Interests

Teaching

Developmental Neuroscience, Stem Cell Biology, Disorders of the Nervous System

Research

Broad Interests: Neuroscience and Stem Cell BiologySpecific Interests: Aging and Neurodegeneration, Role of endogenous neural stem cells in development and disease, Graft-host interactions after neural transplantation, Central nervous system plasticity and regeneration, Disease modeling using patient-specific iPS cells and their derivatives

Courses

Scholarly Contributions

Chapters

• Madhavan, L. (2015). Neural Stem Cells for Intrinsic Brain Repair in Aging and Neural Degeneration. In Neural Stem Cells in Health and Disease. World Scientific Publishing Company.

Journals/Publications

• Corenblum, M. J., McRobbie-Johnson, A., Carruth, E., Bernard, K., Luo, M., Mandarino, L. J., Peterson, S., Billheimer, D., Maley, T., Eggers, E. D., & Madhavan, L. (2023). Parallel Neurodegenerative Phenotypes in Sporadic Parkinson's Disease Fibroblasts and Midbrain Dopamine Neurons. bioRxiv : the preprint server for biology.
  More info

  Understanding the mechanisms causing Parkinson's disease (PD) is vital to the development of much needed early diagnostics and therapeutics for this debilitating condition. Here, we report cellular and molecular alterations in skin fibroblasts of late-onset sporadic PD subjects, that were recapitulated in matched induced pluripotent stem cell (iPSC)-derived midbrain dopamine (DA) neurons, reprogrammed from the same fibroblasts. Specific changes in growth, morphology, reactive oxygen species levels, mitochondrial function, and autophagy, were seen in both the PD fibroblasts and DA neurons, as compared to their respective controls. Additionally, significant alterations in alpha synuclein expression and electrical activity were also noted in the PD DA neurons. Interestingly, although the fibroblast and neuronal phenotypes were similar to each other, they also differed in their nature and scale. Furthermore, statistical analysis revealed novel associations between various clinical measures of the PD subjects and the different fibroblast and neuronal data. In essence, these findings encapsulate spontaneous, in-tandem, disease-related phenotypes in both sporadic PD fibroblasts and iPSC-based DA neurons, from the same patient, and generates an innovative model to investigate PD mechanisms with a view towards rational disease stratification and precision treatments.
• Corenblum, M. J., McRobbie-Johnson, A., Carruth, E., Bernard, K., Luo, M., Mandarino, L. J., Peterson, S., Sans-Fuentes, M. A., Billheimer, D., Maley, T., Eggers, E. D., & Madhavan, L. (2023). Parallel neurodegenerative phenotypes in sporadic Parkinson's disease fibroblasts and midbrain dopamine neurons. Progress in neurobiology, 229, 102501.
  More info

  Understanding the mechanisms causing Parkinson's disease (PD) is vital to the development of much needed early diagnostics and therapeutics for this debilitating condition. Here, we report cellular and molecular alterations in skin fibroblasts of late-onset sporadic PD subjects, that were recapitulated in matched induced pluripotent stem cell (iPSC)-derived midbrain dopamine (DA) neurons, reprogrammed from the same fibroblasts. Specific changes in growth, morphology, reactive oxygen species levels, mitochondrial function, and autophagy, were seen in both the PD fibroblasts and DA neurons, as compared to their respective controls. Additionally, significant alterations in alpha synuclein expression and electrical activity were also noted in the PD DA neurons. Interestingly, although the fibroblast and neuronal phenotypes were similar to each other, they differed in their nature and scale. Furthermore, statistical analysis revealed potential novel associations between various clinical measures of the PD subjects and the different fibroblast and neuronal data. In essence, these findings encapsulate spontaneous, in-tandem, disease-related phenotypes in both sporadic PD fibroblasts and iPSC-based DA neurons, from the same patient, and generates an innovative model to investigate PD mechanisms with a view towards rational disease stratification and precision treatments.
• Sundman, M. H., Avila De Vault, B. E., Chen, A. Y., Madhavan, L., Fuglevand, A. J., & Chou, Y. H. (2023). The (hyper)excitable brain: what can a ubiquitous TMS measure reveal about cognitive aging?. Neurobiology of aging, 132, 250-252.
• Polt, R. L., Falk, T., Heien, M. L., Streicher, J. M., Rowe, R. K., Madhavan, L., Morrison, H. W., Melvin, J., Green, T. R., Giordano, K. R., Saber, M., Ortiz, J. B., Liu, C., Szabò, L., Bartlett, M. J., Molnar, G., Tanguturi, P., Bernard, K., & Apostol, C. R. (2022). Design and Synthesis of Novel Brain Penetrant Glycopeptide Analogues of PACAP with Neuroprotective Potential for Traumatic Brain Injury and Parkinsonism.. Frontiers in drug discovery, Vol. 1:(818003). doi:https://doi.org/10.3389/fddsv.2021.818003
  More info

