Inhibition of Matriptase Activity Results in Decreased Intestinal Epithelial Monolayer Integrity In Vitro. PLoS One. 2015;10:e0141077. [PMID: 26488575 PMCID: PMC4619522 DOI: 10.1371/journal.pone.0141077]

Discovery of diminazene as a dual inhibitor of SARS-CoV-2 human host proteases TMPRSS2 and furin using cell-based assays

The proteases TMPRSS2 (transmembrane protease serine 2) and furin are known to play important roles in viral infectivity including systematic COVID-19 infection through priming of the spike protein of SARS-CoV-2 and related viruses. To discover small-molecules capable of inhibiting these host proteases, we established convenient and cost-effective cell-based assays employing Vero cells overexpressing TMPRSS2 and furin. A cell-based proteolytic assay for broad-spectrum protease inhibitors was also established using human prostate cancer cell line LNCaP. Evaluation of camostat, nafamostat, and gabexate in these cell-based assays confirmed their known TMPRSS2 inhibitory activities. Diminazene, a veterinary medicinal agent and a known furin inhibitor was found to inhibit both TMPRSS2 and furin with IC₅₀s of 1.35 and 13.2 μM, respectively. Establishment and the use of cell-based assays for evaluation TMPRSS2 and furin inhibitory activity and implications of dual activity of diminazene vs TMPRSS2 and furin are presented.

The Effects of Matriptase Inhibition on the Inflammatory and Redox Homeostasis of Chicken Hepatic Cell Culture Models

The function of the transmembrane serine protease matriptase is well described in mammals, but it has not been elucidated in avian species yet. Hence, the aim of the present study was to assess the effects of the 3-amidinophenylalanine (3-AphA)-type matriptase inhibitors MI432 and MI460 on the inflammatory and oxidative state of chicken primary hepatocyte mono-cultures and hepatocyte-nonparenchymal cell co-cultures, the latter serving as a proper model of hepatic inflammation in birds. Cell cultures were exposed to MI432 and MI460 for 4 and 24 h at 10, 25, and 50 µM concentrations, and thereafter the cellular metabolic activity, extracellular interleukin (IL-)6, IL-8, H₂O₂ and malondialdehyde concentrations were monitored. Both inhibitors caused a transient moderate reduction in the metabolic activity following 4 h exposure, which was restored after 24 h, reflecting the fast hepatic adaptation potential to matriptase inhibitor administration. Furthermore, MI432 triggered an intense elevation in the cellular proinflammatory IL-6 and IL-8 production after both incubation times in all concentrations, which was not coupled to enhanced oxidative stress and lipid peroxidation based on unchanged H₂O₂ production, malondialdehyde levels and glutathione peroxidase activity. These data suggest that physiological matriptase activities might have a key function in retaining the metabolic and inflammatory homeostasis of the liver in chicken, without being a major modulator of the hepatocellular redox state.

Exposure of human intestinal epithelial cells and primary human hepatocytes to trypsin-like serine protease inhibitors with potential antiviral effect

Human intestinal epithelial cell line-6 (HIEC-6) cells and primary human hepatocytes (PHHs) were treated with 3-amidinophenylalanine-derived inhibitors of trypsin-like serine proteases for 24 hours. It was proven that treatment with MI-1900 and MI-1907 was tolerated up to 50 μM in HIEC-6. These inhibitors did not cause elevations in extracellular H₂O₂ levels and in the concentrations of interleukin (IL)-6 and IL-8 and did not alter occludin distribution in HIEC-6. It was also found that MI-1900 and MI-1907 up to 50 μM did not affect cell viability, IL-6 and IL-8 and occludin levels of PHH. Based on our findings, these inhibitors could be safely applicable at 50 μM in HIEC-6 and in PHH; however, redox status was disturbed in case of PHH. Moreover, it has recently been demonstrated that MI-1900 prevents the replication and spread of the new SARS-CoV-2 in infected Calu-3 cells, most-likely via an inhibition of the membrane-bound host protease TMPRSS2.

