Squamosamide derivative FLZ protected dopaminergic neuron by activating Akt signaling pathway in 6-OHDA-induced in vivo and in vitro Parkinson's disease models

Novel compound FLZ alleviates rotenone-induced PD mouse model by suppressing TLR4/MyD88/NF-κB pathway through microbiota-gut-brain axis

Parkinson's disease (PD) is the second most common neurodegenerative disease, but none of the current treatments for PD can halt the progress of the disease due to the limited understanding of the pathogenesis. In PD development, the communication between the brain and the gastrointestinal system influenced by gut microbiota is known as microbiota-gut-brain axis. However, the explicit mechanisms of microbiota dysbiosis in PD development have not been well elucidated yet. FLZ, a novel squamosamide derivative, has been proved to be effective in many PD models and is undergoing the phase I clinical trial to treat PD in China. Moreover, our previous pharmacokinetic study revealed that gut microbiota could regulate the absorption of FLZ in vivo. The aims of our study were to assess the protective effects of FLZ treatment on PD and to further explore the underlying microbiota-related mechanisms of PD by using FLZ as a tool. In the current study, chronic oral administration of rotenone was utilized to induce a mouse model to mimic the pathological process of PD. Here we revealed that FLZ treatment alleviated gastrointestinal dysfunctions, motor symptoms, and dopaminergic neuron death in rotenone-challenged mice. 16S rRNA sequencing found that PD-related microbiota alterations induced by rotenone were reversed by FLZ treatment. Remarkably, FLZ administration attenuated intestinal inflammation and gut barrier destruction, which subsequently inhibited systemic inflammation. Eventually, FLZ treatment restored blood-brain barrier structure and suppressed neuroinflammation by inhibiting the activation of astrocytes and microglia in the substantia nigra (SN). Further mechanistic research demonstrated that FLZ treatment suppressed the TLR4/MyD88/NF-κB pathway both in the SN and colon. Collectively, FLZ treatment ameliorates microbiota dysbiosis to protect the PD model via inhibiting TLR4 pathway, which contributes to one of the underlying mechanisms beneath its neuroprotective effects. Our research also supports the importance of microbiota-gut-brain axis in PD pathogenesis, suggesting its potential role as a novel therapeutic target for PD treatment.

A UHPLC-MS/MS method to determine FLZ major active metabolites in human plasma: application to a pharmacokinetic study

Aim: FLZ, a novel promising dopamine neuroprotective agent, is designed to treat Parkinson's disease. F7G and F21G are FLZ major active Phase II metabolites whose exposure are nearly 100-times higher than FLZ, may chiefly produce effectiveness in human. Measurement of F7G and F21G in plasma samples is critical for investigating its pharmacokinetics in clinical studies. Methodology & results: Plasma samples were extracted by SPE method and then analyzed by a newly established ultra-UHPLC-MS/MS method. Conclusion: For the first time, a reliable and robust bioanalytical method for F7G and F21G detection was successfully applied in a first-in-human study.

Maturational Characterization of Mouse Cortical Neurons Three-Dimensionally Cultured in Functional Polymer FP001-Containing Medium

The aim of the present study is to construct and characterize a novel three-dimensional culture system for mouse neurons using the functional polymer, FP001. Stereoscopically extended neurites were found in primary mouse cortical neurons cultured in the FP001-containing medium. Neurons cultured with FP001 were distributed throughout the medium of the observation range whereas neurons cultured without FP001 were distributed only on the bottom of the dish. These results demonstrated that neurons can be three-dimensionally cultured using the FP001-containing medium. The mRNA expression of the glutamatergic neuronal marker vesicular glutamate transporter 1 in neurons cultured in the FP001-containing medium were higher than that in neurons cultured in the FP001-free medium. Expression of the matured neuronal marker, microtubule-associated protein 2 (MAP2) a,b, and the synapse formation marker, Synapsin I, in neurons cultured with FP001 was also higher than that in neurons cultured without FP001. The expression pattern of MAP2a,b in neurons cultured with FP001, but not that in neurons cultured without FP001, was similar to that in the embryonic cerebral cortex. Exposure to glutamate significantly increased 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction activity in neurons cultured with FP001 compared to that in neurons cultured without FP001. These results suggested that glutamatergic neurotransmission in neurons three-dimensionally cultured in the FP001-containing medium may be upregulated compared to neurons two-dimensionally cultured in the FP001-free medium. Thus, neurons with the properties close to those in the embryonic brain could be obtained by three-dimensionally culturing neurons using FP001, compared to two-dimensional culture with a conventional adhesion method.

