The Interplay of Biomechanical and Biological Changes Following Meniscus Injury

PURPOSE OF REVIEW

Meniscus injury often leads to joint degeneration and post-traumatic osteoarthritis (PTOA) development. Therefore, the purpose of this review is to outline the current understanding of biomechanical and biological repercussions following meniscus injury and how these changes impact meniscus repair and PTOA development. Moreover, we identify key gaps in knowledge that must be further investigated to improve meniscus healing and prevent PTOA.

RECENT FINDINGS

Following meniscus injury, both biomechanical and biological alterations frequently occur in multiple tissues in the joint. Biomechanically, meniscus tears compromise the ability of the meniscus to transfer load in the joint, making the cartilage more vulnerable to increased strain. Biologically, the post-injury environment is often characterized by an increase in pro-inflammatory cytokines, catabolic enzymes, and immune cells. These multi-faceted changes have a significant interplay and result in an environment that opposes tissue repair and contributes to PTOA development. Additionally, degenerative changes associated with OA may cause a feedback cycle, negatively impacting the healing capacity of the meniscus. Strides have been made towards understanding post-injury biological and biomechanical changes in the joint, their interplay, and how they affect healing and PTOA development. However, in order to improve clinical treatments to promote meniscus healing and prevent PTOA development, there is an urgent need to understand the physiologic changes in the joint following injury. In particular, work is needed on the in vivo characterization of the temporal biomechanical and biological changes that occur in patients following meniscus injury and how these changes contribute to PTOA development.

The good Samaritan glutathione-S-transferase P1: An evolving relationship in nitric oxide metabolism mediated by the direct interactions between multiple effector molecules

Glutathione-S-transferases (GSTs) are phase II detoxification isozymes that conjugate glutathione (GSH) to xenobiotics and also suppress redox stress. It was suggested that GSTs have evolved not to enhance their GSH affinity, but to better interact with and metabolize cytotoxic nitric oxide (NO). The interactions between NO and GSTs involve their ability to bind and store NO as dinitrosyl-dithiol iron complexes (DNICs) within cells. Additionally, the association of GSTP1 with inducible nitric oxide synthase (iNOS) results in its inhibition. The function of NO in vasodilation together with studies associating GSTM1 or GSTT1 null genotypes with preeclampsia, additionally suggests an intriguing connection between NO and GSTs. Furthermore, suppression of c-Jun N-terminal kinase (JNK) activity occurs upon increased levels of GSTP1 or NO that decreases transcription of JNK target genes such as c-Jun and c-Fos, which inhibit apoptosis. This latter effect is mediated by the direct association of GSTs with MAPK proteins. GSTP1 can also inhibit nuclear factor kappa B (NF-κB) signaling through its interactions with IKKβ and Iκα, resulting in decreased iNOS expression and the stimulation of apoptosis. It can be suggested that the inhibitory activity of GSTP1 within the JNK and NF-κB pathways may be involved in crosstalk between survival and apoptosis pathways and modulating NO-mediated ROS generation. These studies highlight an innovative role of GSTs in NO metabolism through their interaction with multiple effector proteins, with GSTP1 functioning as a "good Samaritan" within each pathway to promote favorable cellular conditions and NO levels.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

An Insight into the Role of Apoptosis and Autophagy in Nitric Oxide-Induced Articular Chondrocyte Cell Death

OBJECTIVE

To investigate the role and characterize the molecular mechanisms regulating apoptosis and autophagy in nitric oxide (NO)-induced chondrocyte cell death.

DESIGN

Cell apoptosis and autophagy were evaluated in chondrocytes treated with sodium nitroprusside (SNP) combined with the presence or absence of interleukin-1 beta (IL-1β) and nutrient-deprived conditions. The concentration of nitrite was determined by Griess reaction. Activation of apoptosis and autophagy were determined by immunocytochemistry, Western blot, and quantitative real-time polymerase chain reaction (qPCR) analysis. Flow cytometry and MTT assay were used to assess cell viability.

RESULTS

Cotreatment of chondrocytes with SNP and IL-1β under nutrient-deprived condition potentially enhanced the effect of NO-induced cell death. Immunocytochemistry, Western blot, and qPCR analysis indicated that treatment of chondrocytes with SNP significantly reduced autophagic activity, autophagic flux, and multiple autophagy-related (Atg) genes expression. These findings were associated with an increase in ERK, Akt, and mTOR phosphorylation, whereas autophagy induction through mTOR/p70S6K inhibition by rapamycin significantly suppressed NO-induced cell apoptosis. Furthermore, the cleavage of poly(ADP-ribose) polymerase (PARP) and caspase-3 activation in response to apoptosis was weakly detected. These results corresponded with a significant increase in apoptosis-inducing factor (AIF) expression, suggesting the involvement of the caspase-independent pathway.

