Isolation and characterization of a cDNA encoding a human liver/bone/kidney-type alkaline phosphatase

Progesterone regulates tissue non-specific alkaline phosphatase (TNSALP) expression and activity in ovine utero-placental tissues

BACKGROUND

Tissue non-specific alkaline phosphatase (TNSALP; encoded by the ALPL gene) has a critical role in the postnatal regulation of phosphate homeostasis, yet how TNSALP activity and expression are regulated during pregnancy remain largely unknown. This study tested the hypothesis that progesterone (P4) and/or interferon tau (IFNT) regulate TNSALP activity during pregnancy in sheep.

METHODS

In Exp. 1, ewes were bred and received daily intramuscular injections of either corn oil vehicle (CO) or 25 mg progesterone in CO (P4) for the first 8 days of pregnancy and were hysterectomized on either Day 9, 12, or 125 of gestation. In Exp. 2, ewes were fitted with intrauterine catheters on Day 7 of the estrous cycle and received daily intramuscular injections of 50 mg P4 in CO and/or 75 mg progesterone receptor antagonist (RU486) in CO from Days 8 to 15, and twice daily intrauterine injections of either control proteins (CX) or IFNT (25 µg/uterine horn/d) from Days 11 to 15 (treatment groups: P4 + CX; P4 + IFNT; RU486 + P4 + CX; and RU486 + P4 + IFNT) and were hysterectomized on Day 16.

RESULTS

In Exp. 1, endometria from ewes administered P4 had greater expression of ALPL mRNA than ewes administered CO on Day 12. TNSALP activity appeared greater in the epithelia, stratum compactum stroma, and endothelium of the blood vessels in the endometrium and myometrium from ewes administered P4 than ewes administered CO on Day 12. On Day 125, TNSALP activity localized to uterine epithelial and endothelial cells, independent of P4 treatment. TNSALP activity in placentomes appeared greater in P4 treated ewes and was detected in endothelial cells and caruncular tissue in P4 treated but not CO treated ewes. In Exp. 2, endometrial homogenates from ewes administered RU486 + P4 + CX had lower TNSALP activity those for P4 + CX and P4 + IFNT ewes. Immunoreactive TNSALP protein appeared greater in the mid- and deep-glandular epithelia in RU486 + P4 + CX treated ewes as compared to the other treatment groups. Enzymatic activity appeared greater on the apical surface of the deep glandular epithelia in endometria from ewes treated with RU486 + P4 + CX compared to the other treatment groups.

CONCLUSIONS

These results suggest that P4, but not IFNT, regulates the expression and activity of TNSALP in utero-placental tissues and has the potential to contribute to the regulation of phosphate availability that is critical for conceptus development during pregnancy.

Glycoproteomic profile of human tissue-nonspecific alkaline phosphatase expressed in osteoblasts

Tissue-nonspecific alkaline phosphatase (TNALP) is a glycoprotein expressed by osteoblasts that promotes bone mineralization. TNALP catalyzes the hydrolysis of the mineralization inhibitor inorganic pyrophosphate and ATP to provide inorganic phosphate, thus controlling the inorganic pyrophosphate/inorganic phosphate ratio to enable the growth of hydroxyapatite crystals. N-linked glycosylation of TNALP is essential for protein stability and enzymatic activity and is responsible for the presence of different bone isoforms of TNALP associated with functional and clinical differences. The site-specific glycosylation profiles of TNALP are, however, elusive. TNALP has 5 potential N-glycosylation sites located at the asparagine (N) residues 140, 230, 271, 303, and 430. The objective of this study was to reveal the presence and structure of site-specific glycosylation in TNALP expressed in osteoblasts. Calvarial osteoblasts derived from Alpl+/- expressing SV40 Large T antigen were transfected with soluble epitope-tagged human TNALP. Purified TNALP was analyzed with a lectin microarray, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and liquid chromatography with tandem mass spectrometry. The results showed that all sites (n = 5) were fully occupied predominantly with complex-type N-glycans. High abundance of galactosylated biantennary N-glycans with various degrees of sialylation was observed on all sites, as well as glycans with no terminal galactose and sialic acid. Furthermore, all sites had core fucosylation except site N271. Modelling of TNALP, with the protein structure prediction software ColabFold, showed possible steric hindrance by the adjacent side chain of W270, which could explain the absence of core fucosylation at N271. These novel findings provide evidence for N-linked glycosylation on all 5 sites of TNALP, as well as core fucosylation on 4 out of 5 sites. We anticipate that this new knowledge can aid in the development of functional and clinical assays specific for the TNALP bone isoforms.

Characterization of TNSALP expression, localization, and activity in ovine utero-placental tissues†

Tissue-nonspecific alkaline phosphatase (TNSALP; encoded by ALPL gene) has a critical role in the regulation of phosphate homeostasis postnatally. However, the utero-placental expression of TNSALP and the role in phosphate transport in pregnancy is poorly understood. Estrous cycles of ewes were synchronized, and ewes were euthanized and hysterectomized on Days 1, 9, or 14 of the estrous cycle or bred to fertile rams and euthanized and hysterectomized on Days 9, 12, 17, 30, 50, 70, 90, 110, or 125 of pregnancy. The expression of ALPL mRNA, immunolocalization of TNSALP protein, and quantification and localization of TNSALP enzymatic activity was performed on ovine endometria and placentomes. Day of the estrous cycle did not alter ALPL mRNA expression or enzymatic activity of TNSALP. TNSALP protein localized to uterine epithelial and stromal cells, blood vessels, myometrium, caruncular, and cotyledonary stroma. TNSALP activity was localized to uterine epithelia, blood vessels, caruncular stroma (from Day 70 of gestation), and the apical surface of chorionic epithelia (from Day 50 of gestation). TNSALP protein and activity localized to the apical surface of uterine epithelia during the estrous cycle and in early pregnancy. Endometrial TNSALP enzymatic activity was downregulated on Days 17 and 30 of gestation (P < 0.05). Expression of ALPL mRNA decreased in late gestation in endometria and placentomes (P < 0.05). TNSALP activity peaked in placentomes on Days 70 and 90 of gestation. Collectively, these results suggest a potential role of TNSALP in the regulation of phosphate transport and homeostasis at the maternal-conceptus interface in ruminants.

Effects of grape seed proanthocyanidin extract on side effects of high-dose methylprednisolone administration in male rats

In this study, we investigated the effects of grape seed proanthocyanidin extract (GSPE) against the side effects of high-dose administration of methylprednisolone (MP) in male rats. A total of 32 adult Wistar male albino rats were divided into four groups: (1) control (CON), received standard food only; (2) MP, received standard food + intraperitoneal injection of 60 mg/kg MP on day 7; (3) GSPE, received standard food + 200 mg/kg/day GSPE; and (4) MP + GSPE, received standard food + 200 mg/kg/day of GSPE + intraperitoneal injection of 60 mg/kg MP on day 7. All animals in the GSPE and GSPE + MP groups were treated once a day by oral gavage for 14 consecutive days. The feed intake of rats in the MP and MP + GSPE groups decreased significantly by 24.14% and 13.52%, respectively (p < 0.05). Administration of MP resulted in significant increases in serum concentrations of blood urea nitrogen (p < 0.001), glucose (p < 0.01), alkaline phosphatase, and adrenocorticotropic hormone (p < 0.05). High-dose MP administration significantly reduced catalase (p < 0.001) and glutathione peroxidase (p < 0.05) concentrations in the liver and kidney tissues of rats, while glutathione concentrations were only reduced in liver tissue (p < 0.05). The expression levels of Bcl-2 and TNF-α in liver, kidney, and testicular tissue were significantly increased, while the expression levels of caspase-3 were reduced (p < 0.001). Furthermore, sperm concentration was significantly affected by GSPE in rats induced by high-dose MP, and sperm loss was significantly reduced in MP + GSPE (p < 0.05). These findings suggest that GSPE could be useful as a supplement to alleviate MP-induced toxicity in rats.

