Differences in Stress-Induced Modulation of the Auditory System Between Wistar and Lewis Rats.

Many aspects of stress-induced physiological and psychological effects have been characterized in people and animals. However, stress effects on the auditory system are less explored and their mechanisms are not well-understood, in spite of its relevance for a variety of diseases, including tinnitus. To expedite further research of stress-induced changes in the auditory system, here we compare the reactions to stress among Wistar and Lewis rats. The animals were stressed for 24 h, and subsequently we tested the functionality of the outer hair cells (OHCs) using distortion product otoacoustic emissions (DPOAEs) and auditory neurons using evoked auditory brainstem responses (ABR). Lastly, using Western blot, we analyzed the levels of plasticity-related proteins in the inferior colliculus, confirming that the inferior colliculus is involved in the adaptive changes that occur in the auditory system upon stress exposure. Surprisingly, the two strains reacted to stress quite differently: Lewis rats displayed a lowering of their auditory threshold, whereas it was increased in Wistar rats. These functional differences were seen in OHCs of the apical region (low frequencies) and in the auditory neurons (across several frequencies) from day 1 until 2 weeks after the experimental stress ended. Wistar and Lewis rats may thus provide models for auditory threshold increase and decrease, respectively, which can both be observed in different patients in response to stress.

Small interfering RNA against transcription factor STAT6 inhibits allergic airway inflammation and hyperreactivity in mice.

In the context of allergic immune responses, activation of STAT6 is pivotal for Th2-mediated IgE production and development of airway inflammation and hyperreactivity. We analyzed whether gene silencing of STAT6 expression by RNA interference was able to suppress allergen-induced immune and airway responses. Knockdown effectiveness of three different STAT6 siRNA molecules was analyzed in murine and human cell cultures. The most potent siRNA was used for further testing in a murine model of allergen-induced airway inflammation and airway hyperreactivity (AHR). BALB/c mice were sensitized with OVA/alum twice i.p. (days 1 and 14), and challenged via the airways with allergen (days 28-30). Intranasal application of STAT6 siRNA before and during airway allergen challenges reduced levels of infiltrating cells, especially of eosinophils, in the bronchoalveolar lavage fluid, compared with GFP siRNA-treated sensitized and challenged controls. Allergen-induced alterations in lung tissues (goblet cell hyperplasia, peribronchial inflammation with eosinophils and CD4 T cells) were significantly reduced after STAT6 siRNA treatment. Associated with decreased inflammation was a significant inhibition of the development of allergen-induced in vivo AHR after STAT6 siRNA treatment, compared with GFP siRNA-treated sensitized and challenged controls. Importantly, mRNA and protein expression levels of IL-4 and IL-13 in lung tissues of STAT6-siRNA treated mice were significantly diminished compared with sensitized and challenged controls. These data show that targeting the key transcription factor STAT6 by siRNA effectively blocks the development of cardinal features of allergic airway disease, like allergen-induced airway inflammation and AHR. It may thus be considered as putative approach for treatment of allergic airway diseases such as asthma.