Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Comparison of the growth kinetics and proteolytic activities of Chryseobacterium species and Pseudomonas fluorescens

The effect of temperature on the growth kinetics and proteolytic activity of Chryseobacterium joostei and Chryseobacterium bovis was determined during this study. The results were compared with the activities of Pseudomonas fluorescens, which is regarded to be a major food spoilage psychrotolerant microorganism. For the growth studies, cultures were incubated in nutrient broth in a temperature gradient incubator (from 9 to 50 °C) and separately at 4 °C, and the optical density was measured at different time intervals. Growth temperature profiles for each organism were constructed. For determination of proteolytic activity, the cultures were incubated in fat-free ultra-high temperature processed milk in the temperature gradient incubator for 72 h (temperature range as above). Cell-free extracts were used to determine the proteolytic activity using the azocasein method. Results of the growth studies showed that C. joostei had the ability to grow over a wider temperature range than C. bovis and P. fluorescens without being affected by changes in the temperature. For the proteolytic activity, C. joostei had significantly (p < 0.001) higher activity per milligram of protein at 15.5 °C, followed by C. bovis and P. fluorescens. The results showed that C. joostei potentially has an even greater spoilage capacity in milk on the basis of growth rate and proteolytic activity than did P. fluorescens.

Calcineurin inhibitor minimization in the Symphony study: observational results 3 years after transplantation

The Symphony study showed that at 1 year posttransplant, a regimen based on daclizumab induction, 2 g mycophenolate mofetil (MMF), low-dose tacrolimus and steroids resulted in better renal function and lower acute rejection and graft loss rates compared with three other regimens: two with low-doses of cyclosporine or sirolimus instead of tacrolimus and one with no induction and standard cyclosporine dosage. This is an observational follow-up for 2 additional years with the same endpoints as the core study. Overall, 958 patients participated in the follow-up. During the study, many patients changed their immunosuppressive regimen (e.g. switched from sirolimus to tacrolimus), but the vast majority (95%) remained on MMF. During the follow-up, renal function remained stable (mean change: -0.6 ml/min), and rates of death, graft loss and acute rejection were low (all about 1% per year). The MMF and low-dose tacrolimus arm continued to have the highest GFR (68.6 +/- 23.8 ml/min vs. 65.9 +/- 26.2 ml/min in the standard-dose cyclosporine, 64.0 +/- 23.1 ml/min in the low-dose cyclosporine and 65.3 +/- 26.2 ml/min in the low-dose sirolimus arm), but the difference with the other arms was not significant (p = 0.17 in an overall test and 0.077, 0.039 and 0.11, respectively, in pair-wise tests). The MMF and low-dose tacrolimus arm also had the highest graft survival rate, but with reduced differences between groups over time, and the least acute rejection rate. In the Symphony study, the largest ever prospective study in de novo kidney transplantation, over 3 years, daclizumab induction, MMF, steroids and low-dose tacrolimus proved highly efficacious, without the negative effects on renal function commonly reported for standard CNI regimens.

Patient with antibody-negative relapse of Goodpasture syndrome

Smoking in young men may trigger anti-GBM disease manifesting with hemoptysis. We present a male adolescent in whom hemoptysis was mistaken to be a sign of airway infection for several months and who later on underwent an unusual antibody-negative relapse. The 16-year-old patient had a history of smoking and therapy-refractant hemoptysis and, later, acute macrohematuria with renal insufficiency necessitating hemodialysis (initial creatinine 4.2 mg/ dl). Chest X-ray showed diffuse lung infiltration. Renal biopsy revealed linear IgG deposits along the glomerular basement membrane (GBM) and cellular crescents in 13/16 glomeruli, simultaneously increased anti-GBM antibodies were detected. Thus, anti-GBM glomerulonephritis was diagnosed. After treatment with prednisone, oral cyclophosphamide and plasmapheresis, chest X-ray and hemoptysis improved, but renal failure persisted. Anti-GBM antibodies were negative. 4 weeks later, the patient presented again with a clinical relapse of severe hemoptysis and respiratory insufficiency after smoke exposition. Despite negative anti-GBM antibodies, he was treated similarly to a relapse and after the second course of plasmapheresis the patients' general condition improved and hemoptysis subsided. During the next 10 months the patient was stable with negative antibodies. He was under intermittent hemodialysis until laboratory measurements showed improved renal function. Now, 30 months after the acute episode, the patient is off dialysis for 17 months with stable creatinine values of 1.9 - 2.4 mg/dl, and is currently being treated with antihypertensive medicaments, calcitriol, calciumacetate, natriumhydrogencarbonate and allopurinol. The prognosis of anti-GBM glomerulonephritis depends on serum creatinine and the need of dialysis at initial presentation. In these patients, one-year survival rate is 67% and 5% for kidney function. Of note, despite the unfavorable prognosis in our patient, renal function recovered after 1 year of hemodialysis treatment. It is important to consider that in patients with anti-GBM disease antibody-negative relapses are possible.

