Rapamycin

C. Peter Verrijzer, Jan A. van der Knaap et al., from Department of Biochemistry and Center for Biomedical Genetics at Erasmus University Medical Center, in collaboration with other institutes, have shown the importance of the formation of GMPS-USP7 deubiquitylating complex in the nucleus under stress conditions and focused on the regulation of p53 tumor suppressor pathway, which is strongly related to cell proliferation and therefore to carcinogenesis. As for the GMPS (Guanine Monophosphate Synthase), which converts XMP (xanthosine 5’-monophoshate) to GMP, they have also pointed out its function as a target gene regulator through USP7-mediated deubiquitylation of H2B histone. Based on de novo synthesis of GMP pathway, there is an enzyme upstream of GMPS, which is of great interest; IMPDH (Inosine-5′-Monophosphate Dehydrogenase) which is responsible for the oxidation of IMP to XMP and also involved in transcription regulation through sequence-specific DNA binding. While identifying GMPS-associated factors in human cells, they have noticed IMPDH2 (one of the two isoforms of IMPDH in humans) and the DUB (deubiquitylating enzyme) USP11. In order to study further the GMPS-USP7 complex’s function under cell stress conditions and the cells’ reaction, we also focused on GMPR (GMP Reductase) and USP11 which proteins were expressed for later antibody production. SNF4, the Drosophilla homologue of mammalian AMPK γ-subunit was also produced to be used for antibody production, as it contains a CBS domain, just like IMPDH. To investigate additional pathways that are regulated by GMPS/USP7, apart from the stabilization of p53 and deubiquitylation of H2B, we treated U2OS and HEK293 cells with different drugs. After immunofluorescence experiments, we concluded that GMPS also regulates PTEN and PML, which both are tumor suppressors.

The mammalian target of rapamycin (mTOR) constitutes an integrator of multiple signals and a master programmer of pivotal cellular functions such as cell growth and proliferation. Due to its complex function, it plays a substantial role in homeostasis at molecular, cellular, tissue and organism level and its aberrant activation is implicated in tumorigenesis and tumor progression. mTOR signaling depends on a number of upstream regulators such as PI3K and Akt, and a number of downstream effectors such as p70 S6 kinase 1 (S6K1) and 4E-BP1. The mTOR pathway seems to be a promising pathway in anticancer treatment and mTOR inhibitors constitute a currently emerging and evaluated class of antitumor agents. Nonetheless, the complexity and multifactorial regulation of this signal transduction pathway make it difficult to determine pivotal parameters such as the optimal therapeutic schedules and the appropriate criteria for the selection of patients most likely to respond, which will enable medical oncologists to proceed to the appropriate use of these agents in clinical setting. The complete dissection of both mTOR signaling and the adjacent pathways will enable experts to develop and implement multi-targeted treatment, which appears to be the most promising approach, due to the persistent and dynamic interaction between different signaling pathways. Under such circumstances, we will be capable of exploiting mTOR signaling and maximizing the benefit of patients. In the present review, we are discussing the regulation of the mTOR signaling, pointing out its implication in the pathogenesis of solid tumors as well as its encouraging therapeutic potential.

Glucocerebrosidase (GBA1) mutations are associated with Gaucher disease (GD), an autosomal recessive disorder caused by functional deficiency of glucocerebrosidase (GBA), a lysosomal enzyme that hydrolyzes glucosylceramide to ceramide and glucose. Neuronopathic forms of GD can be associated with rapid neurological decline (Type II) or manifest as a chronic form (Type III) with a wide spectrum of neurological signs. Furthermore, there is now a well-established link between GBA1 mutations and Parkinson's disease (PD), with heterozygote mutations in GBA1 considered the commonest genetic defect in PD. Here we describe a novel Drosophila model of GD that lacks the two fly GBA1 orthologs. This knockout model recapitulates the main features of GD at the cellular level with severe lysosomal defects and accumulation of glucosylceramide in the fly brain. We also demonstrate a block in autophagy flux in association with reduced lifespan, age-dependent locomotor deficits and accumulation of autophagy substrates in dGBA-deficient fly brains. Furthermore, mech-anistic target of rapamycin (mTOR) signaling is downregulated in dGBA knockout flies, with a concomitant upregulation of Mitf gene expression, the fly ortholog of mammalian TFEB, likely as a compensatory response to the autophagy block. Moreover, the mTOR inhibitor rapamycin is able to partially ameliorate the lifespan, locomotor, and oxidative stress phenotypes. Together, our results demonstrate that this dGBA1-deficient fly model is a useful platform for the further study of the role of lysosomal-autophagic impairment and the potential therapeutic benefits of rapamycin in neuronopathic GD. These results also have important implications for the role of autophagy and mTOR signaling in GBA1-associated PD.

Balanced nutrition and appropriate dietary interventions are fundamental in the prevention and management of viral infections. Additionally, accurate modulation of the inflammatory response is necessary to achieve an adequate antiviral immune response. Many studies, both in vitro with mammalian cells and in vivo with small animal models, have highlighted the antiviral properties of resveratrol, rapamycin and metformin. The current review outlines the mechanisms of action of these three important compounds on the cellular pathways involved with viral replication and the mechanisms of virus-related diseases, as well as the current status of their clinical use.

