title: Proapoptotic Bax is hyperexpressed in isolated human islets compared with antiapoptotic Bcl-2.
abstract: BACKGROUND
  Apoptosis is a well-documented pathway for islet cell death. One potential mechanism is overexpression of death-promoting Bax compared with antiapoptotic Bcl-2 in islets.
  
  
  METHODS
  We isolated islets from 10 human pancreata and measured the expression of Bax mRNA and Bcl-2 mRNA by real-time quantitative polymerase chain reaction; islet and pancreas expression of Bax, Bcl-2, activated caspase-3, and cleaved poly (ADP-ribose) polymerase were also assessed by immunohistochemistry. Islet cell apoptosis was evaluated by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay and by flow cytometry.
  
  
  RESULTS
  The mean (+/-SE) level of Bax mRNA was 336+/-79 copies per nanogram of total RNA, and the level of Bcl-2 mRNA was 36+/-10 (P=0.001). A positive correlation existed between islet expression of Bax mRNA and Bcl-2 mRNA (P=0.001). The islet Bax to Bcl-2 ratio was 10.8+/-1.3 and 1.71+/-0.3 for the spleens (P=0.0001). Bax mRNA (P=0.04), but not Bcl-2 mRNA, was expressed at a higher level in islets compared with spleens. Human islets contained large numbers of cells expressing Bax protein, whereas only infrequent islet cells expressed Bcl-2 protein, activated caspase-3, and poly (ADP-ribose) polymerase. The apoptotic index was 5% by TUNEL assay, and the percentage of apoptotic islet cells was 9.7+/-2.5% by flow cytometry. Sections of human pancreas before islet isolation showed islet staining for Bax but not Bcl-2.
  
  
  CONCLUSIONS
  Our finding that isolated human islets express Bax at a higher level compared with Bcl-2 suggests a molecular mechanism for islet cell death by apoptosis. We hypothesize that reducing islet expression of Bax, or regulating its activation, will help preserve islet cell mass after islet transplantation.
authors.affiliation: Division of Nephrology, Department of Medicine, Weill Medical College of Cornell University, New York, NY, USA.
authors.forename: Dolca
authors.initials: D
authors.lastname: Thomas
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Boffa
authors.forename: Ruchuang
authors.initials: R
authors.lastname: Ding
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Sharma
authors.forename: Milagros
authors.initials: M
authors.lastname: Lagman
authors.forename: Baogui
authors.initials: B
authors.lastname: Li
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hering
authors.forename: Thalachallour
authors.initials: T
authors.lastname: Mohanakumar
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lakey
authors.forename: Sandip
authors.initials: S
authors.lastname: Kapur
authors.forename: Wayne W
authors.initials: WW
authors.lastname: Hancock
authors.forename: Manikkam
authors.initials: M
authors.lastname: Suthanthiran
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000502:physiology*; D015925:Cryopreservation; D005260:Female; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010179:Pancreas; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein