Ethics committee meeting by video-conferencing during Covid-19

The Covid-19 pandemic has created a situation demanding rapid ethical review of research on various aspects of the pandemic, while maintaining social distancing norms. Research during an outbreak is important for understanding the disease and its management and allows scientists to study the disease in situ.

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Correction to: Endoplasmic Reticulum Stress Plays a Key Role in Rotenone-Induced Apoptotic Death of Neurons

The original version of this article unfortunately contained a mistake.

Intranasal Insulin Administration Ameliorates Streptozotocin (ICV)-Induced Insulin Receptor Dysfunction, Neuroinflammation, Amyloidogenesis, and Memory Impairment in Rats

Alzheimer's disease (AD) is associated with reduced insulin level and impairment of insulin receptor (IR) signaling in the brain, which correlates to amyloid pathology, neuroinflammation, and synaptic neurotoxicity. Clinical studies show that intranasal insulin improves memory in AD patients without peripheral hypoglycemia. However, neuroprotective molecular mechanism of the beneficial effect of intranasal insulin in AD pathology is unexplored. Therefore, we investigated the role of intranasal insulin on intracerebroventricular (ICV) streptozotocin (STZ)-induced memory impairment in rats as evaluated in the Morris water maze test. STZ (ICV) treated rats had shown memory impairment along with a significant decrease in IR signaling molecules (IR, pIRS-1, pAkt, and pGSK-3α/β expression) and IDE expression in both hippocampus and cerebral cortex. Intranasal insulin delivery prevented these changes. Moreover, intranasal insulin was found to inhibit significantly glial cell activation (GFAP and Iba-1 expression), neuroinflammation (COX-2 expression, NFκB translocation, TNF-α, and IL-10 level) and amyloidogenic protein expression (BACE-1 and Aβ_1-42 expression) in STZ (ICV)-injected rats. STZ (ICV)-induced caspase activation and postsynaptic neurotoxicity were also prevented by treatment with intranasal insulin. Our findings reveal that insulin has the neuroprotective effect and clearly signifies the potential use of intranasal insulin delivery for the treatment of AD. Graphical Abstract Neuroprotective effects of intranasal insulin administration on streptozotocin (ICV)-induced memory impairment in rats.

Interpretation of alpha-fetoprotein concentrations in cerebrospinal fluid of infants

Background: There are no published reference intervals for concentrations of alpha-fetoprotein (AFP) in the cerebrospinal fluid (CSF) of normal infants. The presence of abnormal concentrations of AFP in plasma or CSF may indicate the presence of a teratoma or a germ cell tumour with yolk sac elements. We measured CSF AFP in infants who did not have malignancy in order to determine its reference intervals.

Methods: AFP was measured in the CSF and/or plasma in 128 infants. Of these, 91 infants had CSF AFP measurements, 94 infants had plasma AFP measurements and in 60 infants AFP concentrations were determined in paired CSF and plasma samples. The patients ranged in age from 1 to 110 days. Both CSF and plasma AFP concentrations were measured by a microparticle enzyme immunoassay using an AxSYM analyser.

Results: Using ages corrected for prematurity, the median CSF AFP concentration for babies -69 to 31 days old was 61 kIU/L (5th-95th centile: 2-889 kIU/L), while the median CSF AFP concentration for infants 32 to 110 days was 1.2 kIU/L (5th-95th centile: 0.1-12.5 kIU/L). By age 6 weeks, the concentrations were close to those found in adult plasma and all CSF AFP concentrations from infants with a corrected age over 2 months were <3 kIU/L.

Conclusion: We have defined reference intervals for CSF AFP concentrations in infants. These results may assist in the diagnosis of CNS tumours, particularly congenital CNS tumours containing yolk sac elements.

Perindopril Attenuates Lipopolysaccharide-Induced Amyloidogenesis and Memory Impairment by Suppression of Oxidative Stress and RAGE Activation

Clinical and preclinical studies account hypertension as a risk factor for dementia. We reported earlier that angiotensin-converting enzyme (ACE) inhibition attenuated the increased vulnerability to neurodegeneration in hypertension and prevented lipopolysaccharide (LPS)-induced memory impairment in normotensive wistar rats (NWRs) and spontaneously hypertensive rats (SHRs). Recently, a receptor for advanced glycation end products (RAGE) has been reported to induce amyloid beta (Aβ1-42) deposition and memory impairment in hypertensive animals. However, the involvement of ACE in RAGE activation and amyloidogenesis in the hypertensive state is still unexplored. Therefore, in this study, we investigated the role of ACE on RAGE activation and amyloidogenesis in memory-impaired NWRs and SHRs. Memory impairment was induced by repeated (on days 1, 4, 7, and 10) intracerebroventricular (ICV) injections of LPS in SHRs (25 μg) and NWRs (50 μg). Our data showed that SHRs exhibited increased oxidative stress (increased gp91-phox/NOX-2 expression and ROS generation), RAGE, and β-secretase (BACE) expression without Aβ1-42 deposition. LPS (25 μg, ICV) further amplified oxidative stress, RAGE, and BACE activation, culminating in Aβ1-42 deposition and memory impairment in SHRs. Similar changes were observed at the higher dose of LPS (50 μg, ICV) in NWRs. Further, LPS-induced oxidative stress was associated with endothelial dysfunction and reduction in cerebral blood flow (CBF), more prominently in SHRs than in NWRs. Finally, we showed that perindopril (0.1 mg/kg, 15 days) prevented memory impairment by reducing oxidative stress, RAGE activation, amyloidogenesis, and improved CBF in both SHRs and NWRs. These findings suggest that perindopril might be used as a therapeutic strategy for the early stage of dementia.

