The Protective Effects of Syringic Acid on Bisphenol A-Induced Neurotoxicity Possibly Through AMPK/PGC-1α/Fndc5 and CREB/BDNF Signaling Pathways

Bisphenol A (BPA), an endocrine disruptor, is commonly used to produce epoxy resins and polycarbonate plastics. Continuous exposure to BPA may contribute to the development of diseases in humans and seriously affect their health. Previous research suggests a significant relationship between the increased incidence of neurological diseases and the level of BPA in the living environment. Syringic acid (SA), a natural derivative of gallic acid, has recently considered much attention due to neuromodulator activity and its anti-oxidant, anti-apoptotic, and anti-inflammatory effects. Therefore, in this study, we aimed to investigate the effects of SA on oxidative stress, apoptosis, memory and locomotor disorders, and mitochondrial function, and to identify the mechanisms related to Alzheimer's disease (AD) in the brain of rats receiving high doses of BPA. For this purpose, male Wistar rats received BPA (50, 100, and 200 mg/kg) and SA (50 mg/kg) for 21 days. The results showed that BPA exposure significantly altered the rats' neurobehavioral responses. Additionally, BPA, by increasing the level of ROS, and MDA level, increased the level of oxidative stress while reducing the level of antioxidant enzymes, such as SOD, CAT, GPx, and mitochondrial GSH. The administration of BPA at 200 mg/kg significantly decreased the expression of ERRα, TFAM, irisin, PGC-1α, Bcl-2, and FNDC5, while it increased the expression of TrkB, cytochrome C, caspase 3, and Bax. Moreover, the Western blotting results showed that BPA increased the levels of P-AMPK, GSK3b, p-tau, and Aβ, while it decreased the levels of PKA, P-PKA, Akt, BDNF, CREB, P-CREB, and PI3K. Meanwhile, SA at 50 mg/kg reversed the behavioral, biochemical, and molecular changes induced by high doses of BPA. Overall, BPA could lead to the development of AD by affecting the mitochondria-dependent apoptosis pathway, as well as AMPK/PGC-1α/FNDC5 and CREB/BDNF/TrkB signaling pathways, and finally, by increasing the expression of tau and Aβ proteins. In conclusion, SA, as an antioxidant, significantly reduced the toxicity of BPA.

Neuroprotective properties of Betulin, Betulinic acid, and Ursolic acid as triterpenoids derivatives: a comprehensive review of mechanistic studies

Cognitive deficits are the main outcome of neurological disorders whose occurrence has risen over the past three decades. Although there are some pharmacologic approaches approved for managing neurological disorders, it remains largely ineffective. Hence, exploring novel nature-based nutraceuticals is a pressing need to alleviate the results of neurodegenerative diseases, such as Alzheimer's disease (AD) and other neurodegenerative disorders. Some triterpenoids and their derivates can be considered potential therapeutics against neurological disorders due to their neuroprotective and cognitive-improving effects. Betulin (B), betulinic acid (BA), and ursolic acid (UA) are pentacyclic triterpenoid compounds with a variety of biological activities, including antioxidative, neuroprotective and anti-inflammatory properties. This review focuses on the therapeutic efficacy and probable molecular mechanisms of triterpenoids in damage prevention to neurons and restoring cognition in neurodegenerative diseases. Considering few studies on this concept, the precise mechanisms that mediate the effect of these compounds in neurodegenerative disorders have remained unknown. The findings can provide sufficient information about the advantages of these compounds against neurodegenerative diseases.

