Apoptotic insults to human chondrocytes induced by sodium nitroprusside are involved in sequential events, including cytoskeletal remodeling, phosphorylation of mitogen-activated protein kinase kinase kinase-1/c-Jun N-terminal kinase, and Bax-mitochondria-mediated caspase activation

Calcium-binding protein 39 overexpression promotes macrophages from 'M1' into 'M2' phenotype and improves chondrocyte damage in osteoarthritis by activating the AMP-activated protein kinase/sirtuin 1 axis

Osteoarthritis (OA) is a degenerative joint disease that affects cartilage and its peripheral tissues. Up-regulation of Calcium-binding protein 39 (CAB39) has a significant protective effect on osteoblasts, but the role and related molecular mechanisms of CAB39 in OA have not yet been reported. CAB39 overexpression and knockdown models were set up in chondrocytes (ATDC5) and macrophages (RAW264.7). The OA cell model was induced in ATDC5 cells with IL-1β (10 ng/mL). Cell viability was tested by the cell counting kit-8 assay, apoptosis was checked by flow cytometry. Western blot was applied for checking the expression of MMP3, MMP13, Aggrecan, the AMPK/Sirt-1 pathway, apoptosis-related proteins (Bax, Bcl-2, and Caspase-3), and macrophage phenotypic markers (CD86, iNOS, CD206, and Arg1). An OA model was constructed in mice, and CAB39 overexpression plasmids were administered to the knee cavity of the OA model mice. As a result, CAB39 was down-regulated in IL-1β-treated chondrocytes and OA mice. Overexpressing CAB39 enhanced ATDC5 cell viability and choked IL-1β-mediated apoptosis. Overexpression of CAB39 boosted the polarization of macrophages from M1-phenotype into M2 phenotype. In addition, overexpressing CAB39 facilitated the AMPK/Sirt-1 pathway activation, and AMPK inhibitors reversed the protective effect of CAB39 overexpression on chondrocytes. Moreover, CAB39 exhibited anti-inflammatory effects in OA mice by activating the AMPK/Sirt-1 pathway. Collectively, overexpressing CAB39 heightened macrophages’ M2 polarization and declined chondrocyte injury in OA by activating the AMPK/Sirt-1 pathway.Abbreviations AMPK: AMP-activated protein kinaseArg1: arginase 1Bax: Bcl-2-associated X proteinBcl-2: B-cell lymphoma-2CAB39: Calcium-binding protein 39CM: Conditioned mediumDMM: destabilization of the medial meniscusECM: extracellular matrixELISA: enzyme-linked immunosorbent assayFCM: Flow cytometryIL-1β: interleukin-1βIL-4: interleukin-4IL-6: interleukin-6IL-10: interleukin-10IFN – γ: Interferon-gammaIHC: ImmunohistochemistryiNOS: Inducible nitric oxide synthaseLKB1: liver kinase B1MMP3: Matrix metalloproteinase3MMP13:Matrix metalloproteinase13NF-κB: NF-kappaBOA: OsteoarthritisqRT-PCR: Quantitative reverse transcription-polymerase chain reactionRT: room temperatureSirt-1: sirtuin 1STRAD: STE20-related adaptor alphaWB: Western blot

Iron homeostasis in arthropathies: From pathogenesis to therapeutic potential

Iron is an essential element for proper functioning of cells within mammalian organ systems; in particular, iron homeostasis is critical for joint health. Excess iron can induce oxidative stress damage, associated with the pathogenesis of iron-storage and ageing-related diseases. Therefore, iron levels in body tissues and cells must be tightly regulated. In the past decades, excess iron content within joints has been found in some patients with joint diseases including hemophilic arthropathy, hemochromatosis arthropathy, and osteoarthritis (OA). Currently, increased evidence has shown that iron accumulation is closely associated with multiple pathological changes of these arthropathies. This review summarizes system-level and intracellular regulation of iron homeostasis, and emphasizes the role of iron in synovial alterations, cartilage degeneration, and subchondral bone of several arthropathies. Of note, we discuss the potential link between iron homeostasis and OA pathogenesis. Finally, we discuss the therapeutic potential of maintaining iron homeostasis in these arthropathies.

Improvement of Chronic Wound Healing by Pre-activated Bone Marrow Cells with Sodium Nitroprusside in Rabbits

AIM OF STUDY

This study investigated whether pre-activated bone marrow cells with sodium nitro prusside have effectiveness in the inhibition of diabetic wound healing in diabetic rabbits. In diabetic skin disorders and conditions involved redox state disturbances. The aim was to determine the effect of two minimum dosages of sodium nitro prusside, and its' potential with bone marrow cells for chronic wound healing in-vivo.

METHODS

Full-thickness skin dorsal wounds were created on diabetic rabbits. The effects of two minimum concentrations of sodium nitro prusside solution with bone marrow cells on wound healing were studied. The useful combination of sodium nitro prusside with bone marrow cells on wound repair may be attributed to its functional influences on inflammation, angiogenesis, cell proliferation, matrix deposition, and remodeling.

RESULTS

The in-vivo experiments confirmed that pre-activated bone marrow cells contributed to wound healing by alleviating oxidative stress, increasing proliferation and migration, decreasing apoptosis. In histological results, improved collagen deposition, enhanced re-epithelization, angiogenesis, and decreased inflammatory infiltration were also detected in wound biopsies.

CONCLUSIONS

For the treatment of chronic wounds, cell-based therapy was an attractive approach. Bone marrow cells have a low ability to differentiate various types of cells or late healing without pretreatment. So it was needed to increase their potency of differentiation. The transplantation of pretreated bone marrow cells with a prime quantity of sodium nitro prusside solution improved chronic wound healing with a greater level of growth factors and a minimum level of oxidative stress.

Rosiglitazone Reduces Apoptosis and Inflammation in Lipopolysaccharide-Induced Human Umbilical Vein Endothelial Cells

BACKGROUND Although the peroxisome proliferator-activated receptor-g (PPARg) agonist rosiglitazone has significant anti-inflammatory properties, no scientific studies have provided new insights in its pharmacological properties with respect to acute respiratory distress syndrome (ARDS). The present investigation aimed to evaluate whether rosiglitazone can reduce apoptosis and inflammation in a lipopolysaccharide (LPS)-induced acute respiratory distress syndrome in vitro model. MATERIAL AND METHODS Human umbilical vein endothelial cells (HUVECs) were treated with 1 µg/ml LPS in the absence or presence of 10 µM rosiglitazone for 24 h. Cell viability was measured by MTT assay. Flow cytometry was used to examine the cell apoptosis and ROS production in HUVECs response to LPS and rosiglitazone. The levels of pro-inflammatory cytokine factors, including TNF-α, IL-6, CXCL12, and CXCR4, were measured by ELISA, real-time PCR, and Western blot assay, respectively. The expression of PPARg, Bcl-2, and Bax and the activity of JAK2 and STAT3 were also investigated by Western blot assay. RESULTS We found that rosiglitazone significantly inhibited LPS-induced cell apoptosis, ROS production, and inflammation in HUVECs. Furthermore, we found a significant reduction of JAK2/STAT3 activation and the Bax/Bcl-2 ratio in LPS-induced HUVECs response to rosiglitazone treatment. CONCLUSIONS Treatment with rosiglitazone can reduce apoptosis and inflammation in HUVECs induced by LPS.

Regulation of cytochrome P450 gene expression by ketamine: a review

INTRODUCTION

Although used as an anesthetic drug for decades, ketamine appears to have garnered renewed interest due to its potential therapeutic uses in pain therapy, neurology, and psychiatry. Ketamine undergoes extensive oxidative metabolism by cytochrome P450 (CYP) enzymes. Considerable efforts have been expended to elucidate the ketamine-induced regulation of CYP gene expression. The safety profile of chronic ketamine administration is still unclear. Understanding how ketamine regulates CYP gene expression is clinically meaningful. Areas covered: In this article, the authors provide a brief review of clinical applications of ketamine and its metabolism by CYP enzymes. We discuss the effects of ketamine on the regulation of CYP gene expression, exploring aspects of cytoskeletal remodeling, mitochondrial functions, and calcium homeostasis. Expert opinion: Ketamine may inhibit CYP gene expression through inhibiting calcium signaling, decreasing ATP levels, producing excessive reactive oxygen species, and subsequently perturbing cytoskeletal dynamics. Further research is still needed to avoid possible ketamine-drug interactions during long-term use in the clinic.

