Kavita Seth

Neuroprotective and neurorescue effect of black tea extract in 6-hydroxydopamine-lesioned rat model of Parkinson's disease

In the present study, an attempt has been made to explore the neuroprotective and neuroreparative (neurorescue) effect of black tea extract (BTE) in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinsons disease (PD). In the neuroprotective (BTE + 6-OHDA) and neurorescue (6-OHDA + BTE) experiments, the rats were given 1.5% BTE orally prior to and after intrastriatal 6-OHDA lesion respectively. A significant recovery in d-amphetamine induced circling behavior (stereotypy), spontaneous locomotor activity, dopamine (DA)-D2 receptor binding, striatal DA and 3-4 dihydroxy phenyl acetic acid (DOPAC) level, nigral glutathione level, lipid peroxidation, striatal superoxide dismutase and catalase activity, antiapoptotic and proapoptotic protein level was evident in BTE + 6-OHDA and 6-OHDA + BTE groups, as compared to lesioned animals. BTE treatment, either before or after 6-OHDA administration protected the dopaminergic neurons, as evident by significantly higher number of surviving tyrosine hydroxylase immunoreactive (TH-ir) neurons, increased TH protein level and TH mRNA expression in substantia nigra. However, the degree of improvement in motor and neurochemical deficits was more prominent in rats receiving BTE before 6-OHDA. Results suggest that BTE exerts both neuroprotective and neurorescue effects against 6-OHDA-induced degeneration of the nigrostriatal dopaminergic system, suggesting that possibly daily intake of BTE may slow down the PD progression as well as delay the onset of neurodegenerative processes in PD.

Olfactory ensheathing cell transplantation restores functional deficits in rat model of Parkinson's disease: a cotransplantation approach with fetal ventral mesencephalic cells

Different strategies have been worked out to promote survival of transplanted fetal ventral mesencephalic cells (VMCs) using trophic and nontrophic support. Olfactory ensheathing cells (OECs) express high level of growth factors including NGF, bFGF, GDNF, and NT3, which are known to play important role in functional restoration or neurodegeneration. In the present investigation, an attempt has been made to study functional restoration in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinsons disease (PD) following cotransplantation of VMC and OECs (cultured from olfactory bulb, OB) in striatal region. The functional restoration was assessed using neurobehavioral, neurochemical, and immunohistochemical approach. At 12 weeks, post-transplantation, a significant recovery (P < 0.001) in D-amphetamine induced circling behavior (73%), and spontaneous locomotor activity (SLA, 81%) was evident in cotransplanted animals when compared with 6-OHDA-lesioned animals. A significant restoration (P < 0.001) in [3H]-spiperone binding (77%), dopamine (DA) (82%) and 3,4-dihydroxy phenyl acetic acid (DOPAC) level (75%) was observed in animals cotransplanted with OECs and VMC in comparison to lesioned animals. A significantly high expression and quantification of tyrosine hydroxylase (TH)-positive cells in cotransplanted animals further confirmed the supportive role of OECs in viability of transplanted dopaminergic cells, which in turn may be helping in functional restoration. This was further substantiated by our observation of enhanced TH immunoreactivity and differentiation in VMC cocultured with OECs under in vitro conditions as compared to VMC alone cultures. The results suggest that cotransplantation of OECs and VMC may be a better approach for functional restoration in 6-OHDA-induced rat model of Parkinsons disease.

Nerve growth factor increases survival of dopaminergic graft, rescue nigral dopaminergic neurons and restores functional deficits in rat model of Parkinson's disease

In the present study, an attempt has been made to explore the neuroprotective and neurorescue effects of nerve growth factor (NGF) on grafted cells and on host nigral dopaminergic neurons, respectively. NGF was co-transplanted with fetal ventral mesencephalic cells (VMC) in the striatum of 6-hydroxydopamine (6-OHDA) lesioned rat model of Parkinsons disease (PD). In the other groups fetal VMC and NGF were transplanted alone. Twelve weeks post-transplantation, a significant restoration was observed in D-amphetamine induced rotations (stereotypy), spontaneous locomotor activity, striatal and nigral dopamine (DA) and 3,4-dihydroxy-phenyl acetic acid (DOPAC) levels in co-transplanted rats as compared to VMC alone transplanted rats. Higher number of surviving tyrosine hydroxylase immunoreactive (TH-ir) neurons and significantly increased fiber outgrowth from graft was evident in co-transplanted rats as compared to VMC alone transplanted rats. Further, a significant increase was also observed in substantia nigra TH-ir neurons count in co-transplanted rats, exhibiting a potential neuroprotective and neurorescue effects of NGF on nigrostriatal dopaminergic neurons. The results suggest that NGF at the time of transplantation exhibits neuroprotective effect on transplanted VMC as well as neurorescue effect on remaining host nigral dopaminergic neurons, leading to better functional restoration.

