An ACE inhibitor reduces Th2 cytokines and TGF-beta1 and TGF-beta2 isoforms in murine lupus nephritis

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.

Identification of retinoic acid in a high content screen for agents that overcome the anti-myogenic effect of TGF-beta-1

BACKGROUND

Transforming growth factor beta 1 (TGF-β1) is an inhibitor of muscle cell differentiation that is associated with fibrosis, poor regeneration and poor function in some diseases of muscle. When neutralizing antibodies to TGF-β1 or the angiotensin II inhibitor losartan were used to reduce TGF-β1 signaling, muscle morphology and function were restored in mouse models of Marfan Syndrome and muscular dystrophy. The goal of our studies was to identify additional agents that overcome the anti-myogenic effect of TGF-β1.

METHODOLOGY/PRINCIPAL FINDINGS

A high-content cell-based assay was developed in a 96-well plate format that detects the expression of myosin heavy chain (MHC) in C2C12 cells. The assay was used to quantify the dose-dependent responses of C2C12 cell differentiation to TGF-β1 and to the TGF-β1 Type 1 receptor kinase inhibitor, SB431542. Thirteen agents previously described as promoting C2C12 differentiation in the absence of TGF-β1 were screened in the presence of TGF-β1. Only all-trans retinoic acid and 9-cis retinoic acid allowed a maximal level of C2C12 cell differentiation in the presence of TGF-β1; the angiotensin-converting enzyme inhibitor captopril and 10 nM estrogen provided partial rescue. Vitamin D was a potent inhibitor of retinoic acid-induced myogenesis in the presence of TGF-β1. TGF-β1 inhibits myoblast differentiation through activation of Smad3; however, retinoic acid did not inhibit TGF-β1-induced activation of a Smad3-dependent reporter gene in C2C12 cells.

CONCLUSIONS/SIGNIFICANCE

Retinoic acid alleviated the anti-myogenic effect of TGF-β1 by a Smad3-independent mechanism. With regard to the goal of improving muscle regeneration and function in individuals with muscle disease, the identification of retinoic acid is intriguing in that some retinoids are already approved for human therapy. However, retinoids also have well-described adverse effects. The quantitative, high-content assay will be useful to screen for less-toxic retinoids or combinations of agents that promote myoblast differentiation in the presence of TGF-β1.

Levels of transforming growth factor-beta are low in systemic lupus erythematosus patients with active disease

OBJECTIVE

Cytokines are central regulators of the immune response but the workings of this complex network in systemic lupus erythematosus (SLE) are not fully understood. We investigated a range of inflammatory and immune-modulating cytokines to determine their value as biomarkers for disease subsets in SLE.

METHODS

This was a cross-sectional study in 102 patients with SLE (87% women, disease duration 10.6 yrs). Circulating concentrations of interleukin 1β (IL-1β), IL-4, IL-6, IL-10, IL-12, IL-17, monocyte chemotactic protein 1 (MCP-1), macrophage inflammatory protein 1 (MIP-1α), MIP-1β, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and total transforming growth factor-β1 (TGF-β1) were related to disease activity (SLE Disease Activity Index; SLEDAI), lymphocyte subsets, autoantibody levels, accrued damage (Systemic Lupus International Collaborating Clinics/ACR Damage Index; SDI), and concomitant treatment.

RESULTS

Patients with SLE had lower levels of TGF-β1 (p = 0.01) and IL-1β (p = 0.0004) compared to controls. TGF-β1 levels were lower in patients with SLEDAI scores 1-10 and SDI > 3; and were correlated with CD4+, CD8+, and natural killer cell counts; and were independent of steroid or cytotoxic drug use. Treatment with cardiovascular drugs was associated with lower IL-12 levels. No consistent disease associations existed for the other cytokines investigated.

CONCLUSION

Lower TGF-β1 was the most consistent cytokine abnormality in patients with SLE. The associations with disease activity, lymphocyte subsets, and damage suggest that TGF-β1 may be a therapeutic target of interest in SLE.

