MMR/c-Abl-dependent activation of ING2/p73α signaling regulates the cell death response to N-methyl-N′-nitro-N-nitrosoguanidine

Agents inducing O⁶-methylguanine (O⁶MeG) in DNA such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) are cytotoxic and a deficiency in mismatch repair (MMR) results in lack of sensitivity to this genotoxin (termed alkylation tolerance). Here, we show that ING2, a member of the inhibitor of growth family, is required for cell death induced by MNNG. We further observe that MNNG treatment increases cellular protein levels of ING2 that is dependent on intact MMR function and that MNNG-induced ING2 localizes and associates with p73α in the nucleus. Suppression of ING2 by short hairpin RNA (shRNA) in MMR-proficient colorectal cancer cells decreased its sensitivity to MNNG and, in addition, abrogated MNNG-induced stabilization and acetylation of p73α. Interestingly, suppression of p73α had a greater impact on MNNG-induced cell death than ING2 leading us to conclude that ING2 regulates the cell death response, in part, through p73α. Inhibition of c-Abl by STI571 or suppression of c-Abl expression by shRNA blocked ING2 induction and p73α acetylation induced by this alkylator. Similarly, suppression of MMR (MLH1) by shRNA abrogated ING2 induction/p73α acetylation. Taken together, these results demonstrate that MLH1/c-Abl-dependent activation of ING2 > p73α signaling regulates cell death triggered by MNNG and further suggests that dysregulation of this event may, in part, be responsible for alkylation tolerance observed in MMR compromised cells.     

Tethering identifies fragment that yields potent inhibitors of human caspase-1

Disulfide Tethering was applied to the active site of human caspase-1, resulting in the discovery of a novel, tricyclic molecular fragment that selectively binds in S4. This fragment was developed into a class of potent inhibitors of human caspase-1. Several key analogues determined the optimal distance of the tricycle from the catalytic residues, the relative importance of various features of the tricycle, and the importance of the linker.     

Aspartate 102 in the heme domain of soluble guanylyl cyclase has a key role in NO activation

Nitric oxide (NO) is involved in the physiology and pathophysiology of the cardiovascular and neuronal systems via activation of soluble guanylyl cyclase (sGC), a heme-containing heterodimer. Recent structural studies have allowed a better understanding of the residues that dictate the affinity and binding of NO to the heme and the resulting breakage of the bond between the heme iron and histidine 105 (H105) of the β subunit of sGC. Still, it is unknown how the breakage of the iron-His bond translates into NO-dependent increased catalysis. Structural studies on homologous H-NOX domains in various states pointed to a role for movement of the H105 containing αF helix. Our modeling of the heme-binding domain highlighted conserved residues in the vicinity of H105 that could potentially regulate the extent to which the αF helix shifts and/or propagate the activation signal once the covalent bond with H105 has been broken. These include a direct interaction of αF helix residue aspartate 102 (D102) with the backbone nitrogen of F120. Mutational analysis of this region points to an essential role of the interactions in the vicinity of H105 for heme stability and identifies D102 as having a key role in NO activation following breakage of the iron-His bond.     

Discovery of a novel class of covalent inhibitor for aldehyde dehydrogenases

Human aldehyde dehydrogenases (ALDHs) comprise a family of 17 homologous enzymes that metabolize different biogenic and exogenic aldehydes. To date, there are relatively few general ALDH inhibitors that can be used to probe the contribution of this class of enzymes to particular metabolic pathways. Here, we report the discovery of a general class of ALDH inhibitors with a common mechanism of action. The combined data from kinetic studies, mass spectrometric measurements, and crystallographic analyses demonstrate that these inhibitors undergo an enzyme-mediated β-elimination reaction generating a vinyl ketone intermediate that covalently modifies the active site cysteine residue present in these enzymes. The studies described here can provide the basis for rational approach to design ALDH isoenzyme-specific inhibitors as research tools and perhaps as drugs, to address diseases such as cancer where increased ALDH activity is associated with a cellular phenotype.     

Problems in seawater industrial desalination processes and potential sustainable solutions: a review

Seawater desalination has significantly developed towards membrane technology than phase change process during last decade. Seawater reverse osmosis (SWRO) in general is the most familiar process due to higher water recovery and lower energy consumption compared to other available desalination processes. Despite major advancements in SWRO technology, desalination industry is still facing significant amount of practical issues. Therefore, the potentials and problems faced by current SWRO industries and essential study areas are discussed in this review for the benefit of desalination industry. It is important to consider all the following five components in SWRO process i.e. (1) intake (2) pre-treatment (3) high pressure pumping (4) membrane separation (performance of membranes and brine disposal) and (5) product quality. Development of higher corrosion resistant piping materials or coating materials, valves, and pumps is believed to be in higher research demand. Furthermore, brine management, that includes brine disposal and resource recovery need further attention. Pre-treatment sludge management and reduced cleaning in place flush volume will reduce the capital costs associated with evaporation ponds and the maintenance costs associated with disposal and transportation reducing the unit cost of water.     

