Inhibition of monocyte chemoattractant protein-1 expression in tubular epithelium attenuates tubulointerstitial alteration in rat Goodpasture syndrome

Mitochondrial Impairment: A Link for Inflammatory Responses Activation in the Cardiorenal Syndrome Type 4

Cardiorenal syndrome type 4 (CRS type 4) occurs when chronic kidney disease (CKD) leads to cardiovascular damage, resulting in high morbidity and mortality rates. Mitochondria, vital organelles responsible for essential cellular functions, can become dysfunctional in CKD. This dysfunction can trigger inflammatory responses in distant organs by releasing Damage-associated molecular patterns (DAMPs). These DAMPs are recognized by immune receptors within cells, including Toll-like receptors (TLR) like TLR2, TLR4, and TLR9, the nucleotide-binding domain, leucine-rich-containing family pyrin domain-containing-3 (NLRP3) inflammasome, and the cyclic guanosine monophosphate (cGMP)-adenosine monophosphate (AMP) synthase (cGAS)-stimulator of interferon genes (cGAS-STING) pathway. Activation of these immune receptors leads to the increased expression of cytokines and chemokines. Excessive chemokine stimulation results in the recruitment of inflammatory cells into tissues, causing chronic damage. Experimental studies have demonstrated that chemokines are upregulated in the heart during CKD, contributing to CRS type 4. Conversely, chemokine inhibitors have been shown to reduce chronic inflammation and prevent cardiorenal impairment. However, the molecular connection between mitochondrial DAMPs and inflammatory pathways responsible for chemokine overactivation in CRS type 4 has not been explored. In this review, we delve into mechanistic insights and discuss how various mitochondrial DAMPs released by the kidney during CKD can activate TLRs, NLRP3, and cGAS-STING immune pathways in the heart. This activation leads to the upregulation of chemokines, ultimately culminating in the establishment of CRS type 4. Furthermore, we propose using chemokine inhibitors as potential strategies for preventing CRS type 4.

Interleukin-18 binding protein therapy is protective in adriamycin nephropathy

Adriamycin nephropathy (AN) is an experimental model of focal segmental glomerulosclerosis (FSGS) in which macrophages are considered to play a pathogenic role. We hypothesize that interleukin-18 (IL-18), largely derived from macrophages, is a key contributor to kidney injury in AN and a potential therapeutic target. In this study, BALB/c mice received adriamycin (9.6 mg/kg) via tail vein injection and subsequently were treated with either neutralizing IL-18 binding protein (IL-18BP; 250 μg) or normal saline (control). At 5 wk, IL-18 was upregulated in AN, and IL-18BP therapy afforded significant protection against the development of AN, resulting in less proteinuria (P < 0.01), kidney dysfunction (P < 0.01), glomerulosclerosis (P < 0.001), and interstitial accumulation of macrophages and T cells (P < 0.001). Gene expression of IL-18 downstream inflammatory molecules, including inducible nitric oxide synthase (P < 0.001), TNF-α (P < 0.001), and IFN-γ (P < 0.01); IL-17 (P < 0.001) and the chemokines CCL2 (P < 0.01) and CCL5 (P < 0.005), was reduced. We demonstrate that IL-18 plays a significant role in the pathogenesis of AN. The protective effect of IL-18BP therapy illustrates the importance of immune mediators in chronic proteinuric kidney disease and highlights the potential of IL-18BP therapy.

Targeted expression of a pan-caspase inhibitor in tubular epithelium attenuates interstitial inflammation and fibrogenesis in nephritic but not nephrotic mice

