Glycerol 3-Phosphate Dehydrogenase: Role of the Protein Conformational Change in Activation of a Readily Reversible Enzyme-Catalyzed Hydride Transfer Reaction

Kinetic parameters are reported for glycerol 3-phosphate dehydrogenase (GPDH)-catalyzed hydride transfer from the whole substrate glycerol 3-phosphate (G3P) or truncated substrate ethylene glycol (EtG) to NAD, and for activation of the hydride transfer reaction of EtG by phosphite dianion. These kinetic parameters were combined with parameters for enzyme-catalyzed hydride transfer in the microscopic reverse direction to give the reaction equilibrium constants Keq. Hydride transfer from G3P is favored in comparison to EtG because the carbonyl product of the former reaction is stabilized by hyperconjugative electron donation from the -CH2R keto substituent. The kinetic data show that the phosphite dianion provides the same 7.6 ± 0.1 kcal/mol stabilization of the transition states for enzyme-catalyzed reactions in the forward [reduction of NAD by EtG] and reverse [oxidation of NADH by glycolaldehyde] directions. The experimental evidence that supports a role for phosphite dianion in stabilizing the active closed form of the GPDH (EC) relative to the ca. 6 kcal/mol more unstable open form (EO) is summarized.

Identifying Residues for Substrate Recognition in Human GPAT4 by Molecular Dynamics Simulations

Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first step in triacylglycerol synthesis. Understanding its substrate recognition mechanism may help to design drugs to regulate the production of glycerol lipids in cells. In this work, we investigate how the native substrate, glycerol-3-phosphate (G3P), and palmitoyl-coenzyme A (CoA) bind to the human GPAT isoform GPAT4 via molecular dynamics simulations (MD). As no experimentally resolved GPAT4 structure is available, the AlphaFold model is employed to construct the GPAT4-substrate complex model. Using another isoform, GPAT1, we demonstrate that once the ligand binding is properly addressed, the AlphaFold complex model can deliver similar results to the experimentally resolved structure in MD simulations. Following the validated protocol of complex construction, we perform MD simulations using the GPAT4-substrate complex. Our simulations reveal that R427 is an important residue in recognizing G3P via a stable salt bridge, but its motion can bring the ligand to different binding hotspots on GPAT4. Such high flexibility can be attributed to the flexible region that exists only on GPAT4 and not on GPAT1. Our study reveals the substrate recognition mechanism of GPAT4 and hence paves the way towards designing GPAT4 inhibitors.

Effect of nanometric β-calcium glycerophosphate supplementation in conventional toothpaste on enamel demineralization: An in vitro study

The aim of this study was to evaluate the effects of supplementing toothpastes containing 1100 ppm F with micrometric or nanometric [beta]-calcium glycerophosphate (β-CaGPm/β-CaGPn) on artificial enamel demineralization, using a pH cycling model. Bovine enamel blocks (4 mm × 4 mm, n = 120) selected using initial surface hardness were randomly allocated to ten toothpaste groups (n = 12): without fluoride or β-CaGPm or β-CaGPn (Negative control), 1100 ppm F (1100 F), and 1100 ppm F plus 0.125%, 0.25%, 0.5%, and 1.0% of β-CaGPm or β-CaGPn. Blocks were treated two times per day with toothpaste slurry and subjected to five pH cycles (demineralizing and remineralizing solutions) at 37 °C. The final surface hardness, percentage of surface hardness loss (%SH), cross-sectional hardness (ΔKHN), and profile analysis and lesion depth subsurface were analysed using polarized light microscopy (PLM). Fluoride (F), calcium (Ca), and phosphorus (P) concentrations were also measured. Data were analysed using ANOVA and Student-Newman-Keuls tests ([alpha] = 0.001). Blocks treated with 1100 F toothpaste containing 0.5%β-CaGPm or 0.25%β-CaGPn showed with reduced %SH values when compared with those treated with 1100 F alone (p < 0.001). Reduced lesion depths (ΔKHN and PLM) were observed for the slurry made up of 1100 F and 0.25%β-CaGPn (p < 0.001). The addition of β-CaGPm and β-CaGPn did not influence the enamel F concentration, with the 1100 F/0.25%β-CaGPn group exhibiting the highest Ca and P enamel concentrations (p < 0.001). Based on the findings of this in vitro study, we can conclude that the fluoride toothpaste produced a superior effect when combined at an appropriate β-CaGP molar ratio. This effect was achieved with a lower proportion of β-CaGP in the form of nanometric particles.

HDAC2 counteracts vascular calcification by activating autophagy in chronic kidney disease

Vascular calcification is a major risk factor for cardiovascular disease mortality, with a significant prevalence in chronic kidney disease (CKD). Pharmacological inhibition of histone acetyltransferase has been proven to protect against from vascular calcification. However, the role of Histone Deacetylase 2 (HDAC2) and molecular mechanisms in vascular calcification of CKD remains unknown. An in vivo model of CKD was established using mouse fed with a high adenine and phosphate diet, and an in vitro model was produced using human aortic vascular smooth muscle cells (VSMCs) stimulated with β-glycerophosphate (β-GP). HDAC2 expression was found to be reduced in medial artery of CKD mice and β-GP-induced VSMCs. Overexpression of HDAC2 attenuated OPN and OCN upregulation, α-SMA and SM22α downregulation, and calcium deposition in aortas of CKD. The in vitro results also demonstrated that β-GP-induced osteogenic differentiation was inhibited by HDAC2. Furthermore, we found that HDAC2 overexpression caused an increase in LC3II/I, a decrease in p62, and an induction of autophagic flux. Inhibition of autophagy using its specific inhibitor 3-MA blocked HDAC2's protective effect on osteogenic differentiation in β-GP-treated VSMCs. Taken together, these results suggest that HDAC2 may protect against vascular calcification by the activation of autophagy, laying out a novel insight for the molecular mechanism in vascular calcification of CKD.

Topical ocular administration using thermosensitive chitosan-glycerophosphate-PRP hydrogels for improved ocular bioavailability

PURPOSE

One of the difficulties in the pharmacy field is the delivery of drugs for the eyes. Topical therapy is one of the most common methods for treating eye diseases. Due to their unique properties, including biocompatibility and suitable degradation, hydrogels are appropriate for biological purposes. Platelet-rich plasma (PRP), as a designated concentration of platelets, is in a smaller volume than the plasma and is considered a rich source of growth factor that has been used in recent years, including applications in eye diseases including corneal wound healing, improvement of dry eye and post-LASIK syndrome.

METHODS

The present study was performed to fabricate Chitosan (CS) and glycerophosphate (GP) based hydrogels that are temperature-sensitive for PRP and investigate their effect on ocular stem cells.

RESULTS

CS-GP-based temperature-sensitive hydrogels containing PRP were successfully fabricated using CS and GP. This hydrogel is liquid at ambient temperature and a gel at ocular temperature. Rheology, FTIR, and SEM tests assessed the properties of the hydrogels. The results of the MTT test showed that the hydrogel made with the optimal formulation was not toxic to LSC cell lines.

CONCLUSIONS

Given this, CS-GP-based hydrogels can be applied as a biocompatible formulation in ocular medication administration with increased bioavailability at the ocular surface and topical delivery of PRP.