ALPL-1 is a target for chimeric antigen receptor therapy in osteosarcoma

Osteosarcoma (OS) remains a dismal malignancy in children and young adults, with poor outcome for metastatic and recurrent disease. Immunotherapies in OS are not as promising as in some other cancer types due to intra-tumor heterogeneity and considerable off-target expression of the potentially targetable proteins. Here we show that chimeric antigen receptor (CAR) T cells could successfully target an isoform of alkaline phosphatase, ALPL-1, which is highly and specifically expressed in primary and metastatic OS. The target recognition element of the second-generation CAR construct is based on two antibodies, previously shown to react against OS. T cells transduced with these CAR constructs mediate efficient and effective cytotoxicity against ALPL-positive cells in in vitro settings and in state-of-the-art in vivo orthotopic models of primary and metastatic OS, without unexpected toxicities against hematopoietic stem cells or healthy tissues. In summary, CAR-T cells targeting ALPL-1 show efficiency and specificity in treating OS in preclinical models, paving the path for clinical translation.

Prophylactic Anti-Osteoporotic Effect of Matricaria chamomilla L. Flower Using Steroid-Induced Osteoporosis in Rat Model and Molecular Modelling Approaches

The anti-osteoporotic activity of ethanol extract from the Matricaria chamomilla L. flower was evaluated using steroid-induced osteoporosis in a rat model for the first time. Biochemical parameters such as serum calcium, phosphate, magnesium, creatinine, and alkaline phosphatase were assessed. At a 400 mg/kg body weight dose, the extract showed 54.01% and 27.73% reduction in serum calcium and phosphate ions serum levels, respectively. Meanwhile, it showed a 20% elevation in serum magnesium level, compared to the steroid-treated group. It also showed a significant decrease in creatinine and alkaline phosphatase levels, by 29.41% and 27.83%, respectively. The obtained results were further supported by biomechanical analyses, which revealed that a 400 mg/kg body weight dose of the flower extract increased bone strength and thickness. At the same time, it does not affect the bone length, compared to the diseased group. Histopathological examination revealed that the extract showed a significant increase in trabecular thickness, and it had restored the architecture of the cortical and trabecular structure with well-organized bone matrix. The possible inhibitory effect of the major phenolic compounds identified from the plant extract on cathepsin K was investigated using molecular docking. Rutin (4) had the best-fitting score within the active site, as evidenced by the free binding energy, (∆G = −54.19 Kcal/mol). ADMET/TOPKAT revealed that the examined compounds had variable pharmacodynamics and pharmacokinetic properties that could be improved to enhance the bioavailability during incorporation in various dosage forms. Thus, it can be concluded that this plant extract showed potential therapeutic benefits for osteoporosis.

A new perspective on the function of Tissue Non-Specific Alkaline Phosphatase: from bone mineralization to intra-cellular lipid accumulation

Tissue-nonspecific alkaline phosphatase (TNAP) is one of four isozymes, which include germ cell, placental and intestinal alkaline phosphatases. The TNAP isozyme has 3 isoforms (liver, bone and kidney) which differ by tissue expression and glycosylation pattern. Despite a long history of investigation, the exact function of TNAP in many tissues is largely unknown. Only the bone isoform has been well characterised during mineralization where the enzyme hydrolyses pyrophosphate to inorganic phosphate, which combines with calcium to form hydroxyapatite crystals deposited as new bone. The inorganic phosphate also increases gene expression of proteins that support tissue mineralization. Recent studies have shown that TNAP is expressed in preadipocytes from several species, and that inhibition of TNAP activity causes attenuation of intracellular lipid accumulation in these and other lipid-storing cells. The mechanism by which TNAP stimulates lipid accumulation is not known; however, proteins that are important for controlling phosphate levels in bone are also expressed in adipocytes. This review examines the evidence that inorganic phosphate generated by TNAP promotes transcription that enhances the expression of the regulators of lipid storage and consequently, that TNAP has a major function of lipid metabolism.

Intestinal Alkaline Phosphatase: A Review of This Enzyme Role in the Intestinal Barrier Function

Intestinal alkaline phosphatase (IALP) has recently assumed a special relevance, being the subject of study in the prevention and treatment of certain diseases related to leaky gut. This brush border enzyme (ecto-enzyme) plays an important role in the maintenance of intestinal microbial homeostasis and intestinal barrier function through its ability to dephosphorylate lipopolysaccharide (LPS). This review addresses how IALP and intestinal barrier dysfunction may be implicated in the pathophysiology of specific diseases such as inflammatory bowel disease, necrotizing enterocolitis, and metabolic syndrome. The use of IALP as a possible biomarker to assess intestinal barrier function and strategies to modulate IALP activity are also discussed.

Tissue-Nonspecific Alkaline Phosphatase, a Possible Mediator of Cell Maturation: Towards a New Paradigm

Alkaline phosphatase (ALP) is a ubiquitous membrane-bound glycoprotein capable of providing inorganic phosphate by catalyzing the hydrolysis of organic phosphate esters, or removing inorganic pyrophosphate that inhibits calcification. In humans, four forms of ALP cDNA have been cloned, among which tissue-nonspecific ALP (TNSALP) (TNSALP) is widely distributed in the liver, bone, and kidney, making it an important marker in clinical and basic research. Interestingly, TNSALP is highly expressed in juvenile cells, such as pluripotent stem cells (i.e., embryonic stem cells and induced pluripotent stem cells (iPSCs)) and somatic stem cells (i.e., neuronal stem cells and bone marrow mesenchymal stem cells). Hypophosphatasia is a genetic disorder causing defects in bone and tooth development as well as neurogenesis. Mutations in the gene coding for TNSALP are thought to be responsible for the abnormalities, suggesting the essential role of TNSALP in these events. Moreover, a reverse-genetics-based study using mice revealed that TNSALP is important in bone and tooth development as well as neurogenesis. However, little is known about the role of TNSALP in the maintenance and differentiation of juvenile cells. Recently, it was reported that cells enriched with TNSALP are more easily reprogrammed into iPSCs than those with less TNSALP. Furthermore, in bone marrow stem cells, ALP could function as a "signal regulator" deciding the fate of these cells. In this review, we summarize the properties of ALP and the background of ALP gene analysis and its manipulation, with a special focus on the potential role of TNSALP in the generation (and possibly maintenance) of juvenile cells.

