IL-10 gene knockout attenuates allergen-induced airway hyperresponsiveness in C57BL/6 mice

Abstract

Intratracheal administration of interleukin-10 (IL-10) has been reported to inhibit allergic inflammation but augment airway hyperresponsiveness (AHR). In the present study, airway and smooth muscle responsiveness to methacholine (MCh) were compared in wild-type (WT) and IL-10-deficient (IL-10-KO) mice to investigate the role of endogenous IL-10 in AHR development. Naive WT and IL-10-KO mice exhibited similar dose-dependent increases in airway resistance (Raw) to intravenous MCh. Sensitization and challenge with ragweed (RW) induced a twofold increase in responsiveness to intravenous MCh in WT mice, but hyperresponsiveness was not observed in similarly treated IL-10-KO mice. Likewise, tracheal rings from RW-sensitized and -challenged WT mice exhibited a fourfold greater responsiveness to MCh than IL-10-KO tracheal preparations. Measurements of airway constriction by whole body plethysmography further supported the Raw and tracheal ring data (i.e., AHR was not observed in the absence of IL-10). Interestingly, factors previously implicated in the development of AHR, including IL-4, IL-5, IL-13, IgA, IgG1, IgE, eosinophilia, and lymphocyte recruitment to the airways, were upregulated in the IL-10-KO mice. Treatment with recombinant murine IL-10 at the time of allergen challenge reduced the magnitude of inflammation but reinstated AHR development in IL-10-KO mice. Adoptive transfer of mononuclear splenocytes to IL-10-sufficient severe combined immunodeficient mice indicated that lymphocytes were an important source of the IL-10 impacting AHR development. These results provide evidence that IL-10 expression promotes the development of allergen-induced smooth muscle hyperresponsiveness.

Alterations in Nitric Oxide and Cytokine Production with Airway Inflammation in the Absence of IL-10

“…Although our AR and inflammation responses generally agree with those of prior studies (30,31,34), they are not consistent with one study in which IL-10 Ϫ/Ϫ mice demonstrated significantly decreased BAL macrophage counts and increased eosinophilia and AR, as compared with the C57 mice (41). Those responses were consistent with what would be expected with a lack of IL-10 as an anti-inflammatory cytokine and are in agreement with phenotypic expectations that would come from human data demonstrating a lack of IL-10 production in asthmatics (7,8).…”

“…This trend was consistent with an AR increase reported previously (30,31); however, its magnitude was small, perhaps due to the mild nature of our inflammatory challenge. Administration of L-NIL resulted in a significant increase in AR in the absence of IL-10 that was not different from the C57 IL-10-sufficient case.…”

“…Earlier studies have shown that elevations in Penh are correlated with eosinophilia in BALB/c mice (37); however, this association has been reported recently to be weak or absent, and there has been some controversy as to whether Penh can accurately reflect alterations in airway responsiveness in C57 mice (38,39). Our data suggest that alterations in AR associated with AI were consistent with expectations of airway hyporesponsiveness in IL-10 Ϫ/Ϫ mice, relative to their C57 IL-10-sufficient counterparts (30,31,33,34). Although we acknowledge some limitations to the Penh technique, we agree with the assertion by DeLorme and Moss (40) that the choice of the Penh measurement should be linked to the study objective and the ability to track alterations in AR previously verified by more invasive measures of lung resistance.…”

“…Although we acknowledge some limitations to the Penh technique, we agree with the assertion by DeLorme and Moss (40) that the choice of the Penh measurement should be linked to the study objective and the ability to track alterations in AR previously verified by more invasive measures of lung resistance. The latter requirement in the C57 and IL-10 Ϫ/Ϫ strains was fulfilled by the prior study of Justice et al (31) in which Penh was shown to display results consistent with measures of lung resistance in situ and airway smooth muscle tension development in vitro.…”

“…The effect of IL-10 on allergen-driven AR has been reported in several previous in vivo and in vitro animal studies (30,31,33,34). The evidence from those studies suggests that IL-10 influences or acts in concert with one or more inflammatory factors to increase smooth muscle activity (31), perhaps involving airway smooth muscle autocrine signaling through IL-5 (33) or regulation of surfactant protein D (35).…”