No abstract

Regulation of intracellular protein stability by the ubiquitin-dependent proteasome system plays a crucial role in cell function. HO-1 (haem oxygenase) is a stress response protein, which confers cytoprotection against oxidative injury and provides a vital function in maintaining tissue homoeostasis. In the present study, we found a novel action of proteasome inhibitors MG132 and MG262 on HO-1 induction, and characterized the underlying mechanisms. MG132 (> or =0.1 microM) treatment resulted in a marked time- and concentration-dependent induction of the steady-state level of HO-1 mRNA in RAW264.7 macrophages, followed by a corresponding increase in HO-1 protein. Actinomycin D and cycloheximide inhibited MG132-responsive HO-1 protein expression, indicating a requirement for transcription and de novo protein synthesis. The involvement of signal pathways in MG132-induced HO-1 gene expression was examined using chemical inhibitors. Antioxidant N -acetylcysteine and SB203580, an antioxidant and inhibitor of p38 MAPK (mitogen-activated protein kinase), abolished MG132-inducible HO-1 expression. Furthermore, MG132 activated the p38 MAPK pathway. The half-life of HO-1 protein was prolonged by MG132, indicating that the upregulation of HO-1 by proteasome inhibitor is partially attributable to the inhibition of protein degradation. MG132 can ablate IkappaBalpha degradation and NF-kappaB (nuclear factor kappaB) activation induced by lipopolysaccharide, similar to the effect of another NF-kappaB inhibitor pyrrolidine dithiocarbamate. We found HO-1 upregulation by MG132 and pyrrolidine dithiocarbamate is unrelated to their inhibition of NF-kappaB, since leptomycin B, another NF-kappaB inhibitor, did not elicit similar induction of HO-1. Taken together, we found a novel effect of proteasome inhibitor on induction of HO-1 expression. This action is ascribed to the activation of the p38 MAPK pathway, but is not dependent on NF-kappaB inhibition.

Background: Results of studies regarding the potential link between acid suppressant use and dementia risk are inconsistent. This study aimed to evaluate the association of cumulative exposure to histamine 2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) with dementia risk in an Asian older cohort aged ≥65 years. Methods: Patients initiating H2RA (the H2RA user cohort, n = 21,449) or PPI (the PPI user cohort, n = 6584) and those without prescription for H2RA (the H2RA non-user cohort, n = 21,449) or PPI (the PPI non-user cohort, n = 6584) between 1 January 2000 and 31 December 2005 without a prior history of dementia were identified from Taiwan’s National Health Insurance Research Database (NHIRD). The outcome of interest was all-cause dementia. Patients’ exposure to H2RAs or PPIs was followed-up from dates of initial prescription to the earliest outcome of incident dementia, death, or the end of 2013. Potential associations between acid suppressant use and dementia risk were analyzed using time-dependent Cox regression estimated hazard ratios (HRs) and 95% confidence intervals (CIs). Results: After mutual adjustment for H2RA and PPI use and other potential confounders, patients with H2RA use had significantly higher risk of developing dementia as compared to those not treated with H2RAs (adjusted HR, 1.84; 95% CI, 1.49–2.20). Likewise, PPI users had significantly elevated risk of dementia compared to PPI non-users (adjusted HR, 1.42; 95% CI, 1.07–1.84). Conclusions: Our results indicate that exposures to H2RAs and PPIs are associated with increased dementia risk.

Nobiletin (NOB) is a polymethoxylated flavonoid isolated from citrus fruit peel that has been shown to possess anti-tumor, antithrombotic, antifungal, anti-inflammatory and anti-atherosclerotic activities. The main purpose of this study was to explore the potential of using NOB to induce apoptosis in human bladder cancer cells and study the underlying mechanism. Using an MTT assay, agarose gel electrophoresis, a wound-healing assay, flow cytometry, and western blot analysis, this study investigated the signaling pathways involved in NOB-induced apoptosis in BFTC human bladder cancer cells. Our results showed that NOB at concentrations of 60, 80, and 100 μM inhibited cell growth by 42%, 62%, and 80%, respectively. Cells treated with 60 μM NOB demonstrated increased DNA fragmentation, and flow cytometry analysis confirmed that the treatment caused late apoptotic cell death. Western blot analysis showed that mitochondrial dysfunction occurred in NOB-treated BFTC cells, leading to cytochrome C release into cytosol, activation of pro-apoptotic proteins (caspase-3, caspase-9, Bad, and Bax), and inhibition of anti-apoptotic proteins (Mcl-1, Bcl-xl, and Bcl-2). NOB-induced apoptosis was also mediated by regulating endoplasmic reticulum stress via the PERK/elF2α/ATF4/CHOP pathway, and downregulating the PI3K/AKT/mTOR pathway. Our results suggested that the cytotoxic and apoptotic effects of NOB on bladder cancer cells are associated with endoplasmic reticulum stress and mitochondrial dysfunction.