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.

Angiotensin II Receptor Blockers Attenuate Lipopolysaccharide-Induced Memory Impairment by Modulation of NF-κB-Mediated BDNF/CREB Expression and Apoptosis in Spontaneously Hypertensive Rats.

Clinical studies demonstrated a positive correlation between hypertension and cognitive decline. Beneficial effects of angiotensin II receptor blockers on cognitive functions have also been reported earlier; however, its role in chronic neuroinflammation-induced memory impairment in the hypertensive state is not well understood. Therefore, in the present study, we investigated the effect of angiotensin II receptor blockers on memory impairment induced by lipopolysaccharide (LPS) in spontaneously hypertensive rats (SHRs). Our data provides the strong evidence that intracerebroventricular (ICV) administration of LPS (25 µg) on the 1st, 4th, 7th, and 10th days leads to sustained neuroinflammation (as indicated by increased TNF-α, GFAP, COX-2, and NF-κB) and oxidative stress (increased reactive oxygen species (ROS) and nitrite levels) resulting in amyloid beta (Aß1-42) deposition, apoptosis (increased Bax and decreased Bcl-2 expression as well as increased caspase-3 activity and TUNEL-positive cells), and memory impairment. Further, we found that exaggerated inflammatory response and oxidative stress were associated with RAS over-activation (as evident from the increased ACE expression, angiotensin II (Ang II) level, and angiotensin type 1 receptor (AT1R) expression) and decreased BDNF and p-CREB expression. Oral administration of candesartan (an AT1R blocker) at a non-anti-hypertensive dose (0.1 mg/kg) for 15 days attenuated LPS-induced (ICV) apoptosis, amyloidogenesis, and memory impairment. Candesartan shows neuroprotection by inhibiting TLR4/Ang II-induced NF-κB inflammatory signaling and by enhancing associated BDNF/CREB expression in SHRs. Our study also demonstrated that when both AT1R and angiotensin type 2 receptor (AT2R) were blocked by candesartan and PD123319 concomitantly, the protective effects of candesartan were blunted suggesting that functionally active AT2R is required for beneficial effects of AT1R blockade.

Intranasal insulin improves cerebral blood flow, Nrf-2 expression and BDNF in STZ (ICV)-induced memory impaired rats.

AIMS: Insulin/insulin receptor signaling is involved in cognitive functions. Clinical studies have shown that intranasal insulin administration improves memory functions. However, the molecular mechanisms associated with improvement in memory functions are largely unexplored. Therefore, we investigated the protective effect of intranasal insulin in intracerebroventricular (ICV) streptozotocin (STZ) induced memory impairment in rats. MAIN METHODS: Rats were injected with STZ (3mg/kg, ICV) bilaterally twice, on days 1 and 3 and intranasal insulin (2IU/rat/day) was given for 14days. Memory was assessed by Morris water maze test. Cerebral blood flow (CBF) was measured by laser-Doppler flowmetry. The biochemical and molecular studies were done in cortex and hippocampus of rat brain. KEY FINDINGS: STZ (ICV) administration caused memory impairment along with the reduction of CBF, ATP level, and Nrf-2 expression. Treatment with intranasal insulin significantly improved memory functions as well as restored CBF, ATP content and Nrf-2 expression in STZ injected rats. STZ administration stimulated oxidative-nitrosative stress as evidenced by a significant increase in ROS, malondialdehyde, NO level and inducible nitric oxide synthase expression and the decrease in glutathione level; which was normalized by intranasal insulin delivery. STZ-induced cholinergic dysfunction (AChE activity and α7-nAChR expression), and mitochondrial hypofunction was largely prevented by treatment with intranasal insulin. Intranasal insulin delivery successfully restored BDNF level and pCREB expression in STZ injected rats. SIGNIFICANCE: The study shows the beneficial effects of intranasal insulin against STZ-induced memory impairment, which attributed to improved CBF, cholinergic function, brain energy metabolism, BDNF, Nrf-2 expression and antioxidative action.

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/ß 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 Aß1-42 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.

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.

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.

Mechanism of Oxidative Stress and Synapse Dysfunction in the Pathogenesis of Alzheimer's Disease: Understanding the Therapeutics Strategies.

