Hydrogen sulfide protects against particle-induced inflammatory response and osteolysis via SIRT1 pathway in prosthesis loosening

ROS-mediated mitophagy and necroptosis regulate osteocytes death caused by TCP particles in MLO-Y4 cells

Our previous data have revealed TCP particles caused cell death of osteocytes, comprising over 95 % of all bone cells, which contribute to periprosthetic osteolysis, joint loosening and implant failure, but its mechanisms are not fully understood. Here, we reported that TCP particles inhibited cell viability of osteocytes MLO-Y4, and caused cell death. TCP particles caused mitochondrial impairment and increased expressions of LC-3 II, Parkin and PINK 1, accompanied by the elevation of autophagy flux and intracellular acidic components, the accumulation of LC-3II, PINK1 and Parkin in damaged mitochondria, and p62 reduction. The increased LC-3II expression and cell death extent were significantly enhanced by the autophagy inhibitor Baf A1, compared with Baf A1 (or TCP particles) alone, indicating that TCP particles increase autophagic flux and lead to cell even death of MLO-Y4 cells, closely associated with mitophagy. Furthermore, TCP particles induced propidium iodide (PI) uptake and the phosphorylation of RIP1, RIP3 and MLKL, thereby increasing necroptosis in MLO-Y4 cells. The pro-necroptotic effect was alleviated by the RIP1 inhibitor Nec-1 or the MLKL inhibitor NSA. Additionally, TCP particles promoted the production of intracellular reactive oxygen species (ROS) and mitochondrial ROS (mtROS), and increased TXNIP expression, but decreased protein levels of TRX1, Nrf2, HO-1 and NQO1, leading to oxidative stress. The ROS scavenger NAC remarkably reversed mitophagy and necroptosis caused by TCP particles, suggesting that ROS is responsible for mitophagy and necroptosis. Collectively, ROS-mediated mitophagy and necroptosis regulate osteocytes death caused by TCP particles in MLO-Y4 cells, which enhances osteoclastogenesis and periprosthetic osteolysis.

Quercetin Reprograms Immunometabolism of Macrophages via the SIRT1/PGC-1α Signaling Pathway to Ameliorate Lipopolysaccharide-Induced Oxidative Damage

The redox system is closely related to changes in cellular metabolism. Regulating immune cell metabolism and preventing abnormal activation by adding antioxidants may become an effective treatment for oxidative stress and inflammation-related diseases. Quercetin is a naturally sourced flavonoid with anti-inflammatory and antioxidant activities. However, whether quercetin can inhibit LPS-induced oxidative stress in inflammatory macrophages by affecting immunometabolism has been rarely reported. Therefore, the present study combined cell biology and molecular biology methods to investigate the antioxidant effect and mechanism of quercetin in LPS-induced inflammatory macrophages at the RNA and protein levels. Firstly, quercetin was found to attenuate the effect of LPS on macrophage proliferation and reduce LPS-induced cell proliferation and pseudopodia formation by inhibiting cell differentiation, as measured by cell activity and proliferation. Subsequently, through the detection of intracellular reactive oxygen species (ROS) levels, mRNA expression of pro-inflammatory factors and antioxidant enzyme activity, it was found that quercetin can improve the antioxidant enzyme activity of inflammatory macrophages and inhibit their ROS production and overexpression of inflammatory factors. In addition, the results of mitochondrial morphology and mitochondrial function assays showed that quercetin could upregulate the mitochondrial membrane potential, ATP production and ATP synthase content decrease induced by LPS, and reverse the mitochondrial morphology damage to a certain extent. Finally, Western blotting analysis demonstrated that quercetin significantly upregulated the protein expressions of SIRT1 and PGC-1α, that were inhibited by LPS. And the inhibitory effects of quercetin on LPS-induced ROS production in macrophages and the protective effects on mitochondrial morphology and membrane potential were significantly decreased by the addition of SIRT1 inhibitors. These results suggested that quercetin reprograms the mitochondria metabolism of macrophages through the SIRT1/PGC-1α signaling pathway, thereby exerting its effect of alleviating LPS-induced oxidative stress damage.

