Gene expression of TWEAK/Fn14 and IP-10/CXCR3 in glomerulus and tubulointerstitium of patients with lupus nephritis

Aim: The role of the tumour necrosis factor‐like weak inducer of apoptosis (TWEAK)/Fn14 and interferon‐inducible protein (IP‐10)/CXCR3 axis in the pathogenesis of lupus nephritis were studied. Methods: The mRNA expression of TWEAK, Fn14, IP‐10 and CXCR3 were quantified in the glomerulus and tubulointerstitium of 42 patients with lupus nephritis (LN group) and 10 healthy controls. Results: As compared to controls, LN patients had higher glomerular expression of TWEAK and Fn14, but glomerular CXCR3 expression was lower in the LN group. Similarly, the LN group had higher tubulointerstitial expression of TWEAK and Fn14, but lower tubulointerstitial expression of CXCR3, than controls. Glomerular TWEAK expression of class V nephritis was significantly higher than class IV nephritis. Glomerular expression of CXCR3 significantly correlated with proteinuria (r = ?0.532; P = 0.019), whereas tubulointerstitial CXCR3 significantly correlated with serum creatinine (r = ?0.447; P = 0.029). Conclusion: In patients with lupus nephritis, there is an increase in intra‐renal expression of TWEAK and Fn14, and a decrease in CXCR3 expression. Intra‐renal expression of CXCR3 correlates with proteinuria and renal function. Our findings suggest that the TWEAK/Fn14 and IP‐10/CXCR3 axis may contribute to the pathogenesis of lupus nephritis.     

TWEAK, a multifunctional cytokine in kidney injury

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a cytokine of the TNF superfamily that activates the Fn14 receptor. TWEAK may regulate cell proliferation, cell death, cell differentiation, and inflammation. TWEAK and Fn14 are constitutively present in the kidney. Sources of TWEAK and Fn14 include intrinsic renal cells and infiltrating leukocytes. Basal Fn14 expression is low, but Fn14 is greatly upregulated during kidney injury. TWEAK contributes to kidney inflammation promoting chemokine secretion by renal cells through canonical and non-canonical NFκB activation. TWEAK also promotes tubular cell proliferation. However, TWEAK induces mesangial and tubular cell apoptosis under proinflammatory conditions. These data indicate that TWEAK is a multifunctional cytokine in the kidney, the actions of which are modulated by the cell microenvironment. Confirmation of the role of TWEAK in kidney injury came from functional studies in experimental animal models. The TWEAK/Fn14 pathway contributed to cell death and interstitial inflammation during acute kidney injury, to glomerular injury in lupus nephritis, to hyperlipidemia-associated kidney injury, and to tubular cell hyperplasia following unilateral nephrectomy. Circulating soluble TWEAK (sTWEAK) levels are a potential biomarker of adverse outcomes in chronic kidney disease and urinary sTWEAK is a potential biomarker of lupus nephritis activity. The available evidence suggests that TWEAK may provide diagnostic information and be a therapeutic target in renal injury. Its role in human kidney disease should be further explored.     

Deficiency of Fibroblast Growth Factor-Inducible 14 (Fn14) Preserves the Filtration Barrier and Ameliorates Lupus Nephritis

TNF ligand superfamily member 12, also known as TNF-related weak inducer of apoptosis (TWEAK), acts through its receptor, fibroblast growth factor-inducible 14 (Fn14), to mediate several key pathologic processes involved in tissue injury relating to lupus nephritis. To explore the potential for renal protection in lupus nephritis by targeting this pathway, we introduced the Fn14 null allele into the MRL-lpr/lpr lupus mouse strain. At 26–38 weeks of age, female Fn14-knockout MRL-lpr/lpr mice had significantly lower levels of proteinuria compared with female wild-type MRL-lpr/lpr mice. Furthermore, Fn14-knockout mice had significantly improved renal histopathology accompanied by attenuated glomerular and tubulointerstitial inflammation. There was a significant reduction in glomerular Ig deposition in Fn14-knockout mice, despite no detectable differences in either serum levels of antibodies or splenic immune cell subsets. Notably, we found that the Fn14-knockout mice displayed substantial preservation of podocytes in glomeruli and that TWEAK signaling directly damaged barrier function and increased filtration through podocyte and glomerular endothelial cell monolayers. Our results show that deficiency of the Fn14 receptor significantly improves renal disease in a spontaneous lupus nephritis model through prevention of the direct injurious effects of TWEAK on the filtration barrier and/or modulation of cytokine production by resident kidney cells. Thus, blocking the TWEAK/Fn14 axis may be a novel therapeutic intervention in immune-mediated proliferative GN.     

