Interleukin-1 beta stimulates human mesangial cells to synthesize and release interleukins-6 and -8

The role of the mesangium in glomerular function

When discussing glomerular function, one cell type is often left out, the mesangial cell (MC), probably since it is not a part of the filtration barrier per se. The MCs are instead found between the glomerular capillaries, embedded in their mesangial matrix. They are in direct contact with the endothelial cells and in close contact with the podocytes and together they form the glomerulus. The MCs can produce and react to a multitude of growth factors, cytokines, and other signaling molecules and are in the perfect position to be a central hub for crosstalk communication between the cells in the glomerulus. In certain glomerular diseases, for example, in diabetic kidney disease or IgA nephropathy, the MCs become activated resulting in mesangial expansion. The expansion is normally due to matrix expansion in combination with either proliferation or hypertrophy. With time, this expansion can lead to fibrosis and decreased glomerular function. In addition, signs of complement activation are often seen in biopsies from patients with glomerular disease affecting the mesangium. This review aims to give a better understanding of the MCs in health and disease and their role in glomerular crosstalk and inflammation.

The Glomerulus According to the Mesangium

The glomerulus is the functional unit for filtration of blood and formation of primary urine. This intricate structure is composed of the endothelium with its glycocalyx facing the blood, the glomerular basement membrane and the podocytes facing the urinary space of Bowman's capsule. The mesangial cells are the central hub connecting and supporting all these structures. The components as a unit ensure a high permselectivity hindering large plasma proteins from passing into the urine while readily filtering water and small solutes. There has been a long-standing interest and discussion regarding the functional contribution of the different cellular components but the mesangial cells have been somewhat overlooked in this context. The mesangium is situated in close proximity to all other cellular components of the glomerulus and should be considered important in pathophysiological events leading to glomerular disease. This review will highlight the role of the mesangium in both glomerular function and intra-glomerular crosstalk. It also aims to explain the role of the mesangium as a central component involved in disease onset and progression as well as signaling to maintain the functions of other glomerular cells to uphold permselectivity and glomerular health.

IL-20 in Acute Kidney Injury: Role in Pathogenesis and Potential as a Therapeutic Target

Acute kidney injury (AKI) causes over 1 million deaths worldwide every year. AKI is now recognized as a major risk factor in the development and progression of chronic kidney disease (CKD). Diabetes is the main cause of CKD as well. Renal fibrosis and inflammation are hallmarks in kidney diseases. Various cytokines contribute to the progression of renal diseases; thus, many drugs that specifically block cytokine function are designed for disease amelioration. Numerous studies showed IL-20 functions as a pro-inflammatory mediator to regulate cytokine expression in several inflammation-mediated diseases. In this review, we will outline the effects of pro-inflammatory cytokines in the pathogenesis of AKI and CKD. We also discuss the role of IL-20 in kidney diseases and provide a potential therapeutic approach of IL-20 blockade for treating renal diseases.

Association of Interleukin-10 Polymorphisms (rs1800872, rs1800871, and rs1800896) with Predisposition to IgA Nephropathy in a Chinese Han Population: A Case-Control Study

BACKGROUND/AIMS

IgA nephropathy (IgAN) is a common form of primary glomerulonephritis worldwide. Previous studies indicated that IL-10 single nucleotide polymorphisms (SNP) play an important role in IgAN pathogenesis, but the results were controversy. This study aimed to investigate the association between IL-10 SNPs (rs1800872, rs1800871, and rs1800896) with IgAN in a Chinese Han population.

METHODS

We conducted a case-control study that included 351 patients with IgAN and 310 age-, gender- and ethnicity-matched healthy controls. Three promoter SNPs (rs1800872, rs1800871, and rs1800896) of IL-10 were genotyped by Sequenom MassARRAY. Odds ratios (ORs) with 95% confidence intervals (CI) were used to assess the relationship with IgAN.

RESULTS

We found that the rs1800896 did not correlate with IgAN risk, whereas rs1800872 and rs1800871 were significantly associated with increased IgAN risk in all genetic models. The haplotype analysis indicated that the CCA haplotype was associated with increased IgAN risk (OR = 1.36; 95% CI = 1.05-1.75). Moreover, there were no associations between these SNPs and blood pressure or gender, whereas the rs1800896 variant was correlated with higher 24-hour urine protein in patients with IgAN.

CONCLUSION

Taken together, these results suggest that IL-10 is a susceptibility gene in patients with IgAN.

Lipoprotein X Causes Renal Disease in LCAT Deficiency

Human familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is characterized by low HDL, accumulation of an abnormal cholesterol-rich multilamellar particle called lipoprotein-X (LpX) in plasma, and renal disease. The aim of our study was to determine if LpX is nephrotoxic and to gain insight into the pathogenesis of FLD renal disease. We administered a synthetic LpX, nearly identical to endogenous LpX in its physical, chemical and biologic characteristics, to wild-type and Lcat-/- mice. Our in vitro and in vivo studies demonstrated an apoA-I and LCAT-dependent pathway for LpX conversion to HDL-like particles, which likely mediates normal plasma clearance of LpX. Plasma clearance of exogenous LpX was markedly delayed in Lcat-/- mice, which have low HDL, but only minimal amounts of endogenous LpX and do not spontaneously develop renal disease. Chronically administered exogenous LpX deposited in all renal glomerular cellular and matrical compartments of Lcat-/- mice, and induced proteinuria and nephrotoxic gene changes, as well as all of the hallmarks of FLD renal disease as assessed by histological, TEM, and SEM analyses. Extensive in vivo EM studies revealed LpX uptake by macropinocytosis into mouse glomerular endothelial cells, podocytes, and mesangial cells and delivery to lysosomes where it was degraded. Endocytosed LpX appeared to be degraded by both human podocyte and mesangial cell lysosomal PLA2 and induced podocyte secretion of pro-inflammatory IL-6 in vitro and renal Cxl10 expression in Lcat-/- mice. In conclusion, LpX is a nephrotoxic particle that in the absence of Lcat induces all of the histological and functional hallmarks of FLD and hence may serve as a biomarker for monitoring recombinant LCAT therapy. In addition, our studies suggest that LpX-induced loss of endothelial barrier function and release of cytokines by renal glomerular cells likely plays a role in the initiation and progression of FLD nephrosis.

TNFα Amplifies DNaseI Expression in Renal Tubular Cells while IL-1β Promotes Nuclear DNaseI Translocation in an Endonuclease-Inactive Form

We have demonstrated that the renal endonuclease DNaseI is up-regulated in mesangial nephritis while down-regulated during progression of the disease. To determine the basis for these reciprocal DNaseI expression profiles we analyse processes accounting for an early increase in renal DNaseI expression. Main hypotheses were that i. the mesangial inflammation and secreted pro-inflammatory cytokines directly increase DNaseI protein expression in tubular cells, ii. the anti-apoptotic protein tumor necrosis factor receptor-associated protein 1 (Trap 1) is down-regulated by increased expression of DNaseI due to transcriptional interference, and iii. pro-inflammatory cytokines promote nuclear translocation of a variant of DNaseI. The latter hypothesis emerges from the fact that anti-DNaseI antibodies stained tubular cell nuclei in murine and human lupus nephritis. The present study was performed on human tubular epithelial cells stimulated with pro-inflammatory cytokines. Expression of the DNaseI and Trap 1 genes was determined by qPCR, confocal microscopy, gel zymography, western blot and by immune electron microscopy. Results from in vitro cell culture experiments were analysed for biological relevance in kidneys from (NZBxNZW)F1 mice and human patients with lupus nephritis. Central data indicate that stimulating the tubular cells with TNFα promoted increased DNaseI and reduced Trap 1 expression, while TNFα and IL-1β stimulation induced nuclear translocation of the DNaseI. TNFα-stimulation resulted in 3 distinct effects; increased DNaseI and IL-1β gene expression, and nuclear translocation of DNaseI. IL-1β-stimulation solely induced nuclear DNaseI translocation. Tubular cells stimulated with TNFα and simultaneously transfected with IL-1β siRNA resulted in increased DNaseI expression but no nuclear translocation. This demonstrates that IL-1β promotes nuclear translocation of a cytoplasmic variant of DNaseI since translocation clearly was not dependent on DNaseI gene activation. Nuclear translocated DNaseI is shown to be enzymatically inactive, which may point at a new, yet unknown function of renal DNaseI.

Relationships of urinary VEGF/CR and IL-6/CR with glomerular pathological injury in asymptomatic hematuria patients

BACKGROUND

Interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) have important functions in injury and repair processes of glomerular intrinsic cells. A study was conducted to analyze the urinary VEGF/creatinine (CR) and IL-6/CR levels in simple hematuria patients after excluding the interference of creatinine. We aimed to investigate the function and relationships of the above indices in the glomerular pathological injury process, and to elaborate the values of urinary VEGF and IL-6 changes in the diagnosis of asymptomatic hematuria or hematuria with proteinuria.

