Yonghwang Ha

Dopamine and Cu+/2+ can induce oligomerization of α-synuclein in the absence of oxygen: Two types of oligomerization mechanisms for α-synuclein and related cell toxicity studies.

α‐Synuclein oligomers can induce neurotoxicity and are implicated in Parkinsons disease etiology and disease progression. Many studies have reported α‐synuclein oligomerization by dopamine (DA) and transition metal ions, but few studies provide insight into joint influences of DA and Cu2+. In this study, DA and Cu2+ were coadministered aerobically to measure α‐synuclein oligomerization under these conditions. In the presence of oxygen, DA induced α‐synuclein oligomerization in a dose‐dependent manner. Cu+/2+ did not effect oligomerization in such a manner in the presence of DA. By electrophoresis, Cu2+ was found easily to induce oligomerization with DA. This implies that oligomerization invoked by DA is reversible in the presence of Cu2+, which appears to be mediated by noncovalent bond interactions. In the absence of oxygen, DA induced less oligomerization of α‐synuclein, whereas DA/Cu2+ induced aerobic‐level amounts of oligomers, suggesting that DA/Cu2+ induces oligomerization independent of oxygen concentration. Radical species were detected through electron paramagnetic resonance (EPR) spectroscopic analysis arising from coincubation of DA/Cu2+ with α‐synuclein. Redox reactions induced by DA/Cu2+ were observed in multimer regions of α‐synuclein oligomers through NBT assay. Cellular toxicity results confirm that, for normal and hypoxic conditions, copper or DA/Cu2+ can induce cell death, which may arise from copper redox chemistry. From these results, we propose that DA and DA/Cu2+ induce different mechanisms of α‐synuclein oligomerization, cross‐linking with noncovalent (or reversible covalent) bonding vs. likely radical‐mediated covalent modification.

Interplay of salicylaldehyde, lysine, and M2+ ions on α-synuclein aggregation: cancellation of aggregation effects and determination of salicylaldehyde neurotoxicity.

In this study, α-synuclein was treated in vitro with salicylaldehyde (SA), lysine (lys) and M(n+) (Cu(2+) or Zn(2+)) in various ratios. SA induced aggregation of α-syn in the ratio of 1:500 (α-syn:SA) after incubation (pH 7.4, PBS buffer, 16-24h). Free lys can thus scavenge SA, inhibiting the aggregation of α-syn up to ∼63% (α-syn:SA:lys=1:1000:5000). When Cu(2+) and Zn(2+) are added to SA and α-syn, protein aggregation is induced. In the case of Zn(2+), the aggregation of α-syn increased to 74% (ratio=1:1000:50). Fluorescence studies support the production of protein-bound Zn(2+)-salicylaldimine species. For Cu(2+), aggregation of α-syn was shown (138%). Thus, possible protective or inducing effects of lys, Cu(2+) and Zn(2+) may exist with α-syn. α-Syn, SA and Cu(2+) can undergo complexation (fluorescence, CD and MALDI data). Cellular toxicity of SA (700μM), Zn(2+) (700μM) and Cu(2+) (700μM) on SH-SY5Y (1×10(5) cells) showed 9.8%, 38.0% and 14.4% compared to control values. Combinations showed more severe toxicities: 71.9% and 93.1% for SA (70μM)+Cu(2+) (700μM) and SA (70μM)+Zn(2+) (700μM), respectively, suggesting complexation itself may be toxic.

Sodium and Potassium Relating to Parkinson's Disease and Traumatic Brain Injury.

