Michiel Vaneker

Low-tidal-volume mechanical ventilation induces a toll-like receptor 4-dependent inflammatory response in healthy mice.

Background:Mechanical ventilation (MV) can induce ventilator-induced lung injury. A role for proinflammatory pathways has been proposed. The current studies analyzed the roles of Toll-like receptor (TLR) 4 and TLR2 involvement in the inflammatory response after MV in the healthy lung. Methods:Wild-type (WT) C57BL6, TLR4 knockout (KO), and TLR2 KO mice were mechanically ventilated for 4 h. Bronchoalveolar lavage fluid was analyzed for presence of endogenous ligands. Lung homogenates were used to investigate changes in TLR4 and TLR2 expression. Cytokines were measured in lung homogenate and plasma, and leukocytes were counted in lung tissue. Results:MV significantly increased endogenous ligands for TLR4 in bronchoalveolar lavage fluid and relative messenger RNA expression of TLR4 and TLR2 in lung tissue. In lung homogenates, MV in WT mice increased levels of keratinocyte-derived chemokine, interleukin (IL)-1α, and IL-1β. In TLR4 KO mice, MV increased IL-1α but not IL-1β, and the increase in keratinocyte-derived chemokine was less pronounced. In plasma, MV in WT mice increased levels of IL-6, keratinocyte-derived chemokine, and tumor necrosis factor α. In TLR4 KO mice, MV did not increase levels of IL-6 or tumor necrosis factor α, and the response of keratinocyte-derived chemokine was less pronounced. MV in TLR2 KO mice did not result in different cytokine levels compared with WT mice. In WT and TLR2 KO mice, but not in TLR4 KO mice, MV increased the number of pulmonary leukocytes. Conclusions:The current study supports a role for TLR4 in the inflammatory reaction after short-term MV in healthy lungs. Increasing the understanding of the innate immune response to MV may lead to future treatment advances in ventilator-induced lung injury, in which TLR4 may serve as a therapeutic target.

Mechanical ventilation in healthy mice induces reversible pulmonary and systemic cytokine elevation with preserved alveolar integrity : An in vivo model using clinical relevant ventilation settings

Background:Mechanical ventilation (MV) may activate the innate immune system, causing the release of cytokines. The resulting proinflammatory state is a risk factor for ventilator-induced lung injury. Cytokine increase results from direct cellular injury but may also result from cyclic stretch alone as demonstrated in vitro: mechanotransduction. To study mechanotransduction in vivo, the authors used an animal MV model with clinically relevant ventilator settings, avoiding alveolar damage. Methods:Healthy C57BL6 mice (n = 82) were ventilated (tidal volume, 8 ml/kg; positive end-expiratory pressure, 4 cm H2O; fraction of inspired oxygen, 0.4) for 30, 60, 120, and 240 min. Assigned animals were allowed to recover for 2 days after MV. Both pulmonary tissue and plasma interleukin (IL)-1&agr;, IL-1&bgr;, tumor necrosis factor &agr;, IL-6, IL-10, and keratinocyte-derived chemokine levels were measured. Histopathologic appearance of lung tissue was analyzed by light microscopy and electron microscopy. Results:In lung tissue, all measured cytokines and keratinocyte-derived chemokine levels increased progressively with MV duration. Light microscopy showed increased leukocyte influx but no signs of alveolar leakage or albumin deposition. Electron microscopy revealed intact epithelial cell and basement membranes with sporadically minimal signs of partial endothelial detachment. In plasma, increased levels of IL-1&agr;, tumor necrosis factor &agr;, IL-6, and keratinocyte-derived chemokine were measured after MV. In the recovery animals, cytokine levels had normalized and no histologic alterations could be found. Conclusions:Mechanical ventilation induces reversible cytokine increase and leukocyte influx with preserved tissue integrity. This model offers opportunities to study the pathophysiologic mechanisms behind ventilator-induced lung injury and the contribution of MV to the “multiple-hit” concept.

Impairments as measured by ISS do not greatly change between one and eight years after CRPS 1 diagnosis

Background Complex Regional Pain Syndrome type 1 (CRPS 1) is a potentially incapacitating complication in which pain seems to be the most disabling factor. We performed a late follow up study of a well‐defined CRPS 1 population more than eight years after diagnosis. The relationships between early and late impairments were studied with a view to outcome prediction and to investigate possible differences in long‐term impairments according to initial CRPS 1 subdiagnosis (i.e. “warm” or “cold”, diagnosed according to skin temperature measured via infrared thermometer).

