Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Aug 14;6(8):2279-2290.
doi: 10.1021/acsinfecdis.0c00403. Epub 2020 Jul 8.

Interaction of Staphylococcus aureus and Host Cells upon Infection of Bronchial Epithelium during Different Stages of Regeneration

Laura M Palma Medina  1   2 , Ann-Kristin Becker  3 , Stephan Michalik  1 , Kristin Surmann  1 , Petra Hildebrandt  1 , Manuela Gesell Salazar  1 , Solomon A Mekonnen  1   2 , Lars Kaderali  3 , Uwe Völker  1 , Jan Maarten van Dijl  2
Affiliations

Interaction of Staphylococcus aureus and Host Cells upon Infection of Bronchial Epithelium during Different Stages of Regeneration

Laura M Palma Medina et al. ACS Infect Dis. .

Abstract

The primary barrier that protects our lungs against infection by pathogens is a tightly sealed layer of epithelial cells. When the integrity of this barrier is disrupted as a consequence of chronic pulmonary diseases or viral insults, bacterial pathogens will gain access to underlying tissues. A major pathogen that can take advantage of such conditions is Staphylococcus aureus, thereby causing severe pneumonia. In this study, we investigated how S. aureus responds to different conditions of the human epithelium, especially nonpolarization and fibrogenesis during regeneration using an in vitro infection model. The infective process was monitored by quantification of the epithelial cell and bacterial populations, fluorescence microscopy, and mass spectrometry. The results uncover differences in bacterial internalization and population dynamics that correlate with the outcome of infection. Protein profiling reveals that, irrespective of the polarization state of the epithelial cells, the invading bacteria mount similar responses to adapt to the intracellular milieu. Remarkably, a bacterial adaptation that was associated with the regeneration state of the epithelial cells concerned the early upregulation of proteins controlled by the redox-responsive regulator Rex when bacteria were confronted with a polarized cell layer. This is indicative of the modulation of the bacterial cytoplasmic redox state to maintain homeostasis early during infection even before internalization. Our present observations provide a deeper insight into how S. aureus can take advantage of a breached epithelial barrier and show that infected epithelial cells have limited ability to respond adequately to staphylococcal insults.

Keywords: Staphylococcus; energy; host−pathogen interaction; infectious disease; metabolism; virulence.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Epithelial cell layers with distinctive polarization states. The cell line 16HBE14o- was cultured for 3 and 11 days in order to obtain confluent cell layers with two different polarization states. The polarization states were monitored by measurements of the TEER and by immunostaining with an antibody specific for Zonula-Occludens 1. The micrographs present the maximum pixel value of the Z-stacks of the epithelial cell layers. Scale bar: 100 μm.
Figure 2
Figure 2
The epithelial cell layer models represent two different stages of wound regeneration. The nonpolarized layer was obtained after 3 days of culturing and the polarized layer, after 11 days of culturing. (A, B) Levels of matrisome-associated proteins and proteins of the core matrisome. (C) Levels of proteins related to major signaling pathways involved in tissue regeneration after injury. The indicated levels of expression are ratios of the levels at 0 h to the mean value quantification for the respective protein in both conditions at every time point of the experiment. The fold change (FC) measured for each individual protein is included in the column FC. Significant differences (p-value < 0.01) are marked with a star. σ = 0.26; Shh, sonic hedgehog signaling pathway; TGFB, transforming growth factor beta signaling pathway; Wnt, Wingless/Integrated pathway.
Figure 3
Figure 3
Dynamics of bacterial and host populations p.i. (A) Development of the S. aureus infection and integrity of the cell layer were tracked by immunofluorescence microscopy. The presented micrographs are the maximum pixel values of the Z-stacks of the infected cell layers. ZO-1 is depicted in magenta and S. aureus, in green. The individual representations of each channel are shown in Figures S2 and S3. Quantification of the bacterial fluorescence is shown in Figure S4. Scale bar: 100 μm. (B, C) Counting of the host and bacterial cell populations by flow cytometry. The changes over time are displayed in relation to 0 h p.i. (t/t0). The proportion of epithelial cells that contain intracellular S. aureus at each time point is represented in panel B by the complemented bars marked with stripes; the respective percentages are indicated above each bar. (D) The polarity of the cell layer was tracked during infection by TEER measurements. All results of panels B–D are the average of 4 independent biological replicates.
Figure 4
Figure 4
Voronoi tree map representation of S. aureus protein levels grouped by major regulators. (A) Proteins that displayed significantly (p-value < 0.05) different dynamics during the first 6.5 h p.i. between the two infection models are highlighted in maroon. (B) Names of the proteins represented in each polygon of the other panels. (C) Changes in protein amounts are presented at every time point relative to the respective protein quantities in the exponential phase. Increased levels are presented in dark red and decreased levels, in blue. The 1 h sample represents the fraction of bacteria in the medium that was neither internalized into nor attached to the host cells after addition of the bacterial master mix.
Figure 5
Figure 5
Central carbon and nitrogen metabolism of S. aureus during infection-related stress conditions. The levels of a selection of proteins related to (A) carbon and nitrogen metabolism and (B) stress conditions are represented in relation to the mean values measured for proteins extracted from the bacteria in the exponential growth phase at OD600 = 0.4. Significant changes (p-value < 0.05) are marked with stars in the last three columns, which relate to changes over time during nonpolarized conditions (N–P), polarized conditions (P), and the comparison of both trends (T). S. aureus proteins without an assigned gene symbol are labeled according to their locus tag without the “SAOUHSC_” identifier.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Lowy F. D. (1998) Staphylococcus aureus Infections. N. Engl. J. Med. 339, 520–532. 10.1056/NEJM199808203390806. - DOI - PubMed
    1. Dastgheyb S. S.; Otto M. (2015) Staphylococcal adaptation to diverse physiologic niches: an overview of transcriptomic and phenotypic changes in different biological environments. Future Microbiol. 10, 1981–1995. 10.2217/fmb.15.116. - DOI - PMC - PubMed
    1. Sollid J. U. E.; Furberg A. S.; Hanssen A. M.; Johannessen M. (2014) Staphylococcus aureus: Determinants of human carriage. Infect., Genet. Evol. 21, 531–541. 10.1016/j.meegid.2013.03.020. - DOI - PubMed
    1. Wertheim H. F.; Melles D. C.; Vos M. C.; van Leeuwen W.; van Belkum A.; Verbrugh H. A.; Nouwen J. L. (2005) The role of nasal carriage in Staphylococcus aureus infections. Lancet Infect. Dis. 5, 751–762. 10.1016/S1473-3099(05)70295-4. - DOI - PubMed
    1. Krismer B.; Liebeke M.; Janek D.; Nega M.; Rautenberg M.; Hornig G.; Unger C.; Weidenmaier C.; Lalk M.; Peschel A. (2014) Nutrient Limitation Governs Staphylococcus aureus Metabolism and Niche Adaptation in the Human Nose. PLoS Pathog. 10, e1003862.10.1371/journal.ppat.1003862. - DOI - PMC - PubMed

Publication types