  There is an unmet clinical need for curative therapies to treat neurodegenerative disorders. Most mainstay treatments currently on the market only alleviate specific symptoms and do not reverse disease progression. The Pituitary adenylate cyclase-activating polypeptide (PACAP), an endogenous neuropeptide hormone, has been extensively studied as a potential regenerative therapeutic. PACAP is widely distributed in the central nervous system (CNS) and exerts its neuroprotective and neurotrophic effects via the related Class B GPCRs PAC1, VPAC1, and VPAC2, at which the hormone shows roughly equal activity. Vasoactive intestinal peptide (VIP) also activates these receptors, and this close analogue of PACAP has also shown to promote neuronal survival in various animal models of acute and progressive neurodegenerative diseases. However, PACAP’s poor pharmacokinetic profile (non-linear PK/PD), and more importantly its limited blood-brain barrier (BBB) permeability has hampered development of this peptide as a therapeutic. We have demonstrated that glycosylation of PACAP and related peptides promotes penetration of the BBB and improves PK properties while retaining efficacy and potency in the low nanomolar range at its target receptors. Furthermore, judicious structure-activity relationship (SAR) studies revealed key motifs that can be modulated to afford compounds with diverse selectivity profiles. Most importantly, we have demonstrated that select PACAP glycopeptide analogues (2LS80Mel and 2LS98Lac) exert potent neuroprotective effects and anti-inflammatory activity in animal models of traumatic brain injury and in a mild-toxin lesion model of Parkinson’s disease, highlighting glycosylation as a viable strategy for converting endogenous peptides into robust and efficacious drug candidates.
• Wondrak, G. T., Snell, J. A., Rounds, L., Park, S. L., Madhavan, L., Jandova, J., & Corenblum, M. J. (2022). Mefloquine induces ER stress and apoptosis in BRAFi-resistant A375-BRAFV600E /NRASQ61K malignant melanoma cells targeting intracranial tumors in a bioluminescent murine model.. Molecular carcinogenesis. doi:10.1002/mc.23407
  More info

  Molecularly targeted therapeutics have revolutionized the treatment of BRAFV600E -driven malignant melanoma, but the rapid development of resistance to BRAF kinase inhibitors (BRAFi) presents a significant obstacle. The use of clinical antimalarials for the investigational treatment of malignant melanoma has shown only moderate promise, attributed mostly to inhibition of lysosomal-autophagic adaptations of cancer cells, but identification of specific antimalarials displaying single-agent antimelanoma activity has remained elusive. Here, we have screened a focused library of clinically used artemisinin-combination therapeutic (ACT) antimalarials for the apoptotic elimination of cultured malignant melanoma cell lines, also examining feasibility of overcoming BRAFi-resistance comparing isogenic melanoma cells that differ only by NRAS mutational status (BRAFi-sensitive A375-BRAFV600E /NRASQ61 vs. BRAFi-resistant A375-BRAFV600E /NRASQ61K ). Among ACT antimalarials tested, mefloquine (MQ) was the only apoptogenic agent causing melanoma cell death at low micromolar concentrations. Comparative gene expression-array analysis (A375-BRAFV600E /NRASQ61 vs. A375-BRAFV600E /NRASQ61K ) revealed that MQ is a dual inducer of endoplasmic reticulum (ER) and redox stress responses that precede MQ-induced loss of viability. ER-trackerTM DPX fluorescence imaging and electron microscopy indicated ER swelling, accompanied by rapid induction of ER stress signaling (phospho-eIF2α, XBP-1s, ATF4). Fluo-4 AM-fluorescence indicated the occurrence of cytosolic calcium overload observable within seconds of MQ exposure. In a bioluminescent murine model employing intracranial injection of A375-Luc2 (BRAFV600E /NRASQ61K ) cells, an oral MQ regimen efficiently antagonized brain tumor growth. Taken together, these data suggest that the clinical antimalarial MQ may be a valid candidate for drug repurposing aiming at chemotherapeutic elimination of malignant melanoma cells, even if metastasized to the brain and BRAFi-resistant.
• Madhavan, L., Teves, J. M., Bhargava, V., Kirwan, K., Corenblum, M. J., Justiniano, R., Wondrak, G. T., Anandhan, A., Flores, A. J., Schipper, D. A., Khalpey, Z., Sligh, J. E., Curiel-Lewansdrowski, C., & Sherman, S. J. (2018). Parkinson’s disease skin fibroblasts display signature alterations in growth, redox homeostasis, mitochondrial function and autophagy. Frontiers in Neuroscience.
  More info

  The discovery of biomarkers for Parkinson’s disease (PD) is challenging due to the heterogeneous nature of this disorder, and a poor correlation between the underlying pathology and the clinically expressed phenotype. An ideal biomarker would inform on PD-relevant pathological changes via an easily assayed biological characteristic, which reliably tracks clinical symptoms. Human dermal (skin) fibroblasts are accessible peripheral cells that constitute a patient-specific system, which potentially recapitulates the PD chronological and epigenetic aging history. Here, we compared primary skin fibroblasts obtained from individuals diagnosed with late-onset sporadic PD, and healthy age-matched controls. These fibroblasts were studied from fundamental viewpoints of growth and morphology, as well as redox, mitochondrial, and autophagic function. It was observed that fibroblasts from PD subjects had higher growth rates, and appeared distinctly different in terms of morphology and spatial organization in culture, compared to control cells. It was also found that the PD fibroblasts exhibited significantly compromised mitochondrial structure and function when assessed via morphological and oxidative phosphorylation assays. Additionally, a striking increase in baseline macroautophagy levels was seen in cells from PD subjects. Exposure of the skin fibroblasts to physiologically relevant stress, specifically ultraviolet irradiation (UVA), further exaggerated the autophagic dysfunction in the PD cells. Moreover, the PD fibroblasts accumulated higher levels of reactive oxygen species (ROS) coupled with lower cell viability upon UVA treatment. In essence, these studies highlight primary skin fibroblasts as a patient-relevant model that captures fundamental PD molecular mechanisms, and supports their potential utility to develop diagnostic and prognostic biomarkers for the disease.
• Corenblum, M. J., Flores, A. J., Badowski, M., Harris, D. T., & Madhavan, L. (2015). Systemic human CD34(+) cells populate the brain and activate host mechanisms to counteract nigrostriatal degeneration. Regenerative medicine, 10(5), 563-77.
  More info

  Here we investigated the neuroprotective potential of systemic CD34(+) human cord blood cells (hCBCs) in a 6-hydroxydopamine rat model of Parkinson's disease.
• Madhavan, L. (2015). Redox-based regulation of neural stem cell function and Nrf2. Biochemical Society transactions, 43(4), 627-31.
  More info

  Neural stem cells (NSCs) play vital roles in the development and maintenance of brain tissues throughout life. They can also potentially act as powerful sources of regeneration and repair during pathology to replace degenerating cells and counteract deleterious changes in the tissue microenvironment. However, both aging and neurodegeneration involve an up-regulation of processes, such as oxidative stress, inflammation, somatic mutations, and reduction in growth factors in neural tissues, which threaten the robust functioning of NSCs. Nevertheless, recent evidence also indicates that NSCs may possess the intrinsic capability to cope with such stressors in their microenvironment. Whereas the mechanisms governing the responses of NSCs to stress are diverse, a common theme that is emerging suggests that underlying changes in intracellular redox status are crucial. Here we discuss such redox-based regulation of NSCs, particularly in relation to nuclear erythroid factor 2-like 2 (Nrf2), which is a key cellular stress resistance factor, and its implications for successfully harnessing NSC therapeutic potential towards developing cell-based therapeutics for nervous system disorders.
• Madhavan, L., Daley, B. F., Davidson, B. L., Boudreau, R. L., Lipton, J. W., Cole-Strauss, A., Steece-Collier, K., & Collier, T. J. (2015). Sonic Hedgehog Controls the Phenotypic Fate and Therapeutic Efficacy of Grafted Neural Precursor Cells in a Model of Nigrostriatal Neurodegeneration. PloS one, 10(9), e0137136.
  More info

  The expression of soluble growth and survival promoting factors by neural precursor cells (NPCs) is suggested to be a prominent mechanism underlying the protective and regenerative effects of these cells after transplantation. Nevertheless, how and to what extent specific NPC-expressed factors contribute to therapeutic effects is not well understood. Using RNA silencing, the current study investigated the roles of two donor NPC molecules, namely glial cell-line derived neurotrophic factor (GDNF) and sonic hedgehog (SHH), in the protection of substantia nigra dopamine neurons in rats treated with 6-hydroxydopamine (6-OHDA). Analyses indicate that as opposed to the knock-down of GDNF, SHH inhibition caused a profound decline in nigrostriatal neuroprotection. Further, SHH silencing also curbed endogenous neurogenesis and the migration of host brdU+/dcx+ neural precursors into the striatum, which was present in the animals receiving control or GDNF silenced NPCs. A change in graft phenotype, mainly reflected by a reduced proportion of undifferentiated nestin+ cells, as well as a significantly greater host microglial activity, suggested an important role for these processes in the attenuation of neuroprotection and neurogenesis upon SHH silencing. Overall these studies reveal core mechanisms fundamental to grafted NPC-based therapeutic effects, and delineate the particular contributions of two graft-expressed molecules, SHH and GDNF, in mediating midbrain dopamine neuron protection, and host plasticity after NPC transplantation.
• Paumier, K. L., Sortwell, C. E., Madhavan, L., Terpstra, B., Celano, S. L., Green, J. J., Imus, N. M., Marckini, N., Daley, B., Steece-Collier, K., & Collier, T. J. (2015). Chronic amitriptyline treatment attenuates nigrostriatal degeneration and significantly alters trophic support in a rat model of parkinsonism. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 40(4), 874-83.
  More info

