Metal complexes designed to bind to amyloid-β for the diagnosis and treatment of Alzheimer\u27s disease

Alzheimer\u27s disease is the most common form of age-related neurodegenerative dementia. The disease is characterised by the presence of plaques in the cerebral cortex. The major constituent of these plaques is aggregated amyloid-β peptide. This review focuses on the molecular aspects of metal complexes designed to bind to amyloid-β. The development of radioactive metal-based complexes of copper and technetium designed as diagnostic imaging agents to detect amyloid burden in the brain is discussed. Separate sections of the review discuss the use of luminescent metal complexes to act as non-conventional probes of amyloid formation and recent research into the use of metal complexes as inhibitors of amyloid formation and toxicity

The hypoxia imaging agent Cu ii(atsm) is neuroprotective and improves motor and cognitive functions in multiple animal models of Parkinson's disease

Parkinson's disease (PD) is a progressive, chronic disease characterized by dyskinesia, rigidity, instability, and tremors. The disease is defined by the presence of Lewy bodies, which primarily consist of aggregated α-synuclein protein, and is accompanied by the loss of monoaminergic neurons. Current therapeutic strategies only give symptomatic relief of motor impairment and do not address the underlying neurodegeneration. Hence, we have identified Cu II(atsm) as a potential therapeutic for PD. Drug administration to four different animal models of PD resulted in improved motor and cognition function, rescued nigral cell loss, and improved dopamine metabolism. In vitro, this compound is able to inhibit the effects of peroxynitrite-driven toxicity, including the formation of nitrated α-synuclein oligomers. Our results show that Cu II(atsm) is effective in reversing parkinsonian defects in animal models and has the potential to be a successful treatment of PD

Inhibition of TDP-43 Accumulation by <em>Bis</em>(thiosemicarbazonato)-Copper Complexes

<div><p>Amyotrophic lateral sclerosis (ALS) is a progressive, fatal, motor neuron disease with no effective long-term treatment options. Recently, TDP-43 has been identified as a key protein in the pathogenesis of some cases of ALS. Although the role of TDP-43 in motor neuron degeneration is not yet known, TDP-43 has been shown to accumulate in RNA stress granules (SGs) in cell models and in spinal cord tissue from ALS patients. The SG association may be an early pathological change to TDP-43 metabolism and as such a potential target for therapeutic intervention. Accumulation of TDP-43 in SGs induced by inhibition of mitochondrial activity can be inhibited by modulation of cellular kinase activity. We have also found that treatment of cells and animal models of neurodegeneration, including an ALS model, with bioavailable <em>bis</em>(thiosemicarbazonato)copper^II complexes (Cu^II(btsc)s) can modulate kinase activity and induce neuroprotective effects. In this study we examined the effect of diacetylbis(-methylthiosemicarbazonato)copper^II (Cu^II(atsm)) and glyoxalbis(-methylthiosemicarbazonato)copper^II (Cu^II(gtsm)) on TDP-43-positive SGs induced in SH-SY5Y cells in culture. We found that the Cu^II(btsc)s blocked formation of TDP-43-and human antigen R (HuR)-positive SGs induced by paraquat. The Cu^II(btsc)s protected neurons from paraquat-mediated cell death. These effects were associated with inhibition of ERK phosphorylation. Co-treatment of cultures with either Cu^II(atsm) or an ERK inhibitor, PD98059 both prevented ERK activation and blocked formation of TDP-43-and HuR-positive SGs. Cu^II(atsm) treatment or ERK inhibition also prevented abnormal ubiquitin accumulation in paraquat-treated cells suggesting a link between prolonged ERK activation and abnormal ubiquitin metabolism in paraquat stress and inhibition by Cu. Moreover, Cu^II(atsm) reduced accumulation of C-terminal (219–414) TDP-43 in transfected SH-SY5Y cells. These results demonstrate that Cu^II(btsc) complexes could potentially be developed as a neuroprotective agent to modulate neuronal kinase function and inhibit TDP-43 aggregation. Further studies in TDP-43 animal models are warranted.</p> </div

Effect of Cu^II(atsm) or CuCl₂ on frequency of cells expressing CTF-TDP-43 219–414 aggregates.

1<p>Per 1,000 GFP-positive transfected cells.</p

Effect of Cu^II(atsm) on TDP-43, HuR and kinase phosphorylation.

