Department of Nutrition, University of Tennessee, Knoxville, Tennessee, United States of America.
PLoS One. 2012;7(10):e46986. doi: 10.1371/journal.pone.0046986. Epub 2012 Oct 9.
Release of pro-inflammatory cytokines from both resident and invading leukocytes within the pancreatic islets impacts the development of Type 1 diabetes mellitus. Synthesis and secretion of the chemokine CCL2 from pancreatic β-cells in response to pro-inflammatory signaling pathways influences immune cell recruitment into the pancreatic islets. Therefore, we investigated the positive and negative regulatory components controlling expression of the CCL2 gene using isolated rat islets and INS-1-derived β-cell lines. We discovered that activation of the CCL2 gene by IL-1β required the p65 subunit of NF-κB and was dependent on genomic response elements located in the -3.6 kb region of the proximal gene promoter. CCL2 gene transcription in response to IL-1β was blocked by pharmacological inhibition of the IKKβ and p38 MAPK pathways. The IL-1β-mediated increase in CCL2 secretion was also impaired by p38 MAPK inhibition and by glucocorticoids. Moreover, multiple synthetic glucocorticoids inhibited the IL-1β-stimulated induction of the CCL2 gene. Induction of the MAP Kinase Phosphatase-1 (MKP-1) gene by glucocorticoids or by adenoviral-mediated overexpression decreased p38 MAPK phosphorylation, which diminished CCL2 gene expression, promoter activity, and release of CCL2 protein. We conclude that glucocorticoid-mediated repression of IL-1β-induced CCL2 gene transcription and protein secretion occurs in part through the upregulation of the MKP-1 gene and subsequent deactivation of the p38 MAPK. Furthermore, the anti-inflammatory actions observed with MKP-1 overexpression were obtained without suppressing glucose-stimulated insulin secretion. Thus, MKP-1 is a possible target for anti-inflammatory therapeutic intervention with preservation of β-cell function.
炎症细胞因子从胰岛固有和浸润白细胞的释放影响 1 型糖尿病的发展。在胰岛中，对促炎信号通路的反应，胰腺 β 细胞合成和分泌趋化因子 CCL2 会影响免疫细胞向胰岛的募集。因此，我们使用分离的大鼠胰岛和 INS-1 衍生的 β 细胞系研究了控制 CCL2 基因表达的正调节和负调节成分。我们发现，IL-1β 对 CCL2 基因的激活需要 NF-κB 的 p65 亚基，并且依赖于位于近端基因启动子的-3.6 kb 区域内的基因组反应元件。CCL2 基因对 IL-1β 的转录反应被 IKKβ 和 p38 MAPK 通路的药理学抑制所阻断。p38 MAPK 抑制和糖皮质激素也损害了 IL-1β 介导的 CCL2 分泌增加。此外，多种合成糖皮质激素抑制了 IL-1β 刺激的 CCL2 基因诱导。糖皮质激素或腺病毒介导的过表达诱导 MAP 激酶磷酸酶-1（MKP-1）基因的表达，降低了 p38 MAPK 的磷酸化，从而减少了 CCL2 基因的表达、启动子活性和 CCL2 蛋白的释放。我们得出结论，糖皮质激素介导的抑制 IL-1β 诱导的 CCL2 基因转录和蛋白分泌部分是通过上调 MKP-1 基因和随后失活 p38 MAPK 来实现的。此外，MKP-1 过表达观察到的抗炎作用是在不抑制葡萄糖刺激的胰岛素分泌的情况下获得的。因此，MKP-1 是保留 β 细胞功能的抗炎治疗干预的一个可能靶点。