A homoeostatic switch causing glycerol-3-phosphate and phosphoethanolamine accumulation triggers senescence by rewiring lipid metabolism

Cellular senescence affects many physiological and pathological processes and is characterized by durable cell cycle arrest, an inflammatory secretory phenotype and metabolic reprogramming. Here, by using dynamic transcriptome and metabolome profiling in human fibroblasts with different subtypes of senescence, we show that a homoeostatic switch that results in glycerol-3-phosphate (G3P) and phosphoethanolamine (pEtN) accumulation links lipid metabolism to the senescence gene expression programme. Mechanistically, p53-dependent glycerol kinase activation and post-translational inactivation of phosphate cytidylyltransferase 2, ethanolamine regulate this metabolic switch, which promotes triglyceride accumulation in lipid droplets and induces the senescence gene expression programme. Conversely, G3P phosphatase and ethanolamine-phosphate phospho-lyase-based scavenging of G3P and pEtN acts in a senomorphic way by reducing G3P and pEtN accumulation. Collectively, our study ties G3P and pEtN accumulation to controlling lipid droplet biogenesis and phospholipid flux in senescent cells, providing a potential therapeutic avenue for targeting senescence and related pathophysiology.

Immp2l Enhances the Structure and Function of Mitochondrial Gpd2 Dehydrogenase

'Inner mitochondrial membrane peptidase 2 like' (IMMP2L) is a nuclear-encoded mitochondrial peptidase that has been conserved through evolutionary history, as has its target enzyme, 'mitochondrial glycerol phosphate dehydrogenase 2' (GPD2). IMMP2L is known to cleave the mitochondrial transit peptide from GPD2 and another nuclear-encoded mitochondrial respiratory-related protein, cytochrome C1 (CYC1). However, it is not known whether IMMP2L peptidase activates or alters the activity or respiratory-related functions of GPD2 or CYC1. Previous investigations found compelling evidence of behavioural change in the Immp2lKD-/- KO mouse, and in this study, EchoMRI analysis found that the organs of the Immp2lKD-/- KO mouse were smaller and that the KO mouse had significantly less lean mass and overall body weight compared with wildtype littermates (p < 0.05). Moreover, all organs analysed from the Immp2lKD-/- KO had lower relative levels of mitochondrial reactive oxygen species (mitoROS). The kidneys of the Immp2lKD-/- KO mouse displayed the greatest decrease in mitoROS levels that were over 50% less compared with wildtype litter mates. Mitochondrial respiration was also lowest in the kidney of the Immp2lKD-/- KO mouse compared with other tissues when using succinate as the respiratory substrate, whereas respiration was similar to the wildtype when glutamate was used as the substrate. When glycerol-3-phosphate (G3P) was used as the substrate for Gpd2, we observed ~20% and ~7% respective decreases in respiration in female and male Immp2lKD-/- KO mice over time. Together, these findings indicate that the respiratory-related functions of mGpd2 and Cyc1 have been compromised to different degrees in different tissues and genders of the Immp2lKD-/- KO mouse. Structural analyses using AlphaFold2-Multimer further predicted that the interaction between Cyc1 and mitochondrial-encoded cytochrome b (Cyb) in Complex III had been altered, as had the homodimeric structure of the mGpd2 enzyme within the inner mitochondrial membrane of the Immp2lKD-/- KO mouse. mGpd2 functions as an integral component of the glycerol phosphate shuttle (GPS), which positively regulates both mitochondrial respiration and glycolysis. Interestingly, we found that nonmitochondrial respiration (NMR) was also dramatically lowered in the Immp2lKD-/- KO mouse. Primary mouse embryonic fibroblast (MEF) cell lines derived from the Immp2lKD-/- KO mouse displayed a ~27% decrease in total respiration, comprising a ~50% decrease in NMR and a ~12% decrease in total mitochondrial respiration, where the latter was consistent with the cumulative decreases in substrate-specific mediated mitochondrial respiration reported here. This study is the first to report the role of Immp2l in enhancing Gpd2 structure and function, mitochondrial respiration, nonmitochondrial respiration, organ size and homeostasis.

PRMT3 methylates HIF-1α to enhance the vascular calcification induced by chronic kidney disease

BACKGROUND

Medial vascular calcification is commonly identified in chronic kidney disease (CKD) patients and seriously affects the health and life quality of patients. This study aimed to investigate the effects of protein arginine methyltransferase 3 (PRMT3) on vascular calcification induced by CKD.

METHODS

A mice model of CKD was established with a two-step diet containing high levels of calcium and phosphorus. Vascular smooth muscle cells (VSMCs) were subjected to β-glycerophosphate (β-GP) treatment to induce the osteogenic differentiation as an in vitro CKD model.

RESULTS

PRMT3 was upregulated in VSMCs of medial artery of CKD mice and β-GP-induced VSMCs. The inhibitor of PRMT3 (SGC707) alleviated the vascular calcification and inhibited the glycolysis of CKD mice. Knockdown of PRMT3 alleviated the β-GP-induced osteogenic transfomation of VSMCs by the repression of glycolysis. Next, PRMT3 interacted with hypoxia-induced factor 1α (HIF-1α), and the knockdown of PRMT3 downregulated the protein expression of HIF-1α by weakening its methylation. Gain of HIF-1α reversed the PRMT3 depletion-induced suppression of osteogenic differentiation and glycolysis of VSMCs.

CONCLUSION

The inhibitory role of PRMT3 depletion was at least mediated by the regulation of glycolysis upon repressing the methylation of HIF-1α.

Development, Establishment, and Validation of a Model for the Mineralization of Periodontium Remodelling Cells: Cementoblasts

Chronic kidney disease (CKD) patients undergoing dialysis are at high risk of bone fractures. CKD-induced mineral and bone disorder is extended to periodontal disease due to changes in the ionic composition of saliva in CKD patients, dysregulating mineralization, hindering regeneration and thereby promoting the progression of dental complications. Despite the importance of cementum for overall oral health, the mechanisms that regulate its development and regeneration are not well comprehended, and a lack of sufficient in vitro experimental models has hindered research progress. In this study, the impact of experimental conditions on the calcification of cementoblasts was systematically investigated, aimed at establishing a standardized and validated model for the calcification of cementoblasts. The effects of phosphate, calcium, ascorbic acid, β-glycerolphosphate, dexamethasone, and fetal calf serum on the calcification process of cementoblasts were analyzed over a wide range of concentrations and time points by investigating calcium content, cell viability, gene expression and kinase activity. Cementoblasts calcified in a concentration- and time-dependent manner with higher concentrations of supplements cause a higher degree of calcification but decreased cell viability. Phosphate and calcium have a significantly stronger effect on cementoblast calcification processes compared to osteogenic supplements: ascorbic acid, β-glycerolphosphate, and dexamethasone induce calcification over a wide range of osteogenic signalling pathways, with osteopontin being a central target of gene regulation. Conversely, treatment with ascorbic acid, β-glycerolphosphate, and dexamethasone leads to activating only selected pathways, especially promoting bone sialoprotein expression. The developed and validated cementoblast calcification protocol, incubating up to 60% confluent cementoblasts with 1.9 mmol L-1 of phosphate supplementation for a reasonable, multi-pathway calcification induction and 10 mmol L-1 β-glycerolphosphate, 75 µmol L-1 ascorbic acid and 10 nmol L-1 dexamethasone for a reasonable osteogenic differentiation-based calcification induction, provides standard in vitro experimental models for better understanding cementoblast function and regeneration.

