Cell apoptosis is one of the main pathological alterations during oxidative stress (OS) injury. Previously, we corroborated that nuclear factor-κB (NF-κB) transactivation confers apoptosis resistance against OS in mammalian cells, yet the underlying mechanisms remain enigmatic. Here we report that microRNA-19a (miR-19a) transcriptionally regulated by reactive oxygen species (ROS) production and NF-κB deactivation prevents OS-initiated cell apoptosis through cylindromatosis (CYLD) repression. CYLD contributes to OS-initiated cell apoptosis, for which NF-κB deactivation is essential. MiR-19a directly represses CYLD via targeting 3' UTR of CYLD, thereby antagonizing OS-initiated apoptosis. CYLD repression by miR-19a restores the IKKβ phosphorylation, RelA disassociation from IκBα, IκBα polyubiquitination and degradation, RelA recruitment at VEGF gene promoter as well as VEGF secretion in the context of OS. Either pharmacological deactivation of NF-κB or genetic upregulation of CYLD compromises the apoptosis-resistant phenotypes of miR-19a. Furthermore, miR-19a is transcriptionally downregulated upon OS in two distinct processes that require ROS production and NF-κB deactivation. VEGF potentiates the ability of miR-19a to activate NF-κB and render apoptosis resistance. Our findings underscore a putative mechanism whereby CYLD repression-mediated and NF-κB transactivation-dependent miR-19a regulatory feedback loop prevents cell apoptosis in response to OS microenvironment.

Fibroblast growth factor-inducible molecule 14 (Fn14) plays a principal role in triggering tubular damage during septic acute kidney injury (AKI). Here, we explore the mechanism underlying Fn14 deregulation in septic AKI. We identify Fn14 as a bona fide target of miR-19a, which directly binds to 3' UTR of Fn14 for repression independent of cylindromatosis (CYLD), the deubiquitinase (DUB) downstream of miR-19a, and thereby antagonizes the LPS-induced tubular cell apoptosis. Genetic ablation of Fn14, but not of CYLD, abolishes the ability of miR-19a to antagonize the tubular apoptosis by lipopolysaccharide (LPS). In mice, systemic delivery of miR-19a confers protection against septic AKI. Our findings implicate that miR-19a may serve as a promising therapeutic candidate in the prevention of septic AKI.

Ascorbate (Vitamin C) has been proposed as a promising therapeutic agent against sepsis in clinical trials, but there is little experimental evidence on its anti-septic efficacy. We report that Toll-like receptor 4 (TLR4) activation by LPS stimuli augments ascorbate uptake in murine and human tubular cells through upregulation of two ascorbate transporters SVCT-1 and -2 mediated by Fn14/SCFFbxw7α cascade. Ascorbate restriction, or knockout of SVCT-1 and -2, the circumstance reminiscent to blockade of ascorbate uptake, endows tubular cells more vulnerable to the LPS-inducible apoptosis, whereas exogenous administration of ascorbate overrides the ruin execution, for which the PINK1-PARK2, rather than BNIP3-NIX axis is required. Ascorbate increases, while SVCT-1 and -2 knockout or ascorbate restriction dampens tubular mitophagy upon LPS stimuli. Treatment of endotoxemic mice with high-dose ascorbate confers mitophagy and substantial protection against mortality and septic acute kidney injury (AKI). Our work provides a rationale for clinical management of septic AKI with high doses of ascorbate.

We investigated the prevalence of microalbuminuria and its association with the metabolic syndrome and its components in a Chinese population.

Tubular damage initiated by inflammatory response and ischemic/hypoxic stress is a hallmark of septic acute kidney injury (AKI), albeit the molecular mechanism coupling the two events remains unclear. We investigated the intrinsic nature of tubular damage with respect to inflammatory/hypoxic stress during septic AKI. Methods: The apoptotic response of tubular cells to LPS stimuli was analyzed before and after hypoxia exposure. Cellular ubiquitination, co-immunoprecipitation, GST-pulldown, in vitro protein kinase assay, immunofluorescence and CRISPR technology were adopted to determine the molecular mechanism underlying this process. In vivo characterization was performed in wild-type and DAPK1-/- mice models of cecal ligation and puncture (CLP). Results: We found that the MyD88-dependent inflammatory response couples to tubular damage during LPS stimuli under hypoxia in a Fn14/SCFFbxw7α-dispensable manner via recruitment of caspase-8 with TRIF-RIP1 signalosome mediated by DAPK1, which directly binds to and phosphorylates Pellino1 at Ser39, leading to Pellino1 poly-ubiquitination and turnover. Either pharmacological deactivation or genetic ablation of DAPK1 makes tubular cells refractory to the LPS-induced damage in the context of hypoxia, while kinase activity of DAPK1 is essential for ruin execution. Targeting DAPK1 effectively protects mice against septic AKI and potentiates the efficacy of a MyD88 homodimerization inhibitor, ST2825. Conclusion: Our findings provide a rationale for the mechanism whereby inflammation intersects with hypoxic tubular damage during septic AKI through a previously unappreciated role of DAPK1-inducible Ser39 phosphorylation in Pellino1 turnover and underscore that combined targeting DAPK1 and MyD88 might be a feasible strategy for septic AKI management.

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.