The MIF receptor CD74 in diabetic podocyte injury.

Although metabolic derangement plays a central role in diabetic nephropathy, a better understanding of secondary mediators of injury may lead to new therapeutic strategies. Expression of macrophage migration inhibitory factor (MIF) is increased in experimental diabetic nephropathy, and increased tubulointerstitial mRNA expression of its receptor, CD74, has been observed in human diabetic nephropathy. Whether CD74 transduces MIF signals in podocytes, however, is unknown. Here, we found glomerular and tubulointerstitial CD74 mRNA expression to be increased in Pima Indians with type 2 diabetes and diabetic nephropathy. Immunohistochemistry confirmed the increased glomerular and tubular expression of CD74 in clinical and experimental diabetic nephropathy and localized glomerular CD74 to podocytes. In cultured human podocytes, CD74 was expressed at the cell surface, was upregulated by high concentrations of glucose and TNF-alpha, and was activated by MIF, leading to phosphorylation of extracellular signal-regulated kinase 1/2 and p38. High glucose also induced CD74 expression in a human proximal tubule cell line (HK2). In addition, MIF induced the expression of the inflammatory mediators TRAIL and monocyte chemoattractant protein 1 in podocytes and HK2 cells in a p38-dependent manner. These data suggest that CD74 acts as a receptor for MIF in podocytes and may play a role in the pathogenesis of diabetic nephropathy.

Renal and metabolic effects of insulin lispro in type 2 diabetic subjects with overt nephropathy.

OBJECTIVE: To assess whether the insulin analog lispro may antagonize the renal effects of IGF-1, a mediator of glomerular hyperfiltration involved in the progression of diabetic and nondiabetic chronic nephropathies. RESEARCH DESIGN AND METHODS: In a randomized crossover study, we compared the renal and metabolic responses to regular or lispro insulin (0.1 units/kg body wt) administered after a euglycemic clamp and 5 and 30 min before a standard meal to 11 type 2 diabetic patients with macroalbuminuria. RESULTS: Two- and four-hour postprandial changes (vs. preprandial euglycemia) in glomerular filtration rate (GFR) followed a significantly different trend (5.8 +/- 5.0 vs. -6.3 +/- 4.7, P < 0.05; and 11.0 +/- 6.8 vs. 0.7 +/- 5.1%, P < 0.05) after regular insulin and lispro injection, respectively. After lispro, postprandial GFR changes were negatively correlated (r = -0.48, P = 0.0001) with plasma insulin concentration. After regular insulin, renal plasma flow increased in parallel with a decrease in renal vascular resistances. Both changes were fully prevented by lispro. Postprandial blood glucose maximum concentration (278 +/- 16 vs. 240 +/- 16 mg/dl, P < 0.01) and area under the curve (79,381 +/- 19,237 vs. 72,810 +/- 16,211 mg/dl per min, P < 0,05) were significantly lower after insulin lispro than after regular insulin injection, respectively, despite comparable postprandial insulin profiles. Changes in total and gluconeogenic amino acids followed a similar trend. Changes in blood glucose and plasma amino acids did not correlate with concomitant changes in GFR. CONCLUSIONS: In overt nephropathy of type 2 diabetes, lispro prevents glomerular hyperfiltration and offsets the renal effects of meal or meal-associated hyperglycemia by mechanisms possibly related to IGF-1 antagonism.

Renal angiotensin II up-regulation and myofibroblast activation in human membranous nephropathy.

BACKGROUND: The molecular mechanisms of renal injury and fibrosis in proteinuric nephropathies are not completely elucidated but the renin-angiotensin system (RAS) is involved. Idiopathic membranous nephropathy (MN), a proteinuric disease, may progress to renal failure. Our aim was to investigate the localization of RAS components in MN and their correlation with profibrotic parameters and renal injury. METHODS: Renal biopsies from 20 patients with MN (11 with progressive disease) were studied for the expression of RAS components [angiotensin-converting enzyme (ACE) and angiotensin II (Ang II)] by immunohistochemistry. Transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF)-BB were studied by by in situ hybridization, and myofibroblast transdifferentiation by alpha-smooth muscle actin (alpha-SMA) staining. RESULTS: ACE immunostaining was elevated in tubular cells and appeared in interstitial cells colocalized in alpha-actin-positive cells in progressive disease. Elevated levels of Ang II were observed in tubules and infiltrating interstitial cells. TGF-beta and PDGF mRNAs were up-regulated mainly in cortical tubular epithelial cells in progressive disease (P < 0.01) and correlated with the myofibroblast transdifferentiation (r = 0.8, P < 0.01 for TGF-beta; r = 0.6, P < 0.01 for PDGF). Moreover, in serial sections of progressive cases, the ACE and Ang II over-expression was associated with the tubular expression of these pro-fibrogenic factors, and with the interstitial infiltration and myofibroblast activation. CONCLUSION: Intrarenal RAS is selectively activated in progressive MN. De novo expression of ACE at sites of tubulointerstitial injury suggests that the in situ Ang II generation could participate in tubular TGF-beta up-regulation, epithelial-myofibroblast transdifferentiation, and disease progression. These results suggest a novel role of Ang II in human tubulointerstitial injury.

Renin-angiotensin system activation and interstitial inflammation in human diabetic nephropathy.

BACKGROUND: The molecular mechanisms of renal injury in diabetic nephropathy (DN) are not completely understood, although inflammatory cells play a key role. The renin-angiotensin system (RAS) is involved in kidney damage; however, few studies have examined the localization of RAS components in human DN. Our aim was to investigate in renal biopsies the expression of RAS and their correlation with proinflammatory parameters and renal injury. METHODS: The biopsies from 10 patients with type 2 diabetes mellitus and overt nephropathy were studied for the expression of RAS components by immunohistochemistry (IH). In addition, by Southwestern histochemistry we studied the in situ detection of the activated nuclear factor kappa B (NFkappaB), and by IH and/or in situ hybridization (ISH), the expression of monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation, normal T cell expressed and secreted (RANTES), whose genes are regulated by NFkappaB. RESULTS: Angiotensin-converting enzyme (ACE) immunostaining was elevated in tubular cells and appeared in interstitial cells. Elevated levels of angiotensin II (Ang II) immunostaining were observed in tubular and infiltrating interstitial cells. There was also a down-regulation of AT1 and up-regulation of AT2 receptors. An activation of NFkappaB and a marked up-regulation of NFkappaB-dependent chemokines mainly in tubular cells was observed. Elevated levels of NFkappaB, chemokines, and Ang II in tubules were correlated with proteinuria and interstitial cell infiltration. CONCLUSIONS: Our results show that in human DN, RAS components are modified in renal compartments, showing elevated local Ang II production, activation of tubular cells, and induction of proinflammatory parameters. These data suggest that Ang II contributes to the renal inflammatory process, and may explain the molecular mechanisms of the beneficial effect of RAS blockade.

The renin-angiotensin system in progression, remission and regression of chronic nephropathies.

Chronic proteinuric nephropathies may progress to end-stage renal disease (ESRD) through a series of events relatively independent of the initial insult that causes parenchymal damage when the injury involves a critical number of nephrons. The key event is enhanced glomerular capillary pressure, which, among other effects, impairs glomerular permeability to proteins, which reach the lumen of the proximal tubule. In this pathological process angiotensin II has a central role. Reabsorption of filtered proteins contributes to the interstitial injury by activating intracellular events, including upregulation of vasoactive and inflammatory genes. Both interstitial inflammation and progression of disease can be limited by angiotensin-converting enzyme (ACE) inhibitors that strengthen the glomerular permeability barrier to proteins, thus limiting proteinuria and filtered protein-dependent inflammatory signals. Clinical evidence suggests that remission is now achievable in some patients with chronic nephropathies. The current lag time between starting treatment and remission, however, is such that a substantial proportion of patients still progress to ESRD before their renal function begins to stabilize. A multimodal approach aimed at reducing or abolishing all the risk factors for progression may shorten the time to remission for the majority of patients with proteinuric nephropathies.

