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Anti-Inflammatory Effects of RTD-1 in a Murine Model of Chronic Pseudomonas aeruginosa Lung Infection: Inhibition of NF-κB, Inflammasome Gene Expression, and Pro-IL-1β Biosynthesis.

ABSTRACT: Vicious cycles of chronic airway obstruction, lung infections with Pseudomonas aeruginosa, and neutrophil-dominated inflammation contribute to morbidity and mortality in cystic fibrosis (CF) patients. Rhesus theta defensin-1 (RTD-1) is an antimicrobial macrocyclic peptide with immunomodulatory properties. Our objective was to investigate the anti-inflammatory effect of RTD-1 in a murine model of chronic P. aeruginosa lung infection. Mice received nebulized RTD-1 daily for 6 days. Bacterial burden, leukocyte counts, and cytokine concentrations were evaluated. Microarray analysis was performed on bronchoalveolar lavage fluid (BALF) cells and lung tissue homogenates. In vitro effects of RTD-1 in THP-1 cells were assessed using quantitative reverse transcription PCR, enzyme-linked immunosorbent assays, immunoblots, confocal microscopy, enzymatic activity assays, and NF-κB-reporter assays. RTD-1 significantly reduced lung white blood cell counts on days 3 (-54.95%; p = 0.0003) and 7 (-31.71%; p = 0.0097). Microarray analysis of lung tissue homogenates and BALF cells revealed that RTD-1 significantly reduced proinflammatory gene expression, particularly inflammasome-related genes (nod-like receptor protein 3, Mediterranean fever gene, interleukin (IL)-1α, and IL-1β) relative to the control. In vitro studies demonstrated NF-κB activation was reduced two-fold (p ≤ 0.0001) by RTD-1 treatment. Immunoblots revealed that RTD-1 treatment inhibited proIL-1β biosynthesis. Additionally, RTD-1 treatment was associated with a reduction in caspase-1 activation (FC = -1.79; p = 0.0052). RTD-1 exhibited potent anti-inflammatory activity in chronically infected mice. Importantly, RTD-1 inhibits inflammasome activity, which is possibly a downstream effect of NF-κB modulation. These findings support that this immunomodulatory peptide may be a promising therapeutic for CF-associated lung disease.

SUBMITTER: Dughbaj MA

PROVIDER: S-EPMC8466744 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:An NF-κB target gene array (Panomics, Inc., Redwood City, CA) was performed to profile the PAO1-dependent expression pattern of 111 NF-kB-regulated genes in primary human airway epithelial cells (HAECs). A small scale microarray was carried out using NF-κB target gene array kit (Panomics, Inc., Redwood City, CA). A long sense-strand oligonucleotide for each of the 111 human genes that have been previously shown to be regulated by NF-KB signaling pathway was spotted in duplicate on the nitrocellulose membrane. Biotinylated DNA was spotted along the right and bottom sides of the array membrane as control. The arrays were performed according to the manufacturer’s instructions. In brief, HAECs were stimulated for 18 hours with the heat-killed bacteria PAO1 (multiplicity of infection: 100:1). Control experiment used PBS instead of bacteria. mRNA of HAECs was isolated using biotin-labeled oligo(dT)20 and streptavidin-conjugated magnetic particles (Roche, Germany). 500 ng mRNA was used to prepare biotin-labeled cDNA probes through incorporation of biotin-dUTP into cDNA via reverse transcription reactions. Each biotin-labeled cDNA probe was hybridized to an array membrane at 42°C overnight in a hybridization incubator (Fisher Scientific, Pittsburgh, PA). The membrane was washed and subjected to further incubations with blocking buffer and subsequent streptavidin-conjugated HRP. The membrane was developed through chemiluminescence reactions and detected immediately by 1 min exposure to Hyperfilm ECL X-ray films (Amersham, Piscataway, NJ). The dots on the array were quantified through densitometric analysis using GeneTools (Syngene, Frederick, MD) and the value of each dot was determined as D = (signal value – background value)/mean value of biotinylated DNA dots. Ratio (Dbacteria: Dcontrol) was used to determine the effect of bacteria stimulation on the gene regulation. Ratio>1 indicated an up-regulation of the gene. The experiments include two samples, one PBS control sample and one PAO1-stimulated sample.

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Anti-Inflammatory Effects of RTD-1 in a Murine Model of Chronic Pseudomonas aeruginosa Lung Infection: Inhibition of NF-κB, Inflammasome Gene Expression, and Pro-IL-1β Biosynthesis.

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