Cytokine cooperation in renal tubular cell injury: the role of TWEAK

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK, TNFSF12) is a member of the TNF superfamily. TWEAK activates the Fn14 receptor, and may regulate apoptosis, proliferation, and inflammation, processes that play a significant role in pathological conditions. However, there is little information on the function and regulation of this system in the kidney. Therefore, TWEAK and Fn14 expression were studied in cultured murine tubular epithelial MCT cells and in mice in vivo. The effect of TWEAK on cell death was determined. We found that TWEAK and Fn14 expression was increased in experimental acute renal failure induced by folic acid. Cultured tubular cells express both TWEAK and the Fn14 receptor. TWEAK did not induce cell death in non-stimulated tubular cells. However, in cells costimulated with TNFalpha/interferon-gamma, TWEAK induced apoptosis through the activation of the Fn14 receptor. Apoptosis was associated with activation of caspase-8, caspase-9, and caspase-3, Bid cleavage, and evidence of mitochondrial injury. There was no evidence of endoplasmic reticulum stress. A pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp prevented TWEAK-induced apoptosis, but it sensitized cells to necrosis via generation of reactive oxygen species. In conclusion, cooperation between inflammatory cytokines results in tubular cell death. TWEAK and Fn14 may play a role in renal tubular cell injury.     

Direct targeting of fibroblast growth factor-inducible 14 protein protects against renal ischemia reperfusion injury

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is known to have pivotal roles in various inflammatory processes. The TWEAK receptor, fibroblast growth factor-inducible 14 (Fn14), has various unique functions under physiological and pathological conditions; however, the therapeutic potential of its direct targeting remains unknown. Here, we found that Fn14 expression was highly upregulated in ischemic renal tissues and tubular epithelial cells of patient biopsies and experimental animal models of renal injury. To clarify the function of Fn14 in ischemia reperfusion injury, we coincubated renal tubular cells with ITEM-2, an anti-Fn14 blocking monoclonal antibody, and found that it inhibited the production of proinflammatory cytokines and chemokines after injury. Furthermore, Fn14 blockade downregulated the local expression of several proinflammatory mediators, reduced accumulation of neutrophils and macrophages in ischemic tissues, and inhibited tubular cell apoptosis. Importantly, Fn14 blockade attenuated the development of chronic fibrosis after ischemia reperfusion injury and significantly prolonged the survival of lethally injured mice. Thus, we conclude that Fn14 is a critical mediator in the pathogenesis of ischemia reperfusion injury.     

The TWEAK/Fn14 pathway is required for calcineurin inhibitor toxicity of the kidneys

Calcineurin inhibitor toxicity (CNT) is a frequent occurrence in transplanted renal grafts and autochthone kidneys from patients undergoing long‐term treatment with calcineurin inhibitors, notably cyclosporin A (CsA) and tacrolimus. Here, we show an indispensable role of the tumor necrosis factor superfamily (TNFS) molecule TNF‐related weak inducer of apoptosis (TWEAK) (TNFSF12) in the pathogenesis of acute CNT lesions in mice. A deficiency in TWEAK resulted in limited tubulotoxicity after CsA exposure, which correlated with diminished expression of inflammatory cytokines and reduced intraparenchymal infiltration with immune cells. We further identified tubular epithelial cells of the kidney as major targets of CsA activity and found that Fn14 (tumor necrosis factor receptor superfamily 12A), the receptor for TWEAK, is a highly CsA‐inducible gene in these cells. Correlating with this, CsA pretreatment sensitized tubular epithelial cells specifically to the pro‐inflammatory activities of recombinant TWEAK in vitro. Moreover, injection of rTWEAK alone into mice induced moderate disease similar to CsA, and rTWEAK combined with CsA resulted in synergistic nephrotoxicity. These findings support the importance of tubular epithelial cells as cellular targets of CsA toxicity and introduce TWEAK as a critical contributor to CNT pathogenesis.     