Evaluation of melatonin levels in saliva in gingivitis and periodontitis cases: A pilot study

Objective:

To evaluate the melatonin levels in saliva in gingivitis and periodontitis cases.

Background:

Melatonin has strong antioxidant, free radical scavenging, and immunomodulating properties, acts on osteoblasts directly to stimulate cell proliferation and synthesis of Type I collagen, and promotes bone formation.

Materials and Methods:

A total of thirty participants were selected and divided into three groups (control group, gingivitis group, and periodontitis group). In each group, ten participants were taken. Salivary melatonin was estimated in each of the three groups.

Results:

Results from this study showed that the mean levels of salivary melatonin increased as severity increased from control to periodontitis, i.e., the mean levels were highest in periodontitis followed by gingivitis and least in control group. The melatonin level of all participants was positively and significantly (P < 0.01) correlated with their gingival index (r = 0.85, P < 0.01) and probing depth (r = 0.72, P < 0.01).

Conclusion:

Salivary melatonin level varied with the severity of gingivitis and periodontitis. With increased severity of periodontal disease, the level of salivary melatonin also increased suggesting that salivary melatonin may act as a diagnostic biomarker for periodontal diseases.

Inhibitory Effect of Memantine on Streptozotocin-Induced Insulin Receptor Dysfunction, Neuroinflammation, Amyloidogenesis, and Neurotrophic Factor Decline in Astrocytes

Our earlier studies showed that insulin receptor (IR) dysfunction along with neuroinflammation and amyloidogenesis played a major role in streptozotocin (STZ)-induced toxicity in astrocytes. N-methyl-D-aspartate (NMDA) receptor antagonist-memantine shows beneficial effects in Alzheimer's disease (AD) pathology. However, the protective molecular and cellular mechanism of memantine in astrocytes is not properly understood. Therefore, the present study was undertaken to investigate the effect of memantine on insulin receptors, neurotrophic factors, neuroinflammation, and amyloidogenesis in STZ-treated astrocytes. STZ (100 μM) treatment for 24 h in astrocytes resulted significant decrease in brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and insulin-degrading enzyme (IDE) expression in astrocytes. Treatment with memantine (1-10 μM) improved STZ-induced neurotrophic factor decline (BDNF, GDNF) along with IR dysfunction as evidenced by a significant increase in IR protein expression, phosphorylation of IRS-1, Akt, and GSK-3 α/β in astrocytes. Further, memantine attenuated STZ-induced amyloid precursor protein (APP), β-site APP-cleaving enzyme-1 and amyloid-β_1-42 expression and restored IDE expression in astrocytes. In addition, memantine also displays protective effects against STZ-induced astrocyte activation showed by reduction of inflammatory markers, nuclear factor kappa-B translocation, glial fibrillary acidic protein, cyclooxygenase-2, tumor necrosis factor-α level, and oxidative-nitrostative stress. The results suggest that besides the NMDA receptor antagonisic activity, effect on astroglial IR and neurotrophic factor may also be an important factor in the beneficial effect of memantine in AD pathology. Graphical Abstract Novel neuroprotective mechanisms of memenatine in streptozotocin-induced toxicity in astrocytes.

Sulforaphane Ameliorates Okadaic Acid-Induced Memory Impairment in Rats by Activating the Nrf2/HO-1 Antioxidant Pathway

Okadaic acid (OKA) causes memory impairment and attenuates nuclear factor erythroid 2-related factor 2 (Nrf2) along with oxidative stress and neuroinflammation in rats. Sulforaphane (dietary isothiocyanate compound), an activator of Nrf2 signaling, exhibits neuroprotective effects. However, the protective effect of sulforaphane in OKA-induced neurotoxicity remains uninvestigated. Therefore, in the present study, the role of sulforaphane in OKA-induced memory impairment in rats was explored. A significant increased Nrf2 expression in the hippocampus and cerebral cortex was observed in trained (Morris water maze) rats, and a significant decreased Nrf2 expression in memory-impaired (OKA, 200 ng icv) rats indicated its involvement in memory function. Sulforaphane administration (5 and 10 mg/kg, ip, days 1 and 2) ameliorates OKA-induced memory impairment in rats. The treatment also restored Nrf2 and its downstream antioxidant protein expression (GCLC, HO-1) and attenuated oxidative stress (ROS, nitrite, GSH), neuroinflammation (NF-κB, TNF-α, IL-10), and neuronal apoptosis in the cerebral cortex and hippocampus of OKA-treated rats. Further, to determine whether modulation of Nrf2 signaling is responsible for the protective effect of sulforaphane, in vitro, Nrf2 siRNA and its downstream HO-1 inhibition studies were carried out in a rat astrocytoma cell line (C6). The protective effects of sulforaphane were abolished with Nrf2 siRNA and HO-1 inhibition in astrocytes. The results suggest that Nrf2-dependent activation of cellular antioxidant machinery results in sulforaphane-mediated protection against OKA-induced memory impairment in rats. Graphical Abstract ᅟ.

