The Effect of Angiotensin II Type 1 Receptor Antagonist on Age-Related Differences in Renal Vascular Responses to Angiotensin II in Male and Female Rats

Background

Advancing age could influence renin angiotensin system components, especially angiotensin type 1 receptor (AT1R). This study examined the effect of AT1R antagonist, losartan, on age-related differences in renal vascular responses to angiotensin II in male and female rats.

Materials and Methods

Forty-eight anesthetized male and female rats (8-12 and 24-28 weeks age ranges) were subjected to catheterize. Then, the responses of mean arterial pressure (MAP), renal perfusion pressure (RPP), renal blood flow (RBF), and renal vascular resistance (RVR) to angiotensin II with or without losartan were determined and evaluated.

Results

There were not significant differences in the basal values of MAP, RPP, RBF, and RVR in males. However, it was observed significant difference in RVR in females (P < 0.05). The blockade of AT1R attenuated basal MAP and RPP in all the groups (P < 0.05). The infusion of losartan altered basal RVR and RBF values in female groups (P < 0.05). Moreover, losartan eliminated vasoconstrictor responses to angiotensin II in female groups (P < 0.05). Also, losartan induced significant vascular responses to angiotensin II in male groups (P < 0.05).

Conclusions

Losartan could maintain RBF changes in response to angiotensin II in both 8-12- and 24-28-week females. Losartan enhanced the RBF response to angiotensin II in 8-12-week males, but not in 24-28-week males. It seems that females (not males) in various age ranges are resistance against RBF changes by acutely increased angiotensin II.

The ACE inhibitor captopril inhibits ACN-1 to control dauer formation and aging

The renin-angiotensin-aldosterone system (RAAS) plays a well-characterized role regulating blood pressure in mammals. Pharmacological and genetic manipulation of the RAAS has been shown to extend lifespan in Caenorhabditis elegans, Drosophila and rodents, but its mechanism is not well defined. Here, we investigate the angiotensin-converting enzyme (ACE) inhibitor drug captopril, which extends lifespan in worms and mice. To investigate the mechanism, we performed a forward genetic screen for captopril-hypersensitive mutants. We identified a missense mutation that causes a partial loss of function of the daf-2 receptor tyrosine kinase gene, a powerful regulator of aging. The homologous mutation in the human insulin receptor causes Donohue syndrome, establishing these mutant worms as an invertebrate model of this disease. Captopril functions in C. elegans by inhibiting ACN-1, the worm homolog of ACE. Reducing the activity of acn-1 via captopril or RNA interference promoted dauer larvae formation, suggesting that acn-1 is a daf gene. Captopril-mediated lifespan extension was abrogated by daf-16(lf) and daf-12(lf) mutations. Our results indicate that captopril and acn-1 influence lifespan by modulating dauer formation pathways. We speculate that this represents a conserved mechanism of lifespan control.

The ACE-inhibitor drug captopril inhibits ACN-1 to control dauer formation and aging

The renin-angiotensin-aldosterone system (RAAS) plays a well-characterized role regulating blood pressure in mammals. Pharmacological and genetic manipulation of the RAAS has been shown to extend lifespan in C. elegans , Drosophila , and rodents, but its mechanism is not well defined. Here we investigate the angiotensin-converting enzyme (ACE) inhibitor drug captopril, which extends lifespan in worms and mice. To investigate the mechanism, we performed a forward genetic screen for captopril hypersensitive mutants. We identified a missense mutation that causes a partial loss-of-function of the daf-2 receptor tyrosine kinase gene, a powerful regulator of aging. The homologous mutation in the human insulin receptor causes Donohue syndrome, establishing these mutant worms as an invertebrate model of this disease. Captopril functions in C. elegans by inhibiting ACN-1, the worm homolog of ACE. Reducing the activity of acn-1 via captopril or RNAi promoted dauer larvae formation, suggesting acn-1 is a daf gene. Captopril-mediated lifespan extension xwas abrogated by daf-16(lf) and daf-12(lf) mutations. Our results indicate that captopril and acn-1 control aging by modulating dauer formation pathways. We speculate that this represents a conserved mechanism of lifespan control.

Summary Statement

Captopril and acn-1 control aging. By demonstrating they regulate dauer formation and interact with daf genes, including a new DAF-2(A261V) mutant corresponding to a human disease variant, we clarified the mechanism.

Control of aging by the renin–angiotensin system: a review of C. elegans, Drosophila, and mammals

The free-living, non-parasitic nematode Caenorhabditis elegans is a premier model organism for the study of aging and longevity due to its short lifespan, powerful genetic tools, and conservation of fundamental mechanisms with mammals. Approximately 70 percent of human genes have homologs in C. elegans, including many that encode proteins in pathways that influence aging. Numerous genetic pathways have been identified in C. elegans that affect lifespan, including the dietary restriction pathway, the insulin/insulin-like growth factor (IGF) signaling pathway, and the disruption of components of the mitochondrial electron transport chain. C. elegans is also a powerful system for performing drug screens, and many lifespan-extending compounds have been reported; notably, several FDA-approved medications extend the lifespan in C. elegans, raising the possibility that they can also extend the lifespan in humans. The renin–angiotensin system (RAS) in mammals is an endocrine system that regulates blood pressure and a paracrine system that acts in a wide range of tissues to control physiological processes; it is a popular target for drugs that reduce blood pressure, including angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs). Emerging evidence indicates that this system influences aging. In C. elegans, decreasing the activity of the ACE homolog acn-1 or treatment with the ACE-inhibitor Captopril significantly extends the lifespan. In Drosophila, treatment with ACE inhibitors extends the lifespan. In rodents, manipulating the RAS with genetic or pharmacological interventions can extend the lifespan. In humans, polymorphisms in the ACE gene are associated with extreme longevity. These results suggest the RAS plays a conserved role in controlling longevity. Here, we review studies of the RAS and aging, emphasizing the potential of C. elegans as a model for understanding the mechanism of lifespan control.

Non-coding RNAs and Cardiac Aging

Aging is an important risk factor for cardiovascular diseases. Aging increasing the morbidity and mortality in cardiovascular disease patients. With the society is aging rapidly in the world, medical burden of aging-related cardiovascular diseases increasing drastically. Hence, it is urgent to explore the underlying mechanism and treatment of cardiac aging. Noncoding RNAs (ncRNAs, including microRNAs, long noncoding RNAs and circular RNAs) have been reported to be involved in many pathological processes, including cell proliferation, cell death differentiation, hypertrophy and aging in wide variety of cells and tissues. In this chapter, we will summarize the physiology and molecular mechanisms of cardiac aging. Then, the recent research advances of ncRNAs in cardiac aging will be provided. The lessons learned from ncRNAs and cardiac aging studies would bring new insights into the regulatory mechanisms ncRNAs as well as treatment of aging-related cardiovascular diseases.

Prospects of Pharmacological Interventions to Organismal Aging

Intense research in the areas of cellular and organismal aging using diverse laboratory model systems has enriched our knowledge in the processes and the signalling pathways involved in normal and pathological conditions. The field finds itself in a position to take decisive steps towards clinical applications and interventions not only for targeted age-related diseases such as cardiovascular conditions and neurodegeneration but also for the modulation of health span and lifespan of a whole organism. Beyond nutritional interventions such as dietary restriction without malnutrition and various regimes of intermittent fasting, accumulating evidence provides promise for pharmacological interventions. The latter, mimic caloric or dietary restriction, tune cellular and organismal stress responses, affect the metabolism of microbiome with subsequent effects on the host or modulate repair pathways, among others. In this mini review, we summarise some of the evidence on drugs that can alter organismal lifespan and the prospects they might offer for promoting healthspan and delaying age-related diseases.

Estudo morfométrico de rins em felinos domésticos (Felis catus)

