Prevention of cataract in diabetic mice by topical pyruvate

KR Hegde1,3, S Kovtun1, SD Varma1,21Ophthalmology and Visual Sciences, 2Biochemistry and Molecular Biology, University of Maryland School of Medicine, 3Coppin State University, Department of Natural Sciences, Baltimore, MD, USABackground: It has been previously reported that oral administration of sodium pyruvate inhibits oxidative stress and cataract formation in diabetic animals. With a view to exploring the clinical usefulness of these findings, this study examined its preventive effect when administered topically as an eye drop.Methods: Diabetes was induced by intraperitoneal injections of streptozotocin. At the onset of diabetes, an eye drop preparation containing 2.5% sodium pyruvate was administered six times a day at 90-minute intervals. Treatment was continued for 6 weeks. Cataract formation was monitored ophthalmoscopically after mydriasis with 1% tropicamide eye drops. Subsequently, the treated and untreated diabetic animals and the age-matched normal controls were euthanized, their eyes enucleated, and the lenses isolated for biochemical assessment of protein glycation and glutathione levels.Results: Treatment with pyruvate eye drops was found to be significantly effective in inhibiting protein glycation. Glutathione levels were also better maintained. In addition, ophthalmoscopic examination revealed that the incidence of cataract in the pyruvate-treated group was only 12% as compared with the untreated diabetics in whom the incidence was 73%. Cataracts at this stage were largely equatorial.Conclusion: The results demonstrate that topical application of pyruvate can potentially be useful in attenuating or preventing cataract formation induced by diabetes and other conditions of oxidative stress.Keywords: pyruvate eye drops, diabetic cataract, protein glycation, oxidative stres

The human DNA glycosylases NEIL1 and NEIL3 excise psoralen-induced DNA-DNA cross-links in a four-stranded DNA structure

Interstrand cross-links (ICLs) are highly cytotoxic DNA lesions that block DNA replication and transcription by preventing strand separation. Previously, we demonstrated that the bacterial and human DNA glycosylases Nei and NEIL1 excise unhooked psoralen-derived ICLs in three-stranded DNA via hydrolysis of the glycosidic bond between the crosslinked base and deoxyribose sugar. Furthermore, NEIL3 from Xenopus laevis has been shown to cleave psoralen- and abasic site-induced ICLs in Xenopus egg extracts. Here we report that human NEIL3 cleaves psoralen-induced DNA-DNA cross-links in three-stranded and four-stranded DNA substrates to generate unhooked DNA fragments containing either an abasic site or a psoralen-thymine monoadduct. Furthermore, while Nei and NEIL1 also cleave a psoralen-induced four-stranded DNA substrate to generate two unhooked DNA duplexes with a nick, NEIL3 targets both DNA strands in the ICL without generating single-strand breaks. The DNA substrate specificities of these Nei-like enzymes imply the occurrence of long uninterrupted three- and four-stranded crosslinked DNA-DNA structures that may originate in vivo from DNA replication fork bypass of an ICL. In conclusion, the Nei-like DNA glycosylases unhook psoralen-derived ICLs in various DNA structures via a genuine repair mechanism in which complex DNA lesions can be removed without generation of highly toxic double-strand breaks

Low glucose under hypoxic conditions induces unfolded protein response and produces reactive oxygen species in lens epithelial cells

Aging is enhanced by hypoxia and oxidative stress. As the lens is located in the hypoglycemic environment under hypoxia, aging lens with diabetes might aggravate these stresses. This study was designed to examine whether low glucose under hypoxic conditions induces the unfolded protein response (UPR), and also if the UPR then generates the reactive oxygen species (ROS) in lens epithelial cells (LECs). The UPR was activated within 1 h by culturing the human LECs (HLECs) and rat LECs in <1.5 mM glucose under hypoxic conditions. These conditions also induced the Nrf2-dependent antioxidant-protective UPR, production of ROS, and apoptosis. The rat LECs located in the anterior center region were the least susceptible to the UPR, whereas the proliferating LECs in the germinative zone were the most susceptible. Because the cortical lens fiber cells are differentiated from the LECs after the onset of diabetes, we suggest that these newly formed cortical fibers have lower levels of Nrf2, and are then oxidized resulting in cortical cataracts. Thus, low glucose and oxygen conditions induce the UPR, generation of ROS, and expressed the Nrf2 and Nrf2-dependent antioxidant enzymes at normal levels. But these cells eventually lose reduced glutathione (GSH) and induce apoptosis. The results indicate a new link between hypoglycemia under hypoxia and impairment of HLEC functions