ASIC2a overexpression enhances the protective effect of PcTx1 and APETx2 against acidosis-induced articular chondrocyte apoptosis and cytotoxicity

Acid hydrarthrosis is another important pathological character in rheumatoid arthritis (RA), and acid-sensing ion channel 1a (ASIC1a) plays a destructive role in acidosis-induced articular chondrocyte cytotoxicity. Recently, ASIC2a has been reported to possess neuroprotective effect on acidosis-induced injury of neuronal cells. However, whether ASIC2a has an enhanced effect on the protective effect of blocking ASIC1a and ASIC3 against acid-induced chondrocyte apoptosis is still unclear. The aim of present study was to investigate the chondroprotective effect of ASIC2a with PcTx1 (ASIC1a specific blocker) and APETx2 (ASIC3 specific blocker) on acidosis-induced chondrocyte apoptosis. Our results revealed that acid (pH 6.0) decreased the cell viability and induced apoptosis of articular chondrocytes. PcTx1 and APETx2 combination significantly attenuated acidosis-induced chondrocyte cytotoxicity due to inhibit apoptosis, and this role could be enhanced by ASIC2a overexpression compared with the PcTx1 and APETx2 combination alone group. Moreover, both the [Ca²⁺]_i levels and the levels of phosphorylated ERK1/2 as well as p38 were further reduced in acidosis-induced chondrocytes after ASIC2a overexpression in the presence of PcTx1 and APETx2. Furthermore, ASIC2a overexpression also reduced acid-induced the expression of ASIC1a. In addition, ASIC2a overexpression further promoted the PcTx1 and APETx2-increased levels of type II collagen in acidosis-induced chondrocytes. Taken together, the current data suggested that ASIC2a overexpression might enhance the anti-apoptotic and protective role of PcTx1 and APETx2 against acid-induced rat articular chondrocyte apoptosis by regulating ASIC1a expression and the [Ca²⁺]_i levels and at least in part, suppressing p38 and ERK1/2 MAPK signaling pathways.

DUSP19, a downstream effector of leptin, inhibits chondrocyte apoptosis via dephosphorylating JNK during osteoarthritis pathogenesis

Increased mitogen-activated protein kinase (MAPK) activity has been found in human osteoarthritis (OA). Dual specificity protein phosphatase 19 (DUSP19), a member of mitogen-activated protein kinase (MAPK) phosphatases (MKPs), controls the activity of various MAPKs. This study was aimed to explore the function of DUSP19 during OA pathogenesis. Here, OA and healthy control data were downloaded from the NCBI Gene Expression Omnibus database (GSE57218). Forty-five patients with OA and 25 healthy donors were enrolled in this study. A rat OA model was induced by anterior cruciate ligament transection. Primary cultured chondrocytes were treated with leptin (10 ng mL(-1)). Cell survival, cell apoptosis and reactive oxygen species (ROS) were identified by CCK-8 and flow cytometry, respectively. In the cartilage of OA patients, DUSP19 was expressed in a lower level than in the cartilage of healthy control. The DUSP19 level was negatively correlated with leptin, which was confirmed by experiments in the rat OA model. Moreover, cell apoptosis and JNK activation in the rat cartilage were increased with the increasing of leptin levels and the decreasing of DUSP19 mRNA levels. In primary culture chondrocytes, exogenous leptin suppressed DUSP19 expression. The ectopic expression of DUSP19 significantly ameliorated leptin-induced apoptosis in damaged chondrocytes, accompanied by the reduced production of ROS. Moreover, the activity of JNK stimulated by leptin was suppressed by DUSP19 overexpression. The present study indicated that DUSP19, a downstream of leptin, inhibited apoptosis of chondrocytes through dephosphorylating JNK.

Dominant roles of Fenton reaction in sodium nitroprusside-induced chondrocyte apoptosis

Sodium nitroprusside (SNP) has been widely used as an exogenous nitric oxide (NO) donor to explore the molecular mechanism of NO-mediated chondrocyte apoptosis during the latest two decades. We have recently found that NO-independent ROS play a key role in SNP-induced apoptosis in rabbit chondrocytes. This study aims to investigate what kind of ROS and how the reliable ROS mediators mediate the SNP-induced apoptosis. Data shows that SNP and NO-exhausted SNP (SNPex) induced ROS production or cytotoxicity to identically degree. SNP induced a marked increase in iron ions, superoxide anion (O2(•-)), hydrogen peroxide (H2O2) and hydroxyl radical ((•)OH) level. H2O2 scavenger (CAT) and (•)OH scavenger (DMSO) significantly inhibited SNP-induced chondrocyte apoptosis. Iron ions chelator (DFO) entirely prevented SNP-induced chondrocyte apoptosis. In contrast, O2(•-) scavenger (SOD) and glutathione depletion agent (BSO) promoted SNP-induced cytotoxicity. K3[Fe(CN)6] exhibited no cytotoxicity, and H2O2 alone up to 250µM or iron ions alone up to 90µM is non-cytotoxic to chondrocytes. Combination of 25µM FeSO4 and 100µM H2O2 in the presence of BSO induced chondrocyte death similar to SNP treatment. Fetal bovine serum (FBS) enhanced iron ions release from SNP and the cytotoxicity of SNP. Our data shows that the extracellular Fenton reaction between iron ions released from SNP and H2O2 induced by SNP plays a key role in SNP-induced chondrocyte apoptosis. Overall, our results indicate that the potential of SNP to increase iron ions and ROS should be especially considered for some biological functions and, possibly, also for clinical applications of this drug.

Rutin protects rat articular chondrocytes against oxidative stress induced by hydrogen peroxide through SIRT1 activation

The progressive degeneration and ossification of articular chondrocytes are main symptoms in the pathogenesis of osteoarthritis (OA). Several flavonoids may provide an adjunctive alternative for the management of moderate OA in humans. Rutin, a natural flavone derivative (quercetin-3-rhamnosylglucoside), is well known for its potent anti-inflammatory and anti-oxidant properties against oxidative stress. However, the protective function of rutin related to OA, which is characterized by deterioration of articular cartilage, remains unclear. The present study investigated the protective effects of rutin, an activator of silent information regulator 1 (SIRT1), involved in the inhibition of NF-κB/MAPK signaling pathway in hydrogen peroxide (H2O2)-induced oxidative stress in rat chondrocytes. SIRT1 activation by rutin attenuated levels of inflammatory cytokines and NF-κB/MAPK signaling, whereas the inhibition of SIRT1 by sirtinol counteracted the beneficial effects of rutin in H2O2-treated chondrocytes. The findings of these studies suggested the potential involvement of SIRT1 in the pathogenesis of OA, and indicated that rutin is a possible therapeutic option for OA.

Biomarkers of Chondrocyte Apoptosis and Autophagy in Osteoarthritis

Cell death with morphological and molecular features of apoptosis has been detected in osteoarthritic (OA) cartilage, which suggests a key role for chondrocyte death/survival in the pathogenesis of OA. Identification of biomarkers of chondrocyte apoptosis may facilitate the development of novel therapies that may eliminate the cause or, at least, slow down the degenerative processes in OA. The aim of this review was to explore the molecular markers and signals that induce chondrocyte apoptosis in OA. A literature search was conducted in PubMed, Scopus, Web of Science and Google Scholar using the keywords chondrocyte death, apoptosis, osteoarthritis, autophagy and biomarker. Several molecules considered to be markers of chondrocyte apoptosis will be discussed in this brief review. Molecular markers and signalling pathways associated with chondroycte apoptosis may turn out to be therapeutic targets in OA and approaches aimed at neutralizing apoptosis-inducing molecules may at least delay the progression of cartilage degeneration in OA.