Decreased incidence of lupus nephritis in northern Norway is linked to increased use of antihypertensive and anticoagulant therapy

BACKGROUND

Lupus nephritis (LN) remains a severe complication in systemic lupus erythematosus (SLE). Over the last decade, antiphospholipid antibodies have become a part of SLE classification criteria, and awareness of cardiovascular morbidity and its risk factors in SLE has increased. This study investigated the potential effect of these alterations on the presentation and severity of LN.

METHODS

This is an observational study of two subsequent SLE inception cohorts based on 1982 American College of Rheumatology (acr) classification criteria (82acr; n=87, enrolled 1978-95) and the updated version in 1997 (97acr: n=62, enrolled 1996-2006). Annual incidence rates (AIR), point prevalence, clinical and histological features, and outcome of LN (defined as proteinuria with urinary casts and/or haematuria) were compared between both cohorts.

RESULTS

Between 1978 and 2006, the AIR for LN decreased from 0.7 to 0.45/100 000, while LN prevalence rose from 7 to 14/100 000. The relative risk reduction in the 97acr for early- and late-onset LN (> 3 months after SLE diagnosis) was 39% and 42%, respectively. Patients developing LN in the 97acr cohort (97LN+; n=11) had similar demographics, more often low avidity anti-dsDNA antibodies (Ab) and/or anti-cardiolipin Ab at SLE diagnosis, lower proteinuria and diastolic blood pressure, and similar histological findings to those in the 83acr cohort (82LN +; n=28). Following LN diagnosis, more 97LN + patients received pulse corticosteroids (55% vs. 7%), anticoagulants (46% vs. 4%) and antihypertensive drugs (46% vs. 11%). Three 82LN+ patients (11%) developed end-stage renal disease versus none in 97LN + during a 10-year follow-up.

CONCLUSIONS

Early detection of low avidity anti-dsDNA and antiphospholipid antibodies, probably in combination with early use of protective cardiovascular measures from SLE diagnosis onwards may contribute to reduced incidence and improved renal survival in LN.

The ACE inhibitors enalapril and captopril modulate cytokine responses in Balb/c and C57Bl/6 normal mice and increase CD4(+)CD103(+)CD25(negative) splenic T cell numbers

Increasing evidence implies beneficial effects of angiotensin-converting enzyme (ACE) inhibitors beyond those of their original indications to control hypertension. One of the most attractive non-hemodynamic properties of ACE inhibitors is their ability to regulate cytokine production. The mechanism(s) underlying the role of ACE inhibitors on cytokine synthesis are not well understood but they have traditionally been attributed to the inhibition of angiotensin (Ang) II formation. In fact, it has been extensively demonstrated that ACE inhibitors decrease Ang II-induced production of proinflammatory cytokines and chemokines. However, it is not well described if inhibition of endogenous Ang II generation by ACE inhibitors modulates systemic cytokine production in mice. To verify that, in this work, we investigated the effects of treatment with the ACE inhibitors enalapril and captopril on cytokine synthesis in C57Bl/6 and Balb/c mice. Our results show that enalapril up regulates IL-10 produced by splenocytes from Balb/c and C57Bl/6 mice and captopril increased it only in Balb/c mice. Furthermore, CD4(+)CD103(+) presented increased IL-10 production after enalapril treatment. Enalapril as well as captopril short-term treatment enhanced IL-2 synthesis in Balb/c mice. Besides, enhanced IL-2 and IL-10 levels correlates with increased CD4(+)CD103(+)CD25(negative) T cells numbers in spleens from enalapril-treated mice.

Urine proteome scans uncover total urinary protease, prostaglandin D synthase, serum amyloid P, and superoxide dismutase as potential markers of lupus nephritis

