Inactivation of fatty acid amide hydrolase exacerbates experimental fibrosis by enhanced endocannabinoid-mediated activation of CB1

Pharmacological Inhibition of N-Acylethanolamine Acid Amidase (NAAA) Mitigates Intestinal Fibrosis Through Modulation of Macrophage Activity

BACKGROUND AND AIMS

Intestinal fibrosis, a frequent complication of inflammatory bowel disease, is characterized by stricture formation with no pharmacological treatment to date. N-acylethanolamine acid amidase (NAAA) is responsible for the hydrolysis of acylethanolamides (AEs, eg, palmitoylethanolamide and oleoylethanolamide). Here, we investigated NAAA and AE signaling in gut fibrosis.

METHODS

NAAA and AE signaling were evaluated in human intestinal specimens from patients with stenotic Crohn's disease (CD). Gut fibrosis was induced by 2,4,6-trinitrobenzenesulfonic acid, monitored by colonoscopy, and assessed by qRT-PCR, histological analyses, and confocal microscopy. Immune cells in mesenteric lymph nodes were analyzed by FACS. Colonic fibroblasts were cultured in conditioned media derived from polarized or non-polarized bone marrow-derived macrophages (BMDMs). IL-23 signaling was evaluated by qRT-PCR, ELISA, FACS, and western blot in BMDMs and in lamina propria CX3CR1+ cells.

RESULTS

In ileocolonic human CD strictures, increased transcript expression of NAAA was observed with a decrease in its substrates oleoylethanolamide and palmitoylethanolamide. NAAA inhibition reduced intestinal fibrosis in vivo, as indicated by a decrease in inflammatory parameters, collagen deposition, and fibrosis-related genes, including those involved in epithelial-to-mesenchymal transition. More in-depth studies revealed modulation of the immune response related to IL-23 following NAAA inhibition. The antifibrotic actions of NAAA inhibition are mediated by Mφ and M2 macrophages that indirectly affect fibroblast collagenogenesis. NAAA inhibitor AM9053 normalized IL-23 signaling in BMDMs and in lamina propria CX3CR1+ cells.

CONCLUSIONS

Our findings provide new insights into the pathophysiological mechanism of intestinal fibrosis and identify NAAA as a promising target for the development of therapeutic treatments to alleviate CD-related fibrosis.

Anandamide is an Early Blood Biomarker of Hermansky-Pudlak Syndrome Pulmonary Fibrosis

Hermansky-Pudlak syndrome (HPS) is a group of rare genetic disorders, with several subtypes leading to fatal adult-onset pulmonary fibrosis (PF) and no effective treatment. Circulating biomarkers detecting early PF have not been identified. We investigated whether endocannabinoids could serve as blood biomarkers of PF in HPS. We measured endocannabinoids in the serum of HPS, IPF, and healthy human subjects and in a mouse model of HPSPF. Pulmonary function tests (PFT) were correlated with endocannabinoid measurements. In a pale ear mouse model of bleomycin-induced HPSPF, serum endocannabinoid levels were measured with and without treatment with zevaquenabant (MRI-1867), a peripheral CB1R and iNOS antagonist. In three separate cohorts, circulating anandamide levels were increased in HPS-1 patients with or without PF, compared to healthy volunteers. This increase was not observed in IPF patients or in HPS-3 patients, who do not have PF. Circulating anandamide (AEA) levels were negatively correlated with PFT. Furthermore, a longitudinal study over the course of 5-14 years with HPS-1 patients indicated that circulating AEA levels begin to increase with the fibrotic lung process even at the subclinical stages of HPSPF. In pale ear mice with bleomycin-induced HpsPF, serum AEA levels were significantly increased in the earliest stages of PF and remained elevated at a later fibrotic stage. Zevaquenabant treatment reduced the increased AEA levels and attenuated progression in bleomycin-induced HpsPF. Circulating AEA may be a prognostic blood biomarker for PF in HPS-1 patients. Further studies are indicated to evaluate endocannabinoids as potential surrogate biomarkers in progressive fibrotic lung diseases.

