Value of serum and synovial fluid activin A and inhibin A in some rheumatic diseases

Serum Activin A Is a Novel Biomarker of Endoscopic Activity in Ulcerative Colitis

Background

Endoscopic healing (EH) is the long-term therapeutic goal for ulcerative colitis (UC). Since repeated colonoscopies are inconvenient and invasive, a surrogate biomarker for endoscopic activity is needed. Activin A is one of the transforming growth factor-β superfamily of proteins and has been shown to be associated with intestinal inflammation.

Methods

This single-center observational study included 27 Japanese patients with UC in clinical remission who underwent colonoscopy and blood sampling. We investigated the correlations between laboratory parameters, including serum activin A levels, and endoscopic activity, classified by the Mayo endoscopic subscore (MES) in these patients.

Results

This study included 15 males and 12 females. The median age was 44.0 years. In terms of endoscopic activity, five patients were diagnosed with MES 0, 14 patients with MES 1, seven patients with MES 2, and one patient with MES 3. The median serum activin level was 134.8 pg/mL (interquartile range (IQR), 105.3 - 188.1). Serum activin A levels were significantly correlated with the MES (Spearman's rank correlation coefficient r = 0.591, P = 0.001), which was better than that of C-reactive protein (CRP) (r = 0.487, P = 0.010). In the comparison between the EH group (MES 0) and non-EH group (MES 1-3), patients without EH had significantly higher serum activin A levels (Mann-Whitney U test, P = 0.047). A cutoff value of 133.6 pg/mL indicated non-EH with a sensitivity and specificity of 0.682 and 1.000, respectively. The area under the curve (AUC) of serum activin A for detecting non-EH was 0.791 (95% confidence interval (CI), 0.618 - 0.964), while that of CRP was 0.723 (95% CI, 0.504 - 0.941).

Conclusions

The serum activin A level is a potential novel biomarker of endoscopic activity in UC.

Single-cell transcriptomics of human cholesteatoma identifies an activin A-producing osteoclastogenic fibroblast subset inducing bone destruction

Cholesteatoma, which potentially results from tympanic membrane retraction, is characterized by intractable local bone erosion and subsequent hearing loss and brain abscess formation. However, the pathophysiological mechanisms underlying bone destruction remain elusive. Here, we performed a single-cell RNA sequencing analysis on human cholesteatoma samples and identify a pathogenic fibroblast subset characterized by abundant expression of inhibin βA. We demonstrate that activin A, a homodimer of inhibin βA, promotes osteoclast differentiation. Furthermore, the deletion of inhibin βA /activin A in these fibroblasts results in decreased osteoclast differentiation in a murine model of cholesteatoma. Moreover, follistatin, an antagonist of activin A, reduces osteoclastogenesis and resultant bone erosion in cholesteatoma. Collectively, these findings indicate that unique activin A-producing fibroblasts present in human cholesteatoma tissues are accountable for bone destruction via the induction of local osteoclastogenesis, suggesting a potential therapeutic target.

Plasma Exosomal Non-Coding RNA Profile Associated with Renal Damage Reveals Potential Therapeutic Targets in Lupus Nephritis

Despite considerable progress in our understanding of systemic lupus erythematosus (SLE) pathophysiology, patient diagnosis is often deficient and late, and this has an impact on disease progression. The aim of this study was to analyze non-coding RNA (ncRNA) packaged into exosomes by next-generation sequencing to assess the molecular profile associated with renal damage, one of the most serious complications of SLE, to identify new potential targets to improve disease diagnosis and management using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The plasma exosomes had a specific ncRNA profile associated with lupus nephritis (LN). The three ncRNA types with the highest number of differentially expressed transcripts were microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and piwi-interacting RNAs (piRNAs). We identified an exosomal 29-ncRNA molecular signature, of which 15 were associated only with LN presence; piRNAs were the most representative, followed by lncRNAs and miRNAs. The transcriptional regulatory network showed a significant role for four lncRNAs (LINC01015, LINC01986, AC087257.1 and AC022596.1) and two miRNAs (miR-16-5p and miR-101-3p) in network organization, targeting critical pathways implicated in inflammation, fibrosis, epithelial-mesenchymal transition and actin cytoskeleton. From these, a handful of potential targets, such as transforming growth factor-β (TGF-β) superfamily binding proteins (activin-A, TGFB receptors, etc.), WNT/β-catenin and fibroblast growth factors (FGFs) have been identified for use as therapeutic targets of renal damage in SLE.

