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Maksoud MJE, Tellios V, Xiang YY, Lu WY. Nitric oxide signaling inhibits microglia proliferation by activation of protein kinase-G. Nitric Oxide 2019; 94:125-134. [PMID: 31759970 DOI: 10.1016/j.niox.2019.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 11/18/2019] [Accepted: 11/20/2019] [Indexed: 02/06/2023]
Abstract
Microglia population is primarily determined by a finely-regulated proliferation process during early development of the central nervous system (CNS). Nitric oxide (NO) is known to inhibit proliferation in numerous cell types. However, how NO signaling regulates microglia proliferation remains elusive. Using wildtype (WT) and inducible nitric oxide synthase knockout (iNOS-/-) mice, this study investigated the role and underlying mechanisms of iNOS/NO signaling in microglia proliferation. Here we reported that iNOS-/- mice displayed significantly more BrdU-labeled proliferating microglia in the cortex than that in WT mice at postnatal day 10. Compared to microglia isolated from WT mouse cortex, significantly more iNOS-/- microglia displayed the specific cell-cycle markers Ki67 and phospho-histone H3 (pH3) in their nuclei. In addition, treating WT microglia with the NOS inhibitor LNAME drastically increased the percentage of cells expressing Ki67 and pH3, whereas treating iNOS-/- microglia with NOC18, a slow-release NO-donor, significantly decreased the percentage of microglia expressing the two cell-cycle markers. Moreover, inhibition of protein kinase-G (PKG) in WT microglia increased the proportion of microglia expressing Ki67 and pH3, whereas activation of PKG signaling using 8Br-cGMP in iNOS-/- microglia significantly decreased the fraction of microglia displaying Ki67 and pH3. Interestingly, in the presence of a PKG inhibitor, NOC18 increased the quantity of iNOS-/- microglia expressing Ki67 and pH3. Together, these results indicate that basal activity of iNOS/NO signaling impedes microglial cell-cycle progression and attenuates proliferation through activation of the cGMP-PKG pathway. However, NO increases microglia cell-cycle progression in the absence of cGMP-PKG signaling.
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Affiliation(s)
- Matthew J E Maksoud
- Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada.
| | - Vasiliki Tellios
- Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada.
| | - Yun-Yan Xiang
- Robarts Research Institute, The University of Western Ontario, Canada.
| | - Wei-Yang Lu
- Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada; Department of Physiology and Pharmacology, University of Western Ontario, Canada.
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Kaur C, Rathnasamy G, Ling EA. Biology of Microglia in the Developing Brain. J Neuropathol Exp Neurol 2017; 76:736-753. [PMID: 28859332 DOI: 10.1093/jnen/nlx056] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Microglia exist in different morphological forms in the developing brain. They show a small cell body with scanty cytoplasm with many branching processes in the grey matter of the developing brain. However, in the white matter such as the corpus callosum where the unmyelinated axons are loosely organized, they appear in an amoeboid form having a round cell body endowed with copious cytoplasm rich in organelles. The amoeboid cells eventually transform into ramified microglia in the second postnatal week when the tissue becomes more compact with the onset of myelination. Microglia serve as immunocompetent macrophages that act as neuropathology sensors to detect and respond swiftly to subtle changes in the brain tissues in pathological conditions. Microglial functions are broadly considered as protective in the normal brain development as they phagocytose dead cells and sculpt neuronal connections by pruning excess axons and synapses. They also secrete a number of trophic factors such as insulin-like growth factor-1 and transforming growth factor-β among many others that are involved in neuronal and oligodendrocyte survival. On the other hand, microglial cells when activated produce a plethora of molecules such as proinflammatory cytokines, chemokines, reactive oxygen species, and nitric oxide that are implicated in the pathogenesis of many pathological conditions such as epilepsy, cerebral palsy, autism, and perinatal hypoxic-ischemic brain injury. Although many studies have investigated the origin and functions of the microglia in the developing brain, in-depth in vivo studies along with analysis of their transcriptome and epigenetic changes need to be undertaken to elucidate their full potential be it protective or neurotoxic. This would lead to a better understanding of their roles in the healthy and diseased developing brain and advancement of therapeutic strategies to target microglia-mediated neurotoxicity.
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Affiliation(s)
- Charanjit Kaur
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; and Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
| | - Gurugirijha Rathnasamy
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; and Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
| | - Eng-Ang Ling
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; and Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
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Abstract
Microglial cells are the resident macrophages in the central nervous system. These cells of mesodermal/mesenchymal origin migrate into all regions of the central nervous system, disseminate through the brain parenchyma, and acquire a specific ramified morphological phenotype termed "resting microglia." Recent studies indicate that even in the normal brain, microglia have highly motile processes by which they scan their territorial domains. By a large number of signaling pathways they can communicate with macroglial cells and neurons and with cells of the immune system. Likewise, microglial cells express receptors classically described for brain-specific communication such as neurotransmitter receptors and those first discovered as immune cell-specific such as for cytokines. Microglial cells are considered the most susceptible sensors of brain pathology. Upon any detection of signs for brain lesions or nervous system dysfunction, microglial cells undergo a complex, multistage activation process that converts them into the "activated microglial cell." This cell form has the capacity to release a large number of substances that can act detrimental or beneficial for the surrounding cells. Activated microglial cells can migrate to the site of injury, proliferate, and phagocytose cells and cellular compartments.
