Stimulation of ERK2 by taurine with enhanced alkaline phosphatase activity and collagen synthesis in osteoblast-like UMR-106 cells

Taurine accelerates the synthesis of ceramides and hyaluronic acid in cultured epidermis and dermal fibroblasts

Taurine is a sulfur-containing amino acid derivative that can be found in the majority of mammalian tissues. Taurine is also present in the skin and is involved in maintaining skin homeostasis by exerting osmoregulatory and antioxidant effects. Previous studies have indicated that taurine treatment is effective against age-, ultraviolet- or detergent-induced skin dysfunction. To determine the mechanism responsible for the beneficial actions of taurine in the skin, the present study aimed to evaluate the effects of taurine on epidermal components (ceramides and filaggrin) and on the dermal extracellular matrix, in three-dimensionally (3D) cultured epidermis and dermal fibroblasts, respectively. These cells were cultured in the presence of 3-50 mM taurine, and cells or culture medium were collected for analysis. The effects of taurine on transepidermal water loss (TEWL) in the skin and the expression of inflammatory cytokines, including IL-1α, IL-1β and IL-1 receptor antagonist, were investigated in acetone-treated 3D-cultured epidermis using a Tewameter and reverse transcription-quantitative PCR (RT-qPCR), respectively. The mRNA expression levels of MMP-1 and hyaluronic acid (HA) production were measured in skin dermal fibroblasts using RT-qPCR and ELISA, respectively. Taurine was found to suppress acetone-induced elevation in TEWL in 3D-cultured epidermis. Taurine also stimulated the mRNA expression of ceramide synthase 4 and filaggrin, a major structural protein in the stratum corneum, in 3D-cultured epidermis. In skin dermal fibroblasts, taurine inhibited the IL-1α-stimulated mRNA and protein expression of MMP-1. In addition, taurine treatment increased HA synthase-2 mRNA expression and in turn HA production. Results from the present study suggest that the protective effect of taurine on the skin is associated with the enhancement of epidermal barrier component expression and modulation of dermal extracellular matrix metabolism.

Anionic diketopiperazine induces osteogenic differentiation and supports osteogenesis in a 3D cryogel microenvironment

Bioactive molecules that enhance or induce osteogenic potential of bone precursor cells have shown vital roles in bone tissue engineering. Herein, we report the design and synthesis of a novel diketopiperazine (DT) that induces osteoblastic differentiation of pre-osteoblasts and bone-marrow-derived stem cells in vitro and enhances the osteogenic potential of cryogel matrix. Such functional diketopiperazines can serve as potential scaffolds for bone healing and regeneration.

A tailored polylactic acid/polycaprolactone biodegradable and bioactive 3D porous scaffold containing gelatin nanofibers and Taurine for bone regeneration

The focus of the current study was to develop a functional and bioactive scaffold through the combination of 3D polylactic acid (PLA)/polycaprolactone (PCL) with gelatin nanofibers (GNFs) and Taurine (Tau) for bone defect regeneration. GNFs were fabricated via electrospinning dispersed in PLA/PCL polymer solution, Tau with different concentrations was added, and the polymer solution converted into a 3D and porous scaffold via the thermally-induced phase separation technique. The characterization results showed that the scaffolds have interconnected pores with the porosity of up to 90%. Moreover, Tau increased the wettability and weight loss rate, while compromised the compressive strengths. The scaffolds were hemo- and cytocompatible and supported cell viability and proliferation. The in vivo studies showed that the defects treated with scaffolds filled with new bone. The computed tomography (CT) imaging and histopathological observation revealed that the PLA/PCL/Gel/Tau 10% provided the highest new bone formation, angiogenesis, and woven bone among the treatment groups. Our finding illustrated that the fabricated scaffold was able to regenerate bone within the defect and can be considered as the effective scaffold for bone tissue engineering application.

