Rab7 empowers renal tubular epithelial cells with autophagy-mediated protection against albumin-induced injury

Most patients with chronic kidney disease (CKD) present with proteinuria and extracellular matrix (ECM) deposition in the interstitium. Matrix metalloproteinase-2 (MMP-2) is important for maintaining ECM metabolism and it affects the formation and development of CKD. Autophagy has been reported to be protective against renal tubular injury, but the role of autophagy related to ECM metabolism is unclear. Rab7 is a shared molecule of endocytosis and autophagy. The aim of this study is to explore the role of autophagy in regulating MMP-2 activity and to determine whether Rab7 functions in regulating MMP-2 activity and injury in albumin-overloaded TECs. In this study, abovine serum albumin (BSA)-overload rat model was first established and collagen deposition and deficient autophagic response were observed in vivo, and stimulation with albumin nanoparticles resulted in MMP-2 overactivation and obstructed autophagic flux induced by lysosomal dysfunction in vitro. Furthermore, overactivation of MMP-2 was mediated by its related regulatory molecules such as membrane-type 1 MMP (MT1-MMP), tissue inhibitor of metalloproteinase-2 (TIMP-2) and reversion-inducing-cysteine-rich protein with kazal motifs (RECK) on the membrane of TECs (HK-2 cellline). After up-regulating Rab7, albumin-induced MMP-2 overactivation was attenuated, which was reversed by chloroquine (CQ; an endocytosis inhibitor). In addition, our data indicated that up-regulation of Rab7 relieved epithelial-mesenchymal transition (EMT) and apoptosis in albumin-treated TECs. Taken together, our study demonstrated that autophagy regulates MMP-2 activity in a Rab7-dependent manner. Thus, Rab7 is a newly developed target for protecting TECs from albumin-induced injury.