Visfatin as a therapeutic target for rheumatoid arthritis

Introduction: The rising prevalence of musculoskeletal pathologies in developed countries has caused a dramatic impact on social welfare. Amidst these musculoskeletal pathologies is Rheumatoid arthritis (RA), a chronic systemic autoimmune disease that mostly affects the synovium. RA metabolic-associated alterations, including distorted adipokine production, enhance RA inflammatory environment. Among the altered adipokines, visfatin is particularly involved in RA inflammation and catabolism and stands out as an essential enzyme linked to critical cell features.

Areas covered: We discuss the potential mechanism supporting the contribution of visfatin to RA and the association between RA and obesity. We discuss the repurposing of cancer-tested drugs to inhibit visfatin in the context of RA. Additionally, we address the possibility of combining these drugs with current RA therapy. Finally, we explore the future of visfatin as an RA biomarker or therapeutic target.

Expert opinion: Inhibition of visfatin has become an interesting therapeutic approach for RA pathology. Such a feat has already been attained in oncology using small molecule inhibitors, which suggest that a similar course of action would be worth pursuing in the RA context. Visfatin will become an important biomarker and therapeutic target for RA.     

脂多糖刺激树突状细胞前后TLR2、3、4基因表达的检测

目的 检测脂多糖作用于树突状细胞前后TLR2、3、4基因的表达情况。方法 从外周血分离单核细胞，加入rhGM-CSF及rhIL-4，培养的第6天，实验组加入脂多糖刺激24h，对照组不加。分别提取细胞总RNA，行半定量RT-PCR，产物进行琼脂糖凝胶电泳分析。结果 单核细胞经GM-CSF及IL-4诱导7d后的DC表达较高水平TLR2、3、4。脂多糖刺激24h后，TLR2、3、4表达下降，TLR4几乎测不到。结论 树突状细胞在受脂多糖刺激前后TLRs的表达有显著变化，推测和它的功能成熟有关。     

Bacterial components regulate the expression of Toll-like receptor 4 on human mast cells

Objectives and design: The aim of this study was to investigate whether the exposure of mast cells (MCs) to bacterial components affects the expression of Toll-like receptor (TLR) 4, and to elucidate the behavior of MCs during the early response to infection. Materials: Two human MC lines, HMC-1 and LAD2, were employed. Messenger RNA expression was observed by RT and real-time PCR. TLR4 expression was determined by Western blotting. TNF-α secretion was analyzed with ELISA. The degranulation ratio was measured with betahexosaminidase assay. Results: Although bacterial components increased TLR4 mRNA, only lipopolysaccharide (LPS) augmented the TLR4 protein expression. LAD2 pre-treated with LPS for 8 h resulted in 2-fold increased TNF-α secretion on LPS restimulation. Conclusion: These results suggest that the exposure of MCs to LPS may reinforce the innate immune system due to up-regulation of MC TLR4, followed by increased TNF-α release. Received 20 April 2006; returned for revision 14 July 2006; accepted by G. Wallace 11 August 2006     

Effects of Dietary Oat Beta-Glucans on Colon Apoptosis and Autophagy through TLRs and Dectin-1 Signaling Pathways—Crohn’s Disease Model Study

