Antioxidant effect of bisphosphonates and simvastatin on chondrocyte lipid peroxidation

Ferroptosis and its implications in bone-related diseases

Ferroptosis, a recently recognized form of regulated cell death (RCD) characterized by iron-dependent lipid peroxide accumulation, has emerged as a noteworthy regulator in various bone-related diseases, including osteoporosis (OP), osteoarthritis (OA), and osteosarcoma (OS). OS primarily afflicts the elderly, rendering them susceptible to fractures due to increased bone fragility. OA represents the most prevalent arthritis in the world, often observed in the aging population. OS predominantly manifests during adolescence, exhibiting an aggressive nature and bearing a significantly unfavorable prognosis. In this review article, we present an overview of the characteristics and mechanism of ferroptosis and its involvement in bone-related diseases, with a particular focus on OP, OA, and OS. Furthermore, we summarize chemical compounds or biological factors that impact bone-related diseases by regulating ferroptosis. Through an in-depth exploration of ferroptosis based on current research findings, this review provides promising insights for potential therapeutic approaches to effectively manage and mitigate the impact of these bone-related pathological conditions.

The Role Played by Ferroptosis in Osteoarthritis: Evidence Based on Iron Dyshomeostasis and Lipid Peroxidation

Ferroptosis, a recently discovered regulated cell death modality, is characterised by iron-dependent accumulation of lipid hydroperoxides, which can reach lethal levels but can be specifically reversed by ferroptosis inhibitors. Osteoarthritis (OA), the most common degenerative joint disease, is characterised by a complex pathogenesis involving mechanical overload, increased inflammatory mediator levels, metabolic alterations, and cell senescence and death. Since iron accumulation and oxidative stress are the universal pathological features of OA, the role played by ferroptosis in OA has been extensively explored. Increasing evidence has shown that iron dyshomeostasis and lipid peroxidation are closely associated with OA pathogenesis. Therefore, in this review, we summarize recent evidence by focusing on ferroptotic mechanisms and the role played by ferroptosis in OA pathogenesis from the perspectives of clinical findings, animal models, and cell research. By summarizing recent research advances that characterize the relationship between ferroptosis and OA, we highlight avenues for further research and potential therapeutic targets.

Low-Molecular-Weight Synthetic Antioxidants: Classification, Pharmacological Profile, Effectiveness and Trends

Mounting research has been performed and published on natural antioxidants, more so than on synthetic ones, as key molecules that control oxidative damage and its pathway to disease. Since the discovery of vitamins, various fully synthetic or natural-identical compounds have been developed as stable small molecules translated into constantly active and completely controlled products which are widely exploited in the food and pharmaceutical industries. There is currently a debate within the literature about their mechanism of action, bioavailability, safety and real benefit for human health. Using a semiquantitative method and eligible criteria of selection, this review aimed to provide a very useful classification of antioxidants and a comprehensive cross-disciplinary description of 32 approved synthetic/natural-identical antioxidants, in terms of regulatory, antioxidant mechanism of action, safety issues, pharmacological properties, effectiveness in human health, timeline and future trends. Enriched interpretation of the data was obtained from summary bibliometrics, useful to portray the “good antioxidant” within the period 1966–2021 and, hopefully, to encourage further research.

Lactoferrin with Zn-ion protects and recovers fibroblast from H2O2-induced oxidative damage

Lactoferrin (LF) has attracted great attention due to its various bioactivities, which depend on the degree of saturation with different cations. This study focused on the synergistic effect of LF and Zn²⁺ on human gingival fibroblasts (hGFs), considering antioxidant activities, cell proliferation, and collagen gene expression levels in these cells to improve the wound healing. The hGFs were cultured in an experimental medium, containing 1000 μg/mL of LF and various concentrations of ZnCl₂. The cells were subjected to oxidative damage by exposure to 600 μM H₂O₂ for 30 min before incubation in the experimental medium. The cell proliferation rate and the relative gene expression levels of genes associated with apoptosis, antioxidant enzymes, and collagen were compared. H₂O₂ decomposition by LF was also measured using a colorimetric assay. LF enhanced hGF proliferation and the expression of collagen. Furthermore, LF directly scavenged H₂O₂ and prevented lipid peroxidation by enhancing the expression of glutathione peroxidase 4 gene expression, resulting in the prevention of apoptosis and recovery of the cells from H₂O₂-induced oxidative damage. The addition of ZnCl₂ enhanced these results. The results indicated that LF with Zn-ion could play an important role in modulating the functions related to wound healing.

