L.K.S. Chauhan

Induction of ROS, mitochondrial damage and autophagy in lung epithelial cancer cells by iron oxide nanoparticles

Autophagy has attracted a great deal of research interest in tumor therapy in recent years. An attempt was made in this direction and now we report that iron oxide NPs synthesized by us selectively induce autophagy in cancer cells (A549) and not in normal cells (IMR-90). It was also noteworthy that autophagy correlated with ROS production as well as mitochondrial damage. Protection of NAC against ROS clearly suggested the implication of ROS in hyper-activation of autophagy and cell death. Pre-treatment of cancer cells with 3-MA also exhibited protection against autophagy and promote cellular viability. Results also showed involvement of classical mTOR pathway in autophagy induction by iron oxide NPs in A549 cells. Our results had shown that bare iron oxide NPs are significantly cytotoxic to human cancer cells (A549) but not to the normal human lung fibroblast cells (IMR-90).In other words our nanoparticles selectively kill cancerous cells. It is encouraging to conclude that iron oxide NPs bear the potential of its applications in biomedicine, such as tumor therapy specifically by inducing autophagy mediated cell death of cancer cells.

Curcumin-Loaded Nanoparticles Potently Induce Adult Neurogenesis and Reverse Cognitive Deficits in Alzheimer’s Disease Model via Canonical Wnt/β-Catenin Pathway

Neurogenesis, a process of generation of new neurons, is reported to be reduced in several neurodegenerative disorders including Alzheimers disease (AD). Induction of neurogenesis by targeting endogenous neural stem cells (NSC) could be a promising therapeutic approach to such diseases by influencing the brain self-regenerative capacity. Curcumin, a neuroprotective agent, has poor brain bioavailability. Herein, we report that curcumin-encapsulated PLGA nanoparticles (Cur-PLGA-NPs) potently induce NSC proliferation and neuronal differentiation in vitro and in the hippocampus and subventricular zone of adult rats, as compared to uncoated bulk curcumin. Cur-PLGA-NPs induce neurogenesis by internalization into the hippocampal NSC. Cur-PLGA-NPs significantly increase expression of genes involved in cell proliferation (reelin, nestin, and Pax6) and neuronal differentiation (neurogenin, neuroD1, neuregulin, neuroligin, and Stat3). Curcumin nanoparticles increase neuronal differentiation by activating the Wnt/β-catenin pathway, involved in regulation of neurogenesis. These nanoparticles caused enhanced nuclear translocation of β-catenin, decreased GSK-3β levels, and increased promoter activity of the TCF/LEF and cyclin-D1. Pharmacological and siRNA-mediated genetic inhibition of the Wnt pathway blocked neurogenesis-stimulating effects of curcumin. These nanoparticles reverse learning and memory impairments in an amyloid beta induced rat model of AD-like phenotypes, by inducing neurogenesis. In silico molecular docking studies suggest that curcumin interacts with Wif-1, Dkk, and GSK-3β. These results suggest that curcumin nanoparticles induce adult neurogenesis through activation of the canonical Wnt/β-catenin pathway and may offer a therapeutic approach to treating neurodegenerative diseases such as AD, by enhancing a brain self-repair mechanism.

Cytogenetic effects of cypermethrin and fenvalerate on the root meristem cells of Allium cepa

Abstract Cytogenetic effects of two commercial formulations of alpha-cyano pyrethroid insecticides viz. cypermethrin (cyperkill 25% EC; CYP) and fenvalerate (Sumicidin 20% EC: FEN) were evaluated in the root meristem cells of Allium cepa . The test concentrations of compounds were selected by determining EC5O (CYP.10 mg l −1 ; FEN 14.25 mg l −1 ) of the Allium root growth. Both the compounds significantly and dose-dependently inhibited the mitotic index (MI) and induced chromosome (CA) and mitotic aberrations (MA) at 6 or 24 h treatment. The root meristem cells exposed to 6 or 24 h and analysed at 24 h post exposure, revealed a considerable frequency of aberrant cells despite substantial recovery. The types of aberrations induced by both the compounds were quite similar, except the induction of unequal distribution of chromosomes and micronucleated cells obtained with CYP. Furthermore, CYP was found to be more toxic as the frequency of aberrant cells was much higher in CYP treated cells than that of FEN. These observations, consistent with earlier reports, indicate that spindle poisoning is the primary mechanism of genotoxic action of these alpha-cyano pyrethroid insecticides, however, mild percentage of chromosome breaks indicate the clastogenic potential of these compounds.

