Molecular mechanism of rhein on inhibiting autophagic protein expression in renal tubular epithelial cells via regulating mTOR signaling pathway activation

Abstract

To explore the effects and molecular mechanisms of rhein on reducing starvation-induced autophagic protein expression in renal tubular epithelial ( NRK-52E) cells. Hank's balanced salt solution (HBSS) was used to induce NRK-52E cells to be in the state of starvation. After the intervention of HBSS for 0, 0.5,1, 2 and 6 hours, firstly, the protein expression of microtubule-associated protein 1 light chain 3(LC3 I/II), which is a key protein in autophagy, was detected. Secondly, the protein expressions of mammalian target of rapamycin (mTOR) and phosphorylated-mTOR Ser2448 (p-mTOR S2448) were examined. And then, after the co-treatment of rhein (5 mg x L(-1)) and HBSS (1 mL) without or with mTOR inhibitor, rapamycin (100 nmol x L(-1)), the protein expressions of LC3 I/II, mTOR and p-mTOR S2448 were tested, respectively. HBSS could induce the up-regulation of LC3 II and the down-regulation of p-mTOR S2448 at protein expression level in NRK-52E cells. The co-treatment of rhein and HBSS could reversely regulate the protein expressions of LC3 II and p-mTOR S2448 in NRK-52E cells significantly. The co-treatment of rapamycin, rhein and HBSS could recover the level of LC3 II protein expression in HBSS-intervened NRK-52E cells. HBSS induces autophagy in renal tubular epithelial cells by inhibiting mTOR signaling pathway activation. Rhein reduces the autophagic protein expression in renal tubular epithelial cells through regulating mTOR signaling pathway activation, which is the possible effects and molecular mechanisms.