Role of Autophagy in Parkinson's Disease

Autophagy is an essential catabolic mechanism that delivers misfolded proteins and damaged organelles to the lysosome for degradation. Autophagy pathways include macroautophagy, chaperone-mediated autophagy and microautophagy, each involving different mechanisms of substrate delivery to lysosome. Defects of these pathways and the resulting accumulation of protein aggregates represent a common pathobiological feature of neurodegenerative disorders such as Alzheimer, Parkinson and Huntington disease. This review provides an overview of the role of autophagy in Parkinson's disease (PD) by summarizing the most relevant genetic and experimental evidence showing how this process can contribute to disease pathogenesis. Given lysosomes take part in the final step of the autophagic process, the role of lysosomal defects in the impairment of autophagy and their impact on disease will also be discussed. A glance on the role of non-neuronal autophagy in the pathogenesis of PD will be included. Moreover, we will examine novel pharmacological targets and therapeutic strategies that, by boosting autophagy, may be theoretically beneficial for PD. Special attention will be focused on natural products, such as phenolic compounds, that are receiving increasing consideration due to their potential efficacy associated with low toxicity. Although many efforts have been made to elucidate autophagic process, the development of new therapeutic interventions requires a deeper understanding of the mechanisms that may lead to autophagy defects in PD and should take into account the multifactorial nature of the disease as well as the phenotypic heterogeneity of PD patients.

Complex deregulation and expression of cytokines and mediators of the immune response in Parkinson's disease brain is region dependent

Neuroinflammation is common in neurodegenerative diseases including Parkinson disease (PD). Expression of 25 mRNAs was assessed with TaqMan-PCR including members of the complement system, colony stimulating factors, Toll family, cytokines IL-8, IL-6, IL-6ST, IL-1B, TNF-α family, IL-10, TGFβ family, cathepsins and integrin family, in the substantia nigra pars compacta, putamen, frontal cortex area 8 and angular gyrus area 39, in a total of 43 controls and 56 cases with PD-related pathology covering stages 1-6 of Braak. Up-regulation of IL-6ST was the only change in the substantia nigra at stages 1-2. Down-regulation of the majority of members examined occurred in the substantia nigra from stage 4 onwards. However, region-dependent down- and up-regulation of selected mRNAs occurred in the putamen and frontal cortex, whereas only mRNA up-regulated mRNAs were identified in the angular cortex from stage 3 onwards in PD cases. Protein studies in frontal cortex revealed increased IL6 expression and reduced IL-10 with ELISA, and increased IL-6 with western blotting in PD. Immunohistochemistry revealed localization of IL-5, IL-6 and IL-17 receptors in glial cells, mainly microglia; IL-5, IL-10 and M-CSF in neurons; TNF-α in neurons and microglia; and active NF-κB in the nucleus of subpopulations of neurons and glial cells in PD. Distinct inflammatory responses, involving pro- and anti-inflammatory cytokines, and variegated mediators of the immune response occur in different brain regions at the same time in particular individuals. Available information shows that altered α-synuclein solubility and aggregation, Lewy body formation, oxidative damage and neuroinflammation converge in the pathogenesis of PD.

Recent Advances in Drug Repurposing for Parkinson's Disease

As a long-term degenerative disorder of the central nervous system that mostly affects older people, Parkinson's disease is a growing health threat to our ever-aging population. Despite remarkable advances in our understanding of this disease, all therapeutics currently available only act to improve symptoms but cannot stop the disease progression. Therefore, it is essential that more effective drug discovery methods and approaches are developed, validated, and used for the discovery of disease-modifying treatments for Parkinson's disease. Drug repurposing, also known as drug repositioning, or the process of finding new uses for existing or abandoned pharmaceuticals, has been recognized as a cost-effective and timeefficient way to develop new drugs, being equally promising as de novo drug discovery in the field of neurodegeneration and, more specifically for Parkinson's disease. The availability of several established libraries of clinical drugs and fast evolvement in disease biology, genomics and bioinformatics has stimulated the momentums of both in silico and activity-based drug repurposing. With the successful clinical introduction of several repurposed drugs for Parkinson's disease, drug repurposing has now become a robust alternative approach to the discovery and development of novel drugs for this disease. In this review, recent advances in drug repurposing for Parkinson's disease will be discussed.

Neuroprotective Effect of Natural Indole and β-carboline Alkaloids against Parkinson's Disease: An Overview

Parkinson's disease (PD) is a devastating neurodegenerative condition that mostly damages dopaminergic neurons in the substantia nigra and impairs human motor function. Males are more likely than females to have PD. There are two main pathways associated with PD: one involves the misfolding of α-synuclein, which causes neurodegeneration, and the other is the catalytic oxidation of dopamine via MAO-B, which produces hydrogen peroxide that can cause mitochondrial damage. Parkin (PRKN), α- synuclein (SNCA), heat shock protein (HSP), and leucine-rich repeat kinase-2 (LRRK2) are some of the target areas for genetic alterations that cause neurodegeneration in Parkinson's disease (PD). Under the impact of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which is also important in Parkinson's disease (PD), inhibition of mitochondrial complex 1 results in enhanced ROS generation in neuronal cells. Natural products are still a superior option in the age of synthetic pharmaceuticals because of their lower toxicity and moderate side effects. A promising treatment for PD has been discovered using betacarboline (also known as "β-carboline") and indole alkaloids. However, there are not many studies done on this particular topic. In the herbs containing β-carbolines and indoles, the secondary metabolites and alkaloids, β-carbolines and indoles, have shown neuroprotective and cognitive-enhancing properties. In this review, we have presented results from 18 years of research on the effects of indole and β-carboline alkaloids against oxidative stress and MAO inhibition, two key targets in PD. In the SAR analysis, the activity has been correlated with their unique structural characteristics. This study will undoubtedly aid researchers in looking for new PD treatment options.