Ptc6 is required for proper rapamycin-induced down-regulation of the genes coding for ribosomal and rRNA processing proteins in S. cerevisiae

Ptc6 is one of the seven components (Ptc1-Ptc7) of the protein phosphatase 2C family in the yeast Saccharomyces cerevisiae. In contrast to other type 2C phosphatases, the cellular role of this isoform is poorly understood. We present here a comprehensive characterization of this gene product. Cells lacking Ptc6 are sensitive to zinc ions, and somewhat tolerant to cell-wall damaging agents and to Li+. Ptc6 mutants are sensitive to rapamycin, albeit to lesser extent than ptc1 cells. This phenotype is not rescued by overexpression of PTC1 and mutation of ptc6 does not reproduce the characteristic geneti

Orally Active Multi-Functional Antioxidants Delay Cataract Formation in Streptozotocin (Type 1) Diabetic and Gamma-Irradiated Rats

Age-related cataract is a worldwide health care problem whose progression has been linked to oxidative stress and the accumulation of redox-active metals. Since there is no specific animal model for human age-related cataract, multiple animal models must be used to evaluate potential therapies that may delay and/or prevent cataract formation.Proof of concept studies were conducted to evaluate 4-(5-hydroxypyrimidin-2-yl)-N,N-dimethyl-3,5-dioxopiperazine-1-sulfonamide (compound 4) and 4-(5-hydroxy-4,6-dimethoxypyrimidin-2-yl)-N,N-dimethyl-3,5-dioxopiperazine-1-sulfonamide (compound 8), multi-functional antioxidants that can independently chelate redox metals and quench free radicals, on their ability to delay the progression of diabetic "sugar" cataracts and gamma radiation-induced cataracts. Prior to 15 Gy of whole head irradiation, select groups of Long Evans rats received either diet containing compound 4 or 8, or a single i.p. injection of panthethine, a radioprotective agent. Compared to untreated, irradiated rats, treatment with pantethine, 4 and 8 delayed initial lens changes by 4, 47, and 38 days, respectively, and the average formation of posterior subcapsular opacities by 23, 53 and 58 days, respectively. In the second study, select groups of diabetic Sprague Dawley rats were administered chow containing compounds 4, 8 or the aldose reductase inhibitor AL1576. As anticipated, treatment with AL1576 prevented cataract by inhibiting sorbitol formation in the lens. However, compared to untreated rats, compounds 4 and 8 delayed vacuole formation by 20 days and 12 days, respectively, and cortical cataract formation by 8 and 3 days, respectively, without reducing lenticular sorbitol. Using in vitro lens culture in 30 mM xylose to model diabetic "sugar" cataract formation, western blots confirmed that multi-functional antioxidants reduced endoplasmic reticulum stress.Multi-functional antioxidants delayed cataract formation in two diverse rat models. These studies provide a proof of concept that a general cataract treatment focused on reducing oxidative stress instead of a specific mechanism of cataractogenesis can be developed

Tumor immunosurveillance in human cancers

Until now, the anatomic extent of tumor (TNM classification) has been by far the most important factor to predict the prognosis of colorectal cancer patients. However, in recent years, data collected from large cohorts of human cancers demonstrated that the immune contexture of the primary tumors is an essential prognostic factor for patients’ disease-free and overall survival. Tumoral and immunological markers predicted by systems biology methods are involved in the shaping of an efficient immune reaction and can serve as targets for novel therapeutic approaches. Global analysis of tumor microenvironment showed that the nature, the functional orientation, the density, and the location of adaptive immune cells within distinct tumor regions influence the risk of relapse events. The density and the immune cell location within the tumor have a prognostic value that is superior to the TNM classification, and tumor invasion is statistically dependent on the host-immune reaction. Thus, the strength of the immune reaction could advance our understanding of cancer evolution and have important consequences in clinical practice

Combined measurements of Higgs boson couplings in proton- proton collisions at v s=13TeV

Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton-proton collision data set recorded with the CMS detector in 2016 at fb-1. The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a W or Z boson, or a top quark-antiquark pair) and the following decay modes: H, ZZ, WW, , bb, and . Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be =1.17 +/- 0.10, assuming a Higgs boson mass of 125.09. Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.Peer reviewe