Angiotensin subtype-2 receptor (AT2 ) negatively regulates subtype-1 receptor (AT1 ) in signal transduction pathways in cultured porcine adrenal medullary chromaffin cells.
BACKGROUND
Two distinct types of angiotensin II (AngII) receptors, AT1 and AT2, have been cloned. We have shown previously that stimulation of AT2 reduces intracellular cyclic guanosine monophosphate (cGMP) levels in cultured porcine chromaffin cells in which AT2 is the predominantly expressed receptor. However, it has not been determined whether AT1 or AT2 affects signal transduction pathways involving mitogen-activated protein kinases (MAPKs) and signal transducers and activators of transcription (STATs) in chromaffin cells. Also, it is unclear whether cGMP/protein kinase G (PKG) is involved in the regulation of MAPKs and STATs in these cells.


METHODS
Chromaffin cells were derived from porcine adrenal medulla. The effects of AngII alone (representing physiological conditions), AngII plus CV-11974 (an AT1 antagonist, which simulates specific AT2 stimulation), AngII plus PD 123319 (an AT2 antagonist, which simulates specific AT1 stimulation), and 8-Br-cGMP (a membrane-permeable cGMP analogue) alone on MAPKs (ERKs, JNK, p-38 MAPK) and STATs (STATs 1, 3 and 5) activity were measured.


METHODS
Phosphorylated MAPKs (extracellular signal-related kinases (ERKs), c-jun N-terminal kinase (JNK) and p38 MAPK) and STATs (STATs 1, 3 and 5) were measured by immunoprecipitation-Western blot analysis (IP-Western blot).


RESULTS
AT1 stimulation markedly increased expression of ERKs, JNK, p38 MAPK via Ca2+-dependent protein kinase C (PKC) isoforms (cPKC), as well as STATs 1, 3 and 5 in cultured porcine chromaffin cells. In contrast, AT2 stimulation markedly decreased the expression of these signaling molecules. Also, 8-Br-cGMP alone induced increases in ERKs, JNK, p38 MAPK, and STATs 1, 3 and 5. Because AT2 inhibits cGMP production, we speculate that AT2 may act to suppress cGMP production, which in turn reduces the activity of both MAPKs and STATs in chromaffin cells.


CONCLUSIONS
AT2 negatively regulates AT1 in signal transduction pathways in chromaffin cells.
Ishii
K
K
Department of Clinical Pathology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Takekoshi
K
K
Shibuya
S
S
Kawakami
Y
Y
Isobe
K
K
Nakai
T
T
D000804:Angiotensin II / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000502:physiology*; D006152:Cyclic GMP / Q000502:physiology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D004338:Drug Combinations; D004789:Enzyme Activation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000502:physiology*; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D013777:Tetrazoles / Q000494:pharmacology; D015534:Trans-Activators / Q000096:biosynthesis
D057911:Angiotensin Receptor Antagonists; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D004268:DNA-Binding Proteins; D004338:Drug Combinations; D007093:Imidazoles; D007527:Isoenzymes; D008894:Milk Proteins; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D013777:Tetrazoles; D015534:Trans-Activators; D000804:Angiotensin II; C073402:PD 123319; D017869:Cyclic GMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D006152:Cyclic GMP; C081643:candesartan