Inflammation In Kidney Disease Research Articles

Hepcidin biology and therapeutic applications

The hepatic peptide hormone hepcidin regulates plasma iron concentrations and tissue iron distribution by inhibiting dietary iron absorption and mobilization of iron from stores in macrophages and hepatocytes. Dysregulation of hepcidin production underlies many iron disorders. Deficient production of hepcidin causes systemic iron overload in hereditary hemochromatosis and iron-loading anemias, such as β-thalassemia, whereas hepcidin excess contributes to the development of anemia in inflammatory disorders and chronic kidney disease, and may cause erythropoietin resistance. The Scientific Program on Iron and Heme session at the 51st ASH annual meeting discussed recent advances in understanding hepcidin biology and explored the potential for hepcidin therapeutic applications. The session included three 30-min presentations.

Atorvastatin-induced modulation of monocyte respiratory burst in vivo in patients with IgA nephropathy: a chronic inflammatory kidney disease

IgA nephropathy (IgAN), the most common chronic inflammatory kidney disease, implies a considerable risk of renal failure and premature cardiovascular disease. Metabolic activation of monocytes has been suggested to be an important link between chronic inflammation, oxidative stress and the development of atherosclerosis. Oxidative stress is also involved in the progression of kidney disease. In this study we investigated the degree of monocyte activation, measured by monocyte respiratory burst in patients with IgAN, since these patients represent a fairly homogenous group of patients with chronic kidney disease, and compared the results to those in healthy subjects. As anti- inflammatory effects have been ascribed to HMG-reductase inhibitors, we also examined whether treatment with atorvastatin influenced monocyte respiratory burst. Monocyte respiratory burst, unstimulated and stimulated by fMLP and PMA, was measured by flow cytometry in 16 patients with biopsy proven IgAN before and after 1 month of treatment with 20 mg atorvastatin/ day. Baseline values were compared to measurements in healthy subjects. Blood and urine samples, before and after statin treatment, were also analyzed for ox-LDL, inflammatory markers (CRP, MCP-1, ICAM-1, TNFR II and NGAL/MMP-9) and renal functional parameters. At baseline, respiratory burst of PMA-stimulated monocytes was higher in patients with IgAN as compared to that in healthy subjects (p = 0.002). After atorvastatin treatment there was a significant reduction of unstimulated, fMLP- and PMA-stimulated monocyte respiratory burst compared to baseline values (p = 0.03, p = 0.003 and p = 0.002, respectively). For ox-LDL and inflammatory serum markers we observed no significant changes. Our study demonstrates a higher monocyte respiratory burst in patients with IgAN compared to in cells from healthy controls as well as a significant reduction of this parameter after short time and low dose atorvastatin treatment.

Tumor Necrosis Factor (TNF-α) and C-reactive Protein (CRP) are Positively Associated with the Risk of Chronic Kidney Disease in Patients with Type 2 Diabetes

PurposeChronic low-grade inflammation may induce chronic kidney disease in patients with type 2 diabetes. This study investigated the relation between inflammatory biomarkers and chronic kidney disease in patients with type 2 diabetes, which has not yet been reported in Asian populations.Materials and MethodsA cross-sectional study was performed in 543 patients recruited from diabetic clinics for an ongoing, prospective study. Multivariate logistic regression was used to evaluate the association between inflammatory biomarkers and the presence of chronic kidney disease (estimated glomerular filtration rate < 60 mL/min per 1.73 m2 by the simplified Modification of Diet in Renal Disease equation using plasma creatinine).ResultsThe risk of chronic kidney disease increased in the highest quartiles of C-reactive protein (CRP) [multivariate odds ratio (OR) = 3.73; 95% CI = 1.19-1.70] and tumor necrosis factor-α (multivariate OR = 4.45; 95% CI = 1.63-12.11) compared to the lowest quartiles after adjustments for age, sex, zinc intake, and other putative risk factors for chronic kidney disease.ConclusionOur results suggest that CRP and tumor necrosis factor-α may be independent risk factors for chronic kidney disease in patients with type 2 diabetes. A causal mechanism of this association should be evaluated in a follow-up study of Korean patients with type 2 diabetes.

