Differential expression of MCP-1 and its receptor CCR2 in glucose primed human mesangial cells

The effect of stromal cell-derived factor 1 in the migration of neural stem cells

Neural stem cells (NSCs) have widely been used in the treatment of human neurological disorders as cell therapy via intracerebral or intraventricular infusion. However, the migration mechanism required for NSCs homing and recruitment remains to be elucidated. Recently, SDF-1/CXCR4 axis was shown to be responsible for in cell migration and differentiation during the neural development stage and involved in the pathophysiological process of neurological disorders. In this study, we investigated the effect of SDF-1 in migration of NSCs in vitro and in vivo. The expression of CXCR4 receptor was examined by immunocytochemistry and RT-PCR. The migratory ability of NSCs induced by SDF-1 was assessed by transwell chemotaxis assay. The traumatic brain injury rat model was well established, and the recruitment of NSCs and expression of SDF-1 were investigated in vivo. Our findings demonstrated that SDF-1, in vitro, significantly induced the migratory of NSCs in a dose-dependent manner. An overexpression of neural stem cell marker Nestin in the hippocampus was observed after TBI, and the expressions of SDF-1 surrounding the lesion areas were significantly increased. Our results suggested that the migration of NSCs was activated by chemotactic effect of SDF-1. It was also proved the relevance of SDF-1 in the migration of endogenous NSCs after brain injury. Taken together, these results demonstrated that SDF-1/CXCR4 axis may play crucial role in the migration of Nestin-positive cell after brain injury.

CCL2/CCR2 augments the production of transforming growth factor-beta1, type 1 collagen and CCL2 by human CD45-/collagen 1-positive cells under high glucose concentrations

BACKGROUND

The migration and activation of circulating profibrotic cells including fibrocytes by the action of the chemokine/chemokine receptor system has been implicated in pathological fibrogenesis. In the present study, the involvement of collagen 1 (Col1)-producing cells, CD45-positive/collagen-1-positive (CD45(+)/Col1(+)) cells originally named as fibrocytes via CC chemokine receptor 2 (CCR2), a cognate receptor of CCL2/monocyte chemoattractant protein, was examined in diabetic conditions.

METHODS

Human CD45(+)/Col1(+) cells originating from the peripheral blood of healthy volunteers were incubated with high concentrations of D-glucose or D-mannitol as an osmotic control for 12, 24 or 48 h. In addition, these cells were preincubated with CCL2 under high glucose concentrations. We also examined the effects of the inhibitors of glucose transporters (GLUTs), reactive oxygen species or CCR2 on the expression of transforming growth factor beta1 (TGF-β1), pro-α1 chain of Col1 (COL1A1), and CCL2.

RESULTS

Stimulation of CD45(+)/Col1(+) cells with high glucose concentrations increased the mRNA and protein levels of TGF-β1 and CCL2 and those of pro-COL1A1, and this effect was mediated in part by increased osmolality. Preincubation of the cells with cytochalasin B (a GLUT inhibitor) or N-acetylcysteine (an antioxidant) blocked the stimulatory effect of high glucose concentrations on these profibrotic molecules. In addition, preincubation of the cells with CCL2 enhanced the high glucose-induced upregulation of TGF-β1, pro-COL1A1 and CCL2 and migration of the cells, and this effect was partly inhibited by treatment with CCR2 inhibitors.

CONCLUSION

These results suggest that CD45(+)/Col1(+) cells may be directly involved, in part through CCL2/CCR2 signaling, in the fibrotic process under diabetic conditions.

Efficacy of antisense monocyte chemoattractant protein-1 (MCP-1) in a rat model of mesangial proliferative glomerulonephritis

OBJECTIVE

The effects of inhibition of monocyte chemoattractant protein-1 (MCP-1) on a rat model of mesangial proliferative glomerulonephritis (MsPGN) were evaluated.

METHODS

The anti-Thy-1 MsPGN model was developed by intravenously injecting anti-Thy-1 monoclonal antibodies into rats, followed by an injection of mesangial cells transfected with antisense MCP-1 into the renal artery. Exogenous cells were detected by in situ hybridization. Rats (40 total) were randomly divided into five groups: SO (sham operation), TG (Thy-1 glomerulonephritis model), MC (non-transfected normal rat mesangial cell), BC (pLXSN empty vector or blank control), and AM (antisense MCP-1 transfection) groups. Effects of exogenous MCP-1 on urinary protein excretion rate, biochemical parameters, and pathological changes were evaluated. Expression of MCP-1 and transforming growth factor-β1 (TGF-β1) were detected by immunohistochemistry. mRNA expression of MCP-1, TGF-β1, and CC chemokine receptor 2 (CCR2) were detected by RT-PCR.

