The present study demonstrates altered topographic distribution and enhanced neuronal expression of major adenosine-metabolizing enzymes, i.e. ecto-5ʹ-nucleotidase (eN) and tissue non-specific ...alkaline phosphatase (TNAP), as well as adenosine receptor subtype A
2A
in the hippocampus and cortex of male rats from early to late adulthood (3, 6, 12 and 15 months old males). The significant effect of age was demonstrated for the increase in the activity and the protein expression of eN and TNAP. At 15-m, enzyme histochemistry demonstrated enhanced expression of eN in synapse-rich hippocampal and cortical layers, whereas the upsurge of TNAP was observed in the hippocampal and cortical neuropil, rather than in cells and layers where two enzymes mostly reside in 3-m old brain. Furthermore, a dichotomy in A
1
R and A
2A
R expression was demonstrated in the cortex and hippocampus from early to late adulthood. Specifically, a decrease in A
1
R and enhancement of A
2A
R expression were demonstrated by immunohistochemistry, the latter being almost exclusively localized in hippocampal pyramidal and cortical superficial cell layers. We did not observe any glial upregulation of A
2A
R, which was common for both advanced age and chronic neurodegeneration. Taken together, the results imply that the adaptative changes in adenosine signaling occurring in neuronal elements early in life may be responsible for the later prominent glial enhancement in A
2A
R-mediated adenosine signaling, and neuroinflammation and neurodegeneration, which are the hallmarks of both advanced age and age-associated neurodegenerative diseases.
D-galactose (d-gal) is broadly used in animal aging studies as its chronic administration mimics learning and memory impairments related to aging in humans. However, within the few studies that ...utilize chronic oral d-gal intake, none of them is focused on alteration in synaptic structure and function. We examined the effects of 6-weeks oral d-gal intake (200 mg/kg and 500 mg/kg, dissolved in tap water) on age-related changes, with emphasis on the prefrontal cortex (PFC) and hippocampus (HIP) of adult male Wistar rats. Memory assessment was followed by histological examination of the PFC and HIP (Nissl staining and Iba-1 immunostaining), while in crude synaptosomal fractions the state of oxidative stress and the expression of proteins involved in glutamatergic signaling was determined. Although applied dosages compromised memory, alterations such as impaired sensory-motor function and aberrant morphology were not detected. In the PFC, analysis of microglia revealed reduction of branching pattern following d-gal intake, in parallel with increased oxidative damage of proteins, lipids and disturbed pro-oxidant antioxidant balance. These changes in the PFC were further accompanied with decreased levels of vesicular glutamate transporter 1, syntaxin-1 and NMDA receptor 2B subunit in both treated groups. Simultaneously, the increased hippocampal oxidative damage of lipids was detected. Results indicate successful provocation of age-related changes following oral d-gal intake, and suggest greater sensitivity of the PFC to d-gal treatment than HIP.
•Chronic oral intake of d-gal dissolved in tap water evoked cognitive impairment.•Absence of PFC and HIP morphological changes.•Microglia was slightly altered in the PFC.•oxidative stress is more pronounced in the PFC than HIP.•NMDA receptor complex components were affected in the PFC, not HIP.
The present study shows that animals with experimental autoimmune encephalomyelitis (EAE) exhibit olfactory dysfunction and impaired general cognitive abilities, as well as anxiety-like behavior. ...Olfactory dysfunction occurs on average at 2 dpi, well before the onset of the first motor signs of EAE (8–10 dpi). After the initial olfactory dysfunction, the EAE animals show a fluctuation in olfactory performance that resembles the relapsing–remitting course of human MS. The study also shows severe neuroinflammation in the olfactory bulb (OB), with numerous infiltrated CD4 + T cells and peripheral macrophages in the superficial OB layers, marked microgliosis, and massive induction of TNF-α, IL-1β, and IL-6. Reduced tyrosine hydroxylase activity in the glomerular layer, pronounced granule cell atrophy, and reduced numbers of type B neuroblasts in the rostral migratory stream also indicate altered plasticity of the neuronal network in the OB. Considering the exceptionally high purinome expression in the OB, the possible involvement of purinergic signaling was also investigated. The study shows that macrophages infiltrating the OB overexpress A 3 R, while highly reactive microglia overexpress the adenosine-producing enzyme eN/CD73 as well as A 2B R, A 3 R, and P2X 4 R. Given the simultaneous induction of complement component C3, the results suggest that the microglial cells develop a functional phenotype of phagocytizing microglia. The study also demonstrates transcriptional and translational upregulation of A 1 R in mitral and tufted cells, which likely influence resting network activity in OB and likely contribute to olfactory dysfunction in EAE. Overall, our study shows that olfactory dysfunction and altered social and cognitive behavior in EAE are associated with increased adenosine signaling via A 1 R, A 2B R, and A 3 R.
