Mitigating gut microbial degradation of levodopa and enhancing brain dopamine: Implications in Parkinson's disease.

Parkinson's disease is managed using levodopa; however, as Parkinson's disease progresses, patients require increased doses of levodopa, which can cause undesirable side effects. Additionally, the oral bioavailability of levodopa decreases in Parkinson's disease patients due to the increased metabolism of levodopa to dopamine by gut bacteria, Enterococcus faecalis, resulting in decreased neuronal uptake and dopamine formation. Parkinson's disease patients have varying levels of these bacteria. Thus, decreasing bacterial metabolism is a promising therapeutic approach to enhance the bioavailability of levodopa in the brain. In this work, we show that Mito-ortho-HNK, formed by modification of a naturally occurring molecule, honokiol, conjugated to a triphenylphosphonium moiety, mitigates the metabolism of levodopa-alone or combined with carbidopa-to dopamine. Mito-ortho-HNK suppresses the growth of E. faecalis, decreases dopamine levels in the gut, and increases dopamine levels in the brain. Mitigating the gut bacterial metabolism of levodopa as shown here could enhance its efficacy.

Design, Synthesis and In Vitro Evaluation of Levodopa Stearic Acid Hydrazide Conjugate for the Management of Parkinson's DiseaseNovel Conjugate for Parkinson's Disease.

Parkinson's disease is the highest prevalent neurodegenerative disease in elderly individuals after Alzheimer's disease. The pathological identification for Parkinson's disease is loss of dopaminergic neurons in substantia nigra region of the brain that in turn leads to dopamine deficiency that affects the body's normal physiological and neurological disorder. The important drawback in the modality of treatment is levodopa is only supplying depleted dopamine in the brain, it does not affect neurodegeneration. Even though levodopa manages the disease, an alternative treatment strategy is required to stop or prevent further degeneration of neuron. The compound with neuroprotector activity suits the requirement. Of them, stearic acid plays a vital role in protecting neurons against oxidative stress through a Phosphoinositide 3-kinase-dependent mechanism. Hence, our present study aimed to design, synthesize, and characterize the levodopa stearic acid hydrazide conjugate. Additionally, evaluate the cytotoxicity of synthesized compound in SHSY5Y: cell lines. In brief, levodopa was conjugated to the stearic acid successfully and was confirmed with Fourier-transform infrared spectroscopy, Nuclear magnetic resonance, and Mass Spectroscopy. In vitro cell viability study in SHSY5Y: cell lines showed elevated cell viability in 0.134 µm concentration of Conjugate, and 0.563 µm concentration of levodopa. Showing that the synthesized compound could offer an improved treatment strategy for Parkinson's disease.

High-resolution structural information of membrane-bound α-synuclein provides insight into the MoA of the anti-Parkinson drug UCB0599.

α-synuclein (αS) is an intrinsically disordered protein whose functional ambivalence and protein structural plasticity are iconic. Coordinated protein recruitment ensures proper vesicle dynamics at the synaptic cleft, while deregulated oligomerization on cellular membranes contributes to cell damage and Parkinson's disease (PD). Despite the protein's pathophysiological relevance, structural knowledge is limited. Here, we employ NMR spectroscopy and chemical cross-link mass spectrometry on 14N/15N-labeled αS mixtures to provide for the first time high-resolution structural information of the membrane-bound oligomeric state of αS and demonstrate that in this state, αS samples a surprisingly small conformational space. Interestingly, the study locates familial Parkinson's disease mutants at the interface between individual αS monomers and reveals different oligomerization processes depending on whether oligomerization occurs on the same membrane surface (cis) or between αS initially attached to different membrane particles (trans). The explanatory power of the obtained high-resolution structural model is used to help determine the mode-of-actionof UCB0599. Here, it is shown that the ligand changes the ensemble of membrane-bound structures, which helps to explain the success this compound, currently being tested in Parkinson's disease patients in a phase 2 trial, has had in animal models of PD.

LUHMES Cells: Phenotype Refinement and Development of an MPP+-Based Test System for Screening Antiparkinsonian Drugs.

