The expression of transforming growth factor-beta1 (TGF-beta1) in hippocampal neurons: a temporary upregulated protein level after transient forebrain ischemia in the rat.
Exogenous TGF-beta1 has been shown to protect neurons from damage induced in vitro and in vivo. In this study we attempted to examine the expression of endogenous TGF-beta1 mRNA and protein in the hippocampus of non-ischemic and ischemic rats, and to localize TGF-beta1 protein and DNA fragmentation by double-staining. Transient ischemia was induced for 10 min in Wistar rats by clamping both common carotid arteries and lowering blood pressure to 40 mmHg. Bioactive TGF-beta1 was selectively determined in CA1 pyramidal neurons of non-ischemic rats. It was upregulated after 3 h and 6 h of reperfusion corresponding to the increase in TGF-beta1 mRNA level detected by RT-PCR. Lectin and GFAP staining showed no detectable activated microglial cells and astrocytes in the hippocampus 3 h and 6 h after ischemia. When neuronal damage proceeded through day 2 to day 4 after ischemia as demonstrated by TUNEL-staining, TGF-beta1 immunoreactivity (ir) disappeared in damaged neurons but persisted in viable neurons although TGF-beta1 mRNA levels continuously increased. Double-staining revealed that TUNEL-positive neurons did not express TGF-beta1, while TUNEL-negative neurons in the CA1 subfield exhibited a distinct TGF-beta1 ir. These data indicate that hippocampal CA1 neurons can express TGF-beta1 under physiological conditions and upregulate its expression during the first hours after ischemia, that is independent of the activation of glial cells. The endogenous TGF-beta1 expressed in neurons may play a role in the pathological process of DNA degradation and delayed neuronal death after transient forebrain ischemia.
Zhu
Y
Y
Institut für Pharmakologie und Toxikologie, Philipps-Universität, Marburg, Germany. zhu@mailer.uni-marburg.de
Roth-Eichhorn
S
S
Braun
N
N
Culmsee
C
C
Rami
A
A
Krieglstein
J
J
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology; D053938:DNA Fragmentation / Q000502:physiology; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020287:In Situ Nick-End Labeling; D008297:Male; D017628:Microglia / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D018696:Neuroprotective Agents / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000503:physiopathology*; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology*
D018696:Neuroprotective Agents; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta