Human tissue kallikreins 3 and 5 can act as plasminogen activator releasing active plasmin

Influence of Anticoagulants and Heparin Contaminants on the Suitability of MMP-9 as a Blood-Derived Biomarker

In contrast to other common anticoagulants such as citrate and low-molecular-weight heparin (LMWH), high-molecular-weight heparin (HMWH) induces the expression of matrix metalloproteinase (MMP)-9, which is also measured as a biomarker for stroke in blood samples. Mechanistically, HMWH-stimulated T cells produce cytokines that induce monocytic MMP-9 expression. Here, the influence of further anticoagulants (Fondaparinux, Hirudin, and Alteplase) and the heparin-contaminating glycosaminoglycans (GAG) hyaluronic acid (HA), dermatan sulfate (DS), chondroitin sulfate (CS), and over-sulfated CS (OSCS) on MMP-9 was analyzed to assess its suitability as a biomarker under various conditions. Therefore, starved Jurkat T cells were stimulated with anticoagulants/contaminants. Subsequently, starved monocytic THP-1 cells were incubated with the conditioned Jurkat supernatant, and MMP-9 mRNA levels were monitored (quantitative (q)PCR). Jurkat-derived mediators secreted in response to anticoagulants/contaminants were also assessed (proteome profiler array). The supernatants of HMWH-, Hirudin-, CS-, and OSCS-treated Jurkat cells comprised combinations of activating mediators and led to a significant (in the case of OSCS, dramatic) MMP-9 induction in THP-1. HA induced MMP-9 only in high concentrations, while LMWH, Fondaparinux, Alteplase, and DS had no effect. This indicates that depending on molecular weight and charge (but independent of anticoagulant activity), anticoagulants/contaminants provoke the expression of T-cell-derived cytokines/chemokines that induce monocytic MMP-9 expression, thus potentially impairing the diagnostic validity of MMP-9.

Recombinant scFv-Fc Anti-kallikrein 7 Antibody-Loaded Thermosensitive Hydrogels Against Skin Desquamation Disorders

Human tissue kallikrein-related peptidase 7 (KLK7) is a serine protease implicated in the physiology of skin desquamation, and its uncontrolled activity can lead to chronic diseases such as psoriasis, atopic dermatitis, and Netherton syndrome. For this reason, kallikrein 7 has been identified as a potential therapeutic target. This work aimed to evaluate Pluronic (PL) hydrogels as topical carriers of four specific scFv-Fc antibodies to inhibit KLK7. The hydrogels comprised PL F127 (30% w/v) alone and a binary F127/P123 (28-2% w/v) system. Each formulation was loaded with 1 μg/mL of each antibody and characterized by physicochemical and pharmaceutical techniques, considering antibody-micelle interactions and hydrogel behavior as smart delivery systems. Results showed that the antibodies were successfully loaded into the PL-based systems, and the sol-gel transition temperature was shifted to high values after the P123 addition. The antibodies released from the gels preserved their rheological properties (G' > G'', 35- to 41-fold) and inhibitory activity against KLK7, even after 24 h. This work presented potential agents targeting KLK7 that may provide strategies for treating skin abnormalities.

Kallikrein-related peptidase 5 contributes to the remodeling and repair of bronchial epithelium

Inflammation, oxidative stress, and protease/protease inhibitor imbalance with excessive production of proteases are factors associated with pathogenesis of the chronic obstructive pulmonary disease (COPD). In this study, we report that kallikrein-related peptidase 5 (KLK5) is a crucial protease involved in extracellular matrix (ECM) remodeling and bronchial epithelial repair after injury. First, we showed that KLK5 degrades the basal layer formed by culture of primary bronchial epithelial cells from COPD or non-COPD patients. Also, exogenous KLK5 acted differently on BEAS-2B cells already engaged in epithelial-to-mesenchymal transition (EMT) or on 16HBE 14o- cells harboring epithelial characteristics. Indeed, by inducing EMT, KLK5 reduced BEAS-2B cell adherence to the ECM. This effect, neutralized by tissue factor pathway inhibitor 2, a kunitz-type serine protease inhibitor, was due to a direct proteolytic activity of KLK5 on E-cadherin, β-catenin, fibronectin, and α5β1 integrin. Thus, KLK5 may strengthen EMT mechanisms and promote the migration of cells by activating the mitogen-activated protein kinase signaling pathway required for this function. In contrast, knockdown of endogenous KLK5 in 16HBE14o- cells, accelerated wound healing repair after injury, and exogenous KLK5 addition delayed the closure repair. These data suggest that among proteases, KLK5 could play a critical role in airway remodeling events associated with COPD during exposure of the pulmonary epithelium to inhaled irritants or smoking and the inflammation process.

