Induction of mitochondrial uncoupling enhances VEGF₁₂₀ but reduces MCP-1 release in mature 3T3-L1 adipocytes: Possible regulatory mechanism through endogenous ER stress and AMPK-related pathways

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• 作者：Kaoru Miyokawa-Gorin^a ; ¹ ; Kazuto Takahashi^a ; ¹ ; Keiko Handa^a ; Atsuko Kitahara^a ; Yoshikazu Sumitani^a ; Hidenori Katsuta^a ; Toshiaki Tanaka^a ; Susumu Nishida^a ; Katsuhiko Yoshimoto^a ; Hideki Ohno^b ; Hitoshi Ishida^a ; ^{ishida@ks.kyorin-u.ac.jp}
• 关键词：Mitochondria ; Uncoupling ; MCP-1 ; VEGF ; Adipocytes
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2012
• 期刊代码：159_0006291x
• 类别：bio
• 出版时间：9 March, 2012
• 卷：419
• 期：2
• 页码：200-205
• 文件大小：604 K

摘要

Although white adipocytes contain a larger number of mitochondria per cytoplasmic volume, adipocyte mitochondrial uncoupling to reduce the efficiency of ATP production on cellular function including secretory regulation of bioactive molecules such as VEGF and MCP-1 remains to be elucidated. Here we induce mitochondrial uncoupling under hypoxia-independent conditions in mature 3T3-L1 adipocytes using a metabolic uncoupler, dinitrophenol (DNP).

MCP-1 release was significantly decreased by 26%(p < 0.01) in 24 h DNP (30 渭mol/L)-treated adipocytes compared to control cells. In contrast, secreted VEGF₁₂₀ lacking a heparin-binding domain was markedly increased 2.0-fold (p < 0.01). CHOP content in these cells also were augmented (p < 0.01), but no significant increase of endogenous oxidative stress was observed. Treatment with thapsigargin, which can induce exogenous endoplasmic reticulum (ER) stress, clearly attenuated MCP-1 release (p < 0.01), but exhibited no effects on VEGF₁₂₀ secretion. On the other hand, exogenous H₂O₂ amplified both MCP-1 and VEGF₁₂₀ secretion (p < 0.05). In addition, under chronic activation of AMPK by AICAR, MCP-1 release was significantly diminished (p < 0.05) but VEGF₁₂₀ secretion was increased (p < 0.01). JNK phosphorylation in mature adipocytes was decreased by treatment with either DNP or AICAR (p < 0.01). Enhanced VEGF₁₂₀ secretion with either DNP or AICAR was markedly suppressed by PI3K inhibitor (p < 0.01).

Thus, induced mitochondrial uncoupling in adipocytes can reduce MCP-1 release through induction of endogenous ER stress and by reduced JNK activities via chronic activation of AMPK. Under this condition, VEGF₁₂₀ secretion was increased through PI3K-dependent pathways, which were chronically activated by AMPK, and not through ER stress. Because the decrease of MCP-1 secretion under mitochondrial uncoupling might attenuate chronic low-grade inflammation by suppressing macrophages recruitment to adipose tissue, clarification of the mechanism might reveal novel therapeutic targets for ameliorating obesity-associated insulin resistance in metabolic syndrome and type 2 diabetes.