BackgroundThe study of the endotoxin tolerance phenomenon in light of the recently defined roles of mast cells and toll-like receptors as essential components of the innate immune response and as orchestrators of acquired immunity may reveal potentially useful mechanisms of immunomodulation of infectious and allergic inflammatory responses, such as sepsis or asthma. Here we evaluated the phenomenon of direct tolerance of endotoxins, as well as the induction of cross-tolerance and synergism by stimulation with toll-like receptor-2 (TLR2) and FcεR1 agonists, in murine mast cells prestimulated with lipopolysaccharide (LPS). Additionally, we evaluated some stimulatory and inhibitory signaling molecules potentially involved in these phenomena.MethodsMC/9 cells and primary bone marrow-derived mast cells obtained from C57BL/6 and TLR4-/- knock-out mice were sensitized to DNP-HSA (antigen) by incubation with DNP-IgE and were prestimulated with LPS for 18 hr prior to stimulation. Cultures were stimulated with LPS or Pam3Cys-Ser-(Lys)4 3HCl (P3C), a TLR2 agonist, individually or in combination with antigen. The production of IL-6 and TNFα, the phosphorylation of NFκB and p38 MAPK, and the expression of TLR4 and SOCS-1 and -3 were analyzed.ResultsWe found that production of TNFα and IL-6 in murine mast cells that have been pretreated with LPS and challenged with TLR4 (LPS) or -2 (P3C) agonists was reduced, phenomena described as endotoxin tolerance (LPS) and cross-tolerance (P3C), respectively. The expression of TLR4 was not affected by LPS pretreatment. Our results show that the FcεR1 agonist DNP-HSA (antigen) interacts synergistically with LPS or P3C to markedly enhance production of cytokines (TNFα and IL-6). This synergistic effect with LPS and P3C was also attenuated by LPS pretreatment and was mediated by TLR4. These results may be attributed to the reduction in phosphorylation of the mitogen-activated protein kinase (MAPK), p38, and the transcription factor NFκB, as well as to an increase in the expression of the suppressors of cytokine signaling (SOCS)-1 and -3 proteins in LPS-pretreated mast cells.ConclusionsThese findings can be explored with respect to the modulation of inflammatory responses associated with infectious and allergic processes in future studies.

Background: The rational use of antibiotics is one of the main strategies to limit the development of bacterial resistance. We therefore sought to evaluate the effectiveness of a C-reactive protein-based protocol in reducing antibiotic treatment time in critically ill patients. Methods: A randomized, open-label, controlled clinical trial conducted in two intensive care units of a university hospital in Brazil. Critically ill infected adult patients were randomly allocated to (i) intervention to receive antibiotics guided by daily monitoring of CRP levels and (ii) control to receive antibiotics according to the best practices for rational use of antibiotics. Results: One hundred thirty patients were included in the CRP (n = 64) and control (n = 66) groups. In the intention-to-treat analysis, the median duration of antibiotic therapy for the index infectious episode was 7.0 (5.0-8.8) days in the CRP and 7.0 (7.0-11.3) days in the control (p = 0.011) groups. A significant difference in the treatment time between the two groups was identified in the curve of cumulative suspension of antibiotics, with less exposure in the CRP group only for the index infection episode (p = 0.007). In the per protocol analysis, involving 59 patients in each group, the median duration of antibiotic treatment was 6.0 (5.0-8.0) days for the CRP and 7.0 (7.0-10.0) days for the control (p = 0.011) groups. There was no between-group difference regarding the total days of antibiotic exposure and antibiotic-free days.

BACKGROUND: Gastroesophageal varices and associated bleeding are a major cause of morbidity and mortality in cirrhotic patients. OBJECTIVE: To evaluate the potential role of the biomarkers HMGB1 (High Mobility Group Box 1) and IL-6 (Interleukin-6) as predictors of infection, acute kidney injury and mortality in these patients. METHODS: It is a prospective, observational study that included 32 cirrhotic patients with variceal bleeding. RESULTS: The subjects’mean age was 52±5 years and 20 (62.5%) were male. The average MELD was 17.53±5 and the average MELD-Na was 20.63±6.06. Thirty patients (93.3%) patients were Child-Pugh class B or C. Infection was present in 9 subjects (28.1%), acute kidney injury was present in 6 (18.1%) and 4 (12.5%) patients died. The median serum levels of HMGB1 were 1487 pg/mL (0.1 to 8593.1) and the median serum level of IL-6 was 62.1 pg/mL (0.1 to 1102.4). The serum levels of HMGB1 and IL-6 were significantly higher in patients who developed infection, acute kidney injury and death (P<0.05). The Spearman’s correlations for HMGB1 and IL-6 were 0.794 and 0.374 for infection, 0.53 and 0.374 for acute kidney injury and 0.467 and 0.404 for death, respectively. CONCLUSION: Serum levels of HMGB1 and IL-6 were higher in patients with the three studied outcomes. HMGB1 serum levels showed a high correlation with infection and a moderate correlation with acute kidney injury and death, while IL-6 showed a moderate correlation with infection and death and a low correlation with acute kidney injury.

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