GDF11 slows excitatory neuronal senescence and brain ageing by repressing p21

As a major neuron type in the brain, the excitatory neuron (EN) regulates the lifespan in C. elegans. How the EN acquires senescence, however, is unknown. Here, we show that growth differentiation factor 11 (GDF11) is predominantly expressed in the EN in the adult mouse, marmoset and human brain. In mice, selective knock-out of GDF11 in the post-mitotic EN shapes the brain ageing-related transcriptional profile, induces EN senescence and hyperexcitability, prunes their dendrites, impedes their synaptic input, impairs object recognition memory and shortens the lifespan, establishing a functional link between GDF11, brain ageing and cognition. In vitro GDF11 deletion causes cellular senescence in Neuro-2a cells. Mechanistically, GDF11 deletion induces neuronal senescence via Smad2-induced transcription of the pro-senescence factor p21. This work indicates that endogenous GDF11 acts as a brake on EN senescence and brain ageing.

Restoring nuclear entry of Sirtuin 2 in oligodendrocyte progenitor cells promotes remyelination during ageing

The age-dependent decline in remyelination potential of the central nervous system during ageing is associated with a declined differentiation capacity of oligodendrocyte progenitor cells (OPCs). The molecular players that can enhance OPC differentiation or rejuvenate OPCs are unclear. Here we show that, in mouse OPCs, nuclear entry of SIRT2 is impaired and NAD⁺ levels are reduced during ageing. When we supplement β-nicotinamide mononucleotide (β-NMN), an NAD⁺ precursor, nuclear entry of SIRT2 in OPCs, OPC differentiation, and remyelination were rescued in aged animals. We show that the effects on myelination are mediated via the NAD⁺-SIRT2-H3K18Ac-ID4 axis, and SIRT2 is required for rejuvenating OPCs. Our results show that SIRT2 and NAD⁺ levels rescue the aged OPC differentiation potential to levels comparable to young age, providing potential targets to enhance remyelination during ageing.

Age-dependent decline in remyelination in the CNS is associated with declined differentiation capacity of oligodendrocyte progenitor cells (OPCs). Here, the authors show nuclear entry of SIRT2 is impaired and NAD+ levels are reduced during ageing in mouse OPCs. β-nicotinamide mononucleotide (β-NMN) supplement delays myelin aging and enhances remyelination in the aged mice.

Neutralization of Hv1/HVCN1 With Antibody Enhances Microglia/Macrophages Myelin Clearance by Promoting Their Migration in the Brain

Microglia dynamically monitor the microenvironment of the central nervous system (CNS) by constantly extending and retracting their processes in physiological conditions, and microglia/macrophages rapidly migrate into lesion sites in response to injuries or diseases in the CNS. Consequently, their migration ability is fundamentally important for their proper functioning. However, the mechanisms underlying their migration have not been fully understood. We wonder whether the voltage-gated proton channel HVCN1 in microglia/macrophages in the brain plays a role in their migration. We show in this study that in physiological conditions, microglia and bone marrow derived macrophage (BMDM) express HVCN1 with the highest level among glial cells, and upregulation of HVCN1 in microglia/macrophages is presented in multiple injuries and diseases of the CNS, reflecting the overactivation of HVCN1. In parallel, myelin debris accumulation occurs in both the focal lesion and the site where neurodegeneration takes place. Importantly, both genetic deletion of the HVCN1 gene in cells in vitro and neutralization of HVCN1 with antibody in the brain in vivo promotes migration of microglia/macrophages. Furthermore, neutralization of HVCN1 with antibody in the brain in vivo promotes myelin debris clearance by microglia/macrophages. This study uncovers a new role of HVCN1 in microglia/macrophages, coupling the proton channel HVCN1 to the migration of microglia/macrophages for the first time.

