DOCA/NaCl-induced chronic kidney disease: a comparison of renal nitric oxide production in resistant and susceptible rat strains

The NOS/NO System in Renal Programming and Reprogramming

Nitric oxide (NO) is a gaseous signaling molecule with renoprotective properties. NO can be produced in NO synthase (NOS)-dependent or -independent manners. NO deficiency plays a decisive role in chronic kidney disease (CKD). Kidney development can be affected in response to adverse intrauterine conditions that induce renal programming, thereby raising the risk of developing CKD in adulthood. Conversely, detrimental programming processes could be postponed or halted prior to the onset of CKD by early treatments, namely reprogramming. The current review provides an overview of the NOS/NO research performed in the context of renal programming and reprogramming. NO deficiency has been increasingly found to interact with the different mechanisms behind renal programming, such as oxidative stress, aberrant function of the renin-angiotensin system, disturbed nutrient-sensing mechanisms, dysregulated hydrogen sulfide signaling, and gut microbiota dysbiosis. The supplementation of NOS substrates, the inhibition of asymmetric dimethylarginine (ADMA), the administration of NO donors, and the enhancement of NOS during gestation and lactation have shown beneficial effects against renal programming in preclinical studies. Although human data on maternal NO deficiency and offspring kidney disease are scarce, experimental data indicate that targeting NO could be a promising reprogramming strategy in the setting of renal programming.

Oxidative Stress-Induced Hypertension of Developmental Origins: Preventive Aspects of Antioxidant Therapy

Hypertension remains the leading cause of disease burden worldwide. Hypertension can originate in the early stages of life. A growing body of evidence suggests that oxidative stress, which is characterized as a reactive oxygen species (ROS)/nitric oxide (NO) disequilibrium, has a pivotal role in the hypertension of developmental origins. Results from animal studies support the idea that early-life oxidative stress causes developmental programming in prime blood pressure (BP)-controlled organs such as the brain, kidneys, heart, and blood vessels, leading to hypertension in adult offspring. Conversely, perinatal use of antioxidants can counteract oxidative stress and therefore lower BP. This review discusses the interaction between oxidative stress and developmental programming in hypertension. It will also discuss evidence from animal models, how oxidative stress connects with other core mechanisms, and the potential of antioxidant therapy as a novel preventive strategy to prevent the hypertension of developmental origins.

Animal Models of Renal Pathophysiology and Disease

Renal diseases remain devastating illnesses with unacceptably high rates of mortality and morbidity worldwide. Animal models are essential tools to better understand the pathomechanisms of kidney-related illnesses and to develop new, successful therapeutic strategies. Magnetic resonance imaging (MRI) has been actively explored in the last decades for assessing renal function, perfusion, tissue oxygenation as well as the degree of fibrosis and inflammation. This chapter aims to provide a comprehensive overview of animal models of acute and chronic kidney diseases, highlighting MRI-specific considerations, advantages, and pitfalls, and thus assisting the researcher in experiment planning.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.

Urinary Markers and Chronic Effect of Physical Exercise

Chronic kidney disease (CKD) is a type of kidney disease in which there is gradual loss of kidney function over a period of months to years. The clinical protocol of CKD forecasts that markers such as serum creatinine, the estimate of the glomerular filtration rate value, microalbuminuria, cystatin c are evaluated as routine markers. In recent years, new studies have identified new markers to diagnose and assess the level of kidney damage.The prevalence of CKD increases in subjects suffering from cardiovascular and metabolic diseases. The highest risk of cardiovascular risk in the CKD patient compared to the general population is related to risk factors such as hypertension, obesity, and specific renal disease factors such as albuminuria.Physical exercise, especially aerobic, has been seen through the analysis of urinary markers, able to mitigate the adverse effect of sedentary, hypertension and interstitial damage in patients with CKD and decrease the urinary levels liver-type fatty acid binding protein (L-FABP) and lower urinary albumin excretion.

5/6 nephrectomy induces different renal, cardiac and vascular consequences in 129/Sv and C57BL/6JRj mice

