Tryptase inhibitor APC 366 prevents hepatic fibrosis by inhibiting collagen synthesis induced by tryptase/protease-activated receptor 2 interactions in hepatic stellate cells

Testicular immune cells and vasculature in Klinefelter syndrome from childhood up to adulthood

STUDY QUESTION

Is the distribution of immune cells and the testicular vasculature altered in testicular biopsies from patients with Klinefelter syndrome (KS)?

SUMMARY ANSWER

Increased numbers of macrophages and mast cells, an increased expression of decorin and an increased blood vessel density were found in KS samples compared to controls.

WHAT IS KNOWN ALREADY

Most KS patients are infertile due to an early germ cell loss. From puberty onwards, testicular fibrosis can be detected. How this fibrotic process is initiated remains unknown.

STUDY DESIGN, SIZE, DURATION

In this study, the number of macrophages, mast cells and their secretory products were evaluated in KS, Sertoli cell only (SCO) and control patient samples. The association between immune cell numbers and level of fibrosis in KS tissue was examined. In addition, the vascularization within these testicular tissue biopsies was studied. For immunohistochemical evaluation, KS patients at different stages of testicular development were included: prepubertal (aged 4-7 years; n = 4), peripubertal (aged 11-17 years; n = 21) and adult (aged >18 years; n = 37) patients. In addition, testicular tissue biopsies of adult SCO (n = 33) and control samples for the three KS age groups (prepubertal n = 9; peripubertal n = 5; adult n = 25) were analysed. Gene expression analysis was performed on adult testicular tissue from KS (n = 5), SCO (n = 5) and control (n = 5) patients.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Adult (>18 years) KS, SCO and control testicular tissue biopsies were obtained during a testicular sperm extraction procedure. KS peripubertal (11-18 years), prepubertal (<11 years) and age-matched control biopsies were obtained from the biobank of the university hospital. Immunohistochemistry was used to determine the tubular structure (H/PAS), the number of spermatogonia (MAGE-A4), macrophages (CD68) and mast cells (tryptase) and the blood vessel density (Von Willebrand factor). In addition, quantitative real-time polymerase chain reaction was used to determine the expression of secretory products of macrophages and mast cells (tryptase, tumour necrosis factor alpha and decorin).

MAIN RESULTS AND THE ROLE OF CHANCE

A significant increase in the number of macrophages (P < 0.0001) and mast cells (P = 0.0008) was found in the peritubular compartment of testes of adult KS patients compared to control samples. However, no association between the number of immune cells and the degree of fibrosis was observed. In adult SCO samples, a significant increase was seen for peritubular macrophage (P < 0.0001) and mast cell (P < 0.0001) numbers compared to control samples. In the interstitial compartment, a significant increase in mast cell number was found in adult SCO samples compared to KS (P < 0.0001) and control (P < 0.0001) tissue. A significant difference (P = 0.0431) in decorin expression could be detected in adult KS compared to control patients. Decorin expression was mostly seen in the walls of the seminiferous tubules. When comparing the vascularization between KS patients and age-matched controls, a significant increase (P = 0.0081) in blood vessel density could be observed only in prepubertal KS testicular tissue.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

As controls for this study, testicular tissue biopsies of men who underwent a vasectomy reversal or orchiectomy were used, but these men may not represent fertile controls. In addition, a high variability in immune cell numbers, secretory products expression and number of blood vessels could be observed amongst all patient samples.

WIDER IMPLICATIONS OF THE FINDINGS

Increased numbers of macrophages and mast cells have previously been described in non-KS infertile men. Our results show that these increased numbers can also be detected in KS testicular tissue. However, no association between the number of macrophages or mast cells and the degree of fibrosis in KS samples could be detected. Decorin has previously been described in relation to fibrosis, but it has not yet been associated with testicular fibrosis in KS. Our results suggest a role for this proteoglycan in the fibrotic process since an increased expression was observed in adult KS tissue compared to controls. Impaired vascularization in KS men was suggested to be responsible for the KS-related disturbed hormone levels. Our results show a significant difference in blood vessel density, especially for the smallest blood vessels, between prepubertal KS samples and age-matched controls. This is the first study to report differences between KS and control testicular tissue at prepubertal age.

