Renal haemodynamic characteristics in patients with lupus nephritis

Autoimmune-mediated renal disease and hypertension

Hypertension is a major risk factor for cardiovascular disease, chronic kidney disease (CKD), and mortality. Troublingly, hypertension is highly prevalent in patients with autoimmune renal disease and hastens renal functional decline. Although progress has been made over the past two decades in understanding the inflammatory contributions to essential hypertension more broadly, the mechanisms active in autoimmune-mediated renal diseases remain grossly understudied. This Review provides an overview of the pathogenesis of each of the major autoimmune diseases affecting the kidney that are associated with hypertension, and describes the current state of knowledge regarding hypertension in these diseases and their management. Specifically, discussion focuses on Systemic Lupus Erythematosus (SLE) and Lupus Nephritis (LN), Immunoglobulin A (IgA) Nephropathy, Idiopathic Membranous Nephropathy (IMN), Anti-Neutrophil Cytoplasmic Antibody (ANCA)-associated glomerulonephritis, and Thrombotic Thrombocytopenic Purpura (TTP). A summary of disease-specific animal models found to exhibit hypertension is also included to highlight opportunities for much needed further investigation of underlying mechanisms and novel therapeutic approaches.

Proliferative Glomerulonephritis: Risk Factor for Hypertension in Lupus

Studies report a high prevalence of hypertension in lupus, reaching up to 74%. The incidence of hypertension in SLE patients is increased with the severity of the kidney damage. This work was carried out with the objective of determining the prevalence of hypertension in lupus nephritis and to seek the existence of an association between the presence of a proliferative glomerulonephritis and hypertension. Patients and Methods. This was a case-control study, carried out in the nephrology department of the Aristide Le Dantec University Hospital in Dakar. All records of patients with lupus nephritis over a 10-year period, from January 01, 2007, to December 31, 2016, were included. Results. During the study period, out of 64 lupus nephritis records collected, 28 patients had hypertension, for a hospital prevalence of 43.75%. The mean age of the patients was 30.64 years ± 10.44. There were 24 women and 4 men. The mean systolic blood pressure was 156 mmHg (110–220) and the mean diastolic blood pressure was 100 mmHg (80–130). The mean serum creatinine was 29.48 mg/l ± 24.99. The mean proteinuria was 4.50 g/24 h ± 2.87. Hypertriglyceridemia was observed in one patient. Hypercholesterolemia was present in 3 patients. HDL levels were normal in all patients and elevated LDL levels were noted in all 4 patients. None of our patients had diabetes. Class III was found in 11 cases, class IV in 14 cases, pure class V in 2 cases, and class II in 1 case. Hypertension was associated with the presence of proliferative glomerulonephritis (odds ratio, 7.45; 95% CI, 1.9 to 29.1; p=0.002). Conclusion. Hypertension is common in lupus nephritis. The presence of a proliferative glomerulonephritis is a risk factor for the development of arterial hypertension. Screening and adequate management of hypertension are essential for the prevention of the progression of chronic kidney disease in lupus.

Blood pressure and albuminuria in a female mouse model of systemic lupus erythematosus: impact of long-term high salt consumption

Hypertension and kidney involvement are common in patients with autoimmune disease. Sodium intake is linked to hypertension in both human and animal studies. Evidence suggests that dietary salt may be an important environmental factor that promotes autoimmune activity. Therefore, we hypothesized that a long-term high-salt diet would accelerate the progression of autoimmunity, hypertension, and albuminuria during systemic lupus erythematosus (SLE), an autoimmune disease that predominantly affects young women and has a high prevalence of hypertension and renal disease. To test this hypothesis, an established experimental model of SLE (female NZBWF1 mice) that develops hypertension and renal disease was used. SLE mice were fed a high-salt (4% NaCl) or normal (0.4% NaCl) diet for 24 wk beginning at 10 wk of age and ending at 34 wk of age, a time by which female NZBWF1 mice typically have hypertension and exhibit signs of renal disease. Plasma anti-dsDNA autoantibodies were measured as an indicator of active SLE disease, and urinary albumin was monitored longitudinally as a marker of renal disease. Arterial pressure was measured in conscious, freely moving mice at 34 wk of age. Urinary endothelin-1 (ET-1) excretion, renal endothelin A and B receptor protein expression, and renal mRNA expression of NOS1, NOS2, NOX2, MCP-1, TNF-α, serum- and glucocorticoid-regulated kinase 1, and interleukin-2 (IL-2) were assessed to determine the impact on gene products commonly altered by a high-salt diet. SLE mice fed a high-salt diet had increased circulating autoantibodies, but the high-salt diet did not significantly affect albuminuria or arterial pressure. Urinary ET-1 excretion was increased, whereas renal endothelin A receptor and IL-2 expression were decreased in response to a high-salt diet. These data suggest that a chronic high-salt diet may not accelerate cardiovascular and renal consequences commonly associated with SLE.

