alpha-MSH inhibits TNF-alpha-induced matrix metalloproteinase-13 expression by modulating p38 kinase and nuclear factor kappaB signaling in human chondrosarcoma HTB-94 cells

The Role of Macrophages in Sarcoma Tumor Microenvironment and Treatment

Sarcomas are a heterogeneous group of malignant mesenchymal tumors, including soft tissue and bone sarcomas. Macrophages in the tumor microenvironment, involved in immunosuppression and leading to tumor development, are called tumor-associated macrophages (TAMs). TAMs are very important in modulating the microenvironment of sarcomas by expressing specific markers and secreting factors that influence immune and tumor cells. They are involved in many signaling pathways, such as p-STAT3/p-Erk1/2, PI3K/Akt, JAK/MAPK, and JAK/STAT3. TAMs also significantly impact the clinical outcomes of patients suffering from sarcomas and are mainly related to poor overall survival rates among bone and soft tissue sarcomas, for example, chondrosarcoma, osteosarcoma, liposarcoma, synovial sarcoma, and undifferentiated pleomorphic sarcoma. This review summarizes the current knowledge on TAMs in sarcomas, focusing on specific markers on sarcoma cells, cell-cell interactions, and the possibly involved molecular pathways. Furthermore, we discuss the clinical significance of macrophages in sarcomas as a potential target for new therapies, presenting clinical relevance, possible new treatment options, and ongoing clinical trials using TAMs in sarcoma treatment.

Regulation and Function of Matrix Metalloproteinase-13 in Cancer Progression and Metastasis

Matrix metalloproteinase-13 (MMP-13) is a member of the Matrix metalloproteinases (MMPs) family of endopeptidases. MMP-13 is produced in low amounts and is well-regulated during normal physiological conditions. Its expression and secretion are, however, increased in various cancers, where it plays multiple roles in tumour progression and metastasis. As an interstitial collagenase, MMP-13 can proteolytically cleave not only collagens I, II and III, but also a range of extracellular matrix proteins (ECMs). Its action causes ECM remodelling and often leads to the release of various sequestered growth and angiogenetic factors that promote tumour cell growth, invasion and angiogenesis. This review summarizes our current understanding of the regulation of MMP-13 expression and secretion and discusses the actions of MMP-13 in cancer progression and metastasis.

α- MSH plays anti-inflammatory and anti-fungal role in Aspergillus Fumigatus keratitis

PURPOSE

To investigate the anti-inflammatory and anti-fungal role of α-melanocyte stimulating hormone (α-MSH) in Aspergillus Fumigatus (A. fumigatus) keratitis.

METHOD

Corneas of C57BL/6 mice were infected with A. Fumigatus. α-MSH (5 ul, 1x10^-4mmol/ml) was given by subconjunctival injection from day 1 to day 3 post infection (p.i.). After 3 days p.i., clinical score was recored and HE staining was tested. Fungal load in mice corneas was observed by plate counting. Pro-inflammatory mediators and pattern recognition receptors (PRRs) were detected. The numbers of neutrophils and macrophages were tested by immunofluorescence staining. The role of α-MSH in RAW264.7 cells after A. fumigatus stimulation were evaluated by PCR and Western blot, and MPKA protein levels including total-JNK (T-JNK), phosphorylated-JNK (P-JNK), total-ERK (T-ERK) and phosphorylated-ERK (P-ERK) were tested via Western blot with or without α-MSH treatment.

RESULTS

Compared with PBS control group, α-MSH treatment alleviated disease response and decreased clinical score at 3 days p.i. HE staining showed less infiltration in corneal tissue after α-MSH treatment. Plate counting experiment showed that number of viable fungus in corneas of α-MSH treated group was less than control group. mRNA levels of IL-1β, TNF-α, IL-6, MIP-2, LOX-1, Dectin-1 and iNOS were decreased. Protein levels of IL-1β, TNF-α, IL-6 and Dectin-1 were decreased. α-MSH treatment also decreased the infiltrating neutrophils and macrophages. The levels of pro-inflammatory cytokines, Dectin-1 and LOX-1 stimulated by A. fumigatus, were also suppressed by pretreatment of α-MSH in RAW264.7 cells. The ratio of P-JNK/T-JNK and P-ERK/T-ERK were down regulated in α-MSH group compared with PBS control group.

CONCLUSION

α-MSH alleviates the severity and decreases fungal load of A. fumigatus keratitis in mice. Migration of neutrophils and macrophages are restrained. α-MSH downregulates the expression of dectin-1 and the ratio of P-JNK/T-JNK and P-ERK/T-ERK in A. fumigatus infection.

Repository corticotropin injection attenuates collagen-induced arthritic joint structural damage and has enhanced effects in combination with etanercept

Background

Melanocortin receptor (MCR) agonists have anti-inflammatory and immunomodulatory properties mediated by receptors expressed on cells relevant to arthritis. Repository corticotropin injection (RCI; Acthar® Gel), an MCR agonist preparation, is approved as adjunctive therapy for rheumatoid arthritis (RA), but its mechanism of action in RA is unclear. This study explored the efficacy of RCI as monotherapy or adjunctive therapy with etanercept (ETN) in an established animal model of collagen-induced arthritis (CIA).

Methods

After induction of CIA, rats (n = 10 per group) were randomized to receive subcutaneous RCI (40, 160, or 400 U/kg twice daily) alone or in combination with ETN (10 mg/kg 3 times daily), ETN alone, or vehicle (on days 13 through 19). Inflammation was assessed via changes in paw edema. Bone damage was determined by microfocal computed tomography histopathology, and immunohistochemistry. Statistical analyses were performed using a 2-way analysis of variance (ANOVA) followed by the Newman-Keuls, Dunn’s, or Dunnett’s multiple comparisons test or a 1-way ANOVA followed by the Dunnett’s or Holm-Sidak multiple comparisons test.

