TNIP1‐mediated TNF‐α/NF‐κB signalling cascade sustains glioma cell proliferation

As a malignant tumour of the central nervous system, glioma exhibits high incidence and poor prognosis. Although TNIP1 and the TNF‐α/NF‐κB axis play key roles in immune diseases and inflammatory responses, their relationship and role in glioma remain unknown. Here, we revealed high levels of TNIP1 and TNF‐α/NF‐κB in glioma tissue. Glioma cell proliferation was activated with TNF‐α treatment and showed extreme sensitivity to the TNF receptor antagonist. Furthermore, loss of TNIP1 disbanded the A20 complex responsible for IκB degradation and NF‐κB nucleus translocation, and consequently erased TNFα‐induced glioma cell proliferation. Thus, our investigation uncovered a vital function of the TNIP1‐mediated TNF‐α/NF‐κB axis in glioma cell proliferation and provides novel insight into glioma pathology and diagnosis.     

Optineurin suppression causes neuronal cell death via NF‐κB pathway

Mutations in more than 10 genes are reported to cause familial amyotrophic lateral sclerosis (ALS). Among these genes, optineurin (OPTN) is virtually the only gene that is considered to cause classical ALS by a loss‐of‐function mutation. Wild‐type optineurin (OPTN^WT) suppresses nuclear factor‐kappa B (NF‐κB) activity, but the ALS‐causing mutant OPTN is unable to suppress NF‐κB activity. Therefore, we knocked down OPTN in neuronal cells and examined the resulting NF‐κB activity and phenotype. First, we confirmed the loss of the endogenous OPTN expression after siRNA treatment and found that NF‐κB activity was increased in OPTN‐knockdown cells. Next, we found that OPTN knockdown caused neuronal cell death. Then, overexpression of OPTN^WT or OPTN^E50K with intact NF‐κB‐suppressive activity, but not overexpression of ALS‐related OPTN mutants, suppressed the neuronal death induced by OPTN knockdown. This neuronal cell death was inhibited by withaferin A, which selectively inhibits NF‐κB activation. Lastly, involvement of the mitochondrial proapoptotic pathway was suggested for neuronal death induced by OPTN knockdown. Taken together, these results indicate that inappropriate NF‐κB activation is the pathogenic mechanism underlying OPTN mutation‐related ALS.

     

Z‐FA.FMK activates duodenal epithelial cell proliferation through oxidative stress,NF‐κB and IL‐1β in d‐GalN/TNF‐α‐administered mice

This study was designed to evaluate the effect of Z‐FA.FMK (benzyloxycarbonyl‐l ‐phenylalanyl‐alanine‐fluoromethylketone), a pharmacological inhibitor of cathepsin B, on the proliferation of duodenal mucosal epithelial cells and the cellular system that controls this mechanism in these cells in vivo. For this investigation, BALB/c male mice were divided into four groups. The first group received physiological saline, the second group was administered Z‐FA.FMK, the third group received d ‐GalN (d ‐galactosamine) and TNF‐α (tumour necrosis factor‐α) and the fourth group was given both d ‐GalN/TNF‐α and Z‐FA.FMK. When d ‐GalN/TNF‐α was administered alone, we observed an increase in IL‐1β‐positive and active NF‐κB‐positive duodenal epithelial cells, a decrease in PCNA (proliferative cell nuclear antigen)‐positive duodenal epithelial cells and an increase in degenerative changes in duodenum. On the other hand, Z‐FA.FMK pretreatment inhibited all of these changes. Furthermore, lipid peroxidation, protein carbonyl and collagen levels were increased, glutathione level and superoxide dismutase activity were decreased, while there was no change in catalase activity by d ‐GalN/TNF‐α injection. On the contrary, the Z‐FA.FMK pretreatment before d ‐GalN/TNF‐α blocked these effects. Based on these findings, we suggest that Z‐FA.FMK might act as a proliferative mediator which is controlled by IL‐1β through NF‐κB and oxidative stress in duodenal epithelial cells of d ‐GalN/TNF‐α‐administered mice.     

Attenuating Smac mimetic compound 3‐induced NF‐κB activation by luteolin leads to synergistic cytotoxicity in cancer cells

Smac mimetics are potential anticancer therapeutics selectively killing cancer cells through autocrine tumor necrosis factor (TNF)‐mediated apoptosis pathway. Our recent study reveal that the Smac mimetic compound 3 (SMC3)‐activated NF‐κB protects cancer cells against apoptosis, thus blunting SMC3's anticancer activity. Based on our previous observations that the nutrient flavonoid luteolin potently blocks TNF‐induced NF‐κB activation in cancer cells, we investigated if the combination of SMC3 and luteolin would achieve a synergistic anticancer activity. The results show that luteolin had no effect on autocrine TNF but it effectively blocked SMC3‐induced nuclear factor kappa B (NF‐κB) activation and expression of anti‐apoptotic NF‐κB targets. When SMC3 and luteolin were combined in treating cancer cells derived from lung and liver tumors, the activation of TNF‐dependent apoptosis was markedly sensitized and a synergistic cytotoxic effect was achieved. In addition, the SMC3 and luteolin co‐treatment had marginal effect on immortalized normal human bronchial epithelial cells. The results suggest that combination of SMC3 and luteolin is an effective approach for improving the anticancer value of SMC3, which has implications in cancer prevention and therapy. J. Cell. Biochem. 108: 1125–1131, 2009. © 2009 Wiley‐Liss, Inc.     