Curcumin attenuates autoimmunity and renal injury in an experimental model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder with prevalent hypertension and renal disease. To avoid side effects of immunosuppressive drugs, alternative therapies are needed. Curcumin has been used in Eastern medicine for its anti‐inflammatory and antioxidant properties. This study tested whether oral curcumin administration attenuates autoimmunity and renal injury during SLE. Female NZBWF1 (model of SLE) and NZW/LacJ (control) mice were administered curcumin (500 mg kg^‐1 day^‐1, oral gavage) for 14 days in two separate groups beginning at either 26 or 32 weeks of age. Body weight and composition were monitored throughout the study. Immune activity was assessed by spleen weight, circulating dsDNA autoantibodies, and B lymphocytes. Renal injury (albumin excretion, glomerulosclerosis, blood urea nitrogen (BUN)) was measured as a hemodynamic function (glomerular filtration rate (GFR), mean arterial pressure (MAP)) in conscious mice. Body weight and composition were maintained in curcumin‐treated SLE mice, but decreased in vehicle‐treated SLE mice. Curcumin‐treated SLE mice had lower spleen weight and renal injury (glomerulosclerosis) compared to vehicle‐treated SLE mice when treatment started at 26 weeks of age. When curcumin treatment started at 32 weeks of age, renal injury (glomerulosclerosis, BUN) was reduced in SLE mice compared to vehicle‐treated SLE mice. GFR was reduced, and MAP was increased in vehicle‐treated SLE mice compared to controls; however, these were not improved with curcumin. No significant changes were observed in curcumin‐treated control mice. These data suggest that curcumin modulates autoimmune activity and may lessen renal injury in female mice with SLE.

Clinical and histopathological features and short-term outcomes of lupus nephritis: a prospective study of 100 Egyptian patients

OBJECTIVE

The short-term outcomes of lupus nephritis (LN) are variable and unpredictable among individuals. We aimed to evaluate the clinical and histopathological features and short-term renal outcomes in LN patients.

METHODS

This was a prospective cohort study carried out at nephrology and rheumatology units in Egypt between 2018 and 2019. A total of 100 patients with biopsy-proven LN were studied. Patients were evaluated for response after six months.

RESULTS

The female-to-male ratio was 8.1:1. About 70% of patients were hypertensive at disease onset, with rates for classes I, II, III, IV, V and VI LN being 1%, 7%, 20%, 53%, 14% and 6%, respectively. Among the immunosuppressive drugs used for induction, mycophenolate mofetil (MMF) represented the most commonly used (44%) followed by cyclophosphamide (CYC; 37%). After six months of follow-up, about two thirds of patients achieved remission. There was no significant difference in remission rate between MMF and CYC. On multivariate analysis, serum creatinine (SCr) at presentation was the most significant predictor of renal recovery. According to the receiver operating characteristic curve, the cut-off value of SCr was 1.6 mg/dL, with a sensitivity of 76% and specificity of 71% predicting renal recovery. Repeat renal biopsy was needed in 10 patients; class and treatment strategy changed in 40% and 70% of them, respectively.

CONCLUSION

Our findings in Egyptian LN patients compare favourably with most studies.

