Activation of CysLT receptors induces astrocyte proliferation and death after oxygen–glucose deprivation

Abstract

We recently found that 5-lipoxygenase (5-LOX) is activated to produce cysteinyl leukotrienes (CysLTs), and CysLTs may cause neuronal injury and astrocytosis through activation of CysLT(1) and CysLT(2) receptors in the brain after focal cerebral ischemia. However, the property of astrocyte responses to in vitro ischemic injury is not clear; whether 5-LOX, CysLTs, and their receptors are also involved in the responses of ischemic astrocytes remains unknown. In the present study, we performed oxygen-glucose deprivation (OGD) followed by recovery to induce ischemic-like injury in the cultured rat astrocytes. We found that 1-h OGD did not injure astrocytes (sub-lethal OGD) but induced astrocyte proliferation 48 and 72 h after recovery; whereas 4-h OGD moderately injured the cells (moderate OGD) and led to death 24-72 h after recovery. Inhibition of phospholipase A(2) and 5-LOX attenuated both the proliferation and death. Sub-lethal and moderate OGD enhanced the production of CysLTs that was inhibited by 5-LOX inhibitors. Sub-lethal OGD increased the expressions of CysLT(1) receptor mRNA and protein, while moderate OGD induced the expression of CysLT(2) receptor mRNA. Exogenously applied leukotriene D(4) (LTD(4)) induced astrocyte proliferation at 1-10 nM and astrocyte death at 100-1,000 nM. The CysLT(1) receptor antagonist montelukast attenuated astrocyte proliferation, the CysLT(2) receptor antagonist BAY cysLT2 reversed astrocyte death, and the dual CysLT receptor antagonist BAY u9773 exhibited both effects. In addition, LTD(4) (100 nM) increased the expression of CysLT(2) receptor mRNA. Thus, in vitro ischemia activates astrocyte 5-LOX to produce CysLTs, and CysLTs result in CysLT(1) receptor-mediated proliferation and CysLT(2) receptor-mediated death.

Leukotriene D4 Stimulates the Migration but Not Proliferation of Endothelial Cells Mediated by the Cysteinyl Leukotriene CysLT1 Receptor via the Extracellular Signal-Regulated Kinase Pathway

“…However, we found that LTD 4 does not affect the proliferation of EA.hy926 cells. It has been reported that LTD 4 induces the proliferation of airway smooth muscle cells, human intestine epithelial cells, and astrocytes through activating CysLT 1 receptors; these effects are associated with airway remodeling, patho-reparation of inflammation, and glial scar formation (12,17,18,20,21,29). Nevertheless, it is also reported that LTD 4 alone can not increase the growth of bronchial fibroblasts and smooth muscle cells, but potentiates the proliferation induced by epidermal growth factor (EGF) (30,31).…”

“…In addition, we have recently reported distinct roles of CysLT 1 and CysLT 2 receptors in astrocytes. The CysLT 1 receptor mediates astrocyte proliferation after mild ischemic stimulation [oxygen-glucose deprivation (OGD) for 1 h] or exposure to lower concentration of LTD 4 (1 -10 nM), while the CysLT 2 receptor mediates astrocyte injury after moderate ischemia (OGD for 4 h) or exposure to higher concentration of LTD 4 (100 -1000 nM) (21). Therefore, these findings imply that CysLT 1 and CysLT 2 receptors may also play distinct roles in the endothelial responses to CysLTs; that is, CysLT 1 receptors may partially mediate angiogenesis while CysLT 2 receptors mediate inflammatory responses.…”

“…The whole cell lysate was isolated as previously described (21). Protein samples (30 μg protein) were loaded for Western blots and probed with the respective antibodies.…”

“…In peripheral tissues, CysLT 1 receptor mediates the proliferation and migration of airway smooth muscle cells, vascular smooth muscle cells, and intestine epithelial cells during airway remodeling, angiosclerosis, and the patho-reparation of inflammation (16 -19). In the central nervous system, the CysLT 1 receptor mediates astrocyte proliferation (20,21); the expression of CysLT 1 receptors is up-regulated in the newly formed capillaries (12,13). However, whether CysLT 1 receptors mediate the proliferation and migration of endothelial cells is still unknown.…”

Aggravated inflammation and increased expression of cysteinyl leukotriene receptors in the brain after focal cerebral ischemia in AQP4-deficient mice

“…CysLT 1 receptor regulates ischemia-induced astrocyte proliferation and glial scar formation as well [27,28] . However, how AQP4 deficiency impacts the expression and localization of CysLT 1 and CysLT 2 receptors remains unknown.…”