[Alteration of signal transduction-associated gene expression in rat cardiac fibroblasts induced by blocking angiotensin II receptors].

To investigate the molecular mechanism of angiotensin II (Ang II) receptor activation in adult rat cardiac fibroblasts, the expressions of cell signal transduction-associated genes were studied by using cDNA microarray. Cardiac fibroblasts of adult Sprague-Dawley rats (230~250 g) were isolated and cultured. The cells were divided into 4 groups: Ang II, Ang II + losartan, Ang II + PD123319, Ang II + losartan + PD123319. The expressions of Ang II receptors were studied by immunohistochemical staining. Total RNA was extracted and purified. After cDNA synthesis and biotin-16-dUTP labeling, the probes were denatured and hybridized with GEArray Q Series mouse G Protein-coupled Receptors Signaling Pathway Finder Gene Array (MM-025) containing 96 genes associated with 11 pathways. The arrays were scanned with a Uniscand1000 scanner and further analyzed with GEArray Analyzer software. RT-PCR was used to further confirm the results of gene microarray. The results of immunohistochemical staining showed that the expression of Ang II type 2 (AT2) receptor was evidently induced by Ang II stimulation when Ang II type 1 (AT1) receptor was blocked. The results of gene array indicated that blocking AT1 receptor changed 34 genes (more than 2 folds), 30 were down-regulated and 4 were up-regulated. The maximum change was not beyond 20 folds. The following 9 pathways were activated: cAMP/PKA, Ca2+, PKC, PLC, MAPK, PI-3 kinase, NO-cGMP, Rho, NF-kappaB pathways. Blockade of AT2 receptor caused 64 genes changing more than 2 folds (48 were down-regulated and 16 were up-regulated). Eleven pathways were basically activated. The change of the following 7 genes was over 30 folds: Cyp19a1 (37 folds), Il1r2 (42 folds), Cflar (53 folds), Bcl21 (31 folds), Pik3cg (278 folds), Cdkn1a (90 folds), Agt (162 folds). According to the activated extent, the signal transduction pathways in turn were PI-3 kinase, NF-kappaB and JAK-STAT pathways. Blocking both AT1 and AT2 receptors changed 46 genes more than 2 folds (36 were down-regulated and 10 were up-regulated). Eleven pathways were basically activated. The results of RT-PCR of IL-1beta and TNF-alpha confirmed the observations in gene microarray. Our results show that Ang II can induce a high expression of AT2 receptor in adult rat cardiac fibroblasts when AT1 receptor is blocked, and the signal mechanism of AT2 receptor is clearly different from that of AT1 receptor.