Expression of monocyte chemoattractant protein-1 in proximal tubular epithelial cells in a rat model of progressive kidney failure

Erlotinib attenuates the progression of chronic kidney disease in rats with remnant kidney

Background

Increasing evidence indicates that epidermal growth factor receptor (EGFR) has a pathogenic role in renal fibrosis. Currently no effective treatment can completely halt the progression of chronic kidney disease (CKD). This study was undertaken to investigate the renoprotective effects of erlotinib, a tyrosine kinase inhibitor that can block EGFR activity in the progression of CKD and the mechanisms involved.

Methods

Sprague Dawley rats with 5/6 nephrectomy were administered either erlotinib or vehicle from 2 weeks after surgery and for a period of 8 weeks. Blood pressure, proteinuria and serum creatinine were measured periodically. Renal morphological investigations were performed at sacrifice. In vitro, we used normal human mesangial cells (NHMCs) and human proximal tubular cells to investigate the inhibitory effects of erlotinib on renal fibrosis-associated signaling pathways by western blotting.

Results

Erlotinib treatment significantly blunted the progression of CKD as evidenced by reduced levels of serum creatinine, proteinuria and renal cortical profibrogenic genes and scores of glomerulosclerosis and tubulointerstitial damage. Tubulointerstitial macrophage infiltration and multiple pro-inflammatory cytokine gene expression levels were also attenuated by erlotinib treatment. In vitro, heparin-binding epidermal growth factor-like growth factor-induced Akt and extracellular-regulated kinase (ERK) 1/2 activation in normal human mesangial cells and human proximal tubular cells was inhibited by pretreatment with erlotinib.

Conclusions

EGFR blocking by erlotinib protected against renal fibrosis in 5/6 nephrectomized rats via inhibition of Akt and ERK 1/2 signaling pathways, which are associated with renal fibrosis. Erlotinib also has anti-inflammatory properties, which may contribute to its renoprotective effects. Erlotinib represents a potential novel therapeutic strategy for the treatment of CKD.

Kidney injury molecule-1 expression in IgA nephropathy and its correlation with hypoxia and tubulointerstitial inflammation

Tubulointerstitial injury plays an important role in the development and progression of chronic kidney disease (CKD). Kidney injury molecule (KIM)-1 is induced in damaged proximal tubules in both acute renal injury and CKD. However, the dynamics of KIM-1 in CKD and effects of KIM-1 expression on disease progression are unknown. Here, we aimed to determine the associations between tubular KIM-1 expression levels, renal function, and inflammation in CKD. The relationships between levels of KIM-1 and clinicopathological parameters were analyzed in patients with progressive and nonprogressive IgA nephropathy. KIM-1 expression was increased in patients with IgA nephropathy, and its expression was significantly correlated with the decrease of renal function. KIM-1 was particularly evident at the site with reduced capillary density, and KIM-1-positive tubules were surrounded by infiltrates of inflammatory cells. Using in vitro cell models, we showed that cellular stressors, including hypoxia, induced KIM-1 expression. KIM-1-expressing cells produced more chemokines/cytokines when cultured under hypoxic conditions. Furthermore, we showed that tubular cells with KIM-1 expression can regulate the immune response of inflammatory cells through the secretion of chemotactic factors. These data suggest that KIM-1-expressing epithelial cells may play a role in the pathogenesis of tubulointerstitial inflammation during chronic renal injury through the secretion of chemokines/cytokines.

