NEIL2-initiated, APE-independent repair of oxidized bases in DNA: Evidence for a repair complex in human cells

DNA glycosylases/AP lyases initiate repair of oxidized bases in the genomes of all organisms by excising these lesions and then cleaving the DNA strand at the resulting abasic (AP) sites and generate 3' phospho alpha,beta-unsaturated aldehyde (3' PUA) or 3' phosphate (3' P) terminus. In Escherichia coli, the AP-endonucleases (APEs) hydrolyze both 3' blocking groups (3' PUA and 3' P) to generate the 3'-OH termini needed for repair synthesis. In mammalian cells, the previously characterized DNA glycosylases, NTH1 and OGG1, produce 3' PUA, which is removed by the only AP-endonuclease, APE1. However, APE1 is barely active in removing 3' phosphate generated by the recently discovered mammalian DNA glycosylases NEIL1 and NEIL2. We showed earlier that the 3' phosphate generated by NEIL1 is efficiently removed by polynucleotide kinase (PNK) and not APE1. Here we show that the NEIL2-initiated repair of 5-hydroxyuracil (5-OHU) similarly requires PNK. We have also observed stable interaction between NEIL2 and other BER proteins DNA polymerase beta (Pol beta), DNA ligase IIIalpha (Lig IIIalpha) and XRCC1. In spite of their limited sequence homology, NEIL1 and NEIL2 interact with the same domains of Pol beta and Lig IIIalpha. Surprisingly, while the catalytically dispensable C-terminal region of NEIL1 is the common interacting domain, the essential N-terminal segment of NEIL2 is involved in analogous interaction. The BER proteins including NEIL2, PNK, Pol beta, Lig IIIalpha and XRCC1 (but not APE1) could be isolated as a complex from human cells, competent for repair of 5-OHU in plasmid DNA.     

Effect of berberine on the antioxidant status, ultrastructural modifications and protein bound carbohydrates in azoxymethane-induced colon cancer in rats

Chemically induced carcinogenesis models in the rat are widely used for studying the biology of cancer and for developing and evaluating cancer prevention strategies. The azoxymethane(AOM)-induced rat colon tumor is a valuable tool for studying the interaction between tumor development and exogenous factors. Malignant conditions are characterized by enhanced levels of lipid peroxidative products, protein bound carbohydrates indicative of membrane damage and an ineffective antioxidant scavenging system. In the present study, AOM-induced rat showed lipid peroxidative damage, alterations in the membrane glycoprotein component and antioxidant defense system, along with ultrastructural changes like disruption in goblet cell and its membrane, swollen mitochondria with cristae dispersed, elongated endoplasmic reticulum and other features of neoplastic invasion. Berberine significantly attenuated the increases in lipid peroxidation, protein bound carbohydrates and enhanced the antioxidative status. The present study suggests that berberine prevents the appearance of malignant morphology and ultrastructural changes of AOM induced cancer by producing apoptosis like changes. Thus berberine inhibits neoplastic transformation by the induction of antioxidant defence system and ability to induce apoptotic like changes—thus elucidating its anti cancer role.     

Mitoapocynin,a mitochondria targeted derivative of apocynin induces mitochondrial ROS generation and apoptosis in multiple cell types including cardiac myoblasts: a potential constraint to its therapeutic use

Mitoapocynin is a triphenylphosphonium conjugated derivative of apocynin that specifically locates to the mitochondria. It has been developed as a mitochondrially targeted therapeutic antioxidant. We attempted to attenuate the mitochondrial ROS induced in H9c2 cardiac myoblast cells treated with norepinephrine. Mitoapocynin was a poor quencher of total ROS as detected by the fluoroprobe DCFH-DA. Using mitochondrial superoxide specific probe MitoSoxRed, we found that 5–10 µM mitoapocynin itself induces superoxide over and above that is generated by the norepinephrine treatment. A supposedly control molecule to mitoapocynin, the synthetic compound PhC11TPP, having the triphenylphosphonium group and a benzene moiety with C11 aliphatic chain spacer was also found to be a robust inducer of mitochondrial ROS. Subsequent assays with several cell lines viz., NIH3T3, HEK293, Neuro2A, MCF-7 and H9c2, showed that prolonged exposure to mitoapocynin induces cell death by apoptosis that can be partially prevented by the general antioxidant N-acetyl cysteine. Analyses of mitochondrial electron transport complexes by Blue Native Polyacrylamide gel electrophoresis showed that both mitoapocynin and PhC11TPP disrupt the mitochondrial Complex I and V, and in addition, PhC11TPP also damages the Complex IV. Our data thus highlights the limitations of the therapeutic use of mitoapocynin as an antioxidant.

     

Host Defense and Recruitment of Foxp3+ T Regulatory Cells to the Lungs in Chronic Mycobacterium tuberculosis Infection Requires Toll-like Receptor 2

