Apomorphine-induced Rotational Behavior Research Articles

Evaluation of damage discrimination in dopaminergic neurons using dopamine transporter PET tracer [18F]FECNT-d4

BackgroundParkinson’s disease (PD) is a prevalent neurodegenerative disorder worldwide, diagnosed based on classic symptoms like motor dysfunction and cognitive impairments. With the development of various radioactive ligands, positron emission tomography (PET) imaging combined with specific radiolabelling probes has proven to be effective in aiding clinical PD diagnosis. Among these probes, 2β-Carbomethoxy-3β-(4-chlorophenyl)-8-(2-[18F]-fluoroethyl) nortropane ([18F]FECNT) has been utilized as a PET tracer to image dopamine transporter (DAT) integrity in striatal presynaptic dopaminergic terminals. However, the presence of brain-penetrant radioactive metabolites produced by [18F]FECNT may impact the accuracy of PET imaging. In previous research, we developed 2β-Carbomethoxy-3β-(4-chlorophenyl)-8-(2-[18F]-fluoroethyl-1,1,2,2-d4) nortropane ([18F]FECNT-d4), a deuterated derivative with enhanced stability in plasma and the striatum, along with a slower washout rate. In this study, we further investigated the potential of [18F]FECNT-d4 to detect dopaminergic neuron degeneration in Parkinson’s disease. This involved PET imaging in unilaterally-lesioned PD model rats and in vitro autoradiography conducted on postmortem brain sections.ResultsPET images revealed reduced specific uptake in the ipsilateral striatum of rats stereotactically injected with 6-hydroxydopamine hydrochloride (6-OHDA). Compared to the sham group, the ratio of standardized uptake value (SUV) in the ipsilateral to contralateral striatum decreased by 13%, 23%, and 63% in the mild, moderate, and severe lesioned groups, respectively. Dopaminergic denervation observed in PET imaging was further supported by behavioral assessments, immunostaining, and monoamine concentration tests. Moreover, the microPET results exhibited positive correlations with these measurements, except for the apomorphine-induced rotational behavior test, which showed a negative correlation. Additionally, [18F]FECNT-d4 uptake was approximately 40% lower in the postmortem striatal sections of a PD patient compared to a healthy subject. Furthermore, estimated human dosimetry (effective dose equivalent: 5.06 E-03 mSv/MBq), extrapolated from rat biodistribution data, remained below the current Food and Drug Administration limit for radiation exposure.ConclusionOur findings demonstrate that [18F]FECNT-d4 accurately estimates levels of dopaminergic neuron degeneration in the 6-OHDA-induced PD rat model and effectively distinguishes between PD patients and healthy individuals. This highly sensitive and safe PET probe holds promising potential for clinical application in the diagnosis and monitoring of Parkinson’s disease.

Dopamine-modified hyaluronic acid (DA-HA) as a novel dopamine-mimetics with minimal autoxidation and cytotoxicity

Dopamine-modified hyaluronic acid (DA-HA) has been initially developed as an efficient coating and adhesion material for industrial uses. However, the biological activity and safety of DA-HA in the brain have not been explored yet. Here, we report a series of evidence that DA-HA exhibits similar functionality as dopamine (DA), but with much lower toxicity arising from autoxidation. DA-HA shows very little autoxidation even after 48-h incubation. This is profoundly different from DA and its derivatives including l-DOPA, which all induce severe neuronal death after pre-autoxidation, indicating that autoxidation is the cause of neuronal death. Furthermore, in vivo injection of DA-HA induces significantly lower toxicity compared to 6-OHDA, a well-known oxidized and toxic form of DA, and alleviates the apomorphine-induced rotational behavior in the 6-OHDA animal model of Parkinson's disease. Our study proposes that DA-HA with DA-like functionalities and minimal toxicity has a great potential to treat DA-related disease.

Abstract TP208: A Novel Rat Model Of Vascular Parkinsonism Using The Vasoconstrictor Endothelin-1

Background: Vascular parkinsonism (VP) results from one or more small strokes in the basal ganglia. Patients with vascular parkinsonism usually are unaware of the individual strokes that occur, until progressive motor symptoms gradually appear. While Parkinson’s Disease (PD) and VP share some common symptoms, patients with VP show clear evidence of cerebrovascular disease, are likely to be older, more likely to present with gait difficulty rather than tremor, and less likely to respond to the use of levodopa compared with patients with PD. There is currently no clinically effective treatment for this condition and no rodent model established in the field to study VP. Methods: To stimulate the onset of VP, male Sprague Dawley rats (10-12 mos) were injected with the vasoconstrictor endothelin-1 (ET-1) into the dorsolateral striatum (DLS) or sham operation. Adhesive-tape removal test (ART) was used to test sensory-motor function at 2- and 5- days post DLS stroke and brains were removed and stained with TTC to assess the location of the infarct. In another set, animals were tested for apomorphine-induced rotational behavior at 21-28 days, in conjunction with immunohistochemistry to assess dopamine loss in the substantia nigra pars compacta. Results: We observed a discrete infarct localized to the DLS in animals injected with ET-1. There was no difference in latency to remove the tape in ART outcomes of ET-1 injected animals at 2- and 5- day post ischemia when compared to sham, consistent the fact that these coordinates resulted in a discrete striatal infarction, rather than a cortico-striatal infarction, which is seen in the ET1-induced middle cerebral artery stroke model in rats. At 21- and 28- days post, there was minimal rotational behavior and minimal loss of tyrosine hydroxylase (TH)-positive cells in the lesioned hemisphere, unlike that of the 6-OHDA model of PD, where rapid changes are seen in rotational behavior and loss of TH-positive cells. Conclusions: These data suggest that ET-1-mediated ischemia into the DLS is a promising model for the slow progression of dopaminergic loss and motor deficits reminiscent to that seen in VP patients. Apomorphine induced rotations and TH immunohistochemistry will be evaluated at 30-, 60- and 90- day timepoints.

DA5-CH and Semaglutide Protect against Neurodegeneration and Reduce α-Synuclein Levels in the 6-OHDA Parkinson’s Disease Rat Model

Insulin desensitization has been observed in the brains of patients with Parkinson's disease (PD), which is a progressive neurodegenerative disorder for which there is no cure. Semaglutide is a novel long-actingglucagon-likepeptide-1 (GLP-1) receptor agonist that is on the market as a treatment for type 2 diabetes. It is in a phase II clinical trial in patients with PD. Two previous phase II trials in PD patients showed good effects with the older GLP-1 receptor agonists, exendin-4 and liraglutide. We have developed a dual GLP-1/GIP receptor agonist (DA5-CH) that can cross the blood-brain barrier (BBB) at a higher rate than semaglutide. We tested semaglutide and DA5-CH in the 6-OHDA-lesion rat model of PD. Treatment was semaglutide or DA5-CH (25 nmol/kg, i.p.) daily for 30 days postlesion. Both drugs reduced the apomorphine-induced rotational behavior and alleviated dopamine depletion and the inflammation response in the lesioned striatum as shown in reduced IL-1β and TNF-α levels, with DA5-CH being more effective. In addition, both drugs protected dopaminergic neurons and increased TH expression in the substantia nigra. Furthermore, the level of monomer and aggregated α-synuclein was reduced by the drugs, and insulin resistance as shown in reduced pIRS-1ser312 phosphorylation was also attenuated after drug treatment, with DA5-CH being more effective. Therefore, while semaglutide showed good effects in this PD model, DA5-CH was superior and may be a better therapeutic drug for neurodegenerative disorders such as PD than GLP-1 receptor agonists that do not easily cross the BBB.

Determination of the Unilaterally Damaged Region May Depend on the Asymmetry of Carotid Blood Flow Velocity in Hemiparkinsonian Monkey: A Pilot Study.