Hypertension exacerbates predisposition to neurodegeneration and memory impairment in the presence of a neuroinflammatory stimulus: Protection by angiotensin converting enzyme inhibition

Hypertension is a risk factor for cognitive impairment. Furthermore, neuroinflammation and neurodegeneration are intricately associated with memory impairment. Therefore, the present study aimed to explore the involvement of hypertension and angiotensin system in neurodegeneration and memory dysfunction in the presence of neuroinflammatory stimulus. Memory impairment was induced by chronic neuroinflammation that was developed by repeated intracerebroventricular (ICV) injections of lipopolysaccharide (LPS) on the 1st, 4th, 7th, and 10th day. Memory functions were evaluated by the Morris water maze (MWM) test on days 13-15, followed by biochemical and molecular studies in the cortex and hippocampus regions of rat brain. LPS at the dose of 25μg ICV caused memory impairment in spontaneously hypertensive rats (SHRs) but not in normotensive Wistar rats (NWRs). Memory deficit was obtained with 50μg of LPS (ICV) in NWRs. Control SHRs already exhibited increased angiotensin converting enzyme (ACE) activity and expression, neuroinflammation (increased TNF-α, GFAP, COX-2 and NF-kB), oxidative stress (increased iNOS, ROS and nitrite levels), TLR-4 expression and TUNEL positive cells as compared to control NWRs. Further, LPS (25μg ICV) exaggerated inflammatory response, oxidative stress and apoptosis in SHRs but similar effects were witnessed at 50μg of LPS (ICV) in NWRs. Oral administration of perindopril (ACE inhibitor), at non-antihypertensive dose (0.1mg/kg), for 15days attenuated LPS induced deleterious changes in both NWRs and SHRs. Our data suggest that susceptibility of the brain for neurodegeneration and memory impairment induced by neuroinflammation is enhanced in hypertension, and that can be protected by ACE inhibition.

Streptozotocin Induced Neurotoxicity Involves Alzheimer's Related Pathological Markers: a Study on N2A Cells

Intracerebroventricular (icv) injection of streptozotocin (STZ) in rat brain causes prolonged impairment of brain energy metabolism and oxidative damage and leads to cognitive dysfunction; however, its mechanistic specific effects on neurons are not known. The present study was conducted to investigate the STZ-induced cellular and molecular alterations in mouse neuronal N2A cells. The N2A cells were treated with STZ (10, 50, 100, 1000 μM) for 48 h, and different assays were performed. STZ treatment caused significant decrease in cell viability, choline levels, increased acetylcholinesterase (AChE) activity, tau phosphorylation and amyloid aggregation. STZ treatment also led to low levels of glucose uptake, elevated mitochondrial stress, translocation of cytochrome c in cytosol, phosphatidylserine externalization, increased expression of caspase-3 and DNA damage. Co-treatment of clinically used drug donepezil (1 μM) offered significant protection against STZ induced neurotoxicity. Donepezil treatment significantly inhibited the STZ induced neurotoxicity, altered choline level, AChE activity, lowered glucose uptake and mitochondrial stress. However, the caspase-3 expression remains unaltered with co-treatment of donepezil. In conclusion, findings showed that STZ treated N2A cells exhibited the Alzheimer's disease (AD) related pathological markers which are attenuated with co-treatment of donepezil. Findings of the study suggested the potent use of STZ treated N2A cells as in vitro experimental test model to study the disease mechanism at cellular level.

6-Hydroxydopamine and lipopolysaccharides induced DNA damage in astrocytes: involvement of nitric oxide and mitochondria

The present study was conducted to investigate the effect of the neurotoxins 6-hydroxydopamine and lipopolysaccharide on astrocytes. Rat astrocyte C6 cells were treated with different concentration of 6-hydroxydopamine (6-OHDA)/lipopolysaccharides (LPS) for 24 h. Both neurotoxins significantly decreased the viability of astrocytes, augmented the expression of inducible nitric oxide synthase (iNOS) and the astrocyte marker--glial fibrillar acidic protein. A significantly decreased mitochondrial dehydrogenase activity, mitochondrial membrane potential, augmented reactive oxygen species (ROS) level, caspase-3 mRNA level, chromatin condensation and DNA damage was observed in 6-OHDA/LPS treated astroglial cells. 6-OHDA/LPS treatment also caused the significantly increased expression of iNOS and nitrite level. Findings showed that 6-OHDA/LPS treatment caused mitochondrial dysfunction mediated death of astrocytes, which significantly involve the nitric oxide. Since we have observed significantly increased level of iNOS along with mitochondrial impairment and apoptotic cell death in astrocytes, therefore to validate the role of iNOS, the cells were co-treated with iNOS inhibitor aminoguanidine (AG, 100 μM). Co-treatment of AG significantly attenuated the 6-OHDA/LPS induced cell death, mitochondrial activity, augmented ROS level, chromatin condensation and DNA damage. GFAP and caspase-3 expression were also inhibited with co-treatment of AG, although the extent of inhibition was different in both experimental sets. In conclusion, the findings showed that iNOS mediated increased level of nitric oxide acts as a key regulatory molecule in 6-OHDA/LPS induced mitochondrial dysfunction, DNA damage and apoptotic death of astrocytes.

Protection of streptozotocin induced insulin receptor dysfunction, neuroinflammation and amyloidogenesis in astrocytes by insulin

Impaired insulin signaling, amyloid pathology and neuroinflammation are closely associated with neurodegenerative disorder like Alzheimer's disease (AD). Our earlier studies showed that intracerebroventricular streptozotocin (STZ) induces insulin receptor (IR) signaling defect in the hippocampus, which is associated with memory impairment in rats. Astrocytes are the most abundant cells in the brain and play a major role in neuroinflammation. However, involvement of astrocytes in STZ induced IR dysfunction has not received much attention. Therefore, the present study was planned to explore the effect of STZ on IR signaling, proinflammatory markers and amyloidogenesis in rat astrocytoma cell line, (C6). STZ (100 μM) treatment in astrocytes (n = 3) for 24 h, resulted significant decrease in IR mRNA and protein expression, phosphorylation of IRS-1, Akt, GSK-3α and GSK-3β (p < 0.01). Further STZ induced amyloidogenic protein expression as evidenced by the increase in APP, BACE-1 and Aβ1-42 expression (p < 0.05) in astrocytes. STZ also significantly induced astrocytes activation as evidenced by increased expression of GFAP and p-P38 MAPK (p < 0.05). STZ treatment caused enhanced translocation of p65 NF-kB, triggered over expression of TNF-α, IL-1β, COX-2, oxidative/nitrosative stress and caspase activation (p < 0.05) in astrocytes. Insulin (25-100 nM) pretreatment (n = 3) significantly prevented changes in IR signaling, amyloidogenic protein expression and levels of proinflammatory markers (p < 0.05) in STZ treated astroglial cells. In the present study, the protective effect of insulin suggests that, IR dysfunction along with amyloidogenesis and neuroinflammation may have played a major role in STZ induced toxicity in astrocytes which are relevant to AD pathology.

