Extinction-based exposure therapy is used to treat anxiety- and trauma-related disorders; however, there is the need to improve its limited efficacy in individuals with impaired fear extinction learning and to promote greater protection against return-of-fear phenomena. Here, using 129S1/SvImJ mice, which display impaired fear extinction acquisition and extinction consolidation, we revealed that persistent and context-independent rescue of deficient fear extinction in these mice was associated with enhanced expression of dopamine-related genes, such as dopamine D1 (Drd1a) and -D2 (Drd2) receptor genes in the medial prefrontal cortex (mPFC) and amygdala, but not hippocampus. Moreover, enhanced histone acetylation was observed in the promoter of the extinction-regulated Drd2 gene in the mPFC, revealing a potential gene-regulatory mechanism. Although enhancing histone acetylation, via administering the histone deacetylase (HDAC) inhibitor MS-275, does not induce fear reduction during extinction training, it promoted enduring and context-independent rescue of deficient fear extinction consolidation/retrieval once extinction learning was initiated as shown following a mild conditioning protocol. This was associated with enhanced histone acetylation in neurons of the mPFC and amygdala. Finally, as a proof-of-principle, mimicking enhanced dopaminergic signaling by L-dopa treatment rescued deficient fear extinction and co-administration of MS-275 rendered this effect enduring and context-independent. In summary, current data reveal that combining dopaminergic and epigenetic mechanisms is a promising strategy to improve exposure-based behavior therapy in extinction-impaired individuals by initiating the formation of an enduring and context-independent fear-inhibitory memory.

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Multiple system atrophy (MSA) is a neurodegenerative movement disorder characterized by parkinsonian symptoms and cerebellar symptoms. Sleep disturbances also play a crucial role in MSA. One of the most convincing animal models in MSA research is the PLP α-SYN model, but to date no studies on sleep disturbances in this mouse model, frequently found in MSA patients are available. We identified spectral shifts within the EEG of the model, strikingly resembling results of clinical studies. We also characterized muscle activity during REM sleep, which is one of the key symptoms in REM sleep behavioral disorder. Spectral shifts and REM sleep-linked muscle activity were age dependent, supporting Face Validity of the PLP α-SYN model. We also strongly suggest our findings to be critically evaluated for Predictive Validity in future studies. Currently, research on MSA lacks potential compounds attenuating or curing MSA. Future drugs must prove its potential in animal models, for this our study provides potential biomarkers.

Despite the large number of drugs available for the treatment of asthma, in 5–10% of the patients this disease is not well controlled. While most treatments palliate symptoms, those suffering from severe and uncontrolled asthma could benefit more from a therapeutic approach addressing the root problem. An siRNA‐based therapy targeting the transcription factor GATA3 in activated T helper cells subtype 2 (TH2 cells), one of the key upstream factors involved in asthma, could therefore represent a promising strategy. However, the difficult‐to‐transfect cell type has not extensively been explored for nucleic acid therapeutics. In this regard, our group first identified a suitable pathway, that is, transferrin receptor mediated uptake, to target efficiently and specifically activated TH2 cells with a transferrin‐polyethyleneimine (PEI) conjugate which forms polyplexes with siRNA. This system, despite efficient uptake in activated T cells (ATCs) in vivo, suffered from poor endosomal release and was later improved by a combination with a melittin‐PEI conjugate. The new formulation showed improved endosomal escape and gene silencing efficacy. Additionally, in order to develop a clinically relevant dosage form for pulmonary delivery of siRNA we have lately focused on a dry powder formulation by spray drying (SD) for the production of inhalable nano‐in‐microparticles. In proof‐of‐concept experiments, DNA/PEI polyplexes were used in order to implement analytics and engineer process parameters to pave the way for SD also siRNA containing polyplexes and more sophisticated systems in general. Ultimately, our efforts are devoted to the development of a novel treatment of asthma that can be translated from bench to bedside and are reviewed and discussed here in the context of the current literature. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Biology‐Inspired Nanomaterials > Nucleic Acid‐Based Structures Biology‐Inspired Nanomaterials > Protein and Virus‐Based Structures

To develop stable and inhalable dry powder formulations with long shelf life, polyplexes consisting of siRNA and a polyethylenimine (PEI)‐based block copolymer in presence of mannitol or trehalose are spray dried. The effect of inlet (T‐In) and outlet (T‐Out) temperature on the recovery of siRNA and adsorption effects within the tubing material are investigated. Choosing a low abrasion silicon tubing prevented siRNA loss due to adsorption. Mannitol and trehalose formulations preserved siRNA integrity regardless of excipient concentration and temperature at T‐Out below the siRNA melting temperature. Trehalose formulations allowed full siRNA recovery whereas mannitol formulations resulted in spray drying induced losses of ≈20% siRNA and of 50–60% polymer. Mannitol formulations showed optimal aerodynamic characteristics as confirmed by next generation impaction analysis based upon siRNA content. All spray dried formulations resulted in green fluorescent protein (GFP) silencing comparable or better than freshly prepared polyplexes. To test if the observed results could be transferred, formulations of siRNA and transferrin‐PEI conjugates are spray dried, characterized, and used to transfect primary human T cells ex vivo. Results confirmed successful silencing of the transcription factor GATA3 in primary CD4+ T cells with spray dried formulations as a potential treatment for severe asthma.

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The cover image is based on the Focus Article TH2‐cell targeted pulmonary siRNA delivery for the treatment of asthma by Tobias W. M. Keil, Domizia Baldassi and Olivia M. Merkel. https://doi.org/10.1002/wnan.1634.

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