| Research in vitro:PPAR-y agonist pioglitazone inhibits exogenous angiotensinⅡ-induced activation of dendritic cells via the MAPK and NF-κB pathwaysObjective:The renin-angiotensin system exerts a profound regulatory effect on the functional features of dendritic cells (DC), thus suggesting a new target of angiotensinⅡ(Ang II) action in the immune system. This study investigated whether peroxisome proliferator-activated receptor-gamma (PPAR-y) activation in DC with pioglitazone (Pio) regulated AngⅡ-induced activation of DC and exploited the possible molecular mechanisms, especially focused on the signaling pathways of mitogen-activated protein kinases (MAPK) and nuclear factor-kappa B (NF-κB).Methods:DC derived from human peripheral blood monouclear cells were cultured in vitro and stimulated with exogenous AngⅡin the presence or absence of the PPAR-y agonist Pio. Then, flow cytometry was used for DC phenotypic analysis, enzyme-linked immunosorbent assay for cytokines secretion of DC, mixed lymphocyte reaction for T-cell proliferation stimulated by DC. Furthermore, MAPK phosphorylation state in DC was analyzed by western blot test and NF-κB/DNA binding activity in DC was assayed by electrophoretic mobility shift assay.Results:Exogenous AngⅡstimulation of human monocyte-derived DC displayed an intermediate state of DC maturation and function characterized of up-regulation of the DC mature marker CD83 and costimulatory molecule CD86 expression but not significant alteration of the costimulatory molecule CD80 and MHC class II molecule HLA-DR, increase secretion of inflammatory cytokines (IL-6 and TNF-a) but not T cell stimulatory cytokines (IL-12), and enhance of allogenic T cell proliferation induced by mature DC but not immature DC. We next pretreated human DC with Pio before Ang II and found that Pio partially inhibited Ang II-induced activation of DC in terms of decrease of CD83 expression but not CD86, reduction of IL-12 and TNF-a secretion but not IL-6, and diminution of T cell activation. In addition, we found that Ang II stimulation of human DC induced the phosphorylation of extracellular regulated kinase (ERK) and p38 MAPK, but not c-Jun N-terminal kinase (JNK). And also AngⅡincreased the DNA binding activity of NF-κB in DC. Finally, when pretreatment of human DC with Pio before Ang II, it was expected that Pio inhibited ERK and p38 MAPK phosphorylation and NF-κB/DNA binding activity in DC induced by AngⅡ.Conclusions:PPAR-y activation in human DC with Pio inhibits the functional activation of DC induced by Ang II, with which involves the regulation of MAPK and NF-κB signaling pathways. These findings may support the important role of these mediators in the regulation of DC-mediated inflammatory and immunologic processes. Research in vivo:PPAR-γagonist pioglitazone inhibits endogenous angiotensinⅡ-induced activation of dendritic cells and increase of atherosclerotic plaque vulnerability in apolipoprotein E deficient miceObjective:Rupture of vulnerable plaques is the main cause of acute cardiovascular events, mechanisms responsible for atherosclerotic plaque destabilization remain elusive. As we had found previously in vitro research that PPAR-γactivation with Pio inhibited the functional activation of DC induced by AngⅡ, we next generated endogenous AngⅡincreased and atherosclerotic ApoE-/- mice to study whether the PPAR-y agonist Pio inhibits the atherosclerotic plaque vulnerability induced by AngⅡin vivo, and exploited the possible mechanisms, especially focused on the inflammatory and immunologic processes mediated by DC.Methods:Two kidney one clip (2K1C) was operated on ApoE-/- mice to generate endogenous high AngⅡatherosclerotic mouse model, and a sham procedure was applied in control mice. The 2K1C ApoE-/- mice were randomly divided into two groups: one group received the PPAR-y agonist Pio (20 mg/kg/d, orally by gastric gavage), named 2K1C+Pio group; and the other group received equivalent normal saline, named 2K1C group. The sham ApoE-/- mice were also randomly divided into two groups:one group received Pio (20 mg/kg/d, orally by gastric gavage), named sham+Pio group; and the other group received equivalent normal saline, named sham group. After treatment for 12 weeks as the protocol, blood pressure were measured by carotid artery manometry, lipid profile and glucose level in blood were detected by biochemical test, plasma rennin activity (PRA) and concentration of AngⅡwere examined by radioimmunology assay. Aortic arch photos and thoracic and abdominal aorta staining with oil-red O were prepared to estimate the plaque burden. The root of aorta was dissected and sections were performed with hematoxylin and eosin staining and smooth muscle cell a-actin immunohistostaining to evaluate the plaque vulnerability, and CD3 immunohistostaining for T lymphocytes, S-100 and C-C chemokine receptor type 7 (CCR7) immunohistochemistry double staining for DC to detect the infiltrating and functional status of immune cells in atherosclerotic plaques.Results:The endogenous high Ang II atherosclerotic mouse model was successfully created. As expected, the blood pressure, PRA and AngⅡwere significantly increased in 2K1C ApoE-/- mice. Treatment of Pio exhibited no difference in blood pressure and Ang II concentration, although higher PRA compared with sham ApoE-/- mice. No difference in body weight, heart rate, lipid profile and glucose level was observed among the various groups of mice. Endogenous high AngⅡin 2K1C ApoE-/- mice promoted atherosclerosis progression in terms of increased plaque burden and enlarged plaque area in aortas; and also led to plaque vulnerability with larger lipid core, thinner fibrous cap or even rupture, decreased smooth muscle cells and increased T lymphocytes in plaques. However, Pio treatment significantly prevented the progression of atherosclerosis in 2K1C ApoE-/- mice in terms of reduced plaque burden and decreased plaque area in aortas; and also inhibited the plaque vulnerability by reducing lipid core, thickening fibrous cap, increasing content of smooth muscle cells and decreasing T lymphocytes infiltrating in plaques. Further study revealed that endogenous high Ang II in 2K1C ApoE-/- mice induced infiltrating and activation of DC in atherosclerotic plaque in terms of increased CCR7 positive DC accumulating in the plaque shoulder and in the marginal parts of the plaque core together with T lymphocytes. In addition, Pio treatment of 2K1C ApoE-/- mice obviously inhibited DC infiltratiing and activation in the atherosclerotic plaque induced by endogenous high AngⅡ. Conclusion:PPAR-γagonist Pio inhibits the atherosclerosis progression and plaque vulnerability induced by endogenous AngⅡin ApoE-/- mouse, with which involves the regulation of the inflammatory and immunologic processes mediated by DC. These findings may support the important role of DC-mediated inflammatory and immunologic mechanism in atherosclerosis progression and plaque vulnerability induced by AngⅡ. That may also provide us more scientific evidence for the potential beneficial effects of PPAR-γagonists such as thiazolidinediones in the prevention or treatment of atherosclerosis. |
PDF Full Text Request