Parkinson’s disease (PD) is a progressive neurodegenerative disorder that currently has no cure, but treatments are available to improve PD symptoms and maintain quality of life. In 2020, about 10 million people worldwide were living with PD. In 1970, the United States Food and Drug Administration approved the drug levodopa as a dopamine replacement to manage PD motor symptoms; levodopa-carbidopa combination became commercialized in 1975. After over 50 years of use, levodopa is still the gold standard for PD treatment. Unfortunately, levodopa therapy-induced dyskinesia and OFF symptoms remain unresolved. Therefore, we urgently need to analyze each current clinical trial’s status and therapeutic strategy to discover new therapeutic approaches for PD treatment. We surveyed 293 registered clinical trials on ClinicalTrials.gov from 2008 to 16 June 2021. After excluded levodopa/carbidopa derivative add-on therapies, we identified 47 trials as PD treatment drugs or therapies. Among them, 19 trials are in phase I (41%), 25 trials are in phase II (53%), and 3 trials are in phase III (6%). The three phase-III trials use embryonic dopamine cell implant, 5-HT_1A receptor agonist (sarizotan), and adenosine A_2A receptor antagonist (caffeine). The therapeutic strategy of each trial shows 29, 5, 1, 5, 5, and 2 trials use small molecules, monoclonal antibodies, plasma therapy, cell therapy, gene therapy, and herbal extract, respectively. Additionally, we discuss the most potent drug or therapy among these trials. By systematically updating the current trial status and analyzing the therapeutic strategies, we hope this review can provide new ideas and insights for PD therapy development.

Currently, neurodegenerative diseases are a major cause of disability around the world. Parkinson’s disease (PD) is the second-leading cause of neurodegenerative disorder after Alzheimer’s disease. In PD, continuous loss of dopaminergic neurons in the substantia nigra causes dopamine depletion in the striatum, promotes the primary motor symptoms of resting tremor, bradykinesia, muscle rigidity, and postural instability. The risk factors of PD comprise environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular injury, aging, and hereditary defects. The pathologic features of PD include impaired protein homeostasis, mitochondrial dysfunction, nitric oxide, and neuroinflammation, but the interaction of these factors contributing to PD is not fully understood. In neurotoxin-induced PD models, neurotoxins, for instance, 6-hydroxydopamine (6-OHDA), 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-Methyl-4-phenylpyridinium (MPP⁺), paraquat, rotenone, and permethrin mainly impair the mitochondrial respiratory chain, activate microglia, and generate reactive oxygen species to induce autooxidation and dopaminergic neuronal apoptosis. Since no current treatment can cure PD, using a suitable PD animal model to evaluate PD motor symptoms’ treatment efficacy and identify therapeutic targets and drugs are still needed. Hence, the present review focuses on the latest scientific developments in different neurotoxin-induced PD animal models with their mechanisms of pathogenesis and evaluation methods of PD motor symptoms.

The study was conducted to evaluate the cardio-protective activity of combination (COMB) of syringic acid (SA) and resveratrol (RV) against isoproterenol (ISO) induced cardio-toxicity in rats. Rats were pre-treated orally with SA (50 mg/kg), RV (50 mg/kg) and combination of SA (25 mg/kg) and RV (25 mg/kg) along with positive control gallic acid (50 mg/kg) for 30 days. The effects of ISO on cardiac markers, lipid profile and lipid peroxidation marker, anti-oxidant enzymes and m-RNA expression of nuclear factor-kappa B (NF-kB) and tumor necrosis factor-α (TNF-α) were observed along with histopathological observations of simple and transmission electron microscopes (TEM). Serum creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH) and alkaline phosphatase were significantly increased while cardiac tissue CK-MB, LDH, superoxide dismutase and catalase were significantly decreased in ISO administered rats, which also exhibited a significant increase in total cholesterol, triglycerides, low density lipoprotein cholesterol, very low density lipoprotein cholesterol and thiobarbutyric acid reactive substances and significant decrease in high density lipoprotein cholesterol in serum and heart. The m-RNA levels of inflammatory markers NF-kB and TNF-α were significantly increased in ISO treated rats. COMB Pre-treatment significantly reversed the ISO actions. Histopathological studies of simple and TEM were also co-related with the above biochemical parameters. Docking studies with NF-kB were also performed. Evidence has shown for the first time in this approach that COMB pre-treatment ameliorated ISO induced cardio-toxicity in rats and revealed cardio-protection.

Pinocembrin (PIN) is a natural flavonoid widely found in bee propolis with potent gastrointestinal protective effects. In consequence, PIN has great potential in preventing inflammatory bowel diseases (IBDs) while scant information is available. In this study, a dextran sulfate sodium (DSS)-induced rats ulcerative colitis model (3.5% DSS in drinking water for 7 days) was applied to explore the protective effects of PIN on macroscopic colitis symptoms, inflammation, intestinal epithelial barrier function, and gut microbiota homeostasis. While DSS-treated rats showed severe colitis clinical symptoms and histological changes (colonic pathological damages and intestinal goblet cells loss), pre-administration of PIN (5 and 10 mg/kg, p.o.) for a week alleviated these symptoms. Pre-administration of PIN also suppressed the pro-inflammatory gene expressions and improved tight junction functions of colonic epithelial cells. Additionally, PIN administration reversed DSS-induced short chain fatty acid loss, and improved the gut microbial diversity assessed by 16S rRNA phylogenetic sequencing. Overall, our results suggest a wide spectrum of protective effects of PIN in preventing IBDs.

Bee pollen (BP) is a natural medicine from the hive with various potential health-promoting benefits, but until now there is no study to determine its protective roles in inflammatory bowel disease (IBD). The aim of this study was to reveal the in vitro gastrointestinal protective effects of BP against IBD using molecular and metabolic methods. Dextran sulfate sodium (DSS) challenged Caco-2 cell monolayers were applied to mimic intestinal epithelial cell dysfunctions and metabolic disorders. The pretreatment with BP extract rich in polyphenols ameliorated DSS-induced cell viability losses. It also exerted protective effects against intestinal barrier impairment by strengthening epithelial integrity and tight junction losses induced by DSS. BP up-regulated anti-oxidant (NQO1, Txnrd1, Nrf2) and down-regulated inflammatory (TNF-α and IL-6) mRNA expressions, in accompany with MAPK signaling inhibition. Furthermore, metabolomics analysis based on UPLC-Q-TOF/MS revealed that BP, and DSS treated Caco-2 cells have different metabolomic profiles, with significant changes on key metabolites involved in glycerophospholipid metabolism. Our results showed that BP has great therapeutic potential throughout the early stages of DSS-induced colitis.