Raquel Herrero

Role of acid sphingomyelinase and IL-6 as mediators of endotoxin-induced pulmonary vascular dysfunction

Background Pulmonary hypertension (PH) is frequently observed in patients with acute respiratory distress syndrome (ARDS) and it is associated with an increased risk of mortality. Both acid sphingomyelinase (aSMase) activity and interleukin 6 (IL-6) levels are increased in patients with sepsis and correlate with worst outcomes, but their role in pulmonary vascular dysfunction pathogenesis has not yet been elucidated. Therefore, the aim of this study was to determine the potential contribution of aSMase and IL-6 in the pulmonary vascular dysfunction induced by lipopolysaccharide (LPS). Methods Rat or human pulmonary arteries (PAs) or their cultured smooth muscle cells (SMCs) were exposed to LPS, SMase or IL-6 in the absence or presence of a range of pharmacological inhibitors. The effects of aSMase inhibition in vivo with D609 on pulmonary arterial pressure and inflammation were assessed following intratracheal administration of LPS. Results LPS increased ceramide and IL-6 production in rat pulmonary artery smooth muscle cells (PASMCs) and inhibited pulmonary vasoconstriction induced by phenylephrine or hypoxia (HPV), induced endothelial dysfunction and potentiated the contractile responses to serotonin. Exogenous SMase and IL-6 mimicked the effects of LPS on endothelial dysfunction, HPV failure and hyperresponsiveness to serotonin in PA; whereas blockade of aSMase or IL-6 prevented LPS-induced effects. Finally, administration of the aSMase inhibitor D609 limited the development of endotoxin-induced PH and ventilation-perfusion mismatch. The protective effects of D609 were validated in isolated human PAs. Conclusions Our data indicate that aSMase and IL-6 are not simply biomarkers of poor outcomes but pathogenic mediators of pulmonary vascular dysfunction in ARDS secondary to Gram-negative infections.

A New Experimental Model of Acid and Endotoxin-Induced Acute Lung Injury in Rats

The majority of the animal models of acute lung injury (ALI) are focused on the acute phase. This limits the studies of the mechanisms involved in later phases and the effects of long-term treatments. Thus the goal of this study was to develop an experimental ALI model of aspiration pneumonia, in which diffuse alveolar damage continues for 72 h. Rats were intratracheally instilled with one dose of HCl (0.1 mol/l) followed by another instillation of one dose of LPS (0, 10, 20, 30, or 40 μg/g body weight) 2 h later, which models aspiration of gastric contents that progresses to secondary lung injury from bacteria or bacterial products. The rats were euthanized at 24, 48, and 72 h after the last instillation. The results showed that HCl and LPS at all doses caused activation of inflammatory responses, increased protein permeability and apoptosis, and induced mild hypoxemia in rat lungs at 24 h postinstillation. However, this lung damage was present at 72 h only in rats receiving HCl and LPS at the doses of 30 and 40 μg/g body wt. Mortality (∼50%) occurred in the first 48 h and only in the rats treated with HCl and LPS at the highest dose (40 μg/g body wt). In conclusion, intratracheal instillation of HCl followed by LPS at the dose of 30 μg/g body wt results in severe diffuse alveolar damage that continues at least 72 h. This rat model of aspiration pneumonia-induced ALI will be useful for testing long-term effects of new therapeutic strategies in ALI.

Selective Digestive Decontamination Attenuates Organ Dysfunction in Critically Ill Burn Patients

Objective: To evaluate whether selective decontamination of the digestive tract (SDD) attenuates organ dysfunction in critically ill burn patients. Background: The effect of SDD on the development and progression of organ dysfunction, as an important determinant of mortality in burned patients, is still unknown. We asked whether organ dysfunction is mitigated by treatment with SDD. Methods: Patients with burns >20% of total body surface or suspected inhalation injury from a randomized placebo-controlled trial were analyzed to determine the relationship between treatment received (placebo or SDD) and the severity of organ dysfunction as measured by the area under the curve of the Sequential Organ Failure Assessment (SOFA) score (and its individual components) from day 1 to day 7 of admission. Results: One hundred seven patients (53 in the SDD group and 54 in the placebo group) were included. Survival was significantly higher in SDD-treated patients (48 of 53, 90.6%) than in placebo-treated patients (39 of 54, 72.2%, P = 0.013). Total (P < 0.01) and respiratory (P < 0.01), cardiovascular (P = 0.04) and hematological (not reaching statistical significance, P = 0.07) organ dysfunction was associated with mortality after adjusting for predicted mortality. In multivariate logistic regression, SDD treatment was independently associated with total (P < 0.01), respiratory (P = 0.02), and hematological (P < 0.01) dysfunction over the first week postinjury. Conclusions: The beneficial effect of SDD on mortality in critically ill burned patients is accompanied by a reduction in the degree of organ dysfunction. SDD seems to be a valuable therapeutic strategy to prevent organ dysfunction and, more specifically, respiratory and hematological dysfunction in severely ill burn patients.