Trans-Blood Brain Barrier Delivery of Dopamine-Loaded Nanoparticles Reverses Functional Deficits in Parkinsonian Rats

Sustained and safe delivery of dopamine across the blood brain barrier (BBB) is a major hurdle for successful therapy in Parkinsons disease (PD), a neurodegenerative disorder. Therefore, in the present study we designed neurotransmitter dopamine-loaded PLGA nanoparticles (DA NPs) to deliver dopamine to the brain. These nanoparticles slowly and constantly released dopamine, showed reduced clearance of dopamine in plasma, reduced quinone adduct formation, and decreased dopamine autoxidation. DA NPs were internalized in dopaminergic SH-SY5Y cells and dopaminergic neurons in the substantia nigra and striatum, regions affected in PD. Treatment with DA NPs did not cause reduction in cell viability and morphological deterioration in SH-SY5Y, as compared to bulk dopamine-treated cells, which showed reduced viability. Herein, we report that these NPs were able to cross the BBB and capillary endothelium in the striatum and substantia nigra in a 6-hydroxydopamine (6-OHDA)-induced rat model of PD. Systemic intravenous administration of DA NPs caused significantly increased levels of dopamine and its metabolites and reduced dopamine-D2 receptor supersensitivity in the striatum of parkinsonian rats. Further, DA NPs significantly recovered neurobehavioral abnormalities in 6-OHDA-induced parkinsonian rats. Dopamine delivered through NPs did not cause additional generation of ROS, dopaminergic neuron degeneration, and ultrastructural changes in the striatum and substantia nigra as compared to 6-OHDA-lesioned rats. Interestingly, dopamine delivery through nanoformulation neither caused alterations in the heart rate and blood pressure nor showed any abrupt pathological change in the brain and other peripheral organs. These results suggest that NPs delivered dopamine into the brain, reduced dopamine autoxidation-mediated toxicity, and ultimately reversed neurochemical and neurobehavioral deficits in parkinsonian rats.

Long-term functional restoration by neural progenitor cell transplantation in rat model of cognitive dysfunction: co-transplantation with olfactory ensheathing cells for neurotrophic factor support

Neural progenitor cell transplantation has emerged as a promising approach for cell replacement therapy in the brain of neurodegenerative diseases. These are multipotent stem cells with self‐renewal capabilities and can give rise to cells of all the three lineages of nervous system and can be maintained and differentiated to desirable neuronal subtypes in vitro with known trophic factors. However, like fetal cells, neural progenitor cells after differentiating to specific neuronal type also require continuous neurotrophic factor support for their long‐term survival following transplantation. Recent reports suggest that olfactory ensheathing cells are capable of providing continuous neurotrophic factor to the transplanted neural progenitor cells for their long‐term survival. In the present investigation, an attempt has been made to validate functional restoration in kainic acid lesioned rat model of cognitive dysfunction following co‐transplantation of neural progenitor cells with olfactory ensheathing cells.

Enhanced survival and function of neural stem cells-derived dopaminergic neurons under influence of olfactory ensheathing cells in parkinsonian rats.

Transplantation of neural stem cell (NSC)‐derived dopamine (DA) neurons is associated with low survival of cells, which could be due to limited striatal innervations and uneven distribution of graft because of its dense neuronal core, limited host–graft interaction, poor axonal outgrowth, lack of continuous neurotrophic factors supply, and an absence of cell adhesion molecules mediated appropriate developmental cues. Olfactory ensheathing cells (OEC) express a variety of growth factors and cell adhesion molecules and promote axonal regrowth and functional recovery in spinal cord injury in animal models and patients. In the present study, we explored the possibility to increase the survival, function, axonal outgrowth and striatal reinnervation of NSC by co‐grafting with OEC in 6‐OHDA lesioned parkinsonian rats. In the presence of OEC, significantly enhanced survival of NSC‐derived DA neurons and axonal fiber outgrowth was evident in the striatum of NSC+OEC co‐grafted rats at 24 weeks post‐grafting as compared with NSC alone grafted rats. The increased survival of NSC and their striatal reinnervation was further manifested in the form of significant and substantial restitution of motor function and neurochemical recovery in the co‐grafted group. Significant enhanced expression of p75NTR (from OEC) and tyrosine hydroxylase (TH) (from NSC) confirmed the co‐localization and survival of both types of cells at the transplantation site in co‐grafted rats. Co‐grafting results co‐related well with our in vitro studies, which suggest that OEC not only significantly increase survival, neurite outgrowth and DA release of NSC‐derived DA neuron but also protect against 6‐OHDA neurotoxicity in co‐culture conditions. These results collectively suggest that OEC increase the survival and function of transplanted NSC in 6‐OHDA lesioned parkinsonian rats.

Mosquito repellent (pyrethroid-based) induced dysfunction of blood-brain barrier permeability in developing brain.

Pyrethroid‐based mosquito repellents (MR) are commonly used to protect humans against mosquito vector. New born babies and children are often exposed to pyrethroids for long periods by the use of liquid vaporizers. Occupational and experimental studies indicate that pyrethroids can cause clinical, biochemical and neurological changes, and that exposure to pyrethroids during organogenesis and early developmental period is especially harmful. The neurotoxicity caused by MR has aroused concern among public regarding their use.