Mechanisms of everolimus-induced glomerulosclerosis after glomerular injury in the rat

Despite the lack of nephrotoxicity, adverse effects of the new antiproliferative immunosuppressant everolimus have been reported. By varying time point and dose of everolimus treatment as well as the degree of glomerular injury, the specific conditions and potential mechanisms leading to adverse actions in the anti-Thy1 model have been determined. Only the combination of early and high-dose everolimus treatment (1-3 mg/kg bw) with a severe glomerular lesion ('full-dose' anti-Thy1 model) caused adverse effects with a high mortality rate, progressive apoptosis, crescent formation and glomerulosclerosis. In contrast, either later start or low-dose (0.3 mg/kg bw) therapy or treatment of a less severe lesion ('reduced dose' anti-Thy1 model) appeared to be relatively safe for the glomerular architecture. The adverse effects of everolimus were linked to its marked inhibition of endothelial cell, but not necessarily mesangial cell proliferation. In addition, everolimus markedly inhibited the angiogenic cytokine vascular endothelial growth factor in nephritic glomeruli in vivo. These experimental results suggest special caution regarding the use of everolimus in all situations of severe glomerular cell injury requiring extensive capillary repair, where at least adaption to a low dose needs to be considered.

Impaired angiogenesis in the aging kidney: vascular endothelial growth factor and thrombospondin-1 in renal disease

We investigated the relationship of changes in the microvasculature to age-related structural and functional changes in the kidney to determine whether there was evidence of impaired angiogenesis and whether the loss of microvasculature could be accounted for by changes in the local production of angiogenic or antiangiogenic factors. Glomerular and peritubular capillary number, density, and endothelial cell proliferation were determined in aging (24 months; n = 9) and young (3 months; n = 8) rat kidneys and correlated with renal functional and structural changes and alterations in renal expression of vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1). Aging rats showed a focal decrease in both peritubular capillary (peritubular capillary staining, 5.4% +/- 1.8% versus 11.3% +/- 2.0% per 100 tubules; rarefaction index, 10.6% +/- 4.6% versus 0.6% +/- 0.1%, aging versus young rats; P < 0.05 and P: < 0.001, respectively) and glomerular capillary loops (27.3 +/- 6.9 versus 50.7 +/- 7.4/glomerulus, aging versus young rats; P < 0.001). The number of proliferating endothelial cells was decreased in aging rats compared with young rats (glomerular, 0.04 +/- 0.01 versus 0.15 +/- 0.03 positive cells/glomerular cross-section; peritubular, 0.7 +/- 0.2 versus 4.3 +/- 2.6 positive cells/mm(2); P < 0.05). In the aging kidney, VEGF expression was focally increased in the cortex compared with young rats, whereas a profound decrease was observed in the outer and inner medulla (total area of VEGF expression, 19.2% +/- 11.4% versus 39.3% +/- 7.6%; P < 0.05). Tubular VEGF expression correlated with peritubular capillary density (r(2) = 0.57; P < 0.01) and inversely correlated with tubular osteopontin (r(2) = -0.55; P < 0.05) and macrophage infiltration (r(2) = -0.64; P < 0.01). TSP-1 staining was increased in the glomeruli and tubulointerstitium of the aging rats. Glomerular TSP-1 score correlated inversely with glomerular capillary number (r(2) = -0.89; P < 0.001). Tubulointerstitial TSP-1 also correlated with percentage of positive staining of peritubular capillary (r(2) = -0.59; P < 0.001). Glomerular capillary number showed significant correlation with glomerulosclerosis score, as well as with 24-hour urinary protein excretion. Peritubular capillary density also inversely correlated with interstitial fibrosis score and urinary protein excretion. In conclusion, glomerular and peritubular capillary loss in the aging kidney correlate with alterations in VEGF and TSP-1 expression and also with the development of glomerulosclerosis and tubulointerstitial fibrosis. These findings suggest that impaired angiogenesis associated with progressive loss in renal microvasculature may have a pivotal role in age-related nephropathy.

Monocyte chemoattractant protein-1 and macrophage infiltration in hypertensive kidney injury

BACKGROUND

We investigated whether monocyte chemoattractant protein-1 (MCP-1) is expressed in hypertensive nephrosclerosis, and tested the effect of angiotensin II type 1 receptor blockade on MCP-1 expression and macrophage (MPhi) infiltration.

METHODS

Rats with two-kidney, one-clip (2K1C) hypertension with and without treatment with the angiotensin II type 1 receptor antagonist valsartan (3 mg/kg/day) were studied. In these animals as well as in spontaneously hypertensive rats (SHR), stroke-prone SHR (SHR-SP), hypertensive mRen-2 transgenic rats (TGR), and respective control strains, MCP-1 expression in the kidney was investigated by Northern and Western blots and by immunohistochemistry. Glomerular and interstitial MPhis were counted.

RESULTS

In the nonclipped kidney of 2K1C rats, MCP-1 expression was elevated at 14 and 28 days when significant MPhi infiltration was present. MCP-1 was localized to glomerular endothelial and epithelial cells, interstitial and tubular cells, MPhis, and vascular smooth muscle cells. A similar pattern of MCP-1 staining was present in TGR kidneys, whereas MCP-1 expression was not increased in SHR and SHR-SP. Valsartan reduced but did not normalize blood pressure, blocked the induction of MCP-1 protein in 2K1C kidneys, and decreased interstitial MPhi infiltration significantly.

CONCLUSION

MCP-1 expression is increased in angiotensin II-dependent models of hypertensive nephrosclerosis and is temporally and spatially related to MPhi infiltration. The angiotensin II type 1 receptor mediates the induction of MCP-1.