The impact of quercetin on a porcine intestinal epithelial cell line exposed to deoxynivalenol

Quercetin (Que) is present in many vegetables and fruits as a secondary antioxidant metabolite. Deoxynivalenol (DON) produced by various Fusarium mould species can induce cytotoxicity and oxidative stress in the gastrointestinal tracts of humans and farm animals. The aim of this study was to investigate the effects of Que on DON-induced oxidative stress in a non-tumourigenic porcine IPEC-J2 cell line. Two experimental designs were used in our experiments as follows: (a) pretreatment with 20 µmol/L Que for 24 h followed by 1-h 1 µmol/L DON treatment and (b) simultaneous application of 20 µmol/L Que and 1 µmol/L DON for 1 h. Cell cytotoxicity, transepithelial electrical resistance (TER) of cell monolayers and extracellular/intracellular redox status were studied. It was found that DON significantly decreased TER and triggered oxidative stress, while Que pretreatments were beneficial in maintaining the integrity of the monolayers and alleviated oxidative stress. However, co-treatment with Que was unable to preserve the integrity and redox balance of the cells exposed to DON. These results indicate that only the 24-h preincubation of cells with 20 µmol/L Que was beneficial in compensating for the disruption caused by DON in extracellular oxidative status.

Regulation of intestinal permeability: The role of proteases

The gastrointestinal barrier is - with approximately 400 m² - the human body’s largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorption of nutrients, water and electrolytes on the one hand, while limiting host contact with noxious luminal antigens on the other hand. To maintain this selective barrier, junction protein complexes seal the intercellular space between adjacent epithelial cells and regulate the paracellular transport. Increased intestinal permeability is associated with and suggested as a player in the pathophysiology of various gastrointestinal and extra-intestinal diseases such as inflammatory bowel disease, celiac disease and type 1 diabetes. The gastrointestinal tract is exposed to high levels of endogenous and exogenous proteases, both in the lumen and in the mucosa. There is increasing evidence to suggest that a dysregulation of the protease/antiprotease balance in the gut contributes to epithelial damage and increased permeability. Excessive proteolysis leads to direct cleavage of intercellular junction proteins, or to opening of the junction proteins via activation of protease activated receptors. In addition, proteases regulate the activity and availability of cytokines and growth factors, which are also known modulators of intestinal permeability. This review aims at outlining the mechanisms by which proteases alter the intestinal permeability. More knowledge on the role of proteases in mucosal homeostasis and gastrointestinal barrier function will definitely contribute to the identification of new therapeutic targets for permeability-related diseases.

The Impact of Acute Matriptase Inhibition in Hepatic Inflammatory Models

Purpose. Dysfunction of matriptase-2 can be involved in iron regulatory disorder via downregulation of hepcidin expression. In the present study, we investigated the effects of 3-amidinophenylalanine-derived matriptase inhibitors on porcine hepatic inflammatory cell models. Methods. Hepatocyte-Kupffer cell cocultures (ratio of 2 : 1 and 6 : 1) were treated with four structurally related matriptase inhibitors at 50 μM. Cell cytotoxicity and relative expressions of IL-6 and IL-8 and the levels of hepcidin were determined by MTS and porcine-specific ELISA. The extracellular H2O2 contents were analyzed by Amplex Red method. Results. Matriptase inhibitors at 50 µM for 24 h did not increase cell death rate. The elevated ROS production observed after short-term application of inhibitor MI-441 could be correlated with lowered hepcidin expression. MI-460 could significantly enhance hepcidin levels in the supernatants of cocultures (by 62.21 ± 26.8% in hepatocyte-Kupffer cell, 2 : 1, and by 42.6 ± 14.3% in hepatocyte-Kupffer cell, 6 : 1, cocultures, resp.). No significant changes were found in IL-6 and IL-8 levels in cocultures exposed to matriptase inhibitors. Conclusions. Based on in vitro findings, administration of MI-460 via modulation of hepcidin expression without cytotoxic and oxidative stress inducing properties might be a reliable alternative to treat iron overload in human and veterinary clinical practice.

In vitro characterization of TMPRSS2 inhibition in IPEC-J2 cells

The transmembrane serine protease, TMPRSS2 is an important target in the treatment of seasonal influenza infections and contributes to prostate carcinogenesis and metastasis. In this study, the effect of the synthetic TMPRSS2 inhibitor I-432 on jejunal IPEC-J2 cell monolayers cultured on membrane inserts was characterized. Using a fluorogenic substrate, it was found that the apical addition of I-432 could suppress trypsin-like activity in the supernatants of IPEC-J2 cells. The inhibition of TMPRSS2 did not affect physiologically produced hydrogen peroxide levels in the apical and in basolateral compartments. Loss of expression of the TMPRSS2 serine protease domain (28 kDa) was also observed when cells were pre-exposed to I-432. Partial decrease in immunofluorescent signal intensities derived from the altered distribution pattern of TMPRSS2 was detected after a 48 h long incubation of IPEC-J2 cells with the inhibitor indicating the efficacy of TMPRSS2 inhibition via I-432 administration in vitro.