Experimental Model Of Rheumatoid Arthritis Research Articles

IL-17-producing γδT cells are regulated by estrogen during development of experimental arthritis

Interleukin-17 (IL-17) drives inflammation and destruction of joints in rheumatoid arthritis (RA). The female sex hormone 17β-estradiol (E2) inhibits experimental arthritis. γδT cells are significant producers of IL-17, thus the aim of this study was to investigate if E2 influenced IL-17(+) γδT cells during arthritis development using a variety of experimental RA models: collagen-induced arthritis (CIA); antigen-induced arthritis (AIA); and collagen antibody-induced arthritis (CAIA). We demonstrate that E2 treatment decreases IL-17(+) γδT cell number in joints, but increases IL-17(+) γδT cells in draining lymph nodes, suggesting an E2-mediated prevention of IL-17(+) γδT cell migration from lymph nodes to joints, in concert with our recently reported effects of E2 on Th17 cells (Andersson et al., 2015). E2 did neither influence the general γδT cell population nor IFNγ(+) γδT cells, implying a selective regulation of IL-17-producing cells. In conclusion, this study contributes to the understanding of estrogen's role in autoimmune disease.

Inhibition of Inflammation and Bone Erosion by RNA Interference-Mediated Silencing of Heterogeneous Nuclear RNP A2/B1 in Two Experimental Models of Rheumatoid Arthritis.

The nuclear protein heterogeneous nuclear RNP A2/B1 (hnRNP A2/B1) is involved in posttranscriptional regulation of gene expression. It is constitutively expressed in lymphoid organs and highly up-regulated in the synovial tissue of patients with rheumatoid arthritis (RA), who may also generate autoantibodies to this protein. This study was undertaken to investigate the potential involvement of hnRNP A2/B1 in the pathogenesis of autoimmune arthritis, by silencing hnRNP A2/B1 expression in 2 animal models of RA. Collagen-induced arthritis (CIA) and the K/BxN serum-transfer model were used as animal models of RA. Efficient silencing of hnRNP A2/B1 was achieved using a liposome-based carrier system for delivery of small interfering RNAs. Expression of hnRNP A2/B1 was analyzed by flow cytometry, reverse transcription-quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. The number of osteoclasts was determined by tartrate-resistant acid phosphatase staining. Cytokine levels and anticollagen antibody levels were measured by enzyme-linked immunosorbent assay. Efficient silencing of hnRNP A2/B1 was achieved in all lymphoid organs. In both experimental models, the incidence and severity of arthritis were largely reduced and bone erosion was not detectable as compared to the control groups. Down-modulation of hnRNP A2/B1 significantly interfered with the production of proinflammatory cytokines from monocyte/macrophages, but not from T cells. Consistent with these findings, production of T cell cytokines was not impaired when cells were restimulated in vitro with type II collagen. Furthermore, levels of anticollagen antibodies were not affected by hnRNP A2/B1 silencing. Our findings suggest that hnRNP A2/B1 has an important role in regulation of the innate immune system, especially at the level of monocyte/macrophage activation. Therefore, down-modulation of hnRNP A2/B1 seems to affect primarily the effector phase of autoimmune arthritis.

The melanocortin receptor type 3 agonist d-Trp(8)-γMSH decreases inflammation and muscle wasting in arthritic rats.