Deciphering novel common gene signatures for rheumatoid arthritis and systemic lupus erythematosus by integrative analysis of transcriptomic profiles

Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE) are the two highly prevalent debilitating and sometimes life-threatening systemic inflammatory autoimmune diseases. The etiology and pathogenesis of RA and SLE are interconnected in several ways, with limited knowledge about the underlying molecular mechanisms. With the motivation to better understand shared biological mechanisms and determine novel therapeutic targets, we explored common molecular disease signatures by performing a meta-analysis of publicly available microarray gene expression datasets of RA and SLE. We performed an integrated, multi-cohort analysis of 1088 transcriptomic profiles from 14 independent studies to identify common gene signatures. We identified sixty-two genes common among RA and SLE, out of which fifty-nine genes (21 upregulated and 38 downregulated) had similar expression profiles in the diseases. However, antagonistic expression profiles were observed for ACVR2A, FAM135A, and MAPRE1 genes. Thirty genes common between RA and SLE were proposed as robust gene signatures, with persistent expression in all the studies and cell types. These gene signatures were found to be involved in innate as well as adaptive immune responses, bone development and growth. In conclusion, our analysis of multicohort and multiple microarray datasets would provide the basis for understanding the common mechanisms of pathogenesis and exploring these gene signatures for their diagnostic and therapeutic potential.

Deletion of activin A in mesenchymal but not myeloid cells ameliorates disease severity in experimental arthritis

Objective

The aim of this study was to assess the extent and the mechanism by which activin A contributes to progressive joint destruction in experimental arthritis and which activin A-expressing cell type is important for disease progression.

Methods

Levels of activin A in synovial tissues were evaluated by immunohistochemistry, cell-specific expression and secretion by PCR and ELISA, respectively. Osteoclast (OC) formation was assessed by tartrat-resistant acid phosphatase (TRAP) staining and activity by resorption assay. Quantitative assessment of joint inflammation and bone destruction was performed by histological and micro-CT analysis. Immunoblotting was applied for evaluation of signalling pathways.

Results

In this study, we demonstrate that fibroblast-like synoviocytes (FLS) are the main producers of activin A in arthritic joints. Most significantly, we show for the first time that deficiency of activin A in arthritic FLS (ActβA^d/d ColVI-Cre) but not in myeloid cells (ActβA^d/d LysM-Cre) reduces OC development in vitro, indicating that activin A promotes osteoclastogenesis in a paracrine manner. Mechanistically, activin A enhanced OC formation and activity by promoting the interaction of activated Smad2 with NFATc1, the key transcription factor of osteoclastogenesis. Consistently, ActβA^d/d LysM-Cre hTNFtg mice did not show reduced disease severity, whereas deficiency of activin A in ColVI-Cre-expressing cells such as FLS highly diminished joint destruction reflected by less inflammation and less bone destruction.

Conclusions

The results highly suggest that FLS-derived activin A plays a crucial paracrine role in inflammatory joint destruction and may be a promising target for treating inflammatory disorders associated with OC formation and bone destruction like rheumatoid arthritis.

Synovial Fluid Biomarkers in Knee Osteoarthritis: A Systematic Review and Quantitative Evaluation Using BIPEDs Criteria

OBJECTIVE

The aim of this systematic review was to analyze the evidence about the efficacy of the several synovial fluid (SF) biomarkers proposed for knee osteoarthritis (OA), categorizing them by both molecular characteristics and clinical use according to the BIPEDs criteria, to provide a comprehensive and structured overview of the current literature.

DESIGN

A systematic review was performed in May 2020 on PubMed, Cochrane Library, and Embase databases about SF biomarkers in patients with knee OA. The search was limited to articles in the last 20 years on human studies, involving patients with knee OA, reporting SF biomarkers. The evidence for each selected SF biomarker was quantified according to the 6 categories of BIPEDs classification.

