Regulation of the CCL2 gene in pancreatic β-cells by IL-1β and glucocorticoids: role of MKP-1

PLoS One. 2012;7(10):e46986. doi: 10.1371/journal.pone.0046986. Epub 2012 Oct 9.

Abstract

Release of pro-inflammatory cytokines from both resident and invading leukocytes within the pancreatic islets impacts the development of Type 1 diabetes mellitus. Synthesis and secretion of the chemokine CCL2 from pancreatic β-cells in response to pro-inflammatory signaling pathways influences immune cell recruitment into the pancreatic islets. Therefore, we investigated the positive and negative regulatory components controlling expression of the CCL2 gene using isolated rat islets and INS-1-derived β-cell lines. We discovered that activation of the CCL2 gene by IL-1β required the p65 subunit of NF-κB and was dependent on genomic response elements located in the -3.6 kb region of the proximal gene promoter. CCL2 gene transcription in response to IL-1β was blocked by pharmacological inhibition of the IKKβ and p38 MAPK pathways. The IL-1β-mediated increase in CCL2 secretion was also impaired by p38 MAPK inhibition and by glucocorticoids. Moreover, multiple synthetic glucocorticoids inhibited the IL-1β-stimulated induction of the CCL2 gene. Induction of the MAP Kinase Phosphatase-1 (MKP-1) gene by glucocorticoids or by adenoviral-mediated overexpression decreased p38 MAPK phosphorylation, which diminished CCL2 gene expression, promoter activity, and release of CCL2 protein. We conclude that glucocorticoid-mediated repression of IL-1β-induced CCL2 gene transcription and protein secretion occurs in part through the upregulation of the MKP-1 gene and subsequent deactivation of the p38 MAPK. Furthermore, the anti-inflammatory actions observed with MKP-1 overexpression were obtained without suppressing glucose-stimulated insulin secretion. Thus, MKP-1 is a possible target for anti-inflammatory therapeutic intervention with preservation of β-cell function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Chemokine CCL2 / genetics*
  • Dual Specificity Phosphatase 1 / genetics
  • Dual Specificity Phosphatase 1 / metabolism*
  • Gene Expression Regulation / drug effects*
  • Glucocorticoids / pharmacology*
  • Humans
  • I-kappa B Kinase / metabolism
  • Insulin-Secreting Cells / cytology
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / metabolism*
  • Interleukin-1beta / pharmacology*
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Glucocorticoid / metabolism
  • Transcription Factor RelA / metabolism
  • Transcriptional Activation / drug effects
  • p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Chemokine CCL2
  • Glucocorticoids
  • Interleukin-1beta
  • Protein Kinase Inhibitors
  • RNA, Messenger
  • Receptors, Glucocorticoid
  • Rela protein, rat
  • Transcription Factor RelA
  • I-kappa B Kinase
  • p38 Mitogen-Activated Protein Kinases
  • Dual Specificity Phosphatase 1

Grants and funding

This work was supported by start-up funds provided by the University of Tennessee, Knoxville (to JJC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.