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Aung, Kyaw Min
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Publications (8 of 8) Show all publications
Lindholm, M., Aung, K. M., Wai, S. N. & Oscarsson, J. (2019). Role of OmpA1 and OmpA2 in Aggregatibacter actinomycetemcomitans and Aggregatibacter aphrophilus serum resistance. Journal of Oral Microbiology, 11(1), Article ID 1536192.
Open this publication in new window or tab >>Role of OmpA1 and OmpA2 in Aggregatibacter actinomycetemcomitans and Aggregatibacter aphrophilus serum resistance
2019 (English)In: Journal of Oral Microbiology, ISSN 2000-2297, E-ISSN 2000-2297, Vol. 11, no 1, article id 1536192Article in journal (Refereed) Published
Abstract [en]

Aggregatibacter actinomycetemcomitans and Aggregatibacter aphrophilus belong to the HACEK group of fastidious Gram-negative organisms, a recognized cause of infective endocarditis. A. actinomycetemcomitans is also implicated in aggressive forms of periodontitis. We demonstrated that A. aphrophilus strains, as A. actinomycetemcomitans are ubiquitously serum resistant. Both species encode two Outer membrane protein A paralogues, here denoted OmpA1 and OmpA2. As their respective pangenomes contain several OmpA1 and OmpA2 alleles, they represent potential genotypic markers. A naturally competent strain of A. actinomycetemcomitans and A. aphrophilus, respectively were used to elucidate if OmpA1 and OmpA2 contribute to serum resistance. Whereas OmpA1 was critical for survival of A. actinomycetemcomitans D7SS in 50% normal human serum (NHS), serum resistant ompA1 mutants were fortuitously obtained, expressing enhanced levels of OmpA2. Similarly, OmpA1 rather than OmpA2 was a major contributor to serum resistance of A. aphrophilus HK83. Far-Western blot revealed that OmpA1AA, OmpA2AA, and OmpA1AP can bind to C4-binding protein, an inhibitor of classical and mannose-binding lectin (MBL) complement activation. Indeed, ompA1 mutants were susceptible to these pathways, but also to alternative complement activation. This may at least partly reflect a compromised outer membrane integrity but is also consistent with alternative mechanisms involved in OmpA-mediated serum resistance.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Aggregatibacter actinomycetemcomitans, Aggregatibacter aphrophilus, serum resistance, outer membrane protein A
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:umu:diva-153103 (URN)10.1080/20002297.2018.1536192 (DOI)000448422100001 ()2-s2.0-85055581204 (Scopus ID)
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2018-11-07Bibliographically approved
Bitar, A., Aung, K. M., Wai, S. N. & Hammarström, M.-L. (2019). Vibrio cholerae derived outer membrane vesicles modulate the inflammatory response of human intestinal epithelial cells by inducing microRNA-146a. Scientific Reports, 9, Article ID 7212.
Open this publication in new window or tab >>Vibrio cholerae derived outer membrane vesicles modulate the inflammatory response of human intestinal epithelial cells by inducing microRNA-146a
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 7212Article in journal (Refereed) Published
Abstract [en]

