Nuclear factor kappaB for the nephrologist

Nephrotoxicity and possible mechanisms of decabrominated diphenyl ethers (BDE-209) exposure to kidney in broilers

The flame retardant decabrominated diphenyl ether (BDE-209) is a widely used chemical in a variety of products and exists extensively in the environment. BDE-209 has been reported to induce kidney injury and dysfunction. However, the causes and mechanisms of its nephrotoxicity are still under investigation. In this study, 150 male broilers were exposed to BDE-209 concentrations of 0, 0.004, 0.04, 0.4, 4.0 g/kg for 42 days. The relative kidney weight, histopathology, markers of renal injury, oxidative stress, inflammation, apoptosis and the expression of MAPK signaling pathways-related proteins were assessed. The results showed that the concentrations of blood urea nitrogen (BUN), creatinine (CRE) and the neutrophil gelatinase-associated lipocalin (NGAL), significantly increased after exposure to BDE-209 with the doses more than 0.04 g/kg. Similarly, severe damage of renal morphology was observed, including atrophy and necrosis of glomeruli, and swelling and granular degeneration of the renal tubular epithelium. In the renal homogenates, the oxidative stress was evidenced by the elevated concentrations of MDA and NO, and decreased levels of GSH-Px, GSH and SOD. Due to the inflammatory response, the level of NF-κB and the pro-inflammatory cytokines TNF-α, IL-1β, IL-18 were remarkably upregulated, while the content of the anti-inflammatory cytokine IL-10 decreased. Additionally, the apoptotic analysis showed notable upregulations of Bax/Bcl-2 ratio, the relative expression of p-ERK1/2 and p-JNK1/2, and the expression of Bax, cytochrome c and caspase 3. The present study indicates that BDE-209 exposure can cause nephrotoxicity in broilers through oxidative stress and inflammation, which activate the phosphorylation of key proteins of the MAPK signaling pathways, and subsequently induce mitochondria-mediated kidney apoptosis.

A Boolean Model of Microvascular Rarefaction to Predict Treatment Outcomes in Renal Disease

Despite advances in renovascular disease (RVD) research, gaps remain between experimental and clinical outcomes, translation of results, and the understanding of pathophysiological mechanisms. A predictive tool to indicate support (or lack of) for biological findings may aid clinical translation of therapies. We created a Boolean model of RVD and hypothesized that it would predict outcomes observed in our previous studies using a translational swine model of RVD. Our studies have focused on developing treatments to halt renal microvascular (MV) rarefaction in RVD, a major feature of renal injury. A network topology of 20 factors involved in renal MV rarefaction that allowed simulation of 5 previously tested treatments was created. Each factor was assigned a function based upon its interactions with other variables and assumed to be “on” or “off”. Simulations of interventions were performed until outcomes reached a steady state and analyzed to determine pathological processes that were activated, inactivated, or unchanged vs. RVD with no intervention. Boolean simulations mimicked the results of our previous studies, confirming the importance of MV integrity on treatment outcomes in RVD. Furthermore, our study supports the potential application of a mathematical tool to predict therapeutic feasibility, which may guide the design of future studies for RVD.

NF-κB in inflammation and renal diseases

Nuclear factor κB (NF-κB) is a family of inducible transcription factors that plays a vital role in different aspects of immune responses. NF-κB is normally sequestered in the cytoplasm as inactive complexes via physical association with inhibitory proteins termed IκBs. In response to immune and stress stimuli, NF-κB members become activated via two major signaling pathways, the canonical and noncanonical pathways, and move to the nucleus to exert transcriptional functions. NF-κB is vital for normal immune responses against infections, but deregulated NF-κB activation is a major cause of inflammatory diseases. Accumulated studies suggest the involvement of NF-κB in the pathogenesis of renal inflammation caused by infection, injury, or autoimmune factors. In this review, we discuss the current understanding regarding the activation and function of NF-κB in different types of kidney diseases.

