Epigenetic mechanisms of particulate matter exposure: air pollution and hazards on human health.

Environmental pollution nowadays has not only a direct correlation with human health changes but a direct social impact. Epidemiological studies have evidenced the increased damage to human health on a daily basis because of damage to the ecological niche. Rapid urban growth and industrialized societies importantly compromise air quality, which can be assessed by a notable accumulation of air pollutants in both the gas and the particle phases. Of them, particulate matter (PM) represents a highly complex mixture of organic and inorganic compounds of the most variable size, composition, and origin. PM being one of the most complex environmental pollutants, its accumulation also varies in a temporal and spatial manner, which challenges current analytical techniques used to investigate PM interactions. Nevertheless, the characterization of the chemical composition of PM is a reliable indicator of the composition of the atmosphere, the quality of breathed air in urbanized societies, industrial zones and consequently gives support for pertinent measures to avoid serious health damage. Epigenomic damage is one of the most promising biological mechanisms of air pollution-derived carcinogenesis. Therefore, this review aims to highlight the implication of PM exposure in diverse molecular mechanisms driving human diseases by altered epigenetic regulation. The presented findings in the context of pan-organic cancer, fibrosis, neurodegeneration and metabolic diseases may provide valuable insights into the toxicity effects of PM components at the epigenomic level and may serve as biomarkers of early detection for novel targeted therapies.

Intrapallidal injection of cannabidiol or a selective GPR55 antagonist decreases motor asymmetry and improves fine motor skills in hemiparkinsonian rats.

Cannabidiol (CBD) presents antiparkinsonian properties and neuromodulatory effects, possibly due to the pleiotropic activity caused at multiple molecular targets. Recently, the GPR55 receptor has emerged as a molecular target of CBD. Interestingly, GPR55 mRNA is expressed in the external globus pallidus (GPe) and striatum, hence, it has been suggested that its activity is linked to motor dysfunction in Parkinson's disease (PD). The present study aimed to evaluate the effect of the intrapallidal injection of both CBD and a selective GPR55 antagonist (CID16020046) on motor asymmetry, fine motor skills, and GAD-67 expression in hemiparkinsonian rats. The hemiparkinsonian animal model applied involved the induction of a lesion in male Wistar rats via the infusion of the neurotoxin 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle via stereotaxic surgery. After a period of twenty days, a second surgical procedure was performed to implant a guide cannula into the GPe. Seven days later, lysophosphatidylinositol (LPI), CBD, or CID16020046 were injected once a day for three consecutive days (from the 28th to the 30th day post-lesion). Amphetamine-induced turning behavior was evaluated on the 14th and 30th days post-injury. The staircase test and fine motor skills were evaluated as follows: the rats were subject to a ten-day training period prior to the 6-OHDA injury; from the 15th to the 19th days post-lesion, the motor skills alterations were evaluated under basal conditions; and, from the 28th to the 30th day post-lesion, the pharmacological effects of the drugs administered were evaluated. The results obtained show that the administration of LPI or CBD generated lower levels of motor asymmetry in the turning behavior of hemiparkinsonian rats. It was also found that the injection of CBD or CID16020046, but not LPI, in the hemiparkinsonian rats generated significantly superior performance in the staircase test, in terms of the use of the forelimb contralateral to the 6-OHDA-induced lesion, when evaluated from the 28th to the 30th day post-lesion. Similar results were also observed for superior fine motor skills performance for pronation, grasp, and supination. Finally, the immunoreactivity levels were found to decrease for the GAD-67 enzyme in the striatum and the ipsilateral GPe of the rats injected with CBD and CID16020046, in contrast with those lesioned with 6-OHDA. The results obtained suggest that the inhibitory effects of CBD and CID16020046 on GPR55 in the GPe could be related to GABAergic overactivation in hemiparkinsonism, thus opening new perspectives to explain, at a cellular level, the reversal of the motor impairment observed in PD models.

Interacting binding insights and conformational consequences of the differential activity of cannabidiol with two endocannabinoid-activated G-protein-coupled receptors.

