Tyrosinase‐catalyzed oxidation of resveratrol produces a highly reactive ortho‐quinone: Implications for melanocyte toxicity

trans‐Resveratrol (3,5,4′‐trihydroxy‐trans‐stilbene, RES), a naturally occurring polyphenol, has recently attracted increased interest as a health‐beneficial agent. However, based on its p‐substituted phenol structure, RES is expected to be a substrate for tyrosinase and to produce a toxic o‐quinone metabolite. The results of this study demonstrate that the oxidation of RES by tyrosinase produces 4‐(3′,5′‐dihydroxy‐trans‐styrenyl)‐1,2‐benzoquinone (RES‐quinone), which decays rapidly to an oligomeric product (RES‐oligomer). RES‐quinone was identified after reduction to its corresponding catechol, known as piceatannol. RES‐quinone reacts with N‐acetylcysteine, a small thiol, to form a diadduct and a triadduct, which were identified by NMR and MS analyses. The production of a triadduct is not common for o‐quinones, suggesting a high reactivity of RES‐quinone. RES‐quinone also binds to bovine serum albumin through its cysteine residue. RES‐oligomer can oxidize GSH to GSSG, indicating its pro‐oxidant activity. These results suggest that RES could be cytotoxic to melanocytes due to the binding of RES‐quinone to thiol proteins.     

Influence of N-glycosylation on effector functions and thermal stability of glycoengineered IgG1 monoclonal antibody with homogeneous glycoforms

Glycosylation of the conserved asparagine residue in each heavy chain of IgG in the CH2 domain is known as N-glycosylation. It is one of the most common post-translational modifications and important critical quality attributes of monoclonal antibody (mAb) therapeutics. Various studies have demonstrated the effects of the Fc N-glycosylation on safety, Fc effector functions, and pharmacokinetics, both dependent and independent of neonatal Fc receptor (FcRn) pathway. However, separation of various glycoforms to investigate the biological and functional relevance of glycosylation is a major challenge, and existing studies often discuss the overall impact of N-glycans, without considering the individual contributions of each glycoform when evaluating mAbs with highly heterogeneous distributions. In this study, chemoenzymatic glycoengineering incorporating an endo-β-N-acetylglucosaminidase (ENGase) EndoS2 and its mutant with transglycosylation activity was used to generate mAb glycoforms with highly homogeneous and well-defined N-glycans to better understand and precisely evaluate the effect of each N-glycan structure on Fc effector functions and protein stability. We demonstrated that the core fucosylation, non-reducing terminal galactosylation, sialylation, and mannosylation of IgG1 mAb N-glycans impact not only on FcγRIIIa binding, antibody-dependent cell-mediated cytotoxicity, and C1q binding, but also FcRn binding, thermal stability and propensity for protein aggregation.     

Non-genomic effects of aldosterone on intracellular ion regulation and cell volume in rat ventricular myocytes

Aldosterone has non-genomic effects that express within minutes and modulate intracellular ion milieu and cellular function. However, it is still undefined whether aldosterone actually alters intracellular ion concentrations or cellular contractility. To clarify the non-genomic effects of aldosterone, we measured [Na+]i, Ca2+ transient (CaT), and cell volume in dye-loaded rat ventricular myocytes, and we also evaluated myocardial contractility. We found the following: (i) aldosterone increased [Na+]i at the concentrations of 100 nmol/L to 10 micromol/L; (ii) aldosterone (up to 10 micromol/L) did not alter CaT and cell shortening in isolated myocytes, developed tension in papillary muscles, or left ventricular developed pressure in Langendorff-perfused hearts; (iii) aldosterone (100 nmol/L) increased the cell volume from 47.5 +/- 3.6 pL to 49.8 +/- 3.7 pL (n=8, p<0.05); (iv) both the increases in [Na+]i and cell volume were blocked by a Na+-K+-2Cl- co-transporter (NKCCl) inhibitor, bumetanide, or by a Na+/H+ exchange (NHE) inhibitor, 5-(N-ethyl-N-isopropyl) amiloride; and (v) spironolactone by itself increased in [Na+]i and cell volume. In conclusion, aldosterone rapidly increased [Na+]i and cell volume via NKCC1 and NHE, whereas there were no changes in CaT or myocardial contractility. Hence the non-genomic effects of aldosterone may be related to cell swelling rather than the increase in contractility.     