The caspase family of enzymes participates in apoptotic and proinflammatory reactions in any cell. Here we studied the role of caspase activation in the tubular epithelium of diseased kidneys using mice transgenic for the baculovirus pan-caspase inhibitor p35 gene held in a nonexpressed state (control mice) but target-expressed in the renal proximal tubule cells when crossed with mice expressing Cre recombinase under the control of the γ-glutamyltransferase promoter. Proinflammatory and profibrogenic parameters such as the number of monocytes and fibroblasts in the kidneys were significantly increased at 28 days in the control mice, but not in the renal tubule-targeted mice expressing p35 in a nephrotoxic serum nephritis model of disease. These cellular changes paralleled the number of apoptotic tubular cells and protein levels of active caspase-3 in the kidneys at 7 and 28 days of both the control and proximal tubule-targeted mice. Surprisingly, all of these parameters were not significantly affected at 7 and 28 days by targeted p35 expression in tubular epithelium when compared with nontargeted control mice in a model of adriamycin nephrosis. Thus, our study shows the critical role of caspase activation in the tubular epithelium in apoptosis along with proinflammatory and profibrogenic processes in nephrotoxic serum nephritis but not adriamycin nephrosis.

WY14,643, a PPARalpha ligand, attenuates expression of anti-glomerular basement membrane disease

Peroxisome proliferator-activated receptor alpha (PPARalpha) ligands are medications used to treat hyperlipidaemia and atherosclerosis. Increasing evidence suggests that these agents are immunosuppressive. In the following studies we demonstrate that WY14,643, a PPARalpha ligand, attenuates expression of anti-glomerular basement membrane disease (AGBMD). C57BL/6 mice were fed 0.05% WY14,643 or control food and immunized with the non-collagenous domain of the alpha3 chain of Type IV collagen [alpha3(IV) NC1] in complete Freund's adjuvant (CFA). WY14,643 reduced proteinuria and greatly improved glomerular and tubulo-interstitial lesions. However, the PPARalpha ligand did not alter the extent of IgG-binding to the GBM. Immunohistochemical studies revealed that the prominent tubulo-interstitial infiltrates in the control-fed mice consisted predominately of F4/80(+) macrophages and WY14,643-feeding decreased significantly the number of renal macrophages. The synthetic PPARalpha ligand also reduced significantly expression of the chemokine, monocyte chemoattractant protein (MCP)-1/CCL2. Sera from mice immunized with AGBMD were also evaluated for antigen-specific IgGs. There was a significant increase in the IgG1 : IgG2c ratio and a decline in the intrarenal and splenocyte interferon (IFN)-gamma mRNA expression in the WY14,643-fed mice, suggesting that the PPARalpha ligand could skew the immune response to a less inflammatory T helper 2-type of response. These studies suggest that PPARalpha ligands may be a novel treatment for inflammatory renal disease.

Urinary excretion of monocyte chemoattractant protein-1: a biomarker of active tubulointerstitial damage in patients with glomerulopathies

BACKGROUND/AIMS

The urinary concentration of the monocyte chemoattractant protein-1 (uMCP-1) chemokine is increased in several proteinuric and/or inflammatory renal diseases. In the present study, we evaluated the association between uMCP-1 and renal function, proteinuria, glomerular and interstitial macrophage infiltration, and renal fibrosis in patients with primary and secondary glomerulopathies diagnosed by renal biopsy.

METHODS

Thirty-seven patients aged 32.6 +/- 7.7 years were studied. uMCP-1 was determined by ELISA. Renal macrophage expression (CD68 positive cells) is reported as number of macrophages/10(4) microm2 of the cortical tubulointerstitial (TI) area or of glomerular capillary tuft area. Cortical interstitial fibrosis was quantitated by PicroSirius red staining under polarized light by a computerized manner.

RESULTS

The uMCP-1 ratio (pg/ml/urinary creatinine mg/ml) was positively correlated (Spearman coefficient) with proteinuria (r = 0.4629; p < 0.005) and number of macrophages in the cortical TI area (r = 0.64; p = 0.0005), and negatively correlated with creatinine clearance (r = -0.4877; p < 0.001). The uMCP-1 ratio was not significantly correlated with number of macrophages/glomerular capillary tuft area (r = 0.27; p = 0.19) or with percent cortical interstitial fibrosis (r = 0.08; p = 0.62).

CONCLUSIONS

The uMCP-1 excretion is a biomarker of the inflammatory activity of the TI area, and does not reflect chronic interstitial damage.

