Interruption of neutrophil extracellular traps formation dictates host defense and tubular HOXA5 stability to augment efficacy of anti-Fn14 therapy against septic AKI.

The immunosuppressive, inflammatory microenvironment orchestrated by neutrophil extracellular traps (NETs) plays a principal role in pathogenesis of sepsis. Fibroblast growth factor-inducible molecule 14 (Fn14) has been established as a potential target for septic acute kidney injury (AKI), making further therapeutic benefits from combined NETs and Fn14 blockade possible. Methods: The concurrence of NETs and Fn14 in mice and patients with septic AKI were assessed by immunofluorescence, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and in silico studies. Survival, histopathological and biochemical analyses of wild-type and PAD4-deficient CMV-Cre; PAD4 fl/fl mice with septic AKI were applied to evaluate the efficacy of either pharmacological or genetic NETs interruption in combination with Fn14 blockade. Molecular mechanisms underlying such effects were determined by CRISPR technology, fluorescence-activated cell sorter analysis (FACS), cycloheximide (CHX) pulse-chase, luciferase reporter and chromatin immunoprecipitation (ChIP) assay. Results: NETs formation is concurred with Fn14 upregulation in murine AKI models of abdominal, endotoxemic, multidrug-resistant sepsis as well as in serum samples of patients with septic AKI. Pharmacological or genetic interruption of NETs formation synergizes with ITEM-2, a monoclonal antibody (mAb) of Fn14, to prolong mice survival and provide renal protection against abdominal sepsis, the effects that could be abrogated by elimination of macrophages. Interrupting NETs formation predominantly perpetuates infiltration and survival of efferocytic growth arrest-specific protein 6+ (GAS6+) macrophages in combination with ITEM-2 therapy and enhances transcription of tubular cell-intrinsic Fn14 in a DNA methyltransferase 3a (DNMT3a)-independent manner through dismantling the proteasomes-mediated turnover of homeobox protein Hox-A5 (HOXA5) upon abdominal sepsis challenge or LPS stimuli. Pharmacological NETs interruption potentiates the anti-septic AKI efficacy of ITEM-2 in murine models of endotoxemic and multidrug-resistant sepsis. Conclusion: Our preclinical data propose that interrupting NETs formation in combination with Fn14 mAb might be a feasible therapeutic strategy for septic AKI.

TWEAK and RIPK1 mediate a second wave of cell death during AKI.

Acute kidney injury (AKI) is characterized by necrotic tubular cell death and inflammation. The TWEAK/Fn14 axis is a mediator of renal injury. Diverse pathways of regulated necrosis have recently been reported to contribute to AKI, but there are ongoing discussions on the timing or molecular regulators involved. We have now explored the cell death pathways induced by TWEAK/Fn14 activation and their relevance during AKI. In cultured tubular cells, the inflammatory cytokine TWEAK induces apoptosis in a proinflammatory environment. The default inhibitor of necroptosis [necrostatin-1 (Nec-1)] was protective, while caspase inhibition switched cell death to necroptosis. Additionally, folic acid-induced AKI in mice resulted in increased expression of Fn14 and necroptosis mediators, such as receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage domain-like protein (MLKL). Targeting necroptosis with Nec-1 or by genetic RIPK3 deficiency and genetic Fn14 ablation failed to be protective at early time points (48 h). However, a persistently high cell death rate and kidney dysfunction (72-96 h) were dependent on an intact TWEAK/Fn14 axis driving necroptosis. This was prevented by Nec-1, or MLKL, or RIPK3 deficiency and by Nec-1 stable (Nec-1s) administered before or after induction of AKI. These data suggest that initial kidney damage and cell death are amplified through recruitment of inflammation-dependent necroptosis, opening a therapeutic window to treat AKI once it is established. This may be relevant for clinical AKI, since using current diagnostic criteria, severe injury had already led to loss of renal function at diagnosis.

Role of TWEAK/Fn14 signalling pathway in lupus nephritis and other clinical settings. / Papel de la vía de señalización del TWEAK/Fn14 en la nefritis lúpica y otros escenarios clínicos.

Knowledge of the signalling pathways involved in various diseases has enabled advances in the understanding of pathophysiological, diagnostic and therapeutic models of several inflammatory and autoimmune diseases. Systemic lupus erythematosus is a widely studied autoimmune disease that can affect multiple organs, with a major impact on morbidity and mortality when it involves the kidneys. Over the past 10 years, interest in the role of the TWEAK/Fn14 signalling pathway in lupus nephritis, as well as other clinical settings, has increased. By reviewing the literature, this article assesses the role of this pathway in lupus nephritis, underlines the importance of TWEAK in urine (uTWEAK) as a biomarker of the disease and stresses the favourable results published in the literature from the inhibition of the TWEAK/Fn14 pathway as a therapeutic target in experimental animal models, demonstrating its potential application in other settings. Results of ongoing clinical trials and future research will give us a better understanding of the real benefit of blocking this pathway in the clinical course of several conditions.