Regulate The Expression Of Cox-2 Signaling Pathway And Cyclosporin A Affect The Mechanism Of Cox-2 Expression To The Macula Densa Cells

BAKEGROUND The juxtaglomerular apparatus in the kidney is important in controlling extracellular volume and renin release. It was suggested that PGE2 is a potent stimulator for renin release. In the previous study the COX-2 expression in MD and adjacent cTALH(cortical thick ascending limb) cells has been confirmed to be increased by low salt diet intake as well as by a reduction in renal perfusion pressure. In the two experimental conditions, the luminal concentration of NaCl at the distal tubular connected to the MD is likely to be reduced. Therefore, there is increasing evidence that COX-2 is an important physiological mediator of kidney function regulation. Although numerous possible regulatory elements have been identified in 5' -flanking regions of COX-2 genes, few study about MD cells has been published. It has been observed that the expression of COX-2 and synthesis of prostanoid in the kidney were strongly attenuated by cyclosporine A (CsA). It was reasonable to believe that the side effect of CsA on the kidney is mediated by this mechanism. The purpose of this study is to observe the expression of COX-2 in a MMDDl cell line in low salt medium as well as in SD rat with low salt diet. The phosphorylated p38, pErk, pJNK expression were observed also in this study. The luciferase reporter assay of AP-1 NFAT NF-kB and expression of c-Jun c-Fos NFAT were also studied in the MMDDl cell line with or without CsA. METHODS SD rats and MMDDlcells were chosen in vivo and in vitro of our study.1. It was conclued eight rats groups in our study, and eight rats each group. Groupl: normal salt diet as controls; Group 2: normal salt diet+ CsA(15mg/d/kg) orally; Group 3: normal salt diet+celecoxib(40mg/d/kg) orally; Group 4: normal salt diet+CsA+ celecoxib ;Group 5: low salt diet; Group 6: low salt diet +CsA; Group 7: low salt diet + celecoxib; Group 8: low salt diet + celecoxib+CsA. The experiment animals were operated at 8th day. COX-2 protein expression was assayed by Western Blotting, COX-2 and renin mRNA expression were measured by RT-PCR. Kidney slides were stained for COX-2 by immunohistochemistry method.2. Confluent MMDDl cells were expored to serum free DMEM in a l:lmixture with isotonic saline (control), 300mM mannitol (to reduce NaCl to half, LS solution).