STUDY FUNDING/COMPETING INTEREST(S)

The project was funded by grants from the Vrije Universiteit Brussel (E.G.) and the scientific Fund Willy Gepts from the UZ Brussel (D.V.S.). D.V.S. is a post-doctoral fellow of the Fonds voor Wetenschappelijk Onderzoek (FWO; 12M2819N). No conflict of interest is declared for this research project.

Mast Cell Tryptase Promotes Inflammatory Bowel Disease-Induced Intestinal Fibrosis

BACKGROUND

Intestinal fibrosis is the final pathological outcome of chronic intestinal inflammation without specific therapeutic drugs, which leads to ileus and surgical intervention. Intestinal fibrosis is characterized by excessive deposition of extracellular matrix (ECM). The role of mast cells (MCs), which are members of the sentinel immune cell population, is unknown in intestinal fibrosis.

METHODS

In this study, we analyzed changes in MCs, tryptase proteins, and ECM components in human fibrotic and control patient intestines. We constructed dextran sodium sulfate-induced intestinal fibrosis models using wild-type mice, MC-reconstituted mice, and MC-deficient mice to explore the role of MCs and tryptase in intestinal fibrosis. The roles and mechanisms of MCs and tryptase on fibroblasts were evaluated using human MCs (HMC-1 and LAD-2), commercial tryptase proteins, human colon fibroblasts (CCD-18Co fibroblasts), the tryptase inhibitor APC366, and the protease-activated receptor-2 (PAR-2) antagonist ENMD-1068.

RESULTS

Regardless of whether the colon was a human colon or a mouse colon, the fibrotic intestinal tissue had increased MC infiltration and a higher expression of ECM proteins or genes than that of the control group. The dextran sodium sulfate-induced intestinal fibrosis in MC-deficient mice was alleviated compared with that in wild-type mice. After MC reconstruction in MC-deficient mice, the alleviating effect disappeared. Tryptase, as a content stored in MC granules, was released into fibrotic intestinal tissues in the form of degranulation, resulting in an increased expression of tryptase. Compared with the control group, the tryptase inhibition group (the APC366 group) had reduced intestinal fibrosis. The CCD-18Co fibroblasts, when cocultured with MCs or treated with tryptase proteins, were activated to differentiate into myofibroblasts and secrete more ECM proteins (such as collagen and fibronectin). The underlying mechanism of fibroblast activation by tryptase was the activation of the PAR-2/Akt/mTOR pathway.

CONCLUSIONS

We found that MC tryptase promotes inflammatory bowel disease-induced intestinal fibrosis. The underlying mechanism is that tryptase promotes the differentiation of fibroblasts into fibrotic-phenotype myofibroblasts by activating the PAR-2/Akt/ mTOR pathway of fibroblasts.

A role for mast cells in geographic atrophy

Mast cells (MCs) are the initial responders of innate immunity and their degranulation contribute to various etiologies. While the abundance of MCs in the choroid implies their fundamental importance in the eye, little is known about the significance of MCs and their degranulation in choroid. The cause of geographic atrophy (GA), a progressive dry form of age-related macular degeneration is elusive and there is currently no therapy for this blinding disorder. Here we demonstrate in both human GA and a rat model for GA, that MC degranulation and MC-derived tryptase are central to disease progression. Retinal pigment epithelium degeneration followed by retinal and choroidal thinning, characteristic phenotypes of GA, were driven by continuous choroidal MC stimulation and activation in a slow release fashion in the rat. Genetic manipulation of MCs, pharmacological intervention targeting MC degranulation with ketotifen fumarate or inhibition of MC-derived tryptase with APC 366 prevented all of GA-like phenotypes following MC degranulation in the rat model. Our results demonstrate the fundamental role of choroidal MC involvement in GA disease etiology, and will provide new opportunities for understanding GA pathology and identifying novel therapies targeting MCs.

Inhibition of mast cell tryptase attenuates neuroinflammation via PAR-2/p38/NFκB pathway following asphyxial cardiac arrest in rats

Background

Cardiac arrest survivors suffer from neurological dysfunction including cognitive impairment. Cerebral mast cells, the key regulators of neuroinflammation contribute to neuroinflammation-associated cognitive dysfunction. Mast cell tryptase was demonstrated to have a proinflammatory effect on microglia via the activation of microglial protease-activated receptor-2 (PAR-2). This study investigated the potential anti-neuroinflammatory effect of mast cell tryptase inhibition and the underlying mechanism of PAR-2/p-p38/NFκB signaling following asphyxia-induced cardiac arrest in rats.

