microRNA-29a inhibition induces Gab1 upregulation to protect OB-6 human osteoblasts from hydrogen peroxide

Neuroligin-3 activates Akt-dependent Nrf2 cascade to protect osteoblasts from oxidative stress

Excessive oxidative stress will cause significant injury to osteoblasts, serving as one major pathological mechanism of osteoporosis. Neuroligin-3 (NLGN3) is a postsynaptic cell adhesion protein and is expressed in the bone. We here explored its potential activity against hydrogen peroxide (H2O2)-induced oxidative injury in cultured osteoblasts. In primary murine and human osteoblasts, NLGN3 stimulation dose-dependently induced Akt, Erk1/2 and S6K activation. NLGN3 pretreatment ameliorated H2O2-induced cytotoxicity and death in osteoblasts. Moreover, H2O2-induced reactive oxygen species (ROS) production and oxidative injury were alleviated with NLGN3 pretreatment in cultured osteoblasts. Further studies showed that NLGN3 activated Nrf2 signaling cascade and induced Nrf2 protein Serine-40 phosphorylation, Keap1-Nrf2 dissociation, Nrf2 protein stabilization and nuclear translocation in osteoblasts. NLGN3 also increased antioxidant response element (ARE) activity and induced expression of Nrf2-ARE-dependent genes (HO1, GCLC and NQO1) in osteoblasts. Moreover NLGN3 mitigated osteoblast oxidative injury by dexamethasone or sodium fluoride (NaF). Nrf2 cascade activation is essential for NLGN3-induced cytoprotective activity in osteoblasts. Nrf2 shRNA or knockout (KO) abolished NLGN3-induced osteoblast cytoprotection against H2O2. Contrarily forced Nrf2 cascade activation by Keap1 KO mimicked NLGN3-induced anti-oxidative activity in murine osteoblasts. Importantly, NLGN3-induced Serine-40 phosphorylation and Nrf2 cascade activation were blocked by an Akt inhibitor MK-2206 or by Akt1 shRNA. Importantly, Akt inhibition, Akt1 silencing or Nrf2 S40T mutation largely inhibited NLGN3-induced osteoblast cytoprotection against H2O2. At last, we showed that NLGN3 mRNA and protein expression was significantly downregulated in necrotic bone tissues of dexamethasone-taken patients. Taken together, NLGN3 activated Akt-dependent Nrf2 cascade to protect osteoblasts from oxidative stress.

Nrf2 signaling activation by a small molecule activator compound 16 inhibits hydrogen peroxide-induced oxidative injury and death in osteoblasts

We explored the potential activity of compound 16 (Cpd16), a novel small molecule Nrf2 activator, in hydrogen peroxide (H₂O₂)-stimulated osteoblasts. In the primary murine/human osteoblasts and MC3T3-E1 murine osteoblastic cells, Cpd16 treatment at micro-molar concentrations caused disassociation of Keap1-Nrf2 and Nrf2 cascade activation. Cpd16 induced stabilization of Nrf2 protein and its nuclear translocation, thereby increasing the antioxidant response elements (ARE) reporter activity and Nrf2 response genes transcription in murine and human osteoblasts. Significantly, Cpd16 mitigated oxidative injury in H₂O₂-stimulited osteoblasts. H₂O₂-provoked apoptosis as well as programmed necrosis in osteoblasts were significantly alleviated by the novel Nrf2 activator. Cpd16-induced Nrf2 activation and osteoblasts protection were stronger than other known Nrf2 activators. Dexamethasone- and nicotine-caused oxidative stress and death in osteoblasts were attenuated by Cpd16 as well. Cpd16-induced osteoblast cytoprotection was abolished by Nrf2 short hairpin RNA or knockout, but was mimicked by Keap1 knockout. Keap1 Cys151S mutation abolished Cpd16-induced Nrf2 cascade activation and osteoblasts protection against H₂O₂. Importantly, weekly Cpd16 administration largely ameliorated trabecular bone loss in ovariectomy mice. Together, Cpd16 alleviates H₂O₂-induced oxidative stress and death in osteoblasts by activating Nrf2 cascade.