Alendronate sodium-polymeric nanoparticles display low toxicity in gastric mucosal of rats and Ofcol II cells

The use of bisphosphonates constitutes the gold-standard therapy for the control and treatment of bone diseases. However, its long-term use may lead to gastric problems, which limits the treatment. Thus, this study aimed to formulate a nanostructured system with biodegradable polymers for the controlled release of alendronate sodium. The nanoparticles were characterized, and its gastric toxicity was investigated in rats. The synthesis process proved to be effective for encapsulating alendronate sodium, exhibiting nanoparticles with an average size of 51.02 nm and 98.5% of alendronate sodium incorporation. The release tests demonstrated a controlled release of the drug in 420 min, while the morphological analyzes showed spherical shapes and no apparent roughness. The biological tests demonstrated that the alendronate sodium nanoformulation reversed the gastric lesions, maintaining the normal levels of malondialdehyde and myeloperoxidase. Also, the encapsulated alendronate sodium showed no toxicity in murine osteoblastic cells, even at high concentrations.

Role of subchondral bone properties and changes in development of load-induced osteoarthritis in mice

OBJECTIVE

Animal models recapitulating post-traumatic osteoarthritis (OA) suggest that subchondral bone (SCB) properties and remodeling may play major roles in disease initiation and progression. Thus, we investigated the role of SCB properties and its effects on load-induced OA progression by applying a tibial loading model on two distinct mouse strains treated with alendronate (ALN).

DESIGN

Cyclic compression was applied to the left tibia of 26-week-old male C57Bl/6 (B6, low bone mass) and FVB (high bone mass) mice. Mice were treated with ALN (26 μg/kg/day) or vehicle (VEH) for loading durations of 1, 2, or 6 weeks. Changes in articular cartilage and subchondral and epiphyseal cancellous bone were analyzed using histology and microcomputed tomography.

RESULTS

FVB mice exhibited thicker cartilage, a thicker SCB plate, and higher epiphyseal cancellous bone mass and tissue mineral density than B6 mice. Loading induced cartilage pathology, osteophyte formation, and SCB changes; however, lower initial SCB mass and stiffness in B6 mice did not attenuate load-induced OA severity compared to FVB mice. By contrast, FVB mice exhibited less cartilage damage, and slower-growing and less mature osteophytes. In B6 mice, inhibiting bone remodeling via ALN treatment exacerbated cartilage pathology after 6 weeks of loading, while in FVB mice, inhibiting bone remodeling protected limbs from load-induced cartilage loss.

CONCLUSIONS

Intrinsically lower SCB properties were not associated with attenuated load-induced cartilage loss. However, inhibiting bone remodeling produced differential patterns of OA pathology in animals with low compared to high SCB properties, indicating that these factors do influence load-induced OA progression.

A new flow cytometry method to measure oxidative status: the Peroxidation of Leukocytes Index Ratio (PLIR)

BACKGROUND AND AIM

A complex relationship between immune system and metabolic pathway exists and can induce oxidative stress. The objective of this study was to design a new methodology allowing the measurement of oxidative status of leukocytes.

METHODS AND RESULTS

We developed a flow cytometry technique, based on C11-BODIPY 581/591 staining, to evaluate peroxidation in leukocytes. We defined the Peroxidation of Leukocytes Index Ratio (PLIR) as the ratio between the damage after AAPH-induced and PMA-induced peroxidation, using Trolox as standard antioxidant. Sensitivity of the method was assessed by correlating results with plasma antioxidant capacity (TRAP and FRAP), levels of endogenous antioxidants (uric acid and sulfhydryls) and markers of metabolic status (cholesterol, triglycerides, glucose and insulin). PLIR measures the ratio between the resistance to exogenous and endogenous ROS injury, independently from baseline level of oxidation, which was directly correlated with plasma cholesterol on lymphocytes (0.738, p=0.029), monocytes (0.691, p=0.047) and neutrophils (0.690, p=0.047). PLIR of lymphocytes was inversely correlated with uric acid (-0.810, p=0.009) and FRAP (-0.738, p=0.029) levels. On the other hand, PLIR of monocytes was directly correlated with the total scavenger antioxidant capacity attributable to nutritional antioxidants (0.738, p=0.029), calculated as the difference between TRAP and the contribution of uric acid and sulfhydryls to its value.

