Rhesus macaque θ-defensin RTD-1 inhibits proinflammatory cytokine secretion and gene expression by inhibiting the activation of NF-κB and MAPK pathways.
θ-Defensins are pleiotropic, macrocyclic peptides that are expressed uniquely in Old World monkeys. The peptides are potent, broad-spectrum microbicides that also modulate inflammatory responses in vitro and in animal models of viral infection and polymicrobial sepsis. θ-Defensins suppress proinflammatory cytokine secretion by leukocytes stimulated with diverse Toll-like receptor (TLR) ligands. Studies were performed to delineate anti-inflammatory mechanisms of rhesus θ-defensin 1 (RTD-1), the most abundant θ-defensin isoform in macaque granulocytes. RTD-1 reduced the secretion of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-8 in lipopolysaccharide (LPS)-stimulated human blood monocytes and THP-1 macrophages, and this was accompanied by inhibition of nuclear factor κB (NF-κB) activation and mitogen-activated protein kinase (MAPK) pathways. Peptide inhibition of NF-κB activation occurred following stimulation of extracellular (TLRs 1/2 and 4) and intracellular (TLR9) receptors. Although RTD-1 did not inhibit MAPK in unstimulated cells, it induced phosphorylation of Akt in otherwise untreated monocytes and THP-1 cells. In the latter, this occurred within 10 min of RTD-1 treatment and produced a sustained elevation of phosphorylated Akt (pAkt) for at least 4 h. pAkt is a negative regulator of MAPK and NF-κB activation. RTD-1 inhibited IκBα degradation and p38 MAPK phosphorylation, and stimulated Akt phosphorylation in LPS-treated human primary monocytes and THP-1 macrophages. Specific inhibition of phosphatidylinositol 3-kinase (PI3K) blocked RTD-1-stimulated Akt phosphorylation and reversed the suppression of NF-κB activation by the peptide. These studies indicate that the anti-inflammatory properties of θ-defensins are mediated by activation of the PI3K/Akt pathway and suppression of proinflammatory signals in immune-stimulated cells.
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA tongaonk@usc.edu selsted@med.usc.edu.
Prasad
P
Tongaonkar
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Katie K
KK
Trinh
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Justin B
JB
Schaal
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Dat
D
Tran
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Percio S
PS
Gulko
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA.
André J
AJ
Ouellette
*Department of Pathology and Laboratory Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; and Division of Rheumatology, Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York, USA tongaonk@usc.edu selsted@med.usc.edu.
Michael E
ME
Selsted
D045744:Cell Line, Tumor; D016207:Cytokines / Q000276:immunology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology*; D008264:Macrophages / Q000166:cytology / Q000276:immunology*; D008297:Male; D009000:Monocytes / Q000166:cytology / Q000276:immunology*; D016328:NF-kappa B / Q000276:immunology*; D010456:Peptides, Cyclic / Q000276:immunology* / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology; D010766:Phosphorylation / Q000187:drug effects / Q000276:immunology; D051057:Proto-Oncogene Proteins c-akt / Q000276:immunology; D051193:Toll-Like Receptors / Q000819:agonists / Q000276:immunology; D023084:alpha-Defensins / Q000276:immunology* / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology
D016207:Cytokines; C429483:DEFA1A3 protein, human; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010456:Peptides, Cyclic; D051193:Toll-Like Receptors; D023084:alpha-Defensins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases
Akt; IκBα; THP-1; TLR; monocytes