and control the design of efficient therapies. In this work, we used models of ECs to represent a breast cancer tumor site as well as the same, healthy tissue. Cells characterization was performed at the transcriptome and protein expression levels, and the cells functional biological responses (angiogenesis and permeability) were assessed. We showed that the expression of proteins specific to ECs (ACE+, VWF+), their differentiation (CD31+, CD 133+, CD105+, CD34-), their adhesion properties (ICAM-1+, VCAM-1+, CD62-L+), and their barrier formation (ZO-1+) were all downregulated in tumor-derived ECs. NGS-based differential transcriptome analysis confirmed CD31-lowered expression and pointed to the increase of Ephrin-B2 and SNCAIP, indicative of dedifferentiation. Functional assays confirmed these differences; angiogenesis was impaired while permeability increased in tumor-derived ECs, as further validated by the distinctly enhanced VEGF production in response to hypoxia, reflecting the tumor conditions. This work showed that endothelial cells differed highly significantly, both phenotypically and functionally, in the tumor site as compared to the normal corresponding tissue, thus influencing the tumor microenvironment.

Tissue-Nonspecific Alkaline Phosphatase in Central Nervous System Health and Disease: A Focus on Brain Microvascular Endothelial Cells

Tissue-nonspecific alkaline phosphatase (TNAP) is an ectoenzyme bound to the plasma membranes of numerous cells via a glycosylphosphatidylinositol (GPI) moiety. TNAP's function is well-recognized from earlier studies establishing its important role in bone mineralization. TNAP is also highly expressed in cerebral microvessels; however, its function in brain cerebral microvessels is poorly understood. In recent years, few studies have begun to delineate a role for TNAP in brain microvascular endothelial cells (BMECs)-a key component of cerebral microvessels. This review summarizes important information on the role of BMEC TNAP, and its implication in health and disease. Furthermore, we discuss current models and tools that may assist researchers in elucidating the function of TNAP in BMECs.

Wheat phytase can alleviate the cellular toxic and inflammatory effects of lipopolysaccharide

The objective of this study was to characterize the enzymatic hydrolysis of lipopolysaccharide (LPS) by wheat phytase and to investigate the effects of wheat phytase-treated LPS on in vitro toxicity, cell viability and release of a pro-inflammatory cytokine, interleukin (IL)-8 by target cells compared with the intact LPS. The phosphatase activity of wheat phytase towards LPS was investigated in the presence or absence of inhibitors such as L-phenylalanine and L-homoarginine. In vitro toxicity of LPS hydrolyzed with wheat phytase in comparison to intact LPS was assessed. Cell viability in human aortic endothelial (HAE) cells exposed to LPS treated with wheat phytase in comparison to intact LPS was measured. The release of IL-8 in human intestinal epithelial cell line, HT-29 cells applied to LPS treated with wheat phytase in comparison to intact LPS was assayed. Wheat phytase hydrolyzed LPS, resulting in a significant release of inorganic phosphate for 1 h (p < 0.05). Furthermore, the degradation of LPS by wheat phytase was nearly unaffected by the addition of L-phenylalanine, the inhibitor of tissue-specific alkaline phosphatase or L-homoarginine, the inhibitor of tissue-non-specific alkaline phosphatase. Wheat phytase effectively reduced the in vitro toxicity of LPS, resulting in a retention of 63% and 54% of its initial toxicity after 1–3 h of the enzyme reaction, respectively (p < 0.05). Intact LPS decreased the cell viability of HAE cells. However, LPS dephosphorylated by wheat phytase counteracted the inhibitory effect on cell viability. LPS treated with wheat phytase decreased IL-8 secretion from intestinal epithelial cell line, HT-29 cell to 14% (p < 0.05) when compared with intact LPS. In conclusion, wheat phytase is a potential therapeutic candidate and prophylactic agent for control of infections induced by pathogenic Gram-negative bacteria and associated LPS-mediated inflammatory diseases in animal husbandry.

Differential expression of alkaline phosphatase gene in proliferating primary lymphocytes and malignant lymphoid cell lines

Alkaline Phosphatase (APase) activity has been shown to be enhanced specifically in mitogen stimulated B lymphocytes committed to proliferation, but not in T lymphocytes. APase gene expression was analyzed in proliferating murine and human primary lymphocytes and human malignant cell lines using reverse transcriptase and real time PCR. In mitogen stimulated murine splenic lymphocytes, enhancement of APase activity correlated well with an increase in APase gene expression. However, in mitogen stimulated murine T lymphocytes and human PBL despite a vigorous proliferative response, no increase in APase enzyme activity or gene expression was observed. A constitutive expression of APase activity concomitant with APase gene expression was observed inhuman myeloma cell line, U266 B1. However, neither enzyme activity nor gene expression of APase were observed in human T cell lymphoma, SUPT-1. The results suggest a differential expression of APase activity and its gene in proliferating primary lymphocytes of mice and humans. The specific expression of APase activity and its gene only in human myeloma cells, but not in proliferating primary B cells can be exploited as a sensitive disease marker.