[Effect of processing excipient suet oil on formation and absorption of baohuoside Ⅰ-bile salt self-assembled micelles]

The fried method with suet oil,which can strengthen the effect of Epimedium in warming kidney and enhancing Yang,has been widely used in the processing of Epimedium in traditional Chinese medicine. Based on the formation mechanism of Epimedium flavonoids self-assembled micelles in vivo,the synergistic mechanism of processing excipient suet oil was investigated in this paper from the perspective of pharmaceutics. Baohuoside Ⅰ,as representative component of processed Epimedium,was selected as model drug.Average size and zeta potential were measured and the morphology of micelles was observed under transmission electron microscopy. Caco-2 monolayer cell model,rat intestinal perfusion model and in vivo serum drug concentration method were established to investigate the effect of suet oil on the formation and absorption of the baohuosideⅠ bile salt self-assembled micelles. Baohuoside Ⅰ can form selfassembled micelles under the action of sodium deoxycholate. While,adding suet oil into the baohuoside Ⅰ-bile salt micelles( BSDOC) can make it form a more stable system with a smaller average size,higher Zeta potential,lower polydispersity index( PDI) value,significantly improved encapsulation efficiency and drug loading,indicating that suet oil could significantly improve the micelle formation in vivo. In addition,the permeability coefficient of baohuoside Ⅰ in Caco-2 monolayer cells and the four intestinal organs( duodenum,jejunum,ileum and colon) was increased and the oral bioavailability was also improved after adding the suet oil to BS-DOC.All the results demonstrated that the suet oil can promote the formation and absorption of baohuoside Ⅰ self-assembled micelles,so as to enhance its synergistic effects.

Effect of Sn Content on the Microstructure and Properties of Wire and Arc Additive Manufactured Al-Cu Alloy Deposits

Al-Cu-Sn alloy deposits with different Sn contents were prepared by the wire and arc additive manufacturing process. The microstructure and mechanical properties of the deposits were examined by metallography, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and tensile tests. The results indicated that the addition of Sn significantly refined the microstructure of the deposits in their as-deposited state, and the grains were transformed from dendrites to equiaxed crystals with a uniform grain size of ∼30 μm. For the deposits with Sn ≥0.15%, the continuous and elongated θ phase on the grain boundary became block-shaped, and the size of the precipitated phase increased. After T6 heat treatment, the θ phase completely dissolved in the substrate in the deposits with Sn ≤0.1%, whereas the θ-phase solid dissolution was incomplete in the deposits with Sn ≥0.15%; the higher the Sn content, the greater the amount of θ phase remaining. After the T6 treatment, the deposits with an Sn content of 0.25% exhibited cracks distributed along the grain boundaries. The addition of Sn significantly increased the density of the θ' phase, which was diffused and uniform in size; with an increase in the Sn content, the distribution density of the θ' phase in the deposits first increased and then decreased as the peak-aging condition was reached. The addition of Sn could effectively improve the mechanical properties of the deposits, which first increased and then decreased with an increase in the Sn content. The mechanical properties of the deposits were optimal at an Sn content of 0.1%, with a tensile strength of 493 MPa, yield strength of 434 MPa, and elongation of 9.5%.

[Mechanism of flavonoid components in Astragali Radix in inhibiting tumor growth and immunoregulation in C57BL/6 tumor bearing mice based on "invigorating Qi for consolidation of exterior"]

Traditional Chinese medicine believes that the occurrence and development of tumors is related to the body's Qi deficiency. " Invigorating Qi for consolidation of exterior" has became an effective way to treat tumors by traditional Chinese medicine. This study is based on the " invigorating Qi for consolidation of exterior" to explore the effect of flavonoid components in Qi-invigorating herbs Astragali Radix( AR) on the growth and immune function of mouse Lewis lung cancer xenografts,and further explore its mechanism of action. In the present study,high performance liquid chromatography was performed to analyze the flavonoid components in AR.The Lewis lung cancer model of C57 BL/6 mice was constructed,and the tumor volume of mice was determined by Visual Sonics Vevo2100 high frequency color ultrasound. The levels of IL~(-1)7 and RORγt in serum and tumor tissues were detected by ELISA and immunohistochemistry. The expression of IRE~(-1)/XBP~(-1) pathway-related proteins in tumor tissues was detected by Western blot. The results revealed that treatment of 5 and 10 g·kg~(-1)·d~(-1) of flavonoid components in AR significantly inhibited tumor growth of C57 BL/6 tumorbearing mice. The inhibition rates at the dose of 5 and 10 g·kg~(-1)·d~(-1) of flavonoid components in AR were( 29. 5±4. 4) % and( 43. 4±5. 2) %,respectively. The expression of IL~(-1)7 and RORγt in serum and tumor tissues of Lewis lung cancer mice were decreased,and the spleen index and thymus index were significantly enhanced by the flavonoid components in AR. Flavonoid components in AR could decrease the expression of X-box binding protein 1( XBP1),inositol-requiring enzyme( IRE1) and glucose regulated protein 78 k D( GRP78),and increase the expression of C/EBP homologous protein( CHOP),and the high-dose group is better,suggesting that the anti-lung cancer effect of flavonoid components in AR is related to the regulation of XBP1 mediated ERs. This study provides new evidence that the flavonoid components in AR could inhibit the tumor growth of C57 BL/6 tumor-bearing mice by regulating the body's immune function through " invigorating Qi for consolidation of exterior".

