The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

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Nitric Oxide and Peroxynitrite in Health and Disease

Inflammation is a biological response of the immune system that can be triggered by a variety of factors, including pathogens, damaged cells and toxic compounds. These factors may induce acute and/or chronic inflammatory responses in the heart, pancreas, liver, kidney, lung, brain, intestinal tract and reproductive system, potentially leading to tissue damage or disease. Both infectious and non-infectious agents and cell damage activate inflammatory cells and trigger inflammatory signaling pathways, most commonly the NF-κB, MAPK, and JAK-STAT pathways. Here, we review inflammatory responses within organs, focusing on the etiology of inflammation, inflammatory response mechanisms, resolution of inflammation, and organ-specific inflammatory responses.

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Inflammatory responses and inflammation-associated diseases in organs

The renin-angiotensin system is a central component of the physiological and pathological responses of cardiovascular system. Its primary effector hormone, angiotensin II (ANG II), not only mediates immediate physiological effects of vasoconstriction and blood pressure regulation, but is also implicated in inflammation, endothelial dysfunction, atherosclerosis, hypertension, and congestive heart failure. The myriad effects of ANG II depend on time (acute vs. chronic) and on the cells/tissues upon which it acts. In addition to inducing G protein- and non-G protein-related signaling pathways, ANG II, via AT(1) receptors, carries out its functions via MAP kinases (ERK 1/2, JNK, p38MAPK), receptor tyrosine kinases [PDGF, EGFR, insulin receptor], and nonreceptor tyrosine kinases [Src, JAK/STAT, focal adhesion kinase (FAK)]. AT(1)R-mediated NAD(P)H oxidase activation leads to generation of reactive oxygen species, widely implicated in vascular inflammation and fibrosis. ANG II also promotes the association of scaffolding proteins, such as paxillin, talin, and p130Cas, leading to focal adhesion and extracellular matrix formation. These signaling cascades lead to contraction, smooth muscle cell growth, hypertrophy, and cell migration, events that contribute to normal vascular function, and to disease progression. This review focuses on the structure and function of AT(1) receptors and the major signaling mechanisms by which angiotensin influences cardiovascular physiology and pathology.

Angiotensin II cell signaling: physiological and pathological effects in the cardiovascular system

Kazuaki SHIMAMOTO, Katsuyuki ANDO, Toshiro FUJITA, Naoyuki HASEBE, Jitsuo HIGAKI, Masatsugu HORIUCHI, Yutaka IMAI, Tsutomu IMAIZUMI, Toshihiko ISHIMITSU, Masaaki ITO, Sadayoshi ITO, Hiroshi ITOH, Hiroshi IWAO, Hisashi KAI, Kazuomi KARIO, Naoki KASHIHARA, Yuhei KAWANO, Shokei KIM-MITSUYAMA, Genjiro KIMURA, Katsuhiko KOHARA, Issei KOMURO, Hiroo KUMAGAI, Hideo MATSUURA, Katsuyuki MIURA, Ryuichi MORISHITA, Mitsuhide NARUSE, Koichi NODE, Yusuke OHYA, Hiromi RAKUGI, Ikuo SAITO, Shigeyuki SAITOH, Kazuyuki SHIMADA, Tatsuo SHIMOSAWA, Hiromichi SUZUKI, Kouichi TAMURA, Norio TANAHASHI, Takuya TSUCHIHASHI, Makoto UCHIYAMA, Shinichiro UEDA, Satoshi UMEMURA, on behalf of The Japanese Society of Hypertension Committee for Guidelines for the Management of Hypertension

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The Japanese Society of Hypertension guidelines for the management of hypertension (JSH 2014)

