Haem oxygenase-1 down-regulates high mobility group box 1 and matrix metalloproteinases in osteoarthritic synoviocytes

The Role of Alarmins in Osteoarthritis Pathogenesis: HMGB1, S100B and IL-33

Osteoarthritis (OA) is a multifactorial disease in which genetics, aging, obesity, and trauma are well-known risk factors. It is the most prevalent joint disease and the largest disability problem worldwide. Recent findings have described the role of damage-associated molecular patterns (DAMPs) in the course of the disease. In particular, alarmins such as HMGB1, IL-33, and S100B, appear implicated in enhancing articular inflammation and favouring a catabolic switch in OA chondrocytes. The aims of this review are to clarify the molecular signalling of these three molecules in OA pathogenesis, to identify their possible use as staging biomarkers, and, most importantly, to find out whether they could be possible therapeutic targets. Osteoarthritic cartilage expresses increased levels of all three alarmins. HMGB1, in particular, is the most studied alarmin with increased levels in cartilage, synovium, and synovial fluid of OA patients. High levels of HMGB1 in synovial fluid of OA joints are positively correlated with radiological and clinical severity. Counteracting HMGB1 strategies have revealed improving results in articular cells from OA patients and in OA animal models. Therefore, drugs against this alarmin, such as anti-HMGB1 antibodies, could be new treatment possibilities that can modify the disease course since available medications only alleviate symptoms.

Roles of Cartilage-Resident Stem/Progenitor Cells in Cartilage Physiology, Development, Repair and Osteoarthritis

Osteoarthritis (OA) is a degenerative disease that causes irreversible destruction of articular cartilage for which there is no effective treatment at present. Although articular cartilage lacks intrinsic reparative capacity, numerous studies have confirmed the existence of cartilage-resident stem/progenitor cells (CSPCs) in the superficial zone (SFZ) of articular cartilage. CSPCs are characterized by the expression of mesenchymal stromal cell (MSC)-related surface markers, multilineage differentiation ability, colony formation ability, and migration ability in response to injury. In contrast to MSCs and chondrocytes, CSPCs exhibit extensive proliferative and chondrogenic potential with no signs of hypertrophic differentiation, highlighting them as suitable cell sources for cartilage repair. In this review, we focus on the organizational distribution, markers, cytological features and roles of CSPCs in cartilage development, homeostasis and repair, and the application potential of CSPCs in cartilage repair and OA therapies.

Endogenous repair theory enriches construction strategies for orthopaedic biomaterials: a narrative review

The development of tissue engineering has led to new strategies for mitigating clinical problems; however, the design of the tissue engineering materials remains a challenge. The limited sources and inadequate function, potential risk of microbial or pathogen contamination, and high cost of cell expansion impair the efficacy and limit the application of exogenous cells in tissue engineering. However, endogenous cells in native tissues have been reported to be capable of spontaneous repair of the damaged tissue. These cells exhibit remarkable plasticity, and thus can differentiate or be reprogrammed to alter their phenotype and function after stimulation. After a comprehensive review, we found that the plasticity of these cells plays a major role in establishing the cell source in the mechanism involved in tissue regeneration. Tissue engineering materials that focus on assisting and promoting the natural self-repair function of endogenous cells may break through the limitations of exogenous seed cells and further expand the applications of tissue engineering materials in tissue repair. This review discusses the effects of endogenous cells, especially stem cells, on injured tissue repairing, and highlights the potential utilisation of endogenous repair in orthopaedic biomaterial constructions for bone, cartilage, and intervertebral disc regeneration.

Pharmacological Targeting of Heme Oxygenase-1 in Osteoarthritis

Osteoarthritis (OA) is a common aging-associated disease that clinically manifests as joint pain, mobility limitations, and compromised quality of life. Today, OA treatment is limited to pain management and joint arthroplasty at the later stages of disease progression. OA pathogenesis is predominantly mediated by oxidative damage to joint cartilage extracellular matrix and local cells such as chondrocytes, osteoclasts, osteoblasts, and synovial fibroblasts. Under normal conditions, cells prevent the accumulation of reactive oxygen species (ROS) under oxidatively stressful conditions through their adaptive cytoprotective mechanisms. Heme oxygenase-1 (HO-1) is an iron-dependent cytoprotective enzyme that functions as the inducible form of HO. HO-1 and its metabolites carbon monoxide and biliverdin contribute towards the maintenance of redox homeostasis. HO-1 expression is primarily regulated at the transcriptional level through transcriptional factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), specificity protein 1 (Sp1), transcriptional repressor BTB-and-CNC homology 1 (Bach1), and epigenetic regulation. Several studies report that HO-1 expression can be regulated using various antioxidative factors and chemical compounds, suggesting therapeutic implications in OA pathogenesis as well as in the wider context of joint disease. Here, we review the protective role of HO-1 in OA with a focus on the regulatory mechanisms that mediate HO-1 activity.