Nitric oxide-associated chondrocyte apoptosis in trauma patients after high-energy lower extremity intra-articular fractures

BACKGROUND

The primary goal of this study was to identify nitric oxide (NO)-induced apoptosis in traumatized chondrocytes in intra-articular lower extremity fractures and the secondary goal was to identify the timeline of NO-induced apoptosis after injury.

MATERIALS AND METHODS

This is a prospective collection of samples of human cartilage harvested at the time of surgery to measure apoptotic cell death and the presence of NO by immunohistochemistry. Three patients met the criteria for control subjects and eight patients sustained high-energy intra-articular fractures and were included in the study. Subjects who sustained intra-articular acetabular, tibial, calcaneal and talus fracture had articular cartilage harvested at the time of surgical intervention. All 8 patients underwent open reduction and internal fixation of the displaced intra-articular fractures. The main outcome measures were rate of apoptosis, degree of NO-induced apoptosis in chondrocytes, and the timeline of NO-induced apoptosis after high-energy trauma.

RESULTS

The percentage of apoptotic chondrocytes was higher in impacted samples than in normal cartilage (56 vs 4 %), confirming the presence of apoptosis after intra-articular fracture. The percentage of cells with NO was greater in apoptotic cells than in normal cells (59 vs 20 %), implicating NO-induction of apoptosis. The correlation between chondrocyte apoptosis and increasing time from injury was found to be -0.615, indicating a decreasing rate of apoptosis post injury.

CONCLUSIONS

The data showed the involvement of NO-induced apoptosis of chondrocytes after high-energy trauma, which decreased with time from injury.

High-Density Lipoprotein Prevents Endoplasmic Reticulum Stress-Induced Downregulation of Liver LOX-1 Expression

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a specific cell-surface receptor for oxidized-low-density lipoprotein (ox-LDL). The impact of high-density lipoprotein (HDL) on endoplasmic reticulum (ER) stress-mediated alteration of the LOX-1 level in hepatocytes remains unclear. We aimed to investigate the impact on LOX-1 expression by tunicamycin (TM)-induced ER stress and to determine the effect of HDL on TM-affected LOX-1 expression in hepatic L02 cells. Overexpression or silencing of related cellular genes was conducted in TM-treated cells. mRNA expression was evaluated using real-time polymerase chain reaction (PCR). Protein expression was analyzed by western blot and immunocytochemistry. Lipid uptake was examined by DiI-ox-LDL, followed by flow cytometric analysis. The results showed that TM induced the upregulation of ER chaperone GRP78, downregulation of LOX-1 expression, and lipid uptake. Knock down of IRE1 or XBP-1 effectively restored LOX-1 expression and improved lipid uptake in TM-treated cells. HDL treatment prevented the negative impact on LOX-1 expression and lipid uptake induced by TM. Additionally, 1–10 μg/mL HDL significantly reduced the GRP78, IRE1, and XBP-1 expression levels in TM-treated cells. Our findings reveal that HDL could prevent the TM-induced reduction of LOX-1 expression via inhibiting the IRE1/XBP-1 pathway, suggesting a new mechanism for beneficial roles of HDL in improving lipid metabolism.

Resveratrol protects rabbit articular chondrocyte against sodium nitroprusside-induced apoptosis via scavenging ROS

This study aims to investigate the mechanism by which resveratrol (RV) prevents sodium nitroprusside (SNP)-induced chondrocyte apoptosis, which is a characteristic feature of osteoarthritis (OA). Rabbit articular chondrocytes were pre-incubated with 100 μM RV for 18 h before 1.5 mM SNP co-treatment for 6 h. Cell viability was evaluated by CCK-8. Annexin V/PI double staining and Hoechst 33258 staining were used to determine the fashion of SNP-induced chondrocytes death. Mitochondrial membrane potential (ΔΨm) was measured by using flow cytometry (FCM) with TMRM and Rhodamine 123 staining. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) levels were confirmed by FCM analysis with DCFH-DA and DAF-FM DA staining. Cytoskeleton proteins of chondrocytes co-stained with Actin-Trakcer Green and Tubulin-Trakcer Red were validated by confocal microscopy. SNP induced time- and dose-dependent chondrocytes apoptosis with decline of ΔΨm, activation of caspases as well as cytoskeletal remodeling. SNP induced a significant induction of both ROS and NO. RV remarkably prevented SNP-induced ROS production and apoptosis as well as cytoskeletal remodeling, but did not prevent SNP-induced NO production. Pretreatment with NO scavengers did not significantly prevent SNP-induced apoptosis and cytoskeletal remodeling. SNP induces NO-independent ROS production which dominates rabbit articular chondrocyte apoptosis, and RV protects chondrocytes against SNP-induced apoptosis via scavenging ROS instead of NO.

Mitochondrial respiratory chain dysfunction modulates metalloproteases -1, -3 and -13 in human normal chondrocytes in culture

BACKGROUND

Mitochondrion has an important role in the osteoarthritis (OA) pathology. We have previously demonstrated that the alteration of the mitochondrial respiratory chain (MRC) contributes to the inflammatory response of the chondrocyte. However its implication in the process of cartilage destruction is not well understood yet. In this study we have investigated the relationship between the MRC dysfunction and the regulation of metalloproteases (MMPs) in human normal chondrocytes in culture.

METHODS

Human normal chondrocytes were isolated from human knees obtained form autopsies of donors without previous history of rheumatic disease. Rotenone, 3-Nitropropionic acid (NPA), Antimycin A (AA), Sodium azide and Oligomycin were used to inhibit the activity of the mitochondrial complexes I, II, III, IV and V respectively. The mRNA expression of MMPs -1, -3 and -13 was studied by real time PCR. The intracellular presence of MMP proteins was evaluated by western blot. The liberation of these proteins to the extracellular media was evaluated by ELISA. The presence of proteoglycans in tissue was performed with tolouidin blue and safranin/fast green. Immunohistochemistry was used for evaluating MMPs on tissue.

RESULTS

Firstly, cells were treated with the inhibitors of the MRC for 24 hours and mRNA expression was evaluated. An up regulation of MMP-1 and -3 mRNA levels was observed after the treatment with Oligomycin 5 and 100 μg/ml (inhibitor of the complex V) for 24 hours. MMP-13 mRNA expression was reduced after the incubation with AA 20 and 60 μg/ml (inhibitor of complex III) and Oligomycin. Results were validated at protein level observing an increase in the intracellular levels of MMP-1 and -3 after Oligomycin 25 μg/ml stimulation [(15.20±8.46 and 4.59±1.83 vs. basal=1, respectively (n=4; *P<0.05)]. However, AA and Oligomycin reduced the intracellular levels of the MMP-13 protein (0.70±0.16 and 0.3±0.24, respectively vs. basal=1). In order to know whether the MRC dysfunction had an effect on the liberation of MMPs, their levels were evaluated in the supernatants. After 36 hours of stimulation, values were: MMP-1=18.06±10.35 with Oligomycin 25 μg/ml vs. basal=1, and MMP-3=8.49±4.32 with Oligomycin 5 μg/ml vs. basal=1 (n=5; *P<0.05). MMP-13 levels in the supernatants were reduced after AA 60 μg/ml treatment (0.50±0.13 vs. basal=1) and Oligomycin 25 μg/ml (0.41±0.14 vs. basal=1); (n=5; *P<0.05). The treatment of explants with Oligomycin, showed an increase in the positivity of MMP-1 and -3. Explants stimulated with AA or Oligomycin revealed a decrease in MMP-13 expression. Proteoglycan staining demonstrated a reduction of proteoglycan levels in the tissues treated with Oligomycin.

CONCLUSIONS

These results reveal that MRC dysfunction modulates the MMPs expression in human normal chondrocytes demonstrating its role in the regulation of the cartilage destruction.