CONCLUSIONS

These results demonstrate that in chondrocyte cultures with cells induced into an osteoarthritis state, NO inhibits autophagy and induces chondrocyte apoptosis mainly, but not completely through the caspase-independent pathway. Our data suggest that autophagy is a protective mechanism in the pathogenesis of osteoarthritis and could be proposed as a therapeutic target for degenerative joint diseases.

LncRNA LINC01088 inhibits the function of trophoblast cells, activates the MAPK-signaling pathway and associates with recurrent pregnancy loss

Long noncoding RNAs (lncRNAs) have been reported to be involved in various cellular processes and to participate in a variety of human diseases. Recently, increasing studies have reported that lncRNAs are related to many reproductive diseases, such as pathogenesis of recurrent pregnancy loss (RPL), preeclampsia (PE) and gestational diabetes mellitus (GDM). In this study, we aimed to investigate the effect of LINC01088 in trophoblast cells and its potential role in pathogenesis of RPL. LINC01088 was found to be upregulated in first-trimester chorionic villi tissues from RPL patients. Increased LINC01088 repressed proliferation, migration and invasion of trophoblast cells, and promoted apoptosis of trophoblast cells. Further exploration indicated that LINC01088 decreased the production of nitric oxide (NO) by binding and increasing Arginase-1 and decreasing eNOS protein levels. Importantly, JNK and p38 MAPK-signaling pathways were active after overexpression of LINC01088. In conclusion, our studies demonstrated that LINC01088 plays an important role in the pathogenesis of RPL, and is a potential therapeutic target for the treatment of RPL.

The Implication of Reactive Oxygen Species and Antioxidants in Knee Osteoarthritis

Knee osteoarthritis (KOA) is a chronic multifactorial pathology and a current and essential challenge for public health, with a negative impact on the geriatric patient's quality of life. The pathophysiology is not fully known; therefore, no specific treatment has been found to date. The increase in the number of newly diagnosed cases of KOA is worrying, and it is essential to reduce the risk factors and detect those with a protective role in this context. The destructive effects of free radicals consist of the acceleration of chondrosenescence and apoptosis. Among other risk factors, the influence of redox imbalance on the homeostasis of the osteoarticular system is highlighted. The evolution of KOA can be correlated with oxidative stress markers or antioxidant status. These factors reveal the importance of maintaining a redox balance for the joints and the whole body's health, emphasizing the importance of an individualized therapeutic approach based on antioxidant effects. This paper aims to present an updated picture of the implications of reactive oxygen species (ROS) in KOA from pathophysiological and biochemical perspectives, focusing on antioxidant systems that could establish the premises for appropriate treatment to restore the redox balance and improve the condition of patients with KOA.

Recent advances in nanotherapeutic strategies that target nitric oxide pathway for preventing cartilage degeneration

Nitric oxide (NO) is an important inflammatory mediator involved in the development and progression of osteoarthritis (OA). Increased production of NO in the affected joints promote cartilage damage. As NO synthesis is catalysed by the inducible NO synthase (iNOS) enzyme, iNOS inhibition serves as an attractive therapeutic target to prevent NO release. Despite a number of direct and indirect iNOS inhibitor molecules demonstrating chondro-protective effect, none have reached the clinic. Its limited bioavailability and adverse side effects served as a deterrent for pursuing clinical trials in OA patients. With the advent of nanotechnology, interest in targeting NO for preventing cartilage degeneration has revived. In this article, we discuss the limitations of the existing molecules and provide an insight on recent nanotechnology-based strategies that have been explored for the diagnosis and inhibition of NO in OA. These approaches hold promise in reviving the hitherto under explored potential of targeting NO to address OA.

An animal model study on the gene expression profile of meniscal degeneration

Meniscal degeneration is a very common condition in elderly individuals, but the underlying mechanisms of its occurrence are not completely clear. This study examines the molecular mechanisms of meniscal degeneration. The anterior cruciate ligament (ACL) and lateral collateral ligament (LCL) of the right rear limbs of seven Wuzhishan mini-pigs were resected (meniscal degeneration group), and the left rear legs were sham-operated (control group). After 6 months, samples were taken for gene chip analysis, including differentially expressed gene (DEG) analysis, gene ontology (GO) analysis, clustering analysis, and pathway analysis. The selected 12 DEGs were validated by real time reverse transcription-polymerase chain reaction (RT-PCR). The two groups showed specific and highly clustered DEGs. A total of 893 DEGs were found, in which 537 are upregulated, and 356 are downregulated. The GO analysis showed that the significantly affected biological processes include nitric oxide metabolic process, male sex differentiation, and mesenchymal morphogenesis, the significantly affected cellular components include the endoplasmic reticulum membrane, and the significantly affected molecular functions include transition metal ion binding and iron ion binding. The pathway analysis showed that the significantly affected pathways include type II diabetes mellitus, inflammatory mediator regulation of TRP channels, and AMPK signaling pathway. The results of RT-PCR indicate that the microarray data accurately reflects the gene expression patterns. These findings indicate that several molecular mechanisms are involved in the development of meniscal degeneration, thus improving our understanding of meniscal degeneration and provide molecular therapeutic targets in the future.

Endoplasmic reticulum stress and protein degradation in chronic liver disease

Endoplasmic reticulum (ER) stress is easily observed in chronic liver disease, which often causes accumulation of unfolded or misfolded proteins in the ER, leading to unfolded protein response (UPR). Regulating protein degradation is an integral part of UPR to relieve ER stress. The major protein degradation system includes the ubiquitin-proteasome system (UPS) and autophagy. All three arms of UPR triggered in response to ER stress can regulate UPS and autophagy. Accumulated misfolded proteins could activate these arms, and then generate various transcription factors to regulate the expression of UPS-related and autophagy-related genes. The protein degradation process regulated by UPR has great significance in many chronic liver diseases, including non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), viral hepatitis, liver fibrosis, and hepatocellular carcinoma(HCC). In most instances, the degradation of excessive proteins protects cells with ER stress survival from apoptosis. According to the specific functions of protein degradation in chronic liver disease, choosing to promote or inhibit this process is promising as a potential method for treating chronic liver disease.

Decreased expression of autophagy markers in culture-positive patients with chronic otitis media

Objective

Abnormal autophagy plays a role in the pathogenesis of various diseases. This study aimed to evaluate associations between the clinical manifestations of chronic otitis media (COM) and expression of autophagy markers.

Methods

Associations between presence of bacteria, otorrhea, and conductive and sensorineural hearing loss and levels of autophagy-related mRNAs were investigated in 47 patients with COM.

Results

Autophagy-related mRNAs were detected in all inflammatory tissues of COM patients. LC3-II showed the highest level of expression, followed by Beclin-1, P13KC3, Rubicon, and mTOR. Beclin-1 mRNA levels were significantly lower in culture-positive than in culture-negative patients.

Conclusion

Autophagy is involved in the pathogenesis of COM. The finding that expression of autophagy markers, especially Beclin-1, was lower in culture-positive than in culture-negative patients suggested that these markers are closely associated with the clinical features of COM.

The evaluation of oxidative stress in osteoarthritis

Osteoarthritis (OA) is a whole joint disease driven by abnormal biomechanics and attendant cell-derived and tissue-derived factors. The disease is multifactorial and polygenic, and its progression is significantly related to oxidative stress and reactive oxygen species (ROS). Augmented ROS generation can cause the damage of structural biomolecules of the joint and, by acting as intracellular signaling component, ROS are associated with various inflammatory responses. By activating several signaling pathways, ROS have a vital importance in the patho-physiology of OA. This review is focused on the mechanism of ROS which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation, along with synovial inflammation and dysfunction of the subcondral bone, targeting the complex oxidative stress signaling pathways.

Nitric oxide and ROS mediate autophagy and regulate Alternaria alternata toxin-induced cell death in tobacco BY-2 cells

Synergistic interaction of nitric oxide (NO) and reactive oxygen species (ROS) is essential to initiate cell death mechanisms in plants. Though autophagy is salient in either restricting or promoting hypersensitivity response (HR)-related cell death, the crosstalk between the reactive intermediates and autophagy during hypersensitivity response is paradoxical. In this investigation, the consequences of Alternaria alternata toxin (AaT) in tobacco BY-2 cells were examined. At 3 h, AaT perturbed intracellular ROS homeostasis, altered antioxidant enzyme activities, triggered mitochondrial depolarization and induced autophagy. Suppression of autophagy by 3-Methyladenine caused a decline in cell viability in AaT treated cells, which indicated the vital role of autophagy in cell survival. After 24 h, AaT facilitated Ca2+ influx with an accumulation of reactive oxidant intermediates and NO, to manifest necrotic cell death. Inhibition of NO accumulation by 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) decreased the level of necrotic cell death, and induced autophagy, which suggests NO accumulation represses autophagy and facilitates necrotic cell death at 24 h. Application of N-acetyl-L-cysteine at 3 h, confirmed ROS to be the key initiator of autophagy, and together with cPTIO for 24 h, revealed the combined effects of NO and ROS is required for necrotic HR cell death.

Dopamine-melanin nanoparticles scavenge reactive oxygen and nitrogen species and activate autophagy for osteoarthritis therapy

Anti-oxidative agents hold great potential in osteoarthritis (OA) therapy. However, most radical scavengers have poor biocompatibility and potential cytotoxicity, which limit their applications. Herein we explore dopamine melanin (DM) nanoparticles as a novel scavenger of reactive oxygen species (ROS) and reactive nitrogen species (RNS). DM nanoparticles show low cytotoxicity and a strong ability to sequester a broad range of ROS and RNS, including superoxides, hydroxyl radicals, and peroxynitrite. This translates to excellent anti-inflammatory and chondro-protective effects by inhibiting intracellular ROS and RNS and promoting antioxidant enzyme activities. With an average diameter of 112.5 nm, DM nanoparticles can be intra-articularly (i.a.) injected into an affected joint and retained at the injection site. When tested in vivo in rodent OA models, DM nanoparticles showed diminished inflammatory cytokine release and reduced proteoglycan loss, which in turn slowed down cartilage degradation. Mechanistic studies suggest that DM nanoparticles also enhance autophagy that benefits OA control. In summary, our study suggests DM nanoparticles as a safe and promising therapeutic for OA.

Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) Reduces Oxidative and Mechanical Stress-Evoked Matrix Degradation in Chondrifying Cell Cultures

Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide also secreted by non-neural cells, including chondrocytes. PACAP signaling is involved in the regulation of chondrogenesis, but little is known about its connection to matrix turnover during cartilage formation and under cellular stress in developing cartilage. We found that the expression and activity of hyaluronidases (Hyals), matrix metalloproteinases (MMP), and aggrecanase were permanent during the course of chondrogenesis in primary chicken micromass cell cultures, although protein levels changed daily, along with moderate and relatively constant enzymatic activity. Next, we investigated whether PACAP influences matrix destructing enzyme activity during oxidative and mechanical stress in chondrogenic cells. Exogenous PACAP lowered Hyals and aggrecanase expression and activity during cellular stress. Expression and activation of the majority of cartilage matrix specific MMPs such as MMP1, MMP7, MMP8, and MMP13, were also decreased by PACAP addition upon oxidative and mechanical stress, while the activity of MMP9 seemed not to be influenced by the neuropeptide. These results suggest that application of PACAP can help to preserve the integrity of the newly synthetized cartilage matrix via signaling mechanisms, which ultimately inhibit the activity of matrix destroying enzymes under cellular stress. It implies the prospect that application of PACAP can ameliorate articular cartilage destruction in joint diseases.

Sevoflurane postconditioning protects against myocardial ischemia/reperfusion injury by restoring autophagic flux via an NO-dependent mechanism

Volatile anesthetics improve postischemic cardiac function and reduce infarction even when administered for only a brief time at the onset of reperfusion. A recent study showed that sevoflurane postconditioning (SPC) attenuated myocardial reperfusion injury, but the underlying mechanisms remain unclear. In this study, we examined the effects of sevoflurane on nitric oxide (NO) release and autophagic flux during the myocardial ischemia/reperfusion (I/R) injury in rats in vivo and ex vivo. Male rats were subjected to 30 min ischemia and 2 h reperfusion in the presence or absence of sevoflurane (1.0 minimum alveolar concentration) during the first 15 min of reperfusion. We found that SPC significantly improved hemodynamic performance after reperfusion, alleviated postischemic myocardial infarction, reduced nicotinamide adenine dinucleotide content loss, and cytochrome c release in heart tissues. Furthermore, SPC significantly increased the phosphorylation of endothelial nitric oxide synthase (NOS) and neuronal nitric oxide synthase, and elevated myocardial NOS activity and NO production. All these effects were abolished by treatment with an NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg, i.v.). We also observed myocardial I/R-induced accumulation of autophagosomes in heart tissues, as evidenced by increased ratios of microtubule-associated protein 1 light chain 3 II/I, up-regulation of Beclin 1 and P62, and reduced lysosome-associated membrane protein-2 expression. SPC significantly attenuated I/R-impaired autophagic flux, which were blocked by L-NAME. Moreover, pretreatment with the autophagic flux blocker chloroquine (10 mg/kg, i.p.) increased autophagosome accumulation in SPC-treated heart following I/R and blocked SPC-induced cardioprotection. The same results were also observed in a rat model of myocardial I/R injury ex vivo, suggesting that SPC protects rat hearts against myocardial reperfusion injury by restoring I/R-impaired autophagic flux via an NO-dependent mechanism.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Nano-sized Al2O3 particle-induced autophagy reduces osteolysis in aseptic loosening of total hip arthroplasty by negative feedback regulation of RANKL expression in fibroblasts

