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Dr. Harish Chandra Pant was Chief of the Section on Neuronal Cytoskeletal Protein Regulation within the National Institute of Neurological Disorders and Stroke at the NIH. A main focus of his group was understanding the mechanisms regulating neuronal cytoskeletal phosphorylation. Phosphorylation of neurofilaments can increase filament stability and confer resistance to proteolysis, but aberrant hyperphosphorylation of neurofilaments can be found in the neurofibrillary tangles that are seen with neurodegenerative diseases like Alzheimer disease (AD). Through his work, Harish would inevitably come across cyclin dependent kinase 5 (Cdk5), a key kinase that can phosphorylate neurofilaments at KSPXK motifs. Cdk5 differs from other Cdks in that its activity is mainly in post-mitotic neurons rather than being involved in the cell cycle in dividing cells. With continued interest in Cdk5, Harish and his group were instrumental in identifying important roles for this neuronal kinase in not only neuronal cytoskeleton phosphorylation but also in neuronal development, synaptogenesis, and neuronal survival. Here, we review the accomplishments of Harish in characterizing the functions of Cdk5 and its involvement in neuronal health and disease., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Enterovirus-A71 (EV-A71) associated Hand, foot and mouth disease (HFMD) is a highly contagious viral infection affecting children in Asia-Pacific region and has become a major threat to public health. Although several EV-A71 genotypes (C, D, and G) were isolated in India in recent years, no recognizable outbreak of EV-A71 caused HFMD, Acute Flaccid paralysis (AFP) or encephalitis have been reported so far. It is essential to study the pathogenicity or cell tropism of these Indian isolates in order to understand their tendency to cause disease. We investigated the susceptibility and cytokine responses of indigenous EV-A71 genotypes (D and G) isolated from cases of AFP and genotype C viruses isolated from cases of HFMD and encephalitis, in human cells in-vitro. Although all three EV-A71 genotypes could infect and replicate in human muscle and neuronal cells, the genotype D virus showed a delayed response in human neuronal cells. Quantification of cytokine secretion in response to these isolates followed by confirmation with gene expression assays in human neuronal cells revealed significantly higher secretion of pro-inflammatory cytokines TNF-α IL-8, IL-6, IP-10 (p < 0.001) in G genotype infected cells as compared to pathogenic C genotypes whereas the genotype D virus could not induce any of the inflammatory cytokines. These findings will help to better understand the host response to indigenous EV-A71 genotypes for management of future EV-A71 outbreaks in India, if any., (© 2021. The Author(s).)

HtrA2, a proapoptotic mitochondrial serine protease, promotes cellular protection against oxidative damage. Literature reports show positive correlation between loss of HtrA2 protease activity and Parkinson's Disease (PD) susceptibility. Homozygous loss-of-function mutations in murine-HtrA2, and when they rarely occur in humans result in severe neurodegeneration and infantile death. Here, we report a novel heterozygous pathogenic HTRA2 variant, c.725C > T (p.T242M) in Indian PD patients. Although, this mutation exhibits no significant conformational changes compared to the wild-type, functional studies with HtrA2-T242M transfected neurons reveal common features of PD pathogenesis such as dysfunction, altered morphology and mitochondrial membrane depolarization. Despite exhibiting two-fold decrease in enzyme activity, observation of excessive cell-death due to over-expression of the mutant has been correlated with it being constitutively active. This interesting behavioral anomaly has been attributed to the loss of phosphorylation-mediated regulatory checkpoint at the T242M mutation site that is otherwise controlled by glycogen synthase kinase-3β (GSK-3β). This study, with seamless amalgamation of biophysical and biomedical research unravels a mechanistic pathway of HtrA2 regulation and delineates its biological role in PD. Therefore, this investigation will not only prove beneficial toward devising therapeutic strategies against HtrA2-associated diseases mediated by GSK-3β but also suggest new avenues for treatment of Parkinsonian phenotype., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Objective: Aloe vera (barbadensis Mill., Family Liliaceae) since ancient times has been used for the treatment of skin disorders, infection, and as a laxative. The present study was undertaken to explore the effect of A. vera (Family Liliaceae) in animal models of learning and memory, depression, and locomotion., Methods: To assess learning and memory, the passive avoidance task and elevated plus-maze were used. For evaluating depression, the forced swim test and tail suspension test were performed, and to assess locomotor activity, the rota rod test and photoactometer were used., Results: A. vera (200 and 400 mg/kg, p.o.) was found to significantly increase the acquisition and retention step-down latency as compared to control in the passive avoidance task. In the elevated plus-maze, the highest administered dose (400 mg/kg, p.o.) of A. vera significantly reduced the transfer latency as compared to control. The forced swim test as well as tail suspension test showed that A. vera at all administered doses (100, 200, and 400 mg/kg, p.o.) decreased the period of immobility significantly. However, the locomotor activity did not show any significant change in the rota rod test and photoactometer., Discussion: Thus from the above observations, it can be proposed that A. vera enhances learning and memory, and also alleviates depression in mice.