The low effectiveness of symptomatic pharmacotherapy for Parkinson's disease (PD), which compensates for dopamine (DA) deficiency under degeneration of nigrostriatal dopaminergic (DAergic) neurons, could apparently be improved with neuroprotective therapy, which slows down neurodegeneration and PD progression. For this, it is necessary to have a DAergic cell line for the development of a PD model to screen neuroprotectors. We used immortalized human embryonic mesencephalon LUHMES cells (LCs) differentiated into DAergic neurons. The aim of this study was to characterize the phenotype of differentiated LCs and develop an 1-methyl-4-phenylpyridinium iodide (MPP+)-based test system for screening neuroprotectors. Using polymerase chain reaction (PCR) and immunocytochemistry, it has been shown that all differentiated LCs express genes and synthesize proteins characteristic of all neurons (microtubule-associated protein 2, bIII-tubulin, synaptotagmin 1) and specifically of DAergic neurons (tyrosine hydroxylase, aromatic L-amino acid decarboxylase, DA transporter, vesicular monoamine transporter 2). Furthermore, LCs are able to produce a small amount of DA, but under special conditions. To assess the mechanisms of neurodegeneration and neuroplasticity under the influence of toxins and antiparkinsonian drugs, including neuroprotectors, we have developed an LCs-based MPP+ PD model and proposed an original panel of markers for testing functional and structural cell disorders.

Behavioral and neurochemical interactions of the tricyclic antidepressant drug desipramine with L-DOPA in 6-OHDA-lesioned rats. Implications for motor and psychiatric functions in Parkinson's disease.

RATIONALE: The pharmacological effects of antidepressants in modulating noradrenergic transmission as compared to serotonergic transmission in a rat model of Parkinson's disease under chronic L-DOPA therapy are insufficiently explored. OBJECTIVES: The aim of the present study was to investigate the effect of the tricyclic antidepressant desipramine administered chronically alone or jointly with L-DOPA, on motor behavior and monoamine metabolism in selected brain structures of rats with the unilateral 6-OHDA lesion. METHODS: The antiparkinsonian activities of L-DOPA and desipramine were assessed behaviorally using a rotation test and biochemically based on changes in the tissue concentrations of noradrenaline, dopamine and serotonin and their metabolites, evaluated separately for the ipsi- and contralateral motor (striatum, substantia nigra) and limbic (prefrontal cortex, hippocampus) structures of rat brain by HPLC method. RESULTS: Desipramine administered alone did not induce rotational behavior, but in combination with L-DOPA, it increased the number of contralateral rotations more strongly than L-DOPA alone. Both L-DOPA and desipramine + L-DOPA significantly increased DA levels in the ipsilateral striatum, substantia nigra, prefrontal cortex and the ipsi- and contralateral hippocampus. The combined treatment also significantly increased noradrenaline content in the ipsi- and contralateral striatum, while L-DOPA alone decreased serotonin level on both sides of the hippocampus. CONCLUSIONS: The performed analysis of the level of monoamines and their metabolites in the selected brain structures suggests that co-modulation of noradrenergic and dopaminergic transmission in Parkinson's disease by the combined therapy with desipramine + L-DOPA may have some positive implications for motor and psychiatric functions but further research is needed to exclude potential negative effects.

Kinetic modeling and statistical optimization of submerged production of anti-Parkinson's prodrug L-DOPA by Pseudomonas fluorescens.