Toll-like Receptor 4 Signaling in Ventilator-induced Diaphragm Atrophy

Background: Mechanical ventilation induces diaphragm muscle atrophy, which plays a key role in difficult weaning from mechanical ventilation. The signaling pathways involved in ventilator-induced diaphragm atrophy are poorly understood. The current study investigated the role of Toll-like receptor 4 signaling in the development of ventilator-induced diaphragm atrophy. Methods: Unventilated animals were selected for control: wild-type (n = 6) and Toll-like receptor 4 deficient mice (n = 6). Mechanical ventilation (8 h): wild-type (n = 8) and Toll-like receptor 4 deficient (n = 7) mice. Myosin heavy chain content, proinflammatory cytokines, proteolytic activity of the ubiquitin-proteasome pathway, caspase-3 activity, and autophagy were measured in the diaphragm. Results: Mechanical ventilation reduced myosin content by approximately 50% in diaphragms of wild-type mice (P less than 0.05). In contrast, ventilation of Toll-like receptor 4 deficient mice did not significantly affect diaphragm myosin content. Likewise, mechanical ventilation significantly increased interleukin-6 and keratinocyte-derived chemokine in the diaphragm of wild-type mice, but not in ventilated Toll-like receptor 4 deficient mice. Mechanical ventilation increased diaphragmatic muscle atrophy factor box transcription in both wild-type and Toll-like receptor 4 deficient mice. Other components of the ubiquitin-proteasome pathway and caspase-3 activity were not affected by ventilation of either wild-type mice or Toll-like receptor 4 deficient mice. Mechanical ventilation induced autophagy in diaphragms of ventilated wild-type mice, but not Toll-like receptor 4 deficient mice. Conclusion: Toll-like receptor 4 signaling plays an important role in the development of ventilator-induced diaphragm atrophy, most likely through increased expression of cytokines and activation of lysosomal autophagy.

The in vitro mechanisms and in vivo efficacy of intravenous lidocaine on the neuroinflammatory response in acute and chronic pain.

The neuroinflammatory response plays a key role in several pain syndromes. Intravenous (iv) lidocaine is beneficial in acute and chronic pain. This review delineates the current literature concerning in vitro mechanisms and in vivo efficacy of iv lidocaine on the neuroinflammatory response in acute and chronic pain.

A single recruitment maneuver in ventilated critically ill children can translocate pulmonary cytokines into the circulation

INTRODUCTION Recruitment maneuvers (RMs) are advocated to prevent pulmonary collapse during low tidal volume ventilation and improve oxygenation. However, convincing clinical evidence for improved outcome is lacking. Recent experimental studies demonstrate that RMs translocate pulmonary inflammatory mediators into the circulation. To determine whether a single RM in ventilated children affects pulmonary and systemic cytokine levels, we performed a prospective intervention study. METHODS Cardiorespiratory stable ventilated patients (0.5-45 months, n = 7) with acute lung injury were subjected to an RM determining opening and closing pressures (peak inspiratory pressure < or =45 cmH(2)O, positive end expiratory pressure (PEEP) < or =30 cmH(2)O). Before and after RM, cardiorespiratory parameters and ventilator settings were recorded, blood gas analysis performed, and bronchoalveolar lavage fluid and plasma TNF-alpha, IL-1beta, IL-6, IL-8, and IL-10 concentrations were determined. RESULTS Fifteen minutes after the RM, an increase was observed in plasma tumor necrosis factor-alpha (400% +/- 390% of baseline, P = .04), IL-6 (120% +/- 35%, P = .08), and IL-1beta (520% +/- 535%, P = .04), which decreased at T = 60 minutes, hence indicative of translocation. Recruitment maneuver did not change the plasma levels of the anti-inflammatory IL-10 (105% +/- 12%, P = .5). Apart from a nonsignificant increase of IL-8 after 360 minutes (415% +/- 590%,P = .1), bronchoalveolar cytokine levels were not influenced by the RM. No increase in oxygenation or improvement of lung kinetics was observed. CONCLUSIONS A single RM can translocate pro-inflammatory cytokines from the alveolar space into the systemic circulation in ventilated critically ill children.

Blueprints of signaling interactions between pattern recognition receptors: implications for the design of vaccine adjuvants.