Using an abnormal increase in postexercise systolic blood pressure to diagnose coronary artery disease in gerontal patients

Data from 66 patients ≥ 60 years old with suspected coronary artery disease (CAD) were studied to determine the diagnostic value of an abnormal increase in postexercise systolic blood pressure (SBP) for detecting CAD in gerontal patients. Treadmill exercise testing (TET) and selective coronary angiography (CAG) were carried out and SBP was measured pre-TET and at each minute during a 6-min post-TET recovery phase. Abnormal increase in postexercise SBP was defined as a higher SBP compared with that measured earlier during the 6-min post-TET period. An abnormal increase of ≥ 7 mmHg in postexercise SBP had a statistically significantly better specificity, and also showed higher sensitivity and accuracy, than ST-segment depression ≥ 1 mV in identifying gerontal patients with CAD. The combination of ST-segment depression and abnormal SBP resulted in further improvement of the specificity for detecting CAD. It is concluded that measurement of abnormal increase in postexercise SBP may be a sensitive indicator of gerontal CAD.

[A study of tracking the superparamagnetic iron oxide and enhanced green fluorescent protein labeled miniature porcine bone marrow stem cells by in vitro MRI]

OBJECTIVES

To track bone marrow stem cells (BMSCs) labeled by enhanced green fluorescent protein (EGFP) and superparamagnetic iron oxide (SPIO)-poly-L-lysine (PLL) compound by MRI in vitro for autotransplantation into pancreas of type 1 diabetes miniature pigs.

METHODS

The BMSCs were isolated by density gradient centrifugation and attachment culture from type 1 diabetes minipigs' bone marrow. Expressional intensity of EGFP in BMSCs transfected lentivirus-EGFP with a multiplicity of infection (MOI) of 30:1 reached the highest level after 96 h from transfection, while the positive rate was 43.2%. Different magnetic resonance scanning protocols were carried out on various density BMSCs labeled by different concentration of SPIO in various time-point in vitro.

RESULTS

When SPIO concentration was 25 mg/L (count in Fe(3+)), the positive Fe(3+)-labeling rate of BMSCs was 93.1%. Most of SPIO particles in BMSCs' cytoplasm were observed in secondary lysosomes, but they were not detected in important organelle as cell nucleus. Comparing with gelatin the MRI of BMSCs labeled with SPIO in the condition with 1 × 10(4)/ml cells density and 25 mg/L Fe(3+) concentration in vitro, the signal intensity changes (ΔSI) after BMSCs labeled with SPIO 3 weeks and 6 weeks in TSE T(1)WI, TSE T(2)WI and FLASH T(2) WI sequences were 12%, 41%, 63% and 7%, 28%, 46% respectively (P < 0.01 and P < 0.05, respectively).

CONCLUSIONS

The data showed that the porcine BMSCs labeled with SPIO and EGFP could be traced successfully in vitro by MRI in the suitable sequences.