Targeting the Hepcidin-Ferroportin Axis in the Diagnosis and Treatment of Anemias

The hepatic peptide hormone hepcidin regulates dietary iron absorption, plasma iron concentrations, and tissue iron distribution. Hepcidin acts by causing the degradation of its receptor, the cellular iron exporter ferroportin. The loss of ferroportin decreases iron flow into plasma from absorptive enterocytes, from macrophages that recycle the iron of senescent erythrocytes, and from hepatocytes that store iron, thereby lowering plasma iron concentrations. Malfunctions of the hepcidin-ferroportin axis contribute to the pathogenesis of different anemias. Deficient production of hepcidin causes systemic iron overload in iron-loading anemias such as beta-thalassemia; whereas hepcidin excess contributes to the development of anemia in inflammatory disorders and chronic kidney disease, and may cause erythropoietin resistance. The diagnosis of different forms of anemia will be facilitated by improved hepcidin assays, and the treatment will be enhanced by the development of hepcidin agonists and antagonists.

THE CHARACTERISTIC OF MEDICAL ACTIVITY AND KNOWLEDGE OF PREGNANT WOMEN WITH CHRONIC INFLAMMATORY DISEASES OF KIDNEYS

The characteristic of medical activity of pregnant women with chronic inflammatory diseases of kidneys before and during pregnancy is presented in the article. Dependence of medical knowledge of women (about available disease, methods of its preventive maintenance, diagnostics and treatment, influence on a current of pregnancy and health of newborn infants) and their medical activity is defined. The obtained data testifies to necessity of target informing of pregnant women from the moment of a capture on the account on pregnancy.

Development of Hepcidin Agonists and Antagonists.

Abstract SCI-27Hepcidin binding to its receptor, the iron exporter ferroportin, leads to degradation of the ligand-receptor complex and decreased flow of iron into plasma from duodenum, macrophages and hepatocytes. Dysregulated production of hepcidin or its aberrant interaction with ferroportin causes a number of iron disorders. Hepcidin deficiency, either relative or absolute, underlies excessive iron loading in hereditary hemochromatosis, beta-thalassemia and hepatitis C. A rare type of hereditary hemochromatosis is also caused by ferroportin resistance to hepcidin. On the other side of the spectrum, hepcidin excess causes iron restriction and anemia, as is observed in patients with iron-refractory iron deficiency anemia. Hepcidin also contributes to development of anemia in different inflammatory disorders and chronic kidney disease, and may cause erythropoietin resistance. Hepcidin agonist and antagonists thus may be useful for treatment of different iron disorders. Antagonist strategies for lowering hepcidin levels have been reported, and include hepcidin-neutralizing monoclonal antibodies or agents interfering with the BMP-related hepcidin production (soluble hemojuvelin and dorsomorphin). To undertake the rational design of drug leads, we analyzed the critical structural features that determine the interaction of hepcidin and Fpn. We showed that the thiol form of Fpn residue Cys326 is essential for hepcidin binding, as is the presence of a disulfide bond on hepcidin. The mechanism of binding appears to involve disulfide exchange between the two molecules. Treatment of ferroportin-expressing cells with thiol-reactive agents prevented hepcidin binding and allowed continuous export of iron from cells. Systematic mutagenesis of additional residues on hepcidin showed that His3, Phe4 and Phe9 are also important for binding to ferroportin. To provide leads for hepcidin agonists, we then synthesized a mini-hepcidin containing only the 9 N-terminal hepcidin residues (DTHFPICIF), and showed that it displayed significant activity in vitro. Proteolysis-resistant analogs of this peptide were also active in vivo after intraperitoneal injection in mice. The small size of these peptides may allow oral bioavailability. Understanding the mechanisms of hepcidin regulation and its interaction with ferroportin will facilitate the development of new agents for the treatment of iron overload disorders and iron-restricted anemias. DisclosuresNemeth:Intrinsic LifeSciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Growth Arrest Specific Protein 6 Participates in DOCA-Induced Target-Organ Damage

