Bovine and human cathelicidin cationic host defense peptides similarly suppress transcriptional responses to bacterial lipopolysaccharide

Abstract

Genomic approaches can be exploited to expose the complexities and conservation of biological systems such as the immune network across various mammalian species. In this study, temporal transcriptional expression profiles were analyzed in human and bovine monocytic cells in response to the TLR-4 agonist, LPS, in the presence or absence of their respective host defense peptides. The cathelicidin peptides, human LL-37 and bovine myeloid antimicrobial peptide-27 (BMAP-27), are homologs, yet they have diverged notably in terms of sequence similarity. In spite of their low sequence similarities, both of these cathelicidin peptides demonstrated potent, antiendotoxin activity in monocytic cells at low, physiologically relevant concentrations. Microarray studies indicated that 10 ng/ml LPS led to the up-regulation of 125 genes in human monocytes, 106 of which were suppressed in the presence of 5 mug/ml of the human peptide LL-37. To confirm and extend these data, temporal transcriptional responses to LPS were assessed in the presence or absence of the species-specific host defense peptides by quantitative real-time PCR. The transcriptional trends of 20 LPS-induced genes were analyzed in bovine and human monocytic cells. These studies demonstrated conserved trends of gene responses in that both peptides were able to profoundly suppress many LPS-induced genes. Consistent with this, the human and bovine peptides suppressed LPS-induced translocation of NF-kappaB subunits p50 and p65 into the nucleus of monocytic cells. However, there were also distinct differences in responses to LPS and the peptides; for example, treatment with 5 mug/ml BMAP-27 alone tended to influence gene expression (RELA, TNF-alpha-induced protein 2, MAPK phosphatase 1/dual specificity phosphatase 1, IkappaBkappaB, NFkappaBIL1, TNF receptor-associated factor 2) to a greater extent than did the same amount of human LL-37. We hypothesize that the immunomodulatory effects of the species-specific host defense peptides play a critical role in regulating inflammation and represent an evolutionarily conserved mechanism for maintaining homeostasis, although the sequence divergence of these peptides is substantial.

Intracellular Receptor for Human Host Defense Peptide LL-37 in Monocytes

“…Despite substantial overlap (Ͼ30%) in the gene responses to LL-37 and IDR-1, both in the absence and presence of the TLR-4 agonist LPS (17,19,20), there are clear differences in functions mediated by these peptides. For example, LL-37 is a modulator of apoptosis in epithelial cells (43,44) and neutrophils (32) and causes degranulation of mast cells (22), whereas IDR-1 does not (17).…”

Host Responses to Persistent Mycobacterium avium Subspecies paratuberculosis Infection in Surgically Isolated Bovine Ileal Segments

“…The concentrations of gamma interferon (IFN-␥) and tumor necrosis factor alpha (TNF-␣) in culture supernatants were determined by capture enzyme-linked immunosorbent assays (ELISAs) as described previously (28,29). Net cytokine secretion was calculated by subtracting the level of spontaneous cytokine release from cells cultured in medium alone from the level of cytokine release induced by stimulation with the M. avium subsp.…”

Cationic Host Defence Peptides: Multifaceted Role in Immune Modulation and Inflammation

“…Cathelicidin peptides such as LL-37, BMAP-28 and mimetics IDR-1 and IDR-1002 have been shown to suppress specific pro-inflammatory responses such as induction of tumour necrosis factor (TNF)-α, IL-1β, NF-ĸB1 (p105/p50), TNF-α-induced protein-2, MMP-3 and nitric oxide in the presence of either pathogenic or immune-mediated inflammatory stimuli, without suppressing production of certain chemokines that are required for cell recruitment and movement. In contrast, these peptides enhance or maintain crucial anti-inflammatory responses such as TNF-α-induced protein-3 (also known as A20), the NF-ĸB inhibitor NFĸBIA, expression of IL-10 and the IL-1 antagonist IL-1RA [10,11,15,20,35,36,37]. Mechanistic studies to date have demonstrated that the anti-inflammatory or immunomodulatory activity of these peptides is very complex and involves intracellular uptake, endocytic mobilization and interaction with several receptors, resulting in altered signalling pathways (such as NF-ĸB, p38 and JNK MAPK, and PI3K) and transcription factor activities with different kinetics.…”