Cannabinoid Compounds as a Pharmacotherapeutic Option for the Treatment of Non-Cancer Skin Diseases

The endocannabinoid system has been shown to be involved in various skin functions, such as melanogenesis and the maintenance of redox balance in skin cells exposed to UV radiation, as well as barrier functions, sebaceous gland activity, wound healing and the skin's immune response. In addition to the potential use of cannabinoids in the treatment and prevention of skin cancer, cannabinoid compounds and derivatives are of interest as potential systemic and topical applications for the treatment of various inflammatory, fibrotic and pruritic skin conditions. In this context, cannabinoid compounds have been successfully tested as a therapeutic option for the treatment of androgenetic alopecia, atopic and seborrhoeic dermatitis, dermatomyositis, asteatotic and atopic eczema, uraemic pruritis, scalp psoriasis, systemic sclerosis and venous leg ulcers. This review provides an insight into the current literature on cannabinoid compounds as potential medicines for the treatment of skin diseases.

Peripheral Hybrid CB1R and iNOS Antagonist MRI-1867 Displays Anti-Fibrotic Efficacy in Bleomycin-Induced Skin Fibrosis

Scleroderma, or systemic sclerosis, is a multi-organ connective tissue disease resulting in fibrosis of the skin, heart, and lungs with no effective treatment. Endocannabinoids acting via cannabinoid-1 receptors (CB1R) and increased activity of inducible NO synthase (iNOS) promote tissue fibrosis including skin fibrosis, and joint targeting of these pathways may improve therapeutic efficacy. Recently, we showed that in mouse models of liver, lung and kidney fibrosis, treatment with a peripherally restricted hybrid CB1R/iNOS inhibitor (MRI-1867) yields greater anti-fibrotic efficacy than inhibiting either target alone. Here, we evaluated the therapeutic efficacy of MRI-1867 in bleomycin-induced skin fibrosis. Skin fibrosis was induced in C57BL/6J (B6) and Mdr1a/b-Bcrp triple knock-out (KO) mice by daily subcutaneous injections of bleomycin (2 IU/100 µL) for 28 days. Starting on day 15, mice were treated for 2 weeks with daily oral gavage of vehicle or MRI-1867. Skin levels of MRI-1867 and endocannabinoids were measured by mass spectrometry to assess target exposure and engagement by MRI-1867. Fibrosis was characterized histologically by dermal thickening and biochemically by hydroxyproline content. We also evaluated the potential increase of drug-efflux associated ABC transporters by bleomycin in skin fibrosis, which could affect target exposure to test compounds, as reported in bleomycin-induced lung fibrosis. Bleomycin-induced skin fibrosis was comparable in B6 and Mdr1a/b-Bcrp KO mice. However, the skin level of MRI-1867, an MDR1 substrate, was dramatically lower in B6 mice (0.023 µM) than in Mdr1a/b-Bcrp KO mice (8.8 µM) due to a bleomycin-induced increase in efflux activity of MDR1 in fibrotic skin. Furthermore, the endocannabinoids anandamide and 2-arachidonylglycerol were elevated 2-4-fold in the fibrotic vs. control skin in both mouse strains. MRI-1867 treatment attenuated bleomycin-induced established skin fibrosis and the associated increase in endocannabinoids in Mdr1a/b-Bcrp KO mice but not in B6 mice. We conclude that combined inhibition of CB1R and iNOS is an effective anti-fibrotic strategy for scleroderma. As bleomycin induces an artifact in testing antifibrotic drug candidates that are substrates of drug-efflux transporters, using Mdr1a/b-Bcrp KO mice for preclinical testing of such compounds avoids this pitfall.

Translational Neuroendocrinology of Human Skin: Concepts and Perspectives

Human skin responds to numerous neurohormones, neuropeptides, and neurotransmitters that reach it via the vasculature or skin nerves, and/or are generated intracutaneously, thus acting in a para- and autocrine manner. This review focuses on how neurohormones impact on human skin physiology and pathology. We highlight basic concepts, major open questions, and translational research perspectives in cutaneous neuroendocrinology and argue that greater emphasis on neuroendocrine human skin research will foster the development of novel dermatological therapies. Furthermore, human skin and its appendages can be used as highly accessible and clinically relevant model systems for probing nonclassical, ancestral neurohormone functions. This calls for close interdisciplinary collaboration between dermatologists, skin biologists, neuroendocrinologists, and neuropharmacologists.

Cutaneous endocannabinoid system: Does it have a role on skin wound healing bearing fibrosis?

INTRODUCTION

Recently, the endocannabinoid system has been identified in skin and it has been linked with the formation of skin fibrosis and wound healing. We aimed to find and analyse reported data on compounds acting in the endocannabinoid system with significant effect in skin fibrosis.