A pathogenic role for JNK signaling in experimental anti-GBM glomerulonephritis

Activation of the c-Jun NH2-terminal kinase (JNK) signaling pathway is involved in the immune response; however, little is known of its role in immune-induced renal injury. In this study, we examine JNK signaling in the rat anti-glomerular basement membrane (GBM) disease model using CC-401, a specific JNK inhibitor. Animals were given CC-401, vehicle alone or no treatment starting before anti-GBM serum injection and continued treatment until killing. In acute disease, CC-401 blocked JNK signaling and reduced proteinuria in the first 24 h. The transient neutrophil influx seen at 3 h of disease was not affected, however. Continued CC-401 treatment suppressed glomerular and tubulointerstitial damage usually seen at 14 days. The protective effect may be due to modulation of macrophage activation, as CC-401 had no effect upon glomerular macrophage infiltration at day 14 despite the suppression of glomerular lesions and a marked reduction in renal tumor necrosis factor-alpha and inducible nitric oxide synthase messenger RNA levels. Treatment with CC-401 had no apparent effect on T cell or humoral immune responses. These studies suggest that JNK signaling promotes renal injury in acute and progressive rat anti-GBM disease. JNK inhibitors may be a novel therapeutic approach for the treatment of human glomerulonephritis.

Deficiency of P-selectin or P-selectin glycoprotein ligand-1 leads to accelerated development of glomerulonephritis and increased expression of CC chemokine ligand 2 in lupus-prone mice

The selectins and their ligands mediate leukocyte rolling on endothelial cells, the initial step in the emigration cascade leading to leukocyte infiltration of tissue. These adhesion molecules have been shown to be key promoters of acute leukocyte emigration events; however, their roles in the development of long-term inflammatory responses, including those that occur during chronic inflammatory diseases such as systemic lupus erythematosus, are unclear. To assess participation of P-selectin in such disorders, we studied the progression of systemic lupus erythematosus-like disease in P-selectin-deficient and control MRL/MpJ-Fas(lpr) (Fas(lpr)) mice. Surprisingly, we found that P-selectin deficiency resulted in significantly earlier mortality, characterized by a more rapid development of glomerulonephritis and dermatitis. Expression of CCL2 (MCP-1) was increased in the kidneys of P-selectin mutant mice and in supernatants of LPS-stimulated primary renal endothelial cell cultures from these mice. A closely similar phenotype, including elevated renal expression of CCL2, was also observed in Fas(lpr) mice deficient in the major P-selectin ligand, P-selectin glycoprotein ligand-1. These results indicate that P-selectin and P-selectin glycoprotein ligand-1 are not required for leukocyte infiltration and the development of autoimmune disease in Fas(lpr) mice, but rather expression of these adhesion molecules is important for modulating the progression of glomerulonephritis, possibly through down-regulation of endothelial CCL2 expression.

A possible anti-inflammatory role of angiotensin II type 2 receptor in immune-mediated glomerulonephritis during type 1 receptor blockade

We previously reported that angiotensin II type 1 receptor (AT1R) blockade attenuates renal inflammation/fibrogenesis in immune-mediated glomerulonephritis via angiotensin II type 2 receptor (AT2R). In the present study, further in vivo experiments revealed that AT2R was expressed in tubular epithelial cells of nephritic kidneys in mice, and feedback activation of the renin-angiotensin system during AT1R blockade significantly reduced p-ERK, but not intranuclear nuclear factor-kappaB, levels via AT2R. This led to reduction in mRNA levels of the proinflammatory mediator monocyte chemoattractant protein-1 and overall interstitial inflammation and subsequent fibrogenesis. Specific blockade of ERK expression in tubular epithelium by anti-sense oligodeoxynucleotides also attenuated interstitial inflammation, mimicking the anti-inflammatory action of AT2R in nephritic kidneys. Alternatively, we succeeded in confirming such an AT(2)R function by demonstrating that AT1R blockade did not confer renoprotection in nephritic, AT2R gene-deficient mice. Additional in vitro experiments revealed that AT2R activation did not affect nuclear factor-kappaB activation by tumor necrosis factor-alpha in cultured tubular epithelial cells, although it inhibited ERK phosphorylation, which reduced monocyte chemoattractant protein-1 mRNA levels. These results suggest that feedback activation of AT2Rs in tubular epithelium of nephritic kidneys plays an important role in attenuating interstitial inflammation.