The Physiological and Pathological Role of Tissue Nonspecific Alkaline Phosphatase beyond Mineralization

Tissue-nonspecific alkaline phosphatase (TNAP) is a key enzyme responsible for skeletal tissue mineralization. It is involved in the dephosphorylation of various physiological substrates, and has vital physiological functions, including extra-skeletal functions, such as neuronal development, detoxification of lipopolysaccharide (LPS), an anti-inflammatory role, bile pH regulation, and the maintenance of the blood brain barrier (BBB). TNAP is also implicated in ectopic pathological calcification of soft tissues, especially the vasculature. Although it is the crucial enzyme in mineralization of skeletal and dental tissues, it is a logical clinical target to attenuate vascular calcification. Various tools and studies have been developed to inhibit its activity to arrest soft tissue mineralization. However, we should not neglect its other physiological functions prior to therapies targeting TNAP. Therefore, a better understanding into the mechanisms mediated by TNAP is needed for minimizing off targeted effects and aid in the betterment of various pathological scenarios. In this review, we have discussed the mechanism of mineralization and functions of TNAP beyond its primary role of hard tissue mineralization.

Effect of Obesity on Plasma Alkaline Phosphatase Activity in Breast Cancer

Background

Breast cancer is most common cancer in women. Obesity is one of related-risk factor in breast cancer. In obese normal subjects, alkaline phosphatase (ALP) has been studied. However, there is no previous study investigate the association between ALP and obesity in breast cancer and its correlation with other clinical characteristics. Therefore, the objective of present study is to investigate the association between ALP and clinical characteristics in generally and obesity in particularly.

Methods

A cross-study 111 new diagnosed breast cancer patients was included. Plasma ALP was measured in different subgroups: patients age <40 vs >40, premenopausal vs postmenopausal, estrogen receptor-positive (ER+) vs estrogen receptor negative (ER-), metastasis vs non-metastasis and obese vs non-obese patients.

Results

Significant increasing on plasma ALP were shown between groups of each age, menopausal status, metastasis, and obesity (p< 0.05, p< 0.05, p< 0.01 and p< 0.05) respectively. Positive correlation was observed between plasma ALP and age, menopausal status, metastasis, and obesity (r: 0.616, p< 0.05; r: 0.667, p< 0.01; r: 0.691, p< 0.005; and r: 0.627, p< 0.01). Multiple regression analysis was indicated that ALP can be determined by menopausal status, metastasis, and obesity (β-Coefficient = 0.428, p< 0.01; β-Coefficient = 0.534; p< 0.001; β-coefficient= 0.545; p= 0.005), respectively.

Conclusion

Together, the relation between ALP and obesity indicates that ALP could have a role in maturation of preadipocytes of breast cancer patients. Further investigations are needed to confirm that there could be a potential hormonal link between ALP and obesity in breast cancer patients.

Clonal osteoblastic cell lines with CRISPR/Cas9-mediated ablation of Pit1 or Pit2 show enhanced mineralization despite reduced osteogenic gene expression

Multiple actions of extracellular Pi on the skeletal cells are likely to be partly mediated by type III sodium/phosphate (Na⁺/Pi) cotransporters Pit1 and Pit2, although the details are not fully understood. In the current study, to determine the roles of Pit1 and Pit2 in osteoblasts, we generated Pit1-knockout (KO) and Pit2-KO osteoblastic cells by applying CRISPR/Cas9 genome editing to an osteoblastic cell line MC3T3-E1 subclone 4. The extracellular Pi level was increased in the Pit1-KO and Pit2-KO clones due to the reduced Pi uptake. Interestingly, in vitro mineralization was accelerated in the Pit1-KO and Pit2-KO clones, although the induction of the expression of osteogenic marker genes was suppressed. In the cells before mineralization, extracellular levels of pyrophosphate (PPi) and adenosine triphosphate (ATP) were increased in the Pit1-KO and Pit2-KO clones, which might be attributable to the reduced expression and activity of tissue-nonspecific alkaline phosphatase (TNSALP). A 24-h treatment with high Pi reduced the expression and activity of TNSALP, suggesting that the suppression of TNSALP in the Pit1-KO and Pit2-KO clones was caused by the increased availability of extracellular Pi. Lentiviral gene transfer of Pit1 and Pit2 restored the changes observed in Pit1-KO and Pit2-KO clones, respectively. The expressions of P2Y2 and P2X7 which encode receptors for extracellular ATP were altered in the Pit1-KO and Pit2-KO clones, suggesting an influence on purinergic signaling. In mineralized cells after long-term culture, intracellular levels of PPi and ATP were higher in the Pit1-KO and Pit2-KO clones. Taken together, ablation of Pit1 or Pit2 in this osteoblastic cell model led to accelerated mineralization, suppressed TNSALP and altered the levels of extracellular and intracellular PPi and ATP, which might be partly mediated by changes in the availability of extracellular Pi.

TNAP as a New Player in Chronic Inflammatory Conditions and Metabolism

This review summarizes important information on the ectoenzyme tissue-nonspecific alkaline phosphatase (TNAP) and gives a brief insight into the symptoms, diagnostics, and treatment of the rare disease Hypophosphatasia (HPP), which is resulting from mutations in the TNAP encoding ALPL gene. We emphasize the role of TNAP beyond its well-known contribution to mineralization processes. Therefore, above all, the impact of the enzyme on central molecular processes in the nervous system and on inflammation is presented here.

Tissue-Nonspecific Alkaline Phosphatase-A Gatekeeper of Physiological Conditions in Health and a Modulator of Biological Environments in Disease

Tissue-nonspecific alkaline phosphatase (TNAP) is a ubiquitously expressed enzyme that is best known for its role during mineralization processes in bones and skeleton. The enzyme metabolizes phosphate compounds like inorganic pyrophosphate and pyridoxal-5′-phosphate to provide, among others, inorganic phosphate for the mineralization and transportable vitamin B6 molecules. Patients with inherited loss of function mutations in the ALPL gene and consequently altered TNAP activity are suffering from the rare metabolic disease hypophosphatasia (HPP). This systemic disease is mainly characterized by impaired bone and dental mineralization but may also be accompanied by neurological symptoms, like anxiety disorders, seizures, and depression. HPP characteristically affects all ages and shows a wide range of clinical symptoms and disease severity, which results in the classification into different clinical subtypes. This review describes the molecular function of TNAP during the mineralization of bones and teeth, further discusses the current knowledge on the enzyme’s role in the nervous system and in sensory perception. An additional focus is set on the molecular role of TNAP in health and on functional observations reported in common laboratory vertebrate disease models, like rodents and zebrafish.

Idiopathic Osteoporosis and Nephrolithiasis: Two Sides of the Same Coin?

Idiopathic osteoporosis and nephrolithiasis are formidable health problems showing a progressive increase in their incidence and prevalence in the last decades. These temporal trends were observed in both pediatric and adult populations worldwide. Epidemiological and experimental studies indicate that both disorders show several common pathogenic environmental and genetic factors. In this review, we analyzed the clinical characteristics common to the two disorders and the state-of-the-art knowledge regarding the genetic predisposition and the environmental factors recognized as triggers in adult and pediatric ages. As a result of this work, we propose to consider idiopathic nephrolithiasis and osteoporosis as two possible expressions of a unique clinical syndrome. Accordingly, the clinical approach to both disorders should be modified in order to program an efficient primary and secondary prevention strategy.