Induction of glial cell line-derived neurotrophic factor by the squamosamide derivative FLZ in astroglia has neuroprotective effects on dopaminergic neurons

Glial cell line-derived neurotrophic factor (GDNF) has neurotrophic activity for the survival of dopaminergic neurons, which is under active investigation for Parkinson's disease (PD) therapy. FLZ is a potential new drug for PD treatment. However, it is unclear whether neurotrophic activity contributes to the neuroprotective effects of FLZ. Here we found that FLZ markedly improved the function of dopaminergic neurons in primary mesencephalic neuron/glia cultures. Further investigation demonstrated that astroglia were required for FLZ to function as a neurotrophic regulator, as FLZ failed to show neurotrophic effects in the absence of astroglia. We clarified that GDNF was responsible for the neurotrophic effects of FLZ since FLZ selectively stimulated GDNF production, which was confirmed by the finding that the neurotrophic effect of FLZ was attenuated by GDNF-neutralizing antibody. Mechanistic study demonstrated that GDNF induction by FLZ was CREB-dependent and that PI3K/Akt was the main pathway regulating CREB activity, which was confirmed by in vivo studies. We also validated that the induction of GDNF by FLZ contributed to PD treatment in vivo. In conclusion, the present data provided evidence that FLZ had robust neurotrophic effects on dopaminergic neurons through sustained induction of GDNF in astroglia by activating the PI3K/Akt/CREB pathway.

SC79, a novel Akt activator, protects dopaminergic neuronal cells from MPP+ and rotenone

In pathogenesis of Parkinson's disease (PD), mitochondrial dysfunction causes substantial reactive oxygen species (ROS) production and oxidative stress, leading to dopaminergic (DA) neuronal cell death. Mitochondrial toxins, including MPP⁺ (1-methyl-4-phenylpyridinium ion) and rotenone, induce oxidative injury in cultured DA neuronal cells. The current study tested the potential effect of SC79, a first-in-class small-molecule Akt activator, against the process. In SH-SY5Y cells and primary murine DA neurons, SC79 significantly attenuated MPP⁺- and rotenone-induced viability reduction, cell death, and apoptosis. SC79 activated Akt signaling in DA neuronal cells. Akt inhibition (by LY294002 and MK-2206) or CRISPR-Cas9-mediated Akt1 knockout completely abolished SC79-induced DA neuroprotection against MPP⁺. Further studies demonstrated that SC79 attenuated MPP⁺- and rotenone-induced ROS production, mitochondrial depolarization, and lipid peroxidation in SH-SY5Y cells and primary DA neurons. Moreover, upregulation of Nrf2-dependent genes (HO1 and NQO1) and Nrf2 protein stabilization were detected in SC79-treated SH-SY5Y cells and primary DA neurons. Together we show that SC79 protects DA neuronal cells from mitochondrial toxins possibly via activation of Akt-Nrf2 signaling.

Simultaneous determination of FLZ and its metabolite (M1) in human plasma and urine by UHPLC-MS/MS: Application to a pharmacokinetic study

FLZ is a novel anti-Parkinson's disease candidate drug. The main active metabolite is FLZ O-dealkylation (M1) in preclinical studies. A reliable ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) quantitation method was developed for the simultaneous determination of FLZ and M1 with low limits of quantitation in human plasma (0.1 ng/mL) and urine (0.5 ng/mL). The plasma and urine samples were both purified by full-automatic solid phase extraction (SPE) method with ensured high extraction recovery and little matrix effect for both analytes, and then separated on a BEH C₁₈ column (2.1 × 50 mm, 1.7 μm). Detection and quantification were performed using an electrospray ionization (ESI) source in positive mode by multiple reaction monitoring (MRM). The precursor to product ion transitions were monitored at m/z 450.3⁺→313.2⁺ for FLZ, m/z 436.3⁺→299.1⁺ for M1, m/z 462.6⁺→142.0⁺ for [D₁₂]-FLZ (internal standard of FLZ) and m/z 447.2⁺→125.2⁺ for [D₁₁]-M1 (internal standard of M1), respectively. This method showed good linearity, accuracy, precision and stability in the range of 0.1-100 ng/mL in plasma and 0.5-500 ng/mL in urine of two analytes. Finally, the developed method was successfully applied to a pharmacokinetic research in Chinese healthy volunteers after oral administration of FLZ tablets.