Dietary taurine stimulates the hepatic biosynthesis of both bile acids and cholesterol in the marine teleost, tiger puffer (Takifugu rubripes)

Taurine (TAU) plays important roles in the metabolism of bile acids, cholesterol and lipids. However, little relevant information has been available in fish where TAU has been identified as a conditionally essential nutrient. The present study aimed to investigate the effects of dietary TAU on the metabolism of bile acids, cholesterol and lipids in tiger puffer, which is both an important aquaculture species and a good research model, having a unique lipid storage pattern. An 8-week feeding trial was conducted in a flow-through seawater system. Three experimental diets differed only in TAU level, that is, 1·7, 8·2 and 14·0 mg/kg. TAU supplementation increased the total bile acid content in liver but decreased the content in serum. TAU supplementation also increased the contents of total cholesterol and HDL-cholesterol in both liver and serum. The hepatic bile acid profile mainly includes taurocholic acid (94·48 %), taurochenodeoxycholic acid (4·17 %) and taurodeoxycholic acid (1·35 %), and the contents of all these conjugated bile acids were increased by dietary TAU. The hepatic lipidomics analysis showed that TAU tended to decrease the abundance of individual phospholipids and increase those of some individual TAG and ceramides. The hepatic mRNA expression study showed that TAU stimulated the biosynthesis of both bile acids and cholesterol, possibly via regulation of farnesoid X receptor and HDL metabolism. TAU also stimulated the hepatic expression of lipogenic genes. In conclusion, dietary TAU stimulated the hepatic biosynthesis of both bile acids and cholesterol and tended to regulate lipid metabolism in multiple ways.

Association between metabolic profiles in urine and bone mineral density of pre- and postmenopausal Chinese women

OBJECTIVE

In the present study, we aimed to characterize the pathological development of menopausal osteoporosis, as well as to explore potential biomarkers and metabolic pathways involved in osteoporosis.

METHODS

Urine samples from 322 female participants categorized by menopause status and different bone conditions were collected and analyzed based on a gas chromatography-mass spectrometry (GC-MS) approach. Multivariate and univariate statistical analyses were carried out for urinary metabolomic profile characterization and comparison.

RESULTS

Seventeen metabolites in the low bone mineral density (BMD) groups were clearly differentiated from those in normal BMD groups. Among these 17 differentiating metabolites, taurine, β-alanine, and 5-hydroxycaproic acid were found to be potential biomarkers of osteoporosis. The taurine metabolic pathway and the β-alanine metabolic pathway were found to be related to menopause and bone loss.

CONCLUSIONS

Based on the GC-MS metabolomic platform, four typical pathological phases during the progression of postmenopausal osteoporosis were described. Several differentiating metabolites and metabolic pathways were found to be closely related to the pathology of postmenopausal osteoporosis. Our results provided a solid foundation for further studies on early diagnosis and pathomechanistic evaluation.

The Effect on Blood Biochemical Factors of a ICR-Mice in a High-Fat Diet with Taurine 20

The purpose of this study was to examine the effects of taurine on lipid levels and liver function and the actions of insulin and leptin by biochemically analyzing the blood of albino mice fed a diet containing 20% taurine. The group fed a high-fat diet (HF) containing 20% taurine (HF + taurine 20%) showed higher blood HDL cholesterol levels as well as significantly lower total cholesterol and triglyceride levels (p < 0.05) than the group fed HF. No significant difference was observed among indicators of liver function, such as alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase activities. However, the HF + taurine 20% group showed significantly lower insulin and leptin levels than the HF group (p < 0.05). These findings show that 20% taurine had a significant effect on blood lipid levels and blood sugar maintenance in mice fed an HF.

Beneficial Function of Taurine on Bone Metabolism in Alcohol-Fed OVX Rat Model

The present study investigates the effects of taurine on bone markers and bone mineral density (BMD) in alcohol-fed ovariectomized (OVX) rat model. We divided twenty four rats into Sham and OVX groups. These two groups were thereafter subdivided into two groups: control and experimental diet containing 2 g/kg of taurine. BMD and bone mineral content (BMC) were estimated by PIXImus. As bone markers, we measured serum calcium, phosphorus, ALP activity, osteocalcin and urine calcium, phosphorus and DPD crosslinks value. The results were as follows: weight gain showed no significant difference and serum calcium concentration was in normal range. Urine DPD crosslink value was significantly decreased in taurine-fed group (p < 0.05). Serum ALP activity and osteocalcin levels, and urine phosphorus concentration did not show any differences among groups. Also the mineral density and content of spinal and femural bone did not show any differences among groups. However, the femur BMD was significantly increased in taurine-fed group (p < 0.05). In conclusion, taurine supplemented diets may have positive results on bone metabolism in alcohol-fed OVX rat model.

