Selective phosphodiesterase-5 (PDE-5) inhibitor vardenafil ameliorates renal damage in type 1 diabetic rats by restoring cyclic 3',5' guanosine monophosphate (cGMP) level in podocytes

BACKGROUND

Diabetic nephropathy (DN) is characterized by podocyte damage and increased phosphodiesterase-5 (PDE-5) activity-exacerbating nitric oxide (NO)-cyclic 3',5' guanosine monophosphate (cGMP) pathway dysfunction. It has been shown that PDE-5 inhibition ameliorates DN. The role of podocytes in this mechanism remains unclear. We investigated how selective PDE-5 inhibition influences podocyte damage in streptozotocin (STZ) diabetic rats.

METHODS

Male Sprague-Dawley rats (250-300 g) were injected with STZ and divided into two groups: (i) STZ control (non-treated, STZ, n=6) and (ii) STZ+vardenafil treatment (10 mg/kg/day, STZ-Vard, n=8). Non-diabetic rats served as negative controls (Control, n=7). Following 8 weeks of treatment, immunohistochemical and molecular analysis of the kidneys were performed.

RESULTS

Diabetic rats had proteinuria, increased renal transforming growth factor (TGF)-β1 expression and podocyte damage when compared with controls. Vardenafil treatment resulted in preserved podocyte cGMP levels, less proteinuria, reduced renal TGF-β1 expression, desmin immunostaining in podocytes and restored both nephrin and podocin mRNA expression. Diabetes led to increased glomerular nitrotyrosine formation and renal neuronal nitric oxide synthase and endothelial nitric oxide synthase mRNA expression, but vardenafil did not influence these parameters.

CONCLUSIONS

Our data suggest that a dysfunctional NO-cGMP pathway exacerbates podocyte damage in diabetes. In conclusion, vardenafil treatment preserves podocyte function and reduces glomerular damage, which indicates therapeutic potential in patients with DN.

Angiotensin II increases the permeability and PV-1 expression of endothelial cells

Angiotensin II (ANG II), the major effector molecule of the renin-angiotensin system (RAS), is a powerful vasoactive mediator associated with hypertension and renal failure. In this study the permeability changes and its morphological attributes in endothelial cells of human umbilical vein (HUVECs) were studied considering the potential regulatory role of ANG II. The effects of ANG II were compared with those of vascular endothelial growth factor (VEGF). Permeability was determined by 40 kDa FITC-Dextran and electrical impedance measurements. Plasmalemmal vesicle-1 (PV-1) mRNA levels were measured by PCR. Endothelial cell surface was studied by atomic force microscopy (AFM), and caveolae were visualized by transmission electron microscopy (TEM) in HUVEC monolayers. ANG II (10(-7) M), similarly to VEGF (100 ng/ml), increased the endothelial permeability parallel with an increase in the number of cell surface openings and caveolae. AT1 and VEGF-R2 receptor blockers (candesartan and ZM-323881, respectively) blunted these effects. ANG II and VEGF increased the expression of PV-1, which could be blocked by candesartan or ZM-323881 pretreatments and by the p38 mitogem-activated protein (MAP) kinase inhibitor SB-203580. Additionally, SB-203580 blocked the increase in endothelial permeability and the number of surface openings and caveolae. In conclusion, we have demonstrated that ANG II plays a role in regulation of permeability and formation of cell surface openings through AT1 receptor and PV-1 protein synthesis in a p38 MAP kinase-dependent manner in endothelial cells. The surface openings that increase in parallel with permeability may represent transcellular channels, caveolae, or both. These morphological and permeability changes may be involved in (patho-) physiological effects of ANG II.

