ATF3 Regulates Osteogenic Function by Mediating Osteoblast Ferroptosis in Type 2 Diabetic Osteoporosis

ATF3 as a response factor to regulate Cd-induced reproductive damage by activating the NRF2/HO-1 ferroptosis pathway

Cadmium (Cd) has garnered significant attention due to reproductive toxicity in inducing ferroptosis. However, the specific mechanisms underlying Cd-induced germ cell ferroptosis remain poorly understood. This study aimed to systematically explore the molecular mechanisms of germ cell ferroptosis by investigating differential changes in transcription factors and proteins in male mice treated orally with CdCl2 (0.5 g/L) reaching postnatal day 60, alongside Leydig cell (TM3) and Sertoli cell (TM4) lines. Results demonstrated that Cd exposure led to increased iron overload and oxidative stress in mouse testes, disrupted intracellular mitochondrial morphology characteristic of ferroptosis. RNA sequencing revealed significant upregulation of Atf3 and Hmox1 in Cd-exposed germ cells, along with increased expression of ATF3 and HO-1. Intervention in ferroptosis or HO-1 effectively rescued cells from Cd-induced mortality by breaking the detrimental cycle between lipid peroxidation and HO-1 activation. Further findings showed that NRF2 and HO-1 expression was notably elevated upon ATF3 overexpression in TM3 and TM4 cells, activating the Keap1-Nrf2 pathway and triggering ferroptosis in testes, whereas NRF2 and HO-1 expression levels were reversed when ATF3 was silenced. This study provides novel insights into ATF3-mediated NRF2/HO-1 signaling in Cd-induced mitochondrial ferroptosis in testes, shedding light on the mechanisms underlying Cd-induced ferroptosis and testicular injury.

Exploring the pharmacological mechanism of Xianlingubao against diabetic osteoporosis based on network pharmacology and molecular docking: An observational study

Xianlinggubao formula (XLGB), is a traditional Chinese compound Medicine that has been extensively used in osteoarthritis and aseptic osteonecrosis, but its curative effect on diabetic osteoporosis (DOP) and its pharmacological mechanisms remains not clear. The aim of the present study was to investigate the possible mechanism of drug repurposing of XLGB in DOP therapy. We acquired XLGB active compounds from the traditional Chinese medicine systems pharmacology and traditional Chinese medicines integrated databases and discovered potential targets for these compounds by conducting target fishing using the traditional Chinese medicine systems pharmacology and Swiss Target Prediction databases. Gene Cards and Online Mendelian Inheritance in Man® database were used to identify the DOP targets. Overlapping related targets between XLGB and DOP was selected to build a protein-protein interaction network. Next, the Metascape database was utilized to enrich the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. In addition, Auto-Dock Vina software was used to verify drug and target binding. In total, 48 hub targets were obtained as the candidate targets responsible for DOP therapy. The anti-DOP effect mediated by XLGB was primarily centralized on the advanced glycation end products (AGEs)-receptor for AGE signaling pathway in diabetic complications and osteoclast differentiation. In addition, AKT serine/threonine kinase 1, tumor necrosis factor, Interleukin-6, vascular endothelial growth factor A and peroxisome proliferator activated receptor gamma, which were considered as potential therapeutic targets. Furthermore, molecular docking results confirm the credibility of the predicted therapeutic targets. This study elucidates that XLGB may through regulating AGEs formation and osteoclast differentiation as well as angiogenesis and adipogenesis against DOP. And this study provides new promising points to find the exact regulatory mechanisms of XLGB mediated anti-DOP effect.

Berberine ameliorates nonalcoholic fatty liver disease-induced bone loss by inhibiting ferroptosis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) may contribute to osteoporosis. Berberine is a traditional Chinese medicine and was recently shown to be beneficial in NAFLD. However, little is known about its impact on bone loss induced by NAFLD.

AIM

We aimed to explore the role of berberine in bone loss and determine its underlying mechanisms in NAFLD.

METHODS

C57BL/6 mice were fed a high-fat high-fructose high-glucose diet (HFFGD) for 16 weeks to establish a NAFLD mouse model. The mice were administered berberine (300 mg/kg/d) by gavage, and fatty liver levels and bone loss indicators were tested.

