Airway inflammation resolution

A role for Bid in eosinophil apoptosis and in allergic airway reaction

Bid, a proapoptotic member of Bcl-2 family, is involved in Fas receptor signaling. Fas activation promotes human eosinophil cell death and is believed to accelerate the resolution of pulmonary Th2-driven allergic reaction in mice. We hypothesized that Bid would regulate eosinophil apoptosis and Ag-induced airway inflammation, particularly eosinophilia. C57BL/6 Bid(-/-) and wild-type mice were immunized and repeatedly challenged with OVA, and bronchoalveolar lavage (BAL) fluid, lung, and spleen were collected 4-240 h after the final challenge. Cultured BAL eosinophils from Bid-deficient mice showed resistance to Fas-mediated apoptotic DNA fragmentation, phosphatidylserine exposure, mitochondria depolarization, and caspase-3 activity. In addition, OVA-challenged Bid(-/-) mice had higher BAL eosinophilia and a lower proportion of BAL apoptotic eosinophils than Bid(+/+) mice. This was accompanied by augmented BAL levels of the eosinophilotactic cytokine, IL-5, and of the eosinophil-associated mediators, TGF-beta1 and fibronectin. Finally, cultured OVA-stimulated lung mononuclear cells and splenocytes from Bid-deficient mice showed increased release of the Th2-type cytokines, IL-4 and IL-5, but no change in cell number. We conclude that Bid modulates BAL eosinophilia by regulating both eosinophil apoptosis and Th2-type cytokine production.

Defective apoptotic cell clearance in asthma and COPD--a new drug target for statins?

Asthma and chronic obstructive pulmonary disease represent increasingly common respiratory conditions with a clear unmet need for more effective and safer therapy. Airway inflammation is key to both asthma pathogenesis and exacerbations of symptoms in chronic obstructive pulmonary disease. Several lines of evidence are now emerging implicating the increased persistence of apoptotic cells in patients with chronic inflammatory lung diseases and that this is largely due to a combination of inhibition of, or defects in, the apoptotic process and/or impaired apoptotic cell removal mechanisms.