BackgroundChronic inflammatory diseases induce cachexia that increases mortality and morbidity of the illness. Adjuvant‐induced arthritis is an experimental model of rheumatoid arthritis that is associated with body weight loss and muscle wasting. Alpha‐melanocyte stimulating hormone has an anti‐inflammatory effect in arthritic rats and decreases muscle wasting. The aim of this work was to elucidate whether the anti‐cachectic action of alpha‐melanocyte stimulating hormone is mediated by the melanocortin receptor type 3 pathway.MethodsArthritis was induced in male Wistar rats by intradermal injection of Freund's adjuvant, and 6 days afterwards, arthritic rats were injected with the selective melanocortin receptor type 3 agonist d‐Trp(8)‐gammaMSH ( d‐Trp(8)‐γMSH) 500 µg/kg subcutaneously. or saline twice a day, for 10 days.Results d‐Trp(8)‐γMSH decreased the external signs of inflammation and body weight loss, but it was not able to modify the anorexigenic effect of arthritis or the increase in hypothalamic cyclooxygenase‐2 (COX‐2) expression. In contrast, d‐Trp(8)‐γMSH prevented arthritis‐induced increase in hypothalamic IL‐1β and serum corticosterone levels and the decrease in serum IGF‐I levels. d‐Trp(8)‐γMSH treatment also prevented arthritis‐induced NF‐kB(p65) phosphorylation and tumour necrosis factor‐α mRNA increase in the gastrocnemius. d‐Trp(8)‐γMSH administration to arthritic rats increased gastrocnemius mass, its cross‐sectional area, and mean fast fibre area. Those effects of d‐Trp(8)‐γMSH were associated with a decreased expression of atrogin‐1 and muscle ring‐finger protein‐1 in the gastrocnemius. In rats treated with saline, arthritis increased the expression of autophagy marker genes LC3b, Bnip‐3, and Gabarap1 as well as the conversion of LC3b I to LC3b II by lipidation in the gastrocnemius. d‐Trp(8)‐γMSH decreased gastrocnemius LC3b, Bnip‐3, and Gabarap1 mRNA expression and prevented the increase in LC3b II in arthritic rats.ConclusionThese data suggest that d‐Trp(8)‐γMSH administration prevents the effect of arthritis on corticosterone and insulin‐like growth factor‐I serum levels and decreases muscle wasting, by down‐regulating atrogenes and autophagy through modifying the NF‐kB(p65)/tumour necrosis factor‐α signalling transduction pathway.

Combination therapy with TNFR-Fc and CTLA4-FasL using the recombinant adeno-associated virus potently suppresses adjuvant-induced arthritis in rats.

The complexity of rheumatoid arthritis (RA) pathogenesis makes combined blockade of key pathogenic factors an attractive therapeutic strategy. We have previously reported a novel recombinant adeno-associated virus (AAV) vector, AAV.TFCF, which mediates separate coexpression of TNFα antagonist TNFR-Fc and T cell antagonist CTLA4-FasL both in vitro and in vivo (the injected joints). The purpose of this study was to examine the efficacy of TNFR-Fc/CTLA4-FasL combination therapy mediated by AAV.TFCF in experimental model of RA. Adjuvant-induced arthritis (AIA) was induced in Lewis rats, and the recombinant AAV.TFCF was injected into rat ankle joints. AAV vector encoding CTLA4-FasL (AAV.CTFA) or TNFR-Fc (AAV.TRFC) was used as the monotherapy control, and an AAV vector mediating the expression of enhanced green fluorescent protein (AAV.EGFP) was used as the negative control. The combination treatment mediated by AAV.TFCF demonstrated a more effective suppression of AIA compared with those monotherapy controls, as reflected in the clinical and histological observations. The synergistic anti-inflammatory effect of TNFR-Fc combining with CTLA4-FasL was proved to be associated with the greater reductions of inflammatory CD4+ T cell infiltration and proinflammatory cytokine TNFα level in the arthritic joints. In addition, the combination therapy was found to be able to increase the frequency of CD4 + CD25 + FoxP3+ regulatory T cell population in rat draining lymph nodes and suppress splenic inflammatory responses. These results suggest that combination treatment with TNFR-Fc and CTLA4-FasL may achieve superior efficacy in suppressing RA, and using this novel recombinant AAV.TFCF to obtain the combined counteraction of both pathogenic T cells and the key proinflammatory cytokine TNFα may provide a more effective and desirable strategy for treatment of RA.