Aseptic loosening is mainly caused by wear debris generated by friction that can increase the expression of receptor activation of nuclear factor (NF)-κB (RANKL). RANKL has been shown to support the differentiation and maturation of osteoclasts. Although autophagy is a key metabolic pathway for maintaining the metabolic homeostasis of cells, no study has determined whether autophagy induced by Al₂O₃ particles is involved in the pathogenesis of aseptic loosening. The aim of this study was to evaluate RANKL levels in patients experiencing aseptic loosening after total hip arthroplasty (THA) and hip osteoarthritis (hOA) and to consequently clarify the relationship between RANKL and LC3II expression. We determined the levels of RANKL and autophagy in fibroblasts treated with Al₂O₃ particles in vitro while using shBECN-1 interference lentivirus vectors to block the autophagy pathway and BECN-1 overexpression lentivirus vectors to promote autophagy. We established a novel rat model of femoral head replacement and analyzed the effects of Al₂O₃ particles on autophagy levels and RANKL expression in synovial tissues in vivo. The RANKL levels in the revision total hip arthroplasty (rTHA) group were higher than those in the hOA group. In patients with rTHA with a ceramic interface, LC3II expression was high, whereas RANKL expression was low. The in vitro results showed that Al₂O₃ particles promoted fibroblast autophagy in a time- and dose-dependent manner and that RANKL expression was negatively correlated with autophagy. The in vivo results further confirmed these findings. Al₂O₃ particles induced fibroblast autophagy, which reduced RANKL expression. Decreasing the autophagy level promoted osteolysis and aseptic prosthetic loosening, whereas increasing the autophagy level reversed this trend.

The Pathobiology of the Meniscus: A Comparison Between the Human and Dog

Serious knee pain and related disability have an annual prevalence of approximately 25% on those over the age of 55 years. As curative treatments for the common knee problems are not available to date, knee pathologies typically progress and often lead to osteoarthritis (OA). While the roles that the meniscus plays in knee biomechanics are well characterized, biological mechanisms underlying meniscus pathophysiology and roles in knee pain and OA progression are not fully clear. Experimental treatments for knee disorders that are successful in animal models often produce unsatisfactory results in humans due to species differences or the inability to fully replicate disease progression in experimental animals. The use of animals with spontaneous knee pathologies, such as dogs, can significantly help addressing this issue. As microscopic and macroscopic anatomy of the canine and human menisci are similar, spontaneous meniscal pathologies in canine patients are thought to be highly relevant for translational medicine. However, it is not clear whether the biomolecular mechanisms of pain, degradation of extracellular matrix, and inflammatory responses are species dependent. The aims of this review are (1) to provide an overview of the anatomy, physiology, and pathology of the human and canine meniscus, (2) to compare the known signaling pathways involved in spontaneous meniscus pathology between both species, and (3) to assess the relevance of dogs with spontaneous meniscal pathology as a translational model. Understanding these mechanisms in human and canine meniscus can help to advance diagnostic and therapeutic strategies for painful knee disorders and improve clinical decision making.

Downregulating PI3K/Akt/NF-κB signaling with allicin for ameliorating the progression of osteoarthritis:in vitroandvivostudies

A schematic illustration of the potential protective effects of allicin on osteoarthritis development.

Compromised autophagy precedes meniscus degeneration and cartilage damage in mice

OBJECTIVE

Autophagy is a cellular homeostasis mechanism that facilitates normal cell function and survival. Objectives of this study were to determine associations between autophagic responses with meniscus injury, joint aging, and osteoarthritis (OA), and to establish the temporal relationship with structural changes in menisci and cartilage.

