Assessment of microplastics and associated ecological risk in the Hirakud Reservoir, Odisha, India.

Microplastic has emerged as a global threat owing to its chronic ubiquity and persistence. Microplastics' small size expedites their ingestion at each trophic level causing biomagnification and bioaccumulation, which has raised public concerns. The present study isolated, quantified and characterized the abundance, shape, size, color, and chemical composition of the microplastics from water and sediments of the Hirakud Reservoir through a scanning electron microscope and FTIR. The ecological risk associated with the microplastics was assessed using the species sensitivity distribution (SSD) method to derive the Predicted No-Effect Concentration (PNEC) value and risk quotient (RQ). The abundance of microplastics in the surface water and sediments of the Hirakud Reservoir was estimated at 82-89 particles/L and 159-163 particles/kg, respectively. Fiber-shaped microplastics dominated both surface water (46.21%) and sediment samples (44.86%). Small-sized microplastics (53-300 µm) prevailed in all samples. Color delineation exhibited an abundance of transparent microplastics. Chemical characterization indicated the dominance of polypropylene (38%), followed by high-density polyethylene, low-density polyethylene, and polystyrene. The calculated PNEC value was 3,954 particles/m3, and the RQ was estimated to be 0.02073-0.04122 indicating negligible ecological risk to freshwater species in all the sampling sites.

An exploration of the binding prediction of anatoxin-a and atropine to acetylcholinesterase enzyme using multi-level computer simulations.

Acetylcholinesterase (AChE) is crucial for the breakdown of acetylcholine to acetate and choline, while the inhibition of AChE by anatoxin-a (ATX-a) results in severe health complications. This study explores the structural characteristics of ATX-a and its interactions with AChE, comparing to the reference molecule atropine for binding mechanisms. Molecular docking simulations reveal strong binding affinity of both ATX-a and atropine to AChE, interacting effectively with specific amino acids in the binding site as potential inhibitors. Quantitative assessment using the MM-PBSA method demonstrates a significantly negative binding free energy of -81.659 kJ mol-1for ATX-a, indicating robust binding, while atropine exhibits a stronger binding affinity with a free energy of -127.565 kJ mol-1. Umbrella sampling calculates the ΔGbindvalues to evaluate binding free energies, showing a favorable ΔGbindof -36.432 kJ mol-1for ATX-a and a slightly lower value of -30.12 kJ mol-1for atropine. This study reveals the dual functionality of ATX-a, acting as both a nicotinic acetylcholine receptor agonist and an AChE inhibitor. Remarkably, stable complexes form between ATX-a and atropine with AChE at its active site, exhibiting remarkable binding free energies. These findings provide valuable insights into the potential use of ATX-a and atropine as promising candidates for modulating AChE activity.

Bioinspired thiazolo-[2,3-b] quinazolin-6-one derivatives as potent anti-cancer agents targeting EGFR: their biological evaluations and in silico assessment.

Cancer is a challenging and second most deadly disease. The epidermal growth factor receptors (EGFRs) dimerize upon ligand bindings to the extracellular domain that intiates the downstream signaling cascades and activates intracellular kinase domain. Thus, activation of autophosphrylation through kinase domain results in metastasis, cell proliferation, and angiogenesis. In this study, we unravel the binding mechanism of newly synthesized thiazolo-[2,3-b] quinazolin-6-one and evaluate their anti-cancer activity against ovary and prostate carcinoma cell lines (OVCAR-3 and PC-3). Synthesized molecules exhibited promising anti-cancer activity against OVCAR-3 and PC-3 carcinoma cell lines with inhibitory concentrations ranging from 13.4 ± 0.43 to 23.6 ± 1.22 µM and 7.5 ± 0.62 to 67.5 ± 1.24 µM, respectively. These compounds induced apoptosis and resulted in cell cycle arrest at G1 and G2/M transition phases. Next, the nude mice models were taken to investigate the toxicity of the 4bi compound, and in vivo investigations revealed no effects upon examined organs (liver and kidney) treated at different concentrations. Moreover, the combined in silico approaches, molecular docking, molecular dynamics simulations, and MM/PBSA methods were performed to assess the binding affinity and stability of bioinspired synthesized congeners with the epidermal growth factor receptor tyrosine kinase (EGFR-TK). The free binding energy (ΔGbind) of the 4bi molecule was found comparable to Erlotinib drug. The test molecule could be competent for further usage to determine its efficicacy in cancer therapeutics.