Enzymatic synthesis of glucuronidated metabolites of two neurological active agents using plant glucuronosyltransferases

Glucuronidation is an important and popular metabolic reaction in vivo of drugs. The further evaluation of biological activity and toxicity of glucuronides is necessary in the course of the drug research and development. However, the synthesis of glucuronides is limited by the lack of efficient approach. Herein, we have developed a new glucuronide synthesis method using plant uridine diphosphate-dependent glucuronosyltransferases (UGTs), UGT88D4, UGT88D7, and EpGT8, enabling the convenient preparation for corresponding O-glucuronide metabolites (1a, 2a, 3a, and 3b) in milligram scale of two neurological active agents, IMM-H004 (1) and FLZ (2). Their structures were characterized by spectroscopic data analyses.

Sulfated Hetero-Polysaccharides Protect SH-SY5Y Cells from H₂O₂-Induced Apoptosis by Affecting the PI3K/Akt Signaling Pathway

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. Recent studies suggest that sulfated hetero-polysaccharides (UF) protect against developing PD. However, the detailed mechanisms of how UF suppress neuronal death have not been fully elucidated. We investigated the cytoprotective mechanisms of UF using human dopaminergic neuroblastoma SH-SY5Y cells as a PD model. UF prevented H₂O₂-induced apoptotic cell death in SH-SY5Y cells in a dose-dependent manner. An examination of the PI3K/Akt upstream pathway revealed that UF-pretreated cells showed a decreased relative density of Akt, PI3K, and TrkA, and increased the phosphorylation of Akt, PI3K, and NGF; the PI3K inhibitor, LY294002, partially prevented this effect. An examination of the PI3K/Akt downstream pathway revealed the increased expression of the apoptosis-associated markers Bax, p53, CytC, and GSK3β, and the decreased expression of Bcl-2 in UF-treated cells. UF-treated cells also exhibited decreased caspase-3, caspase-8, and caspase-9 activities, which induced cell apoptosis. Our results demonstrate that UF affect the PI3K/Akt pathway, as well as downstream signaling. Therefore, the UF-mediated activation of PI3K/Akt could provide a new potential therapeutic strategy for neurodegenerative diseases associated with oxidative injury. These findings contribute to a better understanding of the critical roles of UF in the treatment of PD.

A novel synthetic derivative of squamosamide FLZ inhibits the high mobility group box 1 protein-mediated neuroinflammatory responses in murine BV2 microglial cells

High mobility group box 1 (HMGB1) is a critical pro-inflammatory cytokine that contributes to the pathogenesis of various human diseases. FLZ, a squamosamide derivative, has been demonstrated to have neuroprotective effects in Parkinson's disease models and shows strong anti-inflammatory activity, while the precise mechanism remains unclear. Here, we investigated the anti-inflammatory mechanism of FLZ on HMGB1-mediated inflammatory responses. The effects of FLZ on HMGB1 release from microglial cells induced by lipopolysaccharide were first explored by Western blot assay and ELISA. Then, co-immunoprecipition was used to study FLZ's effect on the interaction between HMGB1 and its receptor TLR4. Finally, we employed HMGB1 to simulate pro-inflammatory responses and then studied the inhibitory effects of FLZ on its bioactivity. FLZ has a significant inhibitory effect on HMGB1 release while it exerts no inhibitory effect on the binding between HMGB1 and TLR4. After the recognition of HMGB1 by TLR4, NF-κB signaling pathway is activated. FLZ could efficaciously alleviate HMGB1-induced inflammatory responses via the suppression of TLR4/MyD88/NF-κB signaling pathway. FLZ could inhibit HMGB1 release as well as HMGB1-induced inflammatory responses, HMGB1 might be one of the FLZ anti-inflammatory targets, and interfering at this inflammatory mediator may have benefit effects on neurodegenerative disorders, such as Parkinson's disease.

