Urinary human L-FABP is a potential biomarker to predict COX-inhibitor-induced renal injury.

Background/aim: A strong demand exists for the development of sensitive biomarkers in the nephrology field. We propose urinary human L-type fatty acid binding protein (L-FABP) as an earlier biomarker to detect the outcome of chronic renal injury induced by cyclooxygenase (COX) inhibitors using human L-FABP transgenic mice.

Methods: After consuming a low-sodium diet for 2 weeks, transgenic mice were administered meloxicam or celecoxib with the low-sodium diet. Mice were sacrificed 2 days and 4 weeks after starting COX inhibitors, and urine was collected 24 and 48 h and 1, 2, 3, and 4 weeks after starting COX inhibitors. Celecoxib-treated mice were divided into responders or nonresponders according to urinary L-FABP levels, and histology, urinary L-FABP and peritubular capillary blood flow were evaluated.

Results: Meloxicam-treated mice showed a higher blood pressure than control mice. Urinary L-FABP was significantly increased in COX inhibitor-treated mice. Peritubular capillary blood flow in all meloxicam-treated mice and in some celecoxib-treated mice was significantly decreased. Although blood urea nitrogen was not increased, interstitial fibrosis and macrophage infiltration were revealed, especially in meloxicam-treated mice. Responders showed an increase of fibrotic areas and correlations between urinary L-FABP and peritubular capillary blood flow.

Conclusion: Urinary L-FABP is capable of revealing chronic renal injury induced by COX inhibitors.