Metformin activates chaperone-mediated autophagy and improves disease pathologies in an Alzheimer disease mouse model

Chaperone-mediated autophagy (CMA) is a lysosome-dependent selective degradation pathway implicated in the pathogenesis of cancer and neurodegenerative diseases. However, the mechanisms that regulate CMA are not fully understood. Here, using unbiased drug screening approaches, we discover Metformin, a drug that is commonly the first medication prescribed for type 2 diabetes, can induce CMA. We delineate the mechanism of CMA induction by Metformin to be via activation of TAK1-IKKα/β signaling that leads to phosphorylation of Ser85 of the key mediator of CMA, Hsc70, and its activation. Notably, we find that amyloid-beta precursor protein (APP) is a CMA substrate and that it binds to Hsc70 in an IKKα/β-dependent manner. The inhibition of CMA-mediated degradation of APP enhances its cytotoxicity. Importantly, we find that in the APP/PS1 mouse model of Alzheimer’s disease (AD), activation of CMA by Hsc70 overexpression or Metformin potently reduces the accumulated brain Aβ plaque levels and reverses the molecular and behavioral AD phenotypes. Our study elucidates a novel mechanism of CMA regulation via Metformin-TAK1-IKKα/β-Hsc70 signaling and suggests Metformin as a new activator of CMA for diseases, such as AD, where such therapeutic intervention could be beneficial.

Diallyl trisulfide inhibited tobacco smoke-mediated bladder EMT and cancer stem cell marker expression via the NF-κB pathway in vivo

OBJECTIVE

This study examined the effect of the NF-κB pathway on tobacco smoke-elicited bladder epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) marker expression in vivo. The effect of diallyl trisulfide (DATS) treatment was also examined.

METHODS

BALB/c mice were exposed to tobacco smoke and treated with an NF-κB inhibitor and DATS. Western blotting, quantitative real-time PCR, and immunohistochemical staining were used to detect the changes of relevant indices.

RESULTS

Phosphorylated inhibitor of kappa-B kinase alpha/beta expression and p65 and p50 nuclear transcription were increased by tobacco smoke exposure, whereas inhibitor of kappa-B expression was decreased. In addition, tobacco smoke reduced the expression of epithelial markers but increased that of mesenchymal and CSC markers. Our study further demonstrated that tobacco smoke-mediated EMT and CSC marker expression were attenuated by inhibition of the NF-κB pathway. Moreover, DATS reversed tobacco smoke-induced NF-κB pathway activation, EMT, and the acquisition of CSC properties in bladder tissues.

CONCLUSIONS

These data suggested that the NF-κB pathway regulated tobacco smoke-induced bladder EMT, CSC marker expression, and the protective effects of DATS.

Pristimerin, a natural anti-tumor triterpenoid, inhibits LPS-induced TNF-α and IL-8 production through down-regulation of ROS-related classical NF-κB pathway in THP-1 cells

Pristimerin, a naturally occurring quinonemethide triterpenoid compound, is known to exert a variety of pharmacological activities. In the present study, we investigated the molecular actions of pristimerin against LPS-induced inflammatory responses in human monocytic THP-1 cells. The results showed that pristimerin inhibited the production of TNF-α and IL-8 in a dose-dependent manner. To explore the possible mechanisms underlying these inhibitions by pristimerin, we examined the intracellular ROS level and the NF-κB protein signaling pathway. Pristimerin clearly scavenged LPS-induced intracellular ROS production. In addition, pristimerin prevented LPS-induced NF-κB activation through the inhibition of phosphorylation of IKKα/β, phosphorylation and degradation of IκBα, as well as phosphorylation and nuclear translocation of NF-κB p65. These findings suggest that pristimerin down-regulates the expression of pro-inflammatory mediators through blocking of NF-κB activation by inhibiting interconnected ROS/IKK/NF-κB signaling pathways.

Novel anti-inflammatory function of NSC95397 by the suppression of multiple kinases

NSC95397 (2,3-bis-[(2-hydroxyethyl)thio]-1,4-naphthoquinone) is a CDC25 inhibitor with anti-cancer properties. Since the anti-inflammatory activity of this compound has not yet been explored, the aim of this study was to examine whether this compound is able to modulate the inflammatory process. Toll like receptor (TLR)-mediated inflammatory responses were induced by lipopolysaccharide (LPS), a TLR4 ligand, and pam3CSK, a TLR2 ligand, in peritoneal macrophages and RAW264.7. The molecular mechanism of NSC95397's anti-inflammatory activity was studied using immunoblotting analysis, nuclear fractionation, immunoprecipitation, overexpression strategies, luciferase reporter gene assays, and kinase assays. NSC95397 dose-dependently suppressed the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, and prostaglandin (PG)E2, and diminished the mRNA expression of inflammatory genes such as inducible NO synthase (iNOS), cyclooxygenase (COX)-2, interferon (IFN)-β, and TNF-α in peritoneal macrophages and RAW264.7 cells that were stimulated by LPS and pam3CSK. This compound also clearly blocked the activation of NF-κB (p65), AP-1 (c-Fos/c-Jun), and IRF-3 in LPS-treated RAW264.7 cells and TRIF- and MyD88-overexpressing HEK293 cells. In addition, biochemical and molecular approaches revealed that this compound targeted AKT, IKKα/β, MKK7, and TBK1. Therefore, these results suggest that the anti-inflammatory function of NSC95397 can be attributed to its inhibition of multiple targets such as AKT, IKKα/β, MKK7, and TBK1.

Microglial derived tumor necrosis factor-α drives Alzheimer's disease-related neuronal cell cycle events

Massive neuronal loss is a key pathological hallmark of Alzheimer's disease (AD). However, the mechanisms are still unclear. Here we demonstrate that neuroinflammation, cell autonomous to microglia, is capable of inducing neuronal cell cycle events (CCEs), which are toxic for terminally differentiated neurons. First, oligomeric amyloid-beta peptide (AβO)-mediated microglial activation induced neuronal CCEs via the tumor-necrosis factor-α (TNFα) and the c-Jun Kinase (JNK) signaling pathway. Second, adoptive transfer of CD11b+ microglia from AD transgenic mice (R1.40) induced neuronal cyclin D1 expression via TNFα signaling pathway. Third, genetic deficiency of TNFα in R1.40 mice (R1.40-Tnfα(-/-)) failed to induce neuronal CCEs. Finally, the mitotically active neurons spatially co-exist with F4/80+ activated microglia in the human AD brain and that a portion of these neurons are apoptotic. Together our data suggest a cell-autonomous role of microglia, and identify TNFα as the responsible cytokine, in promoting neuronal CCEs in the pathogenesis of AD.