Complement activation by polyethoxylated pharmaceutical surfactants: Cremophor-EL, Tween-80 and Tween-20

Immunosafety analysis of pharmaceutical surfactants is an important step in understanding the complex mechanisms by which they induce side effects in susceptible patients. This paper provides experimental evidences that polyethoxylated surfactants, Cremophor-EL and Tween-80, also known as Polysorbate-80, activate the complement system in vitro, in normal human serum and plasma. They appeared to be more efficient reactogens than their structural homolog, Tween-20. Cremophor-EL and Tween-80 promoted the generation of biologically active complement products, C3a, C5a and C5b-9. Consistently, Paclitaxel and Taxotere (Docetaxel), pharmaceuticals formulated in Cremophor-EL and Tween-80, activated the complement system in similar extent. Moreover, comparison of serum reactivity against the drug-loaded and drug-free formulations exhibited a significant linear correlation. Taken together, these results are consistent with the hypothesis that therapeutic side effects, such as acute hypersensitivity and systemic immunostimulation, caused by intravenous nanomedicines containing polyethoxylated detergents such as Cremophor-EL and Tween-80, can be attributed to complement activation-derived inflammatory mediators.

The importance of body composition and dry weight assessments in patients with chronic kidney disease

Chronic volume overload is the major cause of hypertension and other cardiovascular morbidity in dialysis patients. One of the most important goals of physicians who take care of patients with chronic renal failure is to obtain near euvolemia or "dry body weight" in order to maintain or normalize blood pressure and prevent further cardiovascular events. In clinical practice, exact estimation of dry weight in hemodialysis patients remains a major challenge. Alterations in body composition, particularly malnutrition, are common in patients receiving long-term hemodialysis and contribute to a high mortality rate. In contrast, obesity - a known risk factor for cardiovascular morbidity and mortality - is prevalent amongst kidney allograft recipients in - long term after renal transplantation. Several technological tools and biochemical markers for estimation of plasma volume and body composition are available for clinical use. Our aim was to highlight the importance of control of body fluid volume and body composition in patients with chronic kidney disease and to describe the different methods available for such measurements.

In vitro and in vivo complement activation and related anaphylactic effects associated with polyethylenimine and polyethylenimine-graft-poly(ethylene glycol) block copolymers

Complement activation by polymeric gene and drug delivery systems has been overlooked in the past. As more reports appear in the literature concerning immunogenicity of polymers and their impact on gene expression patterns, it is important to address possible immune side effects of polymers, namely complement activation. Therefore, in this study the activity of low and high molecular weight poly(ethylene imine) and two PEGylated derivatives to induce complement activation were investigated in human serum. These in vitro results revealed that PEI 25 kDa caused significant and concentration dependent complement activation, whereas none of the other polymers induced such effects at their IC(50) concentrations determined by MTT-assays. To verify these in vitro results, additionally, studies were carried out in a swine model after intravenous administration, showing complement activation-related pseudoallergy (CARPA), reflected in symptoms of transient cardiopulmonary distress. Injections of PEI 25 kDa or PEI(25k)-PEG(2k)(10) at a dose of 0.05 and 0.1 mg/kg caused strong reactivity, while PEI 5 kDa and with PEI(25k)-PEG(20k)(1) were also reactogenic at 0.1 mg/kg. It was found that PEI 25 kDa caused both self- and cross-tolerance, whereas the PEG-PEIs were neither self- nor cross-reactively tachyphylactic. As a result of this study, it was shown that PEGylation of polycations with PEG of 20 kDa or higher molecular weight may be favorable. However, potential safety concerns in the development of PEI-based polymeric carriers for drugs and nucleic acids and their translation from bench to bedside need to be taken into consideration for human application.

Body mass index, waist circumference and mortality in kidney transplant recipients

Higher body mass index (BMI) appears paradoxically associated with better outcomes in patients with chronic kidney disease. Whereas higher BMI reflects both increased visceral and subcutaneous fat and/or muscle mass, a combined assessment of BMI and waist circumference may enable differentiation of visceral adiposity from muscle and/or nonvisceral fat mass. We examined the association of BMI and waist circumference with all-cause mortality in a prospective cohort of 993 kidney transplant recipients. Associations were examined in Cox models with adjustment for demographic and comorbid conditions and for inflammatory markers. Unadjusted death hazard ratios (95%CI) associated with one standard deviation higher BMI and waist circumference were 0.94 (0.78, 1.13), p = 0.5 and 1.20 (1.00, 1.45), p = 0.05, respectively. Higher BMI was associated with lower mortality after adjustment for waist circumference (0.48 [0.34, 0.69], p < 0.001), and higher waist circumference was more strongly associated with higher mortality after adjustment for BMI (2.18 [1.55-3.08], p < 0.001). The associations of waist circumference with mortality remained significant after additional multivariable adjustments. Higher BMI and waist circumference display opposite associations with mortality in kidney transplant recipients. Waist circumference appears to be a better prognostic marker for obesity than BMI.

Sugar-free, glycine-stabilized intravenous immunoglobulin prevents skin but not renal disease in the MRL/lpr mouse model of systemic lupus

Intravenous immunoglobulin (IVIG) has a therapeutic potential in many autoimmune diseases. Based on its immune modulating and complement inhibiting effects, IVIG has been tested in systemic lupus erythematosus (SLE), but due to osmotic tubular injury caused by immunoglobulin-stabilizing sugar components, lupus nephritis had been accelerated in some patients, thus IVIG use in SLE has been abandoned. The availability of non-sugar-stabilized IVIG raised the possible re-evaluation of IVIG for SLE. We investigated high-dose, long-term non-sugar-stabilized IVIG treatment on skin and renal SLE manifestations in the MRL/lpr mouse model. Animals were treated once a week with glycine-stabilized IVIG or saline (0.2 ml/ 10 g BW) from 6 weeks until they were humanely killed at 5 months of age. IVIG diminished macroscopic cutaneous lupus compared with saline treated mice. Histology and complement-3 immunostaining also demonstrated a significant reduction of skin disease after IVIG treatment. However, renal histology and function were similar in both groups. Compared with typical osmotic tubular damage induced by 5% sucrose and 10% maltose (used for IVIG stabilization), we did not observe any osmotic tubular injury in the glycine-stabilized IVIG treated mice. Our data demonstrate a beneficial effect of IVIG on skin lupus without renal side-effects. Deeper understanding of the organ-specific pathomechanism may aid an individualized SLE therapy.

Cdc42 regulates myocardin-related transcription factor nuclear shuttling and alpha-smooth muscle actin promoter activity during renal tubular epithelial-mesenchymal transition

BACKGROUND/AIMS

Epithelial-mesenchymal transition of tubular cells into alpha-smooth muscle actin (SMA)-expressing myofibroblasts is a central mechanism in tubulointerstitial fibrosis. Previously, a 'two-hit' model was proposed for epithelial-mesenchymal transition wherein an initial injury of the intercellular contacts and TGF-beta(1) are both required for SMA protein expression in LLC-PK1 cells. The Rho-Rho kinase-myosin light chain-myocardin-related transcription factor (MRTF)-serum response factor (SRF) pathway and Rac1, p21-activated kinase (PAK) and p38 were described as important regulators of MRTF localization and SMA expression. Cdc42 is another small G protein situated upstream of PAK and p38, and is activated upon cell contact disassembly. Here, we investigated its potential role in the regulation of MRTF nuclear shuttling and in the regulation of the SMA promoter.

RESULTS

Transfection of a constitutive active (CA) Cdc42 construct alone induced the activation of the SMA promoter. The dominant negative (DN) Cdc42 construct prevented the activation of the promoter induced by cell contact disassembly, and reduced the combined effect of cell contact disruption and TGF-beta(1). SRF showed a marked nuclear accumulation in CA Cdc42-transfected cells. Cdc42 induced the nuclear translocation of MRTF, while DN Cdc42 inhibited its nuclear translocation induced by cell contact disassembly. Blocking PAK, MRTF and p38 by the corresponding DN constructs blunted the effects of CA Cdc42 on the SMA promoter.

CONCLUSION

Cdc42 is involved in the regulation of SMA promoter activation through PAK, p38, MRTF and SRF. Cdc42 may be an important regulator of MRTF cellular localization.

