Abstract
BackgroundBrain inflammation plays a key role in neurological disease. Although much research has been conducted investigating inflammatory events in animal models, potential differences in human brain versus rodent models makes it imperative that we also study these phenomena in human cells and tissue.MethodsPrimary human brain cell cultures were generated from biopsy tissue of patients undergoing surgery for drug-resistant epilepsy. Cells were treated with pro-inflammatory compounds IFNγ, TNFα, IL-1β, and LPS, and chemokines IP-10 and MCP-1 were measured by immunocytochemistry, western blot, and qRT-PCR. Microarray analysis was also performed on late passage cultures treated with vehicle or IFNγ and IL-1β.ResultsEarly passage human brain cell cultures were a mixture of microglia, astrocytes, fibroblasts and pericytes. Later passage cultures contained proliferating fibroblasts and pericytes only. Under basal culture conditions all cell types showed cytoplasmic NFκB indicating that they were in a non-activated state. Expression of IP-10 and MCP-1 were significantly increased in response to pro-inflammatory stimuli. The two chemokines were expressed in mixed cultures as well as cultures of fibroblasts and pericytes only. The expression of IP-10 and MCP-1 were regulated at the mRNA and protein level, and both were secreted into cell culture media. NFκB nuclear translocation was also detected in response to pro-inflammatory cues (except IFNγ) in all cell types. Microarray analysis of brain pericytes also revealed widespread changes in gene expression in response to the combination of IFNγ and IL-1β treatment including interleukins, chemokines, cellular adhesion molecules and much more.ConclusionsAdult human brain cells are sensitive to cytokine challenge. As expected ‘classical’ brain immune cells, such as microglia and astrocytes, responded to cytokine challenge but of even more interest, brain pericytes also responded to such challenge with a rich repertoire of gene expression. Immune activation of brain pericytes may play an important role in communicating inflammatory signals to and within the brain interior and may also be involved in blood brain barrier (BBB) disruption . Targeting brain pericytes, as well as microglia and astrocytes, may provide novel opportunities for reducing brain inflammation and maintaining BBB function and brain homeostasis in human brain disease.
Highlights
Brain inflammation occurs in a number of neurological and psychiatric diseases and is generally thought to worsen disease symptoms and progression [1]
Positive staining for fibronectin and prolyl-4 hydroxylase (P4H), platelet-derived growth factor receptor-beta (PDGFR-β), NG2 and alpha smooth muscle actin, CD45, and glial fibrillary acidic protein (GFAP, astrocyte marker) was seen in early passages of dissociated cultures (Figure 1A-G)
All cells in the later cultures are positive for fibronectin, and approximately 90% of cells are positive for both αSMA and platelet-derived growth factor receptor-β (PDGFRβ) (Figure 1H)
Summary
Brain inflammation occurs in a number of neurological (for example, epilepsy, Alzheimer’s disease, Parkinson’s disease, motor neuron disease) and psychiatric (schizophrenia, depression) diseases and is generally thought to worsen disease symptoms and progression [1]. Many different brain cells are likely to be involved in brain inflammation, most attention has focused on the role of nonnerve brain cells, especially microglia and astrocytes [2,3,4]. Pericytes interact dynamically with astrocytes and microglia and can receive signals from the periphery resulting in central nervous system (CNS) inflammatory molecule production [7,8]. CNS pericytes are in a pivotal position to mediate interactions between systemic and central brain inflammation [9] and have been shown to play a role in recruitment of peripheral immune cells to the brain [10,11,12]. The further increase in brain infiltration of systemic immune molecules and cells as well as other blood components may directly cause neuronal damage and/or promote microglial inflammation [13]. Much research has been conducted investigating inflammatory events in animal models, potential differences in human brain versus rodent models makes it imperative that we study these phenomena in human cells and tissue
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