Novel metal peroxide nanoboxes restrain Clostridioides difficile infection beyond the bactericidal and sporicidal activity

Clostridioides difficile spores are considered as the major source responsible for the development of C. difficile infection (CDI), which is associated with an increased risk of death in patients and has become an important issue in infection control of nosocomial infections. Current treatment against CDI still relies on antibiotics, which also damage normal flora and increase the risk of CDI recurrence. Therefore, alternative therapies that are more effective against C. difficile bacteria and spores are urgently needed. Here, we designed an oxidation process using H2O2 containing PBS solution to generate Cl- and peroxide molecules that further process Ag and Au ions to form nanoboxes with Ag-Au peroxide coat covering Au shell and AgCl core (AgAu-based nanoboxes). The AgAu-based nanoboxes efficiently disrupted the membrane structure of bacteria/spores of C. difficile after 30-45 min exposure to the highly reactive Ag/Au peroxide surface of the nano structures. The Au-enclosed AgCl provided sustained suppression of the growth of 2 × 107 pathogenic Escherichia coli for up to 19 days. In a fecal bench ex vivo test and in vivo CDI murine model, biocompatibility and therapeutic efficacy of the AuAg nanoboxes to attenuate CDI was demonstrated by restoring the gut microbiota and colon mucosal structure. The treatment successfully rescued the CDI mice from death and prevented their recurrence mediated by vancomycin treatment. The significant outcomes indicated that the new peroxide-derived AgAu-based nanoboxes possess great potential for future translation into clinical application as a new alternative therapeutic strategy against CDI.

Dielectrical Properties of Living Epidermis and Dermis in the Frequency Range from 1 kHz to 1 MHz

We determine the in-vivo dielectric properties-resistivity and relative permittivity-of living epidermis and dermis of human skin soaked with a physiological saline solution for one minute between 1 kHz and 1 MHz. This is done by fitting approximate analytical solutions of a mechanistic model for the transport of charges in these layers to a training set comprising impedance measurements at two depth settings on stripped skin on the volar forearm of 24 young subjects. Here, the depth settings are obtained by varying the voltage at a second inject on the electrical-impedance-spectroscopy probe. The model and the dielectric properties are validated with a test set for a third depth setting with overall good agreement. In addition, the means and standard deviations of the thicknesses of living epidermis and dermis are estimated from a literature review as 61±7 μm and 1.0±0.2 mm respectively. Furthermore, extensions to resolve the skin layers in more detail are suggested.

Mechanistic Multilayer Model for Non-invasive Bioimpedance of Intact Skin

An approximate semi-analytical solution based on a Hankel transform of a mechanistic model for electrical impedance spectroscopy (EIS) is derived for a non-invasive axisymmetric concentric probe with m electrodes measuring the response of n layers of human skin. We validate the semi-analytical solution for the case when the skin is treated as a three-layer entity - (i) stratum corneum, (ii) viable skin comprising living epidermis and dermis and (iii) adipose tissue - on the volar forearm in the frequency range 1 kHz to 1 MHz with experimental EIS measurements of 120 young subjects. Overall, we find good agreement for both the mean magnitude and phase of the impedance as well as the natural variability between subjects. Finally, the semi-analytical solution is verified with the full set of equations solved numerically: Good agreement is found for the point-wise potential distribution in the three skin layers.

Protein disulfide isomerase acts as a redox-dependent chaperone to unfold cholera toxin

Cholera toxin is assembled from two subunits in the periplasm of Vibrio cholerae and disassembled in the analogous compartment of target cells, the lumen of the endoplasmic reticulum (ER), before a fragment of it, the A1 chain, is transported into the cytosol. We show that protein disulfide isomerase (PDI) in the ER lumen functions to disassemble and unfold the toxin once its A chain has been cleaved. PDI acts as a redox-driven chaperone; in the reduced state, it binds to the A chain and in the oxidized state it releases it. Our results explain the pathway of cholera toxin, suggest a role for PDI in retrograde protein transport into the cytosol, and indicate that PDI can act as a novel type of chaperone, whose binding and release of substrates is regulated by a redox, rather than an ATPase, cycle.

Attenuation of IL-5-mediated signal transduction, eosinophil survival, and inflammatory mediator release by a soluble human IL-5 receptor

A soluble form of the human IL-5R alpha-chain (IL-5Ra) that contains the extracellular IL-5 binding domain has been evaluated for its effect on IL-5 binding to and activation of human eosinophils and basophils. The truncated receptor was expressed in Escherichia coli and recovered in biologically active form following renaturation and anion exchange chromatography. The soluble receptor formed a 1/1 complex with IL-5 in solution and bound IL-5 with affinity comparable to that of cell-associated IL-5Ra. Soluble IL-5Ra also competed with IL-5 for binding to the native alpha beta IL-5R on human cells and inhibited IL-5-mediated receptor activation and inflammatory mediator production. In this regard, the soluble receptor prevented IL-5-induced tyrosine phosphorylation of JAK2 kinase and IL-5R beta-chain and inhibited IL-5 priming of leukotriene C4 release by human basophils. However, the E. coli-derived receptor failed to inhibit IL-5 in longer term assays, including eosinophil survival and TF-1 cell proliferation, possibly due to its propensity to aggregate in a time- and temperature-dependent manner. In contrast, we observed that a soluble IL-5Ra derived from baculovirus-infected cells was less prone to aggregate and effectively antagonized IL-5-induced cell proliferation and survival. These findings indicate that the extracellular portion of the human IL-5Ra chain can prevent association of IL-5 with cell surface receptors and can attenuate signal transduction, mediator release, and survival of inflammatory cells. As such, soluble IL-5R may be useful in treating diseases such as human asthma, in which pulmonary injury is associated with the activity of IL-5R-bearing cells.

