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Transient expression of endothelins in the amoeboid microglial cells in the developing rat brain
Chun-Yun Wu1, Charanjit Kaur, Jia Lu
1Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Abstract:
Amoeboid microglial cells (AMC) which transiently exist in the corpus callosum in the postnatal rat brain expressed endothelins (ETs), specifically endothelin-1 (ET-1) and ET3 as revealed by real time RT-PCR. ET immunoreactive AMC occurred in large numbers at birth, but were progressively reduced with age and were undetected in 14 days. In rats subjected to hypoxia exposure, ET immunoexpression in AMC was reduced but the incidence of apoptotic cells was not increased when compared with the control suggesting that this was due to its downregulation that may help regulate the constriction of blood vessels bearing ET-A receptor. AMC were endowed ET-B receptor indicating that ET released by the cells may also act via an autocrine manner. In microglia activated by lipopolysaccharide (LPS), ET-1 mNA expression coupled with that of monocyte chemoattractant protein (MCP-1) and stromal derived factor-1 (SDF-1) was markedly increased; ET-3 mRNA, however, remained unaffected. AMC exposed to oxygen glucose deprivation (OGD) in vitro resulted in increase in both ET-1 and ET-3 mRNA expression. It is suggested that the downregulated ETs expression in vivo of AMC subjected to hypoxia as opposed to its upregulated expression in vitro may be due to the complexity of the brain tissue. Furthermore, the differential ET-1 and ET-3 mRNA expression in LPS and OGD treatments may be due to different signaling pathways independently regulating the two isoforms. The present novel finding has added microglia as a new cellular source of ET that may take part in multiple functions including regulating vascular constriction and chemokines release.
Insights
Amoeboid microglial cells (AMC) produce endothelins (ETs), influencing blood vessel constriction and chemokine release. Their expression changes with age and under conditions like hypoxia and inflammation.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Amoeboid microglial cells (AMC) are transiently present in the postnatal rat brain's corpus callosum.
- Endothelins (ETs) are signaling molecules with known roles in vascular function.
Purpose of the Study:
- To investigate the expression and role of endothelins (ETs) in amoeboid microglial cells (AMC) during postnatal development and under specific physiological conditions.
- To determine if ETs produced by AMC influence vascular tone and chemokine release.
Main Methods:
- Real-time RT-PCR was used to quantify ET-1 and ET-3 mRNA expression in AMC.
- Immunohistochemistry was employed to detect ET-immunoreactive AMC and apoptotic cells.
- In vitro experiments exposed AMC to lipopolysaccharide (LPS) and oxygen-glucose deprivation (OGD).
Main Results:
- AMC expressed ET-1 and ET-3, with expression decreasing significantly with age.
- Hypoxia downregulated ET expression in AMC without increasing apoptosis.
- LPS stimulation upregulated ET-1 and MCP-1/SDF-1, while OGD increased both ET-1 and ET-3 mRNA.
- AMC possess ET-B receptors, suggesting autocrine signaling.
Conclusions:
- Microglia represent a novel cellular source of ETs in the brain.
- ETs produced by AMC may play roles in regulating vascular constriction and chemokine release.
- Differential regulation of ET isoforms suggests distinct signaling pathways involved in microglial responses.
