Berberine (BBR) is a renowned natural compound that exhibits potent neuroprotective activities. However, the cellular and molecular mechanisms are still unclear. Hormesis is an adaptive mechanism generally activated by mild oxidative stress to protect the cells from further damage. Many phytochemicals have been shown to induce hormesis. This study aims to investigate whether the neuroprotective activity of BBR is mediated by hormesis and the related signaling pathways in 6-OHDA-induced PC12 cells and zebrafish neurotoxic models. Our results demonstrated that BBR induced a typical hormetic response in PC12 cells, i.e. low dose BBR significantly increased the cell viability, while high dose BBR inhibited the cell viability. Moreover, low dose BBR protected the PC12 cells from 6-OHDA-induced cytotoxicity and apoptosis, whereas relatively high dose BBR did not show neuroprotective activity. The hormetic and neuroprotective effects of BBR were confirmed to be mediated by up-regulated PI3K/AKT/Bcl-2 cell survival and Nrf2/HO-1 antioxidative signaling pathways. In addition, low dose BBR markedly mitigated the 6-OHDA-induced dopaminergic neuron loss and behavior movement deficiency in zebrafish, while high dose BBR only slightly exhibited neuroprotective activities. These results strongly suggested that the neuroprotection of BBR were attributable to the hormetic mechanisms via activating cell survival and antioxidative signaling pathways.

Schisantherin A (SA) is a promising anti-Parkinsonism natural product. However, its poor water solubility and rapid serum clearance impose significant barriers to delivery of SA to the brain. This work aimed to develop SA in a nanoparticle formulation that extended SA circulation in the bloodstream and consequently an increased brain uptake and thus to be potentially efficacious for the treatment of Parkinson's disease (PD). Spherical SA nanoparticles with a mean particle size of 70 nm were prepared by encapsulating SA into methoxy poly(ethylene glycol)-block-poly(d,l)-lactic-co-glycolic acid (mPEG-PLGA) nanoparticles (SA-NPs) with an encapsulation efficiency of ∼91% and drug loading of ∼28%. The in vitro release of the SA-NPs lasted for 48 h with a sustained-release pattern. Using the Madin-Darby canine kidney (MDCK) cell model, the results showed that first intact nanoparticles carrying hydrophobic dyes were internalized into cells, then the dyes were slowly released within the cells, and last both nanoparticles and free dyes were externalized to the basolateral side of the cell monolayer. Fluorescence resonance energy transfer (FRET) imaging in zebrafish suggested that nanoparticles were gradually dissociated in vivo with time, and nanoparticles maintained intact in the intestine and brain at 2 h post-treatment. When SA-NPs were orally administrated to rats, much higher C and AUC were observed in the plasma than those of the SA suspension. Furthermore, brain delivery of SA was much more effective with SA-NPs than with SA suspension. In addition, the SA-NPs exerted strong neuroprotective effects in zebrafish and cell culture models of PD. The protective effect was partially mediated by the activation of the protein kinase B (Akt)/glycogen synthase kinase-3β (Gsk3β) pathway. In summary, this study provides evidence that small-sized mPEG-PLGA nanoparticles may improve cross-barrier transportation, oral bioavailability, brain uptake, and bioactivity of this Biopharmaceutics Classification System (BCS) Class II compound, SA.

Schisantherin A (SA) is a promising anti-Parkinsonism Chinese herbal medicine but with poor water solubility and challenges to be delivered to the brain. We formulated SA as nanocrystals (SA-NC), aiming to improve its solubility and pharmacokinetic profile and thus provide a potential therapeutic agent for the treatment of Parkinson's disease (PD). The rod-shaped SA-NC had a particle size of ∼160 nm with 33.3% drug loading, and the nanocrystals exhibited a fast dissolution rate in vitro. The intact drug nanocrystals could be internalized into Madin-Darby canine kidney (MDCK) cells, which were followed by rapid intracellular release, and most of the drug was transported to the basolateral side in its soluble form. Following oral administration of the SA-NC or an SA suspension, the accumulated concentration of the SA-NC in the plasma and brain was considerably higher than that observed for the SA suspension, but the drug targeting efficiency was similar. The SA-NC significantly reversed the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic (DA) neuronal loss and locomotion deficiency in zebrafish, as well as the 1-methyl-4-phenylpyridinium ion (MPP)-induced damage of neuronal cell culture model. Further Western blot analysis demonstrated that the stronger neuroprotective effect of SA-NC may be partially mediated by the activation of the protein kinase B (Akt)/glycogen synthase kinase-3β (Gsk3β) pathway. Taken together, these data provide solid evidence that the nanocrystal formulation has the potential to improve the bioavailability and brain concentration of this Biopharmaceutics Classification System (BCS) class II compound, SA, for the treatment of PD.

A novel near-infrared (NIR), turn-on fluorescence probe containing a phosphinate group as a recognizing moiety for the selective detection of O2˙(-) with a low limit of detection (LOD, 9.9 nM) was developed. has good cell-membrane permeability, intracellular stability, and low cytotoxicity. In addition, we successfully applied the to visualize O2˙(-) in live zebrafish, mouse and, for the first time, in mouse liver.