Acute tubulointerstitial nephritis (ATIN) is a common cause of acute kidney injury. Although haematuria is a risk factor for the development of renal disease, no previous study has analyzed the significance of haematuria in ATIN. Retrospective, observational analysis of 110 patients with biopsy-proven ATIN was conducted. Results: Haematuria was present in 66 (60%) ATIN patients. A higher percentage of ATIN patients with haematuria had proteinuria than patients without haematuria (89.4% vs. 59.1%, p = 0.001) with significantly higher levels of proteinuria (median (interquartile range) protein:creatinine ratio 902.70 (513-1492) vs. 341.00 (177-734) mg/g, p <0.001). Moreover, those patients with more haematuria intensity had a higher urinary protein:creatinine ratio (1352.65 (665-2292) vs. 849.60 (562-1155) mg/g, p = 0.02). Those patients with higher proteinuria were more likely to need renal replacement therapy (22.7 vs. 0%, p = 0.03) and to suffer relapse (4 vs. 0%, p = 0.03). At the end of follow up, haematuric ATIN patients had higher serum creatinine levels (3.19 ± 2.91 vs. 1.91 ± 1.17 mg/dL, p = 0.007), and a trend towards a higher need for acute dialysis (7 vs. 1%, p = 0.09) and renal replacement therapy (12.1 vs. 2.3%, p = 0.12). Haematuria is common in ATIN and it is associated with worse renal function outcomes.

Data reproducibility and single-center bias are concerns in preclinical research and compromise translation from animal to human. Multicenter preclinical randomized controlled trials (pRCT) may reduce the gap between experimental studies and RCT and improve the predictability of results, for example Jak1/2 inhibition in lupus nephritis. To evaluate this, we conducted the first pRCT in the kidney domain at two Spanish and two German academic sites. Eligible MRL/MpJ-Faslpr mice (female, age13-14 weeks, stress scores of less than two and no visible tumor or signs of infection) were equally randomized to either oral treatment with the Jak1/2 inhibitor baricitinib or vehicle for four weeks. Central blinded histology analysis was performed at an independent fifth site. The primary endpoint was the urinary protein/creatinine ratio. Baricitinib treatment did not significantly affect proteinuria, histological markers of activity and chronicity, or the glomerular filtration rate but significantly improved plasma autoantibody levels and lymphadenopathy. Data heterogeneity was noted across the different centers referring in part to phenotype differences between MRL/MpJ-Faslpr mice bred at different sites, mimicking well patient phenotype diversity in lupus trials. Multicenter pRCT can overcome single-center bias at the cost of increasing variability and reducing effect size. Thus, our pRCT predicts a low effect size of baricitinib treatment on human lupus nephritis in heterogeneous study populations.

TNF-like weak inducer of apoptosis (TWEAK) receptor Fn14 is expressed by podocytes and Fn14 deficiency protects from experimental proteinuric kidney disease. However, the downstream effectors of TWEAK/Fn14 in podocytes are poorly characterized. We have explored TWEAK activation of non-canonical NFκB signaling in cultured podocytes. In cultured podocytes, TWEAK increased the expression of the chemokines CCL21, CCL19 and RANTES in a time-dependent manner. The inhibitor of canonical NFκB activation parthenolide inhibited the CCL19 and the early RANTES responses, but not the CCL21 or late RANTES responses. In this regard, TWEAK induced non-canonical NFκB activation in podocytes, characterized by NFκB2/p100 processing to NFκB2/p52 and nuclear migration of RelB/p52. Silencing by a specific siRNA of NIK, the upstream kinase of the non-canonical NFκB pathway, prevented CCL21 upregulation but did not modulate CCL19 or RANTES expression in response to TWEAK, thus establishing CCL21 as a non-canonical NFκB target in podocytes. Increased kidney Fn14 and CCL21 expression was also observed in rat proteinuric kidney disease induced by puromycin, and was localized to podocytes. In conclusion, TWEAK activates the non-canonical NFκB pathway in podocytes, leading to upregulation of CCL21 expression. The non-canonical NFκB pathway should be explored as a potential therapeutic target in proteinuric kidney disease.