The hemiparkinsonian nonhuman primate model induced by unilateral injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into the carotid artery is used to study Parkinson's disease. However, there have been no studies that the contralateral distribution of MPTP via the cerebral collateral circulation is provided by both the circle of Willis (CoW) and connections of the carotid artery. To investigate whether MPTP-induced unilaterally damaged regions were determined by asymmetrical cerebral blood flow, the differential asymmetric damage of striatal subregions, and examined structural asymmetries in a circle of Willis, and blood flow velocity of the common carotid artery were observed in three monkeys that were infused with MPTP through the left internal carotid artery. Lower flow velocity in the ipsilateral common carotid artery and a higher ratio of ipsilateral middle cerebral artery diameter to anterior cerebral artery diameter resulted in unilateral damage. Additionally, the unilateral damaged monkey observed the apomorphine-induced contralateral rotation behavior and the temporary increase of plasma RANTES. Contrastively, higher flow velocity in the ipsilateral common carotid artery was observed in the bilateral damaged monkey. It is suggested that asymmetry of blood flow velocity and structural asymmetry of the circle of Willis should be taken into consideration when establishing more efficient hemiparkinsonian nonhuman primate models.

Rapid Induction of Dopaminergic Neuron Loss Accompanied by Lewy Body-Like Inclusions in A53T BAC-SNCA Transgenic Mice

Parkinson's disease (PD), the most common neurodegenerative movement disorder, is characterized by dopaminergic neuron loss in the substantia nigra pars compacta (SNpc) and intraneuronal α-synuclein (α-syn) inclusions. It is highly needed to establish a rodent model that recapitulates the clinicopathological features of PD within a short period to efficiently investigate the pathological mechanisms and test disease-modifying therapies. To this end, we analyzed three mouse lines, i.e., wild-type mice, wild-type human α-syn bacterial artificial chromosome (BAC) transgenic (BAC-SNCA Tg) mice, and A53T human α-syn BAC transgenic (A53T BAC-SNCA Tg) mice, receiving dorsal striatum injections of human and mouse α-syn preformed fibrils (hPFFs and mPFFs, respectively). mPFF injections induced more severe α-syn pathology in most brain regions, including the ipsilateral SNpc, than hPFF injections in all genotypes at 1-month post-injection. Although these Tg mouse lines expressed a comparable amount of α-syn in the brains, the mPFF-injected A53T BAC-SNCA Tg mice exhibited the most severe α-syn pathology as early as 0.5-month post-injection. The mPFF-injected A53T BAC-SNCA Tg mice showed a 38% reduction in tyrosine hydroxylase (TH)-positive neurons in the ipsilateral SNpc, apomorphine-induced rotational behavior, and motor dysfunction at 2 months post-injection. These data indicate that the extent of α-syn pathology induced by α-syn PFF injection depends on the types of α-syn PFFs and exogenously expressed α-syn in Tg mice. The mPFF-injected A53T BAC-SNCA Tg mice recapitulate the key features of PD more rapidly than previously reported mouse models, suggesting their usefulness for testing disease-modifying therapies as well as analyzing the pathological mechanisms.

GPER and IGF-1R mediate the anti-inflammatory effect of genistein against lipopolysaccharide (LPS)-induced nigrostriatal injury in rats

Neuroinflammation plays an important role in the pathogenesis of Parkinson's disease (PD). Genistein is an estrogen-like phytoestrogen that can exert biological effects via the crosstalk of estrogen receptor and insulin-like growth factor 1 receptor (IGF-1R). The present study aimed to evaluate the involvement of G protein-coupled estrogen receptor (GPER) and IGF-1R in the anti-inflammatory effects of genistein against lipopolysaccharide (LPS)-induced nigrostriatal injury in ovariectomized rats. Our results showed that genistein treatment could ameliorate the apomorphine-induced rotational behavior in LPS-induced inflammatory PD rat model. Genistein attenuated LPS-induced decrease of the contents of dopamine (DA) and its metabolites in striatum as well as the loss of tyrosine hydroxylase-immunoreactive (TH-IR) neurons in the substantia nigra (SN) of the lesioned side, which could be blocked by GPER antagonist G15 or IGF-1R antagonist JB1. Meanwhile, G15 or JB1 could attenuate the anti-inflammatory effects of genistein in LPS-induced microglial activation and production of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, genistein could inhibit the LPS-induced phosphorylation of p38, JNK, ERK and IκB in the lesioned side of SN and these effects could also be blocked by G15 or JB1. Taken together, our data provide the first evidence that genistein can inhibit the increase of microglia and protect dopaminergic neurons at least in part via GPER and IGF-1R signaling pathways in ovariectomized PD rat model.