The small intestinal epithelium of Vibrio cholerae infected patients expresses the immunomodulatory microRNAs miR-146a and miR-155 at acute stage of disease. V. cholerae release outer membrane vesicles (OMVs) that serve as vehicles for translocation of virulence factors including V. cholerae cytolysin (VCC). The aim was to investigate whether OMVs, with and/or without VCC-cargo could be responsible for induction of microRNAs in intestinal epithelial cells and thereby contribute to immunomodulation. Polarized tight monolayers of T84 cells were challenged with OMVs of wildtype and a VCC deletion mutant of the non-O1/non-O139 (NOVC) V. cholerae strain V:5/04 and with soluble VCC. OMVs, with and without VCC-cargo, caused significantly increased levels of miR-146a. Increase was seen already after 2 hours challenge with OMVs and persisted after 12 hours. Challenge with soluble VCC caused significant increases in interleukin-8 (IL-8), tumour necrosis factor-α (TNF-α), CCL20, IL-1β, and IRAK2 mRNA levels while challenge with OMVs did not cause increases in expression levels of any of these mRNAs. These results suggest that V. cholerae bacteria release OMVs that induce miR-146a in order to pave the way for colonization by reducing the strength of an epithelial innate immune defence reaction and also preventing inflammation in the mucosa that factors like VCC can evoke.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Immunology in the medical area
Identifiers
urn:nbn:se:umu:diva-159266 (URN)10.1038/s41598-019-43691-9 (DOI)000467543700027 ()31076615 (PubMedID)2-s2.0-85065655754 (Scopus ID)
Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-06-19Bibliographically approved
Dongre, M., Singh, B., Aung, K. M., Larsson, P., Miftakhova, R. R., Persson, K., . . . Wai, S. N. (2018). Flagella-mediated secretion of a novel Vibrio cholerae cytotoxin affecting both vertebrate and invertebrate hosts. Communications Biology, 1, Article ID 59.
Open this publication in new window or tab >>Flagella-mediated secretion of a novel Vibrio cholerae cytotoxin affecting both vertebrate and invertebrate hosts
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2018 (English)In: Communications Biology, ISSN 2399-3642, Vol. 1, article id 59Article in journal (Refereed) Published
Abstract [en]

Using Caenorhabditis elegans as an infection host model for Vibrio cholerae predator interactions, we discovered a bacterial cytotoxin, MakA, whose function as a virulence factor relies on secretion via the flagellum channel in a proton motive force-dependent manner. The MakA protein is expressed from the polycistronic makDCBA (motility-associated killing factor) operon. Bacteria expressing makDCBA induced dramatic changes in intestinal morphology leading to a defecation defect, starvation and death in C. elegans. The Mak proteins also promoted V. cholerae colonization of the zebrafish gut causing lethal infection. A structural model of purified MakA at 1.9 Å resolution indicated similarities to members of a superfamily of bacterial toxins with unknown biological roles. Our findings reveal an unrecognized role for V. cholerae flagella in cytotoxin export that may contribute both to environmental spread of the bacteria by promoting survival and proliferation in encounters with predators, and to pathophysiological effects during infections.

Place, publisher, year, edition, pages
Springer Nature Publishing AG, 2018
National Category
Microbiology in the medical area
Research subject
Infectious Diseases; Molecular Biology
Identifiers
urn:nbn:se:umu:diva-155563 (URN)10.1038/s42003-018-0065-z (DOI)000461126500059 ()30271941 (PubMedID)
Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-04-04Bibliographically approved
Zhang, Z., Aung, K. M., Uhlin, B. E. & Wai, S. N. (2018). Reversible senescence of human colon cancer cells after blockage of mitosis/cytokinesis caused by the CNF1 cyclomodulin from Escherichia coli. Scientific Reports, 8, Article ID 17780.
Open this publication in new window or tab >>Reversible senescence of human colon cancer cells after blockage of mitosis/cytokinesis caused by the CNF1 cyclomodulin from Escherichia coli
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 17780Article in journal (Refereed) Published
Abstract [en]

Cytotoxic necrotizing factor 1 (CNF1), a protein toxin produced by extraintestinal pathogenic Escherichia coli, activates the Rho-family small GTPases in eukaryotic cell, thereby perturbing multiple cellular functions. Increasing epidemiological evidence suggests a link between CNF1 and human inflammatory bowel disease and colorectal cancer. At the cellular level, CNF1 has been hypothesized to reprogram cell fate towards survival due to the role in perturbing cell cycle and apoptosis. However, it remains undetermined how cells survive from CNF1 intoxication. In this work, we show that CNF1 treatment blocks mitosis/cytokinesis, elicits endoreplication and polyploidisation in cultured human colon cancer cells, and drives them into reversible senescence, which provides a survival route for cells via depolyploidisation. Senescence in CNF1-treated cells is demonstrated with upregulation of several senescence markers including senescence-associated β-galactosidase activity, p53, p21 and p16, and concomitant inhibition of the retinoblastoma protein phosphorylation. Importantly, progeny derived from CNF1 treatment exhibit genomic instability exemplified by increased aneuploidy and become more resistant to CNF1, but not to 5-fluorouracil and oxaliplatin, the two agents commonly used in chemotherapeutic treatment for colorectal cancer. These observations display survival features of the cell after CNF1 treatment that may have implications for the potential role of CNF1 in carcinogenesis.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-154870 (URN)10.1038/s41598-018-36036-5 (DOI)000452893700003 ()30542142 (PubMedID)2-s2.0-85058540678 (Scopus ID)
Available from: 2019-01-04 Created: 2019-01-04 Last updated: 2019-01-04Bibliographically approved
Bitar, A., De, R., Melgar, S., Aung, K. M., Rahman, A., Qadri, F., . . . Hammarström, M.-L. (2017). Induction of immunomodulatory miR-146a and miR-155 in small intestinal epithelium of Vibrio cholerae infected patients at acute stage of cholera. PLoS ONE, 12(3), Article ID 0173817.
Open this publication in new window or tab >>Induction of immunomodulatory miR-146a and miR-155 in small intestinal epithelium of Vibrio cholerae infected patients at acute stage of cholera
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2017 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 3, article id 0173817Article in journal (Refereed) Published
Abstract [en]

