Role of heme oxygenase in heme-mediated inhibition of rat brain Na+−K+-ATPase: Protection by tin-protoporphyrin

Hemoglobin has been shown to inhibit brain Na⁺–K⁺-ATPase through an iron-dependent mechanism. Both hemoglobin and iron cause spontaneous peroxidation of brain lipids. Release of iron from the heme molecule in animal tissues is dependent on the activity of heme oxygenase. We hypothesized that inhibition of heme catabolism by heme oxygenase prevents the iron-mediated inhibition of Na⁺–K⁺-ATPase and might subsequently reduce the tissue damage. Therefore, we studied the effect of heme and tin-protoporphyrin, an inhibitor of heme oxygenase, on the activity of partially purified Na⁺–K⁺-ATPase from rat brain in the presence and absence of purified hepatic heme oxygenase. Heme alone at a concentration of 30 M did not inhibit Na⁺–K⁺-ATPase. However, in the presence of heme oxygenase, heme inhibited Na⁺–K⁺-ATPase by 75%. Pretreatment of rats with SnCl₂, a known inducer of heme oxygenase, reduced the basal activity of the brain Na⁺–K⁺-ATPase by 50%. Inhibition of heme oxygenase by tin-protoporphyrin (30 M) prevented the inhibition of Na⁺–K⁺-ATPase which occurred in the presence of heme and heme oxygenase. It is concluded that suppression of heme oxygenase by tin-protoporphyrin might be a therapeutic approach to management of hemoglobin-associated brain injury following CNS hemorrhage.     

NMR probing of in silico identification of anti-HPV16 E7 mAb linear peptide epitope

A proteomics-based approach was exploited in order to individuate peptide sequences having the immunogenic potential to evoke humoral response. The epitope search utilized two parameters: the similarity level of the peptide sequence to the host's proteins, and the peptide capability to bind to the major histocompatibility complex class II molecules. By this approach, the human papillomavirus 16 E7(49-63) RAHYNIVTFCCKCDS peptide was individuated as the immunogenic epitope recognized by an anti-HPV16 E7 monoclonal antibody raised against the full-length viral oncoprotein. In this report, two-dimensional nuclear magnetic resonance spectroscopic experiments unequivocally probe the HPV16 E7 epitope individuation.     

Electrochemical sensor for guanine using a self-assembled monolayer of 1,8,15,22-tetraaminophthalocyanatonickel(II) on glassy carbon electrode

This article describes the selective determination of guanine (G) using the self-assembled monolayer (SAM) of 1,8,15,22-tetraaminophthalocyanatonickel(II) (4α-Ni(II)TAPc) modified glassy carbon electrode (GCE) in 0.2 M acetate buffer solution (pH 4.0). The SAM of 4α-Ni(II)TAPc was formed on GCE by spontaneous adsorption of 1 mM 4α-Ni(II)TAPc in dimethylformamide (DMF). It shows two pairs of redox waves corresponding to Ni(III)/Ni(II) and Ni(III)Pc(-1)/Ni(III)Pc(-2) in 0.2 M acetate buffer solution. The SAM modified electrode exhibits excellent electrocatalytic activity toward the oxidation of G by enhancing its oxidation current with 150 mV less positive potential shift in contrast to bare GCE. Furthermore, the SAM modified electrode selectively determines G in the presence of high concentration of adenine (A). In differential pulse voltammetry measurements, the oxidation current response of G was increased linearly in the concentration range of 10 to 100 μM, and a detection limit was found to be 3×10(-8)M (signal/noise=3).     

Protective effect of aminoguanidine against oxidative stress and bladder injury in cyclophosphamide‐induced hemorrhagic cystitis in rat

Cyclophosphamide (CP) is an antineoplastic agent that is used for the treatment of many neoplastic diseases. Hemorrhagic cystitis (HC) is a major dose limiting side effect of CP. Recent studies show that aminogaunidine, an inhibitor of inducible nitric oxide synthase is a potent antioxidant and prevents changes caused by oxidative stress such as depletion of antioxidant activity and tissue injury. The purpose of the study is to investigate the effect of aminoguanidine on parameters of oxidative stress, antioxidant enzymes and bladder injury caused by CP. Adult male rats were randomly divided into four groups. Control rats were administered saline; the AG control group received 200 mg/kg body wt of aminoguanidine; The CP group received a single injection of CP at the dose of 150 mg/kg body wt intraperitoneally. The CP + AG group received aminoguanidine (200 mg/kg body wt) intraperitoneally 1 h before the administration of CP. The rats were sacrificed 16 h after CP/saline administration. The bladder was used for light microscopic studies and biochemical studies. The markers of oxidative damage including protein carbonyl content, protein thiol, malondialdehyde and conjugated dienes were assayed in the homogenates along with the activities of the antioxidant enzymes, superoxide dismutase, glutathione peroxidase, catalase, and glutathione reductase and glutathione S transferase. In the bladders of CP treated rats edema of lamina propria with epithelial and sub‐epithelial hemorrhage was seen. All the parameters of oxidative stress that were studied were significantly elevated in the bladders of CP treated rats. The activities of the antioxidant enzymes were significantly lowered in the bladders of CP treated rats. Aminoguanidine pretreatment prevented CP‐induced oxidative stress, decrease in the activities of anti‐oxidant enzymes and reduced bladder damage. The results of the present study suggest the antioxidant role for aminoguanidine in CP‐induced bladder damage. Copyright © 2008 John Wiley & Sons, Ltd.     

Change in renal heme oxygenase expression in cyclosporine A-induced injury.