RESULTS

A total of 159 articles were included in the qualitative data synthesis and 201 different SF biomarkers were identified. Among these, several were investigated multiple times in different articles, for a total of 373 analyses. The studies included 13,557 patients with knee OA. The most promising SF biomarkers were C4S, IL-6, IL-8, Leptin, MMP-1/3, TIMP-1, TNF-α, and VEGF. The "burden of disease" and "diagnostic" categories were the most represented with 132 and 106 different biomarkers, respectively.

CONCLUSIONS

The systematic review identified numerous SF biomarkers. However, despite the high number of studies on the plethora of identified molecules, the evidence about the efficacy of each biomarker is supported by limited and often conflicting findings. Further research efforts are needed to improve the understanding of SF biomarkers for a better management of patients with knee OA.

Activin A Expressed in Rheumatoid Synovial Cells Downregulates TNFα-Induced CXCL10 Expression and Osteoclastogenesis

OBJECTIVE

Activin A is known to be highly expressed in rheumatoid synovium. In the present study, we investigated the effect of inflammatory cytokines on activin A production and its role in rheumatoid inflammation using freshly prepared rheumatoid synovial cells (fresh-RSC).

METHODS

Fresh-RSC from patients with rheumatoid arthritis were obtained and stimulated with multiple cytokines for activin A production. Gene expression levels of activin A and inflammatory cytokines were determined by quantitative PCR (qPCR) analysis. An enzyme-linked immunosorbent assay (ELISA) was used to measure activin A and CXCL10 in culture supernatants. The osteoclasts generated from human peripheral monocytes by RANKL stimulation were identified by tartrate-resistant acid phosphatase staining and bone resorption assay using Osteo plate. The expression levels of NFATc1 and cathepsin K, critical intracellular proteins for osteoclastogenesis, were determined by Western blotting.

RESULTS

Activin A production in fresh-RSC was markedly enhanced by the synergistic effect of TGF-β1 with inflammatory cytokines, including TNFα, IL-1β, and IL-6. Activin A inhibited TNFα-induced CXCL10, an important chemoattractant for pathogen-activated T cells and monocytes of osteoclast precursors, but it did not affect the expression of inflammatory cytokines and chemokines. In addition, activin A directly inhibited the expression of NFATc1 and cathepsin K, as well as osteoclast formation in human samples.

CONCLUSION

Our data indicated that TGF-β1 is involved in the expression of activin A at inflamed joints. Activin A mainly exerts an anti-inflammatory action, which prevents joint damage via the regulation of CXCL10 and osteoclastogenesis.

Activin-A in the regulation of immunity in health and disease

The TGF-β superfamily of cytokines plays pivotal roles in the regulation of immune responses protecting against or contributing to diseases, such as, allergy, autoimmunity and cancer. Activin-A, a member of the TGF-β superfamily, was initially identified as an inducer of follicle-stimulating hormone secretion. Extensive research over the past decades illuminated fundamental roles for activin-A in essential biologic processes, including embryonic development, stem cell maintenance and differentiation, haematopoiesis, cell proliferation and tissue fibrosis. Activin-A signals through two type I and two type II receptors which, upon ligand binding, activate their kinase activity, phosphorylate the SMAD2 and 3 intracellular signaling mediators that form a complex with SMAD4, translocate to the nucleus and activate or silence gene expression. Most immune cell types, including macrophages, dendritic cells (DCs), T and B lymphocytes and natural killer cells have the capacity to produce and respond to activin-A, although not in a similar manner. In innate immune cells, including macrophages, DCs and neutrophils, activin-A exerts a broad range of pro- or anti-inflammatory functions depending on the cell maturation and activation status and the spatiotemporal context. Activin-A also controls the differentiation and effector functions of Th cell subsets, including Th9 cells, T_FH cells, Tr1 Treg cells and Foxp3⁺ Treg cells. Moreover, activin-A affects B cell responses, enhancing mucosal IgA secretion and inhibiting pathogenic autoantibody production. Interestingly, an array of preclinical and clinical studies has highlighted crucial functions of activin-A in the initiation, propagation and resolution of human diseases, including autoimmune diseases, such as, systemic lupus erythematosus, rheumatoid arthritis and pulmonary alveolar proteinosis, in allergic disorders, including allergic asthma and atopic dermatitis, in cancer and in microbial infections. Here, we provide an overview of the biology of activin-A and its signaling pathways, summarize recent studies pertinent to the role of activin-A in the modulation of inflammation and immunity, and discuss the potential of targeting activin-A as a novel therapeutic approach for the control of inflammatory diseases.