Mesenchymal stem cells genetically engineered to express platelet-derived growth factor and heme oxygenase-1 ameliorate osteoarthritis in a canine model

BACKGROUND

Mesenchymal stem cells (MSCs) are used for the treatment of osteoarthritis (OA), and MSC genetic engineering is expected to enhance cartilage repair. Here, we aimed to investigate the effect of MSCs overexpressing platelet-derived growth factor (PDGF) or heme oxygenase-1 (HO-1) in chondrocytes and synovial cells with an OA phenotype and assess the in vivo efficacy of intra-articular injections of these MSCs in canine OA models.

METHODS

Canine adipose-derived MSCs were transfected with canine PDGF (PDGF-MSCs) or HO-1 (HO-1-MSCs) using lentiviral vectors. Canine chondrocytes or synovial cells were stimulated with lipopolysaccharide (LPS) to mimic the inflammatory OA model and then co-cultured with MSCs, PDGF-MSCs, or HO-1-MSCs for 24 h and 72 h. The mRNA levels of pro-inflammatory, extracellular matrix-degradative/synthetic, or pain-related factors were measured after co-culture by real-time PCR. Furthermore, a surgery-induced canine OA model was established and the dogs were randomized into four groups: normal saline (n = 4), MSCs (n = 4), PDGF-MSCs (n = 4), and HO-1-MSCs (n = 4). The OA symptoms, radiographic OA severity, and serum matrix metallopeptidase (MMP)-13 levels were assessed before and 10 weeks after treatment, to evaluate the safety and efficacy of the modified MSCs.

RESULTS

PDGF or HO-1 overexpression significantly reduced the expression of pro-inflammatory factors, MMP-13, and nerve growth factor elicited by LPS and increased that of aggrecan and collagen type 2 in chondrocytes (P < 0.05). In addition, the expression of aggrecanases was significantly downregulated in synovial cells, whereas that of tissue inhibitor of metalloproteinases was upregulated (P < 0.05). Furthermore, the co-cultured MSCs highly expressed genes that contributed to the maintenance of joint homeostasis (P < 0.05). In vivo studies showed that OA symptoms improved after administration of all MSCs. Also, PDGF-MSCs significantly improved limb function and reduced pain (P < 0.05). The results of the radiographic assessment and serum MMP-13 levels did not vary significantly compared to those of the control.

CONCLUSIONS

Genetically modifying PDGF and HO-1 in MSCs is an effective strategy for treating OA, suggesting that PDGF-MSCs can be novel therapeutic agents for improving OA symptoms.

Relevance of Nrf2 and heme oxygenase-1 in articular diseases

Joint conditions pose an important public health problem as they are a leading cause of pain, functional limitation and physical disability. Oxidative stress is related to the pathogenesis of many chronic diseases affecting the joints such as rheumatoid arthritis and osteoarthritis. Cells have developed adaptive protection mechanisms to maintain homeostasis such as nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) which regulates the transcription of many genes involved in redox balance, detoxification, metabolism and inflammation. Activation of Nrf2 results in the synthesis of heme oxygenase-1 (HO-1) leading to the formation of a number of bioactive metabolites, mainly CO, biliverdin and bilirubin. Ample evidence supports the notion that Nrf2 and HO-1 can confer protection against oxidative stress and inflammatory and immune responses in joint tissues. As a consequence, this pathway may control the activation and metabolism of articular cells to play a regulatory role in joint destruction thus offering new opportunities for better treatments. Further studies are necessary to identify improved strategies to regulate Nrf2 and HO-1 activation in order to enable the development of drugs with therapeutic applications in joint diseases.

The emerging role of fibroblast-like synoviocytes-mediated synovitis in osteoarthritis: An update

Osteoarthritis (OA), the most ubiquitous degenerative disease affecting the entire joint, is characterized by cartilage degradation and synovial inflammation. Although the pathogenesis of OA remains poorly understood, synovial inflammation is known to play an important role in OA development. However, studies on OA pathophysiology have focused more on cartilage degeneration and osteophytes, rather than on the inflamed and thickened synovium. Fibroblast-like synoviocytes (FLS) produce a series of pro-inflammatory regulators, such as inflammatory cytokines, nitric oxide (NO) and prostaglandin E₂ (PGE₂ ). These regulators are positively associated with the clinical symptoms of OA, such as inflammatory pain, joint swelling and disease development. A better understanding of the inflammatory immune response in OA-FLS could provide a novel approach to comprehensive treatment strategies for OA. Here, we have summarized recently published literatures referring to epigenetic modifications, activated signalling pathways and inflammation-associated factors that are involved in OA-FLS-mediated inflammation. In addition, the current related clinical trials and future perspectives were also summarized.

