inflammatory CNS reactions in response to neuronal activity
The CNS is endowed with an elaborated response repertoire termed which enables it to cope with pathogens, toxins, traumata and degeneration.
On the basis of recent publications, we deduce that orchestrated actions of immune cells, vascular cells and pandora shops sydney neurons that constitute neuroinflammation are not only provoked by pathological conditions but can also be induced by increased neuronal activity. We suggest that the technical term neuroinflammation should be used for inflammatory reactions in the CNS in response to neuronal activity. We believe that neurogenic neuro inflammation maintains homeostasis to enable the CNS to cope with enhanced metabolic demands and increases the computational power and plasticity of CNS neuronal networks. However, neurogenic neuroinflammation may also become maladaptive and aggravate the outcomes of pain, stress and epilepsy.
Neuroinflammation can be triggered by factors (infection, autoimmunity or toxins) but also by factors that lead to enhanced neuronal activity (including noxious stimuli, psychological stress and epileptic seizures). Immune cells, vascular cells and neurons promote various independent as well as interacting responses (indicated by plus signs). These can be homeostatic, leading to adaptation, or dysfunctional and/or neurotoxic, leading to pathology. Anti inflammatory mechanisms may be triggered in parallel and serve to terminate neuroinflammation and reduce pathological outcomes (indicated by minus signs). Treatments and interventions may be targeted at various levels to inhibit the triggers and neuroinflammatory processes, or to promote the resolution of inflammation.
The figure shows a primary afferent, peptidergic nerve fibre and elements that contribute to neurogenic inflammation at peripheral nerve terminals. Neurogenic inflammation in the periphery is initiated by neuronal activity generated by a wide range of highly specific (such as transient receptor potential V1 (TRPV1) activation) and less specific stimuli (such as traumatic injury). This results in the generation of orthodromic action potentials that conduct towards the CNS, as well as antidromic action potentials at branch points that conduct towards the peripheral terminals to induce neurogenic inflammation. Neurogenic inflammation results from the release of neurotransmitters and neuropeptides from peripheral nerve terminals (blue box). These rapidly affect various cell types, including vascular cells (endothelial cells), mast cells, macrophages and other immune cells (not shown). T cells and dendritic cells may also be recruited. The different cell types themselves also begin to release substances (shown in coloured boxes), creating the milieu Immune cells, plasma and various mediators can also extravasate into tissue (not shown). Sensory nerve fibres can become sensitized and also lower their threshold for further neurotransmitter and neuropeptide release. Pro and anti inflammatory substances and signalling molecules that are released (shown in light yellow boxes) from various sources bind to receptors on the different cells and modulate their function. Signalling from higher order CNS centres (not shown) may also dampen or aggravate peripheral neurogenic inflammation. BDNF, brain derived neurotrophic factor; BK, bradykinin; CB, cannabinoid; CD, T cell surface glycoprotein CD; CGRP, calcitonin gene related peptide; DA, dopamine; DAMP, danger associated molecular patterns; DRG, dorsal root ganglia; END, endothelin; Glu, glutamate; His, histamine; IgE, immunoglobulin E; NA, noradrenaline; NGF, nerve growth factor; NO, nitric oxide; NPY, neuropeptide Y; PAF, platelet where to buy pandora beads activating factor; PG, prostaglandin; SOM, somatostatin; SP, substance P; TRP, tryptase.
This figure illustrates neurogenic neuroinflammation at spinal or trigeminal terminals. In the CNS, enhanced neuronal activity coming from peripheral sources will result in neurogenic neuroinflammation owing to vesicular and non vesicular release of neurotransmitters and neuropeptides from the primary afferent fibre (blue boxes). This will induce concerted and interacting immune responses, vascular responses and higher order neuronal network responses in the multipartite synapse. This includes, but is not limited to, microglia, astrocytes, the neurovascular unit (composed of endothelial cells, other vascular cells such as pericytes, the presynaptic neuron and the astrocyte endfeet) and second order neurons within the neuronal network (including interneurons, ascending neurons and descending neurons), all of which are primary players in the response to enhanced C fibre activity. Mast cells on the dura, perivascular macrophages, and CD4+ and CD8+ T cells may also participate and release substances. With strong neuronal activity, recruitment of peripheral immune cells (including macrophages, T cells and mast cells), and changes at the blood barrier (for specific substances or involving a regional breakdown) can occur, creating further CNS neuroinflammatory responses. Astrocytes found exclusively in the CNS serve to take up excessive glutamate (Glu) and potassium, thereby providing neuroprotective effects against excitotoxicity. However, they may also participate in neurogenic neuroinflammation to release pro inflammatory mediators. As in the newest pandora charms periphery, both pro and anti inflammatory mediators, and signalling molecules and forces can be released from all cell types (key substances shown in boxes of the respective colour of cell type) in the multipartite synaptic region to further affect receptors or channels present on all cell types shown (key substances acting on cells shown in light yellow boxes). Ongoing neurogenic neuroinflammation may serve to amplify neuronal network activity and the resulting long term potentiation may spread far along the neuraxis, enhancing computational power of the neuronal network. This can serve to elicit appropriate protective responses and behaviours from the organism. In some cases, it may also trigger or aggravate an established pathology. Signalling from higher order CNS centres (descending neurons) can serve to dampen or aggravate neurogenic neuroinflammation. X., Cao, D. L. Gao, Y. J. Spinal injection of docosahexaenoic acid attenuates carrageenan induced inflammatory pain through inhibition of microglia mediated neuroinflammation in the spinal cord.
Dimitris N. XanthosDimitris N. in behavioural neuroscience in the laboratory of T. Coderre at McGill University, Montreal, Canada, studying biological mechanisms of pathological pain states in animal models. He then joined the group of J. Sandk at the Center for Brain Research of the Medical University of Vienna, Austria. He is particularly interested in translational approaches in neurosciences, and the adaptive and maladaptive aspects of nociception price of pandora charms and plasticity. theses on descending inhibition and on opiates at Heidelberg University, Germany. He then joined the group of G. F. Gebhart at the University of Iowa, Iowa City, USA.
After being awarded a Heisenberg Professorship from the Deutsche Forschungsgemeinschaft (DFG), he was a visiting professor at the University of Freiburg, Germany, and Iowa State University, Ames, USA. He has a career long interest in synaptic and cellular mechanisms modulating nociception and opioid effects. J Sandk homepage.
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