Journal: Neurochemical research
This study sought to investigate and compare the interaction of caffeic acid and chlorogenic acid on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and some pro-oxidants (FeSO(4), sodium nitroprusside and quinolinic acid) induced oxidative stress in rat brain in vitro. The result revealed that caffeic acid and chlorogenic acid inhibited AChE and BChE activities in dose-dependent manner; however, caffeic acid had a higher inhibitory effect on AChE and BChE activities than chlorogenic acid. Combination of the phenolic acids inhibited AChE and BChE activities antagonistically. Furthermore, pro-oxidants such as, FeSO(4), sodium nitroprusside and quinolinic acid caused increase in the malondialdehyde (MDA) contents of the brain which was significantly decreased dose-dependently by the phenolic acids. Inhibition of AChE and BChE activities slows down acetylcholine and butyrylcholine breakdown in the brain. Therefore, one possible mechanism through which the phenolic acids exert their neuroprotective properties is by inhibiting AChE and BChE activities as well as preventing oxidative stress-induced neurodegeneration. However, esterification of caffeic acid with quinic acid producing chlorogenic acid affects these neuroprotective properties.
Neuropeptide galanin and its three receptors, galanin receptor type 1-galanin receptor type 3, are known to be involved in the regulation of numerous psychological processes, including depression. Studies have suggested that stimulation of galanin receptor type 2 (GalR2) leads to attenuation of the depression-like behavior in animals. However, due to the lack of highly selective galanin subtype specific ligands the involvement of different receptors in depression-like behavior is yet not fully known. In the present study we introduce a novel GalR2 selective agonist and demonstrate its ability to produce actions consistent with theorized GalR2 functions and analogous to that of the anti-depressant, imipramine.
The cytoskeleton protein Tau present in oligodendrocytes (OLGs) promotes cellular process outgrowth and myelination; whereas abnormally hyperphosphorylated Tau has been shown to be present in the most debilitating form of multiple sclerosis and in selective dementias. This research examined the functional consequences of expressing a truncated form of Tau in OLGs during the second postnatal life. In particular, this truncated form of Tau (∆Tau) retains the Fyn-binding domain but lacks the microtubule-binding domain. Similar to hyperphosphorylated Tau, ∆Tau cannot bind the cytoskeleton and is missorted. The Cre/loxP recombination system was used to generate transgenic (TG) founder lines, which contain a Floxed LacZ-STOP cassette to prevent expression of enhanced green fluorescence protein (EGFP)-∆Tau. The founder lines were then crossed with a Tamoxifen ™-inducible proteolipid protein (PLP)-dependent Cre driver line. Myelin PLP is the major myelin protein in the central nervous system (CNS). TM was given at postnatal day (p) 12 for 3 days, and CNS tissues were collected at p22. Only TG mice with both EGFP-∆Tau and Cre manifested an overt phenotype of loss of balance and stumbles starting around p18. CNS tissues obtained from TM-treated EGFP-∆Tau/Cre double transgenic mice had recombined PCR products, GFP, and diminished brain myelin. GFP was expressed in OLGs, but not in neurons or astrocytes. On the contrary, TM-treated TG mice with only one of the two transgenes, i.e., Cre or Tau, did not have recombinant PCR products, GFP, diminished myelin, or abnormal phenotype. Thus, this inducible model shows for the first time that a non-microtubule-associated Tau protein in OLGs elicits both myelin decrease and gait abnormalities, similar to the occurrence in selective demyelinating and neurodegenerative diseases.
Valproic acid (VPA) is a multi-target drug and an inhibitor of histone deacetylase (HDAC). We have previously demonstrated that prenatal exposure to VPA at embryonic day 12.5 (E12.5), but not at E14.5, causes autism-like behavioral abnormalities in male mouse offspring. We have also found that prenatal VPA exposure causes transient histone hyperacetylation in the embryonic brain, followed by decreased neuronal cell numbers in the prefrontal and somatosensory cortices after birth. In the present study, we examined whether prenatal HDAC inhibition affects neuronal maturation in primary mouse cortical neurons. Pregnant mice were injected intraperitoneally with VPA (500 mg/kg) and the more selective HDAC inhibitor trichostatin A (TSA; 500 µg/kg) at E12.5 or E14.5, and primary neuronal cultures were prepared from the cerebral cortices of their embryos. Prenatal exposure to VPA at E12.5, but not at E14.5, decreased total number, total length, and complexity of neuronal dendrites at 14 days in vitro (DIV). The effects of VPA weakened at 21 DIV. Exposure to TSA at E12.5, but not at E14.5, also delayed maturation of cortical neurons. In addition, real-time quantitative PCR revealed that the prenatal exposure to TSA decreased neuroligin-1 (Nlgn1), Shank2, and Shank3 mRNA levels and increased contactin-associated protein-like 2 mRNA level. The delay in neuronal maturation was also observed in Nlgn1-knockdown cells, which were transfected with Nlgn1 siRNA. These findings suggest that prenatal HDAC inhibition causes changes in gene expression of autism-related molecules linked to a delay of neuronal maturation.