MATERIAL/METHODS

A total of 121 renal hematuria patients diagnosed by clinical and laboratory tests were included as research subjects. The midstream fresh morning urine was collected on the day renal biopsy was performed.

RESULTS

The IL-6/CR value of the group III was significantly greater than in group I (Z=-2.478, P<0.05), with a statistically significant difference between these 2 groups. The VEGF/CR value of group III was significantly greater than in group II (P<0.01). Compared with group I, the VEGF/CR of group III was significantly greater (Z=-4.65, P<0.01), with a statistically significant difference.

CONCLUSIONS

The VEGF/CR and IL-6/CR values in simple hematuria patients were positively correlated with glomerular pathological injury scores. VEGF/CR and IL-6/CR might be used as biological diagnostic indicators in determining the extent of simple hematuria glomerular injury.

Genetic variants in interleukin genes and susceptibility to IgA nephropathy: a meta-analysis

Many existing studies have demonstrated that genetic variants in interleukin (IL) genes might have an impact on an individual's susceptibility to IgA nephropathy (IgAN); but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the relationships between IL genetic variants and IgAN risk. We searched CISCOM, CINAHL, Web of Science, PubMed, Google Scholar, EBSCO, Cochrane Library, and China BioMedicine (CBM) and China National Knowledge Infrastructure (CNKI) databases from inception through August 1, 2013. Meta-analysis was performed using the STATA 12.0 software. Seven case-control studies were included with a total of 1135 IgAN patients and 1603 healthy controls. Our meta-analysis results revealed that genetic variants in IL-1 and IL-1RN genes were associated with an increased risk of IgAN. However, similar associations were not observed in IL-6, IL-10, and IL-22R genes. Subgroup analysis by ethnicity suggested that there were significant associations between IL genetic variants and an increased risk of IgAN among both Asian and Caucasian populations. Meta-regression analyses showed that gene types may be a major source of heterogeneity. No publication bias was detected in this meta-analysis. The present meta-analysis suggests that IL genetic variants may contribute to the risk of IgAN, especially in IL-1 and IL-1RN genes.

Association of interleukin-6 -174 G>C promoter polymorphism with increased risk of type 2 diabetes mellitus patients with diabetic nephropathy in Turkey

OBJECTIVE

Diabetic nephropathy (DN) is a serious complication of diabetes mellitus. We aimed to evaluate the interleukin (IL)-6 gene polymorphisms in type 2 DN and control subjects.

MATERIALS AND METHODS

The patients selected from the Department of Endocrinology and Metabolism Diseases included 43 type 2 diabetes mellitus patients without DN and 43 type 2 diabetes mellitus patients with DN and 340 healthy normal controls. All subjects underwent venous blood drawing for complete hormonal assays, lipid profile, glucose, and insulin and Il-6 gene polymorphism genetic analysis.

RESULTS

IL-6 -174 G>C genotype distribution was different between the control group and the type 2 diabetes mellitus patients (p=0.004). The higher frequency of the polymorphic G allele was also similar for the group with type 2 diabetes mellitus as for the control group. The frequency of the polymorphic G allele was 83.9% in diabetic patients with nephropathy versus 70.9% in those without nephropathy (p=0.039).

CONCLUSION

We suggest that the -174 G>C polymorphism of the IL-6 gene is an independent risk factor for DN in Turkish type 2 diabetes mellitus patients.

Clinical values of urinary IL-6 in asymptomatic renal hematuria and renal hematuria with proteins

Renal hematuria is caused by glomerular disease. Under pathological conditions, the distribution of interleukin-6 (IL-6) in kidney tissue is abnormal and urinary IL-6 levels are increased. Abnormal IL-6 secretion promotes the hyperplasia of mesangial cells and matrix and, thus, affects the permeability of the glomerular filtration membrane. Therefore, the detection of urinary IL-6 levels in patients with renal hematuria is beneficial for disease evaluation. A total of 82 patients with primary renal hematuria were divided into group 1 (UPr/24 h < 150 mg; pure hematuria group), group 2 (150 mg ≤ UPr/24 h ≤ 1,000 mg) and group 3 (UPr/24 h > 1,000 mg). A total of 30 normal individuals were selected as the controls. The urinary IL-6 levels were detected by the enzyme-linked immunosorbent assay (ELISA) method and a renal biopsy was conducted. The urinary IL-6 levels and renal pathological damage scores in groups 1 and 2 were significantly reduced compared with those in group 3, (P<0.001 and 0.01, respectively), with no significant difference between groups 1 and 2 (P>0.05). The correlation coefficient (r) of urinary IL-6 with 24 h urinary protein (UPr/24 h) in groups 1, 2 and 3 was 0.017, 0.045 and 0.747, respectively, and that of urinary IL-6 with renal pathological damage score was 0.627, 0.199 and 0.119, respectively. The UPr/24 h was significantly correlated with IL-6 level (r=0.7320, P<0.000). In group 1, the urinary IL-6 levels were correlated with the degree of renal pathological damage. A positive correlation was observed between urinary IL-6 levels and UPr/24 h.

Bench-to-bedside review: Ventilation-induced renal injury through systemic mediator release--just theory or a causal relationship?

We review the current literature on the molecular mechanisms involved in the pathogenesis of acute kidney injury induced by plasma mediators released by mechanical ventilation. A comprehensive literature search in the PubMed database was performed and articles were identified that showed increased plasma levels of mediators where the increase was solely attributable to mechanical ventilation. A subsequent search revealed articles delineating the potential effects of each mediator on the kidney or kidney cells. Limited research has focused specifically on the relationship between mechanical ventilation and acute kidney injury. Only a limited number of plasma mediators has been implicated in mechanical ventilation-associated acute kidney injury. The number of mediators released during mechanical ventilation is far greater and includes pro- and anti-inflammatory mediators, but also mediators involved in coagulation, fibrinolysis, cell adhesion, apoptosis and cell growth. The potential effects of these mediators is pleiotropic and include effects on inflammation, cell recruitment, adhesion and infiltration, apoptosis and necrosis, vasoactivity, cell proliferation, coagulation and fibrinolysis, transporter regulation, lipid metabolism and cell signaling. Most research has focused on inflammatory and chemotactic mediators. There is a great disparity of knowledge of potential effects on the kidney between different mediators. From a theoretical point of view, the systemic release of several mediators induced by mechanical ventilation may play an important role in the pathophysiology of acute kidney injury. However, evidence supporting a causal relationship is lacking for the studied mediators.

Effects of glutamine supplementation on kidney of diabetic rat

Glutamine is the most important donor of NH(3) in kidney playing an important role in acid-base buffering system. Besides this effect, glutamine presents many other relevant functions in the whole body, such as a precursor of arginine in adult and neonates. In addition to these effects, some studies have shown that glutamine can potentiate renal disease. In the present study, the effect of short-term treatment (15 days) with glutamine on control and diabetic rats was investigated. Using biochemical, histological and molecular biology analysis from control and diabetic rats we verified that glutamine supplementation increase in pro-inflammatory interleukins (IL)-1beta and IL-6 content in renal cortex and induce alteration in glomerular characteristics. This study showed that short-term treatment with glutamine in association with increased glucose levels could cause important alterations in glomerular morphology that may result in fast progression of kidney failure.

HBV X gene transfection upregulates IL-1beta and IL-6 gene expression and induces rat glomerular mesangial cell proliferation

The X gene of HBV encodes a 17-kD protein, termed HBx, which has been shown to function as a transcriptional trans-activator of a variety of viral and cellular promoter/enhancer elements. The aim of this study was to investigate the effect of HBx on gene expression of interleukin (IL)-1 and IL-6, and proliferation of rat mesangial cells in vitro. The X gene of HBV was amplified by PCR assay, and inserted into the eukaryotic expression vector pCI-neo. The structure of recombinant pCI-neo-X plasmid was proved by restrict endonuclease digestion and sequencing analysis. pCI-neo-X was transfected into cultured rat mesangial cell line in vitro via liposome. HBx expression in transfected mesangial cells was detected by Western blot. The IL-1beta and IL-6 mRNA expression in those cells was assayed by semiquantitative RT-PCR. Mesangial cell proliferation was tested by MTT. The results showed that HBx was obviously expressed in cultured mesangial cell line at 36th and 48th h after transfection. The expression of IL-1beta and IL-6 mRNA was simultaneously increased. The cell proliferation was also obvious at the same time. It was concluded that HBx gene transfection could induce IL-1beta and IL-6 gene expression and mesangial cell proliferation. HBx may play a critical role in mesangial cell proliferation through upregulation of the IL-1beta and IL-6 gene expression.