Salicylic acid attenuates gentamicin-induced nephrotoxicity in rats

Gentamicin (GM) is a widely used antibiotic against serious and life-threatening infections, but its usefulness is limited by the development of nephrotoxicity. The present study was designed to determine the protective effect of salicylic acid (SA) in gentamicin-induced nephrotoxicity in rats. Quantitative evaluation of gentamicin-induced structural alterations and degree of functional alterations in the kidneys were performed by histopathological and biochemical analyses in order to determine potential beneficial effects of SA coadministration with gentamicin. Gentamicin was observed to cause a severe nephrotoxicity which was evidenced by an elevation of serum urea and creatinine levels. The significant increases in malondialdehyde (MDA) levels and protein carbonyl groups indicated that GM-induced tissue injury was mediated through oxidative reactions. On the other hand, simultaneous SA administration protected kidney tissue against the oxidative damage and the nephrotoxic effect caused by GM treatment. Exposure to GM caused necrosis of tubular epithelial cells. Necrosis of tubules was found to be prevented by SA pretreatment. The results from our study indicate that SA supplement attenuates oxidative-stress associated renal injury by reducing oxygen free radicals and lipid peroxidation in gentamicin-treated rats.

Novel therapeutic agents for the management of patients with multiple myeloma and renal impairment

Renal impairment is a major complication of multiple myeloma. Patients presenting with severe renal impairment represent a greater therapeutic challenge and generally have poorer outcome. However, once patients with renal impairment achieve remission, their outcomes are comparable with those of patients without renal impairment. Therapies that offer substantial activity in this setting are needed. Bortezomib, thalidomide, and lenalidomide have substantially improved the survival of patients with multiple myeloma. Here we review the pharmacokinetics, activity, and safety of these agents in patients with renal impairment. Bortezomib can be administered at the full approved dose and schedule in renally impaired patients; similarly, no dose reductions are required with thalidomide. The pharmacokinetics of lenalidomide is affected by its renal route of excretion, and dose adjustments are recommended for moderate/severe impairment. Substantial evidence has emerged showing that these novel agents improve outcomes of patients with renal impairment, including impairment reversal. Bortezomib, thalidomide, and lenalidomide (at the recommended doses) are active options for patients with mild to moderate impairment, although limited data are available for thalidomide. Information on lenalidomide-based combinations is still emerging, but the available data indicate considerable activity. Substantial evidence indicates that bortezomib-high-dose dexamethasone with or without a third drug (e.g., cyclophosphamide, thalidomide, or doxorubicin) is an appropriate option for patients with any degree of renal impairment.

Obesity-related glomerulopathy and podocyte injury: a mini review

Obesity-related glomerulopathy (ORG) is morphologically defined as focal segmental glomerulosclerosis and glomerulomegaly. Podocyte hypertrophy and reduced density are related to proteinuria which in a portion of patients is in the nephrotic range and evolvs towards renal failure. This article reviews the pathogenetic mechanisms of podocyte injury or dysfunction and lists new possible antiproteinuric strategies based on pharmaceutical targeting of the reported pathogenetic mechanisms. The pathogenetic mechnisms discussed include: renin angiotensin system, plasminogen activation inhibitor-1 (PAI-1), lipid metabolism, adiponectin, macrophages and proinflammatory cytokines, oxidative stress. The proposed antiproteinuric strategies include: AT2 receptor blockers; adipokine complement C19 TNF-related protein-1 blocker; selective PAI-1 inhibitor; farnesoid x receptor activation; increase of circulating adiponectin; selective antiinflammatory drugs; more potent antioxidants (Heme oxigenase, NOX4 inhibitors). However, because ORG is a rare disease, the need for a long term pharmaceutical approach in obese proteinuric patients should be carefully evaluated and limited to the cases with progressive loss of renal function.

Role of inflammation in túbulo-interstitial damage associated to obstructive nephropathy

Obstructive nephropathy is characterized by an inflammatory state in the kidney, that is promoted by cytokines and growth factors produced by damaged tubular cells, infiltrated macrophages and accumulated myofibroblasts. This inflammatory state contributes to tubular atrophy and interstitial fibrosis characteristic of obstructive nephropathy. Accumulation of leukocytes, especially macrophages and T lymphocytes, in the renal interstitium is strongly associated to the progression of renal injury. Proinflammatory cytokines, NF-κB activation, adhesion molecules, chemokines, growth factors, NO and oxidative stress contribute in different ways to progressive renal damage induced by obstructive nephropathy, as they induce leukocytes recruitment, tubular cell apoptosis and interstitial fibrosis. Increased angiotensin II production, increased oxidative stress and high levels of proinflammatory cytokines contribute to NF-κB activation which in turn induce the expression of adhesion molecules and chemokines responsible for leukocyte recruitment and iNOS and cytokines overexpression, which aggravates the inflammatory response in the damaged kidney. In this manuscript we revise the different events and regulatory mechanisms involved in inflammation associated to obstructive nephropathy.

