Kolaviron neuroprotective effect against okadaic acid-provoked cognitive impairment

Alzheimer's disease (AD) is acknowledged as the main causative factor of dementia that affects millions of people around the world and is increasing at increasing pace. Okadaic acid (OA) is a toxic compound with ability to inhibit protein phosphatases and to induce tau protein hyperphosphorylation and Alzheimer's-like phenotype. Kolaviron (KV) is a bioflavonoid derived from Garcinia kola seeds with anti-antioxidative and anti-inflammation properties. The main goal of this study was to assess whether kolaviron can exert neuroprotective effect against okadaic acid-induced cognitive deficit. Rats had an intracerebroventricular (ICV) injection of OA and pretreated with KV at 50 or 100 mg/kg and examined for cognition besides histological and biochemical factors. OA group treated with KV at 100 mg/kg had less memory deficit in passive avoidance and novel object discrimination (NOD) tasks besides lower hippocampal levels of caspases 1 and 3, tumor necrosis factor α (TNFα) and interleukin 6 (IL-6) as inflammatory factors, reactive oxygen species (ROS), protein carbonyl, malondialdehyde (MDA), and phosphorylated tau (p-tau) and higher level of acetylcholinesterase (AChE) activity, mitochondrial integrity index, superoxide dismutase (SOD), and glutathione (GSH). Moreover, KV pretreatment at 100 mg/kg attenuated hippocampal CA1 neuronal loss and glial fibrillary acidic protein (GFAP) reactivity as a factor of astrogliosis. In summary, KV was able to attenuate cognitive fall subsequent to ICV OA which is partly mediated through its neuroprotective potential linked to mitigation of tau hyperphosphorylation, apoptosis, pyroptosis, neuroinflammation, and oxidative stress and also improvement of mitochondrial health.

Effects of prenatal exposure to inflammation coupled with prepubertal stress on prefrontal white matter structure and related molecules in adult mouse offspring

Maternal immune activation (MIA) by inflammatory agents such as lipopolysaccharide (LPS) and prepubertal stress (PS) may individually and collectively affect the central nervous system (CNS) during adulthood. Here, we intended to assess the effects of MIA, alone or combined with PS, on prefrontal white matter structure and its related molecules in adult mice offspring. Pregnant mice received either an i.p. dose of LPS (50 μg/kg) on gestational day 17 (GD17) or normal saline. Their pups were exposed to stress from postnatal days (PD) 30 to PD38 or no stress during prepubertal development. We randomly chose 56-day-old male offspring (n = 2 offspring per mother) from each group and isolated their prefrontal areas according to relevant protocols. The tissue samples were prepared for structural, histological, and molecular examinations. The LPS + stress group had evidence of increased damage in the white matter structures compared to the control, stress, and LPS groups (p < 0.05). The LPS + stress group also had significant downregulation of the genes involved in white matter formation (Sox10, Olig1, myelin regulatory factor, and Wnt compared with the control, stress, and LPS groups (p < 0.05). In conclusion, although each manipulation individually resulted in small changes in myelination, their combined effects were more pronounced. These changes were parallel to abnormal expression levels of the molecular factors that contribute to myelination.

The 40-Hz White Light-Emitting Diode (LED) Improves the Structure-Function of the Brain Mitochondrial KATP Channel and Respiratory Chain Activities in Amyloid Beta Toxicity

