Non-canonical NFκB activation promotes chemokine expression in podocytes

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.Grants support: FEDER funds and FIS ISCIII-RETIC REDinREN RD12/0021, PI15/00298, PI13/00047, CP14/00133, CP12/03262, Spanish Society of Nephrology, FRIAT-IRSIN, Comunidad de Madrid (CIFRA S2010/ BMD-2378), CYTED IBERERC, Programa Intensificación Actividad Investigadora (ISCIII) to AO, Miguel Servet to MDSN and ABS and FIS to LVR and LG

A polymeric nanomedicine diminishes inflammatory events in renal tubular cells

The polyglutamic acid/peptoid 1 (QM56) nanoconjugate inhibits apoptosis by interfering with Apaf-1 binding to procaspase-9. We now describe anti-inflammatory properties of QM56 in mouse kidney and renal cell models. In cultured murine tubular cells, QM56 inhibited the inflammatory response to Tweak, a non-apoptotic stimulus. Tweak induced MCP-1 and Rantes synthesis through JAK2 kinase and NF-kB activation. Similar to JAK2 kinase inhibitors, QM56 inhibited Tweak-induced NF-kB transcriptional activity and chemokine expression, despite failing to inhibit NF-kB-p65 nuclear translocation and NF-kB DNA binding. QM56 prevented JAK2 activation and NF-kB-p65(Ser536) phosphorylation. The anti-inflammatory effect and JAK2 inhibition by QM56 were observed in Apaf-12/2 cells. In murine acute kidney injury, QM56 decreased tubular cell apoptosis and kidney inflammation as measured by downmodulations of MCP-1 and Rantes mRNA expression, immune cell infiltration and activation of the JAK2-dependent inflammatory pathway. In conclusion, QM56 has an anti-inflammatory activity which is independent from its role as inhibitor of Apaf-1 and apoptosis and may have potential therapeutic relevance.This work was supported by grants from the Instituto de Salud Carlos III (www.isciii.es), FIS: PI07/0020, CP08/1083, PS09/00447 and ISCIII-RETICS REDINREN RD 06/0016; Sociedad Española de Nefrología (www.senefro.org). Álvaro Ucero, Sergio Berzal and Carlos Ocaña supported by Fundacion Conchita Rabago (www.fundacionconchitarabago.net), Alberto Ortiz by the Programa de Intensificación de la Actividad Investigadora in the Sistema Nacional de Salud of the Instituto de Salud Carlos III and the Agencia ‘‘Pedro Lain Entralgo’’ of the Comunidad de Madrid and CIFRA S-BIO 0283/2006 www.madrid.org/lainentralgo) and Adrián Ramos, by FIS (Programa Miguel Servet)

The inflammatory cytokine TWEAK decreases PGC-1α expression and mitochondrial function in acute kidney injury

Studies of mitochondria-targeted nephroprotective agents suggest a key role of mitochondrial injury in AKI. Here we tested whether an improved perception of factors responsible for mitochondrial biogenesis may provide clues to novel therapeutic approaches to AKI. TWEAK is an inflammatory cytokine which is upregulated in AKI. Transcriptomic analysis of TWEAK-stimulated cultured murine tubular epithelial cells and folic acid-induced AKI in mice identified downregulation of peroxisome proliferator- activated receptor-γ coactivador-1α (PGC-1α) and its target genes (mitochondrial proteins Ndufs1, Sdha, and Tfam) as a shared feature. Neutralizing anti-TWEAK antibodies prevented the decrease in kidney PGC-1α and its targets during AKI. TWEAK stimulation decreased kidney PGC-1α expression in healthy mice and decreased expression of PGC-1α and its targets as well as mitochondrial membrane potential in cultured tubular cells. Adenoviral-mediated PGC-1α overexpression prevented TWEAK-induced downregulation of PGC-1α-dependent genes and the decrease in mitochondrial membrane potential. TWEAK promoted histone H3 deacetylation at the murine PGC-1α promoter. TWEAK-induced downregulation of PGC-1α was prevented by histone deacetylase or NF-κB inhibitors. Thus, TWEAK decreases PGC-1α and target gene expression in tubular cells in vivo and in vitro. Approaches that preserve mitochondrial function during kidney injury may be therapeutic for AKI.This study was supported by ISCIII and FEDER funds PI13/00047, PIE13/00051, EUTOX, CP12/03262, CP14-00133, FRIAT Sociedad Española de Nefrología, ISCIII-RETIC REDinREN RD012/0021, and Comunidad de Madrid CIFRA S2010/BMD-2378. The salary support was as follows: F.P.U. to OR-A, ISCIII Miguel Servet MS12/03262 to ABS and MS14/00133 MDS-N, and Programa Intensificación Actividad Investigadora (ISCIII/Agencia Laín-Entralgo/CM) to AO.Peer Reviewe