Cannabidiol (CBD), the major non-psychoactive phytocannabinoid present in the plant Cannabis sativa, has displayed beneficial pharmacological effects in the treatment of several neurological disorders including, epilepsy, Parkinson's disease, and Alzheimer's disease. In particular, CBD is able to modulate different receptors in the endocannabinoid system, some of which belong to the family of G-protein-coupled receptors (GPCRs). Notably, while CBD is able to antagonize some GPCRs in the endocannabinoid system, it also seems to activate others. The details of this dual contrasting functional feature of CBD, that is, displaying antagonistic and (possible) agonistic ligand properties in related receptors, remain unknown. Here, using computational methods, we investigate the interacting determinants of CBD in two closely related endocannabinoid-activated GPCRs, the G-protein-coupled receptor 55 (GPR55) and the cannabinoid type 1 receptor (CB1). While in the former, CBD has been demonstrated to function as an antagonist, the way by which CBD modulates the CB1 receptor remains unclear. Namely, CBD has been suggested to directly trigger receptor's activation, stabilize CB1 inactive conformations or function as an allosteric modulator. From microsecond-length unbiased molecular dynamics simulations, we found that the presence of the CBD ligand in the GPR55 receptor elicit conformational changes associated with antagonist-bound GPCRs. In contrast, when the GPR55 receptor is simulated in complex with the selective agonist ML186, agonist-like conformations are sampled. These results are in agreement with the proposed modulatory function of each ligand, showing that the computational techniques utilized to characterize the GPR55 complexes correctly differentiate the agonist-bound and antagonist-bound systems. Prompted by these results, we investigated the role of the CBD compound on the CB1 receptor using similar computational approaches. The all-atom MD simulations reveal that CBD induces conformational changes linked with agonist-bound GPCRs. To contextualize the results we looked into the CB1 receptor in complex with a well-established antagonist. In contrast to the CBD/CB1 complex, when the CB1 receptor is simulated in complex with the ligand antagonist AM251, inactive conformations are explored, showing that the computational techniques utilized to characterize the CB1 complexes correctly differentiate the agonist-bound and antagonist-bound systems. In addition, our results suggest a previously unknown sodium-binding site located in the extracellular domain of the CB1 receptor. From our detailed characterization, we found particular interacting loci in the binding sites of the GPR55 and the CB1 receptors that seem to be responsible for the differential functional features of CBD. Our work will pave the way for understanding the CBD pharmacology at a molecular level and aid in harnessing its potential therapeutic use.

Prophylactic Zinc Administration Combined with Swimming Exercise Prevents Cognitive-Emotional Disturbances and Tissue Injury following a Transient Hypoxic-Ischemic Insult in the Rat.

Exercise performance and zinc administration individually yield a protective effect on various neurodegenerative models, including ischemic brain injury. Therefore, this work was aimed at evaluating the combined effect of subacute prophylactic zinc administration and swimming exercise in a transient cerebral ischemia model. The prophylactic zinc administration (2.5 mg/kg of body weight) was provided every 24 h for four days before a 30 min common carotid artery occlusion (CCAO), and 24 h after reperfusion, the rats were subjected to swimming exercise in the Morris Water Maze (MWM). Learning was evaluated daily for five days, and memory on day 12 postreperfusion; anxiety or depression-like behavior was measured by the elevated plus maze and the motor activity by open-field test. Nitrites, lipid peroxidation, and the activity of superoxide dismutase (SOD) and catalase (CAT) were assessed in the temporoparietal cortex and hippocampus. The three nitric oxide (NO) synthase isoforms, chemokines, and their receptor levels were measured by ELISA. Nissl staining evaluated hippocampus cytoarchitecture and Iba-1 immunohistochemistry activated the microglia. Swimming exercise alone could not prevent ischemic damage but, combined with prophylactic zinc administration, reversed the cognitive deficit, decreased NOS and chemokine levels, prevented tissue damage, and increased Iba-1 (+) cell number. These results suggest that the subacute prophylactic zinc administration combined with swimming exercise, but not the individual treatment, prevents the ischemic damage on day 12 postreperfusion in the transient ischemia model.