Innate Biomineralization

In vertebrates, biomineralization is a feature considered unique to mature osteoblasts and odontoblasts by which they synthesize hydroxyapatite (HAP), which is deposited in the collagen matrix to construct endoskeleton. For many decades, the mechanisms that modulate differentiation and maturation of these specialized cells have been sought as a key to understanding bone-remodeling defects. Here, we report that biomineralization is an innate ability of all mammalian cells, irrespective of cell type or maturation stage. This innate biomineralization is triggered by the concomitant exposure of living cells to three indispensable elements: calcium ion, phosphoester salt, and alkaline phosphatase. Any given somatic cell, including undifferentiated mononuclear cells, can undergo a biomineralization process to produce calcium-phosphate agglomerates. The biologically generated minerals under such conditions are composed of genuine HAP crystallites of Ca₁₀(PO₄)₆(OH)₂ and 5–10 nanometer (nm) in size. This discovery will profoundly improve our understanding of bone metabolism and ectopic calcifications.

Effects of supplementing yeast fermentate in the feed or drinking water on stress susceptibility, plasma chemistry, cytokine levels, antioxidant status, and stress- and immune-related gene expression of broiler chickens

This study aimed to elucidate the mechanism by which adding Saccharomyces cerevisiae-derived yeast fermentate to the feed (XPC) or drinking water reduces stress in poultry. Day-old male Cobb 500 broiler chicks were assigned to 1 of 3 treatments: stressed control (CS), stressed + XPC (1.25 kg/metric ton feed, day 0-43; XPC), or stressed + AviCare (160 mL/100 L drinking water, day 0-43; AVI). All birds were spray-vaccinated for coccidiosis (day 0), raised on reused litter, spray-vaccinated for Newcastle/Bronchitis (day 18), and exposed to heat stress (32°C-34°C) and feed/water withdrawal for 12 h (day 18). Blood samples were collected to assess plasma corticosterone (CORT) and heterophil/lymphocyte (H/L) ratio (60 birds/treatment; day 40); plasma biochemistry and growth hormone (12 birds/treatment; day 38); and serum serotonin and plasma prolactin, thyroid hormones, antioxidant capacity, and selected cytokines (12 birds/treatment; day 39). Composite asymmetry scores were obtained from 60 birds/treatment on day 41. Organs were collected from 20 birds/treatment on day 43 to measure gene expression of CYP1A2 and melanocortin 2 receptor (MC2R) in the adrenal glands and IL10 and AvBD1 in the spleen. Serotonin was lower in CS than XPC (P = 0.049), whereas AVI was intermediate. Plasma interleukin (IL)-1β was higher in AVI than CS (P = 0.009) and XPC (P = 0.009). The CS treatment had higher CORT than AVI (P = 0.013) and XPC (P = 0.037) and higher H/L ratios than AVI (P = 0.026) and XPC (P = 0.034). Expression of CYP1A2, MC2R, and IL10 was lower (P < 0.05) in XPC and AVI compared with CS. Furthermore, IL10 expression was lower in XPC than AVI (P < 0.05). Adding yeast fermentate to the feed or drinking water reduced measures of stress and MC2R gene expression in birds exposed to acute and rearing stressors. However, differences in IL10 gene expression and circulating serotonin and IL-1β suggest that supplementing yeast fermentate in the feed is slightly more effective than supplementation via the drinking water in mitigating the physiological effects associated with the stress response in broilers.

Hypophosphatasia in Japan: ALPL Mutation Analysis in 98 Unrelated Patients

Hypophosphatasia (HPP) is highly variable in clinical expression and is generally classified into six subtypes. Although it would be beneficial to be able to predict the clinical course from the ALPL genotype, studies on this issue are limited. Here, we aimed to clarify the features of Japanese HPP and the relationships between genotype and clinical manifestations. We analyzed 98 unrelated Japanese patients to investigate the percentage of each clinical form, frequently detected mutations, and the relationship between the genotype and phenotype. Some of the identified mutants were characterized by transfection experiments. Perinatal severe form was the most frequent (45.9%), followed by perinatal benign form (22.4%). Among the 196 alleles, p.Leu520ArgfsX86 (c.1559delT) was detected in 89 alleles, and p.Phe327Leu (c.979T>C) was identified in 23 alleles. All of the homozygotes for p.Leu520ArgfsX86 were classified into perinatal severe form, and patients carrying p.Phe327Leu in one of the alleles were classified into perinatal benign or odonto HPP. Twenty of the 22 patients with perinatal benign HPP were compound heterozygous for p.Phe327Leu and another mutation. Most patients with odonto HPP were found to be monoallelic heterozygotes for dominant-negative mutations or compound heterozygotes with mutants having residual activity. The high prevalence of p.Leu520ArgfsX86 and p.Phe327Leu mutations might underlie the high rate of perinatal severe and perinatal benign forms, respectively, in Japanese HPP. Although ALPL genotyping would be beneficial for predicting the clinical course to an extent, the observed phenotypical variability among patients sharing the same genotypes suggests the presence of modifiers.

Locally Increased Level of Inorganic Phosphate Induced Nodules or Calcification After Bolus Fat Grafting

BACKGROUND

Nodules or calcifications have been a common complication after breast augmentation with fat grafting, especially in cases with partial bolus fat grafting. There are some clinical preventive measures, but mechanisms related to this complication have not been elucidated yet. Inorganic phosphate (PI), being a product of fat metabolism, is a well-known stimulus of other kinds of pathological calcification such as vascular calcification. We aimed to determine whether PI had a similar effect on formation of nodules after fat grafting.

METHODS

Nodules or calcification after fat grafting models using nude mice were created by bolus fat injection. Levels of PI of necrotic liquid located in the central zone and mineralization deposition of graft were examined 1 week, 2 weeks, 1 month, 2 months and 7 months after bolus fat injection. External high phosphate solution was injected 3 times a week to the fat grafts for 2 months, and mineral deposition was examined. In addition, adipose-derived stem cells (ADSCs) were treated with high phosphate osteogenic differentiation medium in various concentrations and times. ADSCs were also treated with osteogenic differentiation in addition to tetramisole which could reduce the level of PI. Mineral depositions of the cells were examined. The central necrotic liquid was extracted from patients who found palpable nodules after breast augmentation with fat grafting. The level of PI of this necrotic liquid and normal lipoaspirates from patients who received normal liposuction for body contouring was compared.

RESULTS

The in vivo study indicated that the local PI concentration of the necrotic zone increased significantly 2 months after large volume bolus fat injection. Calcification was not formed after 2 months, but was formed after 7 months, indicating that the effect of PI on calcification was time-dependent. In addition, with the effect of external injection of high phosphate solution into the fat graft, calcification was formed after 2 months, indicating the effect of PI on calcification was dose-dependent. The in vitro study also indicated PI could induce calcification of ADSC in a time- and dose-dependent manner. The study in humans indicated that the level of PI in the necrotic zone of nodules after fat grafting was higher than that in normal lipoaspirates.

CONCLUSIONS

This study indicated that the level of PI in the central necrotic zone was elevated after bolus fat injection, which could provide an environment to induce calcification of surrounding tissue.