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Li J, Wu L, Cao Q, Yuan Y, Yang L, Guo Z, Kaur C, Sivakumar V, Ling E, Wu C. Endothelins-1/3 and endothelin-A/B receptors expressing glial cells with special reference to activated microglia in experimentally induced cerebral ischemia in the adult rats. Neuroscience 2010; 167:665-77. [DOI: 10.1016/j.neuroscience.2010.02.062] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 02/11/2010] [Accepted: 02/23/2010] [Indexed: 01/23/2023]
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Singh G, Siddiqui MA, Khanna VK, Kashyap MP, Yadav S, Gupta YK, Pant KK, Pant AB. Oxygen glucose deprivation model of cerebral stroke in PC-12 cells: glucose as a limiting factor. Toxicol Mech Methods 2009; 19:154-60. [PMID: 19778261 DOI: 10.1080/15376510802355216] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Optimum time points for oxygen-glucose deprivation (OGD) and re-oxygenation have been identified to suggest the suitability of PC-12 cells as rapid and sensitive in vitro model of cerebral stroke. Further, the precise role of glucose as one of the limiting factors was ascertained. PC-12 cells were subjected to receive OGD of 1-8 h followed by re-oxygenation for 6 to 96 h in medium having glucose 0-10 mg/ml. Loss of cell viability was assessed using trypan blue dye exclusion and MTT assays. The significant (p < 0.05) reduction in percent viable cell count was started at 2 h of OGD (80.7 +/- 2.0) and continued in further OGD periods (3, 4, 5, 6, 7, and 8 h), i.e. 65.7 +/- 3.5, 59.7 +/- 4.6, 54.3 +/- 3.2, 44.7 +/- 2.9, 20.3 +/- 4.3, 5.7 +/- 2.0 of counted cells, respectively. Cells growing in glucose-free medium have shown a gradual (p < 0.001) decrease in cell viability throughout the re-oxygenation. Re-oxygenation of 24 h was found to be first statistically significant time point for all the glucose concentrations. Glucose concentration during re-oxygenation was found to be one of the key factors involved in the growth and proliferation in PC-12 cells. The OGD of 6 h followed by a re-oxygenation period of 24 h with 4-6 mg/ml glucose concentration could be recorded as optimum conditions under our experimental conditions.
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Affiliation(s)
- G Singh
- Industrial Toxicology Research Centre, Lucknow, India
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Kaur C, Ling E. Periventricular white matter damage in the hypoxic neonatal brain: Role of microglial cells. Prog Neurobiol 2009; 87:264-80. [DOI: 10.1016/j.pneurobio.2009.01.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 11/12/2008] [Accepted: 01/08/2009] [Indexed: 01/22/2023]
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Expression of angiotensin II and its receptors in the normal and hypoxic amoeboid microglial cells and murine BV-2 cells. Neuroscience 2009; 158:1488-99. [DOI: 10.1016/j.neuroscience.2008.11.046] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 11/25/2008] [Accepted: 11/26/2008] [Indexed: 01/09/2023]
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Wu CY, Kaur C, Sivakumar V, Lu J, Ling EA. Kv1.1 expression in microglia regulates production and release of proinflammatory cytokines, endothelins and nitric oxide. Neuroscience 2009; 158:1500-8. [DOI: 10.1016/j.neuroscience.2008.11.043] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 11/24/2008] [Accepted: 11/25/2008] [Indexed: 01/14/2023]
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Vidovic M, Chen MM, Lu QY, Kalloniatis KF, Martin BM, Tan AHY, Lynch C, Croaker GDH, Cass DT, Song ZM. Deficiency in endothelin receptor B reduces proliferation of neuronal progenitors and increases apoptosis in postnatal rat cerebellum. Cell Mol Neurobiol 2008; 28:1129-38. [PMID: 18683040 DOI: 10.1007/s10571-008-9292-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 06/17/2008] [Indexed: 12/19/2022]
Abstract
Endothelins regulate cellular functions in the mammalian brain through the endothelin receptors A and B (EDNRA and EDNRB). In this study, we investigated the role of EDNRB on cell proliferation in the cerebellum by using the spotting lethal (sl) rat, which carries a naturally occurring deletion in the EDNRB gene. Proliferating cells in the three genotypes, wild-type (+/+), heterozygous (+/sl) and homozygous mutant (sl/sl) rats were labelled by intraperitoneal injection of 5-bromo-2'-deoxyuridine (BrdU) at postnatal day 2. The density of BrdU-positive cells (per mm(2)) in the external germinal layer of sl/sl rats (Mean +/- SEM, 977 +/- 388) was significantly reduced compared to +/+ (4915 +/- 631) and +/sl (2304 +/- 557) rats. Subsequently, we examined the effects of EDNRB mutation on neural apoptosis by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labelling assay. This showed that the density of apoptotic cells in the cerebella of sl/sl rats (9.3 +/- 0.5/mm(2)) was significantly more increased than +/+ rats (4 +/- 0.7). The expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) were measured with standard ELISA, but were unchanged in all genotypes. These results suggest that ENDRB mediates neural proliferation and have anti-apoptotic effects in the cerebellum of the postnatal rat, and that these effects are independent of changes in the expression of BDNF and GDNF. Our findings will lead to better understanding of the morphological changes in the cerebellum of Hirschsprung's disease patients with congenital EDNRB mutation.
