Dynorphin Activates Quorum Sensing Quinolone Signaling in Pseudomonas aeruginosa

There is now substantial evidence that compounds released during host stress directly activate the virulence of certain opportunistic pathogens. Here, we considered that endogenous opioids might function as such compounds, given that they are among the first signals to be released at multiple tissue sites during host stress. We tested the ability of various opioid compounds to enhance the virulence of Pseudomonas aeruginosa using pyocyanin production as a biological readout, and demonstrated enhanced virulence when P. aeruginosa was exposed to synthetic (U-50,488) and endogenous (dynorphin) κ-agonists. Using various mutants and reporter strains of P. aeruginosa, we identified involvement of key elements of the quorum sensing circuitry such as the global transcriptional regulator MvfR and the quorum sensing-related quinolone signaling molecules PQS, HHQ, and HQNO that respond to κ-opioids. The in vivo significance of κ-opioid signaling of P. aeruginosa was demonstrated in mice by showing that dynorphin is released from the intestinal mucosa following ischemia/reperfusion injury, activates quinolone signaling in P. aeruginosa, and enhances the virulence of P. aeruginosa against Lactobacillus spp. and Caenorhabditis elegans. Taken together, these data demonstrate that P. aeruginosa can intercept opioid compounds released during host stress and integrate them into core elements of quorum sensing circuitry leading to enhanced virulence

Dynorphin Activates Quorum Sensing Quinolone Signaling in Pseudomonas aeruginosa

There is now substantial evidence that compounds released during host stress directly activate the virulence of certain opportunistic pathogens. Here, we considered that endogenous opioids might function as such compounds, given that they are among the first signals to be released at multiple tissue sites during host stress. We tested the ability of various opioid compounds to enhance the virulence of Pseudomonas aeruginosa using pyocyanin production as a biological readout, and demonstrated enhanced virulence when P. aeruginosa was exposed to synthetic (U-50,488) and endogenous (dynorphin) κ-agonists. Using various mutants and reporter strains of P. aeruginosa, we identified involvement of key elements of the quorum sensing circuitry such as the global transcriptional regulator MvfR and the quorum sensing-related quinolone signaling molecules PQS, HHQ, and HQNO that respond to κ-opioids. The in vivo significance of κ-opioid signaling of P. aeruginosa was demonstrated in mice by showing that dynorphin is released from the intestinal mucosa following ischemia/reperfusion injury, activates quinolone signaling in P. aeruginosa, and enhances the virulence of P. aeruginosa against Lactobacillus spp. and Caenorhabditis elegans. Taken together, these data demonstrate that P. aeruginosa can intercept opioid compounds released during host stress and integrate them into core elements of quorum sensing circuitry leading to enhanced virulence

Neural EGF-like protein 1 (NELL-1): Signaling crosstalk in mesenchymal stem cells and applications in regenerative medicine

Bone tissue regeneration holds the potential to solve both osteoporosis and large skeletal defects, two problems associated with significant morbidity. The differentiation of mesenchymal stem cells into the osteogenic lineage requires a specific microenvironment and certain osteogenic growth factors. Neural EGF Like-Like molecule 1 (NELL-1) is a secreted glycoprotein that has proven, both in vitro and in vivo, to be a potent osteo-inductive factor. Furthermore, it has been shown to repress adipogenic differentiation and inflammation. NELL-1 can work synergistically with other osteogenic factors such as Bone Morphogenic Protein (BMP) −2 and −9, and has shown promise for use in tissue engineering and as a systemically administered drug for the treatment of osteoporosis. Here we provide a comprehensive up-to-date review on the molecular signaling cascade of NELL-1 in mesenchymal stem cells and potential applications in bone regenerative engineering

Proposed Activation and Effectors Pathways of P. aeruginosa in Response to Host Stress (Intestinal I/R Injury)

<div><p>(1) Dynorphin is released by intestinal tissues and accumulates in the lumen during ischemia/reperfusion and penetrates the plasma membrane of P. aeruginosa (dark green arrows).</p><p>(2) Dynorphin synergizes with PQS via MvfR to increase the transcription of <i>pqsABCDE</i> leading to the production of HAQs, including HQNO and HHQ.</p><p>(3) Increased HQNO production suppresses the growth of Lactobacillius spp., rendering the intestinal epithelium more vulnerable to invasion and the action of cytotoxins of P. aeruginosa (red arrows).</p><p>(4) HHQ is the immediate precursor of PQS [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030035#ppat-0030035-b023" target="_blank">23</a>], and both compounds play an important role in bacterial cell-to-cell communication [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030035#ppat-0030035-b023" target="_blank">23</a>] (yellow and blue arrows).</p><p>(5) PQS induces the expression of <i>pqsABCDE</i> [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030035#ppat-0030035-b063" target="_blank">63</a>], and is required for <i>phzA1-G1</i>expression<i>,</i> the gene responsible for PCN production (blue arrows). 6.) The release of PCN can induce neutrophils apoptosis and damage epithelial cells [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030035#ppat-0030035-b064" target="_blank">64</a>] (green arrows) allowing for immuno-evasion and deeper penetration of bacteria.</p></div

Dynorphin Binds to P. aeruginosa In Vitro, and Enters the Bacterial Cell Cytoplasm

<div><p>(A–C) Binding of dynorphin to <i>P. aeruginosa;</i> (A) negative control demonstrating no dynorphin staining when cells were not incubated with dynorphin; (B) negative control demonstrating no dynorphin staining when cell were incubated with dynorphin but primary anti-dynorphin antibodies were omitted from staining procedure; and (C) positive staining (brown color) of P. aeruginosa incubated with dynorphin followed by whole procedure of immunostaining.</p><p>(D) Immunoelectron microscopy of P. aeruginosa PAO1 cells incubated with dynorphin, 100 μM. Black arrows show 10-nm gold spots indicating the presence of dynorphin.</p></div

κ-Opioid Receptor Agonists Activate Virulence of P. aeruginosa against Probiotic Bacteria and C. elegans

<div><p>Error bars, mean ± SD.</p><p>(A and B) The exposure of P. aeruginosa PAO1 to U-50,488, 200 μM, increases the inhibiting effect of its extracellular milieu (conditioned media) on the growth of probiotic microorganisms (A) L. plantarum and (B) L. rhamnosus GG.</p><p>(C and D) The exposure of P. aeruginosa PAO1 to dynorphin, 100 μM, increases the inhibiting effect of its extracellular milieu (conditioned media) on the growth of probiotic microorganisms (C) L. plantarum and (D) L. rhamnosus GG.</p><p>(E) The extracellular milieu of P. aeruginosa PAO1 mutant ΔMvfR exposed to dynorphin, 100 μM, did not inhibit the growth of probiotic microorganism L. rhamnosus GG.</p><p>(F and G) P. aeruginosa PAO1 but not mutant ΔMvfR exposed to (F) U-50,488, 200 μM, or (G) dynorphin, 100 μM, suppressed the production of new progeny in C. elegans.</p></div