Neuropathological Aspects of SARS-CoV-2 Infection: Significance for Both Alzheimer's and Parkinson's Disease.

Evidence suggests that SARS-CoV-2 entry into the central nervous system can result in neurological and/or neurodegenerative diseases. In this review, routes of SARS-Cov-2 entry into the brain via neuroinvasive pathways such as transcribrial, ocular surface or hematogenous system are discussed. It is argued that SARS-Cov-2-induced cytokine storm, neuroinflammation and oxidative stress increase the risk of developing neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Further studies on the effects of SARS-CoV-2 and its variants on protein aggregation, glia or microglia activation, and blood-brain barrier are warranted.

The C-terminal domain of the heavy chain of tetanus toxin prevents the oxidative and nitrosative stress induced by acute toxicity of 1-methyl-4-phenylpyridinium, a rat model of Parkinson's disease.

The recombinant carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) exerts neuroprotective and neurorestorative effects on the dopaminergic system of animal models of Parkinson's disease (PD). The present study aimed to determine the effect of the Hc-TeTx fragment on the markers of oxidative stress and nitrosative stress generated by the acute toxicity of 1-methyl-4-phenylpyridinium (MPP+). For this purpose, the Hc-TeTx fragment was administered once a day in three 20 µg/kg consecutive injections into the grastrocnemius muscle of the rats, with an intra-striatal unilateral injection of 1 µL of MPP+ [10 µg/mL] then administered in order to cause a dopaminergic lesion. The results obtained show that the rats treated with Hc-TeTx plus MPP+ presented an increase in the expression of tyrosine hydroxylase (TH), a significantly greater decrease in the levels of the markers of oxidative stress, nitrosative stress, and neurodegeneration than that observed for the group injured with only MPP+. Moreover, it was observed that total superoxide dismutase (SOD) and copper/zinc SOD activity increased with the administration of Hc-TeTx. Finally, immunoreactivity levels were observed to decrease for the levels of 3-nitrotyrosine and the glial fibrillary acidic protein in the ipsilateral striatum of the rats treated with Hc-TeTx plus MPP+, in contrast with those lesioned with MPP+ alone. Our results demonstrate that the recombinant Hc-TeTx fragment may be a potent antioxidant and, therefore, could be suggested as a therapeutic tool against the dopaminergic neuronal impairment observed in the early stages of PD.

The Chronic Oral Administration of Clobenzorex or Amphetamine Decreases Motor Behavior and Induces Glial Activation in the Striatum Without Dopaminergic Degeneration.

Described as amphetamine-like due to their structural and stimulant similarities, clobenzorex is one of the five most-commonly used drugs in Mexico for the treatment of obesity. Various studies have shown that amphetamines induce dopaminergic neurotoxicity and neuroinflammation in the striatum, symptoms which are associated with motor damage. For this reason, the present study aimed to evaluate the effect of chronic clobenzorex administration on motor behaviors, TH immunoreactivity, gliosis, and the neurodegenerative process in the striatum and substantia nigra pars compacta (SNpc). The present research was conducted on three experimental groups of male Wistar rats: the vehicle group, the amphetamine group (2 mg/kg), and the clobenzorex group (30 mg/kg). All groups were subject to oral administration every 24 h for 31 days. Motor activity and motor coordination were evaluated in the open field test and the beam walking test, respectively. The animals were euthanized after the last day of treatment to enable the extraction of their brains for the evaluation of tyrosine hydroxylase (TH) levels, the immunoreactivity of the glial cells, and the neurodegeneration of both the striatum and SNpc via amino-cupric-silver stain. The results obtained show that amphetamine and clobenzorex administration decrease motor activity and motor coordination in the beam walking test and cause increased gliosis in the striatum, while no significant changes were observed in terms of immunoreactivity to TH and neurodegeneration in both the striatum and SNpc. These results suggest that the chronic administration of clobenzorex may decrease motor function in a manner similar to amphetamine, via the neuroadaptive and non-neurotoxic changes caused to the striatum under this administration scheme.

