Simvastatin inhibits ox-LDL-induced inflammatory adipokines secretion via amelioration of ER stress in 3T3-L1 adipocyte.

Adipocytes behave as a rich source of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP-1). Endoplasmic reticulum (ER) stress in adipocytes can alter adipokines secretion and induce inflammation. The aim of this study is to evaluate the effect of simvastatin on the ox-LDL-induced ER stress and expression and secretion of TNF-α and MCP-1 in 3T3-L1 adipocytes. Differentiated adipocytes were treated with various concentrations of ox-LDL (0-100 μg/ml) for 24h with or without simvastatin pre-treatment. The protein expressions of ER stress markers, glucose-regulated protein 78 (GRP78) and C/EBP homology protein (CHOP), were determined by Western blot analysis. The mRNA expressions of TNF-α and MCP-1 were measured by real-time PCR. The protein release of TNF-α and MCP-1 in culture medium were evaluated by ELISA. Ox-LDL treatment led to significant up-regulation of GRP78 and CHOP in dose-dependent manner. The expressions of TNF-α and MCP-1 were dose-dependently increased at mRNA and protein levels after ox-LDL intervention. The effects of ox-LDL on adipocytes were abolished by pre-treatment with 4-phenylbutyrate (4-PBA), a chemical chaperone known to ameliorate ER stress. Simvastatin could inhibit ox-LDL-induced ER stress and reduce the expression of TNF-α and MCP-1 at mRNA and protien level in dose dependent manner. In conclusion, ox-LDL can stimulate the expression and secretion of TNF-α and MCP-1 through its activation of ER stress in adipocytes. Simvastatin might exert direct anti-inflammatory effects in adipocytes through amelioration of ER stress.

Wu ZH ，Chen YQ ，Zhao SP 《-》

Ox-LDL induces ER stress and promotes the adipokines secretion in 3T3-L1 adipocytes.

Chen Y ，Chen M ，Wu Z ，Zhao S ... -  《PLoS One》

High-density lipoprotein inhibits ox-LDL-induced adipokine secretion by upregulating SR-BI expression and suppressing ER Stress pathway.

Song G ，Wu X ，Zhang P ，Yu Y ，Yang M ，Jiao P ，Wang N ，Song H ，Wu Y ，Zhang X ，Liu H ，Qin S ... -  《Scientific Reports》

TNF-α modulates statin effects on secretion and expression of MCP-1, PAI-1 and adiponectin in 3T3-L1 differentiated adipocytes.

Systemic inflammatory conditions, as seen in obesity and in the metabolic syndrome, are associated with high plasmatic levels of proatherogenic and prothromboticadipokines and low levels of adiponectin. Inhibitors of HMG-CoA reductase have beneficial effects in reducing cardiovascular events attributed predominantly to its lipid-lowering effects and recent studies suggest that these effects might be due to its anti-inflammatory properties. Based on the pleiotropic properties of simvastatin we studied the effects of this drug on the secretion and expression of adiponectin, PAI-1 and MCP-1 in mature adipocytes under baseline conditions and after an inflammatory stimulation. The differentiated adipocytes were incubated with 10 μM simvastatin or vehicle and TNF-α 10 ng/mL or vehicle were added to treatment media. After 24h of incubation, the media was harvested and the proteins of interest were analyzed by Multiplex method. Gene expression was analyzed by real time-PCR. The addition of TNF-α increased the expression and secretion of MCP-1 and PAI-1. However, stimulation did not interfere with the secretion of adiponectin, despite having significantly reduced its expression. Our data also demonstrated that simvastatin reduced the expression and secretion of MCP-1, under baseline (770.4 ± 199.9 vs 312.7 ± 113.7 and 1.00 ± 0.14 vs 0.63 ± 0.13, p<0.05, respectively) and inflammatory conditions (14945 ± 228.7 vs 7837.6 ± 847.4 and 24.16 ± 5.49 vs 14.97 ± 2.67, p<0.05, p<0.05, respectively). Simvastatin also attenuated the increase in expression and secretion of PAI-1 induced by TNF-α (16898.6 ± 1663.3 vs 12922.1 ± 843.9 and 5.19 ± 3.12 vs 0.59 ± 0.16, respectively p<0.05), but under baseline conditions had no effect on the expression or secretion of PAI-1. The statin increased the expression of adiponectin under baseline conditions and inflammatory stimulation (1.03 ± 0.08 vs 4.0 ± 0.96 and 0.77 ± 0.19 vs 2.16 ± 0.23, respectively, p<0.05) and also increased the secretion of this adipokine but only with the inflammatory stimulus (5347.7 ± 1789.3 vs 7327.3 ± 753.6, p<0.05). Our findings suggested that simvastatin counteracted the stimulatory effect of TNF-α on secretion and expression of MCP-1, PAI-1 and adiponectin, implying a potential anti-atherogenic effect during the inflammatory process; these pleitropic effects were more pronounced with HMG-CoA reductase inhibitor.

Lobo SM ，Quinto BM ，Oyama L ，Nakamichi R ，Ribeiro AB ，Zanella MT ，Dalboni MA ，Batista MC ... -  《-》

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.

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 24h DNP (30 μmol/L)-treated adipocytes compared to control cells. In contrast, secreted VEGF(120) 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 VEGF(120) secretion. On the other hand, exogenous H(2)O(2) amplified both MCP-1 and VEGF(120) secretion (p<0.05). In addition, under chronic activation of AMPK by AICAR, MCP-1 release was significantly diminished (p<0.05) but VEGF(120) secretion was increased (p<0.01). JNK phosphorylation in mature adipocytes was decreased by treatment with either DNP or AICAR (p<0.01). Enhanced VEGF(120) secretion with either DNP or AICAR was markedly suppressed by PI3K inhibitor LY294002 (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, VEGF(120) 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.

Miyokawa-Gorin K ，Takahashi K ，Handa K ，Kitahara A ，Sumitani Y ，Katsuta H ，Tanaka T ，Nishida S ，Yoshimoto K ，Ohno H ，Ishida H ... -  《-》