Growth arrest-specific protein 6 (Gas 6) is involved in inflammatory kidney diseases, vascular remodeling, cell adhesion, and thrombus formation. We explored a role for Gas 6 in aldosterone-induced target organ damage. We observed that Gas 6 was upregulated in rats with high aldosterone levels. Mineralocorticoid receptor blockade prevented target organ damage and decreased the elevated Gas 6 expression. Vascular smooth muscle cells given aldosterone increased their Gas 6 expression in vitro. To test the pathophysiological relevance, we investigated the effects of deoxycorticosterone acetate (DOCA) on Gas 6 gene-deleted ((-/-)) mice. After 6 weeks DOCA, Gas 6(-/-) mice developed similar telemetric blood pressure elevations compared to wild-type mice but were protected from cardiac hypertrophy. Cardiac expression of interleukin 6 and collagen IV was blunted in Gas 6(-/-) mice, indicating reduced inflammation and fibrosis. Gas 6(-/-) mice also had an improved renal function with reduced albuminuria, compared to wild-type mice. Renal fibrosis and fibronectin deposition in the kidney were also reduced. Gas 6 deficiency reduces the detrimental effects of aldosterone on cardiac and renal remodeling independent of blood pressure reduction. Gas 6 appears to play a role in mineralocorticoid receptor-mediated target organ damage. Furthermore, because warfarin interferes with Gas 6 protein expression, the findings could be of clinical relevance for anticoagulant choices.

Resolution of renal inflammation: a new role for NF-κB1 (p50) in inflammatory kidney diseases

In renal tissue injury, activation of the transcription factor NF-kappaB has a central role in the induction of proinflammatory gene expression, which are involved in the development of progressive renal inflammatory disease. The function of NF-kappaB during the switch from the inflammatory process toward resolution, however, is largely unknown. Therefore, we assessed the time-dependent activation and function of NF-kappaB in two different models of acute nephritis. Our experiments demonstrate a biphasic activation of NF-kappaB in the anti-Thy-1 model of glomerulonephritis in rats and the LPS-induced nephritis in mice, with a first peak during the induction phase and a second peak during the resolution period. After induction of glomerular immune injury in rats, predominantly NF-kappaB p65/p50 heterodimer complexes are shifted to the nucleus whereas during the resolution phase predominantly p50 homodimers could be demonstrated in the nuclear compartment. In addition, we could demonstrate that p50 protein plays a pivotal role in the resolution of LPS-induced renal inflammation since NF-kappaB p50 knockout mice demonstrate significantly higher chemokine expression, prolonged renal inflammatory cell infiltration with consecutive tissue injury, and reduced survival. In conclusion, our studies indicate that NF-kappaB subunit p50 proteins have critical in vivo functions in immunologically mediated renal disease by downregulating inflammation during the resolution period.

Dexamethasone enhances basal and TNF-α-stimulated production of PAI-1 via the glucocorticoid receptor regardless of 11β-hydroxysteroid dehydrogenase 2 status in human proximal renal tubular cells

Long-term treatment with glucocorticoids (GCs) reportedly exaggerates renal fibrosis in chronic progressive inflammatory kidney disease. GCs induce the gene expression of plasminogen activator inhibitor-1 (PAI-1), a fibrosis enhancer in non-renal cells. Tumour necrosis factor-alpha (TNF-alpha) reduces the gene expression of 11beta-hydroxysteroid dehydrogenase (HSD) 2, an inactivator of GCs, and may enhance GC activity. However, the individual and collective effects of adrenal steroids, TNF-alpha and HSD2 status on PAI-1 production are unknown in human proximal renal tubular epithelial cells (HPTECs). Confluent HPTECs were treated with adrenal steroids (10 nM to 10 microM) or TNF-alpha (10 ng/ml) for up to 48 h. The mRNA amounts of the target genes were determined by TaqMan quantitative PCR, and the PAI-1 protein amounts were measured by an immunoassay. Dexamethasone (DXA) maximally increased the amounts of PAI-1 mRNA and protein at 100 nM. Aldosterone (Ald) increased PAI-1 expression dose dependently, but the effect was over 100-fold weaker than that of DXA. The PAI-1-increasing effects of DXA and Ald were abolished completely by U-486, a specific inhibitor of the glucocorticoid receptor (GR) but not by spironolactone, a specific inhibitor of the mineralocorticoid receptor. The effect of DXA was also blocked partially by AG1478 and herbimycin A, tyrosine kinase inhibitors. DXA further increased TNF-alpha-stimulated PAI-1 expression via the GR. Although TNF-alpha treatment caused an 80% reduction in the gene expression of HSD2, an inactivator of GCs, HSD2 inhibition did not enhance DXA-induced PAI-1 production. DXA induces basal and TNF-alpha-stimulated PAI-1 expression via the GR pathway, regardless of HSD2 status in HPTECs. Excess GCs may serve as a pro-fibrotic factor in chronic inflammatory kidney diseases.

Chemokines and B cells in renal inflammation and allograft rejection

Green tea, the most popular beverage next to water, is a rich source of tea catechins and has potential to be developed as a chemopreventive agent for prostate cancer. For centuries it has been used in traditional medicine in Far-East countries. Male populations in these countries where large quantities of green tea are consumed on regular basis have the lowest incidence of prostate cancer. In this review, after a description of prostate cancer and several risk factors associated with the disease, we evaluated studies reported with green tea or its major constituent, (-)-epigallocatechin-3-gallate in inhibition of prostate cancer. This review provides an in-depth overview of various biochemical and signaling pathways affected by green tea in in vivo and in vitro models of prostate cancer. This is followed by a comprehensive discussion of the epidemiological studies and some ongoing clinical trials with green tea catechins. The review concludes with a brief discussion of the future direction and development of clinical trials employing green tea catechins which could be developed for prevention and/or intervention of prostate cancer.

Chemokines and B cells in renal inflammation and allograft rejection

Green tea, the most popular beverage next to water, is a rich source of tea catechins and has potential to be developed as a chemopreventive agent for prostate cancer. For centuries it has been used in traditional medicine in Far-East countries. Male populations in these countries where large quantities of green tea are consumed on regular basis have the lowest incidence of prostate cancer. In this review, after a description of prostate cancer and several risk factors associated with the disease, we evaluated studies reported with green tea or its major constituent, (-)-epigallocatechin-3-gallate in inhibition of prostate cancer. This review provides an in-depth overview of various biochemical and signaling pathways affected by green tea in in vivo and in vitro models of prostate cancer. This is followed by a comprehensive discussion of the epidemiological studies and some ongoing clinical trials with green tea catechins. The review concludes with a brief discussion of the future direction and development of clinical trials employing green tea catechins which could be developed for prevention and/or intervention of prostate cancer.

C3G overexpression in glomerular epithelial cells during anti-GBM-induced glomerulonephritis

The guanine nucleotide exchange factor C3G, along with the CrkII adaptor protein, mediates GTP activation of the small GTPase proteins Rap1 and R-Ras, facilitating their activation of downstream signaling pathways, which had been found to be important in the pathogenesis of glomerulonephritis. We found that expression of C3G protein was upregulated in glomerular epithelial cells in an experimental model of accelerated anti-GBM antibody-induced glomerulonephritis expression. To determine the consequence of its increased expression, we transfected C3G (using adenoviral constructs) into cultured glomerular epithelial cells and measured the activated forms (i.e., GTP-bound) forms of Rap1 and R-Ras. Activation of Rap1 was not affected by C3G; however, the basal level of GTP-bound R-Ras was decreased. Further, C3G over-expression enhanced the activation of R-Ras in response to endothelin. Overexpression of C3G also led to a significant reduction in glomerular epithelial cell spreading and decreased the cells' E-cadherin expression and augmented their migration. We found that C3G was overexpressed in accelerated anti-GBM antibody-induced glomerulonephritis and suggest that this modulates glomerular epithelial cell morphology and behavior.