Methods

Adult male Sprague-Dawley rats resuscitated from 10 min of asphyxia-induced cardiac arrest were randomized to four separate experiments including time-course, short-term outcomes, long-term outcomes and mechanism studies. The effect of mast cell tryptase inhibition on asphyxial cardiac arrest outcomes was examined after intranasal administration of selective mast cell tryptase inhibitor (APC366; 50 μg/rat or 150 μg/rat). AC55541 (selective PAR-2 activator; 30 μg/rat) and SB203580 (selective p38 inhibitor; 300 μg/rat) were used for intervention. Short-term neurocognitive functions were evaluated using the neurological deficit score, number of seizures, adhesive tape removal test, and T-maze test, while long-term cognitive functions were evaluated using the Morris water maze test. Hippocampal neuronal degeneration was evaluated by Fluoro-Jade C staining.

Results

Mast cell tryptase and PAR-2 were dramatically increased in the brain following asphyxia-induced cardiac arrest. The inhibition of mast cell tryptase by APC366 improved both short- and long-term neurological outcomes in resuscitated rats. Such behavioral benefits were associated with reduced expressions of PAR-2, p-p38, NFκB, TNF-α, and IL-6 in the brain as well as less hippocampal neuronal degeneration. The anti-neuroinflammatory effect of APC366 was abolished by AC55541, which when used alone, indeed further exacerbated neuroinflammation, hippocampal neuronal degeneration, and neurologic deficits following cardiac arrest. The deleterious effects aggregated by AC55541 were minimized by p38 inhibitor.

Conclusions

The inhibition of mast cell tryptase attenuated neuroinflammation, led to less hippocampal neuronal death and improved neurological deficits following cardiac arrest. This effect was at least partly mediated via inhibiting the PAR-2/p-p38/NFκB signaling pathway. Thus, mast cell tryptase might be a novel therapeutic target in the management of neurological impairment following cardiac arrest.

Mast Cells in Liver Fibrogenesis

Mast cells (MCs) are immune cells of the myeloid lineage that are present in the connective tissue throughout the body and in mucosa tissue. They originate from hematopoietic stem cells in the bone marrow and circulate as MC progenitors in the blood. After migration to various tissues, they differentiate into their mature form, which is characterized by a phenotype containing large granules enriched in a variety of bioactive compounds, including histamine and heparin. These cells can be activated in a receptor-dependent and -independent manner. Particularly, the activation of the high-affinity immunoglobulin E (IgE) receptor, also known as FcεRI, that is expressed on the surface of MCs provoke specific signaling cascades that leads to intracellular calcium influx, activation of different transcription factors, degranulation, and cytokine production. Therefore, MCs modulate many aspects in physiological and pathological conditions, including wound healing, defense against pathogens, immune tolerance, allergy, anaphylaxis, autoimmune defects, inflammation, and infectious and other disorders. In the liver, MCs are mainly associated with connective tissue located in the surrounding of the hepatic arteries, veins, and bile ducts. Recent work has demonstrated a significant increase in MC number during hepatic injury, suggesting an important role of these cells in liver disease and progression. In the present review, we summarize aspects of MC function and mediators in experimental liver injury, their interaction with other hepatic cell types, and their contribution to the pathogenesis of fibrosis.

IgE-mediated mast cell activation promotes inflammation and cartilage destruction in osteoarthritis

Osteoarthritis is characterized by articular cartilage breakdown, and emerging evidence suggests that dysregulated innate immunity is likely involved. Here, we performed proteomic, transcriptomic, and electron microscopic analyses to demonstrate that mast cells are aberrantly activated in human and murine osteoarthritic joint tissues. Using genetic models of mast cell deficiency, we demonstrate that lack of mast cells attenuates osteoarthritis in mice. Using genetic and pharmacologic approaches, we show that the IgE/FcεRI/Syk signaling axis is critical for the development of osteoarthritis. We find that mast cell-derived tryptase induces inflammation, chondrocyte apoptosis, and cartilage breakdown. Our findings demonstrate a central role for IgE-dependent mast cell activation in the pathogenesis of osteoarthritis, suggesting that targeting mast cells could provide therapeutic benefit in human osteoarthritis.

Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Mast cell tryptase - Marker and maker of cardiovascular diseases

Mast cells are tissue-resident cells, which have been proposed to participate in various inflammatory diseases, among them the cardiovascular diseases (CVDs). For mast cells to be able to contribute to an inflammatory process, they need to be activated to exocytose their cytoplasmic secretory granules. The granules contain a vast array of highly bioactive effector molecules, the neutral protease tryptase being the most abundant protein among them. The released tryptase may act locally in the inflamed cardiac or vascular tissue, so contributing directly to the pathogenesis of CVDs. Moreover, a fraction of the released tryptase reaches the systemic circulation, thereby serving as a biomarker of mast cell activation. Actually, increased levels of circulating tryptase have been found to associate with CVDs. Here we review the biological relevance of the circulating tryptase as a biomarker of mast cell activity in CVDs, with special emphasis on the relationship between activation of mast cells in their tissue microenvironments and the pathophysiological pathways of CVDs. Based on the available in vitro and in vivo studies, we highlight the potential molecular mechanisms by which tryptase may contribute to the pathogenesis of CVDs. Finally, the synthetic and natural inhibitors of tryptase are reviewed for their potential utility as therapeutic agents in CVDs.

The anti-fibrotic role of mast cells in the liver is mediated by HLA-G and interaction with hepatic stellate cells

BACKGROUND & AIMS

We have reported a significant association between HLA-G expression or the number of hepatic mast cells and liver fibrosis. Here, we investigated the role of HLA-G and mast cells in liver fibrosis, focusing, in particular, on interactions between human mast and stellate cells.

METHODS

Human mast cells (HMC cell line, CD34-derived mast cells, or tissue-derived mast cells) were co-cultured with purified human hepatic stellate cells (HSCs), and collagen I production by HSCs was evaluated. Mast cells and HSCs were characterized by immunocytochemistry. Various conditions were tested: different times in direct or indirect contact, presence or absence of cytokines, addition or not of HLA-G, and presence or absence of specific protease inhibitors.

RESULTS

The reciprocal interaction between HSCs and mast cells led to the attraction of mast cells to HSCs in vivo and in vitro, and to a significant decrease in collagen production, at all times of co-culture, following the direct or indirect contact of mast cells with HSCs alone or in the presence of TGF-β, IFN-α or IL-10. We identified the diffusible factors involved in collagen I degradation as mast cell proteases. Moreover, HLA-G expression increased during the co-culture of HSCs and mast cells, with HLA-G acting on both mast cells and HSCs, to enhance collagen I degradation.

CONCLUSIONS

Mast cells play a beneficial, anti-fibrotic role in liver fibrosis, via the HLA-G-mediated decrease of collagen I. These findings are consistent with high levels of cross-communication between mast cells and hepatic stellate cells and the role of HLA-G.

The controversial role of mast cells in fibrosis

Fibrosis is a medical condition characterized by an excessive deposition of extracellular matrix compounds such as collagen in tissues. Fibrotic lesions are present in many diseases and can affect all organs. The excessive extracellular matrix accumulation in these conditions can often have serious consequences and in many cases be life-threatening. A typical event seen in many fibrotic conditions is a profound accumulation of mast cells (MCs), suggesting that these cells can contribute to the pathology. Indeed, there is now substantialv evidence pointing to an important role of MCs in fibrotic disease. However, investigations from various clinical settings and different animal models have arrived at partly contradictory conclusions as to how MCs affect fibrosis, with many studies suggesting a detrimental role of MCs whereas others suggest that MCs can be protective. Here, we review the current knowledge of how MCs can affect fibrosis.

Mechanism of combined use of vitamin D and puerarin in anti-hepatic fibrosis by regulating the Wnt/β-catenin signalling pathway

AIM

To reveal the protective mechanism of the combined use of vitamin D and puerarin in the progression of hepatic fibrosis induced by carbon tetrachloride (CCl₄).