Comparison of Growth Performance and Plasma Metabolomics between Two Sire-Breeds of Pigs in China

The Yorkshire pigs, renowned for their remarkable growth rate, low feed conversion ratio (FCR), and high meat production, emerge as a novel preference for paternal breeding. In this study, we found that purebred paternal Yorkshire pigs (PY) surpass the purebred Duroc breed in terms of growth rate. Specifically, purebred PY attain a weight of 100 kg at an earlier age compared to purebred Duroc (Male, 145.07 vs. 162.91; Female, 145.91 vs. 167.57; p-value < 0.01). Furthermore, different hybrid combinations suggest that offspring involving purebred PY exhibit superior growth performance. Compared with purebred Duroc, the offspring of purebred PY have an earlier age in days (173.23 vs. 183.54; p-value < 0.05) at the same slaughter weight. The changes of plasma metabolites of 60-day-old purebred boars in the two sire-breeds showed that 1335 metabolites in plasma were detected. Compared with Duroc, 28 metabolites were down-regulated and 49 metabolites were up-regulated in PY. Principal component analysis (PCA) discerned notable dissimilarities in plasma metabolites between the two sire-breeds of pigs. The levels of glycerol 3-phosphate choline, cytidine, guanine, and arachidonic acid increased significantly (p-value < 0.05), exerting an impact on their growth and development. According to our results, PY could be a new paternal option as a terminal sire in three-way cross system.

The remediation of uranium-contaminated groundwater via bioreduction coupled to biomineralization with different pH and electron donors

Stimulating indigenous microbes to reduce aqueous U(VI) to insoluble U(IV) by adding an electron donor has been applied as an applicable strategy to remediate uranium-contaminated groundwater in situ. However, biogenic U(IV) minerals are susceptible to oxidative remobilization after exposure to oxygen. To enhance the stability of the end product, glycerol phosphate (GP) was selected to treat artificial uranium-containing groundwater at different pH values (i.e., 7.0 and 5.0) with glycerol (GY) as the control group. The results revealed that removal ratios of uranium with GP were all higher than those with GY, and reduced crystalline U(IV)-phosphate and U(VI)-phosphate minerals (recalcitrant to oxidative remobilization) were generated in the GP groups. Although bioreduction efficiency was influenced at pH 5.0, the stability of the end product with GP was elevated significantly compared with that with GY. Mechanism analysis demonstrated that GP could activate bioreduction and biomineralization of the microbial community, and two stages were included in the GP groups. In the early stage, bioreduction and biomineralization were both involved in the immobilization process. Subsequently, part of the U(VI) precipitate was gradually reduced to U(IV) precipitate by microorganisms. This work implied that the formation of U-phosphate minerals via bioreduction coupled with biomineralization potentially offers a more effective strategy for remediating uranium-contaminated groundwater with long-term stability.

CrrAB regulates PagP-mediated glycerophosphoglycerol palmitoylation in the outer membrane of Klebsiella pneumoniae

The outer membrane (OM) of Gram-negative bacteria is an evolving antibiotic barrier composed of a glycerophospholipid (GP) inner leaflet and a lipopolysaccharide (LPS) outer leaflet. The two-component regulatory system CrrAB has only recently been reported to confer high-level polymyxin resistance and virulence in Klebsiella pneumoniae. Mutations in crrB have been shown to lead to the modification of the lipid A moiety of LPS through CrrAB activation. However, functions of CrrAB activation in the regulation of other lipids are unclear. Work here demonstrates CrrAB activation not only stimulates LPS modification, but also regulates synthesis of acyl-glycerophosphoglycerols (acyl-PGs), a lipid species with undefined functions and biosynthesis. Among all possible modulators of acyl-PG identified from proteomic data, we found expression of lipid A palmitoyltransferase (PagP) was significantly up-regulated in the crrB mutant. Furthermore, comparative lipidomics showed that most of the increasing acyl-PG activated by CrrAB was decreased after pagP knockout with CRISPR-Cas9. These results suggest that PagP also transfers a palmitate chain from GPs to PGs, generating acyl-PGs. Further investigation revealed that PagP mainly regulates the GP contents within the OM, leading to an increased ratio of acyl-PG to PG species, and improving OM hydrophobicity, which may contribute to resistance against certain cationic antimicrobial peptides (CAMP) resistance upon LPS modification. Taken together, this work suggests that CrrAB regulates the outer membrane GP contents of K. pneumoniae through upregulation of PagP, which functions along with LPS to form an outer membrane barrier critical for bacterial survival.

Fermentative Indole Production via Bacterial Tryptophan Synthase Alpha Subunit and Plant Indole-3-Glycerol Phosphate Lyase Enzymes

Indole is produced in nature by diverse organisms and exhibits a characteristic odor described as animal, fecal, and floral. In addition, it contributes to the flavor in foods, and it is applied in the fragrance and flavor industry. In nature, indole is synthesized either from tryptophan by bacterial tryptophanases (TNAs) or from indole-3-glycerol phosphate (IGP) by plant indole-3-glycerol phosphate lyases (IGLs). While it is widely accepted that the tryptophan synthase α-subunit (TSA) has intrinsically low IGL activity in the absence of the tryptophan synthase β-subunit, in this study, we show that Corynebacterium glutamicum TSA functions as a bona fide IGL and can support fermentative indole production in strains providing IGP. By bioprospecting additional bacterial TSAs and plant IGLs that function as bona fide IGLs were identified. Capturing indole in an overlay enabled indole production to titers of about 0.7 g L^-1 in fermentations using C. glutamicum strains expressing either the endogenous TSA gene or the IGL gene from wheat.

Cytotoxicity of Methotrexate Conjugated to Glycerol Phosphate Modified Superparamagnetic Iron Oxide Nanoparticles

A systematic study was carried out to evaluate the uptake and cytotoxicity of methotrexate (MTX) conjugated to superparamagnetic iron oxide nanoparticles (SPIONs) modified with glycerol phosphate (Glyc) and phosphorylethanolamine (PEA), using MCF-7 cancer cell line as model. The ligand shell composition was controlled in such a way to get SPIONs with nine different surface functionalization and up to three co-conjugated ligands but the very iron oxide core, in order to test and compare uptake and cytotoxicity, and verify possible additive effects. Folic acid (FA), the non-toxic analogue of MTX, was also explored as ligand for SPIONs. Glyc was shown to enhance dramatically the cellular uptake despite the high negative zeta potentials, whereas PEA, FA and MTX was found to have a much lower effect on the cellular uptake. Also, a significant ten times lowering of IC₅₀ was observed for the co-conjugated MTX in the SPION-Glyc/PEA/MTX as compared to the free drug, whereas the analogue SPION-Glyc/PEA/FA nanoparticles exhibited no significant cytotoxicity. In short, the conjugation of MTX to SPIONs enhanced dramatically its cytotoxicity and decreased the IC₅₀ value against MCF-7 tumor cells as compared to the free drug, probably due to the enhanced uptake of SPIONs as a result of their surface modification with Glyc/PEA, demonstrating that SPION-Glyc/PEA is a good nanocarrier for co-conjugated methotrexate.