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Lithium-Doped Biological-Derived Hydroxyapatite Coatings Sustain In Vitro Differentiation of Human Primary Mesenchymal Stem Cells to Osteoblasts

This study is focused on the adhesion and differentiation of the human primary mesenchymal stem cells (hMSC) to osteoblasts lineage on biological-derived hydroxyapatite (BHA) and lithium-doped BHA (BHA:LiP) coatings synthesized by Pulsed Laser Deposition. An optimum adhesion of the cells on the surface of BHA:LiP coatings compared to control (uncoated Ti) was demonstrated using immunofluorescence labelling of actin and vinculin, two proteins involved in the initiation of the cell adhesion process. BHA:LiP coatings were also found to favor the differentiation of the hMSC towards an osteoblastic phenotype in the presence of osteoinductive medium, as revealed by the evaluation of osteoblast-specific markers, osteocalcin and alkaline phosphatase. Numerous nodules of mineralization secreted from osteoblast cells grown on the surface of BHA:LiP coatings and a 3D network-like organization of cells interconnected into the extracellular matrix were evidenced. These findings highlight the good biocompatibility of the BHA coatings and demonstrate that the use of lithium as a doping agent results in an enhanced osteointegration potential of the synthesized biomaterials, which might therefore represent viable candidates for future in vivo applications.

A Preliminary Cohort Study Assessing Routine Blood Analyte Levels and Neurological Outcome after Spinal Cord Injury

There is increasing interest in the identification of biomarkers that could predict neurological outcome following a spinal cord injury (SCI). Although initial American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade is a good indicator of neurological outcome, for the patient and clinicians, an element of uncertainty remains. This preliminary study aimed to assess the additive potential of routine blood analytes following principal component analysis (PCA) to develop prognostic models for neurological outcome following SCI. Routine blood and clinical data were collected from SCI patients (n = 82) and PCA used to reduce the number of blood analytes into related factors. Outcome neurology was obtained from AIS scores at 3 and 12 months post-injury, with motor (AIS and total including all myotomes) and sensory (AIS, touch and pain) abilities being assessed individually. Multiple regression models were created for all outcome measures. Blood analytes relating to “liver function” and “acute inflammation and liver function” factors were found to significantly increase prediction of neurological outcome at both 3 months (touch, pain, and AIS sensory) and at 1 year (pain, R² increased by 0.025 and total motor, R² increased by 0.016). For some models “liver function” and “acute inflammation and liver function” factors were both significantly predictive, with the greatest combined R² improvement of 0.043 occurring for 3 month pain prediction. These preliminary findings support ongoing research into the use of routine blood analytes in the prediction of neurological outcome in SCI patients.

ALPL regulates the aggressive potential of high grade serous ovarian cancer cells via a non-canonical WNT pathway

The ALPL gene is linked to hypophosphatasia, a rare genetic disease. Owing to the inverse relationships between ALPL expression and both the International Federation of Gynecology and Obstetrics (FIGO) stages and histological grades assigned to patients with serous ovarian cancer (SOC), this study was designed to explore the role and possible mechanisms of ALPL in cell motility of high grade SOC (HGSOC). The effects of ALPL overexpression on migration and invasion were detected in HGSOC cell lines SKOV3 and HEY. Gene ontology analysis for differential genes with ALPL overexpression identified several biological processes, including EMT, correlated with cell motility. Genes potentially implicated in EMT and associated with ALPL were screened using The Cancer Genome Atlas (TCGA) database. The WNT receptor Frizzled2 (FZD2) was identified and its role in HGSOC cell motility and survival was investigated. It was found that forced expression of ALPL could inhibit migration, invasion, and EMT in HGSOC cells. It also reduced the expression of FZD2 and its ligand WNT5A, accompanied by suppressed expression of their downstream target phosphorylated-STAT3 (pSTAT3). These effects were initiated via the FZD2 knockdown using siRNA and reversed by recombinant WNT5A protein. The relationship between FZD2 expression and poor HGSOC patient survival was also investigated. This data supports that ALPL might restrict the function of WNT5A-FZD2-STAT3 axis, a non-canonical WNT pathway for promoting EMT progression, which results in attenuated migration and invasion in HGSOC cells and improves survival in patients with SOC.

Relationship between serum alkaline phosphatase level, C-reactive protein and leukocyte counts in adults aged 60 years or older

Serum alkaline phosphatase (ALP), a useful marker of hepatobiliary or bone disorders, has been known to be associated with cardiovascular disease (CVD), which is increasingly being viewed as an inflammatory disease. C-reactive protein level and leukocyte count have also been highlighted as independent risk markers of CVD. Thus, the mechanism underlying the link between elevated ALP and CVD could be subclinical low-grade inflammation. This study aimed to examine associations of serum ALP level with inflammatory markers. This cross-sectional study included 2403 participants (1324 men and 1079 women) aged ≥60 years who participated in a health examination program. Serum ALP quartiles were categorized as follows: Q1: ≤51, Q2: 52-61, Q3: 62-74 and Q4: ≥75 U/L. The odds ratios (ORs) and 95% confidence intervals (CIs) for high CRP and leukocyte count (≥75th percentiles) were calculated after adjusting for confounding variables across serum ALP quartiles using multiple logistic regression analysis. Median CRP level and mean leukocyte count increased in accordance with serum ALP quartiles. Compared to the lowest quartile, the ORs (95% CI) of the highest quartile for high CRP and leukocyte count were 2.03 (1.50-2.76) and 1.54 (1.13-2.10) after adjusting for age, sex, body mass index, smoking status, alcohol intake, fasting plasma glucose, log-transformed triglyceride and HDL-cholesterol levels. Serum ALP level was positively and independently associated with inflammatory markers in adults aged 60 years or older.

Alkaline phosphatase: a potential biomarker for stroke and implications for treatment

Stroke is the fifth leading cause of death in the U.S., with more than 100,000 deaths annually. There are a multitude of risks associated with stroke, including aging, cardiovascular disease, hypertension, Alzheimer's disease (AD), and immune suppression. One of the many challenges, which has so far proven to be unsuccessful, is the identification of a cost-effective diagnostic or prognostic biomarker for stroke. Alkaline phosphatase (AP), an enzyme first discovered in the 1920s, has been evaluated as a potential biomarker in many disorders, including many of the co-morbidities associated with stroke. This review will examine the basic biology of AP, and its most common isoenzyme, tissue nonspecific alkaline phosphatase (TNAP), with a specific focus on the central nervous system. It examines the preclinical and clinical evidence which supports a potential role for AP in stroke and suggests potential mechanism(s) of action for AP isoenzymes in stroke. Lastly, the review speculates on the clinical utility of AP isoenzymes as potential blood biomarkers for stroke or as AP-targeted treatments for stroke patients.

A homozygous missense variant in the alkaline phosphatase gene ALPL is associated with a severe form of canine hypophosphatasia

Inherited skeletal disorders affect both humans and animals. In the current study, we have performed series of clinical, pathological and genetic examinations to characterize a previously unreported skeletal disease in the Karelian Bear Dog (KBD) breed. The disease was recognized in seven KBD puppies with a variable presentation of skeletal hypomineralization, growth retardation, seizures and movement difficulties. Exome sequencing of one affected dog revealed a homozygous missense variant (c.1301T > G; p.V434G) in the tissue non-specific alkaline phosphatase gene, ALPL. The identified recessive variant showed full segregation with the disease in a cohort of 509 KBDs with a carrier frequency of 0.17 and was absent from 303 dogs from control breeds. In humans, recessive and dominant ALPL mutations cause hypophosphatasia (HPP), a metabolic bone disease with highly heterogeneous clinical manifestations, ranging from lethal perinatal hypomineralization to a relatively mild dental disease. Our study reports the first naturally occurring HPP in animals, resembling the human infantile form. The canine HPP model may serve as a preclinical model while a genetic test will assist in breeding programs.