METHODS

Eight-week-old male Wistar rats were randomly divided into a normal control group (C group), a CCl₄ group (CCl₄ group), a vitamin D group (V group), a puerarin group (P group), and a combined group of vitamin D and puerarin (V + P group), each of which contained ten rats. In this way, we built a rat model of CCl₄-induced hepatic fibrosis with intervention by vitamin D, puerarin, or a combination of the two. After eight weeks, the mice were sacrificed to collect serum and liver specimens. Blood was collected to detect the hyaluronic acid (HA). We also measured hydroxyproline (Hyp) and prepared paraffin sections of liver. After Sirius red staining, the liver specimens were observed under a microscope. RT-PCR and western blot analysis were adopted to detect the mRNA and the protein levels of Collagen I, Collagen III, Wnt1, and β-catenin in the liver tissues, respectively.

RESULTS

Hepatic fibrosis was observed in the CCl₄ group. In comparison, hepatic fibrosis was attenuated in the V, P, and V + P groups: the HA level in blood and the Hyp level in liver were reduced, and the mRNA levels of Collagen I, Collagen III, Wnt, and β-catenin in liver were also decreased, as well as the protein levels of Wnt1 and β-catenin. Among these groups, the V + P group demonstrated the greatest amelioration of hepatic fibrosis.

CONCLUSION

The combined application of vitamin D and puerarin is capable of alleviating CCl₄-induced hepatic fibrosis of rats. As to the mechanism, it is probably because the combined use is able to silence the Wnt1/β-catenin pathway, suppress the activation of hepatic stellate cells, and reduce the secretion of collagen fibers, therefore improving the anti-hepatic fibrosis effect.

A Novel, Nonpeptidic, Orally Active Bivalent Inhibitor of Human β-Tryptase

β-Tryptase is released from mast cells upon degranulation in response to allergic and inflammatory stimuli. Human tryptase is a homotetrameric serine protease with 4 identical active sites directed toward a central pore. These active sites present an optimized scenario for the rational design of bivalent inhibitors, which bridge 2 adjacent active sites. Using (3-[1-acylpiperidin-4-yl]phenyl)methanamine as the pharmacophoric core and a disiloxane linker to span 2 active sites we have successfully produced a novel bivalent tryptase inhibitor, compound 1a, with a comparable profile to previously described inhibitors. Pharmacological properties of compound 1a were studied in a range of in vitro enzymic and cellular screening assays, and in vivo xenograft models. This non-peptide inhibitor of tryptase demonstrated superior activity (IC50 at 100 pmol/L tryptase = 1.82 nmol/L) compared to monomeric modes of inhibition. X-ray crystallography validated the dimeric mechanism of inhibition, and 1a demonstrated good oral bioavailability and efficacy in HMC-1 xenograft models. Furthermore, compound 1a demonstrated extremely slow off rates and high selectivity against-related proteases. This highly potent, orally bioavailable and selective inhibitor of human tryptase will be an invaluable tool in future studies to explore the therapeutic potential of attenuating the activity of this elusive target.

The emerging role of mast cells in liver disease

The depth of our knowledge regarding mast cells has widened exponentially in the last 20 years. Once thought to be only important for allergy-mediated events, mast cells are now recognized to be important regulators of a number of pathological processes. The revelation that mast cells can influence organs, tissues, and cells has increased interest in mast cell research during liver disease. The purpose of this review is to refresh the reader's knowledge of the development, type, and location of mast cells and to review recent work that demonstrates the role of hepatic mast cells during diseased states. This review focuses primarily on liver diseases and mast cells during autoimmune disease, hepatitis, fatty liver disease, liver cancer, and aging in the liver. Overall, these studies demonstrate the potential role of mast cells in disease progression.

ENMD-1068 inhibits liver fibrosis through attenuation of TGF-β1/Smad2/3 signaling in mice

Protease-activated receptor 2 (PAR-2) plays an important role in the pathogenesis of liver fibrosis. We studied the effect of N1-3-methylbutyryl-N4-6-aminohexanoyl-piperazine (ENMD-1068), a PAR-2 antagonist, on the development of CCl₄-induced liver fibrosis in mice and activation of hepatic stellate cells (HSCs) isolated from the mice. Before CCl₄ injection, the mice were injected intraperitoneally with either 25 mg/kg or 50 mg/kg ENMD-1068 or with 200 μL of the vehicle control twice per week for 4 weeks. The isolated HSCs were stimulated by TGF-β1 with or without ENMD-1068 to evaluate the role of PAR-2 in TGF-β1 induced HSCs activation and collagen production. We showed that the levels of ALT/AST, collagen content, and α-smooth muscle actin (α-SMA) were significantly reduced by treatment with ENMD-1068 in CCl₄-induced fibrotic mice. Interestingly, we found TGF-β1 signaling-related expression levels of α-SMA, type I and III collagen, and C-terminal phosphorylation of Smad2/3 were significantly decreased in the ENMD-1068 treated HSCs. Moreover, we showed ENMD-1068 treatment inhibited trypsin or SLIGRL-NH₂ stimulated calcium release and TGF-β1 induced Smad transcriptional activity in HSCs. We demonstrated that ENMD-1068 reduces HSCs activation and collagen expression through the inhibiton of TGF-β1/Smad signal transduction.