Expression of gremlin, a bone morphogenetic protein antagonist, in glomerular crescents of pauci-immune glomerulonephritis.

BACKGROUND: Recent evidence in vitro and in vivo suggests that gremlin, a bone morphogenetic protein antagonist, is participating in tubular epithelial mesenchymal transition (EMT) in diabetic nephropathy as a downstream mediator of TGF-beta. Since EMT also occurs in parietal epithelial glomerular cells (PECs) leading to crescent formation, we hypothesized that gremlin could participate in this process. With this aim we studied its expression in 30 renal biopsies of patients with pauci-immune crescentic nephritis. METHODS: Gremlin was detected by in situ hybridization (ISH) and immunohistochemistry (IMH) and TGF-beta by ISH and Smads by southwestern histochemistry (SWH). Phosphorylated Smad2, CTGF, BMP-7, PCNA, alpha-SMA, synaptopodin, CD-68, and phenotypic markers of PECs (cytokeratin, E-cadherin), were detected by IMH. In cultured human monocytes, gremlin and CTGF induction by TGF-beta was studied by western blot. RESULTS: We observed strong expression of gremlin mRNA and protein in cellular and fibrocellular crescents corresponding to proliferating PECs and monocytes, in co-localization with TGF-beta. A marked over-expression of gremlin was also observed in tubular and infiltrating interstitial cells, correlating with tubulointerstitial fibrosis (r=0.59; P<0.01). A nuclear Smad activation in the same tubular cells, that are expressing TGF-beta and gremlin, was detected. In human cultured monocytes, TGF-beta induced gremlin production while CTGF expression was not detected. CONCLUSION: We postulate that gremlin may play a role in the fibrous process in crescentic nephritis, both in glomerular crescentic and tubular epithelial cells. The co-localization of gremlin and TGF-beta expression found in glomeruli and tubular cells suggest that gremlin may be important in mediating some of the pathological effects of TGF-beta.

[Chronic kidney disease: classification, mechanisms of progression and strategies for renoprotection]. / Enfermedad renal crónica: clasificación, mecanismos de progresión y estrategias de renoprotección.

Chronic kidney disease is a worldwide health problem. The incidence and prevalence of kidney failure is in constant increase, involving poor outcomes and high costs. The leading causes of kidney failure are type 2 diabetes and hypertension. The new initiative "Kidney Disease Improving Global Outcomes (KDIGO)" is a global public health approach to face this problem. A formal definition for chronic kidney disease and a staging of kidney diseases from kidney damage with preserved function to kidney failure, were proposed. We reviewed the main mechanisms involved in renal disease progression, with emphasis in the proteinuria and the intrarenal activation of renin angiotensin system. Moreover, the evidence in the literature of therapeutical interventions with proved efficacy in slowing the rate of reduction of renal function is discussed, particularly the optimal control of hypertension, reduction of proteinuria and renin angiotensin system blocking. Finally, we recommend a strategy for the clinical management of patients in the different stages of chronic kidney disease.

[Achilles tendinitis associated to levofloxacin: report of 4 cases]. / Tendinitis aquiliana asociada al uso de levofloxacino: comunicación de cuatro casos.

Fluoroquinolone-associated tendinitis are well described in the literature, but these are not frequently observed and usually are related to the oldest fluoroquinolones. Levofloxacin is a recently introduced fluoroquinolone. In this paper we report four cases (three female, aged 39 to 70 years old) of Achilles tendinitis occurring in a period of few months. Two patients on chronic dialysis, one kidney transplant recipient, and one patient with chronic vasculitis, both with normal renal function. All were chronically using corticosteroids. In the four cases, tendinitis had an acute onset with bilateral involvement and was invalidating. In 3 cases the onset of tendinitis was early during levofloxacin treatment and in 1 case, it began 10 days after the end of the treatment. All patients were treated with rest and physiotherapy, two were treated with non-steroidal anti-inflammatory drugs. All patients had a complete recovery alter 3-8 weeks.