It has been described that using noninvasive exposure to 40-Hz white light LED reduces amyloid-beta, a peptide thought to initiate neurotoxic events in Alzheimer's disease (AD). However, the mechanisms remain to be identified. Since AD impairs mitochondrial potassium channels and respiratory chain activity, the objectives of the current study were to determine the effect of 40-Hz white light LED on structure-function of mitoK_ATP channel and brain mitochondrial respiratory chain activity, production of reactive oxygen species (ROS), and ΔΨ_m in AD. Single mitoK_ATP channel was considered using a channel incorporated into the bilayer lipid membrane and expression of mitoK_ATP-Kir6.1 subunit as a pore-forming subunit of the channel was determined using a western blot analysis in Aβ1-42 toxicity and light-treated rats. Our results indicated a severe decrease in mito-K_ATP channel permeation and Kir6.1 subunit expression coming from the Aβ1-42-induced neurotoxicity. Furthermore, we found that Aβ1-42-induced neurotoxicity decreased activities of complexes I and IV and increased ROS production and ΔΨ_m. Surprisingly, light therapy increased channel permeation and mitoK_ATP-Kir6.1 subunit expression. Noninvasive 40-Hz white light LED treatment also increased activities of complexes I and IV and decreased ROS production and ΔΨ_m up to ~ 70%. Here, we report that brain mito-K_ATP channel and respiratory chain are, at least in part, novel targets of 40-Hz white light LED therapy in AD.

Hepatocyte Growth Factor Attenuates the Severity of Status Epilepticus in Kainic Acid-induced Model of Temporal Lobe Epilepsy by Targeting Apoptosis and Astrogliosis

Introduction:

Although pharmacotherapy is the most common treatment for epilepsy, proper seizure control is not achieved with current medications. This study evaluated the protective effects of the Hepatocyte Growth Factor (HGF) in a rat model of Temporal Lobe Epilepsy (TLE) and explored possible molecular mechanisms.

Methods:

A TLE rat model was determined using an intra-hippocampal kainic acid injection (4 μg). Intra-cerebrovascular injection of HGF (6 μg) was performed 30 min before kainic acid injection. Learning and memory impairment were investigated by behavioral tests. The Enzyme-Linked Immunosorbent (ELISA) was used to determine astrogliosis and DNA fragmentation. Changes in neuronal density and mossy fiber sprouting were evaluated by Nissl and Timm staining, respectively.

Results:

Behavioral assessments indicated that kainate-treated rats presented spontaneous seizures. Moreover, their alternation percentage scores in the Y-Maze test were lower (P<0.001). Likewise, the passive avoidance test confirmed learning disability in Kainate-treated rats (P<0.001). HGF administration reduced the number of spontaneous seizures, alternation percentage score (P<0.001), and cognitive disturbances (P<0.001). The histopathological results also showed that a protected HGF administration contributed to the reduction of neuronal loss in the CA3 subregion of the hippocampus and inhibited the formation of aberrant Mossy Fiber Sprouting (MFS) (P<0.01). Furthermore, the ELISA data indicated a significant decrease in GFAP (P<0.01) and DNA fragmentation (P<0.05) following HGF administration.

Conclusion:

Our findings demonstrated the validity of HGF in protection against the progression of the kainate-induced TLE in rats. This measure improved learning, cognitive disturbances and inhibited apoptosis and astrogliosis.

Highlights

Plain Language Summary

Epilepsy is known as a disorder of the CNS which is caused by an imbalance in the electrical activity of neurons that in turn results in derangement in cognitive or causing debilitating seizures. Hepatocyte growth factor is one of neurotrophins secreted from mesenchymal and epithelial cells that regulate the growth, survival and functional changes of cells through signaling pathways such as the tyrosine kinase pathway after binding to its specific receptor. In this study, we tried to find out the effect of hepatocyte growth factor on attenuation of the severity of status epilepticus in kainic acid-induced model of temporal lobe epilepsy. Our results show that hepatocyte growth factor is able to protect against progression of the kainate-induced temporal lobe epilepsy in rats by improvement of learning, cognitive disturbances and inhibiting of apoptosis and astrogliosis.

Intranasal insulin improves the structure-function of the brain mitochondrial ATP-sensitive Ca2+ activated potassium channel and respiratory chain activities under diabetic conditions

Although it is well established that diabetes impairs mitochondrial respiratory chain activity, little is known of the effects of intranasal insulin (INI) on the mitochondrial respiratory chain and structure-function of mitoBKCa channel in diabetes. We have investigated this mechanism in an STZ-induced early type 2 diabetic model. Single ATP-sensitive mitoBKCa channel activity was considered in diabetic and INI-treated rats using a channel incorporated into the bilayer lipid membrane. Because mitoBKCa channels have been involved in mitochondrial respiratory chain activity, a study was undertaken to investigate whether the NADH, complexes I and IV, mitochondrial ROS production, and ΔΨm are altered in an early diabetic model. In this work, we provide evidence for a significant decrease in channel open probability and conductance in diabetic rats. Evidence has been shown that BKCa channel β2 subunits induce a left shift in the BKCa channel voltage dependent curve in low Ca2+ conditions,; our results indicated a significant decrease in mitoBKCa β2 subunits using Western blot analysis. Importantly, INI treatment improved mitoBKCa channel behaviors and β2 subunits expression up to ~70%. We found that early diabetes decreased activities of complex I and IV and increased NADH, ROS production, and ΔΨm. Surprisingly, INI modified the mitochondrial respiratory chain, ROS production, and ΔΨm up to ~70%. Our results thus demonstrate an INI improvement in respiratory chain activity and ROS production in brain mitochondrial preparations coming from the STZ early diabetic rat model, an effect potentially linked to INI improvement in mitoBKCa channel activity and channel β2 subunit expression.

Differential Effect of Amyloid Beta1-40 on Short-term and Long-term Plasticity in Dentate Gyrus of a Rat Model of Alzheimer Disease

Introduction:

Synaptic plasticity is inappropriately affected by neurodegenerative diseases, including Alzheimer Disease (AD). In this study, we examined the effect of intrahippocampal amyloid-beta (Aβ1-40) on dentate gyrus Long-term Potentiation (LTP) and presynaptic short-term plasticity in a rat model of AD.

Methods:

The experimental groups in this research included the control with no treatment, sham-operated receiving the vehicle (normal saline), and Aβ-lesioned groups. For modeling AD, aggregated Aβ1-40 (10 μg/2 μl on each side) was injected into the hippocampal CA1. Three weeks later, Population Spike (PS) amplitude and slope ratios were determined at different Inter-pulse Intervals (IPI) of 10, 20, 30, and 50 ms as a valid indicator of the short-term presynaptic facilitation and/or depression. In addition, PS amplitude and slope were taken as an index of long-term synaptic plasticity after application of High-frequency Stimulation (HFS) to induce LTP in the medial perforant-dentate gyrus pathway.

Results:

No significant differences were noted amongst the experimental groups regarding fEPSP slope and paired-pulse indices as indicators of short-term plasticity. In contrast, fEPSP slope and PS amplitude significantly decreased following the application of HFS in Aβ-injected group. In addition, there was no significant difference between the control and sham-operated groups regarding the mentioned parameters.

Conclusion:

Findings of this study clearly demonstrated that microinjection of Aβ1-40 into the CA1 could impair LTP in dentate gyrus but could not modify short-term plasticity.

Ellagic acid ameliorates neuroinflammation and demyelination in experimental autoimmune encephalomyelitis: Involvement of NLRP3 and pyroptosis

Multiple sclerosis (MS) is presented as the most common autoimmune and demyelinating neurological disorder with incapacitating complications and with no definite therapy. Most treatments for MS mainly focus on attenuation of its severity and recurrence. To model MS reliably to study pathogenesis and efficacy of possible chemicals, experimental autoimmune encephalomyelitis (EAE) condition is induced in rodents. Ellagic acid is a neuroprotective polyphenol that can protect against demyelination. This study was planned and conducted to assess its possible beneficial effect in MOG-induced EAE model of MS with emphasis on uncovering its modes of action. Ellagic acid was given p.o. (at doses of 10 or 50 mg/kg/day) after development of clinical signs of MS to C57BL/6 mice immunized with MOG_35-55. Results showed that ellagic acid can ameliorate severity of the disease and partially restore tissue level of TNFα, IL-6, IL-17A and IL-10. Besides, ellagic acid lowered tissue levels of NLRP3 and caspase 1 in addition to its mitigation of neuroinflammation, demyelination and axonal damage in spinal cord specimens of EAE group. As well, ellagic acid treatment prevented reduction of MBP and decreased GFAP and Iba1 immunoreactivity. Taken together, ellagic acid can decrease severity of EAE via amelioration of astrogliosis, astrocyte activation, demyelination, neuroinflammation and axonal damage that is partly related to its effects on NLRP3 inflammasome and pyroptotic pathway.