Distinctive inhibition of alkaline phosphatase isozymes by thiazol-2-ylidene-benzamide derivatives: Functional insights into their anticancer role

In the recent years, the role of alkaline phosphatase (AP) isozymes in the cause of neoplastic diseases such as breast, liver, renal, and bone cancer has been confirmed and, thus they represent a novel target for the discovery of anticancer drugs. In this study different derivatives of thiazol-2-ylidene-benzamide were evaluated for their potential to inhibit alkaline phosphatase (AP) isozymes. Their anticancer potential was assessed using human breast cancer (MCF-7), bone-marrow cancer (K-562), and cervical cancer (HeLa) cell lines in comparison to normal cells from baby hamster kidney BHK-21. The results suggested that in comparison to other derivatives, compounds 2i, 2e, and 2a showed more sensitivity towards human tissue non-specific alkaline phosphatase (h-TNAP). Among these, 2″-chloro-N-(3-(4'-fluorophenyl)-4-methylthiazol-2(3H)-ylidene) benzamide (2e) was found as the most potent and selective inhibitor for h-TNAP with an IC₅₀ value of 0.079 ± 0.002 μM. Moreover, a significant correlation was observed between the enzyme inhibition profile and cytotoxic data. The compounds exhibiting maximum anticancer potential also induced maximum apoptosis in the respective cell lines. Furthermore, the DNA interaction studies exhibited the non-covalent mode of interaction with the herring sperm-DNA. Molecular docking studies also supported the in vitro inhibitory activity of potent compounds. Our findings suggested that potent and selective inhibitors might be useful candidates for the treatment or prevention of those diseases associated with the higher level of AP. Moreover, the study can be useful for the researcher to explore more molecular mechanisms of such derivatives and their analogues with the exact findings.

Common Variants in ALPL Gene Contribute to the Risk of Kidney Stones in the Han Chinese Population

OBJECTIVE

Kidney stone formation is a complex disorder that likely results from both dietary and genetic factors. A recent study identified an association between the risk of kidney stones and polymorphisms in the ALPL gene, but the study needs replication. To confirm whether the ALPL gene is universally associated with kidney stones, the present study further investigated polymorphisms of the ALPL gene in a Han Chinese population.

METHODS

A total of 331 kidney stone patients and 553 unrelated healthy controls were included in the present case-control study. We conducted genetic analyses to detect the association of 19 tagging single nucleotide polymorphisms (SNPs) with kidney stones. In addition, we examined the relations between targeted SNP(s) and several clinical characteristics of kidney stones in the patients.

RESULTS

Genetic association analyses using logistic regression models identified one ALPL SNP, rs1256328, which was significantly associated with the kidney stone disease status (OR = 1.52, p = 0.0009). No significant results were obtained through association tests between genotypes of this SNP and the various clinical characteristics of kidney stone patients.

CONCLUSION

The ALPL SNP, rs1256328, was identified as being significantly associated with kidney stone disease status in a large Chinese Han cohort. Our study replicated a previous genome-wide association study that was conducted in an Icelandic population.

Molecularly Imprinted Plasmonic Substrates for Specific and Ultrasensitive Immunoassay of Trace Glycoproteins in Biological Samples

Assays of glycoproteins hold significant biological importance and clinical values, for which immunoassay has been the workhorse tool. As immunoassays are associated with disadvantages such as poor availability of high-specificity antibodies, limited stability of biological reagents, and tedious procedure, innovative alternatives that can overcome these drawbacks are highly desirable. Plasmonic immunosandwich assay (PISA) has emerged as an appealing alternative to immunoassay for fast and sensitive determination of trace glycoproteins in biosamples. Plasmonic substrates play key roles in PISA, not only in determining the specificity but also in greatly influencing the detection sensitivity. Herein, we report a new type of molecularly imprinted plasmonic substrates for rapid and ultrasensitive PISA assay of trace glycoproteins in complex real samples. The substrates were fabricated from glass slides, first coated with self-assembled monolayer (SAM) of gold nanoparticles (AuNPs) and then molecularly imprinted with organo-siloxane polymer in the presence of template glycoproteins. The prepared molecularly imprinted substrates exhibited not only a significant plasmonic effect but also excellent binding properties, ensuring the sensitivity as well as the specificity of the assay. Alkaline phosphatase (ALP) and α-fetoprotein (AFP), glycoproteins that are routinely used as disease markers in clinical diagnosis, were used as representative targets. The limit of detection (LOD) was 3.1 × 10^-12 M for ALP and 1.5 × 10^-14 M for AFP, which is the best among the PISA approaches reported. The sample volume required was only 5 μL, and the total time required was within 30 min for each assay. Specific and ultrasensitive determination of ALP and AFP in human serum was demonstrated. Because many disease biomarkers are glycoproteins, the developed PISA approach holds great promise in disease diagnostics.

Isonicotinohydrazones as inhibitors of alkaline phosphatase and ecto-5'-nucleotidase

A series of isonicotinohydrazide derivatives was synthesized and tested against recombinant human and rat ecto-5'-nucleotidases (h-e5'NT and r-e5'NT) and alkaline phosphatase isozymes including both bovine tissue-non-specific alkaline phosphatase (b-TNAP) and tissue-specific calf intestinal alkaline phosphatase (c-IAP). These enzymes are implicated in vascular calcifications, hypophosphatasia, solid tumors, and cancers, such as colon, lung, breast, pancreas, and ovary. All tested compounds were active against both enzymes. The most potent inhibitor of h-e5'NT was derivative (E)-N'-(1-(3-(4-fluorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)ethylidene)isonicotinohydrazide (3j), whereas derivative (E)-N'-(4-hydroxy-3-methoxybenzylidene)isonicotinohydrazide (3g) exhibited significant inhibitory activity against r-e5'NT. In addition, the derivative (E)-N'-(4'-chlorobenzylidene)isonicotinohydrazide (3a) was most potent inhibitor against calf intestinal alkaline phosphatase and the derivative (E)-N'-(4-hydroxy-3-methoxybenzylidene)isonicotinohydrazide (3g) was found to be most potent inhibitor of bovine tissue-non-specific alkaline phosphatase. Furthermore, putative binding modes of potent compounds against e5'NT (human and rat e5'NT) and AP (including b-TNAP and c-IAP) were determined computationally.

Alkaline Phosphatase and Hypophosphatasia

Hypophosphatasia (HPP) results from ALPL mutations leading to deficient activity of the tissue-non-specific alkaline phosphatase isozyme (TNAP) and thereby extracellular accumulation of inorganic pyrophosphate (PPi), a natural substrate of TNAP and potent inhibitor of mineralization. Thus, HPP features rickets or osteomalacia and hypomineralization of teeth. Enzyme replacement using mineral-targeted TNAP from birth prevented severe HPP in TNAP-knockout mice and was then shown to rescue and substantially treat infants and young children with life-threatening HPP. Clinical trials are revealing aspects of HPP pathophysiology not yet fully understood, such as craniosynostosis and muscle weakness when HPP is severe. New treatment approaches are under development to improve patient care.