Immune-related health-relevant changes in natural populations of Norway rat (Rattus norvegicus Berkenhout, 1769): White blood cell counts, leukocyte activity, and peripheral organ infiltration

Basic immune-related health-relevant changes (total and differential white blood cell counts and activity, leukocyte tissue infiltration, and related pathohistology) were assessed in wild Norway rats from urban habitats. Comparative measurements were conducted in individuals of several laboratory strains of Norway rat in order to gain insight into environmental effects on the health of wild rats. Changes in leukocyte counts and activity along with tissue infiltration were noted only in wild rats, indicating systemic as well as tissue inflammation in these animals. Coincidence of these changes with chronic inflammatory pulmonary and kidney disease was observed in the majority of affected rats.

Glycogen Synthase Kinase 3β: A Novel Marker and Modulator of Inflammatory Injury in Chronic Renal Allograft Disease

One key cell-signaling event central to inflammation in kidney diseases, including chronic renal allograft dysfunction or disease (CRAD), is the activation of NF-kappaB, which controls transcription of numerous proinflammatory mediators. Glycogen synthase kinase (GSK) 3beta is an indispensable element of NF-kappaB activation, however, the exact role of GSK3beta in the pathogenesis of inflammatory kidney diseases like CRAD is uncertain and was examined. Immunohistochemistry staining of GSK3beta was weak in normal kidneys, but was markedly induced in inflamed allograft kidneys, with prominent cytoplasmic staining of tubular cells in areas of inflammation. Net GSK3beta activity is regulated by inhibitory phosphorylation of its serine 9 residue, and this occurred in CRAD. Thus, the magnitude of GSK3beta inactivation was inversely correlated with the degree of injury as assessed by Banff criteria. In vitro in cultured human tubular epithelial cells, GSK3beta overexpression augmented, while GSK3beta silencing diminished proinflammatory cellular responses to TNF-alpha stimulation, including NF-kappaB activation and expression of chemokines MCP-1 and RANTES. These inflammatory responses were obliterated by GSK3beta inhibitors. Collectively, GSK3beta plays an important role in mediating proinflammatory NF-kappaB activation and renal inflammation. Suppression of GSK3beta activity might represent a novel therapeutic strategy to treat CRAD.

Characterization of CXCL16 and ADAM10 in the normal and transplanted kidney

The chemokine CXCL16 plays an important role in the recruitment of leukocytes to sites of inflammation influencing the course of experimental glomerulonephritis. Here we show that human kidneys highly express CXCL16 in the distal tubule, connecting tubule and principal cells of the collecting duct with weak expression in the thick ascending limb of Henle. Beside the membrane localization, a soluble form of CXCL16 can be proteolytically released which acts as a chemotactic factor. In human renal tissue the expression pattern of the disintegrin-like metalloproteinase ADAM10 is similar to that of CXCL16, suggesting ADAM10 can potentially cleave CXCL16 in vivo. When we tested this in primary tubular cells we found that blockade of ADAM10 activity inhibited the IFN-gamma induced release of soluble CXCL16. Acute tubular damage in renal allografts was associated with elevated urinary CXCL16 and this correlated with focally increased apical CXCL16 expression in the distal tubules and collecting ducts. Renal allograft biopsies, with a histopathological diagnosis of acute interstitial rejection, showed increased basolateral ADAM10 expression together with high numbers of infiltrating T cells. Our results suggest that CXCL16 and ADAM10 are involved in the recruitment of T cells to the kidney and play an important role in inflammatory kidney diseases.