Background: Crohn’s disease (CD) is characterized by chronic inflammation of the gastrointestinal tract with alternating periods of exacerbation and remission. The aim of this study was to determine the time-dependent effects of dietary oat beta-glucans on colon apoptosis and autophagy in the CD rat model. Methods: A total of 150 Sprague–Dawley rats were divided into two main groups: healthy control (H) and a TNBS (2,4,6-trinitrobenzosulfonic acid)-induced colitis (C) group, both including subgroups fed with feed without beta-glucans (βG−) or feed supplemented with low- (βGl) or high-molar-mass oat beta-glucans (βGh) for 3, 7, or 21 days. The expression of autophagy (LC3B) and apoptosis (Caspase-3) markers, as well as Toll-like (TLRs) and Dectin-1 receptors, in the colon epithelial cells, was determined using immunohistochemistry and Western blot. Results: The results showed that in rats with colitis, after 3 days of induction of inflammation, the expression of Caspase-3 and LC3B in intestinal epithelial cells did not change, while that of TLR 4 and Dectin-1 decreased. Beta-glucan supplementation caused an increase in the expression of TLR 5 and Dectin-1 with no changes in the expression of Caspase-3 and LC3B. After 7 days, a high expression of Caspase-3 was observed in the colitis-induced animals without any changes in the expression of LC3B and TLRs, and simultaneously, a decrease in Dectin-1 expression was observed. The consumption of feed with βGl or βGh resulted in a decrease in Caspase-3 expression and an increase in TLR 5 expression in the CβGl group, with no change in the expression of LC3B and TLR 4. After 21 days, the expression of Caspase-3 and TLRs was not changed by colitis, while that of LC3B and Dectin-1 was decreased. Feed supplementation with βGh resulted in an increase in the expression of both Caspase-3 and LC3B, while the consumption of feed with βGh and βGl increased Dectin-1 expression. However, regardless of the type of nutritional intervention, the expression of TLRs did not change after 21 days. Conclusions: Dietary intake of βGl and βGh significantly reduced colitis by time-dependent modification of autophagy and apoptosis, with βGI exhibiting a stronger effect on apoptosis and βGh on autophagy. The mechanism of this action may be based on the activation of TLRs and Dectin-1 receptor and depends on the period of exacerbation or remission of CD.     

Cover Image,Volume 80, Issue 3

Primary dysmenorrhea affects the quality of life in young women, particularly school and work performance. This study investigated the mechanisms of penehyclidine hydrochloride (PHC) efficacy on a rat model of primary dysmenorrhea. The model was induced by injecting both estradiol benzoate and oxytocin. Different doses of PHC were administrated intraperitoneally following estradiol benzoate administration. Writhing scores were assessed, and pathological changes of the uterus were observed via hematoxylin and eosin staining. Western blot and real-time PCR were used to evaluate the expression level of the M₃ receptor, both TLR₃ and TLR₄ in uterine tissue, and the level of Ca²⁺ was measured in uterine tissues. Writhing scores significantly decreased in the PHC treatment group compared to model, and PHC alleviated the occurrence of edema or necrosis in the uteri compared to model group. PHC can decrease the M₃ receptor, TLR₃, TLR₄ expression, and the Ca²⁺ level compared to the model group. PHC is a potential candidate for the future treatment of primary dysmenorrhea due to its ability to attenuate muscarinic receptors and TLRs.

Chromosomal instability triggers cell death via local signalling through the innate immune receptor Toll

Chromosomal instability (CIN) is a hallmark of cancer and has been implicated in cancer initiation, progression and the development of resistance to traditional cancer therapy. Here we identify a new property of CIN cells, showing that inducing CIN in proliferating Drosophila larval tissue leads to the activation of innate immune signalling in CIN cells. Manipulation of this immune pathway strongly affects the survival of CIN cells, primarily via JNK, which responds to both Toll and TNFα/Eiger. This pathway also activates Mmp1, which recruits hemocytes to the CIN tissue to provide local amplification of the immune response that is needed for effective elimination of CIN cells.     

Toll-like receptors: Significance,ligands, signaling pathways,and functions in mammals

This review attempts to cover the implication of the toll-like receptors (TLRs) in controlling immune functions with emphasis on their significance, function, regulation and expression patterns. The tripartite TLRs are type I integral transmembrane receptors that are involved in recognition and conveying of pathogens to the immune system. These paralogs are located on cell surfaces or within endosomes. The TLRs are found to be functionally involved in the recognition of self and non-self-antigens, maturation of DCs and initiation of antigen-specific adaptive immune responses as they bridge the innate and adaptive immunity. Interestingly, they also have a significant role in immunotherapy and vaccination. Signals generated by TLRs are transduced through NFκB signaling and MAP kinases pathway to recruit pro-inflammatory cytokines and co-stimulatory molecules, which promote inflammatory responses. The excess production of these cytokines leads to grave systemic disorders like tumor growth and autoimmune disorders. Hence, regulation of the TLR signaling pathway is necessary to keep the host system safe. Many molecules like LPS, SOCS1, IRAK1, NFκB, and TRAF3 are involved in modulating the TLR pathways to induce appropriate response. Though quantification of these TLRs helps in correlating the magnitude of immune response exhibited by the animal, there are several internal, external, genetic and animal factors that affect their expression patterns. So it can be concluded that any identification based on those expression profiles may lead to improper diagnosis during certain conditions.     