Alkali metals, especially sodium and potassium, are plentiful and vital in biological systems. They take on important roles in health and disease. Such roles include the regulation of homeostasis, osmosis, blood pressure, electrolytic equilibria, and electric current. However, there is a limit to our present understanding; the ions have a great ability and capacity for action in health and disease, much greater than our current understanding. For the regulation of physiological homeostasis, there is a crucial regulator (renin-angiotensin system, RAS), found at both peripheral and central levels. Misregulation of the Na(+)-K(+) pump, and sodium channels in RAS are important for the understanding of disease progression, hypertension, diabetes, and neurodegenerative diseases, etc. In particular, RAS displays direct or indirect interaction important to Parkinsons disease (PD). In this chapter, the relationship between the regulation of sodium/potassium concentration and PD was sought. In addition, some recent biochemical and clinical findings are also discussed that help describe sodium and potassium in the context of traumatic brain injury (TBI). TBI is caused from the heavy striking of the head; this strongly affects ion flux in the affected tissue (brain) and damages cellular regulation systems. Thus, inappropriate concentrations of ions (hyper- and hyponatremia, and hyper- and hypokalemia) will perturb homeostasis giving rise to important and far reaching effects. These changes also impact osmotic pressure and the concentration of other metal ions, such as the calcium(II) ion.

Mechanochemical versus sol–gel silica loading of phenolate- and acetate-bridged dizinc complexes: toward instant and inexpensive hybrids for controlled binding and release of Zn2+ in pure water

Herein, we have explored expeditious and lowered expense SiO2-loading in the context of fluorescent “off–on” and “on–off” Zn2+ ion detection/controlled release. A simple racemic ligand (H2rlys) (1) prepared in situ can be mechanically SiO2-loaded so as to induce surface sites that allow for “off–on” aqueous fluorescence (λem,max = ∼450 nm) detection of Zn2+; with Cu2+ as a competing input, “inhibit” logic gate behaviour is present. Oppositely, dimeric, chiral fluorescent zinc complexes (ΦF = ∼0.20) prepared in a “one pot” method, and bearing different Zn⋯Zn internuclear spacings, can be incorporated into silica by two methods. Specifically, the chiral Zn2(slysH)2Cl2 (2) and racemic Zn2(rslysH)2(μ-OAc)2 species (3) [slys or rslys = 6-amino-2-{(2-hydroxybenzylidene)amino}hexanoate] were mechanochemically loaded. An adsorption constant was 1.99 × 10−4 (molecules of 2/units SiO2)(min)−1 for times of 5–20 min, as determined by extensive SEM-EDS data. These confirmed the highly selective “on–off” rapid aqueous fluorescent Cu2+ detection (versus, Li+, Na+, Cs+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Ag+, Cd2+, Hg2+, Pb2+) through direct Zn2+ displacement under bulk neat water flow (pH = 7.4) as verified by an authentic sample of [Cu2(slysH)2(NO3)2]–silica (4–silica). With the use of 2·SiO2, Na4EDTA and Cu2+ “inhibit” logic gate behaviour was also found. Sol–gel techniques allowed for loadings of 2 (20–890 mg) up to 1 ∶ 1 (by wt). The preparation of these inorganic hybrids are extremely inexpensive and rapid to prepare from commercial starting materials and can be extended to variegated forms of SiO2; alumina gel was also functionalized with 2. Cu2+ and Zn2+ are metals pertinent to human neurological health promotion and in neurodegenerative diseases.

ICP-MS for the neurodegenerative and brain sciences

ICP-MS (inductively coupled plasma mass spectrometry) allows for the determination of “trace” elements and can be usefully related to tissues relating to neurodegenerative diseases. The accurate determination of trace elemental distributions in AD, PD, ALS, etc., allows in part for a better understanding of such diseases. The sensitivity and scope of the ICP-MS technique is therefore important to discuss. The elements detected can be analyzed for both body tissues and fluids. We discuss the practical use of ICP-MS, the instrumental setup; elements and their detection limits, a brief comparison of ICP-MS with other inorganic analysis instruments, sample preparation, and the analysis method are also treated. Next, we discuss metal ion analysis with ICP-MS in the context of neurodegenerative disease. This includes an introduction of neurodegenerative diseases, tissue analysis, fluid analysis and bioimaging of metals in brain tissue samples, and protein analysis application with metals and ICP-MS. The subtopics of (1) isotope dilution analysis, (2) related immunoassay techniques, and (3) hyphenated instrumental applications are also presented. This chapter is meant to be a primer for a synthetic chemist interested in utilizing ICP-MS and related techniques, and is current through 2011.