Neuroprotective Effect of Intrastriatal Caffeic Acid Phenethyl Ester Treatment in 6-OH Dopamine Model of Parkinson's Disease in Rats.

Parkinson's disease (PD) is the second most common neurodegenerative disorder, and the main cause of PD is still not known. Until now, no cure for Parkinson's disease is yet in sight. Caffeic acid phenethyl ester (CAPE) is a polyphenolic component of the propolis, which can be derived from honeybee hive propolis. We aimed to determine the effect of intrastriatal CAPE administration as a neuroprotective agent on 6-hydroxydopamine (6-OHDA)-induced PD model. Adult male Wistar rats weighing 280–320 g were used. The PD model was induced with unilateral intrastriatal 6-OHDA injection. Treatment groups received 20 μmol/5 μL/4 day and 80 μmol/5 μL/4 day CAPE 24 h after 6-OHDA injection. Eight days after 6-OHDA application, behavioral studies (adhesive tape removal test, open-field test, cylinder test, and apomorphine-induced asymmetric rotational behavior) were performed once more to compare the effects of CAPE on behavior tests. Striatal histological verifications, immunohistochemistry, and stereological quantitation were performed. Our results for the first time showed that, besides improving the motor performance, CAPE treatment also prevents 6-OHDA-induced loss of TH-positive neurons. From our results, CAPE may be a promising clinical agent in the treatment of PD.

Histamine-4 receptor antagonist ameliorates Parkinson-like pathology in the striatum

Growing evidence indicates that microglia activation and a neuroinflammatory trigger contribute to dopaminergic cell loss in Parkinson’s disease (PD). Furthermore, increased density of histaminergic fibers and enhanced histamine levels have been observed in the substantia nigra of PD-postmortem brains. Histamine-induced microglial activation is mediated by the histamine-4 receptor (H4R). In the current study, gene set enrichment and pathway analyses of a PD basal ganglia RNA-sequencing dataset revealed that upregulation of H4R was in the top functional category for PD treatment targets. Interestingly, the H4R antagonist JNJ7777120 normalized the number of nigrostriatal dopaminergic fibers and striatal dopamine levels in a rotenone-induced PD rat model. These improvements were accompanied by a reduction of α-synuclein-positive inclusions in the striatum. In addition, intracerebroventricular infusion of JNJ7777120 alleviated the morphological changes in Iba-1-positive microglia and resulted in a lower tumor necrosis factor-α release from this brain region, as well as in ameliorated apomorphine-induced rotation behaviour. Finally, JNJ7777120 also restored basal ganglia function by decreasing the levels of γ-aminobutyric acid (GABA) and the 5-hydroxyindoleactic acid to serotonin (5-HIAA/5-HT) concentration ratios in the striatum of the PD model. Our results highlight H4R inhibition in microglia as a promising and specific therapeutic target to reduce or prevent neuroinflammation, and as such the development of PD pathology.

Erythropoietin modulates striatal antioxidant signalling to reduce neurodegeneration in a toxicant model of Parkinson's disease

The current study sought to characterize the pro-survival effects of erythropoietin (EPO) in a toxicant model of Parkinson's disease (PD). EPO treatment induced time-dependent elevations of antioxidant glutathione peroxidase (GPx) and anti-apoptotic factors (pAkt and pBad/Bad) within the striatum and substantia nigra pars compacta (SNc). Intriguingly, our results indicated a region- and lesion size- dependence of pro-survival effects of EPO. Indeed, intra-striatal (but not intra-nigral) infusion of EPO was effective at preventing dopaminergic terminal degeneration and sSNc neuronal loss induced by two different doses of 6-OHDA. These neuroprotective consequences were paralleled by a diminution of microglial morphological changes, along with enhanced motor functioning seen through a reduction in apomorphine-induced rotational behaviour. Finally, in the context of the 6-OHDA lesion, EPO again induced anti-apoptotic (Bcl-2) and antioxidant (GPx) factors within the striatum. Taken together, these results raise the possibility of EPO's potential use as an adjuvant therapy in the treatment of PD, or at least, suggest possible brain-region specific targets for the protective effects of EPO.

Antioxidant, anti-inflammatory and neuroprotective effect of kaempferol on rotenone-induced Parkinson’s disease model of rats and SH-S5Y5 cells by preventing loss of tyrosine hydroxylase

• Kaempferol prevented the loss of tyrosine hydroxylase. • Kaempferol reduced lipid peroxidation and the levels of TNF-α and IL-6. • Kaempferol increased GSH, SOD, Gpx and catalase. • Kaempferol increased 5-HT, 5-HIAA and noradrenaline. • Kaempferol reduced ROS. The present study investigated the antioxidant and neuroprotective effect of kaempferol against rotenone-induced Parkinson’s disease (PD). Kaempferol inhibits apomorphine-induced rotational behavior and inhibited lipid peroxidation and interleukin (IL)-6 and tumor necrosis factor (TNF)-α, while antioxidant markers were increased in a PD rat model and SH-S5Y5 cells. Kaempferol increased levels of monoamine in striatum and substantia nigra region of brain. Histopathological analyses showed that kaempferol inhibited apoptosis. Intracellular reactive oxygen species (ROS) and apoptosis were also inhibited by more than 50%. The mRNA expression of tyrosine hydroxylase was increased 0.45- and 1.04-fold at 25 and 50 µM kaempferol respectively, and protein expression of tyrosine hydroxylase was also increased. In addition, In silico molecular docking study confirmed the binding interaction between tyrosine hydroxylase and kaempferol. These results show that kaempferol act as neuroprotective agent against rotenone-induced PD model of rats and SH-S5Y5 cells by preventing the loss of tyrosine hydroxylase expression.

Repeated intrastriatal application of botulinum neurotoxin-A did not influence choline acetyltransferase-immunoreactive interneurons in hemiparkinsonian rat brain – A histological, stereological and correlational analysis

In Parkinson’s disease, dopamine depletion leads to hyperactivity of cholinergic interneurons in the caudate-putamen (CPu). Botulinum neurotoxin-A (BoNT-A) inhibits the release of acetylcholine in the peripheral nervous system and is also thought to act as a local anticholinergic drug when injected intrastriatally. In hemiparkinsonian (hemi-PD) rats, a unilateral intrastriatal injection of 1 ng BoNT-A significantly diminished apomorphine-induced rotation behavior for at least 3 months, the effect fading thereafter. A second intrastriatal BoNT-A application, 6 months after the first one, led to a stronger and longer-lasting, beneficial behavioral reaction.As a single BoNT-A injection was not cytotoxic in the rat striatum and resembled BoNT-A treatment in clinical practice, here, we investigated the structural outcome of repeated intrastriatal BoNT-A injections with respect to striatal volume, the number of choline acetyltransferase-immunoreactive (ChAT-ir) interneurons and of the length of their dendritic arbors, and the numeric density of ChAT-ir BoNT-A-induced varicosities (BiVs). Repeated unilateral intrastriatal BoNT-A application decreased the volume of the injected CPu, but did not significantly change the number of striatal ChAT-ir interneurons. Also, the total dendrite length of ChAT-ir interneurons after repeated BoNT-A application resembled the values in double vehicle-injected hemi-PD rats. In repeatedly BoNT-A-injected hemi-PD rats, the numeric density of ChAT-ir BiVs in the CPu was increased compared with rats only intrastriatally injected once with BoNT-A. Even repeated BoNT-A injections in rat striata did not cause substantial morphological changes in ChAT-ir neuron, except for the increased numeric density of ChAT-ir BiVs.

Olfactory ensheathing cells improve the survival of porcine neural xenografts in a Parkinsonian rat model.