Alprazolam (ALP), a benzodiazepine (BDZ) used to treat anxiety, panic, and sleep disorders, is one of the most prescribed psychotropic drugs worldwide. The side effects associated with long-term ...(mis)use of ALP have become a major challenge in pharmacotherapy, emphasizing the unmet need to further investigate their underlying molecular mechanisms. Prolonged BDZ exposure may induce adaptive changes in the function of several receptors, including the primary target, gammaaminobutyric acid receptor type A (GABA
R), but also other neurotransmitter receptors such as glutamatergic. The present study investigated the potential effects of prolonged ALP treatment on components of glutamatergic neurotransmission, with special emphasis on N-Methyl-D-aspartate receptor (NMDAR) in the hippocampus of adult male Wistar rats. The study revealed behavioral changes consistent with potential onset of tolerance and involvement of the glutamatergic system in its development. Specifically, an increase in NMDAR subunits (NR1, NR2A, NR2B), a decrease in vesicular glutamate transporter 1 (vGlut1), and differential modulation of excitatory amino acid transporters 1 and 2 (EAAT1/2, in vivo and in vitro) were observed, alongside a decrease in α1-containing GABA
R following the treatment. By describing the development of compensatory actions in the glutamatergic system, the present study provides valuable information on neuroadaptive mechanisms following prolonged ALP intake.
Neurodegeneration implies progressive neuronal loss and neuroinflammation further contributing to pathology progression. It is a feature of many neurological disorders, most common being Alzheimer's ...disease (AD). Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive stimulation which modulates excitability of stimulated brain areas through magnetic pulses. Numerous studies indicated beneficial effect of rTMS in several neurological diseases, including AD, however, exact mechanism are yet to be elucidated. We aimed to evaluate the effect of intermittent theta burst stimulation (iTBS), an rTMS paradigm, on behavioral, neurochemical and molecular level in trimethyltin (TMT)-induced Alzheimer's-like disease model. TMT acts as a neurotoxic agent targeting hippocampus causing cognitive impairment and neuroinflammation, replicating behavioral and molecular aspects of AD. Male Wistar rats were divided into four experimental groups-controls, rats subjected to a single dose of TMT (8 mg/kg), TMT rats subjected to iTBS two times per day for 15 days and TMT sham group. After 3 weeks, we examined exploratory behavior and memory, histopathological and changes on molecular level. TMT-treated rats exhibited severe and cognitive deficit. iTBS-treated animals showed improved cognition. iTBS reduced TMT-induced inflammation and increased anti-inflammatory molecules. We examined PI3K/Akt/mTOR signaling pathway which is involved in regulation of apoptosis, cell growth and learning and memory. We found significant downregulation of phosphorylated forms of Akt and mTOR in TMT-intoxicated animals, which were reverted following iTBS stimulation. Application of iTBS produces beneficial effects on cognition in of rats with TMT-induced hippocampal neurodegeneration and that effect could be mediated
PI3K/Akt/mTOR signaling pathway, which could candidate this protocol as a potential therapeutic approach in neurodegenerative diseases such as AD.
Ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2) hydrolyzes extracellular ATP to ADP, which is the ligand for P2Y1,12,13 receptors. The present study describes the distribution of NTPDase2 ...in adult rat brains in physiological conditions, and in hippocampal neurodegeneration induced by trimethyltin (TMT). The study also describes the regulation of NTPDase2 by inflammatory mediators in primary astrocytes and oligodendroglial cell line OLN93. In physiological conditions, NTPDase2 protein was most abundant in the hippocampus, where it was found in fibrous astrocytes and synaptic endings in the synaptic-rich hippocampal layers. In TMT-induced neurodegeneration, NTPDase2-mRNA acutely decreased at 2-dpi and then gradually recovered to the control level at 7-dpi and 21-dpi. As determined by immunohistochemistry and double immunofluorescence, the decrease was most pronounced in the dentate gyrus (DG), where NTPDase2 withdrew from the synaptic boutons in the polymorphic layer of DG, whereas the recovery of the expression was most profound in the subgranular layer. Concerning the regulation of NTPDase2 gene expression, proinflammatory cytokines IL-6, IL-1β, TNFα, and IFNγ negatively regulated the expression of NTPDase2 in OLN93 cells, while did not altering the expression in primary astrocytes. Different cell-intrinsic stressors, such as depletion of intracellular energy store, oxidative stress, endoplasmic reticulum stress, and activation of protein kinase C, also massively disturbed the expression of the NTPDase2 gene. Together, our results suggest that the expression and the activity of NTPDase2 transiently cease in neurodegeneration and brain injury, most likely as a part of the acute adaptive response designed to promote cell defense, survival, and recovery.
Zaleplon is a positive allosteric modulator of the γ-aminobutyric acid (GABA)
receptor approved for the short-term treatment of insomnia. Previous publications on zaleplon have not addressed the ...proteins involved in its mechanism of action but have mostly referred to behavioral or pharmacological studies. Since both GABAergic and glutamatergic signaling have been shown to regulate wakefulness and sleep, we examined the effects of prolonged zaleplon treatment (0.625 mg/kg for 5 days) on these systems in the hippocampus of male Wistar rats. Western blot and immunohistochemical analyses showed that the upregulated components of GABAergic signaling (glutamate decarboxylase, vesicular GABA transporter, GABA, and α1 subunit of the GABA
receptor) were accompanied by increased protein levels in the glutamatergic system (vesicular glutamate transporter 1 and NR1, NR2A, and NR2B subunits of N-methyl-d-aspartate receptor). Our results, showing that zaleplon enhances GABA neurotransmission in the hippocampus, were not surprising. However, we found that treatment also increased glutamatergic signaling. This could be the result of the downregulation of adenosine A1 receptors, important modulators of the glutamatergic system. Further studies are needed to investigate the effects of the zaleplon-induced increase in hippocampal glutamatergic neurotransmission and the possible involvement of the adenosine system in zaleplon's mechanism of action.
Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by the progressive degeneration of the dopaminergic system, leading to a variety of motor and nonmotor ...symptoms. The currently available symptomatic therapy loses efficacy over time, indicating the need for new therapeutic approaches. Repetitive transcranial magnetic stimulation (rTMS) has emerged as one of the potential candidates for PD therapy. Intermittent theta burst stimulation (iTBS), an excitatory protocol of rTMS, has been shown to be beneficial in several animal models of neurodegeneration, including PD. The aim of this study was to investigate the effects of prolonged iTBS on motor performance and behavior and the possible association with changes in the NMDAR subunit composition in the 6-hydroxydopamine (6-OHDA)-induced experimental model of PD. Two-month-old male Wistar rats were divided into four groups: controls, 6-OHDA rats, 6-OHDA + iTBS protocol (two times/day/three weeks) and the sham group. The therapeutic effect of iTBS was evaluated by examining motor coordination, balance, spontaneous forelimb use, exploratory behavior, anxiety-like, depressive/anhedonic-like behavior and short-term memory, histopathological changes and changes at the molecular level. We demonstrated the positive effects of iTBS at both motor and behavioral levels. In addition, the beneficial effects were reflected in reduced degeneration of dopaminergic neurons and a subsequent increase in the level of DA in the caudoputamen. Finally, iTBS altered protein expression and NMDAR subunit composition, suggesting a sustained effect. Applied early in the disease course, the iTBS protocol may be a promising candidate for early-stage PD therapy, affecting motor and nonmotor deficits.
Exposure to the neurotoxin trimethyltin (TMT) selectively induces hippocampal neuronal injury and astrocyte activation accompanied with resultant neuroinflammation, which causes severe behavioral, ...cognitive, and memory impairment. A large body of evidence suggests that flaxseed oil (FSO), as one of the richest sources of essential omega-3 fatty acids, i.e., α-linolenic acids (ALA), displays neuroprotective properties. Here, we report the preventive effects of dietary FSO treatment in a rat model of TMT intoxication. The administration of FSO (1 mL/kg, orally) before and over the course of TMT intoxication (a single dose, 8 mg/kg, i.p.) reduced hippocampal cell death, prevented the activation of astrocytes, and inhibited their polarization toward a pro-inflammatory/neurotoxic phenotype. The underlying protective mechanism was delineated through the selective upregulation of BDNF and PI3K/Akt and the suppression of ERK activation in the hippocampus. Pretreatment with FSO reduced cell death and efficiently suppressed the expression of inflammatory molecules. These beneficial effects were accompanied by an increased intrahippocampal content of n-3 fatty acids. In vitro, ALA pretreatment prevented the TMT-induced polarization of cultured astrocytes towards the pro-inflammatory spectrum. Together, these findings support the beneficial neuroprotective properties of FSO/ALA against TMT-induced neurodegeneration and accompanied inflammation and hint at a promising preventive use of FSO in hippocampal degeneration and dysfunction.
Ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2) hydrolyzes extracellular ATP to ADP, which is the ligand for P2Y 1,12,13 receptors. The present study describes the distribution of ...NTPDase2 in adult rat brains in physiological conditions, and in hippocampal neurodegeneration induced by trimethyltin (TMT). The study also describes the regulation of NTPDase2 by inflammatory mediators in primary astrocytes and oligodendroglial cell line OLN93. In physiological conditions, NTPDase2 protein was most abundant in the hippocampus, where it was found in fibrous astrocytes and synaptic endings in the synaptic-rich hippocampal layers. In TMT-induced neurodegeneration, NTPDase2-mRNA acutely decreased at 2-dpi and then gradually recovered to the control level at 7-dpi and 21-dpi. As determined by immunohistochemistry and double immunofluorescence, the decrease was most pronounced in the dentate gyrus (DG), where NTPDase2 withdrew from the synaptic boutons in the polymorphic layer of DG, whereas the recovery of the expression was most profound in the subgranular layer. Concerning the regulation of NTPDase2 gene expression, proinflammatory cytokines IL-6, IL-1β, TNFα, and IFNγ negatively regulated the expression of NTPDase2 in OLN93 cells, while did not altering the expression in primary astrocytes. Different cell-intrinsic stressors, such as depletion of intracellular energy store, oxidative stress, endoplasmic reticulum stress, and activation of protein kinase C, also massively disturbed the expression of the NTPDase2 gene. Together, our results suggest that the expression and the activity of NTPDase2 transiently cease in neurodegeneration and brain injury, most likely as a part of the acute adaptive response designed to promote cell defense, survival, and recovery.
