Inflammation induces multinucleation of Microglia via PKC inhibition of cytokinesis, generating highly phagocytic multinucleated giant cells

Abstract

Microglia are brain macrophages, which can undergo multinucleation to give rise to multinucleated giant cells that accumulate with ageing and some brain pathologies. However, the origin, regulation and function of multinucleate microglia remain unclear. We found that inflammatory stimuli, including lipopolysaccharide, amyloid b, a-synuclein, tumour necrosis factor-a and interferon c, but not interleukin-4, induced multinucleation of cultured microglia: primary rat cortical microglia and the murine microglial cell line BV-2. Inflammation-induced multinucleation was prevented by a protein kinase C (PKC) inhibitor G€ o6976 (100 nM) and replicated by a PKC activator phorbol myristate acetate (160 nM). Multinucleation was reversible and not because of cell fusion or phagocytosis, but rather failure of cytokinesis. Time-lapse imaging revealed that some dividing cells failed to abscise, even after formation of long cytoplasmic bridges, followed by retraction of bridge and reversal of cleavage furrow to form multinucleate cells. Multinucleate microglia were larger and 2-4 fold more likely to phagocytose large beads and both dead and live PC12 cells. We conclude that multinucleate microglia are reversibly generated by inflammation via PKC inhibition of cytokinesis, and may have specialized functions/dysfunctions including the phagocytosis of other cells.

Retinal pigment epithelial cell multinucleation in the aging eye - a mechanism to repair damage and maintain homoeostasis

“…In these conditions, multinucleation is considered to occur by cell fusion (Abmayr & Pavlath, 2012; Miyamoto, 2013), while multinucleation during development may occur by phagocytosis of live viable cells (Baluska et al ., 2012). Recently, however, multinucleation in microglial cells was shown to occur by a mechanism involving failure of cytokinesis in which DNA synthesis and nuclear replication occurred, but progression to full cell division failed (Hornik et al ., 2014). In the present study, we demonstrate in vitro that exposure to POS, particularly oxPOS, stimulated the formation of multinucleate RPE cells, and this appeared to occur by failure of cytokinesis rather than by cell fusion or phagocytosis of neighbouring RPE cells.…”

“…Previous studies have noted a variable increase in RPE cell size as well as multinucleation with age (Ts'o & Friedman, 1967, 1968), but the significance of these observations is unclear. Giant cell formation with multinucleation is a normal feature of some cells such as osteoclasts and syncytiotrophoblasts (Park & Askin, 2013; Oh et al ., 2014) and also occurs during pathological processes such as foreign body giant cell formation in macrophages (Vignery, 2005; MacLauchlan et al ., 2009), and in microglial cells in some forms of neurodegeneration (Lee et al ., 1993; Hornik et al ., 2014). Giant cell formation and multinucleation, at least in osteoclasts, are formed by cell fusion, but other mechanisms may also explain cells with multiple nuclei such as phagocytosis of live cells or failure of cytokinesis in dividing cells (Hornik et al ., 2014).…”

The role of the surface on microglia function: implications for central nervous system tissue engineering

“…These cells have been found to accumulate with age [50], and are also associated with some neuropathologies, namely HIV-related dementia [51]. Microglia activation to form MGCs can be triggered by inflammatory cytokines [41,52,53] as well as in response to phagocytosis of cell debris [52,54]. MGCs have an increased phagocytic activity [52,54], which may represent an advantage when large amounts of debris accumulate due to Wallerian degeneration.…”

“…Microglia activation to form MGCs can be triggered by inflammatory cytokines [41,52,53] as well as in response to phagocytosis of cell debris [52,54]. MGCs have an increased phagocytic activity [52,54], which may represent an advantage when large amounts of debris accumulate due to Wallerian degeneration. To the best of our knowledge this is the first study that analyses the effect of the biomaterial surface on microglia in light of MGC formation.…”

P2X₇ receptor in the hippocampus is involved in gp120-induced cognitive dysfunction

“…Brain microglia, astrocytes, and innate immune cells of the brain parenchyma are responsible for homeostasis in normal CNS tissue, and are likely affected by ADC as excessive activation of microglial cells can induce CNS injury and neurodegenerative disease (Tambuyzer et al, 2009;Harry 2013;Hornik et al, 2014;Mosher and Wyss-Coray 2014). The P2X 7 receptor plays a major role in the regulation of microglia activity and is involved in inflammation and immune responses, and as such has an important role in neurodegenerative disease (Le Feuvre et al, 2002;Baudelet et al, 2015).…”