Inhibition of mTOR with sirolimus slows disease progression in Han:SPRD rats with autosomal dominant polycystic kidney disease (ADPKD)

Background. Autosomal dominant polycystic kidney disease (ADPKD) is characterized by dysregulated tubular epithelial cell growth, resulting in the formation of multiple renal cysts and progressive renal failure. To date, there is no effective treatment for ADPKD. The mammalian target of rapamycin (mTOR) is an atypical protein kinase and a central controller of cell growth and proliferation. We examined the effect of the mTOR inhibitor sirolimus (rapamycin) on renal functional loss and cyst progression in the Han:SPRD rat model of ADPKD. Methods. Five-week-old male heterozygous cystic (Cy/+) and wild-type normal (+/+) rats were administered sirolimus (2 mg/kg/day) orally through the drinking water for 3 months. The renal function was monitored throughout the treatment phase, and rats were sacrificed thereafter. Kidneys were analysed histomorphometrically, and for the expression and phosphorylation of S6K, a well-characterized target of mTOR in the regulation of cell growth. Results. The steady increase in BUN and creatinine in Cy/+ rats was reduced by 39 and 34%, respectively with sirolimus after 3 months treatment. Kidney weight and 2-kidney/total body weight (2K/TBW) ratios were reduced by 34 and 26% in sirolimus-treated Cy/+ rats. Cyst volume density was also reduced by 18%. Of importance, Cy/+ rats displayed enhanced levels of total and phosphorylated S6K. Sirolimus effectively reduced total and phosphorylated levels of S6K. Conclusion. We conclude that oral sirolimus markedly delays the loss of renal function and retards cyst development in Han:SPRD rats with ADPKD. Our data also suggest that activation of the S6K signalling pathway plays an important role in the pathogenesis of PKD. Sirolimus could be a useful drug to retard progressive renal failure in patients with ADPK

Signs of immunosenescence correlate with poor outcome of mRNA COVID-19 vaccination in older adults

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is effective in preventing COVID-19 hospitalization and fatal outcome. However, several studies indicated that there is reduced vaccine effectiveness among older individuals, which is correlated with their general health status1,2. How and to what extent age-related immunological defects are responsible for the suboptimal vaccine responses observed in older individuals receiving SARS-CoV-2 messenger RNA vaccine, is unclear and not fully investigated1,3–5. In this observational study, we investigated adaptive immune responses in adults of various ages (22–99 years old) receiving 2 doses of the BNT162b2 mRNA vaccine. Vaccine-induced Spike-specific antibody, and T and memory B cell responses decreased with increasing age. These responses positively correlated with the percentages of peripheral naïve CD4+ and CD8+ T cells and negatively with CD8+ T cells expressing signs of immunosenescence. Older adults displayed a preferred T cell response to the S2 region of the Spike protein, which is relatively conserved and a target for cross-reactive T cells induced by human ‘common cold’ coronaviruses. Memory T cell responses to influenza virus were not affected by age-related changes, nor the SARS-CoV-2-specific response induced by infection. Collectively, we identified signs of immunosenescence correlating with the outcome of vaccination against a new viral antigen to which older adults are immunologically naïve. This knowledge is important for the management of COVID-19 infections in older adults

PRAS40 and PRR5-Like Protein Are New mTOR Interactors that Regulate Apoptosis

TOR (Target of Rapamycin) is a highly conserved protein kinase and a central controller of cell growth. TOR is found in two functionally and structurally distinct multiprotein complexes termed TOR complex 1 (TORC1) and TOR complex 2 (TORC2). In the present study, we developed a two-dimensional liquid chromatography tandem mass spectrometry (2D LC-MS/MS) based proteomic strategy to identify new mammalian TOR (mTOR) binding proteins. We report the identification of Proline-rich Akt substrate (PRAS40) and the hypothetical protein Q6MZQ0/FLJ14213/CAE45978 as new mTOR binding proteins. PRAS40 binds mTORC1 via Raptor, and is an mTOR phosphorylation substrate. PRAS40 inhibits mTORC1 autophosphorylation and mTORC1 kinase activity toward eIF-4E binding protein (4E-BP) and PRAS40 itself. HeLa cells in which PRAS40 was knocked down were protected against induction of apoptosis by TNFα and cycloheximide. Rapamycin failed to mimic the pro-apoptotic effect of PRAS40, suggesting that PRAS40 mediates apoptosis independently of its inhibitory effect on mTORC1. Q6MZQ0 is structurally similar to proline rich protein 5 (PRR5) and was therefore named PRR5-Like (PRR5L). PRR5L binds specifically to mTORC2, via Rictor and/or SIN1. Unlike other mTORC2 members, PRR5L is not required for mTORC2 integrity or kinase activity, but dissociates from mTORC2 upon knock down of tuberous sclerosis complex 1 (TSC1) and TSC2. Hyperactivation of mTOR by TSC1/2 knock down enhanced apoptosis whereas PRR5L knock down reduced apoptosis. PRR5L knock down reduced apoptosis also in mTORC2 deficient cells. The above suggests that mTORC2-dissociated PRR5L may promote apoptosis when mTOR is hyperactive. Thus, PRAS40 and PRR5L are novel mTOR-associated proteins that control the balance between cell growth and cell death

