Department of Pharmacology and Toxicology and the Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA.
J Pharmacol Exp Ther. 2012 Sep;342(3):816-26. doi: 10.1124/jpet.112.193003. Epub 2012 Jun 13.
2-Arachidonyl glycerol (2-AG) is an endogenous arachidonic acid derivative released on demand from membrane precursors. 2-AG-mediated suppression of interleukin (IL)-2 depends on cyclooxygenase 2 (COX-2) metabolism and peroxisome proliferator-activated receptor γ (PPARγ) activation. 15-Deoxy-Δ¹²,¹⁴-prostaglandin J₂-glycerol ester (15d-PGJ₂-G), a putative COX-2 metabolite of 2-AG, acts as a PPARγ ligand and produces IL-2 suppression in activated Jurkat T cells, in part, by decreasing nuclear factor of activated T cells (NFAT) transcriptional activity. The objective of the present studies was to investigate the mechanism by which 15d-PGJ₂-G modulates NFAT activity to suppress IL-2. 15d-PGJ₂-G treatment decreased phorbol 12-myristate 13-acetate (PMA)/calcium ionophore (I₀)-induced NFAT DNA binding to the human IL-2 promoter and nuclear NFAT2 accumulation. It is noteworthy that 15d-PGJ₂-G treatment increased active nuclear HDM2 (human homolog of the oncoprotein and E3 ubiquitin ligase murine double minute 2) expression, whereas there was no change in the expression of glycogen synthase kinase 3β, both of which regulate NFAT. 15d-PGJ₂-G and other PPARγ agonists, such as rosiglitazone and ciglitazone, decreased PMA/I₀-mediated elevation in intracellular calcium concentration (Ca²⁺) in activated Jurkat cells. We were surprised to find that the PPARγ antagonists 2-chloro-5-nitro-N-4-pyridinylbenzamide (T0070907) and 2-chloro-5-nitrobenzanilide (GW9662) also decreased the PMA/I₀-mediated elevation in Ca²⁺ in activated T cells. In addition, the presence of T0070907 plus 15d-PGJ₂-G produced an additive decrease in PMA/I₀-mediated elevation of Ca²⁺, suggesting that the 15d-PGJ₂-G effects on calcium might be either PPARγ-independent or -dependent on occupation of the PPARγ ligand binding domain. Collectively, our findings suggest that 15d-PGJ₂-G increases active nuclear HDM2, which could lead to a decrease in NFAT2 and IL-2 suppression.
2-花生四烯酸甘油（2-AG）是一种内源性花生四烯酸衍生物，可按需从膜前体中释放。2-AG 介导的白细胞介素（IL）-2 抑制依赖于环氧化酶 2（COX-2）代谢和过氧化物酶体增殖物激活受体γ（PPARγ）激活。15-去氧-Δ¹²,¹⁴-前列腺素 J₂-甘油酯（15d-PGJ₂-G），一种 2-AG 的假定 COX-2 代谢产物，作为 PPARγ 配体，在激活的 Jurkat T 细胞中产生 IL-2 抑制作用，部分通过降低核因子激活的 T 细胞（NFAT）转录活性。本研究的目的是研究 15d-PGJ₂-G 调节 NFAT 活性以抑制 IL-2 的机制。15d-PGJ₂-G 处理降低佛波醇 12-肉豆蔻酸 13-乙酸酯（PMA）/钙载体（I₀）诱导的人 IL-2 启动子和核 NFAT2 积累的 NFAT DNA 结合。值得注意的是，15d-PGJ₂-G 处理增加了活性核 HDM2（人类同源物的致癌蛋白和 E3 泛素连接酶鼠双微体 2）的表达，而糖原合酶激酶 3β的表达没有变化，两者都调节 NFAT。15d-PGJ₂-G 和其他 PPARγ 激动剂，如罗格列酮和 ciglitazone，降低了激活的 Jurkat 细胞中 PMA/I₀ 介导的细胞内钙浓度（[Ca²⁺]（i））升高。我们惊讶地发现，PPARγ 拮抗剂 2-氯-5-硝基-N-4-吡啶基苯甲酰胺（T0070907）和 2-氯-5-硝基苯甲酰胺（GW9662）也降低了激活的 T 细胞中 PMA/I₀ 介导的 [Ca²⁺]（i）升高。此外，T0070907 加 15d-PGJ₂-G 的存在导致 PMA/I₀ 介导的 [Ca²⁺]（i）升高的附加降低，表明 15d-PGJ₂-G 对钙的影响可能是 PPARγ 非依赖性的，或者依赖于 PPARγ 配体结合域的占据。总之，我们的发现表明，15d-PGJ₂-G 增加了活性核 HDM2，这可能导致 NFAT2 和 IL-2 抑制的减少。
