Stimulation of differentiation in sodium-dependent vitamin C transporter 2 overexpressing MC3T3-E1 osteoblasts

Sodium-dependent vitamin C transporter (SVCT) 2 facilitates reduced ascorbic acid (AA) transport in MC3T3-E1 osteoblasts. Our previous studies suggested that Zn-induced osteoblast differentiation and Ca2+-, PO4(3-)-stimulated osteopontin (OPN) expression might result from their up-regulation effect on SVCT2 expression and AA uptake. Here, we investigated the role of SVCT2 on osteoblast differentiation by using SVCT2-overexpressing cells. Two clones of SVCT2-introduced cells overexpressed SVCT2 mRNA by 2.8- and 3.1-fold those of control cells, which resulted in obvious increase of AA uptake by 2.1- and 2.4-fold in Vmax with no change in Km. Alkaline phosphatase activity, hydroxyproline content significantly increased in SVCT2-overexpressing cells, and the induction of OPN mRNA was through up-regulation of OPN promoter activity by SVCT2 overexpression. Moreover, SVCT2-overexpressing cells exhibited more ability to promote mineralization and increase calcium deposition under the stimulation of 5 mM beta-glycerophosphate. These findings indicate that SVCT2 stimulates osteoblast differentiation and mineralization.     

Zinc-induced sodium-dependent vitamin C transporter 2 expression: potent roles in osteoblast differentiation

Zinc is an essential trace element that increases osteoblast numbers and bone formation. However, the mechanisms involved in the Zn-induced differentiation of osteoblasts are poorly understood. We examined the roles of L-ascorbic acid (AA) and its transporter, sodium-dependent vitamin C transporter (SVCT) 2, in the Zn-induced expression of osteoblastic differentiation markers. Zinc time- and dose-dependently induced SVCT2 mRNA expression in the absence or presence of AA. Western blotting and kinetic assays showed that Zn increased functional SVCT2 protein levels and AA transport. In the presence of AA, 50 microM Zn enhanced mRNA expression of the osteoblastic differentiation markers alkaline phosphatase, alpha(1)(I) procollagen, osteopontin (OPN), and osteocalcin (OCN) by 3.9-, 3.8-, 3.3-, and 3.5-fold, respectively; in the absence of AA, the Zn-induced increase was 2.8-, 2.5-, 1.3-, and 1.1-fold, respectively. These findings suggest that AA and SVCT2 mediate Zn-induced OPN and OCN expression and partly regulate Zn-induced osteoblastic differentiation.     

Bioactive analogs that simulate subsets of biological activities of 1alpha,25(OH)(2)D(3) in osteoblasts

1alpha,25-Dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] treatment of osteoblastic cells elicits a series of measurable responses that include both rapid, membrane-initiated effects and longer-term nuclear receptor-mediated effects. Structural analogs have been identified and characterized that selectively activate subsets of these pathways. Two analogs from over 35 that have been tested were chosen for this comparison because they activate non-overlapping response pathways, presumably representing either membrane-initiated or nuclear receptor-initiated activities. Compound AT [25(OH)-16ene-23yne-D(3)] lacks the 1-hydroxyl essential for interacting with the nuclear receptor, but triggers Ca(2+) influx through plasma membrane Ca(2+) channels, augments parathyroid hormone (PTH)-induced Ca(2+) signals, dephosphorylates the matrix protein osteopontin (OPN), and along with PTH stimulates release of calcium from calvaria in organ culture. Compound BT [1alpha,24(OH)(2)-22ene-24cyclopropyl-D(3)] does not elicit any of the rapid responses or enhance PTH-induced bone resorption, but binds to the nuclear receptor for 1alpha,25(OH)(2)D(3) and increases steady state mRNA levels of both OPN and osteocalcin over a 48 h period. Together, these two analogs recapitulate all of the known actions of 1alpha,25(OH)(2)D(3) on osteoblasts. Based on these findings, we conclude that Ca(2+) release from bone stimulated by 1alpha,25(OH)(2)D(3) and PTH is related to the rapid, membrane-initiated actions and is not likely to involve binding to the nuclear receptor for 1alpha,25(OH)(2)D(3). Longer term stimulation of bone formation by 1alpha,25(OH)(2)D(3), however, appears to involve solely the nuclear receptor-mediated effects. These findings support our model of 1alpha,25(OH)(2)D(3) as a coupling factor for bone resorption and formation during bone remodeling.     