Analysis and classification of B-cell infiltrates in lupus and ANCA-associated nephritis

Intrarenal B cell infiltrates resembling secondary lymphoid tissue have been found in several forms of inflammatory kidney disease. Their role in renal inflammation is not well defined, perhaps because B cell clusters have been regarded as a single entity while being quite heterogeneous. Therefore we characterized intrarenal lymphoid clusters of 32 patients diagnosed with lupus nephritis and 16 with ANCA associated nephritis. We identified four increasingly organized levels of intrarenal aggregates from scattered B cells to highly compartmentalized B cell clusters with central follicular dendritic cell networks. Most B cells displayed a mature non-antibody producing phenotype with antigen presenting ability. In regions of B cell infiltration, expression of the lymphoid chemokine BCA-1 was found in cells of a dendritic-like morphology and most B cells expressed the corresponding receptor CXCR5. Biopsies containing B cells had significantly higher levels of BCA-1 mRNA expression compared to those without, suggesting a role of BCA-1 and CXCR5 for B cell infiltration into the kidney. Our study proposes a new classification of B cell clusters in lupus and ANCA associated nephritis which might help to study the function of intrarenal B cell clusters in a more differentiated manner.

Hepatocyte Growth Factor Suppresses Proinflammatory NFκB Activation through GSK3β Inactivation in Renal Tubular Epithelial Cells

Activation of NFkappaB is a fundamental cellular event central to all inflammatory diseases. Hepatocyte growth factor (HGF) ameliorates both acute and chronic inflammation in a multitude of organ systems through modulating NFkappaB activity; nevertheless, the exact molecular mechanism remains uncertain. Here we report that HGF through inactivation of GSK3beta suppresses NFkappaB p65 phosphorylation specifically at position Ser-468. The Ser-468 of RelA/p65 situates in a GSK3beta consensus motif and could be directly phosphorylated by GSK3beta both in vivo and in vitro, signifying Ser-468 of RelA/p65 as a putative substrate for GSK3beta. In addition, the C terminus of RelA/p65 harbors a highly conserved domain homologue of the consensus docking sequence for GSK3beta. Moreover, this domain was required for efficient phosphorylation of Ser-468 and was indispensable for the physical interaction between RelA/p65 and GSK3beta. HGF substantially intercepted this interaction by inactivating GSK3beta. Functionally, phosphorylation of Ser-468 of RelA/p65 was required for the induced expression of a particular subset of proinflammatory NFkappaB-dependent genes. Diminished phosphorylation at Ser-468 by HGF resulted in a gene-specific inhibition of these genes' expression. The action of HGF on proinflammatory NFkappaB activation was consistently mimicked by a selective GSK3beta inhibitor or GSK3beta knockdown by RNA interference but largely abrogated in cells expressing the mutant uninhibitable GSK3beta. Collectively, our findings suggest that HGF has a potent suppressive effect on NFkappaB activation, which is mediated by GSK3beta, an important signaling transducer controlling RelA/p65 phosphorylation specificity and directing the transcription of selective proinflammatory cytokines implicated in inflammatory kidney disease.

Tumor necrosis factor-α up-regulates the expression of CCL2 and adhesion molecules of human proximal tubular epithelial cells through MAPK signaling pathways