MAPK signaling has stage-dependent osteogenic effects on human adipose-derived stem cells in vitro

OVERVIEW

The use of pro-osteogenic growth factors, such as BMP2, in human adipose-derived stem cell (ASC) osteogenesis is well described. Because these growth factors work via signal transduction pathways, such as the mitogen-activated protein kinase (MAPK) cascade, a study of the relationship between MAPK signaling and ASC osteogenesis was conducted.

MATERIALS AND METHODS

ERK, JNK, and p38MAPK activation were measured in ASCs osteo-induced using either dexamethasone or vitamin D3 and correlated with mineralization. Activation and mineralization were also measured without dexamethasone or using the glucocorticoid, cortisone. The expression of the MAPK phosphatase, MKP1, and its relationship to mineralization was also assessed. The effect of decreasing MAPK activation on mineralization through the use of exogenous inhibitors was examined along with siRNA-knockdown and adenoviral overexpression of ERK1/2. Finally, the effect of ERK1/2 overexpression on ASCs induced on PLGA scaffolds was assessed.

RESULTS

ASC mineralization in dexamethasone or vitamin D3-induced ASCs correlated with both increased ERK1/2 and JNK1/2 activation. ASCs induced without dexamethasone also mineralized, with JNK1/2 signaling possibly mediating this event. No link between cortisone induction and MAPK signaling could be ascertained. ASCs treated with ERK, JNK, or p38MAPK inhibitors showed decreased osteogenic gene expression and diminished mineralization. Mineralization levels were also affected by viruses designed to inhibit or augment ERK1/2 expression and activity. Finally, ASC mineralization appeared to be a balance between the MAPK kinase activity and MKP1.

CONCLUSIONS

It is likely that MAPK signaling plays a significant role in ASC osteogenesis, affecting differentiation in kinase- and stage-specific manners.

Taurine Promotes the Cartilaginous Differentiation of Human Umbilical Cord-Derived Mesenchymal Stem Cells in Vitro

Taurine has been reported to influence osteogenic differentiation, but the role of taurine on cartilaginous differentiation using human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) remains unclear. In this study, we investigated the effect of taurine (0, 1, 5 and 10 mM) on the proliferation and chondrogenesis of hUC-MSCs by analyzing cell proliferation, accumulation of glycosaminoglycans and expression of cartilage specific mRNA. The results show though taurine did not affected the proliferation of hUC-MSCs, 5 mM of taurine is sufficient to enhanced the accumulation of glycosaminoglycans and up-regulate cartilage specific mRNA expression, namely collagen type II, aggrecan and SOX9. Taurine also inhibits chondrocyte dedifferentiation by reducing expression of collagen type I mRNA. Taken together, our study reveals that taurine promotes and maintains the chondrogenesis of hUC-MSCs.

Metabolic analysis of osteoarthritis subchondral bone based on UPLC/Q-TOF-MS

Osteoarthritis (OA), one of the most widespread musculoskeletal joint diseases among the aged, is characterized by the progressive loss of articular cartilage and continuous changes in subchondral bone. The exact pathogenesis of osteoarthritis is not completely clear. In this work, ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF-MS) in combination with multivariate statistical analysis was applied to analyze the metabolic profiling of subchondral bone from 42 primary osteoarthritis patients. This paper described a modified two-step method for extracting the metabolites of subchondral bone from primary osteoarthritis patients. Finally, 68 metabolites were identified to be significantly changed in the sclerotic subchondral bone compared with the non-sclerotic subchondral bone. Taurine and hypotaurine metabolism and beta-alanine metabolism were probably relevant to the sclerosis of subchondral bone. Taurine, L-carnitine, and glycerophospholipids played a vital regulation role in the pathological process of sclerotic subchondral bone. In the sclerotic process, beta-alanine and L-carnitine might be related to the increase of energy consumption. In addition, our findings suggested that the intra-cellular environment of sclerotic subchondral bone might be more acidotic and hypoxic compared with the non-sclerotic subchondral bone. In conclusion, this study provided a new insight into the pathogenesis of subchondral bone sclerosis. Our results indicated that metabolomics could serve as a promising approach for elucidating the pathogenesis of subchondral bone sclerosis in primary osteoarthritis. Graphical Abstract Metabolic analysis of osteoarthritis subchondral bone.