Resumo A saúde renal tem ao longo dos últimos anos chamado atenção dos médicos veterinários, pois o comprometimento deste órgão na insuficiência renal crônica se apresenta como a maior causa de morbidade e mortalidade em felinos. O presente estudo propõe a caracterização biométrica dos rins de gatos, Felis catus, sob os aspectos macroscópicos (comprimento, altura, largura, peso e volume), mesoscópico (altura do córtex e da medula, e a sua inter-relação) e microscópica (volume glomerular), a fim de se estabelecer possíveis diferenças decorrentes de idade, sexo e simetria bilateral. Foram utilizados, rins de 30 animais da espécie Felis catus (gato deméstico), sendo 15 machos e 15 fêmeas com idade variando entre 3 meses a 15 anos, divididos em três grupos: grupo 1 (3-9 meses), grupo 2 (3-5 anos) e grupo 3 (acima de 10 anos). Os rins foram fotografados, pesados, mensurados e processados para histologia. O volume glomerular foi obtido através de estereologia. Os dados macroscópicos permitiram observar uma imparcialidade morfométrica e morfológica quando comparados os lados, independente do grupo e do sexo, sobre o comprimento, altura, largura, peso e volume dos rins. Para o sexo foi detectado diferença significante entre machos e fêmeas independente da faixa etária para comprimento, altura, peso e volume, com exceção da largura. Considerando a idade houve diferença significativa para todos os parâmetros: comprimento, altura, largura, peso e volume. Nas mensurações de córtex, medula e sua inter-relação, quando considerada a simetria bilateral, não foi detectada diferença significante entre rim direito e esquerdo. Para o sexo, não foi detectada diferença entre machos e fêmeas na mesoscopia no córtex, na medula e na inter-relação córtex/medula. Quanto à idade, a mensuração da altura do córtex e a inter-relação córtex/medula apresentou diferença significante, porém essa diferença não foi estabelecida para a medula do rim. Foram encontradas diferenças significantes entre grupos e entre machos e fêmeas, em relação ao volume ocupado pelo glomérulo no parênquima renal. Em todas as técnicas biométricas utilizadas não foram detectadas diferenças entre os rins direito e esquerdo. As mensurações macroscópicas mostraram que machos apresentaram um rim maior em comprimento, altura, largura, peso e volume do que as fêmeas. A faixa etária está diretamente relacionada ao tamanho do rim, que cresce em todas as dimensões, fica mais pesado e com maior volume quando comparados jovens e adultos, e se mostra estável morfometricamente em relação aos adultos e senis. O parênquima renal não difere entre os sexos, mas a altura do córtex e a relação com a medula aumentam com a idade. O volume do glomérulo renal é maior em machos do que em fêmeas e também aumenta em relação à idade. Os rins mostraram um predomínio de colágeno tipo I nos animais do grupo 1 e 2, e colágeno tipo III nos animais do grupo 3.

Angiotensin Converting Enzyme (ACE) Inhibitor Extends Caenorhabditis elegans Life Span

Animal aging is characterized by progressive, degenerative changes in many organ systems. Because age-related degeneration is a major contributor to disability and death in humans, treatments that delay age-related degeneration are desirable. However, no drugs that delay normal human aging are currently available. To identify drugs that delay age-related degeneration, we used the powerful Caenorhabditis elegans model system to screen for FDA-approved drugs that can extend the adult lifespan of worms. Here we show that captopril extended mean lifespan. Captopril is an angiotensin-converting enzyme (ACE) inhibitor used to treat high blood pressure in humans. To explore the mechanism of captopril, we analyzed the acn-1 gene that encodes the C. elegans homolog of ACE. Reducing the activity of acn-1 extended the mean life span. Furthermore, reducing the activity of acn-1 delayed age-related degenerative changes and increased stress resistance, indicating that acn-1 influences aging. Captopril could not further extend the lifespan of animals with reduced acn-1, suggesting they function in the same pathway; we propose that captopril inhibits acn-1 to extend lifespan. To define the relationship with previously characterized longevity pathways, we analyzed mutant animals. The lifespan extension caused by reducing the activity of acn-1 was additive with caloric restriction and mitochondrial insufficiency, and did not require sir-2.1, hsf-1 or rict-1, suggesting that acn-1 functions by a distinct mechanism. The interactions with the insulin/IGF-1 pathway were complex, since the lifespan extensions caused by captopril and reducing acn-1 activity were additive with daf-2 and age-1 but required daf-16. Captopril treatment and reducing acn-1 activity caused similar effects in a wide range of genetic backgrounds, consistent with the model that they act by the same mechanism. These results identify a new drug and a new gene that can extend the lifespan of worms and suggest new therapeutic strategies for addressing age-related degenerative changes.

