Protein kinase C inhibition prevents upregulation of vascular ET(B) and 5-HT(1B) receptors and reverses cerebral blood flow reduction after subarachnoid haemorrhage in rats.

The pathogenesis of cerebral ischaemia after subarachnoid haemorrhage (SAH) still remains elusive. The purpose of the present study was to examine whether specific protein kinas C (PKC) inhibition in rats could alter the transcriptional SAH induced Endothelin (ET) type B and 5-hydroxytryptamine type 1B (5-HT(1B)) receptor upregulation and prevent the associated cerebral blood flow (CBF) reduction. The PKC inhibitor RO-31-7549 or vehicle was injected intracisternally after the induced SAH in rats (n=3 to 10 in each groups for each method). The involvement of the PKC isoforms was investigated with Western blot; only PKCdelta and PKCalpha subtypes were increased after SAH RO-31-7549 treatment abolished this. At 2 days after the SAH basilar and middle cerebral arteries were harvested and the contractile response to endothelin-1 (ET-1; ET(A) and ET(B) receptor agonist) and 5-carboxamidotryptamine (5-CT; 5-HT(1) receptor agonist) were investigated with a myograph. The contractile responses to ET-1 and 5-CT were increased (P<0.05) after SAH compared with sham operated rats. In parallel, the ET(B) and 5-HT(1B) receptor mRNA and protein expression were significantly elevated after SAH, as analysed by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. Administration of RO-31-7549 prevented the upregulated contraction elicited by application of ET-1 and 5-CT in cerebral arteries and kept the ET(B) and 5-HT(1B) receptor mRNA and protein levels at pre-SAH levels. Regional and global CBF evaluated by an autoradiographic technique were reduced by 60%+/-4% after SAH (P<0.05) and prevented by treatment with RO-31-7549. Our study suggests that PKC plays an important role in the pathogenesis of cerebral ischaemia after SAH.

ERK1/2 inhibition attenuates cerebral blood flow reduction and abolishes ET(B) and 5-HT(1B) receptor upregulation after subarachnoid hemorrhage in rat.

Upregulation of endothelin B (ET(B)) and 5-hydroxytryptamine 1B (5-HT(1B)) receptors via transcription has been found after experimental subarachnoid hemorrhage (SAH), and this is associated with enhanced phosphorylation of the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK1/2). In the present study, we hypothesized that inhibition of ERK1/2 alters the ET(B) and 5-HT(1B) receptor upregulation and at the same time prevents the sustained cerebral blood flow (CBF) reduction associated with SAH. The ERK1/2 inhibitor SB386023-b was injected intracisternally in conjunction with and after the induced SAH in rats. At 2 days after the SAH, cerebral arteries were harvested for quantitative real-time polymerase chain reaction, immunohistochemistry and analysis of contractile responses to endothelin-1 (ET-1; ET(A) and ET(B) receptor agonist) and 5-carboxamidotryptamine (5-CT; 5-HT1 receptor agonist) in a sensitive myograph. To investigate if ERK1/2 inhibition had an influence on the local and global CBF after SAH, an autoradiographic technique was used. At 48 h after induced SAH, global and regional CBF were reduced by 50%. This reduction was prevented by treatment with SB386023-b. The ERK1/2 inhibition also decreased the maximum contraction elicited by application of ET-1 and 5-CT in cerebral arteries compared with SAH. In parallel, ERK1/2 inhibition downregulated ET(B) and 5-HT(1B) receptor messenger ribonucleic acid and protein levels compared with the SAH. Cerebral ischemia after SAH involves vasoconstriction and subsequent reduction in the CBF. The results suggest that ERK1/2 inhibition might be a potential treatment for the prevention of cerebral vasospasm and ischemia associated with SAH.