Altered mucosal immune response after acute lung injury in a murine model of Ataxia Telangiectasia

Abstract

Background: Ataxia telangiectasia (A-T) is a rare but devastating and progressive disorder characterized by cerebellar dysfunction, lymphoreticular malignancies and recurrent sinopulmonary infections. In A-T, disease of the respiratory system causes significant morbidity and is a frequent cause of death.

Methods: We used a self-limited murine model of hydrochloric acid-induced acute lung injury (ALI) to determine the inflammatory answer due to mucosal injury in Atm (A-T mutated)- deficient mice (Atm(-/-)).

Results: ATM deficiency increased peak lung inflammation as demonstrated by bronchoalveolar lavage fluid (BALF) neutrophils and lymphocytes and increased levels of BALF pro-inflammatory cytokines (e.g. IL-6, TNF). Furthermore, bronchial epithelial damage after ALI was increased in Atm(-/-) mice. ATM deficiency increased airway resistance and tissue compliance before ALI was performed.

Conclusions: Together, these findings indicate that ATM plays a key role in inflammatory response after airway mucosal injury.

Figure 1

Survival rate after ALI in Atm^-/- and healthy control mice with different dosing strategies. Survival rate 24 hours after ALI in Atm^-/- (black bars) and control mice (grey bars) after instillation of 50 μl HCl in comparison to bodyweight adjusted (1 μl/ g mouse) HCl instillation.

Figure 2

Leukocyte clearance after airway mucosal injury in Atm^-/- and healthy control mice. BALF cell differentiation before ALI between Atm^-/-(a) and control mice (d). Atm^-/- mice show decreased PMNs clearance (b) 24 hours after ALI representing increased inflammation and disturbed resolution compared to control mice (e). These differences have resolved 1 week after ALI (c and f). Atm^-/- mice (a-c), Atm^+/+mice (d-e). Original magnification x100.

Figure 3

ATM deficiency increases leukocyte recruitment after airway mucosal injury. (a)Atm^-/- mice or control mice underwent acute lung injury (ALI) by intratracheal (i.t.) instillation of HCl and bronchoalveolar lavage (BAL) was performed at different time points. Before ALI (b), 24 hours after ALI (c) and one week after ALI (d) BAL was performed and total cells (b-d) were enumerated (see Methods). Values represent the mean ± S.E.M. for n ≥ 4 mice.

Figure 4

ATM deficiency increases polymorphonuclear leukocytes (PMNs) and lymphoytes recruitment after airway mucosal injury.Atm^-/- or control mice underwent acute lung injury (ALI) by i.t. instillation of HCl and bronchoalveolar lavage (BAL) was performed at different time points. Before ALI (a, d, g), 24 hours after ALI (b, e, h) and one week after ALI (c, f, i) BAL was performed and differential cell count for PMNs (a-c), lymphocytes (d-f) and macrophages (MACs) (g-i) was done. Values represent the mean ± S.E.M. for n ≥ 4 mice. * P < 0.05 vs. vehicle group.

Figure 5

ATM deficiency impacts the lung histopathological changes after acid –initiated acute lung injury (ALI). Lung tissue sections were obtained 24 hours after (a-d) and one week after (e-h) ALI from Atm^-/-(a, c, e, g) and control mice (b, d, f, h). Hematoxylin and eosin (H&E) (a, b, e, f) or ABvG (c, d, g, h). Results are representative of n = 3. Black arrowheads, epithelial cell disrupture; white arrowheads, mucus; black arrows, inflammatory cells. Original magnification x200.

Figure 6

Elevation in lung resistance and increased tissue compliance in Atm^-/- mice before and after mucosal injury. Using a flexiVent mouse ventilator, (a) tissue resistance and (b) lung compliance were determined before and 24 hours after acid injury. Values represent the mean ± S.E.M. for n ≥ 5 mice. *P < 0.05 vs. control group.

Figure 7

Impact of ATM deficiency on inflammatory mediator levels after ALI. Aliquots of BALFs obtained before ALI, 24 hours and one week after ALI were analyzed by cytometric bead array (a, b). Values represent the mean ± S.E.M. for n ≥ 3 mice. *P < 0.05 vs. control group.