Yogesh K. Dhuriya

Unraveling the mechanism of neuroprotection of curcumin in arsenic induced cholinergic dysfunctions in rats

Earlier, we found that arsenic induced cholinergic deficits in rat brain could be protected by curcumin. In continuation to this, the present study is focused to unravel the molecular mechanisms associated with the protective efficacy of curcumin in arsenic induced cholinergic deficits. Exposure to arsenic (20mg/kg body weight, p.o) for 28 days in rats resulted to decrease the expression of CHRM2 receptor gene associated with mitochondrial dysfunctions as evident by decrease in the mitochondrial membrane potential, activity of mitochondrial complexes and enhanced apoptosis both in the frontal cortex and hippocampus in comparison to controls. The ultrastructural images of arsenic exposed rats, assessed by transmission electron microscope, exhibited loss of myelin sheath and distorted cristae in the mitochondria both in the frontal cortex and hippocampus as compared to controls. Simultaneous treatment with arsenic (20mg/kg body weight, p.o) and curcumin (100mg/kg body weight, p.o) for 28 days in rats was found to protect arsenic induced changes in the mitochondrial membrane potential and activity of mitochondrial complexes both in frontal cortex and hippocampus. Alterations in the expression of pro- and anti-apoptotic proteins and ultrastructural damage in the frontal cortex and hippocampus following arsenic exposure were also protected in rats simultaneously treated with arsenic and curcumin. The data of the present study reveal that curcumin could protect arsenic induced cholinergic deficits by modulating the expression of pro- and anti-apoptotic proteins in the brain. More interestingly, arsenic induced functional and ultrastructural changes in the brain mitochondria were also protected by curcumin.

Molecularly imprinted polymer coupled with dispersive liquid–liquid microextraction and injector port silylation: A novel approach for the determination of 3-phenoxybenzoic acid in complex biological samples using gas chromatography–tandem mass spectrometry

A novel analytical approach based on molecularly imprinted solid phase extraction (MISPE) coupled with dispersive liquid-liquid microextraction (DLLME), and injector port silylation (IPS) has been developed for the selective preconcentration, derivatization and analysis of 3-phenoxybenzoic acid (3-PBA) using gas chromatography-tandem mass spectrometry (GC-MS/MS) in complex biological samples such as rat blood and liver. Factors affecting the synthesis of MIP were evaluated and the best monomer and cross-linker were selected based on binding affinity studies. Various parameters of MISPE, DLLME and IPS were optimized for the selective preconcentration and derivatization of 3-PBA. The developed method offers a good linearity over the calibration range of 0.02-2.5ngmg(-1) and 7.5-2000ngmL(-1) for liver and blood respectively. Under optimized conditions, the recovery of 3-PBA in liver and blood samples were found to be in the range of 83-91%. The detection limit was found to be 0.0045ngmg(-1) and 1.82ngmL(-1) in liver and blood respectively. SRM transition of 271→227 and 271→197 has been selected as quantifier and qualifier transition for 3-PBA derivative. Intra and inter-day precision for five replicates in a day and for five, successive days was found to be less than 8%. The method developed was successfully applied to real samples, i.e. rat blood and tissue for quantitative evaluation of 3-PBA. The analytical approach developed is rapid, economic, simple, eco-friendly and possess immense utility for the analysis of analytes with polar functional groups in complex biological samples by GC-MS/MS.

Brain cholinergic alterations in rats subjected to repeated immobilization or forced swim stress on lambda-cyhalothrin exposure

Role of immobilization stress (IMS), a psychological stressor and forced swim stress (FSS), a physical stressor was investigated on the neurobehavioral toxicity of lambda-cyhalothrin (LCT), a new generation type-II synthetic pyrethroid. Pre-exposure of rats to IMS (15 min/day) or FSS (3 min/day) for 28 days on LCT (3.0 mg/kg body weight, p.o.) treatment for 3 days resulted to decrease spatial learning and memory and muscle strength associated with cholinergic-muscarinic receptors in frontal cortex and hippocampus as compared to those exposed to IMS or FSS or LCT alone. Decrease in acetylcholinesterase activity, protein expression of ChAT and PKC-β1 associated with decreased mRNA expression of CHRM2, AChE and ChAT in frontal cortex and hippocampus was also evident in rats pre-exposed to IMS or FSS on LCT treatment, compared to rats exposed to IMS or FSS or LCT alone. Interestingly, changes both in behavioral and neurochemical endpoints were marginal in rats subjected to IMS or FSS for 28 days or those exposed to LCT for 3 days alone, compared to controls. The results suggest that stress is an important contributor in LCT induced cholinergic deficits.

Repurposing and Revival of the Drugs: A New Approach to Combat the Drug Resistant Tuberculosis

Emergence of drug resistant tuberculosis like multi drug resistant tuberculosis (MDR-TB), extensively drug-resistant tuberculosis (XDR-TB) and totally drug resistant tuberculosis (TDR-TB) has created a new challenge to fight against these bad bugs of Mycobacterium tuberculosis. Repurposing and revival of the drugs are the new trends/options to combat these worsen situations of tuberculosis in the antibiotics resistance era or in the situation of global emergency. Bactericidal and synergistic effect of repurposed/revived drugs along with the latest drugs bedaquiline and delamanid used in the treatment of MDR-TB, XDR-TB, and TDR-TB might be the choice for future promising combinatorial chemotherapy against these bad bugs.

PI3K/Akt/GSK3β induced CREB activation ameliorates arsenic mediated alterations in NMDA receptors and associated signaling in rat hippocampus: Neuroprotective role of curcumin

HIGHLIGHTSProtective role of curcumin in arsenic induced NMDA receptor alterations investigated.Sodium arsenite decreased expression of BDNF, pAkt, pErk ½, pGSK3&bgr; and pCREB.Curcumin protected sodium arsenite induced changes via PI3/Akt/MAPK pathway in hippocampus.Impaired cognitive deficits by sodium arsenite in rats also recovered by curcumin. ABSTRACT Protective efficacy of curcumin in arsenic induced NMDA receptor dysfunctions and PI3K/Akt/ GSK3&bgr; signalling in hippocampus has been investigated in vivo and in vitro. Exposure to sodium arsenite (in vivo – 20mg/kg, body weight p.o. for 28 days; in vitro – 10&mgr;M for 24h) and curcumin (in vivo – 100mg/kg body weight p.o. for 28 days; in vitro – 20&mgr;M for 24h) was carried out alone or simultaneously. Treatment with curcumin ameliorated sodium arsenite induced alterations in the levels of NMDA receptors, its receptor subunits and synaptic proteins ‐ pCaMKII&agr;, PSD‐95 and SynGAP both in vivo and in vitro. Decreased levels of BDNF, pAkt, pERK1/2, pGSK3&bgr; and pCREB on sodium arsenite exposure were also protected by curcumin. Curcumin was found to decrease sodium arsenite induced changes in hippocampus by modulating PI3K/Akt/GSK3&bgr; neuronal survival pathway, known to regulate various cellular events. Treatment of hippocampal cultures with pharmacological inhibitors for ERK1/2, GSK3&bgr; and Akt individually inhibited levels of CREB and proteins associated with PI3K/Akt/GSK3&bgr; pathway. Simultaneous treatment with curcumin was found to improve sodium arsenite induced learning and memory deficits in rats assessed by water maze and Y‐maze. The results provide evidence that curcumin exercises its neuroprotective effect involving PI3K/Akt pathway which may affect NMDA receptors and downstream signalling through TrK&bgr; and BDNF in arsenic induced cognitive deficits in hippocampus.