Nilotinib attenuates renal injury and prolongs survival in chronic kidney disease

The tyrosine kinase inhibitor imatinib is beneficial in experimental renal diseases, but the effect of the new tyrosine kinase inhibitor nilotinib on the progression of renal failure is unknown. We administered either nilotinib or vehicle to Sprague-Dawley rats beginning 2 weeks after 5/6 nephrectomy (Nx) or laparotomy and continuing for 8 weeks. Serum creatinine levels were significantly lower in the nilotinib group after 6 and 8 weeks of treatment. Furthermore, nilotinib-treated rats had less proteinuria, attenuated glomerulosclerosis and tubulointerstitial damage, and reduced macrophage infiltration into the tubulointerstitium. Treatment with nilotinib also significantly decreased renal cortical expression of profibrogenic genes, such as IL-1β and monocyte chemotactic protein-1, which correlated closely with the tubulointerstitial damage score and ED1-positive macrophages score. In addition, nilotinib treatment significantly prolonged survival. Taken together, these results suggest that nilotinib may limit the progression of chronic kidney disease.

Intratubular hydrodynamic forces influence tubulointerstitial fibrosis in the kidney

PURPOSE OF REVIEW

Renal epithelial cells respond to mechanical stimuli with immediate transduction events (e.g. activation of ion channels), intermediate biological responses (e.g. changes in gene expression), and long-term cellular adaptation (e.g. protein expression). Progressive renal disease is characterized by disturbed glomerular hydrodynamics that contributes to glomerulosclerosis, but how intratubular biomechanical forces contribute to tubulointerstital inflammation and fibrosis is poorly understood.

RECENT FINDINGS

In-vivo and in-vitro models of obstructive uropathy demonstrate that tubular stretch induces robust expression of transforming growth factor beta-1, activation of tubular apoptosis, and induction of nuclear factor-kappaB signaling, which contribute to the inflammatory and fibrotic milieu. Nonobstructive structural kidney diseases associated with nephron loss follow a course characterized by compensatory increases of single nephron glomerular filtration rate and tubular flow rate. Resulting increases in tubular fluid shear stress reduce tissue-plasminogen activator and urokinase enzymatic activity, which diminishes breakdown of extracellular matrix. In models of high dietary Na intake, which increases tubular flow, urinary transforming growth factor beta-1 concentrations and renal mitogen-activated protein kinase activity are increased.

SUMMARY

In conclusion, intratubular biomechanical forces, stretch, and fluid shear stress generate changes in intracellular signaling and gene expression that contribute to the pathobiology of obstructive and nonobstructive kidney disease.

Role of FTY720 on M1 and M2 macrophages, lymphocytes, and chemokines in 5/6 nephrectomized rats

Renal injury is accompanied by the presence of infiltrating inflammatory cells in the glomerulus and tubulointerstitium. FTY720 modifies lymphocyte migration into injured tissues by lymphocyte sequestration to secondary lymphoid organs. The purpose of this study was to examine the potential of FTY720 to influence the inflammatory response in a nonimmunological model of renal failure. Sham-operated and 5/6 nephrectomized (SNX) Sprague-Dawley rats received two different doses of FTY720 or vehicle orally for 14 wk. Treatment with FTY720 reduced glomerular and tubulointerstitial damage in SNX rats but failed to stabilize creatinine clearance. The increase in gene expression of chemokine receptors CCR1, CCR2, and CCR5 in kidneys of vehicle-treated SNX rats was significantly attenuated by high-dose FTY720. Treatment with high-dose FTY720 tended to normalize RANTES and MCP-1 renal gene expression. FTY720 affected not only glomerular and tubulointerstitial lymphocytes, but M1 and M2 phenotype macrophages were also reduced. FTY720 significantly reduced key mediators of renal inflammation and fibrosis. FTY720 also decreased immunoregulation of M2 macrophages, which are beneficial for tissue remodeling and repair.