Temporal hemodynamic changes in a female mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease characterized by circulating autoantibodies, prevalent hypertension, renal injury, and cardiovascular disease. Onset of the disease often occurs in young women of childbearing age. Although kidney involvement is common to patients with SLE, little is known about temporal changes in renal hemodynamic function and its relationship to the pathogenesis of hypertension during autoimmune diseases. We hypothesized that the loss of immunological tolerance and subsequent production of autoantibodies in SLE leads to impaired renal hemodynamic function that precedes the development hypertension. Female NZBWF1 (SLE) mice and female NZW/LacJ (control) mice were instrumented with carotid artery and jugular vein catheters to determine mean arterial pressure (MAP) and glomerular filtration rate, respectively, at ages of 15, 20, 24, 28, 31, and 34 wk. In addition, urinary albumin excretion, blood urea nitrogen, circulating autoantibodies, and glomerulosclerosis were assessed at each age. Levels of circulating autoantibodies are increased between 24 and 28 wk of age in NZBWF1 mice and were significantly greater than in control mice. Glomerular filtration rate was significantly increased at 28 wk of age in NZBWF1 mice followed by a sharp decline at 34 wk of age. NZBWF1 mice had an increase in MAP that occurred by 34 wk of age. These data show that changes in circulating autoantibodies, renal hemodynamic function, and glomerular injury occur in NZBWF1 mice before changes in MAP, suggesting an important mechanistic role for autoimmunity to directly impair renal hemodynamic function and promote the development of hypertension.

High frequency of nocturnal hypertension in lupus nephritis: should ABPM be implemented in usual practice?

INTRODUCTION/OBJECTIVES

Hypertension management in lupus nephritis (LN) is guided by in-office blood pressure (BP); however, recent studies demonstrate that lupus patients frequently have nocturnal hypertension and reduced BP dipping. The aim of the study was to evaluate 24-h blood pressure in patients with active LN and after response to treatment.

METHODS

Seventy active LN patients were evaluated during a LN flare by ambulatory blood pressure monitoring (ABPM). Later, 10 patients with complete response were re-evaluated after 12 months along with 20 matched controls. Overall, daytime and nightime BP, day-to-night dipping, BP load and variability, and the incidence of abnormal BP patterns were assessed. Blood pressure levels were correlated with clinical and histologic parameters and independent associations evaluated by linear regression.

RESULTS

Overall systolic hypertension occurred in 25 (36%) patients and diastolic hypertension in 28 (40%). Nighttime systolic and diastolic hypertension occurred in 35 (50%) and 44 (63%) of patients, respectively. Nocturnal systolic day-to-night BP decrease was abnormal in 59 (84%) patients. Only 18 (26%) were diagnosed with HT by in-office evaluation while 29 (41%) had masked hypertension (MH)/masked uncontrolled hypertension (MUCH), and 3 (4%) had white coat hypertension. Patients with MH had lower eGFR, complement C3, hemoglobin, and higher systolic variability compared with patients with normal BP. Systolic and diastolic BP levels were associated with the years under corticosteroid treatment, activity biomarkers (proteinuria, complement C3), and the degree of interstitial inflammation in the kidney biopsy. A re-evaluation at 12 months showed that although 9 out of 10 patients had normal in-office BP and BP loads improved, still 5 patients remained with MH due to nocturnal hypertension, and 7 remained with abnormal day-to-night dipping. These numbers were higher than those of matched controls.

CONCLUSIONS

Due to the high frequency of nocturnal hypertension and abnormal day-to-night dipping, office BP measurements alone may not be sufficient to guide hypertension management in patients with LN.Key Points• Nocturnal hypertension and abnormal BP patterns are frequent and not detectable by the standard in-office BP evaluation in LN patients.• BP abnormalities may not be fully corrected after a complete clinical response to treatment in lupus nephritis and are only detectable by ABPM.• The degree of interstitial inflammation in the kidney biopsy in LN patients is associated to BP levels. This supports the hypotheses underlining the role of interstitial inflammation in salt sensitivity and hypertension.