Disturbance of the Glutamate-Glutamine Cycle, Secondary to Hepatic Damage, Compromises Memory Function.

Glutamate fulfils many vital functions both at a peripheral level and in the central nervous system (CNS). However, hyperammonemia and hepatic failure induce alterations in glutamatergic neurotransmission, which may be the main cause of hepatic encephalopathy (HE), an imbalance which may explain damage to both learning and memory. Cognitive and motor alterations in hyperammonemia may be caused by a deregulation of the glutamate-glutamine cycle, particularly in astrocytes, due to the blocking of the glutamate excitatory amino-acid transporters 1 and 2 (EAAT1, EAAT2). Excess extracellular glutamate triggers mechanisms involving astrocyte-mediated inflammation, including the release of Ca2+-dependent glutamate from astrocytes, the appearance of excitotoxicity, the formation of reactive oxygen species (ROS), and cell damage. Glutamate re-uptake not only prevents excitotoxicity, but also acts as a vital component in synaptic plasticity and function. The present review outlines the evidence of the relationship between hepatic damage, such as that occurring in HE and hyperammonemia, and changes in glutamine synthetase function, which increase glutamate concentrations in the CNS. These conditions produce dysfunction in neuronal communication. The present review also includes data indicating that hyperammonemia is related to the release of a high level of pro-inflammatory factors, such as interleukin-6, by astrocytes. This neuroinflammatory condition alters the function of the membrane receptors, such as N-methyl-D-aspartate (NMDA), (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) AMPA, and γ-aminobutyric acid (GABA), thus affecting learning and spatial memory. Data indicates that learning and spatial memory, as well as discriminatory or other information acquisition processes in the CNS, are damaged by the appearance of hyperammonemia and, moreover, are associated with a reduction in the production of cyclic guanosine monophosphate (cGMP). Therefore, increased levels of pharmacologically controlled cGMP may be used as a therapeutic tool for improving learning and memory in patients with HE, hyperammonemia, cerebral oedema, or reduced intellectual capacity.

Cannabidiol as a Therapeutic Target: Evidence of its Neuroprotective and Neuromodulatory Function in Parkinson's Disease.

The phytocannabinoids of Cannabis sativa L. have, since ancient times, been proposed as a pharmacological alternative for treating various central nervous system (CNS) disorders. Interestingly, cannabinoid receptors (CBRs) are highly expressed in the basal ganglia (BG) circuit of both animals and humans. The BG are subcortical structures that regulate the initiation, execution, and orientation of movement. CBRs regulate dopaminergic transmission in the nigro-striatal pathway and, thus, the BG circuit also. The functioning of the BG is affected in pathologies related to movement disorders, especially those occurring in Parkinson's disease (PD), which produces motor and non-motor symptoms that involving GABAergic, glutamatergic, and dopaminergic neural networks. To date, the most effective medication for PD is levodopa (l-DOPA); however, long-term levodopa treatment causes a type of long-term dyskinesias, l-DOPA-induced dyskinesias (LIDs). With neuromodulation offering a novel treatment strategy for PD patients, research has focused on the endocannabinoid system (ECS), as it participates in the physiological neuromodulation of the BG in order to control movement. CBRs have been shown to inhibit neurotransmitter release, while endocannabinoids (eCBs) play a key role in the synaptic regulation of the BG. In the past decade, cannabidiol (CBD), a non-psychotropic phytocannabinoid, has been shown to have compensatory effects both on the ECS and as a neuromodulator and neuroprotector in models such as 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and reserpine, as well as other PD models. Although the CBD-induced neuroprotection observed in animal models of PD has been attributed to the activation of the CB1 receptor, recent research conducted at a molecular level has proposed that CBD is capable of activating other receptors, such as CB2 and the TRPV-1 receptor, both of which are expressed in the dopaminergic neurons of the nigro-striatal pathway. These findings open new lines of scientific inquiry into the effects of CBD at the level of neural communication. Cannabidiol activates the PPARγ, GPR55, GPR3, GPR6, GPR12, and GPR18 receptors, causing a variety of biochemical, molecular, and behavioral effects due to the broad range of receptors it activates in the CNS. Given the low number of pharmacological treatment alternatives for PD currently available, the search for molecules with the therapeutic potential to improve neuronal communication is crucial. Therefore, the investigation of CBD and the mechanisms involved in its function is required in order to ascertain whether receptor activation could be a treatment alternative for both PD and LID.

