The extended cleavage specificities of two hematopoietic serine proteases originating from the ray-finned fish spotted gar (Lepisosteus oculatus) have been characterized using substrate phage display. The preference for particular amino acids at, and surrounding the cleavage site was further validated using a panel of recombinant substrates. For one of the enzymes, the gar granzyme G, a strict preference for the aromatic amino acid Tyr was observed at the cleavable P1 position. Using a set of recombinant substrates showed that the gar granzyme G had a high selectivity for Tyr, but also with lower activity cleaving after Phe but not after Trp. The second enzyme, gar DDN1, instead showed a high preference for Leu in the P1 position of substrates. This latter enzyme also showed high preference for Pro in the P2 position and Arg in both P4 and P5 positions. The selectivity for the two Arg residues in positions P4 and P5, suggest a highly specific substrate selectivity of this enzyme. Screening of the gar proteome with the consensus sequences obtained by substrate phage display for these two proteases resulted in a very diverse set of potential targets. Due to this diversity, a clear candidate for a specific immune function of these two enzymes cannot yet be identified. Antisera developed against the recombinant gar enzymes were used to study their tissue distribution. Tissue sections from juvenile fish showed expression of both proteases in cells in Peyer´s patch-like structures in the intestinal region, indicating they may be expressed in T or NK cells. However, due to the lack of antibodies to specific surface markers in the gar, it has not been possible to specify the exact cellular origin. A marked difference in abundance was observed for the two proteases where gar DDN1 was expressed at higher levels than gar granzyme G. However, both appear to be expressed in the same or similar cells, having a lymphocyte-like appearance.

Background: In the domestic pig, neural and non-neuronal cholinergic systems in the gallbladder and extrahepatic bile ducts need a detailed morphological study to identify the type and localization of their structural components. We aimed to quantitatively analyze biliary cholinergic ganglia and nerves as well as non-neuronal cholinergic cells; Methods: Immunohistochemical detection of choline acetyltransferase expression was performed to define cholinergic nerve and non-neuronal structures in gallbladder and extrahepatic bile ducts; Results: The number and dimensions of cholinergic ganglia, perikaryons and nerves forming ganglionic nerve plexuses in the propria, muscular and subserosal layers was estimated. The immunoexpression of choline acetyltransferase in biliary glandular cells and mast cells was also detected and analyzed. Conclusions: Qualitative and quantitative analysis of choline acetyltransferase positive nerves, ganglionic and non-ganglionic nerve plexuses of acetylcholine supplemented the morphological knowledge of the cholinergic innervation of the extrahepatic biliary pathways and non-neuronal sources: glandular cholinergic cells and cholinergic-type mast cells. Original data of the number and dimensions of intramural nerves, mast cells, ganglia and ganglion perikaryons could be used as reference values in the diagnosis of neuropathological processes in biliary pathways. Clarifying the precise mechanisms of gallbladder smooth muscle contractility will contribute to the improvement of therapeutic strategies to prevent biliary stasis and biliary disorders.

The extended cleavage specificity of catfish granzyme-like II has been characterized using substrate phage display. The preference for particular amino acids at and surrounding the cleavage site was further validated by using a panel of recombinant substrates. This serine protease, which has previously been isolated as cDNA from a catfish natural killer-like cell line showed a preference for alanine in the P1 position of the substrate, and for multiple basic amino acids N-terminally of the cleavage site. Using a set of recombinant substrates revealed the enzyme was most active on substrates with an alanine preceded by 3 or 4 basic amino acids in a row, but also showed activity against substrates with two basic amino acids, as well as with two basic amino acids separated by one amino acid just N-terminally of the Ala. The characteristics of this separating amino acid seemed less important, as many different amino acids were accepted in this position, except for proline. The amino acids following the basic amino acids and the P1 Ala residue also appeared to be of major importance for efficient cleavage. The most preferred P1 residue was Ala, and replacing Ala with Gly or Leu resulted in a clear reduction in the cleavage rate. A closely-related zebrafish serine protease (Zebrafish esterase-like) showed a very similar cleavage specificity, indicating an evolutionary conservation of this protease specificity among various fish species. Two catfish serine proteases, originating from NK-like cells, have now been isolated and characterized. One of them is highly specific met-ase with similar characteristics as the mammalian granzyme M. This enzyme may be involved in the induction of apoptosis in virus infected cells, with a potential target in (catfish) caspase 6. In contrast to catfish granzyme -like I, the second enzyme analysed here, doesn’t seem to have a direct counterpart in mammalian NK-cells, and its role in the immune function of catfish NK cells is therefore still not known. However, this enzyme seems to be able to cleave a number of cytoskeletal proteins indicating a separate strategy to induce apoptosis in target cells. Both of these enzymes are very interesting targets for further studies of their roles in catfish immunity, as enzymes with similar specificities have been identified also in zebrafish.