Results

RCI administration resulted in dose-dependent decreases in ankle edema and histopathologic measures of inflammation, pannus formation, cartilage damage, bone resorption, and periosteal bone formation. RCI and ETN showed combined benefits on all parameters measured. Radiographic evidence of bone damage was significantly reduced in rats that received RCI alone or in combination with ETN. This reduction in bone density loss correlated with decreases in the number of CD68-positive macrophages and cathepsin K–positive osteoclasts within the lesions.

Conclusions

As monotherapy or adjunctive therapy with ETN, RCI attenuated CIA-induced joint structural damage in rats. These data support the clinical efficacy of RCI as adjunctive therapy for patients with RA.

Novel anti-inflammatory and chondroprotective effects of the human melanocortin MC1 receptor agonist BMS-470539 dihydrochloride and human melanocortin MC3 receptor agonist PG-990 on lipopolysaccharide activated chondrocytes

Human melanocortin MC1 and MC3 receptors expressed on C-20/A4 chondrocytes exhibit chondroprotective and anti-inflammatory effects when activated by melanocortin peptides. Nearly 9 million people in the UK suffer from osteoarthritis, and bacterial infections play a role in its development. Here, we evaluate the effect of a panel of melanocortin peptides with different selectivity for human melanocortin MC1 (α-MSH, BMS-470539 dihydrochloride) and MC3 ([DTrp⁸]-γ-MSH, PG-990) receptors and C-terminal peptide α-MSH_11-13(KPV), on inhibiting LPS-induced chondrocyte death, pro-inflammatory mediators and induction of anti-inflammatory proteins. C-20/A4 chondrocytes were treated with a panel of melanocortin peptides prophylactically and therapeutically in presence of LPS (0.1 μg/ml). The chondroprotective properties of these peptides determined by cell viability assay, RT-PCR, ELISA for detection of changes in inflammatory markers (IL-6, IL-8 and MMP-1, -3 and -13) and western blotting for expression of the anti-inflammatory protein heme-oxygenase-1. C-20/A4 expressed human melanocortin MC1 and MC3 receptors and melanocortin peptides elevated cAMP. LPS stimulation caused a reduction in C-20/A4 viability, attenuated by the human melanocortin MC1 receptor agonist BMS-470539 dihydrochloride, and MC3 receptor agonists PG-990 and [DTrp⁸]-γ-MSH. Prophylactic and therapeutic regimes of [DTrp⁸]-γ-MSH significantly inhibited LPS-induced modulation of cartilage-damaging IL-6, IL-8, MMPs -1,-3 and -13 mediators both prophylactically and therapeutically, whilst human melanocortin MC1 and MC3 receptor agonists promoted an increase in HO-1 production. In the presence of LPS, activation of human melanocortin MC1 and MC3 receptors provided potent chondroprotection, upregulation of anti-inflammatory proteins and downregulation of inflammatory and proteolytic mediators involved in cartilage degradation, suggesting a new avenue for osteoarthritis treatment.

Melanocortin Regulation of Inflammation

Adrenocorticotropic hormone (ACTH), and α-, β-, and γ-melanocyte-stimulating hormones (α-, β-, γ-MSH), collectively known as melanocortins, together with their receptors (melanocortin receptors), are components of an ancient modulatory system. The clinical use of ACTH in the treatment of rheumatoid arthritis started in 1949, originally thought that the anti-inflammatory action was through hypothalamus-pituitary-adrenal axis and glucocorticoid-dependent. Subsequent decades have witnessed extensive attempts in unraveling the physiology and pharmacology of the melanocortin system. It is now known that ACTH, together with α-, β-, and γ-MSHs, also possess glucocorticoid-independent anti-inflammatory and immunomodulatory effects by activating the melanocortin receptors expressed in the brain or peripheral immune cells. This review will briefly introduce the melanocortin system and highlight the action of melanocortins in the regulation of immune functions from in vitro, in vivo, preclinical, and clinical studies. The potential therapeutic use of melanocortins are also summarized.

Do Neuroendocrine Peptides and Their Receptors Qualify as Novel Therapeutic Targets in Osteoarthritis?

Joint tissues like synovium, articular cartilage, meniscus and subchondral bone, are targets for neuropeptides. Resident cells of these tissues express receptors for various neuroendocrine-derived peptides including proopiomelanocortin (POMC)-derived peptides, i.e., α-melanocyte-stimulating hormone (α-MSH), adrenocorticotropin (ACTH) and β-endorphin (β-ED), and sympathetic neuropeptides like vasoactive intestinal peptide (VIP) and neuropeptide y (NPY). Melanocortins attained particular attention due to their immunomodulatory and anti-inflammatory effects in several tissues and organs. In particular, α-MSH, ACTH and specific melanocortin-receptor (MCR) agonists appear to have promising anti-inflammatory actions demonstrated in animal models of experimentally induced arthritis and osteoarthritis (OA). Sympathetic neuropeptides have obtained increasing attention as they have crucial trophic effects that are critical for joint tissue and bone homeostasis. VIP and NPY are implicated in direct and indirect activation of several anabolic signaling pathways in bone and synovial cells. Additionally, pituitary adenylate cyclase-activating polypeptide (PACAP) proved to be chondroprotective and, thus, might be a novel target in OA. Taken together, it appears more and more likely that the anabolic effects of these neuroendocrine peptides or their respective receptor agonists/antagonists may be exploited for the treatment of patients with inflammatory and degenerative joint diseases in the future.

α-MSH modulates cell adhesion and inflammatory responses of synovial fibroblasts from osteoarthritis patients

INTRODUCTION

The synovium is a target for neuropeptides. Melanocortins have attained particular attention as they elicit antiinflammatory effects. Although synovial fluid from patients with rheumatic diseases contains α-melanocyte-stimulating hormone (α-MSH) it is unknown whether synovial fibroblasts generate α-MSH and respond to melanocortins.