Cyclosporine A (CsA) is the first immunosuppressant used in allotransplantation. Its use is associated with side effects that include nephrotoxicity. This study explored the anatomic structures involved in CsA nephrotoxicity and the effect of heme oxygenase (HO) in preventing CsA injury. Rats were divided into four groups, which were treated with olive oil, CsA (15 mg/kg/day), CsA plus the HO inhibitor (SnMP; 30 microM/kg/day), and with the HO inducer (CoPP; 5 mg/100 g bw). Renal tissue was treated for morphological, biochemical, and immunohistochemical studies. CsA-treated rats showed degenerative changes with renal fibrosis localized mainly around proximal tubules. Collapsed vessels were sometimes seen in glomeruli. No HO-1 expression and increased expression of endothelin-1 (ET-1) were observed in CsA-treated rats compared with controls. In CsA plus SnMP-treated rats, HO-1 expression was further reduced and the morphology was not changed compared to the CsA group, whereas CsA plus CoPP-treated animals again showed normal morphology and with restoration and an increase in HO-1 levels. HO activity and immunohistochemical data showed similar alterations as HO expression. No changes were observed for HO-2 analysis. The observations indicate that HO-1 downregulation and ET-1 upregulation by CsA might be one mechanism underlying CsA-induced nephrotoxicity. Therefore, attempts to preserve HO levels attenuate CsA nephrotoxicity.     

Biosoftening of coir fiber using selected microorganisms

Coir fiber belongs to the group of hard structural fibers obtained from coconut husk. As lignin is the main constituent of coir responsible for its stiffness, microbes that selectively remove lignin without loss of appreciable amounts of cellulose are extremely attractive in biosoftening. Five isolated strains were compared with known strains of bacteria and fungi. The raw fiber treated with Pseudomonas putida and Phanerocheate chrysosporium produced better softened fiber at 30±2 °C and neutral pH. FeSO₄ and humic acid were found to be the best inducers for P. chrysosporium and P. putida, respectively, while sucrose and dextrose were the best C-sources for both. Biosoftening of unretted coir fibers was more advantageous than the retted fibers. Unlike the weak chemically softened fiber, microbial treatment produced soft, whiter fibers having better tensile strength and elongation (44.6–44.8%) properties. Scanning electron microscopy photos showed the mycelia penetrating the pores of the fiber, removing the tylose plug and degrading lignin.     

Healthy individuals that control a latent infection with Mycobacterium tuberculosis express high levels of Th1 cytokines and the IL-4 antagonist IL-4delta2

The majority of healthy individuals exposed to Mycobacterium tuberculosis will not develop disease and identifying what constitutes "protective immunity" is one of the holy grails of M. tuberculosis immunology. It is known that IFN-gamma is essential for protection, but it is also apparent that IFN-gamma levels alone do not explain the immunity/susceptibility dichotomy. The controversy regarding correlates of immunity persists because identifying infected but healthy individuals (those who are immune) has been problematic. We have therefore used recognition of the M. tuberculosis virulence factor early secretory antigenic target 6 to identify healthy, but infected individuals from tuberculosis (TB)-endemic and nonendemic regions (Ethiopia and Denmark) and have compared signals for cytokines expressed directly ex vivo with the pattern found in TB patients. We find that TB patients are characterized by decreased levels of Th1 cytokines and increased levels of IL-10 compared with the healthy infected and noninfected community controls. Interestingly, the healthy infected subjects exhibited a selective increase of message for the IL-4 antagonist, IL-4delta2, compared with both TB patients or noninfected individuals. These data suggest that long-term control of M. tuberculosis infection is associated not just with elevated Th1 responses but also with inhibition of the Th2 response.     

ATR functions as a gene dosage-dependent tumor suppressor on a mismatch repair-deficient background

The ataxia-telangiectasia mutated and rad3-related (ATR) kinase orchestrates cellular responses to DNA damage and replication stress. Complete loss of ATR function leads to chromosomal instability and cell death. However, heterozygous ATR mutations are found in human cancers with microsatellite instability, suggesting that ATR haploinsufficiency contributes to tumorigenesis. To test this possibility, we generated human cell line and mouse model systems in which a single ATR allele was inactivated on a mismatch repair (MMR)-deficient background. Monoallelic ATR gene targeting in MLH1-deficient HCT 116 colon carcinoma cells resulted in hypersensitivity to genotoxic stress accompanied by dramatic increases in fragile site instability, and chromosomal amplifications and rearrangements. The ATR(+/-) HCT 116 cells also displayed compromised activation of Chk1, an important downstream target for ATR. In complementary studies, we demonstrated that mice bearing the same Atr(+/-)/Mlh1(-/-) genotype were highly prone to both embryonic lethality and early tumor development. These results demonstrate that MMR proteins and ATR functionally interact during the cellular response to genotoxic stress, and that ATR serves as a haploinsufficient tumor suppressor in MMR-deficient cells.     

Synthesis and photoluminescence study of molecularly imprinted polymers appended onto CdSe/ZnS core-shells

The Photoluminescence of quantum dots have been found to be a useful tool for the detection of small to medium sized analyte molecules in a host-guest environment. By the incorporation of quantum dots into molecularly imprinted polymers, which can offer shape and selectivity, the former can respond by quenching the photoluminescence emission upon template binding. In this work host polymers were synthesized and cased into thin films using functional monomers such as methacrylic acid (MAA), CdSe/ZnS core-shell derivatized with 4-vinyl pyridine and ethylene glycol dimethacrylic acid (EGDMA) as a cross-linker. The intensity of photoluminescence emission is detected upon analyte binding.