ABSTRACT Innate immunity activation largely depends on recognition of microorganism structures by Pattern Recognition Receptors (PRRs). PRR downstream signaling results in production of pro- and anti-inflammatory cytokines and other mediators. Moreover, PRR engagement in antigen-presenting cells initiates the activation of adaptive immunity. Recent reports suggest that for the activation of innate immune responses and initiation of adaptive immunity, synergistic effects between two or more PRRs are necessary. No systematic analysis of the interaction between the major PRR pathways were performed to date. In this study, a systematical analysis of the interactions between PRR signaling pathways was performed. PBMCs derived from 10 healthy volunteers were stimulated with either a single PRR ligand or a combination of two PRR ligands. Known ligands for the major PRR families were used: Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), and RigI-helicases. After 24 h of incubation, production of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and IL-10 was measured in supernatants by enzyme-linked immunosorbent assay (ELISA). The consistency of the PRR interactions (both inhibitory and synergistic) between the various individuals was assessed. A number of PRR-dependent signaling interactions were found to be consistent, both between individuals and with regard to multiple cytokines. The combinations of TLR2 and NOD2, TLR5 and NOD2, TLR5 and TLR3, and TLR5 and TLR9 acted as synergistic combinations. Surprisingly, inhibitory interactions between TLR4 and TLR2, TLR4 and Dectin-1, and TLR2 and TLR9 as well as TLR3 and TLR2 were observed. These consistent signaling interactions between PRR combinations may represent promising targets for immunomodulation and vaccine adjuvant development.

Mechanical ventilation induces a Toll/interleukin-1 receptor domain-containing adapter-inducing interferon beta-dependent inflammatory response in healthy mice.

Background:Mechanical ventilation (MV) can induce lung injury. Proinflammatory cytokines have been shown to play an important role in the development of ventilator-induced lung injury. Previously, the authors have shown a role for Toll-like receptor 4 signaling. The current study aims to investigate the role of Toll/interleukin-1 receptor domain-containing adapter-inducing interferon-&bgr; (TRIF), a protein downstream of Toll-like receptors, in the development of the inflammatory response after MV in healthy mice. Methods:Wild-type C57BL6 and TRIF mutant mice were mechanically ventilated for 4 h. Lung tissue and plasma was used to investigate changes in cytokine profile, leukocyte influx, and nuclear factor-&kgr;B activity. In addition, experiments were performed to assess the role of TRIF in changes in cardiopulmonary physiology after MV. Results:MV significantly increased messenger RNA expression of interleukin (IL)-1&bgr; in wild-type mice, but not in TRIF mutant mice. In lung homogenates, MV increased levels of IL-1&agr;, IL-1&bgr;, and keratinocyte-derived chemokine in wild-type mice. In contrast, in TRIF mutant mice, only a minor increase in IL-1&bgr; and keratinocyte-derived chemokine was found after MV. Nuclear factor-&kgr;B activity after MV was significantly lower in TRIF mutant mice compared with wild-type mice. In plasma, MV increased levels of IL-6 and keratinocyte-derived chemokine. In TRIF mutant mice, no increase of IL-6 was found after MV, and the increase in keratinocyte-derived chemokine appeared less pronounced. TRIF deletion did not affect cardiopulmonary physiology after MV. Conclusions:The current study supports a prominent role for TRIF in the development of the pulmonary and systemic inflammatory response after MV.

Hypercapnic acidosis attenuates the pulmonary innate immune response in ventilated healthy mice

