Nerve growth factor and its receptors in asthma and inflammation.

Nerve growth factor (NGF) is a high molecular weight peptide that belongs to the neurotrophin family. It is synthesized by various structural and inflammatory cells and activates two types of receptors, the TrkA (tropomyosin-receptor kinase A) receptor and the p75(NTR) receptor, in the death receptor family. NGF was first studied for its essential role in neuronal growth and survival.

Expression of nerve growth factor in the airways and its possible role in asthma.

Nerve growth factor (NGF), in addition to its essential role in neuronal growth and survival, may also act as an inflammatory mediator. As several animal studies have shown, NGF appears to play a part in the development of airway hyperresponsiveness and in the increased sympathetic and sensory innervation of the lung. It also has a profound effect on airway inflammation and asthma-related symptoms.

Transforming growth factor-beta and its role in asthma.

Transforming growth factor-beta (TGF-beta) is an important fibrogenic and immunomodulatory factor that may play a role in the structural changes observed in the asthmatic airways. In vitro as well as in vivo studies have evidenced a dual role for TGF-beta: it can either function as a pro- or anti-inflammatory cytokine on inflammatory cells, participating into the initiation and resultion of inflammatory and immune responses in the airways. TGF-beta is also involved in the remodelling of the airway wall, and has in particular been related to the subepithelial fibrosis.