RESULTS

Exogenous MCP-1 cDNA was successfully transfected into mesangial cells. Exogenous mesangial cells were detected in glomeruli by in situ hybridization. Glomerular mesangial cell proliferation, 24-h urinary protein excretion rate, mRNA expression of MCP-1, TGF-β1, and CCR2, and protein expression of MCP-1 all decreased in the AM group as compared to the control group (p < 0.05), but there was no significant difference in the expression level of TGF-β1 protein.

CONCLUSIONS

(1) Mesangial cells can be used as a vector to transfect exogenous genes into kidneys; (2) antisense MCP-1 decreases mesangial cell proliferation and pathological injury in MsPGN model rats by decreasing expression of MCP-1 and CCR2; and (3) antisense MCP-1 suppressed mesangial cell proliferation and matrix accumulation in anti-Thy-1 MsPGN model rats, which did not entirely depend on TGF-β1.

Interindividual and intraindividual variations in postprandial glycemia peak time complicate precise recommendations for self-monitoring of glucose in persons with type 1 diabetes mellitus

BACKGROUND

In glycemic control, postprandial glycemia may be important to monitor and optimize as it reveals glycemic control quality, and postprandial hyperglycemia partly predicts late diabetic complications. Self-monitoring of blood glucose (SMBG) may be an appropriate technology to use, but recommendations on measurement time are crucial.

METHOD

We retrospectively analyzed interindividual and intraindividual variations in postprandial glycemic peak time. Continuous glucose monitoring (CGM) and carbohydrate intake were collected in 22 patients with type 1 diabetes mellitus. Meals were identified from carbohydrate intake data. For each meal, peak time was identified as time from meal to CGM zenith within 40-150 min after meal start. Interindividual (one-way Anova) and intraindividual (intraclass correlation coefficient) variation was calculated.

RESULTS

Nineteen patients were included with sufficient meal data quality. Mean peak time was 87 ± 29 min. Mean peak time differed significantly between patients (p = 0.02). Intraclass correlation coefficient was 0.29.

CONCLUSIONS

Significant interindividual and intraindividual variations exist in postprandial glycemia peak time, thus hindering simple and general advice regarding postprandial SMBG for detection of maximum values.

Selective CCR2-targeted macrophage depletion ameliorates experimental mesangioproliferative glomerulonephritis

The CCL2/CCR2 chemokine/receptor axis directs the chemotaxis of infiltrating monocytes/macrophages and T cells and plays a pivotal role in tissue damage and fibrosis in kidney diseases. The eradication of the activated leucocytes should diminish the production of inflammatory mediators, limit tissue damage and ameliorate disease. A recombinant fusion protein (OPL-CCL2-LPM) comprised of the human CCL2 (monocyte chemoattractant protein-1) chemokine fused to a truncated form of the enzymatically active A1 domain of Shigella dysenteriae holotoxin (SA1) has been developed. The CCL2 portion binds specifically to CCR2-bearing leucocytes and the fusion protein enters the cells, where the SA1 moiety inhibits protein synthesis resulting in cell death. The compound was tested in a model of anti-thymocyte serum (ATS)-induced mesangioproliferative glomerulonephritis (ATS-GN). Male rats were injected with ATS on day 0 and treated intravenously with vehicle, 50 or 100 microg/kg of OPL-CCL2-LPM Q2D from days 2, 4, 6 and 8. Urine and blood were collected on days 0, 5 and 9. Animals were sacrificed on day 9. No treatment-related effects on body weight or signs of clinical toxicity were observed. Urine protein levels were decreased in treated animals. At the highest dose, histopathological analyses of kidney sections revealed maximum reductions of 36, 31, 30 and 24% for macrophage count, glomerular lesions, alpha-smooth muscle actin and fibronectin respectively. These results indicate a significant protective effect of OPL-CCL2-LPM in this model of nephritis.

MCP-1/CCR2 system is involved in high glucose-induced fibronectin and type IV collagen expression in cultured mesangial cells

Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that plays an important role in the recruitment of macrophages. Although previous studies have demonstrated the importance of MCP-1 in the pathogenesis of diabetic nephropathy (DN) in terms of inflammation, the role of MCP-1 and its receptor (C-C chemokine receptor 2; CCR2) in extracellular matrix (ECM) accumulation under diabetic conditions has been largely unexplored. This study was undertaken to investigate the functional role of the MCP-1/CCR2 system in high glucose-induced ECM (fibronectin and type IV collagen) protein expression in cultured mesangial cells (MCs). Mouse MCs were exposed to medium containing 5.6 mM glucose (NG), NG+24.4 mM mannitol (NG+M), or 30 mM glucose (HG) with or without mutant MCP-1 (mMCP-1), CCR2 small interfering (si)RNA, or CCR2 inhibitor (RS102895). To examine the relationship between MCP-1 and transforming growth factor (TGF)-β1, MCs were also treated with TGF-β1 (2 ng/ml) with or without mMCP-1 or CCR2 siRNA. Transient transfection was performed with Lipofectamine 2000 for 24 h. Cell viability was determined by an MTT assay, mouse and human MCP-1 and TGF-β1 levels by ELISA, and CCR2 and ECM protein expression by Western blotting. Transfections of mMCP-1 and CCR2 siRNA increased human MCP-1 levels and inhibited CCR2 expression, respectively. HG-induced ECM protein expression and TGF-β1 levels were significantly attenuated by mMCP-1, CCR2 siRNA, and RS102895 ( P < 0.05). MCP-1 directly increased ECM protein expression, and this increase was inhibited by an anti-TGF-β1 antibody. In addition, TGF-β1-induced ECM protein expression was significantly abrogated by the inhibition of the MCP-1/CCR2 system ( P < 0.05). These results suggest that an interaction between the MCP-1/CCR2 system and TGF-β1 may contribute to ECM accumulation in DN.

Anti-inflammatory effects of pigment epithelium-derived factor in diabetic nephropathy

Previously, we have reported that pigment epithelium-derived factor (PEDF) ameliorates albuminuria and inhibits matrix protein deposition in the kidney of streptozotocin (STZ)-induced diabetic rats, suggesting a renoprotective effect of PEDF in early stages of diabetic nephropathy. As inflammation is a major contributor to the development and progression of diabetic nephropathy, we examined in the present study whether PEDF inhibits renal inflammation in diabetic kidney. Diabetic rats received an intravenous injection of an adenovirus expressing PEDF (Ad-PEDF) or the same titer of a control virus. Three wk after the injection, diabetic rats treated with the control virus showed significantly elevated renal levels of proinflammatory factors such as ICAM-1, MCP-1, TNF-alpha, and VEGF compared with age-matched nondiabetic controls. Ad-PEDF effectively suppressed the overexpression of these proinflammatory factors in diabetic kidneys. In cultured primary human renal mesangial cells (HMC), the high-glucose medium-induced upregulation of VEGF and MCP-1 was largely blocked by PEDF. Furthermore, PEDF inhibited high glucose-induced activation of NF-kappaB, a key transcription factor mediating inflammatory responses, and hypoxia-inducible factor-1, a major activator of VEGF expression in HMC. These results suggest that the renoprotective effect of PEDF against diabetic nephropathy may be partially through its anti-inflammatory activity, likely by blocking the NF-kappaB and HIF-1 pathways.

Monocyte chemoattractant protein-1 has prosclerotic effects both in a mouse model of experimental diabetes and in vitro in human mesangial cells

AIMS/HYPOTHESIS

Diabetic nephropathy is characterised by mesangial extracellular matrix accumulation. Monocyte chemoattractant protein-1 (MCP-1), a chemokine promoting monocyte infiltration, is upregulated in the diabetic glomerulus. We performed in vitro and in vivo studies to examine whether MCP-1 may have prosclerotic actions in the setting of diabetes, presumably via its receptor, chemokine (C-C motif) receptor 2 (CCR2), which has been described in mesangial cells.

METHODS

Human mesangial cells were exposed to recombinant human (rh)-MCP-1 (100 ng/ml) for 12, 24 and 48 h and to rh-MCP-1 (10, 100 and 200 ng/ml) for 24 h. Fibronectin, collagen IV and transforming growth factor, beta 1 (TGF-beta1) protein levels were measured by ELISA and pericellular polymeric fibronectin levels by western blotting. The intracellular mechanisms were investigated using specific inhibitors for CCR2, nuclear factor kappa B (NF-kappaB), p38 mitogen-activated protein kinase and protein kinase C, and an anti-TGF-beta1 blocking antibody. In both non-diabetic and streptozotocin-induced diabetic mice that were deficient or not in MCP-1, glomerular fibronectin accumulation was examined by immunohistochemistry, while cortical Tgf-beta1 (also known as Tgfb1) and fibronectin mRNA and protein levels were examined by real-time PCR and western blotting.

RESULTS

In mesangial cells, MCP-1 binding to CCR2 induced a 2.5-fold increase in fibronectin protein levels at 24 h followed by a rise in pericellular fibronectin, whereas no changes were seen in collagen IV production. MCP-1-induced fibronectin production was TGF-beta1- and NF-kappaB-dependent. In diabetic mice, loss of MCP-1 diminished glomerular fibronectin protein production and both renal cortical Tgf-beta1 and fibronectin mRNA and protein levels.

CONCLUSIONS/INTERPRETATION

Our in vitro and in vivo findings indicate a role for the MCP-1/CCR2 system in fibronectin deposition in the diabetic glomerulus, providing a new therapeutic target for diabetic nephropathy.

