Atf7ip Inhibits Osteoblast Differentiation via Negative Regulation of the Sp7 Transcription Factor.

Epigenetic modifications are critical for cell differentiation and growth. As a regulator of H3K9 methylation, Setdb1 is implicated in osteoblast proliferation and differentiation. The activity and nucleus localization of Setdb1 are regulated by its binding partner, Atf7ip. However, whether Atf7ip is involved in the regulation of osteoblast differentiation remains largely unclear. In the present study, we found that Atf7ip expression was upregulated during the osteogenesis of primary bone marrow stromal cells and MC3T3-E1 cells, and was induced in PTH-treated cells. The overexpression of Atf7ip impaired osteoblast differentiation in MC3T3-E1 cells regardless of PTH treatment, as measured by the expression of osteoblast differentiation markers, Alp-positive cells, Alp activity, and calcium deposition. Conversely, the depletion of Atf7ip in MC3T3-E1 cells promoted osteoblast differentiation. Compared with the control mice, animals with Atf7ip deletion in the osteoblasts (Oc-Cre;Atf7ipf/f) showed more bone formation and a significant increase in the bone trabeculae microarchitecture, as reflected by µ-CT and bone histomorphometry. Mechanistically, Atf7ip contributed to the nucleus localization of Setdb1 in MC3T3-E1, but did not affect Setdb1 expression. Atf7ip negatively regulated Sp7 expression, and through specific siRNA, Sp7 knockdown attenuated the enhancing role of Atf7ip deletion in osteoblast differentiation. Through these data, we identified Atf7ip as a novel negative regulator of osteogenesis, possibly via its epigenetic regulation of Sp7 expression, and demonstrated that Atf7ip inhibition is a potential therapeutic measure for enhancing bone formation.

Salubrinal-mediated activation of eIF2α signaling improves oxidative stress-induced BMSCs senescence and senile osteoporosis.

Bone cells of various lineages become senescent in bone microenvironment. Senotherapies that clear the senescent bone cells improve bone microarchitecture of aged bones. However, the mechanisms underlie for the formation and maintenance of senescent bone cells are largely unknown. Here, we focus on the relationship between endoplasmic reticulum stress (ER stress)-activated unfolded protein response (UPR) signaling and cellular senescence of bone marrow mesenchymal stem cells (BMSCs). The PKR-like endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor 2 α(eIF2α) signaling branch was specifically activated and tightly regulated in senescent BMSCs induced by hydrogen peroxide (H2O2). However, blocking PERK-eIF2α signaling with AMG'44 could not reverse the cellular senescence phenotype of senescent BMSCs. Treated the senescent cells with salubrinal, an inhibitor for dephosphorylation of eIF2α, decreased SA-ß-Gal positive cells and the expression of markers for cellular senescence. Moreover, salubrinal enhanced the apoptosis of senescent BMSCs and upregulated expression of Chop and BIM. Furthermore, salubrinal treatment significantly improved the osteogenesis capacity of senescent BMSCs as reflected by the increase of Alp, Runx2 and Osteocalcin, the formation of Alp-positive staining cells and matrix mineralization. Salubrinal administration results in significant recovery in the bone microarchitecture of senile SAMP6 mice. Taken together, our data reveal an undefined role of PERK-eIF2α signaling in the maintenance of cellular senescent phenotype in BMSCs. The activation of eIF2α signaling with salubrinal is helpful for the clearance of senescent BMSCs and the improvement of bone integrity of aged mice.

PM2.5 exposure inhibits osteoblast differentiation by increasing the ubiquitination and degradation of Smad4.

Increasing epidemiological evidence has shown that PM2.5 exposure is significantly associated with the occurrence of osteoporosis. It has been well demonstrated that PM2.5 exposure enhanced the differentiation and function of osteoclasts by indirectly causing chronic inflammation, while the mechanism in osteoblasts remains unclear. In our study, toxic effects were evaluated by direct exposure of 20-80 µg/ml PM2.5 to MC3T3-E1 cells and BMSCs. The results showed that PM2.5 exposure did not affect cell viability via proliferation and apoptosis, but significantly inhibited osteoblast differentiation in a dose-dependent manner. Osteogenic transcription factors Runx2 and Sp7 and other biomarkers Alp and Ocn decreased after PM2.5 exposure. RNA-seq revealed TGF-ß signaling was involved in PM2.5 exposure inhibited osteoblast differentiation, which led to P-Smad1/5 and P-Smad2 reduction in the nucleus by increasing the ubiquitination and degradation of Smad4. At last, the inflammation response increased in MC3T3-E1 cells with PM2.5 exposure. Moreover, the mRNA levels of Mmp9 increased in bone marrow-derived macrophage cells treated with the conditional medium collected from MC3T3-E1 cells exposed to PM2.5. Overall, these results indicated that PM2.5 exposure inhibits osteoblast differentiation and concurrently increases the maturation of osteoclasts. Our study provides in-depth mechanistic insights into the direct impact of PM2.5 exposure on osteoblast, which would indicate the unrecognized role of PM2.5 on osteoporosis.