Increased IL-6 in supernatant of rat mesangial cell cultures treated with erythrogenic toxin type B and its precursor isolated from nephritogenic streptococci

BACKGROUND/AIMS

Previous reports have shown the presence of streptococcal erythrogenic toxin type B (ETB), IL-8, transforming growth factor-beta (TGF-beta) and glomerular proliferation in renal biopsies from patients with acute poststreptococcal glomerulonephritis (APSGN). In addition, increased levels of plasma IL-6 and tumor necrosis factor-alpha (TNFalpha) and urinary IL-6 have also been reported in this disease. To determine the effect of ETB in mesangial cell cytokine production and proliferation, the concentration of several cytokines (IL-6, IL-1beta, TNFalpha, IL-10, IL-4, RANTES), soluble TNF receptor I (STNFR-I), soluble TNF receptor II (STNFR-II) and proliferation were measured in rat mesangial cells cultures after treatment with ETB or its precursor (ETBP).

METHODS

To analyze the levels of cytokines and production of soluble receptors as well as proliferation, rat mesangial cells were cultured with ETB or ETBP (50 microg/ml). After 24, 48 and 96 h of incubation, culture supernatants were assessed for cytokines and receptors by ELISA and for proliferation by incorporation of radioactive thymidine.

RESULTS

A significant increase in IL-6 levels was found in mesangial cell cultures treated with either ETBP or ETB when compared with controls. Streptococcal proteins treated mesangial cells also showed elevated levels of proliferation at 96 h. Increased production of IL-6 was not correlated with proliferation. A polyclonal anti-ETB antibody abolished the IL-6 stimulatory effect of ETB on mesangial cells. ETB/ETBP failed to increase the levels of other cytokines and cytokine soluble receptors.

CONCLUSION

Streptococcal ETB/ETBP is capable of inducing increased production of IL-6 and proliferation on mesangial cells. These findings could be relevant in a possible early interaction of streptococcal proteins with mesangial cells and during the course of APSGN.

Leukocyte-derived interleukin-1beta interacts with renal interleukin-1 receptor I to promote renal tumor necrosis factor and glomerular injury in murine crescentic glomerulonephritis

The involvement of proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF) in crescentic glomerulonephritis (GN) is well established. Recently the requirement of intrinsic renal cell participation via their production of TNF in crescentic GN was demonstrated. The current studies address the relative contributions of leukocyte and intrinsic renal cell-derived IL-1beta in the induction of TNF production and glomerular injury by studying bone marrow chimeric mice. Leukocyte-derived IL-1beta was critical in the development of crescentic renal injury because IL-1beta(-/-)-->WT (absent leukocyte IL-1beta) chimeric mice had significantly attenuated TNF expression and were protected from the development of crescentic GN. In contrast, WT-->IL-1beta(-/-) chimeric mice (intact leukocyte but absent renal IL-1beta) developed similar TNF expression and crescentic GN to wild-type mice. To determine the cellular target for IL-1 in this model, IL-RI chimeric mice were studied. IL-1RI(-/-)-->WT chimeric (absent leukocyte IL-1RI expression) mice showed no attenuation of crescentic GN, whereas in the absence of renal IL-1RI (WT-->IL-1RI(-/-) chimeras), glomerular TNF expression and the development of crescentic GN were significantly decreased. These studies demonstrate that leukocytes are the major cellular source of IL-1beta, and that IL-1beta acts principally via the IL-1RI on intrinsic renal cells to induce TNF expression and crescentic glomerular injury.

Interleukin-6 polymorphism (-634C/G) in the promotor region and the progression of diabetic nephropathy in type 2 diabetes

AIMS

Interleukin-6 (IL-6) is a multifunctional cytokine produced by many different cell types, including glomerular mesangial cells. Recently, a novel C/G polymorphism at position -634 in the promotor region of the IL-6 gene has been reported. The aim of this study was to investigate whether the -634C/G polymorphism is associated with an increased risk for progression to diabetic nephropathy as well as elevated levels of IL-6 secretion by peripheral blood mononuclear cells.

METHODS

The frequency of the -634C/G polymorphism was determined in Japanese patients with Type 2 diabetes and either normoalbuminuria (n = 162), microalbuminuria (n = 138), or macroalbuminuria (n = 154) by polymerase chain reaction-restriction fragment length polymorphism analysis. The level of IL-6 secretion in relation to genotype was assessed in lipopolysaccharide or advanced glycation end products-stimulated IL-6 secretion by peripheral mononuclear cells.

RESULTS

The frequency of the -634G/G genotype and -634*G allele was significantly increased in the patients with macroalbuminuria compared with patients with normoalbuminuria (genotype: chi2 = 6.787, Pc = 0.0368; allele: chi2 = 9.080, Pc = 0.0104). Stepwise multiple regression analysis in these patients showed that hypertension (F = 40.48) and IL-6-634 gene polymorphism (F = 5.48) were the relevant variables for the progression of Type 2 diabetic nephropathy. Analysis of the IL-6 secretion data revealed that individuals carrying the -634*G allele had a higher IL-6 secretion capacity than those without the *G allele (P < 0.05).

CONCLUSIONS

These results suggest that the IL-6-634C/G polymorphism may be a possible genetic susceptibility factor for the progression of diabetic nephropathy.

Optimal end point of FR167653 administration and expression of interleukin-8 messenger RNA on extended liver resection with ischemia in dogs

BACKGROUND

FR167653 is a potent suppressant of interleukin-1 and tumor necrosis factor production. We previously reported that FR167653 inhibited the expression of interleukin-1 messenger RNA (mRNA) after ischemia-reperfusion and provided a protective effect against ischemia-reperfusion injury after extended liver resection. In this study we investigated the optimal end point of FR167653 administration and the inhibition of interleukin-8 (IL-8) mRNA expression caused by the administration of FR167653 during extended liver resection with ischemia in a dog model.

STUDY DESIGN

The right portal pedicle was clamped for 60 minutes but the left portal vein was left patent to avoid portal congestion. After reperfusion 75% of the liver was resected. EXPERIMENT I: Adult mongrel dogs were divided into three groups: the control group (n = 9); the FR-2 group (n = 6), which received FR167653 through the portal vein starting 30 minutes before the onset of ischemia until 2 hours after reperfusion; and the FR-6 group (n = 6), which received FR167653 starting 30 minutes before ischemia until 6 hours after reperfusion. Hepatic venous blood was collected to measure liver enzymes. Liver specimens were harvested for histologic study 6 hours after reperfusion and polymorphonuclear neutrophils were counted. EXPERIMENT II: The expression of IL-8 was measured by reverse-transcriptase polymerase chain reaction.

RESULTS

Aspartate aminotransferase and alanine aminotransferase levels after reperfusion and hyaluronic acid levels 6 hours after reperfusion were significantly (p < 0.05) lower in the FR-2 and FR-6 groups than in the control group. There were no significant differences between the FR-2 and FR-6 groups after reperfusion. Histologically liver tissue damage was mild in the FR-2 and FR-6 groups, and polymorphonuclear neutrophil infiltration was significantly lower in the FR-2 and FR-6 groups than in the control group. The 3-day survival rate was statistically (p < 0.05) better in the FR-2 and FR-6 groups than in the control group. IL-8 mRNA expression was inhibited in the FR-treated group.

CONCLUSIONS

FR167653 should be administered until shortly after reperfusion and need not be administered for many hours after reperfusion. FR167653 inhibits IL-8 mRNA production and inhibits polymorphonuclear neutrophil infiltration.

Cytokines and T-cell responses in superantigen-related glomerulonephritis following methicillin-resistant Staphylococcus aureus infection

BACKGROUND

We have previously reported that 10 patients who developed glomerulonephritis (GN) in association with methicillin-resistant Staphylococcus aureus (MRSA) infection showed a marked increase in DR+CD4+ and DR+CD8+ subsets of T cells and in T cells expressing several T-cell receptor (TCR) V beta+cells, perhaps representing V beta-specific T-cell activation by MRSA-derived superantigens (Kidney Int 1995; 47: 207-216). In this study we examine cytokine levels, T-lymphocyte subsets, natural killer NK cells, memory T cells, and the expression of IL-2 receptors in order to better understand the role of bacterial superantigens and cytokines in the pathogenesis of MRSA-associated GN.

METHODS

Twenty-two patients with MRSA infection who later developed GN caused by staphylococcal enterotoxin were evaluated immunologically in comparison with patients whose MRSA infection was not followed by GN (non-GN group) and normal individuals.

RESULTS

Among peripheral lymphocytes, the frequency of T cells expressing several TCR V betas, especially V beta 5-family TCR, was higher in the GN group than in both the non-GN group and the normal healthy control group. GN patients also showed increased serum levels of several cytokines, including tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-2, IL-6, IL-8, and IL-10, which have been implicated in the onset of nephritis. Memory cells, and IL-2 receptors also were elevated in the GN group.

