Natriuretic peptide receptor-C activation attenuates angiotensin II-induced enhanced oxidative stress and hyperproliferation of aortic vascular smooth muscle cells

Phenotypic Modulation of Macrophages and Vascular Smooth Muscle Cells in Atherosclerosis-Nitro-Redox Interconnections

Monocytes/macrophages and vascular smooth muscle cells (vSMCs) are the main cell types implicated in atherosclerosis development, and unlike other mature cell types, both retain a remarkable plasticity. In mature vessels, differentiated vSMCs control the vascular tone and the blood pressure. In response to vascular injury and modifications of the local environment (inflammation, oxidative stress), vSMCs switch from a contractile to a secretory phenotype and also display macrophagic markers expression and a macrophagic behaviour. Endothelial dysfunction promotes adhesion to the endothelium of monocytes, which infiltrate the sub-endothelium and differentiate into macrophages. The latter become polarised into M1 (pro-inflammatory), M2 (anti-inflammatory) or Mox macrophages (oxidative stress phenotype). Both monocyte-derived macrophages and macrophage-like vSMCs are able to internalise and accumulate oxLDL, leading to formation of “foam cells” within atherosclerotic plaques. Variations in the levels of nitric oxide (NO) can affect several of the molecular pathways implicated in the described phenomena. Elucidation of the underlying mechanisms could help to identify novel specific therapeutic targets, but to date much remains to be explored. The present article is an overview of the different factors and signalling pathways implicated in plaque formation and of the effects of NO on the molecular steps of the phenotypic switch of macrophages and vSMCs.

Role of the JAK2/STAT3 pathway in angiotensin II-induced enhanced expression of Giα proteins and hyperproliferation of aortic vascular smooth muscle cells

We earlier showed that angiotensin (Ang) II-induced overexpression of Giα proteins contributes to the hyperproliferation of vascular smooth muscle cells (VSMC). In addition, the implication of the JAK2/STAT3 pathway in Ang II-induced hyperproliferation of VSMC has also been reported. However, the role of the JAK2/STAT3 pathway in Ang II-induced overexpression of Giα proteins and hyperproliferation of VSMC remains unexplored. In the present study, we show that inhibition or knockdown of the JAK2/STAT3 pathway by a specific inhibitor "cucurbitacin I" (CuI) or siRNAs attenuated Ang II-induced overexpression of Giα proteins and hyperproliferation of VSMC. In addition, the enhanced expression of cell cycle proteins induced by Ang II was also attenuated by CuI. Furthermore, Ang II-induced enhanced production of the superoxide anion (O2 -), H2O2, and NADPH oxidase activity, as well as the enhanced expression of NADPH oxidase subunits implicated in enhanced expression of Giα proteins and hyperproliferation, were also attenuated by inhibition of the JAK2/STAT3 pathway. On the other hand, Ang II-induced inhibition and augmentation of the levels of nitric oxide and peroxynitrite, respectively, in VSMC were restored to control levels by CuI. In summary, our results demonstrate that Ang II through the JAK2/STAT3 pathway increases nitroxidative stress, which contributes to the overexpression of Giα proteins and cell cycle proteins and the hyperproliferation of VSMC.

The Role of Natriuretic Peptides in the Regulation of Cardiac Tolerance to Ischemia/Reperfusion and Postinfarction Heart Remodeling

In the past 10 years, mortality from acute myocardial infarction has not decreased despite the widespread introduction of percutaneous coronary intervention. The reason for this situation is the absence in clinical practice of drugs capable of preventing reperfusion injury of the heart with high efficiency. In this regard, noteworthy natriuretic peptides (NPs) which have the infarct-limiting effect, prevent reperfusion cardiac injury, prevent adverse post-infarction remodeling of the heart. Atrial natriuretic peptide does not have the infarct-reducing effect in rats with alloxan-induced diabetes mellitus. NPs have the anti-apoptotic and anti-inflammatory effects. There is indirect evidence that NPs inhibit pyroptosis and autophagy. Published data indicate that NPs inhibit reactive oxygen species production in cardiomyocytes, aorta, heart, kidney and the endothelial cells. NPs can suppress aldosterone, angiotensin II, endothelin-1 synthesize and secretion. NPs inhibit the effects aldosterone, angiotensin II on the post-receptor level through intracellular signaling events. NPs activate guanylyl cyclase, protein kinase G and protein kinase A, and reduce phosphodiesterase 3 activity. NO-synthase and soluble guanylyl cyclase are involved in the cardioprotective effect of NPs. The cardioprotective effect of natriuretic peptides is mediated via activation of kinases (AMPK, PKC, PI3 K, ERK1/2, p70s6 k, Akt) and inhibition of glycogen synthase kinase 3β. The cardioprotective effect of NPs is mediated via sarcolemmal K_ATP channel and mitochondrial K_ATP channel opening. The cardioprotective effect of brain natriuretic peptide is mediated via MPT pore closing. The anti-fibrotic effect of NPs may be mediated through inhibition TGF-β1 expression. Natriuretic peptides can inhibit NF-κB activity and activate GATA. Hemeoxygenase-1 and peroxisome proliferator-activated receptor γ may be involved in the infarct-reducing effect of NPs. NPs exhibit the infarct-limiting effect in patients with acute myocardial infarction. NPs prevent post-infarction remodeling of the heart. To finally resolve the question of the feasibility of using NPs in AMI, a multicenter, randomized, blind, placebo-controlled study is needed to assess the effect of NPs on the mortality of patients after AMI.