[Experimental study on ectopic osteogenesis induced by bone morphogenetic protein 2-derived peptide P24 loaded chitosan-4-thio-butylamidine hydrogel]

OBJECTIVE

To study the ectopic osteogenesis and biocompatibility of bone morphogenetic protein 2 (BMP-2)-derived peptide P24 loaded chitosan-4-thio-butylamidine (CS-TBA) hydrogel.

METHODS

First, the CS-TBA/hydroxyapatite (HA) solution was prepared by using chitosan, 2-iminothiolane hydrochloride, and HA. Then, the different amount of P24 peptides were added to the CS-TBA/HA to prepare the CS-TBA/5%P24/HA and CS-TBA/10%P24/HA solutions. Finally, β-glycerophosphate disodium (β-GP) was added to the CS-TBA/HA, CS-TBA/5%P24/HA, and CS-TBA/10%P24/HA to prepare the CS-TBA/HA/β-GP, CS-TBA/5%P24/HA/β-GP, and CS-TBA/10%P24/HA/β-GP hydrogels, respectively. Eighteen Sprague Dawley female rats were randomly divided into 3 groups ( n=6), which were injected into the back muscle pouches with equal volume CS-TBA/HA/β-GP hydrogel (group A), CS-TBA/5%P24/HA/β-GP hydrogel (group B), and CS-TBA/10%P24/HA/β-GP hydrogel (group C). The animals were sacrificed at 4 and 8 weeks and conducted micro-CT. The ability of biodegradation and osteogenesis of hydrogl was detected by trabecular thickness (Tb.Th), trabecular number (Tb.N), bone mineral density (BMD), and histological staining (HE and Masson).

RESULTS

All the rats in 3 groups survived to the time point of the harvest. Micro-CT results showed that the new bones gradually increased in each group after operation. At the same time, the new bone formation was more obvious in groups B and C than in group A, and with the increase of P24 concentration, new bone formation in group C was much more than that in group B. The Tb.Th, Tb.N, and BMD increased gradually in 3 groups, and the differences between 4 and 8 weeks were significant ( P<0.05) except the Tb.Th in group A. At different time points, the Tb.Th, Tb.N, and BMD were significantly higher in groups B and C than in group A ( P<0.05), and in group C was higher than in group B ( P<0.05), showing significant differences between groups. Histological staining showed that the materials of groups B and C were biodegradable, and the osteogenic effect was increased with the increase of P24 concentration.

CONCLUSION

P24 peptide can improve the ectopic osteogenesis of CS-TBA hydrogel, and the 10% concentration is more effective.

Loss of Tmem106b is unable to ameliorate frontotemporal dementia-like phenotypes in an AAV mouse model of C9ORF72-repeat induced toxicity

Loss-of-function mutations in progranulin (GRN) and a non-coding (GGGGCC)n hexanucleotide repeat expansions in C9ORF72 are the two most common genetic causes of frontotemporal lobar degeneration with aggregates of TAR DNA binding protein 43 (FTLD-TDP). TMEM106B encodes a type II transmembrane protein with unknown function. Genetic variants in TMEM106B associated with reduced TMEM106B levels have been identified as disease modifiers in individuals with GRN mutations and C9ORF72 expansions. Recently, loss of Tmem106b has been reported to protect the FTLD-like phenotypes in Grn-/- mice. Here, we generated Tmem106b-/- mice and examined whether loss of Tmem106b could rescue FTLD-like phenotypes in an AAV mouse model of C9ORF72-repeat induced toxicity. Our results showed that neither partial nor complete loss of Tmem106b was able to rescue behavioral deficits induced by the expression of (GGGGCC)66 repeats (66R). Loss of Tmem106b also failed to ameliorate 66R-induced RNA foci, dipeptide repeat protein formation and pTDP-43 pathological burden. We further found that complete loss of Tmem106b increased astrogliosis, even in the absence of 66R, and failed to rescue 66R-induced neuronal cell loss, whereas partial loss of Tmem106b significantly rescued the neuronal cell loss but not neuroinflammation induced by 66R. Finally, we showed that overexpression of 66R did not alter expression of Tmem106b and other lysosomal genes in vivo, and subsequent analyses in vitro found that transiently knocking down C9ORF72, but not overexpression of 66R, significantly increased TMEM106B and other lysosomal proteins. In summary, reducing Tmem106b levels failed to rescue FTLD-like phenotypes in a mouse model mimicking the toxic gain-of-functions associated with overexpression of 66R. Combined with the observation that loss of C9ORF72 and not 66R overexpression was associated with increased levels of TMEM106B, this work suggests that the protective TMEM106B haplotype may exert its effect in expansion carriers by counteracting lysosomal dysfunction resulting from a loss of C9ORF72.

The disorder metabolic profiling in kidney and spleen of mice induced by mycotoxins deoxynivalenol through gas chromatography mass spectrometry

Gas chromatography mass spectrometry (GC-MS) based metabolomics strategy was implemented for the metabolites detection in kidney and spleen samples of mice, which were treated with 2 mg kg^-1 deoxynivalenol (DON), through intragastric administration for three weeks, for studying the toxicity of DON on the metabolic profiling in kidney and spleen. The spectrum was deconvoluted, aligned and identified with MS DIAL, equipped with Fiehn library. And the data matrix was processed with univariate analysis and multivariate analysis for selection of metabolites with VIP >1, t-test p value < 0.05. The metabolic pathway analysis was analyzed with MetaMapp and drew by CytoScape. Result shows that DON could induce an increased protein synthesis to repair the damaged membrane protein structure, in both kidney and spleen, with decrease of valine, leucine and phenylalanine, et al. essential precursors for protein synthesis and energy production; the energy metabolism in kidney disordered by DON, with the decreasing of ribitol, glycerol 1-phosphate, et al. Furthermore, DON could lead to the disorder in immunity function and nucleotide metabolism in spleen, with decreasing trend of cytidine and alanine.

Algal growth and utilization of phosphorus studied by combined mono-culture and co-culture experiments

Phosphorus (P) plays a critical role in algal growth; therefore, a better understanding of P availability is essential to control harmful algal blooms. Three algae species, Microcystis aeruginosa, Chlorella pyrenoidosa, and Pseudokirchneriella subcapitata, were mono-cultured and co-cultured on three types of P substrates, dissolved inorganic P (DIP), phosphomonoesters glucose-6-phosphate (G-6-P) and β-glycerol phosphate (β-glycerol-P), and phosphonate (glyphosate), to explore their growth and P utilization. All three species could utilize dissolved organic P (DOP) to sustain their growth, whereas DIP was their preferred P substrate in both culture types. Algae could regulate the P uptake capacity under different P conditions, and the added P could be rapidly accumulated at the beginning of the culture and slowly utilized during the subsequent life cycle. M. aeruginosa exhibited wider P selectivity and could utilize all three P substrates, whereas the other two species could only use phosphomonoester (G-6-P and β-glycerol-P) in the mono-cultures. However, in the co-cultures, the relative bioavailability of DOP for M. aeruginosa and C. pyrenoidosa was enhanced, and M. aeruginosa might contribute to the growth of C. pyrenoidosa and P. subcapitata when fed with glyphosate. The three species showed an intrinsic ability to produce alkaline phosphatase (AP), and AP activity (APA) was regulated by Pi stress. However, high APA did not necessarily lead to high Pi release and algal growth on unfavorable substrates. Although M. aeruginosa was not superior in growth rate in the mono-cultures, it showed a better P accumulation ability and maintained stable growth on different P substrates. Moreover, it was a good competitor, suppressing the thriving growth of the other species in co-cultures. Overall, the findings indicated the strategic flexibility of P utilization by algae and the strong competitive ability of M. aeruginosa in Pi-limited and DOP-enriched natural waters.