L-DOPA, a precursor of dopamine, is the drug of choice for Parkinson's disease, which persists due to decreased levels of dopamine in the brain. Present study emphasis the microbial production of L-DOPA rather than the biotransformation of L-DOPA by L-tyrosine. The production of L-DOPA by bacterial isolates had gained more acceptance due to its more straightforward extraction and downstream processes. Pseudomonas fluorescens was used to produce the L-DOPA in a bioreactor system under submerged condition. The design of experiment-based Taguchi orthogonal array method was adopted for the optimization of production. L-9 orthogonal array using the analysis of mean approach was used to study the effect of different factors viz NaCl, lactose, tryptone, and inducer on the microbial production of L-DOPA. The method mentioned above is less time consuming and does not require any harsh chemicals, proving it to be an eco-friendly process. After optimizing selected factors, i.e., NaCl (1.2 g/l), lactose (1.5 g/l), tryptone (4 g/l), and inducer (0.1 g/l), 16.9 % of enhancement in L-DOPA production with 66.6% of process cost saving was observed. The production of L-DOPA was increased from 3.426 ± 0.08 g/l to 4.123 ± 0.05 g/l after optimization. Subsequently, unstructured kinetic models were adopted to simulate the fermentation kinetics and understand the metabolic process. Fisher' F test and determination coefficients (R2) confirmed that the Velhurst-Pearl logistic equation, Luedeking-Piret equation, and modified Luedeking-Piret equation was best fitted with the biomass production, product formation, and substrate utilization, respectively.

A Systematic Review of Parkinson's Disease Pharmacogenomics: Is There Time for Translation into the Clinics?

BACKGROUND: Parkinson's disease (PD) is the second most frequent neurodegenerative disease, which creates a significant public health burden. There is a challenge for the optimization of therapies since patients not only respond differently to current treatment options but also develop different side effects to the treatment. Genetic variability in the human genome can serve as a biomarker for the metabolism, availability of drugs and stratification of patients for suitable therapies. The goal of this systematic review is to assess the current evidence for the clinical translation of pharmacogenomics in the personalization of treatment for Parkinson's disease. METHODS: We performed a systematic search of Medline database for publications covering the topic of pharmacogenomics and genotype specific mutations in Parkinson's disease treatment, along with a manual search, and finally included a total of 116 publications in the review. RESULTS: We analyzed 75 studies and 41 reviews published up to December of 2020. Most research is focused on levodopa pharmacogenomic properties and catechol-O-methyltransferase (COMT) enzymatic pathway polymorphisms, which have potential for clinical implementation due to changes in treatment response and side-effects. Likewise, there is some consistent evidence in the heritability of impulse control disorder via Opioid Receptor Kappa 1 (OPRK1), 5-Hydroxytryptamine Receptor 2A (HTR2a) and Dopa decarboxylase (DDC) genotypes, and hyperhomocysteinemia via the Methylenetetrahydrofolate reductase (MTHFR) gene. On the other hand, many available studies vary in design and methodology and lack in sample size, leading to inconsistent findings. CONCLUSIONS: This systematic review demonstrated that the evidence for implementation of pharmacogenomics in clinical practice is still lacking and that further research needs to be done to enable a more personalized approach to therapy for each patient.

Identification of anti-Parkinson's Disease Lead Compounds from Aspergillus ochraceus Targeting Adenosin Receptors A2A.

Two novel alkaloids compounds together with fifteen know metabolites were identified from Aspergillus ochraceus. The stereochemistry features of the new molecules were determined via HRESIMS, NMR, ECD, and XRD analyses. Amongst these, compounds two compounds exhibited potential efficacy as anti-Parkinson's disease with the EC50 values of 2.30 and 2.45 µM, respectively. ADMET prediction showed that these compounds owned favorable drug-like characteristics and safe toxicity scores towards CNS drugs. Virtual screening analyses manifested that the compounds exhibited not only robust and reliable interactions to adenosine receptors A2A , but also higher binding selectivity to A2A receptors than to A1 and A3 receptors. Molecular dynamics simulation demonstrated the reliability of molecular docking results and the stability of the complexes obtained with the novel compounds and A2A receptors in natural environments. It is the first time that anti-PD lead compounds have been identified from Aspergillus ochraceus and targeting adenosine A2A receptors.

Impact of the apelin/APJ axis in the pathogenesis of Parkinson's disease with therapeutic potential.

