MG132 protects against renal dysfunction by regulating Akt-mediated inflammation in diabetic nephropathy.

Diabetic nephropathy (DN), the leading cause of end-stage renal disease (ESRD). To date, mounting evidence has shown that inflammation may contribute to the pathogenesis of DN. Recent reports have shown that proteasome inhibitors display cytoprotection by reducing the phosphorylation of Akt, a serine/threonine kinase, plays a critical role in cellular survival and metabolism and can crosstalk with inflammation. Therefore, we hypothesized that MG132, specific proteasome inhibitor, could provide renoprotection by suppressing Akt-mediated inflammation in DN. In vivo, male Sprague-Dawley rats were divided into normal control group (NC), diabetic nephropathy group (DN), DN model plus MG132 treatment group (MG132), and DN model plus deguelin treatment group (Deguelin)(deguelin, a specific inhibitor of Akt). In vitro, a human glomerular mesangial cell lines (HMCs) was exposed to 5.5 mmol/L glucose (CON), 30 mmol/L glucose (HG), 30 mmol/L glucose with 0.5 umol/L MG132 (MG132) and 30 mmol/L glucose with 5 umol/L deguelin (Deguelin). Compared with NC, DN showed a significant increase in the urinary protein excretion rate and inflammatory cytokines, as well as p-Akt. Compared with CON, HMCs co-cultured with HG was notably proliferated, which is in accord with α-smooth muscle actin (α-SMA) expression. These alterations were inhibited by administration of MG132 or deguelin. In conclusion, MG132 significantly inhibits the development of DN by regulating Akt phosphorylation-mediated inflammatory activation.

The Antipancreatic Cancer Activity of OSI-027, a Potent and Selective Inhibitor of mTORC1 and mTORC2.

In the present study, we investigated the potential activity of OSI-027, a potent and selective mammalian target of rapamycin (mTOR) complex 1/2 (mTORC1/2) dual inhibitor, against pancreatic cancer cells both in vitro and in vivo. We demonstrated that OSI-027 inhibited survival and growth of both primary and transformed (PANC-1 and MIA PaCa-2 lines) human pancreatic cancer cells. Meanwhile, OSI-027 induced caspase-dependent apoptotic death of the pancreatic cancer cells. On the other hand, caspase inhibitors alleviated cytotoxicity by OSI-027. At the molecular level, OSI-027 treatment blocked mTORC1 and mTORC2 activation simultaneously, without affecting ERK-mitogen-activated protein kinase activation. Importantly, OSI-027 activated cytoprotective autophagy in the above cancer cells. Whereas pharmacological blockage of autophagy or siRNA knockdown of Beclin-1 significantly enhanced the OSI-027-induced activity against pancreatic cancer cells. Specifically, a relatively low dose of OSI-027 sensitized gemcitabine-induced pancreatic cancer cell death in vitro. Further, administration of OSI-027 or together with gemcitabine dramatically inhibited PANC-1 xenograft growth in severe combined immunodeficiency mice, leading to significant mice survival improvement. In summary, the preclinical results of this study suggest that targeting mTORC1/2 synchronously by OSI-027 could be further investigated as a valuable treatment for pancreatic cancer.

GDC-0980-induced apoptosis is enhanced by autophagy inhibition in human pancreatic cancer cells.

Pancreatic cancer remains fatal to the fast majority of affected patients. Activation of phosphoinositide-3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) pathway plays an important role in pancreatic cancer progression and chemo-resistance. In the present study, we examined the activity of GDC-0980, a novel class I PI3K/mTOR kinase inhibitor, against pancreatic cancer cells in vitro. GDC-0980 inhibited AKT-mTOR activation and pancreatic cancer cell (PANC-1 and Capan-1 lines) survival. In both cancer cell lines, GDC-0980 simultaneously activated apoptosis and autophagy, the latter was detected by p62 degradation, Beclin-1 upregulation and light chain 3B (LC3B) conversion from a cytosolic (LC3B-I) to a membrane-bound (LC3B-II) form. Autophagy inhibitors including 3-methyladenine, hydroxychloroquine, NH4Cl and bafilomycin A1 enhanced apoptosis and cytotoxicity by GDC-0980, such an effect was reversed by caspase inhibitors (z-VAD-FMK and z-ITED-FMK). Furthermore, knockdown of LC3B or Beclin-1 through siRNA increased GDC-0980-induced anti-pancreatic cancer cell activity. Thus, inhibition of autophagy sensitizes GDC-0980-induced anti-pancreatic cancer activity, suggesting a novel therapeutic strategy for GDC-0980 sensitization.