Inhibition of mTOR with sirolimus slows disease progression in Han:SPRD rats with autosomal dominant polycystic kidney disease (ADPKD)

Background. Autosomal dominant polycystic kidney disease (ADPKD) is characterized by dysregulated tubular epithelial cell growth, resulting in the formation of multiple renal cysts and progressive renal failure. To date, there is no effective treatment for ADPKD. The mammalian target of rapamycin (mTOR) is an atypical protein kinase and a central controller of cell growth and proliferation. We examined the effect of the mTOR inhibitor sirolimus (rapamycin) on renal functional loss and cyst progression in the Han:SPRD rat model of ADPKD. Methods. Five-week-old male heterozygous cystic (Cy/+) and wild-type normal (+/+) rats were administered sirolimus (2 mg/kg/day) orally through the drinking water for 3 months. The renal function was monitored throughout the treatment phase, and rats were sacrificed thereafter. Kidneys were analysed histomorphometrically, and for the expression and phosphorylation of S6K, a well-characterized target of mTOR in the regulation of cell growth. Results. The steady increase in BUN and creatinine in Cy/+ rats was reduced by 39 and 34%, respectively with sirolimus after 3 months treatment. Kidney weight and 2-kidney/total body weight (2K/TBW) ratios were reduced by 34 and 26% in sirolimus-treated Cy/+ rats. Cyst volume density was also reduced by 18%. Of importance, Cy/+ rats displayed enhanced levels of total and phosphorylated S6K. Sirolimus effectively reduced total and phosphorylated levels of S6K. Conclusion. We conclude that oral sirolimus markedly delays the loss of renal function and retards cyst development in Han:SPRD rats with ADPKD. Our data also suggest that activation of the S6K signalling pathway plays an important role in the pathogenesis of PKD. Sirolimus could be a useful drug to retard progressive renal failure in patients with ADPK

Inhibition of mTOR with sirolimus slows disease progression in Han: SPRD rats with autosomal dominant polycystic kidney disease (ADPKD)

Background. Autosomal dominant polycystic kidney disease (ADPKD) is characterized by dysregulated tubular epithelial cell growth, resulting in the formation of multiple renal cysts and progressive renal failure. To date, there is no effective treatment for ADPKD. The mammalian target of rapamycin (mTOR) is an atypical protein kinase and a central controller of cell growth and proliferation. We examined the effect of the mTOR inhibitor sirolimus (rapamycin) on renal functional loss and cyst progression in the Han:SPRD rat model of ADPKD. Methods. Five-week-old male heterozygous cystic (Cy/+) and wild-type normal (+/+) rats were administered sirolimus (2 mg/kg/day) orally through the drinking water for 3 months. The renal function was monitored throughout the treatment phase, and rats were sacrificed thereafter. Kidneys were analysed histomorphometrically, and for the expression and phosphorylation of S6K, a well-characterized target of mTOR in the regulation of cell growth. Results. The steady increase in BUN and creatinine in Cy/+ rats was reduced by 39 and 34%, respectively with sirolimus after 3 months treatment. Kidney weight and 2-kidney/total body weight (2K/TBW) ratios were reduced by 34 and 26% in sirolimus-treated Cy/+ rats. Cyst volume density was also reduced by 18%. Of importance, Cy/+ rats displayed enhanced levels of total and phosphorylated S6K. Sirolimus effectively reduced total and phosphorylated levels of S6K. Conclusion. We conclude that oral sirolimus markedly delays the loss of renal function and retards cyst development in Han:SPRD rats with ADPKD. Our data also suggest that activation of the S6K signalling pathway plays an important role in the pathogenesis of PKD. Sirolimus could be a useful drug to retard progressive renal failure in patients with ADPK