Stephanie M. Rangel

Production of Outer Membrane Vesicles by the Plague Pathogen Yersinia pestis

Many Gram-negative bacteria produce outer membrane vesicles (OMVs) during cell growth and division, and some bacterial pathogens deliver virulence factors to the host via the release of OMVs during infection. Here we show that Yersinia pestis, the causative agent of the disease plague, produces and releases native OMVs under physiological conditions. These OMVs, approximately 100 nm in diameter, contain multiple virulence-associated outer membrane proteins including the adhesin Ail, the F1 outer fimbrial antigen, and the protease Pla. We found that OMVs released by Y. pestis contain catalytically active Pla that is competent for plasminogen activation and α2-antiplasmin degradation. The abundance of OMV-associated proteins released by Y. pestis is significantly elevated at 37°C compared to 26°C and is increased in response to membrane stress and mutations in RseA, Hfq, and the major Braun lipoprotein (Lpp). In addition, we show that Y. pestis OMVs are able to bind to components of the extracellular matrix such as fibronectin and laminin. These data suggest that Y. pestis may produce OMVs during mammalian infection and we propose that dispersal of Pla via OMV release may influence the outcome of infection through interactions with Pla substrates such as plasminogen and Fas ligand.

The Role of ExoS in Dissemination of Pseudomonas aeruginosa during Pneumonia

Hospital-acquired pneumonia is associated with high rates of morbidity and mortality, and dissemination to the bloodstream is a recognized risk factor for particularly poor outcomes. Yet the mechanism by which bacteria in the lungs gain access to the bloodstream remains poorly understood. In this study, we used a mouse model of Pseudomonas aeruginosa pneumonia to examine this mechanism. P. aeruginosa uses a type III secretion system to deliver effector proteins such as ExoS directly into the cytosol of eukaryotic cells. ExoS, a bi-functional GTPase activating protein (GAP) and ADP-ribosyltransferase (ADPRT), inhibits phagocytosis during pneumonia but has also been linked to a higher incidence of dissemination to the bloodstream. We used a novel imaging methodology to identify ExoS intoxicated cells during pneumonia and found that ExoS is injected into not only leukocytes but also epithelial cells. Phagocytic cells, primarily neutrophils, were targeted for injection with ExoS early during infection, but type I pneumocytes became increasingly injected at later time points. Interestingly, injection of these pneumocytes did not occur randomly but rather in discrete regions, which we designate ““fields of cell injection” (FOCI). These FOCI increased in size as the infection progressed and contained dead type I pneumocytes. Both of these phenotypes were attenuated in infections caused by bacteria secreting ADPRT-deficient ExoS, indicating that FOCI growth and type I pneumocyte death were dependent on the ADPRT activity of ExoS. During the course of infection, increased FOCI size was associated with enhanced disruption of the pulmonary-vascular barrier and increased bacterial dissemination into the blood, both of which were also dependent on the ADPRT activity of ExoS. We conclude that the ADPRT activity of ExoS acts upon type I pneumocytes to disrupt the pulmonary-vascular barrier during P. aeruginosa pneumonia, leading to bacterial dissemination.

The Pseudomonas aeruginosa Type III Translocon Is Required for Biofilm Formation at the Epithelial Barrier

Clinical infections by Pseudomonas aeruginosa, a deadly Gram-negative, opportunistic pathogen of immunocompromised hosts, often involve the formation of antibiotic-resistant biofilms. Although biofilm formation has been extensively studied in vitro on glass or plastic surfaces, much less is known about biofilm formation at the epithelial barrier. We have previously shown that when added to the apical surface of polarized epithelial cells, P. aeruginosa rapidly forms cell-associated aggregates within 60 minutes of infection. By confocal microscopy we now show that cell-associated aggregates exhibit key characteristics of biofilms, including the presence of extracellular matrix and increased resistance to antibiotics compared to planktonic bacteria. Using isogenic mutants in the type III secretion system, we found that the translocon, but not the effectors themselves, were required for cell-associated aggregation on the surface of polarized epithelial cells and at early time points in a murine model of acute pneumonia. In contrast, the translocon was not required for aggregation on abiotic surfaces, suggesting a novel function for the type III secretion system during cell-associated aggregation. Supernatants from epithelial cells infected with wild-type bacteria or from cells treated with the pore-forming toxin streptolysin O could rescue aggregate formation in a type III secretion mutant, indicating that cell-associated aggregation requires one or more host cell factors. Our results suggest a previously unappreciated function for the type III translocon in the formation of P. aeruginosa biofilms at the epithelial barrier and demonstrate that biofilms may form at early time points of infection.

