Numerous therapies used for inflammatory bowel disease (IBD) target the transcription factor NF-kappaB, which is involved in the production of cytokines and chemokines integral for inflammation. Here we show that curcumin, a component of the spice turmeric, is able to attenuate colitis in the dinitrobenzene sulfonic acid (DNB)-induced murine model of colitis. When given before the induction of colitis it reduced macroscopic damage scores and NF-kappaB activation. This was accompanied by a reduction in myeloperoxidase activity, and using semiquantitative RT-PCR, an attenuation of the DNB-induced message for IL-1beta was detected. Western blotting analysis revealed that there was a reproducible DNB-induced activation of p38 MAPK detected in intestinal lysates by using a phosphospecific antibody. This signal was significantly attenuated by curcumin. Furthermore, we show that the immunohistochemical signal is dramatically attenuated at the level of the mucosa by curcumin. We conclude that the widely used food additive curcumin is able to attenuate experimental colitis through a mechanism correlated with the inhibition of the activation of NF-kappaB and effects a reduction in the activity of p38 MAPK. We propose that this agent may have therapeutic implications for human IBD.

Summary Stress‐activated protein kinases (SAPKs) are activated in human inflammatory bowel disease (IBD). Recently it has been demonstrated that p38MAPK (mitogen‐activated protein kinase) inhibition using SB203580 is effective in reducing disease in both dextran sulphate sodium (DSS)‐induced and 2,4,6‐trinitrobenzenesulphonic acid (TNBS)‐induced murine colitides, underscoring the importance of this pathway in gastrointestinal inflammation. However, the contribution of c‐Jun N‐terminal kinase (JNK) in intestinal inflammation is unknown. Based on the known involvement of JNK in tumour necrosis factor‐α (TNF‐α) expression and in mediating the effects of oxidant stress, we hypothesized that JNK inhibition would also affect colitis. Our studies in mice with DSS‐induced colitis treated with the JNK inhibitor SP600125, indicate that there is a significant reduction in wasting as well as a significant reduction in histological damage scores. Both total colonic and mesenteric lymphocyte CD3/CD28‐stimulated TNF‐α levels were dramatically reduced under the same circumstances. This was associated with a reduction in JNK protein expression and activity, as well as a reduction in AP‐1 DNA binding with SP600125. Interestingly, there were no apparent changes in either p38MAPK or p42/44ERKs. Immunofluorescence of the colon for the active form of JNK revealed a prominent signal arising from the infiltrating inflammatory cells. SP600125 reduced this as well as, specifically, macrophage infiltration. Strikingly, we also demonstrate reduced epithelial cell apoptosis in response to treatment with SP600125. We conclude that specific inhibition of JNK is beneficial in the DSS model of colitis, and may be of value in human IBD.

A wealth of evidence supports the notion that curcumin, a phytochemical present in turmeric, is a potent chemopreventive agent for colon cancer. Its mechanism of action remains incompletely understood. Here we report that curcumin's apoptosis-inducing effects in colon cancer cell lines are accompanied by robust ceramide generation. This occurs through de novo synthesis as the increase in ceramide could be attenuated by pre-incubation of the cells with myriocin, and no changes were observed in sphingomyelin levels, or in either acidic or neutral sphingomyelinase activities. Furthermore, cell death could in part be reversed by myriocin, indicating, for the first time, that endogenous ceramide generation by this agent contributes towards its biological activity. We then investigated the role of reactive oxygen species (ROS) in this phenomenon and demonstrated that curcumin induced robust oxidant generation in the cell lines tested, and its reversal by N-acetylcysteine, completely attenuated apoptosis. We next confirmed that curcumin could activate c-jun N-terminal kinase (JNK) and that its modulation could reverse cell death; however, this intervention could not block ceramide generation, or ROS production. Conversely, however, the inhibition of ROS using N-acetylcysteine led to an inhibition of JNK activation. Hence, we conclude that curcumin induces apoptosis via a ROS-associated mechanism that converges on JNK activation, and to a lesser extent via a parallel ceramide-associated pathway.

Tregs have a reduced capacity to activate the PI3K/Akt pathway downstream of the TCR, and the resulting low activity of Akt is necessary for their development and function. The molecular basis for the failure of Tregs to efficiently activate Akt, however, remained unknown. We show that PH-domain Leucine-rich-repeat Protein Phosphatase (PHLPP), which dephosphorylates Akt, is up-regulated in Tregs, thus suppressing Akt activation. Tregs expressed higher levels of PHLPP than conventional T cells and knock-down of PHLPP1 restored TCR-mediated activation of Akt in Tregs. Consistent with their high Akt activity, the suppressive capacity of Tregs from PHLPP1-/- mice was significantly reduced. Moreover, the development of induced Tregs was impaired in PHLPP1-/- mice. The increased level of Akt's negative regulator, PHLPP, provides a novel mechanism used by T cells to control the Akt pathway and the first evidence for a molecular mechanism underlying the functionally essential reduction of Akt activity in Tregs.

From these findings, it is concluded that ILK plays an important role in intestinal epithelial cell proliferation, and that it influences the development of colitis-associated cancer, through modulation of cyclin D1, the extracellular matrix and MMP9.