Omeprazole, a proton pump inhibitor used to treat peptic ulcer and gastroesophageal reflux disease, has been associated to chronic kidney disease and acute interstitial nephritis. However, whether omeprazole is toxic to renal cells is unknown. Omeprazole has a lethal effect over some cancer cells, and cell death is a key process in kidney disease. Thus, we evaluated the potential lethal effect of omeprazole over tubular cells. Omeprazole induced dose-dependent cell death in human and murine proximal tubular cell lines and in human primary proximal tubular cell cultures. Increased cell death was observed at the high concentrations used in cancer cell studies and also at lower concentrations similar to those in peptic ulcer patient serum. Cell death induced by omeprazole had features of necrosis such as annexin V/7-AAD staining, LDH release, vacuolization and irregular chromatin condensation. Weak activation of caspase-3 was observed but inhibitors of caspases (zVAD), necroptosis (Necrostatin-1) or ferroptosis (Ferrostatin-1) did not prevent omeprazole-induced death. However, omeprazole promoted a strong oxidative stress response affecting mitochondria and lysosomes and the antioxidant N-acetyl-cysteine reduced oxidative stress and cell death. By contrast, iron overload increased cell death. An adaptive increase in the antiapoptotic protein BclxL failed to protect cells. In mice, parenteral omeprazole increased tubular cell death and the expression of NGAL and HO-1, markers of renal injury and oxidative stress, respectively. In conclusion, omeprazole nephrotoxicity may be related to induction of oxidative stress and renal tubular cell death.

Crescentic glomerulonephritis is a devastating autoimmune disease that without early and properly treatment may rapidly progress to end-stage renal disease and death. Current immunosuppressive treatment provides limited efficacy and an important burden of adverse events. Epigenetic drugs are a source of novel therapeutic tools. Among them, bromodomain and extraterminal domain (BET) inhibitors (iBETs) block the interaction between bromodomains and acetylated proteins, including histones and transcription factors. iBETs have demonstrated protective effects on malignancy, inflammatory disorders and experimental kidney disease. Recently, Gremlin-1 was proposed as a urinary biomarker of disease progression in human anti-neutrophil cytoplasmic antibody (ANCA)-associated crescentic glomerulonephritis. We have now evaluated whether iBETs could regulate Gremlin-1 in experimental anti-glomerular basement membrane nephritis induced by nephrotoxic serum (NTS) in mice, a model resembling human crescentic glomerulonephritis. In NTS-injected mice, the iBET JQ1 inhibited renal Gremlin-1 overexpression and diminished glomerular damage, restoring podocyte numbers. Chromatin immunoprecipitation assay demonstrated BRD4 enrichment of the Grem-1 gene promoter in injured kidneys, consistent with Gremlin-1 epigenetic regulation. Moreover, JQ1 blocked BRD4 binding and inhibited Grem-1 gene transcription. The beneficial effect of iBETs was also mediated by modulation of NOTCH pathway. JQ1 inhibited the gene expression of the NOTCH effectors Hes-1 and Hey-1 in NTS-injured kidneys. Our results further support the role for epigenetic drugs, such as iBETs, in the treatment of rapidly progressive crescentic glomerulonephritis.

Progressive glomerulonephritis (GN) is characterized by an excessive accumulation of extracellular (ECM) proteins, mainly type IV collagen (COLIV), in the glomerulus leading to glomerulosclerosis. The current therapeutic approach to GN is suboptimal. Epigenetic drugs could be novel therapeutic options for human disease. Among these drugs, bromodomain and extra-terminal domain (BET) inhibitors (iBETs) have shown beneficial effects in experimental kidney disease and fibrotic disorders. Sex-determining region Y-box 9 (SOX9) is a transcription factor involved in regulating proliferation, migration, and regeneration, but its role in kidney fibrosis is still unclear. We investigated whether iBETs could regulate ECM accumulation in experimental GN and evaluated the role of SOX9 in this process. For this purpose, we tested the iBET JQ1 in mice with anti-glomerular basement membrane nephritis induced by nephrotoxic serum (NTS). In NTS-injected mice, JQ1 treatment reduced glomerular ECM deposition, mainly by inhibiting glomerular COLIV accumulation and Col4a3 gene overexpression. Moreover, chromatin immunoprecipitation assays demonstrated that JQ1 inhibited the recruitment and binding of BRD4 to the Col4a3 promoter and reduced its transcription. Active SOX9 was found in the nuclei of glomerular cells of NTS-injured kidneys, mainly in COLIV-stained regions. JQ1 treatment blocked SOX9 nuclear translocation in injured kidneys. Moreover, in vitro JQ1 blocked TGF-β1-induced SOX9 activation and ECM production in cultured mesangial cells. Additionally, SOX9 gene silencing inhibited ECM production, including COLIV production. Our results demonstrated that JQ1 inhibited SOX9/COLIV, to reduce experimental glomerulosclerosis, supporting further research of iBET as a potential therapeutic option in progressive glomerulosclerosis.