Selective Replacement of Cholesterol with Cationic Amphiphilic Drugs Enables the Design of Lipid Nanoparticles with Improved RNA Delivery

The delivery of RNA across biological barriers can be achieved by encapsulation in lipid nanoparticles (LNPs). Cationic amphiphilic drugs (CADs) are pharmacologically diverse compounds with ionizable lipid-like features. In this work, we applied CADs as a fifth component of state-of-the-art LNPs via microfluidic mixing. Improved cytosolic delivery of both siRNA and mRNA was achieved by partly replacing the cholesterol fraction of LNPs with CADs. The LNPs could cross the mucus layer in a mucus-producing air-liquid interface model of human primary bronchial epithelial cells following nebulization. Moreover, CAD-LNPs demonstrated improved epithelial and endothelial targeting following intranasal administration in mice, without a marked pro-inflammatory signature. Importantly, quantification of the CAD-LNP molar composition, as demonstrated for nortriptyline, revealed a gradual leakage of the CAD from the formulation during LNP dialysis. Altogether, these data suggest that the addition of a CAD prior to the rapid mixing process might have an impact on the composition, structure, and performance of LNPs.

Trajectory of neutrophilic responses in a mouse model of pollutant-aggravated allergic asthma

Experimental studies suggest that neutrophils could contribute to allergic asthma pathogenesis, that is mainly driven by type 2 immunity. Inhalation of diesel exhaust particles (DEP) is implicated in both exacerbation and development of asthma. Since exposure to DEP is associated with a neutrophilic component, we aimed to investigate how exposure to the combination of allergens and DEP modulates neutrophilic responses. Human bronchial epithelial cells (HBEC) were exposed to house dust mite (HDM), DEP or HDM + DEP in vitro to determine the expression of neutrophil-recruiting chemokines. Female (C57BL/6 J) mice were intranasally instilled with saline, DEP, HDM or combined HDM + DEP for 3 weeks (subacute) or 6 weeks (chronic). The neutrophilic responses were determined in lung tissue and bronchoalveolar lavage fluid (BALF). Simultaneous exposure to HDM + DEP resulted in increased CXCL1 and CXCL8 mRNA expression by HBEC in vitro. In mice, subacute exposure to HDM + DEP induced a strong mixed eosinophilic/neutrophilic inflammation in BALF and lung and was associated with higher expression of neutrophil-attracting chemokines and NET formation compared to the sole exposures. After chronic HDM + DEP exposure, a similar neutrophilic response was observed, however the NET formation was less pronounced. Interestingly, the increase of BALF eosinophils was also significantly attenuated after chronic HDM + DEP exposure compared to the subacute exposure. Subacute and chronic HDM + DEP exposure induced goblet cell hyperplasia and airway hyperresponsiveness. Our data suggest a role for neutrophils and NETs in pollutant-aggravated eosinophilic allergic asthma. Moreover, subacute exposure to HDM + DEP induces a mixed eosinophilic/neutrophilic response whereas upon chronic HDM + DEP exposure there is a shift in inflammatory response with a more prominent neutrophilic component.

RIPK1 kinase-dependent inflammation and cell death contribute to the pathogenesis of COPD

RATIONALE

Receptor-interacting protein kinase 1 (RIPK1) is a key mediator of regulated cell death (including apoptosis and necroptosis) and inflammation, both drivers of chronic obstructive pulmonary disease (COPD) pathogenesis.

OBJECTIVE

We aimed to define the contribution of RIPK1 kinase-dependent cell death and inflammation in the pathogenesis of COPD.

METHODS

We assessed RIPK1 expression in single-cell RNA-sequencing data from human and mouse lungs and validated RIPK1 levels in lung tissue of COPD patients via immunohistochemistry. Next, we assessed the consequences of genetic and pharmacological inhibition of RIPK1 kinase activity in experimental COPD, using Ripk1^{S25D /S25D} kinase deficient mice and the RIPK1 kinase inhibitor GSK'547.