HISTOCHEMISTRY OF TISSUE CULTURE CELLS: A STUDY OF THE EFFECTS OF FREEZING AND OF SOME FIXATIVES

It has been shown that a) the membranes of HeLa and L cell lysosomes are readily permeable to naphthol AS-AM phosphate when used as a substrate for acid phosphatase, b) freezing as well as fixation affect the permeability of the lysosomal membrane to both naphthol AS-AM phosphate and β-glycerophosphate, c) none of these treatments seem to affect greatly the plasma or the mitochondrial membranes and d) the distribution of phospholipids in the cells is also affected by freezing or fixation.

[Effects and mechanism of fibroblast growth factor 21 on rat vascular smooth muscle cells calcification]

OBJECTIVE

To observe the effect and mechanism of fibroblast growth factor 21 (FGF21) on rat vascular smooth muscle cells (VSMCs) calcification in vitro.

METHODS

VSMCs was treated with calcification medium containing calcium chloride and β-glycerophosphate to induce rat VSMCs calcification in vitro. VSMCs were divided into 5 groups: the control group (cultured in normal medium), the calcification group (incubated in calcified medium), the FGF21 group (cultured in calcified medium and FGF21), the PD166866 group (cultured in calcified medium and FGF21 and PD166866, inhibitor of fibroblast growth factor receptor-1 (FGFR1)), the GW9662 group (cultured in calcified medium and FGF21 and GW9662, inhibitor of peroxisome proliferators activated receptor-γ (PPAR-γ)). The calcification of VSMCs was detected by calcium content, alkaline phosphatase activity and alizarin red staining. The protein and mRNA expression of FGFR1, β-Klotho, osteocalcin and smooth muscle 22α (SM22α) were determined by western blot analysis and realtime-PCR, respectively.

RESULTS

(1) The mRNA (P < 0.01) and protein expressions of β-Klotho and FGFR1 were significantly downregulated in calcification group compared with control group (P < 0.05 or 0.01). (2) The protein levels and mRNA expression of calcium content, alkaline phosphatase activity and osteocalcin were significantly downregulated, while the protein levels and mRNA of SM22α were significantly increased in FGF21 group compared with calcification group (all P < 0.05). Moreover, alizarin red staining verified positive red nodules on calcified VSMCs was significantly reduced in FGF21 group than in calcification group. (3) Calcium content, alkaline phosphatase activity and alizarin red staining were similar between PD166866 group and calcification group (all P > 0.05). (4) Calcium content, alkaline phosphatase activity and alizarin red staining were similar between GW9662 group and calcification group (all P > 0.05).

CONCLUSION

The inhibition of VSMCs calcification by FGF21 is mediated by further downregulating FGFR1 and β-Klotho while activating PPAR-γ pathways.

[Effect of bone morphogenetic protein-2 on human heart valve interstitial cells calcification in vitro]

OBJECTIVE

To establish human heart valve interstitial cells calcification culture model in vitro, and observe the effect of bone morphogenetic protein-2 (BMP-2) on calcification of human heart valve interstitial cells.

METHODS

Human heart valve interstitial cells were cultured in vitro, and divided into control group: cells were cultured in conventional media plus recombinant human BMP-2 treatment and experimental group: besides above treaments, calcification inducers ( recombinant human BMP-2, β-glycerophosphate, L-ascorbic acid, dexamethasone) were added to the culture media. The two group of cells were cultured for 14 days and were stained by Von Kossa, then the cell calcification was observed in this valvular interstitial cells calcification culture model in vitro. Protein expression of intercellular adhesion molecule 1 (ICAM-1), interleukin 8, BMP-2 and BMP-4 was determined by Western blot and BMP-2 secretion was measured by ELISA.

RESULTS

In the control group, the structure of human heart valve interstitial cells was clear, and the spindle and radial growth shaped cellular morphology was visible, and Von Kossa staining was negative. In the experimental group, the nuclei become darker in color, and granular sediment distribution was seen surrounding cells, and Von Kossa staining was positive, the cells were forming nodules of calcification. The protein expression of ICAM-1, interleukin 8, BMP-2 and BMP-4 in the experimental was significantly higher than that of the control group (all P < 0.05). The expression of BMP-2 in the experimental group was also significantly higher than that in control group ((92.5 ± 4.9) pg/ml vs. (22.2 ± 1.9) pg/ml, P < 0.05).

CONCLUSION

Human BMP-2, β-glycerophosphate, L-ascorbic acid, and dexamethasone can induce human heart valve interstitial cells calcification and enhance inflammation in vitro by stimulating the secretion of BMP-2.

[HUMAN ADIPOSE-DERIVED STEM CELLS COMBINED WITH SMALL INTESNITAL SUBMUCOSA POWDER/CHITOSAN CHLORIDE-β-GLYCEROL PHOSPHATE DISODIUM-HYDROXYETHYL CELLULOSE HYBRID FOR ADIPOSE TISSUE ENGINEERING]

OBJECTIVE

To study the feasibility of human adipose-derived stem cells (hADSCs) combined with small intestinal submucosa powder (SISP)/chitosan chloride (CSCl)-β-glycerol phosphate disodium (GP)-hydroxyethyl cellulose (HEC) for adipose tissue engineering.

METHODS

hADSCs were isolated from human breast fat with collagenase type I digestion, and the third passage hADSCs were mixed with SISP/CSCl-GP-HEC at a density of 1 x 10(6) cells/mL. Twenty-four healthy female nude mice of 5 weeks old were randomly divided into experimental group (n = 12) and control group (n=12), and the mice were subcutaneously injected with 1 mL hADSCs+SISP/CSCl-GP-HEC or SISP/CSCl-GP-HEC respectively at the neck. The degradation rate was evaluated by implant volume measurement at 0, 1, 2, 4, and 8 weeks. Three mice were euthanized at 1, 2, 4, and 8 weeks respectively for general, histological, and immunohistochemical observations. The ability of adipogenesis (Oil O staining), angiopoiesis (CD31), and localized the hADSCs (immunostaining for human Vimentin) were identified.

RESULTS

The volume of implants of both groups decreased with time, but it was greater in experimental group than the control group, showing significant difference at 8 weeks (t = 3.348, P = 0.029). The general observation showed that the border of implants was clear with no adhesion at each time point; fat-liked new tissues were observed with capillaries on the surface at 8 weeks in 2 groups. The histological examinations showed that the structure of implants got compact gradually after injection, and SISP gradually degraded with slower degradation speed in experimental group; adipose tissue began to form, and some mature adipose tissue was observed at 8 weeks in the experimental group. The Oil O staining positive area of experimental group was greater than that of the control group at each time point, showing significant difference at 8 weeks (t = 3.41 1, P = 0.027). Immunohistochemical staining for Vemintin showed that hADSCs could survive at each time point in the experimental group; angiogenesis was most remarkable at 2 weeks, showing no significant differences in CD31 possitive area between 2 groups (P > 0.05), but angiogenesis was more homogeneous in experimental group.