Tissue factor pathway inhibitor 2 is a potent kallikrein-related protease 12 inhibitor

The protease activities are tightly regulated by inhibitors and dysregulation contribute to pathological processes such as cancer and inflammatory disorders. Tissue factor pathway inhibitor 2 (TFPI-2) is a serine proteases inhibitor, that mainly inhibits plasmin. This protease activated matrix metalloproteases (MMPs) and degraded extracellular matrix. Other serine proteases are implicated in these mechanisms like kallikreins (KLKs). In this study, we identified for the first time that TFPI-2 is a potent inhibitor of KLK5 and 12. Computer modeling showed that the first Kunitz domain of TFPI-2 could interact with residues of KLK12 near the catalytic triad. Furthermore, like plasmin, KLK12 was able to activate proMMP-1 and -3, with no effect on proMMP-9. Thus, the inhibition of KLK12 by TFPI-2 greatly reduced the cascade activation of these MMPs and the cleavage of cysteine-rich 61, a matrix signaling protein. Moreover, when TFPI-2 bound to extracellular matrix, its classical localisation, the KLK12 inhibition was retained. Finally, TFPI-2 was downregulated in human non-small-cell lung tumour tissue as compared with non-affected lung tissue. These data suggest that TFPI-2 is a potent inhibitor of KLK12 and could regulate matrix remodeling and cancer progression mediated by KLK12.

Kallikrein 13 serves as a priming protease during infection by the human coronavirus HKU1

Unlike SARS-CoV-2, the human coronavirus HKU1 normally causes relatively mild respiratory tract infections; however, it shares with SARS-CoV-2 the mechanism of using its surface spike (S) protein to enter target cells. Because the host receptor for HCoV-HKU1 is unknown, efforts to study the virus in cell culture systems have proved difficult. Milewska et al. found that knockout of the protease kallikrein 13 (KLK13) in human airway epithelial cells blocked their infection by HCoV-HKU1, that overexpression of KLK13 in nonpermissive cells enabled their infection by the virus, and that KLK13 cleaved the viral S protein. Together, these findings suggest that KLK13 is a priming enzyme for viral entry and may help to establish cell lines that can facilitate further investigation of the mechanism of viral pathogenesis.

Human coronavirus HKU1 (HCoV-HKU1) is associated with respiratory disease and is prevalent worldwide, but an in vitro model for viral replication is lacking. An interaction between the coronaviral spike (S) protein and its receptor is the primary determinant of tissue and host specificity; however, viral entry is a complex process requiring the concerted action of multiple cellular elements. Here, we found that the protease kallikrein 13 (KLK13) was required for the infection of human respiratory epithelial cells and was sufficient to mediate the entry of HCoV-HKU1 into nonpermissive RD cells. We also demonstrated the cleavage of the HCoV-HKU1 S protein by KLK13 in the S1/S2 region, suggesting that KLK13 is the priming enzyme for this virus. Together, these data suggest that protease distribution and specificity determine the tissue and cell specificity of the virus and may also regulate interspecies transmission.

Generation of recombinant antibodies against human tissue kallikrein 7 to treat skin diseases