METHODS

Synovial tissue was obtained from osteoarthritis (OA) patients. Cells were isolated and prepared either as primary mixed synoviocytes or propagated as synovial fibroblasts (OASFs). Melanocortin receptor (MC) and proopiomelanocortin (POMC) expression were investigated by endpoint RT-PCR, immunofluorescence and Western immunoblotting. Functional coupling of MC1 was assessed by cAMP and Ca(2+) assays. Cell adhesion was monitored by the xCELLigence system. Secretion of α-MSH, tumour necrosis factor (TNF), interleukin (IL)-6 and IL-8 was determined by ELISA.

RESULTS

OASFs in vitro expressed MC1. MC1 transcripts were present in synovial tissue and appropriate immunoreactivity was detected in synovial fibroblasts in situ. OASFs contained truncated POMC transcripts but neither full-length POMC mRNA, POMC protein nor α-MSH were detectable. In accordance with this only truncated POMC transcripts were present in synovial tissue. α-MSH increased cAMP dose-dependently but did not alter calcium in OASFs. α-MSH also enhanced adhesion of OASFs to fibronectin and reduced TNF, IL-6 and IL-8 secretion in primary mixed synoviocyte cultures. In OASFs, α-MSH modulated basal and TNF/IL-1β-mediated secretion of IL-6 and IL-8.

CONCLUSION

Synovial fibroblasts express MC1in vitro and in situ. α-MSH elicits biological effects in these cells suggesting an endogenous immunomodulatory role of melanocortins within the synovium. Our results encourage in vivo studies with melanocortins in OA models.

MC1R is dispensable for the proteinuria reducing and glomerular protective effect of melanocortin therapy

Melanocortin therapy by using adrenocorticotropic hormone (ACTH) or non-steroidogenic melanocortin peptides attenuates proteinuria and glomerular injury in experimental glomerular diseases and induces remission of nephrotic syndrome in patients with diverse glomerulopathies, even those resistant to steroids. The underlying mechanism remains elusive, but the role of melanocortin 1 receptor (MC1R) has been implicated and was examined here. Four patients with congenital red hair color and nephrotic syndrome caused by idiopathic membranous nephropathy or focal segmental glomerulosclerosis were confirmed by gene sequencing to bear dominant-negative MC1R mutations. Despite prior corticosteroid resistance, all patients responded to ACTH monotherapy and ultimately achieved clinical remission, inferring a steroidogenic-independent and MC1R-dispensable anti-proteinuric effect of melanocortin signaling. In confirmatory animal studies, the protective effect of [Nle⁴, D-Phe⁷]-α-melanocyte stimulating hormone (NDP-MSH), a potent non-steroidogenic pan-melanocortin receptor agonist, on the lipopolysaccharide elicited podocytopathy was completely preserved in MC1R-null mice, marked by reduced albuminuria and diminished histologic signs of podocyte injury. Moreover, in complementary in vitro studies, NDP-MSH attenuated the lipopolysaccharide elicited apoptosis, hypermotility and impairment of filtration barrier function equally in primary podocytes derived from MC1R-null and wild-type mice. Collectively, our findings suggest that melanocortin therapy confers a proteinuria reducing and podoprotective effect in proteinuric glomerulopathies via MC1R-independent mechanisms.

Electroacupuncture protects against articular cartilage erosion by inhibiting mitogen-activated protein kinases in a rat model of osteoarthritis

OBJECTIVE

The therapeutic effects of electroacupuncture (EA) on osteoarthritis (OA) are well documented; however, the precise mechanisms of action have not yet been fully elucidated. The present study aimed to investigate the effect of EA on cartilage in an experimental animal model of OA induced by anterior cruciate ligament transection (ACLT) and to examine for concomitant changes in the expression of mitogen-activated protein kinases (MAPKs) in the articular cartilage.

METHODS

Thirty-three-month-old male Sprague Dawley rats were randomly divided into the following three groups (n=10 each): sham operated group (Control group), ACLT without treatment (ACLT group), and ACLT with EA treatment (ACLT+EA group). One week after ACLT, rats in the ACLT+EA group received 12 weeks of EA treatment. Histological analysis and quantitative real-time PCR were used to investigate the effects of EA on cartilage morphology (quantified using modified Mankin scores) and expression of MAPKs (p38, c-Jun N-terminal kinase (c-Jun), and extracellular signal-regulated kinase (ERK)1), respectively.

RESULTS

ACLT produced coarse cartilage surfaces, fibrous degeneration, and fissuring, all of which were suppressed by EA treatment. Although Mankin scores in the ACLT+EA group were significantly higher compared to the Control group (p<0.01), they were significantly lower than the (untreated) ACLT group (p<0.01). The increase in mRNA expression of p38, c-Jun, ERK1, and matrix metalloproteinase (MMP)-13 observed in cartilage after ACLT was significantly inhibited by EA.

CONCLUSIONS

EA appears to prevent the degeneration of articular cartilage, at least partly through regulation of MMP-13 and inhibition of MAPKs in the cartilage of rats with ACLT-induced OA.

Melanocortin peptides: potential targets in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease resulting in loss of self-tolerance with multiple organs, such as the kidney, skin, joints, and the central nervous system (CNS), being targeted. Numerous immunosuppressant therapies are currently being used for the treatment of SLE, but their clinical utility is somewhat variable because of the clinical heterogeneity. Melanocortins are a family of peptides derived from the common precursor protein pro-opiomelanocortin. These multifunctional peptides activate five subtypes of melanocortin receptors expressed on immune, skin, muscle, bone, and kidney cells and cells within the CNS. Melanocortin peptides have demonstrated a variety of biologic actions including immunomodulation, melanogenesis, and renoprotection. This review aims to introduce the melanocortin system and explore the mechanisms by which they may be beneficial in diseases such as SLE.

α-Melanocyte-stimulating-hormone (α-MSH) modulates human chondrocyte activation induced by proinflammatory cytokines

Background

Alpha-melanocyte-stimulating-hormone (α-MSH) has marked anti-inflammatory potential. Proinflammatory cytokines are critical mediators of the disturbed cartilage homeostasis in osteoarthritis, inhibiting anabolic activities and increasing catabolic activities in chondrocytes. Since human chondrocytes express α-MSH receptors, we evaluated the role of the peptide in modulating chondrocyte production of pro-inflammatory cytokines, matrix metalloproteinases (MMPs), tissue inhibitors of MMPs (TIMPs), inducible nitric oxide synthase (iNOS) and nitric oxide (NO) in response to interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α).

