ß-Secretase-1: In Silico Drug Reposition for Alzheimer's Disease.

The ß-secretase-1 enzyme (BACE-1) performs a key role in the production of beta-Amyloid protein (Aß), which is associated with the development of Alzheimer's disease (AD). The inhibition of BACE-1 has been an important pharmacological strategy in the treatment of this neurodegenerative disease. This study aims to identify new potential candidates for the treatment of Alzheimer's with the help of in silico studies, such as molecular docking and ADME prediction, from a broad list of candidates provided by the DrugBank database. From this analysis, 1145 drugs capable of interacting with the enzyme with a higher coupling energy than Verubecestat were obtained, subsequently only 83 presented higher coupling energy than EJ7. Applying the oral route of administration as inclusion criteria, only 41 candidates met this requirement; however, 6 of them are associated with diagnostic tests and not treatment, so 33 candidates were obtained. Finally, five candidates were identified as possible BACE-1 inhibitors drugs: Fluphenazine, Naratriptan, Bazedoxifene, Frovatriptan, and Raloxifene. These candidates exhibit pharmacophore-specific features, including the indole or thioindole group, and interactions with key amino acids in BACE-1. Overall, this study provides insights into the potential use of in silico methods for drug repurposing and identification of new candidates for the treatment of Alzheimer's disease, especially those targeting BACE-1.

Chronic administration of nicotine enhances NMDA-activated currents in the prefrontal cortex and core part of the nucleus accumbens of rats.

Nicotine is an addictive substance of tobacco. It has been suggested that nicotine acts on glutamatergic (N-methyl-d-aspartate, NMDA) neurotransmission affecting dopamine release in the mesocorticolimbic system. This effect is reflected in neuroadaptative changes that can modulate neurotransmission in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) core (cNAcc) and shell (sNAcc) regions. We evaluated the effect of chronic administration of nicotine (4.23 mg/kg/day for 14 days) on NMDA activated currents in dissociated neurons from the PFC, and NAcc (from core and shell regions). We assessed nicotine blood levels by mass spectrophotometry and we confirmed that nicotine increases locomotor activity. An electrophysiological study showed an increase in NMDA currents in neurons from the PFC and core part of the NAcc in animals treated with nicotine compared to those of control rats. No change was observed in neurons from the shell part of the NAcc. The enhanced glutamatergic activity observed in the neurons of rats with chronic administration of nicotine may explain the increased locomotive activity also observed in such rats. To assess one of the possible causes of increased NMDA currents, we used magnesium, to block NMDA receptor that contains the NR2B subunit. If there is a change in percent block of NMDA currents, it means that there is a possible change in expression of NMDA receptor subunits. Our results showed that there is no difference in the blocking effect of magnesium on the NMDA currents. The magnesium lacks of effect after nicotinic treatment suggests that there is no change in expression of NR2B subunit of NMDA receptors, then, the effect of nicotine treatment on amplitude of NMDA currents may be due to an increase in the quantity of receptors or to a change in the unitary conductance, rather than a change in the expression of the subunits that constitute it.

Prophylactic zinc and therapeutic selenium administration in adult rats prevents long-term cognitive and behavioral sequelae by a transient ischemic attack.

The transient hypoxic-ischemic attack, also known as a minor stroke, can result in long-term neurological issues such as memory loss, depression, and anxiety due to an increase in nitrosative stress. The individual or combined administration of chronic prophylactic zinc and therapeutic selenium is known to reduce nitrosative stress in the first seven days post-reperfusion and, due to an antioxidant effect, prevent cell death. Besides, zinc or selenium, individually administered, also causes antidepressant and anxiolytic effects. Therefore, this work evaluated whether combining zinc and selenium could prevent stroke-elicited cognition and behavior deficits after 30 days post-reperfusion. Accordingly, we assessed the expression of growth factors at 7 days post-reperfusion, a four-time course of memory (from 7 to 28 days post-learning test), and cell proliferation, depression, and anxiety-like behavior at 30 days post-reperfusion. Male Wistar rats with a weight between 190 and 240 g) were treated with chronic prophylactic zinc administration with a concentration of 0.2 mg/kg for 15 days before common carotid artery occlusion (10 min) and then with therapeutic selenium (6 µg/kg) for 7 days post-reperfusion. Compared with individual administrations, the administration combined of prophylactic zinc and therapeutic selenium decreased astrogliosis, increased growth factor expression, and improved cell proliferation and survival in two regions, the hippocampus, and cerebral cortex. These effects prevented memory loss, depression, and anxiety-like behaviors. In conclusion, these results demonstrate that the prophylactic zinc administration combined with therapeutic selenium can reduce the long-term sequelae caused by the transient ischemic attack. Significance statement. A minor stroke caused by a transient ischemic attack can result in psychomotor sequelae that affect not only the living conditions of patients and their families but also the economy. The incidence of these micro-events among young people has increased in the world. Nonetheless, there is no deep understanding of how this population group responds to regular treatments (Ekker and et al., 2018) [1]. On the basis that zinc and selenium have antioxidant, anti-inflammatory, and regenerative properties in stroke animal models, our work explored whether the chronic combined administration of prophylactic zinc and therapeutic selenium could prevent neurological sequelae in the long term in a stroke rat model of unilateral common carotid artery occlusion (CCAO) by 10-min. Our results showed that this combined treatment provided a long-term neuroprotective effect by decreasing astrogliosis, memory loss, anxiety, and depression-like behavior.

Peripheral Administration of Tetanus Toxin Hc Fragment Prevents MPP+ Toxicity In Vivo.

