Sarat Chandra Yenisetti

Turmeric is a centuries-old ethnomedicine in Asia. Previously our laboratory demonstrated in the adult life stage-specific (ALSS) Drosophila model of Parkinson’s disease (PD) that Curcumin (K)-mediated dopaminergic (DAergic) neuroprotection is absent in the transition stage of adult life during which late-onset neurodegenerative disorders like PD sets-in, suggesting its limitation as a therapeutic agent. The present study demonstrates that K can sequester the enhanced levels of brain oxidative stress (OS) during both adult life phases i.e. health and transition stages but confers neuroprotection only during the health phase. However, literature reviews illustrate that efficacy of supposed therapeutic agents was asserted by their ability to sequester OS in only young PD animal models. In this context, it is important to point out that despite encouraging results in animal models, therapeutic efforts to target the general state of OS failed to retard PD progression. To understand this paradigm, we further investigated ALSS regulation of molecular players in the brain of the ALSS fly PD model and discovered that K-mediated differential modulation of adaptive stress response through dFOXO contributes to health phase-specific neuroprotection. These observations suggest that apart from the study of OS markers; it is essential to understand the ALSS regulation of molecular players. The synergistic influence of OS and the ALSS dysfunctional molecular networks could be responsible for the DAergic neurodegeneration in PD. The insights suggest that sequestration of OS by a therapeutic agent is necessary, but inadequate to conclude its neuroprotective efficacy and push it to the next phase of preclinical/clinical evaluation.

Dopaminergic (DAergic) neurodegeneration in the substantia nigra pars compacta of the human brain is the pathological feature associated with Parkinson's disease (PD). Drosophila also exhibits mobility defects and diminished levels of brain dopamine on exposure to neurotoxicants mimicking PD. Our laboratory demonstrated in a Drosophila model of sporadic PD that there is no decrease in DAergic neuronal number; instead, there is a significant reduction in tyrosine hydroxylase (TH) fluorescence intensity (FI). Here, we present a sensitive assay based on the quantification of FI of the secondary antibody (ab). As the FI is directly proportional to the amount of TH synthesis, its reduction under PD conditions denotes the decrease in the TH synthesis, suggesting DAergic neuronal dysfunction. Therefore, FI quantification is a refined and sensitive method to understand the early stages of DAergic neurodegeneration. FI quantification is performed using the ZEN 2012 SP2 single -user software; a license must be acquired to utilize the imaging system to interactively control image acquisition, image processing, and analysis. This method will be of good use to biologists, as it can also be used with little modification to characterize the extent of degeneration and changes in the level of degeneration in response to drugs in different cell types. Unlike the expensive and cumbersome confocal microscopy, the present method will be an affordable option for fund -constrained neurobiology laboratories.

Epidemiological studies illustrate that sexual dysfunction (SD) is common among the majority of patients suffering from neurological disorders (NLDs). However, our understanding of the SD in NLDs is in its infancy. Our effort in this review article reveals how the clinical studies illustrate different phenotypes relating to SD in both men and women suffering from NLDs, with special reference to PD, and how the development of animal models will provide a fantastic opportunity to decipher mechanistic insights into the biological and molecular processes of SD, understanding of which is critical to figure out the causes of SD and to develop therapeutic strategies either by targeting molecular players or altering and/or regulating the profiles of involved genetic targets. Specific emphasis is placed on dopamine-dependent and independent mechanism(s) of SD among PD patients, which is important because certain critical dopamine-independent phenotypes are yet to be characterized and understood in order to decipher the comprehensive pathophysiology of PD. Synergic efforts of both clinicians and bench scientists in this critical direction would significantly improve the quality of life of sufferers of NLDs who are already burdened. This knowledge relating to SD will help us to make one more step in reducing the burden of disease.

Death of dopaminergic (DAergic) neurons in the substantia nigra pars compacta of the human brain is the characteristic pathological feature of Parkinson’s disease (PD). On exposure to neurotoxicants, Drosophila too exhibits mobility defects and diminished levels of brain dopamine. In the fly model of sporadic PD, our laboratory has demonstrated that there is no loss of DAergic neuronal number, however, a significant reduction in fluorescence intensity (FI) of secondary antibodies that target the primary antibody-anti-tyrosine hydroxylase (TH). Here, we present a sensitive, economical, and repeatable assay to characterize neurodegeneration based on the quantification of FI of the secondary antibody. As the intensity of fluorescence correlates with the amount of TH synthesis, its reduction under PD conditions denotes the depletion in the TH synthesis, suggesting DAergic neuronal dysfunction. Reduction in TH protein synthesis is further confirmed through Bio-Rad Stain-Free Western Blotting. Quantification of brain DA and its metabolites (DOPAC and HVA) using HPLC-ECD further demonstrated the depleted DA level and altered DA metabolism as evident from enhanced DA turnover rate. Together all these PD marker studies suggest that FI quantification is a refined and sensitive method to understand the early stages of DAergic neurodegeneration. FI quantification is performed using ZEN 2012 SP2, a licensed software from Carl Zeiss, Germany. This method will be of good use to biologists, as it with few modifications, can also be implemented to characterize the extent of degeneration of different cell types. Unlike the expensive and cumbersome confocal microscopy, the present method using fluorescence microscopy will be a feasible option for fund-constrained neurobiology laboratories in developing countries.

