title: Stress induces substance P in vagal sensory neurons innervating the mouse airways.
abstract: BACKGROUND
  Tachykinins-like substance P (SP) have been shown to play an important role in initiating and perpetuating airway inflammation. Furthermore, they are supposed to be released into tissues in response to stress.
  
  
  OBJECTIVE
  The aim of this study was to investigate the effects of stress alone or in combination with allergic airway inflammation on SP expression in sensory neurons innervating the mouse airways.
  
  
  METHODS
  Balb/c mice were systemically sensitized to ovalbumin (OVA), followed by allergen aerosol exposure, and compared with non-sensitized controls. Additionally, OVA-sensitized and -challenged and non-sensitized mice were exposed to sound stress. SP expression in airway-specific and overall vagal sensory neurons of the jugular and nodose ganglion complex was analysed using retrograde neuronal tracing in combination with immunohistochemistry. Preprotachykinin A (PPT-A) mRNA, the precursor for SP, was quantified in lung tissue by real-time PCR. Bronchoalveolar lavage (BAL) fluid was obtained, and cell numbers and differentiation were determined.
  
  
  RESULTS
  Stress and/or allergic airway inflammation significantly increased SP expression in retrograde-labelled vagal sensory neurons from the mouse lower airways compared with controls [stress: 15.7+/-0.8% (% of retrograde-labelled neurons, mean+/-SEM); allergen: 17.9+/-0.4%; allergen/stress: 13.1+/-0.7% vs. controls: 6.3+/-0.3%]. Similarly, SP expression increased in overall vagal sensory neurons identified by the neuronal marker protein gene product (PGP) 9.5 [stress: 9.3+/-0.6% (% of PGP 9.5-positive neurons, means+/-SEM); allergen: 12.5+/-0.4%; allergen/stress: 10.2+/-0.4% vs. controls: 5.1+/-0.3%]. Furthermore, stress significantly increased PPT-A mRNA expression in lung tissue from OVA-sensitized and -challenged animals, and immune cells were identified as an additional source of SP in the lung by immunohistochemistry. Associated with enhanced neuronal SP expression, a significantly higher number of leucocytes were found in the BAL following allergen exposure. Further, stress significantly increased allergen-induced airway inflammation identified by increased leucocyte numbers in BAL fluids.
  
  
  CONCLUSIONS
  The central event of sound stress leads to the stimulation of SP expression in airway-specific neurons. However, in sensitized stressed mice an additional local source of SP (probably inflammatory cells) might enhance allergic airway inflammation.
authors.affiliation: Department of Internal Medicine, Charite Universitatsmedizin, Berlin. ricarda.joachim@charite.de
authors.forename: R A
authors.initials: RA
authors.lastname: Joachim
authors.forename: L B
authors.initials: LB
authors.lastname: Cifuentes
authors.forename: V
authors.initials: V
authors.lastname: Sagach
authors.forename: D
authors.initials: D
authors.lastname: Quarcoo
authors.forename: E
authors.initials: E
authors.lastname: Hagen
authors.forename: P C
authors.initials: PC
authors.lastname: Arck
authors.forename: A
authors.initials: A
authors.lastname: Fischer
authors.forename: B F
authors.initials: BF
authors.lastname: Klapp
authors.forename: Q T
authors.initials: QT
authors.lastname: Dinh
mesh_terms: D000485:Allergens; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D016535:Bronchial Hyperreactivity; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D007150:Immunohistochemistry / Q000379:methods; D008168:Lung / Q000737:chemistry / Q000294:innervation*; D051379:Mice; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D009434:Neural Pathways; D009475:Neurons, Afferent / Q000737:chemistry / Q000378:metabolism*; D009620:Nodose Ganglion / Q000737:chemistry; D010047:Ovalbumin; D011498:Protein Precursors / Q000032:analysis / Q000235:genetics; D012130:Respiratory Hypersensitivity / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013315:Stress, Psychological / Q000378:metabolism*; D013373:Substance P / Q000032:analysis / Q000378:metabolism*; D015320:Tachykinins / Q000032:analysis / Q000235:genetics; D043222:Ubiquitin Thiolesterase / Q000032:analysis
chemical_list: D000485:Allergens; D015415:Biomarkers; D011498:Protein Precursors; D015320:Tachykinins; C482860:UCHL1 protein, human; C044206:preprotachykinin; D013373:Substance P; D010047:Ovalbumin; D043222:Ubiquitin Thiolesterase