To identify potential biomarkers in immune-mediated nephritis, urine from mice subjected to an augmented passive model of anti-glomerular basement membrane (GBM)-induced experimental nephritis was resolved using two-dimensional gels. The urinary proteome in these diseased mice was comprised of at least 71 different proteins. Using orthogonal assays, several of these molecules, including serum amyloid P (SAP), PG D synthase, superoxide dismutase, renin, and total protease were validated to be elevated in the urine and kidneys of mice during anti-GBM disease, as well as in mice with spontaneously arising lupus nephritis. Among these, urinary protease was the only marker that appeared to be exclusively renal in origin, whereas the others were partly serum-derived. Longitudinal studies in murine lupus demonstrated that total urinary protease had better predictive value for histologically active nephritis (r = 0.78) compared with proteinuria (r = -0.04), azotemia (r = 0.28), or the other markers examined, whereas urine SAP emerged as the single most predictive marker of histological glomerulonephritis. Collectively, these studies uncover total urinary protease, PG D synthase, SAP, and superoxide dismutase as novel biomarkers of anti-GBM disease and lupus nephritis, with stronger correlation to renal disease compared with currently employed biomarkers. These findings could have important diagnostic and prognostic ramifications in the management of these renal diatheses.

Pathogenesis of kidney disease in systemic lupus erythematosus

PURPOSE OF REVIEW

A combination of systemic autoimmunity and tissue response to immune injury underlie renal involvement in lupus erythematosus. In this review, we discuss recent literature investigating pathogenetic mechanisms of lupus glomerulonephritis.

RECENT FINDINGS

In lupus glomerulonephritis, glomerular immune complexes were believed to be the primary mediators of renal disease. Recent studies make it apparent that autoantibodies of multiple specificities participate in the formation of immune complexes, deposited in the kidneys. Renal infiltration by T cells, macrophages, and dendritic cells have a dominant role in the progression of lupus glomerulonephritis leading to renal failure. Activation of Toll-like receptors modulates autoantibody production and systemic interferon responses. However, glomerular cell responses to immune injury influence disease outcome. In addition, new insights on the genetics of susceptibility to end-organ damage in lupus glomerulonephritis have been discovered. Differential glomerular responses reflected in gene expression profiles during disease progression provide potential markers for diagnosis of lupus glomerulonephritis progression and flares. In addition, studies of end-organ responses provide new targets for therapeutic interventions.

SUMMARY

Lupus glomerulonephritis is a prototype of immune complex disease mediated by autoantibodies of multiple specificities, one of which is anti-DNA. Murine models of spontaneous systemic lupus erythematosus have been critical for understanding the underlying disease. Recent studies demonstrate that in addition to systemic autoimmunity, end-organ responses, and end-organ resistance to damage are also critical in determining disease outcome. This understanding should influence design of novel therapeutic approaches in systemic lupus erythematosus.

Antiproteinuric effect of angiotensin-converting enzyme inhibitors and an angiotensin II receptor blocker in patients with lupus nephritis

Although the effects of angiotensin II receptor blockers (ARBs) on non-diabetic glomerulonephritis have been reported, studies of their effects on collagen-vascular diseases, particularly lupus nephritis, are limited. In this retrospective, observational study, systemic lupus erythematosus (SLE) patients (n = 7) with lupus nephritis and uncontrolled proteinuria were treated with an angiotensin-converting enzyme inhibitor followed by the ARB losartan (25 - 50 mg/day). Urinary protein excretion and renal function were evaluated. After 12 months of losartan, mean urinary protein excretion decreased significantly by 84.8%. Mean systolic and diastolic blood pressures also decreased significantly during the 12 months of losartan treatment, although not in normotensive patients. Complement 4, total complement activity and anti-dsDNA antibody levels, which are indices of SLE activity, and serum creatinine levels, which is an index of renal function, showed no change in response to losartan treatment. A more extensive evaluation of the effects of ARBs in patients with lupus nephritis and poorly controlled proteinuria is required.

Glomerular type 1 angiotensin receptors augment kidney injury and inflammation in murine autoimmune nephritis