TLR8 on dendritic cells and TLR9 on B cells restrain TLR7-mediated spontaneous autoimmunity in C57BL/6 mice

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with diverse clinical presentations characterized by the presence of autoantibodies to nuclear components. Toll-like receptor (TLR)7, TLR8, and TLR9 sense microbial or endogenous nucleic acids and are implicated in the development of SLE. In mice TLR7-deficiency ameliorates SLE, but TLR8- or TLR9-deficiency exacerbates the disease because of increased TLR7 response. Thus, both TLR8 and TLR9 control TLR7 function, but whether TLR8 and TLR9 act in parallel or in series in the same or different cell types in controlling TLR7-mediated lupus remains unknown. Here, we reveal that double TLR8/9-deficient (TLR8/9^−/−) mice on the C57BL/6 background showed increased abnormalities characteristic of SLE, including splenomegaly, autoantibody production, frequencies of marginal zone and B1 B cells, and renal pathology compared with single TLR8^−/− or TLR9^−/− mice. On the cellular level, TLR8^−/− and TLR8/9^−/− dendritic cells were hyperesponsive to TLR7 ligand R848, but TLR9^−/− cells responded normally. Moreover, B cells from TLR9^−/− and TLR8/9^−/− mice were hyperesponsive to R848, but TLR8^−/− B cells were not. These results reveal that TLR8 and TLR9 have an additive effect on controlling TLR7 function and TLR7-mediated lupus; however, they act on different cell types. TLR8 controls TLR7 function on dendritic cells, and TLR9 restrains TLR7 response on B cells.Systemic lupus erythematosus (SLE) is a complex chronic autoimmune disease that arises spontaneously and is characterized by production of autoantibodies against self-nucleic acids and associated proteins (1). These autoantibodies bind self-nucleic acids released by dying cells and form immune complexes that accumulate in different parts of the body, leading to inflammation and tissue damage. The kidneys, skin, joints, lungs, serous membranes, as well as, the cardiovascular, nervous and musculoskeletal system become targets of inflammation at onset or during the course of the disease (2). The etiology of SLE is unknown, yet genetics, sex, infectious agents, environmental factors, and certain medications may play a role in the initiation of the disease by causing alterations in lymphoid signaling, antigen presentation, apoptosis, and clearance of immune complexes (3, 4).Toll-like receptors (TLRs) detect specific microbial components widely expressed by bacteria, fungi, protozoa, and viruses, and initiate signaling pathways critical for induction of immune responses to infection (5). In contrast to the cell surface TLRs that detect bacterial cell wall components and viral particles, nucleic acid-sensing TLRs are localized mainly within endosomal compartments (6). Human endosomal TLRs consist of TLR3, which senses viral double-stranded RNA (dsRNA) (7), TLR7 and TLR8, which recognize viral single-stranded RNA (8–10), and TLR9, which detects bacterial and viral unmethylated CpG-containing DNA motifs (11). Interestingly, these endosomal TLRs are also able to detect self-nucleic acids (12–14). Although the endosomal localization isolate TLR3, TLR7, TLR8, and TLR9 away from self-nucleic acids in the extracellular space, still self-RNA or -DNA can become a potent trigger of cell activation when transported into TLR-containing endosomes, and such recognition can result in sterile inflammation and autoimmunity, including SLE (4, 15, 16). The connection of the endosomal TLRs with SLE originates mainly from mouse models, where TLR7 signaling seems to play a central role. TLR7 gene duplication is the cause for the development of lupus in mice bearing the Y chromosome-linked autoimmune accelerating (Yaa) locus that harbors 17 genes, including TLR7 (17, 18). In TLR7 transgenic mouse lines, a modest increase in TLR7 expression promotes autoreactive lymphocytes with RNA specificities and myeloid cell proliferation, but a substantial increase in TLR7 expression