RESULTS

Berberine significantly improved HFFGD-induced weight gain, hepatic lipid accumulation and increases in serum liver enzymes, thereby alleviating NAFLD. Berberine increased trabecular number (Tb. N), trabecular thickness (Tb. Th), bone volume to tissue volume ratio (BV/TV), and decreased trabecular separation (Tb. Sp) and restored bone loss in NAFLD. Mechanistically, berberine significantly inhibited ferroptosis and 4-hydroxynonenal (4-HNE), prostaglandin-endoperoxide synthase 2 (PTGS2), and transferrin (TF) levels and increased ferritin heavy chain (FTH) levels in the femurs of HFFGD-fed mice. Moreover, berberine also activated the solute carrier family 7 member 11 (SLC7A11)/glutathione (GSH)/glutathione peroxidase 4 (GPX4) signaling pathway.

CONCLUSION

Berberine significantly ameliorates bone loss induced by NAFLD by activating the SLC7A11/GSH/GPX4 signaling pathway and inhibiting ferroptosis. Therefore, berberine may serve as a therapeutic agent for NAFLD-induced bone loss.

Research progress on the regulatory cell death of osteoblasts in periodontitis

Periodontitis is a chronic inflammatory disease characterized by progressive destruction of alveolar bone. The most critical mechanism underlying alveolar bone destruction is the imbalance of bone homeostasis, where osteoblast-mediated bone matrix synthesis plays an important role in regulating bone homeostasis. Regulatory cell death is instrumental in both the inflammatory microenvironment and the regulation of bone homeostasis. Chronic inflammation, oxidative stress, and other factors can be directly involved in mitochondrial and death receptor-mediated signaling pathways, modulating B-cell lymphoma 2 (Bcl-2) family proteins and cysteine aspartic acid specific protease (caspase) activity, thereby affecting osteoblast apoptosis and alveolar bone homeostasis. Chronic inflammation and cellular damage induce osteoblast necroptosis via the RIPK1/RIPK3/MLKL signaling pathway, exacerbating the inflammatory response and accelerating alveolar bone destruction. Stimuli such as pathogenic microorganisms and cellular injury may also activate caspase-1-dependent or independent signaling pathways and gasdermin D (GSDMD) family proteins, promoting osteoblast pyroptosis and releasing pro-inflammatory cytokines to mediate alveolar bone damage. Iron overload and lipid peroxidation in periodontitis can trigger ferroptosis in osteoblasts, impacting their survival and function, ultimately leading to bone homeostasis imbalance. This article focuses on the mechanism of periodontal disease affecting bone homeostasis through regulatory cell death, aiming to provide research evidence for the treatment of periodontitis and alveolar bone homeostasis imbalance.

Lipolysis products from triglyceride-rich lipoproteins induce stress protein ATF3 in osteoblasts

High fat diets overwhelm the physiological mechanisms for absorption, storage, and utilization of triglycerides (TG); consequently TG, TG-rich lipoproteins (TGRL), and TGRL remnants accumulate, circulate systemically, producing dyslipidemia. This associates with, or is causative for increased atherosclerotic cardiovascular risk, ischemic stroke, fatty liver disease, and pancreatitis. TGRL hydrolysis by endothelial surface-bound lipoprotein lipase (LPL) generates metabolites like free fatty acids which have proinflammatory properties. While osteoblasts utilize fatty acids as an energy source, dyslipidemia is associated with negative effects on the skeleton. In this study we investigated the effects of TGRL lipolysis products (TGRL-LP) on expression of a stress responsive transcription factor, termed activating transcription factor 3 (ATF3), reactive oxygen species (ROS), ATF3 target genes, and angiopoietin-like 4 (Angptl4) in osteoblasts. As ATF3 negatively associates with osteoblast differentiation, we also investigated the skeletal effects of global ATF3 deletion in mice. TGRL-LP increased expression of Atf3, proinflammatory proteins Ptgs2 and IL-6, and induced ROS in MC3T3-E1 osteoblastic cells. Angptl4 is an endogenous inhibitor of LPL which was transcriptionally induced by TGRL-LP, while recombinant Angptl4 prevented TG-driven Atf3 induction. Atf3 global knockout male mice demonstrated increased trabecular and cortical microarchitectural parameters. In summary, we find that TGRL-LP induce osteoblastic cell stress as evidenced by expression of ATF3, which may contribute to the negative impact of dyslipidemia in the skeleton. Further, concomitant induction of Angptl4 in osteoblasts might play a protective role by reducing local lipolysis.

