Insulin inhibits β-adrenergic action in ischemic/reperfused heart: a novel mechanism of insulin in cardioprotection

Objective Sympathetic overactivity is closely connected with cell injury and contractile dysfunction during myocardial ischemia/reperfusion (MI/R). Insulin exerts protection for the I/R heart and the underlying mechanisms remain unclear. This study aimed to investigate the ability of insulin to modulate β-adrenergic actions on myocardial contraction and post-ischemic injury in acute MI/R and the underlying mechanism. Methods Isolated hearts from adult SD rats were subjected to MI/R (30 min/2 h) and treated with isoproterenol (ISO) or/and insulin. Myocardial contraction, cardiomyocyte apoptosis, myocardial injury and infarction were assessed. In a separate study, isolated ventricular myocytes were subjected to simulated I/R (15/30 min) and myocyte shortening and intracellular Ca²⁺ transient in response to ISO during reperfusion were assessed with presence or absence of insulin. Results In isolated I/R hearts, insulin largely reversed the ISO-associated contractile functional impairment at 2 h after MI/R, inhibiting ISO-induced declines in heart rate and left ventricular systolic pressure by 34.0% and 23.0% and preventing ISO-induced elevation in left ventricular end-diastolic pressure by 28.7% respectively (all P < 0.05). In addition, ISO alone resulted in enlarged infarct size, elevated CK and LDH activity and increased apoptotic index in I/R hearts compared with vehicle, which were inhibited by treatment of insulin (all P < 0.05). Interestingly, in SI/R cardiomyocytes, insulin alone at 10⁻⁷ mol/l increased cell contraction whereas attenuated the positive inotropic response to ISO (10⁻⁹ mol/l) during R as evidenced by a 18.7% reduction in peak twitch amplitude and a 23.9% reduction in calcium transient amplitude (both P < 0.05). Moreover, insulin blunted ISO-mediated increase in PKA activity, enhanced the PKA-dependent phosphorylation of phospholamban (PLB), resulting in increased sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a) activity. Conclusion Insulin attenuated the contractile response to β-AR stimulation and suppressed ISO-elicited cardiac dysfunction and cell injury in MI/R. The inhibitory effect of insulin on the β-adrenergic action involved the inhibition of PKA-mediated Ca²⁺ transient and promotion of post-ischemic Ca²⁺ handling.     

Production of alkali-tolerant cellulase-free xylanase by <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. WLUN024 with wheat bran as the main substrate

An alkali-tolerant cellulase-free xylanase producer, WLI-11, was screened from soil samples collected from a pulp and paper mill in China. It was subsequently identified as a Pseudomonas sp. A mutant, WLUN024, was selected by consecutive mutagenesis by u.v. irradiation and NTG treatment using Pseudomonas sp. WLI-11 as parent strain. Pseudomonas sp. WLUN024 produced xylanase when grown on xylosidic materials, such as hemicellulose, xylan, xylose, and wheat bran. Effects of various nutritional factors on xylanase production by Pseudomonas sp. WLUN024 with wheat bran as the main substrate were investigated. A batch culture of Pseudomonas sp. WLUN024 was conducted under suitable fermentation conditions, where the maximum activity of xylanase reached 1245 U ml⁻¹ after incubating at 37 °C for 24 h. Xylanase produced by Pseudomonas sp. WLUN024 was purified and the molecular weight was estimated as 25.4 kDa. Primary studies on the characteristics of the purified xylanase revealed that this xylanase was alkali-tolerant (optimum pH 7.2–8.0) and cellulase-free. In addition, the xylanase was also capable of producing high quality xylo-oligosaccharides, which indicated its application potential in not only pulp bio-bleaching processes but also in the nutraceutical industry.     

Solid-phase synthesis and antibacterial evaluations of N-demethylvancomycin derivatives

Twenty-five N-demethylvancomycin derivatives were synthesized on solid-support and their structures were determined by LC-MS/MS. Biological evaluation of these compounds indicated that bulky hydrophobic substituent on vancosamine of N-demethylvancomycin can increase antibacterial activity against vancomycin-resistant Enterococcus faecalis.     

