CDK5-induced p-PPARγ(Ser 112) downregulates GFAP via PPREs in developing rat brain: effect of metal mixture and troglitazone in astrocytes.
The peroxisome proliferator-activated receptor gamma (PPARγ), a group of ligand-activated transcriptional factors, is expressed in glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes. Here, we investigated the role of PPARγ in regulating GFAP using a mixture of As, Cd and Pb (metal mixture, MM) that induces apoptosis and aberrant morphology in rat brain astrocytes. We observed a phospho PPARγ (serine 112 (S112)) (p-PPARγ (S112))-mediated downregulation of GFAP in the MM-exposed astrocytes. We validated this using pure PPARγ agonist, troglitazone (TZ). As reported with MM, TZ induced astrocyte damage owing to reduced GFAP. In silico analysis in the non-coding region of GFAP gene revealed two PPARγ response elements (PPREs); inverted repeat 10 and direct repeat 1 sequences. Gel shift and chromatin immunoprecipitation assays demonstrated enhancement in binding of p-PPARγ (S112) to the sequences, and luciferase reporter assay revealed strong repression of GFAP via PPREs, in response to both MM and TZ. This indicated that suppression in GFAP indeed occurs through direct regulation of these elements by p-PPARγ (S112). Signaling studies proved that MM, as well as TZ, activated the cyclin-dependent kinase 5 (CDK5) and enhanced its interaction with PPARγ resulting into increased p-PPARγ (S112). The p-CDK5 levels were dependent on proximal activation of extracellular signal-regulated protein kinase 1/2 and downstream Jun N-terminal kinase. Taken together, these results are the first to delineate downregulation of GFAP through genomic and non-genomic signaling of PPARγ. It also brings forth a resemblance of TZ with MM in terms of astrocyte disarray in developing brain.
Developmental Toxicology, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow 226001, India.
A
A
Rai
Developmental Toxicology, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow 226001, India.
S
S
Tripathi
1] Developmental Toxicology, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow 226001, India [2] Academy of Scientific and Innovative Research, Lucknow 226001, India.
R
R
Kushwaha
Department of Biochemical Engineering & Biotechnology, Indian Institute of Technology, New Delhi 110016, India.
P
P
Singh
Department of Biochemical Engineering & Biotechnology, Indian Institute of Technology, New Delhi 110016, India.
P
P
Srivastava
DTDD Division, CSIR-Central Drug Research Institute, Lucknow 226031, India.
S
S
Sanyal
1] Developmental Toxicology, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow 226001, India [2] Academy of Scientific and Innovative Research, Lucknow 226001, India.
S
S
Bandyopadhyay
D000818:Animals; D001151:Arsenic / Q000633:toxicity; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D002104:Cadmium / Q000633:toxicity; D002839:Chromans / Q000494:pharmacology*; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics* / Q000378:metabolism; D007854:Lead / Q000633:toxicity; D008297:Male; D047495:PPAR gamma / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D020218:Response Elements; D045162:Thiazolidinediones / Q000494:pharmacology*; D000077288:Troglitazone
D002839:Chromans; D005904:Glial Fibrillary Acidic Protein; D047495:PPAR gamma; D045162:Thiazolidinediones; D002104:Cadmium; D007854:Lead; D051360:Cyclin-Dependent Kinase 5; D000077288:Troglitazone; D001151:Arsenic