Anemonin attenuates osteoarthritis progression through inhibiting the activation of IL‐1β/NF‐κB pathway

The osteoarthritis (OA) progression is now considered to be related to inflammation. Anemonin (ANE) is a small natural molecule extracted from various kinds of Chinese traditional herbs and has been shown to inhibiting inflammation response. In this study, we examined whether ANE could attenuate the progression of OA via suppression of IL‐1β/NF‐κB pathway activation. Destabilization of the medial meniscus (DMM) was performed in 10‐week‐old male C57BL/6J mice. ANE was then intra‐articularly injected into joint capsule for 8 and 12 weeks. Human articular chondrocytes and cartilage explants challenged with interleukin‐1β (IL‐1β) were treated with ANE. We found that ANE delayed articular cartilage degeneration in vitro and in vivo. In particular, proteoglycan loss and chondrocyte hypertrophy were significantly decreased in ANE ‐treated mice compared with vehicle‐treated mice. ANE decreased the expressions of matrix metalloproteinase‐13 (MMP13), A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), collagen X (Col X) while increasing Aggrecan level in murine with DMM surgery. ANE treatment also attenuated proteoglycan loss in human cartilage explants treated with IL‐1β ex vivo. ANE is a potent protective molecule for OA; it delays OA progression by suppressing ECM loss and chondrocyte hypertrophy partially by suppressing IL‐1β/NF‐κB pathway activation.     

NDR1/STK38 potentiates NF‐κB activation by its kinase activity

Human NDR1/STK38 belongs to the nuclear‐Dbf2‐related (NDR) family of Ser/Thr kinases. It has been implicated to function in centrosome duplication, control of cell cycle and apoptosis. However, the mechanism of NDR1 signaling pathway remains largely elusive. Here, we report a novel role of NDR1 in NF‐κB activation. By overexpression, NDR1 potentiates NF‐κB activation induced by TNFα, whereas knockdown of NDR1 expression inhibits NF‐κB activation induced by TNFα. Coimmunoprecipitation shows that NDR1 interacts with multiple signal components except p65 in NF‐κB signaling pathway. Furthermore, both phosphorylation and kinase dead mutants of NDR1 lose their synergistic effects on TNFα‐induced NF‐κB activation. siRNA oligo against NDR1 and kinase dead mutant as well mainly block the NF‐κB activation induced by TRAF2 but not RIP1. Furthermore, kinase dead mutant of NDR1 fails to interact with TRAF2. Taken together, our findings suggest an unknown function of NDR1, which may regulate NF‐κB activation by its kinase activity. Copyright © 2012 John Wiley & Sons, Ltd.     

RTP801 Regulates Maneb‐ and Mancozeb‐Induced Cytotoxicity via NF‐κB

Environmental factors have been implicated in the pathogenesis of neurodegenerative diseases. Maneb (MB) and mancozeb (MZ) have been extensively used as pesticides. Exposure to MB lowers the threshold for dopaminergic damage triggered by 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine. MB and MZ potentiate 1‐methyl‐4‐phenylpyridium (MPP⁺)‐induced cytotoxicity in rat pheochromocytoma (PC12) cells partially via nuclear factor kappa B (NF‐κB) activation. RTP801 dramatically increased by oxidative stresses and DNA damage is the possible mechanism of neurotoxins‐induced cell death in many studies. This study demonstrated that MB and MZ induced DNA damage as seen in comet assay. The expressions of RTP801 protein and mRNA were elevated after MB and MZ exposures. By knocking down RTP801 using shRNA, we demonstrated that NF‐κB activation by MB and MZ was regulated by RTP801 and cell death triggered by MB and MZ was associated with RTP801 elevation. This revealed that the toxic mechanisms of dithiocarbamates are via the cross talk between RTP801 and NF‐κB.     

Pannexin3 inhibits TNF‐α‐induced inflammatory response by suppressing NF‐κB signalling pathway in human dental pulp cells

Human dental pulp cells (HDPCs) play a crucial role in dental pulp inflammation. Pannexin 3 (Panx3), a member of Panxs (Pannexins), has been recently found to be involved in inflammation. However, the mechanism of Panx3 in human dental pulp inflammation remains unclear. In this study, the role of Panx3 in inflammatory response was firstly explored, and its potential mechanism was proposed. Immunohistochemical staining showed that Panx3 levels were diminished in inflamed human and rat dental pulp tissues. In vitro, Panx3 expression was significantly down‐regulated in HDPCs following a TNF‐α challenge in a concentration‐dependent way, which reached the lowest level at 10 ng/ml of TNF‐α. Such decrease could be reversed by MG132, a proteasome inhibitor. Unlike MG132, BAY 11‐7082, a NF‐κB inhibitor, even reinforced the inhibitory effect of TNF‐α. Quantitative real‐time PCR (qRT‐PCR) and enzyme‐linked immunosorbent assay (ELISA) were used to investigate the role of Panx3 in inflammatory response of HDPCs. TNF‐α‐induced pro‐inflammatory cytokines, interleukin (IL)‐1β and IL‐6, were significantly lessened when Panx3 was overexpressed in HDPCs. Conversely, Panx3 knockdown exacerbated the expression of pro‐inflammatory cytokines. Moreover, Western blot, dual‐luciferase reporter assay, immunofluorescence staining, qRT‐PCR and ELISA results showed that Panx3 participated in dental pulp inflammation in a NF‐κB‐dependent manner. These findings suggested that Panx3 has a defensive role in dental pulp inflammation, serving as a potential target to be exploited for the intervention of human dental pulp inflammation.