Reversible Deterioration in Hypophosphatasia Caused by Renal Failure With Bisphosphonate Treatment

Hypophosphatasia is an inborn error of metabolism caused by mutations in the ALPL gene. It is characterized by low serum alkaline phosphatase (ALP) activity and defective mineralization of bone, but the phenotype varies greatly in severity depending on the degree of residual enzyme activity. We describe a man with compound heterozygous mutations in ALPL, but no previous bone disease, who suffered numerous disabling fractures after he developed progressive renal failure (for which he eventually needed dialysis treatment) and was prescribed alendronate treatment. A bone biopsy showed marked osteomalacia with low osteoblast numbers and greatly elevated pyrophosphate concentrations at mineralizing surfaces. In vitro testing showed that one mutation, T117H, produced an ALP protein with almost no enzyme activity; the second, G438S, produced a protein with normal activity, but its activity was inhibited by raising the media phosphate concentration, suggesting that phosphate retention (attributable to uremia) could have contributed to the phenotypic change, although a pathogenic effect of bisphosphonate treatment is also likely. Alendronate treatment was discontinued and, while a suitable kidney donor was sought, the patient was treated for 6 months with teriparatide, which significantly reduced the osteomalacia. Eighteen months after successful renal transplantation, the patient was free of symptoms and the scintigraphic bone lesions had resolved. A third bone biopsy showed marked hyperosteoidosis but with plentiful new bone formation and a normal bone formation rate. This case illustrates how pharmacological (bisphosphonate treatment) and physiologic (renal failure) changes in the "environment" can dramatically affect the phenotype of a genetic disorder.

In vivo imaging of endogenous enzyme activities using luminescent 1,2-dioxetane compounds

Background

Here we present a non-invasive imaging method for visualizing endogenous enzyme activities in living animals. This optical imaging method is based on an energy transfer principle termed chemically initiated electron exchange luminescence (CIEEL). The light energy is provided by enzymatic activation of metastable 1,2-dioxetane substrates, whose protective groups are removed by hydrolytic enzymes such as β-galactosidase and alkaline phosphatase. In the presence of a nearby fluorescent recipient, the chemical energy within the activated substrate is then transferred via formation of a charge-transfer complex with the fluorophore, a mechanism closely related to glow stick chemistry.

Results

Efficient CIEEL energy transfer requires close proximity between the trigger enzyme and the fluorescent recipient. Using cells stained with fluorescent dialkylcarbocyanines as the energy recipients, we demonstrated CIEEL imaging of cellular β-galactosidase or alkaline phosphatase activity. In living animals, we used a similar approach to non-invasively image alkaline phosphatase activity in the peritoneal cavity.

Conclusions

In this report, we provide proof-of-concept for CIEEL imaging of in vivo enzymatic activity. In addition, we demonstrate the use of CIEEL energy transfer for visualizing elevated alkaline phosphatase activity associated with tissue inflammation in living animals.

Molecular evolution of the tissue-nonspecific alkaline phosphatase allows prediction and validation of missense mutations responsible for hypophosphatasia

ALPL encodes the tissue nonspecific alkaline phosphatase (TNSALP), which removes phosphate groups from various substrates. Its function is essential for bone and tooth mineralization. In humans, ALPL mutations lead to hypophosphatasia, a genetic disorder characterized by defective bone and/or tooth mineralization. To date, 275 ALPL mutations have been reported to cause hypophosphatasia, of which 204 were simple missense mutations. Molecular evolutionary analysis has proved to be an efficient method to highlight residues important for the protein function and to predict or validate sensitive positions for genetic disease. Here we analyzed 58 mammalian TNSALP to identify amino acids unchanged, or only substituted by residues sharing similar properties, through 220 millions years of mammalian evolution. We found 469 sensitive positions of the 524 residues of human TNSALP, which indicates a highly constrained protein. Any substitution occurring at one of these positions is predicted to lead to hypophosphatasia. We tested the 204 missense mutations resulting in hypophosphatasia against our predictive chart, and validated 99% of them. Most sensitive positions were located in functionally important regions of TNSALP (active site, homodimeric interface, crown domain, calcium site, …). However, some important positions are located in regions, the structure and/or biological function of which are still unknown. Our chart of sensitive positions in human TNSALP (i) enables to validate or invalidate at low cost any ALPL mutation, which would be suspected to be responsible for hypophosphatasia, by contrast with time consuming and expensive functional tests, and (ii) displays higher predictive power than in silico models of prediction.

Alkaline phosphatase: an overview

Alkaline phosphatase (ALP; E.C.3.I.3.1.) is an ubiquitous membrane-bound glycoprotein that catalyzes the hydrolysis of phosphate monoesters at basic pH values. Alkaline phosphatase is divided into four isozymes depending upon the site of tissue expression that are Intestinal ALP, Placental ALP, Germ cell ALP and tissue nonspecific alkaline phosphatase or liver/bone/kidney (L/B/K) ALP. The intestinal and placental ALP loci are located near the end of long arm of chromosome 2 and L/B/K ALP is located near the end of the short arm of chromosome 1. Although ALPs are present in many mammalian tissues and have been studied for the last several years still little is known about them. The bone isoenzyme may be involved in mammalian bone calcification and the intestinal isoenzyme is thought to play a role in the transport of phosphate into epithelial cells of the intestine. In this review, we tried to provide an overview about the various forms, structure and functions of alkaline phosphatase with special focus on liver/bone/kidney alkaline phosphatase.

Autophagy-related gene16L2, a potential serum biomarker of multiple sclerosis evaluated by bead-based proteomic technology

Multiple sclerosis (MS) is an autoimmune disease characterized by neuroinflammation and demyelination that are mediated by T cells. The prolonged survival of autoreactive T cells acts as a primary event to trigger an inflammatory cascade that mediates myelin loss and clinical relapse in MS. Recently, T cell survival has been shown to be modulated by the autophagy-related gene (Atg). In the present study, we performed bead fractionation/matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analyses using serum from 54 MS patients and 55 healthy controls. Eleven peptides were significantly different between the two groups with one being identified as a fragment of Atg16L2. Then the decreased levels of Atg16L2 peptides in MS patients were validated by immunoblotting and real-time PCR. As the Atg12-Atg5·Atg16 multimeric complex plays an essential role in autophagy, our results suggest that Atg16L2 may play an important role in autophagy of T cells and serve as a potential biomarker to predict clinical relapse of MS.

Cellular function and molecular structure of ecto-nucleotidases

Ecto-nucleotidases play a pivotal role in purinergic signal transmission. They hydrolyze extracellular nucleotides and thus can control their availability at purinergic P2 receptors. They generate extracellular nucleosides for cellular reuptake and salvage via nucleoside transporters of the plasma membrane. The extracellular adenosine formed acts as an agonist of purinergic P1 receptors. They also can produce and hydrolyze extracellular inorganic pyrophosphate that is of major relevance in the control of bone mineralization. This review discusses and compares four major groups of ecto-nucleotidases: the ecto-nucleoside triphosphate diphosphohydrolases, ecto-5'-nucleotidase, ecto-nucleotide pyrophosphatase/phosphodiesterases, and alkaline phosphatases. Only recently and based on crystal structures, detailed information regarding the spatial structures and catalytic mechanisms has become available for members of these four ecto-nucleotidase families. This permits detailed predictions of their catalytic mechanisms and a comparison between the individual enzyme groups. The review focuses on the principal biochemical, cell biological, catalytic, and structural properties of the enzymes and provides brief reference to tissue distribution, and physiological and pathophysiological functions.

