title: Rapamycin Inhibition of mTOR Reduces Levels of the Na+/H+ Exchanger 3 in Intestines of Mice and Humans, Leading to Diarrhea.
abstract: OBJECTIVE
  The immunosuppressant rapamycin frequently causes noninfectious diarrhea in organ transplant recipients. We investigated the mechanisms of this process.
  
  
  METHODS
  We performed a retrospective analysis of renal transplant recipients treated with rapamycin from 2003 through 2010 at Albany Medical College, collecting data on serum levels of rapamycin. Levels of the Na+/H+ exchanger 3 (NHE3) were measured in human ileal biopsy specimens from patients who did and did not receive rapamycin (controls), in ileum tissues from rats or mice given rapamycin, and in mice with intestine-specific disruption of mammalian target of rapamycin (Mtor) (mTOR(f/f):Villin-cre mice) or Atg7 (Atg7(flox/flox); Villin-Cre). Exchange activity and intestinal water absorption were measured using a pH-sensitive dye and small intestine perfusion, respectively.
  
  
  RESULTS
  Episodes of noninfectious diarrhea occurred in organ recipients after increases in serum levels of rapamycin. The expression of NHE3 was reduced in the ileal brush border of patients with diarrhea. In rats and mice, continuous administration of low doses of rapamycin reduced levels of NHE3 in intestinal tissues; this effect was not observed in mice with intestinal deletion of ATG7, indicating that autophagy is required for the reduction. Administration of single high doses of rapamycin to mice, to model the spikes in rapamycin levels that occur in patients with severe diarrheal episodes, resulted in reduced phosphorylation of S6 and AKT in ileal tissues, indicating inhibition of the mTOR complex (mTORC1 and mTORC2). The intestines of mice with intestine-specific deletion of mTOR were dilated and contained large amounts of liquid stools; they also had reduced levels of total NHE3 and NHERF1 compared with control mice. We observed a significant reduction in Na(+)/H(+) exchange activity in ileum tissues from these mice.
  