Long-term administration of intranasal insulin improves peripheral glucose concentration in diabetic male rats

Introduction: Experiments in rodents and humans suggest that short-term intranasal insulin administration, which is known to reach the brain, does not affect peripheral glucose concentration under diabetic conditions. Methods: In this work, we provide evidence for the effect of intranasal insulin (10 IU/rat/day for 3 or 10 days) on serum insulin and glucose in streptozotocin-diabetic male rats using insulin measurements in the brain and periphery and a serum glucose assay 18 hours after three or ten days of nasal insulin administration. Results: Our findings revealed peripheral insulin increased and glucose level decreased in the diabetic male rats. Based on insulin kinetics, it seems that brain insulin directly or indirectly regulates serum insulin and glucose metabolism under diabetic conditions. Conclusion: Our results may suggest an insight into the therapeutic benefits of nasal insulin in diabetes.

A new brain mitochondrial sodium-sensitive potassium channel: effect of sodium ions on respiratory chain activity

We have determined the electropharmacological properties of a new potassium channel from brain mitochondrial membrane using a planar lipid bilayer method. Our results show the presence of a channel with a conductance of 150 pS at potentials between 0 and -60 mV in 200 mM cis/50 mM trans KCl solutions. The channel was voltage independent, with an open probability value of approximately 0.6 at different voltages. ATP did not affect current amplitude or open probability at positive and negative voltages. Notably, adding iberiotoxin, charybdotoxin, lidocaine or margatoxin had no effect on the channel behavior. Similarly, no changes were observed by decreasing the cis pH to 6. Interestingly, the channel was inhibited by adding sodium in a dose-dependent manner. Our results also indicated a significant increase in mitochondrial complex IV activity and membrane potential and a decrease in complex I activity and mitochondrial ROS production in the presence of sodium ions. We propose that inhibition of mitochondrial potassium transport by sodium ions on potassium channel opening could be important for cell protection and ATP synthesis.

Neuroprotective and anticonvulsant effects of sinomenine in kainate rat model of temporal lobe epilepsy: Involvement of oxidative stress, inflammation and pyroptosis

Oxidative stress, inflammation and pyroptosis are three of the most important mechanisms in the pathophysiology of temporal lobe epilepsy (TLE). Most people with TLE are refractory to the existing drugs. Sinomenine has shown neuroprotective effects through counteracting oxidative stress, inflammation and pyroptosis. In this study, we evaluated the effect of sinomenine on seizure behavior, oxidative stress, inflammation and pyroptosis markers in addition to its neuroprotective potential in intrahippocampal kainate-induced rat model of TLE. For this purpose, male rats (n = 60) were randomly divided into five groups, i.e., sham, kainate (lesion) with an intrahippocampal injection of kainate, kainate groups receiving sinomenine at doses of 30 or 50 mg/kg, and kainate group receiving valproic acid at a dose of 200 mg/kg (as the positive control). Our obtained data showed that sinomenine administration at a dose of 50 mg/kg can significantly decreases severity of seizures and incidence of status epilepticus (SE), hippocampal aberrant MFS and DNA fragmentation and prevents reduction of neuronal density. It also significantly restored level of ROS, MDA, HO-1 and SOD but its effect on GSH level was not significant. Additionally, sinomenine at a dose of 50 mg/kg partially counteracted the increase of NF-κB, TLR 4, TNFα, GFAP and caspase 1. These results suggest that sinomenine has anticonvulsant and neuroprotective effects by reducing hippocampal oxidative stress, inflammation, pyroptosis and apoptosis in intrahippocampal kainate model of TLE.

