Pseudomonas aeruginosa toxin ExoU induces a PAF-dependent impairment of alveolar fibrin turnover secondary to enhanced activation of coagulation and increased expression of plasminogen activator inhibitor-1 in the course of mice pneumosepsis

<p>Abstract</p> <p>Background</p> <p>ExoU, a <it>Pseudomonas aeruginosa </it>cytotoxin with phospholipase A₂activity, 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).</p> <p>Methods</p> <p>Mice were intratracheally instilled with the ExoU producing PA103 <it>P. aeruginosa </it>or its mutant with deletion of the <it>exoU </it>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.</p> <p>Results</p> <p>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 <it>in vitro </it>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.</p> <p>Conclusion</p> <p>ExoU was shown to induce disturbed fibrin turnover, secondary to enhanced procoagulant and antifibrinolytic activity during <it>P. aeruginosa </it>pneumosepsis, by a PAF-dependent mechanism. Besides its possible pathophysiological relevance, <it>in vitro </it>detection of e<it>xoU </it>gene in bacterial clinical isolates warrants investigation as a predictor of outcome of patients with <it>P. aeruginosa </it>pneumonia/sepsis and as a marker to guide treatment strategies.</p

Shock

Texto completo: acesso restrito. p.315-321To address the question whether ExoU, a Pseudomonas aeruginosa cytotoxin with phospholipase A2 activity, can induce hemostatic abnormalities during the course of pneumosepsis, mice were instilled i.t. with the ExoU-producing PA103 P. aeruginosa or with a mutant obtained by deletion of the exoU gene. Control animals were instilled with sterile vehicle. To assess the role of ExoU in animal survival, mice were evaluated for 72 h. In all the other experiments, animals were studied at 24 h after infection. PA103-infected mice showed significantly higher mortality rate, lower blood leukocyte concentration, and higher platelet concentration and hematocrit than animals infected with the bacterial mutant, as well as evidences of increased vascular permeability and plasma leakage, which were confirmed by our finding of higher protein concentration in bronchoalveolar lavage fluids and by the Evans blue dye assay. Platelets from PA103-infected mice demonstrated features of activation, assessed by the flow cytometric detection of higher percentage of P-selectin expression and of platelet-derived microparticles as well as by the enzyme immunoassay detection of increased thromboxane A2 concentration in animal plasma. Histopathology of lung and kidney sections from PA103-infected mice exhibited evidences of thrombus formation that were not detected in sections of animals from the other groups. Our results demonstrate the ability of ExoU to induce vascular hyperpermeability, platelet activation, and thrombus formation during P. aeruginosa pneumosepsis, and we speculate that this ability may contribute to the reported poor outcome of patients with severe infection by ExoU-producing P. aeruginosa

Leishmanial antigens in the diagnosis of active lesions and ancient scars of American tegumentary leishmaniasis patients

Cutaneous biopsies (n = 94) obtained from 88 patients with American tegumentary leishmaniasis were studied by conventional and immunohistochemical techniques. Specimens were distributed as active lesions of cutaneous leishmaniasis (n = 53) (Group I), cicatricial lesions of cutaneous leishmaniasis (n = 35) (Group II) and suggestive scars of healed mucosal leishmaniasis patients (n = 6) (Group III). In addition, active cutaneous lesions of other etiology (n = 24) (Group C1) and cutaneous scars not related to leishmaniasis (n = 10) (Group C2) were also included in the protocol. Amastigotes in Group I biopsies were detected by routine histopathological exam (30.2%), imprint (28.2%), culture (43.4%), immunofluorescence (41.4%) and immunoperoxidase (58.5%) techniques; and by the five methods together (79.3%). In Group II, 5.7% of cultures were positive. Leishmanial antigen was also seen in the cytoplasm of macrophages and giant cells (cellular pattern), vessel walls (vascular pattern) and dermal nerves (neural pattern). Positive reaction was detected in 49 (92.5%), 20 (57%) and 4 (67%) biopsies of Groups I, II and III, respectively. Antigen persistency in cicatricial tissue may be related to immunoprotection or, on the contrary, to the development of late lesions. We suggest that the cellular, vascular and neural patterns could be applied in the immunodiagnosis of active and cicatricial lesions in which leishmaniasis is suspected

Leishmanial antigens in the diagnosis of active lesions and ancient scars of American tegumentary leishmaniasis patients

Cutaneous biopsies (n = 94) obtained from 88 patients with American tegumentary leishmaniasis were studied by conventional and immunohistochemical techniques. Specimens were distributed as active lesions of cutaneous leishmaniasis (n = 53) (Group I), cicatricial lesions of cutaneous leishmaniasis (n = 35) (Group II) and suggestive scars of healed mucosal leishmaniasis patients (n = 6) (Group III). In addition, active cutaneous lesions of other etiology (n = 24) (Group C1) and cutaneous scars not related to leishmaniasis (n = 10) (Group C2) were also included in the protocol. Amastigotes in Group I biopsies were detected by routine histopathological exam (30.2%), imprint (28.2%), culture (43.4%), immunofluorescence (41.4%) and immunoperoxidase (58.5%) techniques; and by the five methods together (79.3%). In Group II, 5.7% of cultures were positive. Leishmanial antigen was also seen in the cytoplasm of macrophages and giant cells (cellular pattern), vessel walls (vascular pattern) and dermal nerves (neural pattern). Positive reaction was detected in 49 (92.5%), 20 (57%) and 4 (67%) biopsies of Groups I, II and III, respectively. Antigen persistency in cicatricial tissue may be related to immunoprotection or, on the contrary, to the development of late lesions. We suggest that the cellular, vascular and neural patterns could be applied in the immunodiagnosis of active and cicatricial lesions in which leishmaniasis is suspected