Exploring organ-specific features of fibrogenesis using murine precision-cut tissue slices

Fibrosis is the hallmark of pathologic tissue remodelling in most chronic diseases. Despite advances in our understanding of the mechanisms of fibrosis, it remains uncured. Fibrogenic processes share conserved core cellular and molecular pathways across organs. In this study, we aimed to elucidate shared and organ-specific features of fibrosis using murine precision-cut tissue slices (PCTS) prepared from small intestine, liver and kidneys. PCTS displayed substantial differences in their baseline gene expression profiles: 70% of the extracellular matrix (ECM)-related genes were differentially expressed across the organs. Culture for 48 h induced significant changes in ECM regulation and triggered the onset of fibrogenesis in all PCTS in organ-specific manner. TGFβ signalling was activated during 48 h culture in all PCTS. However, the degree of its involvement varied: both canonical and non-canonical TGFβ pathways were activated in liver and kidney slices, while only canonical, Smad-dependent, cascade was involved in intestinal slices. The treatment with galunisertib blocked the TGFβRI/SMAD2 signalling in all PCTS, but attenuated culture-induced dysregulation of ECM homeostasis and mitigated the onset of fibrogenesis with organ-specificity. In conclusion, regardless the many common features in pathophysiology of organ fibrosis, PCTS displayed diversity in culture-induced responses and in response to the treatment with TGFβRI kinase inhibitor galunisertib, even though it targets a core fibrosis pathway. A clear understanding of the common and organ-specific features of fibrosis is the basis for developing novel antifibrotic therapies.     

Wnt/beta-catenin signaling: a promising new target for fibrosis diseases

Wnt/beta-catenin signaling is involved in virtually every aspect of embryonic development and also controls homeostatic self-renewal in a number of adult tissues. Recently, emerging evidence from researches of organ fibrosis suggest that sustained Wnt/beta-catenin pathway reactivation is linked to the pathogenesis of fibrotic disorders. Here we focus on Wnt/beta-catenin-related pathogenic effects in different organs, such as lung fibrosis, liver fibrosis, skin fibrosis and renal fibrosis. Additionally, Wnt/beta-catenin signaling works in a combinatorial manner with TGF-beta signaling in the process of fibrosis, and TGF-beta signaling can induce expression of Wnt/beta-catenin superfamily members and vice versa. Moreover, network analysis, based on pathway databases, revealed that key factors in the Wnt pathway were targeted by some differentially expressed microRNAs detected in fibrosis diseases. These findings demonstrated the crosstalks between Wnt/beta-catenin pathway and TGF-beta signalings, and microRNAs, highlighting the role of Wnts in organ fibrogenesis. Most importantly, nowadays there is a variety of Wnt pathway inhibitors which give us the potential therapeutic feasibility, modulation of the Wnt pathway may, therefore, present as a suitable and promising therapeutic strategy in the future.     

Hedgehog信号通路与脂肪细胞发育育

TGFβ、Wnt、FGF和Hedgehog（Hh)等信号通路是参与胚胎发育的关键信号通路.从果蝇到人类,Hh信号通路广泛存在并高度保守,在多种器官的发育过程中发挥重要作用. 脂肪细胞发育的过程包括多潜能干细胞向前脂肪细胞定向和脂肪细胞终末分化两个阶段.近年来,Hh信号通路在脂肪细胞发育过程中的作用逐渐成为研究热点.越来越多的研究表明,Hh信号通路抑制脂肪细胞发育.本文将对Hh信号通路抑制脂肪细胞发育的作用以及其发挥作用的阶段进行综述,并分析将该信号通路作为靶点治疗肥胖症及相关疾病的可行性.     