CONCLUSION

These results suggest that T cells activated by MRSA-derived staphylococcal enterotoxins and subsequent production of cytokines may play an important role in the pathogenesis of MRSA-associated GN.

Interleukin-8 secretion of cortical tubular epithelial cells is directed to the basolateral environment and is not enhanced by apical exposure to Escherichia coli

In upper urinary tract infections, tubular epithelial cells (TEC) may play a pivotal role in the initiation of the renal inflammatory response. They exert crucial immunological functions such as processing and presentation of foreign antigen, secretion of proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha) and chemokines (IL-8, MCP-1, ENA-78, and RANTES). Since monolayer cultures are a limited model for polarized tubular epithelial cells, we studied the side-dependent IL-8 secretion of TEC by using cell culture inserts as a basement membrane imitation. Primary cultures of proximal TEC were stimulated with differently fimbriated mutants of Escherichia coli, E. coli LPS, S-fimbria isolates, and IL-1alpha. IL-8 protein was measured by enzyme-linked immunosorbent assay, and IL-8-like biological activity was tested by measuring elastase release from polymorphonuclear cells in supernatants of the upper and lower compartments. IL-8 mRNA was compared by competitive PCR. IL-8 secretion by TEC into the basolateral environment was significantly higher than secretion into the apical compartment, representing the tubular lumen. However, stimulation of IL-8 secretion by TEC was restricted to IL-1alpha and was not inducible by E. coli mutants, S fimbriae, or lipopolysaccharide. With this in vitro model of polarized TEC, we show that luminal contact of TEC with uropathogenic E. coli does not result in enhanced IL-8 secretion. The basolaterally directed production of the neutrophil chemotactic factor IL-8 by TEC after stimulation with IL-1alpha might play an important role in the initiation of inflammatory cell influx into the renal parenchyma.

Role of MAP kinase pathways in mediating IL-6 production in human primary mesangial and proximal tubular cells

BACKGROUND

Both interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are pleiotropic cytokines that have been implicated in the development of glomerular and tubular injury in various forms of immune-mediated renal disease, including glomerulonephritis. Although TNF-alpha has been shown to stimulate IL-6 production in renal cells in culture, the signaling mechanisms that regulate IL-6 production are not fully understood. The aim of this study was to examine the role of the p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathways in regulating TNF-alpha-mediated IL-6 production from both primary human mesangial cells (HMCs) and human proximal tubular (HPT) cells.

METHODS

Primary mesangial and proximal tubular cells were prepared from nephrectomized human kidney tissue. Cells were treated for 24 hours with TNF-alpha in the presence and absence of the specific p38 and ERK1,2 MAPK inhibitors SB203580 and PD98059, respectively, either alone or in combination. IL-6 levels in the cell culture media were measured by enzyme-linked immunosorbent assay. MAPK activation was demonstrated by immunoblot for the active kinase (tyrosine/threonine phosphorylated) in whole cell extracts using phospho-specific antibodies. p38 MAPK activity in HPT cells was measured using an in vitro immunokinase assay using ATF2 as the substrate.

RESULTS

TNF-alpha (0.1 to 100 ng/ml) stimulated a dose-dependent increase in IL-6 production in both renal cell types. The activation of the p38 and the ERK1,2 MAPKs occurred following TNF-alpha stimulation. The role of these activations in IL-6 production was confirmed by the ability of both inhibitors SB203580 (1 to 30 microM) and PD98059 (0.01 to 10 microM) to inhibit basal and TNF-alpha-stimulated IL-6 production in both cell types. The addition of both inhibitors in combination caused greater decreases in IL-6 production compared with either inhibitor alone. Pretreatment with SB203580 (10 microM) had no effect on basal or TNF-alpha-stimulated phosphorylation of p38 MAPK but completely abolished TNF-alpha-stimulated p38 MAPK activity. PD98059 decreased both basal and TNF-alpha-stimulated phosphorylation of ERK1,2.

CONCLUSIONS

This study provides evidence that both the p38 and ERK MAPK pathways are important for the regulation of the production of IL-6 from the proximal tubular and glomerular mesangial regions of the nephron. In response to TNF-alpha, the activation of both pathways leads to IL-6 production. These findings could aid in an understanding of the cellular mechanisms that regulate IL-6 production and could provide insights into possible pharmacological strategies in inflammatory renal disease.

c-Rel and p65 trans-activate the monocyte chemoattractant protein-1 gene in interleukin-1 stimulated mesangial cells

BACKGROUND

The chemokine monocyte chemoattractant protein-1 (MCP-1) is secreted by human glomerular mesangial cells in response to interleukin-1 (IL-1) and has a central role in amplifying the inflammatory response during glomerulonephritis. However, the mechanism by which IL-1 regulates its transcription is not understood. Specific members of the nuclear factor kappaB/rel (NF-kappaB) proteins may regulate MCP-1 expression in a stimulus- and tissue-specific manner.

METHODS

Electrophoretic mobility shift assays and Western blot analysis characterized the members of the NF-kappaB family that bound the two NF-kappaB sites of the MCP-1 enhancer (A1 and A2) in vitro. Trans-activation of the MCP-1 gene was investigated by transfer of the MCP-1 enhancer DNA to mesangial cells.

RESULTS

Primary human mesangial cells contained in addition to p50 (NF-kappaB1) and p65 (Rel A) NF-kappaB proteins, the oncoprotein c-rel, and Rel B, but not p52 (NF-kappaB2). IL-1 induced c-rel to form a complex with p65, which bound the MCP-1 A2 site but not the A1 or IL-6 NF-kappaB sites in vitro. IL-1 up-regulated transfected MCP-1 enhancer activity. Cotransfer of the MCP-1 enhancer together with individual members of the NF-kappaB family showed that the heterodimer c-relp65 or (p65)2 can selectively trans-activate the MCP-1 gene via its A1 and A2 sites in mesangial cells.

CONCLUSIONS

This study demonstrates for the first time that the c-rel oncoprotein can enhance MCP-1 transcription in mesangial cells and suggests that it may have an important role in amplifying gene expression in the inflamed glomerulus.

Interleukin (IL)-1 and IL-4 synergistically stimulate NF-IL6 activity and IL-6 production in human mesangial cells

BACKGROUND

While interleukin (IL)-4 inhibits pro-inflammatory cytokine expression by human monocytes, we have observed that it potentiates IL-6 production by IL-1-activated human mesangial cells (MC). To study the mechanism of this cell-type specific interaction between IL-1 and IL-4 in MC, we examined the effect of both cytokines on the activities of nuclear factor kappa B (NF-kappa B) and nuclear IL-6 NL-IL 6), transcription factors that are essential for IL-6 gene expression.

METHODS

We evaluated IL-6 synthesis, mRNA expression, and mRNA stability by ELISA, Northern analysis, and the actinomycin D method, respectively. Activities of NF-kappa B and NF-IL 6 were analyzed by gel shift assay.

RESULTS

IL-4 augmented the IL-1 stimulated IL-6 mRNA levels by about threefold without altering mRNA stability. IL-1 treatment rapidly induced the binding activity of NF-kappa B. In contrast, IL-4 did not affect basal and IL-1-induced NF-kappa B activities. Both IL-1 and IL-4 stimulated NF-IL6 activity as early as 30 minutes after treatment. When MC were treated with both cytokines together, marked activation of NF-IL6 was observed at five hours.

CONCLUSIONS

These results suggest that simultaneous activation of NF-kappa B and NF-IL6 is essential for IL-6 gene expression and that IL-1 and IL-4 cooperatively stimulate MC IL-6 production through their synergistic activation of NF-IL6.

Inhibition of mesangial cell proliferation by E2F decoy oligodeoxynucleotide in vitro and in vivo

The transcription factor E2F coordinately activates several cell cycle-regulatory genes. We attempted to inhibit the proliferation of mesangial cells in vitro and in vivo by inhibiting E2F activity using a 25-bp decoy oligodeoxynucleotide that contained consensus E2F binding site sequence (E2F-decoy) as a competitive inhibitor. The decoy's effect on human mesangial cell proliferation was evaluated by [3H]thymidine incorporation. The E2F decoy inhibited proliferation in a concentration-dependent manner, whereas a mismatch control oligodeoxynucleotide had little effect. Electrophoretic mobility shift assays demonstrated that the decoy's inhibitory effect was due to the binding of the decoy oligodeoxynucleotide to E2F. The effect of the E2F decoy was then tested in a rat anti-Thy 1.1 glomerulonephritis model. The E2F decoy oligodeoxynucleotide was introduced into the left kidney 36 h after the induction of glomerulonephritis. The administration of E2F decoy suppressed the proliferation of mesangial cells by 71%. Furthermore, treatment with the E2F decoy inhibited the glomerular expression of proliferating cell nuclear antigen at the protein level as well as the mRNA level. These findings indicate that decoy oligonucleotides can suppress the activity of the transcription factor E2F, and may thus have a potential in treating glomerulonephritis.