A novel therapeutic approach targeting rheumatoid arthritis by combined administration of morin, a dietary flavanol and non-steroidal anti-inflammatory drug indomethacin with reference to pro-inflammatory cytokines, inflammatory enzymes, RANKL and transcription factors

The present study was designed to assess the combined efficacy of morin, a dietary flavanol and non-steroidal anti-inflammatory drug indomethacin against adjuvant-induced arthritis in rats, an experimental model for rheumatoid arthritis. Arthritis was induced by intradermal injection of complete freund’s adjuvant (0.1ml) into the right hind paw of the Wistar albino rats. Morin (30mg/kg b.wt), indomethacin (3mg/kg b.wt) and combination of morin and indomethacin were administered intraperitoneally (from 11th to 20th day) after adjuvant injection. We have found that the activities/levels of lysosomal acid hydrolases (acid phosphatase, β-galactosidase, N-acetyl glucosaminidase and cathepsin-D), glycoproteins (hexose and hexosamine), urinary constituents (hydroxyproline and glycosaminoglycans), reactive oxygen species (LPO and NO), elastase, inflammatory mediators (TNF-α, IL-1β, MCP-1, VEGF and PGE2) and paw edema were significantly increased in arthritic rats compared to controls. Whereas, the anti-oxidant status (SOD, CAT, GPx, glutathione, and ceruloplasmin), body weight and bone collagen was found to be decreased. The mRNA expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-17, IL-6 and MCP-1), inflammatory enzymes (iNOS and COX-2), RANKL, and transcription factors (NF-kB p65 and AP-1) was found upregulated in the ankle joints of arthritic rats in qRT-PCR analysis. In addition, the increased protein expression of NF-kB p65 and COX-2 was also detected by immunohistochemical analysis. On the other hand, the above said imbalances were regulated back effectively to near normal as evidenced by the histopathological and radiological analysis on combined treatment with morin and indomethacin. Our study indicates that the combination therapy was more effective than either single drug alone in suppressing the pathogenesis of RA.

English

The examination of 144 white mature male rats of mixed population was conducted. Experimental rheumatoid arthritis model was used to study the impact of some ACE inhibitors: omeprazole, cytotek and combinations of omeprazole with ACE inhibitors and cytotek on frequency of erosive ulcerous injuries of gastric mucosa when administered within 5 and 10 days with indometacin. Drugs were administered per os in the form of water suspension. It was established that the combined use of ACE inhibitors, omeprazole and cytotek with indometacin decreases the noci-influence of indometacin on gastric mucosa. Captopril is the most treatment medication among ACE inhibitors. Combined application of ACE inhibitors with omeprazole and cytotek increases the medicine efficacy. Com- bined use of omeprazole and captopril or omeprazole and cytotek is the most effective for prevention of side effect of indometacin on mucosa of gastroduodenal zone.

Fumagillin prodrug nanotherapy suppresses macrophage inflammatory response via endothelial nitric oxide.

Antiangiogenesis has been extensively explored for the treatment of a variety of cancers and certain inflammatory processes. Fumagillin, a mycotoxin produced by Aspergillus fumigatus that binds methionine aminopeptidase 2 (MetAP-2), is a potent antiangiogenic agent. Native fumagillin, however, is poorly soluble and extremely unstable. We have developed a lipase-labile fumagillin prodrug (Fum-PD) that eliminated the photoinstability of the compound. Using αvβ3-integrin-targeted perfluorocarbon nanocarriers to deliver Fum-PD specifically to angiogenic vessels, we effectively suppressed clinical disease in an experimental model of rheumatoid arthritis (RA). The exact mechanism by which Fum-PD-loaded targeted nanoparticles suppressed inflammation in experimental RA, however, remained unexplained. We herein present evidence that Fum-PD nanotherapy indirectly suppresses inflammation in experimental RA through the local production of endothelial nitric oxide (NO). Fum-PD-induced NO activates AMP-activated protein kinase (AMPK), which subsequently modulates macrophage inflammatory response. In vivo, NO-induced AMPK activation inhibits mammalian target of rapamycin (mTOR) activity and enhances autophagic flux, as evidenced by p62 depletion and increased autolysosome formation. Autophagy in turn mediates the degradation of IkappaB kinase (IKK), suppressing the NF-κB p65 signaling pathway and inflammatory cytokine release. Inhibition of NO production by NG-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase inhibitor, reverses the suppression of NF-κB-mediated inflammatory response induced by Fum-PD nanotherapy. These unexpected results uncover an activity of Fum-PD nanotherapy that may be further explored in the treatment of angiogenesis-dependent diseases.