METHODS

A literature search on PUBMED was conducted for studies published in English until February 2020 on cannabinoids and skin fibrosis. The initial search was performed with terms: "cannabinoid" AND "skin". This search retrieved 296 publications from which 18 directly related to skin fibrosis or wound healing process were included in this review.

RESULTS

CB1 receptor inactivation and CB2 receptor activation show anti-fibrotic effects on cellular and animal experimental models of cutaneous fibrosis. CB2 receptor activation also promotes re-epithelization. Other cannabinoid related receptors, like adenosine A2A receptors and PPAR-γ, are also involved. Their activation lead to a pro-fibrotic and anti-fibrotic effect, respectively.

CONCLUSION

Several molecular drug targets for endocannabinoid system were identified in skin. It may be a promising approach for the treatment of excessive skin fibrosis disorders.

2-arachidonoylglycerol reduces chondroitin sulphate proteoglycan production by astrocytes and enhances oligodendrocyte differentiation under inhibitory conditions

The failure to remyelinate and regenerate is a critical impediment to recovery in multiple sclerosis (MS), resulting in severe dysfunction and disability. The chondroitin sulfate proteoglycans (CSPGs) that accumulate in MS lesions are thought to be linked to the failure to regenerate, impeding oligodendrocyte precursor cell (OPC) differentiation and neuronal growth. The potential of endocannabinoids to influence MS progression may reflect their capacity to enhance repair processes. Here, we investigated how 2-arachidonoylglycerol (2-AG) may affect the production of the CSPGs neurocan and brevican by astrocytes in culture. In addition, we studied whether 2-AG promotes oligodendrocyte differentiation under inhibitory conditions in vitro. Following treatment with 2-AG or by enhancing its endogenous tone through the use of inhibitors of its hydrolytic enzymes, CSPG production by rat and human TGF-β1 stimulated astrocytes was reduced. These effects of 2-AG might reflect its influence on TGF-β1/SMAD pathway, signaling that is involved in CSPG upregulation. The matrix generated from 2-AG-treated astrocytes is less inhibitory to oligodendrocyte differentiation and significantly, 2-AG administration directly promotes the differentiation of rat and human oligodendrocytes cultured under inhibitory conditions. Overall, the data obtained favor targeting the endocannabinoid system to neutralize CSPG accumulation and to enhance oligodendrocyte differentiation.

Cannabinoid Signaling in the Skin: Therapeutic Potential of the "C(ut)annabinoid" System

The endocannabinoid system (ECS) has lately been proven to be an important, multifaceted homeostatic regulator, which influences a wide-variety of physiological processes all over the body. Its members, the endocannabinoids (eCBs; e.g., anandamide), the eCB-responsive receptors (e.g., CB₁, CB₂), as well as the complex enzyme and transporter apparatus involved in the metabolism of the ligands were shown to be expressed in several tissues, including the skin. Although the best studied functions over the ECS are related to the central nervous system and to immune processes, experimental efforts over the last two decades have unambiguously confirmed that cutaneous cannabinoid ("c[ut]annabinoid") signaling is deeply involved in the maintenance of skin homeostasis, barrier formation and regeneration, and its dysregulation was implicated to contribute to several highly prevalent diseases and disorders, e.g., atopic dermatitis, psoriasis, scleroderma, acne, hair growth and pigmentation disorders, keratin diseases, various tumors, and itch. The current review aims to give an overview of the available skin-relevant endo- and phytocannabinoid literature with a special emphasis on the putative translational potential, and to highlight promising future research directions as well as existing challenges.

Cannabinoid derivatives acting as dual PPARγ/CB2 agonists as therapeutic agents for systemic sclerosis