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Affiliation(s)
- Maria Vidovic
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia
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Inflammatory responses after endothelin B (ETB) receptor activation in human monocytes: new evidence for beneficial anti-inflammatory potency of ETB-receptor antagonism. Pulm Pharmacol Ther 2008; 21:533-9. [PMID: 18295521 DOI: 10.1016/j.pupt.2007.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/24/2007] [Indexed: 12/01/2022]
Abstract
Endothelin (ET) stimulates potent ETA/ETB receptors important in the pathogenesis of pulmonary arterial hypertension (PAH) and fibrosis. Though therapy with ET-receptor antagonists is well established uncertainty exists whether selective ETA or dual ETA/ETB-receptor antagonism is superior in PAH. The objective of this study was to further elucidate the pro-inflammatory effects of ET-1 on ETB receptors in cultured human monocytes (10(5)/20 h) compared with non-specific stimulation with LPS in vitro and to define the antagonizing effects of bosentan, a dual ETA/ETB-receptor antagonist, on inflammatory mediator production. We further hypothesized that ETB-receptor antagonism reduces the requirement of PGE2 to control inflammatory mediator production. Activation of the monocyte ETB subtype by ET (1 ng/ml) concentration-dependently stimulated TNF-alpha (744%) >PGE2 (570%) > IL-1 beta (112%) and had no effect on 5-lipoxygenase metabolism. Compared with ET a different profile of IL-1 beta >TNF-alpha >PGE2 was induced by LPS. ETB-receptor antagonism attenuated ET- and LPS-responses in monocytes, in particular of TNF-alpha and PGE2 to a similar extend (40%) that were only demonstrable following LPS at therapeutic plasma concentrations of bosentan and had no effect on IL-1 beta. Inhibition of ETB receptors in LPS-stimulated monocytes by bosentan was responded with suppression of PGE2 and increased production of leukotrienes indicating strong effects in the cyclooxygenase pathway that is known to control cellular ET transcription. These data suggest an important signaling pathway between ET-induced cytokine production following ETB-receptor activation with no further control of ET transcription by PGE2 required following ETB receptor antagonism. Therefore, in states of inflammation increased ETB-receptor expression and activation mediated by elevated ET concentrations may be an underestimated mechanism, which warrants the application of combined ETA/ETB-receptor antagonists.
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Kaur C, Dheen ST, Ling EA. From blood to brain: amoeboid microglial cell, a nascent macrophage and its functions in developing brain. Acta Pharmacol Sin 2007; 28:1087-96. [PMID: 17640468 DOI: 10.1111/j.1745-7254.2007.00625.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Amoeboid microglial cells (AMC) in the developing brain are active macrophages. The macrophagic nature of these cells has been demonstrated by many methods, such as the localization of various hydrolytic enzymes and the presence of complement type 3 surface receptors in them. More importantly is the direct visualization of these cells engaged in the phagocytosis of degenerating cells at the ultrastructural level. Further evidence of them being active macrophages is the avid internalization of tracers administered by the intravenous or intraperitoneal routes in developing rats. The potential involvement of AMC in immune functions is supported by the induced expression of major histocompatibility complex class I and II antigens on them when challenged by lipopolysaccharide or interferon-gamma. Immunosuppressive drugs, such as glucocorticoids and immune function-enhancing drugs like melatonin, affect the expression of surface receptors and antigens and the release of cytokines by AMC. Recent studies in our laboratory have shown the expression of insulin-like growth factors, endothelins, 2',3'-cyclic nucleotide 3'-phosphodiesterase, and N-methyl-D-asparate receptors. This along with the release of chemokines, such as stromal derived factor-1a and monocyte chemoattractant protein-1, suggests multiple functional roles of AMC in early brain development.
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Affiliation(s)
- Charanjit Kaur
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
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