Taurine promotes human mesenchymal stem cells to differentiate into osteoblast through the ERK pathway

Taurine has been reported to influence bone metabolism, but the role of taurine on osteogenic differentiation of human mesenchymal stem cells (hMSCs) remains unclear. In the present study, we investigated the effect of taurine on osteogenic differentiation of hMSCs. The results showed that taurine increased the alkaline phosphatase (ALP) activity and mineralized nodules in hMSCs induced by osteogenic induced medium. Meanwhile, RT-PCR analysis showed that taurine up-regulated the mRNA expression of ALP, osteopontin, Runt-related transcription factor 2 (Runx2) and Osterix in a dose-dependent manner. Furthermore, taurine induced activation of extracellular signal regulated kinase (ERK) and pretreatment with the ERK inhibitor U0126 abolished the taurine-induced osteogenesis of hMSCs. Taken together, our study reveals that taurine promotes the osteogenesis of hMSCs by activating the ERK pathway.

Calcium-deficiency assessment and biomarker identification by an integrated urinary metabonomics analysis

BACKGROUND

Calcium deficiency is a global public-health problem. Although the initial stage of calcium deficiency can lead to metabolic alterations or potential pathological changes, calcium deficiency is difficult to diagnose accurately. Moreover, the details of the molecular mechanism of calcium deficiency remain somewhat elusive. To accurately assess and provide appropriate nutritional intervention, we carried out a global analysis of metabolic alterations in response to calcium deficiency.

METHODS

The metabolic alterations associated with calcium deficiency were first investigated in a rat model, using urinary metabonomics based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and multivariate statistical analysis. Correlations between dietary calcium intake and the biomarkers identified from the rat model were further analyzed to confirm the potential application of these biomarkers in humans.

RESULTS

Urinary metabolic-profiling analysis could preliminarily distinguish between calcium-deficient and non-deficient rats after a 2-week low-calcium diet. We established an integrated metabonomics strategy for identifying reliable biomarkers of calcium deficiency using a time-course analysis of discriminating metabolites in a low-calcium diet experiment, repeating the low-calcium diet experiment and performing a calcium-supplement experiment. In total, 27 biomarkers were identified, including glycine, oxoglutaric acid, pyrophosphoric acid, sebacic acid, pseudouridine, indoxyl sulfate, taurine, and phenylacetylglycine. The integrated urinary metabonomics analysis, which combined biomarkers with regular trends of change (types A, B, and C), could accurately assess calcium-deficient rats at different stages and clarify the dynamic pathophysiological changes and molecular mechanism of calcium deficiency in detail. Significant correlations between calcium intake and two biomarkers, pseudouridine (Pearson correlation, r = 0.53, P = 0.0001) and citrate (Pearson correlation, r = -0.43, P = 0.001), were further confirmed in 70 women.

CONCLUSIONS

To our knowledge, this is the first report of reliable biomarkers of calcium deficiency, which were identified using an integrated strategy. The identified biomarkers give new insights into the pathophysiological changes and molecular mechanisms of calcium deficiency. The correlations between calcium intake and two of the biomarkers provide a rationale or potential for further assessment and elucidation of the metabolic responses of calcium deficiency in humans.