The ADP-Ribosyltransferase Domain of the Effector Protein ExoS Inhibits Phagocytosis of Pseudomonas aeruginosa during Pneumonia

ABSTRACT Pseudomonas aeruginosa is a Gram-negative pathogen commonly associated with nosocomial infections such as hospital-acquired pneumonia. It uses a type III secretion system to deliver effector proteins directly into the cytosol of host cells. Type III secretion in P. aeruginosa has been linked to severe disease and worse clinical outcomes in animal and human studies. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. Numerous in vitro studies have investigated the targets and cellular effects of ExoS, linking both its enzymatic activities with inhibition of bacterial internalization. However, little is known about how this toxin facilitates the progression of infection in vivo. In this study, we used a mouse model to investigate the role of ExoS in inhibiting phagocytosis during pneumonia. We first confirmed previous findings that the ADP-ribosyltransferase activity of ExoS, but not the GTPase-activating protein activity, was responsible for bacterial persistence and decreased host survival in this model. We then used two distinct assays to demonstrate that ExoS inhibited phagocytosis during pneumonia. In contrast to the findings of several in vitro studies, this in vivo inhibition was also dependent on the ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS. These results demonstrate for the first time the antiphagocytic function of ExoS in the context of an actual infection and indicate that blocking the ADP-ribosyltransferase activity of ExoS may have potential therapeutic benefit. IMPORTANCE Pseudomonas aeruginosa is a major cause of hospital-acquired infections. To cause severe disease, this bacterium uses a type III secretion system that delivers four effector proteins, ExoS, ExoT, ExoU, and ExoY, into host cells. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. In cell culture models, both enzymatic activities have been associated with decreased bacterial internalization. However, our study is the first to examine a role for ExoS in blocking phagocytosis in an animal model. We report that ExoS does inhibit phagocytosis during pneumonia. The ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS is necessary for this effect. Our findings highlight the ability of P. aeruginosa to manipulate the inflammatory response during pneumonia to facilitate bacterial survival. Pseudomonas aeruginosa is a major cause of hospital-acquired infections. To cause severe disease, this bacterium uses a type III secretion system that delivers four effector proteins, ExoS, ExoT, ExoU, and ExoY, into host cells. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. In cell culture models, both enzymatic activities have been associated with decreased bacterial internalization. However, our study is the first to examine a role for ExoS in blocking phagocytosis in an animal model. We report that ExoS does inhibit phagocytosis during pneumonia. The ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS is necessary for this effect. Our findings highlight the ability of P. aeruginosa to manipulate the inflammatory response during pneumonia to facilitate bacterial survival.

Pseudomonas aeruginosa: breaking down barriers

Many bacterial pathogens have evolved ingenious ways to escape from the lung during pneumonia to cause bacteremia. Unfortunately, the clinical consequences of this spread to the bloodstream are frequently dire. It is therefore important to understand the molecular mechanisms used by pathogens to breach the lung barrier. We have recently shown that Pseudomonas aeruginosa, one of the leading causes of hospital-acquired pneumonia, utilizes the type III secretion system effector ExoS to intoxicate pulmonary epithelial cells. Injection of these cells leads to localized disruption of the pulmonary-vascular barrier and dissemination of P. aeruginosa to the bloodstream. We put these data in the context of previous studies to provide a holistic model of P. aeruginosa dissemination from the lung. Finally, we compare P. aeruginosa dissemination to that of other bacteria to highlight the complexity of bacterial pneumonia. Although respiratory pathogens use distinct and intricate strategies to escape from the lungs, a thorough understanding of these processes can lay the foundation for new therapeutic approaches for bacterial pneumonia.

Multiple sclerosis association with psoriasis: a large U.S. population, single centre, retrospective cross-sectional study

cutaneous vasculitis and arthritis. Possible immune complex syndrome. Mayo Clin Proc 1973; 48: 340–348. 5 Messiaen T, Van Damme B, Kuypers D, Maes B, Vanrenterghem Y. Crescentic glomerulonephritis complicating the course of a hypocomplementemic urticarial vasculitis. Clin Nephrol 2000; 54: 409–412. 6 Grotz W, Baba H, Becker J et al. Hypocomplementemic urticarial vasculitis syndrome. An interdisciplinary challenge. Dtsch Arztebl Int 2009; 106: 756–763. 7 Mehregan D, Hall M, Gibson L. Urticarial vasculitis? A histopathological and clinical review of 72 cases. J Am Acad Dermatol 1992; 26: 441–448. 8 Aydogan K, Karadogan S, Adim S et al. Hypocomplementemic urticarial vasculitis: a rare presentation of systemic lupus erythematosus. Int J Dermatol 2006; 45: 1057–1061. 9 Ghazanfar MN, Thomsen SF. Omalizumab for urticarial vasculitis: case report and review of the literature. Case Rep Dermatol Med 2015; 2015: 576893. 10 Diez LS, Tamayo LM, Cardona R. Omalizumab: therapeutic option in chronic spontaneous urticaria difficult to control with associated vasculitis, report of three cases. Biomedica 2013; 33: 503–512. 11 Kaplan AP, Gim enez-Arnau AM, Saini SS. Mechanisms of action that contribute to efficacy of omalizumab in chronic spontaneous urticaria. Allergy 2017; 72: 519–533.

