Effect of combining ACE inhibitor and statin in lupus-prone mice

Genome-wide association study on Northern Chinese identifies KLF2, DOT1L and STAB2 associated with systemic lupus erythematosus

OBJECTIVES

To identify novel genetic loci associated with systemic lupus erythematosus (SLE) and to evaluate potential genetic differences between ethnic Chinese and European populations in SLE susceptibility.

METHODS

A new genome-wide association study (GWAS) was conducted from Jining, North China, on 1506 individuals (512 SLE cases and 994 matched healthy controls). The association results were meta-analysed with existing data on Chinese populations from Hong Kong, Guangzhou and Central China, as well as GWAS results from four cohorts of European ancestry. A total of 26 774 individuals (9310 SLE cases and 17 464 controls) were included in this study.

RESULTS

Meta-analysis on four Chinese cohorts identifies KLF2 as a novel locus associated with SLE [rs2362475; odds ratio (OR) = 0.85, P=2.00E-09]. KLF2 is likely an Asian-specific locus as no evidence of association was detected in the four European cohorts (OR = 0.98, P =0.58), with evidence of heterogeneity (P=0.0019) between the two ancestral groups. Meta-analyses of results from both Chinese and Europeans identify STAB2 (rs10082873; OR= 0.89, P=4.08E-08) and DOT1L (rs4807205; OR= 1.12, P=8.17E-09) as trans-ancestral association loci, surpassing the genome-wide significance.

CONCLUSIONS

We identified three loci associated with SLE, with KLF2 a likely Chinese-specific locus, highlighting the importance of studying diverse populations in SLE genetics. We hypothesize that DOT1L and KLF2 are plausible SLE treatment targets, with inhibitors of DOT1L and inducers of KLF2 already available clinically.

Centrally Acting Angiotensin-Converting Enzyme Inhibitor Suppresses Type I Interferon Responses and Decreases Inflammation in the Periphery and the CNS in Lupus-Prone Mice

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multi-organ damage. Neuropsychiatric lupus (NPSLE) is one of the most common manifestations of human SLE, often causing depression. Interferon-α (IFNα) is a central mediator in disease pathogenesis. Administration of IFNα to patients with chronic viral infections or cancers causes depressive symptoms. Angiotensin-converting enzyme (ACE) is part of the kallikrein-kinin/renin-angiotensin (KKS/RAS) system that regulates many physiological processes, including inflammation, and brain functions. It is known that ACE degrades bradykinin (BK) into inactive peptides. We have previously shown in an in vitro model of mouse bone-marrow-derived dendritic cells (BMDC) and human peripheral blood mononuclear cells that captopril (a centrally acting ACE inhibitor-ACEi) suppressed Type I IFN responsive gene (IRG) expression. In this report, we used the MRL/lpr lupus-prone mouse model, an established model to study NPSLE, to determine the in vivo effects of captopril on Type I IFN and associated immune responses in the periphery and brain and effects on behavior. Administering captopril to MRL/lpr mice decreased expression of IRGs in brain, spleen and kidney, decreased circulating and tissue IFNα levels, decreased microglial activation (IBA-1 expression) and reduced depressive-like behavior. Serotonin levels that are decreased in depression were increased by captopril treatment. Captopril also reduced autoantibody levels in plasma and immune complex deposition in kidney and brain. Thus, ACEi's may have potential for therapeutic use for systemic and NPSLE.

Targeting the Protective Arm of the Renin-Angiotensin System to Reduce Systemic Lupus Erythematosus Related Pathologies in MRL-lpr Mice

Patients with Systemic Lupus Erythematosus (SLE) suffer from a chronic inflammatory autoimmune disease that results from the body's immune system targeting healthy tissues which causes damage to various organ systems. Patients with lupus are still in need of effective therapies to treat this complex, multi-system disease. Because polymorphisms in ACE are associated with the activity of SLE and lupus nephritis and based on well-documented renal-protective effects of Renin Angiotensin System (RAS)-modifying therapies, ACE-I are now widely used in patients with SLE with significant efficacy. Our research explores alternate ways of modifying the RAS as a potential for systemic therapeutic benefit in the MRL-lpr mouse model of SLE. These therapeutics include; angiotensin (1-7) [A(1-7)], Nor-Leu-3 Angiotensin (1-7) (NorLeu), Losartan (ARB), and Lisinopril (ACE-I). Daily systemic treatment with all of these RAS-modifying therapies significantly reduced the onset and intensity in rash formation and swelling of the paw. Further, histology showed a corresponding decrease in hyperkeratosis and acanthosis in skin sections. Important immunological parameters such as decreased circulating anti-dsDNA antibodies, lymph node size, and T cell activation were observed. As expected, the development of glomerular pathologies was also attenuated by RAS-modifying therapy. Improved number and health of mesenchymal stem cells (MSCs), as well as reduction in oxidative stress and inflammation may be contributing to the reduction in SLE pathologies. Several studies have already characterized the protective role of ACE-I and ARBs in mouse models of SLE, here we focus on the protective arm of RAS. A(1-7) in particular demonstrates several protective effects that go beyond those seen with ACE-Is and ARBs; an important finding considering that ACE-Is and ARBs are teratogenic and can cause hypotension in this population. These results offer a foundation for further pharmaceutical development of RAS-modifying therapies, that target the protective arm, as novel SLE therapeutics that do not rely on suppressing the immune system.

Renal microvascular lesions in lupus nephritis

Renal microvascular lesions, common in lupus nephritis (LN), are associated with long-term poor outcomes. There are mainly five pathological types of renal microvascular lesions in LN: (1) vascular immune complex deposits (ICD), (2) arteriosclerosis (AS), (3) thrombotic microangiopathy (TMA), (4) non-inflammatory necrotizing vasculopathy (NNV), and (5) true renal vasculitis (TRV). The pathogenesis of renal microvascular lesions in LN remains to be elucidated. The activation and dysfunction of endothelial cells, in addition to the contribution of immune system dysfunction, especially the immune complex-induced vascular inflammation and antiphospholipid antibody-associated thrombotic events, are key mechanisms in the development of vascular lesions in LN that need to be further investigated. Alteration of the microvascular environment produces an acute immunological response that recruits immune cells, such as T cells, monocytes, and macrophages, which induces platelet aggregation with microthrombus formation. There is also increased cytotoxicity caused by cytokines produced by immune cells in the kidney. Identifying the mechanism underlying the pathogenesis of renal microvascular lesions in LN might provide potential targets for the development of novel therapies.

Juvenile-onset systemic lupus erythematosus (jSLE) - Pathophysiological concepts and treatment options

The systemic autoimmune/inflammatory condition systemic lupus erythematosus (SLE) manifests before the age of 16 years in 10-20% of all cases. Clinical courses are more severe, and organ complications are more common in patients with juvenile SLE. Varying gender distribution in different age groups and increasing severity with younger age and the presence of monogenic disease in early childhood indicate distinct differences in the pathophysiology of juvenile versus adult-onset SLE. Regardless of these differences, classification criteria and treatment options are identical. In this article, we discuss age-specific pathomechanisms of juvenile-onset SLE, which are currently available and as future treatment options, and propose reclassification of different forms of SLE along the inflammatory spectrum from autoinflammation to autoimmunity.

Kallikrein-Kinin System Suppresses Type I Interferon Responses: A Novel Pathway of Interferon Regulation

The Kallikrein–Kinin System (KKS), comprised of kallikreins (klks), bradykinins (BKs) angiotensin-converting enzyme (ACE), and many other molecules, regulates a number of physiological processes, including inflammation, coagulation, angiogenesis, and control of blood pressure. In this report, we show that KKS regulates Type I IFN responses, thought to be important in lupus pathogenesis. We used CpG (TLR9 ligand), R848 (TLR7 ligand), or recombinant IFN-α to induce interferon-stimulated genes (ISGs) and proteins, and observed that this response was markedly diminished by BKs, klk1 (tissue kallikrein), or captopril (an ACE inhibitor). BKs significantly decreased the ISGs induced by TLRs in vitro and in vivo (in normal and lupus-prone mice), and in human PBMCs, especially the induction of Irf7 gene (p < 0.05), the master regulator of Type I IFNs. ISGs induced by IFN-α were also suppressed by the KKS. MHC Class I upregulation, a classic response to Type I IFNs, was reduced by BKs in murine dendritic cells (DCs). BKs decreased phosphorylation of STAT2 molecules that mediate IFN signaling. Among the secreted pro-inflammatory cytokines/chemokines analyzed (IL-6, IL12p70, and CXCL10), the strongest suppressive effect was on CXCL10, a highly Type I IFN-dependent cytokine, upon CpG stimulation, both in normal and lupus-prone DCs. klks that break down into BKs, also suppressed CpG-induced ISGs in murine DCs. Captopril, a drug that inhibits ACE and increases BK, suppressed ISGs, both in mouse DCs and human PBMCs. The effects of BK were reversed with indomethacin (compound that inhibits production of PGE2), suggesting that BK suppression of IFN responses may be mediated via prostaglandins. These results highlight a novel regulatory mechanism in which members of the KKS control the Type I IFN response and suggest a role for modulators of IFNs in the pathogenesis of lupus and interferonopathies.

Lipopolysaccharide-Induced Acute Kidney Injury Is Dependent on an IL-18 Receptor Signaling Pathway

The proinflammatory cytokine interleukin (IL)-18 is an important mediator of the organ failure induced by endotoxemia. IL-18 (known as an interferon-gamma (IFN-γ) inducing factor), and other inflammatory cytokines have important roles in lipopolysaccharide (LPS)-induced acute kidney injury (AKI). We investigated the effect of inflammatory cytokines and Toll-like receptor 4 (TLR4) expression, an event that is accompanied by an influx of monocytes, including CD4⁺ T cells and antigen-presenting cells (APCs) in IL-18Rα knockout (KO) mice and wild-type (WT) mice after LPS injection. In the acute advanced phase, the IL-18Rα KO mice showed a higher survival rate and a suppressed increase of blood urea nitrogen, increased levels of proinflammatory cytokines such as IFN-γ and IL-18, the infiltration of CD4⁺ T cells and the expression of kidney injury molecule-1 as an AKI marker. In that phase, the renal mRNA expression of the M1 macrophage phenotype and C-C chemokine receptor type 7 as the maturation marker of dendritic cells (DCs) was also significantly decreased in the IL-18Rα KO mice, although there were small numbers of F4/80⁺ cells and DCs in the kidney. Conversely, there were no significant differences in the expressions of mRNA and protein TLR4 after LPS injection between the WT and IL-18Rα KO groups. Our results demonstrated that the IL-18Rα-mediated signaling pathway plays critical roles in CD4⁺ T cells and APCs and responded more quickly to IFN-γ and IL-18 than TLR4 stimulation in the pathogenesis of LPS-induced AKI.

Signaling Rho-kinase mediates inflammation and apoptosis in T cells and renal tubules in cisplatin nephrotoxicity

Nephrotoxicity is a frequent complication of cisplatin-induced chemotherapy, in which T cells are known to promote acute kidney injury (AKI). Apoptosis and necrosis of tubules and inflammatory events also contribute to the nephrotoxicity. A delineation of the mechanisms that underlie the inappropriate renal and tubular inflammation can thus provide important insights into potential therapies for cisplatin-induced AKI. Rho-kinases are known to act as molecular switches controlling several critical cellular functions, including cell migration, cytokine production, and apoptosis. Here, we show that the Rho-kinase inhibitor fasudil attenuated cisplatin nephrotoxicity, resulting in less histological damage, improved renal function, and the infiltration of fewer leukocytes into the kidney. Renal nuclear factor-κB activation and apoptosis were reduced, and the expressions of proinflammatory renal cytokine and chemokine mRNA were decreased. Urinary and renal kidney injury molecule-1 (Kim-1) expression was also reduced, a finding that is consistent with diminished kidney injury. In the current study, we also showed that fasudil could be protective of the impaired tubules. In vitro, fasudil reduced the apoptosis (annexin-V+PI cells) and cytokine production (tumor necrosis factor+ cells) in T cells and the apoptosis (annexin-V+PI cells) and tubular damage (Kim-1+ cells) in proximal tubular cells by flow cytometric analysis. As Rho-kinase plays an important role in promoting cisplatin nephrotoxicity, inhibiting Rho-kinase may be a therapeutic strategy for preventing cisplatin-induced AKI.

Statins and autoimmunity

Statins have immunomodulatory effects. Hence, they could be advantageous for different reasons. First, statins can serve as adjunct therapy in autoimmune diseases. Second, they may play a role in the prevention of accelerated atherosclerosis in the same population. In this review, we discuss the mechanisms of immune regulation by statins and review the literature for their benefit in many autoimmune diseases. In these studies, statins lead to an improvement in the disease activity scores in rheumatoid arthritis patients; a reduction in prothrombotic factors in anti-phospholipid syndrome patients; changes in vasculature, proteinuria, and cardiac events in systemic lupus erythematosus patients; changes in vasculature and proteinuria in patients with vasculitis; disease activity scores in ankylosing spondylitis; and finally vascular changes in patients with systemic sclerosis. Hence, these studies suggest that statins could be used as adjuncts to standard therapy due to their anti-inflammatory, immunomodulatory, and anti-thrombogenic effects. More evidence-based research is required to determine whether statin regimens will become the standard of care in patients with autoimmune diseases.

Statin use and markers of immunity in the Doetinchem cohort study

It has been suggested that statins can both stimulate and suppress the immune system, and thereby, may influence autoimmune diseases. Therefore, we studied effects of statins on innate and adaptive immunity, and self-tolerance by measuring serological levels of C-reactive protein (CRP), neopterin, immunoglobulin E (IgE) antibodies and the presence of autoantibodies (antinuclear antibodies (ANA) and IgM rheumatoid factor (RF)) in the general population. We conducted a nested case-control study within the population-based Doetinchem cohort. Data from health questionnaires, serological measurements and information on medication from linkage to pharmacy-dispensing records were available. We selected 332 statin users (cases) and 331 non-users (controls), matched by age, sex, date of serum collection, history of cardiovascular diseases, diabetes mellitus type II and stroke. Multivariate regression analyses were performed to estimate effect of statins on the immune system. The median level of CRP in statin users (1.28 mg/L, interquartile range (IQR): 0.59-2.79) was lower than in non-users (1.62 mg/L, IQR: 0.79-3.35), which after adjustment was estimated to be a 28% lower level. We observed an inverse association between duration of statin use and CRP levels. Elevated levels of IgE (>100 IU/mL) were more prevalent in statin users compared to non-users. A trend towards increased levels of IgE antibodies in statin users was observed, whereas no associations were found between statin use and levels of neopterin or the presence of autoantibodies. In this general population sub-sample, we observed an anti-inflammatory effect of statin use and a trend towards an increase of IgE levels, an surrogate marker for Th (helper) 2 responses without a decrease in neopterin levels, a surrogate marker for Th1 response and/or self-tolerance. We postulate that the observed decreased inflammatory response during statin therapy may be important but is insufficient to induce loss of self-tolerance.

Do all lupus patients need statins?

Statin therapy decreases cardiovascular morbidity and mortality rates when used as either primary or secondary prevention. An immunomodulating effect of statins has been suggested. Incontrovertible evidence of accelerated atheroma has been obtained in patients with systemic lupus erythematosus (SLE). Routine statin therapy in SLE patients might therefore produce both cardiovascular and immunological benefits. However, routine statin therapy is inappropriate in SLE patients, the main reason being the absence of a vast interventional study done specifically in this population. An immunomodulating role for statins in SLE has not been convincingly established. The effect of statin therapy on markers for subclinical atheroma (intima-media thickness changes over time) is unclear, and there are no studies proving that statins are effective when used for primary or secondary cardiovascular prevention. Nevertheless, we believe that a serum lipid profile should be obtained once a year in all SLE patients. There is a sound rationale for classifying all SLE patients as being at high cardiovascular risk and those receiving secondary prevention as at very high risk. Consequently, the serum LDL-cholesterol level must be kept below 100 mg/dL and 70 mg/dL in these two populations, respectively. Statins are the only widely recommended drugs for achieving these treatment targets. Statin therapy requires specific monitoring precautions (transaminase levels) given the high prevalence of comorbidities and use of concomitant medications in SLE patients.