Incomplete Restoration of Angiotensin II-Induced Renal Extracellular Matrix Deposition and Inflammation Despite Complete Functional Recovery in Rats

Some diseases associated with a temporary deterioration in kidney function and/or development of proteinuria show an apparently complete functional remission once the initiating trigger is removed. While it was earlier thought that a transient impairment of kidney function is harmless, accumulating evidence now suggests that these patients are more prone to developing renal failure later in life. We therefore sought to investigate to what extent renal functional changes, inflammation and collagen deposition are reversible after cessation of disease induction, potentially explaining residual sensitivity to damage. Using a rat model of Angiotensin II (Ang II)-induced hypertensive renal disease we show the development of severe hypertension (212 ± 10.43 vs. 146 ± 1.4 mmHg, p<0.001) and proteinuria (51.4 ± 6.3 vs. 14.7 ± 2.0 mg/24h, p<0.01) with declined creatinine clearance (2.0 ± 0.5 vs. 4.9 ± 0.6 mL/min, p<0.001) to occur after 3 weeks of Ang II infusion. At the structural level, Ang II infusion resulted in interstitial inflammation (18.8 ± 4.8 vs. 3.6 ± 0.5 number of macrophages, p<0.001), renal interstitial collagen deposition and lymphangiogenesis (4.1 ± 0.4 vs. 2.2 ± 0.4 number of lymph vessels, p<0.01). Eight weeks after cessation of Ang II, all clinical parameters, pre-fibrotic changes such as myofibroblast transformation and increase in lymph vessel number (lymphangiogenesis) returned to control values. However, glomerular desmin expression, glomerular and periglomerular macrophages and interstitial collagens remained elevated. These dormant abnormalities indicate that after transient renal function decline, inflammation and collagen deposition may persist despite normalization of the initiating pathophysiological stimulus perhaps rendering the kidney more vulnerable to further damage.

Renin-angiotensin-aldosterone system and the aging kidney

Human senescence induces changes in the renin-angiotensin-aldosterone system (RAAS) which consists of a substantial decrease in its plasma activity. Consequently, the distal tubule´s capability of handling sodium and potassium is significantly reduced in the elderly, while distal tubule acidification is slightly delayed but preserved in this age group. Several studies in animal models support the hypothesis that senile renal structural changes could be induced by the local production of angiotensin II, and also that enalapril significantly decreases senile mesangial expansion, glomerulosclerosis and peritubular and medullar interstitial sclerosis. The same applies to several highly prevalent diseases in the elderly, such as hypertension, obesity, cardiac insufficiency, chronic nephropathy and dementia. In conclusion, the relationship between the RAAS and senescence is complex, since not only does aging cause many changes on this hormonal system, but also RAAS overactivity seems to be one of the main inducing mechanisms for normal senescence, and for many prevalent diseases in the elderly.

Postnatal early overnutrition causes long-term renal decline in aging male rats

BACKGROUND

We evaluated the influence of postnatal early overnutrition on renal pathophysiological changes in aging rats.

METHODS

Three or 10 male pups per mother were assigned to either the small litter (SL) or normal litter (control) groups, respectively, during the first 21 d of life. The effects of early postnatal overnutrition were determined at 12 mo.

RESULTS

SL rats weighed more than controls between 4 d and 6 mo of age (P < 0.05). However, between 6 and 12 mo, body weights in both groups were not different. In the SL group, at 12 mo, systolic blood pressure was higher and creatinine clearance was lower than the same in controls (P < 0.05). Numbers of CD68 (ED1)-positive macrophages and apoptotic cells in renal cortex were higher in SL rats (P < 0.05). Furthermore, index scores for glomerulosclerosis and tubulointerstitial fibrosis were higher in the SL group (P < 0.05). Significantly less glomeruli per section area were found in aging SL rats (P < 0.05). Immunoblotting and immunohistochemistry showed decreased intrarenal renin expression in SL rats (P < 0.05).

CONCLUSION

Early postnatal overnutrition can potentiate structural and functional abnormalities in the aging kidney and can lead to systolic hypertension with reduced intrarenal renin activity.

Involvement of the skeletal renin-angiotensin system in age-related osteoporosis of ageing mice

The local tissue-specific renin-angiotensin system (RAS) was identified. The aim of this study was to investigate the role of local bone RAS in the osteoporosis of aging mice. Twelve-month-old and two-month-old male mice were respectively assigned to the ageing and young groups. The tibias and femurs were collected for an analysis of histomorphology, bone mass, and gene and protein expression. H&E staining and micro-CT measurement showed a loss of the trabecular bone network and decrease of bone mineral density in the proximal tibial metaphysis of the aged mice. The PCR results indicated the significant up-regulation of renin and angiotensinogen (AGT) mRNA expression in both the tibia and femur of the ageing mice. Western blotting data showed that the tibial angiotensin II protein expression was significantly increased in the ageing group. The enhancement of renin and AGT expression in the bone tissue resulted in the increased production of angiotensin II which plays an important role in the pathology of age-related osteoporosis.