METHODS

Constitutive activation of autophagy during aging was measured in GFP-LC3 transgenic reporter mice between 6 and 30 months. Meniscus injury was created by surgically destabilizing the medial meniscus (DMM) to induce posttraumatic OA in C57BL/6J mice. Levels of autophagy proteins and activation were analyzed by confocal microscopy and immunohistochemistry. Associated histopathological changes, such as cellularity, matrix staining, and structural damage, were graded in the meniscus and compared to changes in articular cartilage.

RESULTS

In C57BL/6J mice, basal autophagy was lower in the meniscus than in articular cartilage. With increasing age, expression of the autophagy proteins ATG5 and LC3 was significantly reduced by 24 months. Age-related changes included abnormal Safranin-O staining and reduced cellularity, which preceded structural damage in the meniscus and articular cartilage. In mice with DMM, autophagy was induced in the meniscus while it was suppressed in cartilage. Articular cartilage exhibited the most profound changes in autophagy and structure that preceded meniscus degeneration. Systemic administration of rapamycin to mice with DMM induced autophagy activation in cartilage and reduced degenerative changes in both meniscus and cartilage.

CONCLUSION

Autophagy is significantly affected in the meniscus during aging and injury and precedes structural damage. Maintenance of autophagic activity appears critical for meniscus and cartilage integrity.

Regulation of Cellular Redox Signaling by Matricellular Proteins in Vascular Biology, Immunology, and Cancer

SIGNIFICANCE

In contrast to structural elements of the extracellular matrix, matricellular proteins appear transiently during development and injury responses, but their sustained expression can contribute to chronic disease. Through interactions with other matrix components and specific cell surface receptors, matricellular proteins regulate multiple signaling pathways, including those mediated by reactive oxygen and nitrogen species and H2S. Dysregulation of matricellular proteins contributes to the pathogenesis of vascular diseases and cancer. Defining the molecular mechanisms and receptors involved is revealing new therapeutic opportunities. Recent Advances: Thrombospondin-1 (TSP1) regulates NO, H2S, and superoxide production and signaling in several cell types. The TSP1 receptor CD47 plays a central role in inhibition of NO signaling, but other TSP1 receptors also modulate redox signaling. The matricellular protein CCN1 engages some of the same receptors to regulate redox signaling, and ADAMTS1 regulates NO signaling in Marfan syndrome. In addition to mediating matricellular protein signaling, redox signaling is emerging as an important pathway that controls the expression of several matricellular proteins.

CRITICAL ISSUES

Redox signaling remains unexplored for many matricellular proteins. Their interactions with multiple cellular receptors remains an obstacle to defining signaling mechanisms, but improved transgenic models could overcome this barrier.

FUTURE DIRECTIONS

Therapeutics targeting the TSP1 receptor CD47 may have beneficial effects for treating cardiovascular disease and cancer and have recently entered clinical trials. Biomarkers are needed to assess their effects on redox signaling in patients and to evaluate how these contribute to their therapeutic efficacy and potential side effects. Antioxid. Redox Signal. 27, 874-911.

Curcumin Inhibits Apoptosis of Chondrocytes through Activation ERK1/2 Signaling Pathways Induced Autophagy

Osteoarthritis (OA) is an inflammatory disease of load-bearing synovial joints that is currently treated with drugs that exhibit numerous side effects and are only temporarily effective in treating pain, the main symptom of the disease. Consequently, there is an acute need for novel, safe, and more effective chemotherapeutic agents for the treatment of osteoarthritis and related arthritic diseases. Curcumin, the principal curcuminoid and the most active component in turmeric, is a biologically active phytochemical. Evidence from several recent in vitro studies suggests that curcumin may exert a chondroprotective effect through actions such as anti-inflammatory, anti-oxidative stress, and anti-catabolic activity that are critical for mitigating OA disease pathogenesis and symptoms. In the present study, we investigated the protective mechanisms of curcumin on interleukin 1β (IL-1β)-stimulated primary chondrocytes in vitro. The treatment of interleukin (IL)-1β significantly reduces the cell viability of chondrocytes in dose and time dependent manners. Co-treatment of curcumin with IL-1β significantly decreased the growth inhibition. We observed that curcumin inhibited IL-1β-induced apoptosis and caspase-3 activation in chondrocytes. Curcumin can increase the expression of phosphorylated extracellular signal-regulated kinases 1/2 (ERK1/2), autophagy marker light chain 3 (LC3)-II, and Beclin-1 in chondrocytes. The expression of autophagy markers could be decreased when the chondrocytes were incubated with ERK1/2 inhibitor U0126. Our results suggest that curcumin suppresses apoptosis and inflammatory signaling through its actions on the ERK1/2-induced autophagy in chondrocytes. We propose that curcumin should be explored further for the prophylactic treatment of osteoarthritis in humans and companion animals.

