Pinacidil protects osteoblastic cells against antimycin A-induced oxidative damage

Inflammation produced by senescent osteocytes mediates age-related bone loss

Purpose

The molecular mechanisms of age-related bone loss are unclear and without valid drugs yet. The aims of this study were to explore the molecular changes that occur in bone tissue during age-related bone loss, to further clarify the changes in function, and to predict potential therapeutic drugs.

Methods

We collected bone tissues from children, middle-aged individuals, and elderly people for protein sequencing and compared the three groups of proteins pairwise, and the differentially expressed proteins (DEPs) in each group were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). K-means cluster analysis was then used to screen out proteins that continuously increased/decreased with age. Canonical signaling pathways that were activated or inhibited in bone tissue along with increasing age were identified by Ingenuity Pathway Analysis (IPA). Prediction of potential drugs was performed using the Connectivity Map (CMap). Finally, DEPs from sequencing were verified by Western blot, and the drug treatment effect was verified by quantitative real-time PCR.

Results

The GO and KEGG analyses show that the DEPs were associated with inflammation and bone formation with aging, and the IPA analysis shows that pathways such as IL-8 signaling and acute-phase response signaling were activated, while glycolysis I and EIF2 signaling were inhibited. A total of nine potential drugs were predicted, with rapamycin ranking the highest. In cellular experiments, rapamycin reduced the senescence phenotype produced by the H₂O₂-stimulated osteocyte-like cell MLO-Y4.

Conclusion

With age, inflammatory pathways are activated in bone tissue, and signals that promote bone formation are inhibited. This study contributes to the understanding of the molecular changes that occur in bone tissue during age-related bone loss and provides evidence that rapamycin is a drug of potential clinical value for this disease. The therapeutic effects of the drug are to be further studied in animals.

Mitoflash generated at the Qo site of mitochondrial Complex III

The previous research has shown that mitochondrial flash (mitoflash) genesis are functionally and mechanistically integrated with mitochondrial electron transport chain (ETC) energy metabolism. However, the response of mitoflash to superoxide is not entirely consistent with the response of MitoSOX Red. The generation mechanism of mitoflash is still unclear. Here, we investigated mitoflash activities, using the different combinations of ETC substrates and inhibitors, in permeabilized cardiomyocytes or hearts. We found that blocking the complete electron flow, from Complex I to IV, with any one of ETC inhibitors including rotenone (Rot), antimycin A (AntA), myxothiazol (Myxo), stigmatellin, and sodium cyanide, will lead to the abolishment of mitoflashes triggered by substrates in adult permeabilized cardiomyocytes. However, Myxo boosted mitoflashes triggered by the reverse electron of N,N,N',N'-tetramethyl-p-phenylenediamine/ascorbate. Moreover, Rot and AntA furtherly enhanced mitoflash activity rather than depressed it, suggesting that mitoflashes generated at the Complex III Qo site. Meanwhile, the inhibition of Complex III protein expression resulted in the activity of Complex III decrease, which decreased mitoflash frequency. The function defect (no change of protein level) of the Qo site of Complex III in aging hearts augmented mitoflash generation confirmed the Qo site function was critical to mitoflash genesis. Thus, our results indicate that mitoflash detected by circularly permuted yellow fluorescent protein is generated at the Qo site of Complex III.

[Role of adenosine triphosphate-sensitive potassium channel in hydrogen sulfide-induced inhibition of high glucoseinduced osteoblast damage]

OBJECTIVE

The aim of this study is to identify the role of adenosine triphosphate-sensitive potassium channel (KATP) in hydrogen sulfide (H₂S)-induced inhibition of high glucose (HG)-induced osteoblast damage.

METHODS

Osteoblasts from rat mandible were cultured and identified. The osteoblasts were then treated with HG, H₂S, KATP channel opener pinacidil (Pia), and KATP channel blocker glibenclamide (Gli). Western blot method was performed to detect the expression of KATP channel protein. CCK8, reverse transcriptase polymerase chain reaction (RT-PCR) , and image analysis were used to determine the effects of H₂S-KATP on the proliferation, differentiation, and mineralization of osteoblasts.

RESULTS

The expression of KATP channel protein in osteoblasts was significantly decreased under the influence of HG. H₂S pretreatment significantly inhibited HG on KATP channel protein down-regulation. Moreover, H₂S pretreatment significantly inhibited the effect of HG on the proliferation of osteoblasts, thereby preventing HG-induced inhibition of osteoblasts differentiation and mineralization. Meanwhile, the KATP channel blocker effectively blocked the H₂S on osteoblasts and had a protective effect.

CONCLUSIONS

Through the KATP channel, H₂S inhibited osteoblasts damage induced by HG.