Dexamethasone induces connective tissue growth factor expression in renal tubular epithelial cells in a mouse strain-specific manner

Connective tissue growth factor (CTGF), a downstream mediator of transforming growth factor-beta1, mediates mesangial cell/fibroblast proliferation and extracellular matrix production by renal cells. Here, we show that renal tubular epithelial cells from patients with minimal change nephritic syndrome produced CTGF after glucocorticoid treatment. In addition, the glucocorticoid dexamethasone (DEX) increased CTGF mRNA levels in the kidneys of C57B6 but not SJL mice and produced intermediate CTGF mRNA levels in the kidneys of F1 (C57B6 x SJL) mice, midway between the levels found for parental strains. DEX also increased CTGF mRNA levels in cultured tubular epithelial cells derived from C57B6 (mProx24) but not SJL (MCT) mice via transcriptional up-regulation of CTGF mRNA. Transient transfection experiments using luciferase reporter constructs bearing CTGF promoter fragments revealed that the -897- to -628-bp fragment contained DEX-responsive positive regulatory elements, which were active in mProx24 but not MCT cells. Long-term DEX treatment resulted in fibronectin deposition in the kidneys of C57B6 but not SJL mice, and this effect was inhibited by co-administration of CTGF anti-sense oligodeoxynucleotides. Thus, glucocorticoid-induced renal fibrogenesis seems to be influenced by genetic background, with the critical DEX-responsive elements in the -897- to -628-bp region of the CTGF promoter.

Macrophages and progressive tubulointerstitial disease

Macrophages and progressive tubulointerstitial disease. In chronic renal disease, tubulointerstitial inflammation and injury is associated with infiltrating macrophages. As a consequence of primary injury, proteinuria, chronic hypoxia, and glomerular-derived cytokines may all differentially modulate the expression of factors that promote macrophage recruitment. In addition to adhesion molecules and chemokines, products of complement system and renin-angiotensin system activation may direct this process. Once present at interstitial sites, macrophages interact with resident cells and extracellular matrix to generate a proinflammatory microenvironment that amplifies tissues injury and promotes scarring. There is now increasing evidence for the efficacy of interventions directed against factors that recruit, activate, or are produced by macrophages. A detailed understanding of the biology of this area may lead to the further development of therapies that will improve the outcome of renal disease.

DNA vaccination with naked DNA encoding MCP-1 and RANTES protects against renal injury in adriamycin nephropathy

BACKGROUND

We have previously shown that monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation, normal T-cell expressed and secreted (RANTES) are significantly increased in renal cortex in adriamycin nephropathy. In this study, we tested the effect of DNA vaccination encoding the C-C chemokines MCP-1 and RANTES in a rat model of adriamycin nephropathy.

METHODS

Both reverse transcription-polymerase chain reaction (RT-PCR) products of MCP-1 and RANTES used as constructs were cloned into a pTarget vector for naked DNA vaccination. Two hundred micrograms of DNA was injected into the tibialis anterior muscle four times at weekly intervals. One week after the last DNA vaccination, rats received adriamycin. All animals were sacrificed 4 weeks after adriamycin administration. Changes in renal function and histologic features were assessed. Enzyme-linked immunosorbent assay (ELISA) and Western blot were used for autoantibody determination. Antibody specificity was assessed in in vitro transmigration assays.

RESULTS

Chemokine DNA vaccination significantly reduced proteinuria (P < 0.05) and ameliorated creatinine clearance (P < 0.05) at 2, 3, and 4 weeks after adriamycin administration. Morphometric analysis showed less glomerular sclerosis (P < 0.001) and interstitial infiltrates (P < 0.005) in chemokine DNA vaccination group compared with control groups. Anti-MCP-1 and RANTES autoantibodies were detected in higher concentrations in chemokine DNA vaccinated rats than in control rats (P < 0.001) and serum from vaccinated rats blocked T-cell transmigration to MCP-1 and RANTES.

