Immunohistochemical localization of Nox1, Nox4 and Mn-SOD in mouse femur during endochondral ossification

Mechanisms of chondrocyte regulated cell death in osteoarthritis: Focus on ROS-triggered ferroptosis, parthanatos, and oxeiptosis

Osteoarthritis (OA) is a common chronic inflammatory degenerative disease. Since chondrocytes are the only type of cells in cartilage, their survival is critical for maintaining cartilage morphology. This review offers a comprehensive analysis of how reactive oxygen species (ROS), including superoxide anions, hydrogen peroxide, hydroxyl radicals, nitric oxide, and their derivatives, affect cartilage homeostasis and trigger several novel modes of regulated cell death, including ferroptosis, parthanatos, and oxeiptosis, which may play roles in chondrocyte death and OA development. Moreover, we discuss potential therapeutic strategies to alleviate OA by scavenging ROS and provide new insight into the research and treatment of the role of regulated cell death in OA.

Suramin enhances chondrogenic properties by regulating the p67phox/PI3K/AKT/SOX9 signalling pathway

Aims

Autologous chondrocyte implantation (ACI) is a promising treatment for articular cartilage degeneration and injury; however, it requires a large number of human hyaline chondrocytes, which often undergo dedifferentiation during in vitro expansion. This study aimed to investigate the effect of suramin on chondrocyte differentiation and its underlying mechanism.

Methods

Porcine chondrocytes were treated with vehicle or various doses of suramin. The expression of collagen, type II, alpha 1 (COL2A1), aggrecan (ACAN); COL1A1; COL10A1; SRY-box transcription factor 9 (SOX9); nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX); interleukin (IL)-1β; tumour necrosis factor alpha (TNFα); IL-8; and matrix metallopeptidase 13 (MMP-13) in chondrocytes at both messenger RNA (mRNA) and protein levels was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot. In addition, the supplementation of suramin to redifferentiation medium for the culture of expanded chondrocytes in 3D pellets was evaluated. Glycosaminoglycan (GAG) and collagen production were evaluated by biochemical analyses and immunofluorescence, as well as by immunohistochemistry. The expression of reactive oxygen species (ROS) and NOX activity were assessed by luciferase reporter gene assay, immunofluorescence analysis, and flow cytometry. Mutagenesis analysis, Alcian blue staining, reverse transcriptase polymerase chain reaction (RT-PCR), and western blot assay were used to determine whether p67^phox was involved in suramin-enhanced chondrocyte phenotype maintenance.

Results

Suramin enhanced the COL2A1 and ACAN expression and lowered COL1A1 synthesis. Also, in 3D pellet culture GAG and COL2A1 production was significantly higher in pellets consisting of chondrocytes expanded with suramin compared to controls. Surprisingly, suramin also increased ROS generation, which is largely caused by enhanced NOX (p67^phox) activity and membrane translocation. Overexpression of p67^phox but not p67^phoxAD (deleting amino acid (a.a) 199 to 212) mutant, which does not support ROS production in chondrocytes, significantly enhanced chondrocyte phenotype maintenance, SOX9 expression, and AKT (S473) phosphorylation. Knockdown of p67^phox with its specific short hairpin (sh) RNA (shRNA) abolished the suramin-induced effects. Moreover, when these cells were treated with the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) inhibitor LY294002 or shRNA of AKT1, p67^phox-induced COL2A1 and ACAN expression was significantly inhibited.

Conclusion

Suramin could redifferentiate dedifferentiated chondrocytes dependent on p67^phox activation, which is mediated by the PI3K/AKT/SOX9 signalling pathway.

Cite this article: Bone Joint Res 2022;11(10):723–738.

Angelica gigas root ameliorates ischaemic stroke-induced brain injury in mice by activating the PI3K/AKT/mTOR and MAPK pathways

CONTEXT

Traditionally, the root of Angelica gigas Nakai (Umbelliferae), has long been used to treat ischaemic diseases and is considered safe in humans.