Curcumin attenuates memory impairments and long-term potentiation deficits by damping hippocampal inflammatory cytokines in lipopolysaccharide-challenged rats

Neuroinflammation is a key pathological event triggering neurodegenerative process, resulting in neurologic sequelae. Curcumin (cur) has recently received increasing attention due to its anti-inflammatory properties. Therefore, we investigated the protective effects of curcumin on lipopolysaccharide (LPS)-induced memory impairments, long-term potentiation (LTP) deficits, hippocampal inflammatory cytokines, and neuronal loss in male rats. Rats were randomly divided into four groups as follows: (1) Vehicle; (2) cur; (3) LPS; and (4) cur/LPS. Following curcumin pretreatment (50 mg/kg, per oral via gavage, 14 consecutive days), animals received a single dose of LPS (1 mg/kg, intraperitoneally) or saline. Twenty-four hours after LPS/or saline administration, passive avoidance test (PAT), hippocampal LTP, inflammatory cytokines (TNFα, IL-1β), and neuronal loss were assessed in hippocampal tissue of rats. Our results indicated that pretreatment with curcumin in LPS-challenged rats attenuates memory impairment in PAT, which was accompanied by significant increase in the field excitatory post-synaptic potential (fEPSP) slope and population spike (PS) amplitude. Hence, pretreatment with curcumin in LPS-treated rats decreased hippocampal concentration of tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β), as well as reduced neuronal loss in the hippocampal tissue. This study provide evidence that pretreatment with curcumin attenuates LPS-induced memory impairment and LTP deficiency, which may be partly related to the amelioration of inflammatory cytokines and neuronal loss in the hippocampal tissue.

Sesamin alleviates defects in seizure, behavioral symptoms, and hippocampus electroencephalogram in a pentylenetetrazol rat model

Objectives

Seizure is a prevalent disorder reflected by powerful and sudden activity of neural networks in the brain that leads to tonic-clonic attacks. These signs may be due to an increase in excitatory/inhibitory neurotransmitters ratio. So, the current experiment aimed to examine the seizure and neurobehavioral parameters, as well as the hippocampus local electroencephalogram (EEG) after seizure with and without sesamin pretreatment.

Materials and Methods

Sesamin (15, 30, and 60 mg/kg/5 ml, intraperitoneal or IP, vehicle: dimethyl sulfoxide or DMSO, for 3 days) was administrated before pentylenetetrazol (PTZ) (60 mg/kg/10 ml, IP, vehicle: saline), which induces acute seizure in adult male Wistar rats (230 ± 20 g, six weeks old). Different phases of seizures (score, latency, duration, and frequency), behavioral parameters (passive avoidance memory, anxiety, and locomotor activity), and hippocampus local EEG were evaluated after the injections. At the end of the experiments, oxidative stress markers plus gene expression of phosphoinositide 3-kinase/protein kinase B or PI3K/Akt mRNA were measured in the hippocampus.

Results

Pretreatment with sesamin (30 mg/kg) could significantly decrease seizure scores and oxidative stress in the hippocampus. PTZ injection induced EEG deficits and neurobehavioral impairments which were significantly decreased by sesamin, especially in Beta, Theta, and delta EEG waves. Also, the expression of PI3K/Akt significantly increased in the sesamin (30 mg/kg) group in comparison with the PTZ group.

Conclusion

Sesamin could prevent seizure attacks and neurobehavioral and EEG deficits induced by pentylenetetrazol, probably through the PI3K/Akt signaling pathway.

Protective Effects of Co-administration of Zinc and Selenium Against Streptozotocin-Induced Alzheimer's Disease: Behavioral, Mitochondrial Oxidative Stress, and GPR39 Expression Alterations in Rats