Insulin on activation of autophagy with integrins and syndecans against MPP+-induced α-synuclein neurotoxicity

Parkinson's disease (PD) is the second most common neurodegenerative disease in the elderly caused by dopaminergic neuronal cell death. Human neuroblastoma SH-SY5Y cells differentiated by retinoic acid have been used to study the in vitro PD model induced by 1-methyl-4-phenyl pyridinium (MPP⁺). In this study, pretreatment of insulin inhibited MPP⁺-induced cell membrane damages, which also inhibited the Cox-2 and α-synuclein levels. In addition, MPP⁺ and/or insulin enhanced the autophagy LC3. Furthermore, MPP⁺-induced neurotoxicity diminished the integrins β3, αV and induced the syndecan-1 and -3. Insulin pretreatment enhanced the phosphorylation of integrin-linked kinase and further induced the integrin and syndecan molecules. These findings suggest that insulin prevents MPP⁺-induced α-synuclein apoptosis through the activation of integrin and syndecan pathways in SH-SY5Y+RA cells.

Association of AKT1 gene polymorphisms with sporadic Parkinson's disease in Chinese Han population

Genetic variants of AKT1 have been shown to influence brain function of Parkinson's disease (PD) patients, and in this paper our aim is to investigate the association between the three single-nucleotide polymorphisms (rs2498799; rs2494732; rs1130214) and PD in Han Chinese. 413 Han Chinese PD patients and 450 healthy age and gender-matched controls were genotyped using the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method. Both the patient and control groups show similar genotype frequencies at the three loci: rs2498799, rs2494732 and rs1130214. We are able to identify a significant difference in the frequencies of genotype (p=0.019) and G allele (OR=0.764, 95% CI=0.587-0.995, p=0.045) both at rs2498799 between the patient and control groups. Furthermore, the association of subjects with GG genotypes versus those with GA+AA genotype remain significant after adjusting for age in the Han Chinese female cohort (OR=0.538, 95%CI=0.345-0.841, p=0.006), which is especially evident in the late-onset cohort (OR=0.521, 95%CI=0.309-0.877, p=0.012). In contrast, allele frequencies at rs2494732 and rs1130214 were similar between patients and controls in all subgroup analyses. These results suggest that polymorphism of AKT1 locus is associated with risk of PD and that the G allele at rs2498799 may decrease the risk of PD in the North-eastern part of Han Chinese female population.

Protective effects of activated signaling pathways by insulin on C6 glial cell model of MPP+-induced Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease (AD) associated with mitochondrial dysfunction mediated by oxidative stress. Astrocytes regulate neuronal function via the modulation of synaptic transmission and plasticity, secretion of growth factors, uptake of neurotransmitters, and regulation of extracellular ion concentrations and metabolic support of neurons. Therefore, this study was undertaken to investigate the mechanism of action of insulin on a 1-methyl-4-phenylpyridinium (MPP⁺)-induced toxicity of events associated in cell viability and toxicity to the expression profile of cell signaling pathway proteins and genes in rat C6 glial cells. The various concentrations of MPP⁺ alone inhibited cell viability in a dose-dependent manner. Pretreatment of insulin prevented the cell death and lowered the intracellular reactive oxygen species and calcium ion influx by MPP⁺. Insulin also suppressed the α-synuclein and elevated the insulin signaling pathway molecules IR, IGF-1R, IRS-1 and IRS-2 in C6 cells through phosphorylation of Akt/ERK survival pathways. Moreover, insulin inhibits MPP⁺-induced Bax to Bcl-2 ratio. These results suggest that insulin has a protective effect on the MPP⁺-toxicity in C6 glial cells.

Squamosamide derivative FLZ protected tyrosine hydroxylase function in a chronic MPTP/probenecid mouse model of Parkinson's disease

Parkinson's disease (PD) is a chronic, progressive neurodegenerative disorder characterized by motor impairments and loss of dopaminergic neurons in the substantia nigra. FLZ (formulated as: N-2-(4-hydroxy-phenyl)-ethyl]-2-(2, 5-dimethoxy-phenyl)-3-(3-methoxy-4-hydroxy-phenyl)-acrylamide) is a novel synthetic derivative of squamosamide from a Chinese herb and has been proven to protect dopaminergic neurons in subacute PD models. However, whether FLZ has a neuroprotective effect on chronic PD model is still unknown. The present study was designed to verify the neuroprotection of FLZ on chronic PD mouse model induced by MPTP combined with probenecid (MPTP/p). The results showed that treatment of mice with FLZ for 9 weeks significantly improved motor behavior and dopaminergic neuronal function of mice injected with MPTP/p. The beneficial effects of FLZ attributed to the elevation of dopaminergic neuron number, dopamine level, and tyrosine hydroxylase (TH) activity, as well as decrease of α-synuclein (α-Syn) expression, α-Syn phosphorylation, nitration, and aggregation. Moreover, FLZ decreased the interaction between α-Syn and TH, which eventually improved dopaminergic neuronal function. Mechanistic study demonstrated that FLZ increased Akt and mTOR phosphorylation, suggesting that FLZ activated Akt/mTOR signaling pathway and this might be involved in the neuroprotection of FLZ. The present results provided more elaborate in vivo evidences to support the neuroprotective effect of FLZ on dopaminergic neurons of chronic PD mouse model and the potential of FLZ to be developed as new drug to treat PD.

