These results suggest that stimulation of tran scription, rather than increases in mRNA inhibitor Dasatinib stability, under lie ET induced astrocytic CCL2 and CXCL1 expression. Both rat CCL2 and CXCL1 genes have recognition sequences for NF��B and SP1 on the 5 promotor regions. Through these recognition sites, transcription of CCL2 and CXCL1 are cooperatively stimulated by NF��B and SP1. Agreeing with these findings, the inhibition of astrocytic CCL2 and CXCL1 expression by PDTC, SN50 and mithramycin suggests the involvement of both NF��B and SP1 in the effect of ET 1. MAP kinases, that is, ERK, JNK and p38, regulate the transcription activities of NF��B and SP1 in signal transduction path ways under several receptors. In astrocytes, activation of JNK and p38 was reported to stimulate NF��B.

We also found that ET induced activation of SP1 was reduced by SP600125 in cultured astrocytes. Thus, the in hibition of ET induced CCL2 and CXCL1 expression by SP600125 and SB203580 may indicate that JNK and p38 mediate ET receptor signals to NF��B and SP1. Differing from the effects on CCL2 and Inhibitors,Modulators,Libraries CXCL1 ex pression, the ET induced decrease in CX3CL1 mRNA was inhibited by cycloheximide. This result indicates a requirement of protein de novo synthesis for the effect of ETs on fractalkine expression. Moreover, Ca2 chelation and PKC inhibition, but not MAP kinase inhibition, prevented the effects of ET 1. Rat CX3CL1 mRNA has AU rich elements in the 3 regions, where many regulatory proteins affecting mRNA stability bind.

As is reported in the regulatory mechanisms of some inflammatory factors, ET Inhibitors,Modulators,Libraries may stimulate the induction of regulatory proteins that destabilize CX3CL1 mRNA through Ca2 and PKC dependent signals. Pathophysiological significance of the ET induced changes in astrocytic chemokine production In nerve tissues damaged by brain insults and neurode generative diseases, astrocytes undergo a phenotypic change to reactive astrocytes and alter Inhibitors,Modulators,Libraries their ability to produce various chemokines. By altering the produc tion of astrocyte derived chemokines, the pathophysio logical response of the damaged brain is modulated. In brain pathologies, brain ETs increase in Inhibitors,Modulators,Libraries damaged tissues, which activate astrocytic ETB receptors and induce re active astrocytosis. Accompanied with the con version to reactive astrocytes, ETs modulate the production of various extracellular signaling molecules.

A major finding of the present study is that ETs had different actions on astrocytic chemokine produc tion, ETs increased CCL2 and CXCL1, but decreased CX3CL1 production. The reciprocal regulation of astrocyte derived chemokines would result Inhibitors,Modulators,Libraries in the possible modulation of chemokine induced patho logical brain responses by ETs. In the brain, receptors for CCL2, CXCL1 and CX3CL1 furthermore are expressed in vascu lar endothelial cells, neurons and microglia.