Background Regularly updated data on stroke and its pathological types, including data on their incidence, prevalence, mortality, disability, risk factors, and epidemiological trends, are important for evidence-based stroke care planning and resource allocation. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) aims to provide a standardised and comprehensive measurement of these metrics at global, regional, and national levels. MethodsWe applied GBD 2019 analytical tools to calculate stroke incidence, prevalence, mortality, disability-adjusted life-years (DALYs), and the population attributable fraction (PAF) of DALYs (with corresponding 95% uncertainty intervals [UIs]) associated with 19 risk factors, for 204 countries and territories from 1990 to 2019. These estimates were provided for ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage, and all strokes combined, and stratified by sex, age group, and World Bank country income level. FindingsIn 2019, there were 12•2 million (95% UI 11•0-13•6) incident cases of stroke, 101 million (93•2-111) prevalent cases of stroke, 143 million (133-153) DALYs due to stroke, and 6•55 million (6•00-7•02) deaths from stroke. Globally, stroke remained the second-leading cause of death (11•6% [10•8-12•2] of total deaths) and the third-leading cause of death and disability combined (5•7% [5•1-6•2] of total DALYs) in 2019. From 1990 to 2019, the absolute number of incident strokes increased by 70•0% (67•0-73•0), prevalent strokes increased by 85•0% (83•0-88•0), deaths from stroke increased by 43•0% (31•0-55•0), and DALYs due to stroke increased by 32•0% (22•0-42•0). During the same period, age-standardised rates of stroke incidence decreased by 17•0% (15•0-18•0), mortality decreased by 36•0% (31•0-42•0), prevalence decreased by 6•0% (5•0-7•0), and DALYs decreased by 36•0% (31•0-42•0). However, among people younger than 70 years, prevalence rates increased by 22•0% (21•0-24•0) and incidence rates increased by 15•0% (12•0-18•0). In 2019, the age-standardised stroke-related mortality rate was 3•6 (3•5-3•8) times higher in the World Bank low-income group than in the World Bank high-income group, and the age-standardised stroke-related DALY rate was 3•7 (3•5-3•9) times higher in the low-income group than the high-income group. Ischaemic stroke constituted 62•4% of all incident strokes in 2019 (7•63 million [6•57-8•96]), while intracerebral haemorrhage constituted 27•9% (3•41 million [2•97-3•91]) and subarachnoid haemorrhage constituted 9•7% (1•18 million [1•01-1•39]). In 2019, the five leading risk factors for stroke were high systolic blood pressure (contributing to 79•6 million [67•7-90•8] DALYs or 55•5% [48•2-62•0] of total stroke DALYs), high bodymass index (34•9 million [22•3-48•6] DALYs or 24•3% [15•7-33•2]), high fasting plasma glucose (28•9 million [19•8-41•5] DALYs or 20•2% [13•8-29•1]), ambient particulate matter pollution (28•7 million [23•4-33•4] DALYs or 20•1% [16•6-23•0]), and smoking (25•3 million [22•6-28•2] DALYs or 17•6% [16•4-19•0]...

Renin was first isolated in the kidney by Tigerstedt and Bergman over 100 years ago. Almost 50 additional years were necessary to isolate the renin substrate angiotensinogen and to show its cleavage to angiotensin (Ang). Further studies were then needed to demonstrate that Ang I is converted via an angiotensin-converting enzyme to Ang II. The circulating renin-angiotensin system, with blood pressure regulatory and aldosterone stimulatory roles, served well for decades. However, more recent information on Ang II and its action in terms of cell proliferation, hypertrophy, and hyperplasia as well as immune-modulatory and even intracellular functions, have focused attention on local Ang II generation and effects. These investigations necessarily began in the kidney, but quickly moved to other organs including the brain, heart, adrenal gland, and vessel wall and formed the basis for the concept of independent tissue renin-angiotensin systems. Both renin and Ang II have even been implicated in intracellular activities. This review presents some selected aspects of the historical development of this concept and summarizes discoveries relying primarily on animal models which demonstrate that Ang II is generated locally and acts in tissues as a local peptidergic system. Comprehensiveness in such an endeavor is not possible. We focus largely on work from our own group, not because the work is necessarily worthy of such scrutiny but rather because of our own familiarity with the contents.

Angiotensin-(1-7) [ANG-(1-7)] is a recently described heptapeptide product of the renin-angiotensin system. Because biosynthesis of ANG-(1-7) increases in animals treated with cardioprotective drugs and inactivation of the gene for angiotensin converting enzyme 2 [an enzyme involved in the biosynthesis of ANG-(1-7)] leads to the development of cardiac dysfunction, it has been suggested that ANG-(1-7) has cardioprotective properties. To directly test this possibility, we have generated transgenic rats that chronically overproduce ANG-(1-7) by using a novel fusion protein methodology. TGR(A1-7)3292 rats show testicular-specific expression of a cytomegalovirus promoter-driven transgene, resulting in a doubling of circulating ANG-(1-7) compared with nontransgenic control rats. Radiotelemetry hemodynamic measurements showed that transgenic rats presented a small but significant increase in daily and nocturnal heart rate and a slight but significant increase in daily and nocturnal cardiac contractility estimated by dP/d t measurements. Strikingly, TGR(A1-7)3292 rats were significantly more resistant than control animals to induction of cardiac hypertrophy by isoproterenol. In addition, transgenic rats showed a reduced duration of reperfusion arrhythmias and an improved postischemic function in isolated Langendorff heart preparations. These results support a cardioprotective role for circulating ANG-(1-7) and provide a novel tool for evaluating the functional role of ANG-(1-7).

Angiotensin produced systemically or locally in tissues such as the brain plays an important role in the regulation of blood pressure and in the development of hypertension. We have established transgenic rats [TGR(ASrAOGEN)] expressing an antisense RNA against angiotensinogen mRNA specifically in the brain. In these animals, the brain angiotensinogen level is reduced by more than 90% and the drinking response to intracerebroventricular renin infusions is decreased markedly compared with control rats. Blood pressure of transgenic rats is lowered by 8 mmHg (1 mmHg ‫؍‬ 133 Pa) compared with control rats. Crossbreeding of TGR(ASrAOGEN) with a hypertensive transgenic rat strain exhibiting elevated angiotensin II levels in tissues results in a marked attenuation of the hypertensive phenotype. Moreover, TGR(ASrAOGEN) exhibit a diabetes insipidus-like syndrome producing an increased amount of urine with decreased osmolarity. The observed reduction in plasma vasopressin by 35% may mediate these phenotypes of TGR(ASrAOGEN). This new animal model presenting longterm and tissue-specific down-regulation of angiotensinogen corroborates the functional significance of local angiotensin production in the brain for the central regulation of blood pressure and for the pathogenesis of hypertension.Hypertension is a leading risk factor for cardiovascular diseases, and the molecular dissection of its complex genetic causes is a great challenge. As for most physiological processes, the brain also seems to play a dominant role in the regulation of blood pressure and the pathogenesis of hypertension (1). Already more than 50 years ago, centrally acting drugs have been introduced as effective therapeutics for this disease (2). One of the hormone systems crucially involved in the central control of blood pressure is the renin-angiotensin system (RAS) (1, 3). The genotype of angiotensinogen (AOGEN), the only precursor of the effector peptide angiotensin II, correlates with blood pressure in genetically engineered mice (4-6) and hypertensive patients (7,8). Mice with an AOGEN gene dose increased by transgenesis (4) or gene titration (5) exhibit enhanced blood pressure; animals with zero (6) or only one (5) AOGEN allele are hypotensive. In humans, certain AOGEN alleles are associated with higher plasma AOGEN levels and increased blood pressure (7,8).AOGEN not only is synthesized and secreted into the blood stream by the liver but also is produced locally in several organs, including the brain (9), representing the basis of tissue-based RAS. Because of the blood-brain barrier precluding circulating angiotensin II from accessing most of its central receptors, the brain RAS acts independently from the systemic RAS on blood pressure regulation by influencing the secretion of arginine-vasopressin (AVP) and adrenocorticotropic hormone and modulating the baroreceptor reflex and the sympathetic output (1, 9). However, despite high local production, the function and the significance of AOGEN and angiotensin II in the brain are only partially...