Squamosamide Derivative FLZ Protects Pancreatic β-Cells from Glucotoxicity by Stimulating Akt-FOXO1 Pathway

Chronic hyperglycemia increases apoptosis and reduces glucose-stimulated insulin secretion. Although protective agents have been searched extensively, none has been found so far. Here we tested FLZ, a synthetic derivative of squamosamide from a Chinese herb, as a potential candidate for antiglucotoxicity in INS-1E cells and mouse islets. Chronic culture of β-cells in 30 mM glucose caused progressive reduction of cell viability, accompanied with increased apoptosis and reduced insulin secretion. These effects on apoptosis and insulin were reversed by FLZ in a dose-dependent manner. FLZ treatment also increased forkhead box O1 protein phosphorylation and reduced its nuclear location. On the contrary, FLZ increased pancreatic and duodenal homeobox-1 expression and its nuclear localization, an effect mediated by increased p-Akt. Consistently, Akt selective inhibitor MK-2206 completely abolished antiglucotoxicity effect of FLZ. Furthermore, FLZ treatment increased cytosolic ATP/ADP ratio. Taken together, our results suggest that FLZ could be a potential therapeutic agent to treat the hyperglycemia-induced β-cell failure.

Emergence of Chinese drug discovery research: impact of hit and lead identification

The identification of hits and the generation of viable leads is an early and yet crucial step in drug discovery. In the West, the main players of drug discovery are pharmaceutical and biotechnology companies, while in China, academic institutions remain central in the field of drug discovery. There has been a tremendous amount of investment from the public as well as private sectors to support infrastructure buildup and expertise consolidation relative to drug discovery and development in the past two decades. A large-scale compound library has been established in China, and a series of high-impact discoveries of lead compounds have been made by integrating information obtained from different technology-based strategies. Natural products are a major source in China's drug discovery efforts. Knowledge has been enhanced via disruptive breakthroughs such as the discovery of Boc5 as a nonpeptidic agonist of glucagon-like peptide 1 receptor (GLP-1R), one of the class B G protein-coupled receptors (GPCRs). Most of the original hit identification and lead generation were carried out by academic institutions, including universities and specialized research institutes. The Chinese pharmaceutical industry is gradually transforming itself from manufacturing low-end generics and active pharmaceutical ingredients to inventing new drugs.

RTP801/REDD1: a stress coping regulator that turns into a troublemaker in neurodegenerative disorders

Mechanistic target of Rapamycin (mTOR) pathway regulates essential processes directed to preserve cellular homeostasis, such as cell growth, proliferation, survival, protein synthesis and autophagy. Importantly, mTOR pathway deregulation has been related to many diseases. Indeed, it has become a hallmark in neurodegenerative disorders, since a fine-tuned regulation of mTOR activities is crucial for neuron function and survival. RTP801/REDD1/Dig2 has become one of the most puzzling regulators of mTOR. Although the mechanism is not completely understood, RTP801 inactivates mTOR and Akt via the tuberous sclerosis complex (TSC1/TSC2) in many cellular contexts. Intriguingly, RTP801 protects dividing cells from hypoxia or H₂O₂-induced apoptosis, while it sensitizes differentiated cells to stress. Based on experimental models of Parkinson’s disease (PD), it has been proposed that at early stages of the disease, stress-induced RTP801 upregulation contributes to mTOR repression, in an attempt to maintain cell function and viability. However, if RTP801 elevation is sustained, it leads to neuron cell death by a sequential inhibition of mTOR and Akt. Here, we will review RTP801 deregulation of mTOR in a context of PD and other neurodegenerative disorders.