Adult hippocampal neurogenesis plays a pivotal role in learning and memory. The suppression of hippocampal neurogenesis induced by an increase of oxidative stress is closely related to cognitive impairment. Neural stem cells which persist in the adult vertebrate brain keep up the production of neurons over the lifespan. The balance between pro-oxidants and anti-oxidants is important for function and surviving of neural stem cells. Ginsenoside Rg1 is one of the most active components of Panax ginseng, and many studies suggest that ginsenosides have antioxidant properties. This research explored the effects and underlying mechanisms of ginsenoside Rg1 on protecting neural stem cells (NSCs) from oxidative stress. The sub-acute ageing of C57BL/6 mice was induced by subcutaneous injection of D-gal (120 mg kg(-1) day(-1)) for 42 day. On the 14th day of D-gal injection, the mice were treated with ginsenoside Rg1 (20 mg kg(-1) day(-1), intraperitoneally) or normal saline for 28 days. The study monitored the effects of Rg1 on proliferation, senescence-associated and oxidative stress biomarkers, and Akt/mTOR signalling pathway in NSCs. Compared with the D-gal group, Rg1 improved cognitive impairment induced by D-galactose in mice by attenuating senescence of neural stem cells. Rg1 also decreased the level of oxidative stress, with increased the activity of superoxide dismutase and glutathione peroxidase in vivo and in vitro. Rg1 furthermore reduced the phosphorylation levels of protein kinase B (Akt) and the mechanistic target of rapamycin (mTOR) and down-regulated the levels of downstream p53, p16, p21 and Rb in D-gal treated NSCs. The results suggested that the protective effect of ginsenoside Rg1 on attenuating cognitive impairment in mice and senescence of NSCs induced by D-gal might be related to the reduction of oxidative stress and the down-regulation of Akt/mTOR signaling pathway.
The glymphatic system is a recently discovered macroscopic waste clearance system that utilizes a unique system of perivascular tunnels, formed by astroglial cells, to promote efficient elimination of soluble proteins and metabolites from the central nervous system. Besides waste elimination, the glymphatic system also facilitates brain-wide distribution of several compounds, including glucose, lipids, amino acids, growth factors, and neuromodulators. Intriguingly, the glymphatic system function mainly during sleep and is largely disengaged during wakefulness. The biological need for sleep across all species may therefore reflect that the brain must enter a state of activity that enables elimination of potentially neurotoxic waste products, including β-amyloid. Since the concept of the glymphatic system is relatively new, we will here review its basic structural elements, organization, regulation, and functions. We will also discuss recent studies indicating that glymphatic function is suppressed in various diseases and that failure of glymphatic function in turn might contribute to pathology in neurodegenerative disorders, traumatic brain injury and stroke.
No major advances have been made in improving overall survival for glioblastoma (GBM) in almost 100 years. The current standard of care (SOC) for GBM involves immediate surgical resection followed by radiotherapy with concomitant temozolomide chemotherapy. Corticosteroid (dexamethasone) is often prescribed to GBM patients to reduce tumor edema and inflammation. The SOC disrupts the glutamate-glutamine cycle thus increasing availability of glucose and glutamine in the tumor microenvironment. Glucose and glutamine are the prime fermentable fuels that underlie therapy resistance and drive GBM growth through substrate level phosphorylation in the cytoplasm and the mitochondria, respectively. Emerging evidence indicates that ketogenic metabolic therapy (KMT) can reduce glucose availability while elevating ketone bodies that are neuroprotective and non-fermentable. Information is presented from preclinical and case report studies showing how KMT could target tumor cells without causing neurochemical damage thus improving progression free and overall survival for patients with GBM.