Parkinson's disease (PD) features the motor control deficits resulting from irreversible, progressive degeneration of dopaminergic (DA) neurons of the nigrostriatal pathway. Although intracerebral transplantation of human fetal ventral mesencephalon (hfVM) has been proven effective at reviving DA function in the PD patients, this treatment isclinically limited by availability of hfVMand the relatedethical issues. Homologous tissuesto hfVM, such as porcine fetal ventral mesencephalon (pfVM) thus present a strong clinical potential if immune response following xenotransplantation could be tamed. Olfactory ensheathing cells (OECs) are glial cells showing immunomodulatory properties. It is unclear but intriuging whether these properties can be applied to reducing immune response following neural xenotransplantation of PD. To determine whether OECs may benefit neural xenografts for PD, different compositions of grafting cellswere transplanted into striatum of the PD model rats. We used apomorphine-induced rotational behavior to evaluate effectiveness of the neural grafts on reviving DA function. Immunohistochemistry was applied to investigate the effect of OECs on the survival of neuroxenografts and underlyingmechanisms ofthis effect. Four weeks following the xenotransplantation, we found that the PD rats receiving pfVM+OECs co-graft exhibited a better improvement in apomorphine-induced rotational behavior compared with those receiving only pfVM cells. This result can be explained by higher survival of DA neurons (tyrosine hydroxylase immunoreactivity) in grafted striatum of pfVM+OECs group. Furthermore, pfVM+OECs group has less immune response (CD3+ T cells and OX-6+ microglia) around the grafted area compared with pfVM only group. These results suggest that OECs may enhance the survival of the striatal xenograftsvia dampeningtheimmune responseat the grafted sites. Using allogeneic OECs as a co-graft material for xenogeneic neural grafts could be a feasible therapeutic strategy to enhance results and applicability of the cell replacement therapy for PD.

Antioxidant and anti-inflammatory effects of dexrazoxane on dopaminergic neuron degeneration in rodent models of Parkinson's disease

Emerging evidence has demonstrated that the integrity and the function of blood-brain barrier (BBB) are gradually impaired in the processes of aging and nervous system disorders, including neurodegenerative diseases (e.g. Parkinson's disease, PD). The leakage of BBB contributes to the infiltration of peripheral immune cells and harmful mediators into brain parenchyma, even the drugs that can not cross BBB under physiological conditions. Therefore, PD has been regarded as not only a neurodegenerative disease, but also a systemic disorder. In the present study, we demonstrate for the first time that Dexrazoxane (Dex), a drug clinically used to reduce doxorubicin-induced cardiotoxicity in chemotherapy, can enter into midbrain and striatum through broken BBB in 6-hydroxydopamine (6-OHDA)- and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced rodent models of PD. Unexpectedly, Dex (1.5, 5, 15 mg/kg, i.p.) administration for 3-week significantly ameliorates apomorphine-induced contralateral rotation behavior in 6-OHDA-treated rats and Dex (10 mg/kg, i.p.) treatment for 5-week improves MPTP-induced mouse motor dysfunctions. We find that Dex administration protects dopaminergic neurons against neurotoxin-induced degeneration in SNc, accompanied by the attenuated glial cell activation. Further study indicates that suppression of oxidative stress and endoplasmic reticulum stress, as well as the inhibition of systemic inflammation in both peripheral tissues and brain, contribute to the neuroprotective effects of Dex in PD models. Our study implies that Dex may serve as an effective neuroprotectant to treat neurodegeneration and has potential clinical value in term of PD therapeutics.

Intrapallidal injection of botulinum toxin A recovers gait deficits in a parkinsonian rodent model.

Modulation of electrical activity in the subthalamic nucleus has been therapeutically effective in Parkinson's disease. Pharmacological manipulation of glutamate release from subthalamic neurons could also favourably alter basal ganglia activity to improve motor symptoms. This study investigates the efficacy of selective suppression of hyperactive glutamatergic input from the subthalamic nucleus to the globus pallidus internal segment by botulinum toxin A (BoNT-A) in a parkinsonian model. Unilateral 6-hydroxydopamine lesioned parkinsonian rodents and controls received microinfusions of BoNT-A or vehicle into the ipsilateral internal globus pallidus (n=8 per group). Changes in gait were measured by the CatWalk apparatus, along with assessment of apomorphine-induced rotational behaviour prior to and following BoNT-A injection. Immunofluorescent staining for markers of glutamatergic, GABAergic and total terminals was performed at the internal globus pallidus. Administration of a single dose of BoNT-A (0.5ng) significantly improved the rotational asymmetry and gait abnormalities. Ameliorations in speed, body speed variation, cadence and walking pattern were comparable to pre-lesioned animals, and persisted up to 1month following BoNT-A injection. These changes are associated to BoNT-A's ability to selectively target glutamatergic terminals. Blockade of subthalamic hyperactivity by BoNT-A leads to sufficient reorganization in the basal ganglia needed to generate a consistent rhythmic pattern of walking. This suggests the potential use of intracerebral BoNT-A to produce effective neuromodulation in the parkinsonian brain, as well as expansion into other neurodegenerative disorders linked to excitotoxity.