The potential immunomodulatory role of microRNAs in small intestine of patients with acute watery diarrhea caused by Vibrio cholerae O1 or enterotoxigenic Escherichia coli (ETEC) infection was investigated. Duodenal biopsies were obtained from study-participants at the acute (day 2) and convalescent (day 21) stages of disease, and from healthy individuals. Levels of miR-146a, miR-155 and miR-375 and target gene (IRAK1, TRAF6, CARD10) and 11 cytokine mRNAs were determined by qRT-PCR. The cellular source of microRNAs in biopsies was analyzed by in situ hybridization. The ability of V. cholerae bacteria and their secreted products to cause changes in microRNA- and mRNA levels in polarized tight monolayers of intestinal epithelial cells was investigated. miR-146a and miR-155 were expressed at significantly elevated levels at acute stage of V. cholerae infection and declined to normal at convalescent stage (P<0.009 versus controls; P = 0.03 versus convalescent stage, pairwise). Both microRNAs were mainly expressed in the epithelium. Only marginal down-regulation of target genes IRAK1 and CARD10 was seen and a weak cytokine-profile was identified in the acute infected mucosa. No elevation of microRNA levels was seen in ETEC infection. Challenge of tight monolayers with the wild type V. cholerae O1 strain C6706 and clinical isolates from two study-participants, caused significant increase in miR-155 and miR-146a by the strain C6706 (P<0.01). One clinical isolate caused reduction in IRAK1 levels (P<0.05) and none of the strains induced inflammatory cytokines. In contrast, secreted factors from these strains caused markedly increased levels of IL-8, IL-1β, and CARD10 (P<0.001), without inducing microRNA expression. Thus, miR-146a and miR-155 are expressed in the duodenal epithelium at the acute stage of cholera. The inducer is probably the V. cholerae bacterium. By inducing microRNAs the bacterium can limit the innate immune response of the host, including inflammation evoked by its own secreted factors, thereby decreasing the risk of being eliminated.

National Category
Microbiology in the medical area Immunology
Identifiers
urn:nbn:se:umu:diva-133013 (URN)10.1371/journal.pone.0173817 (DOI)000398945800031 ()28319200 (PubMedID)
Available from: 2017-03-28 Created: 2017-03-28 Last updated: 2018-06-09Bibliographically approved
Aung, K. M., Sjöström, A. E., von Pawel-Rammingen, U., Riesbeck, K., Uhlin, B. E. & Wai, S. N. (2016). Naturally Occurring IgG Antibodies Provide Innate Protection against Vibrio cholerae Bacteremia by Recognition of the Outer Membrane Protein U. Journal of Innate Immunity, 8(3), 269-283
Open this publication in new window or tab >>Naturally Occurring IgG Antibodies Provide Innate Protection against Vibrio cholerae Bacteremia by Recognition of the Outer Membrane Protein U
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2016 (English)In: Journal of Innate Immunity, ISSN 1662-811X, E-ISSN 1662-8128, Vol. 8, no 3, p. 269-283Article in journal (Refereed) Published
Abstract [en]

