Inter- and intrasubject variability of the inflammatory response to segmental endotoxin challenge in healthy volunteers.

Segmental endotoxin challenge with lipopolysaccharide (LPS) can be used as a pharmacodynamic model to safely induce a transient airway inflammation in the peripheral lung of healthy subjects and to test the anti-inflammatory efficacy of investigational new drugs. In contrast to whole lung LPS challenge only a fraction of the dose is required that can be precisely administered to a specific lung region and a vehicle challenged segment as an intra-subject control can be included. The aim of this study was to assess the intra- and inter-individual variability of the response to segmental LPS challenge for the appropriate design and power calculation of future clinical trials. Two cohorts with 10 subjects each underwent two segmental LPS challenges within five weeks. The inflammatory response was evaluated in bronchoalveolar lavage (BAL) fluid at 6 (cohort 1) and 24 h (cohort 2) both in the LPS and in a vehicle challenged segment, as well as in plasma for up to 26 h post LPS challenge. While the cytokine response was more pronounced at 6 h, the influx of neutrophils and monocytes dominated at 24 h; e.g. neutrophils increased from a median (inter-quartile range, IQR) of 0.14 (0.16) and 0.09 (0.08)x10(4) cells/mL BAL fluid at baseline to 10.2 (17.1) and 19.3 (15.9)x10(4) cells/mL 24 h after the two separate challenges. The within-subject variability was higher than the between-subject variability for most of the markers. However, sample size estimations based on the variability of outcome variables found lower or equal numbers with cross-over designs compared to parallel group designs for cellular markers at 24 h and cytokine variables at 6 h. The segmental LPS challenge model was safe. Future study designs have to balance between burden to the study subjects (4 versus 2 bronchoscopies), variability (within-versus between-subject), and the desired outcome variable (cells versus chemo/cytokine).

Natural innate cytokine response to immunomodulators and adjuvants in human precision-cut lung slices.

Prediction of lung innate immune responses is critical for developing new drugs. Well-established immune modulators like lipopolysaccharides (LPS) can elicit a wide range of immunological effects. They are involved in acute lung diseases such as infections or chronic airway diseases such as COPD. LPS has a strong adjuvant activity, but its pyrogenicity has precluded therapeutic use. The bacterial lipopeptide MALP-2 and its synthetic derivative BPPcysMPEG are better tolerated. We have compared the effects of LPS and BPPcysMPEG on the innate immune response in human precision-cut lung slices. Cytokine responses were quantified by ELISA, Luminex, and Meso Scale Discovery technology. The initial response to LPS and BPPcysMPEG was marked by coordinated and significant release of the mediators IL-1ß, MIP-1ß, and IL-10 in viable PCLS. Stimulation of lung tissue with BPPcysMPEG, however, induced a differential response. While LPS upregulated IFN-γ, BPPcysMPEG did not. This traces back to their signaling pathways via TLR4 and TLR2/6. The calculated exposure doses selected for LPS covered ranges occurring in clinical studies with human beings. Correlation of obtained data with data from human BAL fluid after segmental provocation with endotoxin showed highly comparable effects, resulting in a coefficient of correlation >0.9. Furthermore, we were interested in modulating the response to LPS. Using dexamethasone as an immunosuppressive drug for anti-inflammatory therapy, we found a significant reduction of GM-CSF, IL-1ß, and IFN-γ. The PCLS-model offers the unique opportunity to test the efficacy and toxicity of biological agents intended for use by inhalation in a complex setting in humans.

Early onset of regional intestinal ischemia can be detected with carbon dioxide tension measurement inside the peritoneal cavity.

UNLABELLED: Methods for detecting regional gastrointestinal ischemia are rare. An early detection of ischemia in the stomach or ileum can be achieved by the continuous intramucosal PCO(2) (PiCO(2)) measurement in the region. However, physiological consideration suggests that the placement of a fiberoptic CO(2) sensor in the peritoneal cavity should yield comparable results. We tested the hypothesis that a continuous PCO(2) measurement in the peritoneal cavity allows the early detection of regional intestinal ischemia. A laparotomy was performed in six pigs (54.7 +/- 3.7 kg) with a tourniquet being placed around respective vessels to allow complete ischemia of a 2. 75-m part of the ileum. A fiberoptic CO(2) sensor (PiCO(2)-ileum) was placed intraluminally in the ileum outside this segment. A second fiberoptic CO(2) sensor to measure intraperitoneal PCO(2) (i. p.-PCO(2)) was placed inside the peritoneal cavity in close vicinity to the ischemic gut segment. Gastric PiCO(2) was determined by using air tonometry. After baseline measurements, ileal ischemia was induced for 180 min followed by a 30-min reperfusion period. Statistics were performed with a Friedman test followed by Wilcoxon Analysis with P: < 0.01 considered significant. With the onset of local ileal ischemia, a sudden increase in i.p.-PCO(2) from 48.9 (45. 0-51.5) mm Hg (mean and 25-75 percentiles) to 94.3 (87.9-95.5; P: < 0.01) mm Hg was observed. Gastric PiCO(2) (49.0 [47.5-51.0]/53.5 [49. 0-54.0] mm Hg), and ileal PiCO(2) (56.4 [44.6-57.0]/54.3 [46.1-57.8] mm Hg) did not change. With reperfusion, the i.p.-PCO(2) decreased but stayed above baseline values. IMPLICATIONS: Unless systemic changes are induced, regional intestinal perfusion deficits cannot be detected with a PCO(2) measurement in the gastric lumen. In pigs, an occlusion of blood flow to an isolated gut segment resulted in a significant increase in intraperitoneal CO(2) tension. Thus, the measurement of intraperitoneal PCO(2) could allow the early detection of regional intestinal ischemia.