For decades, astrocytes have been considered to be non-excitable support cells of the brain. However, this view has changed radically during the past twenty years. The recent recognition that they are organized in separate territories and possess active properties — notably a competence for the regulated release of 'gliotransmitters', including glutamate — has enabled us to develop an understanding of previously unknown functions for astrocytes. Today, astrocytes are seen as local communication elements of the brain that can generate various regulatory signals and bridge structures (from neuronal to vascular) and networks that are otherwise disconnected from each other. Examples of their specific and essential roles in normal physiological processes have begun to accumulate, and the number of diseases known to involve defective astrocytes is increasing.

Astrocytes, from brain glue to communication elements: the revolution continues.

This review is focused on purinergic neurotransmission, i.e., ATP released from nerves as a transmitter or cotransmitter to act as an extracellular signaling molecule on both pre- and postjunctional membranes at neuroeffector junctions and synapses, as well as acting as a trophic factor during development and regeneration. Emphasis is placed on the physiology and pathophysiology of ATP, but extracellular roles of its breakdown product, adenosine, are also considered because of their intimate interactions. The early history of the involvement of ATP in autonomic and skeletal neuromuscular transmission and in activities in the central nervous system and ganglia is reviewed. Brief background information is given about the identification of receptor subtypes for purines and pyrimidines and about ATP storage, release, and ectoenzymatic breakdown. Evidence that ATP is a cotransmitter in most, if not all, peripheral and central neurons is presented, as well as full accounts of neurotransmission and neuromodulation in autonomic and sensory ganglia and in the brain and spinal cord. There is coverage of neuron-glia interactions and of purinergic neuroeffector transmission to nonmuscular cells. To establish the primitive and widespread nature of purinergic neurotransmission, both the ontogeny and phylogeny of purinergic signaling are considered. Finally, the pathophysiology of purinergic neurotransmission in both peripheral and central nervous systems is reviewed, and speculations are made about future developments.

/pdf/physiology-and-pathophysiology-of-purinergic-1z94g2hz0f.pdf

Physiology and Pathophysiology of Purinergic Neurotransmission

http://www2.neuroscience.umn.edu/eanwebsite/PDF%20GJClub/Trends%20Neurosci%2032%20421%202009.pdf

Tripartite synapses: astrocytes process and control synaptic information

From a structural perspective, the predominant glial cell of the central nervous system, the astrocyte, is positioned to regulate synaptic transmission and neurovascular coupling: the processes of ...

https://www.physiology.org/doi/pdf/10.1152/physrev.00049.2005

Astrocyte Control of Synaptic Transmission and Neurovascular Coupling

There have been many advances in our knowledge about different aspects of P2Y receptor signaling since the last review published by our International Union of Pharmacology subcommittee. More receptor subtypes have been cloned and characterized and most orphan receptors deorphanized, so that it is now possible to provide a basis for a future subdivision of P2Y receptor subtypes. More is known about the functional elements of the P2Y receptor molecules and the signaling pathways involved, including interactions with ion channels. There have been substantial developments in the design of selective agonists and antagonists to some of the P2Y receptor subtypes. There are new findings about the mechanisms underlying nucleotide release and ectoenzymatic nucleotide breakdown. Interactions between P2Y receptors and receptors to other signaling molecules have been explored as well as P2Y-mediated control of gene transcription. The distribution and roles of P2Y receptor subtypes in many different cell types are better understood and P2Y receptor-related compounds are being explored for therapeutic purposes. These and other advances are discussed in the present review.

https://pharmrev.aspetjournals.org/content/pharmrev/58/3/281.full.pdf

International Union of Pharmacology LVIII: Update on the P2Y G Protein-Coupled Nucleotide Receptors: From Molecular Mechanisms and Pathophysiology to Therapy

ATP Released by Astrocytes Mediates Glutamatergic Activity-Dependent Heterosynaptic Suppression

ABSTRACT Neuroinflammation plays a vital role in cerebral ischemic stroke (IS). In the acute phase of IS, microglia are activated toward the pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. Argon, an inert gas, can reduce neuroinflammation and alleviate ischemia/reperfusion (I/R) injury. However, whether argon regulates M1/M2 polarization to protect against I/R injury as well as the underlying mechanism has not been reported. In this study, we analyzed the activation and polarization of microglia after I/R injury with or without argon administration and explored the effects of argon on NLRP3 inflammasome-mediated inflammation in microglia in vitro and in vivo. The results showed that argon application inhibited the activation of M1 microglia/macrophage in the ischemic penumbra and the expression of proteins related to NLRP3 inflammasome and pyroptosis in microglia. Argon administration also inhibited the expression and processing of IL-1β, a primary pro-inflammatory cytokine. Thus, argon alleviates I/R injury by inhibiting pro-inflammatory reactions via suppressing microglial polarization toward M1 phenotype and inhibiting the NF-κB/NLRP3 inflammasome signaling pathway. More importantly, we showed that argon worked better than the specific NLRP3 inflammasome inhibitor MCC950 in suppressing neuroinflammation and protecting against cerebral I/R injury, suggesting the therapeutic potential of argon in neuroinflammation-related neurodegeneration diseases as a potent gas inhibitor of the NLRP3 inflammasome signaling pathway.

Argon mitigates post-stroke neuroinflammation by regulating M1/M2 polarization and inhibiting NF-κB/NLRP3 inflammasome signaling

OBJECTIVE
To investigate the effects and molecular mechanisms of miR-125b-5p on cognitive dysfunction caused by traumatic brain injury (TBI).


METHODS
The rats were randomly divided into control group, TBI group (model group), NC Agomir group (false negative group) and miR-125b-5p agomir group (high expression group), with 5 rats in each group. The false negative group and the high expression group were injected with NC agomir and miR-125b-5p agomir, respectively. The brain injury model was established by modified Feeney method except control group. Animal behavioral experiments were utilized for evaluation of the motor coordination, learning and memory and the degree of nerve damage in rats; and enzyme-linked immunosorbent assays (ELISA) and Western blot (WB) were used for determination of the expression levels of inflammatory factors and nerve-related factors in the hippocampus of rats in each group respectively. Finally, combined with bioinformatics, downstream target genes of miR-125b-5p were predicted and verified by reverse transcription polymerase chain reaction (RT-PCR) and WB.


RESULTS
Compared with control group, mir-125b-5p expression level, motor coordination ability, learning and memory ability, brain-derived neurotrophic factor(BDNF) and nerve growth factor(NGF) expression levels of rats in model group and false negative group were decreased significantly, the MNSS score, the expressions of interleukins (IL-1β, IL 6), tumor necrosis factor-α(TNF-α) and glial fibrillary acid protein(GFAF) were increased significantly (P＜0.01);However, compared with model group and false negative group, the above situation of rats in high expression group was opposite (P＜0.01). Bioassay showed that MMP-15 was the downstream target gene of miR-125b-5p. Compared with the control group, the expression of MMP-15 in model group and false negative group was increased significantly (P＜0.01);Compared with model group and false negative group, the expression of MMP-15 in high expression group was decreased significantly (P＜0.01) .


CONCLUSION
miR-125b-5p can improve cognitive dysfunction induced by TBI in rats, which may be related to regulating the expression level of MMP-15, thereby inhibiting the neuroinflammatory response after TBI and promoting neuronal regeneration.

Zheng Lin Jiang

Papers

ATP Released by Astrocytes Mediates Glutamatergic Activity-Dependent Heterosynaptic Suppression

Argon mitigates post-stroke neuroinflammation by regulating M1/M2 polarization and inhibiting NF-κB/NLRP3 inflammasome signaling

[Intervention effects of miR-125b-5p on cognitive dysfunction induced by traumatic brain injury in rats and its mechanisms].