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Background/Aims: Pulmonary infections with Pseudomonas aeruginosa (P. aeruginosa) or Staphylococcus aureus (S. aureus) are of utmost clinical relevance in patients with cystic fibrosis, chronic obstructive pulmonary disease, after trauma and burn, upon ventilation or in immuno-compromised patients. Many P. aeruginosa and S. aureus strains are resistant to many known antibiotics and it is very difficult or often impossible to eradicate the pathogens in patient´s lungs. We have recently shown that the sphingoid base sphingosine very efficiently kills many pathogens, including for instance P. aeruginosa, S. aureus or Acinetobacter baumannii, in vitro. In vivo experiments of our group on cystic fibrosis mice indicated that inhalation of sphingosine prevents or eliminates existing acute or chronic pneumonia with P. aeruginosa or S. aureus in these mice. We also demonstrated that sphingosine is safe to use for inhalation up to high doses, at least in mice. To facilitate development of sphingosine to an anti-bactericidal drug that can be used in humans for inhalation, safety data on non-rodents, larger animals are absolutely required. Methods: Here, we inhaled mini pigs with increasing doses of sphingosine for 10 days and analyzed the uptake of sphingosine into epithelial cells of bronchi as well as into the trachea and lung and the systemic circulation. Moreover, we measured the generation of ceramide and sphingosine 1-phosphate that potentially mediate inflammation, the influx of leukocytes, epithelial cell death and disruption of the epithelial cell barrier. Results: We demonstrate that inhalation of sphingosine results in increased levels of sphingosine in the luminal membrane of bronchi and the trachea, but not in systemic accumulation. Inhaled sphingosine had no side effects up to very high doses. Conclusion: In summary, we demonstrate that inhalation of sphingosine results in an increase of sphingosine concentrations in the luminal plasma membrane of tracheal and bronchial epithelial cells. The inhalation has no systemic or local side effects. [ABSTRACT FROM AUTHOR]

Background/Aims: We have previously shown that inhibition of the mitochondrial Kv1.3 channel results in an initial mitochondrial hyperpolarization and a release of oxygen radicals that mediate mitochondrial depolarization, cytochrome c release and death. Here, we investigated whether inhibition of Kv1.3 channels can also induce cellular resistance mechanisms that counteract the induction of cell death under certain conditions. Methods: We treated leukemic T cells with the mitochondria-targeted Kv1.3 inhibitor PCARBTP and determined the activity of different kinases associated with cell survival including ZAP70, PI-3-K, AKT, JNK and ERK by measuring the activation-associated phosphorylation of these proteins. Furthermore, we inhibited AKT and JNK and determined the effect of PCARBTP-induced tumor cell death. Results: We demonstrate that treatment of Jurkat T leukemia cells with low doses of the mitochondria-targeted inhibitor of Kv1.3 PCARBTP (0.25 µM or 1 µM) for 10 minutes induced a constitutive phosphorylation/activation of the pro-survival signaling molecules ZAP70, PI-3-K, AKT and JNK, while the phosphorylation/activation of ERK was not affected. Stimulation of Jurkat cells via the TCR/CD3 complex induced an additional activation of a similar pattern of signaling events. Higher doses of the Kv1.3 inhibitor, i.e. 10 µM PCARBTP, reduced the basal phosphorylation/activation of these signaling molecules and also impaired their activation upon stimulation via the TCR/CD3 complex. A low dose of PCARBTP, i.e. 0.25 µM PCARBTP, was almost without any effect on cell death. In contrast, concomitant inhibition of PI-3-K or AKT greatly sensitized Jurkat leukemia cells to the Kv1.3 inhibitor PCARBTP and allowed induction of cell death already at 0.25 µM PCARBTP. Conclusion: These studies indicate that Jurkat leukemia cells respond to low doses of the mitochondria-targeted Kv1.3 inhibitor PCARBTP with an activation of survival signals counteracting cell death. Inhibition of these T cell survival signals sensitizes leukemia cells to death induced by mitochondria-targeted Kv1.3 inhibitors. High doses of the Kv1.3 inhibitor inactivate these signals directly permitting death. [ABSTRACT FROM AUTHOR]

Sphingosine has been previously shown to kill many strains of pathogenic bacteria including Pseudomonas aeruginosa, Staphyloccus aureus, Acinetobacter, and atypical mycobacteria. However, these studies were performed on isolated or extracellular bacteria and it is unknown whether sphingosine also targets intracellular bacteria. Here, we demonstrate that exogenously-added sphingosine directly binds to extracellular P. aeruginosa and S. aureus, but also targets and binds to intracellular bacteria. Intracellular sphingosine and bacteria were identified by sequential immunostainings. We further show that exogenously-added sphingosine also kills intracellular P. aeruginosa and S. aureus using modified gentamycin assays. Intracellular killing of P. aeruginosa and S. aureus by sphingosine is not mediated by improved phagosomal-lysosomal fusion. In summary, our data indicate that sphingosine binds to and most likely also directly kills extra- and intracellular P. aeruginosa and S. aureus., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Staphylococcus aureus ( S. aureus ) infections are among the most common and severe infections, garnering notoriety in an era of increasing resistance to antibiotics. It is therefore important to define molecular mechanisms by which this pathogen attacks host cells. Here, we demonstrate that alpha-toxin, one of the major toxins of S. aureus , induces activation of acid sphingomyelinase and concomitant release of ceramide in endothelial cells treated with the toxin. Activation of acid sphingomyelinase by alpha-toxin is mediated via ADAM10. Infection experiments employing alpha-toxin-deficient S. aureus and the corresponding wild-type strain reveal that activation of acid sphingomyelinase in endothelial cells requires alpha-toxin expression by the pathogen. Activation of acid sphingomyelinase is linked to degradation of tight junctions in endothelial cells in vitro , which is blocked by pharmacological inhibition of acid sphingomyelinase. Most importantly, alpha-toxin induces severe degradation of tight junctions in the lung and causes lung edema in vivo , which is prevented by genetic deficiency of acid sphingomyelinase. These data indicate a novel and important role of the acid sphingomyelinase/ceramide system for the endothelial response to toxins and provide a molecular link between alpha-toxin and the degradation of tight junctions. The data also suggest that inhibition of acid sphingomyelinase may provide a novel treatment option to prevent lung edema caused by S. aureus alpha-toxin., (Copyright © 2017 American Society for Microbiology.)