BackgroundMacrophage‐mediated chronic inflammation is mechanistically linked to insulin resistance and atherosclerosis. Although arginase I is considered antiinflammatory, the role of arginase II (Arg‐II) in macrophage function remains elusive. This study characterizes the role of Arg‐II in macrophage inflammatory responses and its impact on obesity‐linked type II diabetes mellitus and atherosclerosis.Methods and ResultsIn human monocytes, silencing Arg‐II decreases the monocytes’ adhesion to endothelial cells and their production of proinflammatory mediators stimulated by oxidized low‐density lipoprotein or lipopolysaccharides, as evaluated by real‐time quantitative reverse transcription‐polymerase chain reaction and enzyme‐linked immunosorbent assay. Macrophages differentiated from bone marrow cells of Arg‐II–deficient (Arg‐II−/−) mice express lower levels of lipopolysaccharide‐induced proinflammatory mediators than do macrophages of wild‐type mice. Importantly, reintroducing Arg‐II cDNA into Arg‐II−/− macrophages restores the inflammatory responses, with concomitant enhancement of mitochondrial reactive oxygen species. Scavenging of reactive oxygen species by N‐acetylcysteine prevents the Arg‐II–mediated inflammatory responses. Moreover, high‐fat diet–induced infiltration of macrophages in various organs and expression of proinflammatory cytokines in adipose tissue are blunted in Arg‐II−/− mice. Accordingly, Arg‐II−/− mice reveal lower fasting blood glucose and improved glucose tolerance and insulin sensitivity. Furthermore, apolipoprotein E (ApoE)–deficient mice with Arg‐II deficiency (ApoE−/−Arg‐II−/−) display reduced lesion size with characteristics of stable plaques, such as decreased macrophage inflammation and necrotic core. In vivo adoptive transfer experiments reveal that fewer donor ApoE−/−Arg‐II−/− than ApoE−/−Arg‐II+/+ monocytes infiltrate into the plaque of ApoE−/−Arg‐II+/+ mice. Conversely, recipient ApoE−/−Arg‐II−/− mice accumulate fewer donor monocytes than do recipient ApoE−/−Arg‐II+/+ animals.ConclusionsArg‐II promotes macrophage proinflammatory responses through mitochondrial reactive oxygen species, contributing to insulin resistance and atherogenesis. Targeting Arg‐II represents a potential therapeutic strategy in type II diabetes mellitus and atherosclerosis. (J Am Heart Assoc. 2012;1:e000992 doi: 10.1161/JAHA.112.000992.)

SummaryAugmented activities of both arginase and S6K1 are involved in endothelial dysfunction in aging. This study was to investigate whether or not there is a crosstalk between arginase and S6K1 in endothelial inflammation and aging in senescent human umbilical vein endothelial cells and in aging mouse models. We show increased arginase-II (Arg-II) expression ⁄ activity in senescent endothelial cells. Silencing Arg-II in senescent cells suppresses eNOSuncoupling, several senescence markers such as senescence-associated-b-galactosidase activity, p53-S15, p21, and expression of vascular adhesion molecule-1 (VCAM1) and intercellular adhesion molecule-1 (ICAM1). Conversely, overexpressing Arg-II in nonsenescent cells promotes eNOS-uncoupling, endothelial senescence, and enhances VCAM1 ⁄ ICAM1 levels and monocyte adhesion, which are inhibited by co-expressing superoxide dismutase-1. Moreover, overexpressing S6K1 in nonsenescent cells increases, whereas silencing S6K1 in senescent cells decreases Arg-II gene expression ⁄ activity through regulation of Arg-II mRNA stability. Furthermore, S6K1 overexpression exerts the same effects as Arg-II on endothelial senescence and inflammation responses, which are prevented by silencing Arg-II, demonstrating a role of Arg-II as the mediator of S6K1-induced endothelial aging. Interestingly, mice that are deficient in Arg-II gene (Arg-II ) ⁄ ) ) are not only protected from age-associated increase in Arg-II, VCAM1 ⁄ ICAM1, aging markers, and eNOS-uncoupling in the aortas but also reveal a decrease in S6K1 activity. Similarly, silencing Arg-II in senescent cells decreases S6K1 activity, demonstrating that Arg-II also stimulates S6K1 in aging. Our study reveals a novel mechanism of mutual positive regulation between S6K1 and Arg-II in endothelial inflammation and aging. Targeting S6K1 and ⁄ or Arg-II may decelerate vascular aging and age-associated cardiovascular disease development.

Mammalian target of rapamycin (mTOR)/S6K1 signalling emerges as a critical regulator of aging. Yet, a role of mTOR/S6K1 in aging-associated vascular endothelial dysfunction remains unknown. In this study, we investigated the role of S6K1 in aging-associated endothelial dysfunction and effects of the polyphenol resveratrol on S6K1 in aging endothelial cells. We show here that senescent endothelial cells displayed higher S6K1 activity, increased superoxide production and decreased bioactive nitric oxide (NO) levels than young endothelial cells, which is contributed by eNOS uncoupling. Silencing S6K1 in senescent cells reduced superoxide generation and enhanced NO production. Conversely, over-expression of a constitutively active S6K1 mutant in young endothelial cells mimicked endothelial dysfunction of the senescent cells through eNOS uncoupling and induced premature cellular senescence. Like the mTOR/S6K1 inhibitor rapamycin, resveratrol inhibited S6K1 signalling, resulting in decreased superoxide generation and enhanced NO levels in the senescent cells. Consistent with the data from cultured cells, an enhanced S6K1 activity, increased superoxide generation, and decreased bioactive NO levels associated with eNOS uncoupling were also detected in aortas of old WKY rats (aged 20–24 months) as compared to the young animals (1–3 months). Treatment of aortas of old rats with resveratrol or rapamycin inhibited S6K1 activity, oxidative stress, and improved endothelial NO production. Our data demonstrate a causal role of the hyperactive S6K1 in eNOS uncoupling leading to endothelial dysfunction and vascular aging. Resveratrol improves endothelial function in aging, at least in part, through inhibition of S6K1. Targeting S6K1 may thus represent a novel therapeutic approach for aging-associated vascular disease.

Egaña-Gorroño et al. RAGE/DIAPH1, Diabetes, and Cardiovascular Disease knowledge regarding the roles for RAGE and DIAPH1 in the causes and consequences of diabetes, from obesity to CVD. Studies both from human subjects and animal models are presented to highlight the breadth of evidence linking RAGE and DIAPH1 to the cardiovascular consequences of these metabolic disorders.

Rationale Proton pump inhibitors (PPIs) are popular drugs for gastroesophageal reflux, now available for long-term use without medical supervision. Recent reports suggest that PPI use is associated with cardiovascular, renal and neurological morbidity. Objective To study the long-term effect of PPIs on endothelial dysfunction and senescence and investigate the mechanism involved in PPI induced vascular dysfunction. Methods and Results Chronic exposure to PPIs impaired endothelial function and accelerated human endothelial senescence by reducing telomere length. Conclusion Our data may provide a unifying mechanism for the association of PPI use with increased risk of cardiovascular, renal and neurological morbidity and mortality.