Proinflammatory and proliferative responses of human proximal tubule cells to PAR-2 activation

Despite the abundant expression of protease-activated receptor (PAR)-2 in the kidney, its relevance to renal physiology is not well understood. A role for this receptor in inflammation and cell proliferation has recently been suggested in nonrenal tissues. The aims of this study were to demonstrate that human proximal tubule cells (PTC) express functional PAR-2 and to investigate whether its activation can mediate proinflammatory and proliferative responses in these cells. Primary human PTC were cultured under serum-free conditions with or without the PAR-2-activating peptide SLIGKV-NH2 (up to 800 microM), a control peptide, VKGILS-NH2 (200 microM), or trypsin (0.01-100 nM). PAR-2 expression (RT-PCR), intracellular Ca2+ mobilization (fura-2 fluorimetry), DNA synthesis (thymidine incorporation), fibronectin production (ELISA, Western blotting), and monocyte chemotactic protein (MCP)-1 secretion (ELISA) were measured. Trypsinogen expression in kidney and PTC cultures was determined by immunohistochemistry and Western blotting. In the kidney PTC were the predominant cell type expressing PAR-2. SLIGKV-NH2, but not VKGILS-NH2, stimulated a rapid concentration-dependent mobilization of intracellular Ca2+ and ERK1/2 phosphorylation and, by 24 h, increases in DNA synthesis, fibronectin secretion, and MCP-1 secretion. These delayed responses appeared to be independent of ERK1/2. Trypsin produced similar rapid but not delayed responses. Trypsinogen was weakly expressed by PTC in the kidney and in culture. In summary, PTC are the main site of PAR-2 expression in the human kidney. In PTC cultures SLIGKV-NH2 initiates proinflammatory and proliferative responses. Trypsinogen expressed within the kidney has the potential to contribute to PAR-2 activation in certain circumstances.

Increased immunoreactivities against endothelin-converting enzyme-1 and monocyte chemotactic protein-1 in hepatic stellate cells of rat fibrous liver induced by thioacetamide

The progression of rat liver fibrosis induced by intraperitoneal administration of thioacetamide (TAA) was evaluated by immunocytochemistry using anti-alpha-smooth muscle actin (alpha-SMA), antiendothelin-converting enzyme (ECE)-1, and anti-monocyte chemotactic protein (MCP)-1 antibodies. The fibrous septal spaces gradually increased after administration of TAA, and pseudolobules were established in the 7-week TAA-treated groups. Immunoreactivities against alpha-SMA were not detected in hepatic stellate cells (HSCs) of the control group without TAA treatment, although they were observed in the HSCs around the fibrous septal spaces in all TAA-treated groups, indicating that activation of HSCs occurs during the establishment of pseudolobules. Immunoreactivities against ECE-1 and MCP-1 were seen in such HSCs of the TAA-treated groups, but few or no immunoreactivities were detected in the HSCs of the control group. The most significant increase in the ECE-1 immunoreactivities was detected in the 1-week TAA-treated group, whereas that in MCP-1 was observed in the 7-week TAA-treated group. The present immunocytochemistry indicated a difference in the accelerated expression period between immunoreactivities against ECE-1 and MCP-1 in the HSCs during the progression of TAA-induced liver fibrosis, suggesting that ECE-1 is involved in the early phase of liver fibrosis and that MCP-1 plays a role during the later phase.

IL-10 suppresses chemokines, inflammation, and fibrosis in a model of chronic renal disease

IL-10 is a pluripotent cytokine that plays a pivotal role in the regulation of immune and inflammatory responses. Whereas short-term administration of IL-10 has shown benefit in acute glomerulonephritis, no studies have addressed the potential benefits of IL-10 in chronic renal disease. Chronically elevated blood levels of IL-10 in rats were achieved by administration of a recombinant adeno-associated virus serotype 1 IL-10 (rAAV1-IL-10) vector. Control rats were given a similar dose of rAAV1-GFP. Four weeks after injection, IL-10 levels in serum were measured by ELISA, and chronic renal disease was induced by a 5/6 nephrectomy (n = 6 in each group). Eight weeks later, rats were killed and renal tissue was obtained for RNA, protein, and immunohistochemical analysis. Serum levels of IL-10 were 12-fold greater in the rAAV1-IL-10 group by 4 wk after rAAV1-IL-10 administration (345 +/- 169 versus 28 +/- 15 pg/ml; P = 0.001), and levels were maintained throughout the experiment. rAAV1-IL-10 treatment resulted in less proteinuria (P < 0.05), lower serum creatinine (P < 0.05), and higher creatinine clearances (P < 0.01) compared with rAAV1-GFP-treated rats. Renal interstitial infiltration was significantly attenuated by rAAV1-IL-10 administration as assessed by numbers of CD4+, CD8+, monocyte-macrophages (ED-1+) and dendritic (OX-62+) cells (P < 0.05), and this correlated with reductions in the renal expression of monocyte (renal monocyte chemoattractant protein-1 mRNA and protein) and T cell (RANTES mRNA) chemokines. rAAV1-IL-10 administration decreased mRNA levels of IFN-gamma and IL-2 in the kidney. The reduction in inflammatory cells was associated with a significant reduction in glomerulosclerosis and interstitial fibrosis. It is concluded that IL-10 blocks inflammation and improves renal function in this model of chronic renal disease. The feasibility of long-term overexpression of a gene using the AAV serotype 1 vector system in a model of renal disease is also demonstrated.