Synapses are formed by interneuronal connections that permit a neuronal cell to pass an electrical or chemical signal to another cell. This passage usually gets damaged or lost in most of the neurodegenerative diseases. It is widely believed that the synaptic dysfunction and synapse loss contribute to the cognitive deficits in patients with Alzheimer's disease (AD). Although pathological hallmarks of AD are senile plaques, neurofibrillary tangles, and neuronal degeneration which are associated with increased oxidative stress, synaptic loss is an early event in the pathogenesis of AD. The involvement of major kinases such as mitogen-activated protein kinase (MAPK), extracellular receptor kinase (ERK), calmodulin-dependent protein kinase (CaMKII), glycogen synthase-3ß (GSK-3ß), cAMP response element-binding protein (CREB), and calcineurin is dynamically associated with oxidative stress-mediated abnormal hyperphosphorylation of tau and suggests that alteration of these kinases could exclusively be involved in the pathogenesis of AD. N-methyl-D-aspartate (NMDA) receptor (NMDAR) activation and beta amyloid (Aß) toxicity alter the synapse function, which is also associated with protein phosphatase (PP) inhibition and tau hyperphosphorylation (two main events of AD). However, the involvement of oxidative stress in synapse dysfunction is poorly understood. Oxidative stress and free radical generation in the brain along with excitotoxicity leads to neuronal cell death. It is inferred from several studies that excitotoxicity, free radical generation, and altered synaptic function encouraged by oxidative stress are associated with AD pathology. NMDARs maintain neuronal excitability, Ca(2+) influx, and memory formation through mechanisms of synaptic plasticity. Recently, we have reported the mechanism of the synapse redox stress associated with NMDARs altered expression. We suggest that oxidative stress mediated through NMDAR and their interaction with other molecules might be a driving force for tau hyperphosphorylation and synapse dysfunction. Thus, understanding the oxidative stress mechanism and degenerating synapses is crucial for the development of therapeutic strategies designed to prevent AD pathogenesis.

Endoplasmic Reticulum Stress Plays a Key Role in Rotenone-Induced Apoptotic Death of Neurons.

Rotenone, a pesticide, causes neurotoxicity via the mitochondrial complex-I inhibition. The present study was conducted to evaluate the role of endoplasmic reticulum (ER) stress in rotenone-induced neuronal death. Cell viability, cytotoxicity, reactive oxygen species (ROS) generation, nitrite level, mitochondrial membrane potential (MMP), and DNA damage were assessed in rotenone-treated neuro-2A cells. Protein levels of ER stress markers glucose regulated protein 78 (GRP78), growth arrest- and DNA damage-inducible gene 153 (GADD153), and phosphorylation of eukaryotic translation initiation factor 2 subunit α (eIF2-α) were estimated to assess the ER stress. To confirm the apoptotic death of neurons, mRNA levels of caspase-9, caspase-12 and caspase-3 were estimated. Further, to confirm the involvement of ER stress, neuro-2A cells were pretreated with ER stress inhibitor salubrinal. Co-treatment of antioxidant melatonin was also given to assess the role of oxidative stress in rotenone-induced apoptosis. Rotenone (0.1, 0.5, and 1 µM) treatment to neurons caused significantly decreased cell viability, increased cytotoxicity, increased ROS generation, increased expression of GRP78 and GADD, DNA damage and activation of caspase-12 and caspase-3 which were significantly attenuated by pretreatment of salubrinal (25 µM). Rotenone-induced dephosphorylation of eIF2α was also inhibited with salubrinal treatment. However, pretreatment of salubrinal did not affect the rotenone-induced increased nitrite levels, decreased MMP and caspase-9 activation. Co-treatment of antioxidant melatonin (1 mM) did not offer attenuation against rotenone-induced increased expression of caspase-9, caspase-12 and caspase-3. In conclusion, results indicated that ER stress plays a key role in rotenone-induced neuronal death, rather than oxidative stress. Graphical Abstract Pictorial presentation showed the involvement of endoplasmic reticulum (ER) stress, increased reactive oxygen species (ROS), nitrite level, decreased mitochondrial membrane potential (MMP), caspase activation and DNA damage in neuronal cells after rotenone treatment. ER stress inhibitor-salubrinal showed significant attenuation against most of the rotenone-induced adverse effects reflecting its key involvement in rotenone-induced neuronal death.

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.

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 (Aß1-42) 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 ß-secretase (BACE) expression without Aß1-42 deposition. LPS (25 µg, ICV) further amplified oxidative stress, RAGE, and BACE activation, culminating in Aß1-42 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.

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/ß in astrocytes. Further, memantine attenuated STZ-induced amyloid precursor protein (APP), ß-site APP-cleaving enzyme-1 and amyloid-ß1-42 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.

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.

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-3ß (p < 0.01). Further STZ induced amyloidogenic protein expression as evidenced by the increase in APP, BACE-1 and Aß1-42 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-1ß, 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.

Mechanism of synapse redox stress in Okadaic acid (ICV) induced memory impairment: Role of NMDA receptor.