The role of NO and B-50 in neurotoxicity of excitatory amino acids

To investigate the direct evidence for the role which nitric oxide (NO) plays in the neurotoxicity of excitatory amino acids, we evaluated NO level by Greiss testing solution when glutamate (Glu) and kainate (KA) induced neuronal degeneration in primary cortical cultures. Glutamate-induced neurotoxicity was accompanied by a rise in NO. 5 mM hemoglobin (Hb) led to a decrease of NO content and prevented excitotoxicity induced by 1 mM glutamate. 1 mM L-arginine (L-Arg) reversed the effect of hemoglobin by raising the NO level. No change in NO content was found in KA-induced neurotoxicity, which was not affected by L-Arg, Hb or L-Arg + Hb. It is suggested that NO plays an important role in glutamate-, but not KA-induced neurotoxicity in primary cortical cultures. We also investigated the effects of glutamate on a growth-associated protein, B-50. The B-50 level declined significantly 24 h after exposure to 100 microM glutamate for 30 min and then recovered 2 days later. The effect of glutamate on B-50 was concentration-dependent. This indicates that B-50 might be involved in both glutamate neurotoxicity and the following neuronal repair process.

Nerve growth factors prevent glutamate toxicity in cortical neuronal cultures

AIM

To determine if nerve growth factors (NGF) can protect against glutamate-induced cortical neuron damage.

METHODS

Neuron viability and lactate dehydrogenase (LDH) efflux in the bathing medium in primary cultures from 17-d-old mouse fetal cortex were measured to assay NGF effect. Imaging of the calcium indicator dye Fura-2 was used to measure the [Ca2+]i.

RESULTS

The LD50 for NGF-free glutamate was 0.2 mmol.L-1 (95% confidence limits 0-1.6 mmol.L-1). In the presence of NGF 60 micrograms.L-1, 59% of the neurons survived in glutamate 1.6 mmol.L-1. The protective effect afforded by NGF was maximal at 60 micrograms.L-1, at which it prevented the elevation in [Ca2+]i.

CONCLUSION

NGF protect cortical neurons against glutamate-induced toxicity via "stabilizing" [Ca2+]i level or suppression of the rise in [Ca2+]i.

[Effects of morphine on monosodium glutamate neurotoxicity and its mechanism]

The enhancing effects of morphine on monosodium glutamate (MSG) neurotoxicity and its blocking by naloxone were studied through morphological observation, together with detection of concentrations of intracellular free Ca2+ ([Ca2+]i) by Ca2+ indicator Fura-2/AM and lactate dehydrogenase (LDH) efflux in the bathing medium in primary cultures from 14-17 d old mouse fetal cortex. It was found that 10 min pre-incubation of young cortical neurons (7 day in vitro) with morphine 10(-7) or 10(-6) mol.L-1 substantially increased LDH release from 105.7% +/- 19.0% (treated with MSG alone) to 194.5% +/- 17.7% and 214.0% +/- 9.5% respectively after exposure to MSG 0.1 mmol.L-1, but pre-incubation with morphine (10(-7) or 10(-6) mol.L-1) plus naloxone (0.1 mmol.L-1) reversed the LDH release after treatment with the same concentration of MSG. Morphine (10(-7) or 10(-6) mol.L-1) produced little elevation of [Ca2+]i. However, when combined with MSG (0.1 mmol.L-1) morphine elevated the [Ca2+]i level much more than MSG alone. These results suggest that morphine markedly enhances excitotoxic neuron damage, which can be reversed by naloxone. Overloading of intracellular Ca2+ may be a simultaneous pathological mechanism underlying the neuronal damage and death that occur in excitatory toxicity.

Characterization of the gene encoding the largest subunit of Plasmodium falciparum RNA polymerase III

We report here the isolation, sequence analysis, structure, and expression of the gene encoding the largest subunit of RNA polymerase III (RPIII) from Plasmodium falciparum. The P. falciparum RPIII gene consists of 5 exons and 4 introns, is expressed in all of the asexual erythrocytic stages of the parasite as a 8.5-kb mRNA, and is present in a single copy on chromosome 13. The predicted 2339 amino acid residue RPIII subunit contained 5 regions that were conserved between different eukaryotic RPIII subunits, and 4 variable regions that separated the conserved regions. Three of the variable regions were greatly enlarged in comparison to the corresponding variable regions in other RPIII subunits. Variable region C' represented nearly one-third of the P. falciparum RPIII subunit (750 amino acid residues), included a unique repeated decapeptide sequence, and had some homology with yeast DNA topoisomerase II. Noteworthy amino acid sequences and structures were identified in both the conserved regions and in the enlarged variable regions, and their possible role(s) as domains that regulate RPIII enzyme activity is discussed.