Changes in the concentrations of trace metals such as zinc (Zn) and selenium (Se) can pathologically lead to neurodegenerative conditions such as the Alzheimer's disease (AD). Previous studies have shown that mitochondrial dysfunction plays an important role in the pathogenesis of AD. Several male Wistar rats were randomly divided into five groups: sham group, AD group that received 3 mg/kg of streptozotocin (STZ) intracerebroventricularly, AD + Zn group that received 10 mg/kg of Zn intraperitoneally (i.p.) for 1 week, AD + Se group that received 0.1 mg/kg of Se i.p. for 1 week, and AD + Zn + Se group that received 10 mg/kg of Zn i.p. plus 0.1 mg/kg of Se i.p. for 1 week. At end of the study, behavioral tests and mitochondrial oxidative stress and GPR39 gene expression evaluations were carried out. Co-administration of Zn and Se significantly decreased the potential collapse of mitochondrial membrane, reactive oxygen species levels, and lipid peroxidation levels while significantly increased cognitive performance, superoxide dismutase (SOD), glutathione peroxidase, and catalase activity in the brain mitochondria compared with the STZ group. In addition, no significant changes were observed in GPR39 expression in the co-treated group. Findings of the current study showed that ZnR/GPR39 receptor, mitochondrial dysfunction, and oxidative stress play important roles in the pathogenesis of AD. Co-treatment of Zn and Se improved the cognitive performance, mitochondrial dysfunction, and oxidative stress caused by STZ-induced AD. Therefore, therapeutic approaches to improve mitochondrial function could be effective in preventing the initiation and progression of AD.

The protective effect of betulinic acid on microvascular responsivity and protein expression in alzheimer disease induced by cerebral micro-injection of beta-amyloid and streptozotocin

OBJECTIVE

Alzheimer's disease (AD) is mainly caused by accumulation of β-amyloid (Aβ) in vessels or parenchyma of the brain. Accordingly, natural compounds such as betulinic acid (BA) might improve the AD signs by increase in blood flow and through reduction in amyloid plaques.

METHODS

Intra-hippocampal injection of BA (0.2 and 0.4 μmol/L /10 μL DMSO /rat) was done at intervals of 180 and 10 min before co-microinjection of 0.1 μmol/L Aβ dissolved in PBS (5 μL/rat, hippocampi) and 1.5 mg/kg Streptozotocin dissolved in aCSF (10 μL/rat, lateral ventricles). Cerebro-vascular responsivity tested by Laser Doppler, BBB leakage, Elisa assays of cytokines (TNF-α and IL-10), and Western blot analysis of proteins (BDNF and AchE) in the hippocampus were assessed 1 month after the injections.

RESULTS

Microvascular reaction and BBB function were significantly impaired in AD rats, which were improved via BA pretreatment. BA could increase BDNF expression and decrease cytokine levels in the hippocampus of AD rats (especially 0.1 μmol/L Aβ: 0.4 μmol/L BA); however, no significant changes were detected in the blotting of AchE among the groups.

CONCLUSIONS

Betulinic acid could have a role in AD through protecting microcirculation, alleviating inflammation, and up-regulating BDNF expression which is clearer toward 1:4 molar ratios of Aβ to BA.

The effects of betulinic acid on neurobehavioral activity, electrophysiology and histological changes in an animal model of the Alzheimer's disease

Alzheimer's disease (AD) is a common disorder characterized by aggregation and conversion of amyloid beta (Aβ) monomers to fibrils. Betulinic acid (BA) strongly accelerated this pathway through circumventing the oligomeric intermediate state. BA at doses of 0.2 and 0.4μM/10μl/rat (intra-hippocampal or i.h injection, vehicle: DMSO) was bilaterally administrated 180 and 10min before co-administration of Aβ (0.1μM/5μl/rat, i.h injection, vehicle: PBS) and Streptozotocin (STZ, 1.5mg/kg/10μl/rat, intracerebroventricular or i.c.v. injection, vehicle: aCSF). The behavioral assessments (spatial and passive avoidance memory, anxiety, locomotion, depression, and motor coordination), electrophysiological evaluations (hippocampal long- term potentiation (LTP)) as well as histological changes were evaluated 30days after injections. The indices of spatial and passive avoidance memory, anxiety/depression and LTP records were significantly impaired in AD rats in comparison with the sham. Pretreatment of BA (0.4μM) showed a more significant effect on memory, anxiety, all LTP parameters, and histological damage compared to a low dose in contrast to the AD group. Overall, BA pretreatment was able to prevent AD-induced neurobehavioral and LTP deficits in rats and the best effect was observed in molar ratio of 1:4 (Aβ to BA).