Glial activation and post-synaptic neurotoxicity: the key events in Streptozotocin (ICV) induced memory impairment in rats

In the present study the role of glial activation and post synaptic toxicity in ICV Streptozotocin (STZ) induced memory impaired rats was explored. In experiment set up 1: Memory deficit was found in Morris water maze test on 14-16 days after STZ (ICV; 3mg/Kg) administration. STZ causes increased expression of GFAP, CD11b and TNF-α indicating glial activation and neuroinflammation. STZ also significantly increased the level of ROS, nitrite, Ca(2+) and reduced the mitochondrial activity in synaptosomal preparation illustrating free radical generation and excitotoxicity. Increased expression and activity of Caspase-3 was also observed in STZ treated rat which specify apoptotic cell death in hippocampus and cortex. STZ treatment showed decrease expression of post synaptic markers CaMKIIα and PSD-95, while, expression of pre synaptic markers (synaptophysin and SNAP-25) remains unaltered indicating selective post synaptic neurotoxicity. Oral treatment with Memantine (10mg/kg) and Ibuprofen (50 mg/kg) daily for 13 days attenuated STZ induced glial activation, apoptotic cell death and post synaptic neurotoxicity in rat brain. Further, in experiment set up 2: where memory function was not affected i.e. 7-9 days after STZ treatment. The level of GFAP, CD11b, TNF-α, ROS and nitrite levels were increased. On the other hand, apoptotic marker, synaptic markers, mitochondrial activity and Ca(2+) levels remained unaffected. Collective data indicates that neuroinflammatory process and oxidative stress occurs earlier to apoptosis and does not affect memory function. Present study clearly suggests that glial activation and post synaptic neurotoxicity are the key factors in STZ induced memory impairment and neuronal cell death.

LPS induces mediators of neuroinflammation, cell proliferation, and GFAP expression in human astrocytoma cells U373MG: the anti-inflammatory and anti-proliferative effect of guggulipid

Neuroinflammation has been considered to be an integrated part of human neurodegenerative diseases. In this study, we examined the effect of guggulipid on cell proliferation, nitrite release, interleukin IL-6 and IL-1 beta release, and expression of COX-2 and glial fibrillary acidic protein (GFAP) in LPS-stimulated U373MG cells. LPS significantly stimulated human astrocytoma cells U373MG by up-regulating these neuroinflammatory mediators. Guggulipid alone had no effect on the cell proliferation of U373MG cells. The up regulation in nitrite release, cell proliferation, and release of IL-6 and IL-1 beta in LPS stimulated human astrocytoma cells were dose-dependently inhibited by co-treatment with guggulipid. The expression level of COX-2 and GFAP proteins was up regulated by LPS but the increased level of COX-2 and GFAP was significantly down regulated by treatment with guggulipid. These data indicate that guggulipid has a modulatory effect on all these parameters, which might explain its beneficial effect in the treatment of neuroinflammation-associated disorders directly relating to human aspects.

Effect of angiotensin II on spatial memory, cerebral blood flow, cholinergic neurotransmission, and brain derived neurotrophic factor in rats

RATIONAL

Studies have shown the involvement of angiotensin II (Ang II) in neurobehavioral aspects, but the exact role of Ang II in memory is still ambiguous.

OBJECTIVE

This study explored the effect of central Ang II on spatial memory along with cholinergic neurotransmission, brain energy metabolism, cerebral blood flow (CBF), and brain-derived neurotrophic factor (BDNF) in rats.

METHODS

Spatial memory was evaluated by Morris water maze (MWM) after Ang II (ICV) administration in male Sprague-Dawley rats. CBF was measured by laser Doppler flowmetry. Oxidative stress adenosine triphosphate (ATP), BDNF, acetylcholinesterase (AChE), and acetylcholine (ACh) were estimated in the cortex and hippocampus at 1, 24, and 48 h after Ang II administration. The effect of AT1 and AT2 receptor blocker (candesartan and PD123,319, respectively), AChE inhibitor (donepezil), and antioxidant melatonin was studied on memory, CBF, and biochemical parameters.

RESULTS

Ang II caused spatial memory impairment by affecting acquisition, consolidation, and recall in the MWM test along with a significant reduction in CBF. Ang II significantly reduced ACh level and caused oxidative stress in the rat brain 1 h post-injection. No significant change was observed in BDNF, AChE, and ATP level. Candesartan and donepezil prevented Ang II-induced memory impairment, reduction in CBF and ACh level. However, PD123,319 and melatonin failed to prevent Ang II-induced memory impairment but improved CBF partially.

CONCLUSION

This study suggests that Ang II, via the AT1 receptor, affects spatial memory formation, CBF, and ACh level while AT2 receptor has no significant role.