Chrysin alleviates testicular dysfunction in adjuvant arthritic rats via suppression of inflammation and apoptosis: Comparison with celecoxib

Long standing rheumatoid arthritis (RA) is associated with testicular dysfunction and subfertility. Few studies have addressed the pathogenesis of testicular injury in RA and its modulation by effective agents. Thus, the current study aimed at evaluating the effects of two testosterone boosting agents; chrysin, a natural flavone and celecoxib, a selective COX-2 inhibitor, in testicular impairment in rats with adjuvant arthritis, an experimental model of RA. Chrysin (25 and 50mg/kg) and celecoxib (5mg/kg) were orally administered to Wistar rats once daily for 21days starting 1h before arthritis induction. Chrysin suppressed paw edema with comparable efficacy to celecoxib. More important, chrysin, dose-dependently and celecoxib attenuated the testicular injury via reversing lowered gonadosomatic index and histopathologic alterations with preservation of spermatogenesis. Both agents upregulated steroidogenic acute regulatory (StAR) mRNA expression and serum testosterone with concomitant restoration of LH and FSH. Furthermore, they suppressed inflammation via abrogation of myeloperoxidase, TNF-α and protein expression of COX-2 and iNOS besides elevation of IL-10. Alleviation of the testicular impairment was accompanied with suppression of oxidative stress via lowering testicular lipid peroxides and nitric oxide. With respect to apoptosis, both agents downregulated FasL mRNA expression and caspase-3 activity in favor of cell survival. For the first time, these findings highlight the protective effects of chrysin and celecoxib against testicular dysfunction in experimental RA which were mediated via boosting testosterone in addition to attenuation of testicular inflammation, oxidative stress and apoptosis. Generally, the 50mg/kg dose of chrysin exerted comparable protective actions to celecoxib.

STA‐21, a Promising STAT‐3 Inhibitor That Reciprocally Regulates Th17 and Treg Cells, Inhibits Osteoclastogenesis in Mice and Humans and Alleviates Autoimmune Inflammation in an Experimental Model of Rheumatoid Arthritis

To investigate the impact of STA-21, a promising STAT-3 inhibitor, on the development and progression of inflammatory arthritis and to determine the possible mechanisms by which STA-21 has antiarthritic effects in interleukin-1 receptor antagonist-knockout (IL-1Ra-KO) mice, an animal model of rheumatoid arthritis (RA). IL-1Ra-KO mice were treated with intraperitoneal injections of STA-21 (0.5 mg/kg) or vehicle 3 times per week for 3 weeks. The mouse joints were assessed for clinical and histologic features of inflammatory arthritis. CD4+CD25+FoxP3+ Treg cells and CD4+IL-17+ cells were defined. Human peripheral blood mononuclear cell-derived monocytes or mouse bone marrow-derived monocyte/macrophage (BMM) cells were cultured in the presence of macrophage colony-stimulating factor alone or together with RANKL and various concentrations of STA-21, followed by staining of the cells for tartrate-resistant acid phosphatase activity to determine osteoclast formation. STA-21 suppressed inflammatory arthritis in IL-1Ra-KO mice. The proportion of Th17 cells was decreased and the proportion of Treg cells expressing FoxP3 was markedly increased in the spleens of STA-21-treated mice. Adoptive transfer of CD4+CD25+ T cells obtained from STA-21-treated IL-1Ra-KO mice markedly suppressed inflammatory arthritis. In vitro treatment with STA-21 induced the expression of FoxP3 and repressed IL-17 expression in both mouse and human CD4+ T cells. Moreover, STA-21 prevented both mouse BMM cells and human monocytes from differentiating into osteoclasts in vitro. STA-21 improved the clinical course of arthritis in IL-1Ra-KO mice. It increased not only the number of Treg cells but also the function of the Treg cells. It also suppressed Th17 cells and osteoclast formation. These data suggest that STA-21 might be an effective treatment for patients with RA.