A review of non-immune mediated kidney disease in systemic lupus erythematosus: A hypothetical model of putative risk factors

About half of patients with systemic lupus erythematosus (SLE) are diagnosed with lupus nephritis (LN). Patients with SLE are also at increased risk for diabetes, hypertension and obesity, which together account for >70% of end-stage renal disease in the general population. The frequencies of non-LN related causes of kidney disease, and their contribution to kidney disease development and progression among patients with SLE have been inadequately studied. We hypothesize that a substantial, and increasing proportion of kidney pathology in patients with SLE might not directly relate to LN but instead might be explained by non-immune mediated factors such as diabetes, hypertension, and obesity. The goal of the manuscript is to draw attention to hypertension, diabetes and obesity as potential alternative causes of kidney damage in patients with SLE. Further, we suggest that misclassification of kidney disease etiology in patients with SLE might have important ramifications for clinical trial recruitment, epidemiologic investigation, and clinical care. Future studies aiming to elucidate and distinguish discrete causes of kidney disease - both clinically and histologically - among patients with SLE are desperately needed as improved understanding of disease mechanisms is paramount to advancing therapeutic discovery. Collaboration among rheumatologists, pathologists, nephrologists, and endocrinologists, and the availability of dedicated research funding, will be critical to the success of such efforts.

Mechanisms of hypertension in autoimmune rheumatic diseases

Patients with autoimmune rheumatic diseases including rheumatoid arthritis and systemic lupus erythematosus have an increased prevalence of hypertension. There is now a large body of evidence showing that the immune system is a key mediator in both human primary hypertension and experimental models. Many of the proposed immunological mechanisms leading to primary hypertension are paralleled in autoimmune rheumatic disorders. Therefore, examining the link between autoimmunity and hypertension can be informative for understanding primary hypertension. This review examines the prevalent hypertension, the immune mediators that contribute to the prevalent hypertension and their impact on renal function and how the risk of hypertension is potentially influenced by common hormonal changes that are associated with autoimmune rheumatic diseases.

Linked Articles

This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc

Autoimmune Disease-Associated Hypertension

Purpose of Review

To highlight important new findings on the topic of autoimmune disease-associated hypertension.

Recent Findings

Autoimmune diseases including systemic lupus erythematosus and rheumatoid arthritis are associated with an increased risk for hypertension and cardiovascular disease. A complex interaction among genetic, environmental, hormonal, and metabolic factors contribute to autoimmune disease susceptibility while promoting chronic inflammation that can lead to alterations in blood pressure. Recent studies emphasize an important mechanistic role for autoantibodies in autoimmune disease-associated hypertension. Moving forward, understanding how sex hormones, neutrophils, and mitochondrial dysfunction contribute to hypertension in autoimmune disease will be important.

Summary

This review examines the prevalent hypertension in autoimmune disease with a focus on the impact of immune system dysfunction on vascular dysfunction and renal hemodynamics as primary mediators with oxidative stress as a main contributor.

Hypertension: Focus on autoimmunity and oxidative stress

Understanding the causal role of the immune and inflammatory responses in hypertension has led to questions regarding the links between hypertension and autoimmunity. Immune pathology in primary hypertension mimics several autoimmune mechanisms observed in the pathogenesis of systemic lupus erythematosus, psoriasis, systemic sclerosis, rheumatoid arthritis and periodontitis. More importantly, the prevalence of hypertension in patients with these autoimmune diseases is significantly increased, when compared to control populations. Clinical and epidemiological evidence is reviewed along with possible mechanisms linking hypertension and autoimmunity. Inflammation and oxidative stress are linked in a self-perpetuating cycle that significantly contributes to the vascular dysfunction and renal damage associated with hypertension. T cell, B cell, macrophage and NK cell infiltration into these organs is essential for this pathology. Effector cytokines such as IFN-γ, TNF-α and IL-17 affect Na⁺/H⁺ exchangers in the kidney. In blood vessels, they lead to endothelial dysfunction and loss of nitric oxide bioavailability and cause vasoconstriction. Both renal and vascular effects are, in part, mediated through induction of reactive oxygen species-producing enzymes such as superoxide anion generating NADPH oxidases and dysfunction of anti-oxidant systems. These mechanisms have recently become important therapeutic targets of novel therapies focused on scavenging oxidative (isolevuglandin) modification of neo-antigenic peptides. Effects of classical immune targeted therapies focused on immunosuppression and anti-cytokine treatments are also reviewed.

