Lipopolysaccharides-activated human astroglioma cells induce apoptotic death of T-lymphocytes via c-Jun N-terminal kinases-dependent up-regulation of TRAIL

MiR-98 Protects Nucleus Pulposus Cells against Apoptosis by Targeting TRAIL in Cervical Intervertebral Disc Degeneration

The excessive apoptosis of nucleus pulposus (NP) cells is a major risk factor in the progress of cervical intervertebral disc degeneration (IVDD). In this study, we investigated the impact of miR-98 on apoptosis of NP cells and the potential molecular mechanisms. Lipopolysaccharide (LPS) was used to establish an NP cell IVDD model. The sponging effect of miR-98 on TRAIL 3′UTR was predicted by ENCORI and assessed by the dual-luciferase reporter gene system. The expression levels of miR-98, TRAIL, and TRAIL pathway-related genes were tested by qRT-PCR, Western blot, and immunofluorescence analysis. Cell apoptosis was analyzed by Hoechst 33258 staining and flow cytometry. Cell viability was analyzed by MTT assay. It was found that the expression level of miR-98 was downregulated, while the level of TRAIL was upregulated in IVDD tissues, and their levels were negatively and positively associated with the clinical MRI grade, respectively. The LPS treatment resulted in a significant decrease of the miR-98 expression level and an increase of the TRAIL expression level in NP cells. miR-98 reduced NP cell apoptosis under LPS treatment in vitro. miR-98 directly targeted TRAIL. Moreover, the mRNA and protein levels of DR5, FADD, cleaved caspase8, cleaved caspase3, and cleaved PARP were downregulated by miR-98 overexpression. Overexpression of TRAIL partially reversed the suppressive roles of miR-98 on cell apoptosis and activation of the TRAIL pathway. We concluded that miR-98 inhibited apoptosis of NP cells by inactivating the TRAIL pathway via targeting TRAIL in IVDD NP cells. These results indicated that miR-98 might be a therapeutic target for IVDD.

Heat-Labile Enterotoxin-Induced PERK-CHOP Pathway Activation Causes Intestinal Epithelial Cell Apoptosis

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of diarrhea among children and travelers in developing countries, and heat-labile enterotoxin (LT) is one of the most important virulence factors. The pathogenesis of and virulence factors associated with ETEC have been well-characterized; however, the extent to which ETEC damages host cells remains unclear. In this study, we found that LT could induce decreases in intestinal epithelial cell viability and induce apoptosis in a dose- and time- dependent manner in both HCT-8 and Caco-2 cells. We analyzed the expression profiles of apoptosis-related proteins via protein array technology and found that Bax, p-p53(S46), cleaved caspase-3, and TNFRI/TNFRSF1A expression levels were significantly up-regulated in wild-type ETEC- but not in ΔLT ETEC-infected HCT-8 cells. Bax is essential for endoplasmic reticulum (ER) stress-triggered apoptosis, and our RNAi experiments showed that the PERK-eIF2-CHOP pathway and reactive oxygen species (ROS) are also main participants in this process. LT-induced ROS generation was decreased in CHOP-knockdown HCT-8 cells compared to that in control cells. Moreover, pretreatment with the ROS inhibitor NAC down-regulated GRP78, CHOP, Bim, and cleaved caspase-3 expression, resulting in a reduction in the apoptosis rate from 36.2 to 20.3% in LT-treated HCT-8 cells. Furthermore, ROS inhibition also attenuated LT-induced apoptosis in the small intestinal mucosa in the ETEC-inoculation mouse model.

Hypoxia-ischemia upregulates TRAIL and TRAIL receptors in the immature rat brain

The immature brain is susceptible to inflammatory injury induced by hypoxia-ischemia (HI) or infection, which causes serious neurodevelopmental disabilities in the survivors of preterm births. Recently, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptors (death receptor DR4/5 and decoy receptor DcR1/2) were reported to mediate various neuroinflammatory responses. However, little information is available regarding the role of TRAIL and its receptors in the immature brain after HI. The purpose of this study was to evaluate the expression of TRAIL and its receptors in the immature brain after HI and relate this expression to neurological function. We performed right common carotid artery ligation followed by hypoxia (6% O(2), 37°C) for 2.5 h to induce HI in postnatal day 3 rats. The distribution of TRAIL and its receptors, caspase-3 and CD68-labeled microglia/macrophages was evaluated 24 h after HI by immunostaining. The protein and mRNA expression of TRAIL and DR5 was measured by Western blot and real-time PCR, respectively. Delayed neuronal loss was evaluated by NeuN and Nissl staining 7 days after HI. Furthermore, neurological deficits were evaluated by a righting reflex test, time of eye opening and T-maze test. The expression of TRAIL, DR5 and DcR1/2 receptors and caspase-3 was more pronounced in the ipsilateral hemisphere compared with the contralateral part and the control group 24 h after HI. DR5/active caspase-3 double-positive cells were observed at 24 h after HI in the ipsilateral hemisphere but not in the contralateral hemisphere. The TRAIL and CD68 double-labeled cells were more pronounced in the ipsilateral cortical regions compared with the corresponding regions of the contralateral part. HI also resulted in a significant increase in TRAIL and DR5 protein and mRNA expression at 24 h, which corresponded to neuronal cell loss 7 days after HI. Furthermore, the HI group displayed impaired neurobehavioral development compared with the control group (p < 0.05). Altogether our results show that the TNF-α superfamily ligand TRAIL is induced on CD68+ microglia/macrophages after perinatal HI and that one of its receptors, DR5, is induced on neocortical neurons and glial cells. That many DR5+ cells were also caspase-3+ strongly supports the conclusion that these signaling molecules are involved in the delayed loss of neurons in the neocortex and in the neurobehavioral deficits that are often seen after perinatal HI.