Cellular crosstalk during cholestatic liver injury

The functions of the liver are very diverse. From detoxifying blood to storing glucose in the form of glycogen and producing bile to facilitate fat digestion, the liver is a very active and important organ. The liver is comprised of many varied cell types whose functions are equally diverse. Cholangiocytes line the biliary tree and aid in transporting and adjusting the composition of bile as it travels to the gallbladder. Hepatic stellate cells and portal fibroblasts are located in different areas within the liver architecture, but both contribute to the development of fibrosis upon activation after liver injury. Vascular cells, including those that constitute the peribiliary vascular plexus, are involved in functions other than blood delivery to and from the liver, such as supporting the growth of the biliary tree during development. Mast cells are normally found in healthy livers but in very low numbers. However, after injury, mast cell numbers greatly increase as they infiltrate and release factors that exacerbate the fibrotic response. While not an all-inclusive list, these cells have individual roles within the liver, but they are also able to communicate with each other by cellular crosstalk. In this review, we examine some of these pathways that can lead to an increase in the homeostatic dysfunction seen in liver injury.

Tryptase inhibitors: a patent review

INTRODUCTION

Tryptase is one of the main serine-proteinases located in the secretory granules of mast cells, and is released through degranulation, which is involved in the pathogenesis of allergic inflammatory disease, cardiovascular diseases, lung fibrosis and tumor. Therefore, inhibitors targeting tryptase may represent a new direction for the treatment of allergic inflammatory disease and other diseases. Areas covered: In this article, we discussed the history and development of tryptase inhibitors and described a variety of tryptase inhibitors via their structures and biological importance in clinical studies and drug development for tryptase-related diseases. Expert opinion: Initial tryptase inhibitors based on indole structure as the hydrophobic substituent on a benzylamine-piperidine template have low specificity and poor bioavailability. Therefore, designing new and specific inhibitors targeting tryptase should be involved in future clinical studies. Modifications toward indoles with varying N-substitution, introducing an amide bond, and growing the chain length contribute to an increase in the specific selectivity and potency of tryptase inhibitors. Tryptase has become the research hotspot to explore many related diseases. Therefore, there has been growing appreciation for the potential importance of the tryptase inhibitors as a target for treating these diseases.

Inhibition of mast cell-secreted histamine decreases biliary proliferation and fibrosis in primary sclerosing cholangitis Mdr2(-/-) mice

Hepatic fibrosis is marked by activation of hepatic stellate cells (HSCs). Cholestatic injury precedes liver fibrosis, and cholangiocytes interact with HSCs promoting fibrosis. Mast cells (MCs) infiltrate following liver injury and release histamine, increasing biliary proliferation. We evaluated if inhibition of MC-derived histamine decreases biliary proliferation and fibrosis. Wild-type and multidrug resistance 2 knockout mice (9-11 weeks) were treated with cromolyn sodium for 1 week to block MC-derived histamine. Biliary mass and proliferation were evaluated by immunohistochemistry for cytokeratin 19 and Ki-67. Bile flow, bicarbonate excretion, and total bile acids were measured in all mice. Fibrosis was evaluated by sirius red/fast green staining and by quantitative polymerase chain reaction for alpha-smooth muscle actin, fibronectin, collagen type 1a, and transforming growth factor-beta 1. HSC activation was evaluated by quantitative polymerase chain reaction in total liver and immunofluorescent staining in tissues for synaptophysin 9. Histamine serum secretion was measured by enzymatic immunoassay. Mouse liver and human liver samples from control or primary sclerosing cholangitis patients were evaluated for MC markers by quantitative polymerase chain reaction and immunohistochemistry. In vitro, cultured MCs were transfected with histidine decarboxylase short hairpin RNA to decrease histamine secretion and subsequently cocultured with cholangiocytes or HSCs prior to measuring fibrosis markers, proliferation, and transforming growth factor-beta 1 secretion. Treatment with cromolyn sodium decreased biliary proliferation, fibrosis, histamine secretion, and bile flow in multidrug resistance 2 knockout mice. Primary sclerosing cholangitis mice and patients have increased MCs. Knockdown of MC histidine decarboxylase decreased cholangiocyte and HSC proliferation/activation.

