Retinoic acid blocks pro-inflammatory cytokine-induced matrix metalloproteinase production by down-regulating JNK-AP-1 signaling in human chondrocytes

Retinoic acid attenuates ischemic injury-induced activation of glial cells and inflammatory factors in a rat stroke model

Stroke is a leading cause of death and long-term disability which can cause oxidative damage and inflammation of the neuronal cells. Retinoic acid is an active metabolite of vitamin A that has various beneficial effects including antioxidant and anti-inflammatory effects. In this study, we investigated whether retinoic acid modulates oxidative stress and inflammatory factors in a stroke animal model. A middle cerebral artery occlusion (MCAO) was performed on adult male rats to induce focal cerebral ischemia. Retinoic acid (5 mg/kg) or vehicle was injected into the peritoneal cavity for four days before MCAO surgery. The neurobehavioral tests were carried out 24 h after MCAO and cerebral cortex tissues were collected. The cortical damage was assessed by hematoxylin-eosin staining and reactive oxygen species assay. In addition, Western blot and immunohistochemical staining were performed to investigate the activation of glial cells and inflammatory cytokines in MCAO animals. Ionized calcium-binding adapter molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) were used as markers of microglial and astrocyte activation, respectively. Tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were used as representative pro-inflammatory cytokines. Results showed that MCAO damage caused neurobehavioral defects and histopathological changes in the ischemic region and increased oxidative stress. Retinoic acid treatment reduced these changes caused by MCAO damage. We detected increases in Iba-1 and GFAP in MCAO animals treated with vehicle. However, retinoic acid alleviated increases in Iba-1 and GFAP caused by MCAO damage. Moreover, MCAO increased levels of nuclear factor-κB and pro-inflammatory cytokines, including TNF-α and IL-1β. Retinoic acid alleviated the expression of these inflammatory proteins. These findings elucidate that retinoic acid regulates microglia and astrocyte activation and modulates pro-inflammatory cytokines. Therefore, this study suggests that retinoic acid exhibits strong antioxidant and anti-inflammatory properties by reducing oxidative stress, inhibiting neuroglia cell activation, and preventing the increase of pro-inflammatory cytokines in a cerebral ischemia.

Curcumin derived from medicinal homologous foods: its main signals in immunoregulation of oxidative stress, inflammation, and apoptosis

It has been for thousands of years in China known medicinal homologous foods that can be employed both as foods and medicines to benefit human and animal health. These edible herbal materials perform divert roles in the regulation of metabolic disorders, cancers, and immune-related diseases. Curcumin, the primary component derived from medicinal homologous foods like curcuma longa rhizome, is reported to play vital actions in organic activities, such as the numerous pharmacological functions including anti-oxidative stress, anti-inflammation and anti/pro-apoptosis in treating various diseases. However, the potential mechanisms of curcumin-derived modulation still need to be developed and attract more attention worldwide. Given that these signal pathways are enrolled in important bioactive reactions, we collected curcumin's last achievements predominantly on the immune-regulation signals with the underlying targetable strategies in the last 10 years. This mini-review will be helpful to accelerate curcumin and other extracts from medicinal homologous foods use in future human clinical applications.

Hand osteoarthritis: clinical phenotypes, molecular mechanisms and disease management

Osteoarthritis (OA) is a highly prevalent condition, and the hand is the most commonly affected site. Patients with hand OA frequently report symptoms of pain, functional limitations and frustration in undertaking everyday activities. The condition presents clinically with changes to the bone, ligaments, cartilage and synovial tissue, which can be observed using radiography, ultrasonography or MRI. Hand OA is a heterogeneous disorder and is considered to be multifactorial in aetiology. This Review provides an overview of the epidemiology, presentation and burden of hand OA, including an update on hand OA imaging (including the development of novel techniques), disease mechanisms and management. In particular, areas for which new evidence has substantially changed the way we understand, consider and treat hand OA are highlighted. For example, genetic studies, clinical trials and careful prospective imaging studies from the past 5 years are beginning to provide insights into the pathogenesis of hand OA that might uncover new therapeutic targets in the disease.

Anti-inflammatory and anti-osteoarthritis effects of Cm-02 and Ck-02

Osteoarthritis (OA) is a common degenerative joint disease characterized by progressive deterioration of articular cartilage. There have been reports that small molecule inhibitors have anti-osteoarthritis effects; however, the effects of 3-(4-chloro-2-fluorophenyl)-6-(2,4-difluorophenyl)-2H-benzo[e] [1,3]oxazine-2,4(3H)-dione (Cm-02) and 6-(2,4-difluorophenyl)-3-(3,4-difluorophenyl)-2H-benzo[e] [1,3]oxazine-2,4(3H)-dione (Ck-02), small molecule inhibitors which share many structural similarities with quercetin (a potent anti-inflammatory flavonoid), remain unclear. In this study, TNF-α-stimulated porcine and human chondrocyte models were used to investigate the inhibitory effects of Cm-02 and Ck-02 on the molecular mechanisms underlying the anti-OA effects. TNF-α was used to stimulate porcine and human chondrocytes to mimic immunomodulatory potency in-vitro. Anti-osteoarthritic effects were characterized in terms of protein and mRNA levels associated with the pathogenesis of OA. We also examined (1) the inducible nitric oxide synthase (iNOS)-nitric oxide (NO) system in cultured chondrocytes, (2) matrix metalloproteinases (MMPs) in cultured chondrocytes, and (3) aggrecan degradation in cartilage explants. Finally, we tested the activation of nuclear factor-kappaB (NF-κB), interferon regulatory factor-1 (IRF-1), and activate the protein-1 (AP-1), and we tested the signal transduction and activation of transcription-3 (STAT-3). Our results indicate that, in chondrocytes, Cm-02 and Ck-02 inhibit TNF-α induced NO production, iNOS, MMP, the expression of disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), and the enzyme activity of MMP-13. Furthermore, both Cm-02 and Ck-02 were found to stimulate TNF-α, which has been shown to suppress the activation of several transcription factors, including NF-κB, STAT-3, and IRF-1 in porcine and human chondrocytes. Cm-02 and Ck-02 were also found to help prevent the release of proteoglycans from cartilage explants. Our findings demonstrate that both Cm-02 and Ck-02 have potent anti-inflammatory activities and the ability to protect cartilage in an OA cell model. These findings indicate that Cm-02 and Ck-02 have the potential to be further developed for the therapeutic treatment of OA.

Chondroprotective Effects of Genistein against Osteoarthritis Induced Joint Inflammation

Genistein is an isoflavone extracted from soybean (Glycine max). This compound has anti-inflammatory, anti-oxidative, and anti-cancer effects; however, the mechanism underlying the effects of genistein on IL-1β-stimulated human osteoarthritis (OA) chondrocytes remains unknown. Our objectives in this study were to explore the anti-inflammatory effects of genistein on IL-1β-stimulated human OA chondrocytes and to investigate the potential mechanisms which underlie them. Our results from an in-vitro model of osteoarthritis indicate that genistein inhibits the IL-1β-induced expression of the catabolic factors nitric oxide synthase 2 (NOS2), cyclooxygenase 2 (COX-2), and matrix metalloproteinases (MMPs). Genistein was shown to stimulate Ho-1 expression, which has been associated with Nrf-2 pathway activation in human chondrocytes. In a rat model, genistein was also shown to attenuate the progression of traumatic osteoarthritis. Taken together, these results demonstrate the effectiveness of genistein in mediating the inflammation associated with joint disorders. Our results also indicate that genistein could potentially serve as an alternative therapeutic treatment for OA.

