title: Calcium signalling from the type I inositol 1,4,5-trisphosphate receptor is required at early phase of liver regeneration.
abstract: OBJECTIVE
  Liver regeneration is a multistage process that unfolds gradually, with different mediators acting at different stages of regeneration. Calcium (Ca(2+) ) signalling is essential for liver regeneration. In hepatocytes, Ca(2+) signalling results from the activation of inositol 1,4,5-trisphosphate receptors (InsP3 R) of which two of the three known isoforms are expressed (InsP3 R-I and InsP3 R-II). Here, we investigated the role of the InsP3 R-I-dependent Ca(2+) signals in hepatic proliferation during liver regeneration.
  
  
  METHODS
  Partial hepatectomy (HX) in combination with knockdown of InsP3 R-I (AdsiRNA-I) was used to evaluate the role of InsP3 R-I on liver regeneration and hepatocyte proliferation, as assessed by liver to body mass ratio, PCNA expression, immunoblots and measurements of intracellular Ca(2+) signalling.
  
  
  RESULTS
  AdsiRNA-I efficiently infected the liver as demonstrated by the expression of β-galactosidase throughout the liver lobules. Moreover, this construct selectively and efficiently reduced the expression of InsP3 R-I, as evaluated by immunoblots. Expression of AdsiRNA-I in liver decreased peak Ca(2+) amplitude induced by vasopressin in isolated hepatocytes 2 days after HX. Reduced InsP3 R-I expression prior to HX also delayed liver regeneration, as measured by liver to body weight ratio, and reduced hepatocyte proliferation, as evaluated by PCNA staining, at the same time point. At later stages of regeneration, control hepatocytes showed a decreased expression of InsP3 R, as well as reduced InsP3 R-mediated Ca(2+) signalling, events that did not affect liver growth.
  
  
  CONCLUSIONS
  Together, these results show that InsP3 R-I-dependent Ca(2+) signalling is an early triggering pathway required for liver regeneration.
authors.affiliation: Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: André G
authors.initials: AG
authors.lastname: Oliveira
authors.forename: Viviane A
authors.initials: VA
authors.lastname: Andrade
authors.forename: Erika S
authors.initials: ES
authors.lastname: Guimarães
authors.forename: Rodrigo M
authors.initials: RM
authors.lastname: Florentino
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Sousa
authors.forename: Pedro E
authors.initials: PE
authors.lastname: Marques
authors.forename: Flávia M
authors.initials: FM
authors.lastname: Melo
authors.forename: Miguel J
authors.initials: MJ
authors.lastname: Ortega
authors.forename: Gustavo B
authors.initials: GB
authors.lastname: Menezes
authors.forename: M Fatima
authors.initials: MF
authors.lastname: Leite
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D016466:CHO Cells; D020013:Calcium Signaling; D049109:Cell Proliferation; D003412:Cricetulus; D057809:HEK293 Cells; D006498:Hepatectomy / Q000379:methods; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism* / Q000503:physiopathology / Q000601:surgery; D008115:Liver Regeneration; D008297:Male; D009929:Organ Size; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D034622:RNA Interference; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014162:Transfection
chemical_list: D015415:Biomarkers; D053496:Inositol 1,4,5-Trisphosphate Receptors; C488910:Itpr1 protein, rat; D018809:Proliferating Cell Nuclear Antigen
keywords: 1,4,5-trisphosphate receptors; Liver regeneration; calcium signalling