The GSK‑3β/β‑catenin signaling pathway is involved in HMGB1‑induced chondrocyte apoptosis and cartilage matrix degradation

Knee osteoarthritis (KOA) is a common joint disease with a high incidence rate among middle‑aged and elderly individuals. However, the precise underlying pathological mechanisms and effective treatment of this disease remain to be determined. To explore the effect of high mobility group box 1 (HMGB1) on chondrocyte apoptosis and catabolism, the ATDC5 cell line was cultured as an in vitro model for cartilage research. Cultured cells were treated with recombinant HMGB1 at different concentrations. Hoechst staining and flow cytometry demonstrated that HMGB1 administration significantly induced apoptosis of ATDC5 cells, which was the same as the effect of interleukin‑1β treatment. HMGB1 also induced cartilage matrix degradation, as shown by Alcian blue staining. Moreover, HMGB1 markedly upregulated the expression levels of matrix metallopeptidases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), while genetic silencing of HMGB1 significantly suppressed their expressions. The glycogen synthase kinase (GSK)‑3β/β‑catenin pathway was activated upon HMGB1 treatment. Pharmacological inhibitors or HMGB1 knockdown inactivated the GSK‑3β/β‑catenin pathway, inhibited the expression levels of downstream genes, including MMPs and ADAMTS, and attenuated the apoptosis of ATDC5 cells. Furthermore, the data demonstrated that HMGB1 promoted chondrocyte dysfunction via the regulation of estrogen sulfotransferase and Runt‑related transcription factor 2. Thus, the findings of the present study demonstrated that HMGB1 induces chondrocyte cell apoptosis via activation of GSK‑3β/β‑catenin and the subsequent expression of multiple targeted genes.

Induction of brain Nrf2-HO-1 pathway and antinociception after different physical training paradigms in mice

AIM

Activation of the Nrf2-antioxidant response element signaling pathway is a major mechanism in the cellular defense against oxidative or electrophilic stress through conjugative reactions and by enhancing cellular antioxidant capacity. Although exercise training up-regulates antioxidant defenses system, while information regarding the intensity levels of physical exercise that acts on the cellular protection systems is limited.

MAIN METHODS

The present study evaluated the effects of different durations and intensities of physical exercise on the hippocampus, cortex and hypothalamus Nrf2 and HO-1 gene expression and related protein content and the nociception thresholds in adult C57Bl male mice. Exercise training consisted of daily running on a 10-lane rodent motor-driven treadmill for either 3 or 7 weeks at three different intensities. Pain responses were evaluated after exercise and in untrained mice by Von Frey hair test and cold plate test.

KEY FINDINGS

This study confirmed that only vigorous and longer duration aerobic exercise increased Nrf2 protein level in the hippocampus and HO-1 protein level in the cortex and reduced pain perception. Mechanical and thermal hypoalgesia were only observed in exercise groups after 7 weeks of physical training.

SIGNIFICANCE

The overall findings in this study confirm that only the long duration intensive forced exercise reduced inflammatory pain by induction of Nrf2/HO-1 antioxidant signaling pathway.

Carnosic acid attenuates cartilage degeneration through induction of heme oxygenase-1 in human articular chondrocytes

Osteoarthritis (OA) is common age-associated disease, and associated with joint pain, mobility limitations and compromised overall quality of life. OA treatment is currently limited to pain management and joint arthroplasty at end stage disease. Oxidative damage to cartilage extracellular matrix and cells is an important mechanism in joint aging and OA pathogenesis. Evidence from in vitro and in vivo models of OA suggests that pharmaceuticals and natural compounds with antioxidant properties reduce expression of mediators of OA pathogenesis and OA severity in animal models. Among the signaling pathways that control cellular protective mechanisms against oxygen radical damage is heme oxygenase-1 (HO-1). We recently report HO-1 reduced OA severity in a mouse model. This led to the hypothesis that compounds that increase HO-1 expression have therapeutic potential in OA. Carnosic acid (CA), a natural diterpene with oxidant activity, is prevents cartilage degeneration though induction of HO-1. CA induced HO-1 and miR-140 expression in human articular chondrocytes, and cartilage degeneration was attenuated by CA treatment. Induced HO-1 by CA was in part associated with downregulation via miR-140 binding to 3'UTR of BTB and CNC homology 1 (BACH1). These findings suggest that CA attenuates cartilage degradation through HO-1 upregulation and has potential as a supplement for OA prevention.

Nrf2 as a therapeutic target for rheumatic diseases

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a master regulator of cellular protective processes. Rheumatic diseases are chronic conditions characterized by inflammation, pain, tissue damage and limitations in function. Main examples are rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis and osteoporosis. Their high prevalence constitutes a major health problem with an important social and economic impact. A wide range of evidence indicates that Nrf2 may control different mechanisms involved in the physiopathology of rheumatic conditions. Therefore, the appropriate expression and balance of Nrf2 is necessary for regulation of oxidative stress, inflammation, immune responses, and cartilage and bone metabolism. Numerous studies have demonstrated that Nrf2 deficiency aggravates the disease in experimental models while Nrf2 activation results in immunoregulatory and anti-inflammatory effects. These reports reinforce the increasing interest in the pharmacologic regulation of Nrf2 and its potential applications. Nevertheless, a majority of Nrf2 inducers are electrophilic molecules which may present off-target effects. In recent years, novel strategies have been sought to modulate the Nrf2 pathway which has emerged as a therapeutic target in rheumatic conditions.

Myeloid Heme Oxygenase-1 Regulates the Acute Inflammatory Response to Zymosan in the Mouse Air Pouch

Heme oxygenase-1 (HO-1) is induced by many stimuli to modulate the activation and function of different cell types during innate immune responses. Although HO-1 has shown anti-inflammatory effects in different systems, there are few data on the contribution of myeloid HO-1 and its role in inflammatory processes is not well understood. To address this point, we have used HO-1^M-KO mice with myeloid-restricted deletion of HO-1 to specifically investigate its influence on the acute inflammatory response to zymosan in vivo. In the mouse air pouch model, we have shown an exacerbated inflammation in HO-1^M-KO mice with increased neutrophil infiltration accompanied by high levels of inflammatory mediators such as interleukin-1β, tumor necrosis factor-α, and prostaglandin E₂. The expression of the degradative enzyme matrix metalloproteinase-3 (MMP-3) was also enhanced. In addition, we observed higher levels of serum MMP-3 in HO-1^M-KO mice compared with control mice, suggesting the presence of systemic inflammation. Altogether, these findings demonstrate that myeloid HO-1 plays an anti-inflammatory role in the acute response to zymosan in vivo and suggest the interest of this target to regulate inflammatory processes.

Controlled therapeutic gas delivery systems for quality-improved transplants

Therapeutic gases enriched into perfusion solutions have been effectively used for the improvement of organ transplant quality. At present, the enrichment of perfusion solutions with gases requires complex machinery/containers and handling precautions. Alternatively, the gas is generated within the perfusion solution by supplemented carbonylated transition metal complexes with associated toxicological concerns when these metals contact the transplant. Therefore, we developed therapeutic gas releasing systems (TGRSs) allowing for the controlled generation and release of therapeutic gases (carbon monoxide and hydrogen sulfide) from otherwise hermetically sealed containers, such that the perfusion solution for the transplant is saturated with the gas but no other components from the TGRS are liberated in the solution. The release from the TGRS into the perfusion solution can be tailored as a function of the number and thickness of gas permeable membranes leading to release patterns having been linked to therapeutic success in previous trials. Furthermore, the surrogate biomarker HMGB1 was significantly downregulated in ischemic rat liver transplants perfused with enriched CO solution as compared to control. In conclusion, the TGRS allows for easy, reliable, and controlled generation and release of therapeutic gases while removing safety concerns of current approaches, thereby positively impacting the risk benefit profile of using therapeutic gases for transplant quality improvement in the future.

Bach1 deficiency reduces severity of osteoarthritis through upregulation of heme oxygenase-1

Introduction

BTB and CNC homology 1 (Bach1) is a transcriptional repressor of Heme oxygenase-1 (HO-1), which is cytoprotective through its antioxidant effects. The objective of this study was to define the role of Bach1 in cartilage homeostasis and osteoarthritis (OA) development using in vitro models and Bach1^-/- mice.

Methods

HO-1 expression in Bach1^-/- mice was analyzed by real-time PCR, immunohistochemistry and immunoblotting. Knee joints from Bach1^-/- and wild-type mice with age-related OA and surgically-induced OA were evaluated by OA scoring systems. Levels of autophagy proteins and superoxide dismutase 2 (SOD2) were determined by immunohistochemistry. The relationship between HO-1 and the protective effects for OA was determined in chondrocytes treated with small interfering RNA (siRNA) targeting HO-1 gene.

Results

HO-1 expression decreased with aging in articular cartilages and menisci of mouse knees. Bach1^-/- mice showed reduced severity of age-related OA and surgically-induced OA compared with wild-type mice. Microtubule-associated protein 1 light chain 3 (LC3), autophagy marker, and SOD2 were increased in articular cartilage of Bach1^-/- mice compared with wild-type mice. Interleukin-1β (IL-1β) induced a significant increase in Adamts-5 in wild-type chondrocytes but not in Bach1^-/- chondrocytes. The expression of SOD2 and the suppression of apoptosis in Bach1^-/- chondrocytes were mediated by HO-1.

Conclusions

Bach1 deficiency reduces the severity of OA-like changes. This may be due to maintenance of cartilage homeostasis and joint health by antioxidant effects through HO-1 and downregulation of extracellular matrix degrading enzymes. These results suggest that inactivation of Bach1 is a novel target and signaling pathway in OA prevention.

Gene therapy for nucleus pulposus regeneration by heme oxygenase-1 plasmid DNA carried by mixed polyplex micelles with thermo-responsive heterogeneous coronas

Safe and high-efficiency gene therapy for nucleus pulposus (NP) regeneration was urgently desired to treat disc degeneration-associated diseases. In this work, an efficient nonviral cationic block copolymer gene delivery system was used to deliver therapeutic plasmid DNA (pDNA), which was prepared via complexation between the mixed cationic block copolymers, poly(ethylene glycol)-block-poly{N-[N-(2-aminoethyl)-2-aminoehtyl]aspartamide} [PEG-b-PAsp(DET)] and poly(N-isopropylacrylamide)-block-PAsp(DET) [PNIPAM-b-PAsp(DET)], and pDNA at 25 °C. The mixed polyplex micelles (MPMs) containing heterogeneous coronas with hydrophobic and hydrophilic microdomains coexisting could be obtained upon heating from 25 to 37 °C, which showed high tolerability against nuclease and strong resistance towards protein adsorption. The gene transfection efficiency of MPMs in NP cells was significantly higher than that of regular polyplex micelles prepared from sole block copolymer of PEG-b-PAsp(DET) (SPMs) in in vitro and in vivo evaluation due to the synergistic effect of improved colloidal stability and low cytotoxicity. High expression of heme oxygenase-1 (HO-1) in NP cells transfected by MPMs loading HO-1 pDNA significantly decreased the expression activity of matrix metalloproteinases 3 (MMP-3) and cyclo-oxygenase-2 (COX-2) induced by interleukin-1β (IL-1β), and simultaneously increased the NP phenotype-associated genes such as aggrecan, type II collagen, and SOX-9. Moreover, the therapeutic effects of MPMs loading pDNA were tested to treat disc degeneration induced by stab injury. The results demonstrated that administration of HO-1 pDNA carried by MPMs in rat tail discs apparently reduced inflammatory responses induced by need stab and increased glycosaminoglycan (GAG) content, finally achieving better therapeutic efficacy as compared with SPMs. Consequently, MPMs loading HO-1 pDNA were demonstrated to be potential as a safe and high-efficiency nonviral gene delivery system for retarding or regenerating the degenerative discs.

Origin and function of cartilage stem/progenitor cells in osteoarthritis

Articular cartilage is a physiologically non-self-renewing avascular tissue with a singular cell type, the chondrocyte, which functions as the load-bearing surface of the arthrodial joint. Injury to cartilage often progresses spatiotemporally from the articular surface to the subchondral bone, leading to development of degenerative joint diseases such as osteoarthritis (OA). Although lacking intrinsic reparative ability, articular cartilage has been shown to contain a population of stem cells or progenitor cells, similar to those found in many other adult tissues, that are thought to be involved in the maintenance of tissue homeostasis. These so-called cartilage-derived stem/progenitor cells (CSPCs) have been observed in human, equine and bovine articular cartilage, and have been identified, isolated and characterized on the basis of expression of stem-cell-related surface markers, clonogenicity and multilineage differentiation ability. However, the origin and functions of CSPCs are incompletely understood. We review here the current status of CSPC research and discuss the possible origin of these cells, what role they might have in cartilage repair, and their therapeutic potential in OA.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Senescence suppressors: their practical importance in replicative lifespan extension in stem cells

Recent animal and clinical studies report promising results for the therapeutic utilization of stem cells in regenerative medicine. Mesenchymal stem cells (MSCs), with their pluripotent nature, have advantages over embryonic stem cells in terms of their availability and feasibility. However, their proliferative activity is destined to slow by replicative senescence, and the limited proliferative potential of MSCs not only hinders the preparation of sufficient cells for in vivo application, but also draws a limitation on their potential for differentiation. This calls for the development of safe and efficient means to increase the proliferative as well as differentiation potential of MSCs. Recent advances have led to a better understanding of the underlying mechanisms and significance of cellular senescence, facilitating ways to manipulate the replicative lifespan of a variety of primary cells, including MSCs. This paper introduces a class of proteins that function as senescence suppressors. Like tumor suppressors, these proteins are lost in senescence, while their forced expression delays the onset of senescence. Moreover, treatments that increase the expression or the activity of senescence suppressors, therefore, cause expansion of the replicative and differentiation potential of MSCs. The nature of the activities and putative underlying mechanisms of the senescence suppressors will be discussed to facilitate their evaluation.