Methods

Human articular chondrocytes were obtained from osteoarthritic joint cartilage from subjects undergoing hip routine arthroplasty procedures. The cells were cultured with or without α-MSH in the presence of IL-1β or TNF-α. Cell-free supernatants were collected and cells immediately lysed for RNA purification. Expression of cytokines, MMPs, TIMPs, iNOS was determined by Reverse Transcription Real-time Polymerase Chain Reaction and enzyme-linked immunosorbent assay. Griess reaction was used for NO quantification.

Results

Gene expression and secretion of IL-6, IL-8, MMP-3, MMP-13 were significantly increased in IL-1β or TNF-α-stimulated chondrocytes; α-MSH did not modify the release of IL-6 or IL-8 while the peptide significantly reduced their gene expression on TNF-α-stimulated cells. A significant inhibition of MMP3 gene expression and secretion from IL-1β or TNFα-stimulated chondrocytes was induced by α-MSH. On the other hand, α-MSH did not modify the release of MMP-13 by cytokine-stimulated chondrocyte but significantly decreased gene expression of the molecule on TNF-α-stimulated cells. Detectable amount of TIMP-3 and TIMP-4 were present in the supernatants of resting chondrocytes and a significant increase of TIMP-3 gene expression and release was induced by α-MSH on unstimulated cells. TIMP-3 secretion and gene expression were significantly increased in IL-1β-stimulated chondrocytes and α-MSH down-regulated gene expression but not secretion of the molecule. TIMP-4 gene expression (but not secretion) was moderately induced in IL-1β-stimulated chondrocytes with a down-regulation exerted by α-MSH. IL-1β and TNF-α were potent stimuli for NO production and iNOS gene expression by chondrocytes; no inhibition was induced by α-MSH on cytokine-stimulated NO production, while the peptide significantly reduced gene expression of iNOS.

Conclusions

Our results underscore a potential anti-inflammatory and chondroprotective activity exerted by α-MSH, increasing TIMP-3 gene expression and release on resting cells and down- modulating TNF-α-induced activation of human chondrocytes. However, the discrepancy between the influences exerted by α-MSH on gene expression and protein release as well as the difference in the inhibitory pattern exerted by α-MSH in TNF-α- or IL-1β-stimulated cells leave some uncertainty on the role of the peptide on chondrocyte modulation.

Melanocortin 1 receptor-signaling deficiency results in an articular cartilage phenotype and accelerates pathogenesis of surgically induced murine osteoarthritis

Proopiomelanocortin-derived peptides exert pleiotropic effects via binding to melanocortin receptors (MCR). MCR-subtypes have been detected in cartilage and bone and mediate an increasing number of effects in diathrodial joints. This study aims to determine the role of MC1-receptors (MC1) in joint physiology and pathogenesis of osteoarthritis (OA) using MC1-signaling deficient mice (Mc1re/e). OA was surgically induced in Mc1re/e and wild-type (WT) mice by transection of the medial meniscotibial ligament. Histomorphometry of Safranin O stained articular cartilage was performed with non-operated controls (11 weeks and 6 months) and 4/8 weeks past surgery. µCT-analysis for assessing epiphyseal bone architecture was performed as a longitudinal study at 4/8 weeks after OA-induction. Collagen II, ICAM-1 and MC1 expression was analysed by immunohistochemistry. Mc1re/e mice display less Safranin O and collagen II stained articular cartilage area compared to WT prior to OA-induction without signs of spontaneous cartilage surface erosion. This MC1-signaling deficiency related cartilage phenotype persisted in 6 month animals. At 4/8 weeks after OA-induction cartilage erosions were increased in Mc1re/e knees paralleled by weaker collagen II staining. Prior to OA-induction, Mc1re/e mice do not differ from WT with respect to bone parameters. During OA, Mc1re/e mice developed more osteophytes and had higher epiphyseal bone density and mass. Trabecular thickness was increased while concomitantly trabecular separation was decreased in Mc1re/e mice. Numbers of ICAM-positive chondrocytes were equal in non-operated 11 weeks Mc1re/e and WT whereas number of positive chondrocytes decreased during OA-progression. Unchallenged Mc1re/e mice display smaller articular cartilage covered area without OA-related surface erosions indicating that MC1-signaling is critical for proper cartilage matrix integrity and formation. When challenged with OA, Mc1re/e mice develop a more severe OA-pathology. Our data suggest that MC1-signaling protects against cartilage degradation and subchondral bone sclerosis in OA indicating a beneficial role of the POMC system in joint pathophysiology.

Curbing Inflammation through Endogenous Pathways: Focus on Melanocortin Peptides

The resolution of inflammation is now known to be an active process, armed with a multitude of mediators both lipid and protein in nature. Melanocortins are peptides endowed with considerable promise with their proresolution and anti-inflammatory effects in preclinical models of inflammatory disease, with tissue protective effects. These peptides and their targets are appealing because they can be seen as a natural way of inducing these effects as they harness endogenous pathways of control. Whereas most of the information generated about these mediators derives from several acute models of inflammation (such as zymosan induced peritonitis), there is some indication that these mediators may inhibit chronic inflammation by modulating cytokines, chemokines, and leukocyte apoptosis. In addition, proresolving mediators and their mimics have often been tested alongside therapeutic protocols, hence have been tested in settings more relevant to real life clinical scenarios. We provide here an overview on some of these mediators with a focus on melanocortin peptides and receptors, proposing that they may unveil new opportunities for innovative treatments of inflammatory arthritis.