Histamine-4 receptor antagonist JNJ7777120 inhibits pro-inflammatory microglia and prevents the progression of Parkinson-like pathology and behaviour in a rat model

The activation of microglial cells is presumed to play a key role in the pathogenesis of Parkinson's disease (PD). The activity of microglia is regulated by the histamine-4 receptor (H4R), thus providing a novel target that may prevent the progression of PD. However, this putative mechanism has so far not been validated. In our previous study, we found that mRNA expression of H4R was upregulated in PD patients. In the present study, we validated this possible mechanism using the rotenone-induced PD rat model, in which mRNA expression levels of H4R-, and microglial markers were significantly increased in the ventral midbrain. Inhibition of H4R in rotenone-induced PD rat model by infusion of the specific H4R antagonist JNJ7777120 into the lateral ventricle resulted in blockade of microglial activation. In addition, pharmacological targeting of H4R in rotenone-lesioned rats resulted in reduced apomorphine-induced rotational behaviour, prevention of dopaminergic neuron degeneration and associated decreases in striatal dopamine levels. These changes were accompanied by a reduction of Lewy body-like neuropathology. Our results provide first proof of the efficacy of an H4R antagonist in a commonly used PD rat model, and proposes the H4R as a promising target to clinically tackle microglial activation and thereby the progression of PD.

Repeated Intrastriatal Botulinum Neurotoxin-A Injection in Hemiparkinsonian Rats Increased the Beneficial Effect on Rotational Behavior.

Injection of botulinum neurotoxin-A (BoNT-A) into the striatum of hemiparkinsonian (hemi-PD) rats reduced apomorphine-induced rotation behavior significantly, for at least 3 months. Thereafter, rotation behavior increased again. We injected hemi-PD rats with 1 ng BoNT-A twice, the second injection following 6 months after the first one and tested the rats for apomorphine-induced rotations and spontaneous motor behaviors, i.e., corridor task and stepping test. To test the hypothesis that BoNT-A reduced striatal hypercholinism in hemi-PD rats, the acetylcholinesterase inhibitor donepezil was injected prior to separate apomorphine-induced rotation tests. In hemi-PD rats, the first BoNT-A injection led to a clear reduction of the apomorphine-induced rotations, and the second BoNT-A injection to a more massive and prolonged reaction. In hemi-PD rats whose apomorphine-induced rotation behavior was strongly reduced by an intrastriatal BoNT-A, subsequent donepezil injections led to significant increases of the rotation rate. Concerning corridor task and stepping test, neither first nor second BoNT-A injections changed hemi-PD rats’ behavior significantly. The data give evidence for the possibility of repeated intrastriatal administrations of BoNT-A, for treatment of motor symptoms in experimental hemi-PD over a longer time.

Intrastriatal administration of botulinum neurotoxin A normalizes striatal D2 R binding and reduces striatal D1 R binding in male hemiparkinsonian rats.

Cerebral administration of botulinum neurotoxin A (BoNT-A) has been shown to improve disease-specific motor behavior in a rat model of Parkinson disease (PD). Since the dopaminergic system of the basal ganglia fundamentally contributes to motor function, we investigated the impact of BoNT-A on striatal dopamine receptor expression using in vitro and in vivo imaging techniques (positron emission tomography and quantitative autoradiography, respectively). Seventeen male Wistar rats were unilaterally lesioned with 6-hydroxydopamine (6-OHDA) and assigned to two treatment groups 7 weeks later: 10 rats were treated ipsilaterally with an intrastriatal injection of 1 ng BoNT-A, while the others received vehicle (n = 7). All animals were tested for asymmetric motor behavior (apomorphine-induced rotations and forelimb usage) and for striatal expression of dopamine receptors and transporters (D1 R, D2 R, and DAT). The striatal D2 R availability was also quantified longitudinally (1.5, 3, and 5 months after intervention) in 5 animals per treatment group. The 6-OHDA lesion alone induced a unilateral PD-like phenotype and a 13% increase of striatal D2 R. BoNT-A treatment reduced the asymmetry in both apomorphine-induced rotational behavior and D2 R expression, with the latter returning to normal values 5 months after intervention. D1 R expression was significantly reduced, while DAT concentrations showed no alteration. Independent of the treatment, higher interhemispheric symmetry in raclopride binding to D2 R was generally associated with reduced forelimb akinesia. Our findings indicate that striatal BoNT-A treatment diminishes motor impairment and induces changes in D1 and D2 binding site density in the 6-OHDA rat model of PD.

The anti-aging protein klotho alleviates injury of nigrostriatal dopaminergic pathway in 6-hydroxydopamine rat model of Parkinson's disease: Involvement of PKA/CaMKII/CREB signaling

Parkinson's disease (PD) is a prevalent movement disorder in the elderly. PD is hallmarked with progressive deterioration of mesencephalic dopaminergic neurons and development of debilitating motor and non-motor clinical symptoms. Klotho protein is the product of an aging-suppressor gene that its overexpression could protect neurons against oxidative injury. This study was undertaken to explore whether exogenous klotho could alleviate injury of nigrostriatal dopaminergic pathway in 6-hydroxydopamine (6-OHDA) rat model of PD. Intrastriatal 6-OHDA-lesioned rats were pretreated with klotho at a dose of 10μg/rat. Results showed that klotho mitigates apomorphine-induced rotational behavior and reduces the latency to initiate and the total time in the narrow beam test. In addition, beneficial effect of klotho was attenuated following i.c.v. microinjection of protein kinase A (PKA) inhibitor H-89 and Ca(2+)/calmodulin-dependent protein kinase II (CamKII) inhibitor KN-62. Additionally, klotho significantly lowered striatal levels of malondialdehyde (MDA), reactive oxygen species (ROS), glial fibrillary acid protein (GFAP), α synuclein, phospho-cAMP-response element binding protein (pCREB), and DNA fragmentation. Furthermore, klotho was capable to prevent degeneration of tyrosine hydroxylase (TH)-positive neurons within substantia nigra pars compacta (SNC). Collectively, these findings denote neuroprotective potential of exogenous klotho in 6-OHDA rat model of PD through alleviation of astrogliosis, apoptosis, and oxidative stress. It was also obtained that part of its protective effect is dependent on PKA/CaMKII/CREB signaling cascade.

Intrastriatally injected botulinum neurotoxin-A differently effects cholinergic and dopaminergic fibers in C57BL/6 mice

Unilateral intrastriatal BoNT-A injection abolished apomorphine-induced rotational behavior in a rat model of hemiparkinsonism (hemi-PD) up to 6months. It was hypothesized that the beneficial effect of botulinum neurotoxin-A (BoNT-A) grounded on the reduction of the Parkinson’s diseases (PD) associated striatal hypercholinism. Intrastriatal injection of BoNT-A was not cytotoxic in rat brain, but neuronal fiber swellings in the BoNT-A infiltrated striata appeared and named BoNT-A-induced varicosities (BiVs). In the rat BiVs were immunoreactive (ir) either for choline acetyltransferase (ChAT) or tyrosine hydroxylase (TH). In the present study the structural effect of unilateral intrastriatal BoNT-A injection in the naïve mouse brain was analyzed to extend possible therapeutic BoNT-A applications to genetical Parkinsonian strains.We investigated the effect of a single dose of 25pg BoNT-A injected into the right caudate-putamen (CPu) for up to 9months, and of increasing doses up to 200pg on striatal volume, number of ChAT-ir interneurons, and numeric density and volume of the ChAT-ir BiVs in comparison to the uninjected hemisphere.Intrastriatal BoNT-A injection did not alter the number of ChAT-ir interneurons irrespective of survival time and dosage tested. However, the numeric density of the ChAT-ir BiVs at a dose of 25pg increased from 1 to 3months after BoNT-A, followed by a time dependent decrease. In parallel, with increasing BoNT-A survival time, the mean BiV volume increased as the number of small BiVs decreased. Interestingly, in contrast to rats we did not find TH-ir BiVs in BoNT-A injected mouse striatum.