Breathing easy with carbon monoxide

Ancient Greek philosophers extolled moderation in all things. On page 283, Minamoto and colleagues show that carbon monoxide (CO) inhalation is no exception. In a mouse model of trachea transplantation, inhaled CO—in moderation—prevented the development of lethal obstructive airway disease.

CO gas is both a toxic air pollutant and a normal byproduct of cellular heme metabolism. Although CO is well-known for its role as an asphyxiant, recent studies have revealed its virtues, which include anti-inflammatory and anti-apoptotic effects on a variety of cell types. CO has also been shown to inhibit the rejection of xenogeneic heart transplants in rats.

Minamoto et al. now add to that list of virtues by showing that treating mice with low-dose inhaled CO reduced the T cell infiltration and airway obstruction that develops after...