<p>Graphs show densitometric analysis of altered protein expression or phosphorylation from two-three separate experiments relative to loading controls. <b>A</b>: Cells were treated with 1 mM paraquat overnight in the presence or absence of 20 µM SP600125, 1 µM Cu^II(atsm) or 1 µM CuCl₂ and immunoblotted for TDP-43 or HuR. <b>B–C</b>: Cells were treated for 2 hr with paraquat in the presence or absence of 1 µM Cu^II(atsm), 1 µM CuCl₂ or 10 µM PD98059 (ERK inhibitor). Cells were immunoblotted for phospho-ERK (p-ERK), total ERK, phospho-JNK (p-JNK) and total JNK. <b>D–E</b>: Cells were treated overnight with paraquat in the presence or absence of 1 µM Cu^II(atsm), 1 µM CuCl₂ or 10 µM PD98059 (ERK inhibitor). Cells were immunoblotted for phospho-ERK (p-ERK), total ERK, phospho-JNK (p-JNK) and total JNK. <b>F</b>: Effect of CuCl₂ on ERK and JNK phosphorylation. Cells were treated overnight with 1 mM paraquat or paraquat plus 100 µM CuCl₂ and cells were examined for expression ERK and JNK phosphorylation. <b>G:</b> HeLa cells were treated for 1 hr with 500 µM sodium arsenite in presence or absence of 1 µM Cu^II(atsm). Cells were immunoblotted for phospho-ERK (p-ERK), total ERK, phospho-JNK (p-JNK) and total JNK. *p<0.05 compared to untreated control. **p<0.05 compared to treatment alone.</p

Effect of Cu^II(btsc)s on paraquat toxicity.

<p><b>A</b>: Cells were treated overnight with 1 or 10 mM paraquat in the presence or absence of 1 µM Cu^II(atsm), 50 nM Cu^II(gtsm) or 100 µM CuCl₂ and cell death was measured with the LDH assay. *p<0.01 compared to untreated cells. **p<0.01 compared to 10 mM paraquat alone. <b>B</b>: In-gel SOD activity assay. Cells were treated with 1 mM paraquat overnight alone or in the presence of 1 µM Cu^II(atsm), 50 nM Cu^II(gtsm) or 1 µM CuCl₂. Cu^II(atsm), Cu^II(gtsm) and CuCl₂ were also added at the same concentration to cultures without paraquat. Cell lysates were analyzed for SOD activity using a SOD zymography gel assay. The band representing SOD activity was analyzed by densitometry and revealed no significant change compared to untreated control.</p

Effect of Cu^II(atsm) and Cu^II(gtsm) on TDP-43 and HuR localization in SY5Y cells.

<p>Cells were exposed overnight with 1 mM paraquat in the presence or absence of 1 µM Cu^II(atsm) or 50 nM Cu^II(gtsm) and TDP-43 and HuR localization was examined by immunofluorescence. <b>A–D</b>: untreated, <b>E–H</b>: paraquat, <b>I–L</b>: paraquat and Cu^II(atsm), <b>M–P</b>: paraquat and Cu^II(gtsm). Green  =  TDP-43, red  =  HuR, blue  =  DAPI. Bottom panels  =  merged images of TDP-43 and HuR above. Arrows indicate TDP-43 and HuR SGs. Bar  = 10 µm.</p

Effect of Cu^II(atsm) and kinase inhibitors on TDP-43 and HuR-positive SG formation.

<p>Cells were treated overnight with 1 mM paraquat in the presence or absence of 1 µM Cu^II(atsm), 10 µM PD98059 or 20 µM SP600125 and examined for TDP-43 and HuR by immunofluorescence. <b>A–C</b>: untreated, <b>D–F</b>: paraquat, <b>G–I</b>: paraquat and Cu^II(atsm), <b>J–L</b>: paraquat and PD98059, <b>M–O</b>: paraquat and SP600125. Green  =  TDP-43, red  =  HuR, blue  =  DAPI. Arrows indicate TDP-43 and HuR SGs. Bar  = 10 µm. <b>P</b>: SGs (TDP-43 or HuR-positive) per cell after overnight treatment with 1 mM paraquat and co-treatment with Cu^II(atsm) (1 µM), PD98095 or SP600125. **p<0.01 compared to paraquat treatment.</p