NF-kB expression in IgA nephropathy outcome

Degradation of Ubiquitin-Editing Enzyme A20 following Autophagy Activation Promotes RNF168 Nuclear Translocation and NF-κB Activation in Lupus Nephritis

The correlation between ubiquitin-editing enzyme A20 and E3 ubiquitin ligase ring finger protein (RNF) 168 has been reported to be critical for repair of DNA damage. This study aimed to evaluate the potential role of this regulatory interaction in the pathogenesis of lupus nephritis (LN). The expression of RNF168 and A20 was measured in the podocytes derived from MRL/lpr murine lupus as well as patients with LN. Cell-based studies using renal podocytes bearing silenced RNF168, over-expressed A20, autophagy-related gene (Atg) 5 (a ubiquitin-like modifier), or silenced Atg5 were used to assess the effect of RNF168, A20, and Atg5 on DNA damage repair and nuclear factor kappa-B (NF-κB) activation in LN. It was found that podocyte autophagy was over-activated in LN and the abnormal podocyte autophagy led to down-regulation of A20, up-regulation of RNF168, and activation of the NF-κB. RNF168 silencing or A20 restoration inhibited activation of NF-κB pathway and promoted repair of DNA damage, where the level of autophagy was not changed. Activated A20 in podocytes weakened the promoting action of cell autophagy on RNF168. The current results suggest that RNF168 dysfunction may be involved in the pathogenesis of LN via down-regulation of A20 expression. Autophagy and RNF168 may be therapeutic targets for the prevention and treatment of LN.

Spleen Tyrosine Kinase Inhibition Ameliorates Tubular Inflammation in IgA Nephropathy

Spleen tyrosine kinase (Syk) is a non-receptor tyrosine kinase involved in signal transduction in a variety of immune responses. It has been demonstrated that Syk plays a pathogenic role in orchestrating inflammatory responses and cell proliferation in human mesangial cells (HMC) in IgA nephropathy (IgAN). However, whether Syk is involved in tubular damage in IgAN remains unknown. Using human kidney biopsy specimens, we found that Syk was activated in renal tubules of biopsy-proven IgAN patients with an increase in total and phosphorylated levels compared to that from healthy control subjects. In vitro, cultured proximal tubular epithelial cells (PTECs) were stimulated with conditioned medium prepared from human mesangial cells incubated with polymeric IgA (IgA-HMC) from patients with IgAN or healthy control. Induction of IL-6, IL-8, and ICAM-1 synthesis from cultured PTECs incubated with IgA-HMC conditioned medium was significantly suppressed by treatment with the Syk inhibitor R406 compared to that from healthy control. Furthermore, R406 downregulated expression of phosphorylated p65 NF-κB and p-42/p-44 MAPK, and attenuated TNF-α-induced cytokine production in PTECs. Taken together, our findings suggest that Syk mediates IgA-HMC conditioned medium-induced inflammation in tubular cells via activation of NF-κB and p-42/p-44 MAPK signaling. Inhibition of Syk may be a potential therapeutic approach for tubulointerstitial injury in IgAN.

Long-term safety and efficacy of hydroxychloroquine in patients with IgA nephropathy: a single-center experience

BACKGROUND

Hydroxychloroquine (HCQ) has been used as a supportive therapy for IgA nephropathy (IgAN). We aimed to determine the long-term efficacy and safety of HCQ therapy in patients with IgAN.

METHODS

A total of 180 patients with IgAN who had received HCQ therapy for at least 1 year were enrolled in this study. The changes in proteinuria and the estimated glomerular filtration rate (eGFR) were analyzed during the follow-up period.