Diallyl sulfide enhances antioxidants and inhibits inflammation through the activation of Nrf2 against gentamicin-induced nephrotoxicity in Wistar rats

The protective role of diallyl sulfide (DAS) in attenuating gentamicin-induced nephrotoxicity has been reported earlier. However, the mechanism of induction of antioxidants by DAS in nephrotoxicity remains elusive. This study is aimed to elucidate the role of a transcription factor, Nuclear factor E2-related factor 2 (Nrf2) in inducing antioxidants and phase II enzymes during gentamicin toxicity in Wistar rats. DAS was administered intraperitoneally at a dosage of 150 mg/kg body weight once daily for 6 days. Gentamicin was administered intraperitoneally at a dosage of 100 mg/kg body weight, once daily for 6 days. Gentamicin-induced rats showed a significant increase in the levels of kidney markers and the activities of urinary marker enzymes, which was reversed upon treatment with DAS. A significant increase in kidney myeloperoxidase (MPO) and lipid peroxidation (LPO) levels was observed in gentamicin-induced rats, which was reduced upon treatment with DAS. Gentamicin-induced rats also showed a significant decrease in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) and quinone reductase (QR) in rat kidney, which was increased upon treatment with DAS. Immunohistochemical studies in gentamicin-induced rats demonstrated a marked increase in the immunoreactivity of inducible nitric oxide synthase (iNOS), nuclear transcription factor (NF-kappaB) and tumor necrosis factor alpha (TNF-alpha) that were reduced after treatment with DAS. Further, the involvement of Nrf2 in antioxidant induction was analyzed by Western blot and immunofluorescence. To conclude, DAS enhances antioxidants and suppresses inflammatory cytokines through the activation of Nrf2, thereby protecting the cell against oxidative stress induced by gentamicin.

Tubulointerstitial macrophage accumulation is regulated by sequentially expressed osteopontin and macrophage colony-stimulating factor: implication for the role of atorvastatin

Infiltration and local proliferation are known factors that contribute to tubulointerstitial macrophage accumulation. This study explored the time course of these two contributors' roles as tubulointerstitial inflammation and fibrosis progressing, and evaluated the mechanisms of the protective effect of atorvastatin. Unilateral ureteral obstructive (UUO) rats were treated with atorvastatin (10 mg/Kg) or vehicle. Expression of osteopontin (OPN) and macrophage colony-stimulating factor (M-CSF) was evaluated by RT-PCR and immunohistochemistry. Immunohistochemistry staining of ED1 was used to assess macrophage accumulation in interstitium. Histological evaluation was performed to semiquantify tubulointerstitial fibrosis. The results showed that on day 3 after UUO operation, OPN expression significantly increased and positively correlated with the number of the interstitial ED1⁺ cells, while on day 10, M-CSF expression upregulated and correlated with interstitial ED1⁺ cells. In atorvastatin treatment group, the increments of these two factors were attenuated significantly at the two time points, respectively. ED1⁺ cell accumulation and fibrosis also ameliorated in the treatment group. For all the samples of UUO and treatment group on day 10, ED1⁺ cells also correlated with interstitial fibrosis scores. The results suggest that OPN may induce the early macrophage/monocyte infiltration and M-CSF may play an important role in regulating macrophage accumulation in later stage of UUO nephropathy. Statin treatment decreases interstitial inflammation and fibrosis, and this renoprotective effect may be mediated by downregulating the expression of OPN and M-CSF.

Effect of nephrotoxins on tubulointerstitial injury and NF-kappaB activation in Adriamycin nephropathy