TNAP and EHD1 are over-expressed in bovine brain capillary endothelial cells after the re-induction of blood-brain barrier properties

Although the physiological properties of the blood-brain barrier (BBB) are relatively well known, the phenotype of the component brain capillary endothelial cells (BCECs) has yet to be described in detail. Likewise, the molecular mechanisms that govern the establishment and maintenance of the BBB are largely unknown. Proteomics can be used to assess quantitative changes in protein levels and identify proteins involved in the molecular pathways responsible for cellular differentiation. Using the well-established in vitro BBB model developed in our laboratory, we performed a differential nano-LC MALDI-TOF/TOF-MS study of Triton X-100-soluble protein species from bovine BCECs displaying either limited BBB functions or BBB functions re-induced by glial cells. Due to the heterogeneity of the crude extract, we increased identification yields by applying a repeatable, reproducible fractionation process based on the proteins' relative hydrophobicity. We present proteomic and biochemical evidence to show that tissue non-specific alkaline phosphatase (TNAP) and Eps15 homology domain-containing protein 1(EDH1) are over-expressed by bovine BCECs after the re-induction of BBB properties. We discuss the impact of these findings on current knowledge of endothelial and BBB permeability.

Gene activation by bioactive glasses

Bioactive glasses have been shown to regulate gene expression in both hard and soft tissue repair. New resorbable bioactive glass constructs are now being developed that can influence gene expression in the local environment by manipulating material properties such as the surface chemistry, topography and the release of dissolution ions. The success of these scaffolds, however, may depend upon a greater understanding of the bioactive glass stimulated gene expression pathways. This will allow the construction of tissue specific scaffolds with tailored surface chemistry, topography and ion release rates. This paper summarises the advances made in understanding gene expression in response to bioactive glasses and discusses the future steps required for further insights into these molecular mechanisms.

Immunolocalization of tight junction proteins in blood vessels in human germinal matrix and cortex

Brain development occurs in a specialized environment maintained by a blood-brain barrier (BBB). An important structural element of the BBB is the endothelial tight junction (TJ). TJs are present during the embryonic period, but BBB impermeability accrues over an extended gestational interval. In studies of human premature infants, we used immunomicroscopy to determine if amounts of the TJ proteins ZO-1, claudin and occludin increase with gestational age in vessels of germinal matrix (GM) and cortex. By 24 weeks postconception (PC), TJ proteins were present in both GM and cortical vessels, but immunoreactivity in the GM of the youngest subjects was less than in older subjects. At 24 weeks PC, TJ protein immunoreactivity in GM vessels was less than in cortical vessels suggesting that TJ maturation progresses along a superficial to deep brain axis. This concept correlates with conclusions from previous analyses of the expression of brain endothelial cell alkaline phosphatase (AP) activity. AP appears in cortical vessels before appearing in deep white matter and GM vessels. Together, these data indicate that differentiation of some functional specializations is still in progress in GM vessels during the third trimester. This maturation could relate to the pathogenesis of germinal matrix hemorrhage-intraventricular hemorrhage.

Susceptibility of brain microvascular endothelial cells to advanced glycation end products-induced tissue factor upregulation is associated with intracellular reactive oxygen species

There is accumulating evidence that advanced glycation end products (AGEs) are relevant to the formation of vascular complications in diabetes mellitus. The aim of this study was to investigate whether AGEs have a significant effect on tissue factor (TF) expression in brain microvascular endothelial cells compared with that in other arterial endothelial cells. Cultured bovine brain microvascular endothelial cells (BBMECs) and aortic endothelial cells (BAECs) were incubated in medium containing glyceraldehyde-derived AGE (glycer-AGE). TF mRNA expression, protein expression, and activity were measured at multiple time points after glycer-AGE incubation. Participation of reactive oxygen species (ROS) in the effect of glycer-AGE on TF expression was investigated by treatment with a free radical scavenger, edaravone, and intracellular ROS measurements with dihydroethidium (DHE). Basic TF mRNA expression was greater in BBMECs than in BAECs. Glycer-AGE significantly upregulated TF mRNA expression in both cells, and the upregulation was more prominent in BBMECs than in BAECs. TF protein expression and activity were also upregulated with a pattern of being greater in BBMECs than in BAECs. Edaravone significantly attenuated the AGE-induced upregulation of TF mRNA expression, protein expression, and activity. Intracellular ROS levels measured with DHE-stained fluorescent intensity were significantly upregulated by glycer-AGE with a pattern of being greater in BBMECs than in BAECs. AGE-induced ROS upregulation was attenuated by edaravone like AGE-induced TF upregulation. These results suggest that brain microvascular endothelial cells are more susceptible to AGE-induced TF upregulation than aortic endothelial cells, and that this susceptibility is associated with levels of intracellular ROS.