The endocannabinoid system (ECS) may play a role in the pathophysiology of systemic sclerosis (SSc). Cannabinoids acting as dual PPARγ/CB₂ agonists, such as VCE-004.8 and Ajulemic acid (AjA), have been shown to alleviate skin fibrosis and inflammation in SSc models. Since both compounds are being tested in humans, we compared their activities in the bleomycin (BLM) SSc model. Specifically, the pharmacotranscriptomic signature of the compounds was determined by RNA-Seq changes in the skin of BLM mice treated orally with AjA or EHP-101, a lipidic formulation of VCE-004.8. While both compounds down-regulated the expression of genes involved in the inflammatory and fibrotic components of the disease and the pharmacotranscriptomic signatures were similar for both compounds in some pathways, we found key differences between the compounds in vasculogenesis. Additionally, we found 28 specific genes with translation potential by comparing with a list of human scleroderma genes. Immunohistochemical analysis revealed that both compounds prevented fibrosis, collagen accumulation and Tenascin C (TNC) expression. The endothelial CD31⁺/CD34⁺ cells and telocytes were reduced in BLM mice and restored only by EHP-101 treatment. Finally, differences were found in plasmatic biomarker analysis; EHP-101, but not AjA, enhanced the expression of some factors related to angiogenesis and vasculogenesis. Altogether the results indicate that dual PPARγ/CB2 agonists qualify as a novel therapeutic approach for the treatment of SSc and other fibrotic diseases. EHP-101 demonstrated unique mechanisms of action related to the pathophysiology of SSc that could be beneficial in the treatment of this complex disease without current therapeutic options.

The endocannabinoid system of the skin. A potential approach for the treatment of skin disorders

The skin is the largest organ of the body and has a complex and very active structure that contributes to homeostasis and provides the first line defense against injury and infection. In the past few years it has become evident that the endocannabinoid system (ECS) plays a relevant role in healthy and diseased skin. Specifically, we review how the dysregulation of ECS has been associated to dermatological disorders such as atopic dermatitis, psoriasis, scleroderma and skin cancer. Therefore, the druggability of the ECS could open new research avenues for the treatment of the pathologies mentioned. Numerous studies have reported that phytocannabinoids and their biological analogues modulate a complex network pharmacology involved in the modulation of ECS, focusing on classical cannabinoid receptors, transient receptor potential channels (TRPs), and peroxisome proliferator-activated receptors (PPARs). The combined targeting of several end-points seems critical to provide better chances of therapeutically success, in sharp contrast to the one-disease-one-target dogma that permeates current drug discovery campaigns.

N-stearoyltyrosine protects primary cortical neurons against oxygen-glucose deprivation-induced apoptosis through inhibiting anandamide inactivation system

N-stearoylthrosine (NST), a synthesized anandamide (AEA) analogue, plays a neuroprotective role in neurodegenerative diseases and cerebrovascular diseases. Several studies have demonstrated that the endocannabinoids systems (ECS) are involved in the neuroprotective effects against cerebral ischemic injury. Oxygen-glucose deprivation (OGD)-induced neuronal injury elevated the levels of endocannabinoids and activated ECS. This research was conducted to investigate the neuroprotective effect of NST against OGD-induced neuronal injury in cultured primary cortical neurons and the potential mechanism involved. Cortical neurons were treated with NST at indicate concentrations for 30min prior to injury and OGD injured neurons were incubated with normal conditions for 0-24h. The best neuroprotective effect of NST against OGD-induced injury occurred at 10μM. All data indicated that the neuroprotective effect of NST against OGD-induced injury resulted from blocking anandamide membrane transporter (AMT) (IC₅₀=11.74nM) and inhibiting fatty acid amide hydrolase activity (FAAH) (IC₅₀=16.54nM). Our findings demonstrated that NST has an important role in cerebral ischemic injury pathological progression through activating cannabinoid receptors by inhibiting AEA inactivation system. These data suggested a potential role for NST in the therapeutic consideration of cerebral ischemic injury. However, inhibition of AEA inactivation system may provide a neuroprotective effect during cerebral ischemic injury.

Cannabinoid CB1 receptor overactivity contributes to the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a life-threatening disease without effective treatment, highlighting the need for identifying new targets and treatment modalities. The pathogenesis of IPF is complex, and engaging multiple targets simultaneously might improve therapeutic efficacy. To assess the role of the endocannabinoid/cannabinoid receptor 1 (endocannabinoid/CB1R) system in IPF and its interaction with inducible nitric oxide synthase (iNOS) as dual therapeutic targets, we analyzed lung fibrosis and the status of the endocannabinoid/CB1R system and iNOS in mice with bleomycin-induced pulmonary fibrosis (PF) and in lung tissue and bronchoalveolar lavage fluid (BALF) from patients with IPF, as well as controls. In addition, we investigated the antifibrotic efficacy in the mouse PF model of an orally bioavailable and peripherally restricted CB1R/iNOS hybrid inhibitor. We report that increased activity of the endocannabinoid/CB1R system parallels disease progression in the lungs of patients with idiopathic PF and in mice with bleomycin-induced PF and is associated with increased tissue levels of interferon regulatory factor-5. Furthermore, we demonstrate that simultaneous engagement of the secondary target iNOS by the hybrid CB1R/iNOS inhibitor has greater antifibrotic efficacy than inhibition of CB1R alone. This hybrid antagonist also arrests the progression of established fibrosis in mice, thus making it a viable candidate for future translational studies in IPF.