Rational design of biaryl pharmacophore inserted noscapine derivatives as potent tubulin binding anticancer agents.

We have strategically designed a series of noscapine derivatives by inserting biaryl pharmacophore (a major structural constituent of many of the microtubule-targeting natural anticancer compounds) onto the scaffold structure of noscapine. Molecular interaction of these derivatives with α,ß-tubulin heterodimer was investigated by molecular docking, molecular dynamics simulation, and binding free energy calculation. The predictive binding affinity indicates that the newly designed noscapinoids bind to tubulin with a greater affinity. The predictive binding free energy (ΔG(bind, pred)) of these derivatives (ranging from -5.568 to -5.970 kcal/mol) based on linear interaction energy (LIE) method with a surface generalized Born (SGB) continuum solvation model showed improved binding affinity with tubulin compared to the lead compound, natural α-noscapine (-5.505 kcal/mol). Guided by the computational findings, these new biaryl type α-noscapine congeners were synthesized from 9-bromo-α-noscapine using optimized Suzuki reaction conditions for further experimental evaluation. The derivatives showed improved inhibition of the proliferation of human breast cancer cells (MCF-7), human cervical cancer cells (HeLa) and human lung adenocarcinoma cells (A549), compared to natural noscapine. The cell cycle analysis in MCF-7 further revealed that these compounds alter the cell cycle profile and cause mitotic arrest at G2/M phase more strongly than noscapine. Tubulin binding assay revealed higher binding affinity to tubulin, as suggested by dissociation constant (Kd) of 126 ± 5.0 µM for 5a, 107 ± 5.0 µM for 5c, 70 ± 4.0 µM for 5d, and 68 ± 6.0 µM for 5e compared to noscapine (Kd of 152 ± 1.0 µM). In fact, the experimentally determined value of ΔG(bind, expt) (calculated from the Kd value) are consistent with the predicted value of ΔG(bind, pred) calculated based on LIE-SGB. Based on these results, one of the derivative 5e of this series was used for further toxicological evaluation. Treatment of mice with a daily dose of 300 mg/kg and a single dose of 600 mg/kg indicates that the compound does not induce detectable pathological abnormalities in normal tissues. Also there were no significant differences in hematological parameters between the treated and untreated groups. Hence, the newly designed noscapinoid, 5e is an orally bioavailable, safe and effective anticancer agent with a potential for the treatment of cancer and might be a candidate for clinical evaluation.

Design, synthesis, molecular modeling, and biological evaluations of novel chalcone based 4-Nitroacetophenone derivatives as potent anticancer agents targeting EGFR-TKD.

A series of chalcone-based 4-Nitroacetophenone derivatives were designed and synthesized by the single-step condensation method. These compounds were identified by 1H NMR,13C NMR, MS, and FTIR analysis. Further, the derivatives were evaluated against four cancer cell lines H1299, MCF-7, HepG2, and K526. The IC50 value of potent compounds NCH-2, NCH-4, NCH-5, NCH-6, NCH-8, and NCH-10 was 4.5-11.4 µM in H1299, 4.3-15.7 µM in MCF-7, 2.7-4.1 µM in HepG2 and 4.9-19.7 µM in K562. To assess the toxicity against healthy cells all potent molecules were evaluated against the HEK-293T cell line, and IC50 values exhibited by NCH-2, and NCH-3 were 77.8, 74.3, and other molecules showed IC50 values > 100 µM. The EGFR expression was determined by using rabbit anti-EGFR monoclonal antibody and significant EGFR expression was knocked down observed in H1299 treated with NCH-10 as well as erlotinib. The underlying mechanism behind cell death was investigated through bioinformatics. First, the molecules were optimized and docked to the binding site of the EGFR kinase domain. The best complexes were simulated for 100-ns and compounds NCH-2, NCH-4, and NCH-10 achieved stability similar to the erlotinib bound kinase domain. The free energy binding (ΔGbind) of NCH-10 was found to be more negative -226.616 ± 2.148 kJ/mol calculated by Molecular Mechanics Poisson Boltzmann's Surface Area (MM-PBSA) method. Both in vitro and in silico results conclude that the present class of chalcone-based 4-Nitroacetophenone derivatives are potent anti-cancer agents targeting EGFR-TKD and are 39 folds more effective against H1299, MCF-7, HepG2, and K562 carcinoma cell lines than healthy HEK-293T cell lines.Communicated by Ramaswamy H. Sarma.

Identification of anti-cyanobacterial leads targeting carbonic anhydrase from phytochemical database using in silico approach.

In cyanobacteria, carbonic anhydrase (zinc metalloenzyme) is a major enzyme that converts CO2 to HCO3- maintaining the carbon concentration around the vicinity of RuBisCo, leading to cyanobacterial biomass generation. Anthropogenic activities, disposal of leached micro nutrients effluents from industries into the aquatic environment results in cyanobacterial blooms. The harmful cyanobacteria release cyanotoxins in open-water system which on ingression through oral route causes major health issues like hepatotoxicity and immunotoxicity. A database was prepared consisting of approximately 3k phytochemicals curated from previous literatures, earlier identified by GC-MS analysis. The phytochemicals were subjected to online servers to identify the novel lead molecules which followed ADMET and drug-like candidates. The identified leads were optimized by density functional theory method using B3YLP/G* level of theory. Carbonic anhydrase chosen as target to observe the binding interaction through molecular docking simulations. From the molecules included in the database the highest binding energy exhibited by alpha-tocopherol succinate and mycophenolic acid were found to be -9.23 kcal/mol and -14.41 kcal/mol and displayed interactions with GLY A102, GLN B30, ASP A41, LYS A105 including Zn2+ and their adjacent amino acids CYS 101, HIS 98, CYS 39 in both chain A and chain A-B of carbonic anhydrase. The Identified molecular orbitals decipher computed global electrophilicity values (Energy gap, electrophilicity and Softness) of alpha-tocopherol succinate and mycophenolic acid were found to be (5.262, 1.948, 0.380) eV and (4.710, 2.805, 0.424) eV demonstrates both molecules are effective and stable. The identified leads may serve as a better anti-carbonic anhydrase agent because they accommodate in the binding site and hampers the catalytic activity of Carbonic anhydrase thus inhibiting the generation of cyanobacterial biomass. This identified lead molecules may serve as a substructure to design novel phytochemicals against carbonic anhydrase present in cyanobacteria. Further in vitro study is necessary to evaluate the efficacy of these molecules.

Identification of potent EGFR-TKD inhibitors from NPACT database through combined computational approaches.

Cancer is the world's second leading cause of death, and there are no approved herbal therapies. The epidermal growth factor receptor tyrosine kinase (EGFR-TK) receptor is a transmembrane protein with eight domains that is found in almost every cancer type and plays an important role in abnormal cell cellular function and causes malignant outcomes. The current study aimed to virtually screen phytochemicals from the NPACT database against EGFR-TKD and also to identify potential inhibitors of this transmembrane protein among plant candidates for anticancer drug development. The docking scores of the chosen phytochemicals were compared with the control (erlotinib). Kurarinone, (2S)-2-methoxykurarnione, and Sophoraflavanone-G exhibited a stronger binding affinity of -18.102 kcal/mol, -14.243 kcal/mol, and -13.759 kcal/mol than erlotinib -12.783 kcal/mol. Moreover, several online search engines were used to predict ADME and toxicity. The drug-likeness of selected phytochemicals was higher than the reference (erlotinib). A 100 ns molecular dynamic (MD) simulation was also applied to the docked conformations to examine the stability and molecular mechanics of protein-ligand interactions. Furthermore, the calculated molecular mechanics Poisson Boltzmann surface area energy of (2S)-2-methoxykurarnione was found to be -129.555 ± 0.512 kJ/mol, which approximately corresponds to the free energy of the reference molecule -130.595 ± 0.908 kJ/mol. We identify phytoconstituents present in Sophora flavescens from the NPACT database, providing key insights into tyrosine kinase inhibition and may serve as better chemotherapeutic agents. Experimental validation is required to determine the anti-EGFR potency of the potent lead molecules discussed in this study.Communicated by Ramaswamy H. Sarma.

Enriched environment prevents hypobaric hypoxia induced neurodegeneration and is independent of antioxidant signaling.