Studies in humans and animal models indicate a key contribution of angiotensin II to the pathogenesis of glomerular diseases. To examine the role of type 1 angiotensin (AT1) receptors in glomerular inflammation associated with autoimmune disease, we generated MRL-Faslpr/lpr (lpr) mice lacking the major murine type 1 angiotensin receptor (AT1A); lpr mice develop a generalized autoimmune disease with glomerulonephritis that resembles SLE. Surprisingly, AT1A deficiency was not protective against disease but instead substantially accelerated mortality, proteinuria, and kidney pathology. Increased disease severity was not a direct effect of immune cells, since transplantation of AT1A-deficient bone marrow did not affect survival. Moreover, autoimmune injury in extrarenal tissues, including skin, heart, and joints, was unaffected by AT1A deficiency. In murine systems, there is a second type 1 angiotensin receptor isoform, AT1B, and its expression is especially prominent in the renal glomerulus within podocytes. Further, expression of renin was enhanced in kidneys of AT1A-deficient lpr mice, and they showed evidence of exaggerated AT1B receptor activation, including substantially increased podocyte injury and expression of inflammatory mediators. Administration of losartan, which blocks all type 1 angiotensin receptors, reduced markers of kidney disease, including proteinuria, glomerular pathology, and cytokine mRNA expression. Since AT1A-deficient lpr mice had low blood pressure, these findings suggest that activation of type 1 angiotensin receptors in the glomerulus is sufficient to accelerate renal injury and inflammation in the absence of hypertension.

Anti-alpha8 integrin immunoliposomes in glomeruli of lupus-susceptible mice: a novel system for delivery of therapeutic agents to the renal glomerulus in systemic lupus erythematosus

OBJECTIVE

Glomerular mesangial cells are active participants in the pathogenesis of lupus glomerulonephritis (GN). Thus, targeted delivery of therapeutic agents to mesangial cells would be an attractive approach to treatment. However, lack of known unique mesangial cell surface markers has hampered this process. This study was undertaken in a mouse model of lupus GN to identify mesangial markers and to develop a system for targeted drug delivery to the glomerulus.

METHODS

Based on previous observations, alpha8 integrin expressed on the surface of glomerular mesangial cells was selected as a target molecule for delivery. Two mouse strains susceptible to lupus GN, NZM2328 and (NZM2328 x NOD)F1, were studied. Glomerular expression of alpha8 integrin in normal and nephritic mice was confirmed by immunofluorescence and quantitative polymerase chain reaction analysis. Liposomes were formulated and conjugated with an anti-alpha8 integrin antibody. These immunoliposomes were loaded with DiI, a red fluorescent dye, to allow tracking in vivo, and injected into the tail vein of female mice at different ages. Specificity of targeting was studied by fluorescence microscopy and flow cytometry.

RESULTS

Expression of alpha8 integrin was observed in the glomeruli of normal and nephritic mice. Anti-alpha8 integrin immunoliposomes were detected in the glomerulus and glomerular mesangial cells after tail vein injection in normal and nephritic mice. Delivery of DiI by anti-alpha8 integrin immunoliposomes was tissue specific, being observed predominantly in the glomeruli, with some nonspecific uptake by CD11b cells.

CONCLUSION

These findings are the first demonstration of specific delivery of anti-alpha8 integrin immunoliposomes to the mesangium following tail vein injection in mice. Anti-alpha8 integrin immunoliposomes thus offer a novel approach for targeted drug therapy in lupus and other glomerular diseases.

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.

Angiotensin-converting enzyme inhibitors delay the occurrence of renal involvement and are associated with a decreased risk of disease activity in patients with systemic lupus erythematosus--results from LUMINA (LIX): a multiethnic US cohort

OBJECTIVE

To examine if angiotensin-converting enzyme (ACE) inhibitor use delays the occurrence of renal involvement and decreases the risk of disease activity in SLE patients.

METHODS

SLE patients (Hispanics, African Americans and Caucasians) from the lupus in minorities: nature vs nurture (LUMINA) cohort were studied. Renal involvement was defined as ACR criterion and/or biopsy-proven lupus nephritis. Time-to-renal involvement was examined by univariable and multivariable Cox proportional hazards regression analyses. Disease activity was examined with a case-crossover design and a conditional logistic regression model; in the case intervals, a decrease in the SLAM-R score >or=4 points occurred but not in the control intervals.