OBJECTIVE

To investigate the neuroprotective effects of a methanol extract of A. gigas root (AGmex) on the middle cerebral artery occlusion (MCAO)-induced brain injury in mice, and the underlying mechanisms.

MATERIALS AND METHODS

Two hours of transient MCAO (tMCAO) was induced in C57BL/6 mice (MCAO control group and AGmex groups), AGmex was administered to the AGmex group at 300-3,000 mg/kg bw at 1, 1, and 24 h before tMCAO or at 1000 mg/kg bw at 1 h before and after tMCAO. Infarction volumes, tissue staining, and western blotting were used to investigate the mechanism underlying the neuroprotective effects of AGmex.

RESULTS

The median effective dose (ED₅₀) could not be measured because the AGmex treatment did not reduce the infarction volume caused by 2 h of tMCAO to within 50%; however, pre-treatment with AGmex twice at 1,000 mg/kg bw before tMCAO significantly reduced the infarction volumes. The proteins related to cell growth, differentiation, and death were upregulated by this treatment, and the major recovery mechanisms appeared to involve the attenuation of the mitochondrial function of Bcl-2/Bax and activation of the PI3K/AKT/mTOR and MAPK signalling pathways in ischaemic neurons.

CONCLUSIONS

This study provides evidence supporting the use of A. gigas root against ischaemic stroke and suggests a novel developmental starting point for the treatment of ischaemic stroke.

Neuroprotective effects of Korean White ginseng and Red ginseng in an ischemic stroke mouse model

Background

Stroke is a neurological disorder characterized by brain tissue damage following a decrease in oxygen supply to brain due to blocked blood vessels. Reportedly, 80% of all stroke cases are classified as cerebral infarction, and the incidence rate of this condition increases with age. Herein, we compared the efficacies of Korean White ginseng (WG) and Korean Red Ginseng (RG) extracts (WGex and RGex, respectively) in an ischemic stroke mouse model and confirmed the underlying mechanisms of action.

Methods

Mice were orally administered WGex or RGex 1 h before middle cerebral artery occlusion (MCAO), for 2 h; the size of the infarct area was measured 24 h after MCAO induction. Then, the neurological deficit score was evaluated and the efficacies of the two extracts were compared. Finally, their mechanisms of action were confirmed with tissue staining and protein quantification.

Results

In the MCAO-induced ischemic stroke mouse model, WGex and RGex showed neuroprotective effects in the cortical region, with RGex demonstrating superior efficacy than WGex. Ginsenoside Rg1, a representative indicator substance, was not involved in mediating the effects of WGex and RGex.

Conclusion

WGex and RGex could alleviate the brain injury caused by ischemia/reperfusion, with RGex showing a more potent effect. At 1,000 mg/kg body weight, only RGex reduced cerebral infarction and edema, and both anti-inflammatory and anti-apoptotic pathways were involved in mediating these effects.

Redox control of chondrocyte differentiation and chondrogenesis

Chondrogenesis involves the recruitment and migration of mesenchymal cells, mesenchymal condensation, and chondrocyte differentiation and hypertrophy. Multiple factors precisely regulate chondrogenesis. Recent studies have demonstrated that the redox status of chondrocytes plays an essential role in the regulation of chondrocyte differentiation and chondrogenesis. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important factors that change the intracellular redox status. Physiological levels of ROS/RNS act as intracellular signals in chondrocytes, and oxidative stress impairs the metabolism of chondrocytes. Under physiological conditions, the balance between ROS/RNS production and elimination ensures that redox-sensitive signalling proteins function correctly. The redox homeostasis of chondrocytes ensures that they respond appropriately to endogenous and exogenous stimuli. This review focuses on the redox regulation of key signalling pathways and transcription factors that control chondrogenesis and chondrocyte differentiation. Additionally, the mechanism by which ROS/RNS regulate signalling proteins and transcription factors in chondrocytes is also reviewed.