Development of neuropeptide drugs that cross the blood-brain barrier

In recent years, there have been several important advancements in the development of neuropeptide therapeutics. Nevertheless, the targeting of peptide drugs to the CNS remains a formidable obstacle. Delivery of peptide drugs is limited by their poor bioavailability to the brain due to low metabolic stability, high clearance by the liver, and the presence of the blood brain barrier (BBB). Multiple strategies have been devised in an attempt to improve peptide drug delivery to the brain, with variable results. In this review, we discuss several of the strategies that have been used to improve both bioavailability and BBB transport, with an emphasis on antibody based vector delivery, useful for large peptides/small proteins, and glycosylation, useful for small peptides. Further development of these delivery methods may finally enable peptide drugs to be useful for the treatment of neurological disease states.

Morphometric assessment of collagen accumulation in germinal matrix vessels of premature human neonates

Germinal matrix haemorrhage in premature neonates is commonly attributed to vascular immaturity, possibly related to an abbreviated process of angiogenesis. Terminal steps in the progression of angiogenesis are the formation of a subendothelial basal lamina containing collagen IV and an extracellular matrix containing collagens I and III. Immature vessels would predictably be deficient in these collagen subtypes. We analysed germinal matrix (GM), cortical, and white matter (WM) vessels with antibodies specific for collagens I, III and IV to test the hypothesis that GM vessels are immature. Brains were collected during post-mortem from prematurely born human neonates ranging in age from 17 weeks to 36 weeks postconception. All GM vessels were immunoreactive for collagen subtypes I, III and IV. Using digital image analysis, collagen IV immunoperoxidase-labelling was measured in vessels in GM, cortex and WM. Intensity values in GM and WM were normalized relative to cortical intensity within the same subject. At week 17 of gestation, GM vessels exhibited a higher concentration of collagen IV than did WM or cortical vessels. Regression analysis demonstrated that collagen intensity in GM was greater than that in cortex and WM at all stages. We conclude that GM vessels in even the youngest, prematurely born, viable neonates do not exhibit evidence of structural immaturity. The high incidence of GM haemorrhage in premature neonates may be related to factors other than a deficiency in accumulated collagen.

Induction of glomerular alkaline phosphatase after challenge with lipopolysaccharide

Alkaline phosphatase (AP) can be considered as a host defence molecule since this enzyme is able to detoxify bacterial endotoxin at physiological pH. The question emerged whether this anti-endotoxin principle is inducible in the glomerulus and if so, which glomerular cells might be involved in the expression of ectoAP after stimulation with pro-inflammatory agents. Therefore kidneys of rats treated with either lipopolysaccharide (LPS), E. coli bacteria or non-toxic monophosphoryl lipid A (MPLA) were examined for AP activity 6 or 24 h after challenge. In addition cultures of endothelial cells or mesangial cells were evaluated for AP activity after stimulation with either LPS, TNFalpha or IL-6, and mRNA for AP was studied in TNFalpha-stimulated and control mesangial cells. The results show significant up-regulation of glomerular AP in LPS- or E. coli-injected rats compared to rats injected with MPLA. Endothelial and mesangial cells in vitro showed significant up-regulation of AP activity following stimulation with LPS, TNFalpha or IL-6, whereas increased mRNA for AP was observed in mesangial cells after TNFalpha stimulation compared to non-stimulated control cells. Since it appeared that hydrolysis occurred when endotoxin was used as a substrate in the histochemical staining, we concluded that inducible glomerular ectoAP may reflect a local endotoxin detoxifying principle of the kidney.

Induction of vascular endothelial growth factor by fibrin as a dermal substrate for cultured skin substitute