A novel Keap1 inhibitor iKeap1 activates Nrf2 signaling and ameliorates hydrogen peroxide-induced oxidative injury and apoptosis in osteoblasts

An ultra-large structure-based virtual screening has discovered iKeap1 as a direct Keap1 inhibitor that can efficiently activate Nrf2 signaling. We here tested its potential effect against hydrogen peroxide (H₂O₂)-induced oxidative injury in osteoblasts. In primary murine and human osteoblasts, iKeap1 robustly activated Nrf2 signaling at micromole concentrations. iKeap1 disrupted Keap1-Nrf2 association, causing Nrf2 protein stabilization, cytosol accumulation and nuclear translocation in murine and human osteoblasts. The anti-oxidant response elements (ARE) activity and transcription of Nrf2-ARE-dependent genes (including HO1, NQO1 and GCLC) were increased as well. Significantly, iKeap1 pretreatment largely ameliorated H₂O₂-induced reactive oxygen species production, lipid peroxidation and DNA damage as well as cell apoptosis and programmed necrosis in osteoblasts. Moreover, dexamethasone- and nicotine-induced oxidative injury and apoptosis were alleviated by iKeap1. Importantly, Nrf2 shRNA or CRISPR/Cas9-induced Nrf2 knockout completely abolished iKeap1-induced osteoblast cytoprotection against H₂O₂. Conversely, CRISPR/Cas9-induced Keap1 knockout induced Nrf2 cascade activation and mimicked iKeap1-induced cytoprotective actions in murine osteoblasts. iKeap1 was ineffective against H₂O₂ in the Keap1-knockout murine osteoblasts. Collectively, iKeap1 activated Nrf2 signaling cascade to inhibit H₂O₂-induced oxidative injury and death of osteoblasts.

MAFG-driven osteosarcoma cell progression is inhibited by a novel miRNA miR-4660

Osteosarcoma (OS) is the most common primary bone malignancy in the adolescent population. MAFG (v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog G) forms a heterodimer with Nrf2 (NF-E2-related factor 2), binding to antioxidant response element (ARE), which is required for Nrf2 signaling activation. We found that MAFG mRNA and protein expression is significantly elevated in human OS tissues as well as in established and primary human OS cells. In human OS cells, MAGF silencing or knockout (KO) largely inhibited OS cell growth, proliferation, and migration, simultaneously inducing oxidative injury and apoptosis activation. Conversely, ectopic overexpression of MAFG augmented OS cell progression in vitro. MicroRNA-4660 (miR-4660) directly binds the 3′ untranslated region (UTR) of MAFG mRNA in the cytoplasm of OS cells. MAFG 3′ UTR luciferase activity and expression as well as OS cell growth were largely inhibited with forced miR-4660 overexpression but augmented with miR-4660 inhibition. In vivo, MAGF short hairpin RNA (shRNA) or forced overexpression of miR-4660 inhibited subcutaneous OS xenograft growth in severe combined immunodeficient mice. Furthermore, MAFG silencing or miR-4660 overexpression inhibited OS xenograft in situ growth in proximal tibia of the nude mice. In summary, MAFG overexpression-driven OS cell progression is inhibited by miR-4660. The miR-4660-MAFG axis could be novel therapeutic target for human OS.

GDC-0349 inhibits non-small cell lung cancer cell growth

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related human mortality with a clear need for new therapeutic intervention. GDC-0349 is a potent and selective ATP-competitive mTOR inhibitor. In A549 cells and primary human NSCLC cells, GDC-0349 inhibited cell growth, proliferation, cell cycle progression, migration and invasion, while inducing significant apoptosis activation. Although GDC-0349 blocked Akt-mTORC1/2 activation in NSCLC cells, it also exerted cytotoxicity in Akt1-knockout A549 cells. Furthermore, restoring Akt-mTOR activation by a constitutively-active Akt1 only partially attenuated GDC-0349-induced A549 cell apoptosis, indicating the existence of Akt-mTOR-independent mechanisms. In NSCLC cells GDC-0349 induced sphingosine kinase 1 (SphK1) inhibition, ceramide accumulation, JNK activation and oxidative injury. Conversely, N-acetylcysteine, the JNK inhibitor and sphingosine 1-phosphate alleviated GDC-0349-induced NSCLC cell apoptosis. In vivo, daily oral administration of GDC-0349 potently inhibited NSCLC xenograft growth in mice. Akt-mTOR in-activation, SphK1 inhibition, JNK activation and oxidative stress were detected in NSCLC xenograft tissues with GDC-0349 administration. In summary, GDC-0349 inhibits NSCLC cell growth via Akt-mTOR-dependent and Akt-mTOR-independent mechanisms.