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology

Apart from having been used and misused for at least four millennia for, among others, recreational and medicinal purposes, the cannabis plant and its most peculiar chemical components, the plant cannabinoids (phytocannabinoids), have the merit to have led humanity to discover one of the most intriguing and pleiotropic endogenous signaling systems, the endocannabinoid system (ECS). This review article aims to describe and critically discuss, in the most comprehensive possible manner, the multifaceted aspects of 1) the pharmacology and potential impact on mammalian physiology of all major phytocannabinoids, and not only of the most famous one Δ9-tetrahydrocannabinol, and 2) the adaptive pro-homeostatic physiological, or maladaptive pathological, roles of the ECS in mammalian cells, tissues, and organs. In doing so, we have respected the chronological order of the milestones of the millennial route from medicinal/recreational cannabis to the ECS and beyond, as it is now clear that some of the early steps in this long path, which were originally neglected, are becoming important again. The emerging picture is rather complex, but still supports the belief that more important discoveries on human physiology, and new therapies, might come in the future from new knowledge in this field.

Tribbles homologue 3 stimulates canonical TGF-β signalling to regulate fibroblast activation and tissue fibrosis

OBJECTIVES

Tribbles homologue 3 (TRB3) is a pseudokinase that modifies the activation of various intracellular signalling pathways to control fundamental processes extending from mitosis and cell activation to apoptosis and modulation of gene expression. Here, we aimed to analyse the role of TRB3 in fibroblast activation in systemic sclerosis (SSc).

METHODS

The expression of TRB3 was quantified by quantitative PCR, western blot and immunohistochemistry. The role of TRB3 was analysed in cultured fibroblasts and in experimental fibrosis using small interfering RNA (siRNA)-mediated knockdown and overexpression of TRB3.

RESULTS

TRB3 expression was increased in fibroblasts of patients with SSc and in murine models of SSc in a transforming growth factor-β (TGF-β)/Smad-dependent manner. Overexpression of TRB3 stimulated canonical TGF-β signalling and induced an activated phenotype in resting fibroblasts. In contrast, knockdown of TRB3 reduced the profibrotic effects of TGF-β and decreased the collagen synthesis. Moreover, siRNA-mediated knockdown of TRB3 exerted potent antifibrotic effects and ameliorated bleomycin as well as constitutively active TGF-β receptor I-induced fibrosis with reduced dermal thickening, decreased hydroxyproline content and impaired myofibroblast differentiation.

CONCLUSIONS

The present study characterises TRB3 as a novel profibrotic mediator in SSc. TGF-β induces TRB3, which in turn activates canonical TGF-β/Smad signalling and stimulates the release of collagen, thereby inducing a positive feedback loop that may contribute to aberrant TGF-β signalling in SSc.

The cannabinoid quinol VCE-004.8 alleviates bleomycin-induced scleroderma and exerts potent antifibrotic effects through peroxisome proliferator-activated receptor-γ and CB2 pathways

Scleroderma is a group of rare diseases associated with early and transient inflammation and vascular injury, followed by fibrosis affecting the skin and multiple internal organs. Fibroblast activation is the hallmark of scleroderma, and disrupting the intracellular TGFβ signaling may provide a novel approach to controlling fibrosis. Because of its potential role in modulating inflammatory and fibrotic responses, both PPARγ and CB₂ receptors represent attractive targets for the development of cannabinoid-based therapies. We have developed a non-thiophilic and chemically stable derivative of the CBD quinol (VCE-004.8) that behaves as a dual agonist of PPARγ and CB₂ receptors, VCE-004.8 inhibited TGFβ-induced Col1A2 gene transcription and collagen synthesis. Moreover, VCE-004.8 inhibited TGFβ–mediated myofibroblast differentiation and impaired wound-healing activity. The anti-fibrotic efficacy in vivo was investigated in a murine model of dermal fibrosis induced by bleomycin. VCE-004.8 reduced dermal thickness, blood vessels collagen accumulation and prevented mast cell degranulation and macrophage infiltration in the skin. These effects were impaired by the PPARγ antagonist T0070907 and the CB₂ antagonist AM630. In addition, VCE-004.8 downregulated the expression of several key genes associated with fibrosis, qualifying this semi-synthetic cannabinoid as a novel compound for the management of scleroderma and, potentially, other fibrotic diseases.

