Proteomic and computational analyses followed by functional validation of protective effects of trigonelline against calcium oxalate-induced renal cell deteriorations

Trigonelline is a phytoalkaloid commonly found in green and roasted coffee beans. It is also found in decaffeinated coffee. Previous report has shown that trigonelline-rich plant extract exhibits anti-lithiatic effects in a nephrolithiatic rat model. Nevertheless, cellular mechanisms underlying the anti-lithiatic properties of trigonelline remain hazy. Herein, we used nanoLC-ESI-Qq-TOF MS/MS and MaxQuant algorithm to perform label-free quantitative proteomics to identify trigonelline-induced changes in protein expression in MDCK renal cells. From a total of 1,006 and 1,011 proteins identified from control and trigonelline-treated cells, respectively, levels of 62 (23 up-regulated and 39 down-regulated) proteins were significantly changed by trigonelline. Functional enrichment and reactome pathway analyses showed that these 62 altered proteins were related to stress response, cell cycle and cell polarity. Functional validation by corresponding experimental assays revealed that trigonelline prevented calcium oxalate monohydrate crystal-induced renal cell deteriorations by inhibiting crystal-induced overproduction of intracellular reactive oxygen species, cell cycle shift from G0/G1 to G2/M phase, tight junction disruption, and epithelial-mesenchymal transition in renal epithelial cells. These findings provide cellular mechanisms and convincing evidence for the renoprotective effects of trigonelline, particularly in kidney stone prevention.