Signalling pathways involved in hypoxia‐induced renal fibrosis

Renal fibrosis is the common pathological hallmark of progressive chronic kidney disease (CKD) with diverse aetiologies. Recent researches have highlighted the critical role of hypoxia during the development of renal fibrosis as a final common pathway in end‐stage kidney disease (ESKD), which joints the scientist's attention recently to exploit the molecular mechanism underlying hypoxia‐induced renal fibrogenesis. The scaring formation is a multilayered cellular response and involves the regulation of multiple hypoxia‐inducible signalling pathways and complex interactive networks. Therefore, this review will focus on the signalling pathways involved in hypoxia‐induced pathogenesis of interstitial fibrosis, including pathways mediated by HIF, TGF‐β, Notch, PKC/ERK, PI3K/Akt, NF‐κB, Ang II/ROS and microRNAs. Roles of molecules such as IL‐6, IL‐18, KIM‐1 and ADO are also reviewed. A comprehensive understanding of the roles that these hypoxia‐responsive signalling pathways and molecules play in the context of renal fibrosis will provide a foundation towards revealing the underlying mechanisms of progression of CKD and identifying novel therapeutic targets. In the future, promising new effective therapy against hypoxic effects may be successfully translated into the clinic to alleviate renal fibrosis and inhibit the progression of CKD.     

MicroRNA signatures associated with thioacetamide-induced liver fibrosis in mice

Multiple etiologies of liver injury are associated with fibrosis in which the key event is the activation of hepatic stellate cells (HSCs). Although microRNAs (miRNAs) are reportedly involved in fibrogenesis, the complete array of miRNA signatures associated with the disease has yet to be elucidated. Here, deep sequencing analysis revealed that compared to controls, 80 miRNAs were upregulated and 21 miRNAs were downregulated significantly in the thioacetamide (TAA)-induced mouse fibrotic liver. Interestingly, 58 of the upregulated miRNAs were localized to an oncogenic miRNA megacluster upregulated in liver cancer. Differential expression of some of the TAA-responsive miRNAs was confirmed, and their human orthologs were similarly deregulated in TGF-β1-activated HSCs. Moreover, a functional analysis of the experimentally validated high-confidence miRNA targets revealed significant enrichment for the GO terms and KEGG pathways involved in HSC activation and liver fibrogenesis. This is the first comprehensive report of miRNAs profiles during TAA-induced mouse liver fibrosis.     

Innate recognition of microbial-derived signals in immunity and inflammation

Microbes generate a vast array of different types of conserved structural components called pathogen-associated molecular patterns(PAMPs),which canbe recognized by cells of the innate immune system.This recognition of "nonself" signatures occurs through host pattern recognition receptors(PRRs),suggesting that microbial-derived signals are good targets for innate immunity to discriminate between self- and nonself.Such PAMP-PRR interactions trigger multiple but distinct downstream signaling cascades,subsequently leading to production of proinflammatory cytokines and interferons that tailor immune responses to particular microbes.Aberrant PRR signals have been associated with various inflammatory diseases and fine regulation of PRR signaling is essential for avoiding excessive inflammatory immune responses and maintaining immune homeostasis.In this review we summarize the ligands and signal transduction pathways of PRRs and highlight recent progress of the mechanisms involved in microbe-specific innate immune recognition during immune responses and inflammation,which may provide new targets for therapeutic intervention to the inflammatory disorders.     

数据挖掘探究肝-肾-肺纤维化的关键基因

当前用于纤维化治疗的方法很少且疗效有限,为进一步了解纤维化的消退机制以发现潜在的治疗靶点。从Gene Expression Omnibus(GEO)数据库中选取了三个具有代表性的小鼠肝、肾、肺纤维化样本的mRNA数据集,使用GEO2R工具和Venn分析识别了差异表达基因(Differentially Expressed Genes, DEGs)。通过Webgestalt在线工具对DEGs进行基因功能富集。蛋白质-蛋白质相互作用(Protein-Protein Interactions, PPI)网络是由STRING数据库生成的。然后利用CytoHubba插件探索了关键基因,分别选取了三器官共有DEG和肝特异性DEG中MCC (Maximal Clique Centrality)得分最高的前10个作为关键基因。研究中整合分析了基于小鼠模型的肝-肾-肺纤维化的数据集,GSE36066和GSE97546用于第一轮的DEG分析,由于研究除了探究三种器官纤维化共有差异基因,也进一步探究了肝纤维化特有关键基因,所以引入另外一个肝纤维化数据集GSE55747用于验证分析。结果识别出58个肝肺肾纤维化共有DEG和 85个肝纤维化特异性DEG。功能富集分析表明,共有DEG主要在免疫反应和炎症反应过程中富集。肝纤维化特有DEG与脂质和脂肪酸代谢过程有关。之后通过PPI网络选择了20个关键基因。为了评估这些关键基因成为潜在靶点的可能性,进一步分析了它们的成药性(Druggability)。得出以下结论:TYROBP,FCGR3B,ALOX5AP和CD14或可成为纤维化治疗的潜在靶点,CYP8B1和UGT2A3则可能与非酒精性脂肪性肝病(Non-alcoholic Fatty Liver Disease, NAFLD)或非酒精性脂肪性肝炎(Non-Alcoholic Steato-Hepatitis , NASH)相关。对于基因FCGR1B,C1QB,LY86和CD53,目前没有直接的研究证据表明其与纤维化相关,需要进一步验证它们在纤维化发生过程中的功能。     

Backstage players of fibrosis: NOX4, mTOR,HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role.The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins.Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development.In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.     

