Intranasal administration of recombinant progranulin inhibits bronchial smooth muscle hyperresponsiveness in mouse allergic asthma.

Progranulin (PGRN) is a growth factor with multiple biological functions and has been suggested as an endogenous inhibitor of Tumor necrosis factor-α (TNF-α)-mediated signaling. TNF-α is believed to be one of the important mediators of the pathogenesis of asthma, including airway hyperresponsiveness (AHR). In the present study, effects of recombinant PGRN on TNF-α-mediated signaling and antigen-induced hypercontractility were examined in bronchial smooth muscles (BSMs) both in vitro and in vivo. Cultured human BSM cells (hBSMCs) and male BALB/c mice were used. The mice were sensitized and repeatedly challenged with ovalbumin antigen. Animals also received intranasal administrations of recombinant PGRN into the airways 1 h before each antigen inhalation. In hBSMCs, PGRN inhibited both the degradation of IκB-α (an index of NF-κB activation) and the upregulation of RhoA (a contractile machinery-associated protein that contributes to the BSM hyperresponsiveness) induced by TNF-α, indicating that PGRN has an ability to inhibit TNF-α-mediated signaling also in the BSM cells. In BSMs of the repeatedly antigen-challenged mice, an augmented contractile responsiveness to acetylcholine with an upregulation of RhoA was observed: both the events were ameliorated by pretreatments with PGRN intranasally. Interestingly, a significant decrease in PGRN expression was found in the airways of the repeatedly antigen-challenged mice rather than those of control animals. In conclusion, exogenously applied PGRN into the airways ameliorated the antigen-induced BSM hyperresponsiveness, probably by blocking TNF-α-mediated response. Increasing PGRN levels might be a promising therapeutic for AHR in allergic asthma.

Interleukin-17A directly acts on bronchial smooth muscle cells and augments the contractility.

BACKGROUND: Although interleukin-17 (IL-17) contributes to the induction of airway hyperresponsiveness in asthma, its effect on bronchial smooth muscle (BSM) remains largely unknown. Evidence support an involvement of RhoA/Rho-kinase in BSM contraction, and the pathway has now been proposed as a novel target for asthma therapy. To clarify the role of IL-17 on the development of BSM hyperresponsiveness, effects of IL-17A on BSM contractility and RhoA expression were investigated. METHODS: Male BALB/c mice and cultured human BSM cells (hBSMCs) were used. RESULTS: In the murine model of allergic asthma, BSM hyperresponsiveness with an IL-17A up-regulation in bronchoalveolar lavage fluids were observed. RT-PCR analyses revealed the expression of receptors for IL-17A in mouse BSMs and hBSMCs. In the hBSMCs, incubation with IL-17A caused an up-regulation of RhoA protein. Western blot analyses also revealed phosphorylations of JNKs/ERKs and a down-regulation of IκB-α in the IL-17A-treated hBSMCs, indicating that IL-17A could act on BSM cells directly. However, IL-17A did not activate STAT6, which is also known as a signaling molecule that causes an up-regulation of RhoA when activated by IL-13. On the other hand, IL-17A caused a down-regulation of miR-133a-3p, a microRNA that negatively regulates RhoA translation. In the naive mice, in vivo IL-17A treatment to the airways by intranasal instillation induced a BSM hyperresponsiveness with RhoA protein up-regulation. CONCLUSIONS: These findings indicate that IL-17 directly acts on BSM cells and up-regulates RhoA protein probably via a down-regulation of miR-133a-3p, resulting in an induction of the BSM hyperresponsiveness.