CONCLUSION

SISP/CSCl-GP-HEC can use as scaffolds for hADSCs to reconstruct tissue engineered adipose.

Cloning, heterologous expression and biochemical characterization of plastidial sn-glycerol-3-phosphate acyltransferase from Helianthus annuus

The acyl-[acyl carrier protein]:sn-1-glycerol-3-phosphate acyltransferase (GPAT; E.C. 2.3.1.15) catalyzes the first step of glycerolipid assembly within the stroma of the chloroplast. In the present study, the sunflower (Helianthus annuus, L.) stromal GPAT was cloned, sequenced and characterized. We identified a single ORF of 1344base pairs that encoded a GPAT sharing strong sequence homology with the plastidial GPAT from Arabidopsis thaliana (ATS1, At1g32200). Gene expression studies showed that the highest transcript levels occurred in green tissues in which chloroplasts are abundant. The corresponding mature protein was heterologously overexpressed in Escherichia coli for purification and biochemical characterization. In vitro assays using radiolabelled acyl-ACPs and glycerol-3-phosphate as substrates revealed a strong preference for oleic versus palmitic acid, and weak activity towards stearic acid. The positional fatty acid composition of relevant chloroplast phospholipids from sunflower leaves did not reflect the in vitro GPAT specificity, suggesting a more complex scenario with mixed substrates at different concentrations, competition with other acyl-ACP consuming enzymatic reactions, etc. In summary, this study has confirmed the affinity of this enzyme which would partly explain the resistance to cold temperatures observed in sunflower plants.

The influence of lipid composition and surface charge on biodistribution of intact liposomes releasing from hydrogel-embedded vesicles

Mixed drug delivery systems possess advantages over discrete systems, and can be used as a strategy to design more effective formulations. They are more valuable if the embedded particles perform well, rather than using drugs that have been affected by the surrounding vehicle. In order to address this concept, different liposomes have been incorporated into hydrogel to evaluate the potential effect on the controlled release of liposomes. Radiolabeled liposomes, with respect to different acyl chain lengths (DMPC, DPPC, or DSPC) and charges (neutral, negative [DSPG], or positive [DOTAP]) were integrated into chitosan-glycerophosphate. The results obtained from the biodistribution showed that the DSPC liposomes had the highest area under the curve (AUC) values, both in the blood (206.5%ID/gh(-1)) and peritoneum (622.3%ID/gh(-1)), when compared to the DPPC and DMPC formulations, whether in liposomal hydrogel or dispersion. Interesting results were observed in that the hydrogel could reverse the peritoneal retention of negatively charged liposomes, increasing to 8 times its AUC value, to attain the highest amount among all formulations. The interactions between the liposomes and chitosan-glycerophosphate, confirmed by the Fourier transform infrared (FTIR) spectra as shifted characteristic peaks, were observed in the combined systems. Overall, the hydrogel could control the release of intact liposomes, which could be manipulated by both the liposome type and interactions between the two vehicles.

[Cytocompatibility of chitosan-based thermosensitive hydrogel to human periodontal ligament cell]

PURPOSE

The aim of this investigation was to evaluate the cytocompatibility of an in situ chitosan-quaternized chitosan/α, β-glycerophosphate (CS-HTCC/GP) thermosensitive hydrogel in vitro.

METHODS

The primary cells were isolated from human periodontal ligament and cultured. The role of different concentrations of CS-HTCC/GP extract to HPDLCs was evaluated by MTT assay and alkaline phosphatase (ALP) activity. Also, the ultra-architecture of HPDLCs was determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. SPSS13.0 software package was used for statistical analysis.

RESULTS

By immunocytochemical method, the cells were stained positively to antibodies against vimentin, and negatively to antibodies against cytokeratin, which indicated that they were external embryo mesenchymal cell without epithelial cell mixure. CS-HTCC/GP thermosensitive hydrogel promoted proliferation of HPDLCs,especially at 3d and 5d, the results was significantly different (P<0.001). ALP activity was significantly greater in group 2 and 3 than in group 4 after 5d (P<0.001). Also, no negative influence to ultrastructure of HPDLCs was found through SEM and TEM.

CONCLUSIONS

The results indicate that CS-HTCC/GP thermosensitive hydrogel exhibits excellent cytocompatibility and has potential to be used as an in situ injectable local periodontal drug delivery vehicle and a tissue-engineering scaffold for periodontal disease therapy.

[An in vitro evaluation of the antibacterial activity of chitosan-based thermosensitive hydrogel against periodontal pathogens]

PURPOSE

To evaluate the in vitro antibacterial activity of chitosan - quaternized chitosan/alpha, beta-glycerophosphate (CS-HTCC/GP) thermosensitive hydrogel against three periodontal pathogens- P. gingivalis, P. intermedia, and A. actinomycetemcomitans.

METHODS

An agar diffusion method was used to assess the antimicrobial property of CS-HTCC/GP thermosensitive hydrogel with minimum inhibitory concentration (MIC) and inhibitory zone measurement. SPSS13.0 software package was used for Student's t test.

RESULTS

Three periodontal pathogens strains were all susceptible to CS-HTCC/GP thermosensitive hydrogel. Both matrix of thermosensitive hydrogel and antibiotic exhibited stronger antibacterial activity especially when they were combined.

CONCLUSIONS

CS-HTCC/GP thermosensitive hydrogel is not only as the vehicle of antibiotics which joins the local drug delivery system but as an activator which takes part in the antibacterial process.

Electron transfer dissociation of doubly sodiated glycerophosphocholine lipids

The ability to generate gaseous doubly charged cations of glycerophosphocholine (GPC) lipids via electrospray ionization has made possible the evaluation of electron-transfer dissociation (ETD) for their structural characterization. Doubly sodiated GPC cations have been reacted with azobenzene radical anions in a linear ion trap mass spectrometer. The ion/ion reactions proceed through sodium transfer, electron-transfer, and complex formation. Electron-transfer reactions are shown to give rise to cleavage at each ester linkage with the subsequent loss of a neutral quaternary nitrogen moiety. Electron-transfer without dissociation produces [M + 2Na](+.) radical cations, which undergo collision-induced dissociation (CID) to give products that arise from bond cleavage of each fatty acid chain. The CID of the complex ions yields products similar to those produced directly from the electron-transfer reactions of doubly sodiated GPC, although with different relative abundances. These findings indicate that the analysis of GPC lipids by ETD in conjunction with CID can provide some structural information, such as the number of carbons, degree of unsaturation for each fatty acid substituent, and the positions of the fatty acid substituents; some information about the location of the double bonds may be present in low intensity CID product ions.

