Nitric Oxide and Other Inﬂammatory Mediators
The free radical nitric oxide is an important mediator of many biological processes. The molecule appears to be a two-edged sword. Besides the agent’s role as a paracrine messenger, nitric-oxide-derived oxidants are important weapons against invading pathogens. Likewise, the role of nitric oxide in the airways is ambiguous. Besides its role as a bronchodilator, nitric oxide and derivatives have been hypothesized to play a role in the pathophysiology of asthma via their putative damaging effects on the airways. This may be enhanced by a nitrosative response to respiratory tract infections, since both the infectious agent and the host may suffer from the consequent nitrosative stress. Respiratory infections may also compromise the beneﬁcial (bronchodilatory) effects of nitric oxide. In the following paragraphs an overview of the role of nitric oxide and derivatives in the pathophysiology of asthma will be given, after which the effects of respiratory infection in this context will be discussed.