Violacein Treatment Modulates Acute and Chronic Inflammation through the Suppression of Cytokine Production and Induction of Regulatory T Cells

PLoS One. 2015 May 4;10(5):e0125409. doi: 10.1371/journal.pone.0125409. eCollection 2015.

Abstract

Inflammation is a necessary process to control infection. However, exacerbated inflammation, acute or chronic, promotes deleterious effects in the organism. Violacein (viola), a quorum sensing metabolite from the Gram-negative bacterium Chromobacterium violaceum, has been shown to protect mice from malaria and to have beneficial effects on tumors. However, it is not known whether this drug possesses anti-inflammatory activity. In this study, we investigated whether viola administration is able to reduce acute and chronic autoimmune inflammation. For that purpose, C57BL/6 mice were intraperitoneally injected with 1 μg of LPS and were treated with viola (3.5mg/kg) via i.p. at the same time-point. Three hours later, the levels of inflammatory cytokines in the sera and phenotypical characterization of leukocytes were determined. Mice treated with viola presented a significant reduction in the production of inflammatory cytokines compared with untreated mice. Interestingly, although viola is a compound derived from bacteria, it did not induce inflammation upon administration to naïve mice. To test whether viola would protect mice from an autoimmune inflammation, Experimental Autoimmune Encephalomyelitis (EAE)-inflicted mice were given viola i.p. at disease onset, at the 10th day from immunization. Viola-treated mice developed mild EAE disease in contrast with placebo-treated mice. The frequencies of dendritic cells and macrophages were unaltered in EAE mice treated with viola. However, the sole administration of viola augmented the levels of splenic regulatory T cells (CD4+Foxp3+). We also found that adoptive transfer of viola-elicited regulatory T cells significantly reduced EAE. Our study shows, for the first time, that violacein is able to modulate acute and chronic inflammation. Amelioration relied in suppression of cytokine production (in acute inflammation) and stimulation of regulatory T cells (in chronic inflammation). New studies must be conducted in order to assess the possible use of viola in therapeutic approaches in human autoimmune diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adoptive Transfer
  • Animals
  • Anti-Inflammatory Agents / administration & dosage
  • Anti-Inflammatory Agents / pharmacology
  • Biomarkers
  • Cytokines / biosynthesis*
  • Cytokines / genetics
  • Cytokines / metabolism
  • Dendritic Cells / immunology
  • Dendritic Cells / metabolism
  • Disease Models, Animal
  • Encephalomyelitis, Autoimmune, Experimental / diagnosis
  • Encephalomyelitis, Autoimmune, Experimental / immunology
  • Encephalomyelitis, Autoimmune, Experimental / metabolism
  • Encephalomyelitis, Autoimmune, Experimental / therapy
  • Female
  • Indoles / pharmacology*
  • Inflammation / diagnosis
  • Inflammation / immunology*
  • Inflammation / metabolism*
  • Inflammation / therapy
  • Inflammation Mediators / metabolism
  • Lipopolysaccharides / immunology
  • Lymphocyte Count
  • Mice
  • Severity of Illness Index
  • T-Lymphocytes, Regulatory / immunology*
  • T-Lymphocytes, Regulatory / metabolism*

Substances

  • Anti-Inflammatory Agents
  • Biomarkers
  • Cytokines
  • Indoles
  • Inflammation Mediators
  • Lipopolysaccharides
  • violacein

Grants and funding

This work was supported by Sao Paulo Research Foundation (FAPESP, grant #2011/17965-3) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq grant 471066/2012-5). FTMC and LV are CNPq researcher fellows. RT, SCPL and ICNP received FAPESP scholarships (#2014/02631-0, #2011/23664-6 and #2012/01892-0, respectively). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.