Age-related decline in melatonin contributes to enhanced osteoclastogenesis via disruption of redox homeostasis.

BACKGROUND: Increased oxidative stress contributes to enhanced osteoclastogenesis and age-related bone loss. Melatonin (MT) is an endogenous antioxidant and declines with aging. However, it was unclear whether the decline of MT was involved in the enhanced osteoclastogenesis during the aging process. METHODS: The plasma level of MT, oxidative stress status, bone mass, the number of bone marrow-derived monocytes (BMMs) and its osteoclastogenesis were analyzed in young (3-month old) and old (18-month old) mice (n = 6 per group). In vitro, BMMs isolated from aged mice were treated with or without MT, followed by detecting the change of osteoclastogenesis and intracellular reactive oxygen species (ROS) level. Furthermore, old mice were treated with MT for 2 months to investigate the therapeutic effect. RESULTS: The plasma level of MT was markedly lower in aged mice compared with young mice. Age-related decline in MT was accompanied by enhanced oxidative stress, osteoclastogenic potential and bone loss. MT intervention significantly suppressed the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis, decreased intracellular ROS and enhanced antioxidant capacity of BMMs from aged mice. MT supplementation significantly attenuated oxidative stress, osteoclastogenesis, bone loss and deterioration of bone microstructure in aged mice. CONCLUSIONS: These results suggest that age-related decline of MT enhanced osteoclastogenesis via disruption of redox homeostasis. MT may serve as a key regulator in osteoclastogenesis and bone homeostasis, thereby highlighting its potential as a preventive agent for age-related bone loss.

Accumulation of advanced oxidation protein products contributes to age-related impairment of gap junction intercellular communication in osteocytes of male mice.

AIMS: Gap junction intercellular communication (GJIC) in osteocytes is impaired by oxidative stress, which is associated with age-related bone loss. Ageing is accompanied by the accumulation of advanced oxidation protein products (AOPPs). However, it is still unknown whether AOPP accumulation is involved in the impairment of osteocytes' GJIC. This study aims to investigate the effect of AOPP accumulation on osteocytes' GJIC in aged male mice and its mechanism. METHODS: Changes in AOPP levels, expression of connexin43 (Cx43), osteocyte network, and bone mass were detected in 18-month-old and three-month-old male mice. Cx43 expression, GJIC function, mitochondria membrane potential, reactive oxygen species (ROS) levels, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation were detected in murine osteocyte-like cells (MLOY4 cells) treated with AOPPs. The Cx43 expression, osteocyte network, bone mass, and mechanical properties were detected in three-month-old mice treated with AOPPs for 12 weeks. RESULTS: The AOPP levels were increased in aged mice and correlated with degeneration of osteocyte network, loss of bone mass, and decreased Cx43 expression. AOPP intervention induced NADPH oxidase activation and mitochondrial dysfunction, triggered ROS generation, reduced Cx43 expression, and ultimately impaired osteocytes' GJIC, which were ameliorated by NADPH oxidase inhibitor apocynin, mitochondria-targeted superoxide dismutase mimetic (mito-TEMPO), and ROS scavenger N-acetyl cysteine. Chronic AOPP loading accelerated the degradation of osteocyte networks and decreased Cx43 expression, resulting in deterioration of bone mass and mechanical properties in vivo. CONCLUSION: Our study suggests that AOPP accumulation contributes to age-related impairment of GJIC in osteocytes of male mice, which may be part of the pathogenic mechanism responsible for bone loss during ageing. Cite this article: Bone Joint Res 2022;11(7):413-425.

Prrx1 promotes resistance to temozolomide by upregulating ABCC1 and inducing vasculogenic mimicry in glioma.

Gliomas are the most common primary brain tumors with dismal prognoses. Temozolomide (TMZ), the frontline therapeutic agent for gliomas, has shown limited clinical benefit primarily due to the acquired chemoresistance. Although growing evidence has suggested that the multi-drug resistance phenotype and abnormal vascular microenvironment are responsible for the intrinsic and extrinsic TMZ resistance, the molecular mechanism of TMZ resistance remains to be elucidated. In this study, we found Paired-related homeobox 1 (Prrx1) was an independent prognostic factor for the efficacy of chemotherapy-based postoperative treatment. Silencing Prrx1 markedly enhanced the TMZ-induced cytotoxicity both in vitro and in vivo. We also demonstrated that Prrx1 increased the expression of ABCC1, a member of ATP-Binding Cassette (ABC) transporter protein family, through binding to the promoter region of ABCC1 gene and initiating its transcription. Silencing ABCC1 mitigated the TMZ resistance induced by Prrx1. Furthermore, Prrx1 facilitates the formation of vasculogenic mimicry (VM), a critical extrinsic mechanism for glioma TMZ resistance. Collectively, our findings supported the critical role of Prrx1 in TMZ resistance via intrinsic and extrinsic mechanism. Targeting Prrx1 might represent a feasible strategy to overcome therapeutic resistance in glioma.

