Biphasic regulation of cell cycle by nitric oxide donors in promyelocytic HL-60 cell line

Abstract

Nitric oxide (NO) regulates a wide array of cell functions, proliferation, cytostasis and apoptosis. Role of NO in cell proliferation is however is less explored, which has been suggested to be dependent on the NO concentration, cell type and intracellular redox status. Present study explores the effect of NO donors [DETA-NONOate (DETA-NO) and SNAP] on the promyelocytic HL-60 cells. NO induced proliferation of HL-60 cell at lower concentration (1-100 µM), which was evaluated by Thymidine incorporation, BrdU labelling and cell cycle analysis regardless of any apoptosis, while higher concentration (250µM-1mM) promoted apoptosis as evident by change in mitochondrial potential, Caspase activation, nick and PI labelling. To investigate further the mechanism involved, expression profile of various CDK/ cyclins including CDK2, CDK6, Cyclin A, Cyclin B, Cyclin D1, p15, p27 was monitored, Expression of Cyclin B, CDK2 was increased at 10-50 µM by DETA-NO, while most of these cell cycle regulators were reduced at 1 mM DETA-NO. This proliferative effect seems to be redox sensitive as effect was abolished by pretreatment of cells with DTT (2mM). NO (10-50µM) also augmented nitrosylation of various proteins suggesting nitrosylation of important targets. The results obtained thus suggest that NO in a concentration dependent manner modulated cell cycle in the HL-60 cells.