Marco Aurélio Mori

Motor and Non-Motor Features of Parkinson’s Disease – A Review of Clinical and Experimental Studies

Classically, Parkinsons disease (PD) is considered to be a motor system affliction and its diagnosis is based on the presence of a set of cardinal motor signs (e.g. rigidity, bradykinesia, rest tremor and postural reflex disturbance). However, there is considerable evidence showing that non-motor alterations (e.g. anxiety, depression, sleep, gastrointestinal and cognitive functions) precede the classical motor symptoms seen in PD. The management of these nonmotor symptoms remains a challenge. A pattern of regional neurodegeneration that varies considerably depending upon the neuronal population affected may explain the different symptoms. In fact, differential mechanisms of neuronal vulnerability within the substantia nigra pars compacta (SNpc) suggests that factors other than location contribute to the susceptibility of these neurons. In this review we discuss how these factors interact to ultimately target the SNpc. Remarkably, this region consists of approximately 95% of the tyrosine hydroxylase (TH)-immunoreactive neurons in both human and rat brains, and consequently this implicates elevated levels of dopamine metabolites, free radicals and other hazard species in these neurons. An understanding of how these factors promote neuronal death may be useful for the development of novel neuroprotective and/or neurorestorative strategies for PD.

Fish oil improves anxiety-like, depressive-like and cognitive behaviors in olfactory bulbectomised rats

Depression is increasingly present in the population, and its pathophysiology and treatment have been investigated with several animal models, including olfactory bulbectomy (Obx). Fish oil (FO) supplementation during the prenatal and postnatal periods decreases depression‐like and anxiety‐like behaviors. The present study evaluated the effect of FO supplementation on Obx‐induced depressive‐like behavior and cognitive impairment. Female rats received supplementation with FO during habituation, mating, gestation, and lactation, and their pups were subjected to Obx in adulthood; after the recovery period, the adult offspring were subjected to behavioral tests, and the hippocampal levels of brain‐derived neurotrophic factor (BDNF), serotonin (5‐HT) and the metabolite 5‐hydroxyindoleacetic (5‐HIAA) were determined. Obx led to increased anxiety‐like and depressive‐like behaviors, and impairment in the object location task. All behavioral changes were reversed by FO supplementation. Obx caused reductions in the levels of hippocampal BDNF and 5‐HT, whereas FO supplementation restored these levels to normal values. In control rats, FO increased the hippocampal level of 5‐HT and reduced that of 5‐HIAA, indicating low 5‐HT metabolism in this brain region. The present results indicate that FO supplementation during critical periods of brain development attenuated anxiety‐like and depressive‐like behaviors and cognitive dysfunction induced by Obx. These results may be explained by increased levels of hippocampal BDNF and 5‐HT, two major regulators of neuronal survival and long‐term plasticity in this brain structure.

Middle-aged, but not young, rats develop cognitive impairment and cortical neurodegeneration following the four-vessel occlusion/internal carotid artery model of chronic cerebral hypoperfusion

Permanent, stepwise occlusion of the vertebral arteries (VAs) and internal carotid arteries (ICAs) following the sequence VA→ICA→ICA, with an interstage interval (ISI, →) of 7 days, has been investigated as a four‐vessel occlusion (4‐VO)/ICA model of chronic cerebral hypoperfusion. This model has the advantage of not causing retinal damage. In young rats, however, 4‐VO/ICA with an ISI of 7 days fails to cause behavioral sequelae. We hypothesized that such a long ISI would allow the brain to efficiently compensate for cerebral hypoperfusion, preventing the occurrence of cognitive impairment and neurodegeneration. The present study evaluated whether brain neurodegeneration and learning/memory deficits can be expressed by reducing the length of the ISI and whether aging influences the outcome. Young, male Wistar rats were subjected to 4‐VO/ICA with different ISIs (5, 4, 3 or 2 days). An ISI of 4 days was used in middle‐aged rats. Ninety days after 4‐VO/ICA, the rats were tested for learning/memory impairment in a modified radial maze and then examined for neurodegeneration of the hippocampus and cerebral cortex. Regardless of the ISI, young rats were not cognitively impaired, although hippocampal damage was evident. Learning/memory deficits and hippocampal and cortical neurodegeneration occurred in middle‐aged rats. The data indicate that 4‐VO/ICA has no impact on the capacity of young rats to learn the radial maze task, despite 51% hippocampal cell death. Such resistance is lost in middle‐aged animals, for which the most extensive neurodegeneration observed in both the hippocampus and cerebral cortex may be responsible.

Fish oil provides robust and sustained memory recovery after cerebral ischemia: Influence of treatment regimen

We previously reported that long-term treatment with fish oil (FO) facilitates memory recovery after transient, global cerebral ischemia (TGCI), despite the presence of severe hippocampal damage. The present study tested whether this antiamnesic effect resulted from an action of FO on behavioral performance itself, or whether it resulted from an anti-ischemic action. Different treatment regimens were used that were distinguished from each other by their initiation or duration with regard to the onset of TGCI and memory assessment. Naive rats were trained in an eight-arm radial maze, subjected to TGCI (4-VO model, 15 min), and tested for memory performance up to 6 weeks after TGCI. Fish oil (docosahexaenoic acid, 300 mg/kg/day) was given orally according to one of the following regimens: regimen 1 (from 3 days prior to ischemia until 4 weeks post-ischemia), regimen 2 (from 3 days prior to ischemia until 1 week post-ischemia), and regimen 3 (from week 2 to week 5 post-ischemia). When administered according to regimens 1 and 2, FO abolished amnesia completely. This effect persisted for at least 5 weeks after discontinuing the treatment. Such an effect did not occur, however, in the group treated according to regimen 3. Hippocampal and cortical damage was not alleviated by FO. The present results demonstrate that FO-mediated memory recovery (or preservation) following TGCI is a reproducible, robust, and long-lasting effect. Moreover, such an effect was found with a relatively short period of treatment, provided it covered the first days prior to and after ischemia. This suggests that FO prevented amnesia by changing some acute, ischemia/reperfusion-triggered process and not by stimulating memory performance on its own.

Maternal Omega-3 Supplement Improves Dopaminergic System in Pre- and Postnatal Inflammation-Induced Neurotoxicity in Parkinson's Disease Model.

Evidence suggests that idiopathic Parkinson’s disease (PD) is the consequence of a neurodevelopmental disruption, rather than strictly a consequence of aging. Thus, we hypothesized that maternal supplement of omega-3 polyunsaturated fatty acids (ω-3 PUFA) may be associated with neuroprotection mechanisms in a self-sustaining cycle of neuroinflammation and neurodegeneration in lipopolysaccharide (LPS)-model of PD. To test this hypothesis, behavioral and neurochemical assay were performed in prenatally LPS-exposed offspring at postnatal day 21. To further determine whether prenatal LPS exposure and maternal ω-3 PUFAs supplementation had persisting effects, brain injury was induced on PN 90 rats, following bilateral intranigral LPS injection. Pre- and postnatal inflammation damage not only affected dopaminergic neurons directly, but it also modified critical features, such as activated microglia and astrocyte cells, disrupting the support provided by the microenvironment. Unexpectedly, our results failed to show any involvement of caspase-dependent and independent apoptosis pathway in neuronal death mechanisms. On the other hand, learning and memory deficits detected with a second toxic exposure were significantly attenuated in maternal ω-3 PUFAs supplementation group. In addition, ω-3 PUFAs promote beneficial effect on synaptic function, maintaining the neurochemical integrity in remaining neurons, without necessarily protect them from neuronal death. Thus, our results suggest that ω-3 PUFAs affect the functional ability of the central nervous system in a complex way in a multiple inflammation-induced neurotoxicity animal model of PD and they disclose new ways of understanding how these fatty acids control responses of the brain to different challenges.

Cannabidiol reduces neuroinflammation and promotes neuroplasticity and functional recovery after brain ischemia

ABSTRACT This study investigated the effects of cannabidiol (CBD), a non‐psychotomimetic phytochemical present in Cannabis sativa, on the cognitive and emotional impairments induced by bilateral common carotid artery occlusion (BCCAO) in mice. Using a multi‐tiered behavioral testing battery during 21 days, we found that BCCAO mice exhibited long‐lasting functional deficits reflected by increase in anxiety‐like behavior (day 9), memory impairments (days 12–18) and despair‐like behavior (day 21). Short‐term CBD 10 mg/kg treatment prevented the cognitive and emotional impairments, attenuated hippocampal neurodegeneration and white matter (WM) injury, and reduced glial response that were induced by BCCAO. In addition, ischemic mice treated with CBD exhibited an increase in the hippocampal brain derived neurotrophic factor (BDNF) protein levels. CBD also stimulated neurogenesis and promoted dendritic restructuring in the hippocampus of BCCAO animals. Collectively, the present results demonstrate that short‐term CBD treatment results in global functional recovery in ischemic mice and impacts multiple and distinct targets involved in the pathophysiology of brain ischemic injury.

Fish Oil Prevents Oxidative Stress and Exerts Sustained Antiamnesic Effect After Global Cerebral Ischemia

Transient, global cerebral ischemia (TGCI) causes hippocampal/cortical damage and the persistent loss of welltrained, long-term memory (retrograde amnesia). Fish oil (FO), a rich source of omega-3 polyunsaturated fatty acids, abolishes such amnesia in the absence of neurohistological protection. The present study investigated whether FO prevents ischemia-induced oxidative stress and whether such an action contributes to the lasting effect of FO on memory recovery. In a first experiment, FO was administered for 4 days prior to ischemia, and antioxidant status was subsequently measured after 24 h of reperfusion. In another experiment, naive rats were trained in an eight-arm radial maze until they achieved asymptotic performance and then subjected to TGCI. One group of rats received FO as in the first experiment (i.e., 4 days prior to ischemia), whereas another group received FO for 4 days prior to ischemia plus 6 days postischemia. Retrograde memory performance was assessed 2-5 weeks after ischemia. TGCI depleted the level of antioxidant enzymes and increased the amount of protein carbonylation, indicating oxidative damage. Fish oil reversed oxidative damage to control levels. The same treatment that attenuated oxidative stress after 24 h of reperfusion also prevented retrograde amnesia assessed several weeks later. This antiamnesic effect afforded by short preischemia treatment was comparable to 10 days of treatment but not as consistent. These data indicate that an antioxidant action in the hyperacute phase of ischemia/reperfusion may contribute to the long-term, antiamnesic effect of FO.