CONCLUSION

In this study, we have shown that naked DNA vaccination against MCP-1 and RANTES ameliorates the progression of renal disease in the rat adriamycin nephropathy model of chronic proteinuric renal disease. The protective mechanism may involve the production of autoantibodies against MCP-1 and RANTES.

Connective tissue growth factor expressed in tubular epithelium plays a pivotal role in renal fibrogenesis

Connective tissue growth factor (CTGF) is one of the candidate factors that are thought to mediate the downstream profibrotic action of TGF-beta. However, its precise role in renal interstitial fibrogenesis has not yet been clarified. It was demonstrated previously that CTGF was expressed in tubular epithelial cells that had been engulfed by interstitial fibrosis in the remnant kidney of the subtotal nephrectomy (SNx) model. In the present study, co-cultures of tubular epithelial cells (mProx24) and tubulointerstitial fibroblasts (TFB) that mimic the subepithelial mesenchyme in the kidney were used to study the profibrotic effects of TGF-beta1-induced CTGF. In these co-cultures, TGF-beta1 treatment resulted in significantly increased mRNA levels of type I collagen and fibronectin in the TFB. These effects were both direct and indirect, with the latter being mediated by CTGF derived from the co-cultured mProx24. Then TGF-beta1 transgenic mice were subtotally nephrectomized and treated with CTGF antisense oligodeoxynucleotide, and their kidneys were analyzed for fibrosis. Intravenous administration of CTGF antisense oligodeoxynucleotide significantly blocked CTGF expression in the proximal tubular epithelial cells in the remnant kidney of these animals despite the sustained level of TGF-beta1 mRNA. This reduction in CTGF mRNA level paralleled a reduction in mRNA levels of matrix molecules as well as proteinase inhibitors plasminogen activator inhibitor-1 and tissue inhibitor of metalloproteinase-1, suppressing renal interstitial fibrogenesis. In conclusion, tubular CTGF acts as a downstream mediator of the profibrotic effects of TGF-beta1 in the remnant kidney, which is a promising target for antifibrotic drugs designed to treat TGF-beta1-dependent interstitial fibrosis.

Identifying Chemokines as Therapeutic Targets in Renal Disease: Lessons from Antagonist Studies and Knockout Mice

Chemokines, in concert with cytokines and adhesion molecules, play multiple roles in local and systemic immune responses. In the kidney, the temporal and spatial expression of chemokines correlates with local renal damage and accumulation of chemokine receptor-bearing leukocytes. Chemokines play important roles in leukocyte trafficking and blocking chemokines can effectively reduce renal leukocyte recruitment and subsequent renal damage. However, recent data indicate that blocking chemokine or chemokine receptor activity in renal disease may also exacerbate renal inflammation under certain conditions. An increasing amount of data indicates additional roles of chemokines in the regulation of innate and adaptive immune responses, which may adversively affect the outcome of interventional studies. This review summarizes available in vivo studies on the blockade of chemokines and chemokine receptors in kidney diseases, with a special focus on the therapeutic potential of anti-chemokine strategies, including potential side effects, in renal disease.

Modulation of inflammation by slit protein in vivo in experimental crescentic glomerulonephritis

A basic conservation of cell migration guidance mechanisms in the nervous and immune systems was proposed when Slit, known for its role in axon guidance, was found to inhibit chemokine-induced leukocyte chemotaxis in vitro. These studies examined the role of Slit2 in modulating inflammation in vivo. In a rat model of glomerulonephritis, endogenous glomerular Slit2 expression fell after disease induction, and its inhibition during the early disease period accelerated inflammation. Ex vivo glomerular leukocytes showed decreased chemokine and chemoattractant-induced chemotaxis in response to Slit2, suggesting an anti-inflammatory role for glomerular Slit2. In contrast to the effect of inhibition, glomerulonephritis was ameliorated by systemic Slit2 administration. Slit2 treatment improved disease histologically and also improved renal function when given early in the disease course. Leukocytes harvested from rats receiving Slit2 showed decreased monocyte chemoattractant protein-1 (MCP)-1-mediated migration, consistent with a peripheral Slit2 effect. In keeping with this functional alteration, Slit2-mediated inhibition of RAW264.7 cell chemotaxis was associated with decreased levels of active cdc42 and Rac1, implicating GTPases in leukocyte Slit2 signaling. These findings suggest a role for endogenous Slit2 in the inhibition of chemoattractant-mediated signals, demonstrate a potentially important anti-inflammatory effect for Slit2 in vivo, and provide further evidence for conserved mechanisms guiding the process of migration in distinct cell types.