Lead optimization studies towards the discovery of novel carbamates as potent AChE inhibitors for the potential treatment of Alzheimer's disease

The optimization of our previous lead compound 1 (AChE IC(50)=3.31 μM) through synthesis and pharmacology of a series of novel carbamates is reported. The synthesized compounds were evaluated against mouse brain AChE enzyme using the colorimetric method described by Ellman et al. The three compounds 6a (IC(50)=2.57μM), 6b (IC(50)=0.70 μM) and 6i (IC(50)=2.56 μM) exhibited potent in vitro AChE inhibitory activities comparable to the drug rivastigmine (IC(50)=1.11 μM). Among them, the compound 6b has been selected as possible optimized lead for further neuropharmacological studies. In addition, the AChE-carbamate Michaelis complexes of these potent compounds including rivastigmine and ganstigmine have been modeled using covalent docking protocol of GOLD and important direct/indirect interactions contributing to stabilization of the AChE-carbamate Michaelis complexes have been investigated.

The effect of guggulipid and nimesulide on MPTP-induced mediators of neuroinflammation in rat astrocytoma cells, C6

Oxidative stress plays an important role in the pathophysiology of Parkinson's disease (PD) but its mechanism is still not properly explored. Cyclooxygenase-2 (COX-2) inhibition has also been known a major neuroprotective strategy in the various 1-methyl-4-phenyl 1,2,3,6 tetrahydropyridine (MPTP) induced models of Parkinson's disease (PD) but its role in astrocytes is still not properly understood. The present study demonstrated that, guggulipid and nimesulide (preferentially selective COX-2 inhibitor) treatment of rat astrocytoma cells, C6 for 24 h significantly decreased MPTP (400 μM) induced nitrative and oxidative stress and intracellular calcium ion (Ca(2+)) level. Guggulipid and nimesulide also deactivated MPTP-induced P-p38 MAPK (Phosphorylated p38 mitogen-activated protein kinase) and down regulated expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and CHOP (C/EBP, homologous protein 10). At transcriptional level of inflammatory cytokine genes, guggulipid and nimesulide down regulated MPTP-induced tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) mRNA expressions with up regulations in interleukin-6 (IL-6) and interleukin-1α (IL-1α) mRNA expressions. In addition to this, guggulipid and nimesulide inhibited translocation of nuclear factor kappa-B (NF-κB) from cytosol to nucleus. In conclusion, our findings elucidated the potential antioxidant and anti-neuroinflammatory effect of guggulipid and nimesulide in rat astrocytoma cells C6, which may suggest the use of these drugs in the management of neuroinflammation associated pathophysiology of PD.

Role of central angiotensin receptors in scopolamine-induced impairment in memory, cerebral blood flow, and cholinergic function

RATIONAL

Inhibition of renin-angiotensin system (RAS) improves cognitive functions in hypertensive patients. However, role of AT1 and AT2 receptors in memory impairment due to cholinergic hypofunction is unexplored.

OBJECTIVE

This study investigated the role of AT1 and AT2 receptors in cerebral blood flow (CBF), cholinergic neurotransmission, and cerebral energy metabolism in scopolamine-induced amnesic mice.

METHODS

Scopolamine was given to male Swiss albino mice to induce memory impairment tested in passive avoidance and Morris water maze tests after a week long administration of blocker of AT1 receptor, candesartan, and AT2 receptor, PD123, 319. CBF was measured by laser Doppler flowmetry. Biochemical and molecular studies were done in cortex and hippocampus of mice brain.

RESULTS

Scopolamine caused memory impairment, reduced CBF, acetylcholine (ACh) level, elevated acetylcholinesterase (AChE) activity, and malondialdehyde (MDA). Administration of vehicle had no significant effect on any parameter in comparison to control. Candesartan prevented scopolamine-induced amnesia, restored CBF and ACh level, and decreased AChE activity and MDA level. In contrast, PD123, 319 was not effective. However, the effect of AT1 receptor blocker on memory, CBF, ACh level, and oxidative stress was blunted by concomitant blockade of AT2 receptor. Angiotensin-converting enzyme (ACE) activity, ATP level, and mRNA expression of AT1, AT2, and ACE remained unaltered.

CONCLUSION

The study suggests that activation of AT1 receptors appears to be involved in the scopolamine-induced amnesia and that AT2 receptors contribute to the beneficial effects of candesartan. Theses finding corroborated the number of clinical studies that RAS inhibition in hypertensive patients could be neuroprotective.

Melatonin attenuated mediators of neuroinflammation and alpha-7 nicotinic acetylcholine receptor mRNA expression in lipopolysaccharide (LPS) stimulated rat astrocytoma cells, C6

Melatonin has been known to affect a variety of astrocytes functions in many neurological disorders but its mechanism of action on neuroinflammatory cascade and alpha-7 nicotinic acetylcholine receptor (α7-nAChR) expression are still not properly understood. Present study demonstrated that treatment of C6 cells with melatonin for 24 hours significantly decreased lipopolysaccharide (LPS) induced nitrative and oxidative stress, expressions of cyclooxigenase-2 (COX-2), inducible nitric-oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP). Melatonin also modulated LPS-induced mRNA expressions of α7-nAChR and inflammatory cytokine genes. Furthermore, melatonin reversed LPS-induced changes in C/EBP homologous protein 10 (CHOP), microsomal prostaglandin E synthase-1(mPGES-1) and phosphorylated p38 mitogen activated protein kinase (P-p38). Treatment with pyrrolidine dithiocarbamate (PDTC) inhibited α7-nAChR mRNA expression in LPS-induced C6 cells. Our findings explored anti-neuroinflammatory action of melatonin, which may suggests its beneficial roles in the neuroinflammation associated disorders.

