Effect of the calcium sensing receptor on rat bone marrow-derived mesenchymal stem cell proliferation through the ERK1/2 pathway

Migration and proliferation of bone marrowderived mesenchymal stem cells (BMSCs) is critical to treatment of ischemic injury. The calcium sensing receptor (CaSR) has an important role in maintaining systemic calcium homeostasis, which is related to cell proliferation, apoptosis and paracrine signaling. We hypothesize that CaSR may enhance BMSC proliferation. Rat BMSCs were incubated with various calcium concentrations for 48 h in vitro to activate CaSR. To investigate potential mechanisms responsible for growth enhancement by calcium, the rat BMSC cell cycle progression was analyzed by fluorescence-activated cell sorting (FACS), and induction of apoptosis confirmed by cytofluorimetric analysis using propidium iodide and Annexin V-FITC double staining. Since the mitogen-activated protein kinase (MAPK) signaling pathway was one of the most significantly affected by CaSR, MAPK activation was measured by western blotting. Calcium exposure significantly enhanced rat BMSCs proliferation, as well as the proportion of the population in S phase, in a dose-dependent manner, effects which were abolished by NPS2390 (a CaSR antagonist) and U0126 (a MEK1/2 inhibitor). These results demonstrate that CaSR is involved in rat BMSC proliferation, as seen by an increased proliferation index, decreased apoptosis, and ERK1/2 activation, and provide important insight into the cellular and molecular mechanisms by which CaSR affects cell proliferation. A CaSR agonist may prove useful to enhance BMSC survival during transplantation.     

Carbon nanofiber-based composites for the construction of mediator-free biosensors

Carbon nanofibers (CNFs), with typical diameters of approximately 80 nm and lengths of the order of micrometers, are extremely attractive in bioanalytical area as they can combine properties of high surface area, non-toxicity, acceptable biocompatibility, ease of fabrication, chemical and electrochemical stability, good electrical conductivity. In this work, CNF-based composites were successfully used as an immobilization matrix for the construction of a reagentless mediator-free hemoglobin-based H2O2 biosensor. The results revealed that hemoglobin retained its essential secondary structure in the CNF-based composite film. With the advantages of organic-inorganic hybrid materials, dramatically facilitated direct electron transfer of hemoglobin and good bioelectrocatalytic activity towards H2O2 were demonstrated. The biosensor displayed good performance along with good long-term stability. The CNF-based composites were proved to be a promising biosensing platform for the construction of mediator-free biosensors, and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biofuel cell.     

JAB1 accelerates mitochondrial apoptosis by interaction with proapoptotic BclGs

The Bcl-2 family of proteins is the key regulators of cell apoptosis at the mitochondria level. The BH3-only pro-apoptotic member BclGs was unique among the family due to its highly specific expression in human testis and has been demonstrated to induce apoptosis dependent on the BH3 domain. However, the molecular mechanism of BclGs-induced apoptosis remains unclear. Here we show that overexpression of BclGs could induce Bax expression upregulation and translocation to mitochondria, cytochrome c release and activation of caspase-3. Moreover, we identified JAB1 as a novel BclGs-specific binding protein through a yeast two-hybrid screening in a human testis cDNA library. BclGs interacts with JAB1 both in vitro and in vivo. N-terminal region of BclGs (aa 1-67) was required for the interaction. Importantly, JAB1 and BclGs co-expression synergistically induces apoptosis. JAB1 could compete with Bcl-XL/Bcl-2 to bind to BclGs; thus, promote the apoptosis. RNAi-mediated knock-down of JAB1 results in the reduced proapoptotic activity of BclGs. Taken together, our results provided the first evidence that JAB1 is involved in the regulation of mitochondrial apoptotic pathway through specific interaction with BclGs.     

Raf activation is regulated by tyrosine 510 phosphorylation in Drosophila

The proto-oncoprotein Raf is pivotal for mitogen-activated protein kinase (MAPK) signaling, and its aberrant activation has been implicated in multiple human cancers. However, the precise molecular mechanism of Raf activation, especially for B-Raf, remains unresolved. By genetic and biochemical studies, we demonstrate that phosphorylation of tyrosine 510 is essential for activation of Drosophila Raf (Draf), which is an ortholog of mammalian B-Raf. Y510 of Draf is phosphorylated by the c-src homolog Src64B. Acidic substitution of Y510 promotes and phenylalanine substitution impairs Draf activation without affecting its enzymatic activity, suggesting that Y510 plays a purely regulatory role. We further show that Y510 regulates Draf activation by affecting the autoinhibitory interaction between the N- and C-terminal fragments of the protein. Finally, we show that Src64B is required for Draf activation in several developmental processes. Together, these results suggest a novel mechanism of Raf activation via Src-mediated tyrosine phosphorylation. Since Y510 is a conserved residue in the kinase domain of all Raf proteins, this mechanism is likely evolutionarily conserved.     