Morphological development of larval cobia Rachycentron canadum and the influence of dietary taurine supplementation

The morphological development of larval cobia Rachycentron canadum from 3 days post hatch (dph) until weaning (27 dph) was examined using S.E.M. Two groups of fish were studied: a control group (CF), reared under standard feeding protocol, and a group in which prey items were enriched with supplemental taurine (4 g l(-1) day(-1) ; TF). TF fish grew faster (P < 0·001), attained greater size (mean ±s.e. 55·1 ± 1·5 v. 33·9 ± 1·0 mm total length) and had better survival (mean ±s.e. 29·3 ± 0·4 v. 7·1 ± 1·2 %) than CF fish. Canonical variance analysis confirmed findings with respect to differences in growth between the treatment groups with separation being explained by two cranial measurements. S.E.M. revealed that 3 dph larvae of R. canadum (in both groups) possess preopercular spines, superficial neuromasts on the head and body, taste buds in the mouth, an olfactory epithelium which takes the form of simple concave depressions, and primordial gill arches. Gill filaments start to form as early as 6 dph and lamellae buds are visible at 8 dph in both groups. In CF fish, the cephalic lateral line system continues its development at 12-14 dph with invagination of both supra- and infraorbital canals. At the same time, a thorn-like or acanthoid crest forms above the eye. At 14 dph, invaginations of the mandibular and preopercular canals are visible and around 22 dph enclosure of all cranial canals nears completion. In CF larvae, however, completely enclosed cranial canals were not observed within the course of the trial, i.e. 27 dph. In TF larvae, grooves of the cephalic lateral line system form 4 days earlier than observed in CF larvae of R. canadum (i.e. at 8 dph), with enclosure commencing at 16 dph, and completed by 27 dph. Along the flanks of 6 dph larvae of either treatment, four to five equally spaced neuromasts delineate the future position of the trunk lateral line. As myomeres are added to the growing larvae, new neuromasts appear such that at 16 dph a neuromast is associated with each myomere. By 27 dph, the trunk lateral line starts to invaginate in CF larvae, while it initiates closure in TF larvae. These findings elucidate important features of the larval development of R. canadum and show that dietary taurine supplementation benefits larval development, growth and survival in this species. Moreover, they suggest a conditional requirement for taurine in larval R. canadum.

Taurine increases cell proliferation and generates an increase in [Mg2+]i accompanied by ERK 1/2 activation in human osteoblast cells

Taurine has been reported to influence bone metabolism, and its specific transport system, the taurine transporter, is expressed in osteoblasts. The mean [Mg2+]i was 0.51+/-0.01 mM in normal culture media. Taurine caused an increase in [Mg(2+)]i by 0.72+/-0.04 mM in human osteoblast (HOB) cells. This increment in [Mg2+]i was inhibited significantly by PD98059, nifedipine, lidocaine, and imipramine. Taurine was also shown to stimulate the activation of ERK 1/2. This taurine-stimulated ERK 1/2 activation was inhibited by PD98059. In the present study, taurine was shown to increase cell proliferation and generate an increase in [Mg2+]i accompanied by ERK 1/2 activation in HOB cells.

Reduction of plasma taurine level in children affected by Osteogenesis Imperfecta during bisphosphonate therapy

Osteogenesis imperfecta (OI) is a heritable disease of connective tissue characterized by increased bone fragility. To date, bisphosphonates seem to be the most promising therapy, at least for children. In the last decade experimental and clinical studies indicate that several amino acids are implicated in bone mineralization. Particularly, taurine is localized in matrices of the bone and can regulate osteoblast metabolism with antiosteopenic effect. To investigate a possible interaction between pharmacological effects of bisphosphonates and amino acids involved in bone metabolism, we performed plasma and urine amino acids analysis in children affected by OI before and during treatment with bisphosphonates. Fourteen prepubertal children with moderate to severe types of OI, 8 males and 6 females, aged from 2 to 11 years (mean (SD) 6.9+/-2.53) were enrolled in the study. Patients were treated with neridronate infusion (1mg/kg/body weight) every three months. Plasma and urine specimens for amino acid analysis were kept at baseline (T0) and three months after each infusion of four consecutive cycles (T1-T4). A significant decrease in respect to the pre-treatment levels (T0) was observed after the fourth infusion for taurine (p<0.01). In addition, urinary excretion of this amino acid showed a significant decrease after the fourth infusion. No significant correlations were found between plasma level or urinary excretion of hydroxyproline, taurine, arginine and lysine in respect to bone mineral density. The progressive reduction of plasma taurine found in our patients treated with bisphosphonates could be implicated in the action mechanism of this drug in OI and possibly in other disorders of bone metabolism. This knowledge could provide new opportunities to improve treatment with bisphosphonates and address novel strategies for the therapeutic approach to bone disorders.

