title: Connexin-43 prevents hematopoietic stem cell senescence through transfer of reactive oxygen species to bone marrow stromal cells.
abstract: Hematopoietic stem cell (HSC) aging has become a concern in chemotherapy of older patients. Humoral and paracrine signals from the bone marrow (BM) hematopoietic microenvironment (HM) control HSC activity during regenerative hematopoiesis. Connexin-43 (Cx43), a connexin constituent of gap junctions (GJs) is expressed in HSCs, down-regulated during differentiation, and postulated to be a self-renewal gene. Our studies, however, reveal that hematopoietic-specific Cx43 deficiency does not result in significant long-term competitive repopulation deficiency. Instead, hematopoietic Cx43 (H-Cx43) deficiency delays hematopoietic recovery after myeloablation with 5-fluorouracil (5-FU). 5-FU-treated H-Cx43-deficient HSC and progenitors (HSC/P) cells display decreased survival and fail to enter the cell cycle to proliferate. Cell cycle quiescence is associated with down-regulation of cyclin D1, up-regulation of the cyclin-dependent kinase inhibitors, p21(cip1.) and p16(INK4a), and Forkhead transcriptional factor 1 (Foxo1), and activation of p38 mitogen-activated protein kinase (MAPK), indicating that H-Cx43-deficient HSCs are prone to senescence. The mechanism of increased senescence in H-Cx43-deficient HSC/P cells depends on their inability to transfer reactive oxygen species (ROS) to the HM, leading to accumulation of ROS within HSCs. In vivo antioxidant administration prevents the defective hematopoietic regeneration, as well as exogenous expression of Cx43 in HSC/P cells. Furthermore, ROS transfer from HSC/P cells to BM stromal cells is also rescued by reexpression of Cx43 in HSC/P. Finally, the deficiency of Cx43 in the HM phenocopies the hematopoietic defect in vivo. These results indicate that Cx43 exerts a protective role and regulates the HSC/P ROS content through ROS transfer to the HM, resulting in HSC protection during stress hematopoietic regeneration.
authors.affiliation: Research Division, Hoxworth Blood Center, University of Cincinnati, Cincinnati, OH 45267, USA.
authors.forename: Eri
authors.initials: E
authors.lastname: Taniguchi Ishikawa
authors.forename: Daniel
authors.initials: D
authors.lastname: Gonzalez-Nieto
authors.forename: Gabriel
authors.initials: G
authors.lastname: Ghiaur
authors.forename: Susan K
authors.initials: SK
authors.lastname: Dunn
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Ficker
authors.forename: Bhuvana
authors.initials: B
authors.lastname: Murali
authors.forename: Malav
authors.initials: M
authors.lastname: Madhu
authors.forename: David E
authors.initials: DE
authors.lastname: Gutstein
authors.forename: Glenn I
authors.initials: GI
authors.lastname: Fishman
authors.forename: Luis C
authors.initials: LC
authors.lastname: Barrio
authors.forename: Jose A
authors.initials: JA
authors.lastname: Cancelas
mesh_terms: D000818:Animals; D016922:Cellular Senescence / Q000502:physiology*; D018031:Connexin 43 / Q000172:deficiency / Q000378:metabolism*; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000378:metabolism / Q000502:physiology*; D016086:Lentivirus; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D046228:Microarray Analysis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000378:metabolism*; D014161:Transduction, Genetic
chemical_list: D018031:Connexin 43; D017382:Reactive Oxygen Species; D005472:Fluorouracil