A novel IKKα inhibitor, noraristeromycin, blocks the chronic inflammation associated with collagen-induced arthritis in mice

Objectives. To evaluate the therapeutic efficacy of a novel inhibitor for IκB kinase alpha (IKKα), noraristeromycin (NAM), for murine experimental model of rheumatoid arthritis, collagen- induced arthritis (CIA).Methods. NAM has been chemically synthesized as reported earlier. CIA was induced in DBA/1JNCrlj mice by intradermal inoculation of bovine type II collagen (col II) together with Freund Complete Adjuvant. Following the Day 21 booster injection of col II with Freund Incomplete Adjuvant, the animals were monitored for the development of arthritis and clinically evaluated. NAM was administered orally at different doses prior to induction (prophylactic protocol) or after the emergence of definitive arthritis (therapeutic protocol).Results. Here we demonstrate the experimental evidence that oral administration of NAM could completely prevent the occurrence of experimental arthritis in CIA mouse model at 0.3 mg/kg with ED50 value of approximately 0.1 mg/kg twice daily. Moreover, twice daily oral therapeutic dosage of 1 mg/kg of NAM significantly inhibited the paw swelling and disease progression even after the occurrence of experimental CIA. In addition, NAM exhibited an excellent pharmacokinetics in mice and oral administration of NAM could suppress the production of TNFα elicited by lipopolysaccharide (LPS) in a dose-dependent manner.Conclusions. These results indicated that IKKα inhibition is an effective novel therapy for the treatment of chronic inflammatory processes such as those associated with RA and other related conditions.

1.64 Interleukin-33 suppresses experimental arthritis through promoting Foxp3+ regulatory T-cells and type-2 immune responses in mice

Background and ObjectivesInterleukin (IL)-33 is a new member of the IL-1 family that exerts pleiotropic activities in innate and adaptive immunity. With its receptor ST2, they have newly emerged as...

Therapeutic Effect of Human Amniotic Membrane–Derived Cells on Experimental Arthritis and Other Inflammatory Disorders

Rheumatoid arthritis (RA) is an autoimmune disease caused by loss of immunologic self tolerance and characterized by chronic joint inflammation. Cells isolated from human amniotic membrane (HAMCs) were recently found to display immunosuppressive properties. The aim of this study was to characterize the effect of HAMCs on antigen-specific T cell responses in RA patients and to evaluate their therapeutic potential in a preclinical experimental model of RA. We investigated the effects of HAMCs on collagen-reactive T cell proliferation and cytokine production, on the production of mediators of inflammation by synoviocytes, and on the generation of Treg cells in peripheral blood mononuclear cells and synovial membrane cells isolated from RA patients. Mice with collagen-induced arthritis (CIA) were treated with HAMCs after disease onset, and clinical scores and joint levels of mediators of inflammation were evaluated. We determined Th1/Th17-mediated autoreactive responses in the mice by measuring the proliferation and the cytokine profile of lymph node cells restimulated with collagen. Treatment with HAMCs suppressed synovial inflammatory responses and antigen-specific Th1/Th17 activation in cells isolated from RA patients. Moreover, HAMCs stimulated the generation of human CD4+CD25+FoxP3+ Treg cells with a capacity to suppress collagen-specific T cell responses. Systemic infusion of HAMCs significantly reduced the incidence and severity of CIA by down-regulating the 2 deleterious components of disease: Th1-driven autoimmunity and inflammation. In mice with CIA, HAMC treatment decreased the production of various inflammatory cytokines and chemokines in the joints, impaired antigen-specific Th1/Th17 cell expansion in the lymph nodes, and generated peripheral antigen-specific Treg cells. HAMCs also protected the mice from experimental sepsis, inflammatory bowel disease, and autoimmune encephalomyelitis. HAMCs have emerged as attractive candidates for a cell-based therapy for RA.