  In addition to alleviating depression, long-term adaptive changes induced by antidepressants may regulate neural plasticity in the diseased brain, providing symptomatic and disease-modifying effects in Parkinson's disease. The present study investigated whether chronic treatment with a frequently prescribed tricyclic antidepressant was neuroprotective in a 6-hydroxydopamine (6-OHDA) rat model of parkinsonism. In lesioned animals, chronic amitriptyline (AMI; 5 mg/kg) treatment resulted in a significant sparing of tyrosine hydroxylase-immunoreactive (THir) neurons in the substantia nigra pars compacta (SNpc) compared with saline treatment. Additionally, striatal fibers were preserved and functional motor deficits were attenuated. Although 6-OHDA lesions did not induce anhedonia in our model, the dose of AMI utilized had antidepressant activity as demonstrated by reduced immobility. Recent in vitro and in vivo data provide evidence that trophic factors such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) may be key mediators of the therapeutic response to antidepressants. Therefore, we investigated whether AMI mediates changes in these specific trophic factors in the intact and degenerating nigrostriatal system. Chronic AMI treatment mediates an increase in nigral BDNF both before and during ongoing degeneration, suggesting it may contribute to neuroprotection observed in vivo. However, over time, AMI reduced BDNF levels in the striatum, indicating tricyclic therapy differentially regulates trophic factors within the nigrostriatal system. Combined, these results suggest that AMI treatment attenuates dopamine neuron loss and elicits significant trophic changes relevant to dopamine neuron survival.
• Paumier, K. L., Sortwell, C. E., Madhavan, L., Terpstra, B., Daley, B. F., & Collier, T. J. (2015). Tricyclic antidepressant treatment evokes regional changes in neurotrophic factors over time within the intact and degenerating nigrostriatal system. Experimental neurology, 266, 11-21.
  More info

  In addition to alleviating depression, trophic responses produced by antidepressants may regulate neural plasticity in the diseased brain, which not only provides symptomatic benefit but also potentially slows the rate of disease progression in Parkinson's disease (PD). Recent in vitro and in vivo data provide evidence that neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) may be key mediators of the therapeutic response to antidepressants. As such, we conducted a cross-sectional time-course study to determine whether antidepressant-mediated changes in neurotrophic factors occur in relevant brain regions in response to amitriptyline (AMI) treatment before and after intrastriatal 6-hydroxydopamine (6OHDA). Adult male Wistar rats were divided into seven cohorts and given daily injections (i.p.) of AMI (5mg/kg) or saline throughout the duration of the study. In parallel, various cohorts of intact or parkinsonian animals were sacrificed at specific time points to determine the impact of AMI treatment on trophic factor levels in the intact and degenerating nigrostriatal system. The left and right hemispheres of the substantia nigra, striatum, frontal cortex, piriform cortex, hippocampus, and anterior cingulate cortex were dissected, and BDNF and GDNF levels were measured with ELISA. Results show that chronic AMI treatment elicits effects in multiple brain regions and differentially regulates levels of BDNF and GDNF depending on the region. Additionally, AMI halts the progressive degeneration of dopamine (DA) neurons elicited by an intrastriatal 6-OHDA lesion. Taken together, these results suggest that AMI treatment elicits significant trophic changes important to DA neuron survival within both the intact and degenerating nigrostriatal system.
• Gombash, S. E., Lipton, J. W., Collier, T. J., Madhavan, L., Steece-Collier, K., Cole-Strauss, A., Terpstra, B. T., Spieles-Engemann, A. L., Daley, B. F., Wohlgenant, S. L., Thompson, V. B., Manfredsson, F. P., Mandel, R. J., & Sortwell, C. E. (2012). Striatal pleiotrophin overexpression provides functional and morphological neuroprotection in the 6-hydroxydopamine model. Molecular therapy : the journal of the American Society of Gene Therapy, 20(3), 544-54.
  More info