Determinants of the specificity of protease-activated receptors 1 and 2 signaling by factor Xa and thrombin

Factor Xa (FXa) elicits intracellular signaling responses through the activation of protease-activated receptor 2 (PAR2) and possibly also through PAR1 in endothelial cells. In this study, we investigated FXa signaling in endothelial cells when the protease was either in free form or assembled into the prothrombinase complex. Furthermore, we prepared several wild-type and mutant PAR1 and PAR2 cleavage-reporter constructs in which their exodomains were fused to cDNA encoding for a soluble alkaline phosphatase (ALP). In the mutants, P2 residues were exchanged between PAR1 and PAR2 cleavage-reporter constructs and the hirudin-like binding site (HLBS) of PAR1 was inserted into the homologous site of PAR2. In non-transfected cells, FXa elicited a protective response which could be blocked by a specific anti-PAR2 but not by an anti-PAR1 antibody. A similar protective activity was observed for FXa in the prothrombinase complex. Further studies revealed that neither the Gla- nor EGF1-domain of FXa is required for its signaling activity, however, the N-terminus Arg-86 and Lys-87 of the EGF2-domain were essential. In the cleavage-reporter transfected cells, FXa cleaved the PAR2 construct effectively, however, replacing its P2-Gly with P2-Pro of PAR1 impaired its cleavage by FXa but improved it by thrombin. A PAR2 construct containing both P2-Pro and HLBS of PAR1 was poorly cleaved by FXa, but effectively by thrombin. A PAR1 construct containing P2 and P3 residues of PAR2 was poorly cleaved by thrombin but effectively by FXa. These results provide new insight into mechanisms through which coagulation proteases specifically interact with their target PAR receptors.

Expression of osteoblastic and osteoclastic genes during spontaneous regeneration and autotransplantation of goldfish scale: a new tool to study intramembranous bone regeneration

Complementary DNA of osteoblast-specific genes (dlx5, runx2a, runx2b, osterix, RANKL, type I collagen, ALP, and osteocalcin) was cloned from goldfish (Carassius auratus) scale. Messenger RNA expressions were analyzed during spontaneous scale regeneration. Dlx5 had an early peak of expression on day 7, whereas osterix was constantly expressed during days 7-21. Runx2, a major osteoblastic transcription factor in mammalian bone, did not show any significant expression. The expressions of two functional genes, type I collagen and ALP, continually increased after day 7, while that of osteocalcin increased on day 14. As for osteoclastic markers, in addition to the cloning of two functional genes, TRAP and cathepsin K, in our previous study, we here cloned the transcription factor NFATc1 to use as an early osteoclastic marker. Using these bone markers, we investigate the signal key that controls the onset of scale resorption and regeneration by performing intra-scale-pocket autotransplantation of five groups of modified scales, namely, 1) methanol-fixed scale, 2) proteinase K-treated cell-free scale, 3) polarity reversal (upside-down) scale, 4) U-shape trimmed scale, and 5) circular-hole perforated scale. In this autotransplantation, each ontogenic scale was pulled out, modified, and then re-inserted into the same scale pocket. At post-transplant, inside the pockets of all modified transplant groups, new regenerating scales formed, attaching to the ongoing resorbed transplants. Autotransplantation of methanol-fixed scale, proteinase K-treated cell-free scale, and polarity reversal (upside-down) scale triggered scale resorption and scale regeneration. These two processes of scale resorption and regeneration occurred in accordance with osteoclastic and osteoblastic marker gene expressions. These results were microscopically confirmed using TRAP and ALP staining. Regarding the autotransplantation of U-shape trimmed and circular-hole perforated scales, new scales regenerated and grew at the trimmed/perforated part of each transplant, while scale resorption occurred apparently only around the trimmed/perforated area. In contrast, no scale resorption or regeneration was detected in sham transplantations. Our finding suggests that loss of correct cell-to-cell contact between the scale-pocket lining cells and the scale cortex cells is the key to switch on the onset of scale resorption and regeneration. Overall, the present study shows that goldfish scale regeneration shares similarities in gene expression with intramembranous bone regeneration. Improved understanding of goldfish scale regeneration will help elucidate the process of intramembranous bone regeneration and make goldfish scale a possible new tool to study bone regeneration.

Resveratrol exerts dosage and duration dependent effect on human mesenchymal stem cell development

Studies in the past have illuminated the potential benefit of resveratrol as an anticancer (pro-apoptosis) and life-extending (pro-survival) compound. However, these two different effects were observed at different concentration ranges. Studies of resveratrol in a wide range of concentrations on the same cell type are lacking, which is necessary to comprehend its diverse and sometimes contradictory cellular effects. In this study, we examined the effects of resveratrol on cell self-renewal and differentiation of human mesenchymal stem cells (hMSCs), a type of adult stem cells that reside in a number of tissues, at concentrations ranging from 0.1 to 10 µM after both short- and long-term exposure. Our results reveal that at 0.1 µM, resveratrol promotes cell self-renewal by inhibiting cellular senescence, whereas at 5 µM or above, resveratrol inhibits cell self-renewal by increasing senescence rate, cell doubling time and S-phase cell cycle arrest. At 1 µM, its effect on cell self-renewal is minimal but after long-term exposure it exerts an inhibitory effect, accompanied with increased senescence rate. At all concentrations, resveratrol promotes osteogenic differentiation in a dosage dependent manner, which is offset by its inhibitory effect on cell self-renewal at high concentrations. On the contrary, resveratrol suppresses adipogenic differentiation during short-term exposure but promotes this process after long-term exposure. Our study implicates that resveratrol is the most beneficial to stem cell development at 0.1 µM and caution should be taken in applying resveratrol as an anticancer therapeutic agent or nutraceutical supplement due to its dosage dependent effect on hMSCs.

Identification of exosite residues of factor Xa involved in recognition of PAR-2 on endothelial cells

Recent results have indicated that factor Xa (FXa) cleaves protease-activated receptor 2 (PAR-2) to elicit protective intracellular signaling responses in endothelial cells. In this study, we investigated the molecular determinants of the specificity of FXa interaction with PAR-2 by monitoring the cleavage of PAR-2 by FXa in endothelial cells transiently transfected with a PAR-2 cleavage reporter construct in which the extracellular domain of the receptor was fused to cDNA encoding for alkaline phosphatase. Comparison of the cleavage efficiency of PAR-2 by a series of FXa mutants containing mutations in different surface loops indicated that the acidic residues of 39-loop (Glu-36, Glu-37, and Glu-39) and the basic residues of 60-loop (Lys-62 and Arg-63), 148-loop (Arg-143, Arg-150, and Arg-154), and 162-helix (Arg-165 and Lys-169) contribute to the specificity of receptor recognition by FXa on endothelial cells. This was evidenced by significantly reduced activity of mutants toward PAR-2 expressed on transfected cells. The extent of loss in the PAR-2 cleavage activity of FXa mutants correlated with the extent of loss in their PAR-2-dependent intracellular signaling activity. Further characterization of FXa mutants indicated that, with the exception of basic residues of 162-helix, which play a role in the recognition specificity of the prothrombinase complex, none of the surface loop residues under study makes a significant contribution to the activity of FXa in the prothrombinase complex. These results provide new insight into mechanisms through which FXa specifically interacts with its macromolecular substrates in the clotting and signaling pathways.