The Involvement of Reactive Oxygen Species in Polyploidization of the M-07e Human Megakaryocytic Cell Line.

Hematopoietic cells mature in the bone marrow under the control of a diversity of growth factors and the influence of various cell types producing superoxide and other reactive oxygen species (ROS). As ROS may regulate activities of redox-sensitive enzymes implicated in a wide range of cellular processes, we have exposed the human megakaryocytic cell line M-07e to hydrogen peroxide (H₂O₂) at concentrations that increased intracellular ROS and examined whether expression of the megakaryocytic programme could be enhanced. The growth-factor dependent M-07e cells display surface markers characteristic of both early myeloid progenitors and more committed members of the magakaryocyte (Mk) lineage, such as glycoproteins GPIIb-IIIa (CD41) and GPIb (CD42). H₂O₂ significantly reduced cell proliferation without affecting viability. After 4 days of exposure to this reagent, expression of the early Mk marker CD41 was 1.2 times higher than that of control cells. Although no change in the expression of the late Mk marker CD42 was detected, exposure to H₂O₂ was found to increase the incidence of multinucleate cells, polyploidy and abnormal microtubule organising centre numbers. Investigation of this phenomenon on synchronized M-07e cells revealed that H₂O₂ arrested cytokinesis at a late stage and that some nuclei were still able to incorporate bromodeoxyuridine (BrdU). Cell division was similarly impaired when M-07e cells were either exposed to botulin toxin C3 transferase or Y-27362 inhibitor, suggesting that H₂O₂ treatments affected members of the Rho family of small GTP-binding proteins and/or their effectors. Together, these findings indicate that endoreplication in Mk may be linked to changes in the cellular redox state of these cells and support the concept that differentiation and polyploidization are independently regulated events.