Selective depletion of fibroblasts preserves morphology and the functional integrity of peritoneum in transgenic mice with peritoneal fibrosing syndrome

BACKGROUND

A peritoneal fibrosing syndrome (PFS) can progressively reduce peritoneal ultrafiltration during chronic peritoneal dialysis in patients with renal failure. The pathogenesis of PFS is unclear and the role of peritoneal fibroblasts has not been evaluated experimentally.

METHODS

We followed the fate of fibroblasts producing PFS in a mouse model using fibroblast-specific protein 1 (FSP1) as a marker. PFS was induced by daily peritoneal infusions of chlorhexidine gluconate (CHG) saline into transgenic mice expressing the thymidine kinase (Delta tk) gene under the control of the FSP1 promoter (FSP1.Delta tk mice). To demonstrate the role of fibroblasts in PFS, we treated these FSP1.Delta tk mice with a nucleoside analogue to induce DNA chain termination and fibroblast death.

RESULTS

Mice receiving peritoneal infusions of CHG saline every other day for 2 weeks developed increasing numbers of FSP1+ fibroblasts in the subserosal layers of the visceral peritoneum. Mac-3+ monocytes (macrophages) subsequently accumulated over the next 2 weeks in association with increased deposition of type I collagen and increased endothelial vascularity (CD31+) in these subserosal tissues. Since these peritoneal fibroblasts expressed monocyte chemoattractant protein-1 (MCP-1), heat shock protein 47 (HSP47), and vascular endothelial growth factor (VEGF), we suspect they were partially responsible for macrophage recruitment, matrix production, and the neoangiogenesis in the subserosal tissue. Treatment of PFS in FSP1.Delta tk transgenic mice with a nucleoside analogue selectively reduced the numbers of peritoneal fibroblasts and attenuated the attendant changes in peritoneal histology. Rescuing the peritoneal membrane from chronic thickening and neoangiogenesis by reducing the number of fibroblasts also preserved ultrafiltration.

CONCLUSION

Peritoneal fibroblasts play a pivotal role in PFS, and their deletion using a fibroblasts-specific transgene was effective in preventing peritoneal fibrogenesis.

Chemokines and atherosclerosis

Atherosclerosis is an inflammatory disease of the vessel wall, characterized by the accumulation of leukocytes, especially macrophages and T-cells. Chemokines are small heparin-binding polypeptides, whose main function is to attract cells to the areas of developing inflammation. They function by ligating G-protein coupled chemokine receptors initiating different signaling cascades. In vivo and in vitro investigations showed that chemokines are produced by a variety of cells and play important roles in the development and progression of many physiological and pathological conditions including atherosclerosis. Chemokines such as MCP-1, MCP-4, MIP-1 and RANTES may mediate leukocyte trafficking to, and their retention in, the plaque while CXCL16 seems to fulfill the dual function of a chemokine and a scavenger receptor. Chemokine and chemokine receptor homologues are secreted by several viruses, which may also play a role in the pathogenesis of atherosclerosis. Expression levels and gene polymorphisms of some chemokines may become useful clinical markers of atherosclerosis and other cardiovascular diseases. Modulation of chemokines and chemokine receptors' expression as well as their signaling pathways may provide important anti-atherogenic strategies.

