bay-11-7082 and lactacystin

Primary effusion lymphoma (PEL) is an aggressive neoplasm caused by Kaposi's sarcoma-associated herpesvirus (KSHV). This study provides evidence that proteasomal activity is required for both survival of PEL cells stably harboring the KSHV genome and viral replication of KSHV. We evaluated the cytotoxic effects of proteasome inhibitors on PEL cells. The proteasome inhibitors MG132, lactacystin, and proteasome inhibitor I dramatically inhibited cell proliferation and induced apoptosis of PEL cells through the accumulation of p21 and p27. Furthermore, proteasome inhibitors induced the stabilization of NF-κB inhibitory molecule (IκBα) and suppressed the transcriptional activity of NF-κB in PEL cells. The NF-κB specific inhibitor BAY11-7082 also induced apoptosis in PEL cells. The constitutive activation of NF-κB signaling is essential for the survival and growth of B cell lymphoma cells, including PEL cells. NF-κB signaling is upregulated by proteasome-dependent degradation of IκBα. The suppression of NF-κB signaling by proteasome inhibitors may contribute to the induction of apoptosis in PEL cells. In addition, proteasome activity is required for KSHV replication in KSHV latently infected PEL cells. MG132 reduced the production of progeny virus from PEL cells at low concentrations, which do not affect PEL cell growth. These findings suggest that proteasome inhibitors may represent a novel strategy for the treatment of KSHV infection and KSHV-associated lymphomas.

Topics: Acetylcysteine; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Herpesvirus 8, Human; Humans; Leupeptins; Lymphoma, Primary Effusion; NF-kappa B; Nitriles; Oligopeptides; Proteasome Inhibitors; Sulfones; Virus Replication

In a previous publication, we reported that human immunodeficiency virus (HIV) protease inhibitors (PIs) inhibited the differentiation of human preadipocytes in primary culture, reducing the expression and secretion of matrix metalloproteinase 9 (MMP-9). The present work was performed to clarify this mechanism. Interestingly, HIV-PIs have been reported to be inhibitors of the proteasome complex, which is known to regulate nuclear factor (NF)-kappaB activation and transcription of its target genes, among them MMP-9. We thus investigated the potential involvement of the proteasome in the antiadipogenic effects of HIV-PIs. The effect of four HIV-PIs was tested on preadipocyte proteasomal activity, and chronic treatment with the specific proteasome inhibitor lactacystin was performed to evaluate alterations of adipogenesis and MMP-9 expression/secretion. Finally, modifications of the NF-kappaB pathway induced by either HIV-PIs or lactacystin were studied. We demonstrated that preadipocyte proteasomal activity was decreased by several HIV-PIs and that chronic treatment with lactacystin mimicked the effects of HIV-PIs by reducing adipogenesis and MMP-9 expression/secretion. Furthermore, we observed an intracellular accumulation of the NF-kappaB inhibitor, IkappaBbeta, with chronic treatment with HIV-PIs or lactacystin as well as a decrease in MMP-9 expression induced by acute tumor necrosis factor-alpha stimulation. These results indicate that inhibition of the proteasome by specific (lactacystin) or nonspecific (HIV-PIs) inhibitors leads to a reduction of human adipogenesis, and they therefore implicate deregulation of the NF-kappaB pathway and the related decrease of the key adipogenic factor, MMP-9. This study adds significantly to recent reports that have linked HIV-PI-related lipodystrophic syndrome with altered proteasome function, endoplasmic reticulum stress, and metabolic disorders.

Topics: Acetylcysteine; Adipocytes; Adipogenesis; Cell Differentiation; Cells, Cultured; HIV Protease Inhibitors; Humans; I-kappa B Proteins; Matrix Metalloproteinase 9; NF-KappaB Inhibitor alpha; Nitriles; Proteasome Inhibitors; Stem Cells; Sulfones; Transcription Factor RelA; Tumor Necrosis Factor-alpha

The transcription factor nuclear factor kappa-B (NF-kappaB) is generally regarded as an antiapoptotic factor. Accordingly, NF-kappaB activation inhibits death ligand-induced apoptosis. In contrast, ultraviolet light B (UVB)-induced apoptosis is not inhibited but even enhanced upon NF-kappaB activation by interleukin-1 (IL-1). This study was performed to identify the molecular mechanisms underlying this switch of NF-kappaB. Enhancement of UVB-induced apoptosis was always associated with increased release of tumour necrosis factor-alpha (TNF-alpha), which was dependent on NF-kappaB activation. The same was observed when UVA and cisplatin were used, which like UVB induce base modifications. In contrast, apoptosis caused by DNA strand breaks was not enhanced by IL-1, indicating that the type of DNA damage is critical for switching the effect of NF-kappaB on apoptosis. Surprisingly, activated NF-kappaB induced TNF-alpha mRNA expression in the presence of all DNA damage-inducing agents. However, in the presence of DNA strand breaks, there was no release of the TNF-alpha protein, which is so crucial for enhancing apoptosis. Together, this indicates that induction of DNA damage may have a significant impact on biological effects but it is the type of DNA damage that determines the final outcome. This may have implications for the role of NF-kappaB in carcinogenesis and for the application of NF-kappaB inhibitors in anticancer therapy.

Topics: Acetylcysteine; Antineoplastic Agents; Apoptosis; Chromosome Breakage; Cisplatin; Comet Assay; DNA Damage; Doxorubicin; Etoposide; Gamma Rays; Gene Expression Regulation; Humans; I-kappa B Kinase; I-kappa B Proteins; Interleukin-1; Interleukin-6; KB Cells; Leupeptins; NF-kappa B; NF-KappaB Inhibitor alpha; Nitriles; Proteasome Inhibitors; Receptors, Tumor Necrosis Factor, Type I; RNA, Messenger; Sulfones; Transcription, Genetic; Tumor Necrosis Factor-alpha; Ultraviolet Rays

To investigate the inhibition mechanisms of BAY11-7082 (IkappaB-alpha phosphorylation inhibitor) and Lactacystein (proteosome inhibitor) in CD154-induced NF-kappaB activation.. We used recombinant CD154 to stimulate EBV/LMP1 negative Ramos B cell and observed the effects of BAY11-7082 and Lactacystein in CD154-induced NF-kappaB luciferase activation, phosphorylation and degradation of IkappaB-alpha, phosphorylation of p65, and nuclear translocation of NF-kappaB subunits upon CD154 stimulation.. Both BAY11-7082 and Lactacystein abrogated CD154-induced NF-kappaB luciferase activation in Ramos cells. While CD154-induced phosphorylation of p65, phosphorylation and degradation of IkappaB-alpha, and nuclear translocation of p50, p65, and c-Rel were all blocked by BAY11-7082; Lactacystein only inhibited degradation of IkappaB-alpha and p65 nuclear translocation.. BAY11-7082 and Lactacystein inhibit CD154-induced NF-kappaB activation through different mechanisms.

Topics: Acetylcysteine; Apoptosis; Burkitt Lymphoma; CD40 Ligand; Cysteine Proteinase Inhibitors; Enzyme Activation; Humans; NF-kappa B; Nitriles; Sulfones; Tumor Cells, Cultured