Molecular basis and current strategies of therapeutic arginine depletion for cancer

Renewed interest in the use of therapeutic enzymes combined with an improved knowledge of cancer cell metabolism, has led to the translation of several arginine depletion strategies into early phase clinical trials. Arginine auxotrophic tumors are reliant on extracellular arginine, due to the downregulation of arginosuccinate synthetase or ornithine transcarbamylase-key enzymes for intracellular arginine recycling. Engineered arginine catabolic enzymes such as recombinant human arginase (rh-Arg1-PEG) and arginine deiminase (ADI-PEG) have demonstrated cytotoxicity against arginine auxotrophic tumors. In this review, we discuss the molecular events triggered by extracellular arginine depletion that contribute to tumor cell death.

Advances in combining gene therapy with cell and tissue engineering-based approaches to enhance healing of the meniscus

Meniscal lesions are common problems in orthopaedic surgery and sports medicine, and injury or loss of the meniscus accelerates the onset of knee osteoarthritis (OA). Despite a variety of therapeutic options in the clinics, there is a critical need for improved treatments to enhance meniscal repair. In this regard, combining gene-, cell-, and tissue engineering-based approaches is an attractive strategy to generate novel, effective therapies to treat meniscal lesions. In the present work, we provide an overview of the tools currently available to improve meniscal repair and discuss the progress and remaining challenges for potential future translation in patients.

ROS/oxidative stress signaling in osteoarthritis

Osteoarthritis is the most common joint disorder with increasing prevalence due to aging of the population. Its multi-factorial etiology includes oxidative stress and the overproduction of reactive oxygen species, which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation along with synovial inflammation and dysfunction of the subchondral bone. As disease-modifying drugs for osteoarthritis are rare, targeting the complex oxidative stress signaling pathways would offer a valuable perspective for exploration of potential therapeutic strategies in the treatment of this devastating disease.

Autophagy protects chondrocytes from glucocorticoids-induced apoptosis via ROS/Akt/FOXO3 signaling

OBJECTIVE

Glucocorticoids (GCs) have been widely used in the management of osteoarthritis (OA) and rheumatoid arthritis (RA). Nevertheless, there has been some concern about their ability of increasing reactive oxygen species (ROS) in the cartilage. Forkhead-box class O (FOXO) transcription factors have been proved to have a protective role in chondrocytes through regulation of autophagy and defending oxidative stress. The objective of this study was to investigate the role of FOXO3 in Dex-induce up-regulation of ROS.

DESIGN

Healthy cartilages debris from six patients were used for chondrocytes culture. After the treatment of dexamethasone (Dex), the ROS levels, autophagic flux, the expression of FOXO3 in chondrocytes were measured. RNA interference technique was also used to determine the role of FOXO3 in Dex-induced autophagy. The metabolism of the extra-cellular matrix was also investigated.

THE RESULTS

Dex increased intracellular ROS level, the expression of Akt, FOXO3 as well as autophagy flux in human chondrocytes. The expression of aggrecanases also increased after the treatment of Dex. Catalase, the ROS scavenger, suppressed Dex-induced up-regulation of autophagy flux and expression of aggrecanases and Akt. MK-2206 and LY294002, the PI3K/Akt inhibitors, repressed Dex-induced up-regulation of FOXO3. Silencing FOXO3 resulted in down-regulation of Dex-induced autophagy. Moreover, knockdown of FOXO3 increased Dex-induced apoptosis as well as ROS levels in chondrocytes. In addition, up-regulation of autophagy by Rapamycin resulted in decreasing ROS level in chondrocytes.

CONCLUSION

Dex could advance the degenerative process in cartilage. Autophagy was induced in response to Dex-induced up-regulation of ROS via ROS/Akt/FOXO3 signal pathway.

