title: Arsenic, Cadmium, and Lead Like Troglitazone Trigger PPARγ-Dependent Poly (ADP-Ribose) Polymerase Expression and Subsequent Apoptosis in Rat Brain Astrocytes.
abstract: We previously demonstrated that arsenic, cadmium, and lead mixture at environmentally relevant doses induces astrocyte apoptosis in the developing brain. Here, we investigated the mechanism and contribution of each metal in inducing the apoptosis. We hypothesized participation of transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ), reported to affect astrocyte survival. We treated cultured rat astrocytes with single metals and their combinations and performed apoptosis assay and measured PPARγ expression levels. We found that cadmium demonstrated maximum increase in PPARγ as well as apoptosis, followed by arsenic and then lead. Interestingly, we observed that the metals mimicked PPARγ agonist, troglitazone, and enhanced PPARγ-transcriptional activity. Co-treatment with PPARγ-siRNA or PPARγ-antagonist, GW9662, suppressed the astrocyte apoptosis, suggesting a prominent participation of PPARγ in metal(s)-induced astrocyte loss. We explored PPARγ-transcriptional activity and identify its target gene in apoptosis, performed in silico screening. We spotted PPARγ-response elements (PPREs) within poly(ADP-ribose) polymerase (PARP) gene, and through gel-shift assay verified metal(s)-mediated increased PPARγ binding to PARP-PPREs. Chromatin-immunoprecipitation and luciferase-reporter assays followed by real-time PCR and Western blotting proved PPRE-mediated PARP expression, where cadmium contributed most and lead least, and the effects of metal mixture were comparable with troglitazone. Eventually, dose-dependent increased cleaved-PARP/PARP ratio confirmed astrocyte apoptosis. Additionally, we found that PPARγ and PARP expressions were c-Jun N-terminal kinases and cyclin-dependent kinase5-dependent. In vivo treatment of developing rats with the metals corroborated enhanced PPARγ-dependent PARP and astrocyte apoptosis, where yet again cadmium contributed most. Overall, our study enlightens a novel PPARγ-dependent mechanism of As-, Cd-, and Pb-induced astrocyte apoptosis.
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow, India.|Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma GandhiMarg, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kushwaha
authors.affiliation: Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma GandhiMarg, Lucknow, Uttar Pradesh, 226001, India.|Babu Banarasi Das University, Lucknow, 226028, India.
authors.forename: Juhi
authors.initials: J
authors.lastname: Mishra
authors.affiliation: Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma GandhiMarg, Lucknow, Uttar Pradesh, 226001, India.|Amity Institute of Biotechnology, Amity University (Lucknow campus), Lucknow, Uttar Pradesh, 226028, India.
authors.forename: Sachin
authors.initials: S
authors.lastname: Tripathi
authors.affiliation: Central Instrumentation Facility, Developmental Toxicology Division, CSIR-IITR, Vishvigyan Bhavan, 31, Mahatma GandhiMarg, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Puneet
authors.initials: P
authors.lastname: Khare
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow, India. sanghmitra@iitr.res.in.|Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma GandhiMarg, Lucknow, Uttar Pradesh, 226001, India. sanghmitra@iitr.res.in.
authors.forename: Sanghamitra
authors.identifier: http://orcid.org/0000-0002-1490-3599
authors.initials: S
authors.lastname: Bandyopadhyay
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001151:Arsenic / Q000633:toxicity*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D001483:Base Sequence; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002104:Cadmium / Q000633:toxicity*; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D007854:Lead / Q000633:toxicity*; D047495:PPAR gamma / Q000819:agonists* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D000077288:Troglitazone / Q000633:toxicity*
chemical_list: D047495:PPAR gamma; D002104:Cadmium; D007854:Lead; D011065:Poly(ADP-ribose) Polymerases; D000077288:Troglitazone; D001151:Arsenic
keywords: Apoptosis; Astrocyte; Environment; Metals; PARP; PPARγ