ROS-responsive resveratrol-loaded cyclodextrin nanomicelles reduce inflammatory osteolysis

Bone loss in inflammatory disorders such as osteomyelitis, septic arthritis, and periodontitis is caused by excessive osteoclastic activity. Meanwhile, reactive oxygen species (ROS) have been identified as contributors to osteoclast differentiation, and the application of ROS scavengers has emerged as a promising strategy to protect against bone loss. Recently, resveratrol (RSV), a polyphenolic phytoalexin, has been demonstrated to inhibit osteoclastogenesis by scavenging ROS; however, the application of RSV as an antioxidant is limited by its low water solubility, structural instability, and short elimination half-life. In this study, we developed a PEGylated cyclodextrin (CD)-based nanoplatform (PCP) for local delivery of RSV as nanomicelles (RSV-NMs). In addition, polymer functionalization with phenylboronic acid ester in RSV-NMs successfully achieved ROS-responsive release of RSV. The RSV-NMs in a well-dispersed state possessed good biocompatibility as well as improved solubility and stability compared with RSV compound. In vitro, RSV-NMs significantly inhibited the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells and suppressed F-actin (filamentous actin) ring formation. Additionally, the mRNA expressions of osteoclastic marker genes, including matrix metalloprotein-9 (MMP-9), nuclear factor of activated T cells 1 (NFATc1), TRAP, and cathepsin K, were consequently downregulated in the presence of RSV-NMs. In vivo, RSV-NMs provided protection against LPS-induced bone destruction, as evidenced by a decreased number of osteoclasts, increased bone density, and reduced area of bone resorption. Taken together, these results indicate that our ROS-responsive RSV-NMs can be employed as a potential therapeutic agent for the treatment of inflammatory osteolysis.

Photoluminescent carbon dots (PCDs) from sour apple: a biocompatible nanomaterial for preventing UHMWPE wear-particle induced osteolysis via modulating Chemerin/ChemR23 and SIRT1 signaling pathway and its bioimaging application

Photoluminescent nanomaterials have been widely employed in several biological applications both in vitro and in vivo. For the first time, we report a novel application of sour apple-derived photoluminescent carbon dots (PCDs) for reducing ultra-high molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis using mouse calvarial model. Generally, aseptic prosthetic loosening seems to be a significant postoperative problem for artificial joints replacement, which is mainly contributed by UHMWPE-induced osteolysis. Hence, inhibiting osteoclastic bone-resorption could minimize UHMWPE-induced osteolysis for implant loosening. Prior to osteolysis studies, the prepared sour apple-derived PCDs were employed for bioimaging application. As expected, the prepared PCDs effectively inhibited the UHMWPE particle-induced osteoclastogenesis in vitro. The PCDs treatment effectively inhibited the UHMWPE-induced osteoclast differentiation, F-actin ring pattern, and bone resorption in vitro. Also, the PCDs reduced the UHMWPE-induced ROS stress as well as the expression level of pro-inflammatory cytokines, including TNF-α, IL-1, IL-6, and IL-8. Further, the qPCR and western blot results hypothesized that PCDs inhibited the UHMWPE wear particle-induced osteolysis through suppressing chemerin/ChemR23 signaling and NFATc1 pathway, along with upregulation of SIRT1 expression. Overall, these findings suggest that the synthesized PCDs could be a potential therapeutic material for minimizing UHMWPE particle-induced periprosthetic osteolysis to avoid postoperative complications.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Comorbidity of osteoporosis and Alzheimer's disease: Is `AKT `-ing on cellular glucose uptake the missing link?

Osteoporosis and Alzheimer's disease (AD) are both degenerative diseases. Osteoporosis often proceeds cognitive deficits, and multiple studies have revealed common triggers that lead to energy deficits in brain and bone. Risk factors for osteoporosis and AD, such as obesity, type 2 diabetes, aging, chemotherapy, vitamin deficiency, alcohol abuse, and apolipoprotein Eε4 and/or Il-6 gene variants, reduce cellular glucose uptake, and protective factors, such as estrogen, insulin, exercise, mammalian target of rapamycin inhibitors, hydrogen sulfide, and most phytochemicals, increase uptake. Glucose uptake is a fine-tuned process that depends on an abundance of glucose transporters (Gluts) on the cell surface. Gluts are stored in vesicles under the plasma membrane, and protective factors cause these vesicles to fuse with the membrane, resulting in presentation of Gluts on the cell surface. This translocation depends mainly on AKT kinase signaling and can be affected by a range of factors. Reduced AKT kinase signaling results in intracellular glucose deprivation, which causes endoplasmic reticulum stress and iron depletion, leading to activation of HIF-1α, the transcription factor necessary for higher Glut expression. The link between diseases and aging is a topic of growing interest. Here, we show that diseases that affect the same biochemical pathways tend to co-occur, which may explain why osteoporosis and/or diabetes are often associated with AD.