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.

Increased Expression of Mineralocorticoid Effector Mechanisms in Kidney Biopsies of Patients With Heavy Proteinuria

Background— Aldosterone has emerged as a deleterious hormone in the heart, with mineralocorticoid receptor (MR) blockade reducing mortality in patients with severe heart failure. There is also experimental evidence that aldosterone contributes to the development of nephrosclerosis and renal fibrosis in rodent models, but little is known of its role in clinical renal disease.

Methods and Results— We quantified MR, serum- and glucocorticoid-regulated kinase 1 (sgk1), and mRNA expression of inflammatory mediators such as macrophage chemoattractant protein-1 (MCP-1), transforming growth factor-β1, and interleukin-6 in 95 human kidney biopsies in patients with renal failure and mild to marked proteinuria of diverse etiologic origins. We measured renal function, serum aldosterone, urinary MCP-1 protein excretion, and the amount of chronic renal damage. Macrophage invasion was quantified by CD68 and vascularization by CD34 immunostaining. Serum aldosterone correlated negatively with creatinine clearance ( P <0.01) and positively with renal scarring ( P <0.05) but did not correlate with MR mRNA expression or proteinuria. Patients with heavy albuminuria (>2 g/24 h; n=15) had the most renal scarring and the lowest endothelial CD34 staining. This group showed a significant 5-fold increase in MR, a 2.5-fold increase in sgk1 expression and a significant increase in inflammatory mediators (7-fold increase in MCP-1, 3-fold increase in transforming growth factor-β1, and 2-fold increase in interleukin-6 mRNA). Urinary MCP-1 protein excretion and renal macrophage invasion were significantly increased in patients with heavy albuminuria.

Conclusions— These studies support animal data linking aldosterone/MR activation to renal inflammation and proteinuria. Further studies are urgently required to assess the potential beneficial effects of MR antagonism in patients with renal disease.

Donor genomics influence graft events: the effect of donor polymorphisms on acute rejection and chronic allograft nephropathy

BACKGROUND

Organs procured from deceased donors emanate from individuals with diverse genetic backgrounds. Donor organs, therefore, may vary in their response to injury and immune stimuli in a genetically determined manner. We assessed polymorphisms from 244 renal allograft donors to better understand the impact of donor polymorphisms on selected transplant outcomes.

METHODS

Donor genomic DNA restriction fragment length polymorphisms were assayed for evidence of common cytokine [interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-alpha, TGF-beta, interferon (IFN)-gamma] and chemokine (CCR2, CCR5) polymorphisms. Associations between donor polymorphisms and graft events were determined using chi-square, linear regression, and Kaplan-Meier analyses.

RESULTS

Several genotypic polymorphisms demonstrated a modest association with acute rejection, including the transforming growth factor (TGF)-beta T/C codon 10 (P= 0.027) and the CCR5 G/A 59029 (P= 0.039) genes by chi-square analysis. Notably, the presence of the T allele in the IFN-gamma gene (+874) demonstrated a highly significant association with biopsy-proven chronic allograft nephropathy (P < 0.008). This association remained highly significant in a multiple linear regression model that incorporated biopsy-proven acute rejection as a covariate.