Renal cell cytokine production stimulates HIV-1 expression in chronically HIV-1-infected monocytes

Renal infiltration of human immunodeficiency virus type 1 (HIV-1)-infected monocytes might play an important role in the development of HIV-associated nephropathy (HIVAN). In the present study, we investigated the effects of cytokines produced by cultured human mesangial cells (HMC) and proximal tubular epithelial cells (PTEC) on HIV-1 expression in chronically HIV-1-infected promonocytes (U1 cells). Human mesangial cells constitutively secreted interleukin-6 (IL-6) but not tumor necrosis factor-alpha (TNF-alpha) into the culture medium, whereas PTEC constitutively secreted both IL-6 and TNF-alpha. Coculture of U1 cells with HMC or PTEC for 72 hours markedly stimulated HIV-1 expression, with the p24 antigen concentration in the coculture supernatants ranging from approximately 200 to 1850 pg/ml. The presence of anti-IL-6 antibody in the coculture medium nearly completely blocked HIV-1 expression in the HMC/U1 cell cocultures (P < 0.05). Anti-IL-6 antibody and anti-TNF-alpha antibody blocked HIV-1 expression in the PTEC/U1 cell cocultures by 40% and 53%, respectively (P < 0.05). Moreover, the combination of anti-IL-6 and anti-TNF-alpha antibodies additively reduced coculture HIV-1 expression by 87% (P < 0.05). We conclude that renal cell production of IL-6 and TNF-alpha might provide a potent stimulus for HIV-1 expression in HIV-1-infected monocytes that infiltrate the kidney, and that this may play an important role in the pathogenesis of HIVAN.

Abrogation of glomerular injury in nephrotoxic nephritis by continuous infusion of interleukin-6

Interleukin-6 (IL-6) has been reported to have pro- and anti-inflammatory effects. It has also been shown to cause mesangial cell proliferation in vitro and has been suggested as a mediator of injury in proliferative nephritis. We have assessed the effects of continuous infusion of human recombinant (hr) IL-6, by osmotic minipump, on the degree of glomerular injury, and on glomerular and interstitial cell proliferation, in the accelerated autologous phase of nephrotoxic nephritis. Two groups of rats were pre-immunized with 1 mg of normal rabbit IgG in Freund's complete adjuvant. One week later, nephritis was induced by an intravenous injection of 1 ml of rabbit nephrotoxic serum. One day before the induction of nephritis, group 1 (N = 9) was subcutaneously implanted with osmotic minipumps filled with 50 micrograms (200 microliters) of IL-6 (equivalent to a dose of 6 micrograms/day), while in group 2 (N = 11) the minipumps were filled with 200 microliters of normal saline. In group 3 (N = 6) normal rats were infused with 50 micrograms of IL-6 alone. The rats were killed seven days after implantation of minipumps. The administered hrIL-6 was detectable in the circulation within the pathophysiological range, and induced a hepatic acute phase response, as assessed by alpha 2-macroglobulin levels. Continuous treatment with IL-6 resulted in a significant reduction in albuminuria (from 195 +/- 37 mg/20 hr to 60 +/- 15 mg/20 hr on day 1, and from 494 +/- 52 mg/20 hr to 238 +/- 30 mg/20 hr on day 7, P < 0.002) and in the prevalence of glomerular capillary thrombosis (from 19 +/- 3% to 5 +/- 1%, P < 0.002). There was also a reduction in macrophage infiltration (ED1 + ve cells from 524 +/- 34 to 466 +/- 14 per 50 glomeruli, P < 0.02) and activation (ED3 + ve cells from 106 +/- 13 to 42 +/- 5 per 50 glomeruli, P < 0.002). Immunohistology showed fewer interstitial Ia + ve cells (OX3 and OX4) in the IL-6 treated group. Similar results were obtained in a second set of experiments in which the IL-6 treatment was extended until day 14. Kidney sections taken from nephritic rats infused with IL-6 showed no increase in glomerular or interstitial cell proliferation when stained with antibodies to proliferating cell nuclear antigen. There was no difference in the deposition of rabbit IgG or rat IgG along the glomerular basement membrane (GBM), and the titer of rat anti-rabbit IgG was similar in the IL-6 and control treated rats. Infusion of IL-6 alone in normal rats had no functional or pathological effects. In conclusion, these results show that IL-6 has powerful anti-inflammatory effects in a rat model of anti-GBM nephritis, and does not induce mesangial cell proliferation in vivo.

Interleukin-8 can mediate acute-phase protein production by isolated human hepatocytes

During the course of studies designed to identify the role of cytokines in the reprioritization of hepatic protein synthesis associated with cachexia we detected a hepatocyte-stimulating moiety in the supernatants of pancreatic cancer cells that was unrelated to interleukin (IL)-6. This study identifies that moiety as IL-8 and investigates the role of IL-8 in the induction of acute-phase protein production. The human pancreatic cancer cell line MIA PaCa-2 produced >1 ng/ml of IL-8 per 24 h, and supernatants from this cell line induced C-reactive protein (CRP) production from isolated human hepatocytes. Addition of neutralizing anti-human IL-8 antibody to such supernatants produced almost complete inhibition of CRP production. The addition of recombinant human IL-8 to hepatocytes resulted in a dose-dependent increase in CRP, alpha1-acid glycoprotein, and alpha1-antichymotrypsin production and a decrease in the production of transferrin and prealbumin. This study demonstrates that recombinant or tumor-derived IL-8 can modulate acute-phase protein production from isolated human hepatocytes and from human hepatoma cells.

Monocytes-macrophages and cytokines/chemokines in fine-needle aspiration biopsy cultures: enhanced interleukin-1 receptor antagonist synthesis in rejection-free kidney transplant patients

BACKGROUND

Monocytes-macrophages are found within kidney allografts during the first days after surgery, where they perform "housekeeping" tasks, participate in postreperfusion injury, and act as antigen-presenting cells, as well as become involved in the effector phase of acute rejection. They also seem to play a prominent role in chronic rejection. We quantified their presence in fine-needle aspiration biopsies and studied the growth factors that, we hypothesized, would mark the different implications of the presence of monocytes-macrophages.

METHODS

Fine-needle aspiration biopsies were obtained from 56 adult renal transplants and analyzed for CD14+ using the alkaline phosphatase-anti-alkaline phosphatase procedure. Thirty-three patients were studied on the production of interleukin (IL)-1 receptor antagonist (IL-1ra), IL-6, IL-8, macrophage colony-stimulating factor, monocyte chemotactic protein 1, and macrophage inflammatory protein 1alpha by aspiration biopsies cultures using enzyme-linked immunosorbent assay techniques.

RESULTS

CD14+ cells were present at significantly higher numbers in steroid-resistant acute rejections but also during the first days after surgery, especially if acute tubular necrosis was present. We found a significantly higher production of IL-1ra by rejection-free patients compared with acutely rejecting patients, and this difference was already established on day 7 after surgery (10+/-10.5 days before rejection).

CONCLUSIONS

Monocytes-macrophages are present at higher numbers in aspiration biopsies of kidney transplant patients suffering either acute tubular necrosis or steroid-resistant rejections, but they are present during the first days after transplant in stable patients, too. The production of IL-1ra is significantly up-regulated in stable patients, which suggests that monocytes-macrophages may constitute an early key factor in the down-regulation of the anti-allograft immune response.

Interleukin-8 expression in patients after renal transplantation

Cellular invasion and cytokine release are important steps in the initiation of rejection. We studied the release of interleukin-8 (IL-8), a potent proinflammatory and chemotactic cytokine, and its prognostic significance in predicting rejection after renal transplantation. Serum and urine samples were analyzed with an IL-8-specific sandwich enzyme-linked immunosorbent assay. Biopsy tissue specimens (n = 20) were snap-frozen and examined with immunohistochemistry using two monoclonal antibodies against human IL-8 (4G9 and 2A8). Serum IL-8 measurements were of no value in predicting rejection due to low sensitivity (24%). In 45 biopsy-proven acute rejections (< 2 months after transplantation), urinary IL-8 concentrations were elevated in 62% (298 +/- 54 pg/mL; P < 0.01), preceding clinical diagnosis of rejection. After treatment, the IL-8 concentration in urine decreased back to normal (33 +/- 4 pg/mL; P < 0.01). The highest urinary IL-8 concentrations were seen in patients with biopsy-proven rejection in combination with acute tubular necrosis (610 +/- 150 pg/mL). This finding was independent of renal function and urinary volume. Only three of 15 rejection episodes in patients more than 2 months after transplantation showed an elevated IL-8 concentration in urine (94 +/- 60 pg/mL). In 10 of 23 patients with infection, a significant increase of IL-8 in urine was observed as well (157 +/- 67 pg/mL; P < 0.05). IL-8-positive staining was found within interstitial mononuclear cells of all biopsy specimens showing rejection. Additionally, the antibody 4G9 stained arteriolar smooth muscle and tubular cells. Interestingly, a few IL-8-positive cells were present in two donor kidneys before transplantation was performed; control tissue was negative. Further investigations are necessary to determine the clinical value of urinary IL-8 determinations in the diagnosis of rejection and to evaluate the role of IL-8 in the pathogenesis of acute allograft rejection.

