Dissertation committee:
Ευάγγελος Ι. Γιαμαρέλλος- Μπουρμπούλης, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Γεώργιος Δημόπουλος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ηρακλής Τσαγκάρης, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ερυφίλη Χατζηαγγελάκη, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Μιχαήλ Σαμάρκος, Αναπλ. Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ελένη Σαμπατάκου, Αναπλ. Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Αντώνιος Παπαδόπουλος, Αναπλ. Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Hydrogen sulfide (H2S) has recently been recognized as a novel gaseous transmitterwith several anti-inflammatory properties. The role of host- derived H2S in infectionsby Pseudomonas aeruginosa was investigated in clinical and mouse models. H2Sconcentrations and survival was assessed in septic patients with lung infection. Animalexperiments using a model of severe systemic multidrug-resistant P. aeruginosainfection were performed using mice with a constitutive knock-out of cystathionine-γlyase (Cse) gene (Cse-/-) and wild-type mice with a physiological expression (Cse+/+).Experiments were repeated in mice after a) treatment with cyclophosphamide; b) bonemarrow transplantation (BMT) from a Cse+/+ donor; c) treatment with H2S synthesisinhibitor aminooxyacetic acid (ΑΟΑΑ) or propargylglycine (PAG) and d) H2S donorsodium thiosulfate (STS) or GYY3147. Bacterial loads and myeloperoxidase activitywere measured in tissue samples. The expression of quorum sensing genes (QS) wasdetermined in vivo and in vitro. Cytokine concentration was measured in serum andincubated splenocytes. Patients survivors at day 28 had significantly higher serum H2Scompared to non-survivors. A cut- off point of 5.3 μΜ discriminated survivors withsensitivity 92.3%. Mortality after 28 days was 30.9% and 93.7% in patients with H2Shigher and less than 5.3 μΜ (p= 7 x 10-6). In mice expression of Cse and applicationof STS afforded protection against infection with multidrug-resistant P. aeruginosa.Cyclophosphamide pretreatment eliminated the survival benefit of Cse+/+ mice,whereas BMT increased the survival of Cse-/- mice. Cse-/- mice had increasedpathogen loads compared to Cse+/+ mice. Phagocytic activity of leukocytes from Cse-/- mice was reduced but was restored after H2S supplementation. An H2S dependentdown- regulation of quorum sensing genes of P.aeruginosa could be demonstrated invivo and in vitro. Endogenous H2S is a potential independent parameter correlatingwith the outcome of P. aeruginosa. H2S provides resistance to infection by MDRbacterial pathogens.
Keywords:
Hydrogen sulfide, Pseudomonas aeruginosa, Ventilator associated pneumonia, Antimicrobial resistance