The Acute Activation of the CB1 Receptor in the Hippocampus Decreases Neurotoxicity and Prevents Spatial Memory Impairment in Rats Lesioned with ß-Amyloid 25-35.

Given their anti-inflammatory properties, cannabinoids have been shown to be neuroprotective agents and to reduce excitotoxicity, through the activation of the Cannabinoid receptor type 1 (CB1r). These properties have led to CB1r being proposed as pharmacological targets for the treatment of various neurodegenerative diseases. Amyloid-ß 25-35 (Aß25-35) induces the expression of inducible nitric oxide synthase (iNOS) and increases nitric oxide (NO●) levels. It has been observed that increased NO● concentrations trigger biochemical pathways that contribute to neuronal death and cognitive damage. This study aimed to evaluate the neuroprotective effect of an acute activation of CB1r on spatial memory and its impact on iNOS protein expression, NO● levels, gliosis and the neurodegenerative process induced by the injection of Aß(25-35) into the CA1 subfield of the hippocampus. ACEA [1 µM/1 µL] and Aß(25-35) [100 µM/1 µL] and their respective vehicle groups were injected into the CA1 subfield of the hippocampus. The animals were tested for spatial learning and memory in the eight-arm radial maze, with the results revealing that the administration of ACEA plus Aß(25-35) improves learning and memory processes, in contrast with the Aß(25-35) group. Moreover, ACEA plus Aß(25-35) prevented both the increase in iNOS protein and NO● levels and the reactive gliosis induced by Aß(25-35). Importantly, neurodegeneration was significantly reduced by the administration of ACEA plus Aß(25-35) in the CA1 subfield of the hippocampus. The data obtained in the present research suggest that the acute early activation of CB1r is crucial for neuroprotection.

Effectiveness of Fragment C Domain of Tetanus Toxin and Pramipexole in an Animal Model of Parkinson's Disease.

Reports indicate that striatal dopaminergic damage induced by 6-hydoxydopamine (6-OHDA) can be blocked by C-terminal domain of tetanus toxin (Hc-TeTx), suggesting possible therapeutic potential of Hc-TeTx in Parkinson's disease (PD). Pramipexole (PPX), a D2/D3 dopaminergic agonist, is currently used in PD treatment. The purpose of this study was to gain some understanding of the actions of each drug, including potential antioxidant and anti-inflammatory effects and importantly, to determine whether the combination of the two drugs would be superior to each alone. Adult male Wistar rats were administered 6-OHDA into the dorso-lateral striatum, and the effects of Hc-TeTx fragment (20 µg/kg i.m. every 24 h) for 3 days; PPX (1 mg/kg p.o., every 12 h) for 30 days and their combination on various motor and neurochemical parameters were evaluated. Behavioral tests were carried out at 15 and 30 days post-treatments. At day 31, the animals were sacrificed and the levels of tyrosine hydroxylase (TH), reflecting dopaminergic activity in both striatum and substantia nigra, were evaluated. In addition, indices of astrogliosis, microgliosis, as well as oxidative stress in the striatum were determined. Both Hc-TeTx and PPX ameliorated the motor and neurochemical deficits induced by 6-OHDA lesion; however, the combination of the two drugs was not superior to each alone. Hence, at concentrations used in this study, no significant advantage in combining Hc-TeTx with PPX was noted. Although the results suggest similar neurochemical effects of the two compounds, further evaluation of different concentrations of Hc-TeTx and PPX as potential intervention in PD is warranted.