CONCLUSION

MCs are recruited to proliferating cholangiocytes and promote fibrosis. Inhibition of MC-derived histamine decreases fibrosis, and regulation of MC mediators may be therapeutic for primary sclerosing cholangitis. (Hepatology 2016;64:1202-1216).

Proteinase-activated receptor 2 (PAR2) in hepatic stellate cells - evidence for a role in hepatocellular carcinoma growth in vivo

BACKGROUND

Previous studies have established that proteinase-activated receptor 2 (PAR2) promotes migration and invasion of hepatocellular carcinoma (HCC) cells, suggesting a role in HCC progression. Here, we assessed the impact of PAR2 in HCC stromal cells on HCC growth using LX-2 hepatic stellate cells (HSCs) and Hep3B cells as model.

METHODS

PAR2 expression and function in LX-2 cells was analysed by RT-PCR, confocal immunofluorescence, electron microscopy, and [Ca(2+)]i measurements, respectively. The impact of LX-2-expressed PAR2 on tumour growth in vivo was monitored using HCC xenotransplantation experiments in SCID mice, in which HCC-like tumours were induced by coinjection of LX-2 cells and Hep3B cells. To characterise the effects of PAR2 activation in LX-2 cells, various signalling pathways were analysed by immunoblotting and proteome profiler arrays.

RESULTS

Following verification of functional PAR2 expression in LX-2 cells, in vivo studies showed that these cells promoted tumour growth and angiogenesis of HCC xenografts in mice. These effects were significantly reduced when F2RL1 (encoding PAR2) was downregulated by RNA interference (RNAi). In vitro studies confirmed these results demonstrating RNAi mediated inhibition of PAR2 attenuated Smad2/3 activation in response to TGF-β1 stimulation in LX-2 cells and blocked the pro-mitotic effect of LX-2 derived conditioned medium on Hep3B cells. Furthermore, PAR2 stimulation with trypsin or a PAR2-selective activating peptide (PAR2-AP) led to activation of different intracellular signalling pathways, an increased secretion of pro-angiogenic and pro-mitotic factors and proteinases, and an enhanced migration rate across a collagen-coated membrane barrier. Silencing F2RL1 by RNAi or pharmacological inhibition of Src, hepatocyte growth factor receptor (Met), platelet-derived growth factor receptor (PDGFR), p42/p44 mitogen activated protein kinase (MAPK) or matrix-metalloproteinases (MMPs) blocked PAR2-AP-induced migration.

CONCLUSION

PAR2 in HSCs plays a crucial role in promoting HCC growth presumably by mediating migration and secretion of pro-angiogenic and pro-mitotic factors. Therefore, PAR2 in stromal HSCs may have relevance as a therapeutic target of HCC.

Hepatoprotective and Anti-fibrotic Agents: It's Time to Take the Next Step

Hepatic fibrosis and cirrhosis cause strong human suffering and necessitate a monetary burden worldwide. Therefore, there is an urgent need for the development of therapies. Pre-clinical animal models are indispensable in the drug discovery and development of new anti-fibrotic compounds and are immensely valuable for understanding and proofing the mode of their proposed action. In fibrosis research, inbreed mice and rats are by far the most used species for testing drug efficacy. During the last decades, several hundred or even a thousand different drugs that reproducibly evolve beneficial effects on liver health in respective disease models were identified. However, there are only a few compounds (e.g., GR-MD-02, GM-CT-01) that were translated from bench to bedside. In contrast, the large number of drugs successfully tested in animal studies is repeatedly tested over and over engender findings with similar or identical outcome. This circumstance undermines the 3R (Replacement, Refinement, Reduction) principle of Russell and Burch that was introduced to minimize the suffering of laboratory animals. This ethical framework, however, represents the basis of the new animal welfare regulations in the member states of the European Union. Consequently, the legal authorities in the different countries are halted to foreclose testing of drugs in animals that were successfully tested before. This review provides a synopsis on anti-fibrotic compounds that were tested in classical rodent models. Their mode of action, potential sources and the observed beneficial effects on liver health are discussed. This review attempts to provide a reference compilation for all those involved in the testing of drugs or in the design of new clinical trials targeting hepatic fibrosis.