Experimental models of cardiovascular diseases largely depend on the genetic background. Subtotal 5/6 nephrectomy (5/6 Nx) is the most frequently used model of chronic kidney disease (CKD) in rodents. However, in mice, cardiovascular consequences of 5/6 Nx are rarely reported in details and comparative results between strains are scarce. The present study detailed and compared the outcomes of 5/6 Nx in the 2 main strains of mice used in cardiovascular and kidney research, 129/Sv and C57BL/6JRj. Twelve weeks after 5/6 Nx, CKD was demonstrated by a significant increase in plasma creatinine in both 129/Sv and C57BL/6JRj male mice. Polyuria and kidney histological lesions were more pronounced in 129/Sv than in C57BL/6JRj mice. Increase in albuminuria was significant in 129/Sv but not in C57BL/6JRj mice. Both strains exhibited an increase in systolic blood pressure after 8 weeks associated with decreases in cardiac systolic and diastolic function. Heart weight increased significantly only in 129/Sv mice. Endothelium-dependent mesenteric artery relaxation to acetylcholine was altered after 5/6 Nx in C57BL/6JRj mice. Marked reduction of endothelium-dependent vasodilation to increased intraluminal flow was demonstrated in both strains after 5/6 Nx. Cardiovascular and kidney consequences of 5/6 Nx were more pronounced in 129/Sv than in C57BL/6JRj mice.

Role of Nitric Oxide Pathway in Development and Progression of Chronic Kidney Disease in Rats Sensitive and Resistant to its Occurrence in an Experimental Model of 5/6 Nephrectomy

BACKGROUND Understanding the mechanisms conditioning development of chronic kidney disease (CKD) is still a challenge. The aim of this study was to evaluate the activity of the intrarenal nitric oxide (NO) pathway in the context of sensitivity or resistance of different animal strains to the development and degree of renal failure. MATERIAL AND METHODS Two rat strains were used: Wistar (WR) and Sprague-Dawley rats (SDR) in a model of CKD - 5/6 nephrectomy. We assessed parameters of renal failure and expression of nitric oxide synthase (NOS) isoforms in renal cortex and medulla. RESULTS We did not observe renal failure in WR, and CKD developed in SDR with increase of creatinine and urea concentration as well as decrease of diuresis and glomerular filtration. In the renal cortex, baseline expression of NOS2 was higher in WR than in SDR. 5/6 nephrectomy resulted in reduction of NOS2 in both strains and NOS3 in WR. In the renal medulla, baseline NOS2 expression was higher in SDR, and nephrectomy resulted in its decrease only in SDR. Although baseline NOS3 expression was higher in SDR, the NOS3 expression after nephrectomy was higher in WR rats. CONCLUSIONS In model of CKD - 5/6 nephrectomy, SDR proved to be sensitive and WR resistant to development of CKD. The intrarenal activity of the nitric oxide pathway was the factor that differentiated both strains. This mechanism may be responsible for insensitivity of WR to development of renal failure in this model of CKD.

Strain of experimental animals and modulation of nitric oxide pathway: their influence on development of renal failure in an experimental model of hepatorenal syndrome

INTRODUCTION

Pathomechanism of HRS is still poorly understood. The aim of our study was: (1) to test whether different strains of rats could develop typical HRS, and (2) to estimate the influence of activation and inhibition of nitric oxide for development of renal failure in course of HRS.

MATERIAL AND METHODS

First, we used 16 of Wistar and 16 of Sprague-Dawley rats in galactosamine model of HRS. Next, we used 48 of SDR rats, which received saline, N-nitro-L-arginine or L-arginine before and after liver damage. Twenty four hours urine and blood samples were collected 48 h after saline or Ga1N injection. Biochemical parameters were determined in serum or urine and then creatinine clearance and osmolality clearance were calculated. Liver and kidney tissues were collected for histopathological examination.

RESULTS

Liver failure developed in all tested groups with significant increase of bilirubin (p < 0.001), ALT (p < 0.001) and ammonia (p < 0.001). Nevertheless we did not achieve any evidence of renal failure in Wistar, but we found typical renal failure in Sprague-Dawley group with significant decrease in creatinine clearance (p < 0.0012) and increase in concentration of creatinine and urea (p < 0.001) and (p < 0.001) respectively. Inhibition of NOS prevented development of renal failure with significant improvement of GFR both before (p < 0.0017) and after (p < 0.003) Ga1N injection. Injection of L-arginine after Ga1N injection did not caused significant improvement of GFR.

CONCLUSIONS

Our study showed, that genetic factors might be responsible for development of renal failure in course of HRS and nitric oxide play important role in acute model of this syndrome.

Reduced NO production rapidly aggravates renal function through the NF-κB/ET-1/ETA receptor pathway in DOCA-salt-induced hypertensive rats

AIMS

It has been reported that endothelin-1 (ET-1) overproduction and reduced nitric oxide (NO) production are closely related to the progression of renal diseases. In the present study, we examined the interrelation between ET-1 and NO system using rats treated with the combination of deoxycorticosterone acetate (DOCA)-salt and a non selective NO synthase inhibitor N(ω)-nitro-L-arginine (NOARG).

MAIN METHODS

Rats were treated with DOCA-salt (15 mg/kg, plus drinking water containing 1% NaCl) for two weeks, and then additional treatment of NOARG (0.6 mg/ml in the drinking water) was performed for three days.