Prophylactic Zinc and Therapeutic Selenium Administration Increases the Antioxidant Enzyme Activity in the Rat Temporoparietal Cortex and Improves Memory after a Transient Hypoxia-Ischemia.

In the cerebral hypoxia-ischemia rat model, the prophylactic administration of zinc can cause either cytotoxicity or preconditioning effect, whereas the therapeutic administration of selenium decreases the ischemic damage. Herein, we aimed to explore whether supplementation of low doses of prophylactic zinc and therapeutic selenium could protect from a transient hypoxic-ischemic event. We administrated zinc (0.2 mg/kg of body weight; ip) daily for 14 days before a 10 min common carotid artery occlusion (CCAO). After CCAO, we administrated sodium selenite (6 µg/kg of body weight; ip) daily for 7 days. In the temporoparietal cerebral cortex, we determined nitrites by the Griess method and lipid peroxidation by the Gerard-Monnier assay. qPCR was used to measure mRNA of nitric oxide synthases, antioxidant enzymes, chemokines, and their receptors. We measured the enzymatic activity of SOD and GPx and protein levels of chemokines and their receptors by ELISA. We evaluated long-term memory using the Morris-Water maze test. Our results showed that prophylactic administration of zinc caused a preconditioning effect, decreasing nitrosative/oxidative stress and increasing GPx and SOD expression and activity, as well as eNOS expression. The therapeutic administration of selenium maintained this preconditioning effect up to the late phase of hypoxia-ischemia. Ccl2, Ccr2, Cxcl12, and Cxcr4 were upregulated, and long-term memory was improved. Pyknotic cells were decreased suggesting prevention of neuronal cell death. Our results show that the prophylactic zinc and therapeutic selenium administration induces effective neuroprotection in the early and late phases after CCAO.

The restorative effect of intramuscular injection of tetanus toxin C-fragment in hemiparkinsonian rats.

The C-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) is a peptide that has a neuroprotective action against dopaminergic damage by MPP(+), both in vitro and in vivo. The trophic effects of Hc-TeTx have been related to its ability to activate the pathways of the tropomyosin receptor kinase, which are crucial for survival process. Our group had previously shown neuroprotective effect of intramuscular Hc-TeTx treatment on animals with a dopaminergic lesion; however, there is no evidence indicating its restorative effects on advanced dopaminergic neurodegeneration. The aim of our study was to examine the restorative effects of an intramuscular injection of the Hc-TeTx fragment on the nigrostriatal system of hemiparkinsonian rats. The animals were administered with a vehicle or Hc-TeTx (20µg/kg) in the gastrocnemius muscle for three consecutive days post-dopaminergic lesion, which was made using 6-hydroxydopamine. Post-Hc-TeTx treatment, the hemiparkinsonian rats showed constant motor asymmetry. Moreover, the ipsilateral striatum of the post-Hc-TeTx group had a lower number of argyrophilic structures and a major immunorreactivity to Tyrosine Hydroxylase in the striatum and the substantia nigra pars compacta compared to the 6-OHDA group. Our results show the restorative effect of the Hc-TeTx fragment during the dopaminergic neurodegeneration caused by 6-OHDA.

17-AAG improves cognitive process and increases heat shock protein response in a model lesion with Aß25-35.

Molecular chaperones, or heat shock proteins (HSP), have been implicated in numerous neurodegenerative disorders characterized by the accumulation of protein aggregates, such as Alzheimer disease. The agglomeration of insoluble structures of Aß is thought to be responsible for neuronal death, which in turn leads to the loss of cognitive functions. Recent findings have shown that the induction of HSP decreases the level of abnormal protein aggregates, as well as demonstrating that 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), an analogue of geldanamycin (GA), increases Aß clearance through the induction of molecular chaperones in cell culture. In light of this discovery that HSP overexpression can be neuroprotective, the search for a way to pharmacologically induce the overexpression of HSP and other associated chaperones may lead to a promising approach for the treatment of neurodegenerative diseases. The aim of our study was to evaluate both the effect of 17-AAG on the cognitive process and the HSP response in rats injected with Aß25-35 into the CA1 of the hippocampus. The results show that the injection of Aß caused a significant increase in the expression of the HSP involved in the regulation of cellular proteostasis. While the HSP did not reverse excitotoxic damage, given that experimental subjects showed learning and memory deficits, the administration of 17-AAG prior to the injection of Aß25-35 did show an improvement in the behavioral assessment that correlated with the upregulation of HSP70 in subjects injured with Aß. Overall, our data shows that the pharmacological induction of HSP using 17-AAG may be an alternative treatment of neurodegenerative diseases.

The C-terminal domain of the heavy chain of tetanus toxin given by intramuscular injection causes neuroprotection and improves the motor behavior in rats treated with 6-hydroxydopamine.

We have previously shown that the intrastriatal injection of the C-terminal domain of tetanus toxin (Hc-TeTx) protects the nigrostriatal-dopaminergic pathways and improves motor behavior in hemiparkinsonism-rat models caused by MPP(+) (1-methyl-4-phenylpyridinium). Here we have investigated the protective effects of the intramuscular application of the Hc-TeTx on motor asymmetry and neurodegeneration in the striatum of 6-hydroxydopamine (6-OHDA)-treated rats. Adult male rats were intramuscularly injected with the recombinant Hc-TeTx protein (0.1-20µg/kg, daily) 3days before the stereotaxic injection of 6-OHDA into the left striatum. Our results showed that the motor-improvement functions were extended for 4weeks in all Hc-TeTx-treated groups, obtaining the maximum performance with the highest dose of Hc-TeTx (20µg/kg). The improvements found were 97%, 87%, and 70% in the turning behavior, stepping test, and cylinder test, respectively. The striatal levels of dopamine and its metabolites did not vary compared to the control group. Moreover, the peripheral treatment with Hc-TeTx in rats prevents, for 30days, the neurodegeneration in the striatum caused by the toxicity of the 6-OHDA. Our results lead us to believe that the Hc-TeTx could be a potential therapeutic agent in pathologies caused by impairment of dopaminergic innervations such as Parkinson's disease.

Alteration of the sialylation pattern and memory deficits by injection of Aß(25-35) into the hippocampus of rats.

Sialic acid in glycoconjugates participates in important cellular functions associated with normal development, growth, and communication. Therefore we evaluated the sialylation pattern and memory deficits caused by the injection of Aß((25-35)) into the hippocampus (Hp) of rats. The eight-arm maze spatial-learning and memory test indicated that the injection of Aß((25-35)) into subfield CA1 of the Hp impaired both learning and memory. The sialylation pattern was examined using sialic acid-specific lectins. Our results showed that Maackia amurensis agglutinin (MAA, specific for Neu5Acα2,3Gal) showed reactivity in the CA1 and dentate gyrus (DG) subfields of the Hp mainly in the group injected with vehicle, whereas Macrobrachium rosenbergii lectin (MRL, specific for Neu5,9,7Ac) and Sambucus nigra agglutinin (SNA, specific for Neu5Acα2,6Gal-GalNAc) had increased reactivity in the CA1 and DG subfields of the Hp in the Aß((25-35))-injected group. The staining pattern of the antibody specific for polysialic acid (a linear homopolymer of α-2,8-linked sialic acid) increased in the CA1 and DG subfields of the Hp of the Aß((25-35)) group compared to the control group. Our results suggest that injection of Aß((25-35)) causes impairment in spatial memory and alters the sialylation pattern in response to compensatory reorganization and-or sprouting of dendrites and axons of the surviving neurons.

The role of NOS in the impairment of spatial memory and damaged neurons in rats injected with amyloid beta 25-35 into the temporal cortex.

