title: Nanomechanical analysis of insulinoma cells after glucose and capsaicin stimulation using atomic force microscopy.
abstract: OBJECTIVE
  Glucose stimulates insulin secretion from pancreatic islet β cells by altering ion channel activity and membrane potential in the β cells. TRPV1 channel is expressed in the β cells and capsaicin induces insulin secretion similarly to glucose. This study aims to investigate the biophysical properties of the β cells upon stimulation of membrane channels using an atomic force microscopic (AFM) nanoindentation system.
  
  
  METHODS
  ATCC insulinoma cell line was used. Cell stiffness, a marker of reorganization of cell membrane and cytoskeleton due to ion channel activation, was measured in real time using an integrated AFM nanoindentation system. Cell height that represented structural changes was simultaneously recorded along with cell stiffness.
  
  
  RESULTS
  After administration of glucose (16, 20 and 40 mmol/L), the cell stiffness was markedly increased in a dose-dependent manner, whereas cell height was changed in an opposite way. Lower concentrations of capsaicin (1.67 × 10(-9) and 1.67 × 10(-8) mol/L) increased the cell stiffness without altering cell height. In contrast, higher concentrations of capsaicin (1.67 × 10(-6) and 1.67 × 10(-7) mol/L) had no effect on the cell physical properties.
  
  
  CONCLUSIONS
  A unique bio-nanomechanical signature was identified for characterizing biophysical properties of insulinoma cells upon general or specific activation of membrane channels. This study may deepen our understanding of stimulus-secretion coupling of pancreatic islet cells that leads to insulin secretion.
authors.affiliation: College of Engineering, Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Rui-guo
authors.initials: RG
authors.lastname: Yang
authors.forename: Ning
authors.initials: N
authors.lastname: Xi
authors.forename: King Wai-chiu
authors.initials: KW
authors.lastname: Lai
authors.forename: Bei-hua
authors.initials: BH
authors.lastname: Zhong
authors.forename: Carmen Kar-man
authors.initials: CK
authors.lastname: Fung
authors.forename: Chen-geng
authors.initials: CG
authors.lastname: Qu
authors.forename: Donna H
authors.initials: DH
authors.lastname: Wang
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002211:Capsaicin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D048429:Cell Size / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000494:pharmacology*; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure*; D008564:Membrane Potentials / Q000187:drug effects; D018625:Microscopy, Atomic Force; D050916:TRPV Cation Channels / Q000378:metabolism
chemical_list: D050916:TRPV Cation Channels; D005947:Glucose; D002211:Capsaicin