Mechanistic insights and functional determinants of the transport cycle of the ascorbic acid transporter SVCT2. Activation by sodium and absolute dependence on bivalent cations

We characterized the human Na(+)-ascorbic acid transporter SVCT2 and developed a basic model for the transport cycle that challenges the current view that it functions as a Na(+)-dependent transporter. The properties of SVCT2 are modulated by Ca(2+)/Mg(2+) and a reciprocal functional interaction between Na(+) and ascorbic acid that defines the substrate binding order and the transport stoichiometry. Na(+) increased the ascorbic acid transport rate in a cooperative manner, decreasing the transport K(m) without affecting the V(max), thus converting a low affinity form of the transporter into a high affinity transporter. Inversely, ascorbic acid affected in a bimodal and concentration-dependent manner the Na(+) cooperativity, with absence of cooperativity at low and high ascorbic acid concentrations. Our data are consistent with a transport cycle characterized by a Na(+):ascorbic acid stoichiometry of 2:1 and a substrate binding order of the type Na(+):ascorbic acid:Na(+). However, SVCT2 is not electrogenic. SVCT2 showed an absolute requirement for Ca(2+)/Mg(2+) for function, with both cations switching the transporter from an inactive into an active conformation by increasing the transport V(max) without affecting the transport K(m) or the Na(+) cooperativity. Our data indicate that SVCT2 may switch between a number of states with characteristic properties, including an inactive conformation in the absence of Ca(2+)/Mg(2+). At least three active states can be envisioned, including a low affinity conformation at Na(+) concentrations below 20 mM and two high affinity conformations at elevated Na(+) concentrations whose Na(+) cooperativity is modulated by ascorbic acid. Thus, SVCT2 is a Ca(2+)/Mg(2+)-dependent transporter.     

Facilitation of glutamate release by ionotropic glutamate receptors in osteoblasts

Constitutive expression of mRNA was seen for the vesicular glutamate transporter brain-specific Na(+)-dependent inorganic phosphate cotransporter (BNPI), but not differentiation-associated Na(+)-dependent inorganic phosphate cotransporter, in rat calvarial osteoblasts cultured for 7 and 21 days in vitro (DIV). Three different agonists for ionotropic glutamate receptors (iGluR) at 1mM, as well as 50mM KCl, significantly increased the release of endogenous L-glutamate from osteoblasts cultured for 7DIV when determined 5 min after the addition by using a high performance liquid chromatograph. The inhibitor of desensitization of DL-alpha-amino-3-hydroxy-5-methylisoxasole-4-propionate (AMPA) receptors cyclothiazide significantly potentiated and prolonged the release of endogenous L-glutamate evoked by AMPA in a dose-dependent manner. The release evoked by AMPA was significantly prevented by the addition of an AMPA receptor antagonist as well as by the removal of Ca(2+) ions. These results suggest that endogenous L-glutamate could be released from intracellular vesicular constituents associated with BNPI through activation of particular iGluR subtypes expressed in cultured rat calvarial osteoblasts.     

The Integration of Mitochondrial Calcium Transport and Storage

The extraordinary capacity of isolated mitochondria to accumulate Ca(2+) has been established for more than 40 years. The distinct kinetics of the independent uptake and efflux pathways accounts for the dual functionality of the transport process to either modulate matrix free Ca(2+) concentrations or to act as temporary stores of large amounts of Ca(2+) in the presence of phosphate. One puzzle has been the nature of the matrix calcium phosphate complex, since matrix free Ca(2+) seems to be buffered in the region of 1-5 microM in the presence of phosphate while millimolar Ca(2+) remains soluble in in vitro media. The key seems to be the elevated matrix pH and the third-power relationship of the PO(4)(3-) concentration with pH. Taking this into account we may now finally have a model that explains the major features of physiological mitochondrial Ca(2+) transport.     

Intestinal bicarbonate secretion in marine teleost fish-source of bicarbonate, pH sensitivity, and consequences for whole animal acid-base and calcium homeostasis

Whole animal studies using seawater European flounder (Platichthys flesus) revealed that increasing intestinal [Ca(2+)] to 20 mM stimulated net HCO(3)(-) base secretion by 57%, but this was effectively balanced by an increase in net acid secretion, likely from the gills, to maintain whole animal acid-base status. Higher Ca(2+) concentrations (40 and 70 mM) in ambient seawater resulted in reduced plasma total CO(2). This indicates (1) imperfect acid-base compensation, and (2) that endogenous metabolic CO(2) is insufficient to fuel intestinal HCO(3)(-) secretion, under hyper-stimulated conditions. Bicarbonate secretion plays an important role in preventing calcium absorption by precipitating a large fraction of the imbibed calcium as CaCO(3). Indeed, under high Ca(2+) conditions (20 mM), up to 75% of the intestinal Ca(2+) is precipitated as CaCO(3) and then excreted. This is undoubtedly important in protecting the marine teleost kidney from the need for excessive calcium excretion and risk of renal stone formation. Using an in vitro pH-stat technique with the isolated intestinal epithelium, the replacement of serosal CO(2) with a HEPES buffered saline had no effect on HCO(3)(-) secretion, indicating that the endogenous supply of HCO(3)(-) from CO(2) hydration within epithelial cells is adequate for driving baseline secretion rates. Further, in vitro data demonstrated a stimulatory effect of low pH on intestinal HCO(3)(-) secretion. Thus, both luminal Ca(2+) and H(+) can regulate HCO(3)(-) secretion but the precise mechanisms and their potential interaction are currently unresolved.     

Nucleoside phosphorylation by phosphate minerals

In the presence of formamide, crystal phosphate minerals may act as phosphate donors to nucleosides, yielding both 5'- and, to a lesser extent, 3'-phosphorylated forms. With the mineral Libethenite the formation of 5'-AMP can be as high as 6% of the adenosine input and last for at least 10(3) h. At high concentrations, soluble non-mineral phosphate donors (KH(2)PO(4) or 5'-CMP) afford 2'- and 2':3'-cyclic AMP in addition to 5'-and 3'-AMP. The phosphate minerals analyzed were Herderite Ca[BePO(4)F], Hureaulite Mn(2+)(5)(PO(3)(OH)(2)(PO(4))(2)(H(2)O)(4), Libethenite Cu(2+)(2)(PO(4))(OH), Pyromorphite Pb(5)(PO(4))(3)Cl, Turquoise Cu(2+)Al(6)(PO(4))(4)(OH)(8)(H(2)O)(4), Fluorapatite Ca(5)(PO(4))(3)F, Hydroxylapatite Ca(5)(PO(4))(3)OH, Vivianite Fe(2+)(3)(PO(4))(2)(H(2)O)(8), Cornetite Cu(2+)(3)(PO(4))(OH)(3), Pseudomalachite Cu(2+)(5)(PO(4))(2)(OH)(4), Reichenbachite Cu(2+)(5)(PO(4))(2)(OH)(4), and Ludjibaite Cu(2+)(5)(PO(4))(2)(OH)(4)). Based on their behavior in the formamide-driven nucleoside phosphorylation reaction, these minerals can be characterized as: 1) inactive, 2) low level phosphorylating agents, or 3) active phosphorylating agents. Instances were detected (Libethenite and Hydroxylapatite) in which phosphorylation occurs on the mineral surface, followed by release of the phosphorylated compounds. Libethenite and Cornetite markedly protect the beta-glycosidic bond. Thus, activated nucleic monomers can form in a liquid non-aqueous environment in conditions compatible with the thermodynamics of polymerization, providing a solution to the standard-state Gibbs free energy change (DeltaG degrees ') problem, the major obstacle for polymerizations in the liquid phase in plausible prebiotic scenarios.     

Na(+)/Ca(2+) exchange regulates Ca(2+)-dependent duodenal mucosal ion transport and HCO(3)(-) secretion in mice

Stimulation of muscarinic receptors in duodenal mucosa raises intracellular Ca(2+), which regulates ion transport, including HCO(3)(-) secretion. However, the underlying Ca(2+) handling mechanisms are poorly understood. The aim of the present study was to determine whether Na(+)/Ca(2+) exchanger (NCX) plays a role in the regulation of duodenal mucosal ion transport and HCO(3)(-) secretion by controlling Ca(2+) homeostasis. Mouse duodenal mucosa was mounted in Ussing chambers. Net ion transport was assessed as short-circuit current (I(sc)), and HCO(3)(-) secretion was determined by pH-stat. Expression of NCX in duodenal mucosae was analyzed by Western blot, and cytosolic Ca(2+) in duodenocytes was measured by fura 2. Carbachol (100 muM) increased I(sc) in a biphasic manner: an initial transient peak within 2 min and a later sustained plateau starting at 10 min. Carbachol-induced HCO(3)(-) secretion peaked at 10 min. 2-Aminoethoxydiphenylborate (2-APB, 100 muM) or LiCl (30 mM) significantly reduced the initial peak in I(sc) by 51 or 47%, respectively, and abolished the plateau phase of I(sc) without affecting HCO(3)(-) secretion induced by carbachol. Ryanodine (100 muM), caffeine (10 mM), and nifedipine (10 muM) had no effect on either response to carbachol. In contrast, nickel (5 mM) and KB-R7943 (10-30 muM) significantly inhibited carbachol-induced increases in duodenal mucosal I(sc) and HCO(3)(-) secretion. Western blot analysis showed expression of NCX1 proteins in duodenal mucosae, and functional NCX in duodenocytes was demonstrated in Ca(2+) imaging experiments where Na(+) depletion elicited Ca(2+) entry via the reversed mode of NCX. These results indicate that NCX contributes to the regulation of Ca(2+)-dependent duodenal mucosal ion transport and HCO(3)(-) secretion that results from stimulation of muscarinic receptors.     

Environmental factors responsible for switching on the SO₄²⁻ excretory system in the kidney of seawater eels

Eels are unique in that they maintain lower plasma SO(4)(2-) concentration in SO(4)(2-)-rich (～30 mM) seawater (SW) than in SO(4)(2-)-poor (<0.3 mM) freshwater (FW), showing drastic changes in SO(4)(2-) regulation between FW and SW. We previously showed that the expression of renal SO(4)(2-) transporter genes, FW-specific Slc13a1 and SW-specific Slc26a6a, changes profoundly after transfer of FW eels to SW, which results in the decrease in plasma SO(4)(2-) concentration after 3 days in SW. In this study, we attempted to identify the environmental factor(s) that trigger the switching of SO(4)(2-) regulation using changes in plasma and urine SO(4)(2-) concentrations and expression of the transporter genes as markers. Transfer of FW eels to 30 mM SO(4)(2-) or transfer of SW eels to SO(4)(2-)-free SW did not change the SO(4)(2-) regulation. Major divalent cations in SW, Mg(2+) (50 mM) and Ca(2+) (10 mM), were also ineffective, but 50 mM NaCl was effective for switching the SO(4)(2-) regulation. Further analyses using choline-Cl and Na-gluconate showed that Cl(-) is a primary factor and Na(+) is permissive for the Cl(-) effect. Since plasma SO(4)(2-) and Cl(-) concentrations were inversely correlated, we injected various solutions into the blood and found that Cl(-) alone triggered the switching from FW to SW-type regulation. Furthermore, the inhibitor of Na-Cl cotransporter (NCC) added to media significantly impaired the expression of SW-specific Slc26a6a in 150 mM NaCl. In summary, it appears that Cl(-) ions in SW are taken up into the circulation via the NCC together with Na(+), and the resultant increase in plasma Cl(-) concentration enhances SO(4)(2-) excretion by the kidney through downregulation of absorptive Slc13a1 and upregulation of excretory Slc26a6a, resulting in low plasma SO(4)(2-) concentration in SW.     

Analysis and molecular modeling of the formation, structure, and activity of the phosphatidylserine-calcium-phosphate complex associated with biomineralization

The nucleational core of matrix vesicles contains a complex (CPLX) of phosphatidylserine (PS), Ca(2+), and inorganic phosphate (P(i)) that is important to both normal and pathological calcification. Factors required for PS-CPLX formation and nucleational activity were studied using in vitro model systems and molecular dynamic simulations. Ca(2+) levels required for and rates of PS-CPLX formation were monitored by light scattering at 340 nm, assessing changes in amount and particle size. Fourier transform infrared spectroscopy was used to explore changes in chemical structure and composition. Washing with pH 5 buffer was used to examine the role of amorphous calcium phosphate in CPLX nucleational activity, which was assessed by incubation in synthetic cartilage lymph with varied pH values. Addition of 4 Ca(2+)/PS was minimally required to form viable complexes. During the critical first 10-min reaction period, rapid reduction in particle size signaled changes in PS-CPLX structure. Fourier transform infrared spectroscopy revealed increasing mineral phosphate that became progressively deprotonated to PO(4)(3-). This Ca(2+)-mediated effect was mimicked in part by increasing the Ca(2+)/PS reaction ratio. Molecular dynamic simulations provided key insight into initial interactions between Ca(2+) and P(i) and the carboxyl, amino, and phosphodiester groups of PS. Deduced interatomic distances agreed closely with previous radial distribution function x-ray-absorption fine structure measurements, except for an elongated Ca(2+)-N distance, suggesting additional changes in atomic structure during the critical 10-min ripening period. These findings clarify the process of PS-CPLX formation, reveal details of its structure, and provide insight into its role as a nucleator of crystalline calcium phosphate mineral formation.     

HCO(3)(-) ions modify the role of PKC isoforms in the modulation of rat mast cell functions

PKC and the intracellular calcium signal are two well-known intracellular signaling pathways implicated in the induction of mast cell exocytosis. Both signals are modified by the presence or absence of HCO(3)(-) ions in the external medium. In this work, we studied the regulation of the exocytotic process by PKC isozymes and its relationship with HCO(3)(-) ions and PKC modulation of the calcium entry. The calcium entry, induced by thapsigargin and further addition of calcium, was inhibited by PMA, a PKC activator, and enhanced by 500 nM GF109203X, which inhibits Ca(2+)-independent PKC isoforms. PMA inhibition of the Ca(2+) entry was reverted by 500 and 50 nM GF109203X, which inhibit Ca(2+)-independent and Ca(2+)-dependent isoforms, respectively, and G?6976, a specific inhibitor of Ca(2+)-dependent PKCs. Thus, activation of Ca(2+)-dependent and Ca(2+)-independent PKC isoforms inhibit Ca(2+) entry in rat mast cells, either in a HCO(3)(-)-buffered or a HCO(3)(-)-free medium. PMA, GF109203X, G?6976 and rottlerin, a specific inhibitor of PKC delta, were also used to study the role of PKC isoforms in the regulation of exocytosis induced by thapsigargin, ionophore A23187 and PMA. The results demonstrate that Ca(2+)-dependent PKC isoforms inhibit exocytosis in a HCO(3)(-)-dependent way. Moreover, Ca(2+)-independent PKC delta was the main isoform implicated in promotion of Ca(2+)-dependent mast cell exocytosis in the presence or absence of HCO(3)(-). The role of PKC isoforms in the regulation of mast cell exocytosis depends on the stimulus and on the presence or absence of HCO(3)(-) ions in the medium, but it is independent of PKC modulation of the Ca(2+) entry.     

Extracellular calcium chronically induced human osteoblasts effects: specific modulation of osteocalcin and collagen type XV

Fluctuation in extracellular calcium (Ca(2+)) concentration occurs during bone remodeling. Free ionized Ca(2+) plays a critical role in regulating osteoblast functions. We analyzed the effects of different concentrations of free ionized Ca(2+) (0.5, 1.3, and 2.6 mM) on human osteoblasts and we evaluated osteoblastic phenotype (marker expression and cell morphology) and functions (osteogenic differentiation, cell proliferation, and cell signaling). Our data show human osteoblasts that chronically stimulated with 0.5, 1.3, or 2.6 mM Ca(2+) significantly increase intracellular content of alkaline phosphatase, collagen type I, osteocalcin, and bone sialoprotein, whereas collagen type XV was down-modulated and RUNX2 expression was not affected. We also found a Ca(2+) concentration-dependent increase in osteogenic differentiation and cell proliferation, associated to an increase of signaling protein PLCβ1 and p-ERK. Human osteoblast morphology was affected by Ca(2+) as seen by the presence of numerous nucleoli, cells in mitosis, cell junctions, and an increased number of vacuoles. In conclusion, our data show a clear phenotypical and functional effect of extracellular Ca(2+) on human osteoblasts and support the hypothesis of a direct role of this cation in the bone remodeling processes.     

In silico analysis of expression data for identification of genes involved in spatial accumulation of calcium in developing seeds of rice

The calcium (Ca(2+)) transporters, like Ca(2+) channels, Ca(2+) ATPases, and Ca(2+) exchangers, are instrumental for signaling and transport. However, the mechanism by which they orchestrate the accumulation of Ca(2+) in grain filling has not yet been investigated. Hence the present study was designed to identify the potential calcium transporter genes that may be responsible for the spatial accumulation of calcium during grain filling. In silico expression analyses were performed to identify Ca(2+) transporters that predominantly express during the different developmental stages of Oryza sativa. A total of 13 unique calcium transporters (7 from massively parallel signature sequencing [MPSS] data analysis, and 9 from microarray analysis) were identified. Analysis of variance (ANOVA) revealed differential expression of the transporters across tissues, and principal component analysis (PCA) exhibited their seed-specific distinctive expression profile. Interestingly, Ca(2+) exchanger genes are highly expressed in the initial stages, whereas some Ca(2+) ATPase genes are highly expressed throughout seed development. Furthermore, analysis of the cis-elements located in the promoter region of the subset of 13 genes suggested that D of proteins play essential roles in regulating the expression of Ca(2+) transporter genes during rice seed development. Based on these results, we developed a hypothetical model explaining the transport and tissue specific distribution of calcium in developing cereal seeds. The model may be extrapolated to understand the mechanism behind the exceptionally high level of calcium accumulation seen in grains like finger millet.     

A scanning electron microscopic and x-ray microanalytic study of cell surface material during amphibian neurulation.

Treatment with lanthanum (La3+) after fixation in phosphate (PO4-3)-buffered glutaraldehyde results in the deposition of a cell surface material (CSM) primarily on the developing urodele amphibian neural axis. X-ray probe microanalysis indicates that calcium (CA2+) levels are considerably higher in the neural fold region. La3+ displaces Ca2+ from negatively-charged moieties on biological membranes. Once bound, La3+ likely interacts with residual phosphate(s) resulting in deposition of CSM. Elemental X-ray microanalysis shows CSM contains mostly lanthanum and phosphorus. The high level of regional La3+ binding is correlated with inherently greater Ca2+ levels in the developing neural axis.     