Zinc oxide nanoparticles induce apoptosis by enhancement of autophagy via PI3K/Akt/mTOR inhibition.

Zinc oxide nanoparticles (ZnO NPs) induced macrophage cell death and its mechanism remains to be solved. Herein, we report that ZnO NPs induced ROS generation by depleting antioxidant enzymes, increasing lipid peroxidation and protein carbonyl contents in macrophages. The oxidative stress was induced by the inhibition of Nrf2 transcription factor release. ZnO NPs also activated the cleavage of apoptosis markers like caspases 3, 8 and 9. γH2Ax activation and cleavage of poly (ADP-ribose) polymerase (PARP) that are known indicators of genotoxicity were found to be activated by following p53, p21/waf1 signaling. ZnO NPs increased the number of autophagosomes and autophagy marker proteins such as microtubule-associated protein 1 light chain 3-isoform II (MAP-LC3-II) and Beclin 1 after 0.5-24h of treatment. Phosphorylated Akt, PI3K and mTOR were significantly decreased on ZnO NPs exposure. Moreover, the apoptotic and autophagic cell death could be inhibited on blocking of ROS generation by N-acetylcysteine (NAC) which demonstrated the critical role of ROS in both types of cell death. In addition, inhibition of LC3-II by siRNA-dependent knockdown attenuated the cleavage of caspase 3. This study demonstrates autophagy supports apoptosis on ZnO NPs exposure.

Genotoxicity of cadmium on root meristem cells of Allium cepa: cytogenetic and Comet assay approach

Cytogenetic and DNA damaging effects of cadmium (Cd) were examined through chromosome aberrations (CA) and Comet assay on the root meristem cells of Allium cepa. Root meristem cells were exposed to Cd (10, 20, and 40 μM) for 24h and also left in water for 24h recovery. Exposure of Cd revealed significant (P<0.001) inhibition of mitotic index (MI), induction of CA, mitotic aberrations (MA), and micronucleus (MN) formation. Similarly, at 40 μM significant increase in the tail length (85.70 ± 9.40 μm) and tail moment (58.75 ± 5.30 μm) was observed as compared to control 4.50 ± 0.76 and 0.86 ± 0.03 μm, respectively. However, cells examined at 24h post-exposure showed concentration-dependent decline in all the endpoints. Findings of this study confirms the root meristem cells of A. cepa are suitable model for detecting both the environmentally induced CA as well as DNA damage analyzed by Comet assay.

Cytogenetic effects of deltamethrin on rat bone marrow.

Deltamethrin, a synthetic pyrethroid insecticide, was administered to adult female albino rats as a single i.p., s.c., or oral dose of 5.6, 8.4, or 11.2 mg/kg b.w. or repeated i.p. doses of 2.24 mg/kg b.w. for five consecutive days (cumulative dose 11.2 mg/kg b.w.). This treatment inhibited the mitotic index in a dose-dependent manner and increased the frequency of chromosome aberrations in the bone marrow at 24 h post exposure. The parenterally (i.p. and s.c.) administered deltamethrin appeared more effective than the oral gavage for eliciting its cytotoxicity and genetic toxicity potential. The frequency of micronucleated erythrocytes in the bone marrow was also increased at 30 h following a single i.p. dose of 5.6, 8.4, or 11.2 mg/kg b.w. The most prevalent abnormality observed in this study was endomitotic reduplication of chromosomes which, along with mitotic inhibition and micronucleus induction, indicated microtubular/mitotic spindle poisoning by deltamethrin. The increased frequency of chromosome aberrations and micronucleated erythrocytes also suggests a clastogenic potential of deltamethrin. These observations indicate the in vivo susceptibility of mammals to the genetic toxicity potential of deltamethrin.

