ABSTRACT
BACKGROUND/AIM: Bortezomib, used for the treatment of multiple myeloma, has been reported to induce potent neurotoxicity. The present study investigated whether eight popular polyphenols inhibit bortezomib-induced neurotoxicity without affecting its anticancer activity. MATERIALS AND METHODS: Viable cell number was determined with the MTT method. Tumor-specificity was determined by the relative cytotoxicity in human oral squamous cell carcinoma vs. normal oral cells. Neurotoxicity was determined by the relative cytotoxicity in differentiated rat neuronal PC12 cells vs. normal cells. Apoptotic cells were quantified by cell cycle analysis. RESULTS: Bortezomib induced cell shrinkage, disruption of neurites, and accumulation of PC-12 cells in subG1. Only chlorogenic acid and caffeic acid protected PC-12 cells from bortezomib-induced neurotoxicity. Ferulic acid that has one of the two hydroxyl groups replaced by a methoxy group showed a significantly reduced neuroprotective effect. Caffeic acid and the chlorogenic acid also neutralized the anticancer potential of bortezomib. CONCLUSION: Caffeic acid and the chlorogenic acid may reduce the biological activity of bortezomib by forming a conjugate.
Subject(s)
Antineoplastic Agents/pharmacology , Bortezomib/pharmacology , Caffeic Acids/pharmacology , Chlorogenic Acid/pharmacology , Neuroprotective Agents/pharmacology , Animals , Apoptosis/drug effects , Bortezomib/antagonists & inhibitors , Caffeic Acids/chemistry , Cell Cycle/drug effects , Cell Line, Tumor , Cell Survival , Chlorogenic Acid/chemistry , Humans , Neuroprotective Agents/chemistry , PC12 Cells , Polyphenols/chemistry , Polyphenols/pharmacology , RatsABSTRACT
Cell death in human diseases is often a consequence of disrupted cellular homeostasis. If cell death is prevented without restoring cellular homeostasis, it may lead to a persistent dysfunctional and pathological state. Although mechanisms of cell death have been thoroughly investigated1-3, it remains unclear how homeostasis can be restored after inhibition of cell death. Here we identify TRADD4-6, an adaptor protein, as a direct regulator of both cellular homeostasis and apoptosis. TRADD modulates cellular homeostasis by inhibiting K63-linked ubiquitination of beclin 1 mediated by TRAF2, cIAP1 and cIAP2, thereby reducing autophagy. TRADD deficiency inhibits RIPK1-dependent extrinsic apoptosis and proteasomal stress-induced intrinsic apoptosis. We also show that the small molecules ICCB-19 and Apt-1 bind to a pocket on the N-terminal TRAF2-binding domain of TRADD (TRADD-N), which interacts with the C-terminal domain (TRADD-C) and TRAF2 to modulate the ubiquitination of RIPK1 and beclin 1. Inhibition of TRADD by ICCB-19 or Apt-1 blocks apoptosis and restores cellular homeostasis by activating autophagy in cells with accumulated mutant tau, α-synuclein, or huntingtin. Treatment with Apt-1 restored proteostasis and inhibited cell death in a mouse model of proteinopathy induced by mutant tau(P301S). We conclude that pharmacological targeting of TRADD may represent a promising strategy for inhibiting cell death and restoring homeostasis to treat human diseases.
Subject(s)
Apoptosis/drug effects , Homeostasis/drug effects , TNF Receptor-Associated Death Domain Protein/antagonists & inhibitors , TNF Receptor-Associated Death Domain Protein/metabolism , Animals , Autophagy/drug effects , Baculoviral IAP Repeat-Containing 3 Protein/metabolism , Beclin-1/chemistry , Beclin-1/metabolism , Bortezomib/antagonists & inhibitors , Bortezomib/pharmacology , Cell Line , Humans , Huntingtin Protein/metabolism , Inhibitor of Apoptosis Proteins/metabolism , Male , Mice , Models, Molecular , Neurofibrillary Tangles/metabolism , Proteome/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/chemistry , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , TNF Receptor-Associated Death Domain Protein/chemistry , TNF Receptor-Associated Death Domain Protein/deficiency , TNF Receptor-Associated Factor 2/metabolism , Ubiquitination , alpha-Synuclein/metabolism , tau Proteins/metabolismABSTRACT
Muscle contractures are a prominent and disabling feature of many neuromuscular disorders, including the 2 most common forms of childhood neurologic dysfunction: neonatal brachial plexus injury (NBPI) and cerebral palsy. There are currently no treatment strategies to directly alter the contracture pathology, as the pathogenesis of these contractures is unknown. We previously showed in a mouse model of NBPI that contractures result from impaired longitudinal muscle growth. Current presumed explanations for growth impairment in contractures focus on the dysregulation of muscle stem cells, which differentiate and fuse to existing myofibers during growth, as this process has classically been thought to control muscle growth during the neonatal period. Here, we demonstrate in a mouse model of NBPI that denervation does not prevent myonuclear accretion and that reduction in myonuclear number has no effect on functional muscle length or contracture development, providing definitive evidence that altered myonuclear accretion is not a driver of neuromuscular contractures. In contrast, we observed elevated levels of protein degradation in NBPI muscle, and we demonstrate that contractures can be pharmacologically prevented with the proteasome inhibitor bortezomib. These studies provide what we believe is the first strategy to prevent neuromuscular contractures by correcting the underlying deficit in longitudinal muscle growth.