Understanding mechanisms of hypertension in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that predominately affects women of reproductive age. Hypertension is an important cardiovascular risk factor that is prevalent in this patient population. Despite the high incidence of hypertension in women with SLE, the pathophysiological mechanisms underlying the development of hypertension remain poorly understood. This review will focus on disease-related factors, including inflammation, autoantibodies, and sex hormones that may contribute to hypertension in patients with SLE. In addition, we will highlight studies performed by our laboratory using the female NZBWF1 (F1 hybrid of New Zealand Black and New Zealand White strains) mouse model, a spontaneous model of SLE that mimics human disease and develops hypertension and renal injury. Specifically, using female NZBWF1 mice, we have demonstrated that multiple factors contribute to the pathogenesis of hypertension, including the inflammatory cytokine, tumor necrosis factor (TNF)-α, oxidative stress, as well as B-cell hyperactivity and autoantibody production.

Blood pressure and renal hemodynamic responses to acute angiotensin II infusion are enhanced in a female mouse model of systemic lupus erythematosus

Inflammation and immune system dysfunction contributes to the development of cardiovascular and renal disease. Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that carries a high risk for both renal and cardiovascular disease. While hemodynamic changes that may contribute to increased cardiovascular risk have been reported in humans and animal models of SLE, renal hemodynamics have not been widely studied. The renin-angiotensin system (RAS) plays a central role in renal hemodynamic control, and although RAS blockade is a common therapeutic strategy, the role of RAS in hemodynamic function during SLE is not clear. This study tested whether mean arterial pressure (MAP) and renal hemodynamic responses to acute infusions of ANG II in anesthetized animals were enhanced in an established female mouse model of SLE (NZBWF1). Baseline MAP was not different between anesthetized SLE and control (NZWLacJ) mice, while renal blood flow (RBF) was significantly lower in mice with SLE. SLE mice exhibited an enhanced pressor response and greater reduction in RBF after ANG II infusion. An acute infusion of the ANG II receptor blocker losartan increased RBF in control mice but not in mice with SLE. Renin and ANG II type 1 receptor expression was significantly lower, and ANG II type 2 receptor expression was increased in the renal cortex from SLE mice compared with controls. These data suggest that there are fewer ANG II receptors in the kidneys from mice with SLE but that the existing receptors exhibit an enhanced sensitivity to ANG II.

The pathophysiology of hypertension in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that predominantly affects women during their reproductive years. Although SLE can affect any organ system, the kidneys are prominently involved in the form of immune complex glomerulonephritis. In addition, in women with SLE, risk for the development of cardiovascular disease is dramatically increased. Hypertension is a major risk factor for cardiovascular disease and is highly prevalent in women with SLE. Nevertheless, there has been little exploration of the pathophysiological mechanisms that promote SLE hypertension. This review discusses the role of several mechanisms, with an emphasis on the kidney, in SLE hypertension. These mechanisms include the renin-angiotensin system, endothelin, oxidative stress, sex steroids, metabolic changes, peroxisome proliferator-activated receptor-gamma, and, perhaps most importantly, chronic inflammation and cytokines. Growing evidence suggests a link between chronic inflammation and hypertension. Therefore, elucidation of mechanisms that promote SLE hypertension may be of significant value not only for patients with SLE, but also for a better understanding of the basis for essential hypertension.

Prognostic Value of Renal Hemodynamic Characteristics in Patients with Proliferative Lupus Nephritis

BACKGROUND/AIM

Previous studies showed that renal hemodynamic parameters, especially the filtration fraction (FF), are decreased in patients with active lupus nephritis (LN). In this study, we evaluate the prognostic value of renal hemodynamic function tests on the renal outcome in patients with proliferative LN.

METHODS

We performed a retrospective cohort study of our patients with proliferative LN from 1986 to 2005. Glomerular filtration rate (GFR) and FF before treatment were measured. Treatment failure was defined as a renal relapse or development of end-stage renal disease.

RESULTS

Thirty-seven patients were included. The median follow-up period was 8 years. Creatinine clearance, GFR, and FF before treatment correlated with the creatinine clearance at the end of follow-up (p = 0.001, p = 0.006, and p = 0.04, respectively). The FF was decreased in 92% of our patients, but FF and GFR did not have a prognostic value with regard to treatment failure.

CONCLUSIONS

Most patients with proliferative LN had a low FF. Low GFR and FF at baseline were correlated with a worse renal function at the end of follow-up, but this had no prognostic value in individual patients.