MEASUREMENTS AND MAIN RESULTS

RIPK1 expression increased in alveolar type I (AT1), AT2, ciliated and neuroendocrine cells in human COPD. RIPK1 protein levels were significantly increased in airway epithelium of COPD patients, compared to never smokers and smokers without airflow limitation. In mice, exposure to cigarette smoke (CS) increased Ripk1 expression similarly in AT2 cells, and further in alveolar macrophages and T cells. Genetic and/or pharmacological inhibition of RIPK1 kinase activity significantly attenuated airway inflammation upon acute and subacute CS-exposure, as well as airway remodeling, emphysema and apoptotic and necroptotic cell death upon chronic CS-exposure. Similarly, pharmacological RIPK1 kinase inhibition significantly attenuated elastase-induced emphysema and lung function decline. Finally, RNA-sequencing on lung tissue of CS-exposed mice revealed downregulation of cell death and inflammatory pathways upon pharmacological RIPK1 kinase inhibition.

CONCLUSIONS

RIPK1 kinase inhibition is protective in experimental models of COPD and may represent a novel promising therapeutic approach.

Quantification and role of innate lymphoid cell subsets in Chronic Obstructive Pulmonary Disease

Objectives

Innate lymphoid cells (ILCs) secrete cytokines, such as IFN‐γ, IL‐13 and IL‐17, which are linked to chronic obstructive pulmonary disease (COPD). Here, we investigated the role of pulmonary ILCs in COPD pathogenesis.

Methods

Lung ILC subsets in COPD and control subjects were quantified using flow cytometry and associated with clinical parameters. Tissue localisation of ILC and T‐cell subsets was determined by immunohistochemistry. Mice were exposed to air or cigarette smoke (CS) for 1, 4 or 24 weeks to investigate whether pulmonary ILC numbers and activation are altered and whether they contribute to CS‐induced innate inflammatory responses.

Results

Quantification of lung ILC subsets demonstrated that ILC1 frequency in the total ILC population was elevated in COPD and was associated with smoking and severity of respiratory symptoms (COPD Assessment Test [CAT] score). All three ILC subsets localised near lymphoid aggregates in COPD. In the COPD mouse model, CS exposure in C57BL/6J mice increased ILC numbers at all time points, with relative increases in ILC1 in bronchoalveolar lavage (BAL) fluid. Importantly, CS exposure induced increases in neutrophils, monocytes and dendritic cells that remained elevated in Rag2/Il2rg‐deficient mice that lack adaptive immune cells and ILCs. However, CS‐induced CXCL1, IL‐6, TNF‐α and IFN‐γ levels were reduced by ILC deficiency.

Conclusion

The ILC1 subset is increased in COPD patients and correlates with smoking and severity of respiratory symptoms. ILCs also increase upon CS exposure in C57BL/6J mice. In the absence of adaptive immunity, ILCs contribute to CS‐induced pro‐inflammatory mediator release, but are redundant in CS‐induced innate inflammation.

Targeting neutrophils in asthma: A therapeutic opportunity?

Suppression of airway inflammation with inhaled corticosteroids has been the key therapeutic approach for asthma for many years. Identification of inflammatory phenotypes in asthma has moreover led to important breakthroughs, e.g. with specific targeting of the IL-5 pathway as add-on treatment in difficult-to-treat eosinophilic asthma. However, the impact of interfering with the neutrophilic component in asthma is less documented and understood. This review provides an overview of established and recent insights with regard to the role of neutrophils in asthma, focusing on research in humans. We will describe the main drivers of neutrophilic responses in asthma, the heterogeneity in neutrophils and how they could contribute to asthma pathogenesis. Moreover we will describe findings from clinical trials, in which neutrophilic inflammation was targeted. It is clear that neutrophils are important actors in asthma development and play a role in exacerbations. However, more research is required to fully understand how modulation of neutrophil activity could lead to a significant benefit in asthma patients with airway neutrophilia.