Human tissue kallikreins (KLKs) constitute a family of 15 serine proteases that are distributed in various tissues and implicated in several pathological disorders. KLK7 is an unusual serine protease that presents both trypsin-like and chymotrypsin-like specificity and appears to be upregulated in pathologies that are related to skin desquamation processes, such as atopic dermatitis, psoriasis and Netherton syndrome. In recent years, various groups have worked to develop specific inhibitors for this enzyme, as KLK7 represents a potential target for new therapeutic procedures for diseases related to skin desquamation processes. In this work, we selected nine different single-chain variable fragment antibodies (scFv) from a human naïve phage display library and characterized their inhibitory activities against KLK7. The scFv with the lowest IC₅₀ against KLK7 was affinity maturated, which resulted in the generation of four new scFv-specific antibodies for the target protease. These new antibodies were expressed in the scFv-Fc format in HEK293-6E cells, and the characterization of their inhibitory activities against KLK7 showed that three of them presented IC₅₀ values lower than that of the original antibody. The cytotoxicity analysis of these recombinant antibodies demonstrated that they can be safely used in a cellular model. In conclusion, our research showed that in our case, a phage-display methodology in combination with enzymology assays can be a very suitable tool for the development of inhibitors for KLKs, suggesting a new strategy to identify therapeutic protease inhibitors for diseases related to uncontrolled kallikrein activity.

Kallikreins: Essential epidermal messengers for regulation of the skin microenvironment during homeostasis, repair and disease

As the outermost layer of the skin, the epidermis is playing a major role in organism homeostasis providing the first barrier against external aggressions. Although considered as an extracellular matrix (ECM)-poor subtissue, the epidermal microenvironment is a key regulator of skin homeostasis and functionality. Among the proteins essential for upholding the epidermal microenvironment are the members of the kallikrein (KLK) family composed of 15 secreted serine proteases. Most of the members of these epithelial-specific proteins are present in skin and regulate skin desquamation and inflammation. However, although epidermal products, the consequences of KLK activities are not confined to the epidermis but widespread in the skin. In this review starting with the location and proteolytic activation cascade of KLKs, we present KLKs involvement in skin homeostasis, regeneration and pathology. KLKs have a large variety of substrates including ECM proteins, and evidence suggests that they are involved in the different steps of skin wound healing as discussed here. KLKs are also used as prognosis/diagnosis markers for many cancer types and we are focusing later on KLKs in cutaneous cancers, although their pathogenicity remains to be fully elucidated. Dysregulation of the KLK cascade is directly responsible for skin diseases with heavy inflammatory aspects, highlighting their involvement in skin immune homeostasis. Future studies will be needed to support the therapeutic potential of adjusting KLK activities for treatment of inflammatory skin diseases and wound healing pathologies.

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Regulation of the microenvironment even in an extracellular matrix-poor tissue can heavily impact organ function.

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Extracellular activities of kallikreins maintain skin homeostasis by regulating desquamation and inflammation.

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The activation of skin epidermal-specific kallikrein family of proteases is regulated by an intricate proteolytic cascade.

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Kallikreins are emerging as players during skin wound healing.

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Dysregulated kallikrein expression and activity occur in cancers and inflammatory skin diseases.

3-Acyltetramic acids as a novel class of inhibitors for human kallikreins 5 and 7

Human kallikreins 5 and 7 (KLK5 and KLK7) exhibit trypsin- and chymotrypsin-like activities and are involved in pathologies related to skin desquamation process. A series of new 3-acyltetramic acids were developed as a novel class of inhibitors of KLK5, KLK7 and trypsin enzymes. The nature and length of the acyl chain is crucial to the KLK5, KLK7 and trypsin inhibition activities, and the most potent compounds (but not the most selective) 2b, 2c and 2g showed low micromolar IC₅₀ values. While very few of the compounds were selective for KLK5, the selective inhibition of trypsin against chymotrypsin was achieved. Our molecular modelling studies revealed that the double bond in 2g provided the best fit in the binding site of KLK5, while the hydrogen bonding interactions modulated the best fit of 2c in the binding site of KLK7 due to the hydrophobicity of the cavity.

Regulation of Locomotor activity in fed, fasted, and food-restricted mice lacking tissue-type plasminogen activator

Background

Circadian rhythms of physiology and behavior are driven by a circadian clock located in the suprachiasmatic nucleus of the hypothalamus. This clock is synchronized to environmental day/night cycles by photic input, which is dependent on the presence of mature brain-derived neurotrophic factor (BDNF) in the SCN. Mature BDNF is produced by the enzyme plasmin, which is converted from plasminogen by the enzyme tissue-type plasminogen activator (tPA). In this study, we evaluate circadian function in mice lacking functional tPA.