RESULTS

Eighty of 378 patients (21%) were ACE inhibitor users; 298 (79%) were not. The probability of renal involvement free-survival at 10 yrs was 88.1% for users and 75.4% for non-users (P = 0.0099, log rank test). Users developed persistent proteinuria and/or biopsy-proven lupus nephritis (7.1%) less frequently than non-users (22.9%), P = 0.016. By multivariable Cox proportional hazards regression analyses, ACE inhibitors use [hazard ratio (HR) 0.27; 95% CI 0.09, 0.78] was associated with a longer time-to-renal involvement occurrence whereas African American ethnicity (HR 3.31; 95% CI 1.44, 7.61) was with a shorter time. ACE inhibitor use (54/288 case and 254/1148 control intervals) was also associated with a decreased risk of disease activity (HR 0.56; 95% CI 0.34, 0.94).

CONCLUSIONS

ACE inhibitor use delays the development of renal involvement and associates with a decreased risk of disease activity in SLE; corroboration of these findings in other lupus cohorts is desirable before practice recommendations are formulated.

Dual roles of immunoregulatory cytokine TGF-beta in the pathogenesis of autoimmunity-mediated organ damage

Ample evidence suggests a role of TGF-beta in preventing autoimmunity. Multiorgan inflammatory disease, spontaneous activation of self-reactive T cells, and autoantibody production are hallmarks of autoimmune diseases, such as lupus. These features are reminiscent of the immunopathology manifest in TGF-beta1-deficient mice. In this study, we show that lupus-prone (New Zealand Black and White)F(1) mice have reduced expression of TGF-beta1 in lymphoid tissues, and TGF-beta1 or TGF-beta1-producing T cells suppress autoantibody production. In contrast, the expression of TGF-beta1 protein and mRNA and TGF-beta signaling proteins (TGF-beta receptor type II and phosphorylated SMAD3) increases in the target organs, i.e., kidneys, of these mice as they age and develop progressive organ damage. In fact, the levels of TGF-beta1 in kidney tissue and urine correlate with the extent of chronic lesions that represent local tissue fibrosis. In vivo TGF-beta blockade by treatment of these mice with an anti-TGF-beta Ab selectively inhibits chronic fibrotic lesions without affecting autoantibody production and the inflammatory component of tissue injury. Thus, TGF-beta plays a dual, seemingly paradoxical, role in the development of organ damage in multiorgan autoimmune diseases. According to our working model, reduced TGF-beta in immune cells predisposes to immune dysregulation and autoantibody production, which causes tissue inflammation that triggers the production of anti-inflammatory cytokines such as TGF-beta in target organs to counter inflammation. Enhanced TGF-beta in target organs, in turn, can lead to dysregulated tissue repair, progressive fibrogenesis, and eventual end-organ damage.

Renin-angiotensin system blockade is renoprotective in immune complex-mediated glomerulonephritis

Blockade of the renin-angiotensin system is renoprotective in a variety of chronic nephropathies, but the direct effect of such treatment in active, immune complex-mediated glomerulonephritis is unknown. This study investigated the short- and long-term effects of an angiotensin-converting enzyme inhibitor (enalapril) and an angiotensin II type 1 receptor blocker (losartan) in thymic stromal lymphopoietin transgenic (TSLPtg) mice, which develop mixed cryoglobulinemia and severe cryoglobulinemia-associated membranoproliferative glomerulonephritis. Enalapril and losartan each reduced hypertension, proteinuria, glomerular extracellular matrix deposition, and mesangial cell activation in TSLPtg mice. These renoprotective effects were not observed with hydralazine treatment, despite a similar antihypertensive effect. Treatment with enalapril or losartan also decreased renal plasminogen activator inhibitor-1 in TSLPtg mice, assessed by immunohistochemistry and quantitative real-time reverse transcriptase-PCR. None of the treatments affected immune complex deposition or macrophage infiltration. Overall, enalapril- and losartan-treated TSLPtg mice survived significantly longer than untreated TSLPtg mice. These studies demonstrate that angiotensin blockade may provide renoprotective benefits, independent of its BP-lowering effect, in the treatment of active immune complex-mediated glomerulonephritis.