Glucose stimulation of transforming growth factor-beta bioactivity in mesangial cells is mediated by thrombospondin-1

Glucose is a key factor in the development of diabetic complications, including diabetic nephropathy. The development of diabetic glomerulosclerosis is dependent on the fibrogenic growth factor, transforming growth factor-beta (TGF-beta). Previously we showed that thrombospondin-1 (TSP-1) activates latent TGF-beta both in vitro and in vivo. Activation occurs as the result of specific interactions of latent TGF-beta with TSP-1, which potentially alter the conformation of latent TGF-beta. As glucose also up-regulates TSP-1 expression, we hypothesized that the increased TGF-beta bioactivity observed in rat and human mesangial cells cultured with high glucose concentrations is the result of latent TGF-beta activation by autocrine TSP-1. Glucose-induced bioactivity of TGF-beta in mesangial cell cultures was reduced to basal levels by peptides from two different sequences that antagonize activation of latent TGF-beta by TSP, but not by the plasmin inhibitor, aprotinin. Furthermore, glucose-dependent stimulation of matrix protein synthesis was inhibited by these antagonist peptides. These studies demonstrate that glucose stimulation of TGF-beta activity and the resultant matrix protein synthesis are dependent on the action of autocrine TSP-1 to convert latent TGF-beta to its biologically active form. These data suggest that antagonists of TSP-dependent TGF-beta activation may be the basis of novel therapeutic approaches for ameliorating diabetic renal fibrosis.

Dissociation of mesangial cell migration and proliferation in experimental glomerulonephritis

BACKGROUND

Recently, we documented that following in vivo mesangial cell (MC) ablation in the Thy1 model, reconstitution of the mesangium occurs by a coordinated proliferation and migration of Thy1 (OX-7)-positive cells originating from the hilus and extraglomerular mesangium. We investigated the role of basic fibroblast growth factor (bFGF) in the mediation of these events.

METHODS

Rats were injected with antithymocyte serum and 48 hours later were pulsed with 3H-thymidine to label proliferating cells. Ninety minutes later, a baseline renal biopsy was obtained, and rats were injected with neutralizing anti-bFGF antibodies or control IgG. Sacrificial biopsies were obtained at 96 hours of disease. Using computer image analysis, biopsies from both time points were quantitated for the number of radiolabeled MC (proliferation) and their mean distance from the hilus (migration). The effect of bFGF on the migration of MCs in culture was examined using a chemotactic assay.

RESULTS

At sacrifice, autoradiographs of rats receiving anti-bFGF had significantly fewer radiolabeled MCs as compared with rats receiving control IgG (8.7+/-1.9 vs. 14.7+/-3.5, P = 0.0001), yielding an overall 40% reduction in proliferation. There was no difference, however, in the final distance of radiolabeled MCs from the glomerular hilus in the two groups, indicating that the administration of anti-bFGF did not effect MC migration in this model. In an in vitro chemotactic assay, MCs migrated in response to platelet-derived growth factor (PDGF) BB (20 ng/ml), but did not migrate in response to bFGF at a wide range of concentrations (0.5 to 50 ng/ml).

CONCLUSIONS

These studies demonstrate that bFGF is an important mediator of MC proliferation but that it does not significantly influence MC migration. This is the first demonstration showing that the mediators effecting proliferation can be dissociated from those mediating migration in renal injury.

The plasma membrane-actin linking protein, ezrin, is a glomerular epithelial cell marker in glomerulogenesis, in the adult kidney and in glomerular injury

BACKGROUND

Ezrin belongs to a family of plasma membrane-cytoskeleton linking, actin binding proteins (Ezrin-radixin-Moesin family) involved in signal transduction, growth control, cell-cell adhesion, and microvilli formation.

METHODS

The expression of ezrin was examined in glomerular cells in culture, during kidney development, in the mature kidney, and in five different experimental kidney disease models in the rat.

RESULTS

Ezrin was specifically expressed in glomerular epithelial cells in developing glomeruli in mature glomeruli and in glomerular epithelial cells in culture. Distinct from its other family members, moesin and radixin, which are predominantly expressed in glomerular endothelial and mesangial areas, ezrin protein (by immunohistochemistry) was specifically and exclusively modulated during podocyte injury and regeneration. Ezrin immunohistochemistry was able to visualize cell body attenuation, pseudocysts, and in particular vacuolation of injured podocytes, a feature that usually has to be identified at the ultrastructural level, and was strikingly increased in binucleated podocytes or podocytes that were partially or completely detached from the underlying GBM (frequently also binucleated). Infiltrating macrophages also express ezrin, but can easily be differentiated from podocytes by their round shape and higher level of expression.

CONCLUSIONS

Ezrin likely has a role in the cytoskeletal organization, such as reassembling of acting filaments accompanying podocyte injury and regeneration. Since suitable light microscopic markers for the identification of glomerular epithelial cells are rare, ezrin may also be a useful marker for podocytes in normal and injured glomeruli.

Extracellular ATP causes apoptosis and necrosis of cultured mesangial cells via P2Z/P2X7 receptors

Mesangial cells undergo cell death both by apoptosis and necrosis during glomerular disease. Since nucleotides are released from injured and destroyed cells in the glomerulus, we examined whether extracellular ATP and its receptors may regulate cell death of cultured mesangial cells. Addition of extracellular ATP (300 microM to 5 mM) to cultured rat mesangial cells for 90 min caused a 5. 8-fold increase in DNA fragmentation (terminal deoxynucleotidyl transferase assay) and a 4.2-fold increase in protein levels of the tumor suppressor p53, which is thought to regulate apoptosis. Apoptotic DNA fragmentation was confirmed by the diphenylamine assay and by staining with the DNA-specific fluorochrome Hoechst 33258. The necrotic markers, release of lactate dehydrogenase and uptake of trypan blue, were not positive before 3 h of ATP addition. The effects of ATP on DNA fragmentation and p53 expression were reproduced by the purinergic P2Z/P2X7 receptor agonist, 3'-O-(4-benzoylbenzoyl)-ATP, and inhibited by the P2Z/P2X7 receptor blocker, oxidized ATP. Transcripts encoding the P2Z/P2X7 receptor were expressed by cultured mesangial cells as determined by Northern blot analysis. P2Z/P2X7 receptor-associated pore formation in the plasma membrane was demonstrated by the Lucifer yellow assay. We conclude that activation of P2Z/P2X7 receptors by extracellular ATP causes apoptosis and necrosis of cultured mesangial cells. Activation of purinergic P2Z/P2X7 receptors may play a role in causing death of mesangial cells during glomerular disease.