Flavone-based novel antidiabetic and antidyslipidemic agents

The hybrid congeners 62-90 of 6- and 7-hydroxyflavones with aminopropanol have been synthesized and evaluated for their antidiabetic activity in sucrose-challenged low-dosed streptozotocin (STZ)-induced diabetic rats and db/db mice. The optical enantiomers 70a, 70b, 90a, and 90b of two congeners 70 and 90 exhibiting consistent antidiabetic and antidyslipidemic activities were also prepared, and their antidiabetic activity results indicate its association mainly with S isomers. These compounds also lower cholesterol and TG profiles while improving high-density lipoprotein cholesterol to CHOL ratio in db/db mice. The bioavailability of compound 70 and its isomer varies between 27 and 29% whereas that of the more polar compound 90a is poor as determined in rat by oral and intraperitoneal administrations.

Rotenone-induced apoptosis and role of calcium: a study on Neuro-2a cells

Rotenone causes cytotoxicity in astrocytic cell culture by glial activation, which is linked to free radical generation. The present study is an investigation to explore whether rotenone could also cause cellular toxicity in mouse neuroblastoma cells (Neuro-2a) under treatment similar to astroglial cells. The effect of rotenone (0.1, 1, and 10 μM) on mitochondrial dehydrogenase enzyme activity by MTT reduction assay, PI uptake, total reactive oxygen species (ROS)/superoxide levels, nitrite levels, extent of DNA damage (by comet assay), and nuclear morphological alteration by Hoechst staining was studied. Caspase-3 and Ca⁺²/calmodulin-dependent protein kinase II (CaMKIIα) gene expression was determined to evaluate the apoptotic cell death and calcium kinase, respectively. Calcium level was estimated fluorometrically using fura-2A stain. Rotenone decreased mitochondrial dehydrogenase enzyme activity and generated ROS, superoxide, and nitrite. Rotenone treatment impaired cell intactness and nuclear morphology as depicted by PI uptake and chromosomal condensation of Neuro-2a cells, respectively. In addition, rotenone resulted in increased intracellular Ca⁺² level, caspase-3, and CaMKIIα expression. Furthermore, co-exposure of melatonin (300 μM), an antioxidant to cell culture, significantly suppressed the rotenone-induced decreased mitochondrial dehydrogenase enzyme activity, elevated ROS and RNS. However, melatonin was found ineffective to counteract rotenone-induced increased PI uptake, altered morphological changes, DNA damage, elevated Ca⁺², and increased expression of caspase-3 and CaMKIIα. The study indicates that intracellular calcium rather than oxidative stress is a major factor for rotenone-induced apoptosis in neuronal cells.

Inhibition of central angiotensin converting enzyme ameliorates scopolamine induced memory impairment in mice: role of cholinergic neurotransmission, cerebral blood flow and brain energy metabolism

Evidences indicate that inhibition of central Renin angiotensin system (RAS) ameliorates memory impairment in animals and humans. Earlier we have reported involvement of central angiotensin converting enzyme (ACE) in streptozotocin induced neurodegeneration and memory impairment. The present study investigated the role of central ACE in cholinergic neurotransmission, brain energy metabolism and cerebral blood flow (CBF) in model of memory impairment induced by injection of scopolamine in mice. Perindopril (0.05 and 0.1 mg/kg, PO) was given orally for one week before administration of scopolamine (3mg/kg, IP). Then, memory function was evaluated by Morris water maze and passive avoidance tests. CBF was measured by laser Doppler flowmetry. Biochemical and molecular parameters were estimated after the completion of behavioral studies. Scopolamine caused impairment in memory which was associated with reduced CBF, acetylcholine (ACh) level and elevated acetylcholinesterase (AChE) activity and malondialdehyde (MDA) level. Perindopril ameliorated scopolamine induced amnesia in both the behavioral paradigms. Further, perindopril prevented elevation of AChE and MDA level in mice brain. There was a significant increase in CBF and ACh level in perindopril treated mice. However, scopolamine had no significant effect on ATP level and mRNA expression of angiotensin receptors and ACE in cortex and hippocampus. But, perindopril significantly decreased ACE activity in brain without affecting its mRNA expression. The study clearly showed the interaction between ACE and cholinergic neurotransmission and beneficial effect of perindopril can be attributed to improvement in central cholinergic neurotransmission and CBF.

Protective effect of fruits of Morinda citrifolia L. on scopolamine induced memory impairment in mice: a behavioral, biochemical and cerebral blood flow study

ETHNOPHARMACOLOGICAL RELEVANCE

Noni (Morinda citrifolia L.) is widely used for different illnesses including CNS disorders. Recently Noni has been reported to prevent amyloid beta induced memory impairment in mice. However, the influence of Noni on cholinergic system has not been explored so far. Therefore, present study was designed to investigate effect of Noni fruit on memory, cerebral blood flow (CBF), oxidative stress and acetylcholinesterase (AChE) activity in scopolamine induced amnesia model.

MATERIALS AND METHODS

Mice were orally treated with ethanolic extract of Noni fruit and chloroform, ethyl acetate and butanol fractions of ethanolic extract for three days. Scopolamine was administered 5 min prior to acquisition trial and memory function was evaluated by passive avoidance test. CBF was measured by laser doppler flowmetry. AChE activity and oxidative stress parameters were estimated in mice brain at the end of behavioral studies. Further, effect of ethanolic extract and its fractions (5-400 μg/ml) on AChE activity was measured in vitro.