Several studies have shown that intrastriatal application of 1-methyl-4-phenylpyridinium (MPP+) produces similar biochemical changes in rat to those seen in Parkinson's disease (PD), such as dopaminergic terminal degeneration and consequent appearance of motor deficits, making the MPP+ lesion a widely used model of parkinsonism in rodents. Previous results from our group have shown a neuroprotective effect of the carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) under different types of stress. In the present study, pretreatment with the intraperitoneal injection of Hc-TeTx in rats prevents the decrease of tyrosine hydroxylase immunoreactivity in the striatum due to injury with MPP+, when applied stereotaxically in the striatum. Similarly, striatal catecholamine contents are restored, as well as the levels of two other dopaminergic markers, the dopamine transporter (DAT) and the vesicular monoamine transporter-2 (VMAT-2). Additionally, uptake studies of [3H]-dopamine and [3H]-MPP+ reveal that DAT action is not affected by Hc-TeTx, discarding a protective effect due to a reduced entry of MPP+ into nerve terminals. Behavioral assessments show that Hc-TeTx pretreatment improves the motor skills (amphetamine-induced rotation, forelimb use, and adjusting steps) of MPP+-treated rats. Our results lead us to consider Hc-TeTx as a potential therapeutic tool in pathologies caused by impairment of dopaminergic innervation in the striatum, as is the case of PD.

Prophylactic Chronic Zinc Administration Increases Neuroinflammation in a Hypoxia-Ischemia Model.

Acute and subacute administration of zinc exert neuroprotective effects in hypoxia-ischemia animal models; yet the effect of chronic administration of zinc still remains unknown. We addressed this issue by injecting zinc at a tolerable dose (0.5 mg/kg weight, i.p.) for 14 days before common carotid artery occlusion (CCAO) in a rat. After CCAO, the level of zinc was measured by atomic absorption spectrophotometry, nitrites were determined by Griess method, lipoperoxidation was measured by Gerard-Monnier assay, and mRNA expression of 84 genes coding for cytokines, chemokines, and their receptors was measured by qRT-PCR, whereas nitrotyrosine, chemokines, and their receptors were assessed by ELISA and histopathological changes in the temporoparietal cortex-hippocampus at different time points. Long-term memory was evaluated using Morris water maze. Following CCAO, a significant increase in nitrosative stress, inflammatory chemokines/receptors, and cell death was observed after 8 h, and a 2.5-fold increase in zinc levels was detected after 7 days. Although CXCL12 and FGF2 protein levels were significantly increased, the long-term memory was impaired 12 days after reperfusion in the Zn+CCAO group. Our data suggest that the chronic administration of zinc at tolerable doses causes nitrosative stress, toxic zinc accumulation, and neuroinflammation, which might account for the neuronal death and cerebral dysfunction after CCAO.

Amyloid-ß(25-35) induces a permanent phosphorylation of HSF-1, but a transitory and inflammation-independent overexpression of Hsp-70 in C6 astrocytoma cells.

Two hallmarks of Alzheimer diseases are the continuous inflammatory process, and the brain deposit of Amyloid b (Aß), a cytotoxic protein. The intracellular accumulation of Aß(25-35) fractions, in the absence of Heat Shock proteins (Hsps), could be responsible for its cytotoxic activity. As, pro-inflammatory mediators and nitric oxide control the expression of Hsps, our aim was to investigate the effect of Aß(25-35) on the concentration of IL-1ß, TNF-α and nitrite levels, and their relation to pHSF-1, Hsp-60, -70 and -90 expressions, in the rat C6 astrocyte cells. Interleukin-specific ELISA kits, immunohistochemistry with monoclonal anti-Hsp and anti pHSF-1 antibodies, and histochemistry techniques, were used. Our results showed that Aß25-35 treatment of C6 cells increased, significantly and consistently the concentration of IL-1ß, TNF-α and nitrite 3 days after initiating treatment. The immunoreactivity of C6 cells to Hsp-70 reached its peak after 3 days of treatment followed by an abrupt decrease, as opposed to Hsp-60 and -90 expressions that showed an initial and progressive increase after 3 days of Aß(25-35) treatment. pHSF-1 was identified throughout the experimental period. Nevertheless, progressive and sustained cell death was observed during all the treatment times and it was not caspase-3 dependent. Our results suggest that Hsp-70 temporary expression serves as a trigger to inhibit casapase-3 pathway and allow the expression of Hsp-60 and -90 in C6 astrocytoma cells stimulated with Aß(25-35).

Alterations in dendritic morphology of the prefrontal cortical and striatum neurons in the unilateral 6-OHDA-rat model of Parkinson's disease.

We have studied the morphological changes of the dendrites of the pyramidal neurons of the prefrontal cortex (PFC) and the medium spiny neurons of the caudate-putamen (CPu) and nucleus accumbens (NAcc) induced by the injection of 6-hydroxydopamine (6-OHDA) into the substantia nigra pars compacta (SNc). The unilateral 6-OHDA-induced lesion of the SNc was made in Wistar rats to produce the Parkinson model lesion. Two weeks after the injection, the testing of rotational behavior caused by amphetamine injection was done to assess the animals with lesions. Four weeks after the 6-OHDA injection, the morphology of the pyramidal cells of Layer 5 of the PFC and the medium spiny neurons of the CPu and NAcc were quantified by modified Golgi-Cox staining. The results showed that the length of dendrites, the branching, and the density of dendritic spines on the medium spiny neurons of the same side of the caudate-putamen lesion were significantly decreased in rats with the unilateral 6-OHDA-induced lesion of the SNc. The pyramidal neurons of the PFC and medium spiny neurons of the NAcc showed a decrease in the density of dendritic spines without significant changes in dendritic length or arborization. Our data suggest that the SNc lesion with the 6-OHDA, Hemiparkinsonism animal model may lead to altered neuronal plasticity in the CPu, NAcc, and PFC that may have participated in the emergence of the behavioral changes observed in these animals.