Papers by Sudarshan Phani
doi:10.1155/2012/845618 Review Article Classic and New Animal Models of Parkinson’s Disease
Copyright © 2012 Javier Blesa et al. This is an open access article distributed under the Creativ... more Copyright © 2012 Javier Blesa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Neurological disorders can bemodeled in animals so as to recreate specific pathogenic events and behavioral outcomes. Parkinson’s Disease (PD) is the second most common neurodegenerative disease of an aging population, and although there have been several significant findings about the PD disease process, much of this process still remains a mystery. Breakthroughs in the last two decades using animal models have offered insights into the understanding of the PD disease process, its etiology, pathology, and molecular mechanisms. Furthermore, while cellular models have helped to identify specific events, animal models, both toxic and genetic, have replicated almost all of the hallmarks of PD and are useful for testing new neuroprotective...
Experimental Neurology, 2005
There is evidence that BDNF influences the birth of granule cells in the dentate gyrus, which is ... more There is evidence that BDNF influences the birth of granule cells in the dentate gyrus, which is one of the few areas of the brain that demonstrates neurogenesis throughout life. However, studies to date have not examined this issue directly. To do so, we compared the effects of BDNF, phosphate-buffered saline (PBS), or bovine serum albumin (BSA) on neurogenesis after infusion into the hippocampus of the normal adult rat, using osmotic pumps that were implanted unilaterally in the dorsal hilus. BDNF, PBS, and BSA were infused for 2 weeks. The mitotic marker bromodeoxyuridine (BrdU) was administered twice daily during the 2-week infusion period. At least 1 month after infusion ended, brains were processed immunocytochemically using antibodies to BrdU, a neuronal nuclear protein (NeuN), or calbindin D28K (CaBP), which labels mature granule cells. Stereology was used to quantify BrdUlabeled cells in the dorsal hippocampus that were double-labeled with NeuN or CaBP. There was a statistically significant increase in BrdU + / NeuN + double-labeled cells in the granule cell layer after BDNF infusion relative to controls. The values for BrdU + /NeuN + cells were similar to BrdU + /CaBP + cells, indicating that most new neurons were likely to be granule cells. In addition, BrdU + /NeuN +-labeled cells developed in the hilar region after BDNF infusion, which have previously only been identified after severe continuous seizures (status epilepticus) and associated pathological changes. Remarkably, neurogenesis was also increased contralaterally, but BDNF did not appear to spread to the opposite hemisphere. Thus, infusion of BDNF to a local area can have widespread effects on hippocampal neurogenesis. The results demonstrate that BDNF administration to the dentate gyrus leads to increased neurogenesis of granule cells. They also show that ectopic granule cells develop after BDNF infusion, which suggests that ectopic migration is not necessarily confined to pathological conditions. These results are discussed in light of the evidence that BDNF increases neuronal activity in hippocampus. Thus, the mechanisms underlying neurogenesis following BDNF infusion could be due to altered activity as well as direct effects of BDNF itself, and this is relevant to studies of other growth factors because many of them have effects on neuronal excitability that are often not considered.
Abstract 6754: Clinical characteristics, real-world treatment patterns, and clinical outcomes among patients with previously treated metastatic or unresectable EGFR-mutated non-small cell lung cancer in the United States
Cancer Research
Background: A consensus on preferred treatment for patients with EGFR-mutated (EGFRm) advanced or... more Background: A consensus on preferred treatment for patients with EGFR-mutated (EGFRm) advanced or metastatic non-small-cell lung cancer (a/mNSCLC) who have progressed on osimertinib and platinum-based chemotherapy (PBC) has yet to be established. The study objectives were to describe patient characteristics and treatment patterns in this context and assess corresponding clinical outcomes in the US real-world setting. Methods: This study was a retrospective analysis of data sourced from Flatiron’s de-identified database, which included electronic health records and curated cancer data from approximately 280 US cancer clinics (~800 US sites of care). The index line of therapy (LOT) was defined as initiation of a new treatment regimen after osimertinib and PBC. Adults were eligible for inclusion if they: 1) were diagnosed with a/mNSCLC on or after January 1, 2011; 2) had evidence of an activating EGFR mutation (exon 19 or L858R); 3) initiated a new LOT between November 13, 2015, and Ju...