Novel function of TWEAK in inducing intervertebral disc degeneration.

The goal of this research was to examine the role of TWEAK in normal disc cells and to investigate its potential role in disc degeneration. We performed histological examinations of disc tissues and assessed the role of the novel cytokine TWEAK using murine organ disc culture. The expression of both TWEAK and its receptor, Fn14, in discs was confirmed by immunohistochemistry and quantitative real-time PCR. TWEAK induced disc cells to generate MMP-3 in a dose- and time-dependent manner. This induction was strongly inhibited in the presence of a neutralizing antibody to TWEAK or a chimeric Fn14/Fc fusion protein. In disc tissues derived from TNF-alpha receptor 1- or TNF-alpha receptor 2-deficient mice, recombinant TWEAK modestly induced MMP-3. In contrast, in disc cultures lacking TWEAK, tissues from wild-type mice or receptor-deficient mice failed to express MMP-3. Furthermore, aggrecan expression was potently abrogated in a time-dependent manner in the presence of recombinant TWEAK. This is the first report to confirm expression of TWEAK and its receptor Fn14 in murine intervertebral disc tissues. The data suggest that TWEAK plays a role in MMP-3 up-regulation and aggrecan down-regulation in disc tissues, resulting in proteoglycan degradation and promotion of disc degeneration.     

Expression of hypoxia‐inducible factor‐1α and hepatocyte growth factor in development of fibrosis in the transplanted kidney

Late renal graft loss is associated with interstitial fibrosis. Hypoxia‐inducible factor‐1α (HIF‐1α) is thought to facilitate fibrosis through interaction with TGF‐β1, while hepatocyte growth factor (HGF) may act antifibrotic in the kidney allograft. The aim of this study was to investigate the expression of HIF‐1α and HGF in protocol biopsies as possible prognostic biomarkers for renal fibrosis. Thirty‐nine renal transplant recipients were included in the study. Protocol biopsies performed 1 and 2 years after transplantation were used for immunohistochemistry analysis. The correlation between HIF‐1α/HGF and the Banff score was analysed. In addition, progression in renal fibrosis and graft survival among recipients with high or low expression of HIF‐1α/HGF after transplantation was compared. There was no significant correlation between fibrosis and the HIF‐1α expression 1 and 2 years after transplantation, but an inverse significant correlation between the HGF expression and the fibrosis score 1 year after transplantation was shown. Even when adjusting for human leucocyte antigen mismatches, there was a significant relationship between fibrosis and HGF expression. Graft survival was not significantly correlated to HIF‐1α or HGF at 1 year, although the trend was towards better graft survival with high HGF. HGF may have antifibrotic effects in human renal transplants. (Central.Denmark.Region.Committee number: 1‐10‐72‐318‐13)     

TWEAK Signaling Pathway Blockade Slows Cyst Growth and Disease Progression in Autosomal Dominant Polycystic Kidney Disease