Four-octyl itaconate activates Nrf2 cascade to protect osteoblasts from hydrogen peroxide-induced oxidative injury

Four-octyl itaconate (4-OI) is the cell-permeable derivative of itaconate that can activate Nrf2 signaling by alkylating Keap1’s cysteine residues. Here, we tested the potential effect of 4-OI on hydrogen peroxide (H₂O₂)-induced oxidative injury in osteoblasts. In OB-6 cells and primary murine osteoblasts, 4-OI was able to activate Nrf2 signaling cascade and cause Keap1–Nrf2 disassociation, Nrf2 protein stabilization, cytosol accumulation, and nuclear translocation. 4-OI also augmented antioxidant-response element reporter activity and promoted expression of Nrf2-dependent genes (HO1, NQO1, and GCLC). Pretreatment with 4-OI inhibited H₂O₂-induced reactive oxygen species production, cell death, and apoptosis in osteoblasts. Furthermore, 4-OI inhibited H₂O₂-induced programmed necrosis by suppressing mitochondrial depolarization, mitochondrial cyclophilin D-ANT1 (adenine nucleotide translocase 1)-p53 association, and cytosol lactate dehydrogenase release in osteoblasts. Ectopic overexpression of immunoresponsive gene 1 (IRG1) increased endogenous itaconate production and activated Nrf2 signaling cascade, thereby inhibiting H₂O₂-induced oxidative injury and cell death. In OB-6 cells, Nrf2 silencing or CRISPR/Cas9-induced Nrf2 knockout blocked 4-OI-induced osteoblast cytoprotection against H₂O₂. Conversely, forced Nrf2 activation, by CRISPR/Cas9-induced Keap1 knockout, mimicked 4-OI-induced actions in OB-6 cells. Importantly, 4-OI was ineffective against H₂O₂ in Keap1-knockout cells. Collectively, 4-OI efficiently activates Nrf2 signaling to inhibit H₂O₂-induced oxidative injury and death of osteoblasts.

Inhibition of microRNA-29a alleviates hyperoxia-induced bronchopulmonary dysplasia in neonatal mice via upregulation of GAB1

Background

The main features of bronchopulmonary dysplasia (BPD) are alveolar simplification, pulmonary growth arrest, and abnormal lung function. Multiple studies have highlighted microRNA-29 (miR-29) as a potential biomarker for lung diseases and cancers. Upregulation of miR-29a has been known to downregulate GRB2-associated-binding protein 1 (GAB1), which is often highly expressed in the lung. The current study was designed to investigate the potential role of miR-29a in hyperoxia-induced BPD by targeting GAB1 in a neonatal mouse model.

Methods

The expression of miR-29a and GAB1 in lung tissues of neonatal mice with hyperoxia-induced BPD and mouse alveolar epithelial cells (MLE-12) was determined using RT-qPCR and western blot analysis. Subsequently, the relationship between miR-29a and GAB1 was verified using in silico analysis. In order to assess the effects of miR-29a or GAB1 on BPD, the pathological characteristics of alveoli, as well as proliferation and apoptosis of cells were measured through gain- and loss-of-function studies.

Results

Upregulation of miR-29a and downregulation of GAB1 were evident in both lung tissues and MLE-12 cells following BPD modeling. GAB1 was a direct target gene of miR-29a. Inhibition of miR-29a and overexpression of GAB1 were shown to alleviate lung injury, promote cell proliferation and inhibit apoptosis but reduce chord length in lung tissues of neonatal mice following hyperoxia-induced BPD modeling.

Conclusion

Altogether, down-regulation of miR-29a can potentially elevate GAB1 expression, reducing cell apoptosis and stimulating proliferation, ultimately retarding the development of BPD in mice. This study highlights the potential of a promising new target for preventing BPD.

PGK1 depletion activates Nrf2 signaling to protect human osteoblasts from dexamethasone

Activation of nuclear-factor-E2-related factor 2 (Nrf2) cascade can alleviate dexamethasone (DEX)-induced oxidative injury and death of human osteoblasts. A recent study has shown that phosphoglycerate kinase 1 (PGK1) inhibition/depletion will lead to Kelch-like ECH-associated protein 1 (Keap1) methylglyoxal modification, thereby activating Nrf2 signaling cascade. Here, in OB-6 osteoblastic cells and primary human osteoblasts, PGK1 silencing, by targeted shRNA, induced Nrf2 signaling cascade activation, causing Nrf2 protein stabilization and nuclear translocation, as well as increased expression of ARE-dependent genes (HO1, NQO1, and GCLC). Functional studies demonstrated that PGK1 shRNA largely attenuated DEX-induced oxidative injury and following death of OB-6 cells and primary osteoblasts. Furthermore, PGK1 knockout, by the CRISPR/Cas9 method, similarly induced Nrf2 signaling activation and protected osteoblasts from DEX. Importantly, PGK1 depletion-induced osteoblast cytoprotection against DEX was almost abolished by Nrf2 shRNA. In addition, Keap1 shRNA mimicked and nullified PGK1 shRNA-induced anti-DEX osteoblast cytoprotection. At last we show that PGK1 expression is downregulated in human necrotic femoral head tissues of DEX-taking patients, correlating with HO1 depletion. Collectively, these results show that PGK1 depletion protects human osteoblasts from DEX via activation of Keap1-Nrf2 signaling cascade.