Effects of angiotensin II blockade on the development of autoimmune thyroiditis in nonobese diabetic mice

We evaluated the effects of angiotensin II (Ang II) blockers, losartan, an Ang II receptor blocker, and enalapril, an angiotensin converting enzyme inhibitor, on the development of autoimmune thyroiditis in nonobese diabetic (NOD) mice, an animal model of Hashimoto's thyroiditis (HT). Mice were assigned into three groups, untreated, losartan-treated (30 mg/kg/day), and enalapril-treated (10 mg/kg/day) groups. Thyroiditis was induced by iodide ingestion (experiment 1) or mouse thyroglobulin (Tg) immunization (experiment 2). Both procedures effectively induced thyroiditis. While iodide ingestion failed to induce anti-mouse Tg antibody (TgAb) production, Tg immunization resulted in a significant increase in serum TgAb levels. In both experiments, neither losartan nor enalapril interfered with the development of thyroiditis and TgAb production. These results suggest that Ang II may not be associated with the development of autoimmune thyroiditis in NOD mice. Thus, the Ang II blockade may not have therapeutic potential in HT.

Role for Nephritogenic T Cells in Lupus Glomerulonephritis: Progression to Renal Failure Is Accompanied by T Cell Activation and Expansion in Regional Lymph Nodes

Autoreactive T cells are critical in the initiation and maintenance of autoantibody responses that are a hallmark of systemic lupus erythematosus. However, the direct contribution of T cells in end-organ disease like lupus glomerulonephritis (GN) is poorly understood. In this study, we investigated the role of T cells in progression of lupus GN in NZM2328 mice, a murine model of spontaneous systemic lupus erythematosus. At 26 wk of age, NZM2328 female mice showed glomerular immune complex deposits and acute proliferative GN. This was associated with up-regulation of MHC class II and the detection of T cells and CD11c(+) dendritic cells in the glomeruli. The regional lymph nodes (LN) showed preferential activation of T cells and an oligoclonal T cell response with skewed expansion of certain Vbeta families. This suggests an Ag-driven response occurring in the regional LN of nephritic mice during acute GN. In contrast, male NZM2328 mice developed glomerular immune complexes and acute GN, but rarely progressed to fatal chronic GN. Significantly, male kidneys at 40 wk of age did not have detectable dendritic cells and T cells in the glomeruli. Thus, glomerular immune complex deposition initiates an immune response against renal Ags in the regional LN, leading to T cell recruitment into the kidney during acute proliferative GN. This T cell activation and infiltration are influenced by gender-dependent end-organ factors and may determine the progression of acute GN to chronic GN and renal failure.

Accelerated macrophage apoptosis induces autoantibody formation and organ damage in systemic lupus erythematosus

Increased monocyte/macrophage (Mphi) apoptosis occurs in patients with systemic lupus erythematosus (SLE) and is mediated, at least in part, by an autoreactive CD4(+) T cell subset. Furthermore, autoreactive murine CD4(+) T cells that kill syngeneic Mphi in vitro induce a lupus-like disease in vivo. However, it is unclear whether increased Mphi apoptosis in SLE per se is sufficient to accelerate/promote autoimmunity. We have investigated whether increased Mphi apoptosis in vivo, induced by the administration of clodronate liposomes, can exacerbate the autoimmune phenotype in NZB x SWR (SNF(1)) lupus-prone mice, and induce autoantibody production in haplotype-matched BALB/c x DBA1 (DBF(1)) non-lupus-prone mice. Lupus-prone mice SNF(1) mice that were treated with clodronate liposomes, but not mice treated with vehicle, developed significant increases in autoantibodies to dsDNA, nucleosomes, and the idiotypically related family of nephritic Abs Id(LN)F(1), when compared with untreated SNF(1) mice. Furthermore, clodronate treatment hastened the onset of proteinuria and worsened SNF(1) lupus nephritis. When compared with vehicle-treated controls, clodronate-treated non-lupus-prone DBF(1) mice developed significantly higher levels of anti-nucleosome and Id(LN)F(1) Abs but did not develop lupus nephritis. We propose that Mphi apoptosis contributes to the pathogenesis of autoantibody formation and organ damage through both an increase in the apoptotic load and impairment in the clearance of apoptotic material. This study suggests that mechanisms that induce scavenger cell apoptosis, such as death induced by autoreactive cytotoxic T cells observed in SLE, could play a pathogenic role and contribute to the severity of the disease.