Astrocyte mediated toxicity leads to motor neuron death in Spinal Muscular Atrophy (S17.006)
Neurology, Apr 6, 2015
Gene expression studies of the VTA in an animal model of Parkinson's disease and the emergence of gremlin as a dopaminergic neuroprotective factor
Cell Reports, 2015
Neurodegenerative phenotypes reflect complex, time-dependent molecular processes, whose elucidati... more Neurodegenerative phenotypes reflect complex, time-dependent molecular processes, whose elucidation may reveal neuronal class-specific therapeutic targets. The current focus in neurodegeneration has been on individual genes and pathways. In contrast, we assembled a ‡
Neurodegeneration and Inflammation in Parkinson's disease
Parkinsonism & Related Disorders, 2012
Parkinson's disease (PD) is characterized... more Parkinson's disease (PD) is characterized by the progressive degeneration of dopamine (DA) neurons of the substantia nigra pars compacta (SNpc) accompanied by a buildup of proteinaceous aggregates termed Lewy bodies (LB). In addition to protein aggregation and the loss of DA signaling, PD is also characterized by an active immune response. T-cell infiltration accompanies activated microglial and astrocytic accumulation in and around the SNpc. Although potentially beneficial, microglial activation is most likely responsible for furthering disease pathology and DA neuron degeneration through the release of harmful substances such as pro-inflammatory cytokines, reactive oxidative species and reactive nitrogen species. Activation of the NF-κB death pathway has been shown to occur following microglial activation related release of Cox-2, IL-1β, and Toll-like receptor activation, resulting in increased degeneration of DA neurons of the SNpc. Blockade of microglial activation can lead to DA neuron protection in animal models of PD; however, clinical application of anti-inflammatory drugs has not yielded similar benefits. Future therapeutic designs must take into account the multifactorial nature of PD, including the varied roles of the adaptive and innate immune responses.
Neuron, 2014
Most cases of neurodegenerative diseases are sporadic, hindering the use of genetic mouse models ... more Most cases of neurodegenerative diseases are sporadic, hindering the use of genetic mouse models to analyze disease mechanisms. Focusing on the motor neuron (MN) disease amyotrophic lateral sclerosis (ALS), we therefore devised a fully humanized coculture model composed of human adult primary sporadic ALS (sALS) astrocytes and human embryonic stem-cell-derived MNs. The model reproduces the cardinal features of human ALS: sALS astrocytes, but not those from control patients, trigger selective death of MNs. The mechanisms underlying this noncell-autonomous toxicity were investigated in both astrocytes and MNs. Although causal in familial ALS (fALS), SOD1 does not contribute to the toxicity of sALS astrocytes. Death of MNs triggered by either sALS or fALS astrocytes occurs through necroptosis, a form of programmed necrosis involving receptorinteracting protein 1 and the mixed lineage kinase domain-like protein. The necroptotic pathway therefore constitutes a potential therapeutic target for this incurable disease.
Neuron, 2012
Non cell-autonomous processes are thought to play critical roles in the cellular maintenance of t... more Non cell-autonomous processes are thought to play critical roles in the cellular maintenance of the healthy and diseased brain but mechanistic details remain unclear. We report that the interruption of a non-cell autonomous mode of sonic hedgehog (Shh) signaling originating from dopaminergic neurons causes progressive, adult-onset degeneration of dopaminergic, cholinergic, and fast spiking GABAergic neurons of the mesostriatal circuit, imbalance of cholinergic and dopaminergic neurotransmission, and motor deficits reminiscent of Parkinson's disease. Variable Shh signaling results in graded inhibition of muscarinic auto-receptor-and GDNF-expression in the striatum. Reciprocally, graded signals that emanate from striatal cholinergic neurons and engage the canonical GDNF receptor Ret inhibit Shh expression in dopaminergic neurons. Thus, we discovered a novel mechanism for neuronal subtype specific and reciprocal communication that is essential for neurochemical and structural homeostasis in the nigrostriatal circuit. These results provide integrative insights into non cell-autonomous processes likely at play in neurodegenerative conditions such as Parkinson's disease.
Journal of Biomedicine and Biotechnology, 2012
Neurological disorders can be modeled in animals so as to recreate specific pathogenic events and... more Neurological disorders can be modeled in animals so as to recreate specific pathogenic events and behavioral outcomes. Parkinson’s Disease (PD) is the second most common neurodegenerative disease of an aging population, and although there have been several significant findings about the PD disease process, much of this process still remains a mystery. Breakthroughs in the last two decades using animal models have offered insights into the understanding of the PD disease process, its etiology, pathology, and molecular mechanisms. Furthermore, while cellular models have helped to identify specific events, animal models, both toxic and genetic, have replicated almost all of the hallmarks of PD and are useful for testing new neuroprotective or neurorestorative strategies. Moreover, significant advances in the modeling of additional PD features have come to light in both classic and newer models. In this review, we try to provide an updated summary of the main characteristics of these mo...