Static mechanical stress induces apoptosis in rat endplate chondrocytes through MAPK and mitochondria-dependent caspase activation signaling pathways

Mechanical stress has detrimental effects on cartilaginous endplate chondrocytes due to apoptosis in vivo and in vitro. In this study, we investigated the possible apoptosis signaling pathways induced by mechanical stress in cultured rat cervical endplate chondrocytes. Static mechanical load significantly reduced cell viability in a time- and load-dependent manner, as demonstrated by the Cell Counting Kit-8 (CCK-8) assay. Chondrocyte apoptosis induced by mechanical stress was confirmed by annexin V/propidium iodide (PI) staining and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Western blot analysis revealed that static load-induced chondrocyte apoptosis was accompanied by increased phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 mitogen-activated protein kinase (MAPK). The loss of mitochondrial membrane potential (ΔΨm), increased Cytochrome c release, and activated Caspase-9 and Caspase-3, indicating that the mitochondrial pathway is involved in mechanical stress-induced chondrocyte apoptosis. Treatment with inhibitors of JNK (SP600125), p38 MAPK (SB203580), and ERK (PD98059) prior to mechanical stimulation reversed both the static load-induced chondrocyte apoptosis and the activation of JNK, p38 MAPK, and ERK. Taken together, the data presented in this study demonstrate that mechanical stress induces apoptosis in rat cervical endplate chondrocytes through the MAPK-mediated mitochondrial apoptotic pathway.

MicroRNA-210 targets antiapoptotic Bcl-2 expression and mediates hypoxia-induced apoptosis of neuroblastoma cells

MicroRNAs (miRNAs) can regulate cell survival and death by targeting apoptosis-related gene expression. miR-210 is one of the most hypoxia-sensitive miRNAs. In this study, we evaluated the roles of miR-210 in hypoxia-induced insults to neural cells. Treatment of neuro-2a cells with oxygen/glucose deprivation (OGD) induced cell apoptosis in a time-dependent manner. In parallel, OGD time-dependently increased cellular miR-210 levels. Knocking down miR-210 expression using specific antisenses significantly attenuated OGD-induced neural apoptosis. Concurrently, OGD increased hypoxia-inducible factor (HIF)-1α mRNA and protein syntheses. Pretreatment with YC-1, an inhibitor of HIF-1α, reduced OGD-caused cell death. Sequentially, OGD specifically decreased antiapoptotic Bcl-2 mRNA and protein levels in neuro-2a cells. A search by a bioinformatic approach revealed that miR-210-specific binding elements exist in the 3'-untranslated region of Bcl-2 mRNA. Application of miR-210 antisenses simultaneously alleviated OGD-involved inhibition of Bcl-2 mRNA expression. In comparison, overexpression of miR-210 synergistically diminished OGD-caused inhibition of Bcl-2 mRNA expression and consequently induced greater cellular insults. Taken together, this study shows that OGD can induce miR-210 expression through activating HIF-1α. And miR-210 can mediate hypoxia-induced neural apoptosis by targeting Bcl-2.

6-Shogaol Protects against Oxidized LDL-Induced Endothelial Injruries by Inhibiting Oxidized LDL-Evoked LOX-1 Signaling

Endothelial dysfunction and oxLDL are believed to be early and critical events in atherogenesis. 6-Shogaol is the major bioactive compound present in Zingiber officinale and possesses the anti-atherosclerotic effect. However, the mechanisms remain poorly understood. The goal of this study was to investigate the effects of 6-shogaol on oxLDL-induced Human umbilical vein endothelial cells (HUVECs) injuries and its possible molecular mechanisms. Hence, we studied the effects of 6-shogaol on cell apoptosis, cellular reactive oxygen species (ROS), NF-κB activation, Bcl-2 expression, and caspase -3, -8, -9 activities. In addition, E-selectin, MCP-1, and ICAM-1 were determined by ELISA. Our study show that oxLDL increased LOX-1 expression, ROS levels, NF-κB, caspases-9 and -3 activation and decreased Bcl-2 expression in HUVECs. These alterations were attenuated by 6-shogaol. Cotreatment with 6-shogaol and siRNA of LOX-1 synergistically reduced oxLDL-induced caspases -9, -3 activities and cell apoptosis. Overexpression of LOX-1 attenuated the protection by 6-shogaol and suppressed the effects of 6-shogaol on oxLDL-induced oxidative stress. In addition, oxLDL enhanced the activation of NF-κB and expression of adhesion molecules. Pretreatment with 6-shogaol, however, exerted significant cytoprotective effects in all events. Our data indicate that 6-shogaol might be a potential natural antiapoptotic agent for the treatment of atherosclerosis.

Mechanisms mediating propofol protection of pulmonary epithelial cells against lipopolysaccharide-induced cell death

Propofol (2,6-diisopropylphenol) is an anaesthetic agent with anti-oxidant properties. The aim of the present study was to determine whether propofol can protect pulmonary epithelial (A549) cells against lipopolysaccharide (LPS)-induced cell death and, if so, the mechanisms involved. The effects of LPS alone and in combination with propofol on A549 cell death were investigated. Cell viability was determined using the colourimetric 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Apoptotic A549 cells were detected by flow cytometry, as propidium iodide-negative and annexin-V-positive cells, and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL). Mitochondrial membrane potential (MMP), caspase 9 activity, Ca(2+) concentrations and reactive oxygen species (ROS) were analysed by immunofluorescent methods. Aconitase 2 (ACO2), microtubule-associated light chain 3 (LC3) and beclin-1 levels were evaluated using reverse transcription-polymerase chain reaction and/or western blot analysis. Exposure of A549 cells to 1-50 μg/mL LPS for 3-24 h resulted in the concentration- and time-dependent induction of cell death. Cell apoptosis accounted for approximately 77% of cell death induced by LPS. Propofol (5-150 μmol/L) concentration-dependently inhibited LPS-induced A549 cell death. This protective effect of propofol was accompanied by prevention of LPS-induced mitochondrial dysfunction (reductions in MMP, ACO2 expression and ATP) and was associated with the inhibition of LPS-induced activation of apoptotic signals (caspase 9 activity, ROS overproduction and Ca(2+) accumulation). In addition, propofol blocked LPS-induced overexpression of the autophagy-associated proteins LC3 and beclin-1. The data indicate that propofol protects A549 cells against LPS-induced apoptosis, and probably autophagy, by blocking LPS-induced activation of ROS/caspase 9 pathways and upregulation of LC3 and beclin-1, respectively.

Honokiol traverses the blood-brain barrier and induces apoptosis of neuroblastoma cells via an intrinsic bax-mitochondrion-cytochrome c-caspase protease pathway

Neuroblastomas, an embryonic cancer of the sympathetic nervous system, often occur in young children. Honokiol, a small-molecule polyphenol, has multiple therapeutic effects and pharmacological activities. This study was designed to evaluate whether honokiol could pass through the blood-brain barrier (BBB) and induce death of neuroblastoma cells and its possible mechanisms. Primary cerebral endothelial cells (CECs) prepared from mouse brain capillaries were cultured at a high density for 4 days, and these cells formed compact morphologies and expressed the ZO-1 tight-junction protein. A permeability assay showed that the CEC-constructed barrier obstructed the passing of FITC-dextran. Analyses by high-performance liquid chromatography and the UV spectrum revealed that honokiol could traverse the CEC-built junction barrier and the BBB of ICR mice. Exposure of neuroblastoma neuro-2a cells and NB41A3 cells to honokiolinduced cell shrinkage and decreased cell viability. In parallel, honokiol selectively induced DNA fragmentation and cell apoptosis rather than cell necrosis. Sequential treatment of neuro-2a cells with honokiol increased the expression of the proapoptotic Bax protein and its translocation from the cytoplasm to mitochondria. Honokiol successively decreased the mitochondrial membrane potential but increased the release of cytochrome c from mitochondria. Consequently, honokiol induced cascade activation of caspases-9, -3, and -6. In comparison, reducing caspase-6 activity by Z-VEID-FMK, an inhibitor of caspase-6, simultaneously attenuated honokiol-induced DNA fragmentation and cell apoptosis. Taken together, this study showed that honokiol can pass through the BBB and induce apoptotic insults to neuroblastoma cells through a Bax-mitochondrion-cytochrome c-caspase protease pathway. Therefore, honokiol may be a potential candidate drug for treating brain tumors.