Trans-Blood Brain Barrier Delivery of Dopamine-Loaded Nanoparticles Reverses Functional Deficits in Parkinsonian Rats

Sustained and safe delivery of dopamine across the blood brain barrier (BBB) is a major hurdle for successful therapy in Parkinsons disease (PD), a neurodegenerative disorder. Therefore, in the present study we designed neurotransmitter dopamine-loaded PLGA nanoparticles (DA NPs) to deliver dopamine to the brain. These nanoparticles slowly and constantly released dopamine, showed reduced clearance of dopamine in plasma, reduced quinone adduct formation, and decreased dopamine autoxidation. DA NPs were internalized in dopaminergic SH-SY5Y cells and dopaminergic neurons in the substantia nigra and striatum, regions affected in PD. Treatment with DA NPs did not cause reduction in cell viability and morphological deterioration in SH-SY5Y, as compared to bulk dopamine-treated cells, which showed reduced viability. Herein, we report that these NPs were able to cross the BBB and capillary endothelium in the striatum and substantia nigra in a 6-hydroxydopamine (6-OHDA)-induced rat model of PD. Systemic intravenous administration of DA NPs caused significantly increased levels of dopamine and its metabolites and reduced dopamine-D2 receptor supersensitivity in the striatum of parkinsonian rats. Further, DA NPs significantly recovered neurobehavioral abnormalities in 6-OHDA-induced parkinsonian rats. Dopamine delivered through NPs did not cause additional generation of ROS, dopaminergic neuron degeneration, and ultrastructural changes in the striatum and substantia nigra as compared to 6-OHDA-lesioned rats. Interestingly, dopamine delivery through nanoformulation neither caused alterations in the heart rate and blood pressure nor showed any abrupt pathological change in the brain and other peripheral organs. These results suggest that NPs delivered dopamine into the brain, reduced dopamine autoxidation-mediated toxicity, and ultimately reversed neurochemical and neurobehavioral deficits in parkinsonian rats.

Mechanism of uptake of ZnO nanoparticles and inflammatory responses in macrophages require PI3K mediated MAPKs signaling.

The inflammatory responses after exposure to zinc oxide nanoparticles (ZNPs) are known, however, the molecular mechanisms and direct consequences of particle uptake are still unclear. Dose and time-dependent increase in the uptake of ZNPs by macrophages has been observed by flow cytometry. Macrophages treated with ZNPs showed a significantly enhanced phagocytic activity. Inhibition of different internalization receptors caused a reduction in uptake of ZNPs in macrophages. The strongest inhibition in internalization was observed by blocking clathrin, caveolae and scavenger receptor mediated endocytic pathways. However, FcR and complement receptor-mediated phagocytic pathways also contributed significantly to control. Further, exposure of primary macrophages to ZNPs (2.5 μg/ml) caused (i) significant enhancement of Ras, PI3K, (ii) enhanced phosphorylation and subsequent activation of its downstream signaling pathways via ERK1/2, p38 and JNK MAPKs (iii) overexpression of c-Jun, c-Fos and NF-κB. Our results demonstrate that ZNPs induce the generation of reactive nitrogen species and overexpression of Cox-2, iNOS, pro-inflammatory cytokines (IL-6, IFN-γ, TNF-α, IL-17 and regulatory cytokine IL-10) and MAPKs which were found to be inhibited after blocking internalization of ZNPs through caveolae receptor pathway. These results indicate that ZNPs are internalized through caveolae pathway and the inflammatory responses involve PI3K mediated MAPKs signaling cascade.