Glucose transport in brain – effect of inflammation

Glucose is transported across the cell membrane by specific saturable transport system, which includes two types of glucose transporters: 1) sodium dependent glucose transporters (SGLTs) which transport glucose against its concentration gradient and 2) sodium independent glucose transporters (GLUTs), which transport glucose by facilitative diffusion in its concentration gradient. In the brain, both types of transporters are present with different function, affinity, capacity, and tissue distribution. GLUT1 occurs in brain in two isoforms. The more glycosylated GLUT1 is produced in brain microvasculature and ensures glucose transport across the blood brain barrier (BBB). The less glycosylated form is localized in astrocytic end-feet and cell bodies and is not present in axons, neuronal synapses or microglia. Glucose transported to astrocytes by GLUT1 is metabolized to lactate serving to neurons as energy source. Proinflammatory cytokine interleukin (IL)-1β upregulates GLUT1 in endothelial cells and astrocytes, whereas it induces neuronal death in neuronal cell culture. GLUT2 is present in hypothalamic neurons and serves as a glucose sensor in regulation of food intake. In neurons of the hippocampus, GLUT2 is supposed to regulate synaptic activity and neurotransmitter release. GLUT3 is the most abundant glucose transporter in the brain having five times higher transport capacity than GLUT1. It is present in neuropil, mostly in axons and dendrites. Its density and distribution correlate well with the local cerebral glucose demands. GLUT5 is predominantly fructose transporter. In brain, GLUT5 is the only hexose transporter in microglia, whose regulation is not yet clear. It is not present in neurons. GLUT4 and GLUT8 are insulin-regulated glucose transporters in neuronal cell bodies in the cortex and cerebellum, but mainly in the hippocampus and amygdala, where they maintain hippocampus-dependent cognitive functions. Insulin translocates GLUT4 from cytosol to plasma membrane to transport glucose into cells, and GLUT8 from cytosol to rough endoplasmic reticulum to recover redundant glucose to cytosol after protein glycosylation. In autoimmune diseases, the enhanced glucose uptake was found in inflamed peripheral tissue, mainly due to proliferating fibroblasts and activated macrophages. In our experimental model of rheumatoid arthritis (adjuvant arthritis), enhanced 2-deoxy-2[F-18]fluoro-D-glucose was found in the hippocampus and amygdala two days after the induction of the disease which, similarly as in the peripheral joints, can be ascribed to the activated macrophages. The knowledge on the glucose transport and the role of glucose transporters in the brain during systemic autoimmune inflammation is still incomplete and needs further investigations.

18 F-Fluoride positron emission tomography/computed tomography for noninvasive in vivo quantification of pathophysiological bone metabolism in experimental murine arthritis.

IntroductionEvaluation of disease severity in experimental models of rheumatoid arthritis is inevitably associated with assessment of structural bone damage. A noninvasive imaging technology allowing objective quantification of pathophysiological alterations of bone structure in rodents could substantially extend the methods used to date in preclinical arthritis research for staging of autoimmune disease severity or efficacy of therapeutical intervention. Sodium 18 F-fluoride (18 F-NaF) is a bone-seeking tracer well-suited for molecular imaging. Therefore, we systematically examined the use of 18 F-NaF positron emission tomography/computed tomography (PET/CT) in mice with glucose-6-phosphate isomerase (G6PI)–induced arthritis for quantification of pathological bone metabolism.MethodsF-fluoride was injected into mice before disease onset and at various time points of progressing experimental arthritis. Radioisotope accumulation in joints in the fore- and hindpaws was analyzed by PET measurements. For validation of bone metabolism quantified by 18 F-fluoride PET, bone surface parameters of high-resolution μCT measurements were used.ResultsBefore clinical arthritis onset, no distinct accumulation of 18 F-fluoride was detectable in the fore- and hindlimbs of mice immunized with G6PI. In the course of experimental autoimmune disease, 18 F-fluoride bone uptake was increased at sites of enhanced bone metabolism caused by pathophysiological processes of autoimmune disease. Moreover, 18 F-fluoride signaling at different stages of G6PI-induced arthritis was significantly correlated with the degree of bone destruction. CT enabled identification of exact localization of 18 F-fluoride signaling in bone and soft tissue.ConclusionsThe results of this study suggest that small-animal PET/CT using 18 F-fluoride as a tracer is a feasible method for quantitative assessment of pathophysiological bone metabolism in experimental arthritis. Furthermore, the possibility to perform repeated noninvasive measurements in vivo allows longitudinal study of therapeutical intervention monitoring.

Systemic α-melanocyte-stimulating hormone administration decreases arthritis-induced anorexia and muscle wasting

Rheumatoid cachexia is associated with rheumatoid arthritis and it increases mortality and morbidity. Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that causes anorexia and muscle wasting. α-Melanocyte-stimulating hormone (α-MSH) has anti-inflammatory actions, and it is able to decrease inflammation in several inflammatory diseases including experimental arthritis. In this study we tested whether systemic α-MSH treatment is able to ameliorate cachexia in arthritic rats. On day 8 after adjuvant injection control and arthritic rats were treated with α-MSH (50 μg/rat ip) twice a day, until day 16 when all rats were euthanized. Arthritis decreased food intake, but it increased hypothalamic expression of neuropeptide Y (NPY) and Agouti-related peptides (AgRP) as well as interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) mRNA. In arthritic rats, α-MSH decreased the external signs of arthritis and increased food intake (P < 0.01). In addition, α-MSH decreased hypothalamic expression of IL-1β, COX-2, proopiomelanocortin, and prohormone-converting (PC) enzymes PC1/3 and PC2 mRNA in arthritic rats. In control rats, α-MSH did not modify food intake or hypothalamic expression of aforementioned mRNA. α-MSH prevented arthritis-induced increase in gastrocnemius COX-2, muscle-specific RING-finger protein-1 (MuRF1), and atrogin-1 expression, and it increased fast myofiber size. In conclusion our data show that in arthritic rats peripheral α-MSH treatment has an anti-cachectic action increasing food intake and decreasing muscle wasting.

NK4 therapy: a new approach to target angiogenesis and inflammation in rheumatoid arthritis

Rheumatoid arthritis (RA) is a progressive autoimmune disease characterized by synovial membrane hyperplasia, inflammation, and angiogenesis. Hepatocyte growth factor (HGF) and its receptor, c-Met, are both overexpressed in the RA synovium. NK4 is an antagonist of HGF which has been shown to inhibit tumor growth, metastasis, and angiogenesis. In an experimental model of RA, NK4 gene therapy inhibited joint damage and inflammation in both preventative and therapeutic models. NK4 treatment therefore represents a possible therapeutic option in combating RA.

Response to 'Ramipril attenuates lipid peroxidation and cardiac fibrosis in an experimental model of rheumatoid arthritis' - authors' reply

We thank Wang and colleagues for their comments [1] about our recent study [2] and would like to make two points to clarify our reasoning. First, in our study [2], female Lewis rats have been used in order to induce arthritis. This experimental model of arthritis was well described in our previous study published in Molecular Therapy [3]. Actually, a number of researchers use male or female animals to induce arthritis. For example, the use of female rats to induce arthritis has been reported in several recent articles [4-11]. In our unpublished data, we have shown that (a) adjuvant most likely induces arthritis equally in female and male Lewis rats and (b) female and male Lewis rats with arthritis have similar levels of lipid peroxidation products and cardiac fibrosis markers in heart tissues. These data were obtained by using a small cohort of male Lewis rats (n = 3), and we are keeping in mind that additional experiments will be performed in a future project of ours with a large cohort of male rats. Second, in our recent study [2], female Lewis rats with arthritis received ramipril (10 mg/kg per day). The dose of this drug was chosen from the literature [12-14].

Response to 'Ramipril attenuates lipid peroxidation and cardiac fibrosis in an experimental model of rheumatoid arthritis'