  
  CONCLUSIONS
  Rapamycin inhibition of mTOR reduces levels of NHE3 and Na(+)/H(+) exchange activity in intestinal tissues of patients and rodents. This process appears to require the autophagic activity mediated by ATG7. Loss of mTOR regulation of NHE3 could mediate the development of diarrhea in patients undergoing rapamycin therapy.
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York; Center of Cardiovascular Sciences, Albany Medical College, Albany, New York.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York; Center of Cardiovascular Sciences, Albany Medical College, Albany, New York.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York.
authors.forename: Archana
authors.initials: A
authors.lastname: Patel
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York.
authors.forename: Rachana
authors.initials: R
authors.lastname: Potru
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York.
authors.forename: Sadra
authors.initials: S
authors.lastname: Azizi-Ghannad
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York.
authors.forename: Michael
authors.initials: M
authors.lastname: Dolinger
authors.affiliation: Center of Cardiovascular Sciences, Albany Medical College, Albany, New York.
authors.forename: James
authors.initials: J
authors.lastname: Cao
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York.
authors.forename: Catherine
authors.initials: C
authors.lastname: Bartholomew
authors.affiliation: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York.
authors.forename: Joseph
authors.initials: J
authors.lastname: Mazurkiewicz
authors.affiliation: Department of Transplant Surgery, Albany Medical College, Albany, New York.
authors.forename: David
authors.initials: D
authors.lastname: Conti
authors.affiliation: Department of Pathology, Albany Medical College, Albany, New York.
authors.forename: David
authors.initials: D
authors.lastname: Jones
authors.affiliation: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Department of Medicine, Division of Gastroenterology and Hepatology, Albany Medical College, Albany, New York; Center of Cardiovascular Sciences, Albany Medical College, Albany, New York. Electronic address: zhux@mail.amc.edu.
authors.forename: Xinjun Cindy
authors.initials: XC
authors.lastname: Zhu
mesh_terms: D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000071193:Autophagy-Related Protein 7; D001706:Biopsy; D016022:Case-Control Studies; D003967:Diarrhea / Q000188:drug therapy* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020123:Sirolimus / Q000494:pharmacology*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D010750:Phosphoproteins; C000613385:SLC9A3 protein, human; C000613386:Slc9a3 protein, mouse; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D058570:TOR Serine-Threonine Kinases; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; D020123:Sirolimus
keywords: Immunosuppression; Sodium Transport; Transplantation; mTOR
references.citation: J Biol Chem. 2005 Jan 14;280(2):1688-95
references.pmid: 15531580
references.citation: Nature. 2012 Jun 28;486(7404):490-5
references.pmid: 22722868
references.citation: Liver Transpl. 2005 Aug;11(8):881-90
references.pmid: 16035068
references.citation: Curr Opin Cell Biol. 2005 Dec;17(6):596-603
references.pmid: 16226444
references.citation: Mol Cell. 2006 Apr 21;22(2):159-68
references.pmid: 16603397
references.citation: Transplant Proc. 2006 Jun;38(5):1298-300
references.pmid: 16797287
references.citation: J Clin Invest. 2006 Oct;116(10):2682-94
references.pmid: 17016558
references.citation: J Biol Chem. 2007 Aug 24;282(34):25141-51
references.pmid: 17580307
references.citation: Cell. 2008 Jan 11;132(1):27-42
references.pmid: 18191218
references.citation: J Neurosci. 2012 Nov 7;32(45):15704-14
references.pmid: 23136410
references.citation: J Biol Chem. 2013 Jun 7;288(23):16960-74
references.pmid: 23612977
references.citation: Cell. 2013 Aug 29;154(5):1085-99
references.pmid: 23954414
references.citation: PLoS One. 2013;8(12):e81325
references.pmid: 24312548
references.citation: J Clin Pharmacol. 1999 Nov;39(11):1155-61
references.pmid: 10579146
references.citation: Kidney Int. 2001 Jan;59(1):3-16
references.pmid: 11135052
references.citation: J Biol Chem. 2001 Aug 17;276(33):31296-304
references.pmid: 11375999
references.citation: Am J Physiol Gastrointest Liver Physiol. 2001 Dec;281(6):G1385-96
references.pmid: 11705743
references.citation: Am J Physiol Gastrointest Liver Physiol. 2002 May;282(5):G776-84
references.pmid: 11960774
references.citation: Am J Physiol Cell Physiol. 2003 Nov;285(5):C1246-54
references.pmid: 12878493
references.citation: Gastroenterology. 2004 Jan;126(1):122-35
references.pmid: 14699494
references.citation: Transplantation. 1992 Feb;53(2):496-8
references.pmid: 1371198
references.citation: J Cell Sci. 1992 Jan;101 ( Pt 1):219-31
references.pmid: 1569126
references.citation: J Biol Chem. 1993 Dec 5;268(34):25527-35
references.pmid: 8244988
references.citation: Am J Physiol. 1995 Jul;269(1 Pt 1):G1-11
references.pmid: 7631785
references.citation: Transplantation. 1997 Jul 27;64(2):222-8
references.pmid: 9256177
references.citation: Nat Genet. 1998 Jul;19(3):282-5
references.pmid: 9662405
references.citation: Dig Dis Sci. 1998 Oct;43(10):2227-36
references.pmid: 9790458
references.citation: Am J Kidney Dis. 2008 Mar;51(3):478-86
references.pmid: 18295064
references.citation: Methods Mol Biol. 2008;445:77-88
references.pmid: 18425443
references.citation: Autophagy. 2009 Feb;5(2):250-2
references.pmid: 19139628
references.citation: J Exp Biol. 2009 Jun;212(Pt 11):1638-46
references.pmid: 19448074
references.citation: Semin Immunopathol. 2010 Dec;32(4):431-6
references.pmid: 20814791
references.citation: Gastroenterology. 2011 Feb;140(2):560-71
references.pmid: 20977906
references.citation: Nat Cell Biol. 2011 Feb;13(2):132-41
references.pmid: 21258367
references.citation: Am J Physiol Cell Physiol. 2011 Apr;300(4):C771-82
references.pmid: 21191106
references.citation: Geriatr Gerontol Int. 2012 Jan;12(1):131-9
references.pmid: 21794051
references.citation: J Biol Chem. 2011 Oct 7;286(40):34486-96
references.pmid: 21799002
references.citation: J Biol Chem. 2011 Jul 15;286(28):24553-60
references.pmid: 21592956
references.citation: Science. 2005 Feb 18;307(5712):1098-101
references.pmid: 15718470