Granulocyte colony-stimulating factor perturbs lymphocyte mitochondrial function and inhibits cell cycle progression

Area of Science:

• Immunology
• Cell Biology
• Hematology

Background:

• Recombinant human granulocyte colony-stimulating factor (rHuG-CSF) mobilizes CD34(+) peripheral blood progenitors (PBPC).
• Previous studies indicated that serum from rHuG-CSF-treated subjects induces lymphocyte unresponsiveness.
• The effects on early apoptosis and cell cycle entry require further investigation.

Purpose of the Study:

• To evaluate the impact of rHuG-CSF on lymphocyte activation-induced apoptosis.
• To assess rHuG-CSF's effects on lymphocyte cell cycle progression.
• To elucidate the mechanisms behind rHuG-CSF-mediated immune alterations.

Main Methods:

• Collected serum from donors before and after rHuG-CSF administration.
• Challenged normal peripheral blood mononuclear cells (PBMC) with phytohemagglutinin (PHA) in the presence of pre- and post-rHuG-CSF serum.
• Utilized multiparameter flow cytometry to assess mitochondrial function, reactive oxygen species (ROS), and Bcl-2 family protein expression.
• Employed highly sensitive ligation-mediated PCR (LM-PCR) to detect DNA fragmentation.

Main Results:

• Post-rHuG-CSF serum induced perturbation of mitochondrial transmembrane potential (Deltapsi(m)) and ROS hypergeneration in lymphocytes.
• Lymphocytes were arrested in a G(0)-like cell cycle phase and exhibited genomic DNA fragmentation.
• Bax protein was overexpressed, suggesting a role in apoptosis induction via the CD95 signaling pathway.

Conclusions:

• Humoral factors in post-rHuG-CSF serum mediate lymphocyte mitochondrial dysfunction and apoptosis.
• Bax overexpression and altered Bcl-2 family member balance contribute to these effects.
• The clinical implications for graft-versus-host disease following PBPC transplantation warrant further study.