L-谷氨酰胺早期诱导MKP-1抑制特应性皮炎的机制研究

Mitogen-activated protein kinase/cytosolic phospholipase A2 (MAPK/cPLA2) is well-known signaling pathway of inflammation. MAPK phosphatase (MKP) -1 is a major upstream pathway for MAPKs, which is an important negative accomodation for immune regulation. Leukotriene B4 (LTB4) is a downstream pathway for cPLA2, which is a key inflammatory factor in Atopic Dermatitis (AD). L-glutamine (Gln) is known to effective in anti-inflammation. In our previous study of contact dermatitis animal model, we found that Gln is inactivated MAPKs phosphorylation with a rapid induction of MKP-1 and inhibit cPLA2 activity, decreased scracthing and the degree of skin inflammation. There is no report about MKP-1/MAPK/cPLA2/LTB4 pathways and the role of Gln on AD. So we propose to elucidate the mechanism of Gln inhibit MAPKs phosphorylation and decrease the cPLA2 activity via early induction of MKP-1 in vivo and in vitro in AD. This study may provide us new scientific evidence for prevention and drug development of AD.

丝裂原活化蛋白激酶/胞浆型磷脂酶A2（MAPK/cPLA2）信号通路参与各种炎症反应，其上级的MAPK磷酸酶-1（MKP-1）在免疫调控中起着非常重要的负调控作用，而下级的白三烯B4（LTB4）是特应性皮炎（AD）的重要炎症介质。L-谷氨酰胺（Gln）具有较强的抗炎作用，前期研究表明在接触性皮炎动物模型中Gln通过迅速诱导MKP-1，参与MAPK去磷酸化使其灭活和抑制cPLA2活性，减少皮肤瘙痒次数和炎症程度。目前MKP-1/MAPK/cPLA2/LTB4信号通路在AD中的作用及Gln干预机制尚未见报道。因此，我们通过细胞培养和动物实验，阐明AD疾病中Gln早期诱导MKP-1参与MAPK去磷酸化过程和cPLA2活性的机制，明确其作用靶点，为寻找防治AD新药开发提供重要的理论依据。

特应性皮炎（Atopic Dermatitis, AD）好发于婴幼儿和青少年，主要症状为反复、难以忍受的皮肤瘙痒和搔抓引起皮肤损伤，形成“痒－搔抓循环”，常用激素治疗，副作用大。L-谷氨酰胺（Gln）在接触性皮炎动物模型中迅速诱导MKP-1参与MAPK去磷酸化使其灭活和抑制cPLA2活性。通过本研究1）利用BALB/c小鼠成功制备了AD的动物模型，其形态学变化、IgE及Th1/Th2细胞因子结果见模型类似于慢性AD。2）证实了AD模型中Gln明显减少皮肤瘙痒次数及皮肤炎症程度，其机制与Gln参与cPLA2/LTB4的信号通路有关。3）证实了Gln迅速（20 min内）诱导MKP-1蛋白表达，MKP-1的激活使Ca2+迅速增高从而Ras/c-Raf/MEK/ERK信号通路被起动，p-ERK进一步激活MKP-1而抑制p-38和p-JNK活性参与MAPK/cPLA2/LTB4的信号通路。此过程中MKP-1起关键作用。4）MHS和HaCaT细胞实验证实了Gln通过MKP-1的激活参与MAPK/cPLA2的蛋白表达。总之，本研究阐明了Gln通过早期诱导MKP-1参与MAPK/cPLA2/LTB4信号通路而抑制AD的抗瘙痒、抗炎症机制，其中MKP-1为关键靶点，为了治疗AD提供了实验依据。