The Kounis syndrome (KS) is an acute coronary syndrome triggered by allergic or hypersensitiv-ity reactions. Incidence rates vary, with studies reporting 19.4 per 100.000 among all admissions and 3.4% among allergy patients. This review explores the expanding understanding of KS, en-compassing various manifestations, and focusing on both clinical data and forensic findings useful in performing the diagnosis. The pathophysiology of this syndrome involves a complex in-terplay between allergic reactions and the cardiovascular system. Mast cell activation, histamine release, leukotrienes, cytokines, and platelet activation can contribute to the coronary events. A classification system with three types (Allergic Angina, Allergic Myocardial Infarction, Allergic Stent Thrombosis) aids in categorizing presentations. The diagnosis of KS relies on clinical presentation, laboratory findings and imaging. Post mortem assessment of KS is based on the in-tegration of circumstantial data, autopsy and histological findings. Biochemical and immuno-histochemical analyses also contribute to post-mortem diagnosis. In conclusion, a combined, multidisciplinary approach, should be gained to ease diagnostic pro-cess which is crucial for forensic practitioners in confirming KS occurrence.

Abstract: Mast cell (MC) specific proteases are of particular interest for space biology and medicine due to their biological activity in regulating targets of a specific tissue microenvironment. MC tryptase and chymase obtain the ability to remodel connective tissue through direct and indirect mechanisms. Yet, MC specific protease expression under space flight conditions has not been adequately investigated. Using immunohistochemical stainings, we analyzed in this study the protease profile of the jejunal, gastric and hepatic MC populations in three groups of Mongolian gerbils - vivarium control, synchronous experiment, and 12-day orbital flight on the Foton-M3 spacecraft, - and in two groups - vivarium control and anti-orthostatic suspension - included in the experiment simulating effects of weightlessness in the ground-based conditions. After a space flight, there was a decreased number of MCs in the studied organs combined with an increased proportion of chymase-positive MCs and MCs with a simultaneous content of tryptase and chymase; the secretion of specific proteases into the extracellular matrix increased. These changes in the expression of proteases were observed both in the mucosal and connective tissue MC subpopulations of the stomach and jejunum. Notably, the relative content of tryptase-positive MCs in the studied organs of the digestive system decreased. Space flight conditions simulated in the synchronous experiment caused no similar significant changes in the protease profile of MC populations. The space flight conditions resulted in an increased chymase expression combined with a decreased total number of protease-positive MCs apparently due to participating in the processes of extracellular matrix remodeling and regulating the state of the cardiovascular system.

Mast cells play a critical role in allergies and inflammation via secretion of numerous vasoactive, pro-inflammatory and neuro-sensitizing mediators. Secretion may utilize different modes that involve the cytoskeleton, but our understanding of the molecular mechanisms regulating secretion is still not well understood. We previously showed that the ability of the so called mast cell “stabilizer” disodium cromoglycate (cromolyn) to inhibit secretion from rat mast cells closely paralleled the phosphorylation of a 78 kDa protein, and subsequently showed this protein to be moesin, a member of the Ezrin/Radixin/Moesin (ERM) family of proteins, which are involved in linking cell surface-initiated signaling to the actin cytoskeleton. Unlike phosphorylation on the C-terminus Thr558 associated with activation of ERMs, including secretion from macrophages and platelets, we showed that phosphorylation of moesin during inhibition of secretion was on the N-terminal Ser56/74 and Thr66 residues. This phosphorylation pattern could lock moesin in its inactive state and remain inaccessible to bind to the Soluble NSF attachment protein receptors (SNAREs) and synaptosomal associated proteins (SNAPs). Using Confocal microscopic imaging, we showed moesin to colocalize with actin and cluster around secretory granules during inhibition of secretion, In conclusion, the phosphorylation pattern and localization of moesin may be important in the regulation of mast cell secretion and could be targeted for the development of effective inhibitors of secretion from mast cells.

Our knowledge of biology and mast cell (MC) function, as well as disorders associated with the pathologic activation of MCs has been evolving over the last few decades. Anaphylaxis, mast cell activation syndrome (MCAS) and mastocytosis are interrelated yet distinct conditions within the spectrum of mast cell activation disorders. Nevertheless, all three conditions can co-exist in one and same patient, as pathologic MC activation is the key finding in all three. When mediator release is excessive and involves multiple systems, anaphylaxis and MCAS may occur. Furthermore, mastocytosis is a clonal disorder of MCs and often presents with anaphylaxis and MCAS. Nevertheless, in some cases even proliferative and accumulative features of MCs in mastocytosis can account for symptoms and disease progression. In each case, diagnosis can be only made when diagnostic consensus criteria are fulfilled. The current article aims to provide a concise clinical update and pinpoint main difficulties in diagnosing these puzzling disorders of MCs in medical practice.