Accumulating evidences suggest that dopaminergic neuronal loss in the substantia nigra pars compacta (SNpc) during ageing and in Parkinson's disease (PD) is linked to neurodegenerative changes like exponential increase in alpha-synuclein expression and protein misfolding. Lewy body formation is also a quintessential observation in neurodegeneration and PD. In experimental models of PD, GRP78 a neuroprotective endoplasmic reticulum (ER) chaperone protein targets misfolded proteins for degradation and prevents release of caspase12 from the ER. Release of active caspase12 and its translocation to the nucleus induces ER mediated apoptosis. The effect of ageing on these proteins in human nigra is not known. We evaluated alpha-synuclein, caspase12, GRP78 and ubiquitin expression in the SNpc of Asian Indians, using immunohistochemistry and stereology. The number of alpha-synuclein and caspase12 immunoreactive neurons increased gradually with age whereas the number of GRP78-labeled neurons remained stable. In contrast, GRP78 protein expression was significantly upregulated with age, while alpha-synuclein and caspase12 increased slightly. An increase in the size and numbers of marinesco bodies was prominent after the sixth decade. The mild increase in alpha-synuclein expression and occurrence of marinesco bodies suggests ageing induced protein misfolding and GRP78 upregulation indicates presence of ER stress. The logarithmic upregulation of GRP78 could even be an indicator of neuroprotective or neuromodulatory response of ER to protein misfolding and initiation of unfolded protein response pathway. Since dopaminergic neurons are preserved in ageing Asian Indians, our study possibly signifies better proteasomal or ER response and partially explains the lower prevalence of PD in them., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Glial derived neurotrophic factor (GDNF) protects dopaminergic nigral neurons and may prevent the progression of age-related motor deficits and Parkinson's disease. The multi-component receptor complex which mediates the neuroprotective action of GDNF comprises of GDNF receptor alpha1 (GFRalpha1), a ligand binding cell surface component and RET receptor tyrosine kinase (RET) the signaling component. The expression of both these receptors in the normally aging human substantia nigra pars compacta (SNpc) needs to be studied since GDNF infusion is being considered for restoration of the lost nigrostriatal function. In the present study, we used unbiased stereology to quantify the number of GFRalpha1 and RET immunoreactive neurons in human SNpc from 28 weeks of gestation to 88 years (n=31). We further determined the levels of immunostaining intensity using densitometric image analysis to measure changes in levels of receptor expression. Here we report that human nigral dopaminergic neurons express GFRalpha1 and RET receptors at all ages. There was no reduction in the number of neurons expressing these receptors as a function of age. Moreover, there was no age-related decline in immunostaining intensity of both these receptors. It is likely that preservation of GDNF receptors in the nigral neurons is because these receptors are constitutively expressed in the human SNpc and thus it is GDNF responsive thru aging. The sustained receptor protein expression could also be another marker of preserved nigrostriatal function in Asian Indians. The latter possibility explains our earlier observation that the melanized nigral neurons are preserved with age in the Asian Indians., (2010 Elsevier B.V. All rights reserved.)

Age-related loss of melanized nigral neurons reported in the British Caucasians is not observed in Asian Indian, American and French adults. In the Americans, loss of dopaminergic phenotype occurs from midlife, without frank neurodegeneration. Here, we investigated whether nigral dopaminergic neurons in Asian Indians are lost with age or undergo morphological or biochemical dysfunction. Using unbiased stereology we estimated volume, number of melanized, borderline/non-melanized (n=34, 28 gestational weeks to 80 years) and tyrosine hydroxylase (TH)-Nurr1 co-labeled neurons (n=32, 28 gestational weeks to 80 years) in substantia nigra pars compacta. We quantified Nurr1 and TH proteins by immunoblotting (n=18, 28 gestational weeks to 69 years) and apoptotic neurons by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) staining. Nuclear and soma size was estimated by morphometry. There was no age-related decline in volume, neuronal density, neuronal numbers and TH-Nurr1 co-labeled neurons. TH and Nurr1 protein expression remained stable. Lack of TUNEL-TH co-labeled cells confirmed absence of neuronal apoptosis. The neuronal size remained unaltered. Our findings of preserved nigral dopaminergic neurons suggest no age-related loss of nigral function in Asian Indians, unlike the Americans. This may explain the lower incidence of Parkinson's disease in Asian Indians.

Aim of the Study: Bacopa monnieri (Brahmi) is extensively used in traditional Indian medicine as a nerve tonic and thought to improve memory. To examine the neuroprotective effects of Brahmi extract, we tested its protection against the beta-amyloid protein (25-35) and glutamate-induced neurotoxicity in primary cortical cultured neurons., Materials and Methods: Neuroprotective effects were determined by measuring neuronal cell viability following beta-amyloid and glutamate treatment with and without Brahmi extract. Mechanisms of neuroprotection were evaluated by monitoring cellular oxidative stress and acetylcholinesterase activity., Results: Our result demonstrated that Brahmi extract protected neurons from beta-amyloid-induced cell death, but not glutamate-induced excitotoxicity. This neuroprotection was possibly due to its ability to suppress cellular acetylcholinesterase activity but not the inhibition of glutamate-mediated toxicity. In addition, culture medium containing Brahmi extract appeared to promote cell survival compared to neuronal cells growing in regular culture medium. Further study showed that Brahmi-treated neurons expressed lower level of reactive oxygen species suggesting that Brahmi restrained intracellular oxidative stress which in turn prolonged the lifespan of the culture neurons. Brahmi extract also exhibited both reducing and lipid peroxidation inhibitory activities., Conclusions: From this study, the mode of action of neuroprotective effects of Brahmi appeared to be the results of its antioxidant to suppress neuronal oxidative stress and the acetylcholinesterase inhibitory activities. Therefore, treating patients with Brahmi extract may be an alternative direction for ameliorating neurodegenerative disorders associated with the overwhelming oxidative stress as well as Alzheimer's disease.