In vivo heat-shock response in the brain: signalling pathway and transcription factor activation.
We analysed the expression of the hsp70 gene, the phosphorylation status of different members of the mitogen-activated protein kinase (MAPK) family, the behaviour of the Akt-GSK3 pathway, as well as the DNA-binding activity of several transcription factors, potential targets of these kinases, in the brain of rats exposed to a fever-like increase in body temperature. Two different brain regions, the cerebellum and the hippocampus, were studied. Hyperthermia caused HSF activation and the induction of hsp70 mRNA and protein to a greater extent in the cerebellum than in the hippocampus. In the cerebellum, ERK1/2 and p38 MAPK phosphorylation were increased by hyperthermia and returned to basal levels during the recovery from heat stress, whereas JNK3 phosphorylation decreased and recovered to above control levels within 60 min of recovery. JNK1 phosphorylation was never modified. In the hippocampus, ERK phosphorylation did not increase but rather decreased, whereas the behaviour of p38 MAPK and JNK was similar to that observed in the cerebellum. Akt phosphorylation increased after hyperthermia and was accompanied by an increased phosphorylation of two substrates, GSK3 and FKHRL1, in both brain areas, with a major effect in the cerebellum. DNA-binding activities of AP-1, NF-kappaB, and MEF2 were activated by heat shock in the cerebellum, whereas only MEF2 was activated in the hippocampus. Our data indicate that a physiologically relevant increase in body temperature induces brain injury and survival response to it as demonstrated by induction of hsp70 gene expression and activation of specific signalling pathways. Reprogramming of gene expression, by the specific transcription factors activated, probably plays a central role in cell adaptation and survival to heat stress. The hippocampus shows less responsiveness to hyperthermia than the cerebellum.
Maroni
Paola
P
Istituto di Patologia Generale, Università degli Studi di Milano, Via Mangiagalli 31, 20133 Milan, Italy.
Bendinelli
Paola
P
Tiberio
Laura
L
Rovetta
Francesca
F
Piccoletti
Roberta
R
Schiaffonati
Luisa
L
D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002531:Cerebellum / Q000201:enzymology / Q000503:physiopathology; D004268:DNA-Binding Proteins / Q000378:metabolism; D005334:Fever / Q000201:enzymology* / Q000503:physiopathology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology*; D006624:Hippocampus / Q000201:enzymology / Q000503:physiopathology; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System / Q000502:physiology*; D064326:MEF2 Transcription Factors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018006:Myogenic Regulatory Factors; D016328:NF-kappa B / Q000378:metabolism; D009419:Nerve Tissue Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases; D000071161:Forkhead Box Protein O1
D004268:DNA-Binding Proteins; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D018840:HSP70 Heat-Shock Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D064326:MEF2 Transcription Factors; D020928:Mitogen-Activated Protein Kinases; D018006:Myogenic Regulatory Factors; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases; C499515:FOXO3 protein, rat; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1; C494920:Akt1 protein, rat