How to measure alterations in alveolar barrier function as a marker of lung injury.

The alveolar capillary membrane maintains the proper water and solute content of the epithelial lining fluid at the alveolar air‐liquid interface, which is critical for adequate gas exchange in the lung. This is possible due to the alveolar fluid clearance (AFC) capacity of this membrane that assists in the removal of salt and water from the alveolar air spaces. The alveolar capillary membrane also provides a barrier that restricts the passage of proteins and water from the interstitial and vascular compartments into the alveolar air spaces. This restricted passage is due to the presence of tight junctions between adjacent alveolar epithelial cells. Severe injury to the alveolar epithelial/endothelial membrane results in increased protein permeability and impairment of AFC, which leads to the formation of protein‐rich edema with the consequent deterioration of gas exchange. Many animal models of lung injury, focused on damage of the alveolar‐capillary membrane, assess the AFC capacity and the barrier function. We describe a simple method to assess the AFC rate in normal and pathological conditions in mice. We also describe two complementary methods to assess the alveolar‐capillary barrier function, which require measuring the concentration of endogenous plasma proteins in bronchoalveolar lavage fluid and detection of tight‐junction proteins in lung tissue by immunofluorescence.

Intratracheal instillation of alveolar type II cells enhances recovery from acute lung injury in rats

BACKGROUND Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by excess production of inflammatory factors. Alveolar type II (ATII) cells help repair damaged lung tissue, rapidly proliferating and differentiating into alveolar type I cells after epithelial cell injury. In ALI, the lack of viable ATII favors progression to more severe lung injury. ATII cells regulate the immune response by synthesizing surfactant and other anti-inflammatory proteins and lipids. Cross-talk between ATII and other cells such as macrophages may also be part of the ATII function. The aim of this study was to test the anti-inflammatory and reparative effects of ATII cells in an experimental model of ALI. METHODS In this study ATII cells (2.5 × 106 cells/animal) were intratracheally instilled in rats with HCl and lipopolysaccharide (LPS)-induced ALI and in healthy animals to check for side effects. The specific effect of ATII cells was compared with fibroblast transplantation. RESULTS ATII cell transplantation promoted recovery of lung function, decrease mortality and lung inflammation of the animals with ALI. The primary mechanisms for benefit were paracrine effects of prostaglandin E2 (PGE2) and surfactant protein A (SPA) released from ATII cells that modulate alveolar macrophages to an anti-inflammatory phenotype. To our knowledge, these data are the first to provide evidence that ATII cells secrete PGE2 and SPA, reducing pro-inflammatory macrophage activation and ALI. CONCLUSION ATII cells and their secreted molecules have shown an ability to resolve ALI, thereby highlighting a potential novel therapeutic target.

Mirna interference in human pulmonary alveolar epithelial cells (HPAEPIC) undergoing cyclic stretch and in ex vivo ventilated and perfused rat lungs

We have previously demonstrated that the expression of miRNA 27a-5p is associated with DAD in an experimental model of ventilator-induced lung injury and in patients with ARDS.

Effect of the alveolar type ii cells transplantation for the treatment of acute lung injury

Acute lung injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) are a clinical manifestation of respiratory failure caused by a response of the lung to local or systemic injury [1]. Damage of alveolar barrier is a critical event in the early stage of ALI/ARDS. Currently there is no effective treatment for this disease. Alveolar type II cells (ATII) are implicated in the alveoli reparation [2] and the transplant of these cells could be a promising ALI treatment.

0852. Selective decontamination of the digestive tract modulates the metabolic profile in a ventilator-induced lung injury model

Acute lung injury induced by mechanical ventilation [ventilator-induced lung injury (VILI)]is characterized by a particular metabolic profile in the lung and in the systemic compartment [1]. Also, VILI has been associated with an increase in intestinal permeability [2]. We hypothesized that selective decontamination of the digestive tract (SDD) can modulate the metabolic profile associated with mechanical ventilation.

0987. FAS activation alters tight junction proteins in pulmonary alveolar epithelial cells

Active soluble Fas ligand (sFasL) accumulates in lung fluid of patients with acute respiratory distress syndrome (ARDS), and causes apoptosis and inflammation in lung epithelial cells [1]. Alveolar epithelial damage induced by Fas receptor activation results in protein-rich lung edema [2]. Dysfunction of the tight junction proteins may contribute to the formation of lung edema.

0895. Identification and validation of a mirna as a diagnostic biomarker of diffuse alveolar damage in an animal model of acute lung injury and adult respiratory distress syndrome in mechanically ventilated patients

0895. Identification and validation of a mirna as a diagnostic biomarker of diffuse alveolar damage in an animal model of acute lung injury and adult respiratory distress syndrome in mechanically ventilated patients P Cardinal-Fernandez, A Ferruelo, N Rego, Y Rojas, A Ballen-Barragan, R Granados, C Jaramillo, E Lopez-Hernandez, L Martinez-Caro, N Nin, R Herrero, MA de la Cal, A Esteban, JA Lorente