Dual role of inflammation in CNS disease (original) (raw)
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The Role of Inflammation In CNS Injury and Disease
British journal of …, 2006
For many years, the central nervous system (CNS) was considered to be 'immune privileged', neither susceptible to nor contributing to inflammation. It is now appreciated that the CNS does exhibit features of inflammation, and in response to injury, infection or disease, resident CNS cells generate inflammatory mediators, including proinflammatory cytokines, prostaglandins, free radicals and complement, which in turn induce chemokines and adhesion molecules, recruit immune cells, and activate glial cells. Much of the key evidence demonstrating that inflammation and inflammatory mediators contribute to acute, chronic and psychiatric CNS disorders is summarised in this review. However, inflammatory mediators may have dual roles, with detrimental acute effects but beneficial effects in long-term repair and recovery, leading to complications in their application as novel therapies. These may be avoided in acute diseases in which treatment administration might be relatively short-term. Targeting interleukin (IL)-1 is a promising novel therapy for stroke and traumatic brain injury, the naturally occurring antagonist (IL-1ra) being well tolerated by rheumatoid arthritis patients. Chronic disorders represent a greater therapeutic challenge, a problem highlighted in Alzheimer's disease (AD); significant data suggested that anti-inflammatory agents might reduce the probability of developing AD, or slow its progression, but prospective clinical trials of nonsteroidal anti-inflammatory drugs or cyclooxygenase inhibitors have been disappointing. The complex interplay between inflammatory mediators, ageing, genetic background, and environmental factors may ultimately regulate the outcome of acute CNS injury and progression of chronic neurodegeneration, and be critical for development of effective therapies for CNS diseases.
Inflammatory Response in the CNS: Friend or Foe?
Molecular Neurobiology, 2016
Inflammatory reactions could be both beneficial and detrimental to the brain, depending on strengths of their activation in various stages of neurodegeneration. Mild activation of microglia and astrocytes usually reveals neuroprotective effects and ameliorates early symptoms of neurodegeneration; for instance, released cytokines help maintain synaptic plasticity and modulate neuronal excitability, and stimulated toll-like receptors (TLRs) promote neurogenesis and neurite outgrowth. However, strong activation of glial cells gives rise to cytokine overexpression/dysregulation, which accelerates neurodegeneration. Altered mutual regulation of p53 protein, a major tumor suppressor, and NF-κB, the major regulator of inflammation, seems to be crucial for the shift from beneficial to detrimental effects of neuroinflammatory reactions in neurodegeneration. Therapeutic intervention in the p53-NF-κB axis and modulation of TLR activity are future challenges to cope with neurodegeneration.
An Inflammation-Centric View of Neurological Disease: Beyond the Neuron
Frontiers in cellular neuroscience, 2018
Inflammation is a complex biological response fundamental to how the body deals with injury and infection to eliminate the initial cause of cell injury and effect repair. Unlike a normally beneficial acute inflammatory response, chronic inflammation can lead to tissue damage and ultimately its destruction, and often results from an inappropriate immune response. Inflammation in the nervous system ("neuroinflammation"), especially when prolonged, can be particularly injurious. While inflammation may not cause disease, it contributes importantly to disease pathogenesis across both the peripheral (neuropathic pain, fibromyalgia) and central [e.g., Alzheimer disease, Parkinson disease, multiple sclerosis, motor neuron disease, ischemia and traumatic brain injury, depression, and autism spectrum disorder] nervous systems. The existence of extensive lines of communication between the nervous system and immune system represents a fundamental principle underlying neuroinflammation...
Effect of Systemic Inflammation in the CNS: A Silent History of Neuronal Damage
International Journal of Molecular Sciences
Central nervous system (CNS) infections including meningitis and encephalitis, resulting from the blood-borne spread of specific microorganisms, provoke nervous tissue damage due to the inflammatory process. Moreover, different pathologies such as sepsis can generate systemic inflammation. Bacterial lipopolysaccharide (LPS) induces the release of inflammatory mediators and damage molecules, which are then released into the bloodstream and can interact with structures such as the CNS, thus modifying the blood–brain barrier’s (BBB´s) and blood–cerebrospinal fluid barrier´s (BCSFB´s) function and inducing aseptic neuroinflammation. During neuroinflammation, the participation of glial cells (astrocytes, microglia, and oligodendrocytes) plays an important role. They release cytokines, chemokines, reactive oxygen species, nitrogen species, peptides, and even excitatory amino acids that lead to neuronal damage. The neurons undergo morphological and functional changes that could initiate fu...