Mutant dihydrofolate reductase-thymidylate synthase genes in pyrimethamine-resistant Plasmodium falciparum with polymorphic chromosome duplications

We have identified dihydrofolate reductase (DHFR) gene point mutations and chromosomal changes in pyrimethamine-resistant mutants selected in vitro of Plasmodium falciparum strain FCR3. A pyrimethamine-resistant derivative of the pyrimethamine-sensitive strain FCR3, FCR3-D8, that had been grown in the absence of pyrimethamine for an extended time, was grown in two concentrations of pyrimethamine, and surviving drug-resistant parasites were subcloned. One selected mutant, FCR3-D81, that grew at 1 X 10(-6) M pyrimethamine, contained a single point mutation in the DHFR domain which caused an amino acid change (Phe to Ser) at amino acid 223, whereas another mutant, FCR3-D85, that grew at 5 X 10(-6) M pyrimethamine had that same mutation and an additional point mutation that changed amino acid 54 (Asp to Asn). The selection of FCR3-D85, whose nucleotide sequence was identical to that previously reported for FCR3-D8, confirmed that the original FCR3-D8 parasite population had changed during extended growth in vitro in the absence of drug pressure. FCR3-D81 and FCR3-D85 cells contained different pairs of polymorphic chromosomes that hybridized to a DHFR-TS probe as well as to three other chromosome 4 specific DNAs, indicating that at least part of chromosome 4 had been duplicated and that these parasites were aneuploid with 15 rather than 14 chromosomes. The mutant DHFR-TS genes were diploid. We consider the roles of the polymorphic chromosome duplications and DHFR point mutation(s) as causes of pyrimethamine resistance.

Dihydrofolate reductase mutations and chromosomal changes associated with pyrimethamine resistance of Plasmodium falciparum

The nucleotide sequence of the dihydrofolate reductase-thymidylate synthase (DHFR-TS) gene in pyrimethamine-resistant (PyrR) mutants of Plasmodium falciparum selected in vitro was examined to determine if specific mutations in DHFR were associated with drug resistance. We analysed the sequence of genomic DNA from strain FCR3, from eight previously isolated PyrR parasites derived from FCR3, and from strain Honduras-1. We found that: (1) five PyrR FCR3 mutants, FCR3-D4-D8, had an identical nucleotide change and a novel single amino acid change (Phe to Ser) at amino acid 223 of DHFR; (2) our originally reported nucleotide sequence of the DHFR-TS gene was of the PyrR strain Honduras-1, and was not of FCR3; (3) three PyrR mutants, FCR3-D1, D2, and D3, thought to have been derived from the FCR3 strain, were in fact isolates of Honduras-1. We also examined the chromosomal DNA of PyrR mutants by pulsed-field gradient gel (PFG) electrophoresis. The PyrR mutants FCR3-D1, D2, and D3 had several chromosome size polymorphisms compared to FCR3. In two of the PyrR FCR3 mutants, FCR3-D7 and D8, the chromosome 4-size DNA of FCR3 that the DHFR-TS probe normally hybridised to was not observed. Instead, in FCR3-D7, a chromosome larger than the chromosome 4-size DNA was observed to hybridise to the DHFR-TS probe. In FCR3-D8, two chromosomes that hybridised to the DHFR-TS probe were found. One of them was larger than FCR-3 chromosome 4-size DNA, and the other was smaller than FCR3 chromosome 1-size DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

An enlarged largest subunit of Plasmodium falciparum RNA polymerase II defines conserved and variable RNA polymerase domains

We have isolated the gene encoding the largest subunit of RNA polymerase II from Plasmodium falciparum. The RPII gene is expressed in the asexual erythrocytic stages of the parasite as a 9 kb mRNA, and is present as a single copy gene located on chromosome 3. The P. falciparum RPII subunit is the largest (2452 amino acids) eukaryotic RPII subunit, and it contains enlarged variable regions that clearly separate and define five conserved regions of the eukaryotic RPII largest subunits. A distinctive carboxyl-terminal domain contains a short highly conserved heptapeptide repeat domain which is bounded on its 5' side by a highly diverged heptapeptide repeat domain, and is bounded on its 3' side by a long carboxyl-terminal extension.