MMP-3 and MMP-8 in rat mandibular condylar cartilage associated with dietary loading, estrogen level, and aging

OBJECTIVES

The structure of the mandibular condylar cartilage (MCC) is regulated by dynamic and multifactorial processes. The aim of this study was to examine the effects of altered dietary loading, estrogen level, and aging on the structure of the condylar cartilage and the expressions of matrix metalloproteinase (MMP) -3 and MMP-8 of rat MCC.

METHODS

In this study, Crl:CD (SD) female rats were randomly divided into 3 groups according to dietary hardness: hard diet (diet board), normal diet (pellet), and soft diet (powder). In each group, the rats were further divided into 2 subgroups by ovariectomy at the age of 7 weeks. The rats were sacrificed at 5- and 14-month-old. Histomorphometric analysis of the MCC thickness was performed after toluidine blue staining. Immunochemical staining was done for MMP-3 and MMP-8. A linear mixed model was used to assess the effects of dietary loading, estrogen level, and aging.

RESULTS

Increased dietary loading was the main factor to increase the MMP-3 expression and the anterior and central thickness of the MCC. Lack of estrogen was the main factor associated with decreased MMP-8. Aging was associated with the thickness changes of the whole condylar cartilage and the reduced expression of MMP-8.

CONCLUSION

The condylar cartilage structure and metabolism of the female rats are sensitive to dietary loading changes, estrogen level as well as aging. The proper balance of these factors seems to be essential for the maintenance of the condylar cartilage.

Arthroprotective Effects of Cf-02 Sharing Structural Similarity with Quercetin

In this study, we synthesized hundreds of analogues based on the structure of small-molecule inhibitors (SMIs) that were previously identified in our laboratory with the aim of identifying potent yet safe compounds for arthritis therapeutics. One of the analogues was shown to share structural similarity with quercetin, a potent anti-inflammatory flavonoid present in many different fruits and vegetables. We investigated the immunomodulatory effects of this compound, namely 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (Cf-02), in a side-by-side comparison with quercetin. Chondrocytes were isolated from pig joints or the joints of patients with osteoarthritis that had undergone total knee replacement surgery. Several measures were used to assess the immunomodulatory potency of these compounds in tumor necrosis factor (TNF-α)-stimulated chondrocytes. Characterization included the protein and mRNA levels of molecules associated with arthritis pathogenesis as well as the inducible nitric oxide synthase (iNOS)–nitric oxide (NO) system and matrix metalloproteinases (MMPs) in cultured chondrocytes and proteoglycan, and aggrecan degradation in cartilage explants. We also examined the activation of several important transcription factors, including nuclear factor-kappaB (NF-κB), interferon regulatory factor-1 (IRF-1), signal transducer and activator of transcription-3 (STAT-3), and activator protein-1 (AP-1). Our overall results indicate that the immunomodulatory potency of Cf-02 is fifty-fold more efficient than that of quercetin without any indication of cytotoxicity. When tested in vivo using the induced edema method, Cf-02 was shown to suppress inflammation and cartilage damage. The proposed method shows considerable promise for the identification of candidate disease-modifying immunomodulatory drugs and leads compounds for arthritis therapeutics.

Chondroprotective Effects and Mechanisms of Dextromethorphan: Repurposing Antitussive Medication for Osteoarthritis Treatment

Osteoarthritis (OA) is the most common joint disorder and primarily affects older people. The ideal anti-OA drug should have a modest anti-inflammatory effect and only limited or no toxicity for long-term use. Because the antitussive medication dextromethorphan (DXM) is protective in atherosclerosis and neurological diseases, two common disorders in aged people, we examined whether DXM can be protective in pro-inflammatory cytokine-stimulated chondrocytes and in a collagen-induced arthritis (CIA) animal model in this study. Chondrocytes were prepared from cartilage specimens taken from pigs or OA patients. Western blotting, quantitative PCR, and immunohistochemistry were adopted to measure the expression of collagen II (Col II) and matrix metalloproteinases (MMP). DXM significantly restored tumor necrosis factor-alpha (TNF-α)-mediated reduction of collagen II and decreased TNF-α-induced MMP-13 production. To inhibit the synthesis of MMP-13, DXM blocked TNF-α downstream signaling, including I kappa B kinase (IKK)α/β-IκBα-nuclear factor-kappaB (NF-κB) and c-Jun N-terminal kinase (JNK)-activator protein-1 (AP-1) activation. Besides this, DXM protected the CIA mice from severe inflammation and cartilage destruction. DXM seemed to protect cartilage from inflammation-mediated matrix degradation, which is an irreversible status in the disease progression of osteoarthritis. The results suggested that testing DXM as an osteoarthritis therapeutic should be a focus in further research.

MMP-3 and MMP-8 single-nucleotide polymorphisms are related to alcohol-induced osteonecrosis of the femoral head in Chinese males

Our study investigated the association between MMP-3 and MMP-8 single-nucleotide polymorphisms (SNPs) and alcohol-induced osteonecrosis of the femoral head (ONFH) in 695 Chinese males (299 cases and 396 control subjects). The minor allele of MMP-3 rs650108 was associated with a 0.78-fold decrease in alcohol-induced ONFH risk in the allelic model (95% CI = 0.63-0.97, P = 0.026). In the genetic model adjusted for age, rs650108 was associated with decreased risk of alcohol-induced ONFH in the dominant model (OR = 0.68, 95% CI = 0.49-0.95, P = 0.022) and log-additive model (OR = 0.78, 95% CI = 0.63-0.98, P = 0.030); MMP-8 rs11225394 was associated with increased risk in the codominant model (OR = 1.72, 95% CI = 1.15-2.58, P= 0.010), dominant model (OR = 1.67, 95% CI = 1.12-2.48, P = 0.012), over-dominant model (OR = 1.73, 95% CI = 1.16-2.59, P = 0.007) and log-additive model (OR = 1.57, 95% CI= 1.07-2.32, P = 0.022); and MMP-8 rs2012390 was associated with decreased risk in the dominant model (OR = 0.72, 95% CI = 0.53-0.97, P = 0.032) and log-additive model (OR = 0.77, 95% CI = 0.60-0.98, P = 0.035). Haplotype analysis showed that the CGATATGT sequence mediated decreased alcohol-induced ONFH risk (OR = 0.75, 95% CI = 0.57-0.97, P = 0.029). Therefore, among Chinese males, MMP-3 rs650108 and MMP-8 rs2012390 decrease alcohol-induced ONFH risk and MMP-8 rs11225394 increases it. Further study is needed to validate our conclusion.

Physiological concentrations of soluble uric acid are chondroprotective and anti-inflammatory

High uric acid levels are a risk factor for cardiovascular disorders and gout; however, the role of physiological concentrations of soluble uric acid (sUA) is poorly understood. This study aimed to clarify the effects of sUA in joint inflammation. Both cell cultures of primary porcine chondrocytes and mice with collagen-induced arthritis (CIA) were examined. We showed that sUA inhibited TNF-α- and interleukin (IL)-1β–induced inducible nitric oxide synthase, cyclooxygenase-2 and matrix metalloproteinase (MMP)-13 expression. Examination of the mRNA expression of several MMPs and aggrecanases confirmed that sUA exerts chondroprotective effects by inhibiting the activity of many chondro-destructive enzymes. These effects attenuated collagen II loss in chondrocytes and reduced proteoglycan degradation in cartilage explants. These results were reproduced in chondrocytes cultured in three-dimensional (3-D) alginate beads. Molecular studies revealed that sUA inhibited the ERK/AP-1 signalling pathway, but not the IκBα-NF-κB signalling pathway. Increases in plasma uric acid levels facilitated by the provision of oxonic acid, a uricase inhibitor, to CIA mice exerted both anti-inflammatory and arthroprotective effects in these animals, as demonstrated by their arthritis severity scores and immunohistochemical analysis results. Our study demonstrated that physiological concentrations of sUA displayed anti-inflammatory and chondroprotective effects both in vitro and in vivo.