The Aß(25-35) fraction mimics the toxic effects of the complete peptide Aß(1-42) because this decapeptide is able to cause memory impairment and neurodegenerative events. Recent evidence has shown that the injection of Aß(25-35) into the temporal cortex (TCx) of the rat increases the nitric oxide (NO) pathways with several consequences, such as neuronal loss in rats. Our aim was to investigate the effects of each NOS isoform by the prior injection of NOS inhibitors before the injection of the Aß(25-35). One month after the treatment, the animals were tested for their spatial memory in the radial maze. The hippocampus (Hp) and TCx were assessed for NO production, nitration of proteins (3-NT), astrocytosis (GFAP), and neuronal loss. Our findings show a significant impairment in the memory caused by Aß25-35 injection. In contrast NOS inhibitors plus Aß25-35 cause a protection yielding a high performance in the memory test and reduction of cell damage in the TCx and the Hp. Particularly, iNOS is the major source of NO and related to the inflammatory response leading to the memory deficits. The inhibition of iNOS is an important target for neuronal protection against the toxicity of the Aß25-35 over the long term.

The amyloid-beta25-35 injection into the CA1 region of the neonatal rat hippocampus impairs the long-term memory because of an increase of nitric oxide.

Alzheimer's disease (AD) is characterized by the amyloid-beta (Abeta) aggregation but it is unclear when this process begins. Previously, we showed that amyloid-beta(25-35) (Abeta(25-35)) increases the nitric oxide (NO) pathways and causes neurodegenerative effects in rats. The excessive increase of NO during brain development can promote a persistent oxidative stress, but the role of the Abeta(25-35) in the neonatal age and its effects over the long term is unclear. Our aim was to evaluate if the Abeta(25-35) injection on postnatal day 7 causes loss in spatial memory by NO pathways in adult rats. Our results showed that neonatal-Abeta(25-35) injection into the hippocampus (Hp) causes significant impairments in the spatial memory after 90 days. The NO levels were found increased and argynophilic in the Hp. Other evidence of neuronal damage was an increase of the immunoreactivity for 3-nitrotyrosine (3-NT) and the glial-fibrilar acid protein (GFAP) in the Hp of the Abeta(25-35) group. In contrast, these effects were blocked by the administration of L-NAME (inhibitor of nitric oxide synthase) before the injection of Abeta(25-35). The L-NAME plus Abeta(25-35) group showed a better performance in the spatial memory compared to the Abeta(25-35) group. In addition in this group we found a decrease of NO, 3-NT and neurodegeneration in the Hp compared to the Abeta(25-35) group. This finding is a novel result about the role of Abeta(25-35) during the neonatal stage that enhances the NO production, which appears to impair the spatial memory in adult rats.

The carboxyl-terminal domain of the heavy chain of tetanus toxin prevents dopaminergic degeneration and improves motor behavior in rats with striatal MPP(+)-lesions.

Recently it has been shown that the C-terminus fragment of the tetanus toxin (Hc-TeTx) is transported retrogradely and had shown neuroprotective effects, preventing neuronal death by apoptosis. This could be a new alternative preventing ongoing cell death and restoring the motor function in Parkinson's disease (PD), which is characterized by dopaminergic neurodegeneration. Our aim was to evaluate the effects of local administration of Hc-TeTx on motor behavior and the dopamine (DA) levels in the striatum of MPP(+)-treated rats. In the rotational behavior task, the Hc-TeTx [2 microM]+MPP(+) group had a decreased number of contralateral rotations and the cylinder test improved for both forelimb-use asymmetry compared to the MPP(+) group. The staircase test showed that the Hc-TeTx+MPP(+) group had an improvement of fine motor skills compared to the same limb performance of the MPP(+) group. The group of animals with Hc-TeTx+MPP(+) had higher DA and metabolite levels compared to the MPP(+) group. Our study clearly shows that Hc-TeTx improves different motor behavior strongly, which favors the hypothesis of the Hc-TeTx fragment enhancing survival pathways that result in amelioration of the dopaminergic system of rats with a dopaminergic lesion.