Balanced nutrition and appropriate dietary interventions are fundamental in the prevention and management of viral infections. Additionally, accurate modulation of the inflammatory response is necessary to achieve an adequate antiviral immune response. Many studies, both in vitro with mammalian cells and in vivo with small animal models, have highlighted the antiviral properties of resveratrol, rapamycin and metformin. The current review outlines the mechanisms of action of these three important compounds on the cellular pathways involved with viral replication and the mechanisms of virus-related diseases, as well as the current status of their clinical use.

Balanced nutrition and appropriate dietary interventions are fundamental in the prevention and management of viral infections. Additionally, accurate modulation of the inflammatory response is necessary to achieve an adequate antiviral immune response. Many studies, both in vitro with mammalian cells and in vivo with small animal models, have highlighted the antiviral properties of resveratrol, rapamycin and metformin. The current review outlines the mechanisms of action of these three important compounds on the cellular pathways involved with viral replication and the mechanisms of virus-related diseases, as well as the current status of their clinical use.

Increasing life expectancy is causing the prevalence of age-related diseases to rise, and there is an urgent need for new strategies to improve health at older ages. Reduced activity of insulin/insulin-like growth factor signaling (IIS) and mechanistic target of rapamycin (mTOR) nutrient-sensing signaling network can extend lifespan and improve health during aging in diverse organisms. However, the extensive feedback in this network and adverse side effects of inhibition imply that simultaneous targeting of specific effectors in the network may most effectively combat the effects of aging. We show that the mitogen-activated protein kinase kinase (MEK) inhibitor trametinib, the mTOR complex 1 (mTORC1) inhibitor rapamycin, and the glycogen synthase kinase-3 (GSK-3) inhibitor lithium act additively to increase longevity in Drosophila. Remarkably, the triple drug combination increased lifespan by 48%. Furthermore, the combination of lithium with rapamycin cancelled the latter's effects on lipid metabolism. In conclusion, a polypharmacology approach of combining established, prolongevity drug inhibitors of specific nodes may be the most effective way to target the nutrient-sensing network to improve late-life health. aging | polypharmacology | trametinib | rapamycin | lithium

Rapamycin has favorable effects on aging in mice and may eventually be applied to encourage " healthy aging " in humans. This study analyzed raw data from 29 survival studies of rapamycin-and control-treated mice, with the goals of estimating summary statistics and identifying factors associated with effect size heterogeneity. Meta-analysis demonstrated significant heterogeneity across studies, with hazard ratio (HR) estimates ranging from 0.22 (95% confidence interval [CI]: 0.06–0.82) to 0.92 (95% CI: 0.65–1.28). Sex was the major factor accounting for effect size variation, and mortality was decreased more in females (HR = 0.41; 95% CI: 0.35–0.48) as compared with males (HR = 0.63; 95% CI: 0.55–0.71). Rapamycin effects were also genotype dependent, however, with stronger survivorship increases in hybrid mice (14.4%; 95% CI: 12.5–16.3%) relative to pure inbred strains (8.8%; 95% CI: 6.2–11.6%). Number needed to treat was applied as an effect size metric, which consistently identified early senescence as the age of peak treatment benefit. These results provide synthesis of existing data to support the potential translation of findings from mouse to primate species. Because rapamycin's effect on survival depends on sex and genotype, further work is justified to understand how these factors shape treatment response.

The mammalian target of rapamycin (mTOR) pathway has received increasing attention as a potential antiepileptogenic target. Treatment with the mTOR inhibitor rapamycin after status epilepticus reduces the development of epilepsy in a rat model. To study whether rapamycin mediates this effect via restoration of blood-brain barrier (BBB) dysfunction, contrast-enhanced magnetic resonance imaging (CE-MRI) was used to determine BBB permeability throughout epileptogenesis. Imaging was repeatedly performed until 6 weeks after kainic acid-induced status epilepticus in rapamycin (6 mg/kg for 6 weeks starting 4 h after SE) and vehicle-treated rats, using gadobutrol as contrast agent. Seizures were detected using video monitoring in the week following the last imaging session. Gadobutrol leakage was widespread and extensive in both rapamycin and vehicle-treated epileptic rats during the acute phase, with the piriform cortex and amygdala as the most affected regions. Gadobutrol leakage was high...

The purpose of this study was to compare the therapeutic effects of gabapentin (GBP) and different doses of rapamycin (RAPA) in an induced sciatic nerve (SN)-injury rat model. Materials and Methods: The study consisted of 7 groups: Control, Sham, High-dose rapamycin (RAPA-H), Low-dose rapamycin (RAPA-L), GBP, DMSO and DMSO+nerve injury (DMSO+NI). Medical treatment was administered intraperitoneally for 30 days after the induction of SN injury. Results: Significant differences (p<0.001 for all) were found in comparisons between the groups in terms of axon diameter, axon number, and neurofilament (NF) and S100 immunointensity. Among the treatment groups, the highest mean axon diameter value, close to that of the Control group, was seen in the RAPA-L group. In terms of axon number, the value closest to that of the Control group was measured in the GBP group. The NF and S100 immunodensity in the RAPA-L group was similar to that of the GBP group. The S100 immunodensity in the RAPA-L group was closest to that of the Control group. The highest conduction velocity and distal latency values were recorded in the RAPA-L group. Conclusion: The histological and electrophysiological findings observed in this study suggest that RAPA-L treatment is a promising alternative to GBP.