Abstract-Rat models of hypertension, eg, spontaneously hypertensive stroke-prone rats (SHRSP), display reduced angiotensin-converting enzyme 2 (ACE2) mRNA and protein expression compared with control animals. The aim of this study was to investigate the role of ACE2 in the pathogenesis of hypertension in these models. Therefore, we generated transgenic rats on a SHRSP genetic background expressing the human ACE2 in vascular smooth muscle cells by the use of the SM22 promoter, called SHRSP-ACE2. In these transgenic rats vascular smooth muscle expression of human ACE2 was confirmed by RNase protection, real-time RT-PCR, and ACE2 activity assays. Transgene expression leads to significantly increased circulating levels of angiotensin-(1-7), a prominent product of ACE2. Mean arterial blood pressure was reduced in SHRSP-ACE2 compared to SHRSP rats, and the vasoconstrictive response to intraarterial administration of angiotensin II was attenuated. The latter effect was abolished by previous administration of an ACE2 inhibitor. To evaluate the endothelial function in vivo, endothelium-dependent and endothelium-independent agents such as acetylcholine and sodium nitroprusside, respectively, were applied to the descending thoracic aorta and blood pressure was monitored. Endothelial function turned out to be significantly improved in SHRSP-ACE2 rats compared to SHRSP. These data demonstrate that vascular ACE2 overexpression in SHRSP reduces hypertension probably by locally degrading angiotensin II and improving endothelial function. Thus, activation of the ACE2/angiotensin-(1-7) axis may be a novel therapeutic strategy in hypertension. (Hypertension. 2008;52:967-973.)

To evaluate the cardiovascular actions of kinins, we established a transgenic rat line harboring the human tissue kallikrein gene, TGR(hKLK1). Under the control of the zinc-inducible metallothionein promoter, the transgene was expressed in most tissues including the heart, kidney, lung, and brain, and human kallikrein was detected in the urine of transgenic animals. Transgenic rats had a lower 24-h mean arterial pressure in comparison with control rats, which was further decreased when their diet was supplemented with zinc. The day/night rhythm of blood pressure was significantly diminished in TGR(hKLK1) animals, whereas the circadian rhythms of heart rate and locomotor activity were unaffected. Induction of cardiac hypertrophy by isoproterenol treatment revealed a marked protective effect of the kallikrein transgene because the cardiac weight of TGR(hKLK1) increased significantly less, and the expression of atrial natriuretic peptide and collagen III as markers for hypertrophy and fibrosis, respectively, were less enhanced. The specific kinin-B2 receptor antagonist, icatibant, abolished this cardioprotective effect. In conclusion, the kallikrein-kinin system is an important determinant in the regulation of blood pressure and its circadian rhythmicity. It also exerts antihypertrophic and antifibrotic actions in the heart.

Abstract-The potential involvement of the brain renin-angiotensin system in the hypertension induced by subpressor doses of angiotensin II was tested by the use of newly developed transgenic rats with permanent inhibition of brain angiotensinogen synthesis [TGR(ASrAOGEN)]. Basal systolic blood pressure monitored by telemetry was significantly lower in TGR(ASrAOGEN) than in Sprague-Dawley rats (parent strain) (122.5Ϯ1.5 versus 128.9Ϯ1.9 mm Hg, respectively; PϽ0.05). The increase in systolic blood pressure induced by 7 days of chronic angiotensin II infusion was significantly attenuated in TGR(ASrAOGEN) in comparison with control rats (29.8Ϯ4.2 versus 46.3Ϯ2.5 mm Hg, respectively; PϽ0.005). Moreover, an increase in heart/body weight ratio was evident only in Sprague-Dawley (11.1%) but not in TGR(ASrAOGEN) rats (2.8%). In contrast, mRNA levels of atrial natriuretic peptide (ANP) and collagen III in the left ventricle measured by ribonuclease protection assay were similarly increased in both TGR(ASrAOGEN) (ANP, ϫ2.5; collagen III, ϫ1.8) and Sprague-Dawley rats (ANP, ϫ2.4; collagen III, ϫ2) as a consequence of angiotensin II infusion. Thus, the expression of these genes in the left ventricle seems to be directly stimulated by angiotensin II. However, the hypertensive and hypertrophic effects of subpressor angiotensin II are at least in part mediated by the brain renin-angiotensin system. Key Words: renin-angiotensin system Ⅲ collagen Ⅲ angiotensin II Ⅲ hypertrophy Ⅲ atrial natriuretic peptide T he renin-angiotensin system (RAS) is acknowledged to play an important role in the pathophysiology of hypertension and cardiovascular diseases. Since tissue RASs have been postulated, local formation of angiotensin II (Ang II) is consistently invoked to explain that RAS inhibitors can exert beneficial effects in cardiovascular diseases, even in the absence of Ang II plasma levels that directly increase blood pressure (BP). 1 The mechanisms by which increases in plasma Ang II can induce an increase in BP in these situations are still not clearly defined. One experimental animal model designed to mimic human hypertension that is often used to obtain insights regarding its pathophysiological mechanisms is attained by chronic infusion (days to weeks) of subpressor doses of Ang II. 2 Infused doses of Ang II up to 250 ng/kg per minute SC that do not produce direct vasoconstriction are described as "subpressor" or "slow pressor" and can induce a gradual increase of BP. Several studies have indicated that the central nervous system is involved in the effects of the subpressor Ang II. Arguments are based on the elimination of the hypertensive effect of Ang II by ablation of area postrema 3 or lateral parabrachial nucleus. 4 Furthermore, the hypertensive effect of subpressor doses of Ang II can be inhibited by central sympathoinhibitors, 5 ganglionic blockers, 6 nonselective ␣-blockade, 7 or renal denervation, 8 supporting a neurogenic pressor mechanism.The role of the brain RAS in the central control of cardiovascular homeostasis and p...