赭曲霉毒素 A 的高灵敏时间分辨荧光免疫分析

采用时间分辨荧光免疫分析 (TRFIA) 技术建立快速的高灵敏度的赭曲霉毒素 A (OTA) 全自动检测方法 . 将 OTA-BSA 作为免疫分子免疫 Balb/c 小鼠, OTA-KLH 为筛选用抗原包被板,用间接酶联免疫分析 (ELISA) 法筛选出专一针对 OTA 的高效价的阳性克隆 3G9 ,用杂交瘤细胞制备抗 OTA 单克隆抗体 . 用 OTA-BSA 包被 96 孔板为固相抗原,与游离 OTA 共同竞争有限的抗 OTA 单克隆抗体,以稀土离子 Eu3+ 标记的羊抗鼠抗体进行示踪,采用间接竞争免疫分析方法在解离增强荧光免疫分析体系中建立 OTA-TRFIA. 该方法的灵敏度为 0.03 μg /L ,测量范围为 0.03 ~1 000 μg /L ,批内和批间变异分别为 3.7% 和 5.3% ,平均回收率为 94.2% ,与赭曲霉毒素 B 的平均交叉反应为 3.7% ,与黄曲霉毒素 B1 、 牛血清白蛋白和苯基丙氨酸无交叉反应,说明抗体的特异性很好 . 8 条不同时间进行的间接竞争 OTA-TRFIA 的效应点均值 ED80 、 ED50 、 ED20 分别为 (0.33±0.02) μg /L、 (1.44 ±0.08) μg /L 和 (5.22 ± 0.12) μg /L ,说明方法的稳定性好,样品经 TRFIA 和 ELISA 试剂盒同时检测 OTA ,两者的相关系数为 0.925 ,结果相符 . 研究表明, OTA-TRFIA 是目前报道的 OTA 检测中最灵敏的方法,该分析方法稳定性好,可测范围宽,具有很好的应用前景 .     

Selective enhanced phosphorylation of shrimp beta-tubulin by PKC-delta with PEP(taxol), a synthetic peptide encoding the taxol binding region

Beta-tubulin cDNA from the shrimp Penaeus japonicus was isolated by homology cloning. Expression of cDNA in Escherichia coli yielded a 55 kDa polypeptide, positive for monoclonal antibodies against mammalian beta-tubulin. Autoradiography demonstrated the bacterially expressed hepatopancreas beta-tubulin of P. japonicus is specifically phosphorylated by the delta isoenzyme of protein kinase C (PKC-delta) purified from the plasma membrane of the shrimp heart, in the presence of the receptor for activated PKC (RACK), but not in its absence. Purified shrimp heart PKC-delta is able to phosphorylate bacterially expressed shrimp beta-tubulin without the presence of Ca(++), but requires Mg(++). The kinase activity of purified PKC-delta on bacterially expressed beta-tubulin was enhanced by incubation with PEP(taxol), a synthetic peptide encoding the taxol-binding region of beta-tubulin. In other words, PEP(taxol) modulates the kinase activity of PKC-delta through RACK.     

Expression of the p75 TNF receptor is linked to TNF-induced NFkappaB translocation and oxyradical neutralization in glial cells

Tumor necrosis factor (TNF)-family cytokines induce reactive oxygen species (ROS) that injure vulnerable populations of brain cells. Among glia, oligodendrocytes are particularly susceptible to TNF-induced ROS whereas microglia are protected. We previously found that oligodendrocytes in vitro predominantly express the p55 type-1 TNF receptor, while microglial cells express both type-1 and p75 type-2 receptors. We hypothesized that differential TNF receptor expression and attendant signaling underlies the relative vulnerability of oligodendrocytes, versus microglia, to TNF-induced injury. To test this hypothesis, purified cultures of glial cells were incubated 0–48 hr with TNFa or lymphotoxin-alpha, following which levels of ROS, glutathione (GSH), nuclear factor kappa-B (NFB) translocation, and anti-oxidant proteins and activity were measured. 48 hr exposure to TNF increased ROS levels 28% and decreased GSH levels 17% in oligodendrocytes, but decreased levels ROS levels 24% and increased GSH levels 112% increase in microglia. Thirty to 180 min exposure to TNF increased NFkB nuclear translocation to a greater extent and for a longer time in microglia versus oligodendrocytes, and this was followed 24–48 hr later with 3- to 13-fold increases in microglia manganese superoxide dismutase protein levels and 6-fold increases in enzyme activity. Collectively, these data suggest that signals transduced through the p75 receptor activate anti-oxidant mechanisms that protect microglia from TNF-induced injury. Lacking such signals, oligodendrocytes are considerably more vulnerable to the injurious effects of TNF.     