Activin A in Mammalian Physiology

Activins are dimeric glycoproteins belonging to the transforming growth factor beta superfamily and resulting from the assembly of two beta subunits, which may also be combined with alpha subunits to form inhibins. Activins were discovered in 1986 following the isolation of inhibins from porcine follicular fluid, and were characterized as ovarian hormones that stimulate follicle stimulating hormone (FSH) release by the pituitary gland. In particular, activin A was shown to be the isoform of greater physiological importance in humans. The current understanding of activin A surpasses the reproductive system and allows its classification as a hormone, a growth factor, and a cytokine. In more than 30 yr of intense research, activin A was localized in female and male reproductive organs but also in other organs and systems as diverse as the brain, liver, lung, bone, and gut. Moreover, its roles include embryonic differentiation, trophoblast invasion of the uterine wall in early pregnancy, and fetal/neonate brain protection in hypoxic conditions. It is now recognized that activin A overexpression may be either cytostatic or mitogenic, depending on the cell type, with important implications for tumor biology. Activin A also regulates bone formation and regeneration, enhances joint inflammation in rheumatoid arthritis, and triggers pathogenic mechanisms in the respiratory system. In this 30-yr review, we analyze the evidence for physiological roles of activin A and the potential use of activin agonists and antagonists as therapeutic agents.

Mechanisms involved in enhancement of osteoclast formation by activin-A

Several growth factors in bone tissues are reported to be associated with osteoclastogenesis. Activin-A, a member of the transforming growth factor-β (TGF-β) family is known to be present in bone tissues and an important regulator in osteoclastogenesis with SMAD-mediated signaling being crucial for inducing osteoclast differentiation. In the present study, we examined the effect and underlying mechanisms of activin-A on osteoclast formation in vitro culture systems. Activin-A enhanced osteoclast formation in both mouse bone marrow cells and monocyte/macrophage cell line RAW 264.7 cells induced by receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL) and/or macrophage stimulating factor (M-CSF). We also found that activin-A stimulated bone resorption and actin ring formation induced by RANKL and/or M-CSF. Furthermore, activin-A enhanced RANKL-induced expression of nuclear factor of activated T cell cytoplasmic 1 (NFATc1), a key regulator of osteoclastogenesis, thereby increasing osteoclastogenesis-related marker gene expression, including tartrate-resistant acid phosphatase, osteoclast stimulatory transmembrane protein, and cathepsin K. Blockage of receptor binding by follistatin, an activing-binding protein suppressed the activin-A-mediated stimulation of NFATc1. In addition, activin-A increased RANKL-induced c-fos expression without significantly affecting the NF-κB and mitogen-activated protein kinase (MAPK) signaling pathway. Pre-treatment of the cells with a specific inhibitor of SMAD2/3 attenuated the activin-A-induced expression of NFATc1 and co-immunoprecipitation assay revealed that treatment with activin-A increased physical interaction of phosphorylated-c-fos and phosphorylated-SMAD2 protein induced by RANKL. These results suggest that activin-A enhances RANKL-induced osteoclast formation mediated by interaction of c-fos and smad2/3.

Involvement of infiltrating macrophage-derived activin A in the progression of renal damage in MRL-lpr mice