Single-nucleotide polymorphisms of MMP2 in MMP/TIMP pathways associated with the risk of alcohol-induced osteonecrosis of the femoral head in Chinese males: A case-control study

The proportion of alcohol-induced osteonecrosis of the femoral head (ONFH) in all ONFH patients was 30.7%, with males prevailing among the ONFH patients in mainland China (70.1%). Matrix metalloproteinase 2 (MMP2), a member of the MMP gene family, encodes the enzyme MMP2, which can promote osteoclast migration, attachment, and bone matrix degradation. In this case-control study, we aimed to investigate the association between MMP2 and the alcohol-induced ONFH in Chinese males.In total, 299 patients with alcohol-induced ONFH and 396 healthy controls were recruited for a case-control association study. Five single-nucleotide polymorphisms within the MMP2 locus were genotyped and examined for their correlation with the risk of alcohol-induced ONFH and treatment response using Pearson χ test and unconditional logistic regression analysis. We identified 3 risk alleles for carriers: the allele "T" of rs243849 increased the risk of alcohol-induced ONFH in the allele model, the log-additive model without adjustment, and the log-additive model with adjustment for age. Conversely, the genotypes "CC" in rs7201 and "CC" in rs243832 decreased the risk of alcohol-induced ONFH, as revealed by the recessive model. After the Bonferroni multiple adjustment, no significant association was found. Furthermore, the haplotype analysis showed that the "TT" haplotype of MMP2 was more frequent among patients with alcohol-induced ONFH by unconditional logistic regression analysis adjusted for age.In conclusion, there may be an association between MMP2 and the risk of alcohol-induced ONFH in North-Chinese males. However, studies on larger populations are needed to confirm this hypothesis; these data may provide a theoretical foundation for future studies.

Human articular chondrocytes with higher aldehyde dehydrogenase activity have stronger expression of COL2A1 and SOX9

OBJECTIVE

To determine in human articular chondrocytes the activity of Aldehyde dehydrogenase (ALDH), which are reported as stem/progenitor cell marker in various adult tissues and evaluate gene expression of ALDH1A isoforms.

DESIGN

ALDH activity was evaluated by flow cytometry with Aldefluor™ assay in cells, isolated from human osteoarthritic (OA) cartilage. Its coexpression with surface markers was identified. Cells were sorted according to ALDH activity, and gene expression in sorted populations (ALDH(+) and ALDH(-)) was analyzed by RTq-PCR with Taqman(®) assay.

RESULTS

About 40% of freshly isolated chondrocytes demonstrated ALDH activity that remarkably declined during monolayer culture. Markers CD54 and CD55 were significantly stronger expressed, while CD47, CD140b, CD146 and CD166 were depleted in ALDH-expressing (ALDH(pos)) cells. Gene expression analysis revealed significantly higher expression of chondrocyte-specific genes COL2A1, SOX9 and SERPINA1 and lower expression of osteogenic markers RUNX2 and osteocalcin (BGLAP) in sorted ALDH(+) fraction. COL1A1, ACAN, ALPL and stem cell markers NANOG, OCT4, SOX2 and ABCG2 did not differ remarkably between the populations. Genes of isoenzymes ALDH1A2, ALDH1A3 and ALDH2 were strongly expressed, while ALDH1A1 was weakly expressed in chondrocytes. Only ALDH1A2 and ALDH1A3 were significantly enriched in ALDH(+) fraction.

CONCLUSIONS

We identified ALDH activity with significantly stronger expression of CD54 and CD55 in human articular chondrocytes. Gene expression of isotypes ALDH1A2, ALDH1A3 and ALDH2 was identified. Coexpression of ALDH activity with chondrogenic markers suggests its association with collagen II producing chondrocyte phenotype. Isotypes ALDH1A2 and ALDH1A3 can be associated with the ALDH activity in these cells.

A New Application of Parallel Synthesis Strategy for Discovery of Amide-Linked Small Molecules as Potent Chondroprotective Agents in TNF-α-Stimulated Chondrocytes

As part of an effort to profile potential therapeutics for the treatment of inflammation-related diseases, a diversity of amide-linked small molecules was synthesized by using parallel synthesis strategy. Moreover, these new compounds were also evaluated for their inhibitory effects on nitric oxide (NO) by using tumor necrosis factor alpha (TNF-α)-induced inflammatory responses in chondrocytes. Among the tested compounds, N-(3-chloro-4-fluorophenyl)-2-hydroxybenzamide (HS-Ck) was the most potent inhibitor of NO production and inducible nitric oxide synthase (iNOS) expression in TNF-α-stimulated chondrocytes. In addition, our biological results indicated that HS-Ck might suppress the expression levels of iNOS and matrix metalloproteinases-13 (MMP-13) activities through downregulating the activation of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT-3) transcriptional factors. Therefore, the parallel synthesis was successful used to develop a new class of potential anti-inflammatory agents as chondroprotective candidates for the treatment of osteoarthritis.

Anti-inflammatory and anti-hyperalgesic effect of all-trans retinoic acid in carrageenan-induced paw edema in Wistar rats: involvement of peroxisome proliferator-activated receptor-β/δ receptors

Objective:

In this study, we investigated the role of peroxisome proliferator-activated receptors (PPAR)-β/δ receptors in carrageenan-induced inflammation and in the anti-inflammatory effects of all-trans retinoic acid (ATRA).

Materials and Methods:

The λ-carrageenan (0.1 ml of 1% w/v) was injected into intra-plantar (i.pl.) region of the hind paw to produce acute inflammation. Paw volume was measured by using the mercury plethysmography. Further, mechanical and thermal hyperalgesia (TH) were assessed by using the dynamic plantar aesthesiometer and plantar test apparatus, respectively. In addition, markers of oxido-nitrosative stress were assessed spectrophotometrically in the hind paw tissue 5 h post-carrageenan.

Results:

An i.pl injection of carrageenan has produced a marked mechanical hyperalgesia (MH) and TH in ipsilateral paw, which was associated with significant elevated oxido-nitrosative stress. Treatment with ATRA (5 mg/kg/p.o/4 days) and GW0742, a selective PPAR-β/δ receptor agonist (0.1 mg/kg/i.p/4 days), significantly decreased the paw volume, mechanical and TH as compared to vehicle control. Administration of GSK0660, selective PPAR-β/δ receptor antagonist, at a dose of (0.3 mg/kg/i.p/4 days), did not produce a significant effect on carrageenan-induced paw edema, MH and TH. However, co-administration of GSK0660 (0.3 mg/kg/i.p/4 days) along with both ATRA (5 mg/kg/p.o/4 days) and GW0742 (0.1 mg/kg/i.p/4 days), significantly reverse the decreased paw edema, MH, and TH. These observed ameliorative effects on inflammatory pain symptoms are correlated with the extent of reduction of oxido-nitrosative stress.

Conclusion:

From above findings, it can be concluded that ATRA exerts anti-inflammatory and anti-hyperalgesic effect, possibly through activation of PPAR-β/δ and subsequent reduction of oxido-nitrosative stress.