Acute, post-ischemic sensorimotor deficits correlate positively with infarct size but fail to predict its occurrence and magnitude after middle cerebral artery occlusion in rats

This study investigated whether sensorimotor deficits measured soon after reperfusion could predict the occurrence and magnitude of cerebral infarct following middle cerebral artery occlusion (MCAO). Rats were subjected to left MCAO for 2 h according to the intraluminal thread method. At 0, 1, 2, and 3 h after reperfusion, the animals were examined for neurological deficits using an expanded scale comprising the following tests: (A) postural reflex, (B) circling motion, (C) falling to contralateral side, (D) placement of the contralateral forelimb during motion, and (E) general state of alertness or consciousness. Deficits were graded from 0 (normal) to 2 or 3 (severe), and the final neuro-score was a summation of these scores over the various time points and among the various tests. The neuro-score of the animals that survived up to 24 h after MCAO ranged from 0 to 8.2 and positively correlated with infarct size (p=0.0002-0.001). However, at least three animals with moderate neuro-scores (4.5-6.0) did not exhibit any sign of infarcted brain tissue. Other animals having a distinct neuro-score (3.2 and 8.2, respectively) exhibited cerebral infarct with the same size (235 mm³). These data indicate that the extent of neurological deficit assessed within the first 3h after reperfusion does not reliably correspond to the occurrence and magnitude of cerebral infarct. Therefore, the neuro-score, when measured acutely within the first few hours after reperfusion, does not serve as a reliable criterion for preselecting animals with similar infarct size following transient MCAO.

Neuroprotective effect of omega-3 polyunsaturated fatty acids in the 6-OHDA model of Parkinson's disease is mediated by a reduction of inducible nitric oxide synthase

Objective: Parkinsons disease (PD) is characterized by deterioration of the nigrostriatal system and associated with chronic neuroinflammation. Glial activation has been associated with regulating the survival of dopaminergic neurons and is thought to contribute to PD through the release of proinflammatory and neurotoxic factors, such as reactive nitric oxide (NO) that triggers or exacerbates neurodegeneration in PD. Polyunsaturated fatty acids (PUFAs) exert protective effects, including antiinflammatory, antiapoptotic, and antioxidant activity, and may be promising for delaying or preventing PD by attenuating neuroinflammation and preserving dopaminergic neurons. The present study investigated the effects of fish oil supplementation that was rich in PUFAs on dopaminergic neuron loss, the density of inducible nitric oxide synthase (iNOS)-immunoreactive cells, and microglia and astrocyte reactivity in the substantia nigra pars compacta (SNpc) and striatal dopaminergic fibers. Methods: The animals were supplemented with fish oil for 50 days and subjected to unilateral intrastriatal 6-hydroxydopamine (6-OHDA)-induced lesions as a model of PD. Results: Fish oil mitigated the loss of SNpc neurons and nerve terminals in the striatum that was caused by 6-OHDA. This protective effect was associated with reductions of the density of iNOS-immunoreactive cells and microglia and astrocyte reactivity. Discussion: These results suggest that the antioxidant and antiinflammatory properties of fish oil supplementation are closely related to a decrease in dopaminergic damage that is caused by the 6-OHDA model of PD. GRAPHICAL ABSTRACT

Myricitrin induces antidepressant-like effects and facilitates adult neurogenesis in mice

HighlightsMyricitrin repeated treatment results in antidepressant‐like effects in mice.Myricitrin increases cell proliferation and the number of newborn neurons in the hippocampal dentate gyrus.Myricitrin facilitates differentiation of progenitor cells in neurons in the hippocampus. ABSTRACT Myricitrin (MYR) is a natural flavonoid that inhibits nitric oxide (NO) transmission and has an atypical antipsychotic‐like profile in animal models. Considering that several NO inhibitors exert antidepressant‐like effects, the present study evaluated the antidepressant‐like effect of MYR (3–30 mg/kg) in the tail suspension test (TST). Because of the putative relationship between adult neurogenesis and antidepressant activity, we also assessed cell proliferation, survival, and differentiation in adult neurogenic niches, including the subgranular zone (SGZ) and subventricular zone (SVZ). Similar to the positive control imipramine (IMI; 10 mg/kg), repeated treatment with 10 mg/kg MIR but not acute treatment reduced immobility time in the TST, indicating an antidepressant‐like effect. No effect on general motor activity was observed. Myricitrin also facilitated cell proliferation in the SGZ of the hippocampal dentate gyrus and SVZ. In the SGZ, MYR increased the number of doublecortin‐ and 5‐bromo‐2′‐deoxyuridine/neuronal nuclei‐positive cells. Our results suggest that MYR facilitates hippocampal neurogenesis, which might contribute to its antidepressant‐like effect and atypical antipsychotic‐like profile.