International Journal of Molecular and Cellular Medicine (IJMCM)

The role of oxidized high-density lipoprotein (oxHDL) and the protective effects of adiponectin in terms of vascular calcification is not well established. This study was conducted to investigate the effects of oxHDL with regards to inflammation and vascular calcification and to determine the protective role of adiponectin in attenuating the detrimental effects of oxHDL. Cell viability, mineralization, and calcification assays were conducted to optimize the concentration of oxHDL. Then, human vascular smooth muscle cells (HAoVSMCs) were incubated with β-glycerophosphate, HDL, oxHDL, adiponectin, or the combination of oxHDL with adiponectin for 24 h.  Protein expression of IL-6, TNF-α, osterix, RUNX2, ALP, type 1 collagen, osteopontin, osteocalcin, WNT-5a, NF-ĸβ(p65), cAMP and STAT-3 were measured by ELISA kits. OxHDL induced vascular calcification by promoting the formation of mineralization nodules and calcium deposits in HAoVSMCs. This was accompanied by an increased secretion of IL-6, osterix, WNT-5a and NF-ĸβ (p65). Interestingly, these detrimental effects of oxHDL were suppressed by adiponectin. Besides, incubation of adiponectin alone on HAoVSMCs showed a reduction of inflammatory cytokines, osteoblastic markers (RUNX2, osterix and osteopontin), WNT-5a and NF-ĸβ (p65). This study exhibits the ability of oxHDL in inducing inflammation and vascular calcification and these detrimental effects of oxHDL can be attenuated by adiponectin.

The renin–angiotensin system (RAS) exerts profound physiological effects on blood pressure regulation and fluid homeostasis, mainly by modulating renal, cardiovascular, and central nervous systems. Angiotensin (Ang)-(1-7), an end-product of RAS, is recognized by its cardiovascular protective properties through stimulation of the Mas receptor, including vasodilation, anti-inflammatory, and antihypertensive actions, and consequently, counter-regulating the well-known Ang II-elicited actions. The overall hypothesis of this study is that Ang-(1-7) inhibits Ang II-induced ERK1/2 activation in vascular smooth muscle cells (VSMCs), via regulation of mitogen-activated protein phosphatase-1 (MKP-1) activity. Aortas from male Wistar rats were incubated with Ang-(1-7) or vehicle. Concentration-response curves to Ang II were performed in endothelium-denuded aortas, in the presence or absence of ERK1/2 (PD98059) inhibitor or Mas receptor (A-779) antagonist. Expression of proteins was assessed by western blot, and immunohistochemistry was conducted in VSMCs. Ang-(1-7) incubation decreased Ang II-induced contractile response in aortas, and this effect was not observed in the presence of PD98059 or A-779. Stimulation of VSMCs with Ang-(1-7) prevented Ang II-induced ERK1/2 phosphorylation, but not C-Raf-activation. Furthermore, Ang II decreased MKP-1 phosphorylation in VSMCs. Interestingly, simultaneous incubation of Ang-(1-7) with Ang II favored MKP-1 phosphorylation, negatively modulating ERK1/2 activation in VSMCs. The results suggest that Ang-(1-7) counter-regulates actions evoked by Ang II overproduction, as observed in cardiovascular diseases, mainly by modulating MKP-1 activity. This evidence suggests that the role of Ang-(1-7) in MKP-1-regulation represents a target for new therapeutic development.