The N-methyl-D-aspartate (NMDA) receptor is a subtype of ionotropic glutamate receptor that is involved in synaptic mechanisms of learning and memory, and mediates excitotoxic neuronal injury. In this study, we tested the hypothesis that NMDA receptor subunit gene expression is altered in cortex and hippocampus of OKA induced memory impairment. Therefore in the present study, we checked the effect of OKA (ICV) on NMDA receptor regulation and synapse function. The memory function anomalies and synaptosomal calcium ion (Ca(2+)) level were increased in OKA treated rats brain; which was further protected by MK801 (0.05mg/kg. i.p) treatment daily for 13days. To elucidate the involvement of NMDA receptor, we estimated NR1, NR2A and NR2B (subunits) expression in rat brain. Results showed that expression of NR1 and NR2B were significantly increased, but expression of NR2A had no significant change in OKA treated rat brain. We also observed decrease in synapsin-1 mRNA and protein expression which indicates synapse dysfunction. In addition, we detected an increase in MDA and nitrite levels and a decrease in GSH level in synapse preparation which indicates synapse altered redox stress. Moreover, neuronal loss was also confirmed by nissl staining in periventricular cortex and hippocampus. Altered level of oxidative stress markers along with neuronal loss confirmed neurotoxicity. Further, MK801 treatment restored the level of NR1, NR2B and synapsin-1 expression, and protected from neuronal loss and synapse redox stress. In conclusion, Okadaic acid (OKA) induced expression of NR1 and NR2B deteriorates synapse function in rat brain which was confirmed by the neuroprotective effect of MK801.

Molecular and cellular mechanism of okadaic acid (OKA)-induced neurotoxicity: a novel tool for Alzheimer's disease therapeutic application.

Okadaic acid (OKA), a polyether C38 fatty acid toxin extracted from a black sponge Hallichondria okadaii, is a potent and selective inhibitor of protein phosphatase, PP1 and PP2A. OKA has been proved to be a powerful probe for studying the various regulatory mechanisms and neurotoxicity. Because of its property to inhibit phosphatase activity, OKA is associated with protein phosphorylation; it is implicated in hyperphosphorylation of tau and in later stages causes Alzhiemer's disease (AD)-like pathology. AD is a progressive neurodegenerative disorder, pathologically characterized by extracellular amyloid beta (Aß) plaques and intracellular neurofibrillary tangles (NFTs). The density of tau tangles in AD pathology is associated with cognitive dysfunction. Recent studies have highlighted the importance of serine/threonine protein phosphatases in many processes including apoptosis and neurotoxicity. Although OKA causes neurotoxicity by various pathways, the exact mechanism is still not clear. The activation of major kinases, such as Ser/Thr, MAPK, ERK, PKA, JNK, PKC, CaMKII, Calpain, and GSK3ß, in neurons is associated with AD pathology. These kinases, associated with abnormal hyperphosphorylation of tau, suggest that the cascade of these kinases could exclusively be involved in the pathogenesis of AD. The activity of serine/threonine protein phosphatases needs extensive study as these enzymes are potential targets for novel therapeutics with applications in many diseases including cancer, inflammatory diseases, and neurodegeneration. There is a need to pay ample attention on MAPK kinase pathways in AD, and OKA can be a better tool to study cellular and molecular mechanism for AD pathology. This review elucidates the regulatory mechanism of PP2A and MAPK kinase and their possible mechanisms involved in OKA-induced apoptosis, neurotoxicity, and AD-like 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.

Standardized Extract of Bacopa monniera Attenuates Okadaic Acid Induced Memory Dysfunction in Rats: Effect on Nrf2 Pathway.

The aim of the present study is to investigate the effect of standardized extract of Bacopa monnieri (memory enhancer) and Melatonin (an antioxidant) on nuclear factor erythroid 2 related factor 2 (Nrf2) pathway in Okadaic acid induced memory impaired rats. OKA (200 ng) was administered intracerebroventricularly (ICV) to induce memory impairment in rats. Bacopa monnieri (BM-40 and 80 mg/kg) and Melatonin (20 mg/kg) were administered 1 hr before OKA injection and continued daily up to day 13. Memory functions were assessed by Morris water maze test on days 13-15. Rats were sacrificed for biochemical estimations of oxidative stress, neuroinflammation, apoptosis, and molecular studies of Nrf2, HO1, and GCLC expressions in cerebral cortex and hippocampus brain regions. OKA caused a significant memory deficit with oxidative stress, neuroinflammation, and neuronal loss which was concomitant with attenuated expression of Nrf2, HO1, and GCLC. Treatment with BM and Melatonin significantly improved memory dysfunction in OKA rats as shown by decreased latency time and path length. The treatments also restored Nrf2, HO1, and GCLC expressions and decreased oxidative stress, neuroinflammation, and neuronal loss. Thus strengthening the endogenous defense through Nrf2 modulation plays a key role in the protective effect of BM and Melatonin in OKA induced memory impairment in rats.