Synthesis and characterization of oligonucleotides containing 2′-fluorinated thymidine glycol as inhibitors of the endonuclease III reaction

Endonuclease III (Endo III) is a base excision repair enzyme that recognizes oxidized pyrimidine bases including thymine glycol. This enzyme is a glycosylase/lyase and forms a Schiff base-type intermediate with the substrate after the damaged base is removed. To investigate the mechanism of its substrate recognition by X-ray crystallography, we have synthesized oligonucleotides containing 2′-fluorothymidine glycol, expecting that the electron-withdrawing fluorine atom at the 2′ position would stabilize the covalent intermediate, as observed for T4 endonuclease V (Endo V) in our previous study. Oxidation of 5′- and 3′-protected 2′-fluorothymidine with OsO(4) produced two isomers of thymine glycol. Their configurations were determined by NMR spectroscopy after protection of the hydroxyl functions. The ratio of (5R,6S) and (5S,6R) isomers was 3:1, whereas this ratio was 6:1 in the case of the unmodified sugar. Both of the thymidine glycol isomers were converted to the corresponding phosphoramidite building blocks and were incorporated into oligonucleotides. When the duplexes containing 2′-fluorinated 5R- or 5S-thymidine glycol were treated with Escherichia coli endo III, no stabilized covalent intermediate was observed regardless of the stereochemistry at C5. The 5S isomer was found to form an enzyme–DNA complex, but the incision was inhibited probably by the fluorine-induced stabilization of the glycosidic bond

Early Change in Urine Protein as a Surrogate End Point in Studies of IgA Nephropathy: An Individual-Patient Meta-analysis

Background The role of change in proteinuria as a surrogate end point for randomized trials in immunoglobulin A nephropathy (IgAN) has previously not been thoroughly evaluated. Study Design Individual patient–level meta-analysis. Setting & Population Individual-patient data for 830 patients from 11 randomized trials evaluating 4 intervention types (renin-angiotensin system [RAS] blockade, fish oil, immunosuppression, and steroids) examining associations between changes in urine protein and clinical end points at the individual and trial levels. Selection Criteria for Studies Randomized controlled trials of IgAN with measurements of proteinuria at baseline and a median of 9 (range, 5-12) months follow-up, with at least 1 further year of follow-up for the clinical outcome. Predictor 9-month change in proteinuria. Outcome Doubling of serum creatinine level, end-stage renal disease, or death. Results Early decline in proteinuria at 9 months was associated with lower risk for the clinical outcome (HR per 50% reduction in proteinuria, 0.40; 95% CI, 0.32-0.48) and was consistent across studies. Proportions of treatment effect on the clinical outcome explained by early decline in proteinuria were estimated at 11% (95% CI, −19% to 41%) for RAS blockade and 29% (95% CI, 6% to 53%) for steroid therapy. The direction of the pooled treatment effect on early change in proteinuria was in accord with the direction of the treatment effect on the clinical outcome for steroids and RAS blockade. Trial-level analyses estimated that the slope for the regression line for the association of treatment effects on the clinical end points and for the treatment effect on proteinuria was 2.15 (95% Bayesian credible interval, 0.10-4.32). Limitations Study population restricted to 11 trials, all having fewer than 200 patients each with a limited number of clinical events. Conclusions Results of this analysis offer novel evidence supporting the use of an early reduction in proteinuria as a surrogate end point for clinical end points in IgAN in selected settings

A randomized controlled trial of mycophenolate mofetil in patients with IgA nephropathy [ISRCTN62574616]

BACKGROUND: IgAN is the most common type of glomerulonephritis in the world. Between 15 and 40 percent of adults and children diagnosed with IgAN eventually progress to ESRD. Despite the need for effective treatment strategies, very few RCTs for IgAN have been performed. The most effective therapies for IgAN appear to be corticosteroids, ACEi, and FOS that contain a high concentration of omega 3 fatty acids. While ACEi and FOS are generally well tolerated with minimal side effects, the use of high dose steroids over a long course of therapy is often associated with significant morbidity. OBJECTIVE OF THE STUDY: The objective of the study is to test the hypothesis that treatment with the immunosuppressive agent, MMF, will lead to significant and sustained improvement in urinary protein excretion in patients with IgAN who have been pre-treated (and continue to be treated) with ACE(i )and FOS compared to a placebo control group of patients receiving comparable doses of ACEi and FOS without MMF. DESIGN: After a three month treatment period with the ACEi, lisinopril and the FOS, Omacor(®), 100 (2 × 50) patients with IgAN and a urinary P/C ratio ≥ 0.6 (males) and ≥ 0.8 (females) and an estGFR ≥ 40 ml/min/1.73 m2 will be randomized to treatment with either MMF or placebo for one year. All patients will be followed off study drug for a second year, but will continue treatment with lisinopril and Omacor(® )for the two year duration of the study. The primary outcome measure of change in urine P/C ratio will be assessed at the end of years one and two