Mechanisms of progression of chronic renal disease.

Many patients with proteinuric chronic nephropathies progress relentlessly to end-stage renal failure (ESRF). Research in animal and human models has helped to identify the mechanisms involved in this progression and to indicate effective intervention. We review the main factors associated with the progression of chronic renal diseases including systemic and intra-glomerular hypertension, glomerular hypertrophy, proteinuria, hyperlipidemia, and intrarenal precipitation of calcium phosphate. We also describe a therapeutic strategy aimed at achieving maximal reno-protection.

Effects of combined ACE inhibitor and angiotensin II antagonist treatment in human chronic nephropathies.

BACKGROUND: Proteinuria predicts renal disease progression, and its reduction by angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II receptor antagonists (ARA) is renoprotective. METHODS: In this prospective, randomized, cross-over study of 24 patients with nondiabetic, chronic nephropathies, we compared the effects on proteinuria, renal hemodynamics, and glomerular permselectivity of 8 weeks with comparable blood pressure control achieved by benazepril (10 mg/day) and valsartan (80 mg/day) combined therapy with those achieved by benazepril (20 mg/day) or valsartan (160 mg/day) alone. RESULTS: Despite comparable changes in blood pressure and glomerular filtration rate (GFR), combined therapy decreased proteinuria more than benazepril (-56% vs. -45.9%, P=0.02) and valsartan (-41.5%, P=0.002). Changes in urinary protein to creatinine ratio followed the same trend. Filtration fraction and renal vascular resistances (RVR) decreased more with combined (-14.7%,-23.7%) or benazepril (-12.4%, -20.5%) than with valsartan (-2.7%, -12.5%, P < 0.05 vs. both). RVR changes, adjusted for GFR changes, were associated with those in proteinuria (P < 0.05). Changes in glomerular permeability were comparable and did not predict different changes in proteinuria in the three groups. CONCLUSION: At comparable blood pressure, combined ACEi and ARA decreased proteinuria better than ACEi and ARA. The greater antiproteinuric effect most likely depended on an ACEi-related hemodynamic effect, in addition to glomerular size selectivity amelioration. Long-term combined ACEi and ARA therapy may be more renoprotective than treatment with each agent alone.

NF-kappaB activation and overexpression of regulated genes in human diabetic nephropathy.

BACKGROUND: Nuclear factor-kappaB (NF-kappaB) regulates genes involved in renal disease progression, such as the chemokines monocyte chemoattractant protein-1 (MCP-1) and RANTES. NF-kappaB is activated in experimental models of renal injury, and in vitro studies also suggest that proteinuria and angiotensin II could be important NF-kappaB activators. It has been proposed that locally produced MCP-1 may be involved in the development of diabetic nephropathy (DN). We examined the hypothesis that NF-kappaB could be an indicator of renal damage progression in DN. METHODS: Biopsy specimens from 11 patients with type 2 diabeties and overt nephropathy were studied by southwestern histochemistry for the in situ detection of activated NF-kappaB. In addition, by immunohistochemistry and/or in situ hybridization, we studied the expression of MCP-1 and RANTES, whose genes are regulated by NF-kappaB. RESULTS: NF-kappaB was detected mainly in cortical tubular epithelial cells and, to a lesser extent, in some glomerular and interstitial cells. A strong upregulation of MCP-1 and RANTES was observed in all the cases, mainly in tubular cells, and there was a strong correlation between the expression of these chemokines and NF-kappaB activation in the same cells, as observed in serial sections (r = 0.7; P = 0.01). In addition, the tubular expression of these chemokines was correlated mainly with the magnitude of the proteinuria (P = 0.002) and with interstitial cell infiltration (P<0.05). CONCLUSIONS: The activation of NF-kappaB and the transcription of certain pro-inflammatory chemokines in tubular epithelial cells are markers of progressive DN. Proteinuria might be one of the main factors inducing the observed pro-inflammatory phenotype.