Nitric Oxide-Induced Autophagy in MC3T3-E1 Cells is Associated with Cytoprotection via AMPK Activation

Nitric oxide (NO) is important in the regulation of bone remodeling, whereas high concentration of NO promotes cell death of osteoblast. However, it is not clear yet whether NO-induced autophagy is implicated in cell death or survival of osteoblast. The present study is aimed to examine the role of NO-induced autophagy in the MC3T3-E1 cells and their underlying molecular mechanism. The effect of sodium nitroprusside (SNP), an NO donor, on the cytotoxicity of the MC3T3-E1 cells was determined by MTT assay and expression of apoptosis or autophagy associated molecules was evaluated by western blot analysis. The morphological observation of autophagy and apoptosis by acridine orange stain and TUNEL assay were performed, respectively. Treatment of SNP decreased the cell viability of the MC3T3-E1 cells in dose- and time-dependent manner. SNP increased expression levels of p62, ATG7, Beclin-1 and LC3-II, as typical autophagic markers and augmented acidic autophagolysosomal vacuoles, detected by acridine orange staining. However, pretreatment with 3-methyladenine (3MA), the specific inhibitor for autophagy, decreased cell viability, whereas increased the cleavage of PARP and caspase-3 in the SNP-treated MC3T3-E1 cells. AMP-activated protein kinase (AMPK), a major autophagy regulatory kinase, was activated in SNP-treated MC3T3-E1 cells. In addition, pretreatment with compound C, an inhibitor of AMPK, decreased cell viability, whereas increased the number of apoptotic cells, cleaved PARP and caspase-3 levels compared to those of SNP-treated MC3T3-E1 cells. Taken together, it is speculated that NO-induced autophagy functions as a survival mechanism via AMPK activation against apoptosis in the MC3T3-E1 cells.

Nexavar/Stivarga and viagra interact to kill tumor cells

We determined whether the multi‐kinase inhibitor sorafenib or its derivative regorafenib interacted with phosphodiesterase 5 (PDE5) inhibitors such as Viagra (sildenafil) to kill tumor cells. PDE5 and PDGFRα/β were over‐expressed in liver tumors compared to normal liver tissue. In multiple cell types in vitro sorafenib/regorafenib and PDE5 inhibitors interacted in a greater than additive fashion to cause tumor cell death, regardless of whether cells were grown in 10 or 100% human serum. Knock down of PDE5 or of PDGFRα/β recapitulated the effects of the individual drugs. The drug combination increased ROS/RNS levels that were causal in cell killing. Inhibition of CD95/FADD/caspase 8 signaling suppressed drug combination toxicity. Knock down of ULK‐1, Beclin1, or ATG5 suppressed drug combination lethality. The drug combination inactivated ERK, AKT, p70 S6K, and mTOR and activated JNK. The drug combination also reduced mTOR protein expression. Activation of ERK or AKT was modestly protective whereas re‐expression of an activated mTOR protein or inhibition of JNK signaling almost abolished drug combination toxicity. Sildenafil and sorafenib/regorafenib interacted in vivo to suppress xenograft tumor growth using liver and colon cancer cells. From multiplex assays on tumor tissue and plasma, we discovered that increased FGF levels and ERBB1 and AKT phosphorylation were biomarkers that were directly associated with lower levels of cell killing by ‘rafenib + sildenafil. Our data are now being translated into the clinic for further determination as to whether this drug combination is a useful anti‐tumor therapy for solid tumor patients. J. Cell. Physiol. 230: 2281–2298, 2015. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

PDE5 inhibitors enhance celecoxib killing in multiple tumor types

The present studies determined whether clinically relevant phosphodiesterase 5 (PDE5) inhibitors interacted with a clinically relevant NSAID, celecoxib, to kill tumor cells. Celecoxib and PDE5 inhibitors interacted in a greater than additive fashion to kill multiple tumor cell types. Celecoxib and sildenafil killed ex vivo primary human glioma cells as well as their associated activated microglia. Knock down of PDE5 recapitulated the effects of PDE5 inhibitor treatment; the nitric oxide synthase inhibitor L-NAME suppressed drug combination toxicity. The effects of celecoxib were COX2 independent. Over-expression of c-FLIP-s or knock down of CD95/FADD significantly reduced killing by the drug combination. CD95 activation was dependent on nitric oxide and ceramide signaling. CD95 signaling activated the JNK pathway and inhibition of JNK suppressed cell killing. The drug combination inactivated mTOR and increased the levels of autophagy and knock down of Beclin1 or ATG5 strongly suppressed killing by the drug combination. The drug combination caused an ER stress response; knock down of IRE1α/XBP1 enhanced killing whereas knock down of eIF2α/ATF4/CHOP suppressed killing. Sildenafil and celecoxib treatment suppressed the growth of mammary tumors in vivo. Collectively our data demonstrate that clinically achievable concentrations of celecoxib and sildenafil have the potential to be a new therapeutic approach for cancer.