Kidney fibrosis is a complex polyetiological progressive disease manifesting as an intraorgan proliferation of the connective tissue with the appearance of cicatricial changes. However, pathogenetic mechanisms of renal fibrosis remain poorly understood. The paper highlights features of the protease phenotype and histotopography of mast cells (MCs) found in the kidney, as the key players in extracellular matrix remodeling in nephrofibrosis, detected in a patient diagnosed with "nephrosclerosis with the non-functioning upper pole of the duplex right kidney in the junction of refluxing megaureter of the upper pole of the duplex right kidney". The highest content of MCs was found in the kidney areas with fibrotic changes. MCs were actively involved in the development of inflammatory and fibrotic changes in limited loci of the specific tissue microenvironment of the kidney through targeted secretion of tryptase, chymase, and carboxypeptidase A3 to the vascular endothelium, nephron epithelium, interstitium cells, and components of the intercellular substance. The formation of a profibrotic environment in the kidney interstitium was facilitated by epigenetic effects of tryptase promoting epithelial-mesenchymal transition (EMT) of the nephron epithelium. A selectively increased number and targeted secretory activity of MCs in limited loci of the kidney parenchyma without visible pathological changes evidence a trigger pathogenetic role of specific proteases in the formation of a local microenvironment with a profibrogenic metabolic profile. Thus, MCs are actively involved in the mechanisms of formation and evolution of fibrogenic niches in the kidney; this fact can be used to develop new strategies for therapeutic options of tubulointerstitial fibrosis resulted from chronic kidney injury. Further study of the molecular phenotype of mast cells reveals new fundamental mechanisms of fibrosis pathogenesis being a significant tool for personalized therapy in nephrology.

Mast cells (MC) are resident tissue cells found primarily at the interphase between tissues and environment. These evolutionary old cells store large amounts of proteases within cytoplasmic granules, and one of the most abundant of these proteases is the tryptase. To look deeper into the question their in vivo targets, we have analyzed the activity of the human MC tryptase on 69 different human cytokines and chemokines, and the activity of the mouse tryptase (mMCP-6) on 56 mouse cytokines and chemokines. These enzymes were found to be remarkably restrictive in their cleavage of these potential targets. Only five were efficiently cleaved by the human tryptase: TSLP, IL-21, MCP3, MIP-3b and eotaxin. This strict specificity indicates a regulatory function of these proteases and not primarily as unspecific degrading enzymes. We recently showed that the human MC chymase also had a relatively strict specificity, indicating that both of these proteases have regulatory functions. One of the most interesting such regulatory functions may involve controlling excessive TH2 mediated inflammation by cleaving several of the most important TH2-promoting inflammatory cytokines, including IL-18, IL-33, TSLP, IL-15 and IL-21 indicating a potent negative feedback loop on TH2 immunity.

Studies of mast cell biology is dependent on relevant and validated in vitro models. We here present detailed information concerning the phenotype of both freshly isolated human skin mast cells (MCs), and of in vitro cultures of these cells that was obtained by analyzing their total transcriptome. Transcript levels of MC-related granule proteins and transcription factors were found to be remarkably stable over a 3-week culture period. Relatively modest changes were also seen for important cell surface receptors including the high affinity receptor for IgE, FCER1A, the low affinity receptor for IgG, FCGR2A, and the receptor for stem cell factor, KIT. FCGR2A was the only Fc receptor for IgG expressed by these cells. Comparisons of the present transcriptome against previously reported transcriptomes of mouse peritoneal MCs and mouse bone marrow derived MCs (BMMCs) revealed both similarities and major differences. Strikingly, cathepsin G was the most highly expressed granule protease in human skin MCs, in contrast to the almost total absent of this protease in both mouse MCs. Transcript levels for the majority of cell surface receptors were also very low compared to the granule proteases in both mouse and human MCs, with a difference of almost two orders of magnitude. An almost total absence of T cell granzymes was observed in human skin MCs, indicating that granzymes have no or only a minor role in human MC biology. Ex vivo skin MCs expressed high levels of selective immediate early genes and transcripts of heat-shock proteins. In validation experiments, we determined that this expression was an inherent property of the cells and not the result of the isolation process. Three to four weeks in culture results in an induction of cell growth related genes accompanying their expansion by 6-10-fold, which increases the number of cells for in vitro experiments. Collectively, we show that cultured human skin MCs resemble their ex vivo equivalents in many respects and are a more relevant in vitro model compared to mouse BMMCs for studies of MC biology, in particular human MC biology.