Activation of dynamin-related protein 1 - dependent mitochondria fragmentation and suppression of osteosarcoma by cryptotanshinone

Background

Discovering how to regulate mitochondrial function to reduce cancer growth holds great potential for future cancer therapy development. Here we explore the effects of cryptotanshinone (CPT), a natural product derived from Salvia miltiorrhiza, on mitochondria of osteosarcoma (OS) both in vitro and in vivo, and further elucidate the underlying molecular mechanisms.

Methods

Cytotoxicity in the CPT treated OS cells was analyzed by flow cytometry, CCK8, TUNEL assay and colony formation assays. Flow cytometric analysis was performed to evaluate the effect of CPT on cell cycle of OS cells. Mitochondrial morphology was examined by staining with the mitochondrial membrane potential -sensitive fluorochrome, MitoTracker Red (CMXRos). Immunoblotting, confocal-immunofluorescence staining, co-immunoprecipitation were used to examine the expression and interaction between CPT-mediated Drp1 and Bax. Finally, the synergistic effect of CPT on OS cells was validated using a mouse xenograft tumor model.

Results

In this study, we found CPT treatment induced S-phase arrest, apoptosis, and mitochondrial fragmentation in OS cells. CPT also effectively activated caspase-dependent apoptosis, which could be blocked by pan-caspase inhibitor Z-VAD-FMK. Moreover, we herein provide evidence that treatment with CPT resulted in mitochondrial fragmentation, which is mediated by dynamin-related protein 1 (Drp1), a key mediator of mitochondrial fission. Pursuing this observation, downregulation of Drp1 via silencing RNA could abrogate the induction of apoptosis and mitochondrial fragmentation induced by CPT. Finally, we demonstrate that CPT induced Drp1, which interacted directly with Bcl-2-associated X protein (Bax), which contributed to driving Bax translocation from the cytosol to the mitochondria.

Conclusions

Our findings offer insight into the crosstalk between mitochondrial fragmentation and inhibition of osteosarcoma cell growth in response to CPT.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-1008-8) contains supplementary material, which is available to authorized users.

A CFD study of the deep bed filtration mechanism for submicron/nano-particle suspension

The mechanism of the deep bed filtration for submicron and nano particles suspension was conducted by means of a force analysis on the suspended particles flow path through order-packed granular filter beds. The flow fields through the filter beds were calculated by using the commercial available CFD software--Fluent. Various types of granular packing structures, such as the simple cubic packing, body-centered packing and face-centered packing structures were chosen for analysis. The motion of suspended particle of 2.967, 0.816, 0.460 and 0.050 microm in diameter, respectively, were tracked by considering the following forces including a net gravitational force, hydraulic drag force, lift force, Brownian force, van der Waals force and a double layer force. The effects of the granular bed packing structure, the porosity of these beds and the suspended particle diameter on the capture efficiency of a granular filter bed were examined. The force analysis depicts that the inertial effect and van der Waals force increased the capture probability of particles on the granular filter bed while the lift force and the Brownian force decreased the particle deposition. Simulated results show that among the chosen packing structures, the face-center packed granular bed gives the greatest pressure drop and capture efficiency of particles due to the lower packing porosity. The simple cubic packed filter bed showed the lowest pressure drop and capture efficiency of particles due to the greatest packing porosity among the chosen packing structures. It is mainly due to the simple cubic packing structure in which there exists the free vertical downward flowing path and thus exhibits a higher packing porosity. The comparisons of the simulated capture efficiency with experimental results depicted that the body-centre packed granular bed showed the best approximation of capture efficiency compared to that of the randomly packed granular bed.