Both circulating and urinary tumor necrosis factor (TNF)- α levels have been shown to increase in inflammatory chronic kidney diseases and TNF- α can induce secretion of other inflammatory mediators from many cell types. Chemokine, mononuclear chemoattractant protein-1 (CCL2/MCP-1), and cell surface adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), in renal proximal tubular epithelial cells (PTEC) are important for promoting recruitment and adhesion of infiltrating macrophages and lymphocytes to inflamed renal tissue. This study aimed to investigate the effect of TNF- α on the expression of these inflammation-related molecules of human PTEC and the underlying intracellular mitogen-activated protein kinase (MAPK) regulatory signaling mechanisms. Cytokine expression profile of TNF- α-activated PTEC was assayed by protein array. The concentration of CCL2 was analyzed by ELISA, while the expression of cell surface ICAM-1 and VCAM-1 and intracellular phosphorylated p38 MAPK, c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) was assessed using flow cytometry. TNF- α could significantly induce CCL2, ICAM-1 and VCAM-1 expression of PTEC. Selective inhibitors of p38 MAPK (SB203580), JNK (SP600125) and ERK (PD98059) could suppress TNF- α-induced CCL2 and ICAM-1 expression, while only p38 MAPK and ERK inhibitors could suppress TNF- α-induced VCAM-1 expression. JNK inhibitor was found to up-regulate VCAM-1 expression but did not elicit any additive effect with TNF- α on VCAM-1 expression. Moreover, p38 MAPK inhibitor was found to abrogate the TNF- α-induced ERK phosphorylation, suggesting that there was a one-way interaction between p38 MAPK and ERK pathways during the TNF- α activation. TNF- α can play a crucial role in the immunopathogenesis of nephritis by the induction of CCL2, ICAM-1 and VCAM-1 expression via the activation of the intracellular MAPK signaling pathway, which may contribute to macrophage and lymphocyte infiltration.

TLR4 Links Podocytes with the Innate Immune System to Mediate Glomerular Injury

Toll-like receptors (TLR) classically recognize pathogen-associated danger signals but are also activated via endogenous ligands. For evaluation of their role in inflammatory kidney disease, the function of TLR was analyzed in two mouse models of cryoglobulinemic membranoproliferative glomerulonephritis (MPGN; mice transgenic for thymic stromal lymphopoietin [TSLP], with or without deletion of the Fcgamma receptor IIb). Expression of TLR1 through 9 and TLR11 mRNA was detectable in whole kidneys and in isolated glomeruli of wild-type mice, with TLR3 and TLR4 having the highest absolute levels of expression. TLR1, 2, and 4 were increased in TSLP transgenic mice and even higher in TSLP transgenic FcgammaRIIb-deficient mice. TLR5 through 9 and 11 were upregulated to similar degrees in TSLP transgenic and TSLP transgenic FcgammaRIIb-deficient mice. Immunohistochemical studies of nephritic glomeruli localized TLR4 protein to podocytes. Cultured podocytes also expressed TLR4, and stimulation with TLR4-specific ligands resulted in a marked induction of chemokines; this was reduced by specific knockdown of TLR4 with siRNA. Fibrinogen, a potential endogenous TLR4 ligand, was shown to induce a similar profile of chemokines. In conclusion, it was demonstrated that TLR4 is constitutively expressed by podocytes and is upregulated in MPGN, where it may mediate glomerular injury by modulating expression of chemokines; therefore, TLR4 may link podocytes with the innate immune system to mediate MPGN triggered by the deposition of immune complexes.

Factor I is required for the development of membranoproliferative glomerulonephritis in factor H-deficient mice.

The inflammatory kidney disease membranoproliferative glomerulonephritis type II (MPGN2) is associated with dysregulation of the alternative pathway of complement activation. MPGN2 is characterized by the presence of complement C3 along the glomerular basement membrane (GBM). Spontaneous activation of C3 through the alternative pathway is regulated by 2 plasma proteins, factor H and factor I. Deficiency of either of these regulators results in uncontrolled C3 activation, although the breakdown of activated C3 is dependent on factor I. Deficiency of factor H, but not factor I, is associated with MPGN2 in humans, pigs, and mice. To explain this discordance, mice with single or combined deficiencies of these factors were studied. MPGN2 did not develop in mice with combined factor H and I deficiency or in mice deficient in factor I alone. However, administration of a source of factor I to mice with combined factor H and factor I deficiency triggered both activated C3 fragments in plasma and GBM C3 deposition. Mouse renal transplant studies demonstrated that C3 deposited along the GBM was derived from plasma. Together, these findings provide what we believe to be the first evidence that factor I-mediated generation of activated C3 fragments in the circulation is a critical determinant for the development of MPGN2 associated with factor H deficiency.