Effects of TNF alpha on verocytotoxin cytotoxicity in purified human glomerular microvascular endothelial cells

In the pathogenesis of the hemolytic uremic syndrome (HUS), endothelial damage of glomeruli and arterioles of the kidney appears to play a central role. Previous studies have shown that verocytotoxin-1 (VT-1) cytotoxicity on human vein endothelial cells require additional stimuli, in particular the inflammatory mediator tumor necrosis factor alpha (TNF alpha). In this study the effects of VT on human glomerular microvascular endothelial cells (GMVEC) were examined. A reproducible method was developed for the isolation and purification of large numbers of highly purified GMVEC. The obtained GMVEC were over 99% pure; their endothelial origin was demonstrated by the expression of the endothelial antigens von Willebrand factor, EN-4, PECAM-1 and V,E-cadherin. Upon stimulation with TNF alpha the cells expressed the endothelial-specific adhesion molecule E-selectin. A limited number of fenestral structures was observed by scanning electron microscopy (SEM), suggesting glomerular origin of the endothelial cells. Cytotoxicity of VT-1 to GMVEC was evaluated by determination of the number of viable adherent cells and by assay of overall protein synthesis after exposure to varying concentrations of VT-1. In non-stimulated GMVEC, cytotoxicity of VT-1 was inversely related to the degree and duration of confluence, subconfluent cells being the most sensitive. In highly confluent GMVEC, VT cytotoxicity required pre-exposure of the cells to the inflammatory mediator TNF alpha, which induced an increase in the number of VT receptors on GMVEC. Thin layer chromatography of extracted glycolipids from the GMVEC showed binding of VT-1 to globotriaosylceramide (Gb3), known to be the functional receptor for VT. There were no major differences in protein synthesis inhibition with equal concentrations VT-1 and VT-2. In conclusion, in this study we provide a reproducible method to isolate, purify and culture well characterized human GMVEC on a routine basis. In vitro studies with these GMVEC demonstrate that VT cytotoxicity depends on the degree of confluence and the additional preexposure to the inflammatory mediator TNF alpha. These observations provide further insight into the complex events that may occur in glomeruli in the pathogenesis of HUS.

Group II phospholipase A2 as an autocrine growth factor mediating interleukin-1 action on mesangial cells

The proliferation of mesangial cells plays a central role in the progression of glomerulonephritis. We studied the role of group II phospholipase A2 in interleukin-1-stimulated proliferation of mesangial cells. Cultured rat mesangial cells secreted 5.3 units group II phospholipase A2/24 h per 10(5) cells in response to stimulation of 200 U/ml of interleukin-1. Northern hybridization analysis showed that mRNA for group II phospholipase A2 was induced by exogenously added group II phospholipase A2 (15 U/ml) as well as interleukin-1. The pretreatment of quiescent mesangial cells with interleukin-1 augmented [3H]thymidine incorporation caused by platelet derived growth factor. Exogenous group II phospholipase A2 (5-36 U/ml) purified homogeneously from rat spleen also increased [3H]thymidine incorporation by platelet derived growth factor-stimulated mesangial cells in a dose dependent manner (36 U/ml phospholipase A2; 1.9-fold). The stimulatory effect of interleukin-1 on DNA synthesis of mesangial cells was specifically blunted by immunoglobulin raised against group II phospholipase A2. Group II phospholipase A2 (16 U/ml) amplified a platelet derived growth factor-stimulated increase in the mesangial cell number by 1.5-fold. Among the products of the phospholipase A2-catalyzed reaction, lysophospholipids including lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidic acid, but not fatty acids, mimicked the stimulatory effect of interleukin-1 and phospholipase A2. These results suggest that group II phospholipase A2 acts as a signaling molecule that mediates interleukin-1-induced growth of rat mesangial cells through yielding lysophospholipids.

Role of interleukin-6 in mediating mesangial cell proliferation and matrix production in vivo

Mesangial cell proliferation and matrix overproduction characterize many progressive glomerular diseases. Based on currently available data, the role of interleukin-6 (IL-6) in mediating mesangial cell proliferation and matrix production is controversial. The present study attempts to clarify this issue by showing that: (1) IL-6 knock out mice develop a normal glomerular architecture and in particular a normal mesangium. (2) Mesangioproliferative glomerulonephritis induced by Habu snake venom is equally severe in IL-6 knock out mice as in control mice. (3) A continuous seven-day intraperitoneal infusion of 50 micrograms recombinant human IL-6 into rats with a prior minimal (subnephritogenic) injury to mesangial cells does not induce glomerular cell activation, cell proliferation, matrix production, leukocyte influx, platelet influx or proteinuria. (4) A continuous seven-day IL-6 infusion into rats with mesangioproliferative nephritis (anti-Thy 1.1 nephritis) increases matrix protein transcription in the absence of detectable effects on matrix protein accumulation and otherwise has no effect on the natural course of the disease. We conclude from these findings that IL-6 is not an important mediator of mesangial cell proliferation and matrix overproduction in vivo, and that currently little rationale exists to advocate anti-IL-6 therapy in mesangioproliferative disease states.

Molecular biology of cytokines

The development of the technological armamentarium of molecular biology has revolutionized biomedical research in general and nephrologic investigation in particular. In addition to the recent identification of several genes involved in normal kidney function and pathologic conditions, our knowledge regarding the role of cytokines in primary renal diseases, transplant rejection, and dialysis effects has expanded greatly. In particular, molecular biologic methodology has provided insight into the mechanisms controlling cytokine gene regulation, which occurs primarily at the transcriptional level and is mediated by DNA-binding proteins interacting with specific recognition motifs in genetic promoter and enhancer elements. Interleukin-6 (IL-6) is discussed as an example because it is a secretory product of mesangial cells and participates in the cytokine network that determines glomerular and interstitial inflammation. In our analysis of IL-6 gene regulation employing reporter gene and electrophoretic mobility shift assays, we have found that bacterial lipopolysaccharide and cyclic adenosine monophosphate synergistically induce IL-6 expression in macrophages through at least four transcription factors, including AP-1, cAMP-responsive element-binding protein (CREB), NF-IL6, and NF-kappa B. One of the most exciting areas of future research will focus on transcription factor activation in experimental and clinical disease states. Novel therapeutic approaches targeting transcriptional regulation are currently being explored.

Chemokines and renal disease

Chemokines are low molecular weight inflammatory cytokines with chemoattractant properties as their major biologic effect. They are classified into at least two families. C-X-C chemokines (alpha subfamily) act primarily on neutrophils, while C-C chemokines act preferentially on monocytes. Chemokine receptors are G protein-coupled receptors that form a family of structurally and functionally related proteins. Chemokines are induced in cells and tissue in response to proinflammatory cytokines. They are produced by glomerular, tubular interstitial, and blood vessel cells. There is good evidence that chemokines contribute to neutrophil and mononuclear cell infiltration in glomeruli and interstitium. Their expression is increased in renal disease, and neutralization studies using antibodies in vivo demonstrated a role for certain chemokines in mediating renal pathology and proteinuria. Interleukin-8, RANTES, and monocyte chemotactic peptide are the best-studied chemokines in the kidney. Development of specific antibodies and receptor antagonists should help establish the precise role of these mediators in renal disease. Important therapeutic implications may result from this work.

