Apoptosis and the loss of chondrocyte survival signals contribute to articular cartilage degradation in osteoarthritis

Effects of curcumin (diferuloylmethane) on nuclear factor kappaB signaling in interleukin-1beta-stimulated chondrocytes

Curcumin (diferuloylmethane) is a nontoxic dietary pigment in tumeric and curry and a potent inhibitor of the common transcription factor Nuclear Factor kappaB (NF-kappaB) in several cell types. It is well established that some of the catabolic effects of the proinflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha in osteoarthritis are regulated by the activation of NF-kappaB. Therefore, the aim of this study was to determine whether curcumin modifies the catabolic response of chondrocytes to IL-1beta. Human articular chondrocytes were prestimulated with 10 ng/mL IL-1beta for 0, 4, 8, 12, or 24 h and then cotreated with 50 microM curcumin for 0, 12, 24, 36, or 48 h. Synthesis of the cartilage-specific collagen type II and matrix-degrading enzyme matrix metalloproteinase-3 (MMP-3) was investigated in chondrocytes by Western blot analysis. Activation and nuclear translocation of NF-kappaB were observed by immunofluorescence microscopy. IL-1beta induced a decrease in collagen type II and upregulation of MMP-3 in a time-dependent manner. Upregulation of MMP-3 was inhibited by curcumin in a time-dependent manner. In addition, IL-1beta-induced a decrease in type II collagen, which was relieved by curcumin treatment. In response to IL-1beta, NF-kappaB translocated to the nucleus, but translocation was inhibited by curcumin, as revealed by immunofluorescence microscopy. Taken together, these results confirmed an IL-1beta-mediated upregulation of proinflammatory MMP-3 in chondrocytes via an NF-kappaB activation mechanism. Curcumin protected chondrocytes from the catabolic effects of IL-1beta, such as MMP-3 upregulation, and interestingly also relieved cytokine-induced suppression of matrix protein synthesis. Therefore, curcumin antagonizes crucial catabolic effects of IL-1beta signaling that are known to contribute to the pathogenesis of osteoarthritis.

Nutraceutical Therapies for Degenerative Joint Diseases: A Critical Review

There is growing recognition of the importance of nutritional factors in the maintenance of bone and joint health, and that nutritional imbalance combined with endocrine abnormalities may be involved in the pathogenesis of osteoarthritis (OA) and osteochondritis dissecans (OCD). Despite this, dietary programs have played a secondary role in the management of these connective tissue disorders. Articular cartilage is critically dependent upon the regular provision of nutrients (glucose and amino acids), vitamins (particularly vitamin C), and essential trace elements (zinc, magnesium, and copper). Therefore, dietary supplementation programs and nutraceuticals used in conjunction with non-steroidal, anti-inflammatory drugs (NSAIDs) may offer significant benefits to patients with joint disorders, such as OA and OCD. This article examines the available clinical evidence for the efficacy of nutraceuticals, antioxidant vitamin C, polyphenols, essential fatty acids, and mineral cofactors in the treatment of OA and related joint disorders in humans and veterinary species. This article also attempts to clarify the current state of knowledge. It also highlights the need for additional targeted research to elucidate the changes in nutritional status and potential alterations to the expression of plasma membrane transport systems in synovial structures in pathophysiological states, so that current therapy and future treatments may be better focused.

Effects of cannabinoids on nitric oxide production by chondrocytes and proteoglycan degradation in cartilage