Sirt1 regulates canonical TGF-β signalling to control fibroblast activation and tissue fibrosis

BACKGROUND

Sirt1 is a member of the sirtuin family of proteins. Sirt1 is a class III histone deacetylase with important regulatory roles in transcription, cellular differentiation, proliferation and metabolism. As aberrant epigenetic modifications have been linked to the pathogenesis of systemic sclerosis (SSc), we aimed to investigate the role of Sirt1 in fibroblast activation.

METHODS

Sirt1 expression was analysed by real-time PCR, western blot and immunohistochemistry. Sirt1 signalling was modulated with the Sirt1 agonist resveratrol and by fibroblast-specific knockout. The role of Sirt1 was evaluated in bleomycin-induced skin fibrosis and in mice overexpressing a constitutively active transforming growth fac-tor-β (TGF-β) receptor I (TBRIact).

RESULTS

The expression of Sirt1 was decreased in patients with SSc and in experimental fibrosis in a TGF-β-dependent manner. Activation of Sirt1 potentiated the profibrotic effects of TGF-β with increased Smad reporter activity, elevated transcription of TGF-β target genes and enhanced release of collagen. In contrast, knockdown of Sirt1 inhibited TGF-β/SMAD signalling and reduced release of collagen in fibroblasts. Consistently, mice with fibroblast-specific knockdown of Sirt1 were less susceptible to bleomycin- or TBRIact-induced fibrosis.

CONCLUSIONS

We identified Sirt1 as a crucial regulator of TGF-β/Smad signalling in SSc. Although Sirt1 is downregulated, this decrease is not sufficient to counterbalance the excessive activation of TGF-β signalling in SSc. However, augmentation of this endogenous regulatory mechanism, for example, by knockdown of Sirt1, can effectively inhibit TGF-β signalling and exerts potent antifibrotic effects. Sirt1 may thus be a key regulator of fibroblast activation in SSc.

S100A4 amplifies TGF-β-induced fibroblast activation in systemic sclerosis

OBJECTIVES

S100A4 is a calcium binding protein with regulatory functions in cell homeostasis, proliferation and differentiation that has been shown to promote cancer progression and metastasis. In the present study, we evaluated the role of S100A4 in fibroblast activation in systemic sclerosis (SSc).

METHODS

The expression of S100A4 was analysed in human samples, murine models of SSc and in cultured fibroblasts by real-time PCR, immunohistochemistry and western blot. The functional role of S100A4 was evaluated using siRNA, overexpression, recombinant protein and S100A4 knockout (S100A4(-/-)) mice. Transforming growth factor β (TGF-β) signalling was assessed by reporter assays, staining for phosphorylated Smad2/3 and analyses of target genes.

RESULTS

The expression of S100A4 was increased in SSc skin and in experimental fibrosis in a TGF-β/Smad-dependent manner. Overexpression of S100A4 or stimulation with recombinant S100A4 induced an activated phenotype in resting normal fibroblasts. In contrast, knockdown of S100A4 reduced the pro-fibrotic effects of TGF-β and decreased the release of collagen. S100A4(-/-) mice were protected from bleomycin-induced skin fibrosis with reduced dermal thickening, decreased hydroxyproline content and lower myofibroblast counts. Deficiency of S100A4 also ameliorated fibrosis in the tight-skin-1 (Tsk-1) mouse model.