In the initial phase of wound healing, endogenous fibrin clots are known to form a provisional matrix and to promote angiogenesis. Growth factors such as vascular endothelial growth factor (VEGF) increase in wounds to stimulate angiogenesis. However, it remains unknown whether VEGF is induced when fibrin is used as a dermal substrate for cultured skin substitutes. The authors investigated the effect of fibrin gel as a dermal substrate for a cultured skin substitute, using human keratinocytes and dermal fibroblasts. A collagen-cultured skin substitute was also examined for comparison. VEGF in the culture supernatant in both types was measured by enzyme-linked immunosorbent assay, and VEGF mRNA was determined semiquantitatively by reverse-transcriptase polymerase chain reaction after 2 days of incubation. Experiments were performed using 12 cultured skin substitutes: four for histologic examination before transplantation, four for VEGF assay in vitro, and four for the transplantation to athymic mice. Three independent experiments were performed for each step. VEGF concentration in the fibrin-cultured supernatant was 84.3 +/- 11.8 pg/ml, whereas it was 27.8 +/- 4.68 pg/ml in the case of the collagen substrate. The relative levels of VEGF mRNA were 1.088 +/- 0.100 and 0.698 +/- 0.226, respectively. In in vivo transplantation, the fibrin-type cultured skin substitute showed an excellent take on the wound bed, and a normally proliferating keratinocyte layer with emergence of vascular endothelial cells in the transplanted floor was seen 3 days after transplantation. Vascular endothelial cells, which were identified using alkaline phosphatase stain, were significantly increased in the fibrin-type cultured skin substitute. The use of fibrin as a dermal substrate for cultured skin substitute increases the secretion of VEGF, improves regeneration of mature epidermal structure after in vivo transplantation, and promotes the migration of vascular endothelial cells.

Alkaline phosphatases reduce toxicity of lipopolysaccharides in vivo and in vitro through dephosphorylation

Intestinal alkaline phosphatase (AP), as a host defense factor, was first investigated in vivo using rats orally exposed to lipopolysaccharide (LPS). After the oral administration of LPS to rats, serum LPS content was increased within 2 hr and then decreased to 6 hr. In contrast, when L-phenylalanine (L-Phe), an inhibitor of intestinal-type AP isozymes, was simultaneously administered with LPS, serum LPS content significantly increased from 1 hr and the area under the concentration-time curve of serum LPS was augmented approximately 2-fold, suggesting that APs in the gastrointestinal tract reduced serum LPS content. In addition, LPS toxicity diminished by a treatment in vitro with intestinal APs, were recovered by the treatment in the co-presence of L-Phe. In the experiment using human aortic endothelial cells (HAECs), we observed that the cell viability decreased in a dose-dependent manner of LPS-exposure, and the LPS dose, exhibiting 50% viability of the cells, was 0.05 microg/ml. When the cells were exposed to LPS pretreated with 50 nIU/ml of intestinal AP at pH 10.0 and 8.0, the 50% viability was at 2.0 microg/ml of LPS. These results strongly suggest that the APs reduced the toxicity of LPS, as a host defense factor against LPS.

Interferon-beta counteracts inflammatory mediator-induced effects on brain endothelial cell tight junction molecules-implications for multiple sclerosis

To elucidate mechanisms of endothelial cell (EC) dysfunction in CNS inflammatory responses and beneficial effects of interferon-beta (IFN-gamma) in multiple sclerosis (MS), we analyzed effects of individual and combinations of soluble inflammatory mediators on the intracellular localization of the EC tight junction-associated molecules zonula occludens-1 and -2 (ZO-1 and ZO-2) in human brain ECs. The cytoplasm in the majority of cells in control EC cultures was clear; ZO-1 and ZO-2 were localized peripherally near sites of cell contact and associated with submembranous cytoplasmic filaments. H2O2 induced reversible time- and concentration-dependent translocation of ZO-1 and ZO-2 to a random distribution within EC cytoplasm and retraction of EC borders. For low concentrations, these effects were accompanied by less prominent submembranous filaments but not by evidence of cytotoxicity, increased cell death or altered amounts of ZO-1. Tumor necrosis factor-beta induced similar alterations but interferon-y did not. Co-treatment with either cytokine increased H2O2 effects whereas IFN-beta reversed H2O2-induced effects. In control white matter samples, EC cytoplasm was clear and ZO-1 was located on cell borders. In inflammatory/demyelinating lesions, EC ZO-1 was diffuse, indicating that the alterations induced in vitro mimic those in active MS lesions. These findings suggest that in MS patients, IFN-beta treatment may counteract inflammatory mediator effects on CNS EC tight junction molecules, thereby preserving EC barrier function.

Peptide drug modifications to enhance bioavailability and blood-brain barrier permeability

Peptides have the potential to be potent pharmaceutical agents for the treatment of many central nervous system derived maladies. Unfortunately peptides are generally water-soluble compounds that will not enter the central nervous system, via passive diffusion, due to the existence of the blood-brain barrier. Peptides can also undergo metabolic deactivation by peptidases, thus further reducing their therapeutic benefits. In targeting peptides to the central nervous system consideration must be focused both on increasing bioavailability and enhancing brain uptake. To date multiple strategies have been examined with this focus. However, each strategy comes with its own complications and considerations. In this review we assess the strengths and weaknesses of many of the methods currently being examined to enhance peptide entry into the central nervous system.