  Neurotrophic factors are integrally involved in the development of the nigrostriatal system and in combination with gene therapy, possess great therapeutic potential for Parkinson's disease (PD). Pleiotrophin (PTN) is involved in the development, maintenance, and repair of the nigrostriatal dopamine (DA) system. The present study examined the ability of striatal PTN overexpression, delivered via psueudotyped recombinant adeno-associated virus type 2/1 (rAAV2/1), to provide neuroprotection and functional restoration from 6-hydroxydopamine (6-OHDA). Striatal PTN overexpression led to significant neuroprotection of tyrosine hydroxylase immunoreactive (THir) neurons in the substantia nigra pars compacta (SNpc) and THir neurite density in the striatum, with long-term PTN overexpression producing recovery from 6-OHDA-induced deficits in contralateral forelimb use. Transduced striatal PTN levels were increased threefold compared to adult striatal PTN expression and approximated peak endogenous developmental levels (P1). rAAV2/1 vector exclusively transduced neurons within the striatum and SNpc with approximately half the total striatal volume routinely transduced using our injection parameters. Our results indicate that striatal PTN overexpression can provide neuroprotection for the 6-OHDA lesioned nigrostriatal system based upon morphological and functional measures and that striatal PTN levels similar in magnitude to those expressed in the striatum during development are sufficient to provide neuroprotection from Parkinsonian insult.
• Madhavan, L., Daley, B. F., Sortwell, C. E., & Collier, T. J. (2012). Endogenous neural precursors influence grafted neural stem cells and contribute to neuroprotection in the parkinsonian rat. The European journal of neuroscience, 35(6), 883-95.
  More info

  Neuroprotective and neurorescue effects after neural stem/precursor cell (NPC) transplantation have been reported, but the mechanisms underlying such phenomena are not well understood. Our recent findings in a rat Parkinson's disease (PD) model indicate that transplantation of NPCs before a 6-hydroxydopamine (6-OHDA) insult can result in nigrostriatal protection which is associated with endogenous NPC proliferation, migration and neurogenesis. Here, we sought to determine whether the observed endogenous NPC response (i) contributes to transplanted NPC-mediated neuroprotection; and/or (ii) affects graft phenotype and function. Host Fischer 344 rats were administered the antimitotic agent cytosine-β-d-arabinofuranoside (Ara-C) to eliminate actively proliferating endogenous neural precursors before being transplanted with NPCs and treated with 6-OHDA to induce nigrostriatal degeneration. Behavioral and histological analyses demonstrate that the neuroprotective response observed in NPC transplanted animals which had not received Ara-C was significantly attenuated in animals which did receive pre-transplant Ara-C. Also, while grafts in Ara-C-treated animals showed no decrease in cell number, they exhibited significantly reduced expression of the neural stem cell regulators nestin and sonic hedgehog. In addition, inhibition of the endogenous NPC response resulted in an exaggerated host glial reaction. Overall, the study establishes for the first time that endogenous NPCs contribute to transplanted NPC-mediated therapeutic effects by affecting both grafted and mature host cells in unique ways. Thus, both endogenous and transplanted NPCs are important in creating an environment suitable for neural protection and rescue, and harnessing their synergistic interaction may lead to the optimization of cell-based therapies for PD.
• Paumier, K. L., Siderowf, A. D., Auinger, P., Oakes, D., Madhavan, L., Espay, A. J., Revilla, F. J., Collier, T. J., & , P. S. (2012). Tricyclic antidepressants delay the need for dopaminergic therapy in early Parkinson's disease. Movement disorders : official journal of the Movement Disorder Society, 27(7), 880-7.
  More info

  This study examined whether antidepressants delay the need for dopaminergic therapy or change the degree of motor impairment and disability in a population of early Parkinson's disease (PD) patients. Preclinical studies have indicated that antidepressants modulate signaling pathways involved in cell survival and plasticity, suggesting they may serve to both treat PD-associated depression and slow disease progression. A patient-level meta-analysis included 2064 patients from the treatment and placebo arms of the following trials: FS1, FS-TOO, ELLDOPA, QE2, TEMPO, and PRECEPT. Depression severity was determined at baseline, and antidepressant use was reported in a medication log each visit. Kaplan-Meier curves and time-dependent Cox proportional hazards models determined associations between depression severity and antidepressant use with the primary outcome, time to initiation of dopaminergic therapy. ANCOVAs determined associations with the secondary outcome, degree of motor impairment and disability, reported as annualized change in UPDRS scores from baseline to final visit. When controlling for baseline depression, the initiation of dopaminergic therapy was delayed for subjects taking tricyclic antidepressants compared with those not taking antidepressants. No significant differences were found in UPDRS scores for subjects taking antidepressants compared with those not taking antidepressants. Tricyclic antidepressants are associated with a delay in reaching the end point of need to start dopaminergic therapy. The lack of change in overall UPDRS scores suggests the delay was not attributable to symptomatic effects.
• Kordower, J. H., Dodiya, H. B., Kordower, A. M., Terpstra, B., Paumier, K., Madhavan, L., Sortwell, C., Steece-Collier, K., & Collier, T. J. (2011). Transfer of host-derived α synuclein to grafted dopaminergic neurons in rat. Neurobiology of disease, 43(3), 552-7.
  More info