慢性乙型肝炎患者肝组织和外周血白细胞中钠离子依赖性维生素C转运体的表达

用免疫组化和Western blot技术检测SVCT1和SVCT2蛋白在慢性乙型肝炎患者及正常人外周血白细胞中的表达.免疫组化结果显示：在慢性乙型肝炎患者肝组织中SVCT1和SVCT2蛋白的阳性表达率和阳性表达强度显著低于正常肝组织（P〈0.01）;Western-blot检测显示,慢性乙型肝炎患者外周血白细胞中SVCT1表达缺失,SVCT2蛋白表达强度为0.481&#177;0.056,均显著低于正常人（分别为0.325&#177;0.085和0.971&#177;0.140）（P〈0.01）.提示慢性乙型肝炎患者体内肝细胞和外周血白细胞存在SVCT1和SVCT2蛋白表达低下或缺失;SVCT1和SVCT2蛋白表达低下或缺失可能是乙型肝炎病毒易感性的主要原因之一.     

Osteopontin inhibition of miR-129-3p enhances IL-17 expression and monocyte migration in rheumatoid arthritis

BackgroundOsteopontin (OPN) is an important proinflammatory cytokine in rheumatoid arthritis (RA). Levels of OPN have been shown to be significantly correlated with interleukin-17 (IL-17) production and expression of Th17 cells in the synovial fluid of RA patients. Here, we investigated the role of OPN in monocyte migration, IL-17 production and osteoblasts.MethodsOPN and IL-17 expression profiles in osteoarthritis (OA) and RA synovial fluid were determined by enzyme-linked immunosorbent assay (ELISA). The expression of the microRNA, miR-129-3p, in osteoblasts was analyzed by real-time quantitative polymerase chain reaction (qPCR). Immunoreactive proteins were spotted by Western blotting. We used the collagen-induced arthritis (CIA) mouse model to investigate the role of OPN in monocyte migration during RA.ResultsOPN and IL-17 expression were higher in RA synovial fluid as compared to OA samples. We also found that OPN promotes IL-17 expression in osteoblasts and thereby enhances monocyte migration via the Syk/PI3K/Akt signaling pathway. miR-129-3p expression was found to be negatively regulated by OPN via the Syk/PI3K/Akt signal cascade. In contrast, lentiviral vectors expressing short hairpin RNA inhibited OPN expression and ameliorated articular swelling, cartilage erosion and monocyte infiltration in the ankle joints of CIA mice.ConclusionTo our knowledge, our study is the first to describe how OPN promotes monocyte migration by upregulating IL-17 expression in osteoblasts in RA disease.SignificanceThese findings indicate that OPN could serve as a potential therapeutic target for the treatment of RA.     

Modeling and optimization of photosynthetic hydrogen gas production by green alga Chlamydomonas reinhardtii in sulfur-deprived circumstance

Biological hydrogen production by the green alga Chlamydomonas reinhardtii under sulfur-deprived conditions has attracted great interest due to the fundamental and practical importance of the process. The photosynthetic hydrogen production rate is dependent on various factors such as strain type, nutrient composition, temperature, pH, and light intensity. In this study, physicochemical factors affecting biological hydrogen production by C. reinhardtii were evaluated with response surface methodology (RSM). First, the maximum specific growth rate of the alga associated with simultaneous changes of ammonium, phosphate, and sulfate concentrations in the culture medium were investigated. The optimum conditions were determined as NH(4+) 8.00 mM, PO(4)(3-) 1.11 mM, and SO(4)(2-) 0.79 mM in Tris-acetate-phosphate (TAP) medium. The maximum specific growth rate with the optimum nutrient concentrations was 0.0373 h(-1). Then, the hydrogen production rate of C. reinhardtii under sulfur-deprivation conditions was investigated by simultaneously changing two nutrient concentrations and pH in the medium. The maximum hydrogen production was 2.152 mL of H(2) for a 10-mL culture of alga with density of 6 x 10(6) cells mL(-1) for 96 h under conditions of NH(4)(+) 9.20 mM, PO(4)(3-) 2.09 mM, and pH 7.00. The obtained hydrogen production rate was approximately 1.55 times higher than that with the typical TAP medium under sulfur deficiency.