Wogonoside Shows Antifibrotic Effects in an Experimental Regression Model of Hepatic Fibrosis

BACKGROUD

Wogonoside (WO), a flavonoid extracted from Huangqin, plays multiple physiological roles. However, it has remained elusive how WO regulates hepatic fibrogenesis until now.

AIM

The purpose of the study was to investigate the potential protective effects of WO against liver fibrosis induced by carbon tetrachloride (CCl4).

METHODS

In this study, male rats were randomly allocated into four groups: a control group, the CCl4 group, the CCl4 and WO (4 mg/kg) group, and CCl4 and WO (8 mg/kg) group. Hepatic fibrosis was induced by subcutaneous injection of CCl4 twice a week for a continuous 6-week period. Then the rats were intragastrically administrated with WO daily for 4 weeks before being killed.

RESULTS

As expected, histopathological assessment, Masson trichrome staining, and Sirius red staining demonstrated that WO drastically ameliorated the hepatic fibrosis caused by CCl4. WO significantly attenuated the CCl4-induced upregulations of liver indices including alanine aminotransferase, aspartate aminotransferase, tumor necrosis factor-α, interleukin-1β, IL-6, hexadecenoic acid and laminin in serum, as well as hydroxyproline, malondialdehyde and phosphatidylinositol 3-kinase (PI3K)/protein Kinase B(Akt)/mechanistic target of rapamycin (mTOR)/nuclear factor-kappa B signalings in liver. Meanwhile, WO also effectively recovered the depletions of superoxide dismutase, glutathione and IL-10. Furthermore, we evaluated the effects of WO on the alpha smooth muscle actin, type I collagen expressions, and PI3K/Akt/ mTOR/ribosomal protein S6 kinase 70 kDa (p70S6K) signaling in transforming growth factor (TGF-β) stimulated hepatic stellate cell-T6 cells.

CONCLUSIONS

These results suggested that WO had significant protective effects against liver fibrosis induced by CCl4.

Interventional effects of Plumbago zeylanica L. decoction on CCl4-induced hepatic fibrosis in rats

AIM: To investigate the intervention effects of Plumbago zeylanica L. decoction (PZL) on carbon tetrachloride (CCl4)-induced hepatic fibrosis in rats.

METHODS: A model of hepatic fibrosis was established by subcutaneous injection of 40% CCl₄ in rats. SD rats were randomly divided into five groups (10 rats in each group): a model group, a positive control group (colchicines 0.25 mg/kg), high-, medium- and low-dose PZL groups. A blank control group was also established. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were tested using a ultraviolet-visible pectrophotometer (UV). Serum levels of total bilirubin (TBIL), direct bilirubin (DBIL) and indirect bilirubin (IBIL) were detected by the method of vanadate oxidation. The contents of hyaluronic acid (HA), laminin (LN), procollagen type Ⅲ (P3NP), and type Ⅳ collagen (CⅣ) were detected by radioimmunoassay. HE staining was used to examine the degree of hepatic fibrosis, and the expression of collagen type Ⅰ and Ⅲ and α-SMA in hepatic tissues was detected by immunohistochemistry.

RESULTS: Compared with the model group, the levels of ALT, AST, TBIL, DBIL and IBIL were significantly decreased in the PZL groups. PZL could also significantly reduce the contents of HA, LN, P3NP, and CⅣ. HE staining showed that PZL could significantly reduce the degree of hepatic fibrosis. Immunohistochemistry showed that the expression of collagen type Ⅰ and Ⅲ and α-SMA in hepatic tissues was decreased by PZL (P < 0.05 or P < 0.01), and the effect was dose-dependent.

CONCLUSION: PZL has a protective effect against CCl₄-induced liver fibrosis in rats possibly by improving the liver function, inhibiting liver cell degeneration and necrosis, reducing secretion of collagen by hepatic stellate cells and promoting extracellular matrix degradation.