Bcl-2 over-expression and activation of protein kinase C suppress the Trail-induced apoptosis in Jurkat T cells

Trail, a tumor necrosis factor-related apoptosis-inducing ligand, is a novel potent endogenous activator of the cell death pathway through the activation of cell surface death receptors Trail-R1 and Trail-R2. Its role, like FasL in activation-induced cell death (AICD), has been demonstrated in immune system. However the mechanism of Trail induced apoptosis remains unclear. In this report, the recombinant Trail protein was expressed and purified. The apoptosis-inducing activity and the regulation mechanism of recombinant Trail on Jurkat T cells were explored in vitro. Trypan blue exclusion assay demonstrated that the recombinant Trail protein actively killed Jurkat T cells in a dose-dependent manner. Trail-induced apoptosis in Jurkat T cells were remarkably reduced by Bcl-2 over expression in Bcl-2 gene transfected cells. Treatment with PMA (phorbol 12-myristate 13-acetate), a PKC activator, suppressed Trail-induced apoptosis in Jurkat T cells. The inhibition of apoptosis by PMA was abolished by pretreatment with Bis, a PKC inhibitor. Taken together, it was suggested that Bcl-2 over-expression and PMA activated PKC actively down-regulated the Trail-mediated apoptosis in Jurkat T cell.

Killing effect of TNF-related apoptosis inducing ligand regulated by tetracycline on gastric cancer cell line NCI-N87

AIM: To clone the cDNA fragment of human TRAIL (TNF-related apoptosis inducing ligand) into a tetracycline-regulated gene expression system, the RevTet-On system, transduce expression vectors into a gastric carcinoma cell line-NCI-N87 and examine the effects of controlled expression of TRAIL in vitro on the gastric carcinoma cells. METHODS: The full-length cDNA of TRAIL was inserted into a vector under the control of the tetracycline-responsive element (TRE) to obtain the plasmid pRevTRE-TRAIL, which was transfected into a packaging cell line PT67. In addition, vector pRev-Tet On and pRevTRE were also transfected into PT67 separately. After hygromycin and G418 selection, the viral titer was determined. The medium containing retroviral vectors was collected and used to transduce a gastric carcinoma cell line NCI-N87. The resulting cell line NCI-N87-Tet On TRE-TRAIL and a control cell line, NCI-N87 Tet On-TRE, were established. TRAIL expression in the cell line was induced by incubating cells with doxycycline (Dox), which is a tetracycline analogue. The killing effect on gastric carcinoma cells was analyzed after induction. RESULTS: The recombinant plasmid pRev-TRE-TRAIL was constructed. After hygromycin or G418 selection, the producer cell lines PT67-TRE, PT67-TRE-TRAIL and PT67-Tet On were obtained,with titers of about 10(8)CFU.L(-1). By transducing NCI-N87 cells with retroviral vectors from these cell lines, stable cell lines NCI-N87-Tet-On TRE-TRAIL (NN3T) and control cell line NCI-N87-Tet-On-TRE (NN2T) were established. The growth curves of the selected cell lines were the same with the wild type NCI-N87. When Dox was added, cell death was obvious in the test groups (29%-77%), whereas no difference was observed in control and wild type cell lines. With the addition of a medium from the test group, human leukemia cell line Jurkat was activated till death (83%), indicating the secretion of active TRAIL proteins from the test cells to the medium. CONCLUSION: With the use of the RevTet-On system, a regulated expression system for TRAIL was constructed. Using this system, the selected killing effect of TRAIL on gastric carcinoma cell line NCI-N87 could be observed.

Flavone from Zhongjiefeng(Herba Sarcandrae Glabrae) inhibits platelet apoptosis in immune-induced bone marrow failure through mitochondrial pathway

OBjECTIVE: To investigate the effect of Flavone from Zhongjiefeng(Herba Sarcandrae Glabrae) on the platelet number in immune-induced bone marrow failure(BMF) and its mechanism of mitochondrial apoptotic pathway.METHODS: Immune-induced BMF model, established in mice, was randomly divided into four groups: normal control group without BMF, BMF control group, cyclosporine(CSA) group and flavone group(n = 10 in each group). Mice were given0.027 g/kg cyclosporine or 0.2 g/kg flavone lavage daily in either the cyclosporine or flavone group respectively. Platelet count, mitochondrial transmembrane potential(ΔΨm), cytochrome C(Cyt C), phosphatidylserine(PS), changes of calcium ion(Ca^(2+)),and protein expression of mitochondrial apoptotic pathway including B-cell lymphoma-2(bcl-2) Homologous Antagonist-Killer Protein(Bak), bcl-2-associated X protein(Bax), caspase-3, caspase-8, and caspase-9 were examined and compared.RESULTS: Compared with the normal control group, the BMF group had significantly lower levels of platelet count, ΔΨm, and expressions of caspase family proteins as well as higher levels of Cyt C, PS,Ca^(2+), and expressions of Bak and Bax(all P < 0.05).Compared with the BMF group, the CSA and flavone groups had significantly higher ΔΨm and expressions of caspase family proteins(all P < 0.05)whereas the levels of Cyt C, PS, Ca^(2+), and expressions of Bak and Bax were reduced(all P < 0.05).More importantly, the flavone group had higher levels of Cyt C, Ca^(2+)and expressions of Bak and Bax compared with the CSA group(all P < 0.05), while the levels of PS and caspase family proteins were reduced(all P < 0.05).CONCLUSION: Flavone from Zhongjiefeng(Herba Sarcandrae Glabrae) significantly increases the platelet number and prevents its apoptosis through mitochondrial pathway.

Neuroprotective Effect of Fructus broussonetiae on APP/PS1 Mice via Upregulation of AKT/β-Catenin Signaling

Objective:To evaluate the mechanisms underlying the protective effect of Chinese herbal medicine Fructus broussonetiae(FB)in both mouse and cell models of Alzheimer’s disease(AD).Methods:APP/PS1 mice treated with FB for 2 months and vehicle-treated controls were run through the Morris water maze and object recognition test to evaluate learning and memory capacity.RNA-Seq,Western blotting,and immunofluorescence staining were also conducted to evaluate the effects of FB treatment on various signaling pathways altered in APP/PS1 mice.To further explore the mechanisms underlying FB’s protective effect,PC-12 cells were treated with Aβ25–35 in order to establish an in vitro model of AD.Results:FB-treated mice showed improved learning and memory capacity on both the Morris water maze and object recognition tests.RNA-seq of hippocampal tissue from APP/PS1 mice showed that FB had effects on multiple signaling pathways,specifically decreasing cell apoptotic signaling and increasing AKT and β-catenin signaling.Similarly,FB up-regulated both AKT and β-catenin signaling in PC-12 cells pre-treated with Aβ25–35,in which AKT positively regulated β-catenin signaling.Further study showed that AKT promoted β-catenin signaling via enhancing β-catenin(Ser552)phosphorylation.Moreover,AKT and β-catenin signaling inhibition both resulted in the attenuated survival of FB-treated cells,indicating the AKT/β-catenin signaling is a crucial mediator in FB promoted cell survival.Conclusions:FB exerted neuroprotective effects on hippocampal cells of APP/PS1 mice,as well as improved cell viability in an in vitro model of AD.The protective actions of FB occurred via the upregulation of AKT/β-catenin signaling.