Plasminogen activator inhibitor-1 gene deficiency attenuates TGF-β1-induced kidney disease

BACKGROUND

Transforming growth factor-beta1 (TGF-beta1) stimulates the deposition of extracellular matrix (ECM), which is a hallmark in end-stage renal disease. The importance of TGF-beta1-induced changes in protease activity in this process is not fully elucidated. TGF-beta1 up-regulates plasminogen activator inhibitor type 1 (PAI-1), which lowers matrix degradation. Our aim was to investigate the importance of PAI-1 in TGF-beta1-induced kidney disease.

METHODS

TGF-beta1 transgenic mice were bred with PAI-1 gene deficient mice. The effect of PAI-1 gene knockout on TGF-beta1-induced glomerular disease was investigated by measuring morphologic changes in the glomeruli. Interstitial changes were assessed by measurement of total collagen content and expression and localization of ECM components. Finally, protease activity was evaluated by plasmin activity measurement and by gel and in situ gelatin zymography.

RESULTS

TGF-beta1 elevated PAI-1 expression fourfold. PAI-1 gene deficiency attenuated the TGF-beta1-induced mesangial expansion and basement membrane thickening. Furthermore, PAI-1 knockout diminished collagen accumulation in TGF-beta1-positive mice. The expression of both collagen type I and III were reduced. Interestingly, no difference in protease activity could be ascertained as cause of the decreased ECM accumulation.

CONCLUSION

We show that PAI-1 gene deficiency attenuates TGF-beta1-induced kidney disease, decreasing both glomerular and interstitial ECM deposition. Thus, PAI-1 mediates some of the biological effects of TGF-beta1 in vivo. However, we could not find evidence supporting the notion that the effect was mediated through increased protease activity.

Captopril effect on prostaglandin E2, thromboxane B2 and proteinuria in lupus nephritis patients

OBJECTIVE

High urinary Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels have been reported in lupus nephritis (LN). Captopril diminishes proteinuria and improves glomerular filtration rate (GFR), and may have effect on immune function. We evaluate captopril effect on urinary PGE2, and TxB2.

METHODS

Eighteen LN patients were randomly assigned to two groups. Group 1 received only prednisone plus cyclophosphamide. Group 2 received also captopril. Serum creatinine, GFR, RPF, urinary proteins, PGE2 and TxB2, were assessed.

RESULTS

There were no differences between the initial and final assessments in Group 1. Group 2 showed a significant decrement in proteinuria (p=0.003) and serum creatinine (p=0.01) at the end of the study. PGE2 decreased significantly when compared with the initial value (p=0.02).

CONCLUSION

Captopril plus usual treatment, improved serum creatinine and decreased proteinuria in parallel with prostaglandin E2 reduction. This effect is not related to changes in GFR or RPF. Captopril may have an immunomodulatory effect on local inflammatory processes in lupus nephritis.

SLE: translating lessons from model systems to human disease

Systemic lupus erythematosus (SLE, lupus) results from immune-mediated damage to multiple organs. Its pathogenesis should be viewed as a series of steps, beginning with impaired immune regulation that permits self-reactive T-B-cell activation, which results in the production of autoantibodies. Activated T and B cells then infiltrate tissues, which along with autoantibody and immune complex deposition, triggering local events that ultimately cause organ damage. Although improved understanding of early autoimmune events might open up avenues for disease prevention, future investigations must focus on the mechanisms of end-organ damage in model systems and how to translate this knowledge into human disease. Understanding the mechanisms of each pathogenetic step would provide a rational basis for the development of disease stage-specific diagnostic markers and treatments.

Disease modification and cardiovascular risk reduction: two sides of the same coin?