  Multiple laboratories have recently demonstrated that long-term dopaminergic transplants form Lewy bodies in patients with Parkinson's disease. Debate has arisen as to whether these Lewy bodies form from the transfer of α synuclein from the host to the graft or whether they form from intrinsic responses of the graft from being placed into what was, or became, an inflammatory focus. To test whether the former hypothesis was possible, we grafted fetal rat ventral mesencephalon into the dopamine depleted striatum of rats that had previously received 6-hydroxydopamine lesions. One month after the transplant, rats received viral over expression of human α synuclein (AAV2/6-α synuclein) or green fluorescent protein (AAV2/6-GFP) into the striatum rostral to the grafts. Care was taken to make sure that the AAV injections were sufficiently distal to the graft so no cells would be directly transfected. All rats were sacrificed five weeks after the virus injections. Double label immunohistochemistry combined with confocal microscopy revealed that a small number of grafted tyrosine hydroxylase (TH) neurons (5.7% ± 1.5% (mean ± SEM) of grafted dopamine cells) expressed host derived α synuclein but none of the grafted cells expressed host-derived GFP. The α synuclein in a few of these cells was misfolded and failed to be digested with proteinase K. These data indicate that it is possible for host derived α synuclein to transfer to grafted neurons supporting the concept that this is one possible mechanism by which grafted dopamine neurons form Lewy bodies in Parkinson's disease patients.
• Madhavan, L., & Collier, T. J. (2010). A synergistic approach for neural repair: cell transplantation and induction of endogenous precursor cell activity. Neuropharmacology, 58(6), 835-44.
  More info

  Stem cell research offers enormous potential for treating many diseases of the nervous system. At present, therapeutic strategies in stem cell research segregate into two approaches: cell transplantation or endogenous cell stimulation. Realistically, future cell therapies will most likely involve a combination of these two approaches, a theme of our current research. Here, we propose that there exists a 'synergy' between exogenous (transplanted) and endogenous stem cell actions that can be utilized to achieve therapeutic ends. Elucidating mechanisms underlying this exogenous-endogenous stem cell synergism may lead to the development of optimal cell therapies for neural disorders.
• Madhavan, L., Daley, B. F., Paumier, K. L., & Collier, T. J. (2009). Transplantation of subventricular zone neural precursors induces an endogenous precursor cell response in a rat model of Parkinson's disease. The Journal of comparative neurology, 515(1), 102-15.
  More info

  Realistically, future stem cell therapies for neurological conditions including Parkinson's disease (PD) will most probably entail combination treatment strategies, involving both the stimulation of endogenous cells and transplantation. Therefore, this study investigates these two modes of neural precursor cell (NPC) therapy in concert in order to determine their interrelationships in a rat PD model. Human placental alkaline phosphatase (hPAP)-labeled NPCs were transplanted unilaterally into host rats which were subsequently infused ipsilaterally with 6-hydroxydopamine (6-OHDA). The reaction of host NPCs to the transplantation and 6-OHDA was tracked by bromodeoxyuridine (BrdU) labeling. Two weeks after transplantation, in animals transplanted with NPCs we found evidence of elevated host subventricular zone NPC proliferation, neurogenesis, and migration to the graft site. In these animals, we also observed a significant preservation of striatal tyrosine hydroxylase (TH) expression and substantia nigra TH cell number. We have seen no evidence that neuroprotection is a product of dopamine neuron replacement by NPC-derived cells. Rather, the NPCs expressed glial cell line-derived neurotrophic factor (GDNF), sonic hedgehog (Shh), and stromal cell-derived factor 1 alpha (SDF1alpha), providing a molecular basis for the observed neuroprotection and endogenous NPC response to transplantation. In summary, our data suggests plausible synergy between exogenous and endogenous NPC actions, and that NPC implantation before the 6-OHDA insult can create a host microenvironment conducive to stimulation of endogenous NPCs and protection of mature nigral neurons.
• Madhavan, L., Ourednik, V., & Ourednik, J. (2008). Neural stem/progenitor cells initiate the formation of cellular networks that provide neuroprotection by growth factor-modulated antioxidant expression. Stem cells (Dayton, Ohio), 26(1), 254-65.
  More info