Taurine promotes connective tissue growth factor (CTGF) expression in osteoblasts through the ERK signal pathway

Taurine is found in bone tissue, but its function in skeletal tissue is not fully understood. The present study was undertaken to investigate regulation of gene expression of connective tissue growth factor (CTGF), and the roles of mitogen-activated protein kinases (MAPKs) in murine osteoblast MC3T3-E1 cells treated with taurine. Western blot analysis showed taurine stimulated CTGF protein secretion in a dose- and time-dependent manner. Taurine induced activation of extracellular signal-regulated kinase (ERK), but not p38 and c-jun N-terminal Kinase (JNK), in osteoblasts. Furthermore, pretreatment of osteoblasts with the ERK inhibitor PD98059 abolished the taurine-induced CTGF production. These data indicate that taurine induces CTGF secretion in MC3T3-E1 cells mediated by the ERK pathway, and suggest that osteoblasts are direct targets of taurine.

Taurine transporter is expressed in osteoblasts

Taurine influences bone metabolism and is taken up by cells via a specific transport system, the taurine transporter (TAUT). We report a link between taurine and bone homeostasis by demonstrating transcription and translation of TAUT in bone-forming cells. TAUT was expressed in human primary osteoblasts, the human osteosarcoma osteoblast-like cell line MG63, and the mouse osteoblastic cell line MC3T3-E1. Immunostaining with polyclonal antibodies also demonstrated the presence of TAUT in both human and murine osteoblasts. TAUT mRNA expression and [(3)H]taurine uptake increased during differentiation of MG63 cells in culture. Supplementation of culture medium with taurine enhanced alkaline phosphatase activity and osteocalcin secretion. The regulation and detailed function of taurine and TAUT in bone remain unclear, but our findings suggest a functional role for them in bone homeostasis.

Biocompatibility Evaluation of Zeolite Compared to Bone HA, Calcium Phosphate (Ca2PO4) and Eugenol Paste

The biocompatibility of Zeolite was evaluated, in vitro, compared to a control and to three different biomaterials: hydroxyapatite from bovine bone, calcium phosphate and a commercial eugenol paste. The Zeolite did not affect cellular proliferation neither the alkaline phosphatase and collagen production. The apoptosis index of the zeolite groups were similar to control and optical microscopy observations did not show any morphological cell change, except the some cytoplasmatic vacuole formation.

Extracellular Oxidation by Taurine Chloramine Activates ERK via the Epidermal Growth Factor Receptor

Taurine is present in high concentrations in neutrophils, and when the cells are stimulated taurine can react with hypochlorous acid (HOCl) to form taurine-chloramine (Tau-Cl). This compound retains oxidant activity and can affect the neutrophil itself or surrounding tissue cells. We have investigated the effects of Tau-Cl on MAPK signaling in human umbilical vein endothelial cells (HUVEC). Tau-Cl caused no loss in intracellular glutathione or inactivation of the thiol-sensitive enzyme glyceraldehyde-3-phosphate dehydrogenase, indicating that it had not entered the cells. However, stimulation of HUVEC with Tau-Cl (20-100 microM) induced the rapid activation of ERK within 10 min. This activation was abolished by inhibition of MEK by U0126, indicating that it was not because of direct oxidation of ERK. No activation of p38 was detected. These results suggest that Tau-Cl reacts with a cell membrane target that results in intracellular ERK activation. Tau-Cl over the same concentration range and time scale stimulated epidermal growth factor (EGF) receptor tyrosine phosphorylation in A431 cells and HUVEC. The EGF receptor inhibitor PD158780 significantly attenuated Tau-Cl-induced phosphorylation of both the EGF receptor and ERK. This implicates the EGF receptor in the upstream activation of ERK. The Src tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolol[3,4-d]pyrimidine had no effect on Tau-Cl-induced EGF receptor or ERK activation. We propose that Tau-Cl acts on an oxidant-sensitive target on the cell surface, this being either the EGF receptor itself or another target that can interact with the EGF receptor, with consequential activation of ERK.

