Transforming growth factor β1-induced astrocyte migration is mediated in part by activating 5-lipoxygenase and cysteinyl leukotriene receptor 1.
BACKGROUND
Transforming growth factor-β 1 (TGF-β 1) is an important regulator of cell migration and plays a role in the scarring response in injured brain. It is also reported that 5-lipoxygenase (5-LOX) and its products, cysteinyl leukotrienes (CysLTs, namely LTC₄, LTD₄ and LTE₄), as well as cysteinyl leukotriene receptor 1 (CysLT₁R) are closely associated with astrocyte proliferation and glial scar formation after brain injury. However, how these molecules act on astrocyte migration, an initial step of the scarring response, is unknown. To clarify this, we determined the roles of 5-LOX and CysLT₁R in TGF-β 1-induced astrocyte migration.


METHODS
In primary cultures of rat astrocytes, the effects of TGF-β 1 and CysLT receptor agonists on migration and proliferation were assayed, and the expression of 5-LOX, CysLT receptors and TGF-β1 was detected. 5-LOX activation was analyzed by measuring its products (CysLTs) and applying its inhibitor. The role of CysLT₁R was investigated by applying CysLT receptor antagonists and CysLT₁R knockdown by small interfering RNA (siRNA). TGF-β 1 release was assayed as well.


RESULTS
TGF-β 1-induced astrocyte migration was potentiated by LTD₄, but attenuated by the 5-LOX inhibitor zileuton and the CysLT₁R antagonist montelukast. The non-selective agonist LTD₄ at 0.1 to 10 nM also induced a mild migration; however, the selective agonist N-methyl-LTC₄ and the selective antagonist Bay cysLT2 for CysLT₂R had no effects. Moreover, CysLT₁R siRNA inhibited TGF-β 1- and LTD₄-induced astrocyte migration by down-regulating the expression of this receptor. However, TGF-β 1 and LTD4 at various concentrations did not affect astrocyte proliferation 24 h after exposure. On the other hand, TGF-β 1 increased 5-LOX expression and the production of CysLTs, and up-regulated CysLT1R (not CysLT₂R), while LTD4 and N-methyl-LTC4 did not affect TGF-β 1 expression and release.


CONCLUSIONS
TGF-β 1-induced astrocyte migration is, at least in part, mediated by enhanced endogenous CysLTs through activating CysLT₁R. These findings indicate that the interaction between the cytokine TGF-β 1 and the pro-inflammatory mediators CysLTs in the regulation of astrocyte function is relevant to glial scar formation.
Department of Pharmacology, Key Laboratory of Medical Neurobiology of Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou 310058, China.
Xue-Qin
XQ
Huang
Xia-Yan
XY
Zhang
Xiao-Rong
XR
Wang
Shu-Ying
SY
Yu
San-Hua
SH
Fang
Yun-Bi
YB
Lu
Wei-Ping
WP
Zhang
Er-Qing
EQ
Wei
D000818:Animals; D000831:Animals, Newborn; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism* / Q000502:physiology; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D002465:Cell Movement / Q000276:immunology* / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D017998:Leukotriene D4 / Q000494:pharmacology; D061251:Primary Cell Culture; D051381:Rats; D017207:Rats, Sprague-Dawley; D018077:Receptors, Leukotriene / Q000378:metabolism* / Q000502:physiology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology / Q000502:physiology*
D018077:Receptors, Leukotriene; D053773:Transforming Growth Factor beta1; D017998:Leukotriene D4; D001094:Arachidonate 5-Lipoxygenase; C083169:leukotriene D4 receptor