Chronic activation of glomerular mitogen-activated protein kinases in Dahl salt-sensitive rats.
The in vivo role of mitogen-activated protein kinases (MAPK) in the development of glomerular injury is poorly understood. In the present study, glomerular MAPK activities, including extracellular signal-regulated kinases (ERK), c-Jun NH2-terminal kinases (JNK), and transcriptional factor, activator protein-1 (AP-1) were examined in glomerular injury of salt-induced hypertensive rats. Six-week-old Dahl salt-sensitive (Dahl-S) and salt-resistant (Dahl-R) rats were maintained on a high-salt (8.0% NaCl) diet for 1, 5, and 10 wk. In Dahl-S rats, as shown by in-gel kinase assay, an increase in BP by a high-salt diet was followed by chronic activation of glomerular ERK and JNK, which continued until 10 wk after a high-salt diet. Western blot analysis demonstrated a significant increase in the protein expression of glomerular ERK and JNK in Dahl-S rats fed a high-salt diet. As determined by gel-mobility shift assay, ERK and JNK activations were associated with an increase in glomerular AP-1 DNA binding activity. On the other hand, in Dahl-R rats fed a high-salt diet, BP remained normal throughout the experiments. However, glomerular ERK and JNK activities and AP-1 DNA binding activity in Dahl-R rats were not affected by 1 or 5 wk of a high-salt diet, but significantly increased by 10 wk of treatment with a high-salt diet, indicating that chronic sodium overload itself stimulated glomerular ERK and JNK and AP-1 activities. These kinase activations in both Dahl-S and Dahl-R rats were accompanied by an increase in urinary protein excretion and renal growth. These observations provide the first evidence that salt-sensitive hypertension causes chronic activation of glomerular ERK and JNK, probably leading to the activation of AP-1. Thus, glomerular MAPK may be responsible for the development of salt-induced glomerular injury.
Hamaguchi
Akinori
A
Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
Kim
Shokei
S
Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
Izumi
Yasukatsu
Y
Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
Iwao
Hiroshi
H
Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
D000818:Animals; D002908:Chronic Disease; D046508:Culture Techniques; D004247:DNA / Q000378:metabolism; D004195:Disease Models, Animal; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases; D007668:Kidney / Q000473:pathology; D007678:Kidney Glomerulus / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009929:Organ Size; D011507:Proteinuria / Q000378:metabolism; D051381:Rats; D020303:Rats, Inbred Dahl; D017673:Sodium Chloride, Dietary; D018808:Transcription Factor AP-1 / Q000235:genetics
D017673:Sodium Chloride, Dietary; D018808:Transcription Factor AP-1; D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases