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Ishijima T, Nakajima K. Mechanisms of Microglia Proliferation in a Rat Model of Facial Nerve Anatomy. BIOLOGY 2023; 12:1121. [PMID: 37627005 PMCID: PMC10452325 DOI: 10.3390/biology12081121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/27/2023] [Accepted: 08/09/2023] [Indexed: 08/27/2023]
Abstract
Although microglia exist as a minor glial cell type in the normal state of the brain, they increase in number in response to various disorders and insults. However, it remains unclear whether microglia proliferate in the affected area, and the mechanism of the proliferation has long attracted the attention of researchers. We analyzed microglial mitosis using a facial nerve transection model in which the blood-brain barrier is left unimpaired when the nerves are axotomized. Our results showed that the levels of macrophage colony-stimulating factor (M-CSF), cFms (the receptor for M-CSF), cyclin A/D, and proliferating cell nuclear antigen (PCNA) were increased in microglia in the axotomized facial nucleus (axotFN). In vitro experiments revealed that M-CSF induced cFms, cyclin A/D, and PCNA in microglia, suggesting that microglia proliferate in response to M-CSF in vivo. In addition, M-CSF caused the activation of c-Jun N-terminal kinase (JNK) and p38, and the specific inhibitors of JNK and p38 arrested the microglial mitosis. JNK and p38 were shown to play roles in the induction of cyclins/PCNA and cFms, respectively. cFms was suggested to be induced through a signaling cascade of p38-mitogen- and stress-activated kinase-1 (MSK1)-cAMP-responsive element binding protein (CREB) and/or p38-activating transcription factor 2 (ATF2). Microglia proliferating in the axotFN are anticipated to serve as neuroprotective cells by supplying neurotrophic factors and/or scavenging excite toxins and reactive oxygen radicals.
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Affiliation(s)
- Takashi Ishijima
- Graduate School of Science and Engineering, Soka University, Tokyo 192-8577, Japan;
| | - Kazuyuki Nakajima
- Graduate School of Science and Engineering, Soka University, Tokyo 192-8577, Japan;
- Glycan & Life Systems Integration Center, Soka University, Tokyo 192-8577, Japan
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Events Occurring in the Axotomized Facial Nucleus. Cells 2022; 11:cells11132068. [PMID: 35805151 PMCID: PMC9266054 DOI: 10.3390/cells11132068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/26/2022] [Accepted: 06/27/2022] [Indexed: 01/27/2023] Open
Abstract
Transection of the rat facial nerve leads to a variety of alterations not only in motoneurons, but also in glial cells and inhibitory neurons in the ipsilateral facial nucleus. In injured motoneurons, the levels of energy metabolism-related molecules are elevated, while those of neurofunction-related molecules are decreased. In tandem with these motoneuron changes, microglia are activated and start to proliferate around injured motoneurons, and astrocytes become activated for a long period without mitosis. Inhibitory GABAergic neurons reduce the levels of neurofunction-related molecules. These facts indicate that injured motoneurons somehow closely interact with glial cells and inhibitory neurons. At the same time, these events allow us to predict the occurrence of tissue remodeling in the axotomized facial nucleus. This review summarizes the events occurring in the axotomized facial nucleus and the cellular and molecular mechanisms associated with each event.
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Molnár K, Nógrádi B, Kristóf R, Mészáros Á, Pajer K, Siklós L, Nógrádi A, Wilhelm I, Krizbai IA. Motoneuronal inflammasome activation triggers excessive neuroinflammation and impedes regeneration after sciatic nerve injury. J Neuroinflammation 2022; 19:68. [PMID: 35305649 PMCID: PMC8934511 DOI: 10.1186/s12974-022-02427-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 03/01/2022] [Indexed: 12/12/2022] Open
Abstract
Background Peripheral nerve injuries are accompanied by inflammatory reactions, over-activation of which may hinder recovery. Among pro-inflammatory pathways, inflammasomes are one of the most potent, leading to release of active IL-1β. Our aim was to understand how inflammasomes participate in central inflammatory reactions accompanying peripheral nerve injury. Methods After axotomy of the sciatic nerve, priming and activation of the NLRP3 inflammasome was examined in cells of the spinal cord. Regeneration of the nerve was evaluated after coaptation using sciatic functional index measurements and retrograde tracing. Results In the first 3 days after the injury, elements of the NLRP3 inflammasome were markedly upregulated in the L4–L5 segments of the spinal cord, followed by assembly of the inflammasome and secretion of active IL-1β. Although glial cells are traditionally viewed as initiators of neuroinflammation, in this acute phase of inflammation, inflammasome activation was found exclusively in affected motoneurons of the ventral horn in our model. This process was significantly inhibited by 5-BDBD, a P2X4 receptor inhibitor and MCC950, a potent NLRP3 inhibitor. Although at later time points the NLRP3 protein was upregulated in microglia too, no signs of inflammasome activation were detected in these cells. Inhibition of inflammasome activation in motoneurons in the first days after nerve injury hindered development of microgliosis in the spinal cord. Moreover, P2X4 or inflammasome inhibition in the acute phase significantly enhanced nerve regeneration on both the morphological and the functional levels. Conclusions Our results indicate that the central reaction initiated by sciatic nerve injury starts with inflammasome activation in motoneurons of the ventral horn, which triggers a complex inflammatory reaction and activation of microglia. Inhibition of neuronal inflammasome activation not only leads to a significant reduction of microgliosis, but has a beneficial effect on the recovery as well. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-022-02427-9.
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Affiliation(s)
- Kinga Molnár
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary
| | - Bernát Nógrádi
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary.,Theoretical Medicine Doctoral School, University of Szeged, Szeged, Hungary.,Department of Neurology, University of Szeged, Szeged, Hungary
| | - Rebeka Kristóf
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary.,Theoretical Medicine Doctoral School, University of Szeged, Szeged, Hungary
| | - Ádám Mészáros
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary.,Doctoral School of Biology, University of Szeged, Szeged, Hungary
| | - Krisztián Pajer
- Department of Anatomy, Histology and Embryology, University of Szeged, Szeged, Hungary
| | - László Siklós
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary
| | - Antal Nógrádi
- Department of Anatomy, Histology and Embryology, University of Szeged, Szeged, Hungary
| | - Imola Wilhelm
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary. .,Institute of Life Sciences, Vasile Goldiş Western University of Arad, Arad, Romania.
| | - István A Krizbai
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH), Temesvári krt. 62, 6726, Szeged, Hungary. .,Institute of Life Sciences, Vasile Goldiş Western University of Arad, Arad, Romania.
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Nógrádi B, Nyúl-Tóth Á, Kozma M, Molnár K, Patai R, Siklós L, Wilhelm I, Krizbai IA. Upregulation of Nucleotide-Binding Oligomerization Domain-, LRR- and Pyrin Domain-Containing Protein 3 in Motoneurons Following Peripheral Nerve Injury in Mice. Front Pharmacol 2020; 11:584184. [PMID: 33328988 PMCID: PMC7732612 DOI: 10.3389/fphar.2020.584184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 10/21/2020] [Indexed: 12/17/2022] Open
Abstract
Neuronal injuries are accompanied by release and accumulation of damage-associated molecules, which in turn may contribute to activation of the immune system. Since a wide range of danger signals (including endogenous ones) are detected by the nucleotide-binding oligomerization domain-, LRR- and pyrin domain-containing protein 3 (NLRP3) pattern recognition receptor, we hypothesized that NLRP3 may become activated in response to motor neuron injury. Here we show that peripheral injury of the oculomotor and the hypoglossal nerves results in upregulation of NLRP3 in corresponding motor nuclei in the brainstem of mice. Although basal expression of NLRP3 was observed in microglia, astroglia and neurons as well, its upregulation and co-localization with apoptosis-associated speck-like protein containing a caspase activation and recruitment domain, suggesting inflammasome activation, was only detected in neurons. Consequently, increased production of active pro-inflammatory cytokines interleukin-1β and interleukin-18 were detected after hypoglossal nerve axotomy. Injury-sensitive hypoglossal neurons responded with a more pronounced NLRP3 upregulation than injury-resistant motor neurons of the oculomotor nucleus. We further demonstrated that the mitochondrial protector diazoxide was able to reduce NLRP3 upregulation in a post-operative treatment paradigm. Our results indicate that NLRP3 is activated in motoneurons following acute nerve injury. Blockade of NLRP3 activation might contribute to the previously observed anti-inflammatory and neuroprotective effects of diazoxide.
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Affiliation(s)
- Bernát Nógrádi
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Foundation for the Future of Biomedical Sciences in Szeged, Szeged Scientists Academy, Szeged, Hungary
| | - Ádám Nyúl-Tóth
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Department of Biochemistry and Molecular Biology, Vascular Cognitive Impairment and Neurodegeneration Program, Reynolds Oklahoma Center on Aging/Oklahoma Center for Geroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Mihály Kozma
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Theoretical Medicine Doctoral School, University of Szeged, Szeged, Hungary
| | - Kinga Molnár
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Theoretical Medicine Doctoral School, University of Szeged, Szeged, Hungary
| | - Roland Patai
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary
| | - László Siklós
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary
| | - Imola Wilhelm
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Institute of Life Sciences, Vasile Goldiş Western University of Arad, Arad, Romania
| | - István A Krizbai
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Institute of Life Sciences, Vasile Goldiş Western University of Arad, Arad, Romania
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