Chondroprotective and anti-inflammatory role of melanocortin peptides in TNF-α activated human C-20/A4 chondrocytes

BACKGROUND AND PURPOSE

Melanocortin MC(1) and MC(3 ) receptors, mediate the anti-inflammatory effects of melanocortin peptides. Targeting these receptors could therefore lead to development of novel anti-inflammatory therapeutic agents. We investigated the expression of MC(1) and MC(3) receptors on chondrocytes and the role of α-melanocyte-stimulating hormone (α-MSH) and the selective MC(3) receptor agonist, [DTRP(8) ]-γ-MSH, in modulating production of inflammatory cytokines, tissue-destructive proteins and induction of apoptotic pathway(s) in the human chondrocytic C-20/A4 cells.

EXPERIMENTAL APPROACH

Effects of α-MSH, [DTRP(8) ]-γ-MSH alone or in the presence of the MC(3/4) receptor antagonist, SHU9119, on TNF-α induced release of pro-inflammatory cytokines, MMPs, apoptotic pathway(s) and cell death in C-20/A4 chondrocytes were investigated, along with their effect on the release of the anti-inflammatory cytokine IL-10.

KEY RESULTS

C-20/A4 chondrocytes expressed functionally active MC(1,3) receptors. α-MSH and [DTRP(8) ]-γ-MSH treatment, for 30 min before TNF-α stimulation, provided a time-and-bell-shaped concentration-dependent decrease in pro-inflammatory cytokines (IL-1β, IL-6 and IL-8) release and increased release of the chondroprotective and anti-inflammatory cytokine, IL-10, whilst decreasing expression of MMP1, MMP3, MMP13 genes.α-MSH and [DTRP(8) ]-γ-MSH treatment also inhibited TNF-α-induced caspase-3/7 activation and chondrocyte death. The effects of [DTRP(8) ]-γ-MSH, but not α-MSH, were abolished by the MC(3/4) receptor antagonist, SHU9119.

CONCLUSION AND IMPLICATIONS

Activation of MC(1) /MC(3) receptors in C-20/A4 chondrocytes down-regulated production of pro-inflammatory cytokines and cartilage-destroying proteinases, inhibited initiation of apoptotic pathways and promoted release of chondroprotective and anti-inflammatory cytokines. Developing small molecule agonists to MC(1) /MC(3) receptors could be a viable approach for developing chondroprotective and anti-inflammatory therapies in rheumatoid and osteoarthritis.

Standardized butanol fraction of WIN-34B suppresses cartilage destruction via inhibited production of matrix metalloproteinase and inflammatory mediator in osteoarthritis human cartilage explants culture and chondrocytes

Background

WIN-34B is a novel Oriental medicine, which represents the n-butanol fraction prepared from dried flowers of Lonicera japonica Thunb and dried roots of Anemarrhena asphodeloides BUNGE. The component herb of WIN-34B is used for arthritis treatment in East Asian countries. The aim of this study was to determine the cartilage-protective effects and mechanisms of WIN-34B and its major phenolic compounds, chlorogenic acid and mangiferin, in osteoarthritis (OA) human cartilage explants culture and chondrocytes.

Methods

The investigation focused on whether WIN-34B and its standard compounds protected cartilage in interleukin (IL)-1β-stimulated cartilage explants culture and chondrocytes derived from OA patients. Also, the mechanisms of WIN-34B on matrix metalloproteinases (MMPs), tissue inhibitor of matrix metalloproteinases (TIMPs), inflammatory mediators, and mitogen-activated protein kinases (MAPKs) pathways were assessed.

Results

WIN-34B was not cytotoxic to cultured cartilage explants or chondrocytes. WIN-34B dose-dependently inhibited the release of glycosaminoglycan and type II collagen, increased the mRNA expression of aggrecan and type II collagen, and recovered the intensity of proteoglycan and collagen by histological analysis in IL-1β-stimulated human cartilage explants culture. The cartilage protective effect of WIN-34B was similar to or better than that of chlorogenic acid and mangiferin. Compared to chlorogenic acid and mangiferin, WIN-34B displayed equal or greater decreases in the levels of MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5, and markedly up-regulated TIMP-1 and TIMP-3. WIN-34B inhibited inflammatory mediators involved in cartilage destruction, such as prostaglandin E2, nitric oxide, tumor necrosis factor-alpha, and IL-1β. The phosphorylation of extracellular signal-regulated kinase, c-Jun N-terminal kinase (JNK), and p38 was significantly reduced by WIN-34B treatment, while phosphorylation of JNK was only inhibited by chlorogenic acid or mangiferin in IL-1β-stimulated chondrocytes.

Conclusions

WIN-34B is potentially valuable as a treatment for OA by virtue of its suppression of MMPs, ADAMTSs, and inflammatory mediators, and it’s up-regulation of TIMP-1 and TIMP-3 involved in the MAPK pathway.

Role of proopiomelanocortin-derived peptides and their receptors in the osteoarticular system: from basic to translational research

Proopiomelanocortin (POMC)-derived peptides such as melanocortins and β-endorphin (β-ED) exert their pleiotropic effects via binding to melanocortin receptors (MCR) and opioid receptors (OR). There is now compelling evidence for the existence of a functional POMC system within the osteoarticular system. Accordingly, distinct cell types of the synovial tissue and bone have been identified to generate POMC-derived peptides like β-ED, ACTH, or α-MSH. MCR subtypes, especially MC1R, MC2R (the ACTH receptor), MC3R, and MC4R, but also the μ-OR and δ-OR, have been detected in various cells of the synovium, cartilage, and bone. The respective ligands of these POMC-derived peptide receptors mediate an increasing number of newly recognized biological effects in the osteoarticular system. These include bone mineralization and longitudinal growth, cell proliferation and differentiation, extracellular matrix synthesis, osteoprotection, and immunomodulation. Importantly, bone formation is also regulated by the central melanocortin system via a complex hormonal interplay with other organs and tissues involved in energy metabolism. Among the POMC-derived peptides examined in cell culture systems from osteoarticular tissue and in animal models of experimentally induced arthritis, α-MSH, ACTH, and MC3R-specific agonists appear to have the most promising antiinflammatory actions. The effects of these melanocortin peptides may be exploited in future for the treatment of patients with inflammatory and degenerative joint diseases.