Monosodium Urate and Tumor Necrosis Factor-α Increase Apoptosis in Human Chondrocyte Cultures

Monosodium urate and tumor necrosis factor-α, are two potent mediators of separate inflammatory response pathways in arthritic joints where inflammation may be accompanied by the loss of chondrocyte vitality via apoptosis. To address this possibility in vitro, chondrocyte cultures were employed to determine the extent to which monosodium urate and recombinant TNF-α altered the frequency of apoptotic chondrocytes. Apoptosis as a function of the activation of p38 kinase, C-Jun-terminal kinase, signal transducer and activator of transcription-3 and/or the activity of xanthine oxidase was also studied. Using normal human chondrocytes, monosodium urate or recombinant tumor necrosis factor-α increased the frequency of apoptosis and activity of xanthine oxidase. However, the xanthine oxidase-specific inhibitor, febuxostat, failed to blunt this response. Monosodium urate, tumor necrosis factor-α or the Janus kinase inhibitor, AG-490, increased the frequency of apoptotic nuclei in macroaggregate pellet cultures initiated from juvenile human chondrocytes, but not in pellet cultures derived from mesenchymal stem cells. In OA chondrocytes, activation of p38, C-Jun-NH₂-kinase and signal transducer and activator of transcription-3 preceded apoptosis. Activation of signal transducer and activator of transcription-3 also was seen in pellet cultures initiated from juvenile chondrocytes and MSCs incubated with MSU, recombinant tumor necrosis factor-α or febuxostat, but apoptosis was increased only in the pellet cultures derived from juvenile chondrocytes. Although AG-490 or the combination of AG-490 and febuxostat inhibited signal transducer and activator of transcription-3 activation, apoptosis was unaffected. These results showed that recombinant tumor necrosis factor-α, monosodium urate and AG-490 increased apoptosis in normal human chondrocytes, OA chondrocytes and human juvenile chondrocyte pellet cultures, but not in chondrocyte pellet cultures initiated from MSCs. The increased frequency of apoptotic chondrocytes in response to recombinant tumor necrosis factor-α or monosodium urate was not dependent on either activation of STAT3 or the activity of XO.

Physiology and pathophysiology of nitrosative and oxidative stress in osteoarthritic joint destruction

Osteoarthritis (OA) is one of the most common chronic diseases, with increasing importance due to increased life expectancy. On a cellular level, the pathophysiology of joint function impairment and ultimate destruction associated with OA remains poorly understood. Free radicals are highly reactive molecules involved in both normal intracellular signal transduction and degenerative cellular processes. An imbalance between the free radical burden and cellular scavenging mechanisms, defined as oxidative stress, has been identified as a relevant factor in OA pathogenesis. This literature review elucidates the involvement of nitrosative and oxidative stress in cellular ageing in joints, cell senescence, and apoptosis. Free radical exposure is known to promote cellular senescence and apoptosis, and the involvement of radical oxygen species (ROS) in inflammation, fibrosis control, and pain nociception has been proven. A relatively novel approach to OA pathophysiology considers the joint to be a dynamic system consisting of 3, continuously interacting compartments, cartilage, synovial tissue, and subchondral bone. Current knowledge concerning free radical involvement in paracrine signalling in OA is reviewed. The interrelationship between oxidative imbalances and OA pathophysiology may provide a novel approach to the comprehension, and therefore modification, of OA disease progression and symptom control.

Resveratrol attenuates oxidized LDL-evoked Lox-1 signaling and consequently protects against apoptotic insults to cerebrovascular endothelial cells

Cerebrovascular endothelial cells (CECs) are crucial components of the blood-brain barrier. Our previous study showed that oxidized low-density lipoprotein (oxLDL) induces apoptosis of CECs. This study was designed to further evaluate the effects of resveratrol on oxLDL-induced CEC insults and its possible molecular mechanisms. Resveratrol decreased the oxidation of LDL into oxLDL. Additionally, the oxLDL-caused oxidative stress and cell damage were attenuated by resveratrol. Exposure of CECs to oxLDL induced cell shrinkage, DNA fragmentation, and cell apoptosis, but resveratrol defended against such injuries. Application of Lox-1 small interference (si)RNA into CECs reduced the translation of this membrane receptor, and simultaneously increased resveratrol protection from oxLDL-induced cell apoptosis. By comparison, overexpression of Lox-1 attenuated resveratrol protection. Resveratrol inhibited oxLDL-induced Lox-1 mRNA and protein expressions. Both resveratrol and Lox-1 siRNA decreased oxLDL-enhanced translocation of proapoptotic Bcl-2-associated X protein (Bax) from the cytoplasm to mitochondria. Sequentially, oxLDL-induced alterations in the mitochondrial membrane potential, cytochrome c release, and activities of caspases-9, -3, and -6 were decreased by resveratrol. Pretreatment with Z-VEID-FMK (benzyloxycarbonyl-Leu-Glu-His-Asp-fluoromethyl ketone) synergistically promoted resveratrol's protection against DNA fragmentation and cell apoptosis. Therefore, this study shows that resveratrol can protect CECs from oxLDL-induced apoptotic insults via downregulating Lox-1-mediated activation of the Bax-mitochondria-cytochrome c-caspase protease pathway.

Effect of nitric oxide on mitochondrial activity of human synovial cells

Background

Nitric oxide (NO) is a messenger implicated in the destruction and inflammation of joint tissues. Cartilage and synovial membrane from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) have high levels of NO. NO is known to modulate various cellular pathways and, thus, inhibit the activity of the mitochondrial respiratory chain (MRC) of chondrocytes and induce the generation of reactive oxygen species (ROS) and cell death in multiple cell types. For these reasons, and because of the importance of the synovial membrane in development of OA pathology, we investigated the effects of NO on survival, mitochondrial function, and activity of fibroblastic human OA synovial cells.

Methods

Human OA synovia were obtained from eight patients undergoing hip joint replacement. Sodium nitroprusside (SNP) was used as a NO donor compound and cell viability was evaluated by MTT assays. Mitochondrial function was evaluated by analyzing the mitochondrial membrane potential (Δψm) with flow cytometry using the fluorofore DePsipher. ATP levels were measured by luminescence assays, and the activities of the respiratory chain complexes (complex I: NADH CoQ₁ reductase, complex II: succinate dehydrogenase, complex III: ubiquinol-cytochrome c reductase, complex IV: cytochrome c oxidase) and citrate synthase (CS) were measured by enzymatic assay. Protein expression analyses were performed by western blot.

Results

SNP at a concentration of 0.5 mM induced cell death, shown by the MTT method at different time points. The percentages of viable cells at 24, 48 and 72 hours were 86.11 ± 4.9%, 74.31 ± 3.35%, and 43.88 ± 1.43%, respectively, compared to the basal level of 100% (*p < 0.05). SNP at 0.5 mM induced depolarization of the mitochondrial membrane at 12 hours with a decrease in the ratio of polarized cells (basal = 2.48 ± 0.28; SNP 0.5 mM = 1.57 ± 0.11; *p < 0.01). The time course analyses of treatment with SNP at 0.5 mM demonstrated that treatment reliably and significantly reduced intracellular ATP production (68.34 ± 14.3% vs. basal = 100% at 6 hours; *p < 0.05). The analysis of the MRC at 48 hours showed that SNP at 0.5 mM increased the activity of complexes I (basal = 36.47 ± 3.92 mol/min/mg protein, SNP 0.5 mM = 58.08 ± 6.46 mol/min/mg protein; *p < 0.05) and III (basal = 63.87 ± 6.93 mol/min/mg protein, SNP 0.5 mM = 109.15 ± 30.37 mol/min/mg protein; *p < 0.05) but reduced CS activity (basal = 105.06 ± 10.72 mol/min/mg protein, SNP at 0.5 mM = 66.88 ± 6.08 mol/min/mg protein.; *p < 0.05), indicating a decrease in mitochondrial mass. Finally, SNP regulated the expression of proteins related to the cellular cycle; the NO donor decreased bcl-2, mcl-1 and procaspase-3 protein expression.

Conclusions

This study suggests that NO reduces the survival of OA synoviocytes by regulating mitochondrial functionality, as well as the proteins controlling the cell cycle.

Inorganic phosphate induces mammalian growth plate chondrocyte apoptosis in a mitochondrial pathway involving nitric oxide and JNK MAP kinase

Chondrocytes in the hypertrophic zone of the growth plate undergo apoptosis during endochondral bone development via mechanisms that involve inorganic phosphate (Pi) and nitric oxide (NO). Recent evidence suggests that Pi-dependent NO production plays a role in apoptosis of cells in the resting zone as well. This study examined the mechanism by which Pi induces NO production and the signaling pathways by which NO mediates its effects on apoptosis in these cells. Pi decreased the number of viable cells based on MTT activity; the number of TUNEL-positive cells and the level of DNA fragmentation were increased, indicating an increase in apoptosis. Blocking NO production using the NO synthase (NOS) inhibitor L: -NAME or cells from eNOS(-/-) mice blocked Pi-induced chondrocyte apoptosis, indicating that NO production is necessary. NO donors NOC-18 and SNOG both induced chondrocyte apoptosis. SNOG also upregulated p53 expression, the Bax/Bcl-2 expression ratio, and cytochrome c release from mitochondria, as well as caspase-3 activity, indicating that NO induces apoptosis via a mitochondrial pathway. Inhibition of JNK, but not of p38 or ERK1/2, MAP kinase was able to block NO-induced apoptosis, indicating that JNK is necessary in this pathway. Pi elevates NO production via eNOS in resting zone chondrocytes, which leads to a mitochondrial apoptosis pathway dependent on JNK.

Resveratrol protects against oxidized LDL-induced breakage of the blood-brain barrier by lessening disruption of tight junctions and apoptotic insults to mouse cerebrovascular endothelial cells

Cerebrovascular endothelial cells (CEC) comprise the blood-brain barrier (BBB). In a previous study, we showed that oxidized LDL (oxLDL) can induce apoptosis of mouse CEC. Resveratrol possesses chemopreventive potential. This study aimed to evaluate the effects of resveratrol on oxLDL-induced insults to mouse CEC and its possible mechanisms. Exposure of mouse CEC to 200 μmol/L oxLDL for 1 h did not cause cell death but significantly altered the permeability and transendothelial electrical resistance of the cell monolayer. However, resveratrol completely normalized such injury. As for the mechanisms, resveratrol completely protected oxLDL-induced disruption of F-actin and microtubule cytoskeletons as well as occludin and zona occludens-1 (ZO-1) tight junctions. The oxLDL-induced decreases in the mitochondrial membrane potential and intracellular ATP levels were normalized by resveratrol. Exposure of mouse CEC to 200 μmol/L oxLDL for 24 h elevated oxidative stress and simultaneously induced cell apoptosis. However, resveratrol partially protected against oxLDL-induced CEC apoptosis. The oxLDL-induced alterations in levels of Bcl-2, Bax, and cytochrome c were completely normalized by resveratrol. Consequently, resveratrol partially decreased oxLDL-induced activation of caspases-9 and -3. Therefore, in this study, we show that resveratrol can protect against oxLDL-induced damage of the BBB through protecting disruption of the tight junction structure and apoptotic insults to CEC.

GATA-3 transduces survival signals in osteoblasts through upregulation of bcl-x(L) gene expression

GATA-3, a transcription factor, participates in regulating cell development, proliferation, and death. This study was aimed at evaluating the roles of GATA-3 in protecting osteoblasts against oxidative stress-induced apoptotic insults and their possible mechanisms. Pretreatment with nitric oxide (NO) for 24 hours protected osteoblasts, prepared from neonatal rat calvaria, against oxidative stress-induced apoptotic insults. Such protection involved enhancement of Bcl-X(L) messenger mRNA and protein syntheses and the translocation of this antiapoptotic protein from the cytoplasm to mitochondria. GATA-3 was detected in rat osteoblasts, and GATA-3-specific DNA-binding elements exist in the promoter region of the bcl-x(L) gene. NO preconditioning attenuated oxidative stress-caused suppression of GATA-3 mRNA and protein synthesis and the translocation of this transcription factor from the cytoplasm to nuclei. Application of GATA-3 small interfering siRNA into osteoblasts decreased the levels of this transcription factor and simultaneously inhibited Bcl-X(L) mRNA synthesis. Pretreatment with NO lowered the oxidative stress-caused alteration in the binding of GATA-3 to its specific DNA motifs. Oxidative stress-inhibited Runx2 mRNA expression, but NO preconditioning decreased such inhibition. NO pretreatment time-dependently enhanced the association of GATA-3 with Runx2. Knocking down the translation of GATA-3 using RNA interference significantly decreased the protection of NO preconditioning against oxidative stress-induced alterations of cell morphologies, DNA fragmentation, and cell apoptosis. In comparison, overexpression of GATA-3 could promote NO preconditioning-involved Bcl-X(L) expression and cell survival. Therefore, this study shows that GATA-3 plays critical roles in mediating survival signals in osteoblasts, possibly through upregulating bcl-x(L) gene expression.

Lipoteichoic acid-induced TNF-α and IL-6 gene expressions and oxidative stress production in macrophages are suppressed by ketamine through downregulating Toll-like receptor 2-mediated activation oF ERK1/2 and NFκB

Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that ketamine has anti-inflammatory and antioxidant effects on gram-negative LPS-induced macrophage activation. In this study, we further evaluated the effects of ketamine on the regulation of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production in macrophages and its possible mechanisms. Exposure of macrophages to a therapeutic concentration of ketamine (100 microM) inhibited LTA-induced TNF-alpha and IL-6 expressions at protein or mRNA levels. In parallel, ketamine at 100 microM reduced LTA-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Sequentially, ketamine reduced the LTA-triggered translocation of nuclear factor-kappaB (NFkappaB) from the cytoplasm to nuclei and its transactivation activity. Pretreatment with PD98059, an inhibitor of ERK, decreased LTA-enhanced NFkappaB activation and TNF-alpha and IL-6 mRNA syntheses. Cotreatment with ketamine and PD98059 synergistically suppressed the LTA-induced translocation and transactivation of NFkappaB and biosyntheses of TNF-alpha and IL-6 mRNA. Application of Toll-like receptor 2 (TLR2) small interfering RNA (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LTA-augmented NFkappaB transactivation and consequent production of TNF-alpha and IL-6 mRNA. Cotreatment with ketamine and TLR2 siRNA synergistically lowered TNF-alpha and IL-6 mRNA syntheses in LTA-activated macrophages. Ketamine and TLR2 siRNA could reduce the LTA-induced increases in production of nitrite and intracellular reactive oxygen species in macrophages, and their combination had better effects than a single exposure. Thus, this study shows that one possible mechanism involved in ketamine-induced inhibition of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production is through downregulating TLR2-mediated phosphorylation of ERK1/2 and the subsequent translocation and transactivation of NFkappaB.

Runx2-mediated bcl-2 gene expression contributes to nitric oxide protection against hydrogen peroxide-induced osteoblast apoptosis

Nitric oxide (NO) can regulate osteoblast activities. This study was aimed to evaluate the protective effects of pretreatment with sodium nitroprusside (SNP) as a source of NO on hydrogen peroxide-induced osteoblast insults and its possible mechanisms. Exposure of human osteosarcoma MG63 cells to hydrogen peroxide significantly increased cellular oxidative stress, but decreased ALP activity and cell viability, inducing cell apoptosis. Pretreatment with 0.3 mM SNP significantly lowered hydrogen peroxide-induced cell insults. Treatment of human MG63 cells with hydrogen peroxide inhibited Bcl-2 mRNA and protein production, but pretreatment with 0.3 mM SNP significantly ameliorated such inhibition. Sequentially, hydrogen peroxide decreased the mitochondrial membrane potential, but increased the levels of cytochrome c and caspase-3 activity. Pretreatment with 0.3 mM SNP significantly lowered such alterations. Exposure to hydrogen peroxide decreased Runx2 mRNA and protein syntheses. However, pretreatment with 0.3 mM SNP significantly lowered the suppressive effects. Runx2 knockdown using RNA interference inhibited Bcl-2 mRNA production in human MG63 cells. Protection of pretreatment with 0.3 mM SNP against hydrogen peroxide-induced alterations in ALP activity, caspase-3 activity, apoptotic cells, and cell viability were also alleviated after administration of Runx2 small interference RNA. Thus, this study shows that pretreatment with 0.3 mM SNP can protect human MG63 cells from hydrogen peroxide-induced apoptotic insults possibly via Runx2-involved regulation of bcl-2 gene expression.

Protein geranylgeranylation controls collagenase expression in osteoarthritic cartilage

OBJECTIVE

Statins possess anti-inflammatory properties. This study was undertaken to characterize the mechanism of action of statin drugs on collagenase expression in primary human osteoarthritic cartilage tissue.

METHOD

Human articular chondrocytes and cartilage explants from osteoarthritic donors were exposed to simvastatin in the presence or absence of interleukin-1 beta (IL-1beta). Collagenase expression was determined by quantifying levels of matrix metalloproteinase 13 (MMP-13) and MMP-1 mRNA and MMP-13 protein. The mechanism of statin action was tested by addition of farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) or by using inhibitors of farnesyl transferase (FT) and geranylgeranyl transferase (GGT-1).

RESULTS

Treatment of osteoarthritic chondrocytes with simvastatin decreased mRNA levels of MMP-13 and MMP-1 whether under basal conditions or during stimulation with IL-1beta. MMP-13 protein secreted into the culture media was also decreased. Genes involved in cartilage synthesis (type II collagen and aggrecan) were not down-regulated by simvastatin. Exogenous addition of GGPP completely reversed the statin-mediated decrease in MMP-13 mRNA and protein levels whereas FPP partially reversed the statin-mediated effect. An inhibitor of GGT-1 mimicked the simvastatin-mediated reduction in MMP-13 expression by chondrocytes. Finally, consistent with impacts on MMP-13 and MMP-1 expression, simvastatin as well as the GGT-1 inhibitor both blocked type II collagen degradation in primary human articular cartilage explants.

CONCLUSION

These results suggest that statins modulate chondrocyte metabolism by reducing prenylation of key signaling molecules that control the expression of collagen-degrading enzymes. Our results strongly support the hypothesis that protein prenyltransferases including geranylgeranyl transferase regulate chondrocyte collagenase expression in osteoarthritis.

Joint aging and chondrocyte cell death

Articular cartilage extracellular matrix and cell function change with age and are considered to be the most important factors in the development and progression of osteoarthritis. The multifaceted nature of joint disease indicates that the contribution of cell death can be an important factor at early and late stages of osteoarthritis. Therefore, the pharmacologic inhibition of cell death is likely to be clinically valuable at any stage of the disease. In this article, we will discuss the close association between diverse changes in cartilage aging, how altered conditions influence chondrocyte death, and the implications of preventing cell loss to retard osteoarthritis progression and preserve tissue homeostasis.

Hyaluronic acid inhibits nitric oxide-induced apoptosis and dedifferentiation of articular chondrocytes in vitro

OBJECTIVE

Nitric oxide is an important mediator in Osteoarthritis (OA), and causes apoptosis and dedifferentiation in articular chondrocytes. Protein kinase Calpha is involved in modulating apoptosis and dedifferentiation of articular chondrocytes induced by nitric oxide. Hyaluronic acid is widely used in the treatment of osteoarthritis and exerts significant chondroprotective effects. The exact mechanisms of its chondroprotective action are not yet fully elucidated. The present study was performed to investigate the effects and mechanisms of hyaluronic acid in NO-induced apoptosis and dedifferentiation of chondrocytes.

METHODS

The ratio of apoptotic cell and cell viability was surveyed by TUNEL, MTT assay and flow cytometry. The expression of aggrecan, type II collagen, and PKCalpha were determined by real-time PCR and Western blot. The expression changes of caspase-3 and bcl-2 was detected by Western blot. The mitochondrial membrane potential (DeltaPsim) was evaluated by Rhodamine-123 fluorescence.

RESULTS

HA reduces the TUNEL positive cell, nuclei fragment and the impairment of DeltaPsim. NO-induced chondrocyte dedifferentiation was blocked by HA, which restores expression of aggrecan and type II collagen of chondrocytes and cell viability. HA can block inhibition of PKC-alpha by NO.

CONCLUSION

Our results show that HA blocks NO-induced apoptosis and dedifferentiation of articular chondrocytes by modulation of DeltaPsim and PKCalpha.

MST kinases monitor actin cytoskeletal integrity and signal via c-Jun N-terminal kinase stress-activated kinase to regulate p21Waf1/Cip1 stability

As well as providing a structural framework, the actin cytoskeleton plays integral roles in cell death, survival, and proliferation. The disruption of the actin cytoskeleton results in the activation of the c-Jun N-terminal kinase (JNK) stress-activated protein kinase (SAPK) pathway; however, the sensor of actin integrity that couples to the JNK pathway has not been characterized in mammalian cells. We now report that the mammalian Ste20-like (MST) kinases mediate the activation of the JNK pathway in response to the disruption of the actin cytoskeleton. One consequence of actin disruption is the JNK-mediated stabilization of p21(Waf1/Cip1) (p21) via the phosphorylation of Thr57. The expression of MST1 or MST2 was sufficient to stabilize p21 in a JNK- and Thr57-dependent manner, while the stabilization of p21 by actin disruption required MST activity. These data indicate that, in addition to being components of the Salvador-Warts-Hippo tumor suppressor network and binding partners of c-Raf and the RASSF1A tumor suppressor, MST kinases serve to monitor cytoskeletal integrity and couple via the JNK SAPK pathway to the regulation of a key cell cycle regulatory protein.

Lipopolysaccharide triggers macrophage activation of inflammatory cytokine expression, chemotaxis, phagocytosis, and oxidative ability via a toll-like receptor 4-dependent pathway: validated by RNA interference

RNA interference has been extensively used to knock-down the translation of certain genes. Toll-like receptor 4 (TLR4) produced by macrophages can be activated in response to endotoxin stimulation. This study used the RNA interference technique to evaluate the roles of TLR4 in lipopolysaccharide (LPS)-stimulated activation of macrophages from the aspects of cytokine production, chemotaxis, phagocytosis, and oxidative ability. Exposure of macrophages to 1, 25, 50, 100 ng/mL LPS for 1, 6, and 24 h did not affect cell viability. Meanwhile, treatment with 100 ng/mL LPS induced interleukin (IL)-1beta protein and mRNA syntheses in a time-dependent manner. Application of TLR4 small interference (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LPS-induced IL-1beta and IL-6 mRNA production. Transwell analysis showed that LPS increased chemotactic activity of macrophages, but application of TLR4 siRNA reduced such an effect. Phagocytic activities of macrophages were significantly augmented following LPS treatment. However, knocking-down the translation of TLR4 mRNA using RNA interference lowered the LPS-enhanced phagocytic activity. Analysis of flow cytometry revealed that LPS increased oxidative ability of macrophages, but TLR4 siRNA inhibited such development. This study used RNA interference techniques to show that TLR4 can mediate LPS-induced macrophage activations of IL-1beta and IL-6 gene expression, chemotaxis, phagocytosis, and oxidative ability.