RESULTS

The level of proteinuria decreased from 1.69 [1.24, 2.30] to 1.01 [0.59, 1.74] g/day (- 37.58 [- 57.52, 8.24] %, P < 0.001) at 12 months and to 1.00 [0.59, 1.60] g/day (- 55.30 [- 71.09, - 3.44] %, P < 0.001) at 24 months. There was no significant change in the eGFR of these patients at 12 months (65.82 ± 25.22 vs. 63.93 ± 25.96 ml/min/1.73 m², P = 0.411); however, the eGFR decreased from 65.82 ± 25.22 to 62.15 ± 25.81 ml/min/1.73 m² at 24 months (P = 0.003). The cumulative frequency of all patients with a 50% decrease in proteinuria was 72.78% at 12 months. Sixty (33.3%) patients changed to corticosteroid therapy during the follow-up period. No serious adverse effects were documented during HCQ treatment.

CONCLUSIONS

HCQ effectively and safely reduces proteinuria in IgAN patients with different levels of eGFR, supporting the maintenance of stable kidney function in the long term.

Zhen-Wu-Tang Protects IgA Nephropathy in Rats by Regulating Exosomes to Inhibit NF-κB/NLRP3 Pathway

Immunoglobulin A nephropathy (IgAN) is one of the most frequent kinds of primary glomerulonephritis characterized by IgA immune complexes deposition and glomerular proliferation. Zhen-wu-tang (ZWT), a well-known traditional Chinese formula has been reported to ameliorate various kidney diseases. However, its pharmacological mechanism remains unclear. Exosomes have been described in diverse renal diseases by mediating cellular communication but rarely in the IgAN. The purpose of the present study is to explore whether the underlying mechanisms of the effect of ZWT on IgAN is correlated to exosomes. Our results demonstrated that in human renal tubular epithelial cells (HK-2) stimulated by lipopolysaccharide, exosomes are obviously released after ZWT-containing serum treatment especially with 10% ZWT. In addition, once released, HK-2-derived exosomes were uptaked by human mesangial cells (HMC), which impeded the activation of NF-κB/NLRP3 signaling pathway to exert anti-inflammatory effects in a lipopolysaccharide induced proliferation model. Moreover, IgAN rat model was established by bovine serum albumin, CCL₄ mixed solution and LPS. We found that 10% ZWT could significantly promote the release of exosomes from HK-2 and inhibit HMC proliferation to improve inflammation. Thus HK-2-derived exosomes treated with 10% ZWT (ZWT-EXO) were administered to the rats by tail vein injection. Our results showed that ZWT-EXO decreased the levels of 24 h proteinuria, urinary erythrocyte, IgA deposition in glomerulus and renal pathological injury which ameliorated the kidney damage. In addition, ZWT was able to dramatically promote secretion of exosomes in renal tissues while blocked NF-κB nuclear translocation as well as activation of NLRP3 inflammasome, leading to the inhibition of IL-1β and caspase-1. In conclusion, our study reveal that ZWT has protective effects on IgAN by regulating exosomes secretion to inhibit the activation of NF-κB/NLRP3 pathway, thereby attenuating the renal dysfunction. These findings may provide a new therapeutic target for the treatment of IgAN.

Critical roles of PI3K/Akt/NF‑κB survival axis in angiotensin II‑induced podocyte injury