Direct contact between human peripheral blood mononuclear cells and renal fibroblasts facilitates the expression of monocyte chemoattractant protein-1

BACKGROUND

Cell-to-cell interaction is thought to be an important feature of a variety of biological processes. As far as the proinflammatory process is concerned, the interaction between mesangial cells and monocytes/macrophages induces the expression of monocyte chemoattractant protein-1 (MCP-1), and this may play a role in glomerulonephritis. In this study, we investigated whether the cell-to-cell interaction between immune cells and renal fibroblasts induces MCP-1 gene expression, which may be involved in interstitial inflammation in the kidney.

METHODS

Human renal fibroblast cell lines, tNKF (from a normal kidney) and tFKIF (from a kidney with fibrosis), and peripheral blood mononuclear cells (PBMC) were used to assess the effect of cell-to-cell contact on the expression of MCP-1 mRNA in the fibroblasts. The expression of the MCP-1 gene in the fibroblasts was also examined after stimulation with tumor necrosis factor-alpha (TNF-alpha) and the culture supernatant from PBMC. RT-PCR was used to detect MCP-1 mRNA expression. Neutralizing antibodies to intercellular adhesion molecule-1 (ICAM-1) and vascular endothelial adhesion molecule-1 (VCAM-1) were used to block the cell-to-cell contact between the fibroblasts and PBMC.

RESULTS

TNF-alpha and the culture supernatant from PBMC increased MCP-1 gene expression in tNKF cells. Contact culture with PBMC also significantly increased MCP-1 gene expression in tNKF cells. Although the basal level of MCP-1 mRNA was higher in tFKIF than tNKF cells, tFKIF cells did not respond significantly to any stimulation in this study. Following pretreatment with anti-ICAM-1 antibody, MCP-1 gene expression in tNKF cells was significantly suppressed in contact culture with PBMC. Anti-VCAM-1 antibody treatment had no effects.

CONCLUSION

It is suggested that the interaction between renal fibroblasts and PBMC was mediated through direct contact and by secreted humoral factors. ICAM-1 on renal fibroblasts may be involved in the direct cell-to-cell interaction inducing MCP-1 gene expression, which seems to be involved in renal interstitial inflammation.

Gene transfer of truncated IkappaBalpha prevents tubulointerstitial injury

BACKGROUND

Severe proteinuria not only indicates the presence of progressive glomerular disease, but also causes tubular epithelial cells to produce inflammatory mediators leading to tubulointerstitial (TI) injury. We investigated the role of nuclear factor-kappaB (NF-kappaB) in tubular epithelial cells in the development of proteinuria-induced TI injury.

METHODS

To specifically inhibit NF-kappaB activation, a recombinant adenovirus vector expressing a truncated form of IkappaBalpha (AdexIkappaBDeltaN) was injected into renal arteries of protein-overloaded rats, a model of TI injury characterized by infiltration of mononuclear cells and fibrosis.

RESULTS

Activation of NF-kappaB in the renal cortex, observed in protein-overloaded rats treated with a control vector, recombinant lacZ adenovirus, was prevented in AdexIkappaBDeltaN-injected rats. Microscopic examination revealed AdexIkappaBDeltaN treatment to markedly attenuate proteinuria-induced TI injury. Increased immunostaining of vascular cell adhesion molecule-1, transforming growth factor-beta, and fibronectin in TI lesions also was suppressed by AdexIkappaBDeltaN injection.

CONCLUSIONS

These findings provide evidence of the critical role of NF-kappaB activation in TI injury and suggest the therapeutic potential of adenovirus-mediated IkappaBDeltaN gene transfer into the kidney as a means of interrupting the process of TI damage.

Chemokines and chemokine receptors are involved in the resolution or progression of renal disease