New insights into circulating cell-endothelium interactions and their significance for glomerular pathophysiology

Neutrophil and monocyte infiltration of kidney glomeruli is a striking pathologic finding in the early stages of most forms of glomerulonephritis and appears to be an important determinant of glomerular injury. Recent research has permitted to clarify the mechanisms of leukocyte trafficking to inflamed glomeruli, which appear to involve several coordinated steps: chemotaxis along a concentration gradient of chemoattractants, adhesion to endothelial cells, diapedesis between endothelial cells, and interaction with resident renal cells. In glomerulonephritis, the deposition of immune complexes within glomerular capillaries triggers the local synthesis of chemotactic factors, including complement fragments, platelet-activating factor, leukotrienes, interleukin-8, and monocyte chemotactic protein-1, which promote attraction of neutrophils and monocytes within the glomerular tuft. Adhesion to resident glomerular cells, a critical step in the process of leukocyte infiltration, is a dynamic process that results from opposite factors: (1) shear forces generated by the movement of blood within the glomerular microcirculation that tend to detach inflammatory cells from the vascular wall and (2) adhesion glycoproteins expressed on the surface of leukocytes and endothelial cells, which are upregulated in human and experimental glomerulonephritis. It has been proposed that P-selectin, which is rapidly expressed on the surface of endothelial cells exposed to various stimuli, is a principal mediator of initial low-affinity binding of leukocytes (rolling). The tethering component mediated by P-selectin facilitates interaction of leukocytes with platelet-activating factor, a biologically active phospholipid that is rapidly synthesized by activated endothelial cells and is coexpressed with P-selectin on the endothelial cell plasma membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of neutrophil influx in glomerulonephritis in the rat with anti-macrophage inflammatory protein-2 (MIP-2) antibody

The role of the chemokine, macrophage inflammatory protein-2 (MIP-2), during anti-glomerular basement membrane (GBM) antibody (Ab) glomerulonephritis (GN) was studied. Rat MIP-2 cDNA had been cloned previously. Recombinant rat MIP-2 (rMIP-2) from Escherichia coli exhibited neutrophil chemotactic activity and produced neutrophil influx when injected into the rat bladder wall. By using a riboprobe derived from the cDNA and an anti-rMIP-2 polyclonal Ab, MIP-2 was found to be induced in glomeruli with anti-GBM Ab GN as mRNA by 30 min and protein by 4 h, with both disappearing by 24 h. The expression of MIP-2 correlated with glomerular neutrophil influx. A single dose of the anti-MIP-2 Ab 30 min before anti-GBM Ab was effective in reducing neutrophil influx (40% at 4 h, P < 0.01) and periodic acid-Schiff deposits containing fibrin (54% at 24 h, P < 0.01). The anti-rMIP-2 Ab had no effect on anti-GBM Ab binding (paired-label isotope study). Functional improvement in the glomerular damage was evidenced by a reduction of abnormal proteinuria (P < 0.05). These results suggest that MIP-2 is a major neutrophil chemoattractant contributing to influx of neutrophils in Ab-induced glomerular inflammation in the rat.

IL-8 release from cultured peripheral blood monocytes of patients with glomerulonephritis

IL-8 is a chemotactic cytokine with proinflammatory and growth-promoting activities. The release of IL-8 was measured in supernatants of cultured peripheral blood monocytes (PBM) that were obtained from patients with glomerulonephritis (GN) and healthy controls. Spontaneous and lipopolysaccharide (LPS)-induced IL-8 release was significantly higher in PBM isolated from patients with IgA nephropathy (IgAN) and membranous nephropathy (MN) compared with normal controls. These results raise the question of whether IL-8 contributes to the ongoing pathogenesis of GN. We cannot relate IL-8 release to clinical and laboratory parameters in IgAN and MN patients. Thus, disease progression in vivo may not be accompanied by increased or sustained IL-8 release.

Mesangial cell apoptosis: the major mechanism for resolution of glomerular hypercellularity in experimental mesangial proliferative nephritis

Increases in mesangial cell number may herald glomerular scarring, but they are not irreversible. This study sought mechanisms by which surplus glomerular mesangial cells can be cleared. A small proportion of cultured mesangial cells exhibited typical morphological features of apoptosis (programmed cell death), which was increased by growth factor deprivation or exposure to cycloheximide, stimuli known to increase apoptosis in other cell types. Apoptosis was confirmed by typical internucleosomal chromatin cleavage. In vivo, clear morphological evidence of mesangial apoptosis leading to phagocytosis by neighboring mesangial cells was obtained in self-limited mesangial proliferation induced in rats by Thy1.1 antibody, apoptosis occurring approximately 10-fold more frequently than in the healthy rat glomerulus. Indeed, changes in glomerular cell number in Thy1.1 nephritis strongly suggested that apoptosis is the major cell clearance mechanism counterbalancing cell division, thereby mediating resolution of glomerular hypercellularity in experimental mesangial proliferation.

Prevention of proteinuria by the administration of anti-interleukin 8 antibody in experimental acute immune complex-induced glomerulonephritis

Glomerular infiltration by neutrophils is a hallmark of acute glomerulonephritis. The pathophysiological role of interleukin 8 (IL-8), a potent neutrophil chemotactic cytokine (chemokine), was explored in an animal model of acute immune complex-mediated glomerulonephritis by administering a neutralizing antibody against IL-8. Repeated injection of bovine serum albumin (BSA) into rabbits caused the deposition of immune complexes consisting of BSA and rabbit IgG in glomeruli. Histological analyses revealed a small but significant number of neutrophils in glomeruli and the fusion of epithelial cell foot processes. Concomitantly, urinary levels of protein and albumin increased markedly (3.20 +/- 0.97 and 1.39 +/- 0.53 mg/h, respectively) compared with those of untreated animals (0.77 +/- 0.21 and 0.01 +/- 0.01 mg/h, respectively). Anti-IL-8 antibody treatment decreased the number of neutrophils in glomeruli by 40% and dramatically prevented the fusion of epithelial cell foot process. Furthermore, treatment with anti-IL-8 antibody completely normalized the urinary levels of protein and albumin (0.89 +/- 0.15 and 0.02 +/- 0.01 mg/h, respectively). These results indicated that IL-8 participated in the impairment of renal functions in experimental acute immune complex-mediated glomerulonephritis through activating as well as recruiting neutrophils.

Interleukin-6 and interleukin-6 receptor are expressed by cultured glomerular epithelial cells

Interleukin-6 (IL-6) has been extensively studied in mesangial cells but little is known about the expression of this cytokine and its receptor in glomerular epithelial cells (GEC). IL-6 was detected in the culture supernatants of human GEC and its production was enhanced in time and dose dependent manner by lipopolysaccharide (LPS), interleukin-1 beta (IL-1 beta) and tumour necrosis alpha (TNF-alpha). Quiescent, serum-starved GEC did not express clearly IL-6 mRNA. Stimulation of cells with LPS, TNF-alpha or IL-1 beta resulted in an increase of detectable IL-6 mRNA. Interestingly, it was found that IL-6 induced its own mRNA attesting that this cytokine was secreted in autocrine fashion by GEC. GEC expressed IL-6 receptor (IL-6R) as demonstrated directly by the existence of IL-6R mRNA detected by northern blotting. Stimulation of GEC by pro-inflammatory mediators such as LPS increased the expression of IL-6R mRNA. The soluble form of IL-6 receptor (sIL-6R) was not detectable in the culture supernatants harvested from untreated or cytokine-treated cells. We investigated further, whether IL-6 may influence growth of cultured GEC. Incubation of GEC with recombinant (r) IL-6 resulted in a dose dependent increase in 3H thymidine incorporation indicating that IL-6 acts as an autocrine growth factor for GEC. We conclude that GEC are a potent source of IL-6, the local excessive expression of IL-6 and its receptor may play a substantive role in the regulation of processes which appear critical to the initiation of progressive glomerular disease such as cell proliferation.

Detection of urinary interleukin-8 in glomerular diseases

To clarify the mechanism of neutrophil infiltration in glomerulonephritis, both urinary and plasma levels of a potent neutrophil chemotactic cytokine, interleukin-8 (IL-8), were measured in 40 healthy volunteers and 96 patients with various renal diseases. The plasma IL-8 levels were less than 16 pg/ml. The urinary IL-8 levels were elevated in several renal diseases including IgA nephropathy (17 of 43), acute glomerulonephritis (4 of 6), lupus nephritis (11 of 15), purpura nephritis (2 of 4), membranoproliferative glomerulonephritis (1 of 1), and cryoglobulinemia (2 of 2). IL-8 was detected immunohistochemically in diseased glomeruli, suggesting its local production. Elevated urinary IL-8 levels during the acute phase or exacerbations were found to be decreased during spontaneous or steroid pulse therapy-induced convalescence in all patients examined. The urinary IL-8 levels were higher in patients with glomerular leukocyte infiltration than in those without infiltration. Collectively, local production of IL-8 in diseased glomeruli might be involved in the pathogenesis of the glomerular diseases and measurement of IL-8 in the urine might be useful for monitoring the glomerular diseases.

Interleukin-6 and interleukin-8 in the urine of children with acute pyelonephritis

Interleukin-6 (IL-6) and interleukin-8 (IL-8) are important mediators of the inflammatory response in serious bacterial infections. We studied the levels of these two cytokines (standardised for urinary creatinine) in the urine of infants and children during and 6 weeks after acute pyelonephritis and in non-renal febrile controls and healthy children without apparent infection. IL-6 was detected in the urine of 52% of children with pyelonephritis compared with 15% of other children (P < 0.001). The median urinary IL-6 level in acute pyelonephritis was 4 pg/mumol compared with undetectable levels in the control group (P < 0.001). IL-8 was detected in 98% of children with pyelonephritis and 42% of other children (P < 0.001). The median concentration of IL-8 was 188 pg/mumol in pyelonephritis; it was undetectable in controls (P < 0.001). IL-8 levels were higher in children less than 1 year of age (P < 0.001).