RESULTS

Scopolamine caused memory impairment along with reduced CBF, increased AChE activity and oxidative stress in mice brain. Ethanolic extract of Noni fruits and its chloroform and ethyl acetate fractions significantly improved memory and CBF. However, butanol fraction had no effect. Further, increased oxidative stress and AChE activity following scopolamine was significantly attenuated by ethanolic extract of Noni and its fractions. Moreover ethanolic extract and its fractions showed dose dependent inhibition of AChE activity in vitro.

CONCLUSION

These observations suggest that Noni may be useful in memory impairment due to its effect on CBF, AChE and oxidative stress.

Astrocytes and microglia: responses to neuropathological conditions

Activated astrocytes and microglia, hallmark of neurodegenerative diseases release different factors like array of pro and anti-inflammatory cytokines, free radicals, anti-oxidants, and neurotrophic factors during neurodegeneration which further contribute to neuronal death as well as in survival mechanisms. Astrocytes act as double-edged sword exerting both detrimental and neuroprotective effects while microglial cells are attributed more in neurodegenerative mechanisms. The dual and insufficient knowledge about the precise role of glia in neurodegeneration showed the need for further investigations and thorough review of the function of glia in neurodegeneration. In this review, we consolidate and categorize the glia-released factors which contribute in degenerative and protective mechanisms during neuropathological conditions.

Cholinergic influence on memory stages: A study on scopolamine amnesic mice

Objectives:

The study was planned to determine cholinergic influence on different stages of memory - acquisition, consolidation and recall in scopolamine-induced amnesia (memory impairment) in mice.

Materials and Methods:

To study acquision, consolidation and recall stages of memory, we administered scopolamine (0.75, 1.5 and 3 mg/kg ip) 30 minutes and five minutes prior to first trial acquisition and consolidation and 30 minutes prior to second trial recall of passive avoidance (PA) test, respectively, in separate groups. Tacrine (5 mg/kg po) and rivastigmine (5 mg/kg po) were administered one hour prior to first trial in separate groups which received scopolamine (3 mg/kg ip) 30 minutes and five minutes prior to first trial where as the control group received vehicle only.

Results:

In the control group, there was a significant (P < 0.01) increase in transfer latency time (TLT) in the second trial compared to first indicating successful learning. In scopolamine treated groups, administering scopolamine 30 minutes or five minutes prior to first trial did not show any significant (P > 0.05) change in TLT whereas mice treated with scopolamine 30 minutes prior to second trial showed significant (P < 0.01) increase in TLT in second trial as compared to the first. Both tacrine and rivastigmine administration in scopolamine treated mice showed significant (P < 0.05-0.01) increase in TLT in second trial as compared to first trial while the rivastigmine treated group showed greater percentage retention compared to tacrine treated group.

Conclusion:

Results show that acquisition and consolidation are more susceptible to the scopolamine effects than recall. Thus, it may be concluded that cholinergic influence is more on acquisition and consolidation as compared to recall.

ICV STZ induced impairment in memory and neuronal mitochondrial function: A protective role of nicotinic receptor

The present study was planned to evaluate the cholinergic influence on mitochondrial activity and neurodegeneration associated with impaired memory in intracerebroventricular (ICV) streptozotocin (STZ) treated rats. STZ (3mg/kg), administered ICV twice with an interval of 48h between the two doses, showed significant impairment in spatial memory tested by water maze test 14 days after first dose without altering blood glucose level and locomotor activity. Animals were sacrificed on 21st day of ICV administration. STZ significantly increased malondialdehyde (MDA), reactive oxygen species (ROS), Ca(2+) ion influx, caspase-3 activity and decreased glutathione (GSH) level. Acetylcholinesterase inhibitors tacrine and donepezil (5mg/kg, PO) pretreatment significantly prevented STZ induced memory deficit, oxidative stress, Ca(2+) influx and caspase-3 activity. Carbachol, a muscarinic cholinergic agonist (0.01mg/kg, SC) did not show any significant effect on ROS generation, Ca(2+) ion influx and caspase-3 activity. While nicotinic cholinergic agonist, nicotine, significantly attenuated ICV STZ induced mitochondrial dysfunction and caspase-3 activity. The results indicate that instead of muscarinic receptors nicotinic receptors may be involved in neuroprotection by maintaining mitochondrial functions.

Evaluation of guggulipid and nimesulide on production of inflammatory mediators and GFAP expression in LPS stimulated rat astrocytoma, cell line (C6)

AIM OF THE STUDY

The present study was designed to investigate effect of guggulipid, a drug developed by CDRI and nimesulide on LPS stimulated neuroinflammatory changes in rat astrocytoma cell line (C6).

MATERIALS AND METHODS

Rat astrocytoma cells (C6) were stimulated with LPS (10 microg/ml) alone and in combinations with different concentrations of guggulipid or nimesulide for 24h of incubation. Nitrite release in culture supernatant, ROS in cells, expressions of COX-2, GFAP and TNF-alpha in cell lysate were estimated.

RESULTS

LPS (10 microg/ml) stimulated C6 cells to release nitrite, ROS generation, up regulated COX-2 and GFAP expressions at protein level and TNF-alpha at mRNA level. Both guggulipid and nimesulide significantly attenuated nitrite release, ROS generation and also down regulated expressions of COX-2, GFAP and TNF-alpha. Guggulipid and nimesulide per se did not have any significant effect on C6 cells.

CONCLUSION

Results demonstrate the anti-inflammatory effect of guggulipid comparable to nimesulide which suggest potential use of guggulipid in neuroinflammation associated conditions in CNS disorders.