causes fatal acute inflammatory pathology and profound dendritic cell (DC) dysregulation (17). In addition, studies in several lupus-prone mouse strains have revealed that TLR7-deficiency ameliorates disease, but TLR9-deficiency exacerbates it. Interestingly, this controversy can be explained by the enhanced TLR7 activity in the TLR9-deficient lupus mice (19, 20). Although murine TLR8 does not seem so far to be able to sense a ligand (21, 22), we have shown previously that it plays an important biological role in controlling TLR7-mediated lupus. Indeed, TLR8-deficiency in mice (on the C57BL/6 background that is not prone to lupus) leads to lupus development because of increased TLR7 expression and signaling in DCs (23). Thus, tight control and regulation of TLR7 is pivotal for avoiding SLE and inflammatory pathology in mice. Recent studies in humans have also revealed that increased expression of TLR7 is associated with increased risk for SLE (24–26).Nucleic acid TLRs are expressed in many cell types, including DCs, plasmacytoid DCs (pDCs) and B cells, all of which play a central role in SLE development. TLR7, TLR8, and TLR9 signal through the adaptor molecule myeloid differentiation primary response gene 88 (MyD88), whereas TLR3 signals via the adaptor TRIF (Toll/IL-1 receptor domain-containing adaptor inducing IFN-β) (5). MyD88-deficiency abrogates most attributes of lupus in several lupus-prone mouse strains (19, 27–29). Moreover, deficiency for Unc93B1, a multipass transmembrane protein that controls trafficking of TLRs from the endoplasmic reticulum to endolysosomes and is required for nucleic acid-sensing TLR function (30), also abrogates many clinical parameters of disease in mouse lupus strains, suggesting that endosomal TLRs are critical in this disease (31). Interestingly, TLR9 competes with TLR7 for Unc93B1-dependent trafficking and predominates over TLR7 (32). TLR9 predominance is reversed to TLR7 by a D34A mutation in Unc93B1 and mice that carry this mutation show TLR7-dependent, systemic lethal inflammation (32).Thus, in mice both TLR8 and TLR9 control TLR7-mediated lupus, but it is unknown if these TLRs act in parallel or in series in the same or different cell types and if they have an additive effect or not in controlling TLR7. To address these issues, we generated double TLR8/TLR9-deficient (TLR8/9^−/−) mice and analyzed and compared the lupus phenotype in TLR8^−/−, TLR9^−/−, and TLR8/9^−/− mice. Our data revealed that TLR8/9^−/− mice have increased abnormalities characteristic of SLE and that both TLR8 and TLR9 keep TLR7-mediated lupus under control, but they act in different cell types. On DCs TLR7 function is ruled by TLR8, whereas on B cells TLR7 is mastered by TLR9.     

A built-in co-carcinogenic effect due to viruses involved in latent or persistent infections

A new hypothesis for some cancers, which combines the chromosomal instability theories with a co-carcinogenic effect of viruses causing latent or persistent infection, is presented. The hypothesis incorporates the multi-step model of cancer and that pre-cancerous cells reach a state of chromosomal instability. Because of chromosomal instability, the genome of these cell lines will lead to changes from generation to generation and will face a remarkable selection pressure both from lost traits, apoptosis, and from the immune system. Viruses causing latent or persistent infections have evolved many different genes capable to evade the immune system. If these viruses are harboured in the genome of pre-cancerous cells they could provide them with "superpowers" and with genes that may assist the cells to elude the immune system. The theory explains why cancer predominantly is a disease of old age. Upon aging, the immune system becomes reduced including the ability to control and suppress the viruses that cause latent or persistent infections. The risk of cancer could thereby increase as the immune functions decrease. The theory provides new insights to the genesis of cancers.