Blocking TNF-α enhances Pseudomonas aeruginosa-induced mortality in burn mice through induction of IL-1ß.

PURPOSE: Tumor necrosis factor (TNFα) is a proinflammatory cytokine and has been a target for intervention in human sepsis. However, inhibition of TNF-α with a high dose of a TNF-receptor fusion protein in patients with septic shock worsened patient survival. This study was designed to investigate whether blocking TNF-α enhances mortality in infected burn mice through the induction of IL-1ß. METHODS: WT or Tnfrsf1a(-/-) mice received Pseudomonas aeruginosa injection in the back at 8h after burn injury. The animals were sacrificed at 24h after burn and lung tissues were harvested and examined for determining myeloperoxidase (MPO) activity, pulmonary microvascular dysfunction, NF-κB DNA binding activity, and IL-1ß expression. Also, the lung and blood were harvested for bacterial count assay. RESULT: Thermal injury alone induced NF-κB DNA binding activity and neutrophil infiltration in the lung in WT but not in Tnfrsf1a(-/-) mice. A 50% total body surface area (TBSA) burn induced a significant increase of mortality in WT compared with Tnfrsf1a(-/-) mice. In contrast, P. aeruginosa injection with a 30% TBSA burn pretreatment enhanced IL-1ß expression, bacterial counts in lung and blood, pulmonary microvascular dysfunction, and mortality in Tnfrsf1a(-/-) mice compared with WT mice. Injection of the IL-1 receptor antagonist, Anakinra, reduced P. aeruginosa infection with burn pretreatment-induced blood bacterial counts, IL-1ß levels as well as permeability of lung, and mortality in Tnfrsf1a(-/-) mice. CONCLUSIONS: Our findings suggest that thermal injury induces lung NF-κB activation and neutrophil sequestration through TNFα signaling. However, blocking TNF-α enhances P. aeruginosa infection-induced lung damage in burn mice via induction of IL-1ß. Using an IL-1 receptor antagonist combined with the neutralization of TNF-α could be a useful strategy for decreasing P. aeruginosa infection-induced mortality in burn patients.

Effect of Arsenate and p-Phenylenediamine on the Expression of Aquaporins in Cultured Human Urothelial Cells.

BACKGROUND: Exposure to arsenic (As) or p­phenylenediamine (PPD) can lead to dysfunction, or even cancer, in various types of organs, including the urinary bladder, yet the underlying mechanisms remain unclear. Aquaporins (AQPs) are widely expressed small water channel proteins that provide the major route for the transport of water and other small molecules across plasma membranes in diverse cell types. Altered expression of AQPs has been associated with pathologies in all major organs, including the urinary bladder. OBJECTIVE: The present in vitro study was performed as a first step towards exploring the possible involvement of AQPs in As- and PPD­induced bladder diseases. METHODS: An immortalized normal human urothelial cell line was employed. Cells were exposed to different concentrations of sodium arsenate (0­20 µM) or PPD (0­200 µM) for 48 h. Cell viability was subsequently assessed. The mRNA and protein expression levels of AQPs (specifically, AQP3, 4, 7, 9, and 11) were analyzed using reverse transcription­quantitative polymerase chain reaction and Western blot analyses, respectively. RESULTS: The viability of the cells was decreased in a concentration-dependent manner upon exposure to arsenate. The mRNA and protein expression levels of AQP3, 4, 7, and 9 were substantially reduced, whereas the expression of AQP11 was largely unchanged. As for the experiments with PPD, treatment with increasing concentrations of PPD induced a gradual decrease in cell viability. The mRNA and protein expression levels of AQP3, 4, and 11 were generally unaltered; however, a marked reduction in the expression levels of AQP7 was observed, contrasting with a gradual concentration-dependent decrease in the expression of AQP9. CONCLUSION: The importance of the differential expression profiles of the AQPs induced by arsenate and PPD requires further investigation; nevertheless, the findings of the present study suggest that AQPs have a role in As­ and PPD­induced bladder diseases.