Hypobaric hypoxia (HH) induced neurodegeneration has been attributed to several factors including increased oxidative stress, glutamate excitotoxicity, decreased growth factors, apoptosis, etc. Though enriched environment (EE) has been known to have beneficial effects in various neurological disorders, its effect on HH mediated neurodegeneration remains to be studied. Therefore, the present study was conducted to explore the effect of EE on HH induced neurodegeneration. Male Sprague-Dawley rats were placed in enriched and standard conditions during exposure to HH (7 days) equivalent to an altitude of 25,000 ft. The effect of EE on oxidative stress markers, apoptosis, and corticosterone level in hippocampus was investigated. EE during exposure to HH was found to decrease neurodegeneration as evident from decreased caspase 3 expression and LDH leakage. However, no significant changes were observed in ROS, MDA, and antioxidant status of hippocampus. HH elevates corticosterone level and affected the diurnal corticoid rhythm which may contribute to neurodegeneration, whereas EE ameliorate this effect. Because of the association of neurotrophins and stress and/or corticosterone the BDNF and NGF levels were also examined and it was found that HH decreases their level but concurrent exposure to EE maintains their level. Moreover, inhibition of Tyrosine kinase receptor (Trk) with K252a nullifies the protective effect of EE, whereas Trk activation with agonist, amitriptyline showed protective effect similar to EE. Taken together, we conclude that EE has a potential to ameliorate HH mediated neuronal degeneration which may act through antioxidant independent pathway by modulation of neurotrophins.

Structural insights into conformational stability and binding of thiazolo-[2,3-b] quinazolinone derivatives with EGFR-TKD and in-vitro study.

Heterocyclic molecules are well-known drugs against various diseases including cancer. Many tyrosine kinase inhibitors including erlotinib, osimertinib, and sunitinib were developed and approved but caused adverse effects among treated patients. Which prevents them from being used as cancer therapeutics. In this study, we strategically developed heterocyclic thiazolo-[2,3-b]quinazolinone derivatives by an organic synthesis approach. These synthesized molecules were assessed against the epidermal growth factor receptor tyrosine kinase domain (EGFR-TKD) by in silico methods. Molecular docking simulations unravel derivative 17 showed better binding energy scores and followed Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) properties. The binding affinity displayed by synthetic congener and reference molecule erlotinib was found to be -8.26 ± 0.0033 kcal/mol and -7.54 ± 0.1411 kcal/mol with the kinase domain. Further, molecular dynamic simulations were conducted thrice to validate the molecular docking study and achieved significant results. Both synthetic derivative and reference molecule attained stability in the active site of the TKD. The synthetic congener and erlotinib showed free energy binding (ΔGbind) -102.975 ± 3.714 kJ/mol and -130.378 ± 0.355 kJ/mol computed by Molecular Mechanics Poison Boltzmann Surface Area (MM-PBSA) method. In addition, the motions of each sampled system including the Apo complex were determined by the principal component analysis and Gibbs energy landscape analysis. The in-vitro apoptosis study was performed using MCF-7 and H-1299 cancer cell lines. However, thiazolo-[2,3-]-quinazoline derivative 17 showed fair anti-proliferative activity against MCF-7 and H-1299. Further, the in-vivo study is necessary to determine the effectivity of the potent anti-proliferative, non-toxic molecule against TKD.

In Silico and In Vitro Evaluations of Fluorophoric Thiazolo-[2,3-b]quinazolinones as Anti-cancer Agents Targeting EGFR-TKD.

Epidermal growth factor receptor tyrosine kinase domain (EGFR-TKD) plays a pivotal role in cellular signaling, growth, and metabolism. The EGFR-TKD is highly expressed in cancer cells and was endorsed as a therapeutic target for cancer management to overcome metastasis, cell proliferation, and angiogenesis. The novel thiazolo-[2,3-b]quinazolinones series were strategically developed by microwave-assisted organic synthesis and multi dominos reactions aimed to identify the potent thiazolo-[2,3-b]quinazolinone inhibitor against EGFR-TKD. This study explores the binding stability and binding strength of newly developed series via molecular docking, molecular dynamics simulation, and MM/PBSA and MM/GBSA calculations. The binding interaction was observed to be through the functional groups on aryl substituents at positions 3 and 5 of the thiazolo-[2, 3-b]quinazolinone scaffold. The methyl substituents at position 8 of the ligands had prominent hydrophobic interactions corroborating their bindings similar to the reference FDA-approved drug erlotinib in the active site. ADMET predictions reveal that derivatives 5ab, 5aq, and 5bq are drug-like and may be effective in in vitro study. Molecular dynamics simulation for 100 ns of docked complexes revealed their stability at the atomistic level. The ΔGbinding of thiazolo-[2,3-b]quinazolinone was found to be 5ab - 22.45, 5aq - 22.23, and 5bq - 20.76 similar to standard drug, and erlotinib - 24.11 kcal/mol was determined by MM/GBSA method. Furthermore, the anti-proliferative activity of leads of thiazolo-[2,3-b]quinazolinones (n = 3) was studied against breast cancer cell line (MCF-7) and non-small lung carcinoma cell line (H-1299). The highest inhibitions in cell proliferation were shown by 5bq derivatives, and the IC50 was found to be 6.5 ± 0.67 µM against MCF-7 and 14.8 µM against H-1299. The noscapine was also taken as a positive control and showed IC50 at higher concentrations 37 ± 1 against MCF-7 and 46.5 ± 1.2 against H-1299.