Developing cellular models of sporadic Alzheimer’s disease (sAD) is challenging due to the unknown initiator of disease onset and the slow disease progression that takes many years to develop in vivo. The use of human induced pluripotent stem cells (iPSCs) has revolutionised the opportunities to model AD pathology, investigate disease mechanisms and screen potential drugs. The majority of this work has, however, used cells derived from patients with familial AD (fAD) where specific genetic mutations drive disease onset. While these provide excellent models to investigate the downstream pathways involved in neuronal toxicity and ultimately neuronal death that leads to AD, they provide little insight into the causes and mechanisms driving the development of sAD. In this review we compare the data obtained from fAD and sAD iPSC-derived cell lines, identify the inconsistencies that exist in sAD models and highlight the potential role of Aβ clearance mechanisms, a relatively under-investigated area in iPSC-derived models, in the study of AD. We discuss the development of more physiologically relevant models using co-culture and three-dimensional culture of iPSC-derived neurons with glial cells. Finally, we evaluate whether we can develop better, more consistent models for sAD research using genetic stratification of iPSCs and identification of genetic and environmental risk factors that could be used to initiate disease onset for modelling sAD. These considerations provide exciting opportunities to develop more relevant iPSC models of sAD which can help drive our understanding of disease mechanisms and identify new therapeutic targets.
Here we demonstrate for the first time that cannabidiol (CBD) acts to protect synaptic plasticity in an in vitro model of Alzheimer’s disease (AD). The non-psycho active component of Cannabis sativa, CBD has previously been shown to protect against the neurotoxic effects of beta amyloid peptide (Aβ) in cell culture and cognitive behavioural models of neurodegeneration. Hippocampal long-term potentiation (LTP) is an activity dependent increase in synaptic efficacy often used to study cellular mechanisms related to memory. Here we show that acute application of soluble oligomeric beta amyloid peptide (Aβ1-42) associated with AD, attenuates LTP in the CA1region of hippocampal slices from C57Bl/6 mice. Application of CBD alone did not alter LTP, however pre-treatment of slices with CBD rescued the Aβ1-42mediated deficit in LTP. We found that the neuroprotective effects of CBD were not reversed by WAY100635, ZM241385 or AM251, demonstrating a lack of involvement of 5HT1A, adenosine (A2A) or Cannabinoid type 1 (CB1) receptors respectively. However in the presence of the PPARγ antagonist GW9662 the neuroprotective effect of CBD was prevented. Our data suggests that this major component of Cannabis sativa, which lacks psychoactivity may have therapeutic potential for the treatment of AD.
Peroxisome proliferator activated receptor alpha (PPAR-α) belongs to the family of ligand-regulated nuclear receptors (PPARs). These receptors after heterodimerization with retinoid X receptor (RXR) bind in promotor of target genes to PPAR response elements (PPREs) and act as a potent transcription factors. PPAR-α and other receptors from this family, such as PPAR-β/δ and PPAR-γ are expressed in the brain and other organs and play a significant role in oxidative stress, energy homeostasis, mitochondrial fatty acids metabolism and inflammation. PPAR-α takes part in regulation of genes coding proteins that are involved in glutamate homeostasis and cholinergic/dopaminergic signaling in the brain. Moreover, PPAR-α regulates expression of genes coding enzymes engaged in amyloid precursor protein (APP) metabolism. It activates gene coding of α secretase, which is responsible for non-amyloidogenic pathway of APP degradation. It also down regulates β secretase (BACE-1), the main enzyme responsible for amyloid beta (Aβ) peptide release in Alzheimer Diseases (AD). In AD brain expression of genes of PPAR-α and PPAR-γ coactivator-1 alpha (PGC-1α) is significantly decreased. PPARs are altered not only in AD but in other neurodegenerative/neurodevelopmental and psychiatric disorder. PPAR-α downregulation may decrease anti-oxidative and anti-inflammatory processes and could be responsible for the alteration of fatty acid transport, lipid metabolism and disturbances of mitochondria function in the brain of AD patients. Specific activators of PPAR-α may be important for improvement of brain cells metabolism and cognitive function in neurodegenerative and neurodevelopmental disorders.