Ginkgo biloba extract individually inhibits JNK activation and induces c-Jun degradation in human chondrocytes: potential therapeutics for osteoarthritis

Osteoarthritis (OA) is a common joint disorder with varying degrees of inflammation. The ideal anti-OA drug should have immunomodulatory effects while at the same time having limited or no toxicity. We examined the anti-inflammatory effects of Ginkgo biloba extract (EGb) in interleukin-1 (IL-1)-stimulated human chondrocytes. Chondrocytes were prepared from cartilage specimens taken from patients with osteoarthritis who had received total hip or total knee replacement. The concentrations of chemokines and the degree of cell migration were determined by ELISA and chemotaxis assays, respectively. The activation of inducible nitric oxide synthase (iNOS), mitogen-activated protein kinases (MAPKs), activator protein-1 (AP-1), and nuclear factor-kappaB (NF-κB) was determined by immunoblotting, immunohistochemistry, and electrophoretic mobility shift assay. We found that EGb inhibited IL-1-induced production of chemokines, which in turn resulted in attenuation of THP-1 cell migration toward EGb-treated cell culture medium. EGb also suppressed IL-1-stimulated iNOS expression and release of nitric oxide (NO). The EGb-mediated suppression of the iNOS-NO pathway correlated with the attenuation of activator protein-1 (AP-1) but not nuclear factor-kappaB (NF-κB) DNA-binding activity. Of the mitogen-activated protein kinases (MAPKs), EGb inhibited only c-Jun N-terminal kinase (JNK). Unexpectedly, EGb selectively caused degradation of c-Jun protein. Further investigation revealed that EGb-mediated c-Jun degradation was preceded by ubiquitination of c-Jun and could be prevented by the proteosome inhibitor MG-132. The results imply that EGb protects against chondrocyte degeneration by inhibiting JNK activation and inducing ubiquitination-dependent c-Jun degradation. Although additional research is needed, our results suggest that EGb is a potential therapeutic agent for the treatment of OA.

The roles of catabolic factors in the development of osteoarthritis

Osteoarthritis (OA) is the most prevalent disease of articular joints characterized by joint space narrowing on X-ray, joint pain, and a loss of joint function through progressive cartilage degradation and intermittent synovial inflammation. Current in vitro models of OA are often monolayer cultured primary cells exposed to high concentrations of cytokines or chemokines, usually IL-1β or TNF-α. IL-1β could play a role in the early progression or even initiation of OA as evidenced by many of the in vitro studies. However, the inconsistent or outright lack of detectable IL-1β combined with high concentrations of the natural inhibitor IL-1Ra in the OA synovial fluid makes the idea of OA being IL-1β-driven questionable. Further, other stimulants, including IL-6 and matrix fragments, have been shown in vitro to cause many of the effects seen in OA at relevant concentrations found in the OA synovial fluid. More work with these stimulants and IL-1β-independent models needs to be done. Concurrently, research should be conducted with patients with OA as early as possible in the progression of their disease to be able to potentially identify, target, and treat the initiation of the disease.

Slug/β-catenin-dependent proinflammatory phenotype in hypoxic breast cancer stem cells

Cancer stem cell survival relies on the activation of inflammatory pathways, which is speculatively triggered by cell autonomous mechanisms or by microenvironmental stimuli. Here, we observed that hypoxic bone marrow stroma-derived transforming growth factor-β 1 promotes the growth of human breast cancer stem cells as mammospheres. The ensuing Slug-dependent serine 139 phosphorylation of the DNA damage sensor H2AX in breast cancer stem cells induces tumor necrosis factor-α and IL-8 mRNAs, whose stability is enhanced by cytoplasmic β-catenin. β-Catenin also up-regulates and binds miR-221, reducing the stability of the miR-221 targets Rad51 and ERα mRNAs. Our data show that the Slug/β-catenin-dependent activation of DNA damage signaling triggered by the hypoxic microenvironment sustains the proinflammatory phenotype of breast cancer stem cells.

Future trends for unicompartmental arthritis of the knee: injectables & stem cells

Arthritis is one of the most frequent musculoskeletal problems, causing pain, disability, and a significant economic burden. In this article, we discuss current nonsurgical injectable treatment options as well as future trends for cartilage lesions and early arthritis of the knee. We cover some potential treatments for knee osteoarthritis, including stem cell and gene therapies.

Matrix metalloproteinase, vitamin A and methylprednisolone effects on experimentally induced amyloid arthropathy

We evaluated the role of some matrix metalloproteinases (MMPs) in enhancing the effect of vitamin A and the inhibiting effect of methylprednisolone on amyloid arthropathy in brown layer chicks. We used 100 one-day-old Isa brown layer chicks. The chicks were allocated to one of four groups as follows: negative control group (I), vitamin A group (II), positive control group (III) and methylprednisolone group (IV). Amyloid arthropathy was induced by injections of complete Freund's adjuvant into the left intertarsal joints of the chicks. Serum vitamin A and tissue MMP (MMP-1, MMP-2, MMP-9) levels were measured and differences among the groups were investigated. Serum vitamin A rates (μg/dl) were: 63.57 ± 4.10, 47.13 ± 10.62, 53.26 ± 10.79, 98.48 ± 8.20 in groups I, II, III and IV, respectively (p < 0.001). MMP-1, MMP-2 and MMP-9 levels were evaluated in tissues from the chickens with amyloid arthropathy. Methylprednisolone significantly suppressed the release of MMP-1 and MMP-2, and increased the release of MMP-9 in birds with amyloid arthropathy. In addition, vitamin A significantly increased the release of MMP-1, MMP-2 and MMP-9.

Effect of low-intensity pulsed ultrasound on MMP-13 and MAPKs signaling pathway in rabbit knee osteoarthritis

We evaluated the effect of low-intensity pulsed ultrasound (LIPUS) on MMP-13 and MAPKs expression in rabbit knee osteoarthritis (OA). For this purpose, 18 New Zealand white rabbits were randomly and equally divided into O + L, O - L, and SO groups. In O + L group, animals underwent right back leg ACLT operation and LIPUS radiation. In O - L group, animals underwent ACLT but no LIPUS treatment. In SO (control) group, animals underwent sham operation without LIPUS. After 6 weeks, we assessed the pathologic changes in the articular surface of femoral condyle and compared using Mankin scores. Also, expression of type-II collagen, MMP-13, ERK1/2, p38, and JNK was measured by Western blot. Compared with controls, Mankin scores were higher in O + L (P < 0.05)/O - L (P < 0.01) groups. Compared with O + L group, score was higher in O - L group (P < 0.05). Compared with controls, type-II collagen expression was less in O + L/O - L groups, with more significant decrease in O - L group (P < 0.05). Contrarily, expression of MMP-13, p-ERK1/2, and p-p38 was enhanced in O + L/O - L groups as compared with controls, with more significant increase in O - L group (P < 0.01). Compared with O + L group, expression was higher in O - L group (P < 0.05). We, therefore, concluded that LIPUS application promoted cartilage repair in OA through the downregulation of MMP-13, ERK1/2, and p38.

Nuclear receptors agonists exert opposing effects on the inflammation dependent survival of breast cancer stem cells

Recent literature highlights the importance of pro-inflammatory cytokines in the biology of breast cancer stem cells (CSCs), unraveling differences with respect to their normal counterparts. Expansion of mammospheres (MS) is a valuable tool for the in vitro study of normal and cancer mammary gland stem cells. Here, we expanded MSs from human breast cancer and normal mammary gland tissues, as well from tumorigenic (MCF7) and non-tumorigenic (MCF10) breast cell lines. We observed that agonists for the retinoid X receptor (6-OH-11-O-hydroxyphenanthrene), retinoic acid receptor (all-trans retinoic acid (RA)) and peroxisome proliferator-activated receptor (PPAR)-γ (pioglitazone (PGZ)), reduce the survival of MS generated from breast cancer tissues and MCF7 cells, but not from normal mammary gland or MCF10 cells. This phenomenon is paralleled by the hampering of pro-inflammatory Nuclear Factor-κB (NF-κB)/Interleukin-6 (IL6) axis that is hyperactive in breast cancer-derived MS. The hindrance of such pathway associates with the downregulation of MS regulatory genes (SLUG, Notch3, Jagged1) and with the upregulation of the differentiation markers estrogen receptor-α and keratin18. At variance, the PPARα agonist Wy14643 promotes MS formation, upregulating NF-κB/IL6 axis and MS regulatory genes. These data reveal that nuclear receptors agonists (6-OH-11-O-hydroxyphenanthrene, RA, PGZ) reduce the inflammation dependent survival of breast CSCs and that PPARα agonist Wy14643 exerts opposite effects on this phenotype.

