Type 2 inflammation in asthma develops with exposure to stimuli to include inhaled allergens from house dust mites (HDM). Features include mucus hypersecretion and the formation of pro-secretory ion transport characterised by elevated basal Cl- current. Studies using human sinonasal epithelial cells treated with HDM extract report a higher protease activated receptor-2 (PAR-2) agonist-induced calcium mobilisation that may be related to airway sensitisation by allergen-associated proteases. Herein, this study aimed to investigate the effect of HDM on Ca2+ signalling and inflammatory responses in asthmatic airway epithelial cells. Primary bronchial epithelial cells (hPBECs) from asthma donors cultured at air-liquid interface were used to assess electrophysiological, Ca2+ signalling and inflammatory responses. Differences were observed regarding Ca2+ signalling in response to PAR-2 agonist 2-Furoyl-LIGRLO-amide (2-FLI), and equivalent short-circuit current (Ieq) in response to trypsin and 2-FLI, in ALI-asthma and healthy hPBECs. HDM treatment led to increased levels of intracellular cations (Ca2+, Na+) and significantly reduced the 2-FLI-induced change of Ieq in asthma cells. Apical HDM-induced Ca2+ mobilisation was found to mainly involve the activation of PAR-2 and PAR-4-associated store-operated Ca2+ influx and TRPV1. In contrast, PAR-2, PAR-4 antagonists and TRPV1 antagonist only showed slight impact on basolateral HDM-induced Ca2+ mobilisation. HDM trypsin-like serine proteases were the main components leading to non-amiloride sensitive Ieq and also increased interleukin-33 (IL-33) and thymic stromal lymphopoietin (TSLP) from asthma hPBECs. These studies add further insight into the complex mechanisms associated with HDM-induced alterations in cell signalling and their relevance to pathological changes within asthma.

The universal proteinase inhibitor α2-macroglobulin (α₂-MG) exhibiting antiviral and immunomodulatory activities, is considered as an important participant in the infectious process. The activity of α₂-MG in the new coronavirus infection and post-covid syndrome (long COVID) has not been studied yet. We examined 85 patients diagnosed with community-acquired bilateral polysegmental pneumonia developed under conditions of a new coronavirus infection SARS-CoV-2. For assessment of the post-COVID period, 60 patients were examined 5.0±3.6 months after the coronavirus infection. Among these patients, 40 people had complications, manifested in the form of neurological, cardiological, gastroenterological, dermatological, bronchopulmonary symptoms. The control group included 30 conditionally healthy individuals with a negative PCR result for SARS-CoV-2 RNA and lack of antibodies to the SARS-CoV-2 virus. The α₂-MG activity in serum samples of patients with coronavirus infection dramatically decreased, up to 2.5% of the physiological level. This was accompanied by an increase in the activity of the α₁-proteinase inhibitor, elastase- and trypsin-like proteinases by 2.0-, 4.4- and 2.6-fold respectively as compared with these parameters in conditionally healthy individuals of the control. In the post-COVID period, despite the trend towards normalization of the activity of inhibitors, the activity of elastase-like and especially trypsin-like proteinases in serum remained elevated. In overweight individuals, the increase in the activity of trypsin-like proteinases was most pronounced and correlated with an increase in the antibody titer to the SARS-CoV-2 virus. In the post-COVID period, the α₂-MG activity not only normalized, but also exceeded the control level, especially in patients with dermatological and neurological symptoms. In patients with neurological symptoms or with dermatological symptoms, the α₂-MG activity was 1.3 times and 2.1 times higher than in asymptomatic persons. Low α₂-MG activity in the post-COVID period persisted in overweight individuals. The results obtained can be used to monitor the course of the post-COVID period and identify risk groups for complications.

The trypsin-like proteases (TLPs) play widespread and diverse roles, in a host of physiological and pathological processes including clot dissolution, extracellular matrix remodelling, infection, angiogenesis, wound healing and tumour invasion/metastasis. Moreover, these enzymes are involved in the disruption of normal lung function in a range of respiratory diseases including allergic asthma where several allergenic proteases have been identified. Here, we report the synthesis of a series of peptide derivatives containing an N-alkyl glycine analogue of arginine, bearing differing electrophilic leaving groups (carbamate and triazole urea), and demonstrate their function as potent, irreversible inhibitors of trypsin and TLPs, to include activities from cockroach extract. As such, these inhibitors are suitable for use as activity probes (APs) in activity-based profiling (ABP) applications.