From Immune Sanctuary to Neurological Battlefield: The Role of Neuroimmune Cells
2024
The brain, traditionally regarded as immune-privileged due to the blood-brain barrier, harbors a sophisticated immune system crucial for maintaining neural health and resilience against various challenges. Microglia, the resident immune cells of the central nervous system, actively monitor their environment, participating in immune surveillance, synaptic pruning, and neuroprotection. Astrocytes also play vital roles by regulating neurotransmitter levels, supporting metabolism, and maintaining the blood-brain barrier integrity. Recent research underscores the involvement of T cells and monocytes in modulating neuroinflammation and immune responses within the brain. Neurological disorders such as Alzheimer's and Parkinson's disease highlight the brain's vulnerability to immune dysregulation. This review aimed to elucidate the role of neuroimmune cells in brain health and the progression of neurological diseases. It aimed to identify critical mechanisms to enhance therapeutic strategies and improve outcomes. Understanding these interactions is essential for developing targeted therapies to mitigate neuroinflammation and preserve cognitive functions. This review critically examines neuroinflammation related to aging and disease, with a focus on neuroimmune cells and their underlying mechanisms. It highlights how chronic inflammation, driven by activated microglia and astrocytes, exacerbates neuronal damage, synaptic dysfunction, and cognitive decline. The disruption of immune privilege in these conditions involves complex pathways that trigger inflammatory responses, impairing essential neural functions. Despite its immune-privileged status, the brain's immune system, primarily involving microglia and astrocytes, is crucial for maintaining homeostasis and managing illness. Our review strongly suggests that neurological diseases, influenced by genetic, environmental, and aging factors, often involve heightened neuroinflammation. Targeted therapies are needed to address infections, chronic inflammation, and environmental impacts. Additionally, research into mental health disorders and advancements in imaging techniques are critical for understanding immune dysfunction and enhancing treatment strategies.
Advances in experimental medicine and biology, 2002
Lesions in the nervous system induce rapid activation of glial cells and under certain conditions additional recruitment of granulocytes, T-cells and monocytes/macrophages from the blood stream triggered by upregulation of cell adhesion molecules, chemokines and cytokines. Hematogenous cell infiltration is not restricted to infectious or autoimmune disorders of the nervous system, but also occurs in response to cerebral ischemia and traumatic lesions. Neuroinflammation can cause neuronal damage, but also confers neuroprotection. Granulocytes occlude vessels during reperfusion after transient focal ischemia, while the functional role of T-cells and macrophages in stroke development awaits further clarification. After focal cerebral ischemia neurotoxic mediators released by microglia such as the inducible nitric oxide synthase (leading to NO synthesis) and the cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) are upregulated prior to cellular inflammat...
Inflammation: the Common Link in Brain Pathologies
Parkinson's disease (PD), an idiopathic neurodegenerative disorder, is characterized by dopaminergic neuronal degeneration in the substantia nigra pars compacta of brain. Recent findings suggest the multifactorial etiology of the disease. Neuroinflammation and infiltration of peripheral inflammatory cells, chemokines, and cytokines may have a crucial role in PD pathogenesis. During the onset of the disease acute inflammation sets in to prevent dopaminergic neuronal death, but as the disease progresses neuroinflammation becomes chronic and promotes neurodegeneration. Rampant release of proinflammatory cytokines (TNF-α and IFN-γ), infiltration of peripheral CD4 and CD8 lymphocytes and augmented rate of reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation act as key players in disease progression. These proinflammatory factors are released by astrocytes stimulated by neuron derived α-synuclein which in turn recruit and activate microglia. These activated microglia contribute hugely to the progressive neurodegeneration in PD. In this chapter, we have summarized and discussed the findings on the neuroinflammarotry status in PD patients emphasizing on the role of cells and molecules involved. In addition, we have also discussed the plausible therapeutic interventions that may prove to be beneficial to PD patients.
Neurotrauma and Inflammation: CNS and PNS Responses
Mediators of Inflammation, 2015
Traumatic injury to the central nervous system (CNS) or the peripheral nervous system (PNS) triggers a cascade of events which culminate in a robust inflammatory reaction. The role played by inflammation in the course of degeneration and regeneration is not completely elucidated. While, in peripheral nerves, the inflammatory response is assumed to be essential for normal progression of Wallerian degeneration and regeneration, CNS trauma inflammation is often associated with poor recovery. In this review, we discuss key mechanisms that trigger the inflammatory reaction after nervous system trauma, emphasizing how inflammations in both CNS and PNS differ from each other, in terms of magnitude, cell types involved, and effector molecules. Knowledge of the precise mechanisms that elicit and maintain inflammation after CNS and PNS tissue trauma and their effect on axon degeneration and regeneration is crucial for the identification of possible pharmacological drugs that can positively af...
Mediators of Inflammation
The concept of central nervous system (CNS) inflammation has evolved over the last decades. Neuroinflammation is the response of reactive CNS components to altered homeostasis, regardless of the cause to be endogenous or exogenous. Neurological diseases, whether traumatic, neoplastic, ischemic, metabolic, toxic, infectious, autoimmune, developmental, or degenerative, involve direct and indirect immune-related neuroinflammation. Brain infiltrates of the innate and adaptive immune system cells appear in response to an infective or otherwise noxious agent and produce inflammatory mediators. Mediators of inflammation include local and recruited cells and signals. Processes derived from extrinsic and intrinsic CNS diseases also elicit the CNS inflammatory response. A deeper understanding of immune-related inflammation in health and disease is necessary to find potential therapeutic targets for preventing or reducing CNS damage. This review is aimed at discussing the innate and adaptive i...