Lupus nephritis is a life-threatening complication of systemic lupus erythematosus (SLE). Various growth factors, cytokines, and chemokines are implicated in the development of SLE. However, the pathophysiological processes involved in the development of lupus nephritis still remain unclear. In this study, we examined the involvement of activin A, a member of the transforming growth factor β (TGF-β) superfamily, in the progression of renal damage in lupus-prone MRL- lpr mice. Activin A was not expressed in the kidneys of control MRL-MpJ mice but was detectable in perivascular infiltrating cluster of differentiation 68 (CD68)-positive cells in the kidneys of MRL- lpr mice. Urinary activin A, which was also absent in MRL-MpJ mice, was detectable in MRL- lpr mice from 16 wk onward. Urinary activin A levels were significantly correlated with the number of perivascular inflammatory cell layers, the number of crescentic glomeruli, and the percentage of Elastica van Gieson (EVG)-positive fibrotic areas, but not with urinary protein levels or serum activin A. When activin action was blocked in vivo by the intraperitoneal administration of an activin antagonist, follistatin, the number of crescentic glomeruli, percentage of EVG-positive fibrotic areas, CD68-positive cell infiltration, and proteinuria were significantly reduced in a dose-dependent manner. These data suggest that infiltrating macrophage-derived activin A is involved in the progression of renal damage in MRL- lpr mice.

Smad-dependent mechanisms of inflammatory bone destruction

Homeostatic bone remodelling becomes disturbed in a variety of pathologic conditions that affect the skeleton, including inflammatory diseases. Rheumatoid arthritis is the prototype of an inflammatory arthritis characterised by chronic inflammation, progressive cartilage destruction and focal bone erosions and is a prime example for a disease with disturbed bone homeostasis. The inflammatory milieu favours the recruitment and activation of osteoclasts, which have been found to be the cells that are primarily responsible for bone erosions in many animal models of inflammatory arthritis. Among the inflammatory modulators, members of the transforming growth factor (TGF)-β super family are shown to be important regulators in osteoclastogenesis with Smad-mediated signalling being crucial for inducing osteoclast differentiation. These findings have opened a new field for exploring mechanisms of osteoclast differentiation under inflammatory conditions. Recent studies have shown that the TGF-β superfamily members TGF-β1, myostatin and activin A directly regulate osteoclast differentiation through mechanisms that depend on the RANKL–RANK interplay. These growth factors transduce their signals through type I and II receptor serine/threonine kinases, thereby activating the Smad pathway. In this review, we describe the impact of inflammation-induced Smad signalling in osteoclast development and subsequently bone erosion in rheumatoid arthritis.

Kinetics of gene expression and bone remodelling in the clinical phase of collagen-induced arthritis

Introduction

Pathological bone changes differ considerably between inflammatory arthritic diseases and most studies have focused on bone erosion. Collagen-induced arthritis (CIA) is a model for rheumatoid arthritis, which, in addition to bone erosion, demonstrates bone formation at the time of clinical manifestations. The objective of this study was to use this model to characterise the histological and molecular changes in bone remodelling, and relate these to the clinical disease development.

Methods

A histological and gene expression profiling time-course study on bone remodelling in CIA was linked to onset of clinical symptoms. Global gene expression was studied with a gene chip array system.

Results

The main histopathological changes in bone structure and inflammation occurred during the first two weeks following the onset of clinical symptoms in the joint. Hereafter, the inflammation declined and remodelling of formed bone dominated.

Global gene expression profiling showed simultaneous upregulation of genes related to bone changes and inflammation in week 0 to 2 after onset of clinical disease. Furthermore, we observed time-dependent expression of genes involved in early and late osteoblast differentiation and function, which mirrored the histopathological bone changes. The differentially expressed genes belong to the bone morphogenetic pathway (BMP) and, in addition, include the osteoblast markers integrin-binding sialoprotein (Ibsp), bone gamma-carboxyglutamate protein (Bglap1), and secreted phosphoprotein 1 (Spp1). Pregnancy-associated protein A (Pappa) and periostin (Postn), differentially expressed in the early disease phase, are proposed to participate in bone formation, and we suggest that they play a role in early bone formation in the CIA model. Comparison to human genome-wide association studies (GWAS) revealed differential expression of several genes associated with human arthritis.

Conclusions

In the CIA model, bone formation in the joint starts shortly after onset of clinical symptoms, which results in bony fusion within one to two weeks. This makes it a candidate model for investigating the relationship between inflammation and bone formation in inflammatory arthritis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0531-7) contains supplementary material, which is available to authorized users.