Proliferating and migrating mesangial cells responding to injury express a novel receptor protein-tyrosine phosphatase in experimental mesangial proliferative glomerulonephritis

The mesangial cell provides structural support to the kidney glomerulus. A polymerase chain reaction-based cDNA display approach identified a novel protein-tyrosine phosphatase, rPTP-GMC1, whose transcript expression is transiently and dramatically up-regulated during the period of mesangial cell migration and proliferation that follows mesangial cell injury in the anti-Thy 1 model of mesangial proliferative glomerulonephritis in the rat. In situ hybridization analysis confirmed that rPTP-GMC1 mRNA is up-regulated specifically by mesangial cells responding to the injury and is not detectable in other cells in the kidney or in many normal tissues. In cell culture, rPTP-GMC1 is expressed by mesangial cells but not by glomerular endothelial or epithelial cells (podocytes). The longest transcript (7.5 kilobases) encodes a receptor-like protein-tyrosine phosphatase consisting of a single catalytic domain, a transmembrane segment, and 18 fibronectin type III-like repeats in the extracellular segment. A splice variant predicts a truncated molecule missing the catalytic domain. rPTP-GMC1 maps to human chromosome 12q15 and to the distal end of mouse chromosome 10. The predicted structure of rPTP-GMC1 and its pattern of expression in vivo and in culture suggest that it plays a role in regulating the adhesion and migration of mesangial cells in response to injury.

Endogenous fibroblast growth factor-2 mediates cytotoxicity in experimental mesangioproliferative glomerulonephritis

Fibroblast growth factor-2 (FGF-2) is released from mesangial cells in experimental mesangioproliferative glomerulonephritis induced with anti-Thy 1.1 antibody. To investigate the functional role of released FGF-2, rats received either neutralizing anti-FGF-2 IgG or a functional peptide antagonist of FGF-2 (FGF119-126) before or shortly after induction of anti-Thy 1.1 nephritis. In additional experiments, rats were treated with bolus injections of FGF-2 from 2 to 6 h after disease induction. The data showed that anti-FGF-2 therapy led to significant reductions of early mesangial cell injury (mesangiolysis, microaneurysm formation) and the subsequent mesangioproliferative changes (glomerular de novo expression of alpha-smooth muscle actin, mesangial cell proliferation, matrix accumulation, and platelet influx). Conversely, injections of FGF-2 augmented both mesangial injury and the subsequent mesangioproliferative changes. Studies on the mechanisms underlying the amplification of mesangial cell injury by FGF-2 showed that anti-FGF-2 therapy reduced cell death at 2 and 8 h after disease induction by 58 and 54%, respectively. This was associated with significant reductions in the number of glomerular H2O2- and OH -producing cells, as well as reduced glomerular production of nitric oxide. These data suggest that release of constitutively expressed FGF-2 after immune-mediated cell injury contributes to glomerular cell damage and thus identify FGF-2 as a novel mediator of cytotoxicity.

Thrombospondin 1 precedes and predicts the development of tubulointerstitial fibrosis in glomerular disease in the rat

Tubulointerstitial fibrosis is one of the most important histologic features that predicts progression in kidney disease. Thrombospondin 1 is an extracellular matrix protein that can activate latent TGF-beta, a cytokine implicated in the pathogenesis of tubulointerstitial fibrosis. We examined the expression of thrombospondin 1 in several animal models of glomerulonephritis (anti-Thy1 model, aminonucleoside nephrosis, passive Heymann nephritis) that are associated with tubulointerstitial disease. Thrombospondin 1 mRNA and protein were transiently increased in tubular cells, myofibroblasts and some macrophages in areas of tubulointerstitial injury. Thrombospondin 1 expression always preceded the development of tubulointerstitial fibrosis, and correlated quantitatively and spatially with the later development of interstitial fibrosis. Thrombospondin 1 expression predicted the severity of tubulointerstitial fibrosis better than the degree of macrophage or myofibroblast accumulation. Thrombospondin 1 expression was associated with increased expression and activation of TGF-beta1 and decreased expression of LAP-TGF-beta in areas of tubulointerstitial injury. We conclude that thrombospondin 1 is an early marker predicting the development of tubulointerstitial kidney disease. De novo expression of thrombospondin 1 is associated and colocalized with increased expression of TGF-beta1 and decreased expression of LAP-TGF-beta during the development of tubulointerstitial disease in vivo. These data are consistent with the possibility that thrombospondin 1 may be an endogenous activator of TGF-beta.