Effects of chronic low-level lead (Pb) exposure on cognitive function and hippocampal neuronal ferroptosis: An integrative approach using bioinformatics analysis, machine learning, and experimental validation.

Lead (Pb), a pervasive and ancient toxic heavy metal, continues to pose significant neurological health risks, particularly in regions such as Southeast Asia. While previous research has primarily focused on the adverse effects of acute, high-level lead exposure on neurological systems, studies on the impacts of chronic, low-level exposure are less extensive, especially regarding the precise mechanisms linking ferroptosis - a novel type of neuron cell death - with cognitive impairment. This study aims to explore the potential effects of chronic low-level lead exposure on cognitive function and hippocampal neuronal ferroptosis. This research represents the first comprehensive investigation into the impact of chronic low-level lead exposure on hippocampal neuronal ferroptosis, spanning clinical settings, bioinformatic analyses, and experimental validation. Our findings reveal significant alterations in the expression of genes associated with iron metabolism and Nrf2-dependent ferroptosis following lead exposure, as evidenced by comparing gene expression in the peripheral blood of lead-acid battery workers and workers without lead exposure. Furthermore, our in vitro and in vivo experimental results strongly suggest that lead exposure may precipitate cognitive dysfunction and induce hippocampal neuronal ferroptosis. In conclusion, our study indicates that chronic low-level lead exposure may activate microglia, leading to the promotion of ferroptosis in hippocampal neurons.

Curcumin nicotinate increases LDL cholesterol uptake in hepatocytes through IDOL/LDL-R pathway regulation.

BACKGROUND: Curcumin nicotinate (Curtn), derived from curcumin and niacin, reduces serum LDL-C levels, partly due to its influence on PCSK9. This study investigates IDOL's role in Curtn's lipid-lowering effects. OBJECTIVE: To elucidate Curtn's regulation of the IDOL/LDLR pathway and potential molecular mechanisms in hepatocytes. METHODS: Differential metabolites in Curtn-treated HepG2 cells were identified via LC-MS. Molecular docking assessed Curtn's affinity with IDOL. Cholesterol content and LDLR expression effects were studied in high-fat diet Wistar rats. In vitro evaluations determined Curtn's influence on IDOL overexpression's LDL-C uptake and LDLR expression in hepatocytes. RESULTS: Lipids were the main differential metabolites in Curtn-treated HepG2 cells. Docking showed Curtn's higher affinity to IDOL's FERM domain compared to curcumin, suggesting potential competitive inhibition of IDOL's binding to LDLR. Curtn decreased liver cholesterol in Wistar rats and elevated LDLR expression. During in vitro experiments, Curtn significantly enhanced the effects of IDOL overexpression in HepG2 cells, leading to increased LDL-C uptake and elevated expression of LDL receptors. CONCLUSION: Curtn modulates the IDOL/LDLR pathway, enhancing LDL cholesterol uptake in hepatocytes. Combined with its PCSK9 influence, Curtn emerges as a potential hyperlipidemia therapy.

Concurrent impairment of nucleus and mitochondria for synergistic inhibition of cancer metastasis.

