Proteolysis of fibrinogen deposits enables hydrogen peroxide-stimulated polymorphonuclear leukocytes to spread in an acidified environment

Pt-MWCNT modified carbon electrode strip for rapid and quantitative detection of H2O2 in food

A single-use screen-printed carbon electrode strip was designed and fabricated. Nanohybrids, prepared by deposition of platinum (Pt) nanoparticles on multi-wall carbon nanotube (MWCNT), was modified on the surface of screen-printed carbon electrode for the development of a fast, sensitive and cost-effective hydrogen peroxide (H2O2) detection amperometric sensor strip. With Pt-MWCNT nanohybrids surface modification, current generated in response to H2O2 by the screen-printed carbon electrode strip was enhanced 100 fold with an applied potential of 300 mV. Quality of as-prepared electrode strip was assured by the low coefficient of variation (CV) (<5%) of currents measured at 5 s. Three linear detection ranges with sensitivity of 75.2, 120.7, and 142.8 μA mM-1 cm-2 were observed for H2O2 concentration in the range of 1-15 mM, 0.1-1 mM, and 10-100 μM, respectively. The lowest H2O2 concentration could be measured by the as-prepared strip was 10 μM. H2O2 levels in green tea infusion and pressed Tofu could be rapidly detected with results comparable to that measured by ferrous oxidation xylenol orange (FOX) assay and peroxidase colorimetric method.

On the roles of polyvalent binding in immune recognition: perspectives in the nanoscience of immunology and the immune response to nanomedicines

Immunology often conveys the image of large molecules, either in the soluble state or in the membrane of leukocytes, forming multiple contacts with a target for actions of the immune system. Avidity names the ability of a polyvalent molecule to form multiple connections of the same kind with ligands tethered to the same surface. Polyvalent interactions are vastly stronger than their monovalent equivalent. In the present review, the functional consequences of polyvalent interactions are explored in a perspective of recent theoretical advances in understanding the thermodynamics of such binding. From insights on the structural biology of soluble pattern recognition molecules as well as adhesion molecules in the cell membranes or in their proteolytically shed form, this review documents the prominent role of polyvalent interactions in making the immune system a formidable barrier to microbial infection as well as constituting a significant challenge to the application of nanomedicines.

Restraint of spreading-dependent activation of polymorphonuclear leukocyte NADPH oxidase in an acidified environment

Elucidation of the mechanisms by which environmental pH affects or regulates the functions of polymorphonuclear leukocytes (PMNs) is important because severe acidification of the microenvironment often prevails at sites of inflammation where they act in host defense. In the present study, we investigated the effect of an acidic environment on spreading-dependent activation of O2- -producing NADPH oxidase in PMNs. We found that PMNs underwent spreading spontaneously over type I collagen and plastic surfaces at both neutral and acidic pH, although spreading over fibrinogen surfaces, for which cellular stimulation with H2O2 is required, was inhibited by acidic pH. At acidic pH, however, PMNs were unable to undergo spreading-dependent production of O2-. Pharmacological experiments showed that p38 mitogen-activated protein kinase (MAPK) was involved in the signaling pathways mediating the spreading-dependent activation of NADPH oxidase, and that its spreading-dependent phosphorylation of Thr-180 and Tyr-182, a hallmark of activation, was impaired at acidic pH. Furthermore, the inhibition by acidic pH of O2- production as well as p38 MAPK phosphorylation subsequent to spreading induction was reversible; environmental neutralization and acidification after induction of spreading at acidic and neutral pH, respectively, up- and down-regulated the two phenomena. Acidic pH did not affect the O2- production activity of NADPH oxidase pre-activated by phorbol 12-myristate 13-acetate (PMA). These results suggest that, in PMNs, the p38 MAPK-mediated signaling pathway functions as a pH-sensing regulator of spreading-dependent NADPH oxidase activation.

Oxidative stress-mediated bimodal regulation of polymorphonuclear leukocyte spreading by polyphenolic compounds

Pyrogallol-bearing polyphenolic compounds induce spreading of polymorphonuclear leukocytes (PMNL), although their optimal concentrations for induction of spreading are quite different (2000, 200, and 2 μM for pyrogallol, (-)-epigallocatechin gallate (EGCG), and tannic acid (TA), respectively), and TA tends to inhibit spreading at higher concentrations. In this study, we examined the involvement of oxidative stress in the regulation of PMNL spreading by these compounds. All three compounds in solution generated H(2)O(2) to a similar extent. Adsorption of the polyphenols to cell surfaces and their accumulation within cells were assessed by detection of the H(2)O(2) precursor O(2)(-) produced by the compounds through reduction of cytochrome c and p-nitro-blue tetrazolium, respectively. TA showed the highest degree of adsorption. EGCG adhered only to PMNL pre-fixed by paraformaldehyde, whereas pyrogallol did not adhere. None of the compounds caused intracellular O(2)(-) generation. A non-pyrogallic compound, 1,2,4-benzenetriol (BT), also produced H(2)O(2); it had no stimulatory effect on PMNL spreading, but inhibited spreading induced by other stimuli. BT did not adhere to PMNL but accumulated within them, and generated O(2)(-) in the presence of glycine. Thiol antioxidants abrogated all of the above spreading-regulatory effects of the polyphenolic compounds. We conclude that H(2)O(2)-generating polyphenols bimodally regulate the spreading of PMNL by subjecting them to oxidative stress. The ability of polyphenol to adhere to, or accumulate within, PMNL may govern the nature of the oxidative stress and determine the optimal concentration of each compound for induction of spreading, as well as whether spreading is promoted or inhibited.