KEY FINDINGS

Combined treatment of DOCA-salt and NOARG drastically developed the severe renal dysfunction and tissue injury. This treatment additionally enhanced renal ET-1 production compared to the rats treated with DOCA-salt alone, whereas a selective ET(A) receptor antagonist ABT-627 completely prevented renal dysfunction and tissue injury. On the other hand, combined treatment of DOCA-salt and NOARG induced the phosphorylation of inhibitory protein kappa B (IκB), followed by the activation of nuclear factor-kappa B (NF-κB) in the kidney. In addition, pyrrolidine-dithiocarbamate completely suppressed not only NF-κB activation but also renal dysfunction and ET-1 overproduction.

SIGNIFICANCE

These results suggest that NF-κB/ET-1/ET(A) receptor-mediated actions are responsible for the increased susceptibility to DOCA-salt induced renal injuries in the case of reduced NO production.

Association between an increment of 30-minute postchallenge plasma glucose and urine albumin excretion exists in postmenopausal women but not in premenopausal women

OBJECTIVE

Usually, the increment of 30-minute postchallenge plasma glucose (ΔG30-0) represents the highest glucose spike in the population with normal glucose regulation (NGR). The aim of this study was to explore the differences in ΔG30-0 and urinary albumin excretion, a marker for widespread vascular damage, between premenopausal and postmenopausal women, and the relationship between ΔG30-0 and urinary albumin excretion.

METHODS

A population-based cross-sectional study, consisting of 5,289 participants aged 20 to 75 years from six different communities, was conducted in Shanghai between 2007 and 2008. We assessed postchallenge blood glucose and insulin at 0-, 30-, and 120-minute urinary albumin and creatinine. ΔG30-0 was calculated as 30-minute postchallenge glucose minus fasting plasma glucose, and the albumin-to-creatinine ratio (ACR) was used to reflect urinary albumin excretion. Among these, the data of 2,240 women with NGR were analyzed.

RESULTS

(1) Postmenopausal women had higher ΔG30-0 and ACR than did premenopausal women (3.55 ± 1.52 mmol/L vs 3.21 ± 1.49 mmol/L and 6.92 [4.91-10.99] mg/g vs 6.18 [4.17-10.07] mg/g, respectively; all P < 0.001). (2) Multivariable logistic regression showed that ΔG30-0 was independently associated with increased ACR in postmenopausal women with NGR (odds ratio, 1.10; P = 0.048) but not in premenopausal women. (3) The main factor associated with ΔG30-0 was the early-phase glucose disposition index drawn from the multivariable linear regression, which explained approximately 19% and 28% of the variation of ΔG30-0 in premenopausal and postmenopausal women, respectively (both P < 0.001).

CONCLUSIONS

In the NGR population, postmenopausal women have higher ΔG30-0 and ACR compared with premenopausal women. The relationship between ΔG30-0 and increased urine albumin excretion existed in postmenopausal women.

Chronic nitric oxide deficiency and progression of kidney disease after renal mass reduction in the C57Bl6 mouse

BACKGROUND/AIMS

the C57Bl6 mouse is resistant to chronic kidney disease (CKD) induced by reduction of renal mass (RRM). Nitric oxide (NO) deficiency exacerbates CKD progression so this study investigated whether combination of RRM and NO deficiency would render the C57Bl6 mouse vulnerable to CKD.

METHODS

we used wild-type (WT) mice with RRM, chronic NO synthase (NOS) inhibition and a combination. Also, endothelial NOS (eNOS) knockout (KO) C57Bl6 mice were studied with and without RRM. Primary endpoints were albuminuria and structural damage.

RESULTS

both nonselective (+L-NAME) and neuronal NOS 'selective' (+7NI) NOS inhibition greatly exacerbated the albuminuria and structural damage seen with RRM in the WT mice; NOS inhibition alone had little effect. The eNOS KO mice showed marked structural damage and significant albuminuria in the shams and RRM produced minimal exacerbation of structural damage although the albuminuria was massively amplified.

CONCLUSION

these studies demonstrate that the C57Bl6 mouse is rendered vulnerable to RRM-induced CKD when concomitant NO deficiency is produced. This observation supports previous work in CKD-resistant rats and suggests that NO deficiency is required for progression of CKD.

