VEGF promotes tumorigenesis and angiogenesis of human glioblastoma stem cells

There is increasing evidence for the presence of cancer stem cells (CSCs) in malignant brain tumors, and these CSCs may play a pivotal role in tumor initiation, growth, and recurrence. Vascular endothelial growth factor (VEGF) promotes the proliferation of vascular endothelial cells (VECs) and the neurogenesis of neural stem cells. Using CSCs derived from human glioblastomas and a retrovirus expressing VEGF, we examined the effects of VEGF on the properties of CSCs in vitro and in vivo. Although VEGF did not affect the property of CSCs in vitro, the injection of mouse brains with VEGF-expressing CSCs led to the massive expansion of vascular-rich GBM, tumor-associated hemorrhage, and high morbidity, suggesting that VEGF promoted tumorigenesis via angiogenesis. These results revealed that VEGF induced the proliferation of VEC in the vascular-rich tumor environment, the so-called stem cell niche.     

Isolation of Zn2+ as an endogenous agonist of GPR39 from fetal bovine serum

We attempted to determine natural agonists of GPR39 in fetal bovine serum (FBS). FBS was conditioned to extract peptides and fractionated by two types of HPLC. The activity of each fraction was monitored by intracellular calcium mobilization. Then the purified active ingredient was analyzed by inductively coupled plasma mass spectrometry. In this fashion, Zn2+ ion was identified as an agonist of GPR39, though no peptidergic molecules were found. The calcium-mobilizing activity of Zn2+ was not abolished by pertussis toxin but was by a phospholipase C (PLC) inhibitor, U73122, indicating that the activity of GPR39 is mediated through the Gqalpha -PLC pathway. In addition, Zn2+ also activated mouse and rat GPR39, showing that the function of GPR39 as a Zn2+ receptor is conserved across species. This study is the first exploration of GPR39 agonists in FBS and indicates that GPR39 functions as a Gq-coupled Zn2+-sensing receptor.     

Roles of accumulated endogenous nitric oxide synthase inhibitors, enhanced arginase activity, and attenuated nitric oxide synthase activity in endothelial cells for pulmonary hypertension in rats

Nitric oxide (NO) has been suggested to play a key role in the pathogenesis of pulmonary hypertension (PH). To determine which mechanism exists to affect NO production, we examined the concentration of endogenous nitric oxide synthase (NOS) inhibitors and their catabolizing enzyme dimethylarginine dimethylaminohydrolase (DDAH) activity and protein expression (DDAH1 and DDAH2) in pulmonary artery endothelial cells (PAECs) of rats given monocrotaline (MCT). We also measured NOS and arginase activities and NOS protein expression. Twenty-four days after MCT administration, PH and right ventricle (RV) hypertrophy were established. Endothelium-dependent, but not endothelium-independent, relaxation and cGMP production were significantly impaired in pulmonary artery specimens of MCT group. The constitutive NOS activity and protein expression in PAECs were significantly reduced in MCT group, whereas the arginase, which shares l-arginine as a common substrate with NOS, activity was significantly enhanced in PAECs of MCT group. The contents of monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA), were increased in PAECs of MCT group. The DDAH activity and DDAH1, but not DDAH2, protein expression were significantly reduced in PAECs of MCT group. These results suggest that the impairment of cGMP production as a marker of NO production is possibly due to the blunted endothelial NOS activity resulting from the downregulation of endothelial NOS protein, accumulation of endogenous NOS inhibitors, and accelerated arginase activity in PAECs of PH rats. The decreased overall DDAH activity accompanied by the downregulation of DDAH1 would bring about the accumulation of endogenous NOS inhibitors.     

Mg2+ activates the ryanodine receptor type 2 (RyR2) at intermediate Ca2+ concentrations

