[The role of the PI3K/AKT signaling pathway in DADS-induced apoptosis of K562 cells].

OBJECTIVE: To study the role of the PI3K/AKT signaling pathway in the diallyl disulfide (DADS)-induced apoptosis of K562 cells. METHODS: K562 cells in the logarithmic growth phase were treated with 10, 20, 40, or 80 mg/L DADS for 48 hours, then fixed and stained with acridine orange/ethidium bromide (AO/EB), and examined for cellular morphological changes under an inverted microscope. Annexin V-FITC/PI staining was used for determining the apoptotic rates, and Western blot for measuring the expression of AKT, p-AKT, and Caspase-3. Two control groups, blank and solvent, were used as references. RESULTS: K562 cells treated with DADS for 48 hours exhibited the characteristic morphological features of apoptosis including cell shrinkage, irregular cell shape, and membrane blebbing. AO/EB staining results demonstrated that the number of apoptotic cells with cell shrinkage, pyknotic or bead-like nuclei, chromatin condensation, and orange staining increased with the increasing DADS concentration, and 40 mg/L DADS had the most significant effect. The apoptotic rates of cells treated with 10, 20, 40, and 80 mg/L DADS were all significantly higher than those in the control groups (P<0.05). There were no significant differences in AKT protein expression between the K562 cells treated with different concentrations of DADS; the p-AKT protein expression decreased with the increasing DADS concentration, while the Caspases-3 protein expression increased with the increasing DADS concentration (P<0.05). CONCLUSIONS: DADS induces the apoptosis of K562 cells, probably through inhibiting the protein expression in the PI3K/AKT signaling pathway.

Cathepsin B contributes to traumatic brain injury-induced cell death through a mitochondria-mediated apoptotic pathway.

It has been reported that lysosomal proteases play important roles in ischemic and excitotoxic neuronal cell death. We have previously reported that cathepsin B expression increased remarkably after traumatic brain injury (TBI). The present study sought to investigate the effects of a selective cathepsin B inhibitor (CBI) [N-L-3-trans-prolcarbamoyloxirane-2-carbonyl)-L-isoleucyl-L-proline] on cell death and behavioral deficits in our model. We examined the levels of cathepsin B enzymatic activity and its expression by double labelling damaged cells in the brain slice with propidium iodide (PI) and anticathepsin B. The results showed an elevated enzymatic activity associated with TBI-induced increase in a mature form of cathepsin B, suggesting that cathepsin B may play a role in TBI-induced cell injury. PI was found to label cells positive for the neuronal-specific nuclear marker NeuN, whereas fewer GFAP-positive cells were labelled by PI, suggesting that neurons are more sensitive to cell death induced by TBI. Additionally, we found that pretreatment with CBI remarkably attenuated TBI-induced cell death, lesion volume, and motor and cognitive dysfunction. To analyze the mechanism of action of cathepsin B in the cell death signaling pathway, we assessed DNA fragmentation by electrophoresis, Bcl-2/Bax protein expression levels, Bid cleavage, cytochrome c release, and caspase-3 activation. The results imply that cathepsin B contributes to TBI-induced cell death through the present programmed cell necrosis and mitochondria-mediated apoptotic pathways.