Inhibition of Caspase-8 Activity Improves Freezing Efficiency of Male Germline Stem Cells in Mice

Cryopreservation of male germline stem cells (GSCs) is an essential technique for their long-term preservation and utilization in various fields. However, the specific apoptosis pathways involved in cryoinjury during freezing remain unclear. Therefore, our study sought to identify the pathways involved in cryoinjury-induced apoptosis and thereby to improve freezing efficiency during GSC cryopreservation through the creation of a specific molecular-based cryoprotectant. The activities of caspase-8, caspase-9, caspase-3, and caspase-7 were assessed by Western blot analyses to determine the role of specific apoptosis pathways in GSC cryoinjury. Specifically, the role of a specific caspase was identified by recovery rate, relative proliferation rate, Annexin V/propidium iodide co-staining, and caspase activity using its inhibitor and activator. Moreover, the safety of the cryoprotectant was assessed by immunofluorescence and quantitative real-time polymerase chain reaction (qRT-PCR). Furthermore, the efficacy of the molecular-based cryoprotectant was assessed using frozen cells in the presence of dimethyl sulfoxide (DMSO) (control), trehalose, a caspase-8 inhibitor Z-IETD-FMK [ZIF], or a mixture of the aforementioned compounds, after which the changes in Src signaling were measured. Our results demonstrated that caspase-8 plays a major role in cryoinjury-induced apoptosis and therefore its inhibition improves freezing efficiency. Specifically, a significantly higher relative proliferation rate was observed in the Z-IETD-FMK 0.01 μM-treated cells than in the DMSO control (100% ± 6.2% vs. 189.8% ± 9.5%), with decreases in both early apoptosis (16.6% ± 2.2% vs. 7.5% ± 1.0%) and caspase-8 activity (1.0-fold vs. 0.4-fold). The relative proliferation rate was significantly higher in the cryoprotectant mixture (246.0% ± 12.2%) than other individual treatment groups (trehalose 200 mM, 189.8% ± 9.5%; Z-IETD-FMK 0.01 μM, 189.7% ± 2.2%) with no significant differences in Src signaling. Therefore, our findings provide novel insights into the development of freezing protocols to enhance GSC freezing efficiency, thereby facilitating the wider adoption of GSCs in the livestock industry and/or clinical trials.

Upregulation of death receptor 5 and activation of caspase 8/3 play a critical role in ergosterol peroxide induced apoptosis in DU 145 prostate cancer cells

Background

Though ergosterol peroxide (EP) derived from Neungyi mushrooms (Sarcodon aspratus) was known to have cytotoxic, apoptotic, anti-inflammatory and antimycobacterial effects, the underlying molecular mechanism of EP still remains unclear. Thus, in the present study, the apoptotic mechanism of EP was elucidated in DU 145 prostate cancer cells.

Methods

Cell viability of prostate cancer cells was measured by MTT assay. To see whether EP induces the apoptosis, FACS, western blot and TUNEL assay were performed. To determine the role of Death receptor (DR) 5 molecules in EP-induced apoptosis in DU 145 prostate cancer cells, the silencing of DR 5 was performed by using siRNAs.

Results

EP showed significant cytotoxicity against DU 145, PC 3, M2182 prostate cancer cells. Also, EP effectively increased the sub G1 population and terminal deoxynucleotidyl transferase DUTP nick end labeling (TUNEL) positive cells in DU 145 prostate cancer cells. Furthermore, western blotting revealed that EP cleaved poly (ADP-ribose) polymerase (PARP) and caspase 8/3, attenuated the expression of fluorescence loss in photobleaching (FLIP), Bcl-_XL and Bcl-2 as well as activated Bax, Fas-associated death domain (FADD) and DR 5 in a concentration dependent manner in DU 145 prostate cancer cells. Conversely, caspase 8 inhibitor Z-IETD-FMK blocked the apoptotic ability of EP to cleave PARP and an increase of sub G1 population in DU 145 prostate cancer cells. Likewise, the silencing of DR 5 suppressed the cleavages of PARP induced by EP in DU 145 prostate cancer cells.

Conclusion

Overall, our findings suggest that ergosterol peroxide induces apoptosis via activation of death receptor 5 and caspase 8/3 in DU 145 prostate cancer cells as a cancer chemopreventive agent or dietary factor.