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

Steroids in the Treatment of IgA Nephropathy to the Improvement of Renal Survival: A Systematic Review and Meta-Analysis

Studies have shown that steroids can improve kidney survival and decrease the risk of proteinuria in patients with Immunoglobulin A nephropathy, but the overall benefit of steroids in the treatment of Immunoglobulin A nephropathy remains controversial. The aim of this study was to evaluate the benefits and risks of steroids for renal survival in adults with Immunoglobulin A nephropathy.We searched the Cochrane Renal Group Specialized Register, Cochrane Controlled Trial Registry, MEDLINE and EMBASE databases. All eligible studies were measuring at least one of the following outcomes: end-stage renal failure, doubling of serum creatinine and urinary protein excretion. Fifteen relevant trials (n = 1542) that met our inclusion criteria were identified. In a pooled analysis, steroid therapy was associated with statistically significant reduction of the risk in end-stage renal failure (RR: 0.46, 95% CI: 0.27 to 0.79), doubling of serum creatinine (RR = 0.34, 95%CI = 0.15 to 0.77) and reduced urinary protein excretion (MD = −0.47g/day, 95%CI = −0.64 to −0.31).We identified that steroid therapy was associated with a decrease of proteinuria and with a statistically significant reduction of the risk in end-stage renal failure. Moreover, subgroup analysis also suggested that long-term steroid therapy had a higher efficiency than standard and short term therapy

Hydrogen in Drinking Water Reduces Dopaminergic Neuronal Loss in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine Mouse Model of Parkinson's Disease

It has been shown that molecular hydrogen (H2) acts as a therapeutic antioxidant and suppresses brain injury by buffering the effects of oxidative stress. Chronic oxidative stress causes neurodegenerative diseases such as Parkinson's disease (PD). Here, we show that drinking H2-containing water significantly reduced the loss of dopaminergic neurons in PD model mice using both acute and chronic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The concentration-dependency of H2 showed that H2 as low as 0.08 ppm had almost the same effect as saturated H2 water (1.5 ppm). MPTP-induced accumulation of cellular 8-oxoguanine (8-oxoG), a marker of DNA damage, and 4-hydroxynonenal (4-HNE), a marker of lipid peroxidation were significantly decreased in the nigro-striatal dopaminergic pathway in mice drinking H2-containing water, whereas production of superoxide (O2•−) detected by intravascular injection of dihydroethidium (DHE) was not reduced significantly. Our results indicated that low concentration of H2 in drinking water can reduce oxidative stress in the brain. Thus, drinking H2-containing water may be useful in daily life to prevent or minimize the risk of life style-related oxidative stress and neurodegeneration

Epistatic Roles for Pseudomonas aeruginosa MutS and DinB (DNA Pol IV) in Coping with Reactive Oxygen Species-Induced DNA Damage

Pseudomonas aeruginosa is especially adept at colonizing the airways of individuals afflicted with the autosomal recessive disease cystic fibrosis (CF). CF patients suffer from chronic airway inflammation, which contributes to lung deterioration. Once established in the airways, P. aeruginosa continuously adapts to the changing environment, in part through acquisition of beneficial mutations via a process termed pathoadaptation. MutS and DinB are proposed to play opposing roles in P. aeruginosa pathoadaptation: MutS acts in replication-coupled mismatch repair, which acts to limit spontaneous mutations; in contrast, DinB (DNA polymerase IV) catalyzes error-prone bypass of DNA lesions, contributing to mutations. As part of an ongoing effort to understand mechanisms underlying P. aeruginosa pathoadaptation, we characterized hydrogen peroxide (H2O2)-induced phenotypes of isogenic P. aeruginosa strains bearing different combinations of mutS and dinB alleles. Our results demonstrate an unexpected epistatic relationship between mutS and dinB with respect to H2O2-induced cell killing involving error-prone repair and/or tolerance of oxidized DNA lesions. In striking contrast to these error-prone roles, both MutS and DinB played largely accurate roles in coping with DNA lesions induced by ultraviolet light, mitomycin C, or 4-nitroquinilone 1-oxide. Models discussing roles for MutS and DinB functionality in DNA damage-induced mutagenesis, particularly during CF airway colonization and subsequent P. aeruginosa pathoadaptation are discussed