It is important to understand the molecular mechanisms of bladder cancer progression not only to prevent cancer progression but also to detect new therapeutic targets against advanced bladder cancer. The integrin-linked kinase (ILK) is a major signaling integrator in mammalian cells and plays an important role in epithelial-mesenchymal transition (EMT) of human cancers, but its mechanisms are not completely understood. In this study, we investigated the importance and mechanisms of ILK in bladder cancer progression. When the expression of ILK in bladder cancer cell lines and N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced murine bladder cancer was evaluated, ILK has a tendency to be overexpressed in invasive cell lines and invasive BBN-induced murine bladder cancer. Overexpression of ILK in 253J bladder cancer cells suppressed E-cadherin expression, resulting in the promotion of cell invasion. Conversely, ILK knockdown by siRNA suppresses cell invasion in invasive bladder cancer cells through the regulation of E-cadherin or matrix metalloprotease 9 (MMP-9). To regulate Ecadherin expression, our results showed that the glycogen synthase kinase 3b (GSK3b)-Zeb1 pathway may play an important role downstream of ILK. Finally, the results of a human bladder tissue microarray (TMA) showed that ILK expression correlates with the invasiveness of human bladder cancer. Our study suggests that ILK is overexpressed in invasive bladder cancer and plays an important role in the EMT of bladder cancer via the control of E-cadherin and MMP-9 expression. ILK may be a new molecular target to suppress tumor progression in advanced and high-risk bladder cancer patients.Metastatic or invasive bladder cancer is a life-threatening disease despite radical surgery or chemotherapy. Although approximately 70% of bladder cancers are non-muscle invasive at initial diagnosis, 1 unfortunately, transurethral resection or adjuvant treatment options, including intravesical therapy, are limited in preventing tumor recurrence or progression, and 20-30% of those tumors progress into more aggressive and potentially lethal tumors. Therefore, it is important to understand the molecular mechanisms of bladder cancer progression to prevent cancer progression from superficial to invasive cancer or to detect new therapeutic targets against advanced bladder cancer.Epithelial-mesenchymal transition (EMT) has been implicated as having a role in tumor invasion/migration and metastasis.2 Loss of E-cadherin expression is a hallmark of the EMT process, which is probably required for epithelial cells to undergo changes in cell morphology and motility and to adopt mesenchymal characteristics. A reduction or loss in expression of E-cadherin has been recognized as an important primary event in bladder tumorigenesis often linked to a poor prognosis. Expression of E-cadherin is controlled by several transcriptional repressors, including Twist, Snail1, Snail2/Slug, E47, Zeb1/TCF8 and Zeb2/SIP1, which bind to E-boxes in the E-cadherin promoter, and the importance of th...

During cell division integrin-linked kinase (ILK) has been shown to regulate microtubule dynamics and centrosome clustering, processes involved in cell cycle progression, and malignant transformation. In this study, we examine the effects of downregulating ILK on mitotic function in human retinoblastoma cell lines. These retinal cancer cells, caused by the loss of function of two gene alleles (Rb1) that encode the retinoblastoma tumour suppressor, have elevated expression of ILK. Here we show that inhibition of ILK activity results in a concentration-dependent increase in nuclear area and multinucleated cells. Moreover, inhibition of ILK activity and expression increased the accumulation of multinucleated cells over time. In these cells, aberrant cytokinesis and karyokinesis correlate with altered mitotic spindle organization, decreased levels of cortical F-actin and centrosome de-clustering. Centrosome de-clustering, induced by ILK siRNA, was rescued in FLAG-ILK expressing Y79 cells as compared to those expressing FLAG-tag alone. Inhibition of ILK increased the proportion of cells exhibiting mitotic spindles and caused a significant G2/M arrest as early as 24 hours after exposure to QLT-0267. Live cell analysis indicate ILK downregulation causes an increase in multipolar anaphases and failed cytokinesis (bipolar and multipolar) of viable cells. These studies extend those indicating a critical function for ILK in mitotic cytoskeletal organization and describe a novel role for ILK in cytokinesis of Rb deficient cells.

Intestinal epithelial cells (IEC) are constantly exposed to enteric microbes. Although IECs express TLRs that recognize bacterial products, activation of these TLRs is strictly controlled through poorly understood mechanisms, producing a state of hypo-responsiveness and preventing unwanted inflammation. The Single IgG IL-1 related receptor (Sigirr) is a negative regulator of TLRs that is expressed by IEC and recently shown to inhibit experimental colitis. However, the importance of Sigirr in IEC hyporesponsiveness and its distribution within the human colon is unknown. In this study, we investigated the role of Sigirr in regulating epithelial specific TLR responses and characterize its expression in colonic biopsies. Transformed and non-transformed human IEC were cultured as monolayers. Transient gene silencing and stable over-expression of Sigirr was performed to assess innate IEC responses. Sigirr expression in human colonic biopsies was examined by immunohistochemistry. Bacterial infection of IEC and exposure to flagellin transiently decreased Sigirr protein expression, concurrent with secretion of the neutrophil chemokine IL-8. Sigirr gene silencing augmented chemokine responses to bacterial flagellin, Pam3Cys and the cytokine IL-1β. Conversely, stable over-expression of Sigirr diminished NF-κB mediated IL-8 responses to TLR ligands. We also found that Sigirr expression increased as IECs differentiated in culture. This observation was confirmed in biopsy sections, where Sigirr expression within colonic crypts was prominent in IECs at the apex and diminished at the base. Our findings show that Sigirr broadly regulates innate responses in differentiated human IEC, and may therefore modulate epithelial involvement in infectious and inflammatory bowel diseases.