A common denominator in the etiology of adult respiratory distress syndrome

Lung Purinoceptor Activation Triggers Ventilator-Induced Brain Injury

Mechanical ventilation can cause ventilator-induced brain injury via afferent vagal signaling and hippocampal neurotransmitter imbalances. The triggering mechanisms for vagal signaling during mechanical ventilation are unknown. The objective of this study was to assess whether pulmonary transient receptor potential vanilloid type-4 (TRPV4) mechanoreceptors and vagal afferent purinergic receptors (P2X) act as triggers of ventilator-induced brain injury.

99MTc-Hexamethylpropyleneamine Oxime Imaging for Early Detection of Acute Lung Injury in Rats Exposed to Hyperoxia or Lipopolysaccharide Treatment

Tc-Hexamethylpropyleneamine oxime (HMPAO) is a clinical single-photon emission computed tomography biomarker of tissue oxidoreductive state. Our objective was to investigate whether HMPAO lung uptake can serve as a preclinical marker of lung injury in two well-established rat models of human acute lung injury (ALI).Rats were exposed to >95% O2 (hyperoxia) or treated with intratracheal lipopolysaccharide (LPS), with first endpoints obtained 24 h later. HMPAO was administered intravenously before and after treatment with the glutathione-depleting agent diethyl maleate (DEM), scintigraphy images were acquired, and HMPAO lung uptake was quantified from the images. We also measured breathing rates, heart rates, oxygen saturation, bronchoalveolar lavage (BAL) cell counts and protein, lung homogenate glutathione (GSH) content, and pulmonary vascular endothelial filtration coefficient (Kf).For hyperoxia rats, HMPAO lung uptake increased after 24 h (134%) and 48 h (172%) of exposure. For LPS-treated rats, HMPAO lung uptake increased (188%) 24 h after injury and fell with resolution of injury. DEM reduced HMPAO uptake in hyperoxia and LPS rats by a greater fraction than in normoxia rats. Both hyperoxia exposure (18%) and LPS treatment (26%) increased lung homogenate GSH content, which correlated strongly with HMPAO uptake. Neither of the treatments had an effect on Kf at 24 h. LPS-treated rats appeared healthy but exhibited mild tachypnea, BAL, and histological evidence of inflammation, and increased wet and dry lung weights. These results suggest the potential utility of HMPAO as a tool for detecting ALI at a phase likely to exhibit minimal clinical evidence of injury.

Early organ-specific mitochondrial dysfunction of jejunum and lung found in rats with experimental acute pancreatitis

INTRODUCTION

Multiple organ dysfunction is the main cause of death in severe acute pancreatitis. Primary mitochondrial dysfunction plays a central role in the development and progression of organ failure in critical illness. The present study investigated mitochondrial function in seven tissues during early experimental acute pancreatitis.

METHODS

Twenty-eight male Wistar rats (463 ± 2 g; mean ± SEM) were studied. Group 1 (n= 8), saline control; Group 2 (n= 6), caerulein-induced mild acute pancreatitis; Group 3 (n= 7) sham surgical controls; and Group 4 (n= 7), taurocholate-induced severe acute pancreatitis. Animals were euthanased at 6 h from the induction of acute pancreatitis and mitochondrial function was assessed in the heart, lung, liver, kidney, pancreas, duodenum and jejunum by mitochondrial respirometry.

RESULTS

Significant early mitochondrial dysfunction was present in the pancreas, lung and jejunum in both models of acute pancreatitis, however, the Heart, liver, kidney and duodenal mitochondria were unaffected.

CONCLUSIONS

The present study provides the first description of early organ-selective mitochondrial dysfunction in the lung and jejunum during acute pancreatitis. Research is now needed to identify the underlying pathophysiology behind the organ selective mitochondrial dysfunction, and the potential benefits of early mitochondrial-specific therapies in acute pancreatitis.

Preventive effect of phosphoenolpyruvate on hypoxemia induced by oleic acid in Guinea pigs

Oleic acid-induced hypoxemia is an animal model of acute respiratory distress syndrome (ARDS). Increased capillary permeability is a cause of hypoxemia in lung injury. Endothelial cells form a major capillary barrier, and disruption of the barrier appears to involve a decreased level of ATP in the cells. Phosphoenolpyruvate (PEP) is an endogenous substance that is one of the ATP precursors and can cross some cell membranes via anion exchanger. We examined the effect of PEP on oleic acid-induced lung injury in guinea pigs. An intravenous injection of oleic acid (15 microl/kg) caused severe hypoxemia. Pretreatment with PEP at a dose of 2, 20, or 200 micromol/kg attenuated the oleic acid-induced decrease in the arterial partial pressure of oxygen in a dose-dependent manner. Furthermore, PEP attenuated the oleic acid-induced increase in vascular permeability in the proximal and distal bronchi, as indicated by the extravascular leakage of Evans Blue dye. The combination of PEP with ATP (4 micromol/kg) showed no additional inhibitory effect on oleic acid-induced lung injury, compared with PEP alone. We suggest that PEP is a promising candidate to prevent hypoxemia in acute lung injuries associated with increased vascular permeability, such as ARDS.