Neurotrophins, including
nerve growth factor (
NGF), partially mediate many features of allergic airways disease including
airway hyperresponsiveness.
Diesel exhaust particulates (
DEP) associated with the combustion of
diesel fuel exacerbate many of these allergic airways responses in humans. We tested the hypothesis that
DEP-induced enhancement of allergic airways disease in a murine model is dependent on normal function of the low affinity pan-
neurotrophin receptor p75(NTR), or
tyrosine kinase A (trkA), the primary receptor for
NGF.
Ovalbumin (OVA)-sensitized and nonallergic BALB/c mice were intranasally instilled with anti-p75(NTR), anti-trkA, or vehicle, 1 h before OVA
aerosol challenge, and then exposed nose-only to the
particulate matter fraction that was less than 2.5 microns in aerodynamic diameter fraction of Standard Reference Material 2975
DEP (2.0 mg/m(3)) or filtered air for 5 h. One day later,
DEP-exposed OVA-allergic mice had significantly greater increases in ventilatory responses to
methacholine (Mch), but not increased lung resistance, suggesting that the airflow changes may have originated in the nasal passages.
DEP-exposed OVA-allergic mice also had increased lung
IL-4 levels relative to all other groups. The instillation of anti-p75(NTR) or anti-trkA completely reversed the
DEP-induced increases in ventilatory responses and lung
IL-4 protein to levels similar to control mice. OVA-allergic
DEP-exposed mice treated with anti-p75(NTR) had significantly less lung resistance in response to Mch relative to OVA-allergic
DEP-exposed mice treated with anti-trkA. The results of this study demonstrate that the enhancement of allergic airways responses by
DEP exposure is partly dependent on
neurotrophins in mice. In addition,
neurotrophins that bind p75(NTR), but not trkA, may mediate pulmonary central airways and tissue resistance responses to
allergen and
DEP exposure.