Inflammatory rheumatic diseases are associated with a substantial increase in accelerated atherosclerosis, with complex interactions between traditional and disease-related risk factors. Therefore, cardiovascular risk reduction should be considered as integral to the control of disease activity in the care plans of patients with RA, SLE and, arguably any chronic inflammatory disease. Shared care structures, already established for the monitoring of DMARDs, could be adapted to communicate and monitor cardiovascular risk reduction objectives. We review the evidence for the efficacy of a range of therapeutic strategies, the majority of which impact on both disease activity and cardiovascular risk. The algorithm proposed here attempts to distil the latest advice from specialist panels at the National Cholesterol Education Program and the British Hypertension Society, as well as incorporating the existing data on SLE and RA patients. The algorithm is structured to minimize clinic time and resources necessary to stratify patients into groups for ROUTINE, SUBSTANTIAL or INTENSIVE risk management; the associated table summarizes optimal therapeutic objectives in each of these groups. The implication of this algorithm is that management of cardiovascular risk should be much more aggressive than is currently the norm in patients with chronic inflammatory diseases, such as RA and SLE. Long-term studies of such interventions are needed to further clarify the benefits of intensive cardiovascular risk management in these patients.

Renal tubular dysfunction in children with systemic lupus erythematosus

Renal tubular and glomerular function was studied in patients under 18 years of age with childhood-onset systemic lupus erythematosus (SLE) in relation to disease activity in two groups: patients with clinical or laboratory evidence of lupus nephritis and those without (lupus non-nephritis). We reviewed 11 patients with lupus non-nephritis and 10 patients with lupus nephritis over a 12-month period. The measured glomerular filtration rates had a tendency to be lower in the lupus nephritis group. Glomerular dysfunction was manifest in the lupus nephritis group with elevated urinary albumin/creatinine ratios (P <0.001). Markers of tubular function were measured and compared with data from 94 controls. The lupus nephritis group had elevated urinary NAG [N-acetyl-beta-D-glucosaminidase (P =0.001)] and RBP [retinol-binding protein (P =0.03)] levels. Tubular dysfunction with elevated urinary NAG levels was present in 2 lupus non-nephritis patients with no evidence of glomerular disease. The cohort of patients in this study was followed and 2 lupus non-nephritis patients with the highest urinary RBP levels developed evidence of glomerular dysfunction and biopsy-proven lupus nephritis. Evidence of tubular dysfunction in lupus non-nephritis patients may help to identify lupus nephritis prior to the onset of albuminuria.

Alternatively spliced isoforms of fibronectin in immune-mediated glomerulosclerosis: the role of TGF? and IL-4

Fibronectin (FN) is the main extracellular matrix component in glomerulosclerotic lesions. There are different FN isoforms that result from alternative splicing at the EDA and EDB regions of FN mRNA. Increased inclusion of EDA and EDB, which can be elicited by TGFbeta, may be conducive to the development of glomerulosclerosis (GS). TGFbeta and IL-4 have previously been shown to play a role in the development of GS. In this study, the mRNA splicing patterns for EDA+ and EDB+ fibronectin were investigated in vivo in various experimental sclerotic glomerulopathies, in vitro in rat mesangial cells (MC) that were stimulated by TGFbeta or transfected with IL-4, and in human kidney biopsies with GS from patients with various kidney diseases. Analysis of glomerular FN mRNA demonstrated inclusion of both ED regions in rats with anti-Thy1 nephritis or chronic serum sickness and in mice with anti-GBM glomerulonephritis. Inclusion of both the EDA and EDB regions was associated with glomerular TGFbeta expression. In contrast, in mice with Th2-mediated graft-versus-host disease, a model for lupus nephritis, the FN transcripts included neither the EDA nor the EDB region, and renal TGFbeta expression was absent. Compared to normal MCs in culture, MCs transfected with IL-4 produced lower amounts of FN and demonstrated less EDA inclusion, while MC that had been treated with TGFbeta showed increased production of FN and more EDA inclusion. Renal biopsies from patients with renal diseases, except those taken from patients with lupus nephritis, showed higher TGFbeta levels, higher FN levels, and more EDA inclusion than controls. TGFbeta may be a key player in the development of GS by inducing local FN production and alternative splicing of FN mRNA. In lupus glomerulonephritis, in which the involvement of TGFbeta in GS is less prominent, Th2 cytokines such as IL-4 probably account for increased intrarenal collagen synthesis and subsequent FN accumulation from the circulation. In conclusion, neither alternative FN splicing, nor a high transcription level of TGFbeta, appears to be a general prerequisite for the development of GS.