Protective effect of quercetin against intracerebral streptozotocin induced reduction in cerebral blood flow and impairment of memory in mice

The aim of the present study is to investigate the effect of quercetin, a naturally occurring flavonoid, on cerebral blood flow (CBF), brain energy metabolism, memory impairment, oxidative stress and cholinergic dysfunction in brain following intracerebral (i.c.) streptozotocin (STZ) administration in mice. STZ (0.5mg/kg, i.c.) was administered twice at an interval of 48h. We found a significant reduction in CBF as measured by Laser Doppler Flowmetry (LDF). The brain energy metabolism was also altered as evidenced by significant reduction in brain ATP content. Daily treatment with quercetin (2.5, 5 and 10mg/kg, p.o.) starting from the first dose of STZ showed a dose-dependent restoration of CBF and ATP content. Further, quercetin prevented STZ induced memory impairment as assessed by Morris water maze and passive avoidance tests. Biochemical analysis revealed that STZ significantly increased malondialdehyde (MDA), nitrite and depleted glutathione (GSH) levels in the mice brain. Quercetin decreased oxidative and nitrosative stress as evidenced by a significant decrease in MDA, nitrite and increase in GSH levels. Quercetin also attenuated elevated acetylcholinesterase activity in the STZ-treated mice. Neither STZ (i.c.) nor quercetin showed any change in locomotor activity and blood glucose level. The present study demonstrates the beneficial effects of quercetin in improving CBF along with preventing memory impairment, oxidative stress, altered brain energy metabolism and cholinergic dysfunction caused by STZ in mice. Therefore, consumption of dietary stuff rich in quercetin should be encouraged to ward off dementia associated with vascular and neurodegenerative disorders.

Okadaic acid (ICV) induced memory impairment in rats: a suitable experimental model to test anti-dementia activity

Okadaic acid (OKA) is a potent and selective inhibitor of protein phosphatases, PP2A and PP1. In the present study, we evaluated effect of intracerebroventricular (ICV) bilateral injection of OKA (100 and 200 ng) on memory function and oxidative stress in rats. ICV injection of OKA (200 ng) produced memory impairment as evidenced by no significant decrease in latency time to reach the hidden platform in water maze test. It produced increase in malondialdehyde (MDA), nitrite level, reactive oxygen species (ROS) generation, mitochondrial calcium ion [Ca(2)](i) level and decreased glutathione (GSH) level in rat brain areas, indicating oxidative stress. Furthermore, we evaluated the effect of anti-dementia drugs memantine, a NMDA antagonist, and donepezil, a cholinesterase inhibitor, on OKA ICV induced memory impairment. Administration of memantine (10 mg/kg, p.o.) and donepezil (5 mg/kg, p.o.) for 13 days starting from the OKA injection improved performance in memory tests and also significantly restored GSH, MDA, nitrite levels, ROS generation and [Ca(2+)](i) level. This study demonstrates that the clinically used anti-dementic drugs are effective in OKA induced free radical generation and memory impairment in rats. Thus, OKA ICV induced memory impairment in rat appeared as a useful test model to screen anti-dementia drugs.

Melatonin alleviates memory deficits and neuronal degeneration induced by intracerebroventricular administration of streptozotocin in rats

In the present study the effect of melatonin on intracerebroventricularly administered streptozotocin (STZ)-induced neurodegeneration was investigated in rats. STZ (3mg/kg), administered twice with an interval of 48 h between the two doses, showed impairment in spatial memory tested by water maze test after 14 days of 1st dose. Administration of melatonin (2.5, 5.0 and 10mg/kg, i.p.) was started 1h prior to 1st dose of STZ and continued up to 14 days. Glutathione and malondialdehyde were used as biochemical markers of oxidative stress in different brain regions. Histopathological changes were examined by using hematoxylin and eosin stain. STZ administration caused significant decrease in glutathione and increase in malondialdehyde as compared to control and artificial Cerebrospinal Fluid treated rats indicating oxidative stress. Brain sections of STZ-treated rats showed increased vacuoles in the periventricular cortical area, damaged periventricular cells and damaged cells in the hippocampal CA4 region as compared to control and artificial Cerebrospinal Fluid treated groups. Melatonin treatment significantly attenuated the effect of STZ-induced oxidative stress and histopathological changes. The results indicate that melatonin is effective in providing protection against memory deficit, oxidative stress and neuronal damage induced by STZ.

Cholinergic protection via alpha7 nicotinic acetylcholine receptors and PI3K-Akt pathway in LPS-induced neuroinflammation

The present study was planned to investigate the effect of anti-cholinesterase drugs donepezil and neostigmine on neuroinflammation induced by intracerebroventricular administration of lipopolysaccharide (LPS, 50 microg) in rat. Proinflammatory cytokines (TNF-alpha and IL-1beta), expressions of iNOS and COX-2, acetylcholinesterase activity, malondialdehyde and reduced glutathione were studied in different brain regions at 24h of LPS injection. Donepezil was found to decrease the LPS-induced AChE activity and oxidative stress in all the brain regions. It also inhibited the LPS-induced proinflammatory cytokines and iNOS expression but did not affect the increased COX-2 expression whereas neostigmine treatment had no effect on LPS-induced proinflammatory cytokines. Methyllycaconitine (MLA), a alpha7 nicotinic acetylcholine receptor antagonist, significantly antagonized the donepezil mediated inhibition of LPS-induced proinflammatory cytokines, indicating that alpha7 nicotinic acetylcholine receptor subunit was playing a role in regulation of neuroinflammation. The phosphorylation of Akt, an effector of PI3K, increased with donepezil treatment. These results suggest that increased cholinergic activity in brain by donepezil prevents LPS-induced neuroinflammation via alpha7-nAChRs, followed by the PI3K-Akt pathway and this system may form the basis for the development of novel agents for reversing neuroinflammation or provide new indications for existing drugs.