Extraglomerular origin of the mesangial cell after injury. A new role of the juxtaglomerular apparatus

We investigated the origin of the glomerular mesangial cell, a smooth muscle-like cell that provides structural support in the glomerulus. Injection of anti-Thy 1 antibody that binds the Thy 1 antigen on rat mesangial cells eliminated (> 95%) the mesangial population at 20-28 h, while Thy 1-positive cells in the juxtaglomerular apparatus (JGA) were sequestered from the circulation and survived. Single pulse labeling with [3H]thymidine at 36 h labeled Thy 1-positive cells in the JGA and hilus. Serial biopsies demonstrated the progressive migration (5-15 micron/d) and proliferation of these mesangial reserve cells until the entire glomerulus was repopulated. The regenerating mesangial population expressed contractile and migratory proteins preferentially at the leading edge of the migratory front. Single as well as multiple pulse labeling with [3H]thymidine confirmed that the entire mesangial cell repopulation originated from only a few mesangial reserve cells. These reserve cells resided in the extraglomerular mesangium in the JGA and were not renin-secreting cells, macrophages, smooth muscle cells, or endothelial cells. These studies document mesangial cell migration in the anti-Thy 1 model of mesangial proliferative glomerulonephritis and provide evidence for a new role for the juxtaglomerular apparatus in the maintenance of the mesangial cell population.

Cyclin kinase inhibitors are increased during experimental membranous nephropathy: potential role in limiting glomerular epithelial cell proliferation in vivo

The inadequate proliferative response of the visceral glomerular epithelial cell (GEC) following injury in vivo may contribute to the development of progressive glomerulosclerosis in many forms of glomerular disease. Cell proliferation is ultimately controlled by cell-cycle regulatory proteins, including cyclins that bind to cyclin dependent kinases (CDK), and the active complex formed is necessary for progression through the cell-cycle. By inhibiting cyclin-CDK complexes, cyclin kinase inhibitors arrest the cell-cycle and prevent proliferation. To determine the mechanisms that may be responsible for the lack of GEC proliferation in vivo, we examined GEC expression of specific cell-cycle proteins in normal rats and in the passive Heymann nephritis (PHN) model of membranous nephropathy, where the GEC are the target of complement-mediated injury. Following antibody deposition and complement activation there was a marked up-regulation in the cyclin kinase inhibitors p21 and p27 in rats with PHN. By associating with cyclin A-CDK2 complexes, p21 and p27 limited the kinase activity of CDK2. Giving bFGF to rats with PHN was associated with an increase in GEC mitosis and ploidy and a decrease in expression of p21, but not CDK2 or p27. Furthermore, apoptosis was not present in PHN, but was increased in rats given bFGF. In conclusion, this study shows that the low proliferative capacity of the GEC in vivo in response to immune injury may be due to an increase in the expression of specific cyclin kinase inhibitors. The increase in mitosis in PHN rats given bFGF may be due to a decrease in p21. Thus, changes in cell cycle regulatory proteins may regulate the response of GEC to injury and underlie the development of progressive glomerulosclerosis in diseases of the GEC.

Effects of early and late antihypertensive treatment on extracellular matrix proteins and mononuclear cells in uninephrectomized SHR

The efficacy of an early and late treatment with the angiotensin converting enzyme inhibitor lisinopril or the angiotensin II receptor blocker ICI D8731 was investigated in uninephrectomized spontaneously hypertensive rats (SHR). Rats that underwent uninephrectomy (UNX) at six weeks of age were randomly assigned to receive no treatment, lisinopril shortly after UNX, lisinopril starting 16 weeks after UNX, ICI D8731 shortly after UNX, and ICI D8731 starting 16 weeks after UNX. Blood pressure was normalized with both treatments. After six months inulin clearance was not significant different, while proteinuria and prevalence of interstitial fibrosis were significantly reduced in all treatment groups. Immunohistochemical studies revealed an interstitial, periglomerular and perivascular increase of extracellular matrix proteins in all rats, but a markedly reduced expression of collagen I, IV and fibronectin after early and late treatment compared to untreated controls. We found a significant reduction of infiltrating macrophages and T-lymphocytes in all treated animals compared to untreated controls after 2, 4 and 6 months. Especially early treatment was associated with lower numbers of infiltrating cells. Both treatments reduced proliferation of tubular and interstitial cells. There were no striking differences with regard to nephroprotection between the ACE inhibitor and angiotensin II receptor blocker. These findings show that both treatments have beneficial effects on kidney structure and function. They suggest that both ACE inhibition and angiotensin II blockade decrease renal cell proliferation and suppress the infiltration of mononuclear cells that may trigger expression of extracellular matrix proteins and progressive nephrosclerosis.

Neutrophil fate in experimental glomerular capillary injury in the rat. Emigration exceeds in situ clearance by apoptosis

Neutrophils (PMNs) and their toxic contents can injure glomeruli, but to date their fate in glomerulonephritis has been unknown. We studied glomerulonephritis induced in rats by formation of concanavalin A (Con A)/anti-Con A immune complexes on glomerular endothelial cells. PMN infiltration, which was almost exclusively confined to the lumen of glomerular capillaries, was transient, peaking at 4 hours, with only 9.0 +/- 4.1% (mean +/- SEM) of the maximum remaining at 24 hours. There was clear evidence of PMN apoptosis leading to phagocytosis in situ by intraluminal macrophages. However, the kinetics of leukocyte infiltration and PMN apoptosis, the preferential location at 24 hours of apoptotic PMNs within occluded capillary loops, and tracking of radiolabeled PMNs all indicated that in situ phagocytic clearance after apoptosis was the fate of a minority of PMNs, amounting to no more than one-fifth of the peak infiltrating load. Instead, the majority of infiltrating PMNs (72.9 +/- 3.1%) had emigrated from inflamed glomeruli by 24 hours, apparently returning to the circulation. We conclude that PMN emigration from inflamed glomeruli is a hitherto unrecognized mechanism for regulation of PMN-mediated glomerular injury.