CONCLUSIONS

This study reports a feasible and reproducible new flow cytometry assay for assessing the leukocytes redox status. PLIR discriminates between reducing and scavenger activities and is able to appreciate the potentially dangerous effect of uric acid on innate immune response.

Modulating P2X7 Receptor Signaling during Rheumatoid Arthritis: New Therapeutic Approaches for Bisphosphonates

P2X7 receptor-mediated purinergic signaling is a well-known mechanism involved in bone remodeling. The P2X7 receptor has been implicated in the pathophysiology of various bone and cartilage diseases, including rheumatoid arthritis (RA), a widespread and complex chronic inflammatory disorder. The P2X7 receptor induces the release into the synovial fluid of the proinflammatory factors (e.g., interleukin-1β, prostaglandins, and proteases) responsible for the clinical symptoms of RA. Thus, the P2X7 receptor is emerging as a novel anti-inflammatory therapeutic target, and various selective P2X7 receptor antagonists are under clinical trials. Extracellular ATP signaling acting through the P2X7 receptor is a complex and dynamic scenario, which varies over the course of inflammation. This signaling is partially modulated by the activity of ectonucleotidases, which degrade extracellular ATP to generate other active molecules such as adenosine or pyrophosphates. Recent evidence suggests differential extracellular metabolism of ATP during the resolution of inflammation to generate pyrophosphates. Extracellular pyrophosphate dampens proinflammatory signaling by promoting alternative macrophage activation. Our paper shows that bisphosphonates are metabolically stable pyrophosphate analogues that are able to mimic the anti-inflammatory function of pyrophosphates. Bisphosphonates are arising per se as promising anti-inflammatory drugs to treat RA, and this therapy could be improved when administrated in combination with P2X7 receptor antagonists.

The effect of alendronate sodium on human erythrocytes

Alendronate sodium is a medicine, which is commonly used in osteoporosis treatment. Nowadays, this substance is given to patients in tablets, but in future it is planned that it will be administrated into human organisms as intravenous infusions; therefore, significant interactions of this medicine with erythrocytes will be inevitable. It is the reason why we decided to investigate the interaction of alendronate sodium with human erythrocytes. The effect of this medicine on acetylcholinesterase activity, lipid and protein peroxidation, as well as cellular thiol content was examined. Moreover, the effect of alendronate sodium on alterations in erythrocytes morphology was assessed. Human erythrocytes were incubated with alendronate sodium in the concentrations ranging from 0.33 to 100 μM for 1 h and 24 h. No changes have been observed in the parameters examined after 1h of incubation of the erythrocytes with this medicine excluding the carbonyl groups level. Moreover, no alterations in the activity of acetylcholinesterase, the level of thiols as well as in morphology of the erythrocytes incubated with alendronate sodium for 24h have been observed. It was also proven that alendronate sodium increased the level of reactive oxygen species (ROS) but only after 24h of incubation. We have not observed any severe changes in cells studied even at the highest dose of bisphosphonates examined, thus their usage should not be dangerous for the erythrocytes of people treated with these medicines.

Novel macrophage polarization model: from gene expression to identification of new anti-inflammatory molecules

Plasticity is a well-known property of macrophages that is controlled by different changes in environmental signals. Macrophage polarization is regarded as a spectrum of activation phenotypes adjusted from one activation extreme, the classic (M1), to the other, the alternative (M2) activation. Here we show, in vitro and in vivo, that both M1 and M2 macrophage phenotypes are tightly coupled to specific patterns of gene expression. Novel M2-associated markers were characterized and identified as genes controlling the extracellular metabolism of ATP to generate pyrophosphates (PPi). Stimulation of M1 macrophages with PPi dampens both NLR and TLR signaling and thus mediates cytokine production. In this context extracellular PPi enhanced the resolution phase of a murine peritonitis model via a decrease in pro-inflammatory cytokine production. Therefore, our study reveals an additional level of plasticity modulating the resolution of inflammation.

Statins and the joint: multiple targets for a global protection?

OBJECTIVES

Evidence exists that the pleiotropic properties of the hydroxy-methyl-glutaryl Coenzyme A reductase inhibitors (statins) are not restricted to the cardiovascular system, as they can also favorably affect the joints, with intriguing implications for the treatment of many rheumatic diseases. In the view of the increasing interest on this topic, we here review the current state of the art.