Cardiac aging: from molecular mechanisms to significance in human health and disease

Cardiovascular diseases (CVDs) are the major causes of death in the western world. The incidence of cardiovascular disease as well as the rate of cardiovascular mortality and morbidity increase exponentially in the elderly population, suggesting that age per se is a major risk factor of CVDs. The physiologic changes of human cardiac aging mainly include left ventricular hypertrophy, diastolic dysfunction, valvular degeneration, increased cardiac fibrosis, increased prevalence of atrial fibrillation, and decreased maximal exercise capacity. Many of these changes are closely recapitulated in animal models commonly used in an aging study, including rodents, flies, and monkeys. The application of genetically modified aged mice has provided direct evidence of several critical molecular mechanisms involved in cardiac aging, such as mitochondrial oxidative stress, insulin/insulin-like growth factor/PI3K pathway, adrenergic and renin angiotensin II signaling, and nutrient signaling pathways. This article also reviews the central role of mitochondrial oxidative stress in CVDs and the plausible mechanisms underlying the progression toward heart failure in the susceptible aging hearts. Finally, the understanding of the molecular mechanisms of cardiac aging may support the potential clinical application of several "anti-aging" strategies that treat CVDs and improve healthy cardiac aging.

Inhibition of NF-κB-induced inflammatory responses by angiotensin II antagonists in aged rat kidney

In this study, we explored the mechanisms by which the angiotensin converting enzyme inhibitor (ACEI), enalapril, and the Ang II receptor blocker (ARB), losartan suppress oxidative stress and NF-κB activation-induced inflammatory responses in aged rat kidney. The experimentations were carried out utilizing aged (24-month-old) Brown Norway×Fischer 344 (F1) male rats which were randomized into 3 groups and administered enalapril (40 mg/kg), losartan (30 mg/kg) or placebo for 6 months (daily p.o.). The level of reactive species (RS), peroxynitrite (ONOO(-)), GSH/GSSG and lipid peroxidation were measured. The activity of the pro-inflammatory transcription factor NF-κB, and gene expression of proteins in upstream signaling cascades were measured by electro-mobility shift assay (EMSA) and Western blotting. Enalapril and losartan differentially attenuated redox imbalance and the redox-sensitive transcription factor, the NF-κB pathway. Furthermore, stimulation of the NF-κB activation pathway by phosphorylation of p65 was attenuated by both compounds. Moreover, mediation of phosphorylation of p65 by phosphorylation of IκB kinase αβ (IKKαβ) and mitogen- and stress-activated protein kinase-1 (MSK-1), were also inhibited by enalapril and losartan. Finally, both compounds also lowered expression of NF-κB-dependent inflammatory genes, such as cyclooxygenase-2 (COX-2), and inducible NO synthase (iNOS). Only losartan lowered levels of 5-lipoxygenase (5-LOX). These findings indicate that enalapril and losartan differentially suppress inflammatory responses via inhibition of oxidative stress-induced NF-κB activation in aged rat kidney.

Angiotensin inhibition and longevity: a question of hydration

With the advancement of medical and investigative science, it is somewhat surprising that although it is possible to stabilise medical patients with hypertension and the associated kidney dysfunction, obesity, diabetes and even cancer, there is still no clear method of significantly reducing these chronic disease pathologies, and thus, extending life expectancy. There is one hormone common to these pathologies, the antagonism of which goes some way to clinical improvements, and this is angiotensin, which is released during hypovolaemia. Angiotensin antagonists are used to treat many of these pathologies, and it has been shown in the obesity literature that angiotensin antagonists decrease weight, but also increase the drinking of water. Increased cellular hydration, and hence, improved mitochondrial metabolism could be one of the mechanisms for the reduction in weight seen in these studies, as well as for reducing the other pathologies, all showing metabolic dysfunction. It appears that the application of straightforward physiological regulation might be an appropriate medical approach to the prevention of hypertension, kidney disease, obesity, diabetes and cancer, and thus, to an increased life expectancy.