Premature release of Plasmodium falciparum from swollen erythrocytes induced by some antimalarials

Qinghaosu and chloroquine, but not pyrimethamine, treatment of Plasmodium falciparum cultures resulted in the formation of swollen red blood cells (RBCs) and the expulsion of degenerate trophozoites and schizonts, but not ring-stage parasites, from the infected RBCs. The parasite release resulted in the formation of RBCs with holes, that had otherwise retained their structural integrity. Membranes of swollen RBCs and their ghosts associated with parasites were efficiently visualized by Giemsa staining of thin smears for 18-24 hr but not by standard Giemsa staining for 20 min.

The chemotherapy of rodent malaria, XXXIX. Ultrastructural changes following treatment with artemisinine of Plasmodium berghei infection in mice, with observations of the localization of [3H]-dihydroartemisinine in P. falciparum in vitro

Ultrastructural changes were followed in Plasmodium berghei after the treatment of the mouse host with a single 10 mg kg-1 dose of artemisinine (qinghaosu). After 30 minutes, changes in the limiting and other membranes of the parasite were seen, together with alterations in ribosomal organization and endoplasmic reticulum. No changes were noted in digestive vacuoles or pigment, but nuclear membrane blebbing developed after one hour and segregation of the nucleoplasm after three hours. Further degenerative changes with disorganization and death occurred from eight hours onwards. The morphological changes in ribosomes and endoplasmic reticulum correlate in time with the depression in protein synthesis observed in P. falciparum in vitro. Similarly, the onset of nucleoplasmic segregation correlates with the development of nucleic acid synthesis inhibition. Tritiated reduced drug was shown to be localized in parasite membranes, indicating that changes in membrane integrity might precede the early depression of protein synthesis. Membrane association of artemisinine may be related to its amphipathic characteristics and similarity in some respects to a sterol.

Uptake of [3H] dihydroartemisinine by erythrocytes infected with Plasmodium falciparum in vitro

Artemisinine ( qinghaosu ) was reduced and radio-labelled using tritiated borohydride. The tritiated dihydroartemisinine produced was differentially accumulated from low concentrations in culture medium into erythrocytes infected with Plasmodium falciparum. Uninfected erythrocytes concentrated the drug less than two-fold whereas infected erythrocytes achieved more than 300 times the medium concentration. The uptake process is reversible and saturable, with a dissociation constant (Kd) at the hypothetical receptor of 10.5 nmol.l-1. Competition studies indicate that the receptor is the same as that for artemether , another quinghaosu derivative. Chloroquine showed an interesting partial inhibition of uptake but was unable to release the bound radio-labelled drug from infected cells.

Rapid action of Qinghaosu and related drugs on incorporation of [3H]isoleucine by Plasmodium falciparum in vitro

Using the incorporation of [3H]isoleucine into acid-insoluble products as an index of protein-synthetic activity, it was shown that Qinghaosu and two related drugs had a rapid effect on this process in human erythrocytes infected with Plasmodium falciparum in vitro. Inhibition could be seen 1 hr or less after addition of the drugs at concentrations from 5 mumole/1. to 50 nmole/1. It is recommended that the effects of these drugs be studied in cell-free protein-synthetic systems.

Effects of qinghaosu and related compounds on incorporation of [G-3H] hypoxanthine by Plasmodium falciparum in vitro

The effects of qinghaosu (QHS), dihydroqinghaosu (DHQ), artemether and alpha-propoxycarbonyl dihydroartemisine (SM242) on incorporation of [G-3H] hypoxanthine into Plasmodium falciparum were studied in vitro. Antimalarial activity in vitro is enhanced by reduction of the keto group, since DHQ, artemether and SM242 were more than 100 times more active than QHS.