BackgroundIn autosomal dominant polycystic kidney disease (ADPKD), cyst development and enlargement lead to ESKD. Macrophage recruitment and interstitial inflammation promote cyst growth. TWEAK is a TNF superfamily (TNFSF) cytokine that regulates inflammatory responses, cell proliferation, and cell death, and its receptor Fn14 (TNFRSF12a) is expressed in macrophage and nephron epithelia.MethodsTo evaluate the role of the TWEAK signaling pathway in cystic disease, we evaluated Fn14 expression in human and in an orthologous murine model of ADPKD. We also explored the cystic response to TWEAK signaling pathway activation and inhibition by peritoneal injection.ResultsMeta-analysis of published animal-model data of cystic disease reveals mRNA upregulation of several components of the TWEAK signaling pathway. We also observed that TWEAK and Fn14 were overexpressed in mouse ADPKD kidney cysts, and TWEAK was significantly high in urine and cystic fluid from patients with ADPKD. TWEAK administration induced cystogenesis and increased cystic growth, worsening the phenotype in a murine ADPKD model. Anti-TWEAK antibodies significantly slowed the progression of ADPKD, preserved renal function, and improved survival. Furthermore, the anti-TWEAK cystogenesis reduction is related to decreased cell proliferation–related MAPK signaling, decreased NF-κB pathway activation, a slight reduction of fibrosis and apoptosis, and an indirect decrease in macrophage recruitment.ConclusionsThis study identifies the TWEAK signaling pathway as a new disease mechanism involved in cystogenesis and cystic growth and may lead to a new therapeutic approach in ADPKD.     

Diagnostic value of TWEAK for predicting active lupus nephritis in patients with systemic lupus erythematosus: a systematic review and meta-analysis

Purpose Accumulative studies showed that tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) was up-regulated in the blood and urine from patients diagnosed with lupus nephritis (LN) and that it might be used as a novel biomarker for active LN. This meta-analysis aimed to determine the diagnostic value of TWEAK in active LN.Methods We searched the Cochrane Library, Embase, PubMed, Springer, Wanfang and CNKI databases for articles published up to 20 August 2020. The diagnostic capacity of TWEAK for active LN was assessed using pooled sensitivity and specificity, positive and negative likelihood ratios (PLR and NLR), diagnostic odds ratio (DOR), and area under the receiver operating characteristic curve (AUC). Quality assessment and publication bias were also evaluated. STATA 11.0 and Meta-Disc 1.4 were used to perform these analyses.Results Nine cross-sectional studies were included in this meta-analysis. The overall pooled sensitivity of TWEAK for the diagnosis of active LN was 0.69 (95% CI, 0.63–0.75), and specificity was 0.77 (95% CI, 0.71–0.82). The overall pooled PLR and NLR were 3.31 (95% CI, 2.05–5.35) and 0.38 (95% CI, 0.26–0.55), respectively, with a DOR of 10.89 (95% CI, 6.73–17.63) and AUC (SE) of 0.8276 (0.0289). Deeks’ funnel plot revealed that the publication bias was insignificant in the study (p = .32).Conclusions Our results suggest that TWEAK might be a potential biomarker for patients with active LN. Future cross-sectional and longitudinal studies are needed to confirm its diagnostic value, as well as to establish more definite cutoff for active LN.     

Dyslipidaemia in patients with lupus nephritis

Aim: There is little data on the prevalence and severity of dyslipidaemia in Asian patients with lupus nephritis (LN). Whether the dyslipidaemia in LN patients differs from subjects with comparable levels of renal impairment also remains undefined. Methods: Lipid profiles of 100 Chinese patients with quiescent LN (age 46.3 ± 9.3 years, 83% female, maintenance prednisolone dose 5.80 ± 2.43 mg/day) were studied and compared with 100 controls who had non‐lupus non‐diabetic chronic kidney diseases (CKD), matched for sex, age and renal function. Results: LN patients and CKD controls had similar renal function and proteinuria, while blood pressure was higher in controls. Twenty‐five percent of LN patients and 17% of controls were receiving statin treatment. Despite this, 59% of LN patients and 46% CKD controls showed abnormal lipid parameters (P = 0.066). LN patients showed higher levels of total cholesterol (TC) and triglycerides (TG) than controls (5.28 ± 0.12 vs 4.86 ± 0.08 mmol/L, P = 0.004; and 1.62 ± 0.12 vs 1.20 ± 0.07 mmol/L, P = 0.002, respectively). More LN patients had abnormal TC, TG or low‐density lipoprotein cholesterol (LDL‐C) (54%, 16% and 38%; P = 0.016, = 0.005 and = 0.021, respectively). Hydroxychloroquine (HCQ) treatment was associated with lower TC, LDL‐C and HDL‐cholesterol. Conclusion: Dyslipidaemia is prevalent in LN patients and is more severe than controls with a similar degree of CKD despite disease quiescence, low steroid dose and low level of proteinuria. Concomitant corticosteroid and renal impairment are likely contributing factors. HCQ treatment is associated with reduced severity of dyslipidaemia in LN patients.     