Acute resistance to low dose M. tuberculosis (Mtb) infection is not dependent on Toll-like receptor (TLR) 2. However, whether TLR2 contributes to resistance in chronic Mtb infection has remained uncertain. Here we report that, following low dose aerosol infection with Mtb, mice lacking TLR2 (TLR2KO), in comparison with wild type (WT) mice, exhibit enhanced cellular infiltration and inflammation in the lungs, and fail to stably control bacterial burden during chronic infection. IFNγ and IL-17 was expressed at equivalent levels in the two groups; however, the characteristic accumulation of Foxp3⁺ T regulatory cells (Tregs) in pulmonary granulomas was significantly reduced in TLR2KO mice. Nonetheless, this reduction in Tregs was independent of whether Tregs expressed TLR2 or not. To directly link the reduced number of Tregs to the increased inflammation present in the TLR2KO mice, we used a macrophage adoptive transfer model. At seven weeks post-Mtb infection, TLR2KO mice, which were adoptively transferred with WT macrophages, displayed enhanced accumulation of Tregs in the lungs and a concomitant reduction in inflammation in contrast with control mice that received TLR2KO macrophages. However, the pulmonary bacterial burden between the two groups remained similar indicating that TLR2''s role in modulating immunopathology is functionally distinct from its role in restricting Mtb growth in chronic infection. Together, these findings unequivocally demonstrate that TLR2 contributes to host resistance against chronic Mtb infection and reveal a novel role for TLR2 in mediating the recruitment of Foxp3⁺ Tregs to the lungs to control inflammation.     

PHYTOREMEDIATION POTENTIAL OF VETIVER GRASS [CHRYSOPOGON ZIZANIOIDES (L.)] FOR TETRACYCLINE

The presence of veterinary and human antibiotics in soil and surface water is an emerging environmental concern. The current study was aimed at evaluating the potential of using vetiver grass as a phytoremediation agent in removing Tetracycline (TC) from aqueous media. The study determined uptake, translocation, and transformation of TC in vetiver grass as function of initial antibiotic concentrations and exposure time. Vetiver plants were grown for 60 days in a greenhouse in TC contaminated hydroponic system. Preliminary results show that complete removal of tetracycline occurred within 40 days in all TC treatments. Initial concentrations of TC had significant effect (p < 0.0001) on the kinetics of removal. Tetracycline was detected in the root as well as shoot tissues, confirming uptake and root-to-shoot translocation. Liquid-chromatography-tandem-mass-spectrometry analysis of plant tissue samples suggest presence of metabolites of TC in both root and shoot tissues of vetiver grass. The current data is encouraging and is expected to aid in developing a cost-effective, in-situ phytoremediation technique to remove TC group of antibiotics from wastewater.     

Interaction between surface shape and intra-surface viscous flow on lipid membranes

The theory of intra-surface viscous flow on lipid bilayers is developed by combining the equations for flow on a curved surface with those that describe the elastic resistance of the bilayer to flexure. The model is derived directly from balance laws and augments an alternative formulation based on a variational principle. Conditions holding along an edge of the membrane are emphasized, and the coupling between flow and membrane shape is simulated numerically.     

The Effect of PPE-Induced Emphysema and Chronic LPS-Induced Pulmonary Inflammation on Atherosclerosis Development in APOE*3-LEIDEN Mice

Background

Chronic obstructive pulmonary disease (COPD) is characterized by pulmonary inflammation, airways obstruction and emphysema, and is a risk factor for cardiovascular disease (CVD). However, the contribution of these individual COPD components to this increased risk is unknown. Therefore, the aim of this study was to determine the contribution of emphysema in the presence or absence of pulmonary inflammation to the increased risk of CVD, using a mouse model for atherosclerosis. Because smoke is a known risk factor for both COPD and CVD, emphysema was induced by intratracheal instillation of porcine pancreatic elastase (PPE).

Methods

Hyperlipidemic APOE*3-Leiden mice were intratracheally instilled with vehicle, 15 or 30 µg PPE and after 4 weeks, mice received a Western-type diet (WTD). To study the effect of emphysema combined with pulmonary inflammation on atherosclerosis, mice received 30 µg PPE and during WTD feeding, mice were intranasally instilled with vehicle or low-dose lipopolysaccharide (LPS; 1 µg/mouse, twice weekly). After 20 weeks WTD, mice were sacrificed and emphysema, pulmonary inflammation and atherosclerosis were analysed.

Results

Intratracheal PPE administration resulted in a dose-dependent increase in emphysema, whereas atherosclerotic lesion area was not affected by PPE treatment. Additional low-dose intranasal LPS administration induced a low-grade systemic IL-6 response, as compared to vehicle. Combining intratracheal PPE with intranasal LPS instillation significantly increased the number of pulmonary macrophages and neutrophils. Plasma lipids during the study were not different. LPS instillation caused a limited, but significant increase in the atherosclerotic lesion area. This increase was not further enhanced by PPE.

Conclusion

This study shows for the first time that PPE-induced emphysema both in the presence and absence of pulmonary inflammation does not affect atherosclerotic lesion development.     

Ablation of SGK1 Impairs Endothelial Cell Migration and Tube Formation Leading to Decreased Neo-Angiogenesis Following Myocardial Infarction

Serum and glucocorticoid inducible kinase 1 (SGK1) plays a pivotal role in early angiogenesis during embryonic development. In this study, we sought to define the SGK1 downstream signalling pathways in the adult heart and to elucidate their role in cardiac neo-angiogenesis and wound healing after myocardial ischemia. To this end, we employed a viable SGK1 knockout mouse model generated in a 129/SvJ background. Ablation of SGK1 in these mice caused a significant decrease in phosphorylation of SGK1 target protein NDRG1, which correlated with alterations in NF-κB signalling and expression of its downstream target protein, VEGF-A. Disruption of these signalling pathways was accompanied by smaller heart and body size. Moreover, the lack of SGK1 led to defective endothelial cell (ECs) migration and tube formation in vitro, and increased scarring with decreased angiogenesis in vivo after myocardial infarct. This study underscores the importance of SGK1 signalling in cardiac neo-angiogenesis and wound healing after an ischemic insult in vivo.