Enteropathogenic Escherichia coli Mediates CoCrMo Particle-Induced Peri-Implant Osteolysis by Increasing Peripheral 5-HT

The human gut microbiota has been proven to have great effects on the regulation of bone health. However, the association between gut microbiota and particle-induced osteolysis, which is the primary cause of aseptic loosening, is still unknown. In this study, we used a combination of wide-spectrum antibiotics to eliminate the majority of gut microbiota and found that reduction of gut commensal bacteria significantly alleviated the progression of osteolysis, in which anaerobe was the biggest culprit in the exacerbation of osteolysis. Furthermore, colonization of enteropathogenic Escherichia coli (EPEC), a subspecies of anaerobe, could promote the development of particle-induced osteolysis by increasing the secretion of peripheral 5-hydroxytryptamine (5-HT) from the colon. Elevated 5-HT level decreased the phosphorylation of CREB and inhibited the proliferation of osteoblasts. Collectively, these results indicated EPEC colonization suppressed the bone formation and aggravated particle-induced osteolysis in vivo. Thus, clearance of EPEC is expected to become a potential preventive approach to treat debris-induced osteolysis and aseptic loosening.

H2S Donor and Bone Metabolism

Hydrogen sulfide (H2S) has been recognized as the third gasotransmitter, following nitric oxide and carbon monoxide, and it exerts important biological effects in the body. Growing evidence has shown that H2S is involved in many physiological processes in the body. In recent years, much research has been carried out on the role of H2S in bone metabolism. Bone metabolic diseases have been linked to abnormal endogenous H2S functions and metabolism. It has been found that H2S plays an important role in the regulation of bone diseases such as osteoporosis and osteoarthritis. Regulation of H2S on bone metabolism has many interacting signaling pathways at the molecular level, which play an important role in bone formation and absorption. H2S releasing agents (donors) have achieved significant effects in the treatment of metabolic bone diseases such as osteoporosis and osteoarthritis. In addition, H2S donors and related drugs have been widely used as research tools in basic biomedical research and may be explored as potential therapeutic agents in the future. Donors are used to study the mechanism and function of H2S as they release H2S through different mechanisms. Although H2S releasers have biological activity, their function can be inconsistent. Additionally, donors have different H2S release capabilities, which could lead to different effects. Side effects may form with the formation of H2S; however, it is unclear whether these side effects affect the biological effects of H2S. Therefore, it is necessary to study H2S donors in detail. In this review, we summarize the current information about H2S donors related to bone metabolism diseases and discuss some mechanisms and biological applications.

Quercetin Attenuates Trauma-Induced Heterotopic Ossification by Tuning Immune Cell Infiltration and Related Inflammatory Insult

Heterotopic ossification (HO) is one of the most intractable disorders following musculoskeletal injury and is characterized by the ectopic presence of bone tissue in the soft tissue leading to severe loss of function in the extremities. Recent studies have indicated that immune cell infiltration and inflammation are involved in aberrant bone formation. In this study, we found increased monocyte/macrophage and mast cell accumulation during early HO progression. Macrophage depletion by clodronate liposomes and mast cell stabilization by cromolyn sodium significantly impeded HO formation. Therefore, we proposed that the dietary phytochemical quercetin could also suppress immune cell recruitment and related inflammatory responses to prevent HO. As expected, quercetin inhibited the monocyte-to-macrophage transition, macrophage polarization, and mast cell activation in vitro in a dose-dependent manner. Using a murine burn/tenotomy model, we also demonstrated that quercetin attenuated inflammatory responses and HO in vivo. Furthermore, elevated SIRT1 and decreased acetylated NFκB p65 expression were responsible for the mechanism of quercetin, and the beneficial effects of quercetin were reversed by the SIRT1 antagonist EX527 and mimicked by the SIRT agonist SRT1720. The findings in this study suggest that targeting monocyte/macrophage and mast cell activities may represent an attractive approach for therapeutic intervention of HO and that quercetin may serve as a promising therapeutic candidate for the treatment of trauma-induced HO by modulating SIRT1/NFκB signaling.