Macrophages from the synovium of active rheumatoid arthritis exhibit an activin A-dependent pro-inflammatory profile

Rheumatoid arthritis (RA) is a chronic inflammatory disease whose pathogenesis and severity correlates with the presence of macrophage-derived pro-inflammatory cytokines within the inflamed synovium. Macrophage-derived cytokines fuel the pathological processes in RA and are targets of clinically successful therapies. However, although macrophage polarization determines cytokine production, the polarization state of macrophages in RA joints remains poorly defined. To dissect the molecular basis for the tissue-damaging effects of macrophages in RA joints, we undertook the phenotypic and transcriptomic characterization of ex vivo isolated CD14(+) RA synovial fluid (RA-SF) macrophages. Flow cytometry and gene profiling indicated that RA-SF macrophages express pro-inflammatory polarization markers (MMP12, EGLN3, CCR2), lack expression of markers associated with homeostatic and anti-inflammatory polarization (IGF1, HTR2B) and exhibit a transcriptomic profile that resembles the activin A-dependent gene signature of pro-inflammatory in vitro-generated macrophages. In fact, high levels of Smad-activating activin A were found in RA-SF and, accordingly, the Smad signalling pathway was activated in ex vivo-isolated RA-SF macrophages. In vitro experiments on monocytes and macrophages indicated that RA-SF promoted the acquisition of pro-inflammatory markers (INHBA, MMP12, EGLN3, CCR2) but led to a significant reduction in the expression of genes associated with homeostasis and inflammation resolution (FOLR2, SERPINB2, IGF1, CD36), thus confirming the pro-inflammatory polarization ability of RA-SF. Importantly, the macrophage-polarizing ability of RA-SF was inhibited by an anti-activin A-neutralizing antibody, thus demonstrating that activin A mediates the pro-inflammatory macrophage-polarizing ability of RA-SF. Moreover, and in line with these findings, multicolour immunofluorescence evidenced that macrophages within RA synovial membranes (RA-SM) also express pro-inflammatory polarization markers whose expression is activin A-dependent. Altogether, our results demonstrate that macrophages from RA synovial fluids and membranes exhibit an MMP12(+) EGLN3(+) CCR2(+) pro-inflammatory polarization state whose acquisition is partly dependent on activin A from the synovial fluid.

Angiogenic cytokine expression profiles in plasma and synovial fluid of primary knee osteoarthritis

PURPOSE

The aim of this study was to compare angiogenic cytokine levels in knee osteoarthritis (OA) patients and healthy controls and to investigate the relationships between angiogenic cytokines and the OA severity.

METHODS

Thirty-one knee OA patients and 15 healthy controls were recruited. Nine angiogenic cytokines (angiopoietin-2, follistatin, granulocyte-colony stimulating factor (G-CSF), hepatocyte growth factor (HGF), interleukin (IL)-8, leptin, platelet-derived growth factor-BB (PDGF-BB), platelet endothelial cell adhesion molecule (PECAM)-1, and vascular endothelial growth factor (VEGF)) in plasma and synovial fluid were measured using a multiplex immunoassay.

RESULTS

PECAM-1, HGF, VEGF, angiopoietin-2, follistatin, G-CSF, and IL-8 concentrations in plasma were significantly higher in OA patients than those in controls. Plasma angiopoietin-2 was significantly greater in advanced OA than in early OA. Synovial fluid VEGF was positively correlated with the severity (r = 0.367, P = 0.04). Plasma follistatin was significantly lower in advanced knee OA than in early OA and was negatively correlated with the severity (r = -0.374, P < 0.05).

CONCLUSIONS

Angiogenic cytokine concentrations in plasma can distinguish between controls and OA patients. Local and circulating levels of angiogenic cytokines could give an insight into the pathophysiology of OA. Follistatin, angiopoietin-2, and VEGF may have potential as biochemical markers for the assessment of OA severity.