Role of taurine uptake on the induction of long-term synaptic potentiation

Taurine application in the CA1 area of rat hippocampal slices induces a long-lasting potentiation of excitatory synaptic transmission that has some mechanistic similitude with the late phase of long-term potentiation (L-LTP). Previous indirect evidence such as temperature and sodium dependence indicated that taurine uptake is one of the primary steps leading to the taurine-induced synaptic potentiation. We show that taurine-induced potentiation is not related to the intracellular accumulation of taurine and is not impaired by 2-guanidinoethanesulphonic acid, a taurine transport inhibitor that is a substrate of taurine transporter. We have found that taurine uptake in hippocampal synaptosomes was inhibited by SKF 89976A, a GABA uptake blocker that is not transportable by GABA transporters. SKF 89976A prevents the induction of synaptic potentiation by taurine application. This effect is neither mimicked by nipecotic acid, a broad inhibitor of GABA transporters that does not affect taurine uptake, nor by NO-711, a specific and potent inhibitor of GABA transporter GAT-1. In addition, L-LTP induced by trains of high-frequency stimulation is also inhibited by SKF 89976A, and taurine, at a concentration that does not change basal synaptic transmission, overcomes such inhibition. We conclude that taurine induces synaptic potentiation through the activation of a system transporting taurine and that taurine uptake is required for the induction of synaptic plasticity phenomena such as L-LTP.

Immunomodulating Activities of Polysaccharides Isolated fromPanax ginseng

Panax ginseng C.A. Meyer has been traditionally used for the prevention and treatment of various chronic diseases and infections. Ginseng marc is a fibrous and insoluble by-product remaining after the extraction process of ginseng. In this research an extrusion process was employed to disintegrate the insoluble ginseng marc structure, and water-soluble ginseng marc polysaccharide (GMP) was isolated. GMP was examined for immunomodulatory effects in murine peritoneal macrophages. GMP significantly increased the lysosomal phosphatase activity and the phagocytic index of peritoneal macrophages (P<.05). The peritoneal macrophages treated with GMP also produced significantly more H(2)O(2) and nitrite than the control without GMP treatment (P<.05). In addition, GMP (100 microg/mL) significantly increased the cell viability of peritoneal macrophages (P<.05). These results suggest that GMP is an effective nonspecific immunomodulatory agent, and its immunostimulating effects may be due to its ability to stimulate the production of reactive oxygen intermediates.

Taurine-induced synaptic potentiation and the late phase of long-term potentiation are related mechanistically

The application of taurine (2-aminoethanesulfonic acid) induces a long-lasting increase of synaptic efficacy and axon excitability (LLP-TAU) in rat hippocampal CA1 area. After taurine withdrawal, LLP-TAU lasted at least 3 h. This fact prompted us to assess whether the mechanisms involved in the maintenance of this particular potentiation were similar to those implicated in the late phase of long-term potentiation (L-LTP). In the presence of KN-62, an inhibitor of calcium/calmodulin-dependent protein kinase, taurine perfusion (10 mM, 30 min) did not affect the induction of LLP-TAU. However, LLP-TAU maintenance was completely suppressed by KT5720, an inhibitor of the cAMP-dependent protein kinase (PKA). Moreover, the late phase of LLP-TAU was blocked by inhibiting protein synthesis with anisomycin. In addition, taurine perfusion increased the phosphorylation of cAMP response element-binding protein (CREB), although did not affect cAMP levels. These features of LLP-TAU do not appear to be caused by the activation of D1/D5 dopamine receptors, as taurine also induced synaptic potentiation in the presence of SCH23390, an antagonist of this type of receptors. Finally, the late phase of both L-LTP and LLP-TAU occluded mutually. These results suggest that taurine triggers the sequence of some of the molecular events involved in the induction of L-LTP.