Grape seed proanthocyanidins and metformin act by different mechanisms to promote insulin signaling in rats fed high calorie diet

Key pathways like insulin signaling, AMP activated kinase (AMPK) activation and inflammatory signaling are involved in the complex pathological network of hepatic insulin resistance. Our aim is to investigate whether grape seed proanthocyanidins (GSP) and metformin (MET) target any of these pathways in insulin resistant rat liver. Albino Wistar rats were rendered insulin resistant by feeding a high fat-fructose diet (HFFD). Either GSP (100 mg/kg b.w), MET(50 mg/kg b.w) or both were administered to insulin resistant rats as therapeutic options. HFFD-feeding caused hyperglycemia, hyperinsulinemia, increased gluconeogenesis, decreased tyrosine phosphorylation of insulin receptor-β(IR-β) and insulin receptor substrate-1 (IRS-1) and increased serine phosphorylation of IRS-1. The association of p85α subunit of phosphotidyl inositol 3 kinase(PI3K) with IRS-1 and subsequent Akt phosphorylation were reduced while the expression of mitogen activated protein kinases (MAPK) were increased in HFFD rats. Both MET and GSP reduced hyperglycemia and hyperinsulinemia and improved glycolysis, tyrosine phosphorylation of IR-β and IRS-1, IRS-1-PI3K association and Akt activation. However, activation of tumor necrosis factor-α, interleukin-6, leptin and suppressor of cytokine signaling-3 and reduction in adiponectin caused by chronic HFFD feeding were reversed by GSP better than by MET. Activation of AMPK by GSP was much less compared to that by MET. These findings suggest that GSP might activate PI3K pathway and promote insulin action by reducing serine kinase activation and cytokine signaling and MET by targeting AMPK. The beneficial effects were enhanced during combination therapy. Thus, combination therapy with MET and GSP may be considered for the management of metabolic syndrome.     

Bioavailability and metabolism of fucoxanthin in rats: structural characterization of metabolites by LC-MS (APCI)

This study reports bioavailability and metabolism of fucoxanthin (FUCO) from brown algae Padina tetrastromatica in rats. Rats were divided into two groups (n = 25/group). Group one was fed basal diet (control) while the group two received retinol deficient diet (RD group) for 8 weeks. After confirmed RD in blood (0.53 μmol/l), rats were further sub-grouped (n = 5/sub group), intubated a dose of FUCO (0.83 μmol) and killed after 0, 2, 4, 6 and 8 h. The plasma levels (area under curve/8 h) of FUCO (fucoxanthinol (FUOH) + amarouciaxanthin (AAx)) was 2.93 (RD group) and 2.74 pmol/dl (control), respectively. No newly formed retinol was detected in RD rats intubated with FUCO. Besides FUOH (m/z 617 (M+H)⁺) and AAx (m/z 617 (M+H^?)⁺), other deacetylated, hydrolyzed and demethylated metabolites of bearing molecular mass at m/z 600.6 (FUOH–H₂O), m/z 597 (AAx–H₂O), m/z 579 (AAx–2H₂O+1), m/z 551 (AAx–2H₂O–2CH₃+2) and m/z 523 (AAx–2H₂O–4CH₃+4) were also detected in plasma and liver by LC-MS (APCI). Although biological functions of FUCO metabolites need thorough investigation, this is the first detailed report on FUCO metabolites in rats.     

Discovery of a potent and selective aurora kinase inhibitor

This communication describes the discovery of a novel series of Aurora kinase inhibitors. Key SAR and critical binding elements are discussed. Some of the more advanced analogues potently inhibit cellular proliferation and induce phenotypes consistent with Aurora kinase inhibition. In particular, compound 21 (SNS-314) is a potent and selective Aurora kinase inhibitor that exhibits significant activity in pre-clinical in vivo tumor models.     

Psoralen production in hairy roots and adventitious roots cultures of Psoralea coryfolia

Psoralea corylifolia is an endangered plant producing various compounds of medical importance. Adventitious roots and hairy roots were induced in cultures prepared from hypocotyl explants. Psoralen content was evaluated in both root types grown either in suspension cultures or on agar solidified medium. Psoralen content was ~3 mg g⁻¹ DW in suspension grown hairy roots being higher than in solid grown hairy roots and in solid and suspension-grown adventitious roots.