Type 2 diabetic mellitus related osteoporosis: focusing on ferroptosis

With the aging global population, type 2 diabetes mellitus (T2DM) and osteoporosis(OP) are becoming increasingly prevalent. Diabetic osteoporosis (DOP) is a metabolic bone disorder characterized by abnormal bone tissue structure and reduced bone strength in patients with diabetes. Studies have revealed a close association among diabetes, increased fracture risk, and disturbances in iron metabolism. This review explores the concept of ferroptosis, a non-apoptotic cell death process dependent on intracellular iron, focusing on its role in DOP. Iron-dependent lipid peroxidation, particularly impacting pancreatic β-cells, osteoblasts (OBs) and osteoclasts (OCs), contributes to DOP. The intricate interplay between iron dysregulation, which comprises deficiency and overload, and DOP has been discussed, emphasizing how excessive iron accumulation triggers ferroptosis in DOP. This concise overview highlights the need to understand the complex relationship between T2DM and OP, particularly ferroptosis. This review aimed to elucidate the pathogenesis of ferroptosis in DOP and provide a prospective for future research targeting interventions in the field of ferroptosis.

FNDC5/irisin ameliorates bone loss of type 1 diabetes by suppressing endoplasmic reticulum stress‑mediated ferroptosis

BACKGROUND

Ferroptosis is known to play a crucial role in diabetic osteopathy. However, key genes and molecular mechanisms remain largely unclear. This study aimed to identify a crucial ferroptosis-related differentially expressed gene (FR-DEG) in diabetic osteopathy and investigate its potential mechanism.

METHODS

We identified fibronectin type III domain-containing protein 5 (FNDC5)/irisin as an essential FR-DEG in diabetic osteopathy using the Ferroptosis Database (FerrDb) and GSE189112 dataset. Initially, a diabetic mouse model was induced by intraperitoneal injection of streptozotocin (STZ), followed by intraperitoneal injection of irisin. MC3T3-E1 cells treated with high glucose (HG) were used as an in vitro model. FNDC5 overexpression plasmid was used to explore underlying mechanisms in vitro experiments. Femurs were collected for micro-CT scan, histomorphometry, and immunohistochemical analysis. Peripheral serum was collected for ELISA analysis. Cell viability was assessed using a CCK-8 kit. The levels of glutathione (GSH), malondialdehyde (MDA), iron, reactive oxygen species (ROS), and lipid ROS were detected by the corresponding kits. Mitochondria ultrastructure was observed through transmission electron microscopy (TEM). Finally, mRNA and protein expressions were examined by quantitative real-time PCR (qRT-PCR) and western blot analysis.

RESULTS

The expression of FNDC5 was found to be significantly decreased in both in vivo and in vitro models. Treatment with irisin significantly suppressed ferroptosis and improved bone loss. This was demonstrated by reduced lipid peroxidation and iron overload, increased antioxidant capability, as well as the inhibition of the ferroptosis pathway in bone tissues. Furthermore, in vitro studies demonstrated that FNDC5 overexpression significantly improved HG-induced ferroptosis and promoted osteogenesis. Mechanistic investigations revealed that FNDC5 overexpression mitigated ferroptosis in osteoblasts by inhibiting the eukaryotic initiation factor 2 alpha (eIF2α)/activated transcription factor 4 (ATF4)/C/EBP-homologous protein (CHOP) pathway.

CONCLUSIONS

Collectively, our study uncovered the important role of FNDC5/irisin in regulating ferroptosis of diabetic osteopathy, which might be a potential therapeutic target.

Fructus Ligustri Lucidi inhibits ferroptosis in ovariectomy‑induced osteoporosis in rats via the Nrf2/HO‑1 signaling pathway

Postmenopausal osteoporosis (PMOP) has increased in prevalence in recent years, thus researchers have evaluated alternative medicine therapies. Fructus Ligustri Lucidi (FLL) can inhibit bone loss, and ferroptosis serves an important role in osteoporosis. Therefore, the present study assessed the presence of ferroptosis in PMOP and whether FLL could inhibit ferroptosis to improve bone microstructure in ovariectomized rats. Ovariectomized rats were treated with FLL (1.56 g/kg/day) for 12 weeks. Micro-CT was performed to evaluate the bone microstructure and bone mineral density. Western blotting and reverse transcription-quantitative PCR were performed to assess the relative expression levels of proteins and mRNA. Subsequently, malondialdehyde (MDA) and Fe2+ assay kits were used to quantify the MDA and Fe2+ content, respectively. The results demonstrated that ovariectomy (OVX) resulted in iron overload and the accumulation of lipid peroxide. Furthermore, the expression of key factors that inhibited ferroptosis, glutathione peroxidase 4 and solute carrier family 7 member 11 was significantly downregulated in ovariectomized rats, which was significantly reversed by FLL treatment. Furthermore, bone formation was assessed using the expression of osteogenesis-related genes, runt-related transcription factor 2 and osterix, which revealed significantly higher levels in FLL-treated rats compared with ovariectomized rats. The levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were also significantly recovered following FLL treatment. In the present study, OVX of postmenopausal osteoporotic rats was found to induce ferroptosis by enhancing lipid peroxidation and Fe2+ levels. FLL significantly suppressed ferroptosis, protected the osteogenic ability of ovariectomized rats and promoted the Nrf2/HO-1 signaling pathway.

The Dual Roles of Activating Transcription Factor 3 (ATF3) in Inflammation, Apoptosis, Ferroptosis, and Pathogen Infection Responses

Transcription factors are pivotal regulators in the cellular life process. Activating transcription factor 3 (ATF3), a member of the ATF/CREB (cAMP response element-binding protein) family, plays a crucial role as cells respond to various stresses and damage. As a transcription factor, ATF3 significantly influences signal transduction regulation, orchestrating a variety of signaling pathways, including apoptosis, ferroptosis, and cellular differentiation. In addition, ATF3 serves as an essential link between inflammation, oxidative stress, and immune responses. This review summarizes the recent advances in research on ATF3 activation and its role in regulating inflammatory responses, cell apoptosis, and ferroptosis while exploring the dual functions of ATF3 in these processes. Additionally, this article discusses the role of ATF3 in diseases related to pathogenic microbial infections. Our review may be helpful to better understand the role of ATF3 in cellular responses and disease progression, thus promoting advancements in clinical treatments for inflammation and oxidative stress-related diseases.

Acid sphingomyelinase mediates ferroptosis induced by high glucose via autophagic degradation of GPX4 in type 2 diabetic osteoporosis

BACKGROUND

Ferroptosis has been implicated in the pathological process of type 2 diabetic osteoporosis (T2DOP), although the specific underlying mechanisms remain largely unknown. This study aimed to clarify the role and possible mechanism of acid sphingomyelinase (ASM)-mediated osteoblast ferroptosis in T2DOP.

METHODS

We treated hFob1.19 cells with normal glucose (NG) and different concentrations of high glucose (HG, 26.25 mM, 35 mM, or 43.75 mM) for 48 h. We then measured cell viability and osteogenic function, quantified ferroptosis and autophagy levels, and measured the levels of ASM and ceramide in the cells. To further investigate the specific mechanism, we examined these indicators by knocking down ASM expression, hydroxychloroquine (HCQ) treatment, or N-acetylcysteine (NAC) treatment. Moreover, a T2DOP rat model was induced and microcomputed tomography was used to observe the bone microstructure. We also evaluated the serum levels of iron metabolism-associated factors, ceramide and lipid peroxidation (LPO) and measured the expression of ASM, LC3 and GPX4 in bone tissues.

RESULTS

HG inhibited the viability and osteogenic function of osteoblasts by inducing ferroptosis in a concentration-dependent manner. Furthermore, the expression of ASM and ceramide and autophagy levels were increased by HG treatment, and these factors were required for the HG-induced reactive oxygen species (ROS) generation and LPO. Similarly, inhibiting intracellular ROS also reduced HG-induced ASM activation and autophagy. ASM-mediated activation of autophagy was crucial for HG-induced degradation of GPX4, and inhibiting ASM improved osteogenic function by decreasing HG-induced autophagy, GPX4 degradation, LPO and subsequent ferroptosis. We also found that inhibiting ASM could alleviated ferroptosis and autophagy and improved osteogenic function in a T2DOP rat model.

CONCLUSION

ASM-mediated autophagy activation induces osteoblast ferroptosis under HG conditions through the degradation of GPX4, providing a novel mechanistic insight into the treatment and prevention of T2DOP.

Programmed cell death of periodontal ligament cells

The periodontal ligament is a crucial tissue that provides support to the periodontium. Situated between the alveolar bone and the tooth root, it consists primarily of fibroblasts, cementoblasts, osteoblasts, osteoclasts, periodontal ligament stem cells (PDLSCs), and epithelial cell rests of Malassez. Fibroblasts, cementoblasts, osteoblasts, and osteoclasts are functionally differentiated cells, whereas PDLSCs are undifferentiated mesenchymal stem cells. The dynamic development of these cells is intricately linked to periodontal changes and homeostasis. Notably, the regulation of programmed cell death facilitates the clearance of necrotic tissue and plays a pivotal role in immune response. However, it also potentially contributes to the loss of periodontal supporting tissues and root resorption. These findings have significant implications for understanding the occurrence and progression of periodontitis, as well as the mechanisms underlying orthodontic root resorption. Further, the regulation of periodontal ligament cell (PDLC) death is influenced by both systemic and local factors. This comprehensive review focuses on recent studies reporting the mechanisms of PDLC death and related factors.

5-ALA-PDT induced ferroptosis in keloid fibroblasts via ROS, accompanied by downregulation of xCT, GPX4

Keloids display many cancerous properties, including uncontrolled and invasive growth, high rates of recurrence as well as similar bioenergetics. 5-aminolevulinic acid-based photodynamic therapy (5-ALA-PDT) is an effective treatment that performs cytotoxic effects by producing reactive oxygen species (ROS), which is linked to lipid peroxidation and ferroptosis. Herein, we explored underlying mechanisms of 5-ALA-PDT against keloids. We identified that 5-ALA-PDT led to elevated levels of ROS and lipid peroxidation in keloid fibroblasts, accompanied by downregulation of xCT and GPX4, which are associated with anti-oxidation effects and ferroptosis inhibition. These results may indicate that 5-ALA-PDT treatment increases ROS while inhibiting xCT and GPX4, thus promoting lipid peroxidation to induce ferroptosis in keloid fibroblasts.

Iron metabolism and ferroptosis in diabetic bone loss: from mechanism to therapy

Osteoporosis, one of the most serious and common complications of diabetes, has affected the quality of life of a large number of people in recent years. Although there are many studies on the mechanism of diabetic osteoporosis, the information is still limited and there is no consensus. Recently, researchers have proven that osteoporosis induced by diabetes mellitus may be connected to an abnormal iron metabolism and ferroptosis inside cells under high glucose situations. However, there are no comprehensive reviews reported. Understanding these mechanisms has important implications for the development and treatment of diabetic osteoporosis. Therefore, this review elaborates on the changes in bones under high glucose conditions, the consequences of an elevated glucose microenvironment on the associated cells, the impact of high glucose conditions on the iron metabolism of the associated cells, and the signaling pathways of the cells that may contribute to diabetic bone loss in the presence of an abnormal iron metabolism. Lastly, we also elucidate and discuss the therapeutic targets of diabetic bone loss with relevant medications which provides some inspiration for its cure.