title: Zinc Oxide Nanoparticle Induces Microglial Death by NADPH-Oxidase-Independent Reactive Oxygen Species as well as Energy Depletion.
abstract: Zinc oxide nanoparticle (ZnO-NP) is one of the most widely used engineered nanoparticles. Upon exposure, nanoparticle can eventually reach the brain through various routes, interact with different brain cells, and alter their activity. Microglia is the fastest glial cell to respond to any toxic insult. Nanoparticle exposure can activate microglia and induce neuroinflammation. Simultaneous to activation, microglial death can exacerbate the scenario. Therefore, we focused on studying the effect of ZnO-NP on microglia and finding out the pathway involved in the microglial death. The present study showed that the 24 h inhibitory concentration 50 (IC50) of ZnO-NP for microglia is 6.6 μg/ml. Early events following ZnO-NP exposure involved increase in intracellular calcium level as well as reactive oxygen species (ROS). Neither of NADPH oxidase inhibitors, apocynin, (APO) and diphenyleneiodonium chloride (DPIC) were able to reduce the ROS level and rescue microglia from ZnO-NP toxicity. In contrary, N-acetyl cysteine (NAC) showed opposite effect. Exogenous supplementation of superoxide dismutase (SOD) reduced ROS significantly even beyond control level but partially rescued microglial viability. Interestingly, pyruvate supplementation rescued microglia near to control level. Following 10 h of ZnO-NP exposure, intracellular ATP level was measured to be almost 50 % to the control. ZnO-NP-induced ROS as well as ATP depletion both disturbed mitochondrial membrane potential and subsequently triggered the apoptotic pathway. The level of apoptosis-inducing proteins was measured by western blot analysis and found to be upregulated. Taken together, we have deciphered that ZnO-NP induced microglial apoptosis by NADPH oxidase-independent ROS as well as ATP depletion.
authors.affiliation: Immunotoxicology Laboratory, Food, Drug and Chemical Toxicology Group and Nanotherapeutics and Nanomaterial Toxicology Group, CSIR-Indian Institute of Toxicology Research, Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Anuj Kumar
authors.initials: AK
authors.lastname: Sharma
authors.affiliation: Immunotoxicology Laboratory, Food, Drug and Chemical Toxicology Group and Nanotherapeutics and Nanomaterial Toxicology Group, CSIR-Indian Institute of Toxicology Research, Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India.|Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR Campus, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Vikas
authors.initials: V
authors.lastname: Singh
authors.affiliation: Immunotoxicology Laboratory, Food, Drug and Chemical Toxicology Group and Nanotherapeutics and Nanomaterial Toxicology Group, CSIR-Indian Institute of Toxicology Research, Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India.|Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR Campus, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Ruchi
authors.initials: R
authors.lastname: Gera
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR Campus, Lucknow, Uttar Pradesh, 226001, India.|Water Analysis Laboratory, Nanotherapeutics and Nanomaterial Toxicology Group, CSIR-Indian Institute of Toxicology Research, Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Mahaveer Prasad
authors.initials: MP
authors.lastname: Purohit
authors.affiliation: Immunotoxicology Laboratory, Food, Drug and Chemical Toxicology Group and Nanotherapeutics and Nanomaterial Toxicology Group, CSIR-Indian Institute of Toxicology Research, Vishvigyan Bhawan, 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India. debabrata.ghosh@iitr.res.in.|Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR Campus, Lucknow, Uttar Pradesh, 226001, India. debabrata.ghosh@iitr.res.in.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Ghosh
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D053768:Metal Nanoparticles / Q000008:administration & dosage*; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009861:Onium Compounds / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D019289:Pyruvic Acid / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015034:Zinc Oxide / Q000008:administration & dosage*
chemical_list: D000098:Acetophenones; D004791:Enzyme Inhibitors; D009861:Onium Compounds; D017382:Reactive Oxygen Species; C007517:diphenyleneiodonium; D019289:Pyruvic Acid; C056165:acetovanillone; D019255:NADPH Oxidases; D015034:Zinc Oxide
keywords: ATP; Apoptosis; Microglia; NADPH oxidase; Zinc oxide nanoparticle