Journal
INFLAMMATION RESEARCH
Volume 69, Issue 6, Pages 579-588Publisher
SPRINGER BASEL AG
DOI: 10.1007/s00011-020-01340-2
Keywords
Antimicrobial peptide; Cathelicidin; Cytokines; Innate immunity; Poly I; C
Categories
Funding
- Lund University
- Alfred osterlund Foundation [301118]
- Swedish Dental Society [311017]
- Research Funds for Oral Health Related Research by Region Skane [OFRS732821]
- Novo Nordisk [150917]
- Karolinska Institutet
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Objective The importance of human host defense peptide LL-37 in vascular innate immunity is not understood. Here, we assess the impact of LL-37 on double-stranded RNA (dsRNA) signaling in human vascular smooth muscle cells. Materials and methods Cellular import of LL-37 and synthetic dsRNA (poly I:C) were investigated by immunocytochemistry and fluorescence imaging. Transcript and protein expression were determined by qPCR, ELISA and Western blot. Knockdown of TLR3 was performed by siRNA. Results LL-37 was rapidly internalized, suggesting that it has intracellular actions. Co-stimulation with poly I:C and LL-37 enhanced pro-inflammatory IL-6 and MCP-1 transcripts several fold compared to treatment with poly I:C or LL-37 alone. Poly I:C increased IL-6 and MCP-1 protein production, and this effect was potentiated by LL-37. LL-37-induced stimulation of poly I:C signaling was not associated with enhanced import of poly I:C. Treatment with poly I:C and LL-37 in combination increased expression of dsRNA receptor TLR3 compared to stimulation with poly I:C or LL-37 alone. In TLR3 knockdown cells, treatment with poly I:C and LL-37 in combination had no effect on IL-6 and MCP-1 expression, showing loss of function. Conclusions LL-37 potentiates dsRNA-induced cytokine production through up-regulation of TLR3 expression representing a novel pro-inflammatory mechanism.
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