Oxidative Stress Response in Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells

Reactive oxygen species (ROS) can irreversibly damage biological molecules, a process known as oxidative stress. Elevated ROS levels are associated with immune cell activation. Sustained immune system activation can affect many different cells in the environment. One cell type that has been detected in almost all tissues of the body is mesenchymal stem/stromal cells (MSC). MSC possess proliferation and differentiation potential, thus facilitating regeneration processes. However, the regenerative capacity of MSC might be impaired by oxidative stress, and the effects of long-term oxidative stress on MSC functions are sparsely described. The examination of oxidative stress is often performed by exposure to H₂O₂. Since H₂O₂ is rapidly degraded, we additionally exposed the cell cultures to glucose oxidase (GOx), resulting in sustained exposure to H₂O₂. Using these model systems, we have focused on the effects of short- and long-term oxidative stress on viability, migration, differentiation, and signaling. All cellular functions examined were affected by the applied oxidative stress. The differences that occur between pulsed and sustained oxidative stress indicated higher oxidative stress in MSC upon direct H₂O₂ exposure, whereas the GOx-induced prolonged exposure to H₂O₂ seems to allow for better cellular adaptation. The mechanisms underlying these different responses are currently unknown.     

化学抑制剂对果蔬食品多酚氧化酶性质影响的研究进展

多酚氧化酶(polyphenol oxidase,PPO)引起的酶促褐变会导致果蔬食品色泽劣变,营养成分降低,甚至使其丧失商品价值.化学抑制剂对PPO具有较好的抑制效果,并且使用方便,在果蔬食品中广泛使用,因此对它的研究具有理论和实际意义.该文论述了羧酸、抗坏血酸及其衍生物、含硫氨基酸、酚酸及其他抑制剂对PPO的抑制作...     

Electrochemical properties of enzyme electrode covalently immobilized on a graphite oxide/cobalt hydroxide/chitosan composite mediator for biofuel cells

A critical factor for the performance of a biofuel cell is an immobilization of the redox enzyme for continuous catalytic reaction and efficient electron transfer. However, the main obstacle associated with enzyme electrode is the reduced surface area for the accommodation of enzymes, leading to poor power output. This study aimed to optimize the efficient electrical communication for glucose oxidase (GOx) on the surface of a graphite oxide/cobalt hydroxide/chitosan composite as mediator, thereby enhancing the generation of power output. Immobilization efficiency was affected by the different concentrations of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)/N-hydroxysuccinimide (NHS). Also, the surface of enzyme electrode was observed by XPS, Raman, and AFM, respectively. The electrochemical characterization showed that the immobilized GOx possesses the highest activity at EDC:NHS(40:80 mM) concentration. The power output under the optimal condition was found to be 2.24 mWcm^?2 of power density using the three-electrode cell in 0.1 M PBS solution at room temperature.     

Hydrothermally synthesized defective NiMoSe2 nanoplates decorated on the surface of functionalized SWCNTs doped polypyrrole scaffold for enzymatic biofuel cell applications

The prospective of this work is to synthesize a new nanocomposite that serves as an electrode material for the immobilization of biomolecules. In this work surface-functionalized single-walled carbon nanotubes (f–COOH–SWCNTs), and hydrothermally synthesized surface defected 2D nanoplates wrapped by polpyrrole matrix was developed. The developed nanocomposite was utilized as the anode material for the immobilization of enzymes. Nanocomposite f-SWCNTs@Ppy@NiMoSe₂ was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the electrochemical methods including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The electrochemically controlled bioanode reached to the open circuit potential (OCV) of 0.35 V and delivered the maximum current density of 9.01 mA cm^?2 in 50 mM glucose concentration prepared in phosphate buffer solution (PBS) (pH 7.0) as the testing solution at 100 mVs^?1 scan rates.     

Roles of Lysyl Oxidase Family Members in the Tumor Microenvironment and Progression of Liver Cancer

The lysyl oxidase (LOX) family members are secreted copper-dependent amine oxidases, comprised of five paralogues: LOX and LOX-like l-4 (LOXL1-4), which are characterized by catalytic activity contributing to the remodeling of the cross-linking of the structural extracellular matrix (ECM). ECM remodeling plays a key role in the angiogenesis surrounding tumors, whereby a corrupt tumor microenvironment (TME) takes shape. Primary liver cancer includes hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), ranked as the seventh most common cancer globally, with limited therapeutic options for advanced stages. In recent years, a growing body of evidence has revealed the key roles of LOX family members in the pathogenesis of liver cancer and the shaping of TME, indicating their notable potential as therapeutic targets. We herein review the clinical value and novel biological roles of LOX family members in tumor progression and the TME of liver cancers. In addition, we highlight recent insights into their mechanisms and their potential involvement in the development of target therapy for liver cancer.     

Identification and Characterization of Citrus Peel Uronic Acid Oxidase

Uronic acid-rich plant materials such as pectin are potential renewable feedstocks for the chemical industry. Uronic acid oxidase activity was first reported in extracts of citrus leaves, and was subsequently found to be widely distributed in plants, with the highest activity detected in extracts of the pectin-rich citrus peel. Herein we report the identification of the primary sequence of uronic acid oxidase from extracts of the peel of Citrus sinensis, by partial purification and protein mass spectrometry. Activity of the enzyme, a member of the berberine bridge family, was confirmed by recombinant expression in Pichia pastoris. Biochemical characterization of the recombinant enzyme is reported. Our findings facilitate further investigation of the biological function of uronic acid oxidation in the economically important orange fruit, and also provide a basis for the development of a catalyst for bioconversion of uronic acids.     

New Evidence on the Role of D-Aspartate Metabolism in Regulating Brain and Endocrine System Physiology: From Preclinical Observations to Clinical Applications

The endogenous amino acids serine and aspartate occur at high concentrations in free D-form in mammalian organs, including the central nervous system and endocrine glands. D-serine (D-Ser) is largely localized in the forebrain structures throughout pre and postnatal life. Pharmacologically, D-Ser plays a functional role by acting as an endogenous coagonist at N-methyl-D-aspartate receptors (NMDARs). Less is known about the role of free D-aspartate (D-Asp) in mammals. Notably, D-Asp has a specific temporal pattern of occurrence. In fact, free D-Asp is abundant during prenatal life and decreases greatly after birth in concomitance with the postnatal onset of D-Asp oxidase expression, which is the only enzyme known to control endogenous levels of this molecule. Conversely, in the endocrine system, D-Asp concentrations enhance after birth during its functional development, thereby suggesting an involvement of the amino acid in the regulation of hormone biosynthesis. The substantial binding affinity for the NMDAR glutamate site has led us to investigate the in vivo implications of D-Asp on NMDAR-mediated responses. Herein we review the physiological function of free D-Asp and of its metabolizing enzyme in regulating the functions of the brain and of the neuroendocrine system based on recent genetic and pharmacological human and animal studies.