CONCLUSIONS

We characterised S100A4 as a downstream mediator of the stimulatory effects of TGF-β on fibroblasts in SSc. TGF-β induces the expression of S100A4 to stimulate the release of collagen in SSc fibroblasts and induce fibrosis. Since S100A4 is essentially required for the pro-fibrotic effects of TGF-β and neutralising antibodies against S100A4 are currently evaluated, S100A4 might be a candidate for novel antifibrotic therapies.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

Endocannabinoid signaling at the periphery: 50 years after THC

In 1964, the psychoactive ingredient of Cannabis sativa, Δ(9)-tetrahydrocannabinol (THC), was isolated. Nearly 30 years later the endogenous counterparts of THC, collectively termed endocannabinoids (eCBs), were discovered: N-arachidonoylethanolamine (anandamide) (AEA) in 1992 and 2-arachidonoylglycerol (2-AG) in 1995. Since then, considerable research has shed light on the impact of eCBs on human health and disease, identifying an ensemble of proteins that bind, synthesize, and degrade them and that together form the eCB system (ECS). eCBs control basic biological processes including cell choice between survival and death and progenitor/stem cell proliferation and differentiation. Unsurprisingly, in the past two decades eCBs have been recognized as key mediators of several aspects of human pathophysiology and thus have emerged to be among the most widespread and versatile signaling molecules ever discovered. Here some of the pioneers of this research field review the state of the art of critical eCB functions in peripheral organs. Our community effort is aimed at establishing consensus views on the relevance of the peripheral ECS for human health and disease pathogenesis, as well as highlighting emerging challenges and therapeutic hopes.

Inhibition of casein kinase II reduces TGFβ induced fibroblast activation and ameliorates experimental fibrosis

OBJECTIVES

Casein kinase II (CK2) is a constitutively active serine/threonine protein kinase that plays a key role in cellular transformation and tumorigenesis. The purpose of the study was to characterise whether CK2 contributes to the pathologic activation of fibroblasts in patients with SSc and to evaluate the antifibrotic potential of CK2 inhibition.

METHODS

Activation of CK2, JAK2 and STAT3 in human skin and in experimental fibrosis was analysed by immunohistochemistry. CK2 signalling was inhibited by the selective CK2 inhibitor 4, 5, 6, 7-Tetrabromobenzotriazole (TBB). The mouse models of bleomycin-induced and TGFβ receptor I (TBR)-induced dermal fibrosis were used to evaluate the antifibrotic potential of specific CK2 inhibition in vivo.

RESULT

Increased expression of CK2 was detected in skin fibroblasts of SSc patients. Inhibition of CK2 by TBB abrogated the TGFβ-induced activation of JAK2/STAT3 signalling and prevented the stimulatory effects of TGFβ on collagen release and myofibroblasts differentiation in cultured fibroblasts. Inhibition of CK2 prevented bleomycin-induced and TBR-induced skin fibrosis with decreased dermal thickening, lower myofibroblast counts and reduced accumulation of collagen. Treatment with TBB also induced regression of pre-established fibrosis. The antifibrotic effects of TBB were accompanied by reduced activation of JAK2/STAT3 signalling in vivo.

CONCLUSIONS

We provide evidence that CK2 is activated in SSc and contributes to fibroblast activation by regulating JAK2/STAT3 signalling. Inhibition of CK2 reduced the pro-fibrotic effects of TGFβ and inhibited experimental fibrosis. Targeting of CK2 may thus be a novel therapeutic approach for SSc and other fibrotic diseases.

The endocannabinoid system in advanced liver cirrhosis: pathophysiological implication and future perspectives

Endogenous cannabinoids (EC) are ubiquitous lipid signalling molecules providing different central and peripheral effects that are mediated mostly by the specific receptors CB1 and CB2. The EC system is highly upregulated during chronic liver disease and consistent experimental and clinical findings indicate that it plays a role in the pathogenesis of liver fibrosis and fatty liver disease associated with obesity, alcohol abuse and hepatitis C. Furthermore, a considerable number of studies have shown that EC and their receptors contribute to the pathogenesis of the cardio-circulatory disturbances occurring in advanced cirrhosis, such as portal hypertension, hyperdynamic circulatory syndrome and cirrhotic cardiomyopathy. More recently, the EC system has been implicated in the development of ascites, hepatic encephalopathy and the inflammatory response related to bacterial infection. Rimonabant, a selective CB1 antagonist, was the first drug acting on the EC system approved for the treatment of obesity. Unfortunately, it has been withdrawn from the market because of its neuropsychiatric side effects. Compounds able to target selectively the peripheral CB1 receptors are under evaluation. In addition, molecules stimulating CB2 receptor or modulating the activity of enzymes implicated in EC metabolism are promising areas of pharmacological research. Liver cirrhosis and the related complications represent an important target for the clinical application of these compounds.