Interleukin-1 as an injury signal mobilizes retinyl esters in hepatic stellate cells through down regulation of lecithin retinol acyltransferase

Retinoids are mostly stored as retinyl esters in hepatic stellate cells (HSCs) through esterification of retinol and fatty acid, catalyzed by lecithin-retinol acyltransferase (LRAT). This study is designated to address how retinyl esters are mobilized in liver injury for tissue repair and wound healing. Initially, we speculated that acute inflammatory cytokines may act as injury signal to mobilize retinyl esters by down-regulation of LRAT in HSCs. By examining a panel of cytokines we found interleukin-1 (IL-1) can potently down-regulate mRNA and protein levels of LRAT, resulting in mobilization of retinyl esters in primary rat HSCs. To simulate the microenvironment in the space of Disse, HSCs were embedded in three-dimensional extracellular matrix, by which HSCs retaine quiescent phenotypes, indicated by up-regulation of LRAT and accumulation of lipid droplets. Upon IL-1 stimulation, LRAT expression went down together with mobilization of lipid droplets. Secreted factors from Kupffer cells were able to suppress LRAT expression in HSCs, which was neutralized by IL-1 receptor antagonist. To explore the underlying mechanism we noted that the stability of LRAT protein is not significantly regulated by IL-1, indicating the regulation is likely at transcriptional level. Indeed, we found that IL-1 failed to down-regulate recombinant LRAT protein expressed in HSCs by adenovirus, while transcription of endogenous LRAT was promptly decreased. Following liver damage, IL-1 was promptly elevated in a close pace with down-regulation of LRAT transcription, implying their causative relationship. After administration of IL-1, retinyl ester levels in the liver, as measured by LC/MS/MS, decreased in association with down-regulation of LRAT. Likewise, IL-1 receptor knockout mice were protected from injury-induced down-regulation of LRAT. In summary, we identified IL-1 as an injury signal to mobilize retinyl ester in HSCs through down-regulation of LRAT, implying a mechanism governing transition from hepatic injury to wound healing.

Apo-10'-lycopenoic acid impacts adipose tissue biology via the retinoic acid receptors

Apo-10'-lycopenoic acid (apo-10-lycac), a metabolite of lycopene, has been shown to possess potent biological activities, notably via the retinoic acid receptors (RAR). In the current study, its impact on adipose tissue and adipocytes was studied. In microarray experiments, the set of genes regulated by apo-10-lycac treatments was compared to the set of genes regulated by all-trans retinoic acid (ATRA), the natural ligand of RAR, in adipocytes. Approximately 27.5% of the genes regulated by apo-10-lycac treatments were also regulated by ATRA, suggesting a common ability in terms of gene expression modulation, possibly via RAR transactivation. The physiological impact of apo-10-lycac on adipose tissue biology was evaluated. If it had no effect on adipogenesis in the 3T3-L1 cell model, this metabolite may have a preventative effect against inflammation, by preventing the increase in the inflammatory markers, interleukin 6 and interleukin 1β in various dedicated models. The ability of apo-10-lycac to transactivate the RAR and to modulate the transcription of RAR target gene was brought in vivo in adipose tissue. While apo-10-lycac was not detected in adipose tissue, a metabolite with a molecular weight with 2Da larger mass was detected, suggesting that a dihydro-apo-10'-lycopenoic acid, may be present in adipose tissue and that this compound could active or may lead to further active RAR-activating apo-10-lycac metabolites. Since apo-10-lycac treatments induce anti-inflammatory effects in adipose tissue but do not inhibit adipogenesis, we propose that apo-10-lycac treatments and its potential active metabolites in WAT may be considered for prevention strategies relevant for obesity-associated pathologies.

A benzamide-linked small molecule HS-Cf inhibits TNF-α-induced interferon regulatory factor-1 in porcine chondrocytes: a potential disease-modifying drug for osteoarthritis therapeutics

BACKGROUND

Using tumor necrosis factor-alpha (TNF-α)-activated porcine chondrocytes as a screening tool, we aim to synthesize and identify small-molecule inhibitors preserving immunomodulatory effects as therapeutics for osteoarthritis (OA).

METHODS

Chondrocytes were isolated from pig joints. A minilibrary of 300 benzamide-linked small molecules was established. The levels of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) were measured by Western blot and Griess reaction, respectively. Proteoglycan degradation in cartilage explants was determined by histochemistry analysis. The activation of transcription factors and protein kinases was determined by electrophoretic mobility shift assays or Western blots. Zymography and real-time reverse transcriptase-polymerase chain reaction were used to determine enzyme activity and expression of matrix metalloproteinases (MMPs) and aggrecanases, respectively.

RESULTS

Bioassay screening of benzamide-linked small molecules revealed that 2-hydroxy-N-[3-(trifluoromethyl)phenyl]benzamide (HS-Cf) was a potent inhibitor of NO production and iNOS expression in TNF-α-stimulated porcine chondrocytes. HS-Cf suppressed TNF-α-induced activity of MMP-13 and expressions of several aggrecanases and prevented TNF-α-mediated reduction of collagen II. Histochemistry analysis confirmed that HS-Cf could prevent TNF-α-induced degradation and release of proteoglycan/aggrecan in cartilage explants. Such effects by HS-Cf were likely through suppressing TNF-α-induced interferon regulatory factor-1 (IRF-1) but not nuclear factor-kappaB signaling. The significance of IRF-1 was further confirmed by short hairpin knockdown studies.

CONCLUSIONS

In a minilibrary containing 300 small molecules, we identified a benzamide-linked small molecule, HS-Cf, that through down-regulating TNF-α-induced IRF-1 activity suppressed chondrocyte activation and prevented cartilage destruction. HS-Cf might be a potential disease-modifying drug for OA therapeutics.

RAR/RXR and PPAR/RXR Signaling in Spinal Cord Injury

The retinoid acid receptors (RAR) and peroxisome proliferator-activated receptors (PPAR) have been implicated in the regulation of inflammatory reactions. Both receptor families contain ligand-activated transcription factors which form heterodimers with retinoid X receptors (RXR). We review data that imply RAR/RXR and PPAR/RXR pathways in physiological reactions after spinal cord injury. Experiments show how RAR signaling may improve axonal regeneration and modulate reactions of glia cells. While anti-inflammatory properties of PPAR are well documented in the periphery, their possible roles in the central nervous system have only recently become evident. Due to its anti-inflammatory function this transcription factor family promises to be a useful target after spinal cord or brain lesions.

Advanced glycation end products cause collagen II reduction by activating Janus kinase/signal transducer and activator of transcription 3 pathway in porcine chondrocytes

OBJECTIVES

The major risk factor for OA is ageing; however, the mechanisms remain largely unclear. We investigated the effects and mechanisms of advanced glycation end products (AGEs) that accumulate in aged joints in chondrocytes.

METHODS

Porcine chondrocytes or cartilage fragments were prepared. Gene expression of MMPs and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) was assessed by real-time RT-PCR. Gelatin zymography was used to determine MMP-13 enzyme activity. Histochemistry or immunoblotting analysis was applied to determine the expression of collagen II, proteoglycan and aggrecan. Electrophoretic mobility shift assay and immunoblotting were used to study the activation of signal transducer and activator of transcription 3 (STAT3). Genetic manipulations with short hairpin RNA (shRNA) or dominant negative constructs were applied.

