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Effects of cytokines on microglial phenotypes and astroglial coupling in an inflammatory coculture model
Daniel Hinkerohe1, Dirk Smikalla, Aiden Haghikia
1Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Bochum, Germany.
Abstract:
Cytokines play an important role in the onset, regulation, and propagation of immune and inflammatory responses within the central nervous system (CNS). The main source of cytokines in the CNS are microglial cells. Under inflammatory conditions, microglial cells are capable of producing pro- and antiinflammatory cytokines, which convey essential impact on the glial and neuronal environment. One paramount functional feature of astrocytes is their ability to form a functionally coupled syncytium. The structural link, which is responsible for the syncytial behavior of astrocytes, is provided by gap junctions. The present study was performed to evaluate the influence of inflammation related cytokines on an astroglial/microglial inflammatory model. Primary astrocytic cultures of newborn rats were cocultured with either 5% (M5) or 30% (M30) microglial cells and were incubated with the following proinflammatory cytokines: tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interferon-gamma (IFN-gamma), and the antiinflammatory cytokines transforming growth factor-beta1 (TGF-beta1) and IFN-beta. Under these conditions, i.e., incubation with the inflammatory cytokines and the high fraction of microglia (M30), microglial cells revealed a significant increase of activated round phagocytotic cells accompanied by a reduction of astroglial connexin 43 (Cx43) expression, a reduced functional coupling together with depolarization of the membrane resting potential (MRP). When the antiinflammatory mediator TGF-beta1 was added to proinflammatory altered M30 cocultures, a reversion of microglial activation and reconstitution of functional coupling together with recovery of the astroglial MRP was achieved. Finally IFN-beta, added to M5 cocultures was able to prevent the effects of the proinflammatory cytokines TNF-alpha, IL-1beta, and IFN-gamma.
Insights
Inflammatory cytokines activate microglia and impair astrocyte function in the CNS. Anti-inflammatory cytokines like TGF-beta1 and IFN-beta can reverse these effects, offering potential therapeutic targets for neuroinflammation.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Cytokines are key mediators of immune and inflammatory responses in the central nervous system (CNS).
- Microglial cells are the primary source of cytokines in the CNS, producing both pro- and anti-inflammatory types.
- Astrocytes form a functionally coupled syncytium via gap junctions, influencing the CNS environment.
Purpose of the Study:
- To investigate the impact of pro- and anti-inflammatory cytokines on an astroglial/microglial co-culture model.
- To evaluate how cytokine-induced inflammation affects astrocyte function, including connexin 43 expression and functional coupling.
- To determine the potential of anti-inflammatory cytokines to counteract inflammatory effects in the CNS model.
Main Methods:
- Primary rat astrocyte cultures were co-cultured with varying percentages of microglial cells (5% M5, 30% M30).
- Co-cultures were incubated with pro-inflammatory cytokines (TNF-alpha, IL-1beta, IL-6, IFN-gamma) and anti-inflammatory cytokines (TGF-beta1, IFN-beta).
- Assessed microglial activation, astroglial connexin 43 (Cx43) expression, functional coupling, and membrane resting potential (MRP).
Main Results:
- High microglial fractions (M30) with pro-inflammatory cytokines led to increased activated microglia, reduced Cx43 expression, impaired astrocyte coupling, and depolarized MRP.
- Addition of TGF-beta1 to M30 co-cultures reversed microglial activation and restored astrocyte coupling and MRP.
- IFN-beta in M5 co-cultures prevented the detrimental effects of pro-inflammatory cytokines TNF-alpha, IL-1beta, and IFN-gamma.
Conclusions:
- Inflammatory cytokines significantly disrupt astrocyte function and glial network integrity.
- Anti-inflammatory cytokines TGF-beta1 and IFN-beta demonstrate a capacity to mitigate cytokine-induced neuroinflammation and restore normal cell function.
- These findings highlight the critical role of cytokine balance in CNS health and suggest potential therapeutic avenues for neuroinflammatory diseases.