Cancer metastasis, which increases the mortality in a short period of time, has been considered as the main challenge in tumor treatment. However, tumor growth suppression also should not be ignored in cancer metastasis treatment. Recently, accumulating evidences have suggested that mitochondria play an important role in mitigating caner metastasis. Nucleus, as the repository of genetic information, plays a key role in cell proliferation. However, it remains elusive that the concurrent impairment of nucleus and mitochondria may achieve better anti-tumor and anti-metastatic effects. Here, we designed a mitochondria-penetrating peptide modified doxorubicin (MPP-Dox) loaded N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer conjugates (PM), as well as a nuclear accumulating HPMA copolymer Dox conjugates (PN) by the nuclear tendency of Dox. After co-delivering the two copolymers (abbreviation for PMN), PM promoted cell apoptosis and inhibited tumor metastasis by damaging mitochondria, whereas PN suppressed cell proliferation and promoted apoptosis by destroying nucleus. Importantly, PM and PN complemented each other as expected. The mitochondrial dysfunction and tumor metastasis inhibition of PM was improved by PN, while cell proliferation suppression and apoptosis by nucleus destroying of PN was enhanced by PM. As a result, tumor growth of breast cancer 4T1 cells in vivo was significantly restrained and lung metastasis was potently decreased and almost eradicated, fully reflecting the advantages of organelle targeting combination therapy. As a consequence, our work showed that concurrent impairment of nucleus and mitochondria was feasible and beneficial to metastatic cancer treatment.

Combination of mitochondria targeting doxorubicin with Bcl-2 function-converting peptide NuBCP-9 for synergistic breast cancer metastasis inhibition.

Distant organ metastasis is the main cause of death in breast cancer patients. Evidences have shown that mitochondria also play a crucial role in tumor metastasis, except for as apoptosis center. However, the treatment of tumor growth and metastasis was reported to be limited by mitochondria-associated protein Bcl-2, which are gatekeepers of apoptosis and are found to reside in mitochondria mainly. Herein, we designed a mitochondria-targeting doxorubicin delivery system as well as a mitochondrial distributed Bcl-2 function-converting peptide NuBCP-9 delivery system, which are both based on N-(2-hydroxypropyl)methacrylamide copolymers, to achieve a synergistic effect on tumor regression and metastasis inhibition by combination therapy. After mitochondria were damaged by mitochondria-targeting peptide-modified doxorubicin, apoptosis was effectively enhanced by mitochondrial specifically distributed NuBCP-9 peptides, which converted Bcl-2 function from anti-apoptotic to pro-apoptotic and paved the way for the development of mitochondrial impairment. The combination treatment exhibited significant damage to mitochondria, including excess reactive oxygen species (ROS), the permeabilization of mitochondrial outer membrane (MOMP), and apoptosis initiation on 4T1 breast cancer cells. Meanwhile, besides enhanced tumor growth suppression, the combination treatment also improved the inhibition of 4T1 breast cancer metastasis both in vitro and in vivo. By increasing the expression of cytochrome C and decreasing the expression of Bcl-2, metal matrix protease-9 (MMP-9) as well as vascular endothelial growth factor (VEGF), the combination treatment successfully decreased 84% lung metastasis. Overall, our work provided a promising strategy for metastatic cancer treatment through mitochondria-targeting anti-cancer drug delivery and combination with mitochondrial distributed Bcl-2 function-converting peptide.

A novel mitochondrial targeted hybrid peptide modified HPMA copolymers for breast cancer metastasis suppression.

Primary tumor metastasis remains to be a tough obstacle for clinical breast cancer treatment. Since evidences have shown that mitochondria play a crucial role in tumor metastasis, we designed a mitochondrial targeted drug delivery system (P-D-R8MTS) based on N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers to simultaneously inhibit breast cancer progression and metastasis. A novel mitochondrial targeted hybrid peptide R8MTS, which consists of a cell penetrating peptide octaarginine (R8) and a mitochondrial targeting sequence ALD5MTS, was used as targeting ligand and attached to doxorubicin (DOX) as model drug (DOX-R8MTS). After entering into the tumor cells, DOX-R8MTS was pH-responsibly released from HPMA copolymer backbone in acidic lysosome and efficiently targeted to mitochondria, resulting in enhanced reactive oxygen species (ROS) generation and apoptosis initiation. By destroying mitochondria, P-D-R8MTS not only inhibited cell proliferation but also suppressed migration and invasion of breast cancer 4T1 and MDA-MB-231 cells in vitro. Moreover, P-D-R8MTS exhibited superior inhibition of tumor growth and showed no apparent lung metastatic nodules on 4T1-bearing mice in vivo, which was partially via down-regulation of typical proteins associated with tumor metastasis and invasion: matrix metalloproteinases-2 (MMP-2), vascular endothelial growth factor (VEGF) and transforming growth factor-ß (TGF-ß). Collectively, our work provided a prospectively potential strategy for metastatic cancer treatment through mitochondrial targeted drug delivery.