Coronary heart disease

High blood pressure (HBP) has been associated with elevated C-reactive protein (CRP), a marker of chronic mild inflammation. However, the association between HBP and other inflammatory markers, particularly interleukin 6 (IL-6) and tumour necrosis alpha (TNF-alpha), has not been evaluated in well-controlled studies. We examined the cross-sectional relationship between IL-6, TNF-alpha, and CRP and HBP in a random sample of 196 healthy subjects. All markers were measured in duplicate with high-sensitivity ELISA tests. Three blood pressure (BP) measurments were averaged for the analysis, and subjects with systolic BP >or=140 and/or diastolic BP >or=90 mmHg were considered hypertensive. Log binomial regression was used to estimate multivariate-adjusted prevalence ratios (PR) of HBP. Of the subjects, 40% (79) were hypertensive (mean age: 44 years; range 30-64). After adjustment for age, sex, body mass index, family history of HBP, and the level of the other inflammatory markers, subjects in the second (PR: 3.10, P=0.003), third (PR: 2.32; P=0.031), and fourth quartiles (PR: 2.30; P=0.036) of IL-6 were more than twice as likely to be hypertensive than those in the first quartile. Corresponding PR estimates for TNF-alpha levels were 1.41 (P=0.014) for the second; 1.59 (P=0.001) for the third; and 1.61 (P=0.025) for the fourth quartile. The CRP-HBP association was not statistically significant. Our results suggest that TNF-alpha and IL-6 could be independent risk factors for HBP in apparently healthy subjects. Nevertheless, the temporal relationship between elevated inflammation markers and HBP should be ascertained in prospective cohort studies.

Independent association between inflammatory markers (C-reactive protein, interleukin-6, and TNF-α) and essential hypertension

Total plasma homocysteine level and risk of cardiovascular disease: A meta-analysis of prospective cohort studies

Preeclampsia is a pregnancy-specific disorder characterised by hypertension and proteinuria occurring after the 20th week of gestation. Delivery of the placenta results in resolution of the condition, implicating the placenta as a central culprit in the pathogenesis of preeclampsia. In preeclampsia, an inadequate placental trophoblast invasion of the maternal uterine spiral arteries results in poor placental perfusion, leading to placental ischaemia. This could result in release of factors into the maternal circulation that cause widespread activation or dysfunction of the maternal endothelium. Factors in the maternal circulation might induce oxidative stress and/or elicit an inflammatory response in the maternal endothelium, resulting in the altered expression of several genes involved in the regulation of vascular tone. This review addresses the potential circulating factors and the molecular mechanisms involved in the alteration of vascular function that occurs in preeclampsia.

Preeclampsia: current understanding of the molecular basis of vascular dysfunction

Angiotensin II (ANG II) has been etiologically linked to vascular disease; however, its role in the alterations of endothelial function that occur in vascular disorders is not completely understood...

https://www.physiology.org/doi/pdf/10.1152/ajpcell.00398.2003

Angiotensin II-induced MMP-2 release from endothelial cells is mediated by TNF-α

Objective: To investigate the effects of estrogen on left ventricle (LV) mass and collagen deposition, and on the expression of receptors for estrogen (ERα, ERβ) and Ang II (AT2R, AT1R) in the heart of aged female rats. Methods: Aged (∼12 months old) intact ( n =7), ovariectomized plus placebo (OVX, n =7), and estrogen-replaced (E2, n =6) as well as young (∼3 months old, n =4) female Sprague–Dawley rats were used in this study. After 1 month of treatment, the left ventricular weight/body weight ratio (LVW/BW), changes in myosin heavy chain expression (MHC), matrix metalloproteinase (MMP)-2 activity, the collagen I/III ratio, and the expression of ERs and Ang II receptors in the LV were evaluated. Results: In aged rats, OVX increased LVW/BW associated with a higher expression of β-MHC isoform, increased collagen I/III ratio, and decreased MMP-2 activity compared to intact rats. Furthermore, the OVX group had a decrease in ERs α and β as well as AT2R but an increase in AT1R expression. Estrogen replacement prevented the effects of ovariectomy on heart remodeling as well as increased further expression of ERβ and decreased AT1R expression. Conclusion: Removal of ovarian hormones increased LV remodeling in the aged rat, which could be attenuated by estrogen replacement. Moreover, regulation of Ang II receptor expression could be a mechanism by which estrogen may modulate heart remodeling.

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Ivan A. Arenas

Papers

Independent association between inflammatory markers (C-reactive protein, interleukin-6, and TNF-α) and essential hypertension

Total plasma homocysteine level and risk of cardiovascular disease: A meta-analysis of prospective cohort studies

Preeclampsia: current understanding of the molecular basis of vascular dysfunction

Angiotensin II-induced MMP-2 release from endothelial cells is mediated by TNF-α

Estrogen modulation of left ventricular remodeling in the aged heart.