To clarify whether activity of the ryanodine receptor type 2 (RyR2) is reduced in the sarcoplasmic reticulum (SR) of cardiac muscle, as is the case with the ryanodine receptor type 1 (RyR1), Ca²⁺-dependent [³H]ryanodine binding, a biochemical measure of Ca²⁺-induced Ca²⁺ release (CICR), was determined using SR vesicle fractions isolated from rabbit and rat cardiac muscles. In the absence of an adenine nucleotide or caffeine, the rat SR showed a complicated Ca²⁺ dependence, instead of the well-documented biphasic dependence of the rabbit SR. In the rat SR, [³H]ryanodine binding initially increased as [Ca²⁺] increased, with a plateau in the range of 10–100 µM Ca²⁺, and thereafter further increased to an apparent peak around 1 mM Ca²⁺, followed by a decrease. In the presence of these modulators, this complicated dependence prevailed, irrespective of the source. Addition of 0.3–1 mM Mg²⁺ unexpectedly increased the binding two- to threefold and enhanced the affinity for [³H]ryanodine at 10–100 µM Ca²⁺, resulting in the well-known biphasic dependence. In other words, the partial suppression of RyR2 is relieved by Mg²⁺. Ca²⁺ could be a substitute for Mg²⁺. Mg²⁺ also amplifies the responses of RyR2 to inhibitory and stimulatory modulators. This stimulating effect of Mg²⁺ on RyR2 is entirely new, and is referred to as the third effect, in addition to the well-known dual inhibitory effects. This effect is critical to describe the role of RyR2 in excitation-contraction coupling of cardiac muscle, in view of the intracellular Mg²⁺ concentration. [³H]ryanodine binding; CICR; stimulation by physiological Mg²⁺, excitation-contraction coupling in the heart     

Non-fucosylated therapeutic antibodies: the next generation of therapeutic antibodies

Therapeutic antibody IgG1 has two N-linked oligosaccharide chains bound to the Fc region. The oligosaccharides are of the complex biantennary type, composed of a trimannosyl core structure with the presence or absence of core fucose, bisecting N-acetylglucosamine (GlcNAc), galactose, and terminal sialic acid, which gives rise to structural heterogeneity. Both human serum IgG and therapeutic antibodies are well known to be heavily fucosylated. Recently, antibody-dependent cellular cytotoxicity (ADCC), a lytic attack on antibody-targeted cells, has been found to be one of the critical effector functions responsible for the clinical efficacy of therapeutic antibodies such as anti-CD20 IgG1 rituximab (Rituxan^®) and anti-Her2/neu IgG1 trastuzumab (Herceptin^®). ADCC is triggered upon the binding of lymphocyte receptors (FcγRs) to the antibody Fc region. The activity is dependent on the amount of fucose attached to the innermost GlcNAc of N-linked Fc oligosaccharide via an α-1,6-linkage, and is dramatically enhanced by a reduction in fucose. Non-fucosylated therapeutic antibodies show more potent efficacy than their fucosylated counterparts both in vitro and in vivo, and are not likely to be immunogenic because their carbohydrate structures are a normal component of natural human serum IgG. Thus, the application of non-fucosylated antibodies is expected to be a powerful and elegant approach to the design of the next generation therapeutic antibodies with improved efficacy. In this review, we discuss the importance of the oligosaccharides attached to the Fc region of therapeutic antibodies, especially regarding the inhibitory effect of fucosylated therapeutic antibodies on the efficacy of non-fucosylated counterparts in one medical agent. The impact of completely non-fucosylated therapeutic antibodies on therapeutic fields will be also discussed.     

PGC-1α-mediated changes in phospholipid profiles of exercise-trained skeletal muscle

Exercise training influences phospholipid fatty acid composition in skeletal muscle and these changes are associated with physiological phenotypes; however, the molecular mechanism of this influence on compositional changes is poorly understood. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a nuclear receptor coactivator, promotes mitochondrial biogenesis, the fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. Because exercise training induces these adaptations, together with increased PGC-1α, PGC-1α may contribute to the exercise-mediated change in phospholipid fatty acid composition. To determine the role of PGC-1α, we performed lipidomic analyses of skeletal muscle from genetically modified mice that overexpress PGC-1α in skeletal muscle or that carry KO alleles of PGC-1α. We found that PGC-1α affected lipid profiles in skeletal muscle and increased several phospholipid species in glycolytic muscle, namely phosphatidylcholine (PC) (18:0/22:6) and phosphatidylethanolamine (PE) (18:0/22:6). We also found that exercise training increased PC (18:0/22:6) and PE (18:0/22:6) in glycolytic muscle and that PGC-1α was required for these alterations. Because phospholipid fatty acid composition influences cell permeability and receptor stability at the cell membrane, these phospholipids may contribute to exercise training-mediated functional changes in the skeletal muscle.     

New glycosides of the campesterol derivative from the rhizomes of Tacca chantrieri

Seven new glycosides of the campesterol derivative (24R,25S)-ergost-5-ene-3beta,26-diol (1-7) were isolated from the rhizomes of Tacca chantrieri (Taccaceae). Their structures were determined by extensive spectroscopic analysis, including 2D NMR data, and a few chemical transformations.