Bacopa monniera leaf extract ameliorates hypobaric hypoxia induced spatial memory impairment.

Hypobaric hypoxia induced memory impairment has been attributed to several factors including increased oxidative stress, depleted mitochondrial bioenergetics, altered neurotransmission and apoptosis. This multifactorial response of the brain to hypobaric hypoxia limits the use of therapeutic agents that target individual pathways for ameliorating hypobaric hypoxia induced memory impairment. The present study aimed at exploring the therapeutic potential of a bacoside rich leaf extract of Bacopa monniera in improving the memory functions in hypobaric conditions. The learning ability was evaluated in male Sprague Dawley rats along with memory retrieval following exposure to hypobaric conditions simulating an altitude of 25,000 ft for different durations. The effect of bacoside administration on apoptosis, cytochrome c oxidase activity, ATP levels, and oxidative stress markers and on plasma corticosterone levels was investigated. Expression of NR1 subunit of N-methyl-d-aspartate receptors, neuronal cell adhesion molecules and was also studied along with CREB phosphorylation to elucidate the molecular mechanisms of bacoside action. Bacoside administration was seen to enhance learning ability in rats along with augmentation in memory retrieval and prevention of dendritic atrophy following hypoxic exposure. In addition, it decreased oxidative stress, plasma corticosterone levels and neuronal degeneration. Bacoside administration also increased cytochrome c oxidase activity along with a concomitant increase in ATP levels. Hence, administration of bacosides could be a useful therapeutic strategy in ameliorating hypobaric hypoxia induced cognitive dysfunctions and other related neurological disorders.

Isradipine antagonizes hypobaric hypoxia induced CA1 damage and memory impairment: Complementary roles of L-type calcium channel and NMDA receptors.

Hypobaric hypoxia leads to cognitive dysfunctions due to increase in intracellular calcium through ion channels. The purpose of this study was to examine the temporal contribution of L-type calcium channels and N-methyl-D-aspartate receptors (NMDARs) in mediating neuronal death in male Sprague Dawley rats exposed to hypobaric hypoxia simulating an altitude of 25,000 ft for different durations. Decreasing exogenous calcium loads by blocking voltage-gated calcium influx with isradipine (2.5 mg kg(-1)), and its efficacy in providing neuroprotection and preventing memory impairment following hypoxic exposure was also investigated. Effect of isradipine on calcium-dependent enzymes mediating oxidative stress and apoptotic cell death was also studied. Blocking of L-type calcium channels with isradipine reduced hypoxia-induced activation of calcium dependent xanthine oxidases, monoamine oxidases, cytosolic phospholipase A(2) and cycloxygenases (COX-2) along with concomitant decrease in free radical generation and cytochrome c release. Increased expression of calpain and caspase 3 was also observed following exposure to hypobaric hypoxia along with augmented neurodegeneration and memory impairment which was adequately prevented by isradipine administration. Administration of isradipine during hypoxic exposure protected the hippocampal neurons following 3 and 7 days of exposure to hypobaric hypoxia along with improvement in spatial memory.

Neuroprotective Role of L-NG-Nitroarginine Methyl Ester (L-NAME) against Chronic Hypobaric Hypoxia with Crowding Stress (CHC) Induced Depression-Like Behaviour.