Looping mediated interaction between the promoter and 3' UTR regulates type II collagen expression in chondrocytes

Type II collagen is the major component of articular cartilage and is mainly synthesized by chondrocytes. Repeated sub-culturing of primary chondrocytes leads to reduction of type II collagen gene (Col2a1) expression, which mimics the process of chondrocyte dedifferentiation. Although the functional importance of Col2a1 expression has been extensively investigated, mechanism of transcriptional regulation during chondrocyte dedifferentiation is still unclear. In this study, we have investigated the crosstalk between cis-acting DNA element and transcription factor on Col2a1 expression in primary chondrocytes. Bioinformatic analysis revealed the potential regulatory regions in the Col2a1 genomic locus. Among them, promoter and 3′ untranslated region (UTR) showed highly accessible chromatin architecture with enriched recruitment of active chromatin markers in primary chondrocytes. 3′ UTR has a potent enhancer function which recruits Lef1 (Lymphoid enhancer binding factor 1) transcription factor, leading to juxtaposition of the 3′ UTR with the promoter through gene looping resulting in up-regulation of Col2a1 gene transcription. Knock-down of endogenous Lef1 level significantly reduced the gene looping and subsequently down-regulated Col2a1 expression. However, these regulatory loci become inaccessible due to condensed chromatin architecture as chondrocytes dedifferentiate which was accompanied by a reduction of gene looping and down-regulation of Col2a1 expression. Our results indicate that Lef1 mediated looping between promoter and 3′ UTR under the permissive chromatin architecture upregulates Col2a1 expression in primary chondrocytes.

Neuroendocrine and non-neuroendocrine markers of inflammation associated with performance in endurance horses

REASONS FOR PERFORMING STUDY

The inflammatory and neuroendocrine response to endurance exercise and relationship of these parameters to performance is not well documented in horses. HYPOTHESES OR OBJECTIVES: Evidence of systemic inflammation is associated with poor performance in horses competing in endurance events.

METHODS

Blood was collected prior to and at the finish or elimination point from horses competing in both the 80 and 160 km American Endurance Ride National Championship competitions in 2006. Immunoreactive alpha-melanocyte stimulating hormone (α-MSH) and tumour necrosis factor-alpha (TNF-α) were quantified utilising radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques, respectively. The concentration of total thiobarbituric acid reactive substances (TBARS) was measured fluorometrically.

RESULTS

Thirty horses were included in the study. Endurance exercise was associated with a significant increase in TBARS in the 80 km group but not the 160 km group. TNF-α and α-MSH did not significantly change as a result of exercise in either distance group. Precompetition TBARS was significantly higher in horses that failed to finish the 80 km race, as well as when distances were combined. In addition, precompetition α-MSH was significantly lower in nonfinishers in the 160 km group. Furthermore, competition speed was positively correlated with precompetition α-MSH in the 80 km and negatively correlated with precompetition TNF-α when distances were combined.

CONCLUSIONS

Our results suggest that basal oxidative stress markers, circulating cytokines and anti-inflammatory neuroendocrine hormones appear to correlate with endurance performance in horses.

POTENTIAL RELEVANCE

Basal oxidative stress markers, circulating cytokines and anti-inflammatory neuroendocrine hormones may be predictive of athletic performance in endurance horses. Future studies evaluating the effect of training on these markers in endurance horses are warranted.

The Bone Niche of Chondrosarcoma: A Sanctuary for Drug Resistance, Tumour Growth and also a Source of New Therapeutic Targets

Chondrosarcomas are malignant cartilage-forming tumours representing around 20% of malignant primary tumours of bone and affect mainly adults in the third to sixth decade of life. Unfortunately, the molecular pathways controlling the genesis and the growth of chondrosarcoma cells are still not fully defined. It is well admitted that the invasion of bone by tumour cells affects the balance between early bone resorption and formation and induces an “inflammatory-like” environment which establishes a dialogue between tumour cells and their environment. The bone tumour microenvironment is then described as a sanctuary that contributes to the drug resistance patterns and may control at least in part the tumour growth. The concept of “niche” defined as a specialized microenvironment that can promote the emergence of tumour stem cells and provide all the required factors for their development recently emerges in the literature. The present paper aims to summarize the main evidence sustaining the existence of a specific bone niche in the pathogenesis of chondrosarcomas.

Melanin and melanogenesis in adipose tissue: possible mechanisms for abating oxidative stress and inflammation?

Obesity has become a worldwide epidemic and can lead to multiple chronic diseases. Adipose tissue is increasingly thought to play an active role in obesity-related pathologies such as insulin resistance and non-alcoholic fatty liver disease. Obesity has been strongly associated with systemic inflammation and, to a lesser degree, with oxidative stress, although the causal relationships among these factors are unclear. A recent study demonstrating an expression of the components of the melanogenic pathway and the presence of melanin in visceral adipose has raised questions regarding the possible role of melanogenesis in adipose tissue. As this study also found larger amounts of melanin in the adipose tissue of obese patients relative to lean ones, we hypothesize that melanin, a pigment known for its antioxidant and anti-inflammatory properties, may scavenge reactive oxygen species and abate oxidative stress and inflammation in adipose tissue. This review considers the evidence to support such a hypothesis, and speculates on the role of melanin within adipocytes. Furthermore, we consider whether the α-melanocyte-stimulating hormone or its synthetic analogues could be used to stimulate melanin production in adipocytes, should the hypothesis be supported in future experiments.