Glycyrrhizin mitigates inflammatory bone loss and promotes expression of senescence-protective sirtuins in an aging mouse model of periprosthetic osteolysis

Although periprosthetic osteolysis induced by wear debris particles is significantly elevated in senior (65+ years old) patients, most of the published pre-clinical studies were performed using young (less than three-month old) mice indicating the critical need to employ experimental models of particle-induced osteolysis involving mice with advanced age. Emerging evidence indicates that currently available antiresorptive bone therapies have serious age-dependent side effects. However, a resurgence of healthcare interest has occurred in glycyrrhizin (GLY), a natural extract from the licorice roots, as alternative sources of drugs for treating inflammatory bone lytic diseases and prevention of cellular senescence. This study investigated the effects of GLY on inflammatory bone loss as well as expression patterns of senescence-associated secretory phenotype and senescence-protective markers using an experimental calvarium osteolytic model induced in aged (twenty-four-month-old) mice by polymethylmethacrylate (PMMA) particles. Our results indicate that local treatment with GLY significantly diminished the size of inflammatory osteolytic lesions in aged mice via the number of CXCR4+OCPs and Tartrate-resistant acid phosphatase positive (TRAP+) osteoclasts. Furthermore, GLY dramatically decreased the amounts of senescence-associated secretory phenotype markers, including pro-inflammatory macrophage migration inhibitory factor (MIF) chemokine, and cathepsins B and K in the bone lesions of aged mice. By contrast, GLY significantly elevated expression patterns of senescence-protective markers, including homeostatic stromal derived factor-1 (SDF-1) chemokine, and sirtuin-1, and sirtuin-6, in the PMMA particle-induced calvarial lesions of aged mice. Collectively, these data suggest that GLY can be used for the development of novel therapies to control bone loss and tissue aging in senior patients with periprosthetic osteolysis.

Hydrogen sulfide ameliorates high glucose-induced pro-inflammation factors in HT-22 cells: Involvement of SIRT1-mTOR/NF-κB signaling pathway

Hyperglycemia-induced neuroinflammation promotes the progression of diabetic encephalopathy. Hydrogen sulfide (H₂S) exerts anti-inflammatory and neuroprotective activities against neurodegenerative diseases. However, the effects of H₂S on hyperglycemia-induced neuroinflammation has not been investigated in neurons. Herein, by using HT-22 neuronal cells, we found that high glucose decreased the levels of endogenous H₂S and its catalytic enzyme, cystathionine-β-synthase (CBS). The administration of sodium hydrosulfide (NaHS, a H₂S donor) or S-adenosylmethionine (SAMe, an allosteric activator of CBS) restored high glucose-induced downregulation of CBS and H₂S levels. Importantly, H₂S ameliorated high glucose-induced inflammation in HT-22 cells, evidenced by NaHS or SAMe inhibited the pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) expression in HT-22 cells exposed to high glucose. Furthermore, NaHS or SAMe restored the SIRT1 level and the phosphorylation of mTOR and NF-κB p65 disturbed by high glucose in HT-22 cells, suggesting H₂S reversed high glucose-induced alteration of SIRT1-mTOR/NF-κB signaling pathway. Our results demonstrated that exogenous H₂S treatment or enhancing endogenous H₂S synthesis prevents the inflammatory processes in the neurons with the exposure of high glucose. Therefore, increasing the H₂S level using NaHS or SAMe might shed light on the prophylactic treatment of diabetic encephalopathy.

Resveratrol-enhanced SIRT1-mediated osteogenesis in porous endplates attenuates low back pain and anxiety behaviors

Low back pain (LBP) is a major clinical problem that lacks effective treatments. The sensory innervation in porous vertebral endplates and anxiety contributes to spinal hyperalgesia. We hypothesized that SIRT1 activator resveratrol alleviates LBP and anxiety via promotion of osteogenesis in the porous endplates. The hyperalgesia and anxiety-related behaviors; sensory innervation, inflammation and porosity of endplates; and osteogenic/osteoclastic factors expression were measured following resveratrol treatment after lumbar spine instability (LSI) surgery. To explore whether resveratrol promotes endplates osteogenesis and thus alleviates LBP through activation of SIRT1 in the osteoprogenitor cells of endplates, SIRT1OSX-/- mice were employed. Additionally, the levels of inflammation markers, phosphorylation of cAMP response element-binding protein (pCREB), and brain-derived neurotrophic factor (BDNF) in hippocampus were evaluated. After 4 or 8 weeks LSI surgery, the mice suffered from hyperalgesia and anxiety, which were efficiently attenuated by resveratrol at 8 weeks. Resveratrol treatment-enhanced osteogenesis and decreased endplates porosities accompanied with the reduction of TNFα, IL-1β, and COX2 levels and CGRP+ nerve fibers innervation in porous endplates. Resveratrol-mediated endplates osteogenesis, decreased endplates porosities, and analgesic and antianxiety effects were abrogated in SIRT1OSX-/- mice. Furthermore, resveratrol relieved inflammation and increased pCREB and BDNF expression in the hippocampus after 8 weeks, which alleviate anxiety-related behaviors. This study provides that resveratrol-mediated porous endplates osteogenesis via the activation of SIRT1 markedly blocked sensory innervation and inflammation in endplates, therefore, alleviating LSI surgery-induced LBP and hippocampus-related anxiety.