Improper neuroimmune responses following chronic stress exposure have been reported to cause neuronal dysfunctions leading to memory impairment, anxiety and depression like behaviours. Though several factors affecting microglial activation and consequent alteration in neuro-inflammatory responses have been well studied, role of NO and its association with microglia in stress induced depression model is yet to be explored. In the present study, we validated combination of chronic hypobaric hypoxia and crowding (CHC) as a stress model for depression and investigated the role of chronic stress induced elevated nitric oxide (NO) level in microglia activation and its effect on neuro-inflammatory responses in brain. Further, we evaluated the ameliorative effect of L-NG-Nitroarginine Methyl Ester (L-NAME) to reverse the stress induced depressive mood state. Four groups of male Sprague Dawley rat were taken and divided into control and CHC stress exposed group with and without treatment of L-NAME. Depression like behaviour and anhedonia in rats were assessed by Forced Swim Test (FST) and Sucrose Preference Test (SPT). Microglial activation was evaluated using Iba-1 immunohistochemistry and proinflammatory cytokines were assessed in the hippocampal region. Our result showed that exposure to CHC stress increased the number of active microglia with corresponding increase in inflammatory cytokines and altered behavioural responses. The inhibition of NO synthesis by L-NAME during CHC exposure decreased the number of active microglia in hippocampus as evident from decreased Iba-1 positive cells. Further, L-NAME administration decreased pro-inflammatory cytokines in hippocampus and improved behaviour of rats. Our study demonstrate that stress induced elevation of NO plays pivotal role in altered microglial activation and consequent neurodegenerative processes leading to depression like behaviour in rat.

Early mood behavioral changes following exposure to monotonous environment during isolation stress is associated with altered hippocampal synaptic plasticity in male rats.

Social isolation stress and its effect on mood have been well reported, but the effect of monotony (a state of repetition of events for a considerable period of time without variation) on mood and hippocampal synaptic plasticity needs to be addressed. Present study was conducted on male Sprague-Dawley rats. Singly housed (SH) rats were subjected to monotony stress by physical, visual and pheromonal separation in specially designed animal segregation chamber. Fluoxetine (a selective serotonin reuptake inhibitor) was administered orally. Behavioral assessment showed anxiety and depression like traits in SH group. Monotony stress exposure to SH group resulted in increased pyknosis, decreased apical dendritic arborization and increased asymmetric (excitatory) synapses with the corresponding decrease in the symmetric (inhibitory) synapses in the hippocampal CA3 region. Monotonous environment during isolation stress also decreased the serotonin level and reduced the expression of synaptophysin and pCREB in the hippocampus. Fluoxetine administration to singly housed rats resulted in amelioration of altered mood along with improvement in serotonin and decrease in excitatory synaptic density but no change in altered inhibitory synaptic density in the hippocampus. These findings suggest that monotony during isolation contributes to early impairment in mood state by altering hippocampal synaptic density and neuronal morphology.

Withanolide A prevents neurodegeneration by modulating hippocampal glutathione biosynthesis during hypoxia.

Withania somnifera root extract has been used traditionally in ayurvedic system of medicine as a memory enhancer. Present study explores the ameliorative effect of withanolide A, a major component of withania root extract and its molecular mechanism against hypoxia induced memory impairment. Withanolide A was administered to male Sprague Dawley rats before a period of 21 days pre-exposure and during 07 days of exposure to a simulated altitude of 25,000 ft. Glutathione level and glutathione dependent free radicals scavenging enzyme system, ATP, NADPH level, γ-glutamylcysteinyl ligase (GCLC) activity and oxidative stress markers were assessed in the hippocampus. Expression of apoptotic marker caspase 3 in hippocampus was investigated by immunohistochemistry. Transcriptional alteration and expression of GCLC and Nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) were investigated by real time PCR and immunoblotting respectively. Exposure to hypobaric hypoxia decreased reduced glutathione (GSH) level and impaired reduced gluatathione dependent free radical scavenging system in hippocampus resulting in elevated oxidative stress. Supplementation of withanolide A during hypoxic exposure increased GSH level, augmented GSH dependent free radicals scavenging system and decreased the number of caspase and hoescht positive cells in hippocampus. While withanolide A reversed hypoxia mediated neurodegeneration, administration of buthionine sulfoximine along with withanolide A blunted its neuroprotective effects. Exogenous administration of corticosterone suppressed Nrf2 and GCLC expression whereas inhibition of corticosterone synthesis upregulated Nrf2 as well as GCLC. Thus present study infers that withanolide A reduces neurodegeneration by restoring hypoxia induced glutathione depletion in hippocampus. Further, Withanolide A increases glutathione biosynthesis in neuronal cells by upregulating GCLC level through Nrf2 pathway in a corticosterone dependenet manner.