Trypsin-like proteases (TLPs) belong to a family of serine enzymes with primary substrate specificities for the basic residues, lysine and arginine, in the P1 position. Whilst initially perceived as soluble enzymes that are extracellularly secreted, a number of novel TLPs that are anchored in the cell membrane have since been discovered. Muco-obstructive lung diseases (MucOLDs) are characterised by the accumulation of hyper-concentrated mucus in the small airways, leading to persistent inflammation, infection and dysregulated protease activity. Although neutrophilic serine proteases, particularly neutrophil elastase, have been implicated in the propagation of inflammation and local tissue destruction, it is likely that the serine TLPs also contribute to various disease-relevant processes given the roles that a number of these enzymes play in the activation of both the epithelial sodium channel (ENaC) and protease-activated receptor 2 (PAR2). More recently, significant attention has focused on the activation of viruses such as SARS-CoV-2 by host TLPs. The purpose of this review was to highlight key TLPs linked to the activation of ENaC and PAR2 and their association with airway dehydration and inflammatory signalling pathways, respectively. The role of TLPs in viral infectivity will also be discussed in the context of the inhibition of TLP activities and the potential of these proteases as therapeutic targets.

OBJECTIVE: Intestinal epithelial cells [IECs] from inflammatory bowel disease [IBD] patients exhibit an excessive induction of endoplasmic reticulum stress [ER stress] linked to altered intestinal barrier function and inflammation. Colonic tissues and the luminal content of IBD patients are also characterized by increased serine protease activity. The possible link between ER stress and serine protease activity in colitis-associated epithelial dysfunctions is unknown. We aimed to study the association between ER stress and serine protease activity in enterocytes and its impact on intestinal functions.
METHODS: The impact of ER stress induced by Thapsigargin on serine protease secretion was studied using either human intestinal cell lines or organoids. Moreover, treating human intestinal cells with protease-activated receptor antagonists allowed us to investigate ER stress-resulting molecular mechanisms that induce proteolytic activity and alter intestinal epithelial cell biology.
RESULTS: Colonic biopsies from IBD patients exhibited increased epithelial trypsin-like activity associated with elevated ER stress. Induction of ER stress in human intestinal epithelial cells displayed enhanced apical trypsin-like activity. ER stress-induced increased trypsin activity destabilized intestinal barrier function by increasing permeability and by controlling inflammatory mediators such as C-X-C chemokine ligand 8 [CXCL8]. The deleterious impact of ER stress-associated trypsin activity was specifically dependent on the activation of protease-activated receptors 2 and 4.
CONCLUSIONS: Excessive ER stress in IECs caused an increased release of trypsin activity that, in turn, altered intestinal barrier function, promoting the development of inflammatory process.

In cystic fibrosis (CF) airways excessive levels of serine trypsin-like proteases (TLPs) activate the epithelial sodium channel (ENaC) resulting in airways dehydration and promotion of mucus secretion. Despite this the relationship of TLP activity and clinical outcome has not been studied.
We analysed supernatant (sol) prepared from CF sputum from adult CF patients in two study cohorts (29 and 33 samples, respectively). Protease activities were determined by measuring the hydrolysis of peptide-based substrates or by ELISA. Lung function was assessed by spirometry (FEV1). Mortality data was retrospectively obtained and time in months until death or transplantation used for subsequent survival analysis.
TLP activity inversely correlated with percent predicted FEV1 (r = -0.4, p = 0.03) and was greater in individuals who did not survive beyond 5-years from the time of sample collection. A Kaplan-Meier analysis demonstrated significantly reduced survival (p = 0.04) for individuals with high TLP activity [hazard ratio (HR) of 7.21 per log unit TLP activity (p = 0.03)]. In contrast, neutrophil elastase displayed no significant associations with lung function or patient survival. Similar findings were evident in the second study cohort.
Sputum TLP activity may represent a novel non-invasive biomarker and/or therapeutic target for CF lung disease.