ABSTRACT
Dopaminergic neuronal loss is the main pathological character of Parkinson's disease (PD). Abnormal tau hyperphosphorylation will lead to dopaminergic neuronal loss. An indazole derivative 6-amino-1-methyl-indazole (AMI) successfully synthesized to inhibit tau hyperphosphorylation may exert a neuroprotective effect. The in vitro study showed that AMI effectively increased cell viability and alleviated the apoptosis induced by MPP+ in SH-SY5Y cells. In addition, AMI treatment significantly decreased the expression of p-tau and upstream kinases GSK-3ß. In the MPTP-induced PD mice models, we found AMI apparently preserved dopaminergic neurons in the substantia nigra and improved the PD behavioral symptoms. Our results demonstrate that AMI exerts a neuroprotective effect by inhibiting tau hyperphosphorylation, representing a promising new candidate for PD treatment.
ABSTRACT
<p><b>OBJECTIVE</b>To prepare an insulin-loaded nanoparticle assembled using pH-sensitive poly(ethylene glycol)-poly(ε-caprolactone)-poly(N,N-diethylamino-2-ethylmethaerylate) (mPEG-PCL-PDEAEMA) and investigate its performance of sustained insulin release in vitro and its hypoglycemic effects in diabetic rats. METHDOS: mPEG-PCL-PDEAEMA triblock copolymers with different hydrophobic lengths were synthesized by ring opening polymerization (ROP) combined with atom transfer radical polymerization (ATRP). The copolymers were characterized using Fourier-transform Infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance spectroscopy (H-NMR). Insulin-loaded nanoparticles were prepared by nanoprecipitation technique, in which the reversible swelling of the pH-sensitive material was used for insulin loading and release. The obtained nanoparticles were further confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The entrapment efficiency (EE%), drug loading (DL%) and in vitro release characteristics of the insulin- loaded nanoparticles were assessed using BCA protein assay kit. The hypoglycemic effects of the nanoparticles were evaluated by monitoring the glucose levels.</p><p><b>RESULTS</b>The size of the nanoparticles decreased as pH value increased within the range of 1.2 to 7.4. Using copolymers mPEG5k-PCL13k- PDEAEMA10k and mPEG5k-PCL10k-PDEAEMA10k as the drug carriers, the nanoparticles prepared with an optimal insulin-coplymer mass ratio of 90% had an average size of 181.9∓6.67 nm and 169∓7.1 nm, maximal EE% of (81.99∓1.77)% and (53.12∓0.62)%, and maximal DL% of (42.46∓0.53)% and (32.34∓0.26)%, respectively. Compared with free insulin, the insulin-loaded nanoparticles was capable of sustained insulin release and the release rate was lowered as the hydrophobic length increases. In diabetic rats, the insulin-loaded nanoparticles based on mPEG5k-PCL13k- PDEAEMA10k maintained a sustained hypoglycemic effect for 48 h, which was significantly longer than the time of free insulin.</p><p><b>CONCLUSION</b>The pH-sensitive triblock copolymer mPEG-PCL-PDEAEMA can serve as a promising candidate of carrier for sustained release of insulin.</p>
ABSTRACT
This study aimed to explore the neuroprotective role of 6-hydroxy-1H-indazole on dopaminergic neurons in a 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD). Forty 12-week-old C57BL/6 male mice were were randomized divided into 4 groups. Mice were treated with 2mg/kg and 4mg/kg 6-hydroxy-1H-indazole (i.p.) 1d before the initiation of MPTP administration (30mg/kg), and the 6-hydroxy-1H-indazole were daily injected half an hour before MPTP treatment in the following 5 days. The MPTP group was given normal saline on day 1 (i.p.), followed by 30mg/kg MPTP treatment in the following 5 days. Control group received an equivalent volume of normal saline. Ten days after the final injection of MPTP, the mice were killed. The results showed that MPTP decreased the dopaminergic neurons in the substantia nigra and dopamine in the striatum, downregulated the expression of tyrosine hydroxylase (TH), induced the impairment of behavior and hyperphosphorylation of tau, However, 6-hydroxy-1-H-indazole decreased the loss of dopaminergic neurons, increased dopamine concentration and TH expression, alleviated the behavioral damage and level of phosphor-tau in the MPTP-induced model of PD in C57BL/6 mice. These findings showed that 6-hydroxy-1-H-indazole-mediated neuroprotection was related to the inactivation of tau. In addition, 6-hydroxy-1-H-indazole may be a potential drug candidate for PD.