HMGB1 acts in synergy with lipopolysaccharide in activating rheumatoid synovial fibroblasts via p38 MAPK and NF-κB signaling pathways

Synovial fibroblasts (SF) play a central role in the inflammatory and destructive process in rheumatoid arthritis (RA). High-mobility group box chromosomal protein 1 (HMGB1) or lipopolysaccharide (LPS) alone failed to induce significant changes in proliferation of cultured SF from RA patients, but premixed HMGB1 with LPS (HMGB1-LPS) significantly facilitated SF proliferation. HMGB1 alone failed to induce IL-6, MMP-3, and MMP-13 production in cultured SF but greatly enhanced LPS-induced expression of IL-6, MMP-3, and MMP-13 at both mRNA and protein levels. HMGB1-LPS synergistically upregulated TLR4 and receptor for advanced glycation endproducts (RAGE) expression on the surface of SF. Both blockers of TLR4 and RAGE significantly inhibited the synergistic effects of HMGB1-LPS on the production of IL-6 and MMPs, but blocking antibodies to TLR2 failed. HMGB1-LPS synergistically increased intracellular levels of phosphorylated p38 and phosphorylated IκB. Furthermore, both NF-κB inhibitor Bay11-7085 and p38 inhibitor SB203580 significantly suppressed the enhanced production of IL-6 and MMPs induced by HMGB1-LPS. In conclusion, HMGB1 acts in synergy with LPS to upregulate TLR4 and RAGE expression on the surface of SF in RA and then to augment IL-6, MMP-3, and MMP-13 production, which depends on p38 MAPK and NF-κB activation.

Local gene delivery of heme oxygenase-1 by adeno-associated virus into osteoarthritic mouse joints exhibiting synovial oxidative stress

OBJECTIVE

To evaluate the role of synovial oxidative stress on joint pathology in a spontaneous mouse model of osteoarthritis (OA) by intra-articular (IA) delivery of recombinant adeno-associated virus (rAAV) expressing anti-oxidant protein heme oxygenase-1 (HO-1).

METHODS

Joint transduction by rAAV vectors was evaluated with serotype 1, 2, 5 and 8 capsids carrying LacZ gene administered by IA injections into STR/ort mice. Transduced cell types were identified by β-galactosidase staining in sectioned joints. Effect of oxidative stress on AAV transduction of primary synoviocytes in vitro was quantitated by fluorescence-activated cell sorting (FACS) analysis. In vivo, the efficacy of rAAV1/HO-1 was tested by IA administration into STR/ort mice followed by histopathological scoring of cartilage. Levels of 3-nitrotyrosine (3-NT) and HO-1 were assessed by immunohistochemistry (IHC) of joint sections.

RESULTS

Administration of a rAAV1 based vector into OA mouse joints resulted in transduction of the synovium, joint capsule, adipocytes and skeletal muscle while none of the serotypes showed significant cartilage transduction. All OA joints exhibited significantly elevated levels of oxidative stress marker, 3-NT, in the synovium compared to OA-resistant CBA-strain of mice. In vitro studies demonstrated that AAV transgene expression in primary synoviocytes was augmented by oxidative stress induced by H(2)O(2) and that a rAAV expressing HO-1 reduced the levels of oxidative stress. In vivo, HO-1 was increased in the synovium of STR/ort mice. However, delivery of rAAV1/HO-1 into OA joints did not reduce cartilage degradation.

CONCLUSIONS

AAV-mediated HO-1 delivery into OA joints during active disease was not sufficient to improve cartilage pathology in this model.

Heme oxygenase 1 attenuates interleukin-1β-induced cytosolic phospholipase A2 expression via a decrease in NADPH oxidase/reactive oxygen species/activator protein 1 activation in rheumatoid arthritis synovial fibroblasts

OBJECTIVE

Reactive oxygen species (ROS) produced by cytokines induce the expression of inflammatory mediators in rheumatoid arthritis (RA). Heme oxygenase 1 (HO-1) exerts an antiinflammatory effect. The aim of this study was to examine the mechanisms underlying interleukin-1β (IL-1β)-induced cytosolic phospholipase A2 (cPLA2) expression through ROS generation as modulated by HO-1 in RA synovial fibroblasts (RASFs).

METHODS

IL-1β-induced ROS generation was determined by flow cytometry. The involvement of MAPKs and NADPH oxidase (NOX)/ROS in IL-1β-induced cPLA2 expression was investigated using pharmacologic inhibitors and transfection with small interfering RNAs (siRNAs) and was analyzed by Western blotting and promoter assay. Overexpression of HO-1 was performed by transfection of RASFs with a recombinant adenovirus containing human HO-1 plasmid. SCID mice with inflammation caused by IL-1β were infected with adenovirus containing HO-1. Histologic characterization of joint inflammation and local expression of cPLA2 were evaluated after treatment.

RESULTS

IL-1β-induced cPLA2 expression was mediated through NOX activation/ROS production, which was attenuated by N-acetylcysteine (NAC; a scavenger of ROS), the inhibitors of NOX (diphenyleneiodonium chloride and apocynin), MEK-1/2 (U0126), and JNK-1/2 (SP600125), transfection with the respective siRNAs, and the overexpression of HO-1 in RASFs. IL-1β-induced cPLA2 expression was mediated through recruitment of activator protein 1 (AP-1) to the cPLA2 promoter region, which was attenuated by NAC and overexpression of HO-1. Furthermore, HO-1 overexpression inhibited IL-1β-mediated cPLA2 expression in SCID mice.