Background:Mechanical ventilation with small tidal volumes reduces the development of ventilator-induced lung injury and mortality, but may increase Paco2. It is not clear whether the beneficial effect of a lung-protective strategy results from reduced ventilation pressures/tidal volumes or is mediated by the effects of hypercapnic acidosis on the inflammatory response involved in the pathogenesis of ventilator-induced lung injury. Objective:To analyze whether hypercapnic acidosis affects lung tissue cytokine levels and leukocyte influx in healthy ventilated mice. Study Design:Analysis of lung tissue and plasma concentrations of interleukin (IL)-1&bgr;, tumor necrosis factor (TNF)-&agr;, IL-6, IL-10, and keratocyte-derived chemokine after 2 hrs of mechanical ventilation (Vt 8 mL/kg, positive end-expiratory pressure 4 cm H2O) with 0.06% CO2 (room air), 2% CO2, or 4% CO2. Subjects:Healthy C57BL6 mice (n = 40). Measurements/Results:Paco2 and pH were within normal range when ventilated with 0.06% CO2 and significantly changed with 2% and 4% CO2: (mean ± sd) pH 7.23 ± 0.06 and 7.15 ± 0.04, Paco2 7.9 ± 1.4 and 10.8 ± 0.7 kPa, respectively (p < 0.005). Blood pressure remained within normal limits in all animals. Quantitative microscopic analysis showed a 4.7 ± 3.7-fold increase (p < 0.01) in pulmonary leukocyte influx in normocapnic ventilated animals and a significant reduction in leukocyte influx of 57 ± 32% (p < 0.01) and 67 ± 22% (p < 0.01) when ventilated with 2% and 4% CO2, respectively. Normocapnic ventilation induced a significant elevation of lung tissue IL-1&bgr; (1516 ± 119 ng/mL), TNF-&agr; (344 ± 88 ng/mL), IL-6 (6310 ± 807 ng/mL), IL-10 (995 ± 152 ng/mL), and keratocyte-derived chemokine (36,966 ± 15,294 ng/mL) (all p-values <0.01). Hypercapnic acidosis with 2% respectively 4% CO2 significantly attenuated this increase with 25 ± 32% and 54 ± 32% (IL-1&bgr;, p < 0.01); 17 ± 36% and 58 ± 33% (TNF-&agr;, p < 0.02); 22 ± 34% and 89 ± 6% (IL-6, p < 0.01); 20 ± 31% and 67 ± 17% (IL-10, p < 0.01) and 16 ± 44% and 45 ± 30% (keratocyte-derived chemokine, p = 0.07). Conclusion:Hypercapnic acidosis attenuates the mechanical ventilation-induced immune response independent from reduced tidal volumes/pressures and may protect the lung from ventilator induced lung injury.

Use of recruitment maneuvers during mechanical ventilation in pediatric and neonatal intensive care units in the Netherlands

Although the beneficial effects of recruitment maneuvers (RM) during conventional mechanical ventilation (CMV) are unclear and the incidence of adverse effects is unknown [1], RM seem to be widely employed. We investigated the use of RM in all Dutch pediatric (n = 8) and neonatal (n = 10) intensive care units. RM were defined as any intervention intended to increase the number of alveoli participating in ventilation. The results of this survey reveal that 8/8 PICUs and 7/10 NICUs perform RM regularly, either manually using a balloon (PICU 100%, NICU 85%) or mechanically by using the ventilator (PICU 100%, NICU 57%). Ventilator RM modes can be divided into isolated PIP elevation (8%), sustained PEEP elevation (25%) and combined elevation (58%). Maximal applied pressures are substantially higher in PICUs than in NICUs: (PICU 80%, NICU 46%). Manual RM after PEEP loss is mostly done by nursing staff; mechanical recruitment maneuvers are exclusively performed by medical staff. Effects of RM are evaluated by TcSaO 2 (PICU 100%, NICU 100%), PaO 2 (PICU 25%, NICU 28%), pressure–volume loop/minute ventilation measurements (PICU 25%, NICU 28%), and chest X-rays (PICU 25%, NICU 71%). Adverse effects reported are blood pressure decrease and oxygen desaturation (PICU 50%, NICU 28%); no gross barotrauma (pneu-mothorax, pulmonary emphysema) has been reported. These data show a diversity corresponding with numerous publications on RM with different strategies and inconsistent results which we recently reviewed extensively [1]. A combined PIP and PEEP elevation, as used by most centers, is theoretically the most effective mode, as recruitment and derecruitment are continuous processes throughout the ventilatory cycle, during which PIP recruits alveoli and PEEP maintains alveolar patency [2]. An isolated PIP increase – e.g. manual RM – carries the risk of alveolar overdistension and increased shear stress forces in non-stabilized alveoli, possibly leading to lung injury. Sustained elevation of PEEP level seems less injurious and increases pulmonary aeration in experimental studies [3]. Only after MV disconnection or endotracheal suctioning is temporary PIP increase rational, as it rapidly recruits collapsed alveoli [4] and repeated derecruitments are harmful [5]. Several studies indicate that in the late phase of respiratory failure RM rarely improve oxygenation. Interestingly, the phase of disease was not reported to influence RM indications. The maximal reported RM pressures – significantly higher in PICUs than in NICUs – are similar to those applied in clinical studies [1]. The recruitment pressures needed to open alveoli depend …