NADPH oxidases in bone homeostasis and osteoporosis

Bone is a tissue with constant remodeling, where osteoblasts form and osteoclasts degrade bone. Both cell types are highly specialized in their function and both form from precursors and have to be replaced on a regular basis. This replacement represents one control level of bone homeostasis. The second important level would be the control of the function of osteoblasts and osteoclasts in order to keep the balance of bone -formation and -degradation. Both differentiation and control of cellular function are potentially redox sensitive processes. In fact, reactive oxygen species (ROS) are utilized by a wide range of cells for differentiation and control of cellular signaling and function. A major source of ROS is the family of NADPH oxidases. The sole function of those enzymes is the formation of ROS in a controlled and targeted manner. Importantly the members of the NADPH oxidase family differ in their localization and in the type and amount of ROS produced. Accordingly the impact of the members of the NADPH oxidase family on differentiation and function differs between cell types. This review will highlight the function of different NADPH oxidases in differentiation and function of bone cells and thereby will discuss the role of NADPH oxidases in bone homeostasis and osteoporosis.

NOX4 Deletion in Male Mice Exacerbates the Effect of Ethanol on Trabecular Bone and Osteoblastogenesis

Chronic alcohol consumption increases bone resorption and decreases bone formation. A major component of ethanol (EtOH) pathology in bone is the generation of excess reactive oxygen species (ROS). The ROS-generating NADPH oxidase-4 (NOX4) is proposed to drive much of the EtOH-induced suppression of bone formation. Here, 13-week-old male wild-type (WT) and NOX4^-/- mice were pair fed (PF) a high-fat (35%), Lieber-DeCarli liquid diet with or without EtOH at 30% of their total calories for 12 weeks. Micro-computed tomography analysis demonstrated significant decreases in trabecular bone volume/total volume (BV/TV) percentage and cortical thickness in WT, EtOH-fed mice compared with PF controls. EtOH-fed NOX4^-/- mice also displayed decreased trabecular BV/TV and trabecular number compared with PF (P < 0.05). However, NOX4^-/- mice were protected against EtOH-induced decreases in cortical thickness (P < 0.05) and decreases in collagen1 and osteocalcin mRNA expression in cortical bone (P < 0.05). In WT and NOX4^-/- vertebral bone, EtOH suppressed expression of Wnt signaling components that promote osteoblast maturation. A role for NOX4 in EtOH inhibition of osteoblast differentiation was further demonstrated by protection against EtOH inhibition of osteoblastogenesis in ex vivo bone marrow cultures from NOX4^-/-, but not p47^phox-/- mice lacking active NADPH oxidase-2. However, bone marrow cultures from NOX4^-/- mice formed fewer osteoblastic colonies compared with WT cultures (P < 0.05), suggesting a role for NOX4 in the maintenance of mesenchymal progenitor cell populations. These data suggest that NOX4 deletion is partially protective against EtOH effects on osteoblast differentiation, but may predispose bone to osteogenic impairments.

Role of Reactive Oxygen Species during Low-Intensity Pulsed Ultrasound Application in MC-3 T3 E1 Pre-osteoblast Cell Culture

We evaluated the activation of mitogen-activated protein kinase (MAPK) activation through reactive oxygen species (ROS) by application of low-intensity ultrasound (LIPUS) to MC-3 T3 E1 pre-osteoblasts. The cells were subjected to one LIPUS application for either 10 or 20 min, and the control group was exposed to a sham transducer. For ROS inhibition, 10 μM diphenylene iodonium (DPI) was added to the cells an hour before LIPUS application. Samples were collected 1, 3, 6, 12 and 24 h after LIPUS application, and cells were evaluated for ROS generation, cell viability, gene expression and MAPK activation by immunoblot analyses. LIPUS caused a significant increase in ROS and cell viability in the non-DPI-treated group. Expression of RUNX2, OCN and OPN mRNA was higher in the LIPUS-treated groups at 1 h in both the DPI-treated and non-DPI-treated groups; RUNX2 and OCN mRNA levels increased at 6 h. ERK1/2 activation was increased in the LIPUS-treated groups. These results indicate that LIPUS activates MAPK by ROS generation in MC-3 T3 E1 pre-osteoblasts.