Potential utility of telmisartan, an angiotensin II type 1 receptor blocker with peroxisome proliferator-activated receptor-gamma (PPAR-gamma)-modulating activity for the treatment of cardiometabolic disorders

The metabolic syndrome is strongly associated with insulin resistance and consists of a constellation of factors such as hypertension and hyperlipidemia that raise the risk for cardiovascular diseases and diabetes mellitus. There is widespread agreement that the renin-angiotensin system (RAS) plays a pivotal role in the pathogenesis of insulin resistance and cardiovascular disease in diabetes. Indeed, large clinical trials have demonstrated substantial benefit of the blockade of this system for cardiovascular end-organ protection. Thus the blockade of the RAS may be a promising strategy for the treatment of the patients with the metabolic syndrome. Although several types of angiotensin II type 1 (AT(1)) receptor blockers (ARBs) are commercially available for the treatment of patients with hypertension, we have recently found that telmisartan (Micardis) could have the strongest binding affinity to AT(1) receptor. Further, telmisartan is reported to act as a partial agonist of peroxisome proliferator-activated receptor-gamma (PPAR-gamma). These observations suggest that, due to its unique PPAR-gamma-modulating activity, telmisartan may be one of the most promising sartans for the treatment of cardiometabolic disorders. In this paper, we reviewed the potential utility of telmisartan in insulin resistance and vascular complications in diabetes.     

AMPK mediates autophagy during myocardial ischemia in vivo

We have recently shown that autophagy is induced by ischemia and reperfusion in the mouse heart in vivo. Ischemia stimulates autophagy through an AMP activated protein kinase (AMPK)-dependent mechanism, whereas reperfusion after ischemia stimulates autophagy through a Beclin 1-dependent, but AMPK-independent, mechanism. Autophagy plays distinct roles during ischemia and reperfusion: autophagy may be protective during ischemia, whereas it may be detrimental during reperfusion. We will discuss the role of AMPK in mediating autophagy during myocardial ischemia in vivo.     

Sex Change in Protogynous Fish Red-Belted Anthias Pseudanthias rubrizonatus (Serranidae) in Kagoshima Bay,Japan

Journal of Ichthyology - The Serranidae are well known for protogynous sex change. The red-belted anthias Pseudanthias rubrizonatus inhabits Kagoshima Bay. We aimed to estimate the body size and...     

Transcriptome analysis of soybean (Glycine max) root genes differentially expressed in rhizobial,arbuscular mycorrhizal,and dual symbiosis

Journal of Plant Research - Soybean (Glycine max) roots establish associations with nodule-inducing rhizobia and arbuscular mycorrhizal (AM) fungi. Both rhizobia and AM fungi have been shown to...     

Genetic basis of a spontaneous mutation’s expressivity

Genetic background often influences the phenotypic consequences of mutations, resulting in variable expressivity. How standing genetic variants collectively cause this phenomenon is not fully understood. Here, we comprehensively identify loci in a budding yeast cross that impact the growth of individuals carrying a spontaneous missense mutation in the nuclear-encoded mitochondrial ribosomal gene MRP20. Initial results suggested that a single large effect locus influences the mutation’s expressivity, with 1 allele causing inviability in mutants. However, further experiments revealed this simplicity was an illusion. In fact, many additional loci shape the mutation’s expressivity, collectively leading to a wide spectrum of mutational responses. These results exemplify how complex combinations of alleles can produce a diversity of qualitative and quantitative responses to the same mutation.     

A novel serine/threonine kinase gene,Gek1, is expressed in meiotic testicular germ cells and primordial germ cells

We have isolated a novel serine/threonine kinase gene designated Gek1 from mouse primordial germ cell-derived embryonic germ cell. Gek1 is preferentially expressed in meiotic testicular germ cells and primordial germ cells. Gek1 mRNA is also detected in several other tissues, including hematopoietic organs in adult mice and central nervous system in embryos. The Gek1 cDNA encodes a protein with the consensus sequence of the catalytic domain of protein kinases in its N-terminal region. The deduced amino acid sequence of Gek1 in the kinase domain is related to those encoded by the Saccharomyces cerevisiae STE20, CDC15, and Drosophila melanogaster ninaC. The patterns of expression and the structural features of Gek1 suggest that the gene product is involved in signal transduction or nuclear division of germ cells and other proliferating cells. We also show that Gek1 locates on chromosome 11, near the wr locus, showing neuronal and reproductive defects. © 1996 Wiley-Liss, Inc.