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.     

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.     

Fluorofenidone attenuates pulmonary inflammation and fibrosis via inhibiting the activation of NALP3 inflammasome and IL‐1β/IL‐1R1/MyD88/NF‐κB pathway

Interleukin (IL)‐1β plays an important role in the pathogenesis of idiopathic pulmonary fibrosis. The production of IL‐1β is dependent upon caspase‐1‐containing multiprotein complexes called inflammasomes and IL‐1R1/MyD88/NF‐κB pathway. In this study, we explored whether a potential anti‐fibrotic agent fluorofenidone (FD) exerts its anti‐inflammatory and anti‐fibrotic effects through suppressing activation of NACHT, LRR and PYD domains‐containing protein 3 (NALP3) inflammasome and the IL‐1β/IL‐1R1/MyD88/NF‐κB pathway in vivo and in vitro. Male C57BL/6J mice were intratracheally injected with Bleomycin (BLM) or saline. Fluorofenidone was administered throughout the course of the experiment. Lung tissue sections were stained with haemotoxylin and eosin and Masson's trichrome. Cytokines were measured by ELISA, and α‐smooth muscle actin (α‐SMA), fibronectin, collagen I, caspase‐1, IL‐1R1, MyD88 were measured by Western blot and/or RT‐PCR. The human actue monocytic leukaemia cell line (THP‐1) were incubated with monosodium urate (MSU), with or without FD pre‐treatment. The expression of caspase‐1, IL‐1β, NALP3, apoptosis‐associated speck‐like protein containing (ASC) and pro‐caspase‐1 were measured by Western blot, the reactive oxygen species (ROS) generation was detected using the Flow Cytometry, and the interaction of NALP3 inflammasome‐associated molecules were measured by Co‐immunoprecipitation. RLE‐6TN (rat lung epithelial‐T‐antigen negative) cells were incubated with IL‐1β, with or without FD pre‐treatment. The expression of nuclear protein p65 was measured by Western blot. Results showed that FD markedly reduced the expressions of IL‐1β, IL‐6, monocyte chemotactic protein‐1 (MCP‐1), myeloperoxidase (MPO), α‐SMA, fibronectin, collagen I, caspase‐1, IL‐1R1 and MyD88 in mice lung tissues. And FD inhibited MSU‐induced the accumulation of ROS, blocked the interaction of NALP3 inflammasome‐associated molecules, decreased the level of caspase‐1 and IL‐1β in THP‐1 cells. Besides, FD inhibited IL‐1β‐induced the expression of nuclear protein p65. This study demonstrated that FD, attenuates BLM‐induced pulmonary inflammation and fibrosis in mice via inhibiting the activation of NALP3 inflammasome and the IL‐1β/IL‐1R1/MyD88/ NF‐κB pathway.     

KiSS1 suppresses TNFα‐induced breast cancer cell invasion via an inhibition of RhoA‐Mediated NF‐κB activation

Tumor necrosis factor‐alpha (TNFα) induces cancer development and metastasis, which is prominently achieved by nuclear factor‐kappa B (NF‐κB) activation. TNFα‐induced NF‐κB activation enhances cellular mechanisms including proliferation, migration, and invasion. KiSS1, a key regulator of puberty, was initially discovered as a tumor metastasis suppressor. The expression of KiSS1 was lost or down‐regulated in different metastatic tumors. However, it is unclear whether KiSS1 regulates TNFα‐induced NF‐κB activation and further tumor cell migration. In this study, we demonstrate that KiSS1 suppresses the migration of breast cancer cells by inhibiting TNFα‐induced NF‐κB pathway and RhoA activation. Both KiSS1 overexpression and KP10 (kisspeptin‐10) stimulation inhibited TNFα‐induced NF‐κB activity, suppressed TNFα‐induced cell migration and cell attachment to fibronectin in breast cancer cells while KP10 has little effect on cancer cell proliferation. Furthermore, KP10 inhibited TNFα‐induced cell migration and RhoA GTPase activation. Therefore, our data demonstrate that KiSS1 inhibits TNFα‐induced NF‐κB activation via downregulation of RhoA activation and suppression of breast cancer cell migration and invasion. J. Cell. Biochem. 107: 1139–1149, 2009. © 2009 Wiley‐Liss, Inc.     

Linear polyubiquitination: a new regulator of NF‐κB activation

The ubiquitin‐conjugation system regulates a vast range of biological phenomena by affecting protein function mostly through polyubiquitin conjugation. The type of polyubiquitin chain that is generated seems to determine how conjugated proteins are regulated, as they are recognized specifically by proteins that contain chain‐specific ubiquitin‐binding motifs. An enzyme complex that catalyses the formation of newly described linear polyubiquitin chains—known as linear ubiquitin chain‐assembly complex (LUBAC)—has recently been characterized, as has a particular ubiquitin‐binding domain that specifically recognizes linear chains. Both have been shown to have crucial roles in the canonical nuclear factor‐κB (NF‐κB)‐activation pathway. The ubiquitin system is intimately involved in regulating the NF‐κB pathway, and the regulatory roles of K63‐linked chains have been studied extensively. However, the role of linear chains in this process is only now emerging. This article discusses the possible mechanisms underlying linear polyubiquitin‐mediated activation of NF‐κB, and the different roles that K63‐linked and linear chains have in NF‐κB activation. Future directions for linear polyubiquitin research are also discussed.     

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.     

Stachydrine prevents LPS‐induced bone loss by inhibiting osteoclastogenesis via NF‐κB and Akt signalling

Osteoclast overactivation‐induced imbalance in bone remodelling leads to pathological bone destruction, which is a characteristic of many osteolytic diseases such as rheumatoid arthritis, osteoporosis, periprosthetic osteolysis and periodontitis. Natural compounds that suppress osteoclast formation and function have therapeutic potential for treating these diseases. Stachydrine (STA) is a bioactive alkaloid isolated from Leonurus heterophyllus Sweet and possesses antioxidant, anti‐inflammatory, anticancer and cardioprotective properties. However, its effects on osteoclast formation and function have been rarely described. In the present study, we found that STA suppressed receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL)‐induced osteoclast formation and bone resorption, and reduced osteoclast‐related gene expression in vitro. Mechanistically, STA inhibited RANKL‐induced activation of NF‐κB and Akt signalling, thus suppressing nuclear factor of activated T cells c1 induction and nuclear translocation. In addition, STA alleviated bone loss and reduced osteoclast number in a murine model of LPS‐induced inflammatory bone loss. STA also inhibited the activities of NF‐κB and NFATc1 in vivo. Together, these results suggest that STA effectively inhibits osteoclastogenesis both in vitro and in vivo and therefore is a potential option for treating osteoclast‐related diseases.     

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.