Identification of stiffness-induced signalling mechanisms in cells from patent and fused sutures associated with craniosynostosis

Craniosynostosis is a bone developmental disease where premature ossification of the cranial sutures occurs leading to fused sutures. While biomechanical forces have been implicated in craniosynostosis, evidence of the effect of microenvironmental stiffness changes in the osteogenic commitment of cells from the sutures is lacking. Our aim was to identify the differential genetic expression and osteogenic capability between cells from patent and fused sutures of children with craniosynostosis and whether these differences are driven by changes in the stiffness of the microenvironment. Cells from both sutures demonstrated enhanced mineralisation with increasing substrate stiffness showing that stiffness is a stimulus capable of triggering the accelerated osteogenic commitment of the cells from patent to fused stages. The differences in the mechanoresponse of these cells were further investigated with a PCR array showing stiffness-dependent upregulation of genes mediating growth and bone development (TSHZ2, IGF1), involved in the breakdown of extracellular matrix (MMP9), mediating the activation of inflammation (IL1β) and controlling osteogenic differentiation (WIF1, BMP6, NOX1) in cells from fused sutures. In summary, this study indicates that stiffer substrates lead to greater osteogenic commitment and accelerated bone formation, suggesting that stiffening of the extracellular environment may trigger the premature ossification of the sutures.

Lymphangiogenesis and NOS Localization in Healing Process after Tooth Extraction in Akita Mouse

Type I diabetes, an autoimmune disease, induces insulin deficiency, which then disrupts vascular endothelial cell function, affecting blood and lymphatic vessels. Nitric oxide (NO) is an immune-induced destructive mediator in type I diabetes, and inhibition of its production promotes arteriosclerosis. In this study, lymphangiogenesis and expression of NO synthase (NOS) during the healing process after tooth extraction were investigated immunohistochemically in control (C57BL) and Akita mice as a diabetes model. Between 1, 4, and 10 days after extraction, expression of NOS, vascular endothelial growth factor-C (VEGF-C), VEGF receptor-3 (VEGFR-3), and von Willebrand factor was strongest during the granulation tissue phase. This suggests that severe inflammation triggers regulation of NOS and these other angiogenic and lymphangiogenic factors. During the callus phase, a few days after extraction, induced osteoblasts were positive for VEGF-C and VEGFR-3 in both the control and Akita mice, suggesting that bone formation is active in this period. Bone formation in the Akita group exceeded that in the controls. Bone tissue formation was disrupted under hyperglycemic conditions, however, suggesting that such activity would be insufficient to produce new bone.

Production and physiological role of NO in the oral cavity

Nitric oxide (NO) is a free radical which is produced from a wide variety of cells and tissues in the human body. NO is involved in the regulation of many physiological processes, such as vascular relaxation, neurotransmission, immune regulation, and cell death. NO is generated by nitric oxide synthase (NOS), which has three identified isoforms: neuronal type NOS (nNOS), endothelial type NOS (eNOS), and inducible type NOS (iNOS). Different isoforms are expressed depending on the organs, tissues, and cells, and investigation of the types and functions of enzymes expressed in various tissues is underway. The oral cavity is a space in which marked changes have been detected in NO levels, and each tissue is constantly influenced by NO. NO is a component of saliva and is produced by oral bacteria in the oral cavity and released by NOS expressed in oral mucosa. NOS isoforms expressed under normal conditions differ among the oral organs. In addition, the overexpression of NOS was involved in carcinogenesis and tumor growth progression. This review summarized the expression of NOS and functions of NO in oral cavity organs, and their roles in diseases and the influences of treatments.