Results

tPA^−/− mice have normal circadian periods, but show decreased nocturnal wheel-running activity. This difference is eliminated or reversed on the second day of a 48-h fast. Similarly, when placed on daily cycles of restricted food availability the genotypic difference in total wheel-running activity disappears, and tPA^−/− mice show equivalent amounts of food anticipatory activity to wild type mice.

Conclusions

These data suggest that tPA regulates nocturnal wheel-running activity, and that tPA differentially affects SCN-driven nocturnal activity rhythms and activity driven by fasting or temporal food restriction.

Electronic supplementary material

The online version of this article (10.1186/s12899-018-0036-0) contains supplementary material, which is available to authorized users.

The effects of benzylsulfonyl-D-Ser-homoPhe-(4-amidino-benzylamide), a dual plasmin and urokinase inhibitor, on facial skin barrier function in subjects with sensitive skin

OBJECTIVE

The aim of this study was to optimize the synthesis of the plasmin and urokinase (uPA) inhibitor benzylsulfonyl-D-Ser-homoPhe-(4-amidino-benzylamide) (BSFAB), to characterize its activity and mechanism of action and to assess its use to improve stratum corneum (SC) barrier function.

METHODS

Peptide coupling methods were used to synthesize BSFAB, and high-performance liquid chromatography-mass spectrometry (HPLC-MS) together with ¹ H- and ¹³ C-nuclear magnetic resonance spectroscopy (NMR) were applied to clarify its structure and determine its purity. Its binding mode was determined by docking studies to the catalytic domains of plasmin and uPA. Inhibition constants (K_i ) were determined by enzyme kinetic studies, and the effect of BSFAB on plasmin, uPA and transglutaminase 1 expression was evaluated in non-cytokine and cytokine-stimulated keratinocytes. A vehicle-controlled clinical study on SC barrier function was conducted on facial skin of subjects with self-perceived sensitive skin.

RESULTS

BSFAB was synthesized with high purity (97.3%). In silico studies indicated that the amidine moiety of BSFAB was anchored in the S1 pocket of both enzymes by binding to Asp189, Ser190 and Gly219, whereas the backbone of the D-Ser residue makes an anti-parallel β-sheet interaction with Gly216. BSFAB was shown to be an effective inhibitor of plasmin and uPA with K_i values of 29 and 25 nM, respectively. BSFAB also inhibited keratinocyte-secreted protease activities in basal (plasmin inhibition 37.7%, P < 0.05 and uPA inhibition 96.6%, P < 0.01) and cytokine-induced conditions (plasmin inhibition 41.1%, P < 0.05 and uPA inhibition 97.0%, P < 0.001) and stimulated the gene expression of transglutaminase 1 in cytokine-stimulated keratinocytes (approximately 4.5 times increased expression, P < 0.01). Clinically, BSFAB was shown to improve SC barrier integrity (P < 0.02 on day 29) and subjective improvements in the perception of healthy skin (P < 0.05 on day 28).

CONCLUSION

BSFAB binds as a reversible competitive inhibitor to the active sites of plasmin and uPA. Additionally, BSFAB positively improved keratinocyte differentiation gene expression (transglutaminase 1). These effects were translated into improvements in SC barrier integrity clinically in subjects with dry and sensitive skin and improved their perception of having a healthy skin condition.

Isomannide-based peptidomimetics as inhibitors for human tissue kallikreins 5 and 7

Human kallikrein 5 (KLK5) and 7 (KLK7) are potential targets for the treatment of skin inflammation and cancer. Previously, we identified isomannide derivatives as potent and competitive KLK7 inhibitors. The introduction of N-protected amino acids into the isomannide-based scaffold was studied. Some KLK5 inhibitors with submicromolar affinity (K i values of 0.3-0.7 μM) were identified, and they were 6- to 13-fold more potent than our previous hits. Enzyme kinetics studies and the determination of the mechanism of inhibition confirmed that the new isomannide-based derivatives are competitive inhibitors of both KLK5 and KLK7. Molecular docking and MD simulations of selected inhibitors into the KLK5 binding site provide insight into the molecular mechanism by which these compounds interact with the enzyme. The promising results obtained in this study open new prospects on the design and synthesis of highly specific KLK5 and KLK7 inhibitors.