Age-related accumulation of advanced oxidation protein products promotes osteoclastogenesis through disruption of redox homeostasis.

Enhanced osteoclastogenesis is one of the major causes of age-related bone loss. Aging is accompanied by accumulation of advanced oxidation protein products (AOPPs). However, whether AOPPs accumulation contributing to the osteoclastogenesis with aging remains unclear. Here, we showed that AOPPs accumulation was associated with the enhanced osteoclastogenesis and deterioration of bone microstructure in aged mice. In vitro, AOPPs directly induced osteoclastogenesis by interaction with receptor activator of nuclear factor κ B (RANK) and the receptor for advanced glycation end products (RAGE) in the primary bone marrow monocytes. Bindings of AOPPs to RANK and RAGE were able to activate nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, trigger generation of reactive oxygen species, then induce phosphorylation of mitogen-activated protein kinases and c-fos, upregulation of the nuclear factor of activated T cell c1, eventually induce bone marrow monocytes to differentiate into mature osteoclasts. Chronic exposure to AOPPs enhanced osteoclastogenesis and bone loss in mice, which could be alleviated by NADPH oxidase inhibitor apocynin. Local injection of AOPPs into subperiosteal area induced bone resorption at the site of administration, which was similar to the effect of RANK ligand. Together, these results suggested that AOPPs could serve as a novel regulator of osteoclastogenesis and AOPPs accumulation might play an important role in the development of age-related bone loss.

LncRNA NEAT1 Promotes Gastric Cancer Progression Through miR-17-5p/TGFßR2 Axis Up-Regulated Angiogenesis.

BACKGROUND: Long non-coding RNAs (lncRNAs) have been indicated to play critical roles in gastric cancer (GC) tumorigenesis and progression. However, their roles in GC remain to be further elucidated. METHODS: RT-qPCR and fluorescence in situ hybridzation (FISH) were conducted to detect the expression of lncRNA NEAT1 in GC tissues and cell lines. Gene Set Enrichment Analysis (GSEA) was performed to screen out potential phenotypes and pathways that NEAT1 may participate in. NEAT1-silenced AGS and MGC803 cells were constructed and a series of functional experiments to investigate the roles of NEAT1 in GC angiogenesis both in vitro and in vivo. RNA pull down and luciferase reporter assays were utilized to illustrate the mechanisms underlying the functions of NEAT1 in GC. RESULTS: We observed that NEAT1 was upregulated in most GC specimens and cell lines. NEAT1 high was correlated with poor prognosis of GC patients. In vitro experiments showed that NEAT1 promoted GC angiogenesis by enhancing proliferation, migration, and tube formation ability of endothelial cells. Mechanism researches revealed that NEAT1 could competitively sponge miR-17-5p which targeted TGFßR2 directly. Subsequently, activate TGFß/Smad pathway by following with upregulation of a series of classical proangiogenic factors especially VEGF. CONCLUSION: The study unveiled that the LncRNA NEAT1/miR-17-5p/TGFßR2 axis is a novel mechanism in GC angiogenesis. Disrupting this axis may be a potential strategy for GC treatment.

Leukemia Inhibitory Factor Receptor Suppresses the Metastasis of Clear Cell Renal Cell Carcinoma Through Negative Regulation of the Yes-Associated Protein.

The role of leukemia inhibitory factor receptor (LIFR), which is important in the signal transduction of the interleukin-6 cytokine family, is still undefined in clear cell renal cell carcinoma (ccRCC). Thus, we examined the function and mechanism of LIFR in ccRCC. Low LIFR expression correlated with a poor prognosis and an aggressive tumor phenotype. Moreover, integrated LIFR DNA and mRNA analysis revealed that promoter methylation and copy number variation contributed to the reduced LIFR expression. LIFR knockdown increased 786-O and Caki-2 cell invasion and migration. Notably, the Hippo pathway was highlighted as a potential downstream target of LIFR, where loss of LIFR inhibited the kinase activity of the pathway and increased the intracellular Yes-associated protein (YAP) level. Conversely, YAP inhibition impaired the LIFR-silencing promotion of cell migration, invasion, and cancer stem cell marker expression. Moreover, drug sensitivity analysis and the Cancer Cell Line Encyclopedia database revealed that LIFR-deficient cells had high sensitivity to a YAP inhibitor and to two other anticancer drugs (PHA-665752, PF2341066). Our study revealed that LIFR attenuates tumor metastasis by suppressing YAP expression, suggesting that LIFR may serve as a potential target for ccRCC treatment.

Highly selective aerobic oxidation of alcohol catalyzed by a gold(I) complex with an anionic ligand.

Highly selective aerobic oxidation of alcohols to carbonyl compounds was catalyzed by a gold(I) complex with an anionic ligand in solution.