Infarct volume after transient middle cerebral artery occlusion (MCAo) can be reduced by attenuation but not by inactivation of c-Jun action

Stroke therapy aims to save penumbral tissue from apoptosis that is activated in response to the ischemic injury. Since the c-Jun transcription factor plays a crucial role in promoting apoptosis, inhibition of its activation might reduce the final infarct size and thus increase functional outcome. To test this hypothesis we made use of four genetically modified mouse lines influencing the c-Jun pathway at various steps. Upon transient middle cerebral artery occlusion for 90 min and 24 h of reperfusion, infarct volume and number of ATF-2-, TUNEL- and cleaved Caspase-3-positive cells were determined in conditional c-Jun knock-out mice (cond. c-Jun), mice overexpressing JunB (JunBtg), mice lacking the phosphoacceptor serines 63 and 73 of c-Jun (JunAA) and in mice overexpressing Bcl-2 (Bcl-2tg). Cond. c-Jun as well as JunAA mice did not show significant differences in the infarct size when compared to their non-mutant controls. By contrast smaller infarct volumes were detected in transgenic mice merely attenuating c-Jun action (JunBtg and Bcl-2tg). ATF-2, TUNEL or cleaved Caspase-3 staining revealed no significant differences between the experimental groups. A complete lack of functional c-Jun might be compensated by other cellular mechanisms, in contrast to its reduced function. Thus, our data suggest that attenuation rather than a complete block of c-Jun action appears to be more promising for therapy of stroke.

Dendritic cell-based active specific immunotherapy for malignant glioma

Immunotherapy is an appealing therapeutic modality for malignant gliomas because of its potential to selectively target residual tumor cells that have invaded the normal brain. Most immunotherapeutic studies are designed to exploit the capacity of dendritic cells for inducing cell-mediated effects as well as immune memory responses for destroying residual tumor cells and preventing recurrence. Although initial clinical studies on dendritic cell-based immunotherapy resulted in very limited success, they have prompted many new studies on exploring strategies to induce a more robust antitumor immune response by using novel adjuvants for maturation and activation of dendritic cells. More studies have focused on the mechanisms of immune suppression by tumor cells and the role of regulatory T cells in tumor growth and progression. In this article, the authors review the evolution of dendritic cell-based immunotherapeutic strategies for adjuvant treatment of malignant gliomas. The authors also discuss how new knowledge on tumor-intrinsic mechanisms of tolerance induction and immunosuppression are likely to shape the future of immunotherapy for high-grade gliomas.

Trail interacts redundantly with nitric oxide in rat astrocytes: potential contribution to neurodegenerative processes

The proapoptotic cytokine TRAIL has been shown to enhance amyloid-beta-dependent neurotoxicity. Here are reported interactions between TRAIL and nitric oxide (NO) in cultured rat astrocytes in vitro. Rat astrocytes expressed all TRAIL receptor mRNAs and proteins. However, TRAIL failed in inducing apoptosis of astrocytes, whereas these cells released substantial amounts of nitrites. A TRAIL-neutralizing antibody was able to prevent LPS-induced iNOS expression in astrocytes. Interestingly, TRAIL induced its own expression in astrocytes. These data suggest that redundancy between TRAIL and NO in astrocytes could be fueling neuronal damage/death processes, potentially uncovering novel molecular targets for the treatment of neurodegenerative disorders.

Inhibition of transcription factor NF-κB in the central nervous system ameliorates autoimmune encephalomyelitis in mice

Activation of transcription factor NF-kappaB in the central nervous system (CNS) has been linked to autoimmune demyelinating disease; however, it remains unclear whether its function is protective or pathogenic. Here we show that CNS-restricted ablation of 'upstream' NF-kappaB activators NEMO or IKK2 but not IKK1 ameliorated disease pathology in a mouse model of multiple sclerosis, suggesting that 'canonical' NF-kappaB activation in cells of the CNS has a mainly pathogenic function in autoimmune demyelinating disease. NF-kappaB inhibition prevented the expression of proinflammatory cytokines, chemokines and the adhesion molecule VCAM-1 from CNS-resident cells. Thus, NF-kappaB-dependent gene expression in non-microglial cells of the CNS provides a permissive proinflammatory milieu that is critical for CNS inflammation and tissue damage in autoimmune demyelinating disease.