CONCLUSION

These data suggest that many of the donor polymorphisms studied in this analysis may influence a recipient's immune response to a renal allograft. However, their greatest impact may be demonstrated in long-term outcomes.

Urinary excretion of monocyte chemoattractant protein-1 in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) progresses to renal insufficiency in >50% of patients and is characterized by interstitial inflammation and fibrosis in the end stage. In a rat model of ADPKD, monocytes accumulate within the renal interstitium in association with increased levels of monocyte chemoattractant protein-1 (MCP-1) in cyst mural cells and increased excretion of this chemokine into the urine. For determining the extent to which this chemokine is abnormally expressed in patients with ADPKD, a cross-section study was performed of MCP-1 in urine, serum, and cyst fluid and MCP-1 production by mural epithelial cells cultured from the cysts of human patients with ADPKD. Upper boundaries for urinary MCP-1 excretion (>263 pg/mg creatinine) and serum creatinine concentration (>1.5 mg/dl) determined in 19 normal individuals were used to sort 55 ADPKD patients into three groups. In group 1 (n = 13), urine MCP-1 excretion (136 +/- 14 pg/mg creatinine) was not different from normal volunteers (152 +/- 16 pg/mg); serum creatinine levels and urine total protein excretion were normal as well. In group 2 (n = 27), urine MCP-1 excretion was increased (525 +/- 39 pg/mg creatinine), but serum creatinine levels and urine protein excretion were not different from normal. In group 3 (n = 15), urine MCP-1 excretion increased further (1221 +/- 171 pg/mg), serum creatinine levels increased to 4.3 +/- 0.8 mg/dl, and urine protein excretion rose to 0.64 +/- 0.28 mg/mg creatinine. Serum MCP-1 levels of ADPKD patients (84 +/- 9.9 pg/ml; n = 15) did not differ from normal. Levels of MCP-1 much higher than in serum or urine were found in cyst fluids obtained from nephrectomy specimens (range, 767 to 40,860 pg/ml; mean, 6434 +/- 841 pg/ml; n = 73). Polarized, confluent cultures of ADPKD cyst epithelial cells secreted MCP-1 into the apical fluid to levels eightfold greater than in the basolateral medium. Similar results were obtained with tubule epithelial cells cultured from normal human renal cortex. On the basis of these results, it is concluded that urinary excretion of MCP-1 is increased in the majority of adult patients with ADPKD and that the source of some of this chemokine may be the mural epithelium of cysts. Furthermore, it seemed that urinary MCP-1 excretion may have increased in these ADPKD patients before appreciable increases in serum creatinine concentration or urine protein excretion were detected. It is reasonable to include urine MCP-1 excretion among candidate surrogate markers in controlled, longitudinal studies of ADPKD.

Low-dose radiation modifies the progression of chronic renal failure

Previous studies have indicated that the application of low dose radiation to an arterial ligation has the potential to subsequently reduce or eliminate restenosis caused by smooth muscle cell proliferation. Sufficient kidney irradiation causes a radiation nephropathy and often leads to renal failure. In order to evaluate the effect of low-dose irradiation on the kidney we hypothesized that this particular therapy modifies renal injury in rats with renal ablation and subsequently slows the rate of the progression. For further clarification of the effect of irradiation at low doses, we determined proliferating cell nuclear antigen (PCNA) and monocyte chemoattractant protein-1 (MCP-1) expression in remnant kidneys after low-dose radiation. Adult Wistar rats (n = 10) were studied during the two weeks after renal ablation. The left kidney was irradiated 24 hours after an operation in anaesthetised animals with 3 Grey in a single dose. Ablated rats without irradiation (n = 9) served as nephrectomized animals group. Rats without surgery and without radiation (n = 10) served as healthy controls. Renal damage was assessed using the following parameters: urine protein excretion rate (UprotV, mg/day), awake systolic blood pressure (SBP, mm Hg), serum creatinine (SCr, micromol/l). The indirect immunofluorescence method was used for the detection of PCNA and MCP-1 expression. Glomerular and tubular immunostaining was scored semiquantitatively. Numerous PCNA positive cells and MCP-1 expression were present in the glomerulus and tubulointerstitium in nephrectomized rat kidneys. Low-dose radiation application was associated with a significant reduction in PCNA and low MCP-1 expression. This study shows that the application of low-dose irradiation has the potential to modify the progression of chronic renal failure in rats.