The pathogenesis of Parkinson's disease (PD) remains elusive. There is still no available disease-modifying strategy against PD, whose management is mainly symptomatic. A growing amount of preclinical evidence shows that a complex interplay between autophagy dysregulation, mitochondrial impairment, endoplasmic reticulum stress, oxidative stress, and excessive neuroinflammation underlies PD pathogenesis. Identifying key molecules linking these pathological cellular processes may substantially aid in our deeper understanding of PD pathophysiology and the development of novel effective therapeutic approaches. Emerging preclinical evidence indicates that apelin, an endogenous neuropeptide acting as a ligand of the orphan G protein-coupled receptor APJ, may play a key neuroprotective role in PD pathogenesis, via inhibition of apoptosis and dopaminergic neuronal loss, autophagy enhancement, antioxidant effects, endoplasmic reticulum stress suppression, as well as prevention of synaptic dysregulation in the striatum, excessive neuroinflammation, and glutamate-induced excitotoxicity. Underlying signaling pathways involve phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin, extracellular signal-regulated kinase 1/2, and inositol requiring kinase 1α/XBP1/C/EBP homologous protein. Herein, we discuss the role of apelin/APJ axis and associated molecular mechanisms on the pathogenesis of PD in vitro and in vivo and provide evidence for its challenging therapeutic potential.

Striatal ΔFosB gene suppression inhibits the development of abnormal involuntary movements induced by L-Dopa in rats.

L-Dopa-induced dyskinesia (LID) is associated with the upregulation of striatal ∆FosB in animal models and patients with Parkinson's disease (PD). A mechanistic role of ∆FosB is suspected because its transgenic overexpression leads to the early appearance of LID in rodents and primates. This study in rodents is aimed at exploring the therapeutic potential of striatal ∆FosB gene suppression to control LID in patients with PD. To determine the effect of reducing striatal ∆FosB expression, we used RNAi gene knockdown in a rat model of PD and assessed abnormal involuntary movements (AIMs) in response to L-Dopa. Rats with dopamine depletion received striatal injections of rAAV-∆FosB shRNA or a control virus before exposure to chronic L-Dopa treatment. The development of AIMs during the entire L-Dopa treatment period was markedly inhibited by ∆FosB gene knockdown and its associated molecular changes. The antiparkinsonian action of L-Dopa was unchanged by ∆FosB gene knockdown. These results suggest a major role for ∆FosB in the development of LID and support exploring strategies to reduce striatal ∆FosB levels in patients with PD.

Biomaterials in the treatment of Parkinson's disease.

Parkinson's disease is a neurodegenerative disease, the treatment of which is mainly centred around supplementation of dopamine. Additional targets have been identified and newer chemotherapeutic agents have been introduced but their clinical efficacy is limited due to solubility, bioavailability issues and inability to cross the blood-brain barrier (BBB). A wide range of biomaterials ranging from biomolecules, polymers, inorganic metal and metal oxide nanoparticles have been employed to assist the delivery of these therapeutic agents into the brain. Additionally, strategies to deliver cells to restore the dopaminergic neurons also have shown promise due to the integration of biocompatible materials that aid neurogenesis through a combination of topographical, chemical and mechanical cues. Neuroprosthetics is an area that may become significant in treatment of motor deficits associated with Parkinson's disease, and involves development of highly conductive and robust electrode materials with excellent cytocompatibility. This review summarizes the major role played by biomaterials in design of novel strategies and in the improvement of existing therapeutic methods as well as the emerging trends in this domain.

Gut bacterial deamination of residual levodopa medication for Parkinson's disease.

BACKGROUND: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by both motor and non-motor symptoms. Gastrointestinal tract dysfunction is one of the non-motor features, where constipation is reported as the most common gastrointestinal symptom. Aromatic bacterial metabolites are attracting considerable attention due to their impact on gut homeostasis and host's physiology. In particular, Clostridium sporogenes is a key contributor to the production of these bioactive metabolites in the human gut. RESULTS: Here, we show that C. sporogenes deaminates levodopa, the main treatment in Parkinson's disease, and identify the aromatic aminotransferase responsible for the initiation of the deamination pathway. The deaminated metabolite from levodopa, 3-(3,4-dihydroxyphenyl)propionic acid, elicits an inhibitory effect on ileal motility in an ex vivo model. We detected 3-(3,4-dihydroxyphenyl)propionic acid in fecal samples of Parkinson's disease patients on levodopa medication and found that this metabolite is actively produced by the gut microbiota in those stool samples. CONCLUSIONS: Levodopa is deaminated by the gut bacterium C. sporogenes producing a metabolite that inhibits ileal motility ex vivo. Overall, this study underpins the importance of the metabolic pathways of the gut microbiome involved in drug metabolism not only to preserve drug effectiveness, but also to avoid potential side effects of bacterial breakdown products of the unabsorbed residue of medication.