SPARC is expressed in renal interstitial fibrosis and in renal vascular injury

Tubulointerstitial inflammation and fibrosis are critical determinants for renal function and prognosis in a variety of human nephropathies. Yet, the pathophysiology of the injury remains obscure. We investigated the expression of SPARC (secreted protein acidic and rich in cysteine) by immunohistochemistry and in situ hybridization in experimental models characterized by tubulointerstitial fibrosis and matrix expansion in rats. SPARC is a secreted glycoprotein that has been demonstrated to affect cellular interaction with matrix proteins, modulate cell proliferation, bind to and/or inhibit growth factors such as PDGF and bFGF, and regulate angiogenesis. Interstitial expression of SPARC was most prominent in passive Heyman nephritis (PHN), chronic cyclosporine A (CsA) nephropathy, and the remnant kidney model and, to a lesser extent, in angiotensin II (Ang II)-infused animals. SPARC protein and mRNA were substantially increased at sites of tubulointerstitial fibrosis/matrix expansion. In the PHN model, SPARC protein was expressed by interstitial fibroblasts that also produced alpha-smooth muscle actin ("myofibroblasts") and correlated both temporally (r = 0.97) and spatially with sites of type I collagen deposition. Interstitial cell proliferation preceded the development of interstitial fibrosis, and maximal SPARC expression (d15) coincided with the initial decline in interstitial proliferation. In the Ang II-infusion model, which is characterized by arteriolopathy and tubulointerstitial injury, an increase in SPARC protein and mRNA was also seen in injured blood vessels. SPARC was shown to be expressed by vascular smooth muscle cells and also by cells in the adventitia of hypertrophied arteries. In summary, SPARC was transiently expressed by interstitial fibroblasts at sites of tubulointerstitial injury and fibrosis, and by smooth muscle cells and cells in the adventitia of injured arteries in the Ang II-model. In addition to its proposed role in extracellular matrix deposition. the antiproliferative properties of SPARC might contribute to the resolution of interstitial fibroblast proliferation in the PHN model.

Changes in cell-cycle protein expression during experimental mesangial proliferative glomerulonephritis

A characteristic response to mesangial cell injury is proliferation, which is closely linked to mesangial matrix accumulation and the progression of glomerular disease. Cell proliferation in non-renal cells in vitro is regulated at the level of the cell-cycle by specific cyclins and their catalytic partners, cyclin dependent kinases (CDK). Cyclin kinase inhibitors (CKI) prevent proliferation by inhibiting cell-cycle progression. However, the expression of cell-cycle regulatory proteins in the kidney and in renal disease is unknown. To determine this we studied the expression of cell-cycle proteins in vivo in normal rats and rats with experimental mesangial proliferative glomerulonephritis (Thy1 model). Normal quiescent rat glomeruli have a differential expression for CKI's, where p27Kip1 is highly expressed, and the levels for p21 (Cip1, Waf1, Sdi1, Cap20) (p21) are low. The onset of mesangial cell proliferation in Thy1 glomerulonephritis is associated with a reduction in p27Kip1 levels when mesangial cell proliferation is maximal. Mesangial cell proliferation in vivo is also associated with an increase in glomerular expression of cyclin A, and an increase in expression and activity for CDK2. The resolution of mesangial cell proliferation was associated with a return to baseline levels for p27Kip1, while the expression for p21 increased substantially. Furthermore, mesangial cell p21 expression was maintained following the resolution of proliferation. These results provide evidence for a complex interplay of cell-cycle regulatory proteins during the glomerular response to injury in vivo. The marked increase in CDK2 expression during mesangial cell proliferation and the sustained increase in p21 expression following the resolution of mesangial cell proliferation suggests that the in vivo expression of certain cell-cycle proteins may differ from that described in non-renal cells in vitro.

The cytoskeletal linking proteins, moesin and radixin, are upregulated by platelet-derived growth factor, but not basic fibroblast growth factor in experimental mesangial proliferative glomerulonephritis

The expression of the two cytoskeletal linking proteins, moesin and radixin, was examined in experimental mesangial proliferative nephritis in rats (anti-Thy1 model). Moesin and radixin mRNA and protein are constitutively expressed in all cell types of normal rat glomeruli, except podocytes. In the anti-Thy1 model the expression of moesin and radixin was increased in infiltrating macrophages and in activated, alpha-smooth muscle actin-positive mesangial cells and was concentrated in the cellular extensions of mesangial cells in areas of glomerular remodelling. Studies using neutralizing antibodies demonstrated that the increase in moesin and radixin expression by mesangial cells is mediated by PDGF, but not bFGF. The increase in these cytoskeletal proteins appears to be regulated primarily (radixin) or partially (moesin) posttranscriptionally. The data suggest that PDGF mediated upregulation of the cytoskeletal proteins, moesin and radixin, is important for cell migration and other changes that accompany the coordinated restoration of glomerular architecture after injury.

