RESUMO
Aldosterone-induced hypertension is associated with renal damage that may be mediated by endothelin-1 (ET-1). We evaluated whether inflammatory cell infiltration and DNA-binding activity of the transcription factors nuclear factor kappa B (NF-kappa B) and activator protein-1 (AP-1) were increased in kidneys from aldosterone-infused rats. The role of ET-1 in these processes was evaluated by treating rats with the ET(A)-receptor blocker, BMS 182874. Rats were infused with aldosterone (0.75 microg/h) via a mini-osmotic pump and were given 1% NaCl in the drinking water in the absence and presence of BMS 182874 or of the aldosterone receptor blocker, spironolactone. Renal sections were used to assess inflammatory cell infiltration, which was identified immunocytochemically using monoclonal antibodies against macrophages (ED1+). Electrophoretic mobility shift assays evaluated the DNA-binding activity of NF-kappa B and AP-1 in renal tissue. Systolic blood pressure (BP) was increased in the aldosterone-infused group compared with controls (123+/-6 versus 110+/-10 mmHg, P<0.05). BMS 182874 and spironolactone significantly decreased BP (P<0.05). Macrophage infiltration was increased in the kidneys of aldosterone-infused rats compared with controls. Renal binding activity (arbitrary units) of AP-1, in contrast with that of NF-kappa B, increased in aldosterone-infused rats compared with control rats (AP-1, 4.2+/-0.3 versus 1.0+/-0.1, P<0.05; NF-kappa B, 1.6+/-0.5 versus 1.2+/-0.5). BMS 182874 and spironolactone decreased macrophage infiltration (by 70% and 50% respectively) and AP-1 binding activity (1.0+/-0.3 and 0.8+/-0.3 respectively). In conclusion, kidneys from aldosterone-infused rats exhibited macrophage infiltration and increased AP-1 DNA-binding activity. These processes were attenuated by BMS 182874. Our findings suggest that renal damage in aldosterone-dependent hypertension is associated with inflammatory processes that are mediated in part via ET-1.
Assuntos
Compostos de Dansil/farmacologia , Antagonistas dos Receptores de Endotelina , Endotelina-1/metabolismo , Hipertensão/metabolismo , Rim/metabolismo , Fator de Transcrição AP-1/metabolismo , Aldosterona , Análise de Variância , Animais , DNA/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Hipertensão/imunologia , Imuno-Histoquímica , Rim/imunologia , Macrófagos/imunologia , Masculino , Antagonistas de Receptores de Mineralocorticoides , NF-kappa B/metabolismo , Ratos , Ratos Sprague-Dawley , Receptor de Endotelina A , Espironolactona/farmacologiaRESUMO
This study hypothesizes that endothelin-1 induces renal damage by increasing expression of growth/inflammatory factors, important in renal fibrosis. Male stroke-prone spontaneously hypertensive rats (SHRSPs) (8-weeks, n = 24) were randomized into three groups: control group, high-salt group (4% NaCl), and salt plus an endothelin A receptor antagonist, BMS 182874 (40 mg/kg/d). After 20 weeks treatment, rats were killed. Messenger RNA (mRNA) expression of renal preproendothelin-1, endothelin A and B receptors, and procollagen I and III was evaluated by reverse transcription polymerase chain reaction. Expression of transforming growth factor (TGF)-beta1 and basic fibroblast growth factor (bFGF) was determined by immunoblotting. Matrix metalloproteinase-2 (MMP-2) activity was measured by zymography. In salt-loaded SHRSPs, preproendothelin-1 mRNA expression was increased 1.6-fold, and endothelin A receptor mRNA expression was decreased (70% of control). Salt-loaded SHRSPs had increased renal expression of TGF-b1 and procollagens. MMP-2 activity was augmented fivefold. BMS decreased (p < 0.01) expression of TGF-beta1, bFGF, and procollagen I and reduced MMP-2 activity. Thus severe hypertension and renal dysfunction in salt-loaded SHRSPs are associated with increased expression of renal endothelin-1, growth factors, and collagen. BMS treatment alleviated these effects, suggesting that nephroprotection by endothelin A receptor blockade is mediated by normalizing expression of growth factors, reducing extracellular matrix deposition, and decreasing MMP activity.