Rapamycin inhibits the TOR kinases, which regulate cell proliferation and mRNA translation and are conserved from yeast to man. The TOR kinases also regulate responses to nutrients, including sporulation, autophagy, mating, and ribosome biogenesis. We have analyzed gene expression in yeast cells exposed to rapamycin using arrays representing the whole yeast genome. TOR inhibition by rapamycin induces expression of nitrogen source utilization genes controlled by the Ure2 repressor and the transcriptional regulator Gln3, and globally represses ribosomal protein expression. gln3 mutations were found to confer rapamycin resistance, whereas ure2 mutations confer rapamycin hypersensitivity, even in cells expressing dominant rapamycin-resistant TOR mutants. We find that Ure2 is a phosphoprotein in vivo that is rapidly dephosphorylated in response to rapamycin or nitrogen limitation. In summary, our results reveal that the TOR cascade plays a prominent role in regulating transcription in response to nutrients in addition to its known roles in regulating translation, ribosome biogenesis, and amino acid permease stability.

Sirolimus is a immunosuppressive agent for renal transplant recipients. Monitoring of whole blood sirolimus concentration is necessary in order to improve clinical outcomes. An increasing number of clinical laboratories (4-14% during 2005) are using microparticle enzyme immunoassay (MEIA) for sirolimus quantitation but previous reports indicated a high variability, with a mean difference of 17% for MEIA method vs. high-performance liquid chromatography/ultraviolet (HPLC/UV). This study was aimed at comparing the reliability of MEIA with the HPLC/UV method. Blood samples from transplant patients were processed using both HPLC/UV and MEIA assays. Comparison and Bland-Altman plots, as well as regression analysis and paired t-test were used to compare results of the assays. Concentrations were stratified into three groups and used to investigate whether any observed difference between methods could be influenced by sirolimus concentration. Regression analysis yielded a coefficient of correlation R of 0.9756, the line of best fit being y=0.9832x+0.1976. The statistical analysis showed no difference between the two sets of experimental data. The average percentage difference between the two methods was found to be -0.2+/-19.2%. On the basis of our present results, the tested MEIA assay is able to quantify sirolimus concentration with a clinically acceptable imprecision, similar to that of HPLC/UV method.

Post-transplant lymphoproliferative disorders (PTLD) are a complication of chronic immunosuppressive therapy in solid organ transplantation with a high mortality rate. Alternative treatments such as rapamycin have been explored. A detailed retrospective analysis was performed according to data collected from 13 patients with PTLD. At the time of PTLD diagnosis, immunosuppressive therapy was decreased and rapamycin administered. Overall survival, disease-free survival of patients and graft survival were determined. Among 590 kidney transplant recipients, 13 adult patients with PTLD were included in this study. The mean age of the patients was 42.15 (range: 25-58) years at the time of PTLD diagnosis, and 9 patients were male. Histology was distributed in 9 diffuse large B cell, 1 Malt lymphoma, 1 Burkitt lymphoma, 2 Hodgkin-like PTLD. The response rate to rapamycin alone was 30.8%. The mean overall survival period was 23.38 months and 11 patients are still alive. In total, 10 patients...

Background: Cisplatin-induced ototoxicity affects a high percentage of new cancer patients worldwide. The detailed mechanism of cisplatin-induced ototoxicity is not completely understood. We investigated whether rapamycin could protect rats from cisplatin-induced ototoxicity. Methods: Forty-eight male Wistar rats were randomly divided into six groups. Three groups were intra-peritoneally (IP) infused with cisplatin at a dose of 16 mg/kg and immediately injected with either dimethylsulfoxide (DMSO), rapamycin, or chloroquine (CQ). The remaining three groups were treated with rapamycin, CQ, or saline alone. The auditory brainstem response (ABR) test was performed to detect the rats' hearing status. Serum was isolated to measure the level of the oxidative marker malondialde-hyde (MDA), the basilar membrane was prepared to count the outer hair cell loss, and soft tissue samples extracted from the cochleae were lysed to analyze the microtubule-associated protein light chain 3 (LC3) and Beclin-1. Results: The rapamycin treatment significantly attenuated cisplatin-induced hearing loss, decreased oxidative stress, and alleviated the hair cell damage that was associated with the upregulation of the LC3-II/GAPDH ratio and increased Beclin-1 expression. Conclusion: Our results demonstrated that rapamycin has an otoprotective effect; it attenuates cisplatin-induced ototoxicity, probably by attenuating oxidative damage and inducing autophagy.