We read with great interest the recent issue of Arthritis Research & Th erapy i n which Shi and colleagues [1] investi gated the eff ects of ramipril on oxidative stress and fi brosis in the heart of rat s with adjuvant arthritis. Th e authors concluded that ramipril reversed arthritis scoring and decreased markers of oxidative stress, infl ammation, and tissue fi brosis. Undoubtedly, their fi ndings will promote the attempt to diminish the cardiovascular risk of patients with rheumatoid arthritis (RA) by using angio tensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) or both. However, several important aspects should be considered in the interpretation of this study. As described by the authors, adjuvant arthritis was induced successfully in female rats with a 100% incidence rate, but actually the male rats were use d in most cases [2-4]. Th ere fore, we speculate that this discrepancy may be related to th e impact of arthritis on cardiac fi brosis and oxidative stress status in the heart o f rats with adjuvant arthritis. In addition, the dosage of ramipril is a matter of debate. In a randomized and double-blind clinical study, treatment with 10 mg/day ramipril eff ectively improved endothelial function in patients with RA [5]. Intriguingly, how was the ramipril dosage (10 mg/kg per day) used in this animal study calculated? Unlike previous reports focusing on the eff ect of ramipril and ARBs on vascular function with RA and experimental models [2,5], the article by Shi and colleagues reported that ramipril improved c ardiac function in rats with adjuvant arthritis. Although we list some methodological issues here, we believe that the authors’ fi ndings strongly suggest a promising therapeutic role of ACEIs and ARBs on both card iovascular risk and arthritis in patients with RA.

Thrombin-sensitive dual fluorescence imaging and therapeutic agent for detection and treatment of synovial inflammation in murine rheumatoid arthritis

We have developed a thrombin-sensitive polymeric photosensitizer prodrug (T-PS) to selectively image and eradicate inflammatory lesions in rheumatoid arthritis (RA). Thrombin is a serine protease up-regulated in synovial tissues of rheumatoid arthritis (RA) patients. T-PS consists of a polymeric backbone, to which multiple photosensitizer (PS) units are tethered via short thrombin-cleavable peptide linkers.Fluorescence emission and phototoxicity of the prodrug are efficiently quenched due to the interaction of neighboring photosensitizer units. The prodrug is passively delivered to the inflammation site via the enhanced permeability and retention (EPR) effect. Subsequent site-selective proteolytic cleavage of the peptide linkers restores its photoactivity by increasing the mutual distance between PS.Whole animal imaging in murine collagen-induced arthritis, an experimental model of RA revealed a dose-dependent fluorescence increase in arthritic paws after systemic prodrug injection. In addition, administration of T-PS resulted in much higher fluorescence selectivity for arthritic joints as compared to the free PS. Irradiation of the arthritic joints induced light dose dependent phototoxic effects such as apoptosis, vascular damage and local hemorrhage. Long-term observations showed complete regression of the latter. Irradiated non-arthritic tissues or non-irradiated arthritic tissues showed no histological effects after photodynamic therapy with T-PS.This illustrates that T-PS can localize inflammatory lesions with excellent selectivity and induce apoptosis and vascular shut down after irradiation.

Protective role of systemic furin in immune response–induced arthritis

Rheumatoid arthritis (RA) is an autoimmune joint disease associated with chronic inflammation of the synovium that causes profound damage of joints. Inflammation results in part from the influx of immune cells secreting inflammatory cytokines and the reduction in the number of Treg cells. We undertook this study to assess the effect of furin, a proteinase implicated in the proteolytic activity of various precursor proteins and involved in the regulation of both proteinase maturation and immune cells, in an experimental model of RA. The effect of furin and its inhibitor α1-PDX was tested in mice with collagen-induced arthritis (CIA). Joints were processed for histology and protein expression. Levels of cytokines were measured in joint tissue, and Treg cell numbers were measured in spleens. Furin expression and activity were high in the synovial pannus in RA patients and mice with CIA. Systemic administration of furin prevented increases in the arthritis score, joint destruction, and bone loss, in contrast to systemic administration of the furin inhibitor α1-PDX, which enhanced these parameters. By preventing the development of synovial pannus, furin reduced the expression of metalloproteinases in the joints. In contrast, α1-PDX enhanced synovial proliferation and the expression and activity of matrix metalloproteinases. Furthermore, furin reversed the local Th1/Th2 balance and restored the number of Treg cells in the spleen, indicating mediation by immune cells. These findings show the protective role of exogenous furin against RA, mediated by an immune response. The data suggest the potential therapeutic use of furin or its derivatives in autoimmune diseases including RA.