The MCP-1/CCR2 system has direct proinflammatory effects in human mesangial cells

Both inflammatory and haemodynamic factors have been implicated in the pathogenesis of diabetic and other progressive glomerulopathies. Mesangial cell exposure to mechanical stretch induces both intercellular adhesion molecule 1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) expression. CC Chemokine receptor 2 (CCR2), the cognate MCP-1 receptor, has been recently demonstrated in human mesangial cells (HMCs). We tested whether MCP-1 binding to CCR2 affects ICAM-1 expression in HMCs and, secondly, if stretch-induced ICAM-1 is mediated by MCP-1 via an autocrine mechanism. Serum-deprived HMCs were exposed to either rh-MCP-1 (0.1-1-10-50-100 ng/ml) or mechanical stretch in the presence and in the absence of RS102895, a specific CCR2 inhibitor. ICAM-1 expression was assessed both by immunofluorescence and cytofluorimetry. Monocyte-HMC interaction was tested by adhesion assay. CCR2 expression was studied by reverse transcriptase-polymerase chain reaction, immunoblotting, and flow cytometry. HMCs exposure to rh-MCP-1 induced a significant twofold increase in ICAM-1 expression at 24 h, leading to enhanced monocyte adhesion. This effect occurred via the CCR2 receptor as CCR2 was expressed in HMCs and CCR2 blockade prevented ICAM-1 upregulation. Stretch-induced ICAM-1 expression was not altered by CCR2 blockade and stretch significantly reduced CCR2 mRNA and protein expression via an MCP-1-independent mechanism. In conclusion, stretch and MCP-1 independently induce ICAM-1 expression in HMCs. Stretch-induced CCR2 downregulation may favour MCP-1 paracrine activity.

Therapeutic potential of angiostatin in diabetic nephropathy

Angiostatin is a proteolytic fragment of plasminogen and a potent angiogenic inhibitor. Previous studies have shown that angiostatin inhibits retinal neovascularization and reduces retinal vascular permeability in diabetic retinopathy. Here, it is reported for the first time that angiostatin is also implicated in diabetic nephropathy (DN). Angiostatin levels are dramatically decreased in the kidney of streptozotocin-induced diabetic rats. Consistently, diabetic kidneys also showed decreased expression and proteolytic activities of matrix metalloproteinase-2, an enzyme that releases angiostatin from plasminogen. Adenovirus-mediated delivery of angiostatin significantly alleviated albuminuria and attenuated the glomerular hypertrophy in diabetic rats. Moreover, angiostatin treatment downregulated the expression of vascular endothelial growth factor and TGF-beta1, two major pathogenic factors of DN, in diabetic kidneys. In cultured human mesangial cells, angiostatin blocked the overexpression of vascular endothelial growth factor and TGF-beta1 that were induced by high glucose while increasing the levels of pigment epithelium-derived factor, an endogenous inhibitor of DN. Moreover, angiostatin effectively inhibited the high-glucose-and TGF-beta1-induced overproduction of proinflammatory factors and extracellular matrix proteins via blockade of the Smad signaling pathway. These findings suggest that the decrease of angiostatin levels in diabetic kidney may contribute to the pathologic changes such as inflammation and fibrosis in DN. Therefore, angiostatin has therapeutic potential in DN as a result of its anti-inflammatory and antifibrosis activities.

Diabetes and nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy is the single most common disorder leading to renal failure. Its annual incidence has more than doubled in the past decade to reach 44% of all end-stage renal disease, despite recent therapeutic advances. Thus, research into diabetic nephropathy pathophysiology that could lead to new treatment approaches is urgently needed and this review aims to summarize the work performed in this area in the past year.

RECENT FINDINGS

There have been advances in the understanding of diabetic nephropathy pathology. Clearly, structural changes may be advanced before any clinical findings are apparent. Not all functional consequences of the condition are explained by current structural analyses. Genetic studies have connected the disorder risk to multiple candidate genes and a few genetic loci, but the exact genetic predisposition or protectors are not fully described. Perturbations in multiple metabolic pathways are associated with diabetic nephropathy in animals and humans, but their relative importance requires further work. Glycemia and blood pressure control are crucial for diabetic nephropathy prevention and treatment, but new modalities are needed.

SUMMARY

Recent advances in molecular biology and genetics will bring new insights to the mechanisms involved in diabetic nephropathy development. This will allow early identification of patients at risk of, or safe from, diabetic nephropathy and will hopefully lead to preventive strategies, based on the understanding of the pathophysiology of the disorder. Meanwhile, aggressive implementation of proven therapies to prevent (glycemic control) and slow (antihypertensive therapy, especially with renin-angiotensin system blockers) the progression of diabetic nephropathy are strongly recommended.