Background: A survey was executed to estimate the extent of entomophagy practiced by the tribal population in Nagaland. From the survey, two consumed stink bugs, namely Tessaratoma javanica and Coridius singhalanus, were assessed. Nutrient contents were assessed following the AOAC guidelines and elements were quantised using ICP-OES. Results: About 55% of the people surveyed consumed T. javanica, and 49% were consumers of C. singhalanus. The survey also indicated that the non-consumer respondents did not have any aversion towards the consumption of these insects. Biochemical analysis revealed that except for carbohydrate and moisture contents, all the other evaluated parameters (ash, crude fats, crude protein, and fibre content) were found to be comparatively higher in C. singhalanus, although the difference was significant (p ≤ 0.05) only for crude fat, carbohydrate, and fibre content. Trace elements analysis revealed that calcium (107.74 ± 0.213 mg/100 g), iron (22.17 ± 0.080 mg/100 g), and sodium (120.34 ± 0.214 mg/100 g) contents were significantly higher in T. javanica, whereas magnesium (76.06 ± 0.166 mg/100 g) content was significantly higher in C. singhalanus. Conclusions: Both the bugs show good nutritive contents and are liked for their distinctive smell and flavour.

Sexual dysfunction (SD) is one of the most common non-motor symptoms of Parkinson’s disease (PD) and remains the most neglected, under-reported, and under-recognized aspect of PD. Studies have shown that Dopamine (DA) in the hypothalamus plays a role in regulating sexual behavior. But the detailed mechanism of SD in PD is not known. Drosophila melanogaster shares several genes and signaling pathways with humans which makes it an ideal model for the study of a neurodegenerative disorder such as PD. Courtship behavior of Drosophila is one such behavior that is closely related to human sexual behavior and so plays an important role in understanding sexual behavior in diseased conditions as well. In the present study, a sporadic SD model of PD using Drosophila was developed and SD phenotype was observed based on abnormalities in courtship behavior markers. The Drosophila SD model was developed in such a way that at the window of neurotoxin paraquat (PQ) treatment [PQ is considered a crucial risk factor for PD due to its structural similarity with 1-methyl-4-phenyl pyridinium (MPP+), the active form of PD-inducing agent, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)], it does not exhibit mobility defects but shows SD. The whole brain tyrosine hydroxylase immunostaining showed no observable dopaminergic (DAergic) degeneration (number of DA neurons and fluorescence intensity of fluorescently labeled secondary antibodies that target anti-TH primary antibody) of the SD model. Similarly, there was no significant depletion of brain DA and its metabolite levels (HVA and DOPAC) as determined using HPLC-ECD (High-Performance Liquid Chromatography using Electrochemical Detector). The present study illustrates that the traits associated with courtship and sexual activity provide sensitive markers at the earlier stage of PD onset. This PQ-induced SD fly model throws an opportunity to decipher the molecular basis of SD under PD conditions and to screen nutraceuticals/potential therapeutic molecules to rescue SD phenotype and further to DAergic neuroprotection.

Parkinson’s disease (PD) affects almost 1% of the population worldwide over the age of 50 years. Exposure to environmental toxins like paraquat and rotenone is a risk factor for sporadic PD which constitutes 95% of total cases. Herbicide rotenone has been shown to cause Parkinsonian symptoms in multiple animal models. Drosophila is an excellent model organism for studying neurodegenerative diseases (NDD) including PD. The aging process is characterized by differential expression of genes during different life stages. Hence it is necessary to develop life-stage-matched animal models for late-onset human disease(s) such as PD. Such animal models are critical for understanding the pathophysiology of age-related disease progression and important to understand if a genotropic drug/nutraceutical can be effective during late stages. With this idea, we developed an adult life stage-specific (health and transition phase, during which late-onset NDDs such as PD sets in) rotenone-mediated Drosophila model of idiopathic PD. Drosophila is susceptible to rotenone in dose-time dependent manner. Rotenone-mediated fly model of sporadic PD exhibits mobility defects (independent of mortality), inhibited mitochondrial complex I activity, dopaminergic (DAergic) neuronal dysfunction (no loss of DAergic neuronal number; however, reduction in rate-limiting enzyme tyrosine hydroxylase (TH) synthesis), and alteration in levels of dopamine (DA) and its metabolites; 3,4-Dihydroxyphenylacetic acid (DOPAC) and Homovanilic acid (HVA) in brain-specific fashion. These PD-linked behaviors and brain-specific phenotypes denote the robustness of the present fly model of PD. This novel model will be of great help to decipher life stage-specific genetic targets of small molecule mediated DAergic neuroprotection; understanding of which is critical for formulating therapeutic strategies for PD.

Open access peer-reviewed chapter

Parkinson’s disease (PD) is a medical condition that has been known since ancient times. It is the second most common neurodegenerative disorder affecting approximately 1% of the population over 50 years. It is characterized by both motor and non-motor symptoms. Most of PD cases are sporadic while 5–10% cases are familial. Environment factors such as exposure to pesticides, herbicides and other heavy metals are expected to be the main cause of sporadic form of the disease. Mutation of the susceptible genes such as SNCA, PINK1, PARKIN, DJ1, and others are considered to be the main cause of the familial form of disease. Drosophila offers many advantages for studying human neurodegenerative diseases and their underlying molecular and cellular pathology. Shorter life span; large number of progeny; conserved molecular mechanism(s) among fly, mice and human; availability of many techniques, and tools to manipulate gene expression makes drosophila a potential model system to understand the pathology associated with PD and to unravel underlying molecular mechanism(s) responsible for dopaminergic neurodegeneration in PD—understanding of which will be of potential assistance to develop therapeutic strategies to PD. In the present review, we made an effort to discuss the contribution of fly model to understand pathophysiology of PD, in understanding the biological functions of genes implicated in PD; to understand the gene-environment interaction in PD; and validation of clues that are generated through genome-wide association studies (GWAS) in human through fly; further to screen and develop potential therapeutic molecules for PD. In nutshell, fly has been a great model system which has immensely contributed to the biomedical research relating to understand and addressing the pathology of human neurological diseases in general and PD in particular.