HIV-1 antiviral activity of recombinant natural killer cell enhancing factors,NKEF-A and NKEF-B,members of the peroxiredoxin family

CD8(+) T-cells are a major source for the production of non-cytolytic factors that inhibit HIV-1 replication. In order to characterize further these factors, we analyzed gene expression profiles of activated CD8(+) T-cells using a human cDNA expression array containing 588 human cDNAs. mRNA for the chemokine I-309 (CCL1), the cytokines granulocyte-macrophage colony-stimulating factor and interleukin-13, and natural killer cell enhancing factors (NKEF) -A and -B were up-regulated in bulk CD8(+) T-cells from HIV-1 seropositive individuals compared with seronegative individuals. Recombinant NKEF-A and NKEF-B inhibited HIV-1 replication when exogenously added to acutely infected T-cells at an ID(50) (dose inhibiting HIV-1 replication by 50%) of approximately 130 nm (3 microg/ml). Additionally, inhibition against dual-tropic simian immunodeficiency virus and dual-tropic simian-human immunodeficiency virus was found. T-cells transfected with NKEF-A or NKEF-B cDNA were able to inhibit 80-98% HIV-1 replication in vitro. Elevated plasma levels of both NKEF-A and NKEF-B proteins were detected in 23% of HIV-infected non-treated individuals but not in persons treated with highly active antiviral therapy or uninfected persons. These results indicate that the peroxiredoxin family members NKEF-A and NKEF-B are up-regulated in activated CD8(+) T-cells in HIV infection, and suggest that these antioxidant proteins contribute to the antiviral activity of CD8(+) T-cells.     

耐冷菌Bacillus cereus SYP-A3-2低温蛋白酶的发酵条件

研究了营养因子及环境条件对中国冰川1号耐冷菌Bacillus cereus SYP-A3-2产低温蛋白酶的影响。结果表明对该菌产酶影响较大的因素分别是温度、酪蛋白浓度和pH,在酪蛋白浓度0．8％、pH7、15℃下摇瓶发酵48h产酶水平可达3,800U／mL。     

In vitro modulation of filament bundling in f-actin and keratins by annexin II and calcium

Summary In our preliminary subcellular localization experiment we demonstrated that annexin II co-localized with submembranous actin in subpopulations of both cultured fibroblasts and keratinocytes. To investigate the physical interaction between annexin II and actin at the cell periphery, in vitro reconstitution experiments were carried out with keratins used as a control. Annexin II, isolated by immunoaffinity column chromatography, was found to exist as globular structures measuring 10 to 25 nm in diameter by rotary shadowing, similar to a previous report. We believe that these structures represent its polymeric forms. By negative staining, monomeric annexin II was detectable as tapered rods, measuring 6 nm in length and 1 to 2 nm in diameter. When annexin II was mixed with actin in 3 mM piperazine-N, N-bis-2-ethanesulfonic acid (PIPES) buffer with 10 mM NaCl₂, 2 mM MgCl₂ and 0.1 mM CaCl₂, thick twisting actin bundles formed, confirming previous reports. This bundling was much reduced when calcium was removed. In the presence of 5 mM ethylenediamine tetra-acetic acid (EDTA) in 5 mM tris, pH 7.2, keratins were found to form a network of filaments, which began to disassemble when the chelator was removed and became fragmented when 0.1 mM CaCl₂ was added. Keratins under the same conditions did not fragment when annexin II was present. These results suggest that annexin II, in conjunction with Ca²⁺, may be involved in a flexible system accommodating changes in the membrane cytoskeletal framework at the cell periphery in keratinocytes.     

IL-6 enhances the cytotoxic activity of thymocyte-derived CD56+ cells.

Thymocyte-derived lymphokine-activated killer (LAK) cells were used as a model for the study of the cytokine driven development of cytotoxicity. These cells are devoid of initial cytotoxic activity but upon culture in IL-2 they develop into cytotoxic effectors. The parameters of the response of thymocytes to IL-6 are similar to that of PBL in that IL-6, at concentrations as low as 1 mu/ml, increases cytotoxicity of thymocyte-LAK cells when generated in low doses (25-50 mu/ml) of IL-2. IL-6-enhanced thymocyte-LAK cytotoxicity is observed when tested against both NK-resistant and NK-sensitive tumor cell lines. IL-6 alone does not induce any cytotoxicity from thymocytes nor does IL-6 change the time course of thymocyte-LAK cell generation in IL-2 culture. IL-6 does not affect DNA synthesis, total cell number, proportion of CD56+ cells, or the expression of IL-2R (both P55 and P75 glycoproteins) in IL-2-cultured thymocytes. Instead, IL-6 used to treat mature thymocyte-LAK effector cells for as little as 1 hr prior to 51Cr-release assay increases LAK cytotoxicity. This enhancement is abrogated by pretreatment of effector cells with cycloheximide, suggesting that protein synthesis is required for IL-6 to enhance LAK cell activity. The precursor phenotypes of IL-6-responsive thymocyte-LAK cells are CD3-/CD5-. The effector phenotypes of IL-6-enhanced thymocyte-LAK cells are CD5-/CD56+. Thus, IL-6 depends on synthesis of rapid-turnover proteins to act on mature CD56+/CD5- LAK cells to increase their cytotoxic function.