RESULTS

AGE enhanced expression and enzyme activity of MMP and ADAMTS genes and resulted in reduction of collagen II. Both janus kinase 2 (JAK2) and JAK3 inhibitors suppressed AGE-induced MMP-13, ADAMTS-4 and ADAMTS-5 expression and enzyme activity. Inhibition of JAK2 or JAK3 prevented AGE-mediated decrease of collagen II in chondrocytes and proteoglycan (aggrecan) degradation in cartilage fragments. In addition, interference of STAT3 expression inhibited AGE-induced MMP-13 and ADAMTS enzyme activities and mRNA levels. Furthermore, expression of the dominant negative receptor of AGE (DN-RAGE) blocked AGE-induced STAT3 phosphorylation.

CONCLUSION

Blocking JAK/STAT3 signalling pathway inhibited AGE-induced activation of MMP-13 and ADAMTS and prevented AGE-mediated decrease of collagen II and proteoglycan (aggrecan). The results indicated that JAK/STAT3 pathway may be a potential target for designing disease-modifying drugs for the treatment of OA.

Matrix metalloproteinase-13 expression in IL-1β-treated chondrocytes by activation of the p38 MAPK/c-Fos/AP-1 and JAK/STAT pathways

Matrix metalloproteinase-13 (MMP-13, mammalian collagenase) degrades the cartilage matrix in pathological conditions such as osteoarthritis. Here, to establish the signaling pathway to MMP-13 induction, effects of mitogen-activated protein kinase (MAPK) pathway and the possibility of some other signaling pathways involved are investigated in interleukin-1β (IL-1β)-treated human chondrosarcoma cell line, SW1353 cells. IL-1β (10 ng/mL) treatment induced MMP-13 in SW1353 cells, with concomitant activation of nuclear factor-κB, activator protein-1 (AP-1) and MAPKs, including extracellular signal-regulated protein kinase, p38 MAPK and c-Jun N-terminal kinase. Among these MAPKs, only p38 MAPK inhibitor (SB203580) blocked MMP-13 induction and AP-1 activation in IL-1β-treated SW1353 cells. SB203580 also inhibited c-Fos translocation to the nucleus (but not c-Jun). Importantly, IL-1β treatment induced Janus kinase 2 (JAK2) and signal transducer and activator of transcription 1/2 (STAT1/2) activation. The JAK2 inhibitor (AG490) blocked STAT1/2 activation as well as MMP-13 induction in IL-1β-treated SW1353 cells. STAT1/2 siRNA transfection also reduced MMP-13 expression levels. Thus, from the present study, it is concluded that p38 MAPK/c-Fos/AP-1 and JAK2/STAT1/2 are involved in MMP-13 induction of IL-1β-treated human chondrocytes, SW1353 cells. Blocking these signaling pathways may have chondroprotective effects in cartilage degeneration.

Adiponectin is a potential catabolic mediator in osteoarthritis cartilage

Introduction

Adiponectin has been implicated in the pathogenesis of osteoarthritis (OA). We studied the effects of adiponectin on the OA cartilage homeostasis.

Methods

Immunohistochemical analysis was performed to evaluate differential expression of adiponectin receptors (AdipoRs) in nonlesional and lesional areas of OA cartilage. Cartilage and chondrocytes from the knee joints of primary OA patients were cultured in the presence of adiponectin (0~30 μg/ml). The levels of total nitric oxide (NO), matrix metalloproteinase (MMP)-1, -3, and -13, and tissue inhibitor of metalloproteinase (TIMP)-1 were measured in the conditioned media. The levels of inducible NO synthase (iNOS) and MMPs were determined with the quantitative real-time reverse transcription-polymerase chain reaction. The concentrations of collagenase-cleaved type II collagen neoepitope (C1-2C) were determined in the supernatant of adiponectin-stimulated OA cartilage explants. The effects of kinase and NOS inhibitors were evaluated in the adiponectin-stimulated chondrocytes.

Results

The expression levels of both AdipoR1 and AdipoR2 were significantly higher in lesional than in nonlesional areas of OA cartilage. The increased rate of AdipoR1-positive chondrocytes was twice that of AdipoR2-positive chondrocytes when compared between nonlesional and lesional areas. Adiponectin-stimulated OA chondrocytes showed increased total NO and MMP-1, -3, and -13 levels compared with nonstimulated cells. The TIMP-1 level was not affected. The C1-2C levels were increased by adiponectin in OA cartilage explant culture. AMP-activated protein kinase (AMPK) and c-Jun N-terminal kinase (JNK) inhibitors (compound C and SP600125) significantly suppressed adiponectin-induced production of total NO and MMP-1, -3, and -13. Inducible NOS inhibitors enhanced the expression of the adiponectin-induced MMPs.

Conclusions

Adiponectin causes matrix degradation in OA cartilage and increases MMPs and iNOS expression via the AMPK and JNK pathways in human OA chondrocytes. The catabolic effects of adiponectin may be counteracted by NO.

Thymoquinone inhibits matrix metalloproteinase expression in rabbit chondrocytes and cartilage in experimental osteoarthritis

Thymoquinone (TQ) is the main constituent of Nigella sativa oil, which has been traditionally used against arthritis in the Middle East. In this study, we investigated the effect of TQ against matrix metalloproteinase (MMP) expression in both rabbit chondrocytes and animal mode of osteoarthritis (OA) induced by anterior cruciate ligament transection and tested whether or not nuclear factor kappa B (NF- κB) was involved in this process. TQ down-regulated MMP-1, MMP-3 and MMP-13 expression and up-regulated tissue inhibitors of metalloproteinase-1 expression as assessed by quantitative realtime polymerase chain reaction. In addition, NF- κB p65 protein level as well as its translocation induced by interleukin-1 β were inhibited by TQ. Our findings suggest the potential of TQ in the treatment of OA.

Advanced glycation end products induce T cell apoptosis: Involvement of oxidative stress, caspase and the mitochondrial pathway

Accumulation of advanced glycation end products (AGEs) is a hallmark in aged people. T cells play important roles in maintaining homeostasis of immune function. This study investigated the effects of AGEs-bovine serum albumin (AGEs) in human T cells. Incubation of Jurkat and several immortalized T cell lines with AGEs resulted in cell death dose-dependently. AGEs-induced cell death was partially but significantly blocked by neutralizing antibodies recognizing receptor of AGEs. In addition to detecting DNA nick, simultaneous stainings of annexin V with 7-amino-actinomycin D further confirmed the apoptotic nature of cell death. AGEs also caused apoptosis in purified T cells. Although AGEs-induced apoptosis could be blocked by the pan-caspase inhibitor, Ala-Asp-fluomethyl ketone (Z-VAD-fmk), there was no activation of caspase-3, -5, -8 and -9. AGEs caused mitochondrial outer membrane permeabilization and this process was prevented by an antioxidant or Z-VAD-fmk. Furthermore, AGEs treatment led to translocation of apoptosis inducing factor (AIF) from the mitochondria into the nucleus. Altogether, this report demonstrated that AGEs induced T cell apoptosis in an oxidative stress-associated and caspase-dependent manner with involvement of the mitochondrial pathway. It is likely that AGEs-induced T cell apoptosis may play a role in T cell homeostasis in ageing.

Chondroprotective effects and mechanisms of resveratrol in advanced glycation end products-stimulated chondrocytes

Introduction

Accumulation of advanced glycation end products (AGEs) in joints contributes to the pathogenesis of cartilage damage in osteoarthritis (OA). We aim to explore the potential chondroprotective effects of resveratrol on AGEs-stimulated porcine chondrocytes and cartilage explants.