Cytokine-induced expression of leukemia inhibitory factor in renal mesangial cells

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine, which shares many characteristics with interleukin-6 (IL-6). Recent observations indicate a role for LIF in inflammatory processes. To examine the potential involvement of LIF in the regulation of mesangial cell behavior, we studied LIF expression in early primary cultures of rat and human mesangial cells, as well as the response of mesangial cells to exogenous LIF. Growing or growth-arrested rat mesangial cells constitutively expressed very low levels of LIF mRNA, barely detectable by Northern blot analysis. Strong induction of LIF mRNA expression was caused by cytokines, such as interleukin-1 beta (5 ng/ml), tumor necrosis factor alpha (100 ng/ml) and PDGF (100 ng/ml), as well as LPS (200 ng/ml). The induction was transient with a peak after three to five hours. Dexamethasone (0.1 microM) almost completely inhibited the induction of LIF. Weak induction of LIF mRNA was observed after stimulation with basic fibroblast growth factor, endothelin and transforming growth factor beta. In combination with IL-1 beta, TGF beta showed synergistic effects on LIF induction. LIF itself or IL-6 had no effect on LIF mRNA expression. A similar induction pattern was observed for the expression of IL-6 mRNA. LIF protein was detected by specific ELISA in the supernatants of human mesangial cells stimulated by LPS or IL-1 beta. In addition, we found that mesangial cells not only express LIF but they are also target cells for LIF. Recombinant LIF effectively induced transient expression of the immediate early genes, c-fos, jun-B and Egr-1 in rat mesangial cells, with a maximum at 30 to 60 minutes. LIF was not mitogenic for mesangial cells. Our findings indicate that glomerular mesangial cells produce and react to LIF. As a cytokine with autocrine potential, LIF may play a physiological and/or pathophysiological role in the glomerulus, the exact nature and relevance of which remain to be explored.

A granulocyte inhibitory protein overexpressed in chronic renal disease regulates expression of interleukin 6 and interleukin 8

Growing evidence suggests that cytokine expression is influenced by locally produced mediators, thus modifying the pluripotential effects of cytokines toward a tissue-specific inflammatory reaction. The granulocyte inhibitory protein (GIP), a 23-kDa protein found to be significantly overexpressed in patients with chronic renal failure, increases autocrine transcription and expression of interleukin (IL) 6 and IL-8 in human mesangial cells. Moreover, GIP alone induced the transcription of c-jun mRNA; however, in combination with IL-6, it stimulated de novo synthesis of DNA and the transcription of both c-jun and c-fos genes. The data suggest that the overall effect of GIP results in the modulation of the glomerular response to injury and contributes to the progression of glomerulosclerosis.

Modulation of antibody-mediated glomerular injury in vivo by interleukin-6

We have shown previously that pretreatment with small doses of bacterial lipopolysaccharide (LPS), human recombinant interleukin-1 beta (hrIL-1 beta) and human recombinant tumor necrosis factor-alpha (hrTNF) increase injury in the heterologous phase of nephrotoxic nephritis (NTN). All three pretreatments induce synthesis of interleukin-6 (IL-6) which in some systems down-regulates synthesis of IL-1 and TNF. We have now investigated the influence of IL-6 on injury in both heterologous and autologous phases of NTN in rats. Injection of hrIL-6 in doses sufficient to induce hepatic synthesis of acute phase proteins (assessed by plasma alpha 2-macroglobulin concentration) had no effect on glomerular injury in the heterologous phase of NTN (albuminuria in NTAb alone 9 +/- 6; LPS/NTAb 34 +/- 10 and IL-6/NTAb 2 +/- 1 mg/24 hr, P < 0.001, Wilcoxon test). In contrast, IL-6 pretreatment partially abrogated the effect of LPS on albumin excretion (NTAb 4 +/- 2; LPS/NTAb 85 +/- 11 and IL-6/LPS/NTAb 32 +/- 6 mg/24 hr, P < 0.002), percentage of glomerular capillary thrombi (3 +/- 1%; 39 +/- 8%; and 6 +/- 1%, P < 0.001) and glomerular neutrophil infiltrate (29 +/- 3; 58 +/- 5; and 34 +/- 2 neutrophils/50 glomeruli in section, P < 0.001, respectively) at 24 hours. The effect of IL-6 was also evident four hours after induction of nephritis and was associated with a marked reduction in glomerular concentration of mRNA for IL-1 beta and TNF, without change in that of tubulin. Serum TNF concentrations were also significantly reduced at four hours in IL-6 treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-specific regulation of type II phospholipase A2 expression in rat mesangial cells

IL-1 stimulates mesangial cells to synthesize specific proteins, including a non-pancreatic (Type II) phospholipase A2 (PLA2). We have studied the regulation of PLA2 by proinflammatory mediators, implicated in the pathogenesis of glomerulonephritis, and have assessed whether the activation of second messenger systems modulates or mimics PLA2 gene expression by cytokines. IL-1 alpha and beta, TNF alpha, and LPS, but not serum, IL-2, or PDGF, potently induce PLA2 mRNA, and enzyme expression. IL-1-stimulated mesangial cells express a 1.0 kB PLA2 mRNA transcript that is induced in a dose- and time-dependent manner. IL-1-stimulated increases in steady-state PLA2 mRNA abundance result from a moderate increase in PLA2 transcription rate that is amplified by the prolonged persistence of the transcript. Forskolin and dibutyryl cAMP potentiate IL-1-induced PLA2 mRNA and enzyme expression, but have no effect in the absence of cytokine. 12-tetradecanoyl phorbol 13-acetate, sn-1, 2-dioctanoyl glycerol or 1-oleoyl-2-acetyl-sn-glycerol fail to induce PLA2 expression or to alter the effect of IL-1 when coincubated with the cytokine. In contrast, serum deprivation for 24 h specifically enhances IL-1-stimulated PLA2. Genistein potentiates PLA2 mRNA expression in cells exposed to both IL-1 and serum. The inhibitory effect of serum on IL-1-induced PLA2 mRNA abundance is reproduced by PDGF but not dexamethasone. These data demonstrate that the signaling pathways directly engaged by IL-1 to induce PLA2 expression in mesangial cells interact with several second messenger systems in a cell-specific manner. We speculate that IL-1 induces specialized changes in mesangial cell structure and function through direct activation of a transcription factor(s), that result in induction of a specific gene set.

In situ expression of cytokines in IgA nephritis

We studied mRNA and protein expression of interleukins (IL) and tumor necrosis factor (TNF) in renal tissues biopsied from 40 patients with IgA nephritis. Immunofluorescent staining with antibodies to IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF-alpha, and TNF-beta was intense in the cytoplasm of cells in glomeruli, which were dual-stained with an anti-monocyte-macrophage antibody. In addition, moderate immunofluorescence for TNF-alpha, and weak staining for IL-1 alpha and IL-6 were occasionally found in resident glomerular cells. Immunoperoxidase-in situ hybridization dual-labeling revealed that IL-1 alpha, IL-6, and TNF-alpha mRNA signals were present in intraglomerular cells reactive with anti-monocyte-macrophage antibody, which further supported the immunofluorescent findings. Cells expressing IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF-alpha, and TNF-beta were also observed in the interstitium. Most of these cells were also labeled with the anti-monocyte-macrophage antibody. The number of IL-1 alpha, IL-6, and TNF-alpha-positive cells infiltrating the glomerulus significantly correlated with mesangial hypercellularity. IL-8 and TNF-alpha-positive intraglomerular cells were correlated with the magnitude of proteinuria. The population of interstitial cells positive for IL-1 alpha, IL-6, IL-8, and TNF-alpha was associated with the grade of tubulointerstitial changes and proteinuria. There was no correlation between local IL-1 alpha, IL-6, and TNF-alpha expression in glomeruli or interstitium and serum or urinary levels of the respective cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)

C3 and C4 gene expression and interferon-gamma-mediated regulation in human glomerular mesangial cells

The glomerular mesangial cell (GMC) plays a key role in the maintenance of glomerular structure and function and in the mediation of glomerular injury. To explore the potential of this cell to produce complement and react to local inflammatory signals, we studied the synthesis and regulation of the third and fourth components of complement in cultured human GMC. Using metabolic labelling and immunoprecipitation, we found that C3 and C4 polypeptide chains were synthesized and secreted by GMC. Interferon-gamma (IFN-gamma) led to an increase in C4 protein synthesis, but not C3 synthesis. There was a corresponding increase in C4 mRNA in IFN-gamma-activated cells, but no increase in C3 mRNA, as determined by semi-quantitative polymerase chain reaction (PCR) estimation. These results demonstrate that human GMC can synthesize C3 and C4 proteins, and that regulation of expression of the C4 gene is mediated by IFN-gamma. We hypothesize that GMC production of complement could influence the clearance of immune aggregates by the kidney and the mediation of glomerular injury.