Numerous studies have reported that angiotensin (Ang) II, nephrin, and podocin serve pivotal roles in podocyte injury, and thus can lead to the occurrence of proteinuria and the progression of kidney diseases. This study aimed to investigate the effects of Ang II on the production of nephrin and podocin, and their relationship with podocyte injury. We also aimed to determine whether nephrin, podocin and caspase-9 production depends on the PI3K/Akt/nuclear factor (NF)-κB signaling pathway in cultured mouse podocytes. We treated mouse podocytes with different doses of Ang II (10⁻⁹, 10⁻⁸, 10⁻⁷ and 10⁻⁶ mol/l) for 12, 24, and 48 h to analyse cell viability, and at 10⁻⁶ mol/l Ang II for 12, 24, and 48 h to evaluate cell apoptosis. Cells were treated with 10⁻⁶ mol/l of Ang II and/or LY294002 (inhibitor of Akt) or 740Y-P (activator of PI3K) for 48 h to detect Akt, phosphorylated (phospho)-Akt, p65 NF-κB, and phospho-p65 NF-κB, nephrin, podocin and caspase-9 expression, and podocyte apoptosis. Treatment with Ang II suppressed the viability and promoted the apoptosis of podocytes in a dose- and time-dependent manner. Ang II decreased phospho-Akt, phospho-p65 NF-κB, nephrin, and podocin and increased caspase-9 expression, while podocyte apoptosis was promoted. LY294002 further enhanced Ang II-induced downregulation of Akt and p65 NF-κB activation, as well as upregulation of caspase-9 mRNA and protein, and promoted the apoptosis of podocytes. Of note, 740Y-P restored Ang II-induced downregulation of Akt and p65 NF-κB activation, and upregulation of caspase-9, and decreased podocyte apoptosis. Interestingly, LY294002 and 740Y-P were determined to have no notable effects on the expression of nephrin and podocin. The data suggested that Ang II could regulate the expression of nephrin, podocin and caspase-9. Collectively, our findings suggested that the PI3K/Akt/NF-κB survival axis may serve a pivotal role in podocyte injury.

NFκB and Kidney Injury

The global burden of chronic kidney disease will increase during the next century. As NFκB, first described more than 30 years ago, plays a major role in immune and non-immune-mediated diseases and in inflammatory and metabolic disorders, this review article summarizes current knowledge on the role of NFκB in in vivo kidney injury and describes the new and so far not completely understood crosstalk between canonical and non-canonical NFκB pathways in T-lymphocyte activation in renal disease.

NF-κβ: A Potential Target in the Management of Vascular Complications of Diabetes

Diabetes is a metabolic disorder affecting large percentage of population worldwide. NF-κβ plays key role in pathogenesis of vascular complications of diabetes. Persistent hyperglycemia activates NF-κβ that triggers expression of various cytokines, chemokines and cell adhesion molecules. Over-expression of TNF-α, interleukins, TGF-β, Bcl2 and other pro-inflammatory proteins and pro-apoptotic genes by NF-κβ is key risk factor in vascular dysfunction. NF-κβ over-expression also triggers calcification of endothelial cells leading to endothelial dysfunction and further vascular complications. Inhibition of NF-κβ pro-inflammatory pathway is upcoming novel target for management of vascular complications of diabetes. Various natural and synthetic inhibitors of NF-κβ have been studied in management of diabetic complications. Recent preclinical and clinical studies validate NF-κβ as promising target in the management of vascular complications of diabetes.

Effect of Vitamin D and Tacrolimus Combination Therapy on IgA Nephropathy

Background

To explore the effects and the mechanism of vitamin D (VD) and tacrolimus (TAC) combinatorial therapy in the treatment of IgA nephropathy (IgAN) in a rat model.

Material/Methods

IgAN rat models constructed by oral immunization with bovine serum albumin (BSA) and lipopolysaccharide (LPS) (n=30) and were treated with: saline (model group), TAC (TAC group), or TAC+VD therapy (TAC+VD group) through gavage daily for 14 days. Serum creatinine (Scr), albumin (ALB), blood urea nitrogen (BUN), and urinary protein (UAE) levels were determined. Histopathology of renal tissues was examined after hematoxylin and eosin (H&E) staining. The levels of cytokines TGF-β1, IL-5, IFN-γ, and IL-4 in serum were detected by enzyme-linked immunosorbent assay (ELISA). Changes in TLR4/NF-κB pathway were evaluated by western blot.

Results

Both TAC and TAC+VD treatment significantly restored the dysregulated Scr, ALB, BUN, and UAE levels in IgAN rats. TAC+VD therapy more prominently restored Scr and UAE levels (p<0.05). TAC+VD therapy demonstrated superior efficacy in reducing glomerular mesangial cells hyperplasia, reducing thickening of the glomerular basement membrane and glomerular infiltration of inflammatory cells. Thymus and spleen indexes were also increased (p<0.05). The levels of TGF-β1, IL-5, and IL-4 of the TAC+VD group were also lower than those of the TAC group (p<0.05). The TAC+VD group also demonstrated increased IFN-γ, and decreased p-P65/P65 and TLR4 compared to the TAC group.