Astaxanthin ameliorates oxidative stress and neuronal apoptosis via SIRT1/NRF2/Prx2/ASK1/p38 after traumatic brain injury in mice

BACKGROUND AND PURPOSE

Oxidative stress and neuronal apoptosis play key roles in traumatic brain injury. We investigated the protective effects of astaxanthin against traumatic brain injury and its underlying mechanisms of action.

EXPERIMENTAL APPROACH

A weight-drop model of traumatic brain injury in vivo and hydrogen peroxide exposure in vitro model were established. Brain oedema, behaviour tests, western blot, biochemical analysis, lesion volume, histopathological study and cell viability were performed.

KEY RESULTS

Astaxanthin significantly reduced oxidative insults on Days 1, 3 and 7 after traumatic brain injury. Neuronal apoptosis was also ameliorated on Day 3. Additionally, astaxanthin improved neurological functions up to 3 weeks after traumatic brain injury. Astaxanthin treatment dramatically enhanced the expression of peroxiredoxin 2 (Prx2), nuclear factor-erythroid 2-related factor 2 (NRF2/Nrf2) and sirtuin 1 (SIRT1), while it down-regulated the phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) and p38. Inhibition of Prx2 by siRNA injection reversed the beneficial effects of astaxanthin against traumatic brain injury. Additionally, Nrf2 knockout prevented the neuroprotective effects of astaxanthin in traumatic brain injury. In contrast, overexpression of Prx2 in Nrf2 knockout mice attenuated the secondary brain injury after traumatic brain injury. Moreover, inhibiting SIRT1 by EX527 dramatically inhibited the neuroprotective effects of astaxanthin and suppressed SIRT1/Nrf2/Prx2/ASK1/p38 pathway both in vivo and in vitro.

CONCLUSION AND IMPLICATIONS

Astaxanthin improved the neurological functions and protected the brain from injury after traumatic brain injury, primarily by reducing oxidative stress and neuronal death via SIRT1/Nrf2/Prx2/ASK1/p38 signalling pathway and might be a new candidate to ameliorate traumatic brain injury.

A Modified Murine Calvarial Osteolysis Model Exposed to Ti Particles in Aseptic Loosening

Aim

To investigate the different effects on osteolysis between commercial pure Ti particles and TiAl6V4 particles obtained from prosthesis of patients with aseptic loosening.

Method

Scanning electron microscope, energy dispersive X-ray spectrometry, and X-ray diffraction were used for the size test, chemical composition test, and phase analysis of two kinds of Ti particles. Microcomputed tomography (micro-CT) and 3-dimensional reconstruction analysis were applied to analyze the bone loss quantitatively and radiologically. Hematoxylin-eosin (HE) staining and tartrate-resistant acid phosphatase (TRAP) staining were used to assess the histologic difference.

Result

TiAl6V4 particles were constituted by FeO, Al₄₅V₇, and Al₃Ti while pure Ti particles were constituted by Ti, Ti₃O, and C₄H₇NO₃. Similar particle size of nanoscale was detected of two Ti particles. A TiAl6V4 osteolysis model had more severe bone loss when scanned with micro-CT and assessed by quantitative analysis. TiAl6V4 also presented deeper and wider calvarial bone loss in HE staining and more activated osteoclasts in TRAP staining.

Conclusion

A mouse calvarial model is the most effective animal model for the primary in vivo research of aseptic loosening. Compared with commercial Ti particles, TiAl6V4 particles derived from prosthesis of an aseptic loosening patient had more severe bone loss and more activated osteoclast, which was more consistent with pathogenesis of aseptic loosening in vivo, had high success rate of establishment of a model, and was more desired in animal modeling.

The Effects of Biomaterial Implant Wear Debris on Osteoblasts

Aseptic loosening subsequent to periprosthetic osteolysis is the leading cause for the revision of arthroplasty failure. The biological response of macrophages to wear debris has been well established, however, the equilibrium of bone remodeling is not only dictated by osteoclastic bone resorption but also by osteoblast-mediated bone formation. Increasing evidence shows that wear debris significantly impair osteoblastic physiology and subsequent bone formation. In the present review, we update the current state of knowledge regarding the effect of biomaterial implant wear debris on osteoblasts. The interaction of osteoblasts with osteoclasts and macrophages under wear debris challenge, and potential treatment options targeting osteoblasts are also presented.