Enriched environment prevents hypobaric hypoxia induced memory impairment and neurodegeneration: role of BDNF/PI3K/GSK3ß pathway coupled with CREB activation.

Adverse environmental conditions such as hypobaric hypoxia (HH) cause memory impairment by affecting cellular machinery leading to neurodegeneration. Providing enriched environment (EE) is found to be beneficial for curing several neurodegenerative disorders. The protective role of EE in preventing HH induced neuronal death has been reported previously but the involved mechanism is still not clearly understood. The present study is an attempt to verify the impact of EE on spatial memory during HH and also to explore the possible role of neurotrophin in EE mediated neuroprotection. Signaling mechanism involved in neuroprotection was also explored. Male Sprague Dawley rats were simulated to HH condition in an Animal Decompression Chamber at an altitude of 25000 feet in standard and enriched cages for 7 days. Spatial memory was assessed through Morris Water Maze. Role of different neurotrophins was explored by gene silencing and inhibitors for their respective receptors. Further, using different blockers signaling pathway was also explored. Finding of the present study suggested that EE prevents HH mediated memory impairment and neurodegeneration. Also brain-derived neurotrophic factor (BDNF) plays a major role in EE mediated neuroprotection and it effectively prevented neurodegeneration by activating PI3K/AKT pathway resulting in GSK3ß inactivation which further inhibits apoptosis. Moreover GSK3ß phosphorylation and hence its inactivation upregulates CREB phosphorylation which may also accounts for activation of survival machinery in cells and provides neuroprotection. From these observations it can be postulated that EE has a therapeutic potential in amelioration of HH induced memory impairment and neurodegeneration. Hence it may be used as a non invasive and non pharmacological intervention against various neurological disorders.

Inhibition of glucocorticoid receptors ameliorates hypobaric hypoxia induced memory impairment in rat.

Chronic exposure to hypobaric hypoxia (HH) causes neurodegeneration and loss of memory. The underlying mechanisms of HH induced memory impairment have been attributed to prolonged elevated corticosterone level in hippocampus leading to augmented glutamate excitotoxicity, oxidative stress, alteration of neurotransmitter level or their receptors and calcium mediated signaling. Whether this corticosterone mediated neurodegenerative effect occurs through overstimulation of glucocorticoid receptors (GRs) or is independent of the GRs, is not known. Four groups of rats were taken and GR blocker mifepristone was administered intraperitoneally during exposure to HH from 3rd to 7th days. Our results showed a duration dependent transcriptional upregulation of GRs and MRs following exposure to HH. Prolonged exposure to HH for 7 days augmented the translocation of GRs from cytosol to nucleus. Inhibition of GRs during hypoxic exposure improved the hippocampal ATP level and modulated the apoptotic markers like p53, Bcl(2) and Bax. Decreased expression of L-type calcium channel and NR1 subunit of NMDA receptors were also observed following administration of mifepristone during hypoxic exposure. Morphological studies following mifepristone administration during hypoxic exposure showed decreased number of pyknotic cells in hippocampus and decrease in apoptotic and necrotic cells in the CA3 region of hippocampus. The study indicates that elevated corticosterone level during hypoxic exposure causes neurodegeneration and acts through its binding to GRs indicating that inhibition of GRs may provide therapeutic effect in ameliorating HH induced memory impairment.

Quercetin reverses hypobaric hypoxia-induced hippocampal neurodegeneration and improves memory function in the rat.

Inadequate oxygen availability at high altitude causes elevated oxidative stress, resulting in hippocampal neurodegeneration and memory impairment. Though oxidative stress is known to be a major cause of neurodegeneration in hypobaric hypoxia, neuroprotective and ameliorative potential of quercetin, a flavonoid with strong antioxidant properties in reversing hypobaric hypoxia-induced memory impairment has not been studied. Four groups of male adult Sprague Dawley rats were exposed to hypobaric hypoxia for 7 days in an animal decompression chamber at an altitude of 7600 meters. Rats were supplemented with quercetin orally by gavage during 7 days of hypoxic exposure. Spatial working memory was assessed by a Morris Water Maze before and after exposure to hypobaric hypoxia. Changes in oxidative stress markers and apoptotic marker caspase 3 expression in hippocampus were assessed. Histological assessment of neurodegeneration was performed by cresyl violet and fluoro Jade B staining. Our results showed that quercetin supplementation during exposure to hypobaric hypoxia decreased reactive oxygen species levels and consequent lipid peroxidation in the hippocampus by elevating antioxidant status and free radical scavenging enzyme system. There was reduction in caspase 3 expression, and decrease in the number of pyknotic and fluoro Jade B-positive neurons in hippocampus after quercetin supplementation during hypoxic exposure. Behavioral studies showed that quercetin reversed the hypobaric hypoxia-induced memory impairment. These findings suggest that quercetin provides neuroprotection to hippocampal neurons during exposure to hypobaric hypoxia through antioxidative and anti-apoptotic mechanisms, and possesses promising therapeutic potential to ameliorate hypoxia-induced memory dysfunction.