Conclusions

TAC+VD combinatorial therapy can effectively alleviate renal tissue damage in IgAN rats by regulating immune response and the NF-κB/TLR4 pathway.

Association Between IFN-γ Gene Polymorphisms and IgA Nephropathy in a Chinese Han Population

BACKGROUND/AIMS

IFN-γ was reported to be involved in the development and progression of Immunoglobulin A nephropathy (IgAN), however, few studies have investigated the association between IFN-γ polymorphisms and IgAN. Therefore, we performed a case-control study to assess the association between IFN-γ polymorphisms and the risk of IgAN.

METHODS

Sequenom MassARRAY was used to genotype two SNPs (rs1861494 and rs2430561) in 351 patients with IgAN and 310 healthy controls. Associations were evaluated as odd ratios (OR) with 95% confidence intervals (CI).

RESULTS

No association was found between IFN-γ rs1861494 and IgAN risk or clinical parameters. For rs2430561, the AA genotype was more common in patients with IgAN, compared with controls (AT vs. AA: OR = 0.57, P = 0.035). IFN-γ-rs2430561 T allele may be a protective factor for IgAN susceptibility (T vs. A: OR = 0.59, P = 0.04). Subgroup analysis based on clinical features revealed no significant association between rs2430561 polymorphism and clinical data such as gender, 24-h urine protein, blood pressure, Oxford classifcation and estimated glomerular fltration rate. IgAN patients had a higher IFN-γ serum level than healthy controls and patients with rs1861494 AA genotype had a higher IFN-γ serum level compared with those with AG/GG genotypes.

CONCLUSIONS

IFN-γ polymorphisms may be involved in the development and progression of IgAN.

Inhibitor of NFκB Kinase Subunit 2 Blockade Hinders the Initiation but Aggravates the Progression of Crescentic GN

The NFκB transcription factor family facilitates the activation of dendritic cells (DCs) and CD4(+) T helper (Th) cells, which are important for protective adaptive immunity. Inappropriate activation of these immune cells may cause inflammatory disease, and NFκB inhibitors are promising anti-inflammatory drug candidates. Here, we investigated whether inhibiting the NFκB-inducing kinase IKK2 can attenuate crescentic GN, a severe DC- and Th cell-dependent kidney inflammatory disease. Prophylactic pharmacologic IKK2 inhibition reduced DC and Th cell activation and ameliorated nephrotoxic serum-induced GN in mice. However, therapeutic IKK2 inhibition during ongoing disease aggravated the nephritogenic immune response and disease symptoms. This effect resulted from the renal loss of regulatory T cells, which have been shown to protect against crescentic GN and which require IKK2. In conclusion, although IKK2 inhibition can suppress the induction of nephritogenic immune responses in vivo, it may aggravate such responses in clinically relevant situations, because it also impairs regulatory T cells and thereby, unleashes preexisting nephritogenic responses. Our findings argue against using IKK2 inhibitors in chronic GN and perhaps, other immune-mediated diseases.

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.

Intermedin ameliorates IgA nephropathy by inhibition of oxidative stress and inflammation

IgA nephropathy (IgAN) is the most frequent form of glomerulonephritis worldwide. The role of oxidative stress and inflammation in the pathogenesis of IgAN has been reported. Intermedin (IMD) is a newly discovered peptide that is closely related to adrenomedullin. We have recently reported that IMD can significantly reduce renal ischemia/reperfusion injury by diminishing oxidative stress and suppressing inflammation. The present study was designed to explore whether IMD ameliorates IgAN via oxidative stress- and inflammation-dependent mechanisms. Our results showed that IMD administration resulted in the prevention of albuminuria and ameliorated renal pathomorphological changes. These findings were associated with (1) decreased renal TGF-β1 and collagen IV expression, (2) an increased SOD level and reduced MDA level, (3) the inhibition of the renal activation of NF-κB p65 and (4) the downregulation of the expression of inflammatory factors (TNF-α, MCP-1 and MMP-9) in the kidney. These results indicate that IMD in the kidney protects against IgAN by reducing oxidative stress and suppressing inflammation.

