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.

Gene expression and molecular changes in cerebral arteries following subarachnoid hemorrhage in the rat.

OBJECT: The authors investigated early changes in the cerebral arteries of rats that occur after subarachnoid hemorrhage (SAH). METHODS: Messenger RNA was investigated by performing microarray and quantitative real-time polymerase chain reaction (PCR) analyses, and protein expression was shown by performing immunohistochemical studies. The array data indicated that the initial processes that occur after SAH involve activation of genes involved in angiogenesis, inflammation, and extracellular matrix (ECM) remodeling. The real-time PCR investigation confirmed upregulation of genes that were observed using the microarray to be regulated, including iNOS, MMP13, and cxcl2. The authors also verified the upregulation of previously implicated genes for G-protein-coupled receptors (endothelin B [ETB], angiotensin 1 [AT1], and AT2) and metalloproteinase 9. The results of an immunohistochemical study confirmed that receptor genes that were seen to be regulated produced an increase in protein expression. Double immunostaining of rat cerebral arteries with endothelial cell- or smooth-muscle cell-specific antibodies verified that an increase in ETB, 5-hydrotryptamine (5-HT1B), and 5-HT1D receptor expression occurs in smooth-muscle cells. CONCLUSIONS: Processes occurring after SAH lead to enhanced arterial contractility and ECM remodeling either directly or through angiogenesis and inflammation. These processes are active via an increase in metalloproteinase expression, the presence of proangiogenic factors, and the expression of proinflammatory genes.

Inhibition of PKC activity blocks the increase of ETB receptor expression in cerebral arteries.

BACKGROUND: Previous studies have shown that there is a time-dependent upregulation of contractile endothelin B (ETB) receptors in middle cerebral arteries (MCA) after organ culture. This upregulation is dependent on mitogen-activated protein kinases and possibly protein kinase C (PKC). The aim of this study was to examine the effect of PKC inhibitors with different profiles on the upregulation of contractile ETB receptors in rat MCA. Artery segments were incubated for 24 hours at 37 degrees C. To investigate involvement of PKC, inhibitors were added to the medium before incubation. The contractile endothelin-mediated responses were measured and real-time PCR was used to detect endothelin receptor mRNA levels. Furthermore, immunohistochemistry was used to demonstrate the ETB receptor protein distribution in the MCA and Western blot to measure which of the PKC subtypes that were affected by the inhibitors. RESULTS: The PKC inhibitors bisindolylmaleimide I, Ro-32-0432 and PKC inhibitor 20-28 attenuated the ETB receptor mediated contractions. Furthermore, Ro-32-0432 and bisindolylmaleimide I decreased ETB receptor mRNA levels while PKC inhibitor 20-28 reduced the amount of receptor protein on smooth muscle cells. PKC inhibitor 20-28 also decreased the protein levels of the five PKC subtypes studied (alpha, betaI, gamma, delta and epsilon). CONCLUSION: The results show that PKC inhibitors are able to decrease the ETB receptor contraction and expression in MCA smooth muscle cells following organ culture. The PKC inhibitor 20-28 affects the protein levels, while Ro-32-0432 and bisindolylmaleimide I affect the mRNA levels, suggesting differences in activity profile. Since ETB receptor upregulation is seen in cerebral ischemia, the results of the present study provide a way to interfere with the vascular involvement in cerebral ischemia.