Inhibition of cartilage damage by pro-opiomelanocortin prohormone overexpression in a rat model of osteoarthritis

Pro-opiomelanocortin (POMC) is a precursor of various neuropeptides. POMC-derived neuropeptides are potent inflammation inhibitors and immunosuppressants. Evidence that osteoarthritis (OA) is an inflammatory disease is accumulating. We assessed whether intra-articular gene delivery of POMC ameliorates experimentally induced OA in a rat model. OA was induced in Wistar rats by anterior cruciate ligament-transection (ACLT) in the knee of one hind limb. Adenoviral vector encoding human POMC (AdPOMC) was injected intra-articularly into the knee joints after ACLT. The transgene expression and the inflammatory responses were evaluated using immunoblotting, immunohistochemistry and enzyme-linked immunosorbent assay. The treated joints were assessed histologically for manifestations of the disease. Human POMC was expressed in the chondrocytes and synovial membrane after the intra-articular injection. POMC gene transfer reduced nuclear factor- κB activity and the levels of interleukin-1 β in HTB-94 chondrosarcoma cells and Raw 264.7 macrophages; it also reduced microvessel density in the synovium. Histological examination showed that symptoms of OA in AdPOMC-treated rats were less severe than in rats treated with either empty adenoviral vector (AdNull) or normal saline. Intra-articular injection of adenoviral vectors expressing POMC significantly suppressed the progression and severity of OA, and reduced inflammatory responses and angiogenesis. POMC gene delivery may offer novel therapeutic approach for treating OA.

Glomerular angiotensinogen is induced in mesangial cells in diabetic rats via reactive oxygen species--ERK/JNK pathways

Whereas intra-renal angiotensinogen is predominantly localized in proximal tubular cells under basal conditions, it has been previously reported that angiotensinogen expression is induced in glomeruli under pathological conditions. However, there is no detailed information regarding the mechanism of the induced glomerular angiotensinogen. We used genetic pairs of Zucker diabetic fatty (ZDF) obese and lean rats to determine glomerular angiotensinogen expression. The levels of glomerular angiotensinogen immunoreactivity in ZDF obese rats were higher than those in ZDF lean rats. Double staining by IHC or IF with angiotensinogen and Thy1.1 antibodies showed that the majority of angiotensinogen in glomeruli was seen in mesangial cells. The levels of glomerular immunoreactivity for 4-HNE and urinary excretion of 8-isoprostane-markers of ROS-in ZDF obese rats were higher than those in ZDF lean rats. To confirm this system, primary rat mesangial cells were treated with hydrogen peroxide (H₂O₂) to clarify the signal transduction pathway for glomerular angiotensinogen expression. H₂O₂ induced an increase in angiotensinogen expression in a dose- and time-dependent manner, and the H₂O₂-induced upregulation of angiotensinogen was suppressed by catalase. Furthermore, the H₂O₂-induced upregulation of angiotensinogen was inhibited by a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor and a c-Jun N-terminal kinase (JNK) inhibitor, but not inhibited by a p38 MAPK inhibitor. These data suggest that the majority of angiotensinogen was induced in mesangial cells in glomeruli under pathological conditions such as diabetic nephropathy, and angiotensinogen expression in mesangial cells was mediated by H₂O₂ and the subsequent activation of extracellular-regulated kinase (ERK)/JNK pathways.

MAPKs are essential upstream signaling pathways in proteolytic cartilage degradation--divergence in pathways leading to aggrecanase and MMP-mediated articular cartilage degradation

OBJECTIVES

Matrix metalloproteinases (MMPs) and aggrecanases are essential players in cartilage degradation. However, the signaling pathways that results in MMP and/or aggrecanase synthesis and activation are not well understood. We investigated the molecular events leading to MMP- and aggrecanase-mediated cartilage degradation.

METHODS

Cartilage degradation was induced in bovine articular cartilage explants by oncostatin M (OSM) and tumor necrosis factor (TNF), in the presence or absence of specific inhibitors of the mitogen-activated protein kinases (MAPKs) P38, P44/42 and Src family. Toxicity was followed by the AlamarBlue colorimetric assay. MMP-activity was assessed using a fluorescent substrate assay and MMP-9 and -2 activities by gelatinase zymography. MMP-mediated collagen type II degradation and MMP as well as aggrecanase-mediated aggrecan degradation was investigated with specific ELISA and hydroxyproline release by standard methods. The findings were verified by immunohistochemistry and histology.

RESULTS

Stimulation of cartilage degradation by OSM+TNF resulted in 100-fold induction of CTX-II release (P<0.01). This was dose-dependently inhibited by MAPK P38 inhibitors and by the MAPK P44/42 inhibitors. MMP-activity and expression was significantly decreased, as evaluated by cleavage of fluorescence MMP-substrate and zymography. Immunohistochemistry confirmed these findings. Interestingly, only the P44/42 inhibitors abrogated aggrecanase-mediated aggrecan degradation.

CONCLUSION

We found that inhibition of MAPK P38, P44/42 and Src family abrogated proteolytic cartilage degradation by blocking MMP synthesis and activity. However, only MAPK P44/42 was essential for aggrecanase-mediated aggrecan degradation. These data suggest that various aspects of cartilage degradation can be targeted independently by inhibiting specific upstream signaling pathway.

Upregulation of MMP-9 production by TNFalpha in keratinocytes and its attenuation by vitamin D

MMP-9, a member of the matrix metalloproteinase family that degrades collagen IV and processes chemokines and cytokines, participates in epidermal remodeling in response to stress and injury. Limited activity of MMP-9 is essential while excessive activity is deleterious to the healing process. Tumor necrosis factor (TNFalpha), a key mediator of cutaneous inflammation, is a powerful inducer of MMP-9. Calcitriol, the hormonally active vitamin D metabolite, and its analogs are known to attenuate epidermal inflammation. We aimed to examine the modulation of MMP-9 by calcitriol in TNFalpha-treated keratinocytes. The immortalized HaCaT keratinocytes were treated with TNFalpha in the absence of exogenous growth factors or active ingredients. MMP-9 production was quantified by gelatin zymography and real-time RT-PCR. Activation of signaling cascades was assessed by western blot analysis and DNA-binding activity of transcription factors was determined by EMSA. Exposure to TNFalpha markedly increased the protein and mRNA levels of MMP-9, while pretreatment with calcitriol dose dependently reduced this effect. Employing specific inhibitors we established that the induction of MMP-9 by TNFalpha was dependent on the activity of the epidermal growth factor receptor, c-Jun-N-terminal kinase (JNK), NFkappaB and extracellular signal-regulated kinase-1/2. The effect of calcitriol was associated with inhibition of JNK activation and reduction of DNA-binding activities of the transcription factors activator protein-1 (AP-1) and NFkappaB following treatment with TNFalpha. By down-regulating MMP-9 levels active vitamin D derivatives may attenuate deleterious effects due to excessive TNFalpha-induced proteolytic activity associated with cutaneous inflammation.

The melanocortin system in articular chondrocytes: melanocortin receptors, pro-opiomelanocortin, precursor proteases, and a regulatory effect of alpha-melanocyte-stimulating hormone on proinflammatory cytokines and extracellular matrix components

OBJECTIVE

The pro-opiomelanocortin (POMC)-derived neuropeptide alpha-melanocyte-stimulating hormone (alpha-MSH) mediates its effects via melanocortin (MC) receptors. This study was carried out to investigate the expression patterns of the MC system and the effects of alpha-MSH in human articular chondrocytes.

METHODS

Articular chondrocytes established from human osteoarthritic joint cartilage were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting for the expression of MC receptors, POMC, and prohormone convertases (PCs). MC-1 receptor (MC-1R) expression in articular cartilage was further studied by immunohistochemistry. Ca(2+) and cAMP assays were used to monitor alpha-MSH signaling, while studies of alpha-MSH function were performed in cultures with chondrocyte micromass pellets stimulated with alpha-MSH. Expression of cytokines and extracellular matrix (ECM) components was determined by real-time RT-PCR, Western immunoblotting, and enzyme-linked immunosorbent assays.

RESULTS

MC-1R expression was detected in articular chondrocytes in vitro and in articular cartilage in situ. In addition, expression of transcripts for MC-2R, MC-5R, POMC, and PCs was detected in articular chondrocytes. Stimulation with alpha-MSH increased the levels of intracellular cAMP, but not Ca(2+), in chondrocytes. Both messenger RNA and protein expression of various proinflammatory cytokines, collagens, matrix metalloproteinases (MMPs), and SOX9 was modulated by alpha-MSH.

CONCLUSION

Human articular chondrocytes are target cells for alpha-MSH. The effects of alpha-MSH on expression of cytokines and MMPs suggest that this neuropeptide plays a role in inflammatory and degenerative processes in cartilage. It is conceivable that inflammatory reactions can be mitigated by the induction of endogenous MCs or administration of alpha-MSH to the affected joints. The induction pattern of regulatory and structural ECM components such as collagens as well as SOX9 and anabolic and catabolic cytokines points to a function of alpha-MSH as a trophic factor in skeletal development during endochondral ossification rather than as a factor in homeostasis of permanent cartilage.

Elevation of intracellular cyclic AMP inhibits NF-kappaB-mediated thymosin beta4 expression in melanoma cells

Thymosin beta4 (Tbeta4) is a major actin-sequestering protein that has been implicated in the growth, survival, motility, and metastasis of certain tumors and is considered an indicator for malignant progression. Therefore, identifying compounds that can downregulate Tbeta4 expression is very important for the development of anti-cancer chemotherapies. In this study, we investigated the effects of elevated cAMP on Tbeta4 expression and the metastatic potential of murine B16 melanoma cells. In addition, we also dissected the mechanism underlying cAMP-mediated Tbeta4 suppression. We found that treatment with the cAMP-inducing compounds alpha-MSH (alpha-melanocyte stimulating hormone) and IBMX (3-isobutyl-1-methylxanthine) significantly suppressed Tbeta4 expression and regulated EMT-associated genes through the suppression of NF-kappaB activation in B16F10 cells. Along with decreased Tbeta4 expression, the in vitro invasiveness and anchorage-independent growth in a semi-solid agar of these cells were also inhibited. In animal experiments, the metastatic potential of the alpha-MSH- or IBMX-treated B16F10 melanoma cells was decreased compared to untreated control cells. Collectively, our data demonstrate that elevated intracellular cAMP significantly suppresses Tbeta4 expression and reduces MMP-9 activity, which leads to decreased metastatic potential. Moreover, suppression of NF-kappaB activation by alpha-MSH or IBMX is critical for inhibiting Tbeta4 expression.

Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases

Alpha-MSH is a tridecapeptide derived from proopiomelanocortin. Many studies over the last few years have provided evidence that alpha-MSH has potent protective and antiinflammatory effects. These effects can be elicited via centrally expressed melanocortin receptors that orchestrate descending neurogenic antiinflammatory pathways. alpha-MSH can also exert antiinflammatory and protective effects on cells of the immune system and on peripheral nonimmune cell types expressing melanocortin receptors. At the molecular level, alpha-MSH affects various pathways implicated in regulation of inflammation and protection, i.e., nuclear factor-kappaB activation, expression of adhesion molecules and chemokine receptors, production of proinflammatory cytokines and mediators, IL-10 synthesis, T cell proliferation and activity, inflammatory cell migration, expression of antioxidative enzymes, and apoptosis. The antiinflammatory effects of alpha-MSH have been validated in animal models of experimentally induced fever; irritant and allergic contact dermatitis, vasculitis, and fibrosis; ocular, gastrointestinal, brain, and allergic airway inflammation; and arthritis, but also in models of organ injury. One obstacle limiting the use of alpha-MSH in inflammatory disorders is its pigmentary effect. Due to its preserved antiinflammatory effect but lack of pigmentary action, the C-terminal tripeptide of alpha-MSH, KPV, has been delineated as an alternative for antiinflammatory therapy. KdPT, a derivative of KPV corresponding to amino acids 193-195 of IL-1beta, is also emerging as a tripeptide with antiinflammatory effects. The physiochemical properties and expected low costs of production render both agents suitable for the future treatment of immune-mediated inflammatory skin and bowel disease, fibrosis, allergic and inflammatory lung disease, ocular inflammation, and arthritis.