Abstract-To study whether the brain renin-angiotensin system plays a role in the long-term and short-term control of blood pressure and heart rate variability, we examined in transgenic rats [TGR(ASrAOGEN)] with low brain angiotensinogen levels the 24-hour variation of blood pressure and heart rate. Telemetry recordings were made during basal and hypertensive conditions induced by a low-dose subcutaneous infusion of angiotensin II for 7 days. Short-term blood pressure and heart rate variability were evaluated by spectral analysis, and as a measure of baroreflex sensitivity, the average transfer gain between the pressure and heart rate variations was calculated. During the angiotensin II infusion in control but not TGR(ASrAOGEN) rats, the 24-hour rhythm of blood pressure was inverted (5.8Ϯ2 versus Ϫ0.4Ϯ1.8 mm Hg/group of day-night differences of blood pressure, PϽ0.05, respectively). In both the control and TGR(ASrAOGEN) rats, the 24-hour heart rate rhythms remained unaltered and paralleled those of locomotor activity. The transfer gain between 0.3 to 0.6 Hz was significantly higher in TGR(ASrAOGEN) than in control rats during control (0.71Ϯ0.1 versus 0.35Ϯ0.06, PϽ0.05) but not during angiotensin II infusion (0.6Ϯ0.07 versus 0.4Ϯ0.1, PϾ0.05). These results demonstrate that the brain renin-angiotensin system plays an important role in mediating the effects of angiotensin II on the circadian variation of blood pressure. Furthermore, these data indicate that a permanent deficiency in the brain renin-angiotensin system alters the reflex control of heart rate in rats. Key Words: renin-angiotensin system Ⅲ blood pressure Ⅲ baroreflex Ⅲ circadian rhythm Ⅲ brain M ultiple clinical studies have implicated blood pressure (BP) and heart rate (HR) variability in the diagnosis and prognosis of arterial hypertension and cardiovascular diseases. 1,2 It has been shown, for instance, that patients with essential or secondary forms of hypertension can be divided into 2 groups: "dippers" and "nondippers." 3 In "dippers," circadian rhythm of BP is preserved, whereas "nondippers" lack the characteristic nocturnal fall in BP. Cross-sectional studies have indicated that target-organ damage is more pronounced in "nondippers" than in "dipper" patients with comparable clinical blood pressure. 4,5 Furthermore, a circadian pattern becomes obvious in the occurrence of acute cardiovascular diseases such as ischemia, infarction, stroke, and sudden death, 6 and investigators are using new chronotherapeutic approaches in antihypertensive therapy to exploit the knowledge of circadian rhythms to reduce these events. 7 Furthermore, it has been demonstrated that short-term (beatto-beat) variations of BP and HR contain information about the activity of the autonomic nervous system, 8 and power spectral analysis of these parameters shows promise for studying the mechanisms involved in cardiovascular disease. 9,10 There is evidence that in humans, the HR and HR variability (HRV) can be genetically determined. 11 Recently developed approaches based on g...