Effects of Benzo[α]pyrene on Mucus Secretion and Tissue Remodeling in a Rat Model of Allergic Rhinitis

OBJECTIVES

Exposure to benzo[α]pyrene (BaP) increases the incidence and severity of allergic rhinitis (AR), but the underlying mechanisms remain unclear. Thus, we investigated the in vivo effects of BaP exposure on mucus hypersecretion and tissue remodeling in a rat model of AR.

METHODS

Female Sprague-Dawley rats were randomly divided into 4 groups: a negative control group, a group of healthy rats exposed to BaP, a group of rats with ovalbumin (OVA)-induced AR, and a group of AR model rats exposed to BaP. Nasal symptoms and levels of OVA-specific serum immunoglobulin E (IgE) were measured in each individual rat. Moreover, examination of goblet cell hyperplasia and collagen deposition was carried out with periodic acid-Schiff (PAS) staining and Masson trichrome (MT) staining. Mucin 5AC (MUC5AC) expression was assessed by immunohistochemistry.

RESULTS

BaP significantly increased the number of sneezes, the number of nasal rubs and the levels of OVA-specific serum IgE in rats with AR. Statistically significant differences in goblet cell hyperplasia and collagen deposition were observed between the BaP-exposed AR model group and the AR model group. Immunohistochemical results showed that the nasal mucosa of AR model rats displayed markedly elevated MUC5AC expression after BaP exposure.

CONCLUSION

Our data indicate that mucus hypersecretion and the development of nasal remodeling might be pathophysiologic mechanisms underlying increased susceptibility to AR after exposure to BaP.

Nasal lavage cytology and mucosal histopathological alterations in patients with rhinitis

Introduction

The extent of epithelial lesion in allergic and non-allergic rhinitis and its association with inflammatory changes in nasal lavage has not been clarified.

Objective

To verify the association between the inflammatory cells in the nasal lavage, epithelial lesion extent and basement membrane thickness, in the nasal mucosa of patients with rhinitis; to determine the cutoff point of the percentage of eosinophils in the nasal lavage associated with the atopic patients.

Methods

Patients with rhinitis and indication for septoplasty and (or) turbinectomy for turbinate hypertrophy were selected, and were submitted to allergy skin tests, nasal lavage with measurement of albumin and interleukin-8 levels, total and differential counting of cells, and mucosal histopathological analysis to determine the extent of epithelial lesion, and degree of basement membrane thickening.

Results

Fifty-six patients with a median age of 24.5 years and a diagnosis of allergic rhinitis (n = 36) and non-allergic rhinitis (n = 20) were studied. In atopic subjects, allergy skin tests were positive for Dermatophagoides pteronyssinus in 35 (97.0%) and Lolium perenne in 18 (50.0%). Atopic subjects showed a higher clinical score index of rhinitis compared to non-atopic ones. The total count of cells, neutrophils, and levels of albumin and IL-8 were not different in the nasal lavage of atopic and non-atopic subjects. The cutoff point for eosinophil count in nasal fluid for the distinction between allergic rhinitis and non-allergic rhinitis was 4%. Some degree of epithelial lesion was more frequent in allergic rhinitis (94%) than in non-allergic rhinitis (65%) patients. In the presence of basement membrane thickness, as a marker of remodeling, there was no difference in the nasal lavage of patients with allergic rhinitis and non-allergic rhinitis.

Conclusion

In this series, 4% was the cutoff point for the number of eosinophils in the nasal lavage, for atopy differentiation. Upper airway remodeling accessed by basement membrane thickness showed similar inflammatory cell infiltrate in the nasal lavage, regardless of the presence of atopy.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in nasal lavage after an inhalation challenge with flour

OBJECTIVES/HYPOTHESIS

The existence of nasal mucosa remodeling in allergic rhinitis is controversial. Few data are available on the dynamics of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in nasal fluid after an allergen challenge. We examined whether an immediate allergic reaction that induces nasal congestion and inflammation is able to also induce changes in remodeling parameters in nasal fluid.

STUDY DESIGN

Controlled experimental study.

METHODS

Ten patients with allergic occupational rhinitis due to flour underwent a control and active inhalation challenge with serial monitoring of nasal congestion and nasal symptoms with acoustic rhinometry and a visual analogue scale. Levels of remodeling markers (MMP-2, MMP-7, MMP-9, MMP-13, TIMP-1, TIMP-2) and inflammatory cells in nasal fluid were measured before the challenge and at 30 minutes, 6 hours, and 24 hours following the challenge.

RESULTS

In contrast to the control challenge, the flour challenge induced nasal symptoms and significant decreases in nasal volume in all subjects. After the flour challenge, a significant increase in nasal levels of TIMP-2 and a nonsignificant increase in TIMP-1 levels were observed, whereas no significant changes in nasal levels of MMPs were documented.

CONCLUSIONS

This study showed that after an inhalation challenge with an occupational allergen, the nasal mucosa displayed an imbalance in favor of TIMPs enzymes activity as compared to MMPs enzymes activity, represented in an increase in nasal levels of TIMP-2 during the course of the early reaction following the allergen challenge.