Withania somnifera root extract ameliorates hypobaric hypoxia induced memory impairment in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Withania somnifera (WS) root extract has been used traditionally in ayurvedic system of medicine as a memory enhancer and anti-stress agent. AIM OF THE STUDY: To evaluate the neuroprotective and prophylactic potential of WS root extract in ameliorating hypobaric hypoxia (HH) induced memory impairment and to explore the underlying molecular mechanism. MATERIALS AND METHODS: WS root extract was administered to male Sprague Dawley rats during a period of 21 days pre-exposure and 07 days exposure to a simulated altitude of 25,000 ft. Spatial memory was assessed by Morris Water Maze. Neurodegeneration, corticosterone, acetylcholine (Ach) levels, acetylcholine esterase (AchE) activity, oxidative stress markers and nitric oxide (NO) concentration were assessed in the hippocampus. Synaptic and apoptotic markers were also investigated by immunoblotting. To study the role of NO in regulating corticosterone mediated signaling, the neuronal nitric oxide synthase (n-NOS) inhibitor, L-Nitro-arginine methyl ester (L-Name) and NO agonist sodium nitroprusside (SNP) were administered from 3rd to 7th day of hypoxic exposure. RESULTS: Administration of WS root extract prevented HH induced memory impairment and neurodegeneration along with decreased NO, corticosterone, oxidative stress and AchE activity in hippocampal region. Inhibition of NO synthesis by administration of L-Name reduced corticosterone levels in hippocampus during hypoxic exposure while co-administration of corticosterone increased neurodegeneration. Administration of sodium nitroprusside (SNP) along with WS root extract supplementation during hypoxic exposure increased corticosterone levels and increased the number of pyknotic cells. CONCLUSION: WS root extract ameliorated HH induced memory impairment and neurodegeneration in hippocampus through NO mediated modulation of corticosterone levels.

Corticosterone synthesis inhibitor metyrapone ameliorates chronic hypobaric hypoxia induced memory impairment in rat.

Chronic exposure to hypobaric hypoxia causes oxidative stress and neurodegeneration leading to memory impairment. The present study aimed at investigating the role of corticosterone in hypoxia induced neurodegeneration and effect of metyrapone, a corticosterone synthesis inhibitor that reduces the stress induced elevation of corticosterone without affecting the basal level, in ameliorating chronic hypobaric hypoxia induced cognitive decline. Rats were exposed to simulated altitude of 25,000 ft for 0, 3, 7, 14 and 21 days to determine the temporal alterations in corticosterone and its receptors following exposure to hypobaric hypoxia. Our results showed an elevation of corticosterone in plasma and hippocampal tissue following 7 days of exposure, which declined on prolonged hypoxic exposure for 21 days. A concomitant increase in ROS and lipid peroxidation was observed along with depletion of intracellular antioxidants. Glucocorticoid and mineralocorticoid receptors were upregulated on 3 and 7 days of hypoxic exposure. Though expression of Glut1 and Glut3 were upregulated on 3 days of hypoxic exposure, sharp decline in Glut1 expression following 7 days of hypoxic exposure leads to reduced neuronal glucose uptake. Administration of metyrapone from 3rd to 7th day of hypoxic exposure to suppress hypoxia induced increase in corticosterone levels resulted in reduced oxidative damage, neurodegeneration and improvement of intracellular energy status. The metyrapone treated hypoxic animals performed better in the Morris Water Maze. Further, administration of exogenous corticosterone along with metyrapone during hypoxic exposure blunted the neuroprotective effect of metyrapone indicating a role for corticosterone in mediating hypobaric hypoxia induced neurodegeneration and memory impairment.