Deciphering the robustness of pyrazolo-pyridine carboxylate core structure-based compounds for inhibiting α-synuclein in transgenic C. elegans model of Synucleinopathy.

Parkinson's disease (PD), a calamitous neurodegenerative disorder with no cure till date, is closely allied with the misfolding and aggregation of α-Synuclein (α -Syn). Inhibition of α-Syn aggregation is one of the optimistic approaches for the treatment for PD. Here, we carried out hypothesis-driven studies towards synthesising a series of pyrazolo-pyridine carboxylate containing compounds (7a-7m) targeted at reducing deleterious α-Syn aggregation. The target compounds were synthesized through multi-step organic synthesis reactions. From docking studies, compounds 7b, 7g and 7i displayed better interaction with the key residues of α-Syn with values: -6.8, -8.9 and -7.2 Kcal/mol, respectively. In vivo transgenic C. elegans model of Synucleinopathy was used to evaluate the ability of the designed and synthesized compounds to inhibit α-Syn aggregation. These lead compounds 7b, 7g and 7i displayed 1.7, 2.4 and 1.5-fold inhibition of α-Syn with respect to the control. Further, the strategy of employing pyrazolo-pyridine-based compounds worked with success and these scaffolds could be further modified and validated for betterment of endpoints associated with PD.

Design and development of 1,3,5-triazine-thiadiazole hybrids as potent adenosine A2A receptor (A2AR) antagonist for benefit in Parkinson's disease.

Various studies showed adenosine A2A receptors (A2ARs) antagonists have profound therapeutic efficacy in Parkinsons Disease (PD) by improving dopamine transmission, thus being active in reversing motor deficits and extrapyramidal symptoms related to the disease. Therefore, in the presents study, we have showed the development of novel 1,3,5-triazine-thiadiazole derivative as potent A2ARs antagonist. In the radioligand binding assay, these molecules showed excellent binding affinity with A2AR compared to A1R, with significant selectivity. Results suggest, compound 7e as most potent antagonist of A2AR among the tested series. In docking analysis with A2AR protein model, compound 7e found to be deeply buried into the cavity of receptor lined via making numerous interatomic contacts with His264, Tyr271, His278, Glu169, Ala63, Val84, Ile274, Met270, Phe169. Collectively, our study demonstrated 1,3,5-triazine-thiadiazole hybrid as a highly effective scaffold for the design of new A2A antagonists.

In vitro and in vivo evaluation of levodopa-loaded nanoparticles for nose to brain delivery.

Parkinson's disease (PD) is a neurodegenerative disease which is characterized by the loss of dopaminergic neurons in the brain. Levodopa is the drug of choice in the treatment of PD but it exhibits low oral bioavailability (30%) and very low brain uptake due to its extensive metabolism by aromatic amino acid decarboxylase in the peripheral circulation. Moreover, levodopa has psychic, gastrointestinal, and cardiovascular side effects, and most importantly, short and frequent stimulation of dopamine receptors lead to undesirable conditions such as dyskinesia over time. The challenges are to increase the therapeutic efficiency, the bioavailability and decreasing the unfavourable side effects of levodopa. Biocompatible nano-sized drug carriers could address these challenges at molecular level. For this purpose, levodopa-loaded Poly (lactide-co-glycolide) acid nanoparticles were prepared by double emulsion-solvent evaporation method for nose to brain drug delivery. Parameters such as homogenization speed, and external and internal phase content were modified to reach the highest loading efficiency. F1-1 coded formulation showed prolonged release up to 9 h. Carbodiimide method was used for surface modification studies of nanoparticles. The efficacy of the selected nanoparticle formulation has been demonstrated by in vivo experiments in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine induced PD model in mice.

