The expression of cyclooxygenase-2 (COX-2) is increased in human cholangiocarcinoma. However, the biologic function and molecular mechanisms of COX-2 in the control of cholangiocarcinoma cell growth have not been well established. This study was designed to examine the direct effect of COX-2 and its inhibitor celecoxib on the growth of human intrahepatic cholangiocarcinoma cells. Overexpression of COX-2 or treatment with prostaglandin E₂ (PGE₂) enhanced human cholangiocarcinoma cell growth, whereas antisense depletion of COX-2 in these cells decreased PGE₂ production and inhibited growth. These findings demonstrate a direct role of COX-2-mediated PGE₂ in the growth regulation of human cholangiocarcinoma cells. Furthermore, the COX-2 inhibitor celecoxib induced a dose-dependent inhibition of cell growth, cell cycle arrest at the G₁-S checkpoint, and induction of cyclin-dependent kinase inhibitors p21^waf1/cip1 and p27^kip1. However, the high concentration of celecoxib (50 μm) required for inhibition of growth, the incomplete protection of celecoxib-induced inhibition of cell growth by PGE₂ or COX-2 overexpression, and the fact that overexpression or antisense depletion of COX-2 failed to alter the level of p21^waf1/cip1 and p27^kip1 indicate the existence of a COX-2-independent mechanism in celecoxib-induced inhibition of cholangiocarcinoma cell growth.

Alzheimer’s disease (AD) is a dreadful neurodegenerative disease that leads to severe impairment of cognitive function, leading to a drastic decline in the quality of life. The primary pathological features of AD include senile plaques (SPs) and intracellular neurofibrillary tangles (NFTs), comprising aggregated amyloid β (Aβ) and hyperphosphorylated tau protein, respectively, in the hippocampus of AD patients. Histone deacetylase 6 (HDAC6) is a key enzyme in this neurodegenerative disease, in particular, as it relates to tau hyperphosphorylation. This study aimed to investigate the protective effects and mechanism of the novel HDAC6 inhibitor, MPT0G211, using an AD model. Our results indicated that MPT0G211 significantly reduced tau phosphorylation and aggregation, the processes highly correlated with the formation of NFTs. This HDAC6 inhibitory activity resulted in an increase in acetylated Hsp90, which decreased Hsp90 and HDAC6 binding, causing ubiquitination of phosphorylated tau proteins. In addition, a significant increase of phospho-glycogen synthase kinase-3β (phospho-GSK3β) on Ser9 (the inactive form) through Akt phosphorylation was associated with the inhibition of phospho-tau Ser396 in response to MPT0G211 treatment. In AD in vivo models, MPT0G211 appeared to ameliorate learning and memory impairment in animals. Furthermore, MPT0G211 treatment reduced the amount of phosphorylated tau in the hippocampal CA1 region. In summary, MPT0G211 treatment appears to be a promising strategy for improving the AD phenotypes, including tau hyperphosphorylation and aggregation, neurodegeneration, and learning and memory impairment, making it a valuable agent for further investigation.

Recent evidence indicates that the decoy receptor 3 (DcR3) of the TNF receptor superfamily, which initially though prevents cytokine responses of FasL, LIGHT and TL1A by binding and neutralization, can modulate monocyte function through reverse signaling. We show in this work that DcR3 can induce osteoclast formation from human monocytes, murine RAW264.7 macrophages, and bone marrow cells. DcR3-differentiated cells exhibit characteristics unique for osteoclasts, including polynuclear giant morphology, bone resorption, TRAP, CD51/61, and MMP-9 expression. Consistent with the abrogation of osteoclastogenic effect of DcR3 by TNFR-Fc, DcR3 treatment can induce osteoclastogenic cytokine TNF-α release through ERK and p38 MAPK signaling pathways. We conclude that DcR3 via coupling reverse signaling of ERK and p38 MAPK and stimulating TNF-α synthesis is a critical regulator of osteoclast formation. This action of DcR3 might play an important role in significant osteoclastic activity in osteolytic bone metastases.