Apremilast and suicidality – a retrospective analysis of three large databases: the FAERS, EudraVigilance and a large single-centre US patient population

438–443. 3 Seideg ard J, Vorachek WR, Pero RW, Pearson WR. Hereditary differences in the expression of the human glutathione transferase active on trans-stilbene oxide are due to a gene deletion. Proc Natl Acad Sci USA 1988; 85: 7293–7297. 4 Sprenger R, Schlagenhaufer R, Kerb R et al. Characterization of the glutathione S-transferase GSTT1 deletion: discrimination of all genotypes by polymerase chain reaction indicates a trimodular genotype-phenotype correlation. Pharmacogenetics 2000; 10: 557–565. 5 Ibbotson SH, Dawe RS, Dinkova-Kostova AT et al. Glutathione S-transferase genotype is associated with sensitivity to psoralen-ultraviolet A photochemotherapy. Br J Dermatol 2012; 166: 380–388. 6 Kanetsky PA, Holmes R, Walker A et al. Interaction of glutathione S-transferase M1 and T1 genotypes and malignant melanoma. Cancer Epidemiol Biomarkers Prev 2001; 10: 509–513. 7 Solak B, Karkucak M, Turan H et al. Glutathione S-transferase M1 and T1 gene polymorphisms in patients with chronic plaque-type psoriasis: a casecontrol study. Med Princ Pract 2015; 25: 155–158.

Rosacea and subsequent diagnosis for Parkinson's disease: a large, urban, single center, US patient population retrospective study

U.N. Saikia, R. Kapoor, R.S. Mavuduru Department of Dermatology, Venereology and Leprology, Post Graduate Institute of Medical Education and Research, Chandigarh, India, Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India, Radiotherapy, Post Graduate Institute of Medical Education and Research, Chandigarh, India, Urology, Post Graduate Institute of Medical Education and Research, Chandigarh, India *Correspondence: T. Narang. E-mail: narangtarun@yahoo.co.in

The convergence theory for vitiligo: A reappraisal

Vitiligo is characterized by progressive loss of skin pigmentation. The search for aetiologic factors has led to the biochemical, the neurologic and the autoimmune theory. The convergence theory was then proposed several years ago to incorporate existing theories of vitiligo development into a single overview of vitiligo aetiology. The viewpoint that vitiligo is not caused only by predisposing mutations, or only by melanocytes responding to chemical/radiation exposure, or only by hyperreactive T cells, but rather results from a combination of aetiologic factors that impact melanocyte viability, has certainly stood the test of time. New findings have since informed the description of progressive depigmentation. Understanding the relative importance of such aetiologic factors combined with a careful selection of the most targetable pathways will continue to drive the next phase in vitiligo research: the development of effective therapeutics. In that arena, it is likewise important to acknowledge that pathways affected in some patients may not be altered in others. Taken together, the convergence theory continues to provide a comprehensive viewpoint of vitiligo aetiology. The theory serves to intertwine aetiologic pathways and will help to define pathways amenable to disease intervention in individual patients.

Malignant melanoma associated with chronic once daily aspirin exposure in males: a large, single-center, urban, U.S. patient population cohort study from the Research on Adverse Drug events And Reports (RADAR) project

To the Editor: Conflicting evidence exists for the risk of malignant melanoma (MM) subsequent to chronic aspirin exposure. Although a study in the Journal of the American Academy of Dermatology demonstrated that chronic aspirin exposure before and after MM diagnosis in a large midwestern US population was associated with overall prolonged survival, the risk of MM subsequent to chronic aspirin exposure remains uncertain. The aim of this study, which was also conducted within a large midwestern US patient population, was to determine whether there was a detectable risk for MM after 1 year or more of chronic aspirin exposure. Using the methodology of the ‘‘Research on Adverse Drug events And Report’’, the Northwestern Medicine Enterprise Data Warehouse,