SPARC is expressed by mesangial cells in experimental mesangial proliferative nephritis and inhibits platelet-derived-growth-factor-medicated mesangial cell proliferation in vitro

Mesangial cell proliferation is a characteristic feature of many glomerular diseases and often precedes extracellular matrix expansion and glomerulosclerosis. This study provides the first evidence that SPARC (secreted protein acidic and rich in cysteine) could be an endogenous factor mediating resolution of experimental mesangial proliferative nephritis in the rat. SPARC is a platelet-derived-growth-factor-binding glycoprotein that inhibits proliferation of endothelial cells and fibroblasts. We now show that SPARC is synthesized by mesangial cells in culture and that SPARC mRNA levels are increased by platelet-derived growth factor and basic fibroblast growth factor. Recombinant SPARC or the synthetic SPARC peptide 2.1 inhibited platelet-derived-growth-factor-induced mesangial cell DNA synthesis in vitro. In a model of experimental mesangioproliferative glomerulonephritis, SPARC mRNA was increased 5-fold by day 7 and was identified in the mesangium by in situ hybridization. Similarly, SPARC was increased in glomerular mesangial cells and visceral epithelial cells by day 5 and reached maximal expression levels by day 7. Mesangial cell proliferation increased by 36-fold on day 5 and decreased abruptly on day 7. Maximal expression of SPARC was correlated with the resolution of mesangial cell proliferation. We propose that SPARC functions in part as an endogenous inhibitor of platelet-derived-growth-factor-mediated mesangial cell proliferation in glomerulonephritis and that it could account for the resolution of cellular proliferation in this disease.

Thrombospondin 1 is expressed by proliferating mesangial cells and is up-regulated by PDGF and bFGF in vivo

Thrombospondin 1 has been shown to be linked to PDGF-mediated mesangial cell proliferation and migration in vitro, but little is known regarding its expression or regulation in glomerular disease. Experimental mesangial proliferative nephritis was induced in rats by injection of anti-Thy1 antibody. Mesangial cell proliferation was associated with de novo expression of thrombospondin 1 mRNA (detected by Northern blot and in situ hybridization) and protein (by Western blot and immunostaining). Although some thrombospondin 1 was expressed by platelets and macrophages, double labeling showed that most thrombospondin 1 mRNA and protein were expressed by proliferating alpha-actin-positive mesangial cells. Thrombospondin 1 expression in anti-Thy1 nephritis was complement-dependent and could be reduced by treatment with anti-PDGF or anti-bFGF antibodies. Thrombospondin 1 could also be induced in normal rats by infusion of PDGF and in rats which were primed with low dose anti-Thy1 antibody by infusion of PDGF of bFGF. Thus, this study demonstrates that proliferating mesangial cells express thrombospondin 1 de novo in disease and that thrombospondin 1 expression in vivo is regulated by PDGF and bFGF.

Participation of glomerular endothelial cells in the capillary repair of glomerulonephritis

In many glomerular diseases severe injury to the mesangium may occur, leading to matrix dissolution and damage to the glomerular capillaries. Although the destruction of glomerular architecture may lead to permanent injury, in some cases spontaneous recovery occurs. The mechanisms that mediate this recovery are unknown. In this study we provide evidence for glomerular capillary repair (angiogenesis) in the adult injured glomerulus. Injection of anti-Thy 1 antibody into rats results in severe mesangiolysis with capillary ballooning, microaneurysm formation, and loss of endothelial cells in addition to mesangial cells. Although mesangial proliferation is a major response to injury, proliferation of endothelial cells also can be documented from days 2 to 14 in association with repair of the capillaries. The endothelial cell proliferation peaks on days 2 and 7, when it is seven- to ninefold greater than normal. Many of the endothelial cells display morphological features of angiogenesis. The initial wave of endothelial cell proliferation can be reduced by 40% with neutralizing anti-basic fibroblast growth factor antibodies (P < 0.001). The later glomerular endothelial cell proliferation is associated with upregulated expression of vascular permeability factor/endothelial cell growth factor (VPF/VEGF) and an increase of flk, a VPF/VEGF receptor. Although PDGF is expressed in this model, anti-PDGF antibody treatment did not affect the endothelial cell proliferative response. In summary, glomerular endothelial cells have an active role in the glomerular response to injury. Glomeruli are capable of healing microaneurysms, and the mechanism involves basic fibroblast growth factor- and VPF/VEGF-mediated endothelial proliferative responses.

Pathogenesis of cyclosporine nephropathy: roles of angiotensin II and osteopontin

Low-salt-diet, cyclosporine (CsA; 15 mg/kg per day)-treated rats develop striped interstitial fibrosis, arteriolar hyalinosis, and azotemia similar to the chronic nephropathy observed in humans. To examine the role of angiotensin II in this model, rats on a low-salt diet were given CsA, CsA and the angiotensin II receptor Type I antagonist Losartan (10 mg/kg per day), CsA and hydralazine/furosemide, or vehicle. At Day 35, CsA-treated rats had tubular injury, arteriolopathy of the afferent arteriole, increased expression of the monocyte-macrophage adhesive protein osteopontin, interstitial macrophage infiltration, increased interstitial transforming growth factor-beta expression, and interstitial fibrosis. This study provides new insight in both pathogenic and therapeutic aspects of CsA nephropathy. The pathogenesis of CsA nephropathy involves the expression of osteopontin by tubular epithelial cells, the level of which closely correlates with the degree of macrophage infiltration and interstitial fibrosis in all groups (r = 0.79 and 0.74, respectively; P < 0.001). Therapeutic conclusions can be drawn from the observation that both losartan and hydralazine/furosemide reduced osteopontin expression, macrophage infiltration, transforming growth factor-beta expression, and interstitial fibrosis, but did not prevent the decrease in GFR. Treatment with losartan, but not with hydralazine and furosemide, markedly reduced arteriolopathy. It was concluded that angiotensin II contributes to the vasculopathy (hyalinosis) induced by CsA. In contrast, the interstitial fibrosis mediated by CsA can be partially prevented by both an angiotensin II Type I receptor antagonist or by hydralazine and furosemide. This suggests that the interstitial fibrosis can be dissociated from the vascular effects of CsA. The beneficial effects of lowering blood pressure or vasodilation per se may be difficult to distinguish from the specific effects of angiotensin II receptor blockade.