Activation of Autophagic Flux against Xenoestrogen Bisphenol-A-induced Hippocampal Neurodegeneration via AMP kinase (AMPK)/Mammalian Target of Rapamycin (mTOR) Pathways

Background: The effects of xenoestrogen bisphenol-A on autophagy, and association with oxidative stress and apoptosis are still elusive. Results: Transient activation of autophagy protects against bisphenol-A-induced neurodegeneration via AMPK activation and mTOR down-regulation. Conclusion: Autophagy induction against bisphenol-A is an early cells tolerance response. Significance: Autophagy provides an imperative biological marker for evaluation of neurotoxicity by xenoestrogen. The human health hazards related to persisting use of bisphenol-A (BPA) are well documented. BPA-induced neurotoxicity occurs with the generation of oxidative stress, neurodegeneration, and cognitive dysfunctions. However, the cellular and molecular mechanism(s) of the effects of BPA on autophagy and association with oxidative stress and apoptosis are still elusive. We observed that BPA exposure during the early postnatal period enhanced the expression and the levels of autophagy genes/proteins. BPA treatment in the presence of bafilomycin A1 increased the levels of LC3-II and SQSTM1 and also potentiated GFP-LC3 puncta index in GFP-LC3-transfected hippocampal neural stem cell-derived neurons. BPA-induced generation of reactive oxygen species and apoptosis were mitigated by a pharmacological activator of autophagy (rapamycin). Pharmacological (wortmannin and bafilomycin A1) and genetic (beclin siRNA) inhibition of autophagy aggravated BPA neurotoxicity. Activation of autophagy against BPA resulted in intracellular energy sensor AMP kinase (AMPK) activation, increased phosphorylation of raptor and acetyl-CoA carboxylase, and decreased phosphorylation of ULK1 (Ser-757), and silencing of AMPK exacerbated BPA neurotoxicity. Conversely, BPA exposure down-regulated the mammalian target of rapamycin (mTOR) pathway by phosphorylation of raptor as a transient cells compensatory mechanism to preserve cellular energy pool. Moreover, silencing of mTOR enhanced autophagy, which further alleviated BPA-induced reactive oxygen species generation and apoptosis. BPA-mediated neurotoxicity also resulted in mitochondrial loss, bioenergetic deficits, and increased PARKIN mitochondrial translocation, suggesting enhanced mitophagy. These results suggest implication of autophagy against BPA-mediated neurodegeneration through involvement of AMPK and mTOR pathways. Hence, autophagy, which arbitrates cell survival and demise during stress conditions, requires further assessment to be established as a biomarker of xenoestrogen exposure.

Unequivocal evidence of genotoxic potential of argemone oil in mice

Consumption of mustard oil adulterated with argemone oil leads to a clinical condition, commonly referred to as “Epidemic Dropsy.” Since in vitro studies have shown that sanguinarine, an active benzophenanthridine alkaloid of argemone oil, intercalates DNA molecule, the in vivo clastogenic and DNA damaging potential of argemone oil was investigated in mice. Swiss albino mice were intraperitoneally administered 0.5, 1.0, 2.0 and 4.0 ml/kg body wt. of argemone oil to analyze chromosome aberrations and micronucleus test, while 0.25, 0.5, 1.0 and 2.0 ml/kg body wt. were given for alkaline comet assay. The frequencies of chromosomal aberrations and micronucleated erythrocytes formation in mouse bone marrow cells increased in a dose‐dependent manner following argemone oil treatment. However, significant induction in chromosomal aberrations (83%) and micronucleated erythrocytes formation (261%) were observed at a minimum dose of 1.0 ml/kg. The results of comet assay revealed DNA damage in blood, bone marrow and liver cells following argemone oil treatment. Olive tail moment (OTM) and tail DNA showed significant increase in bone marrow (35–44%) and blood cells (25–40%) even at a dose of 0.25 ml/kg body wt. of argemone oil. In liver cells, OTM was significantly increased (20%) at a dose of 0.25 ml/kg, while all the comet parameters including OTM, tail length and tail DNA showed significant increase (31–101%) at a dose of 0.5 ml/kg. These results clearly suggest that single exposure of argemone oil even at low doses produces genotoxic effects in mice.