CONCLUSION

In RASFs, IL-1β induced cPLA2 expression via activation of p42/p44 MAPK and JNK-1/2, leading to p47phox phosphorylation, ROS production, and AP-1 activation. The induction of HO-1 exerted protective effects on the pathogenesis of RA.

Haem oxygenase-1 counteracts the effects of interleukin-1β on inflammatory and senescence markers in cartilage-subchondral bone explants from osteoarthritic patients

IL (interleukin)-1β plays an important role in cartilage extracellular matrix degradation and bone resorption in OA (osteoarthritis) through the induction of degradative enzymes and pro-inflammatory mediators. In the present study, we have determined the consequences of HO-1 (haem oxygenase-1) induction on markers of inflammation and senescence in the functional unit cartilage-subchondral bone stimulated with IL-1β. Cartilage-subchondral bone specimens were obtained from the knees of osteoarthritic patients. Treatment with the HO-1 inducer CoPP (cobalt protoporphyrin IX) counteracted the stimulatory effects of IL-1β on IL-6, nitrite, PGE2 (prostaglandin E2), TGF (transforming growth factor) β2, TGFβ3 and osteocalcin. Immunohistochemical analyses indicated that CoPP treatment of explants down-regulated iNOS (inducible nitric oxide synthase), COX-2 (cyclooxygenase-2) and mPGES-1 (microsomal prostaglandin E synthase-1) induced by IL-1β. In contrast, the expression of HMGB1 (high-mobility group box 1) was not significantly modified. In addition, CoPP decreased the expression of iNOS and mPGES-1 in cells isolated from the explants and stimulated with IL-1β, which was counteracted by an siRNA (small interfering RNA) specific for human HO-1. In isolated primary chondrocytes, we determined senescence-associated β-galactosidase activity and the expression of senescence markers by real-time PCR. We have found that HO-1 induction could regulate senescence markers in the presence of IL-1β and significantly affected telomerase expression, as well as β-galactosidase activity and hTERT (human telomerase reverse transcriptase) and p21 expression in chondrocytes. The findings of the present study support the view that HO-1 induction results in the down-regulation of inflammatory and senescence responses in OA articular tissues.

Heme oxygenase-1 mediates protective effects on inflammatory, catabolic and senescence responses induced by interleukin-1β in osteoarthritic osteoblasts

Osteoarthritis (OA) is a chronic degenerative joint disease showing altered bone metabolism. Osteoblasts contribute to the regulation of cartilage metabolism and bone remodeling. We have shown previously that induction of heme oxygenase-1 (HO-1) protects OA cartilage against inflammatory and degradative responses. In this study, we investigated the effects of HO-1 induction on OA osteoblast metabolism. HO-1 was induced with cobalt protoporphyrin IX (CoPP) and by transduction with LV-HO-1. In osteoblasts stimulated with interleukin (IL)-1β, CoPP enhanced mineralization, the expression of a number of markers of osteoblast differentiation such as Runx2, bone morphogenetic protein-2, osteocalcin, and collagen 1A1 and 1A2, as well as the ratio osteoprotegerin/receptor activator of nuclear factor-κB ligand. HO-1 induction significantly reduced the expression of matrix metalloproteinase (MMP)-1, MMP-2 and MMP-3, and the production of pro-inflammatory cytokines such as tumor necrosis factor-α and IL-6 whereas IL-10 levels increased. HO-1 also exerted inhibitory effects on prostaglandin (PG)E(2) production which could be dependent on cyclooxygenase-2 and microsomal PGE synthase-1 down-regulation. The activity of senescence-associated β-galactosidase and the expression of the senescence marker caveolin-1 were significantly decreased after HO-1 induction. The inhibition of nuclear factor-κB activation induced by IL-1β in OA osteoblasts may contribute to some HO-1 effects. Our results have shown that HO-1 decreases the production of relevant inflammatory and catabolic mediators that participate in OA pathophysiology thus eliciting protective effects in OA osteoblasts.

Control of cell migration and inflammatory mediators production by CORM-2 in osteoarthritic synoviocytes

Background

Osteoarthritis (OA) is the most widespread degenerative joint disease. Inflamed synovial cells contribute to the release of inflammatory and catabolic mediators during OA leading to destruction of articular tissues. We have shown previously that CO-releasing molecules exert anti-inflammatory effects in animal models and OA chondrocytes. We have studied the ability of CORM-2 to modify the migration of human OA synoviocytes and the production of chemokines and other mediators sustaining inflammatory and catabolic processes in the OA joint.