The effects simultaneous inhibition of dipeptidyl peptidase-4 and P2X7 purinoceptors in an in vivo Parkinson's disease model

Loss of dopaminergic neurons following Parkinson's disease (PD) diminishes quality of life in patients. The present study was carried out to investigate the protective effects of simultaneous inhibition of dipeptidyl peptidase-4 (DPP-4) and P2X7 purinoceptors in a PD model and explore possible mechanisms. The 6-hydroxydopamine (6-OHDA) was used as a tool to establish PD model in male Wister rats. The expressions of SIRT1, SIRT3, mTOR, PGC-1α, PTEN, P53 and DNA fragmentation were evaluated by ELISA assay. Behavioral impairments were determined using apomorphine-induced rotational and narrow beam tests. Dopamine synthesis and TH-positive neurons were detected by tyrosine hydroxylase (TH) immunohistochemistry. Neuronal density was determined by Nissl staining. OHDA-lesioned rats exhibited behavioral impairments that reversed by BBG, lin and lin + BBG. We found significant reduced levels of SIRT1, SIRT3, PGC-1α and mTOR in both mid brain and striatum from OHDA-lesioned rats that reversed by BBG, lin and lin + BBG. Likewise, significant increased levels of PTEN and P53 were found in both mid brain and striatum from OHDA-lesioned rats that was reversed by BBG, lin and lin + BBG. TH-positive neurons and neuronal density were markedly reduced OHDA-lesioned rats that reversed by BBG, lin and lin + BBG. Collectively, our results showed protective effects of simultaneous inhibition of DPP-4 and P2X7 purinoceptors in a rat model of PD can be linked to targeting SIRT1/SIRT3, PTEN-mTOR pathways. Moreover, our findings demonstrated that simultaneous inhibition of DPP-4 and P2X7 purinoceptors might have stronger effect on mitochondrial biogenesis compared to only one.

Trigonelline protects hippocampus against intracerebral Aβ(1-40) as a model of Alzheimer's disease in the rat: insights into underlying mechanisms

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common phenotype of dementia. Trigonelline is an alkaloid found in medicinal plants such as fenugreek seeds and coffee beans with neuroprotective potential and according to existing evidences, a favorable agent for treatment of neurodegenerative disorders. In this study, the possible protective effect of trigonelline against intracerebral Aβ(1-40) as a model of AD in the rat was investigated. For induction of AD, aggregated A(1-40) (10 μg/2 휇l for each side) was bilaterally microinjected into the hippocampal CA1 area. Trigonelline was administered p.o. at a dose of 100 mg/kg. The results showed that trigonelline pretreatment of Aβ-microinjected rats significantly improves spatial recognition memory in Y maze and performance in novel object recognition (NOR) task, mitigates hippocampal malondialdehyde (MDA), protein carbonyl, lactate dehydrogenase (LDH), and improves mitochondrial membrane potential (MMP), glutathione (GSH), and superoxide dismutase (SOD) with no significant change of catalase activity, nitrite level, caspase 3 activity, and DNA fragmentation. Additionally, trigonelline ameliorated hippocampal levels of glial fibrillary acidic protein (GFAP), S100b, cyclooxygenase 2 (Cox2), tumor necrosis factor α (TNFα), and interleukin 6 (IL-6) with no significant alteration of inducible nitric oxide synthase (iNOS). In addition, trigonelline pretreatment prevented loss of hippocampal CA1 neurons in Aβ-microinjected group. Therefore, our results suggest that trigonelline pretreatment in Aβ model of AD could improve cognition and is capable to alleviate neuronal loss through suppressing oxidative stress, astrocyte activity, and inflammation and also through preservation of mitochondrial integrity.