Effect of glial cell line-derived neurotrophic factor (GDNF) co-transplantation with fetal ventral mesencephalic cells (VMC) on functional restoration in 6-hydroxydopamine (6-OHDA) lesioned rat model of Parkinson’s disease: neurobehavioral, neurochemical and immunohistochemical studies

Among trophic factors already known, glial cell line‐derived neurotrophic factor (GDNF) and other members of its family have potent and specific action on dopaminergic neurons. In the present investigation an attempt has been made to validate the role of GDNF co‐transplantation with fetal ventral mesencephalic cells (VMC) on functional viability and restoration using neurobehavioral, neurochemical and immunohistochemical parameters at 6 weeks post‐transplantation in 6‐hydroxydopamine (6‐OHDA) lesioned rat model of Parkinsons disease (PD). A significant restoration (P<0.01) in d‐amphetamine induced rotations, spontaneous and apomorphine induced locomotor activity in rats co‐transplanted with VMC and GDNF was observed as compared to VMC alone transplanted rats. Level of dopamine (DA), 3,4‐dihydroxy‐phenyl acetic acid (DOPAC) and dopamine D2 (DA‐D2) receptors in the caudate putamen (CPu) were significantly (P<0.001) restored in co‐transplanted group as compared to VMC transplanted or GDNF administered animals. The functional viability of transplanted VMC was confirmed by tyrosine hydroxylase (TH) expression and quantification of TH‐positive cells by image analysis revealed a significant restoration in TH‐IR fibers density as well as TH‐IR neurons counts in co‐transplanted animals over VMC transplanted animals. Results suggest that co‐transplantation of VMC and GDNF may be a better approach towards functional restoration in 6‐OHDA lesioned rat model of Parkinsons disease.

Co-transplantation of carotid body and ventral mesencephalic cells as an alternative approach towards functional restoration in 6-hydroxydopamine-lesioned rats: implications for Parkinson's disease.

Exogenous administration of various neurotrophic factors has been shown to protect neurons in animal model of Parkinsons disease (PD). Several attempts are being made to search a tissue source simultaneously expressing many of these neurotrophic factors. Carotid body (CB) contains oxygen‐sensitive glomus cells rich in dopamine (DA) and expresses glial cell line‐derived neurotrophic factor, brain‐derived neurotrophic factor and neurotrophin‐3. We have attempted to study the functional restoration following co‐transplantation of CB cells and ventral mesencephalic cells (VMC) in a 6‐hydroxydopamine‐lesioned rat model of PD. A significant recovery (p < 0.001) in d‐amphetamine‐induced circling behavior (80%) and spontaneous locomotor activity (85%) was evident in co‐transplanted animals at 12 weeks post‐transplantation as compared to lesioned animals. Similarly, a significant (p < 0.001) restoration was observed in DA‐D2 receptor binding (77%), striatal DA (87%) and 3,4‐dihydroxyphenylacetic acid (DOPAC) (85%) levels and nigral DA (75%) and DOPAC (74%) levels. Functional recovery was accompanied by tyrosine hydroxylase (TH) expression and quantification of TH‐positive cells by image analysis revealed a significant restoration in TH‐immunoreactive (IR) fiber density in striatum, as well as TH‐IR neurons in substantia nigra pars compacta in co‐transplanted animals over VMC‐transplanted animals. The result suggests that co‐transplantation of CB cells along with VMC provides better and long‐term functional restoration in the rat model of PD, possibly by supporting the survival of newly grafted cells as well as remaining host DA neurons.

Induced expression of early response genes/oxidative injury in rat pheochromocytoma (PC12) cell line by 6-hydroxydopamine: implication for Parkinson's disease

The expression of early response gene proteins c-Fos, c-Jun, and GAP-43 and their association with 6-hydroxydopamine (6-OHDA)-mediated oxidative injury were investigated using catecholaminergic PC12 cell line. Significant induction in the expression of c-Fos (P < 0.01), c-Jun (P < 0.001) and GAP-43 (P < 0.05) was observed following 2 h exposure to 6-OHDA (10(-6) M), which persisted during 24 h of observation. The exposed cells exhibited an increase in lipid peroxidation (48, 59 and 33%) along with decreased catalase activity (49, 30 and 13%) and glutathione levels (39, 28 and 16%) following 24, 48 and 72 h exposure, respectively. A concentration-dependent functional impairment of mitochondria as studied by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and decreased cell survival were also observed following 6-OHDA (10(-4), 10(-5) M) exposure for 24, 48 and 72 h. The results indicate a role of the early response gene in oxidative stress-mediated dopaminergic cell death by 6-OHDA. Similar mechanisms may also be operative in the development of Parkinsons disease, as an increased presence/formation of endogenous 6-OHDA has been reported in Parkinsons patients.