Uranium biomineralization as a result of bacterial phosphatase activity: insights from bacterial isolates from a contaminated subsurface

Uranium contamination is an environmental concern at the Department of Energy's Field Research Center in Oak Ridge, Tennessee. In this study, we investigated whether phosphate biomineralization, or the aerobic precipitation of U(VI)-phosphate phases facilitated by the enzymatic activities of microorganisms, offers an alternative to the more extensively studied anaerobic U(VI) bioreduction. Three heterotrophic bacteria isolated from FRC soils were studied for their ability to grow and liberate phosphate in the presence of U(VI) and an organophosphate between pH 4.5 and 7.0. The objectives were to determine whether the strains hydrolyzed sufficient phosphate to precipitate uranium, to determine whether low pH might have an effect on U(VI) precipitation, and to identify the uranium solid phase formed during biomineralization. Two bacterial strains hydrolyzed sufficient organophosphate to precipitate 7395% total uranium after 120 h of incubation in simulated groundwater. The highest rates of uranium precipitation and phosphatase activity were observed between pH 5.0 and 7.0. EXAFS spectra identified the uranyl phosphate precipitate as an autunite/meta-autunite group mineral. The results of this study indicate that aerobic heterotrophic bacteria within a uranium-contaminated environment that can hydrolyze organophosphate, especially in low pH conditions, may play an important role in the bioremediation of uranium.

Salivary Fluoride from Fluoride Dentifrices or Rinses after Use of a Calcium Pre-Rinse or Calcium Dentifrice

The low concentration of available calcium (Ca) in oral fluids limits the formation of Ca-mediated fluoride deposits that maintain oral fluoride (F) after a topical F treatment. The purpose of this study was to examine if a high concentration of Ca would increase salivary F when used before a F rinse or dentifrice. We found that a Ca pre-rinse (150 mmol/l Ca lactate) or Ca dentifrice (0.084 g Ca glycerolphosphate per gram dentifrice) used immediately before a 60 s 228-ppm F rinse (12 mmol/l NaF) produced a 4.6x or 3.6x increase (p < 0.05) respectively in the 1 h salivary F concentrations over the F rinse alone. Reducing the post-Ca F rinse to 10 s still produced a significant 2.2x increase in salivary F compared to the 60 s F rinse alone. Used with a conventional 1,100 ppm F (i.e. 1,100 microg F per gram) NaF dentifrice (Crest), the above Ca pre-rinse increased 1 h salivary F levels by 2.3x over the F dentifrice alone. However, a F rinse given before a Ca rinse produced no increase in 1 h salivary F concentrations. Although the persistence of these increases requires further study, these results suggest that a moderately high concentration of Ca given shortly before a F rinse or F dentifrice may increase the cariostatic effect of the F product.

A novel endoscopic marker: safety experiments in the rat stomach

BACKGROUND AND STUDY AIMS

The study aimed to assess a newly developed endoscopic marker designed to cause only minor inflammatory reactions.

MATERIALS AND METHODS

Chitosan and carbon powder were used in the marker substance. The product was a viscoelastic solution, which was injected into the submucosa in rat stomach walls. The tissue reactions were then examined histopathologically. The structure of the injected marker substance was examined with electron microscopy into rat stomach walls. India ink, which is currently used as an endoscopic marker, served as the control.

RESULTS

Histopathological examination showed that inflammatory reactions with the novel agent were remarkably mild in the rat organs, while submucosally applied india ink caused severe inflammation in situ. The electron-microscopic findings showed that the carbon particles used were completely spherical in shape and that the carbon in the marker substance was entrapped in the chitosan networks. The india ink was shown to consist of a mixture of fine carbon particles and adhesive additives.

CONCLUSIONS

The chitosan-carbon solution appears to be a promising endoscopic marker substance, causing significantly reduced inflammation.

[Culture and characteristics of human dental papilla cells in vitro]

OBJECTIVE

To culture human dental papilla cells (HDPCs)and to study its cytobiological characters in vitro.

METHODS

HDPCs were isolated and cultured with explant culture technique in vitro; Type I collagen, fibronection and laminin were detected in HDPCs and its secreted matrix with the immunocyto-chemical stain; HDPCs were incubated in mineralized promoting solution containing 10 mmol/L beta-glycerophosphate, 100 mg/L of ascorbic acid and 10 nmol/L dexamethasone supplemented with 10% FBS and the form of mineralized nodules was tested with Alizarin Red S stainning.

RESULTS

Cultured HDPCs in vitro were well growing in DMEM/F12. Type I collagen, fibronection and laminin staining were all positive in both HDPCs and its secreted matrix, and laminin was stained with bunchiness in matrix. Mineralized nodules formed after cultured 27 days by Alizarin Red S stainning.

CONCLUSION

HDPCs isolated and cultured are well growing in vitro, have a capability of synthesizing and secreting matrix and in mineralized promoting solution, are able to form mineralizer, so, HDPCs have a capacity of seed cell of tissue engineering regeneration tooth.

[Osteogenic differentiation of synovial mesenchymal stem cells in vitro]

OBJECTIVE

To investigate the potential of synovial mesenchymal stem cells (SMSC) in osteogenic differentiation.

METHODS

SMSC were obtained by limited dilution method and expanded to culture in 25-milliliter flasks. The attached cells were treated with inductive medium containing dexamethasone, glycerophosphate and vitamin C at 3rd passage SMSC. The mineralized nodule was stained by Von Kossa method. The expression of ALP and osteopontin were detected by histochemical, immunohistological staining technique, respectively, while the expression of cbfa1 mRNA by RT-PCR.

RESULTS

Pure SMSC which were of spindle shape and star shape, uniform in size, could be induced to pleomorphism osteoblast in vitro, which were intensive positive in ALP and osteopontin. The expression of cbfa1 mRNA were also verified by RT-PCR and the polygonal cells formed nodular structure at 4 weeks. All these were coincident with the characters of osteoblast.

CONCLUSION

SMSC can be purified and induced into osteoblast in vitro.

Alteration of heme-oxygenase-carbon monoxide pathway in calcified rat vascular smooth muscle cells

OBJECTIVE

The aim of the present study was to investigate the changes in heme-oxygenase (HO)-carbon monoxide (CO)-cyclic guanosine monophosphate (cGMP) pathway in clacified rat vascular smooth muscle cells (VSMCs).

METHODS

Calcification of cultured rat VSMCs was induced by incubation of VSMCs with beta-glycerophosphate. Cellular calcium content, ALP activities and (45)Ca uptake were measured. HO activity, HbCO formation and content of cGMP in VSMCs were determined. Immunocytochemistry for HO-1 expression was observed.

RESULTS

In comparison of control VSMCs, the cellular calcium content, ALP activity and (45)Ca uptake in calcified VSMCs were obviously increased. Immunocytochemistry showed that HO-1 expression was weak and not well distributed in calcified cells as compared to non-calcified VSMCs, but interestingly, there was stronger staining in calcified nodules than in VSMCs. Compared with VSMCs, HO-1 activity in calcified cells decreased by 42.7% [36.4 +/- 2.8 pmol (mg Pr x h)(-1) vs 63.5 x 5.3 pmol (mg Pr x h)(-1), p < 0.01], and HbCO formation decreased by 39.2% (3.38 x 0.69 micromol/mg Pr vs 5.56 +/- 0.48 micromol/mg Pr, p < 0.05). The cGMP content in calcified VSMCs was 78.1% lower than that of non-calcified VSMCs (4.3 +/- 0.51 vs 19.6 +/- 1.2 pmol/mg, p < 0.01).

