Compromised DNA Repair and Signalling in Human Granulocytes

Abstract

In previous studies, we showed impaired DNA repair in human monocytes. Here, we addressed the question of whether human neutrophilic granulocytes that arise from the same precursor as monocytes exhibit a similar phenotype and are impaired in repairing their DNA. We show that neutrophilic granulocytes isolated from peripheral blood display a lack of the same repair proteins that are missing in monocytes and do not show repair of their DNA when damaged by ionising radiation (IR) or chemical ROS. Contrary to T cells, we observed no decline in the number of single-strand breaks following γ-radiation. Also, granulocytes did not show γH2AX foci formation while T cells and peripheral blood lymphocytes (PBL) responded. In comparison to PBL, XRCC1, PARP-1 and ligase III were not expressed and there was also no discernible signal for key damage response proteins ATM, ATR and DNA-PK_CS as well as γH2AX in neutrophils. Time course and dose-response experiments confirmed the absence of H2AX phosphorylation after radiation treatment although an accumulation of double-strand breaks was detected in the neutral Comet assay. Overall, the data indicate that terminally differentiated neutrophilic granulocytes in the peripheral blood display strong downregulation of DNA repair and DNA damage response factors, which should be taken into account if studies with whole peripheral blood containing granulocytes are performed, causing a significant intra-experimental variation in the cellular repair capacity.

Persistent DNA damage triggers activation of the integrated stress response to promote cell survival under nutrient restriction

“…Acute genotoxic stress could lead to temporal exhaustion of BER capacity, leading to delays in repair of DNA damage, potentially giving rise to genetic instability. Importantly, however, there are also numerous physiological circumstances in which cells have been described to selectively induce a BER deficiency [40][41][42][43][44]. While the general idea has been that downregulation of (See figure on previous page.)…”

Interaction between Fibroblasts and Immune Cells Following DNA Damage Induced by Ionizing Radiation

“…Surprisingly, DNA repair efficiency in immune cells may also vary depending on the cell type. While B and T lymphocyte development requires the generation of DSBs during the V(D)J recombination, and B cells have an additional DNA repair-dependent class switch recombination process [34][35][36], monocytes and granulocytes lack certain DNA repair mechanisms [37][38][39][40]. Furthermore, macrophages and dendritic cells re-express DNA repair factors and are resistant to modest levels of DNA damage [38,39,41].…”

“…Granulocytes, mainly neutrophils, or polymorphonuclear neutrophilic granulocytes, arise from the same precursor as monocytes and possess similar DNA repair defects to monocytes (Figure 3) [37]. Resembling monocytes, granulocytes also lack key DNA repair factors XRCC1, LIG3, PARP1 and DNA-PKcs.…”

“…Furthermore, a unique feature of granulocytes is lack of ATM, ATR and inability to phosphorylate histone H2AX (γH2AX). DNA damage-dependent apoptosis is detected in T cells/PBL, but not in granulocytes ( Figure 2) [37].…”

Interaction between Fibroblasts and Immune Cells Following DNA Damage Induced by Ionizing Radiation

“…Surprisingly, DNA repair efficiency in immune cells may also vary depending on the cell type. While B and T lymphocyte development requires the generation of DSBs during the V(D)J recombination, and B cells have additional DNA repair-dependent class switch recombination process [17][18][19][20], monocytes and granulocytes lack certain DNA repair mechanisms [21][22][23][24]. Furthermore, macrophages and dendritic cells re-express DNA repair factors and are resistant to modest levels of DNA damage [22,23,25].…”