Cytoprotective effect of Fufang Lurong Jiangu capsule against hydrogen peroxide-induced oxidative stress in bone marrow stromal cell-derived osteoblasts through the Nrf2/HO-1 signaling pathway

OBJECTIVE

Oxidative stress is increasingly recognized as a risk factor associated with the development and progression of osteoporosis. Fufang Lurong Jiangu Capsule (FLJC) has a known anti-osteoporotic effect, but its pharmacological effect on osteoblasts is not clearly understood. This study was designed to investigate FLJC effects/mechanisms on in vitro hydrogen peroxide (H₂O₂)-induced oxidative damage of osteoblasts and on in vivo lipopolysaccharide (LPS)-induced mice bone loss. FLJC alleviates osteoporosis via unknown pharmacological mechanisms.

METHODS

Chemical compositions of FLJC preparations were analyzed using high-performance liquid chromatographic fingerprinting. After rat bone marrow mesenchymal stem cell differentiation induction, resulting osteoblasts received various 48 h FLJC pretreatments before H₂O₂-based (200 μM) oxidative stress exposure. FLJC effects were measured on osteoblast cell viability, morphological changes, levels of intracellular reactive oxygen species (ROS), localization of mitochondria, activity of antioxidant enzymes, alkaline phosphatase (ALP) and mineralization, the secretion of Col I and expression of osteogenic markers. The percentages of apoptosis were determined by flow cytometric analysis; apoptosis-related protein levels, including nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase-1 (HO-1) with or without Nrf2 inhibitor were analyzed via western blot. Hematoxylin and eosin (H&E) and ALP staining revealed in vivo FLJC effect on mice LPS-induced bone loss.

RESULTS

Five chemical components in FLJC were identified, and fingerprint analysis showed good reproducibility. FLJC pretreatment significantly reduced H₂O₂-induced ROS levels in osteoblasts and increased antioxidant enzyme activities to reduce oxidative damage. With regard to osteoblast differentiation, FLJC pretreatment increased ALP expression, as well as levels of mineralization and osteoblast markers. Additionally, FLJC protected against H₂O₂-induced apoptosis by inhibiting changes in expression of major Bcl-2 family effector proteins of the mitochondrial apoptosis pathway. Furthermore, FLJC protected cells from H₂O₂-induced oxidative damage by up-regulating Nrf2 and HO-1 protein levels. Finally, we confirmed that FLJC administration could reverse the bone loss in LPS-induced mice.

CONCLUSION

These results indicate that FLJC may significantly attenuate oxidative damage of osteoblasts induced by H₂O₂ via the Nrf2/HO-1 signaling pathway, providing new insights to guide development of treatments for osteoporosis induced by oxidative injury.

Dexamethasone-induced cytotoxicity in human osteoblasts is associated with circular RNA HIPK3 downregulation

Dexamethasone (DEX) exerts potent cytotoxicity against cultured human osteoblasts. The current study examined the role of the circular RNA HIPK3 (circHIPK3) in the mechanism of cell death. We found that circHIPK3 expression was downregulated in DEX-treated human osteoblasts and circHIPK3 levels decreased in human necrotic femoral head tissues. In OB-6 osteoblastic cells and primary human osteoblasts ectopic overexpression of circHIPK3 potently suppressed DEX-induced apoptosis and programmed necrosis. Conversely, knockdown of circHIPK3by targeted siRNAs enhanced DEX-induced cytotoxicity in human osteoblasts. We further observed that microRNA-124 (miR-124), a key miRNA sponged by circHIPK3, accumulated following DEX treatment in OB-6 cells and primary osteoblasts. Confirming the role of miR-124 in DEX-induced cytotoxicity, miR-124 inhibitor attenuated cell death in human osteoblasts. Conversely, forced overexpression of miR-124 mimicked DEX-induced actions and induced cytotoxicity in human osteoblasts. We conclude that DEX-induced cytotoxicity in human osteoblasts is associated with circHIPK3 downregulation.