Acute respiratory distress syndrome: physiology and new management strategies.

The acute respiratory distress syndrome (ARDS) has been recognized for more than three decades as a cause of respiratory failure in patients with a variety of illnesses. Clinically, it is characterized by pulmonary edema, refractory hypoxemia, diffuse pulmonary infiltrates, and altered lung compliance. Pathologically, it is distinguished by infiltration of the lungs with inflammatory cells, interstitial and alveolar edema, hyaline membrane formation, and ultimately fibrosis. Although we have learned much about the pathophysiology of this inflammatory syndrome since its earliest descriptions, ARDS continues to claim the lives of 40%-70% of its victims. Many treatment strategies have been used to prevent or treat ARDS, but thus far the most encouraging strategy to prevent lung injury and improve survival is mechanical ventilation with low tidal volumes and high levels of positive end-expiratory pressure.

Anti-inflammatory effects of triptolide in human bronchial epithelial cells.

Triptolide (PG490, 97% pure) is a diterpenoid triepoxide with potent anti-inflammatory and immunosuppressive effects in transformed human bronchial epithelial cells and T cells (Qiu D, Zhao G, Aoki Y, Shi L, Uyei A, Nazarian S, Ng JC-H, and Kao PN. J Biol Chem 274: 13443-13450, 1999). Triptolide, with an IC(50) of approximately 20-50 ng/ml, inhibits normal and transformed human bronchial epithelial cell expression of interleukin (IL)-6 and IL-8 stimulated by phorbol 12-myristate 13-acetate (PMA), tumor necrosis factor-alpha, or IL-1 beta. Nuclear runoff and luciferase reporter gene assays demonstrate that triptolide inhibits IL-8 transcription. Triptolide also inhibits the transcriptional activation, but not the DNA binding, of nuclear factor-kappa B. A cDNA array and clustering algorithm analysis reveals that triptolide inhibits expression of the PMA-induced genes tumor necrosis factor-alpha, IL-8, macrophage inflammatory protein-2 alpha, intercellular adhesion molecule-1, integrin beta(6), vascular endothelial growth factor, granulocyte-macrophage colony-stimulating factor, GATA-3, fra-1, and NF45. Triptolide also inhibits constitutively expressed cell cycle regulators and survival genes cyclins D1, B1, and A1, cdc-25, bcl-x, and c-jun. Thus anti-inflammatory, antiproliferative, and proapoptotic properties of triptolide are associated with inhibition of nuclear factor-kappa B signaling and inhibition of genes known to regulate cell cycle progression and survival.

Longitudinal lung function study in heterozygous PiMZ phenotype subjects.

It is a matter of controversy whether subjects who are heterozygous (PiMZ) for alpha 1-antitrypsin deficiency are at risk of developing pulmonary emphysema. To assess the role of MZ phenotype in the development of abnormal lung function the authors performed a 10 year follow-up study of 28 PiMZ subjects, compared to 28 matched-paired normal PiMM subjects. Maximal expiratory flows and mechanical properties of the lungs were studied, in order to determine the changes of the lung function parameters characteristic of pulmonary emphysema. Total lung capacity and residual volume increased, whereas forced expiratory volume in one second, expiratory flows, diffusing capacity of the lungs for carbon monoxide, and static transpulmonary pressures decreased in the PiMZ patients. The majority of the controlled functional parameters were found to deteriorate significantly in PiMZ patients during the 10 year period. Trypsin inhibitory capacity in the PiMZ group (mean +/- SD) was 0.65 +/- 0.17 mg.ml-1 as compared to 1.52 +/- 0.3 mg.ml-1 in the PiMM group. These changes exceeded the values expected as physiological changes due to ageing. The findings in the present longitudinal study--especially the decrease in elasticity, which is the primary pathophysiological damage in alpha 1-antitrypsin deficiency--support the concept that the PiMZ phenotype is a risk factor for the development of pulmonary emphysema at younger age than in those without the deficiency.