Soy isoflavone genistein attenuates lipopolysaccharide-induced cognitive impairments in the rat via exerting anti-oxidative and anti-inflammatory effects

Systemic inflammation during infectious disorders usually accompanies chronic complications including cognitive dysfunction. Neuroinflammation and cognitive deficit are also observed in some debilitating neurological disorders like Alzheimer's and Parkinson's diseases. Genistein is a soy isoflavone with multiple beneficial effects including anti-inflammatory, anti-oxidative, and protective properties. In this research study, the effect of genistein in prevention of lipopolysaccharide (LPS)-induced cognitive dysfunction was investigated. LPS was given i.p. (500 μg/kg/day) and genistein was orally given (10, 50, or 100 mg/kg) for one week. Findings showed that genistein could dose-dependently attenuate spatial recognition, discrimination, and memory deficits. Additionally, genistein treatment of LPS-challenged group lowered hippocampal level of malondialdehyde (MDA) and increased activity of superoxide dismutase (SOD) and catalase and glutathione (GSH) level. Furthermore, genistein ameliorated hippocampal acetylcholinesterase (AChE) activity in LPS-challenged rats. Furthermore, genistein administration to LPS-injected group lowered hippocampal level of interleukin 6 (IL-6), nuclear factor-kappaB (NF-κB) p65, toll-like receptor 4 (TLR4), tumor necrosis factor α (TNFα), cyclooxygenase-2 (COX2), inducible nitric oxide synthase (iNOS), glial fibrillary acidic protein (GFAP), and increased hippocampal level of antioxidant element nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In conclusion, genistein alleviated LPS-induced cognitive dysfunctions and neural inflammation attenuation of oxidative stress and AChE activity and appropriate modulation of Nrf2/NF-κB/IL-6/TNFα/COX2/iNOS/TLR4/GFAP.

Electro-pharmacological profiles of two brain mitoplast anion channels: Inferences from single channel recording

We have characterized the conduction and blocking properties of two different chloride channels from brain mitochondrial inner membranes after incorporation into planar lipid bilayers. Our experiments revealed the existence of channels with a mean conductance of 158 ± 7 and 301 ± 8 pS in asymmetrical 200 mM cis/50 mM trans KCl solutions. We determined that the channels were ten times more permeable for Cl⁻ than for K⁺, calculated from the reversal potential using the Goldman-Hodgkin-Katz equation. The channels were bell-shaped voltage dependent, with maximum open probability 0.9 at ± 20 mV. Two mitochondrial chloride channels were blocked after the addition of 10 µM DIDS. In addition, 158 pS chloride channel was blocked by 300 nM NPPB, acidic pH and 2.5 mM ATP, whereas the 301 pS chloride channel was blocked by 600 µM NPPB but not by acidic pH or ATP. Gating and conducting behaviors of these channels were unaffected by Ca²⁺. These results demonstrate that the 158 pS anion channel present in brain mitochondrial inner membrane, is probably identical to IMAC and 301 pS Cl channel displays different properties than those classically described for mitochondrial anion channels.

Evidence for a KATP Channel in Rough Endoplasmic Reticulum (rerKATP Channel) of Rat Hepatocytes

We report in a previous study the presence of a large conductance K⁺ channel in the membrane of rough endoplasmic reticulum (RER) from rat hepatocytes incorporated into lipid bilayers. Channel activity in this case was found to decrease in presence of ATP 100 µM on the cytoplasmic side and was totally inhibited at ATP concentrations greater than 0.25 mM. Although such features would be compatible with the presence of a K_ATP channel in the RER, recent data obtained from a brain mitochondrial inner membrane preparation have provided evidence for a Maxi-K channel which could also be blocked by ATP within the mM concentration range. A series of channel incorporation experiments was thus undertaken to determine if the ATP-sensitive channel originally observed in the RER corresponds to K_ATP channel. Our results indicate that the gating and permeation properties of this channel are unaffected by the addition of 800 nM charybdotoxin and 1 µM iberiotoxin, but appeared sensitive to 10 mM TEA and 2.5 mM ATP. Furthermore, adding 100 µM glibenclamide at positive potentials and 400 µM tolbutamide at negative or positive voltages caused a strong inhibition of channel activity. Finally Western blot analyses provided evidence for Kir6.2, SUR1 and/or SUR2B, and SUR2A expression in our RER fractions. It was concluded on the basis of these observations that the channel previously characterized in RER membranes corresponds to K_ATP, suggesting that opening of this channel may enhance Ca²⁺ releases, alter the dynamics of the Ca²⁺ transient and prevent accumulation of Ca²⁺ in the ER during Ca²⁺ overload.