MicroRNAs在系统性硬化症纤维化中的作用及机制

微RNA（microRNAs,miRNAs）是在基因编码中起负性调控作用的内源性短链非编码RNA（non-coding RNAs,ncRNAs）,是生理和病理过程中基因表达必不可少的转录后调控物。miRNAs占人类基因组的1%～2%,通过与各自的mRNA结合并抑制其翻译,调节大于50%的人类基因及60%的哺乳动物蛋白质编码基因。系统性硬化症（systemic sclerosis,SSc）的发病机制由复杂的miRNAs网络调控。这些miRNAs位于与SSc纤维化相关的基因组区域,通过参与调节重要的细胞信号通路,如TGF-β、Wnt/β-catenin、TLR-4、IL和PDGF-β等,在SSc纤维化过程中发挥作用。同时,还与细胞信号转导、基质修复与重塑、成纤维细胞凋亡、胶原蛋白质合成和细胞外基质（extracellular matrix,ECM）沉积等相关。充分了解miRNAs在SSc纤维化中的重要性,有助于为SSc的诊断提供新的生物标记,为治疗提供新策略。本文综述了miRNAs在SSc纤维化过程中参与调节的这些复杂细胞信号通路的作用及机制,以期为SSc诊断、严重程度判断、预后评估,以及寻求潜在治疗靶点提供新思路。     

Integrated analysis of co-expressed MAP kinase substrates in Arabidopsis thaliana

MAP kinase (MAPK) signal transduction cascades are conserved eukaryotic pathways that modulate stress responses and developmental processes. In a recent report we have identified novel Arabidopsis MAPKK/MAPK/Substrate signaling pathways using microarrays containing 2,158 unique Arabidopsis proteins. Subsequently, several WRKY and TGA targets phosphorylated by MAPKs were verified in planta. We have also reported that specific MAPKK/MAPK modules expressed in Nicotiana benthamiana induced a cell death phenotype related to the immune response. We have generated a MAPK phosphorylation network based on our protein microarray experimental data. Here we further analyze our network by integrating phosphorylation and gene expression information to identify biologically relevant signaling modules. We have identified 108 phosphorylation events that occur among 96 annotated genes with highly similar pairwise expression profiles. Our analysis brings a new perspective on MAPK signaling by revealing new relationships between components of signaling pathways.Key words: MAPK, protein microarray, network, cell death, co-expression, signaling     

Targeting the TGFbeta, endothelin-1 and CCN2 axis to combat fibrosis in scleroderma

Fibrosis affects organs such as the skin, liver, kidney and lung and is a cause of significant morbidity. There is no therapy for fibrosis. Recent significant molecular insights into the signaling underlying the fibrosis in the autoimmune connective tissue disease scleroderma (systemic sclerosis, SSc) have been made. Transforming growth factor beta (TGFbeta) signaling is a major contributor to fibrogenesis, including in SSc. However, it is now appreciated that TGFbeta-dependent and TGFbeta-independent mechanisms play key roles in the pathological fibrosis in SSc. In particular the potent pro-fibrotic proteins endothelin-1 (ET-1) and CCN2 (connective tissue growth factor, CTGF) are believed to play an essential role in this process. This review summarizes these recent crucial observations.     