Osthole mitigates progressive IgA nephropathy by inhibiting reactive oxygen species generation and NF-κB/NLRP3 pathway

Renal reactive oxygen species (ROS) and mononuclear leukocyte infiltration are involved in the progressive stage (exacerbation) of IgA nephropathy (IgAN), which is characterized by glomerular proliferation and renal inflammation. The identification of the mechanism responsible for this critical stage of IgAN and the development of a therapeutic strategy remain a challenge. Osthole is a pure compound isolated from Cnidiummonnieri (L.) Cusson seeds, which are used as a traditional Chinese medicine, and is anti-inflammatory, anti-apoptotic, and anti-fibrotic both in vitro and in vivo. Recently, we showed that osthole acts as an anti-inflammatory agent by reducing nuclear factor-kappa B (NF-κB) activation in and ROS release by activated macrophages. In this study, we examined whether osthole could prevent the progression of IgAN using a progressive IgAN (Prg-IgAN) model in mice. Our results showed that osthole administration resulted in prevention of albuminuria, improved renal function, and blocking of renal progressive lesions, including glomerular proliferation, glomerular sclerosis, and periglomerular mononuclear leukocyte infiltration. These findings were associated with (1) reduced renal superoxide anion levels and increased Nrf2 nuclear translocation, (2) inhibited renal activation of NF-κB and the NLRP3 inflammasome, (3) decreased renal MCP-1 expression and mononuclear leukocyte infiltration, (4) inhibited ROS production and NLRP3 inflammasome activation in cultured, activated macrophages, and (5) inhibited ROS production and MCP-1 protein levels in cultured, activated mesangial cells. The results suggest that osthole exerts its reno-protective effects on the progression of IgAN by inhibiting ROS production and activation of NF-κB and the NLRP3 inflammasome in the kidney. Our data also confirm that ROS generation and activation of NF-κB and the NLRP3 inflammasome are crucial mechanistic events involved in the progression of the renal disorder.

Association of urinary laminin G-like 3 and free K light chains with disease activity and histological injury in IgA nephropathy

BACKGROUND AND OBJECTIVES

IgA nephropathy has variable clinical presentation and progression. Its definitive diagnosis and prognosis require renal biopsy. The identification of new biomarkers allowing noninvasive diagnosis and monitoring of disease activity would be advantageous. This study analyzed the urine proteome of IgA nephropathy patients at an early stage of disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urine from 49 IgA nephropathy patients, 42 CKD patients, and 40 healthy individuals was analyzed by surface-enhanced laser desorption/ionization time of flight/mass spectrometry. Differentially excreted proteins were identified by matrix-enhanced laser desorption/ionization time of flight/mass spectrometry, confirmed by immunologic methods, and validated in an independent set of patients (14 IgA nephropathy and 24 CKD). All patients were recruited at the Division of Nephrology of the University of Foggia from January of 2005 to March of 2007.

RESULTS

Two proteins, with 21,598 and 23,458 m/z, were significantly decreased in IgA nephropathy and identified as Perlecan laminin G-like 3 peptide and Ig κ light chains, respectively. Western blot analysis confirmed the lower urinary excretion of laminin G-like 3 in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunonephelometry analysis confirmed the lower urinary excretion of free κ light chains in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunohistochemistry analysis justified the urinary excretion profile of such proteins in IgA nephropathy. Finally, urinary free κ light chains and laminin G-like 3 concentration inversely correlated with severity of clinical and histologic features of our IgA nephropathy cohort.

CONCLUSIONS

Laminin G-like 3 and free κ light chains can contribute to the noninvasive assessment of IgA nephropathy disease activity.