Human liver-type fatty acid-binding protein protects against tubulointerstitial injury in aldosterone-induced renal injury

To demonstrate the renoprotective function of human liver-type fatty acidbinding protein (hL-FABP) expressed in proximal tubules in aldosterone (Aldo)-induced renal injury, hL-FABP chromosomal transgenic (Tg) and wild-type (WT) mice received systemic Aldo infusions (Tg-Aldo and WT-Aldo, respectively) were given 1% NaCl water for 28 days. In this model, elevation of systolic blood pressure, monocyte chemoattractant protein-1 expression, macrophage infiltration in the interstitium, tubulointerstitial damage, and depositions of type I and III collagens were observed. Elevation of systolic blood pressure did not differ in WT-Aldo vs. Tg-Aldo animals, however, renal injury was suppressed in Tg-Aldo compared with WT-Aldo mice. Dihydroethidium fluorescence was used to evaluate reactive oxidative stress, which was suppressed in Tg-Aldo compared with WT-Aldo mice. Gene expression of angiotensinogen in the kidney was upregulated, and excretion of urinary angiotensinogen was increased in WT-Aldo mice. This exacerbation was suppressed in Tg-Aldo mice. Expression of hL-FABP was upregulated in proximal tubules of Tg-Aldo mice. Urinary excretion of hL-FABP was significantly greater in Tg-Aldo than in Tg-control mice. In conclusion, hL-FABP ameliorated the tubulointerstitial damage in Aldo-induced renal injury via reducing oxidative stress and suppressing activation of the intrarenal reninangiotensin system.