Propofol inhibits lipoteichoic acid-induced iNOS gene expression in macrophages possibly through downregulation of toll-like receptor 2-mediated activation of Raf-MEK1/2-ERK1/2-IKK-NFkappaB

Our previous study showed that propofol suppressed Gram-negative bacterial LPS-induced NO biosynthesis. Lipoteichoic acid (LTA), an outer membrane component of Gram-positive bacteria, can induce septic shock. This study was further aimed to evaluate the effects of propofol on LTA-induced iNOS gene expression in macrophages and its possible molecular mechanisms. Exposure of macrophages to LTA increased production of nitrite and intracellular reactive oxygen species, but propofol reduced such enhancements in concentration- and time-dependent manners. Treatment of macrophages with LTA-induced iNOS mRNA and protein productions. Meanwhile, propofol at a clinically relevant concentration of 50 microM significantly inhibited LTA-caused augmentations of iNOS mRNA and protein syntheses. In parallel, exposure to LTA increased translocation of nuclear factor-kappa B (NFkappaB) from the cytoplasm to nuclei. Propofol at 50 microM decreased such translocation. Analyses by an electrophoretic mobility shift and reporter gene further showed that propofol could alleviate LTA-induced transactivation of NFkappaB. Sequentially, propofol decreased phosphorylation of IKK, ERK1/2, MEK1/2, and Raf in LTA-stimulated macrophages. Application of toll-like receptor 2 (TLR2) small interference (si)RNA decreased the translation of this receptor and Raf phosphorylation in LTA-stimulated macrophages. Co-treatment with propofol and TLR2 siRNA synergistically ameliorated LTA-induced iNOS mRNA expression and nitrite production. Thus, this study shows that propofol can downregulate NO biosynthesis via inhibiting iNOS gene expression. The suppressive mechanism occurs possibly through reduction of TLR2-mediated sequential activation of Raf-MEK1/2-ERK1/2-IKK-NFkappaB.

Cytoskeleton interruption in human hepatoma HepG2 cells induced by ketamine occurs possibly through suppression of calcium mobilization and mitochondrial function

Ketamine is an intravenous anesthetic agent often used for inducing and maintaining anesthesia. Cytoskeletons contribute to the regulation of hepatocyte activity of drug biotransformation. In this study, we attempted to evaluate the effects of ketamine on F-actin and microtubular cytoskeletons in human hepatoma HepG2 cells and its possible molecular mechanisms. Exposure of HepG2 cells to ketamine at Collapse

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MESH Headings

• Adenosine Triphosphate/biosynthesis
• Base Sequence
• Calcium/metabolism
• Cell Line, Tumor
• Cytoskeletal Proteins/genetics
• Cytoskeletal Proteins/metabolism
• Cytoskeleton/drug effects
• Cytoskeleton/metabolism
• DNA Primers
• Humans
• Ketamine/pharmacology
• Microscopy, Confocal
• Mitochondria/physiology
• RNA, Messenger/biosynthesis
• RNA, Messenger/genetics
• Reverse Transcriptase Polymerase Chain Reaction

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Affiliation(s)

Huai-Chia Chang Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, 250 Wu-Xing St., Taipei 110, Taiwan
Ta-Liang Chen
Ruei-Ming Chen

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Collaborators Collapse

Apoptotic insults to human HepG2 cells induced by S-(+)-ketamine occurs through activation of a Bax-mitochondria-caspase protease pathway

BACKGROUND

Ketamine is widely used as an i.v. anaesthetic agent and as a drug of abuse. Hepatocytes contribute to the metabolism of endogenous and exogenous substances. This study evaluated the toxic effects of S-(+)-ketamine and possible mechanisms using human hepatoma HepG2 cells as the experimental model.

METHODS

HepG2 cells were exposed to S-(+)-ketamine. Cell viability and the release of lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GPT) were measured to determine the toxicity of S-(+)-ketamine to HepG2 cells. Cell morphology, DNA fragmentation, and apoptotic cells were analysed to evaluate the mechanism of S-(+)-ketamine-induced cell death. Amounts of Bax, an apoptotic protein, and cytochrome c in the cytoplasm or mitochondria were quantified by immunoblotting. Cellular adenosine triphosphate levels were analysed using a bioluminescence assay. Caspases-3, -9, and -6 were measured fluorometrically.

RESULTS

Exposure of HepG2 cells to S-(+)-ketamine increased the release of LDH and GPT, but decreased cell viability (all P<0.01). S-(+)-Ketamine time-dependently caused shrinkage of HepG2 cells. Exposure to S-(+)-ketamine led to significant DNA fragmentation and cell apoptosis (P=0.003 and 0.002). S-(+)-Ketamine increased translocation of Bax from the cytoplasm to mitochondria, but decreased the mitochondrial membrane potential and cellular adenosine triphosphate levels (all P<0.01). Sequentially, cytosolic cytochrome c levels and activities of caspases-9, -3, and -6 were augmented after S-(+)-ketamine administration (all P<0.001). Z-VEID-FMK, an inhibitor of caspase-6, alleviated the S-(+)-ketamine-induced augmentation of caspase-6 activity, DNA fragmentation, and cell apoptosis (all P<0.001).

CONCLUSIONS

This study shows that S-(+)-ketamine can induce apoptotic insults to human HepG2 cells via a Bax-mitochondria-caspase protease pathway. Thus, we suggest that S-(+)-ketamine at a clinically relevant or an abused concentration may induce liver dysfunction possibly due to its toxicity to hepatocytes.

Nitric oxide in inflammation and pain associated with osteoarthritis

Osteoarthritis (OA) is a degenerative disease involving chondrocytes, cartilage and other joint tissues, and has a number of underlying causes, including both biochemical and mechanical factors. Although proinflammatory factors including nitric oxide (NO) are associated with OA, there is recent evidence suggesting that NO and its redox derivatives may also play protective roles in the joint. However, the mechanisms that underlie the development and progression of OA are not completely understood. Experiments have demonstrated that NO plays a catabolic role in the development of OA and mediates the inflammatory response, is involved in the degradation of matrix metalloproteinases, inhibits the synthesis of both collagen and proteoglycans, and helps to mediate apoptosis. However, there is also evidence that in cultured chondrocytes the addition of exogenous NO may inhibit proinflammatory activation by preventing the nuclear localization of the transcription factor nuclear factor-κB, whereas the presence of peroxynitrite – a redox derivative of NO – appears to enhance the inflammatory response by sustaining the nuclear localization of nuclear factor-κB. In addition, under some conditions exogenous NO can stimulate collagen synthesis in cultured rat fibroblasts and human tendon cells. The protective roles of NO in multiple cell types, along with the opposing activities in cultured chondrocytes, suggest that NO may play additional protective roles in chondrocyte function. NO and its derivatives have a similarly complicated involvement in nociception and pain, which may contribute to the functional disability of OA. Further research may help to elucidate a potential role for NO-donating agents in the management of OA.

Stimulatory effects of insulin-like growth factor-I on growth plate chondrogenesis are mediated by nuclear factor-kappaB p65

Insulin-like growth factor-I (IGF-I) is an important regulator of endochondral ossification. However, little is known about the signaling pathways activated by IGF-I in growth plate chondrocytes. We have previously shown that NF-kappaB-p65 facilitates growth plate chondrogenesis. In this study, we first cultured rat metatarsal bones with IGF-I and/or pyrrolidine dithiocarbamate (PDTC), a known NF-kappaB inhibitor. The IGF-I-mediated stimulation of metatarsal growth and growth plate chondrogenesis was neutralized by PDTC. In rat growth plate chondrocytes, IGF-I induced NF-kappaB-p65 nuclear translocation. The inhibition of NF-kappaB-p65 expression and activity (by p65 short interfering RNA and PDTC, respectively) in chondrocytes reversed the IGF-I-mediated induction of cell proliferation and differentiation and the IGF-I-mediated prevention of cell apoptosis. Moreover, the inhibition of the phosphatidylinositol 3-kinase and Akt abolished the effects of IGF-I on NF-kappaB activation. In conclusion, our findings indicate that IGF-I stimulates growth plate chondrogenesis by activating NF-kappaB-p65 in chondrocytes.