7,8,3′-Trihydroxyflavone ameliorate oxidative stress in vivo and promotes neurite regeneration in vitro in rat retinal ganglion cells

7,8,3'-Trihydroxyflavone prevents doxorubicin-induced cardiotoxicity and mitochondrial dysfunction via activating Akt signaling pathway in H9c2 cells

Clinical application of the widely used chemotherapeutic agent, doxorubicin (DOX), is limited by its cardiotoxicity. Mitochondrial dysfunction has been revealed as a crucial factor in DOX-induced cardiotoxicity. 7,8,3'-Trihydroxyflavone (THF) is a mimetic brain-derived neurotrophic factor with neuroprotective effects. However, the potential effects of THF on DOX-induced cardiomyocyte damage and mitochondrial disorders remain unclear. H9c2 cardiomyoblasts were exposed to DOX and/or THF at different concentrations. Cardiomyocyte injury was evaluated using lactate dehydrogenase (LDH) assay and Live/Dead cytotoxicity kit. Meanwhile, mitochondrial membrane potential (MMP), morphology, mitochondrial reactive oxygen species (mito-ROS) production, and the oxygen consumption rate of cardiomyocytes were measured. The protein levels of key mitochondria-related factors such as adenosine monophosphate-activated protein kinase (AMPK), mitofusin 2 (Mfn2), dynamin-related protein 1 (Drp1), and optic atrophy protein 1 (OPA1) were examined. We found that THF reduced LDH content and death ratio of DOX-treated cardiomyocytes in a concentration-dependent manner, while increasing MMP without significantly affecting the routine and maximum capacity of mitochondrial respiration. Mechanistically, THF increased the activity of Akt and protein levels of Mfn2 and heme oxygenase 1 (HO-1). Moreover, inhibition of Akt reversed the protective role of THF, increased mito-ROS levels, and repressed Mfn2 and HO-1 expression. Therefore, we conclude, THF relieves DOX-induced cardiotoxicity and improves mitochondrial function by activating Akt-mediated Mfn2 and HO-1 pathways. This finding provides promising therapeutic insights for DOX-induced cardiac dysfunction.

A modified fabrication procedure of retinal explant and optimized formulation of culture medium in a three-dimensional retinal culture system

BACKGROUND

Three-dimensional culture system of retinal explant is commonly used to study retinal ganglion cell (RGC) axon regeneration in vitro. The retinal explants fabricated by traditional procedure in culture system, however, are usually too small (merely 0.5 × 0.5 mm) to be easily detected or treated by current experimental techniques. Also, the constituents of culture medium have not been fully elucidated.

NEW METHOD

A fabrication procedure was developed to enlarge the retinal explants and explore the reasonable concentration of fetal bovine serum (FBS) for evaluating axonal regeneration.

RESULTS

There were no significant differences in the density or length of regenerative neurites in the retinal explants fabricated by traditional and modified procedures. Increased FBS concentrations promoted neurite regeneration, decreased RGCs apoptosis, and activated tyrosine kinase B (TrkB) receptors, all reaching a plateau at 1 % FBS.

COMPARISON WITH EXISTING METHODS

Compared with traditional procedure, the modified fabrication procedure facilitates application of experimental techniques to retinal explants, increases the efficiency of obtaining observation area of regenerating neurites, and reduces the wastage of retinal tissues. The recommended FBS concentration determined in this study is shown to be more suitable for studying neuronal regeneration.

CONCLUSION

The retinal explants made by the modified fabrication procedure are successfully applied to the three-dimensional culture system, and presented several advantages over the traditional one. Furthermore, a preliminary experiment must be performed to determine the suitable concentration of FBS in each study to ensure accuracy and stability of the results obtained from the three-dimension retinal culture system.

6,7,4'-Trihydroxyflavone inhibits osteoclast formation and bone resorption in vitro and in vivo

The balance between the osteoblasts and the osteoclasts is important for the maintenance of the skeleton of the human body. The osteoclasts absorb bone after differentiated into polymorphonuclear cells by the fusion of monocytes/macrophages. We have found that 6,7,4'-Trihydroxyflavone (THF), a compound from the heartwood of Dalbergia Odorifera inhibits receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation, actin ring formation, and bone resorption in RAW 264.7 cells and bone marrow macrophage. THF significantly inhibited the c-Jun-N-terminal kinase signaling pathway without affecting extracellular signal-regulated kinase, p38, and AKT signaling. Moreover, THF inhibited the expression of c-Fos, nuclear factor-activated T cells cytoplasm 1, cathepsin K, and c-src by RANKL. We used a lipopolysaccharide (LPS)-induced bone loss model in mice. Consequently, bone volume per tissue volume, trabecular number's reduction was recovered in THF-treated mice, and trabecular separation's augmentation was also attenuated by THF administration. In summary, THF inhibits RANKL-induced osteoclast differentiation by MAPK signaling pathway and inhibits bone resorption by destroying the actin ring in mature osteoclasts. THF also prevented LPS-induced bone loss in a mice model. Thus, THF may be useful in the treatment of bone diseases associated with excessive osteoclast differentiation and bone resorption.