A single blunt impact on cartilage promotes fibronectin fragmentation and upregulates cartilage degrading stromelysin‐1/matrix metalloproteinase‐3 in a bovine ex vivo model

Post‐traumatic osteoarthritis (PTOA) is characterized by progressive cartilage degeneration in injured joints. Since fibronectin‐fragments (Fn‐fs) degrade cartilage mainly through up‐regulating matrix metalloproteinases (MMPs) and pro‐inflammatory cytokines, we hypothesized that Fn‐fs play a key role in PTOA by promoting chondrolysis in and around injured cartilage. To test this hypothesis, we profiled the catabolic events focusing on fibronectin fragmentation and proteinase expression in bovine osteochondral explants following a single blunt impact on cartilage with a drop tower device which created partial‐thickness tissue damage. Injured and control explants were cultured for up to 14 days. The presence of Fn‐fs, MMPs (‐1, ‐3, ‐13), ADAMTS‐5 in culture media and in cartilage was determined with immunoblotting. The daily proteoglycan (PG) depletion of cartilage matrix was assessed with DMMB assay. The effect of explant‐conditioned media on chondrocytes was also examined with immunoblotting. Impacted cartilage released significantly higher amount of native Fn, three chondrolytic Fn‐fs and PG than non‐impacted controls did. Those increases coincided with up‐regulation of MMP‐3 both in culture media and in impacted cartilage. These findings support our hypothesis that PTOA may be propelled by Fn‐fs which act as catabolic mediators through up‐regulating cartilage‐damaging proteinases. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:811–818, 2014.     

Predictors of poor renal outcome in patients with biopsy‐proven lupus nephritis

Aim: The development of lupus nephritis (LN) is associated with increased morbidity and mortality. In view of scarce data from South Africa on factors affecting renal outcome in LN, the authors' experience was reviewed to identify predictors of poor renal outcome. Methods: This is a retrospective review of 105 patients with biopsy‐proven LN under our care from January 1995 to December 2007. Results: Forty‐three (41.0%) patients reached the composite end‐point of persistent doubling of the serum creatinine over the baseline value, development of end‐stage renal disease (ESRD) or death during a mean follow‐up period of 51.1 months (range 1–137 months). Baseline factors associated with the composite end‐point included presence of systemic hypertension (P = 0.016), mean systolic blood pressure (SBP) (P = 0.004), mean diastolic blood pressure (DBP) (P = 0.001), mean serum creatinine (P = 0.001), estimated glomerular filtration rate (eGFR) (P = 0.003) and diffuse proliferative glomerulonephritis (World Health Organization class IV) (P = 0.024). Interstitial inflammation (P = 0.049), failure of remission in the first year following therapy (P < 0.001), the mean SBP on follow up (P < 0.001) and mean DBP on follow up (P < 0.001) were also associated with composite end‐point. On multivariate analysis, baseline serum creatinine, non‐remission following therapy (P = 0.038) and mean SBP on follow up (P = 0.016) were predictors of poor renal outcome. Conclusion: Baseline serum creatinine, failure of remission in the first year and mean SBP were predictors of poor renal outcome.     