Analysis of differentially expressed genes between rheumatoid arthritis and osteoarthritis based on the gene co-expression network

The aim of the current study was to investigate disease-associated genes and related molecular mechanisms of osteoarthritis (OA) and rheumatoid arthritis (RA). Using GSE7669 datasets downloaded from Gene Expression Omnibus databases, the differentially expressed genes (DEGs) between RA and OA synovial fibroblasts (SFBs) (n=6 each) were screened. DEG-associated co-expression and topological properties were analyzed to determine the rank of disease-associated genes. Specifically, the fold change of differentially expressed genes, the clustering coefficient and the degree of differential gene co-expression were integrated to determine the disease-associated gene ranking. The underlying molecular mechanisms of these crucial disease-associated genes were investigated by gene ontology (GO) enrichment analysis. A total of 1313 DEGs, including 1068 upregulated genes and 245 downregulated genes were observed. The top 20 disease-associated genes were identified, including proteoglycan 4, inhibin β B, carboxypeptidase M, alcohol dehydrogenase 1C and integrin β2. The major GO biological processes of these top 20 disease-associated genes were highly involved in the immune system, such as responses to stimuli, immune responses and inflammatory responses. This large-scale gene expression study observed disease-associated genes and their associated GO function in RA and OA, which may provide opportunities for biomarker development and novel insights into the molecular mechanisms of these two diseases.

Role of activin A in carbon tetrachloride-induced acute liver injury

AIM: To investigate the expression and role of activin A in a mouse model of acute chemical liver injury.

METHODS: Acute liver injury in C57BL/6 male mice was induced by intraperitoneal injection with carbon tetrachloride (CCl₄) (0.5 mL/kg, body weight) dissolved in olive oil (1:19 v/v). Mice were sacrificed 1, 3, 5 and 7 d after the treatment. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum were examined and pathological changes of liver observed by hematoxylin and eosin staining to evaluate the liver injury. Activin A protein levels in serum and hepatic tissue homogenate of mice were detected by enzyme-linked immunosorbent assay, and the expression pattern of activin A protein in livers of mice was examined by immunohistochemistry. Activin type IIA receptor (ActRIIA) and Smad3 expressions in the liver were analyzed by real-time quantitative reverse transcription-polymerase chain reaction. In order to further investigate the role of activin A, we also utilized activin A blocking experiment by anti-activin A antibody (500 μg/kg, body weight) injection into mouse tail vein.

RESULTS: In CCl₄-treated mice, serum ALT and AST levels were significantly increased, compared with that in control mice (P < 0.01). Furthermore, the serious necrosis was observed around hepatic portal areas in CCl₄-treated mice. Simultaneously, activin A levels in serum and hepatic tissue homogenate of mice treated with CCl₄ for 1, 3 and 5 d increased significantly, compared with that in control mice (P < 0.01). Activin A protein expression in hepatocytes not within the necrotic area was also upregulated in mice following CCl₄ treatment. Not only activin A, but also ActRIIA and activin signaling molecule Smad3 mRNA expressions in injury liver induced by CCl₄ were significantly higher than that in control liver. In addition, levels of serum ALT and AST in CCl₄-treated mice were significantly decreased by injection of anti-activin A antibody to block endogenous activin A action, compared with that in CCl₄-treated mice by injection of immunoglobulin G instead of anti-activin A antibody (P < 0.01), and the severity of liver injury was also reduced remarkably.

CONCLUSION: These data show that activin A is involved in CCl₄-induced acute liver injury. Blocking activin A actions may be a therapeutic approach for acute liver injury.

New targets for old hormones: inhibins clinical role revisited

Inhibins are gonadal peptide hormones belonging to the transforming growth factor-β (TGF-β) superfamily that regulate the pituitary follicle stimulating hormone (FSH) secretion by negative feedback mechanisms. It is evident that the understanding of inhibins function in the hypothalamic-pituitary-gonadal axis will provide insights into physiology and pathology of the gonadal function. In recent years, a great deal of attention has been focussed on clinical relevance of measuring circulating inhibins in normal and disease state. The past few years also have witnessed the emergence and discovery of extra pituitary action of inhibins that might provide further insights into the underlying diseases like cancer especially in the reproductive axis and various other new endocrine target organs. In this review after systematic analysis of literature, we discuss briefly the known and recent advances in function of these hormones highlighting also its structure, production and mechanisms of signal transduction. Also this review discusses about the physiological relevance of inhibin association in the normal function to the development of reproductive cancers. Finally, we describe evidence from various emerging studies that inhibins make an important contribution to other physiological functions apart from reproduction which reveals new endocrine target organs of inhibins. The emerging view is inhibin participates in multiple ways to regulate the function in different cell types and still complete repertoire of its actions is under investigation.