title: PPARgamma agonist, rosiglitazone, regulates angiotensin II-induced vascular inflammation through the TLR4-dependent signaling pathway.
abstract: Atherosclerosis is increasingly recognized as a chronic inflammatory disease. Angiotensin II (Ang II) is a critical factor in inflammatory responses, so as to promote the pathogenesis of atherosclerosis. Toll-like receptor 4 (TLR4) activates signaling pathways leading to the expression of pro-inflammatory cytokines implicated in the etiology of atherosclerosis. Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists are considered to be important in modulating vascular inflammation and atherosclerosis. Herein, we investigated the modulatory effects of rosiglitazone on Ang II-mediated inflammatory responses both in vivo and in vitro. We also examined whether TLR4-dependent signaling pathway was involved in the inhibitory effects of rosiglitazone on Ang II-induced pro-inflammatory responses in vascular smooth muscle cells (VSMCs). Male Sprague-Dawley rats received Ang II by subcutaneous infusion and/or rosiglitazone per os for 7 days. Systolic blood pressure rise in Ang II-infused rats was attenuated by rosiglitazone. Rosiglitazone also reduced Ang II-induced generation of pro-inflammatory mediators (TLR4, matrix metalloproteinase-9 and tumor necrosis factor-alpha), but enhanced production of anti-inflammatory mediators (PPARgamma and 6-keto-PGF(1alpha)) both in vivo and in vitro. Furthermore, treatment of VSMCs with both the TLR4 inhibitor and TLR4 small-interfering RNA (siRNA) showed that the modulatory effects of rosiglitazone on Ang II-mediated inflammatory responses in VSMCs were related to TLR4. Treatment of the cells with rosiglitazone had little effect on Ang II receptors expression (AT1 and AT2), but downregulated AT1-dependent ERK1/2 activation. Then, treatment of VSMCs with TLR4 siRNA, interferon-gamma-inducible protein 10 (IP-10) siRNA and with the special protein kinase C (PKC) inhibitor further revealed that the signaling pathway (TLR4/IP-10/PKC/NF-kappaB) was involved in the inhibitory effects of rosiglitazone on Ang II-induced pro-inflammatory responses in VSMCs. In conclusion, TLR4 may be a drug target involved in the ameliorative effects of PPARgamma agonist, rosiglitazone, on Ang II-mediated inflammatory responses in VSMCs. Moreover, rosiglitazone exerts its anti-inflammatory effect by interfering with the TLR4-dependent signaling pathway (ERK1/2/TLR4/IP-10/PKC/NF-kappaB) to prevent and treat atherosclerotic diseases.
authors.affiliation: Department of Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an, PR China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Ji
authors.forename: Juntian
authors.initials: J
authors.lastname: Liu
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Gou
mesh_terms: D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004195:Disease Models, Animal; D015870:Gene Expression / Q000187:drug effects; D020868:Gene Silencing; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D047495:PPAR gamma / Q000819:agonists* / Q000187:drug effects; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077154:Rosiglitazone; D015398:Signal Transduction / Q000187:drug effects; D045162:Thiazolidinediones / Q000494:pharmacology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014657:Vasculitis / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology
chemical_list: D007004:Hypoglycemic Agents; D047495:PPAR gamma; D034741:RNA, Small Interfering; D045162:Thiazolidinediones; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D000077154:Rosiglitazone; D000804:Angiotensin II