Locally secreted chemokines mediate leukocyte recruitment during the initiation and amplification phase of renal inflammation. In turn, the infiltrating leukocytes contribute to renal damage by releasing inflammatory and profibrotic factors. Rapid down modulation of the chemokine signal will support resolution of acute inflammation, whereas progression occurs if ongoing or repeated renal injury maintains continuous local chemokine secretion and leukocyte influx into the glomerulus or the interstitial space. In glomerular injury proteinuria itself as well as glomerular secreted cytokines stimulate downstream tubular epithelial cells to also secrete chemokines. During primary tubular injury, tubular epithelial cells directly become a major site of chemokine production. This in turn supports leukocyte infiltration and activation. Infiltrating leukocytes stimulate fibroblast proliferation and matrix synthesis, leading to widening of the interstitial space. The specific and intricate renal vascular architecture renders the organ susceptible to ischemic damage as interstitial volume increases. Ischemia in turn serves as a stimulus for chemokine and cytokine production and matrix synthesis. The mutual stimulation between fibroblasts and infiltrating leukocytes supports progressive tubular damage, renal fibrosis, and glomerulosclerosis. Potentially this vicious circle leading to progression of chronic nephropathies offers the opportunity for therapeutic intervention. Interfering with the chemokine network that mediates leukocyte recruitment may represent a promising therapeutic option for progressive renal disorders and renal fibrosis. This article summarizes the present data on the role of chemokines in acute and chronic renal disease with special emphasis on their potential role in mediating resolution or progression of renal disease as well as on therapeutic options.

Renal fibroblast-like cells in Goodpasture syndrome rats

BACKGROUND

The extent of renal fibrosis is the best predictor for functional outcomes in a variety of progressive renal diseases. Interstitial fibroblast-like cells (FbLCs) are presumably involved in the fibrotic process. However, such FbLCs have never been well characterized in the kidney.

METHODS

We characterized renal FbLCs in the nephritic kidney (in which the number of FbLCs and extracellular matrix accumulation were significantly increased) with regards to their expression of phenotypic and functional markers using day 49 Goodpasture syndrome (GPS) rats.

RESULTS

Within the renal cortical interstitium, there were a number of alpha-smooth muscle actin(+) (alpha-SMA(+)) FbLCs, negative for vimentin (VIM) and transforming growth factor-beta 1, and not equipped with well-developed rough endoplasmic reticulum and actin-stress fibers. All of these findings were incompatible with the typical features of granulation tissue alpha-SMA(+) myofibroblasts. On the other hand, FbLCs negative for alpha-SMA and VIM produced alpha1(I) procollagen in the nephritic kidney.

CONCLUSION

A number of FbLC populations reside within the cortical interstitium of the kidney in GPS rats, each of which is likely to have developed independently in response to the local conditions of the nephritic kidney, contributing to renal fibrogenesis. Further studies are needed to clarify the key type of FbLC that orchestrates other members to produce renal fibrosis.

Tubulointerstitial renal disease

Tubulointerstitial damage, in progressive chronic renal disease of all types, arises because of a complex interplay between factors in the tubular lumen, tubular epithelial cells, peritubular capillaries, resident and infiltrating interstitial cells and extracellular matrix. Particularly in proteinuric renal disease, tubular epithelial cells play a central role in orchestrating these events. In response to mediators arising systemically, in the tubular lumen or from other renal cells, tubular epithelial cells undergo a complex series of structural and functional changes and produce a bewildering number of soluble and fixed mediators, which in turn lead to interstitial inflammation and fibrosis. Knowledge of these interactions has increased exponentially over the past decade, and has defined a number of new targets for treatment. Both expansion and consolidation of this knowledge is needed to determine which of these targets holds the most promise for future treatment.

Chemokines as therapeutic targets in renal disease

Increased understanding of the fundamental importance of the role of chemokines and their receptors in inflammation, together with the demonstration of their involvement in human and experimental inflammatory renal disease, make these molecules potential therapeutic targets. A number of recent studies using genetically deficient mice and chemokine receptor antagonists in animal models have demonstrated that chemokine inhibition can attenuate experimental renal injury. Because there is simultaneous expression of multiple chemokines and receptors in disease, strategies that are aimed at antagonizing multiple chemokines receptor interactions are likely to be more effective than therapies that target a single chemokine. It is also now recognized that chemokines are involved in normal immune development and immune regulation. These observations, together with the results of studies that have demonstrated deleterious effects of chemokine receptor antagonism in experimental renal disease, highlight the need for thorough understanding of the role of individual chemokines in the pathogenesis of different types of renal disease before optimal therapeutic interventions may be achieved.