Changes in peptidyl-prolyl cis/trans isomerase activity and FK506 binding protein expression following neuroprotection by FK506 in the ischemic rat brain.

FK506 is an immunosuppressant also showing neuroprotection following cerebral ischemia. FK506 binds to intracellular proteins (FKBP) which have a wide range of functions but have in common the peptidyl-prolyl cis/trans isomerase activity. Following transient focal ischemia, we have analyzed the expression of FKBP12, 52 and 65 and the total FKBP enzyme activity. Furthermore, we have investigated the effect of FK506 on signal transduction in neurons and perfusion changes in the infarct area. After 90 min of transient middle cerebral artery occlusion in male rats the expression of FKBP12, 52 and 65 was analyzed by Western blot in FK506-treated and control animals and the peptidyl-prolyl cis/trans isomerase activity was determined. Magnetic resonance imaging was used to measure tissue perfusion, development of vasogenic edema and infarct size. To investigate the neuronal stress signal cascade, activating transcription factor 2 (ATF-2), Fas-ligand (Fas-L) and c-Jun expression and phosphorylation were analyzed by immunohistochemistry. FK506 decreased the cerebral infarct volume by 53% and reduced the cytotoxic edema. The total FKBP enzymatic activity in the infarct area was increased and blocked dose dependently by FK506. FKBP expression was selectively up-regulated by cerebral ischemia. FK506 treatment does not influence the expression patterns. c-Jun phosphorylation in neurons of the peri-infarct area and Fas-L expression was reduced by FK506 treatment whereas ATF-2 expression was preserved. Cerebral ischemic damage to the brain was reduced by FK506. It was shown for the first time that neuroprotection by FK506 also included the suppression of the cerebral peptidyl-prolyl cis/trans isomerase activity of FKBP in vivo whereas the expression levels of FKBP12, 52 and 65 following ischemia changed slightly and FK506 treatment does not suppress the expression patterns. However, changes of FKBP enzymatic activity result in suppression of the stress cell body response in the peri-infarct area as observed by suppression of c-Jun phosphorylation and Fas-L expression.