mTORC1/2 and rapamycin in female Han:SPRD rats with polycystic kidney disease

Abstract

Rapamycin slows disease progression in the male Han:SPRD (Cy/+) rat with polycystic kidney disease (PKD). The aim of this study was to determine the effect of rapamycin on PKD and the relative contributions of the proproliferative mammalian target of rapamycin complexes 1 and 2 (mTORC1 and mTORC2) in female Cy/+ rats. Female Cy/+ rats were treated with rapamycin from 4 to 12 wk of age. In vehicle-treated Cy/+ rats, kidney volume increased by 40% and cyst volume density (CVD) was 19%. Phosphorylated S6 (p-S6) ribosomal protein, a marker of mTORC1 activity, was increased in Cy/+ rats compared with normal littermate controls (+/+) and decreased by rapamycin. Despite activation of mTORC1 in female Cy/+ rats, rapamycin had no effect on kidney size, CVD, number of PCNA-positive cystic tubular cells, caspase-3 activity, or the number of terminal deoxynucleotidyl transferase dUTP-mediated nick-end label-positive apoptotic cells. To determine a reason for the lack of effect of rapamycin, we studied the mTORC2 signaling pathway. On immunoblot of kidney, phosphorylated (Ser473) Akt (p-Akt), a marker of mTORC2 activity, was increased in female Cy/+ rats treated with rapamycin. Phosphorylated (Ser657) PKCα, a substrate of mTORC2, was unaffected by rapamycin in females. In contrast, in male rats, where rapamycin significantly decreases PKD, p-Akt (Ser473) was decreased by rapamcyin. PKCα (Ser657) was increased in male Cy/+ rats but was unaffected by rapamycin. In summary, in female Cy/+ rats, rapamycin had no effect on PKD and proproliferative p-Akt (Ser473) activity was increased by rapamycin. There were differential effects of rapamycin on mTORC2 signaling in female vs. male Cy/+ rats.

Sex-Specific mTOR Signaling Determines Sexual Dimorphism in Myocardial Adaptation in Normotensive DOCA-Salt Model

“…Sex differences in response to mTOR inhibition have been observed in the Han:SPRD (Cy/+) rat, a polycystickidney disease model. 22 Similar to our model, beneficial effects were observed only in males, whereas cyst size remained unaffected in females. 22 However, in these cystic kidneys rapamycin inhibited mTORC2 only in males and not in females.…”

“…22 Similar to our model, beneficial effects were observed only in males, whereas cyst size remained unaffected in females. 22 However, in these cystic kidneys rapamycin inhibited mTORC2 only in males and not in females. Our findings, that relatively low concentrations of rapamycin inhibited both mTORC1 and mTORC2 in females, together with the difference in maladaptive cardiac responses in males and females is novel.…”

Scattered Deletion of PKD1 in Kidneys Causes a Cystic Snowball Effect and Recapitulates Polycystic Kidney Disease

“…[25][26][27] Also, activation of AKT and ERK1/2 has been associated with cystic disease, and analysis of phosphorylated CREB has been used before as a readout for cAMP, an important second messenger involved in PKD. [28][29][30][31][32][33] In addition, Ki-67 expression was analyzed as a marker for proliferation. Indeed, the expression of these proteins was frequently elevated in tissue near cysts compared with tissue more distant to cysts.…”

“…Therefore, we performed immunohistochemistry to analyze phospho-STAT3 (pSTAT3), phospho-CREB, phospho-AKT, phospho-ERK1/2, and LCN2 expressions, which have been shown to be involved in PKD. 18,[23][24][25][26][27][28][29][30][31][32][33] The clustered distribution of cysts in an iKsp-Pkd1 del,lox mouse that was treated with low-dose tamoxifen, unilateral nephrectomy, and DCVC and euthanized 6 months after tamoxifen treatment (clustering is shown in Figure 6A), indeed, cooccurred with increased expression of these proteins specifically near cysts or clusters of cysts ( Figure 6B). We quantified the number of cysts/clusters that showed this effect in renal sections at two different locations in the kidneys of seven other mildly affected mice.…”

Canonical Wnt inhibitors ameliorate cystogenesis in a mouse ortholog of human ADPKD

“…Several studies have reported that many promising drugs showed potential therapeutic effects for ADP-KD in a large number of preclinical and clinical trials (1,7,(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54). However, some of those in clinical trials -these promising drugs included mTOR inhibitors (55,56), somatostatin analogs (57,58), ACEI/ ARB (59,60), and tyrosine kinase inhibitor (61) -did not prevent the decline of EGFR in ADPKD patients.…”