Renal protective effect of N-acetyl-seryl-aspartyl-lysyl-proline in dahl salt-sensitive rats

N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural tetrapeptide with anti-inflammatory and antifibrotic properties. Its effect on salt-sensitive (SS) hypertension is unknown. We hypothesized that in Dahl SS rats on high-salt (HS) diet, Ac-SDKP prevents loss of nephrin expression and renal immune cell infiltration, leading to a decrease in albuminuria, renal inflammation, fibrosis, and glomerulosclerosis. To test this, Dahl SS rats and consomic SS13BN controls were fed either a low-salt (0.23% NaCl) or HS (4% NaCl) diet and treated for 6 weeks with vehicle or Ac-SDKP at either low or high dose (800 or 1600 μg/kg per day, respectively). HS increased systolic blood pressure in SS rats (HS+vehicle, 186±5 versus low salt+vehicle, 141±3 mm Hg; P<0.005) but not in SS13BN rats. Ac-SDKP did not affect blood pressure. Compared with low salt, HS-induced albuminuria, renal inflammation, fibrosis, and glomerulosclerosis in both strains, but the damages were higher in SS than in SS13BN. Interestingly, in SS13BN rats, Ac-SDKP prevented albuminuria induced by HS (HS+vehicle, 44±8 versus HS+low Ac-SDKP, 24±3 or HS+high Ac-SDKP, 8±1 mg/24 h; P<0.05), whereas in SS rats, only high Ac-SDKP dose significantly attenuated albuminuria (HS+vehicle, 94±10 versus HS+high Ac-SDKP, 57±7 mg/24 h; P<0.05). In both strains, Ac-SDKP prevented HS-induced inflammation, interstitial fibrosis, and glomerulosclerosis. In summary, in SS rats on HS diet, at low and high doses, Ac-SDKP prevented renal damage without affecting the blood pressure. Only the high dose of Ac-SDKP attenuated HS-induced albuminuria. Conversely, in SS13BN rats, both doses of Ac-SDKP prevented HS-induced renal damage and albuminuria.