Methodology/Principal Findings

OA synoviocytes were stimulated with interleukin(IL)-1β in the absence or presence of CORM-2. Migration assay was performed using transwell chambers. Gene expression was analyzed by quantitative PCR and protein expression by Western Blot and ELISA. CORM-2 reduced the proliferation and migration of OA synoviocytes, the expression of IL-8, CCL2, CCL20, matrix metalloproteinase(MMP)-1 and MMP-3, and the production of oxidative stress. We found that CORM-2 reduced the phosphorylation of extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase1/2 and to a lesser extent p38. Our results also showed that CORM-2 significantly decreased the activation of nuclear factor-κB and activator protein-1 regulating the transcription of chemokines and MMPs in OA synoviocytes.

Conclusion/Significance

A number of synoviocyte functions relevant in OA synovitis and articular degradation can be down-regulated by CORM-2. These results support the interest of this class of agents for the development of novel therapeutic strategies in inflammatory and degenerative conditions.

Hemoglobin and iron handling in brain after subarachnoid hemorrhage and the effect of deferoxamine on early brain injury

The purpose of this study was to investigate hemoglobin and iron handling after subarachnoid hemorrhage (SAH), examine the relationship between iron and neuroglial cell changes, and determine whether deferoxamine (DFX) can reduce SAH-induced injury. The SAH was induced in Sprague-Dawley rats (n=110) using an endovascular perforation technique. Animals were treated with DFX (100 mg/kg) or vehicle 2 and 6 hours after SAH induction followed by every 12 hours for 3 days. Rats were killed at 6 hours, Days 1 and 3 to determine nonheme iron and examine iron-handling proteins using Western blot and immunohistochemistry. 8-Hydroxyl-2'-deoxyguanosine and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining were performed to assess oxidative DNA damage and neuronal cell death. After SAH, marked heme-oxygenase-1 (HO-1) upregulation at Day 3 (P<0.01) was accompanied by elevated nonheme iron (P<0.01), transferrin (Tf) (P<0.01), Tf receptor (P<0.05), and ferritin levels (P<0.01). Deferoxamine treatment reduced SAH-induced mortality (12% versus 29%, P<0.05), brain nonheme iron concentration, iron-handling protein expression, oxidative stress, and neuronal cell death at Day 3 (P<0.01) after SAH. These results suggest that iron overload in the acute phase of SAH causes oxidative injury leading to neuronal cell death. Deferoxamine effectively reduced oxidative stress and neuronal cell death, and may be a potential therapeutic agent for SAH.

High mobility group box 1 potentiates the pro-inflammatory effects of interleukin-1β in osteoarthritic synoviocytes

Introduction

High mobility group box 1 (HMGB1) is released by necrotic cells or secreted in response to inflammatory stimuli. Extracellular HMGB1 may act as a pro-inflammatory cytokine in rheumatoid arthritis. We have recently reported that HMGB1 is released by osteoarthritic synoviocytes after activation with interleukin-1beta (IL-1β) The present study investigated the role of HMGB1 in synovial inflammation in osteoarthritis (OA).

Methods

HMGB1 was determined in human synovium using immunohistochemistry, comparing normal to OA. OA synoviocytes were incubated with HMGB1 at 15 or 25 ng/ml in the absence or presence of IL-1β (10 ng/ml). Gene expression was analyzed by quantitative PCR and protein expression by Western Blot and ELISA. Matrix metalloproteinase (MMP) activity was studied by fluorometric procedures and nuclear factor (NF)-κB activation by transient transfection with a NF-κB-luciferase plasmid.

Results

In the normal synovium, HMGB1 was found in the synovial lining cells, sublining cells, and in the vascular wall cells. The distribution of HMGB1 in OA synovium was similar but the number of HMGB1 positive cells was higher and HMGB1 was also present in infiltrated cells. In normal synovial membrane cells, HMGB1 was found mostly in the nuclei, whereas in OA, HMGB1 was generally found mostly in the cytoplasm. In OA synoviocytes, HMGB1 alone at concentrations of 15 or 25 ng/ml did not affect the production of IL-6, IL-8, CCL2, CCL20, MMP-1 or MMP-3, but in the presence of IL-1β, a significant potentiation of protein and mRNA expression, as well as MMP activity was observed. HMGB1 also enhanced the phosphorylated ERK1/2 and p38 levels, with a lower effect on phosphorylated Akt. In contrast, JNK1/2 phosphorylation was not affected. In addition, HMGB1 at 25 ng/ml significantly potentiated NF-κB activation in the presence of IL-1β.

Conclusions

Our results indicate that HMGB1 is overexpressed in OA synovium and mostly present in extracellular form. In OA synoviocytes, HMGB1 cooperates with IL-1β to amplify the inflammatory response leading to the production of a number of cytokines, chemokines and MMPs. Our data support a pro-inflammatory role for this protein contributing to synovitis and articular destruction in OA.