[The flab method of intraoperative radiotherapy]

PURPOSE

Improvement of the relapse rate by locally increasing the tumor dose.

METHODS

To increase the dose in the tumor bed a method for intraoperative radiation therapy has been developed. The radiation is applied using a high-dose-rate afterloading system. Flexible plastic flabs are used as applicators. Each flab contains tubes for the alterloading source. The size of the applicator is chosen to correspond to the size of the target volume. In the dosage system we use the dwell times at all source positions are equal. The dwell time has been precalculated to give the reference dose at the reference position which is located at the surface of the flab in the center of the target volume.

RESULTS

The dose distributions around the flab have been calculated as a function of the thickness of the flab. If the source is not placed on a regular grid within the applicator due to a non ideal positioning of the tubes within the applicator, the dose distribution is not altered too much, if the positioning error is not larger than +/- 2 mm. The influence of a curvature of the flab has been evaluated and methods to decrease the dose at critical organs are discussed.

CONCLUSION

The flab methods for IORT is safe and easy and has been demonstrated for more than 150 cases. This method allows the increase in tumor dose even in regions which are not easily treated by electron IORT due to the rigid electron applicators. Because of the rapid dose fall off, the flab method can only be used for flat target volumes like the tumor bed.

Quit and win smoking cessation contests: how should effectiveness be evaluated?

BACKGROUND

In societies where there are both multiple influences on smoking cessation and a downward secular cessation trend, the attribution of cessation effects to particular interventions poses challenging evaluation problems. Quit smoking lotteries are gaining popularity as mass-reach smoking cessation strategies. Most published evaluations of the lotteries have reported impressive cessation rates within samples of entrants. However, none has considered the possibility that the lotteries merely concentrate a secular quitting trend around a researched event or whether they increase the cessation rate of the whole community from which entrants derive.

RESULTS

Results from a lottery run in a smoking population (n = 101,277) are presented. Of the 1,167 people who entered, 29.2% self-reported being smoke-free at 4 months. These results are considered against a prediction that the campaign might increase the cumulative background 4-month quit rate (708/101,277 or 0.7%) by a minimum of 10%.

CONCLUSION

It is concluded that such a realistic hope, even if achieved, could in practice never be measured. Implications for evaluating the impact of discrete health promotion evaluations in large communities are discussed in terms of the dilemmas posed by the case study.

Parathyroid hormone modulates the release of atrial natriuretic peptide during acute volume expansion

In this study we investigated the effect of volume expansion on plasma and atrial concentrations of atrial natriuretic peptide (ANP) in the presence and absence of the parathyroid gland and under normocalcemic and hypocalcemic conditions. After volume expansion ANP concentration in plasma was significantly (p < 0.001) higher in intact (702 +/- 86 pg/ml) than in hypocalcemic parathyroidectomized (PTX) (271 +/- 38 pg/ml) rats. Plasma ANP of PTX rats rendered normocalcemic with oral calcium supplementation increased to 402 +/- 85 pg/ml after volume expansion. Results from this study suggest that parathyroid hormone (PTH) is required for augmented ANP secretion in response to acute volume loading and alterations of extracellular calcium may modulate volume-induced ANP release in PTX rats. We would discuss that a parathyroid gland-cardiac atria interaction exists and that changes in serum level of PTH may play a role in the regulation of fluid homeostasis via ANP secretion.

Effects of aldosterone and dexamethasone on atrial natriuretic peptide levels in preoptic and hypothalamic nuclei of adrenalectomized and intact rats

The effect of aldosterone and dexamethasone on the concentrations of atrial natriuretic peptide (ANP) in preoptic and hypothalamic nuclei was examined in adrenalectomized and intact rats. Five days after adrenalectomy, increased ANP levels in those brain areas which control water intake, i.e. in the subfornical organ, supraoptic nucleus, and in the so-called hypothalamic drinking centers (perifornical nucleus, lateral hypothalamic area) were measured. In contrast to this, adrenalectomy decreased ANP levels markedly in the organum vasculosum laminae terminalis and preoptic periventricular nucleus, which are reportedly involved in the central regulation of salt and water homeostasis. ANP contents of these two preoptic structures were restored almost completely by daily administration of 0.9% sodium chloride or aldosterone but not dexamethasone. The daily administration of aldosterone elevated ANP levels in the supraoptic, paraventricular and perifornical nuclei as well as in the lateral hypothalamus both in control and adrenalectomized rats. Dexamethasone which was without any significant effect on preoptic and hypothalamic nuclei in control rats elevated ANP levels in the supraoptic and perifornical nuclei and in the lateral hypothalamic area of adrenalectomized animals. Since neither adrenalectomy, nor aldosterone or dexamethasone treatment influenced plasma ANP levels, altered ANP contents measured in preoptic and hypothalamic nuclei may represent a direct effect of adrenal corticoids (mainly aldosterone) on brain ANP-containing neurons which may participate in the control of body fluid and electrolyte homeostasis.