  Recent studies indicate that transplanted neural stem/progenitor cells (NSPs) can interact with the environment of the central nervous system and stimulate protection and regeneration of host cells exposed to oxidative stress. Here, a set of animals grafted with NSPs and treated with 3-nitropropionic acid (3-NP) exhibited reduced behavioral symptoms and less severe damage of striatal cytoarchitecture than sham transplanted controls including better survival of neurons. Sites of tissue sparing correlated with the distribution pattern of donor cells in the host brain. To investigate the cellular and molecular bases of this phenomenon, we treated cocultures of NSPs and primary neural cell cultures with 3-NP to induce oxidative stress and to study NSP-dependent activation of antioxidant mechanisms and cell survival. Proactive presence of NSPs significantly improved cell viability by interfering with production of free radicals and increasing the expression of neuroprotective factors. This process was accompanied by elevated expression of ciliary neurotrophic factor (CNTF) and vascular endothelial growth factor (VEGF) in a network of NSPs and local astrocytes. Intriguingly, both in vitro and in vivo, enhanced growth factor secretion stimulated a robust upregulation of the antioxidant enzyme superoxide dismutase 2 (SOD2) in neurons and resulted in their improved survival. Our findings thus reveal a so far unrecognized mechanism of interaction between NSPs and surrounding cells accompanying neuroprotection: through mutual, NSP-triggered stimulation of growth factor production and activation of antioxidant mechanisms, cellular networks may shield the local environment from the arriving impact of oxidative stress.
• Madhavan, L., Ourednik, V., & Ourednik, J. (2006). Increased "vigilance" of antioxidant mechanisms in neural stem cells potentiates their capability to resist oxidative stress. Stem cells (Dayton, Ohio), 24(9), 2110-9.
  More info

  Although the potential value of transplanted and endogenous neural stem cells (NSCs) for the treatment of the impaired central nervous system (CNS) has widely been accepted, almost nothing is known about their sensitivity to the hostile microenvironment in comparison to surrounding, more mature cell populations. Since many neuropathological insults are accompanied by oxidative stress, this report compared the alertness of antioxidant defense mechanisms and cell survival in NSCs and postmitotic neural cells (PNCs). Both primary and immortalized cells were analyzed. At steady state, NSCs distinguished themselves in their basal mitochondrial metabolism from PNCs by their lower reactive oxygen species (ROS) levels and higher expression of the key antioxidant enzymes uncoupling protein 2 (UCP2) and glutathione peroxidase (GPx). Following exposure to the mitochondrial toxin 3-nitropropionic acid, PNC cultures were marked by rapidly decreasing mitochondrial activity and increasing ROS content, both entailing complete cell loss. NSCs, in contrast, reacted by fast upregulation of UCP2, GPx, and superoxide dismutase 2 and successfully recovered from an initial deterioration. This recovery could be abolished by specific antioxidant inhibition. Similar differences between NSCs and PNCs regarding redox control efficiency were detected in both primary and immortalized cells. Our first in vivo data from the subventricular stem cell niche of the adult mouse forebrain corroborated the above observations and revealed strong baseline expression of UCP2 and GPx in the resident, proliferating NSCs. Thus, an increased "vigilance" of antioxidant mechanisms might represent an innate characteristic of NSCs, which not only defines their cell fate, but also helps them to encounter oxidative stress in diseased CNS.
• Madhavan, L., Ourednik, V., & Ourednik, J. (2005). Grafted neural stem cells shield the host environment from oxidative stress. Annals of the New York Academy of Sciences, 1049, 185-8.
  More info

  Here, we present our preliminary data showing that neural stem cells (NSCs) can prevent the degeneration of striatal neurons when transplanted into the CNS prior to intoxication with 3-nitropropionic acid (3-NP). In the adult CNS, the number of NSCs, a major source of neural cell populations and plasticity-modulating factors, is relatively low if compared to that of the developing brain. This, together with the adult growth-inhibitory environment, limits its regenerative capacity. Our recent observation has shown that grafted NSCs may rescue/protect neurons in the chronically impaired mesostriatal system. On the basis of this study and because we were also intrigued by our recent observations regarding the rescue/protective role of NSCs in vitro, we decided to test the hypothesis that grafted NSCs can also be deposited preventively in the CNS (and perhaps join the pool of endogenous NSCs of the intact host brain) for later buffering and maintenance of homeostasis when the host is exposed to oxidative stress.
• Madhavan, L., Freed, W. J., Anantharam, V., & Kanthasamy, A. G. (2003). 5-hydroxytryptamine 1A receptor activation protects against N-methyl-D-aspartate-induced apoptotic cell death in striatal and mesencephalic cultures. The Journal of pharmacology and experimental therapeutics, 304(3), 913-23.
  More info

