Elastin degradation products in acute lung injury induced by gastric contents aspiration

Background

Gastric contents aspiration is a high-risk condition for acute lung injury (ALI). Consequences range from subclinical pneumonitis to respiratory failure, depending on the volume of aspirate. A large increment in inflammatory cells, an important source of elastase, potentially capable of damaging lung tissue, has been described in experimental models of aspiration. We hypothesized that in early stages of aspiration-induced ALI, there is proteolytic degradation of elastin, preceding collagen deposition. Our aim was to evaluate whether after a single orotracheal instillation of gastric fluid, there is evidence of elastin degradation.

Methods

Anesthesized Sprague-Dawley rats received a single orotracheal instillation of gastric fluid and were euthanized 4, 12 and 24 h and at day 4 after instillation (n = 6/group). We used immunodetection of soluble elastin in lung tissue and BALF and correlated BALF levels of elastin degradation products with markers of ALI. We investigated possible factors involved in elastin degradation and evaluated whether a similar pattern of elastin degradation can be found in BALF samples of patients with interstitial lung diseases known to have aspirated. Non-parametric ANOVA (Kruskall-Wallis) and linear regression analysis were used.

Results

We found evidence of early proteolytic degradation of lung elastin. Elastin degradation products are detected both in lung tissue and BALF in the first 24 h and are significantly reduced at day 4. They correlate significantly with ALI markers, particularly PMN cell count, are independent of acidity and have a similar molecular weight as those obtained using pancreatic elastase. Evaluation of BALF from patients revealed the presence of elastin degradation products not present in controls that are similar to those found in BALF of rats treated with gastric fluid.

Conclusions

A single instillation of gastric fluid into the lungs induces early proteolytic degradation of elastin, in relation to the magnitude of alveolar-capillary barrier derangement. PMN-derived proteases released during ALI are mostly responsible for this damage. BALF from patients showed elastin degradation products similar to those found in rats treated with gastric fluid. Long-lasting effects on lung elastic properties could be expected under conditions of repeated instillations of gastric fluid in experimental animals or repeated aspiration events in humans.

Acute lung injury induced by whole gastric fluid: hepatic acute phase response contributes to increase lung antiprotease protection

Background

Gastric contents aspiration in humans is a risk factor for severe respiratory failure with elevated mortality. Although aspiration-induced local lung inflammation has been studied in animal models, little is known about extrapulmonary effects of aspiration. We investigated whether a single orotracheal instillation of whole gastric fluid elicits a liver acute phase response and if this response contributes to enrich the alveolar spaces with proteins having antiprotease activity.

Methods

In anesthetized Sprague-Dawley rats receiving whole gastric fluid, we studied at different times after instillation (4 h −7 days): changes in blood cytokines and acute phase proteins (fibrinogen and the antiproteases alpha1-antitrypsin and alpha2-macroglobulin) as well as liver mRNA expression of the two antiproteases. The impact of the systemic changes on lung antiprotease defense was evaluated by measuring levels and bioactivity of antiproteases in broncho-alveolar lavage fluid (BALF). Markers of alveolar-capillary barrier derangement were also studied. Non-parametric ANOVA (Kruskall-Wallis) and linear regression analysis were used.

Results

Severe peribronchiolar injury involving edema, intra-alveolar proteinaceous debris, hemorrhage and PMNn cell infiltration was seen in the first 24 h and later resolved. Despite a large increase in several lung cytokines, only IL-6 was found elevated in blood, preceding increased liver expression and blood concentration of both antiproteases. These changes, with an acute phase response profile, were significantly larger for alpha2-macroglobulin (40-fold increment in expression with 12-fold elevation in blood protein concentration) than for alpha1-antitrypsin (2–3 fold increment in expression with 0.5-fold elevation in blood protein concentration). Both the increment in capillary-alveolar antiprotease concentration gradient due to increased antiprotease liver synthesis and a timely-associated derangement of the alveolar-capillary barrier induced by aspiration, contributed a 58-fold and a 190-fold increase in BALF alpha1-antitrypsin and alpha2-macroglobulin levels respectively (p < 0.001).

Conclusions

Gastric contents-induced acute lung injury elicits a liver acute phase response characterized by increased mRNA expression of antiproteases and elevation of blood antiprotease concentrations. Hepatic changes act in concert with derangement of the alveolar capillary barrier to enrich alveolar spaces with antiproteases. These findings may have significant implications decreasing protease burden, limiting injury in this and other models of acute lung injury and likely, in recurrent aspiration.

Mobilization and collection of peripheral blood stem cells: guidelines for blood volume to process, based on CD34-positive blood cell count in adults and children

We report 189 mobilizations and 489 collections of peripheral blood stem cells (PBSC) performed in 139 autologous transplantation patients and in 28 donors for allogeneic transplantations whose ages ranged from 2-68 years. We observed a correlation (P < .001; Pearson's coefficient 0.64) between CD34-positive cells and granulocyte-macrophage colony-forming units examined to estimate PBSC. In a subset of 287 collections (97 adults and 49 children) we obtained peripheral blood (PB) CD34-positive cell counts at 2 to 4 hours before leukapheresis. We noted a correlation between PB CD34-positive cell counts before leukapheresis and the number of CD34-positive cells per kilogram of body weight collected in the whole apheresis of the day (P < .001; Pearson's coefficient 0.82). An even better correlation was obtained between PB CD34-positive cells preapheresis and the yield of each individual blood volume (BV) processed (P < .001; Pearson's coefficient 0.87). Healthy donors and patients in each age group behaved similarly. In addition, the collection yield was greater among children than adults. These findings allowed us to develop a simple predictive model to estimate the BV to process for a target dose of CD34-positive cells per kilogram, based on the level of PBSC before apheresis in children and adults.

[Antitransglutaminase antibodies determination for the diagnosis of celiac disease]

BACKGROUND

The diagnosis of celiac disease is based in clinical features, serology and intestinal biopsy. There are recent reports that antiglutaminase antibodies have a good correlation with anti endomisial antibodies.

AIM

To assess the sensitivity and specificity of antitransglutaminase antibodies in the diagnosis of celiac disease and their correlation with antiendomisial antibodies.

MATERIAL AND METHODS

Forty nine patients with celiac disease (mean age 30 years, 12 male) were studied. Thirty were symptomatic and 19, asymptomatic. As controls, 34 subjects (mean age 27 years, seven male), with normal duodenal biopsies, were studied. Sera was processed for the determination of antigliadin IgA by ELISA, antiendomisium IgA by indirect immunofluorescence, and antitransglutaminase IgA by ELISA.

RESULTS

Antigliadin antibodies had a sensitivity of 73%, a specificity of 96%, a positive predictive value of 93% and a negative predictive value of 82% for the diagnosis of celiac disease. Antiendomisium and antitransglutaminase antibodies had a specificity and positive predictive value of 100%, sensitivities of 89 and 92% respectively and negative predictive values of 92 and 94% respectively. No significant differences in the diagnostic yield of antiendomisium and antitransglutaminase antibodies, were observed.

CONCLUSIONS

In this group of patients, antitransglutaminase antibodies had a high concordance with antiendomisium antibodies, for the diagnosis of celiac disease. Considering that the determination of antitransglutaminase antibodies is of lower cost and less complicated than antiendomisium antibodies, it is a useful tool for the diagnosis and follow up of patients with celiac disease.