Treatment with N-acetyl-seryl-aspartyl-lysyl-proline prevents experimental autoimmune myocarditis in rats

Myocarditis is commonly associated with cardiotropic infections and has been linked to development of autoimmunity. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a naturally occurring tetrapeptide that prevents inflammation and fibrosis in hypertension and other cardiovascular diseases; however, its effect on autoimmune-mediated cardiac diseases remains unknown. We studied the effects of Ac-SDKP in experimental autoimmune myocarditis (EAM), a model of T cell-mediated autoimmune disease. This study was conducted to test the hypothesis that Ac-SDKP prevents autoimmune myocardial injury by modulating the immune responses. Lewis rats were immunized with porcine cardiac myosin and treated with Ac-SDKP or vehicle. In EAM, Ac-SDKP prevented both systolic and diastolic cardiac dysfunction, remodeling as shown by hypertrophy and fibrosis, and cell-mediated immune responses without affecting myosin-specific autoantibodies or antigen-specific T cell responses. In addition, Ac-SDKP reduced cardiac infiltration by macrophages, dendritic cells, and T cells, pro-inflammatory cytokines [interleukin (IL)-1α, tumor necrosis factor-α, IL-2, IL-17] and chemokines (cytokine-induced neutrophil chemoattractant-1, interferon-γ-induced protein 10), cell adhesion molecules (intercellular adhesion molecule-1, L-selectin), and matrix metalloproteinases (MMP). Ac-SDKP prevents autoimmune cardiac dysfunction and remodeling without reducing the production of autoantibodies or T cell responses to cardiac myosin. The protective effects of Ac-SDKP in autoimmune myocardial injury are most likely mediated by inhibition of 1) innate and adaptive immune cell infiltration and 2) expression of proinflammatory mediators such as cytokines, chemokines, adhesion molecules, and MMPs.

Recent progress in the treatment of lupus nephritis

The treatment of lupus nephritis has seen significant advances during the past decade mainly due to the publication of well-designed randomized clinical trials (RCTs). The choice of treatment is guided by the histopathologic classification but is also influenced by demographic, clinical, and laboratory characteristics that allow for the identification of patients at risk for more aggressive disease. For the induction arm, low-dose cyclophosphamide regimens and mycophenolate mofetil have been validated as alternatives to the established National Institutes of Health regimen of high-dose cyclophosphamide; for the maintenance phase, azathioprine and mycophenolate compete for treatment of first choice. Rituximab is efficacious in real-life clinical practice but ineffective in clinical trials. The role of recently approved belimumab in lupus nephritis eagerly awaits further documentation. Aggressive management of comorbid conditions, such as hypertension and dyslipidemia, is of utmost importance. Here, we review the latest advances in lupus nephritis therapy with a focus on recent RCTs as well as new biologic agents under development. Furthermore, we propose a therapeutic algorithm in an effort to facilitate clinical decision-making in this gradually changing landscape. Upcoming European and American recommendations should provide further clarification.

The pleiotropic effects of the hydroxy-methyl-glutaryl-CoA reductase inhibitors in rheumatologic disorders: a comprehensive review

The hydroxy-methyl-glutaryl-CoA reductase inhibitors (statins) are used extensively in the treatment for hyperlipidemia. They have also demonstrated a benefit in a variety of other disease processes, including a wide range of rheumatologic disorders. These secondary actions are known as pleiotropic effects. Our paper serves as a focused and updated discussion on the pleiotropic effects of statins in rheumatologic disorders and emphasizes the importance of randomized, placebo-controlled trials to further elucidate this interesting phenomenon.

Murine models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disorder. The study of diverse mouse models of lupus has provided clues to the etiology of SLE. Spontaneous mouse models of lupus have led to identification of numerous susceptibility loci from which several candidate genes have emerged. Meanwhile, induced models of lupus have provided insight into the role of environmental factors in lupus pathogenesis as well as provided a better understanding of cellular mechanisms involved in the onset and progression of disease. The SLE-like phenotypes present in these models have also served to screen numerous potential SLE therapies. Due to the complex nature of SLE, it is necessary to understand the effect specific targeted therapies have on immune homeostasis. Furthermore, knowledge gained from mouse models will provide novel therapy targets for the treatment of SLE.

Statin therapy in lupus-mediated atherogenesis: two birds with one stone?

The atherosclerotic process is accelerated in patients with systemic lupus erythematosus (SLE). In addition to a robust lipid-lowering effect, various immunomodulatory functions have been ascribed to statins. By virtue of the latter they may be able to reduce atherosclerotic vascular disease in SLE by inhibiting immune activation within the arterial wall and by attenuating lupus activity. The effects of statins on SLE as well as on lupus-mediated atherogenesis in vivo are discussed in this viewpoint.