Mechanistic understanding of β-cryptoxanthin and lycopene in cancer prevention in animal models

To better understand the potential function of carotenoids in the chemoprevention of cancers, mechanistic understanding of carotenoid action on genetic and epigenetic signaling pathways is critically needed for human studies. The use of appropriate animal models is the most justifiable approach to resolve mechanistic issues regarding protective effects of carotenoids at specific organs and tissue sites. While the initial impetus for studying the benefits of carotenoids in cancer prevention was their antioxidant capacity and pro-vitamin A activity, significant advances have been made in the understanding of the action of carotenoids with regards to other mechanisms. This review will focus on two common carotenoids, provitamin A carotenoid β-cryptoxanthin and non-provitamin A carotenoid lycopene, as promising chemopreventive agents or chemotherapeutic compounds against cancer development and progression. We reviewed animal studies demonstrating that β-cryptoxanthin and lycopene effectively prevent the development or progression of various cancers and the potential mechanisms involved. We highlight recent research that the biological functions of β-cryptoxanthin and lycopene are mediated, partially via their oxidative metabolites, through their effects on key molecular targeting events, such as NF-κB signaling pathway, RAR/PPARs signaling, SIRT1 signaling pathway, and p53 tumor suppressor pathways. The molecular targets by β-cryptoxanthin and lycopene, offer new opportunities to further our understanding of common and distinct mechanisms that involve carotenoids in cancer prevention.This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.     

Discoidin domain receptor 1 interactions with myosin motors contribute to collagen remodeling and tissue fibrosis

Discoidin Domain Receptor (DDR) genes and their homologues have been identified in sponges, worms and flies. These genes code for proteins that are implicated in cell adhesion to matrix proteins. DDRs are now recognized as playing central regulatory roles in several high prevalence human diseases, including invasive cancers, atherosclerosis, and organ fibrosis. While the mechanisms by which DDRs contribute to these diseases are just now being delineated, one of the common themes involves cell adhesion to collagen and the assembly and organization of collagen fibers in the extracellular matrix. In mammals, the multi-functional roles of DDRs in promoting cell adhesion to collagen fibers and in mediating collagen-dependent signaling, suggest that DDRs contribute to multiple pathways of extracellular matrix remodeling, which are centrally important processes in health and disease. In this review we consider that interactions of the cytoplasmic domains of DDR1 with cytoskeletal motor proteins may contribute to matrix remodeling by promoting collagen fiber alignment and compaction. Poorly controlled collagen remodeling with excessive compaction of matrix proteins is a hallmark of fibrotic lesions in many organs and tissues that are affected by infectious, traumatic or chemical-mediated injury. An improved understanding of the mechanisms by which DDRs mediate collagen remodeling and collagen-dependent signaling could suggest new drug targets for treatment of fibrotic diseases.     

Signaling pathways involving adenosine A<Subscript>2A</Subscript> and A<Subscript>2B</Subscript> receptors in wound healing and fibrosis

Collagen and matrix deposition by fibroblasts is an essential part of wound healing but also contributes to pathologic remodeling of organs leading to substantial morbidity and mortality. Adenosine, a small molecule generated extracellularly from adenine nucleotides as a result of direct stimulation, hypoxia, or injury, acts via a family of classical seven-pass G protein-coupled protein receptors, A_2A and A_2B, leading to generation of cAMP and activation of downstream targets such as PKA and Epac. These effectors, in turn, lead to fibroblast activation and collagen synthesis. The regulatory actions of these receptors likely involve multiple interconnected pathways, and one of the more interesting aspects of this regulation is opposing effects at different levels of cAMP generated. Additionally, adenosine signaling contributes to fibrosis in organ-specific ways and may have opposite effects in different organs. The development of drugs that selectively target these receptors and their signaling pathways will disrupt the pathogenesis of fibrosis and slow or arrest the progression of the important diseases they underlie.     

Right place,right time: Spatiotemporal light regulation of plant growth and development

Recent advances in our understanding of the roles of photoreceptors in light-dependent regulation of plant growth and development have been rapid and significant. Developments have been reported for numerous plant photoreceptor signaling pathways, yet researchers have made the most progress in increasing our comprehension of the roles of phytochrome family members, as well as the intracellular roles of phytochromes and phytochrome-interacting proteins in light-dependent signaling. An understudied, but vitally important, area of phytochrome biology centers on the roles phytochromes play in intercellular and interorgan signaling at the molecular level that results in the coordination of growth responses between distinct tissues and organs. This frontier of research into the spatiotemporal roles of phytochromes, and more generally plant photoreceptors, which is only beginning to be investigated and understood at the molecular genetic level, has a rich history of physiological data.Key words: cryptochrome, photomorphogenesis, photoreception, photoreceptor, phytochrome, spatiotemporal