Physical activity and albuminuria

Higher urinary albumin excretion predicts future cardiovascular disease, hypertension, and chronic kidney disease. Physical activity improves endothelial function so activity may reduce albuminuria. Among diabetics, physical activity decreases albuminuria. In nondiabetics, prior studies have shown no association. The authors explored the cross-sectional association between physical activity and albuminuria in 3,587 nondiabetic women in 2 US cohorts, the Nurses' Health Study I in 2000 and the Nurses' Health Study II in 1997. Physical activity was expressed as metabolic equivalents per week. The outcome was the top albumin/creatinine ratio (ACR) decile. Multivariate logistic regression was used. Secondary analyses explored the ACR association with strenuous activity and walking. The mean age was 58.6 years. Compared with women in the lowest physical activity quintile, those in the highest quintile had a multivariate-adjusted odds ratio for the top ACR decile of 0.65 (95% confidence interval (CI): 0.46, 0.93). The multivariate-adjusted odds ratio for the top ACR decile for those with greater than 210 minutes per week of strenuous activity compared with no strenuous activity was 0.61 (95% CI: 0.37, 0.99), and for those in the highest quintile of walking compared with the lowest quintile, it was 0.69 (95% CI: 0.47, 1.02). Greater physical activity is associated with a lower ACR in nondiabetic women.

Post-menopausal hormone use and albuminuria

BACKGROUND

Higher levels of urinary albumin excretion predict future hypertension and chronic kidney disease. Post-menopausal hormone use may influence the renin-angiotensin system and renal endothelial function, impacting albumin excretion. The association between post-menopausal hormone use and albuminuria is not well defined.

METHODS

We explored the cross-sectional association between duration of PMH use and albuminuria in 2445 post-menopausal, non-diabetic women from the Nurses' Health Study. Women were categorized as hormone non-users, past users or current users grouped by 3-year intervals of duration of use, from < or =3 years to >15 years. The outcome was the top decile of urine albumin/creatinine ratio (ACR). Multivariate logistic regression was used to assess the association between duration of PMH use and risk of being in the top decile.

RESULTS

The mean age was 66.8 years, and 57% were currently using PMH. The median ACR was 2.9 mg/g, and the 90th percentile was 9.2 mg/g. Compared with women with no history of PMH use, the odds ratio for being in the top ACR decile was lower for women with use of >6-9 years, >9-12 years, >12-15 years and >15 years, but there was no dose-response. The overall odds ratio was 0.55 (95% CI: 0.39-0.77) among women with >6 years of current PMH use compared with non-users. Current hormone use of shorter duration and past hormone use were not associated with albumin excretion.

CONCLUSIONS

Current PMH use of >6 years is associated with a lower urinary ACR in non-diabetic women.

Endothelin and NOS1/nitric oxide signaling and regulation of sodium homeostasis

PURPOSE OF REVIEW

In general, the nitric oxide and endothelin signaling pathways in the kidney promote natriuresis. The basis for this statement will first be reviewed for each of these systems. Next, this review will outline the progression of data providing support for our hypothesis that an intra-renal mechanism of endothelin activation of ETB receptors stimulates NOS1 activity and nitric oxide production to promote sodium excretion.

RECENT FINDINGS

New information in recent years has provided considerable evidence that both nitric oxide and endothelin function to regulate sodium and water balance by the kidney. Furthermore, dysfunction of these pathways may play a role in salt-sensitivity and hypertension. While a strong picture has emerged to suggest these systems are important and powerful players in sodium homeostasis, many questions remain to be answered before we can apply these mechanisms to an understanding of clinical hypertension.

SUMMARY

Salt-sensitive hypertension contributes to the growing population of patients resistant to conventional antihypertensive therapy. Thus, a thorough understanding of the mechanisms related to the control of sodium excretion will allow a more focused approach for future therapeutic studies.

Nitric oxide deficiency in chronic kidney disease

The overall production of nitric oxide (NO) is decreased in chronic kidney disease (CKD) which contributes to cardiovascular events and further progression of kidney damage. There are many likely causes of NO deficiency in CKD and the areas surveyed in this review are: 1. Limitations on substrate (l-Arginine) availability, probably due to impaired renal l-Arginine biosynthesis, decreased transport of l-Arginine into endothelial cells and possible competition between NOS and competing metabolic pathways, such as arginase. 2. Increased circulating levels of endogenous NO synthase (NOS) inhibitors, in particular asymmetric dimethylarginine (ADMA). Increased methylation of proteins and their subsequent breakdown to release free ADMA may contribute but the major culprit is probably reduced ADMA catabolism by the enzymes dimethylarginine dimethylaminohydrolases. 3. Reduced renal cortex abundance of the neuronal NOS (nNOS)α protein correlates with injury while increasing nNOSβ abundance may provide a compensatory, protective response. Interventions that can restore NO production by targeting these various pathways are likely to reduce the cardiovascular complications of CKD as well as slowing the rate of progression.