Frontiers in Pharmacology, 2012
Amyotrophic lateral sclerosis (ALS) is a fatal, adult-onset neurodegenerative disease that is cha... more Amyotrophic lateral sclerosis (ALS) is a fatal, adult-onset neurodegenerative disease that is characterized by the death of upper and lower motor neurons. Recent studies have made it clear that although motor neurons are the primary targets of the degenerative process, other cell types play key roles in the death of motor neurons. Most notably, cells of the immune system, including astrocytes and microglia have come under increasing scrutiny, after multiple lines of evidence have shown these cells to be deleterious to motor neurons. Both in vitro and in vivo experiments have shown that astrocytes and microglia containing mutated SOD1 are harmful to motor neurons. Several studies on ALS and other neurodegenerative diseases have revealed that reactive astrocytes and microglia are capable of releasing pro-inflammatory factors such as cytokines and chemokines, which are harmful to neighboring neurons. In addition, it is believed that diseased astrocytes can specifically kill motor neurons through the release of toxic factors. Furthermore, in an animal model of the disease, it has been shown that the reduction of SOD1 in microglia may be able to slow the progression of ALS symptoms. Although the exact pathways of motor neuron death in ALS have yet to be elucidated, studies have suggested that they die through aBaxdependent signaling pathway. Mounting evidence suggests that neuroinflammation plays an important role in the degeneration of motor neurons. Based on these findings, antiinflammatory compounds are currently being tested for their potential to reduce disease severity; however, these studies are only in the preliminary stages. While we understand that astrocytes and microglia play a role in the death of motor neurons in ALS, much work needs to be done to fully understand ALS pathology and the role the immune system plays in disease onset and progression.
Brain Research, 2010
Parkinson's disease and its characteristic symptoms are thought to arise from the progressive deg... more Parkinson's disease and its characteristic symptoms are thought to arise from the progressive degeneration of specific midbrain dopamine (DA) neurons. In humans, DA neurons of the substantia nigra (SN) and their projections to the striatum show selective vulnerability, while neighboring DA neurons of the ventral tegmental area (VTA) are relatively spared from degeneration. This pattern of cell loss is mimicked in humans, primates, and certain rodents by the neurotoxin MPTP. In this study, we aimed to test the hypothesis that there are factors in the VTA that are potentially neuroprotective against MPTP and that these factors change over time. We have found a dynamic transcriptional response within the cells of the VTA to sustained exposure to a low dose of MPTP. Specifically, the VTA has increased expression of 148 genes as an early response to MPTP and 113 genes as a late response to MPTP toxicity. This response encompasses many areas of cellular function, including protein regulation (Phf6) and ion/metal regulation (PANK2 and Car4). Notably, these responses were largely absent from the cells of the SN. Our data show a clear dynamic response in maintaining the homeostasis and viability of the neurons in the VTA that is lacking in the SN after neurotoxin challenge.
Gremlin is a novel VTA derived neuroprotective factor for dopamine neurons
Brain Research, 2013
Parkinson&#39... more Parkinson's disease and its characteristic symptoms are thought to arise from the progressive degeneration of specific midbrain dopamine (DA) neurons. In humans, DA neurons of the substantia nigra (SN) and their projections to the striatum show selective vulnerability, while neighboring DA neurons of the ventral tegmental area (VTA) are relatively spared from degeneration. Recent studies from our laboratory have shown that the VTA exhibits a unique transcriptional response when exposed to MPTP (Phani et al., 2010), a neurotoxin able to mimic the selective cell loss observed in PD (Schneider et al., 1987). In this study, we focus on gremlin, a peptide that is transcriptionally increased in the VTA in response to MPTP. We describe a novel role for gremlin as a neuroprotective agent both in vitro and in vivo and show that gremlin is capable of protecting SN DA neurons and several DA cell lines against MPP+/MPTP. We propose that this protection is mediated by VEGFR2, and by the MAP kinase signaling pathway downstream of the receptor. Our data indicate that gremlin may be a key factor in protecting the VTA against MPTP-induced cell death, and that exogenous application of gremlin is capable of protecting SN DA neurons, and therefore may provide an opportunity for the development of novel PD therapeutic compounds.
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Papers by Sudarshan Phani