In a previous study we found that an episode of acute subclinical nephrotoxicity with gentamicin (G) (but not that induced by another proximal tubular cell nephrotoxin: ferric nitrilotriacetate, FeNTA), paradoxically reduced the progression of renal function and injury in uninephrectomized rats with nephrotic glomerular disease due to Adriamycin nephropathy (AN). Here, we hypothesized that subclinical exposure to G reduces early renal cortical tubulointerstitial inflammation and NF-kappaB activation in AN. To test this hypothesis, male Wistar rats with established AN received either G (10, 40, or 80 mg/kg by daily s.c.i. for 3 days), FeNTA (1.25, 5, or 10 mg/kg by a single i.p.i.), or vehicle (n=8 per group), 13 to 15 days after disease induction. Although G and FeNTA caused acute tubular necrosis in a dose-dependant manner (day 17), only the highest doses (10 mg/kg and 80 mg/kg) produced an acute elevation in the serum creatinine. On day 33, chronic tubulointerstitial inflammation (tubular atrophy, interstitial ED-1+/CD8+ cell accumulation) and NF-kappaB activation were exacerbated only in the groups that caused functional nephrotoxicity. These data suggest that: 1) the protective effect of subclinical G nephrotoxicity in chronic AN does not involve early changes in interstitial inflammation or NF-kappaB activation; and 2) a single episode of G exposure must be accompanied by clinically apparent nephrotoxicity in order to accelerate progression in a nonuremic model of chronic glomerular disease.

C-reactive protein induces NF-kappaB activation through intracellular calcium and ROS in human mesangial cells

BACKGROUND

C-reactive protein (CRP) is known to have a direct proinflammatory effect in endothelial cells. However, little is known about the effect of CRP in intrinsic renal cells. We investigated the effects of CRP on the nuclear factor-kappaB (NF-kappaB) activation and monocyte chemoattractant protein-1 (MCP-1) gene expression in human mesangial cells and also examined whether intracellular calcium and reactive oxygen species (ROS) were involved in the CRP- induced NF-kappaB activation.

METHODS

NF-kappaB binding activity and MCP-1 mRNA expression were measured by electrophoretic mobility shift assay and Northern blot analysis, respectively. Intracellular calcium was monitored by confocal microscopy using calcium sensitive dye, Fluo-3 and intracellular ROS production was determined, using 2',7'-dichlorofluorescin diacetate.

RESULTS

CRP increased NF-kappaB binding activity in a dose-dependent manner (12.5-100 microg/ml), which was induced within 1 h after incubation and peaked around 3 h. CRP also increased the MCP-1 mRNA expression via activation of NF-kappaB. Both intracellular calcium and ROS was induced by CRP. Calcium chelator, BAPTA-AM and anti-oxidants such as N-acetylcysteine and tiron suppressed CRP-induced NF-kappaB activation.

CONCLUSION

CRP exerted a proinflammatory effect in human mesangial cells by inducing MCP-1 gene expression via NF-kappaB activation, which was mediated, at least in part, through intracellular calcium and ROS.

NF-kappaB as a molecular link between psychosocial stress and organ dysfunction

It is well accepted that psychosocial stress contributes to the pathogenesis of hypertension, cardiovascular disease, and renal disease. Although even lay persons are aware that stress can be dangerous to health, the molecular mechanisms by which psychosocial events contribute to cellular dysfunction have hitherto been poorly understood by scientists. The pro-inflammatory transcription factor NF-kappaB has recently been identified as a potential critical bridge between stress and cellular activation. NF-kappaB activation, in turn, is known to play a pivotal role in vascular and renal disease. Activation of NF-kappaB, evoked by psychosocial stress, may directly target vessels and kidneys and thus represent an additional risk factor for cardiovascular and renal disease.

Pyrrolidine dithiocarbamate reduces renal dysfunction and injury caused by ischemia/reperfusion of the rat kidney

Dithiocarbamates can modulate the expression of genes associated with inflammation or development of ischemia/reperfusion injury. Here, we investigate the effects of pyrrolidine dithiocarbamate, an inhibitor of nuclear factor (NF)-kappaB activation, on the renal dysfunction and injury caused by ischemia/reperfusion of the rat kidney. Bilateral clamping of renal pedicles (45 min) followed by reperfusion (6 h) caused significant renal dysfunction and marked renal injury. Pyrrolidine dithiocarbamate (100 mg/kg, administered i.v.) significantly reduced biochemical and histological evidence of renal dysfunction and injury caused by ischemia/reperfusion of the rat kidney. Furthermore, pyrrolidine dithiocarbamate markedly reduced the expression of inducible nitric oxide synthase (iNOS) protein and significantly reduced serum levels of nitric oxide. Finally, pyrrolidine dithiocarbamate inhibited the activation of NF-kappaB by preventing its translocation from the cytoplasm into the nuclei of renal cells. These results demonstrate that pyrrolidine dithiocarbamate reduces renal ischemia/reperfusion injury and that dithiocarbamates may provide beneficial actions against ischemic acute renal failure.