Attenuation of IL-5-mediated signal transduction, eosinophil survival, and inflammatory mediator release by a soluble human IL-5 receptor

A soluble form of the human IL-5R alpha-chain (IL-5Ra) that contains the extracellular IL-5 binding domain has been evaluated for its effect on IL-5 binding to and activation of human eosinophils and basophils. The truncated receptor was expressed in Escherichia coli and recovered in biologically active form following renaturation and anion exchange chromatography. The soluble receptor formed a 1/1 complex with IL-5 in solution and bound IL-5 with affinity comparable to that of cell-associated IL-5Ra. Soluble IL-5Ra also competed with IL-5 for binding to the native alpha beta IL-5R on human cells and inhibited IL-5-mediated receptor activation and inflammatory mediator production. In this regard, the soluble receptor prevented IL-5-induced tyrosine phosphorylation of JAK2 kinase and IL-5R beta-chain and inhibited IL-5 priming of leukotriene C4 release by human basophils. However, the E. coli-derived receptor failed to inhibit IL-5 in longer term assays, including eosinophil survival and TF-1 cell proliferation, possibly due to its propensity to aggregate in a time- and temperature-dependent manner. In contrast, we observed that a soluble IL-5Ra derived from baculovirus-infected cells was less prone to aggregate and effectively antagonized IL-5-induced cell proliferation and survival. These findings indicate that the extracellular portion of the human IL-5Ra chain can prevent association of IL-5 with cell surface receptors and can attenuate signal transduction, mediator release, and survival of inflammatory cells. As such, soluble IL-5R may be useful in treating diseases such as human asthma, in which pulmonary injury is associated with the activity of IL-5R-bearing cells.

Differential phosphorylation of the T lymphocyte costimulatory receptor CD28. Activation-dependent changes and regulation by protein kinase C

Treatment of T lymphocytes with phorbol ester and anti-CD28 monoclonal antibody (mAb) can induce proliferation and interleukin 2 production by triggering still undefined intracellular signaling pathways. We have developed a deglycosylation procedure that allows the precise identification of a distinct CD28 protein band, facilitating the analysis of activation-dependent changes in the phosphorylation state of CD28. Phorbol 12-myristate 13-acetate (PMA) treatment induced the in vitro phosphorylation of CD28 on threonine as detected in immune complex kinase assays. This effect of PMA was (i) rapid, preceding a PMA-induced increase in CD28 surface expression; (ii) occurred using kinase buffer containing either manganese or magnesium; and (iii) was found in human peripheral T cells, Jurkat T cells, and in a Jurkat subclone, J.Cam1, that is deficient in Lck tyrosine kinase activity. In contrast, anti-CD28 monoclonal antibody stimulation led to in vitro phosphorylation of CD28 on tyrosine that was manganese-dependent and required Lck tyrosine kinase activity, as it was undetectable in J.Cam1 cells. Importantly, CD28 was phosphorylated on tyrosine in vivo as detected with anti-phosphotyrosine antibodies after stimulation with anti-CD28 monoclonal antibody. The in vivo tyrosine phosphorylation of CD28 was inhibited by PMA treatment and was absent in J.Cam1 cells. Thus, the CD28 coreceptor can trigger different intracellular signaling pathways, depending upon the nature of the initial costimulatory signal.

Phorbol ester treatment inhibits phosphatidylinositol 3-kinase activation by, and association with, CD28, a T-lymphocyte surface receptor

CD28 is a costimulatory receptor found on the surface of most T lymphocytes. Engagement of CD28 induces interleukin 2 (IL-2) production and cell proliferation when combined with an additional signal such as treatment with phorbol ester, an activator of protein kinase C. Recent studies have established that after CD28 ligation, the cytoplasmic domain of CD28 can bind to the 85-kDa subunit of phosphatidylinositol 3-kinase (PI3 kinase). There is a concomitant increase in PI3 lipid kinase activity that may be important in CD28 signaling. Despite the requirement of phorbol 12-myristate 13-acetate (PMA) for effector function, we have found, however, that treatment of Jurkat T cells with the phorbol ester PMA dramatically inhibits (i) the association of PI3 kinase with CD28, (ii) the ability of p85 PI3 kinase to be immunoprecipitated by anti-phosphotyrosine antibodies, and (iii) the induction of PI3 kinase activity after stimulation of the cells with the anti-CD28 monoclonal antibody 9.3. These changes occur within minutes of PMA treatment and are persistent. In addition, we have found that wortmannin, a potent inhibitor of PI3 kinase, does not interfere with the induction of IL-2 after stimulation of Jurkat T cells with anti-CD28 monoclonal antibody and PMA. We conclude that PI3 kinase activity may not be required for CD28-dependent IL-2 production from Jurkat T cells in the presence of PMA.