Cholera epidemics are caused by Vibrio cholerae serogroups O1 and O139, whereas strains collectively known as non-O1/non-O139 V. cholerae are found in cases of extraintestinal infections and bacteremia. The mechanisms and factors influencing the occurrence of bacteremia and survival of V. cholerae in normal human serum have remained unclear. We found that naturally occurring IgG recognizing V. cholerae outer membrane protein U (OmpU) mediates a serum-killing effect in a complement C1q-dependent manner. Moreover, outer membrane vesicles (OMVs) containing OmpU caused enhanced survival of highly serum-sensitive classical V. cholerae in a dose-dependent manner. OMVs from wild-type and ompU mutant V. cholerae thereby provided a novel means to verify by extracellular transcomplementation the involvement of OmpU. Our data conclusively indicate that loss, or reduced expression, of OmpU imparts resistance to V. cholerae towards serum killing. We propose that the difference in OmpU protein levels is a plausible reason for differences in serum resistance and the ability to cause bacteremia observed among V. cholerae biotypes. Our findings provide a new perspective on how naturally occurring antibodies, perhaps induced by members of the microbiome, may play a role in the recognition of pathogens and the provocation of innate immune defense against bacteremia.

Keywords
Vibrio cholerae, Outer membrane vesicles, Outer membrane protein U, Serum resistance, Naturally occurring IgG antibodies, C1q
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-118731 (URN)10.1159/000443646 (DOI)000375803900006 ()26934383 (PubMedID)
Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2018-06-07Bibliographically approved
Seibt, H., Aung, K. M., Ishikawa, T., Sjöström, A., Atkinson, G. C., Wai, S. N. & Shingler, V.Elevated levels of VCA0117 in response to external signals activates type VI secretion in Vibrio cholerae A1552.
Open this publication in new window or tab >>Elevated levels of VCA0117 in response to external signals activates type VI secretion in Vibrio cholerae A1552
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(English)Manuscript (preprint) (Other academic)
National Category
Genetics
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-155403 (URN)
Available from: 2019-01-15 Created: 2019-01-15 Last updated: 2019-01-16
Bitar, A., Kyaw, M. A., Marie-Louise, H. & Wai, S. N. Vibrio cholerae derived outer membrane vesicles modulate the inflammatory response ofhuman intestinal epithelial cells by inducing microRNA-146a. Scientific Reports
Open this publication in new window or tab >>Vibrio cholerae derived outer membrane vesicles modulate the inflammatory response ofhuman intestinal epithelial cells by inducing microRNA-146a
(English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322Article in journal (Refereed) Submitted
Abstract [en]

The small intestinal epithelium of Vibrio cholerae infected patients expresses the immunomodulatory microRNAs miR-146a and miR-155 at acute stage of disease. V. cholerae release outer membrane vesicles (OMVs) that serve as vehicles for translocation of virulencefactors including V. cholerae cytolysin (VCC). The aim was to investigate whether OMVs, with and/or without VCC-cargo could be responsible for induction of microRNAs in intestinal epithelial cells and thereby contribute to immunomodulation. Polarized tight monolayers of T84 cells were challenged with OMVs of wild-type and a VCC deletion mutant of the non-O1/non-O139 (NOVC) V. cholerae strain V:5/04 and with soluble VCC. OMVs, with and without VCC-cargo, caused significantly increased levels of miR-146a. Challenge with soluble VCC caused significant increases in interleukin-8 (IL-8), tumour necrosis factor-α(TNF-α), CCL20, IL-1β, and IRAK2 mRNA levels while challenge with OMVs did not causeany changes. Notably, OMVs from the VCC deficient mutant caused significant decreases in CCL20 and IL-18 mRNA levels. These results suggest that V. cholerae bacteria release OMVs that induce miR-146a in order to pave the way for colonization by reducing thestrength of an epithelial innate immune defence reaction and also preventing inflammation inthe mucosa that factors like VCC can evoke.

Keywords
Vibrio cholerae, intestinal epithelial cells, immunomodulation, microRNA, OMV, T84 monolayer, miR-146, miR-155, VCC, IL-8, TNF-a, IL-1b, IL-18, CCL20, IRAK2, inflammation
National Category
Immunology in the medical area
Research subject
Microbiology; Medicine; Molecular Biology
Identifiers
urn:nbn:se:umu:diva-147536 (URN)
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-09
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