Methods

Chondrocytes were isolated from pig joints. Activation of the IκB kinase (IKK)-IκBα-nuclear factor-kappaB (NF-κB) and c-Jun N-terminal kinase (JNK)/extracellular signal-regulated kinase (ERK)-activator protein-1 (AP-1) pathways was assessed by electrophoretic mobility shift assay (EMSA), Western blot and transfection assay. The levels of inducible nitric oxide synthase (iNOS)-NO and cyclooxygenase-2 (COX-2)-prostaglandin E₂ (PGE₂) were measured by Western blot, Griess reaction or ELISA. The expression and enzyme activity of matrix metalloproteinase-13 (MMP-13) were determined by real time RT/PCR and gelatin zymography, respectively.

Results

We show that AGEs-induced expression of iNOS and COX-2 and production of NO and PGE₂ were suppressed by resveratrol. Such effects of resveratrol were likely mediated through inhibiting IKK-IκBα-NF-κB and JNK/ERK-AP-1 signaling pathways induced by AGEs. By targeting these critical signaling pathways, resveratrol decreased AGEs-stimulated expression and activity of MMP-13 and prevented AGEs-mediated destruction of collagen II. Histochemistry analysis further confirms that resveratrol could prevent AGEs-induced degradation of proteoglycan and aggrecan in cartilage explants.

Conclusions

The present study reveals not only the effects and mechanisms regarding how resveratrol may protect cartilage from AGEs-mediated damage but also the potential therapeutic benefit of resveratrol in the treatment of OA.

10-Hydroxy-2-decenoic acid from Royal jelly: a potential medicine for RA

AIM OF THE STUDY

Rheumatoid arthritis synovial fibroblasts (RASFs) are known to produce matrix metalloproteinases (MMPs) and cause joint destruction. The purpose of this study is to develop a potential medicine for rheumatoid arthritis (RA).

MATERIALS AND METHODS

To this end, first, the MMPs inhibition factor was purified from an alkali-solubilized fraction of RJ (Apis mellifera) by C18 reverse-phase column chromatography and identified as 10-hydroxy-2-decenoic acid (10H2DA) by LTQ XL analysis. Next, Experimental test 10H2DA how to inhibited the activities of MMPs: with RASFs isolated from rheumatoid tissues by enzymatic digestion, cultures in monolayers were treated with 10H2DA (0.5mM, 1mM, and 2mM) or PBS for 2h followed by stimulation with TNF-alpha (10 ng/ml) for 2h, mRNA. Protein levels of MMP-1 and MMP-3 were measured by real-time PCR and enzyme-linked immunosorbent assay (ELISA), the DNA-binding activity of activator protein-1 (AP-1) and nuclear factor kappaB (NF-kappaB) by electrophoretic mobility shift assay (EMSA), and the protein kinase activity of p38, ERK and JNK by kinase assay.

RESULTS

The molecular investigation revealed that the 10H2DA-mediated suppression was likely to occur through blocking p38 kinase and c-Jun N-terminal kinase-AP-1 signaling pathways. In contrast, 10H2DA had no effect on extracellular signal-regulated kinase activity, NF-kappaB DNA-binding activity and IkappaBalpha degradation.

CONCLUSION

These results suggest that 10H2DA may be of potential therapeutic value in inhibiting joint destruction in RA.

Ligands for retinoic acid receptors are elevated in osteoarthritis and may contribute to pathologic processes in the osteoarthritic joint

OBJECTIVE

Vitamin A derivatives, including all-trans-retinoic acid (ATRA), have a well-established role during skeletal development and limb formation and have been shown to have profound effects on chondrocyte phenotype. The aim of this study was to elucidate the effects of retinoids and components of the retinoid metabolic pathway on chondrocyte phenotype in the tibiofemoral joints of patients with osteoarthritis (OA), to show that the retinoids can have multiple effects relevant to the OA disease process.

METHODS

Human explant tissue and a chondrocyte-like cell line were treated with ATRA, and the responses of 4 key markers of chondrocyte phenotype were analyzed. In addition, the effects of ATRA on a number of novel genes associated with OA were assessed using a low-density microarray containing 80 disease marker genes.

RESULTS

Vitamin A metabolite levels were elevated in synovial fluid, serum, and cartilage from patients with OA. Expression profiling of a retinoic acid receptor alpha coactivator protein, P/CAF, demonstrated elevated expression in patients with OA, suggesting the potential for increased signaling via the retinoid receptors in the disease. ATRA increased the levels of matrix metalloproteinase 13 and aggrecanase activity in human cartilage explants and in a human chondrocyte cell line. Furthermore, ATRA altered the expression of a wide range of relevant genes, including the types I, II, IX, and XI collagen genes, toward a nonchondrogenic and OA-like phenotype.

CONCLUSION

These results suggest that retinoid signaling could have a central role in OA, and that components of the pathway may provide potential disease biomarkers or targets for therapeutic intervention.

COX-2 and iNOS are critical in advanced glycation end product-activated chondrocytes in vitro

BACKGROUND

The advanced glycation end products (AGEs) accumulate in joints of osteoarthritis patients. This study aimed to investigate the roles of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) pathways in AGE-mediated cartilage damage.

MATERIALS AND METHODS

Methylglyoxal-modified albumin was used as the source of AGE. Porcine and human chondrocytes were prepared from the joint cartilage of pigs and osteoarthritis patients. The activation of COX-2, iNOS, nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and protein kinases was determined by Western blotting, kinase assay, electrophoretic mobility shift assay (EMSA) or transfection assay. Prostaglandin E(2) (PGE(2)) and NO concentrations were determined by enzyme-linked immunosorbent assay (ELISA) and Griess reaction respectively. The enzymatic activity of COX was determined by measuring the conversion of arachidonic acid to PGE(2). The release of sulphated glycosaminoglycan and the intensity of Safranin O staining were used to measure cartilage degradation.

RESULTS

AGE potently induced COX-2-PGE(2) and iNOS-NO activation in porcine and human chondrocytes. Meanwhile, the upstream molecules regulating COX-2/iNOS activation, such as AP-1, NF-kappaB, extracellular signal regulated protein kinase (ERK) and c-jun N-terminal kinase (JNK), were activated by AGE. Although AGE could not activate p38 directly, by measuring COX enzyme activity, the inhibition of p38 resulted in suppressing AGE-induced conversion of arachidonic acid to PGE(2). Furthermore, successful blockage of either COX-2 or NOS activity significantly reduced AGE-mediated proteoglycan release and cartilage degradation.

CONCLUSIONS

This study highlights the significance of COX-2 and iNOS pathways in AGE-mediated OA pathogenesis and their potential as therapeutic targets that are beyond pain killing for OA treatment.

All-trans retinoic acid suppresses interleukin-6 expression in interleukin-1-stimulated synovial fibroblasts by inhibition of ERK1/2 pathway independently of RAR activation

INTRODUCTION

Interleukin-6 (IL-6) is thought to play a pathogenic role in rheumatoid arthritis and synovium is a major source of IL-6 release. We investigated the ability of retinoids to suppress IL-6 expression in IL-1-stimulated synovial fibroblasts, with special care to the contribution of retinoic acid receptor (RAR) and retinoid X receptor (RXR) subtypes, and the implication of the mitogen-activated protein kinase (MAPK) pathway.

METHODS

RAR-alpha, -beta, and -gamma and RXR-alpha, -beta, and -gamma levels were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) or Western blot in rat synovial fibroblasts stimulated with 10 ng/mL of IL-1beta. Stimulated levels of IL-6 were assessed by RT-qPCR or immunoassays in the presence or absence of 1 microM all-trans retinoic acid (ATRA) (RAR agonist) or 0.3 microM BMS-649 (RXR agonist). The contribution of RAR subtypes was checked with selective agonists or small interfering RNAs. The effect of ATRA on upstream MAPK (p38 MAPK, c-Jun N-terminal kinase [JNK], and extracellularly regulated kinase 1/2 [ERK1/2]) was assessed by Western blot, and the contribution of the ERK1/2 pathway to the activation of pro-inflammatory transcription factors was studied by TransAm assays.