Voltage-dependent potassium channels are involved in staurosporine-induced apoptosis of rat mesenchymal stem cells

The strategy of mesenchymal stem cells (MSCs) transplantation is limited by the inability to deliver a large number of grafted cells that resist peri-transplantation apoptosis in ischemic tissues, and this led us to investigate methods of improving the viability of these cells. We demonstrate the presence of voltage-gated potassium channels in rat MSCs that can be activated by staurosporine (ST). MSCs exposed to ST underwent apoptotic cell changes. Tetraethylammonium (TEA), a classic blocker of K+ channels, blocked the ST-induced augmentation of K+ currents, and reduced ST-induced apoptosis. Furthermore, we found that TEA prevented the ST-induced increase in expression of the pro-apoptotic protein Bax and decrease of the anti-apoptotic protein Bcl-2. Taken together, our findings suggest that voltage-gated potassium is involved in ST-induced apoptosis of rat MSCs. TEA blocks the ST-induced augmentation of K+ currents, alters the expression of Bcl-2 family proteins induced by ST, and attenuates the apoptosis of rat MSCs.     

降解尿酸乳酸菌复合菌系的筛选与菌株组合提升降解效果

【背景】高尿酸症由血液中尿酸含量明显升高而导致,利用乳酸菌对人体的益生作用缓解高尿酸血症越来越受到关注。【目的】获得具有降解尿酸能力的乳酸菌复合菌系与纯培养菌株。【方法】以泡菜为样品来源,以尿酸为底物,采用MRS培养基筛选降解尿酸的乳酸菌复合菌系,通过高效液相色谱法测定复合菌系对尿酸的降解能力。【结果】得到一组乳酸菌复合菌系,当培养温度为37 °C、pH值为6.20、静置培养72 h后复合菌系对尿酸的降解率为12.08%;通过优化培养条件,当该菌系在以牛肉膏为单一氮源、初始pH值为5.00、温度为35 °C的条件下培养72 h,尿酸降解率上升至17.19%,降解率比优化前提高了42.3%;从该菌系中分离出两株具有尿酸降解能力的菌株UA-1与UA-2,它们的尿酸降解率分别为10.85%和8.65%;通过形态学观察和16S rRNA基因序列分析,经鉴定两株菌均为布氏乳杆菌(Lactobacillus buchneri)。将两株单菌组合降解尿酸试验发现,UA-1与UA-2比例为2:1的尿酸降解率为20.2%,比原复合菌系的降解能力提高了67.22%。【结论】研究证明了乳酸菌复合菌系对尿酸的降解能力优于单个菌株,为后续利用乳酸菌复合菌系应用提供了数据支持。     

Exogenous Spermidine Modulates Osmoregulatory Substances and Leaf Stomata to Alleviate the Damage to Lettuce Seedlings Caused by High Temperature Stress

Lettuce (Lactuca sativa L.) prefers cool environments, and high temperatures affect its yield and quality. Polyamines (PAs) have a mitigating effect on plant abiotic stresses. The effect of exogenous spermidine (Spd) on the osmoregulatory substances and stomata of seedlings of the non-heat-tolerant lettuce variety ‘Bei San 3’ under high temperature stress was investigated at 35 °C/30 °C (day/night) under spray treatment with Spd. The results showed that exogenous Spd increased the total fresh weight, root-to-shoot ratio, leaf length, leaf width, root volume, and root surface area of lettuce under high temperature stress and reduced levels of malondialdehyde. The endogenous polyamine content was changed, and endogenous spermidine (Spd) and putrescine (Put) were increased. The accumulation of six organic osmoregulatory substances was promoted, resulting in enhanced betaine aldehyde dehydrogenase (BADH), choline monooxygenase (CMO), proline catalase pyrroline-5-carboxylate synthase (P5CS), ornithine aminotransferase (OAT), and pyrroline-5-carboxylate reductase (P5CR) activity. The production and activity of the degrading enzymes proline dehydrogenase (PDH) and proline oxidase (POX) were inhibited, and the activity of glutamic acid decarboxylase (GAD), the key enzyme of γ-aminobutyric (GABA), was suppressed. In addition, exogenous Spd increased the contents of Ca, K, Fe, Mn, Zn, and NO₃^? ions in lettuce leaves under high temperature stress, promoted K⁺ efflux and Ca²⁺ influx, and reduced the relative stomatal aperture. In summary, exogenous Spd mitigates lettuce injury caused by high temperature stress by increasing the content of osmoregulatory substances and altering stomatal morphology.