Lupus nephritis reoccurs following transplantation in the lupus prone mouse

The incidence and pathomechanism of recurrent lupus nephritis (RLN) after transplantation is not clearly understood. Burning out of the autoimmune process or local immunoregulatory mechanisms in the kidney may be responsible for the low incidence of recurrence. These mechanisms cannot be investigated in human subjects, due to post-transplant immunosuppression. To investigate the pathomechanisms of RLN, male and female kidneys were transplanted from FAS deficient lupus prone (LPR) or control (FAS intact) MRL mice into either LPR or MRL recipients. Urinary protein and blood urea were assessed. Double negative (DN) lymphocyte proliferation was determined by flow cytometry. Two months after transplantation inflammatory infiltration of the glomerular, vascular and interstitial compartments were determined. Renal function as demonstrated by blood urea levels was normal in MRL recipients, but elevated in LPR recipients, independent of the donor strain. Paralleling functional results, inflammatory infiltration was mild or absent in MRL recipients of MRL grafts, and mild to moderate in MRL recipients of LPR grafts, suggesting that kidney removal from the autoimmune (LPR) environment significantly reduced inflammation. Graft infiltration was most severe in LPR recipients: grafts were similarly inflamed independent of the donor. All LPR recipients had significantly less CD4+ Th cells versus MRL mice. Transplantation of LPR grafts into MRL recipients reduced CD4+ Th cell percentage, accompanied by a slight induction of lupus autoantibody production. Our results demonstrate that lupus nephritis is not kidney specific in the LPR model with recurrence after transplantation in the absence of immunosuppression.

Intrarenal renin-angiotensin system

Phylogenetically the renin-angiotensin system (RAS) is an ancient regulatory system which has attracted the attention of researchers for about a century. As a result of their efforts, different types of RAS inhibitors are now widely used as therapeutic medicines. The scientific enthusiasm toward RAS remains undiminished and new findings and discoveries are to be expected. Early investigators described the role of RAS in the local control of renal hemodynamics. This correlated well with the morphology of juxtaglomerular apparatus (JGA). Recently developed imaging techniques has allowed for in vivo visualization of cellular functions and the use of molecular biological tools have shed new light on the morphology and physiology of renal RAS, especially in connection with the tubular system. RAS has gained recognition to be more than just an endocrine regulatory system for regulating hemodynamics and water/salt metabolism. RAS is a local tissue and/or cellular regulator with a wide range of effects exerted via various receptors. Local RAS is crucially involved in basic physiological processes like ontogenesis and cell proliferation as well as pathophysiological conditions such as inflammation and tissue fibrosis. These findings may open new frontiers for novel therapeutic approaches. This review focuses only on some specific - less discussed and recently described or hypothesized - morphological and functional aspects of intrarenal RAS, including in vivo imaging of RAS, its effects on juxtaglomerular apparatus and possible cooperative mechanisms among various local renal RAS systems.

[Comparison of guttapercha points of different brands]

Many new devices and instruments have been developed in the field of endodontics, however, even today guttapercha is the most commonly used root canal filling material and lateral condensation is still widely the technique of choice. It is crucial that the guttapercha point should not bend away during insertion into the root canal, and that the size of the guttapercha point is in accordance with the size-coding marked on the container. However, there is no data on the difference between the dimensional accuracy and the rigidity of guttapercha points produced by various manufacturers. The aim of the authors' study was to compare guttapercha points of different brands (ANTEOS, DENTSPLY, DIADENT, EXPORDENT, FKG, META, ROEKO, ROSA BECHT, SURE ENDO). The rigidity of guttapercha points (n = 10 in each group) and the dimensional accuracy has been measured (n = 10 in each group) with an instrument developed for this purpose. Statistical analysis has been performed by ANOVA, level of significance was (p < 0.05). In the group FKG significant (p < 0.05) higher forces were necessary to bend guttapercha points. No other significant difference has been shown between the investigated groups (p > 0.05). In the dimensional accuracy there were significant differences (p < 0.05). The least deviation from the assigned dimension has been found in the ROSABECHT group, and the highest in the FKG group. In the dimensional accuracy the least standard error has been found in ROSABECHT group, and the highest in EXPORDENT group. The most extreme deviations have been shown in META and DENTSPLY group. The results of the present study show that guttapercha points frequently deviate from the marked dimension: a guttapercha point from the ISO 25 container may even reach the size of an ISO 30 guttapercha. This has to be taken into account during root canal obturation.