RESULTS

Synovial fibroblasts expressed all RAR and RXR subtypes except RXR-gamma. In IL-1-stimulated cells, ATRA, but not BMS-649, reduced IL-6 expression whereas selective RAR agonists were inactive. The inhibitory effect of ATRA on IL-6 was not affected by the silencing of RAR subtypes. ATRA also reduced the phosphorylation of ERK1/2, but not of p38 MAPK or of JNK. The suppressive effect of ATRA on the activation of activator protein-1 (AP-1) and nuclear factor-IL-6 (NF-IL-6) was reproduced by the MEK1 (mitogen-activated protein extracellularly regulated kinase kinase 1) inhibitor PD-98059, whereas ATRA and PD-98059 had no effect on NF-kappaB activation.

CONCLUSIONS

Among RAR and RXR agonists, only ATRA inhibited IL-1-induced IL-6 expression in rat synovial fibroblasts by inhibiting ERK1/2 pathway and subsequent activation of AP-1 and NF-IL-6 independently of RAR.

Glucosamine affects intracellular signalling through inhibition of mitogen-activated protein kinase phosphorylation in human chondrocytes

The aim of this study was to determine the effects of glucosamine on matrix metalloprotease (MMP) production, on mitogen-activated protein kinase (MAPK) phosphorylation, and on activator protein (AP)-1 transcription factor activation in human chondrocytes. The human immortalized cell line lbpva55 and healthy human chondrocytes (obtained from healthy donors) were subjected to challenge with 10 ng/ml IL-1β after pretreatment with 2.5 or 10 mmol/l glucosamine. MMP mRNA expression levels were evaluated using quantitative real-time PCR, and MMP protein production levels were evaluated in the culture supernatant using ELISA. MAPK phosphorylation was evaluated using Western blotting. AP-1 transcription factor activation was evaluated by measuring AP-1 DNA-binding activity. After IL-1β stimulation, levels of MMP-1, MMP-3 and MMP-13 production were markedly increased. Treatment with 2.5 and 10 mmol/l glucosamine reduced expression of these metalloproteases. MMP expression is regulated by transcription factors such as the AP-1 complex, which is activated by phosphorylated MAPKs. IL-1β stimulated phosphorylation of c-jun amino-terminal kinase, p38 MAPK and extracellular signal-regulated kinase-1/2. Glucosamine inhibited c-jun amino-terminal kinase and p38 phosphorylation, and consequently c-jun binding activity. These findings demonstrate, for the first time, that glucosamine inhibits IL-1β-stimulated MMP production in human chondrocytes by affecting MAPK phosphorylation.

Platelet-derived growth factor C plays a role in the branchial arch malformations induced by retinoic acid

BACKGROUND

All-trans-retinoic acid (RA) can produce branchial arch abnormalities in postimplantation rodent embryos cultured in vitro. Platelet-derived growth factor C (PDGF-C) was recently identified as a member of the PDGF ligand family. Many members of the PDGF family are essential for branchial arch morphogenesis and can be regulated by RA. The roles of PDGF-C in branchial arch malformations induced by RA and possible mechanisms were investigated.

METHODS

In whole embryo culture (WEC), mouse embryos were exposed to RA at 0, 0.1, 0.4, 1.0, or 10.0 microM, PDGF-C at 25, 50, or 75 ng/mL, or PDGF-C at 25, 50, or 75 ng/mL containing 0.4 microM RA. After 48 h of culture, mouse embryos were examined for dysmorphogenesis, and whole-mount immunohistochemistry was applied to PDGF-C. In explant cultures, explants were exposed to the same doses of RA and PDGF-C as WEC. Semiquantitative RT-PCR, zymography, and reverse zymography were used to evaluate the expressions and activities of matrix metalloproteinase (MMP)-2, MMP-14, and tissue inhibitor of metalloproteinase (TIMP)-2.

RESULTS

PDGF-C was reduced by RA, and exogenous PDGF-C rescued the branchial arch malformations induced by RA. Moreover, PDGF-C prevented RA-induced inhibition of the migratory ability of mesenchymal cells in the first branchial arch, by regulating the expressions of MMP-2, MMP-14, and TIPM-2.

CONCLUSIONS

Our results suggest that RA exposure reduces the expression of PDGF-C. The branchial arch malformations resulting from fetal RA exposure are caused at least partially by loss of PDGF-C and subsequent misregulations of the expressions of MMP-2, MMP-14, and TIMP-2.

MAP kinase activation is required for the MMP-9 induction by TNF-stimulation

MMP-9 is a metalloproteinase capable of basement membrane degradation in vivo. Expression of MMP-9 can be found in normal conditions such as trophoblasts, osteoclasts, and leukocytes and their precursors. They also occur as well as in pathological conditions, such as the invasive growth of primary tumors, metastasis, angiogenesis, rheumatoid arthritis, and periodontal diseases. MMP-9 upregulation can be highly induced by a wide range of agents. These agents include growth factors, cytokines, cell-cell, and cell-ECM adhesion molecules, and agents altering cell shape. Here, we observed that TNF-alpha stimulated human monocytic cell line, HL-60 produced MMP-9 in a dose and time dependent manner. Real time PCR results indicated transcriptional upregulation of MMP-9 as early as 3 h post TNF-alpha stimulation. To investigate the signaling pathway underlined in TNF-alpha induced MMP-9 expression, three MAP kinase inhibitors were added to cells 1 h prior to TNF-alpha treatment. The ERK inhibitor completely abolished MMP-9 expression by TNF-alpha. But neither p38 MAP kinase nor JNK inhibitor had an effect on TNF-alpha induced MMP-9 expression, suggesting that ERK activation is required for the MMP-9 induction by TNF-alpha. Taken together, we found that TNF-alpha stimulation facilitates ERK activation, which results in the transcriptional upregulation of MMP-9 gene and subsequent MMP-9 production and secretion.

Helicobacter pylori encoding the pathogenicity island activates matrix metalloproteinase 1 in gastric epithelial cells via JNK and ERK

Helicobacter pylori colonizes the human gastric epithelium and induces an inflammatory response that is a trigger for gastric carcinogenesis. Matrix metalloproteinases (MMPs) have recently been shown to be up-regulated in gastric epithelial cells infected with H. pylori and might contribute to the pathogenesis of peptic ulcer. The aim of this study was to extend the knowledge about the effect of H. pylori infection on MMP-1 expression by gastric epithelial cells, the kinetics of induction, the pathogenetic properties of the bacterium, and the intracellular signaling pathways required for MMP-1 up-regulation. Expression of MMP-1 was induced more than 10-fold by co-culture of AGS+cells with H. pylori strains carrying the pathogenicity island (PAI). H. pylori strains with mutations in the PAI and a defective type IV secretion system had no effect on MMP-1. Double immunofluorescence revealed strong MMP-1 staining in epithelial cells of gastric biopsies at sites of bacterial attachment. In vitro, MMP-1 is up-regulated by interleukin-1beta and tumor necrosis factor-alpha, but these regulatory mechanisms are not operating in H. pylori infection as shown by inhibitory antibodies. Specific inhibitors of JNK kinase and ERK1/2 kinase were found to suppress the H. pylori-induced MMP-1 expression and activity. AGS cells treated with antisense MMP-1 showed a significantly reduced potential to degrade reconstituted basement membrane. Our results suggest that in gastric epithelial cells, H. pylori up-regulates MMP-1 in a type IV secretion system-dependent manner via JNK and ERK1/2. Induction of MMP-1 is further implicated in complex processes induced by H. pylori, resulting in tissue degradation and remodeling of the gastric mucosa.