PGC-1α deficiency causes spontaneous kidney inflammation and increases the severity of nephrotoxic AKI

PGC‐1α (peroxisome proliferator‐activated receptor gamma coactivator‐1α, PPARGC1A) regulates the expression of genes involved in energy homeostasis and mitochondrial biogenesis. Here we identify inactivation of the transcriptional regulator PGC‐1α as a landmark for experimental nephrotoxic acute kidney injury (AKI) and describe the in vivo consequences of PGC‐1α deficiency over inflammation and cell death in kidney injury. Kidney transcriptomic analyses of WT mice with folic acid‐induced AKI revealed 1398 up‐ and 1627 downregulated genes. Upstream transcriptional regulator analyses pointed to PGC‐1α as the transcription factor potentially driving the observed expression changes with the highest reduction in activity. Reduced PGC‐1α expression was shared by human kidney injury. Ppargc1a−/− mice had spontaneous subclinical kidney injury characterized by tubulointerstitial inflammation and increased Ngal expression. Upon AKI, Ppargc1a−/− mice had lower survival and more severe loss of renal function, tubular injury, and reduction in expression of mitochondrial PGC‐1α‐dependent genes in the kidney, and an earlier decrease in mitochondrial mass than WT mice. Additionally, surviving Ppargc1a−/− mice showed higher rates of tubular cell death, compensatory proliferation, expression of proinflammatory cytokines, NF‐κB activation, and interstitial inflammatory cell infiltration. Specifically, Ppargc1a−/− mice displayed increased M1 and decreased M2 responses and expression of the anti‐inflammatory cytokine IL‐10. In cultured renal tubular cells, PGC‐1α targeting promoted spontaneous cell death and proinflammatory responses. In conclusion, PGC‐1α inactivation is a key driver of the gene expression response in nephrotoxic AKI and PGC‐1α deficiency promotes a spontaneous inflammatory kidney response that is magnified during AKI.Sandra Zazo and Federico Rojo of the IIS‐FJD Biobank (B.0000647). FIS/Fondos FEDER (PI15/00298, CP14/00133, PI16/02057, PI16/01900, ISCIII‐RETIC REDinREN RD016/0009), Sociedad Española de Nefrología, FRIAT, Comunidad de Madrid en Biomedicina B2017/BMD‐3686 CIFRA2‐CM. Grants from the Spanish ‘Ministerio de Economía Industria y Competitividad’ (MINEICO) and FEDER funds (Grant numbers SAF2015‐63904‐R, SAF2015‐71521‐REDC), and from the EC H2020 framework program Grant MSCA‐ITN‐2016‐721236 to MM. Salary support: ISCIII Miguel Servet and to ABS and MDS‐N. ISCIII Sara Borrell to JM‐MM, and Fundación Conchita Rabago to DMS. Consejería de Educación, Juventud y Deporte (Comunidad de Madrid/FSE) to MF‐B.Peer reviewe