Do neurotrophins play a role in allergic diseases and asthma?

Neurotrophins in clinical diagnostics: pathophysiology and laboratory investigation

There is now growing evidence that a number of multifunctional signaling molecules, originally discovered as signal molecules in specific cells, exert their effects in various other tissue compartments. Neurotrophins, a class of homologues growth factors initially discovered to promote neuronal growth and survival, display such a dual activity and contribute to the development of a variety of non-neuronal tissues. Nowadays, several examples of essential non-neuronal functions played by neurotrophins and of variations of neurotrophin expression that accompany these processes can be presented. As will be shown, neurotrophins are found in many body tissues produced by a variety of non-neuronal cell types such as immune cells, adipocytes, endothelia, epithelia, fibroblasts, keratinocytes and endocrine cells. Assuming a general role as growth and survival factors, changes in neurotrophin expression may reflect physiological or pathological processes, such as activation, proliferation or repair followed by injury in the tissues. Neurotrophins were also present in the systemic blood circulation and variations in blood concentrations indicate vascular as well as peripheral production. In this review, we will discuss changes in local and systemic neurotrophin concentrations as well as their known pathophysiological relationship in various inflammatory and non-inflammatory disorders. Beside the nervous system, these will include diseases of the airways, skin and joints as well as systemic autoimmune diseases. Furthermore, new aspects of neurotrophin actions in maintenance of body energy balance and in reproductive endocrinology will be presented.

Nerve growth factor and the immune system: old and new concepts in the cross-talk between immune and resident cells during pathophysiological conditions

PURPOSE OF REVIEW

This review provides an overview of nerve growth factor and its involvement in the immune system. Furthermore, recent data are provided revealing new important insights into the mechanisms of action of nerve growth factor in allergic reaction.

RECENT FINDINGS

Recent studies on the effects of nerve growth factor on the immune cells involved allergic reaction, and on the potential role of nerve growth factor in tissue remodelling are presented.

SUMMARY

Nerve growth factor has an extended function from the nervous system to a wide range of activities in the immune system. Several papers have highlighted the role of the factor in allergic inflammation. This review describes old and new concepts of nerve growth factor in the immune system: the relation between nerve growth factor and the main cells taking part in allergic inflammatory disorders, structural cells, mediators and cytokines/chemokines, as well as the mechanisms leading to nerve growth factor increase. Understanding these complex mechanisms will introduce new therapeutic approaches for nerve growth factor in the immune system, in addition to those already established in the nervous system.