Integrins induce expression of monocyte chemoattractant protein-1 via focal adhesion kinase in mesangial cells

BACKGROUND

Integrins are major adhesion receptors that not only regulate cytoskeletal organization, but also trigger a variety of intracellular signal transduction pathways. We examined the effects of increased extracellular matrix (ECM) accumulation on monocyte chemoattractant protein-1 (MCP-1) expression, which is known to play an important role in the progression of various glomerular diseases.

METHODS

MCP-1 mRNA and protein expression in cultured rat mesangial cells (MC) attached to ECM proteins were examined by reverse transcription (RT)-polymerase chain reaction (PCR) and Western blotting, respectively. Phosphorylation of focal adhesion kinase (FAK) was measured by Western blotting. Effects of wild-type and dominant-negative FAK on MCP-1 expression were examined by a transient transfection assay.

RESULTS

Cell adhesion to fibronectin-induced phosphorylation of FAK and MCP-1 mRNA expression in time- and dose-dependent manners followed by increased MCP-1 protein expression. All integrin-interacting substrates (laminin and types I, III, and IV collagens) also increased levels of FAK phosphorylation and MCP-1 expression, whereas nonspecific adhesive substrates (polylysine and concanavalin A) had no significant effects. Overexpression of wild-type FAK increased phosphorylation of FAK and expression of MCP-1 mRNA and protein, whereas transfection of dominant-negative FAK abolished adhesion-induced MCP-1 expression. Adhesion-induced expression of MCP-1 mRNA was inhibited by genistein and tosyl phenylalanyl chloromethylketone (TPCK), suggesting that tyrosine kinases [e.g., FAK, and nuclear factor kappa B (NF-kappa B)] are necessary in this signaling.

CONCLUSION

Our results indicate that integrin-mediated cell adhesion to the ECM can induce MCP-1 expression through activation of FAK, and suggest a role for altered ECM deposition in the progression of glomerular diseases by affecting gene expression.

Tubulointerstitial disease: role of ischemia and microvascular disease

PURPOSE OF REVIEW

Tubulointerstitial injury is characteristic of aging-associated renal injury and progressive renal disease. Salt-sensitive hypertension is also associated with tubulointerstitial inflammation, especially when accompanied by microvascular disease. Here we summarize recent studies on the pathogenesis and consequences of tubulointerstitial disease, emphasizing the role of ischemia and the microvasculature.

RECENT FINDINGS

Tubulointerstitial injury occurs via several mechanisms of which one of the most important is chronic ischemia. Recent studies suggest that chronic vasoconstriction may contribute to the renal injury associated with angiotensin II, catecholamines, nitric oxide inhibition, hypokalemia, hyperuricemia, and cyclosporine nephropathy. Salt-sensitivity may result as a consequence of the tubulointerstitial inflammatory response to these conditions, and this appears to be perpetuated by the development of preglomerular vascular disease. With progression of tubulointerstitial disease there is also a loss of peritubular capillaries, and stimulating microvascular growth with angiogenic factors can stabilize renal function in these models.

SUMMARY

Ischemia secondary to vasoconstriction or to structural changes of the renal vasculature may have important consequences both in terms of mediating salt-sensitive hypertension and renal progression. Angiogenic factors may have potential benefit in preventing or treating these conditions.