Abstract
Lipopolysaccharide (LPS) is a potent microbial virulence factor that can trigger production of proinflammatory mediators involved in the pathogenesis of localized and systemic inflammation. Importantly, the role of nuclear transport of stress responsive transcription factors in this LPS-generated “genomic storm” remains largely undefined. We developed a new nuclear transport modifier (NTM) peptide, cell-penetrating cSN50.1, which targets nuclear transport shuttles importin α5 and importin β1, to analyze its effect in LPS-induced localized (acute lung injury) and systemic (lethal endotoxic shock) murine inflammation models. We analyzed a human genome database to match 46 genes that encode cytokines, chemokines and their receptors with transcription factors whose nuclear transport is known to be modulated by NTM. We then tested the effect of cSN50.1 peptide on proinflammatory gene expression in murine bone marrow-derived macrophages stimulated with LPS. This NTM suppressed a proinflammatory transcriptome of 37 out of 84 genes analyzed, without altering expression of housekeeping genes or being cytotoxic. Consistent with gene expression analysis in primary macrophages, plasma levels of 23 out of 26 LPS-induced proinflammatory cytokines, chemokines, and growth factors were significantly attenuated in a murine model of LPS-induced systemic inflammation (lethal endotoxic shock) while the anti-inflammatory cytokine, interleukin 10, was enhanced. This anti-inflammatory reprogramming of the endotoxin-induced genomic response was accompanied by complete protection against lethal endotoxic shock with prophylactic NTM treatment, and 75% protection when NTM was first administered after LPS exposure. In a murine model of localized lung inflammation caused by direct airway exposure to LPS, expression of cytokines and chemokines in the bronchoalveolar space was suppressed with a concomitant reduction of neutrophil trafficking. Thus, calming the LPS-triggered “genomic storm” by modulating nuclear transport with cSN50.1 peptide attenuates the systemic inflammatory response associated with lethal shock as well as localized lung inflammation.
Highlights
Bacterial endotoxin, known as lipopolysaccharide (LPS), is one of the most potent microbial virulence factors in the pathogenesis of localized and systemic inflammation caused by Gram-negative bacteria [1]
Binding of LPS to its cognate receptor, TLR4, induces robust signaling to the nucleus mediated by a cascade of signal transducers engaged in a stream of protein-protein interactions and posttranslational modifications [4], culminating in nuclear translocation of NF-kB along with other stress-responsive transcription factors (SRTFs), including activator protein-1 (AP-1), nuclear factor of activated T cells (NFAT), and signal transducer and activator of transcription 1 (STAT-1) [5]
Our results document the essential role of nuclear transport in development of a ‘‘genomic storm’’ and its sequelae induced by bacterial endotoxin
Summary
Known as lipopolysaccharide (LPS), is one of the most potent microbial virulence factors in the pathogenesis of localized and systemic inflammation caused by Gram-negative bacteria [1]. Binding of LPS to its cognate receptor, TLR4, induces robust signaling to the nucleus mediated by a cascade of signal transducers engaged in a stream of protein-protein interactions and posttranslational modifications [4], culminating in nuclear translocation of NF-kB along with other stress-responsive transcription factors (SRTFs), including activator protein-1 (AP-1), nuclear factor of activated T cells (NFAT), and signal transducer and activator of transcription 1 (STAT-1) [5]. These SRTFs, either alone or in various combinations, regulate the genomic response to Gram-negative bacteria and other microbial agents [5]. SRTFs respond to signaling pathways emanating from cytokine/chemokine receptors [6,7]
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