Managing Parkinson's disease: moving ON with NOP.

The opioid-like neuropeptide nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP receptor) contribute to Parkinson's disease (PD) and motor complications associated with levodopa therapy. The N/OFQ-NOP receptor system is expressed in cortical and subcortical motor areas and, notably, in dopaminergic neurons of the substantia nigra compacta. Dopamine depletion, as in rodent models of PD results in up-regulation of N/OFQ transmission in the substantia nigra and down-regulation of N/OFQ transmission in the striatum. Consistent with this, NOP receptor antagonists relieve motor deficits in PD models by reinstating the physiological balance between excitatory and inhibitory inputs impinging on nigro-thalamic GABAergic neurons. NOP receptor antagonists also counteract the degeneration of nigrostriatal dopaminergic neurons, possibly by attenuating the excitotoxicity or modulating the immune response. Conversely, NOP receptor agonists attenuate levodopa-induced dyskinesia by attenuating the hyperactivation of striatal D1 receptor signalling in neurons of the direct striatonigral pathway. The N/OFQ-NOP receptor system might represent a novel target in the therapy of PD.

Discovery and inhibition of an interspecies gut bacterial pathway for Levodopa metabolism.

The human gut microbiota metabolizes the Parkinson's disease medication Levodopa (l-dopa), potentially reducing drug availability and causing side effects. However, the organisms, genes, and enzymes responsible for this activity in patients and their susceptibility to inhibition by host-targeted drugs are unknown. Here, we describe an interspecies pathway for gut bacterial l-dopa metabolism. Conversion of l-dopa to dopamine by a pyridoxal phosphate-dependent tyrosine decarboxylase from Enterococcus faecalis is followed by transformation of dopamine to m-tyramine by a molybdenum-dependent dehydroxylase from Eggerthella lenta These enzymes predict drug metabolism in complex human gut microbiotas. Although a drug that targets host aromatic amino acid decarboxylase does not prevent gut microbial l-dopa decarboxylation, we identified a compound that inhibits this activity in Parkinson's patient microbiotas and increases l-dopa bioavailability in mice.

Gut bacterial tyrosine decarboxylases restrict levels of levodopa in the treatment of Parkinson's disease.

Human gut microbiota senses its environment and responds by releasing metabolites, some of which are key regulators of human health and disease. In this study, we characterize gut-associated bacteria in their ability to decarboxylate levodopa to dopamine via tyrosine decarboxylases. Bacterial tyrosine decarboxylases efficiently convert levodopa to dopamine, even in the presence of tyrosine, a competitive substrate, or inhibitors of human decarboxylase. In situ levels of levodopa are compromised by high abundance of gut bacterial tyrosine decarboxylase in patients with Parkinson's disease. Finally, the higher relative abundance of bacterial tyrosine decarboxylases at the site of levodopa absorption, proximal small intestine, had a significant impact on levels of levodopa in the plasma of rats. Our results highlight the role of microbial metabolism in drug availability, and specifically, that abundance of bacterial tyrosine decarboxylase in the proximal small intestine can explain the increased dosage regimen of levodopa treatment in Parkinson's disease patients.

Balancing Apoptosis and Autophagy for Parkinson's Disease Therapy: Targeting BCL-2.

Apoptosis and autophagy are important intracellular processes that maintain organism homeostasis and promote survival. Autophagy selectively degrades damaged cellular organelles and protein aggregates, while apoptosis removes damaged or aged cells. Maintaining a balance between autophagy and apoptosis is critical for cell fate, especially for long-lived cells such as neurons. Conversely, their imbalance is associated with neurodegenerative diseases such as Parkinson's disease (PD), which is characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Restoring the balance between autophagy and apoptosis is a promising strategy for the treatment of PD. Some core proteins engage in cross talk between apoptosis and autophagy, including B cell lymphoma (BCL)-2 family members. This Review summarizes the role of BCL-2 members in the regulation of apoptosis and autophagy and discusses potential therapeutic approaches that target this balance for PD treatment.