Effects of methylprednisolone on intracellular bacterial growth

Gianfranco Meduri, S. Kanangat, M. Bronze, D. R. Patterson, C. U. Meduri, C. Pak, Elizabeth Tolley, D. R. Schaberg

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. Patients presenting with acute respiratory distress syndrome (ARDS) and high levels of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-α), interleukin 1β (IL-1β), and IL-6, have increased risk for developing nosocomial infections attributable to organisms such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter spp., compared to those patients with lower levels. Our previous in vitro studies have demonstrated that these bacterial strains exhibit enhanced growth extra-cellularly when supplemented with high concentrations of pure recombinant TNF-α, IL-β, or IL-6. In addition, we have shown that the intracellular milieu of phagocytic cells that are exposed to supraoptimal concentrations of TNF-α, IL-1β, and IL-6 or lipopolysaccharide (LPS) favors survival and replication of ingested bacteria. Therefore, we hypothesized that under conditions of intense inflammation the host's micromilieu favors bacterial infections by exposing phagocytic cells to protracted high levels of inflammatory cytokines. Our clinical studies have shown that methylprednisolone is capable of reducing the levels of TNF-α, IL-1β, and IL-6 in ARDS patients. Hence, we designed a series of in vitro experiments to test whether human monocytic cells (U937 cells) that are activated with high concentrations of LPS, which upregulate the release of proinflammatory cytokines from these phagocytic cells, would effectively kill or restrict bacterial survival and replication after exposure to methylprednisolone. Fresh isolates of S. aureus, P. aeruginosa, and Acinetobacter were used in our studies. Our results indicate that, compared with the control, stimulation of U937 cells with 100-ng/ml, 1.0-μg/ml, 5.0-μg/ml, or 10.0-μg/ml concentrations of LPS enhanced the intracellular survival and replication of all three species of bacteria significantly (for all, P = 0.0001). Stimulation with ≤10.0 ng of LPS generally resulted in efficient killing of the ingested bacteria. Interestingly, when exposed to graded concentrations of methylprednisolone, U937 cells that had been stimulated with 10.0 μg of LPS were able to suppress bacterial replication efficiently in a concentration-dependent manner. Significant reduction in numbers of CFU was observed at ≥150 μg of methylprednisolone per mi (P values were 0.032, 0.008, and 0.009 for S. aureus, P. aeruglnosa, and Acinetobacter, respectively). We have also shown that steady-state mRNA levels of TNF-α, IL-1β, and IL-6 in LPS-activated cells were reduced by treatment of such cells with methylprednisolone, in a concentration-dependent manner. The effective dose of methylprednisolone was 175 mg, a value that appeared to be independent of priming level of LPS and type of mRNA. We therefore postulate that a U.shaped relationship exists between the level of expression of TNF-α, IL-1β, and IL-6 within the phagocytic cells and their abilities to suppress active survival and replication of phagocytized bacteria.

Original languageEnglish (US)
Pages (from-to)1156-1163
Number of pages8
JournalClinical and Diagnostic Laboratory Immunology
Volume8
Issue number6
DOIs
StatePublished - Nov 17 2001

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Methylprednisolone
Lipopolysaccharides
Interleukin-6
Interleukin-1
Tumor Necrosis Factor-alpha
Phagocytes
U937 Cells
Acinetobacter
Growth
Bacteria
Staphylococcus aureus
Adult Respiratory Distress Syndrome
Cytokines
Bacterial Infections
Pseudomonas aeruginosa
Survival
Messenger RNA
Cross Infection
Up-Regulation
Cells

All Science Journal Classification (ASJC) codes

  • Immunology and Allergy
  • Immunology
  • Clinical Biochemistry
  • Microbiology (medical)

Cite this

Meduri, G., Kanangat, S., Bronze, M., Patterson, D. R., Meduri, C. U., Pak, C., ... Schaberg, D. R. (2001). Effects of methylprednisolone on intracellular bacterial growth. Clinical and Diagnostic Laboratory Immunology, 8(6), 1156-1163. https://doi.org/10.1128/CDLI.8.6.1156-1163.2001

Effects of methylprednisolone on intracellular bacterial growth. / Meduri, Gianfranco; Kanangat, S.; Bronze, M.; Patterson, D. R.; Meduri, C. U.; Pak, C.; Tolley, Elizabeth; Schaberg, D. R.

In: Clinical and Diagnostic Laboratory Immunology, Vol. 8, No. 6, 17.11.2001, p. 1156-1163.

Research output: Contribution to journalArticle

Meduri, G, Kanangat, S, Bronze, M, Patterson, DR, Meduri, CU, Pak, C, Tolley, E & Schaberg, DR 2001, 'Effects of methylprednisolone on intracellular bacterial growth', Clinical and Diagnostic Laboratory Immunology, vol. 8, no. 6, pp. 1156-1163. https://doi.org/10.1128/CDLI.8.6.1156-1163.2001
Meduri, Gianfranco ; Kanangat, S. ; Bronze, M. ; Patterson, D. R. ; Meduri, C. U. ; Pak, C. ; Tolley, Elizabeth ; Schaberg, D. R. / Effects of methylprednisolone on intracellular bacterial growth. In: Clinical and Diagnostic Laboratory Immunology. 2001 ; Vol. 8, No. 6. pp. 1156-1163.
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