ABSTRACT
l-3,4-Dihydroxyphenylalanine (l-DOPA) is the most effective therapeutic agent for Parkinson's disease (PD). l-DOPA is traditionally believed to be an inert amino acid that exerts actions and effectiveness in PD through its conversion to dopamine. In contrast to this generally accepted idea, l-DOPA is proposed to be a neurotransmitter. Recently, GPR143 (OA1), the gene product of ocular albinism 1 was identified as a receptor candidate for l-DOPA. GPR143 is widely expressed in the central and peripheral nervous system. GPR143 immunoreactivity was colocalized with phosphorylated α-synuclein in Lewy bodies in PD brains. GPR143 may contribute to the therapeutic effectiveness of l-DOPA and might be related to pathogenesis of PD.
ABSTRACT
Alzheimer's disease (AD) is an incurable neurodegenerative disease characterized by memory loss and neurotoxic amyloid beta (Aß) plaques accumulation. Numerous pharmacological interventions targeting Aß plaques accumulation have failed to alleviate AD. Also, the pathological alterations in AD start years before the onset of clinical symptoms. To identify proteins at play during the early stage of AD, we conducted proteomic analysis of the hippocampus of young AppNL-F mice model of AD at the preclinical phase of the disease. This was followed by interactome ranking of the proteome into hubs that were further validated in vivo using immunoblot analysis. We also performed double-immunolabeling of these hub proteins and Aß to quantify colocalization. Behavioral analysis revealed no significant difference in memory performance between 8-month-old AppNL-F and control mice. The upregulation and downregulation of several proteins were observed in the AppNL-F mice compared to control. These proteins corresponded to pathways and processes related to Aß clearance, inflammatory-immune response, transport, mitochondrial metabolism, and glial cell proliferation. Interactome analysis revealed several proteins including DLGP5, DDX49, CCDC85A, ADCY6, HEPACAM, HCN3, PPT1 and TNPO1 as essential proteins in the AppNL-F interactome. Validation by immunoblot confirmed the over-expression of these proteins except HCN3 in the early-stage AD mice hippocampus. Immunolabeling revealed a significant increase in ADCY6/Aß and HEPACAM/Aß colocalized puncta in AppNL-F mice compared to WT. These data suggest that these proteins may be involved in the early stage of AD. Our work suggests new targets and biomarkers for AD diagnosis and therapeutic intervention.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Hippocampus/metabolism , Proteome/metabolism , Proteomics/methods , Animals , Disease Models, Animal , Male , Mice , Mice, Inbred C57BL , Mice, TransgenicABSTRACT
Blood pressure is regulated by extrinsic factors including noradrenaline, the sympathetic neurotransmitter that controls cardiovascular functions through adrenergic receptors. However, the fine-tuning system of noradrenaline signaling is relatively unknown. We here show that l-3,4-dihydroxyphenylalanine (L-DOPA), a precursor of catecholamines, sensitizes the vascular adrenergic receptor alpha1 (ADRA1) through activation of L-DOPA receptor GPR143. In WT mice, intravenous infusion of the ADRA1 agonist phenylephrine induced a transient elevation of blood pressure. This response was attenuated in Gpr143 gene-deficient (Gpr143-/y) mice. Specific knockout of Gpr143 in vascular smooth muscle cells (VSMCs) also showed a similar phenotype, indicating that L-DOPA directly modulates ADRA1 signaling in the VSMCs. L-DOPA at nanomolar concentrations alone produced no effect on the VSMCs, but it enhanced phenylephrine-induced vasoconstriction and intracellular Ca2+ responses. Phenylephrine also augmented the phosphorylation of extracellular signal-regulated kinases in cultured VSMCs from WT but not Gpr143-/y mice. In WT mice, blood pressure increased during the transition from light-rest to dark-active phases. This elevation was not observed in Gpr143-/y mice. Taken together, our findings provide evidence for L-DOPA/GPR143 signaling that exerts precursor control of sympathetic neurotransmission through sensitizing vascular ADRA1.
Subject(s)
Levodopa/pharmacology , Muscle Tonus/drug effects , Muscle, Smooth, Vascular/drug effects , Receptors, Adrenergic, alpha-1/drug effects , Animals , Calcium/metabolism , Cells, Cultured , Extracellular Signal-Regulated MAP Kinases/metabolism , Eye Proteins/genetics , Eye Proteins/metabolism , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Mice , Mice, Knockout , Muscle, Smooth, Vascular/metabolism , Muscle, Smooth, Vascular/physiology , Phenylephrine/pharmacology , Phosphorylation , Receptors, Adrenergic, alpha-1/metabolism , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolism , Signal Transduction , Vasoconstrictor Agents/pharmacologyABSTRACT
AIM OF THE STUDY: The extract of the leaves of Alchornea cordifolia (AC) is extensively used in ethnomedicine for ulcers, rheumatic pains, febrile convulsions and for enhancing physical performance. In this study, the anti-stress and anticonvulsant activities of the aqueous leaf extract of Alchornea cordifolia were investigated in mice. MATERIALS AND METHODS: The anti-stress activity was assessed based on the ability of the extract to alter the duration of immobility, in the forced swim endurance test, whilst a picrotoxin-treated animal, was employed as the model for convulsive seizures. RESULTS: The extract (100-400 mg/kg) given orally was found to significantly (p<0.05) reduce the duration of immobility, which suggest an anti-stress/anti-fatigue property. However, AC when tested at doses between 100 and 400 mg/kg did not prevent convulsions induced by picrotoxin in mice. The acute toxicity study carried out in mice revealed that the extract was well tolerated by the animals, as no death was observed at oral doses of 500-4000 mg/kg. CONCLUSIONS: The results of this preliminary study provide evidence, which may support the use of Alchornea cordifolia against stress or fatigue in ethnomedicine.