Cannabinoids have been reported to have anti-inflammatory effects and reduce joint damage in animal models of arthritis. This suggests a potential therapeutic role in arthritis of this group of compounds. Cannabinoids were studied to determine whether they have direct effects on chondrocyte metabolism resulting in cartilage protection. Synthetic cannabinoids, R-(+)-Win-55,212 (Win-2) and S-(-)-Win-55,212 (Win-3) and the endocannabinoid, anandamide, were investigated on unstimulated or IL-1-stimulated nitric oxide (NO) production in bovine articular chondrocytes as well as on cartilage proteoglycan breakdown in bovine nasal cartilage explants. Win-2 significantly inhibited (P < 0.05) NO production in chondrocytes at 1-10 microM concentrations. The combined CB(1) and CB(2) cannabinoid receptor antagonists, AM281 and AM630, respectively, at 100 microM did not block this effect, but instead they potentiated it. Anandamide and Win-2 (5-50 microM) also inhibited the release of sulphated glycosaminoglycans in bovine cartilage explants. The results suggest that some cannabinoids may prevent cartilage resorption, in part, by inhibiting cytokine-induced NO production by chondrocytes and also by inhibiting proteoglycan degradation.

Microarray analysis of gene expression in chondrosarcoma cells treated with bee venom

Bee venom (BV) has a broad array of clinical applications in Korean medicine, including treatment of inflammatory conditions such as arthritis. The final common pathway of many arthropathies is the destruction of articular cartilage and consequent loss of articular function. Chondrocyte dysfunction plays a key role in the pathogenesis of such disorders. To explore the global gene expression profiles in a human chondrocyte-like cell line treated with BV, microarray analysis was performed. The HTB-94 human chondrosarcoma cells were treated with BV, lipopolysaccharide (LPS), or both. Of the 344 genes profiled in this study, with a cut-off level of 4-fold change in the expression, (1) 35 were downregulated following BV treatment, (2) 16 were upregulated and 7 downregulated following LPS treatment, and (3) 32 were downregulated following co-stimulation of BV and LPS. The results of the present study shows that treatment of BV reversed the LPS-induced upregulation of such genes as interleukin-6 (IL-6) receptor, matrix metalloproteinase 15 (MMP-15), tumor necrosis factor (ligand) superfamily-10, caspase-6 and tissue inhibitor of metalloproteinase-1 (TIMP-1). It is thought that microarrays will play an ever-growing role in the advance of our understanding of the pharmacologic actions of BV in the treatment of arthritis.

Mediation of spontaneous knee osteoarthritis by progressive chondrocyte ATP depletion in Hartley guinea pigs

OBJECTIVE

Because articular chondrocytes reside in a hypoxic milieu, anaerobic glycolysis is central in generating ATP to support chondrocyte matrix synthesis and viability, with mitochondrial oxidative phosphorylation possibly providing physiologic reserve ATP generation. Nitric oxide (NO) potently suppresses mitochondrial oxidative phosphorylation. Because enhanced cartilage NO generation occurs in osteoarthritis (OA), we systematically tested for mitochondrial dysfunction in the pathogenesis of OA.

METHODS

We assessed chondrocytes for ATP depletion and for in situ changes in mitochondrial ultrastructure prior to and during the evolution of spontaneous knee OA in male Hartley guinea pigs, a model in which chondrocalcinosis also supervenes.

RESULTS

Spontaneous NO release from knee cartilage samples in organ culture doubled between ages 2 months and 8 months as knee OA developed. Concomitantly, chondrocyte intracellular ATP levels declined by approximately 50%, despite a lack of mitochondrial ultrastructure abnormalities in knee chondrocytes. As ATP depletion progressed with aging in knee chondrocytes, an increased ratio of lactate to pyruvate was observed, consistent with an adaptive augmentation of glycolysis to mitochondrial dysfunction. Furthermore, we observed progressive elevation of chondrocyte ATP-scavenging nucleotide pyrophosphatase/phosphodiesterase (NPP) activity and extracellular levels of the NPP enzymatic end product inorganic pyrophosphate (PPi), which stimulate chondrocalcinosis.

CONCLUSION

Profound chondrocyte ATP depletion develops in association with heightened NO generation in guinea pig knee OA. Increased NPP activity and concordant increases in extracellular PPi, which are strongly associated with human aging-associated degenerative arthropathy and directly stimulate chondrocalcinosis, may be primarily driven by chondrocyte ATP depletion. Our findings implicate a decreased mitochondrial bioenergetic reserve as a pathogenic factor in both degenerative arthropathy and chondrocalcinosis in aging.