CONCLUSION

The results showed that HO-CO-cGMP pathway in calcified vascular cells obviously changed, which might contribute to disturbance of vascular function.

Taurine prevents ?-glycerophosphate-induced calcification in cultured rat vascular smooth muscle cells

Vascular calcification is an ectopic calcification that commonly occurs in atherosclerosis. Because taurine was previously shown to protect against cardiovascular diseases, the effect of taurine on vascular calcification was evaluated in calcified vascular smooth muscle cells (VSMCs) of rat in vitro in the present study. Osteoblastic differentiation, calcification, and proliferation in VSMCs were detected in the presence and absence of taurine. Alkaline phosphatase (ALP), cellular calcium content, and (45)Ca accumulation were measured as the indicators of osteoblastic differentiation and calcification. Incubation of VSMCs with Beta-glycerophosphate for 10 days induced an osteoblast-like morphological change. The activity of ALP was enhanced. Calcium content and (45)Ca uptake were increased in these cells. Calcification of these VSMCs was demonstrated with Beta-glycerophosphate treatment. In association with these alterations, cell proliferation, detected by cell counting, [(3)H]thymidine ([(3)H]TdR), and [(3)H]leucine ([(3)H]Leu) incorporation, was also increased in these calcified VSMCs. Taurine at 20 mmol/l decreased calcium content, (45)Ca(2+) uptake, and ALP activity both after early and late treatment, in which a reduction of the cell count, [(3)H"]TdR, and [(3)H]Leu incorporation of calcified VSMCs was also noted. Compared with the calcified group, morphological changes in the VSMCs of the early-treated group were deferred. These results demonstrated that calcification of VSMCs could be alleviated by taurine. Taurine treatment appeared to be more beneficial when the treatment was started earlier.

Cell structure and the metabolism of insect flight muscle

The biochemical properties of insect flight muscle were investigated to ascertain the mechanisms whereby energy is made available for the contractile processes. It was found: 1. The endogenous respiration of muscle homogenates was diminished by starving the flies. The substrate for this respiration was probably glycogen. 2. To obtain the maximal rate of oxidation of glucose, the homogenate had to be fortified with inorganic phosphate, Mg ions, ATP, and cytochrome c. The nucleotides, AMP and ADP, were not as effective as ATP. The addition of DPN or TPN was not necessary for this system. 3. Flight muscle homogenates oxidized glycogen, some sugars, and amino acids, as well as the intermediates of the glycolytic and tricarboxylic acid cycles. Other evidence demonstrated the substrate specificity of the muscle. 4. By centrifugation, the muscle homogenate was divided into two fractions: one, a soluble fraction representing the sarcoplasm; the other, the particulate fraction which contained the fibrils and the sarcosomes. 5. The particulate fraction, alone, oxidized all the citric acid cycle intermediates, α-glycerophosphate, phosphopyruvate, and the amino acids, glutamic, proline, and cysteine. Regardless of the substrate, no oxygen uptake was found with the sarcoplasm by itself. 6. A recombination of the sarcoplasm and the particulate component was required for the oxidation of glycogen, the hexoses, and all the phosphorylated intermediates of glycolysis, except phosphopyruvate. 7. Isolated mitochondria accounted for all the enzymatic activity of the particulate fraction. These results demonstrate that the enzymes of intermediate metabolism are localized in the sarcoplasm or sarcosomes. The third cytological entity, the myofibrils, plays no role in the energy-providing scheme. From a functional viewpoint, the sarcoplasm and the mitochondria, in combination, furnish the energy for the actomyosin contraction. The results are discussed in relation to analogous findings in other insects and vertebrates.

On the role of alphaThr183 in the allosteric regulation and catalytic mechanism of tryptophan synthase

The catalytic activity and substrate channeling of the pyridoxal 5'-phosphate-dependent tryptophan synthase alpha(2)beta(2) complex is regulated by allosteric interactions that modulate the switching of the enzyme between open, low activity and closed, high activity states during the catalytic cycle. The highly conserved alphaThr183 residue is part of loop alphaL6 and is located next to the alpha-active site and forms part of the alpha-beta subunit interface. The role of the interactions of alphaThr183 in alpha-site catalysis and allosteric regulation was investigated by analyzing the kinetics and crystal structures of the isosteric mutant alphaThr183Val. The mutant displays strongly impaired allosteric alpha-beta communication, and the catalytic activity of the alpha-reaction is reduced one hundred fold, whereas the beta-activity is not affected. The structural work establishes that the basis for the missing inter-subunit signaling is the lack of loop alphaL6 closure even in the presence of the alpha-subunit ligands, 3-indolyl-D-glycerol 3'-phosphate, or 3-indolylpropanol 3'-phosphate. The structural basis for the reduced alpha-activity has its origins in the missing hydrogen bond between alphaThr183 and the catalytic residue, alphaAsp60.

Smooth muscle cell phenotypic transition associated with calcification: upregulation of Cbfa1 and downregulation of smooth muscle lineage markers

Bovine aortic smooth muscle cell (BASMC) cultures undergo mineralization on addition of the organic phosphate donor, beta-glycerophosphate (betaGP). Mineralization is characterized by apatite deposition on collagen fibrils and the presence of matrix vesicles, as has been described in calcified vascular lesions in vivo as well as in bone and teeth. In the present study, we used this model to investigate the molecular mechanisms driving vascular calcification. We found that BASMCs lost their lineage markers, SM22alpha and smooth muscle alpha-actin, within 10 days of being placed under calcifying conditions. Conversely, the cells gained an osteogenic phenotype as indicated by an increase in expression and DNA-binding activity of the transcription factor, core binding factor alpha1 (Cbfa1). Moreover, genes containing the Cbfa1 binding site, OSE2, including osteopontin, osteocalcin, and alkaline phosphatase were elevated. The relevance of these in vitro findings to vascular calcification in vivo was further studied in matrix GLA protein null (MGP(-/-)) mice whose arteries spontaneously calcify. We found that arterial calcification was associated with a similar loss in smooth muscle markers and a gain of osteopontin and Cbfa1 expression. These data demonstrate a novel association of vascular calcification with smooth muscle cell phenotypic transition, in which several osteogenic proteins including osteopontin, osteocalcin, and the bone determining factor Cbfa1 are gained. The findings suggest a positive role for SMCs in promoting vascular calcification.

The occurrence of polyglycerophosphate as an antigenic component of various gram-positive bacterial species

A bacterial substance has been described which gives a precipitin reaction with certain antisera to Group A streptococci. The precipitating antigen is present in various Gram-positive bacteria, including most hemolytic streptococci, staphylococci, and aerobic sporulating bacilli. It is not present in any of the Gram-negative species examined or in pneumococci, clostridia, or corynebacteria. Analysis of purified preparations obtained from Group A streptococci indicates that the antigen is a simple polymer of glycerophosphate. The identification has been confirmed by immunochemical studies, including precipitin tests and specific inhibition with synthetic polyglycerophosphates. In addition, the infrared spectra of bacterial and synthetic polyglycerophosphate are shown to be closely similar. Immunochemical analysis suggests that the amount of polyglycerophosphate present in Group A streptococci and staphylococci is approximately 1 per cent of the dry weight of the cells. The cellular localization and function of the polyglycerophosphate have not been established.