Outcome in African-American children of neuropsychiatric lupus and lupus nephritis

The present study reviews the course of lupus nephritis (LN) with the added complication of neuropsychiatric systemic lupus erythematosus (NPSLE) in a predominantly African-American population in order to identify the risk factors accounting for the increased morbidity and mortality in African-American children. Previous studies, including those at our center, have demonstrated the poor prognosis for African-American children with LN. A possible factor is the involvement of the central nervous system (CNS), resulting in a heightened risk of morbidity, although to date there are no reports suggesting an association between NPSLE and patient and renal survival in children with lupus nephritis. To this end, we retrospectively analyzed charts of 72 children with lupus nephritis seen at our center from 1965 to 1999. These 72 patients formed two groups, with group 1 consisting of patients with lupus nephritis and NP manifestations and group 2 only lupus nephritis. We then examined various demographic factors such as age, sex and race along with the histopathologic class of lupus nephritis, occurrence of hypertension, incidence of end stage renal disease (ESRD), time to ESRD and mortality in both groups with the aid of Fisher’s exact t-test and the chi-square test. Briefly, the results revealed significantly higher class III or IV histopathologic lesions on biopsy, incidence of hypertension, progression to ESRD and mortality in children with NPSLE and LN (group 1) compared to LN alone (group 2) in spite of aggressive immunosuppressive therapy. In conclusion, we report that NPSLE with LN is associated with an increased rate of ESRD and mortality in our predominantly African-American children. Received: 26 March 2001 / Revised: 13 August 2001 / Accepted: 13 August 2001     

Upregulation of heparin‐binding epidermal growth factor‐like growth factor and osteopontin in experimental hydronephrosis

SUMMARY This study examined the expression of heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) and osteopontin in unilateral ureteral obstruction (UUO) in the rat, a model of obstructive uropathy. HB‐EGF mRNA was upregulated 5.5‐fold at 4 h post‐obstruction (P < 0.05) and 4.5‐fold after 12 h (P < 0.05). Immunohistochemical staining for HB‐EGF demonstrated an increase in protein in the distended tubules. To determine what effects increased HB‐EGF might have in the obstructed kidney, we attempted to determine whether HB‐EGF upregulates osteopontin and α‐smooth muscle actin (α‐SMA) in the tubular line NRK‐52E. Both of these molecules are increased in UUO. Osteopontin mRNA was upregulated in NRK‐52E cells after 24, 48 and 72 h HB‐EGF stimulation. In contrast, HB‐EGF caused a downregulation of α‐SMA protein by Western blot in NRK‐52E cells. When a blocking mAb against secreted HB‐EGF was administered, however, there was no effect on osteopontin mRNA levels or immunohistochemical staining for α‐smooth muscle actin. These data suggest that the action of HB‐EGF in UUO may be to increase osteopontin and reduce α‐smooth muscle actin expression by tubular epithelial cells by an autocrine or intracrine mechanism. By reducing α‐SMA expression, HB‐EGF may also act to maintain epithelial cell morphology in this model.     

Renal haemodynamic characteristics and their correlation with renal pathology in patients with systemic lupus erythematosus

SUMMARY: To clarify the characteristics of renal haemodynamics and their correlation with renal pathology in patients with systemic lupus erythematosus (SLE), renal function and renal biopsy findings from 101 SLE patients were analysed retrospectively. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were examined simultaneously. Filtration fraction (FF) was calculated from the values obtained for GFR and RPF (GFR/RPF). The GFR was low in one-third and within normal limits in two-thirds of class IV patients with lupus nephritis (LN). In contrast, high RPF was observed in half of class IV patients. As a result, over 70% of class IV patients possessed a very low FF (less than 15%). The sensitivity of very low FF for class IV LN was significantly higher than that of low GFR. In conclusion, low FF was frequently recognized, especially in patients with diffuse proliferative LN. Decreased FF was a highly sensitive indicator of diffuse proliferative LN. Thus, determination of renal haemodynamics, including FF, may be a useful clinical parameter for evaluating renal involvement in patients with SLE.