Differences in susceptibility to German cockroach frass and its associated proteases in induced allergic inflammation in mice

Abstract Background Cockroach exposure is a major risk factor for the development of asthma. Inhalation of fecal remnants (frass) is the likely sensitizing agent; however isolated frass has not been tested for its ability to induce experimental asthma in mice. Methods Mice (Balb/c or C57Bl/6) were sensitized and challenged with GC frass or GC frass devoid of proteases and measurements of airway inflammation and hyperresponsiveness were performed (interleukin (IL)-5, -13, and interferon gamma (IFNγ) levels in bronchoalveolar lavage fluid, serum IgE levels, airway hyperresponsiveness, cellular infiltration, and mucin production). Results Sensitization and challenge of Balb/c mice with GC frass resulted in increased airway inflammation and hyperresponsiveness. C57Bl/6 mice were not susceptible to this model of sensitization; however they were sensitized to GC frass using a more aggressive sensitization and challenge protocol. In mice that were sensitized by inhalation, the active serine proteases in GC frass played a role in airway hyperresponsiveness as these mice had less airway hyperresponsiveness to acetylcholine and less mucin production. Proteases did not play a role in mediating the allergic inflammation in mice sensitized via intraperitoneal injection. Conclusion While both strains of mice were able to induce experimental asthma following GC frass sensitization and challenge, the active serine proteases in GC frass only play a role in airway hyperresponsiveness in Balb/c mice that were susceptible to sensitization via inhalation. The differences in the method of sensitization suggest genetic differences between strains of mice.</p

Histological assessment of lung sections from PBS or GC frass exposed C57Bl/6 mice

<p><b>Copyright information:</b></p><p>Taken from "Differences in susceptibility to German cockroach frass and its associated proteases in induced allergic inflammation in mice"</p><p>http://respiratory-research.com/content/8/1/91</p><p>Respiratory Research 2007;8(1):91-91.</p><p>Published online 8 Dec 2007</p><p>PMCID:PMC2222603.</p><p></p> Haematoxylin and eosin (H&E) staining of sectioned lungs from PBS (A) and GC frass (B) treated C57Bl/6 mice. Periodic Acid Schiff (PAS) staining of sectioned lungs from PBS (C) and GC frass (D) treated C57Bl/6 mice. Representative slides are shown of sections from 6–7 mice per group

Histological assessment of lung sections from Balb/c mice exposed to GC frass or protease-depleted GC frass

<p><b>Copyright information:</b></p><p>Taken from "Differences in susceptibility to German cockroach frass and its associated proteases in induced allergic inflammation in mice"</p><p>http://respiratory-research.com/content/8/1/91</p><p>Respiratory Research 2007;8(1):91-91.</p><p>Published online 8 Dec 2007</p><p>PMCID:PMC2222603.</p><p></p> Periodic Acid Schiff (PAS) staining of sectioned lungs from GC frass (A) and aprotinin-treated GC frass (D) treated Balb/c mice. Representative slides are shown of sections from 8 mice per group

GC frass serine proteases regulate airway inflammation and airway hyperresponsiveness in Balb/c mice

<p><b>Copyright information:</b></p><p>Taken from "Differences in susceptibility to German cockroach frass and its associated proteases in induced allergic inflammation in mice"</p><p>http://respiratory-research.com/content/8/1/91</p><p>Respiratory Research 2007;8(1):91-91.</p><p>Published online 8 Dec 2007</p><p>PMCID:PMC2222603.</p><p></p> Balb/c mice were challenged on day 0, 7, and 14 with PBS, PBS pretreated with aprotinin (10 μg/ml), GC frass (40 μg) or GC frass pretreated with aprotinin. On day 17, mice were anesthetized and acetylcholine was injected after establishment of a stable airway pressure. A. AHR was measured as airway pressure time index (APTI) in cm-HO × sec (* p < 0.001). B. Lungs from the mice were excised, and cells dissociated and maintained in a single suspension culture for 3 days in the presence of Con A (10 μg/ml). Supernatants were removed and ELISAs were run for IL-5, IL-13 and IFNγ. These data are represented as cytokine (listed on the x-axis) in ng/ml from PBS or frass treated mice. C. Serum IgE levels were analyzed by ELISA (*p < 0.001). In all cases the data are expressed as mean ± SEM and represent 13–14 mice per group and statistical significance determined by ANOVA