METHODS

The PubMed database was searched for articles published between 1966 and 2010 for key words referring to statins and joint diseases. All relevant English-written articles were reviewed.

RESULTS

Many pivotal studies clearly demonstrated that HMG-CoA reductase inhibitors exert a wide spectrum of beneficial effects on the 3 main compartments of the joint, ie, the synovium, the cartilage, and the subchondral bone. Such (1) anti-inflammatory, (2) immunomodulating, and (3) anabolic effects strongly support a potential role of these drugs in the treatment and/or the prevention of the most important chronic joint diseases. However, although the majority of the in vivo studies with statins on animal models of inflammatory and degenerative joint diseases showed a marked protective activity substantially confirming the in vitro experiments, data arising from clinical trials are less probative and more conflicting.

CONCLUSIONS

Statins display multiple joint-protective effects. Since oral administration of statins could result in a relatively low drug bioavailability to the joints, alternative routes of administration of the drug (transdermal, intra-articular) and/or specific delivery systems should be developed to establish the entire therapeutic potential of statins in this clinical setting.

Positive effect of alendronate on subchondral bone healing and subsequent cartilage repair in a rabbit osteochondral defect model

BACKGROUND

Cartilage and subchondral bone have recently been considered an osteochondral unit. The treatment of osteochondral lesions is still challenging, but better subchondral bone repair may result in higher quality repaired cartilage.

HYPOTHESES

Alendronate accelerates bone formation in osteochondral defects and affects the quality of the repaired cartilage.

STUDY DESIGN

Controlled laboratory study.

METHODS

Osteochondral defects were made on the left trochleas of 50 rabbits, which were assigned to 1 of 3 groups: control, ALN (weekly subcutaneous injection of 0.14 mg/mL alendronate), and ALN-S (alendronate injection in the first 8 weeks only). They were evaluated at 4, 8, 24, and 52 weeks. Bone repair was evaluated with microcomputed tomography and histologic evaluation. Cartilage repair was evaluated with ultrasound and histologic analyses.

RESULTS

At 4 weeks, the defects were filled, and cartilage-like repair tissue was observed in the ALN group, whereas the defects were incompletely filled in the control group. Alendronate treatment enhanced early bone formation and mineralization in the osteochondral defect for the first 8 weeks. The continuous injection of alendronate for 24 weeks resulted in delayed bone remodeling, but the rabbits in the ALN-S group showed good integrity of the subchondral bone plate, without delayed remodeling. At 52 weeks, the ALN-S group had a columnar arrangement of chondrocytes that had less fibrillation and looked superior to those in the ALN and control groups. Ultrasound analysis showed better quality of repaired cartilage of the ALN and ALN-S group than the control group.

CONCLUSION

Alendronate accelerated bone formation without inhibiting its mineralization but thereafter inhibited bone remodeling in an osteochondral defect. The withdrawal of alendronate at 8 weeks avoided the delayed remodeling and showed better subchondral bone repair. At 52 weeks, better subchondral bone repair resulted in better cartilage quality.

CLINICAL RELEVANCE

Alendronate administered in the early period accelerates bone formation and improves the quality of the repaired cartilage.

Dynamics of macrophage polarization reveal new mechanism to inhibit IL-1beta release through pyrophosphates

In acute inflammation, extracellular ATP activates P2X₇ ion channel receptors (P2X₇R) on M1 polarized macrophages to release pro-inflammatory IL-1β through activation of the caspase-1/nucleotide-binding domain and leucine-rich repeat receptor containing pyrin domain 3 (NLRP3) inflammasome. In contrast, M2 polarized macrophages are critical to the resolution of inflammation but neither actions of P2X₇R on these macrophages nor mechanisms by which macrophages switch from pro-inflammatory to anti-inflammatory phenotypes are known. Here, we investigated extracellular ATP signalling over a dynamic macrophage polarity gradient from M1 through M2 phenotypes. In macrophages polarized towards, but not at, M2 phenotype, in which intracellular IL-1β remains high and the inflammasome is intact, P2X₇R activation selectively uncouples to the NLRP3-inflammasome activation but not to upstream ion channel activation. In these intermediate M1/M2 polarized macrophages, extracellular ATP now acts through its pyrophosphate chains, independently of other purine receptors, to inhibit IL-1β release by other stimuli through two independent mechanisms: inhibition of ROS production and trapping of the inflammasome complex through intracellular clustering of actin filaments.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.