Prenatal exposure to lambda-cyhalothrin impairs memory in developing rats: Role of NMDA receptor induced post-synaptic signalling in hippocampus

HIGHLIGHTSPrenatal exposure to LCT altered expression of NMDA receptors in developing rats.Alteration in postsynaptic signaling in hippocampus of developing rats also evident.Changes associated with impairment in memory of rats on PD22 and PD45.Changes found to persist in developing rats exposed at high dose (3 mg/kg bw). ABSTRACT Effect of prenatal exposure to lambda‐cyhalothrin (LCT) has been assessed on the integrity of NMDA receptors and associated post‐synaptic signalling in hippocampus of developing rats. Decrease in the binding of [3H]‐MK 801, known to label NMDA receptors was observed in hippocampus of rats prenatally exposed to LCT (1 and 3 mg/kg body weight) on PD22, compared to controls. Consistent with this, decrease in the mRNA and protein expression of NR1 and NR2B subunits of NMDA receptors was evident in rats prenatally exposed to LCT (1 and 3 mg/kg body weight) on PD22. There was no change in mRNA and protein expression of NR2A subunit of NMDA receptors. Prenatal exposure to LCT (1 and 3 mg/kg body weight) decreased the expression of positive regulators (PSD95, pERK1/2, CaMKII&agr; & pCREB) and increased the expression of negative regulators (Cdk5 & SynGAP) associated with NMDA receptor dependent synaptic plasticity in hippocampus and impaired learning and memory of rats on PD22. The neurobehavioral changes continued to persist in rats exposed to LCT at high dose (3 mg/kg body weight) while exhibited trend of recovery in those exposed at moderate dose (1 mg/kg body weight) on PD45, compared to controls. No change in any of the neurobehavioral endpoint was observed in developing rats prenatally exposed to LCT at low dose (0.5 mg/kg body weight) on PD22 and PD45. The results exhibit that alterations in NMDA receptors on prenatal exposure to LCT may affect postsynaptic signalling associated with impaired learning and memory in developing rats.

Influence of immobilization and forced swim stress on the neurotoxicity of lambda-cyhalothrin in rats: Effect on brain biogenic amines and BBB permeability.

HIGHLIGHTSInfluence of stress in the neurotoxicity of LCT investigated in rats.Marginal change in plasma corticosterone & BBB on pre‐exposure to stress or LCT alone.No significant change in brain neurotransmitters evident on exposure to stress or LCT.Intense neurochemical changes observed in rats co‐exposed to stress and LCT.Pre‐exposure to stress enhanced vulnerability of rats to neurotoxic response of LCT. ABSTRACT Experimental studies have been carried out on rats to understand the influence of immobilization stress (IMS), a psychological stressor and forced swim stress (FSS), a physical stressor in the neurotoxicity of lambda‐cyhalothrin (LCT), a new generation type II synthetic pyrethroid with extensive applications. No significant change in plasma corticosterone levels and blood brain barrier (BBB) permeability was observed in rats subjected to IMS (one session of 15 min/day), FSS (one session of 3 min/day) for 28 days or LCT treatment (3.0 mg/kg body weight, p.o. suspended in groundnut oil) for 3 days (26th, 27th and 28th day) as compared to controls. Marginal changes in the levels of biogenic amines and their metabolites (NE, EPN, DA, HVA, DOPAC, 5‐HT) in hypothalamus, frontal cortex, hippocampus, and corpus striatum were observed in rats subjected to IMS or FSS or LCT alone as compared to controls. It was interesting to note that pre‐exposure to IMS or FSS followed by LCT treatment for 3 days caused a marked increase in plasma corticosterone levels associated with disruption in the BBB permeability as compared to rats exposed to IMS or FSS or LCT alone. Pre‐exposure to IMS or FSS followed by LCT treatment for 3 days resulted to alter the levels of biogenic amines and their metabolites in hypothalamus, frontal cortex, hippocampus, and corpus striatum as compared to rats exposed to IMS or FSS or LCT alone. Although neurochemical changes were more intense in rats pre‐exposed to IMS as compared to those subjected to FSS on LCT treatment, the results indicate that both psychological and physical stress could be important influencing factors in the neurotoxicity of LCT.

Involvement of PKA/DARPP-32/PP1α and β- arrestin/Akt/GSK-3β Signaling in Cadmium-Induced DA-D2 Receptor-Mediated Motor Dysfunctions: Protective Role of Quercetin

Given increasing risk of cadmium-induced neurotoxicity, the study was conducted to delineate the molecular mechanisms associated with cadmium-induced motor dysfunctions and identify targets that govern dopaminergic signaling in the brain involving in vivo, in vitro, and in silico approaches. Selective decrease in dopamine (DA)-D2 receptors on cadmium exposure was evident which affected the post-synaptic PKA/DARPP-32/PP1α and β-arrestin/Akt/GSK-3β signaling concurrently in rat corpus striatum and PC12 cells. Pharmacological inhibition of PKA and Akt in vitro demonstrates that both pathways are independently modulated by DA-D2 receptors and associated with cadmium-induced motor deficits. Ultrastructural changes in the corpus striatum demonstrated neuronal degeneration and loss of synapse on cadmium exposure. Further, molecular docking provided interesting evidence that decrease in DA-D2 receptors may be due to direct binding of cadmium at the competitive site of dopamine on DA-D2 receptors. Treatment with quercetin resulted in the alleviation of cadmium-induced behavioral and neurochemical alterations. This is the first report demonstrating that cadmium-induced motor deficits are associated with alteration in postsynaptic dopaminergic signaling due to a decrease in DA-D2 receptors in the corpus striatum. The results further demonstrate that quercetin has the potential to alleviate cadmium-induced dopaminergic dysfunctions.

Postnatal exposure to poly (I:C) impairs learning and memory through changes in synaptic plasticity gene expression in developing rat brain

&NA; Viral infection during early stage of life influences brain development and results in several neurodevelopmental disorders such as schizophrenia, autism and behavioral abnormalities. However, the mechanism through which infection causes long‐term behavioral defects is not well known. To elucidate this, we have used synthetic polyinosinic‐polycytidylic acid [poly (I:C)] which acts as a dsRNA molecule and interacts with toll‐like receptor‐3 (TLR‐3) of microglia cells to evoke the immune system, thus mimicking the viral infection. Rat pups of postnatal day (PND) 7 were infused with a single dose of poly (I:C) (5 mg/kg BW) and vehicle alone to controls. When these pups grew to 3, 6 and 12 weeks, their spatial and fear conditioning memory were impaired as assessed by Morris water maze and passive avoidance test, respectively. We checked the immune activation by staining of TNF‐&agr; in the hippocampus and observed that poly (I:C) exposure elevated the number of TNF‐&agr; positive cells immediately after 12 h of infusion in one week rat and it persisted up to postnatal age of 3 and 12 weeks. Moreover, poly (I:C) significantly decreased the binding of 3H‐QNB to the cholinergic receptors in the frontal cortex and hippocampus of 3 and 6 weeks rats as compared to control but did not change significantly in 12 weeks rats. RT‐PCR and immunoblotting results showed that poly (I:C) exposure upregulated the expression of memory associated genes (BDNF, Arc, EGR1) at mRNA and protein level in frontal cortex and hippocampus of 3 weeks rats as compared to control. However, long‐time persistence of poly (I:C) effects significantly decreased the expression of these genes in both brain regions of 12 weeks rats. Taken together, it is evident that early life exposure to poly (I:C) has a long‐term effect and impairs learning and memory, probably through TNF‐&agr; mediated neuroinflammation and alteration in the expression of memory associated genes in frontal cortex and hippocampus of rats.

Necroptosis: a regulated inflammatory mode of cell death

Programmed cell death has a vital role in embryonic development and tissue homeostasis. Necroptosis is an alternative mode of regulated cell death mimicking features of apoptosis and necrosis. Necroptosis requires protein RIPK3 (previously well recognized as regulator of inflammation, cell survival, and disease) and its substrate MLKL, the crucial players of this pathway. Necroptosis is induced by toll-like receptor, death receptor, interferon, and some other mediators. Shreds of evidence based on a mouse model reveals that deregulation of necroptosis has been found to be associated with pathological conditions like cancer, neurodegenerative diseases, and inflammatory diseases. In this timeline article, we are discussing the molecular mechanisms of necroptosis and its relevance to diseases.