No abstract

Figure 3. p4 exhibits rapid concentration-dependent lytic activity against E. coli. A, E. coli HB101 was incubated with the indicated concentrations of p4 for 2 h. Cell viability was analyzed by MDA assay. n ϭ 3, mean Ϯ S.D. B, E. coli HB101 was incubated with 100 M p4 or vehicle for the indicated times. Cell viability was analyzed by MDA assay, n ϭ 3; mean Ϯ S.D. C, human erythrocytes were incubated with 1% Triton X-100, the indicated concentration of p4, or vehicle for 2 h. Hemolysis of erythrocytes is shown relative to lysis caused by Triton X-100. n ϭ 3, mean Ϯ S.D. D, E. coli HB101 was incubated with 100 M p4 or vehicle for the indicated times. Bacterial morphology was assessed by TEM. E, E. coli HB101 was incubated with 100 M p4 for 5 min. Alterations in bacterial permeability were visualized by fluorescence imaging. Bacteria were treated with FITC-labeled p4 (green), stained with PI (red), and counterstained with Hoechst to visualize DNA (blue). Arrows point to accumulation of p4 at the cell surface. F, ␤-galexpressing E. coli JM83 was incubated with the indicated concentrations of p4 for 15 min. The ␤-gal activity present in supernatants of p4-treated bacteria is shown as a percentage of the vehicle-treated bacteria. n ϭ 3, mean Ϯ S.D. G, E. coli HB101 was treated with p4 for 45 min, followed by TEM. Arrows and asterisks indicate outer membrane perturbations and the discontinuous inner membrane, respectively. H, intracellular localization of p4 is shown by immunogold labeling. E. coli HB101 was treated with biotin-p4 or p4 as a control, fixed, and stained with mouse anti-biotin Abs, followed by anti-mouse Abs conjugated to gold particles. Arrowheads indicate gold particles. The enlarged image (i) demonstrates interaction of p4 with the cell membrane. ***, p Ͻ 0.001; **, p Ͻ 0.01; *, p Ͻ 0.05 by Kruskal-Wallis one-way ANOVA with post hoc Dunn's test. TEM and fluorescence microscopy images are from one experiment and are representative of at least three experiments.

Neutrophils are broadly classified into conventional neutrophils (PMNs) and low-density granulocytes (LDGs). LDGs are better than PMNs at generating neutrophil extracellular traps (NETs), which may contribute to the pathology of autoimmune diseases. We hypothesized that LDGs and PMNs differ in their levels of unrestrained NE that supports NET generation. Here, we show that individuals with psoriasis contain elevated levels of LDGs and that in contrast to PMNs, the LDGs display higher staining for NE and lower staining for its inhibitor SLPI. The heterogeneity between blood-derived LDGs and PMNs was somewhat reminiscent of the differences in the NE and SLPI staining patterns observed in psoriasis skin-infiltrating neutrophils. Distinctive staining for NE and SLPI in LDGs and PMNs did not result from differences in their protein levels nor manifested in higher total proteolytic activity of NE in LDGs; rather, it likely depended on different cytosolic sequestration of these proteins. The disparate profile of NE and SLPI in LDGs and PMNs coincided with altered migratory responses of these cells to cutaneous chemoattractants. Collectively, differential NE and SLPI staining identifies common attributes of both circulating and skin-infiltrating neutrophils, which may guide neutrophil migration to distinct skin regions and determine the localization of LDGs-mediated cutaneous pathology.

Epithelia in the skin, gut and other environmentally exposed organs display a variety of mechanisms to control microbial communities and limit potential pathogenic microbial invasion. Naturally occurring antimicrobial proteins/peptides and their synthetic derivatives (here collectively referred to as AMPs) reinforce the antimicrobial barrier function of epithelial cells. Understanding how these AMPs are functionally regulated may be important for new therapeutic approaches to combat microbial infections. Some AMPs are subject to redox-dependent regulation. This review aims to: (i) explore cysteine-based redox active AMPs in skin and intestine; (ii) discuss casual links between various redox environments of these barrier tissues and the ability of AMPs to control cutaneous and intestinal microbes; (iii) highlight how bacteria, through intrinsic mechanisms, can influence the bactericidal potential of redox-sensitive AMPs.

Skin is the largest, environmentally exposed (barrier) organ, capable of integrating various signals into effective defensive responses. The functional significance of interactions among the epidermis and the immune and nervous systems in regulating and maintaining skin barrier function is only now becoming recognized in relation to skin pathophysiology. This review focuses on newly described pathways that involve soluble mediator-mediated crosstalk between these compartments. Dysregulation of these connections can lead to chronic inflammatory diseases and/or pathologic conditions associated with chronic pain or itch.