RESUMEN
High glucose concentration in the airway surface liquid (ASL) is an important feature of diabetes that predisposes to respiratory infections. We investigated the role of alveolar epithelial SGLT1 activity on ASL glucose concentration and bacterial proliferation. Non-diabetic and diabetic rats were intranasally treated with saline, isoproterenol (to increase SGLT1 activity) or phlorizin (to decrease SGLT1 activity); 2 hours later, glucose concentration and bacterial proliferation (methicillin-resistant Sthaphylococcus aureus, MRSA and Pseudomonas aeruginosa, P. aeruginosa) were analyzed in bronchoalveolar lavage (BAL); and alveolar SGLT1 was analyzed by immunohistochemistry. BAL glucose concentration and bacterial proliferation increased in diabetic animals: isoproterenol stimulated SGLT1 migration to luminal membrane, and reduced (50%) the BAL glucose concentration; whereas phlorizin increased the BAL glucose concentration (100%). These regulations were accompanied by parallel changes of in vitro MRSA and P. aeruginosa proliferation in BAL (r = 0.9651 and r = 0.9613, respectively, Pearson correlation). The same regulations were observed in in vivo P. aeruginosa proliferation. In summary, the results indicate a relationship among SGLT1 activity, ASL glucose concentration and pulmonary bacterial proliferation. Besides, the study highlights that, in situations of pulmonary infection risk, such as in diabetic subjects, increased SGLT1 activity may prevent bacterial proliferation whereas decreased SGLT1 activity can exacerbate it.
Asunto(s)
Diabetes Mellitus Experimental/metabolismo , Glucosa/metabolismo , Pulmón/metabolismo , Neumonía Bacteriana/metabolismo , Infecciones por Pseudomonas/metabolismo , Transportador 1 de Sodio-Glucosa/genética , Infecciones Estafilocócicas/metabolismo , Aloxano , Células Epiteliales Alveolares/efectos de los fármacos , Células Epiteliales Alveolares/metabolismo , Células Epiteliales Alveolares/microbiología , Animales , Líquido del Lavado Bronquioalveolar/química , Líquido del Lavado Bronquioalveolar/microbiología , Broncodilatadores/farmacología , Recuento de Colonia Microbiana , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/complicaciones , Diabetes Mellitus Experimental/genética , Regulación de la Expresión Génica , Isoproterenol/farmacología , Pulmón/efectos de los fármacos , Pulmón/microbiología , Pulmón/patología , Masculino , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Staphylococcus aureus Resistente a Meticilina/crecimiento & desarrollo , Florizina/farmacología , Neumonía Bacteriana/complicaciones , Neumonía Bacteriana/genética , Neumonía Bacteriana/patología , Infecciones por Pseudomonas/complicaciones , Infecciones por Pseudomonas/genética , Infecciones por Pseudomonas/patología , Pseudomonas aeruginosa/efectos de los fármacos , Pseudomonas aeruginosa/crecimiento & desarrollo , Ratas , Ratas Wistar , Transportador 1 de Sodio-Glucosa/agonistas , Transportador 1 de Sodio-Glucosa/antagonistas & inhibidores , Transportador 1 de Sodio-Glucosa/metabolismo , Infecciones Estafilocócicas/complicaciones , Infecciones Estafilocócicas/genética , Infecciones Estafilocócicas/patologíaRESUMEN
BACKGROUND: ExoU, a Pseudomonas aeruginosa cytotoxin with phospholipase A2 activity, was shown to induce vascular hyperpermeability and thrombus formation in a murine model of pneumosepsis. In this study, we investigated the toxin ability to induce alterations in pulmonary fibrinolysis and the contribution of the platelet activating factor (PAF) in the ExoU-induced overexpression of plasminogen activator inhibitor-1 (PAI-1). METHODS: Mice were intratracheally instilled with the ExoU producing PA103 P. aeruginosa or its mutant with deletion of the exoU gene. After 24 h, animal bronchoalveolar lavage fluids (BALF) were analyzed and lung sections were submitted to fibrin and PAI-1 immunohistochemical localization. Supernatants from A549 airway epithelial cells and THP-1 macrophage cultures infected with both bacterial strains were also analyzed at 24 h post-infection. RESULTS: In PA103-infected mice, but not in control animals or in mice infected with the bacterial mutant, extensive fibrin deposition was detected in lung parenchyma and microvasculature whereas mice BALF exhibited elevated tissue factor-dependent procoagulant activity and PAI-1 concentration. ExoU-triggered PAI-1 overexpression was confirmed by immunohistochemistry. In in vitro assays, PA103-infected A549 cells exhibited overexpression of PAI-1 mRNA. Increased concentration of PAI-1 protein was detected in both A549 and THP-1 culture supernatants. Mice treatment with a PAF antagonist prior to PA103 infection reduced significantly PAI-1 concentrations in mice BALF. Similarly, A549 cell treatment with an antibody against PAF receptor significantly reduced PAI-1 mRNA expression and PAI-1 concentrations in cell supernatants, respectively. CONCLUSION: ExoU was shown to induce disturbed fibrin turnover, secondary to enhanced procoagulant and antifibrinolytic activity during P. aeruginosa pneumosepsis, by a PAF-dependent mechanism. Besides its possible pathophysiological relevance, in vitro detection of exoU gene in bacterial clinical isolates warrants investigation as a predictor of outcome of patients with P. aeruginosa pneumonia/sepsis and as a marker to guide treatment strategies.