  Apoptosis and glutamate-mediated excitotoxicity may play a role in the pathogenesis of many neurodegenerative disorders, including Parkinson's disease (PD). In the present study, we investigated whether stimulation of the 5-hydroxytryptamine 1A (5-HT1A) receptor attenuates N-methyl-D-aspartate- (NMDA) and 1-methyl-4-phenylpyridinium (MPP(+))-induced apoptotic cell death in cell culture models. A brief exposure (20 min) of M213-2O striatal cells to NMDA and glutamate produced a delayed increase in caspase-3 activity and DNA fragmentation in a dose- and time-dependent manner. NMDA-induced caspase-3 activity and DNA fragmentation were almost completely blocked by the 5-HT1A agonists 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) and (R)-5-fluoro-8 hydroxy-2-(dipropylamino)-tetralin (R-UH-301). Additionally, the protective effects of 8-OH-DPAT and R-UH-301 on NMDA-induced caspase-3 activation and apoptosis were reversed by pretreatment with the 5-HT1A antagonists N-[2-[4-(2-methoxyphenyl)-1-piperazinyl] ethyl]-N-(2-pyridinyl) cyclohexane carboxamide (WAY 100635) and S-UH-301, respectively. Similarly, dose- and time-dependent increases in caspase-3 activity and DNA fragmentation were observed in rat primary mesencephalic neurons after a brief exposure to NMDA and glutamate. Caspase-3 activation and DNA fragmentation in primary mesencephalic neurons were almost completely inhibited by 8-OH-DPAT. This neuroprotective effect of 8-OH-DPAT was reversed by WAY 100635. Additionally, 8-OH-DPAT blocked tyrosine hydroxylase (TH)-positive cell death after NMDA exposure and also almost completely attenuated the NMDA-induced Ca(2+) influx in primary mesencephalic cultures. Furthermore, 8-OH-DPAT and R-UH-301 blocked apoptotic cell death in the primary mesencephalic neurons that were exposed to the Parkinsonian toxin MPP(+). Together, these results suggest that 5-HT1A receptor stimulation may be a promising pharmacological approach in the development of neuroprotective agents for PD.

Poster Presentations

• Falk, T., Madhavan, L., Hay, M., Polt, R. L., Corenblum, M., Mota, J., & Bernard, K. (2023, Fall). PNA5, a glycosylated Angiotensin (1-7) peptide, improves cognition in a chronic progressive mouse model of Parkinson’s disease.. Society for Neuroscience Meeting. Washington DC.
• Madhavan, L., Falk, T., Polt, R. L., Streicher, J. M., Szabò, L. Z., Apostol, C. R., Tanguturi, P., Bartlett, M. J., Saez, J. L., Corenblum, M. J., Lujan, A., & Bernard, K. (2022, Spring). Multimodal effects of systemic PACAP glycopeptide delivery in rodent models of Parkinson’s disease.. 16th International Conference on Alzheimer’s and Parkinson’s Diseases and related neurological disorders, AD/PD™.
• Bernard, K., Falk, T., Bartlett, M. J., Heien, M. L., Liu, C., Polt, R. L., Molnar, G., Streicher, J. M., Apostol, C., Madhavan, L., Szabo, L., Sherman, S. J., Szabo, L., Sherman, S. J., Apostol, C., Madhavan, L., Molnar, G., Streicher, J. M., Liu, C., , Polt, R. L., et al. (2021, Spring). Evaluation of a neuroprotective PACAP glycopeptide as systemically delivered CNS active drug to treat motor and cognitive symptoms in two rodent models of Parkinson’s disease.. 15th International Conference on Alzheimer’s and Parkinson’s Diseases and related neurological disorders, AD/PD™.
• Falk, T., Heien, M. L., Polt, R. L., Streicher, J. M., Madhavan, L., Sherman, S. J., Szabo, L., Apostol, C., Molnar, G., Liu, C., Bartlett, M. J., & Bernard, K. (2021, January). Evaluation of a neuroprotective PACAP glycopeptide as systemically delivered CNS active drug to treat Parkinson’s disease.. Society for Neuroscience Global Connectome Conference.
• Falk, T., Heien, M. L., Polt, R. L., Streicher, J. M., Madhavan, L., Sherman, S. J., Szabò, L., Apostol, C. R., Molnar, G., Liu, C., Bartlett, M. J., Morrison, H. W., Lujan, A., & Bernard, K. (2021, Fall). Evaluation of a systemically delivered PACAP glycopeptide as a neuroprotective agent in 2 rodent models of Parkinson’s Disease.. Society for Neuroscience Meeting.
• Miller, J. E., Madhavan, L., Eckhardt, J., Corenblum, M., Munger, S. J., & Medina, C. A. (2021). An analysis of vocalization-associated molecular pathways and gene networks within the basal ganglia of mouse and finch Parkinson’s disease models. . Society for Neuroscience Annual Meeting.
• Miller, J. E., Madhavan, L., Eckhardt, J., Corenblum, M., Munger, S., & Medina, C. A. (2021). An analysis of vocalization-associated molecular pathways and gene networks within the basal ganglia of mouse and finch Parkinson’s disease models.. Society for Neuroscience Annual Meeting-Virtual.
• Madhavan, L. (2020, Spring). A novel mouse model to study the role of Alpha-Synuclein in Parkinson’s disease. UBRP conference at UA.