title: Continuous administration of the mTORC1 inhibitor everolimus induces tolerance and decreases autophagy in mice.
abstract: Everolimus is an allosteric inhibitor of the mechanistic target of rapamycin complex 1 (mTORC1) widely known for its potent autophagy stimulating properties. Because everolimus shows poor solubility and stability in aqueous solutions, long-term in vivo administration in preclinical models is challenging. The aim of the present study was to evaluate the effects of short-term and long-term everolimus administration on mTORC1 inhibition and autophagy induction in mice.
  
  
  
  We developed a vehicle in which everolimus was solubilized and stable at 37°C for at least 1 month. Using osmotic minipumps, GFP microtubule-associated protein light chain 3 transgenic mice were treated continuously either with vehicle or everolimus (1.5 mg·kg-1per day) for 3 or 28 days. Alternatively, a regimen consisting of intermittent everolimus administration (every other day) for 56 days by oral gavage was used. Autophagy markers and mTORC1 activation status were investigated in the liver.
  
  
  
  As expected, everolimus inhibited mTORC1 and stimulated autophagy in the liver after 3 days of treatment. However, continuous administration for 28 days resulted in hyperactivation of the Akt1-mTORC1 pathway accompanied by a remarkable decrease in autophagy markers. Everolimus given intermittently for 56 days partially rescued mTORC1 sensitivity to the drug but without inducing autophagy. The failure to induce autophagy following long-term everolimus administration was due to uncoupling of the mTORC1 substrate unc-51 like autophagy activating kinase 1.
  
  
  
  Our data encourage the use of intermittent everolimus regimens to prevent tolerance and to extend its activity.
authors.affiliation: Laboratory of Physiopharmacology, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Ammar
authors.initials: A
authors.lastname: Kurdi
authors.affiliation: Laboratory for TDM and Toxicology, ZNA Stuivenberg, Antwerp, Belgium.
authors.forename: Mireille
authors.initials: M
authors.lastname: De Doncker
authors.affiliation: Laboratory of Physiopharmacology, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Arthur
authors.initials: A
authors.lastname: Leloup
authors.affiliation: Laboratory for TDM and Toxicology, ZNA Stuivenberg, Antwerp, Belgium.|Toxicological Centre, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Hugo
authors.initials: H
authors.lastname: Neels
authors.affiliation: Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Timmermans
authors.affiliation: Laboratory of Pharmacology, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: Lemmens
authors.affiliation: Natural Products and Food Research and Analysis (NatuRA), Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Sandra
authors.initials: S
authors.lastname: Apers
authors.affiliation: Laboratory of Physiopharmacology, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Guido R Y
authors.initials: GRY
authors.lastname: De Meyer
authors.affiliation: Laboratory of Physiopharmacology, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Martinet
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D004334:Drug Administration Schedule; D004355:Drug Stability; D004361:Drug Tolerance; D000068338:Everolimus / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1 / Q000037:antagonists & inhibitors*; D051379:Mice; D008822:Mice, Transgenic; D012995:Solubility; D013997:Time Factors
chemical_list: D007166:Immunosuppressive Agents; D000068338:Everolimus; D000076222:Mechanistic Target of Rapamycin Complex 1