RIPK3 and kidney disease / RIPK3 y nefropatía

Receptor interacting protein kinase 3 (RIPK3) is an intracellular kinase at the crossroads of cell death and inflammation. RIPK3 contains a RIP homotypic interaction motif (RHIM) domain which allows interactions with other RHIM-containing proteins and a kinase domain that allows phosphorylation of target proteins. RIPK3 may be activated through interaction with RHIM-containing proteins such as RIPK1, TRIF and DAI (ZBP1, DLM-1) or through RHIM-independent mechanisms in an alkaline intracellular pH. RIPK3 mediates necroptosis and promotes inflammation, independently of necroptosis, through either activation of NFκB or the inflammasome. There is in vivo preclinical evidence of the contribution of RIPK3 to both acute kidney injury (AKI) and chronic kidney disease (CKD) and to the AKI-to-CKD transition derived from RIPK3 deficient mice or the use of small molecule RIPK3 inhibitors. In these studies, RIPK3 targeting decreased inflammation but kidney injury improved only in some contexts. Clinical translation of these findings has been delayed by the potential of some small molecule inhibitors of RIPK3 kinase activity to trigger apoptotic cell death by inducing conformational changes of the protein. A better understanding of the conformational changes in RIPK3 that trigger apoptosis, dual RIPK3/RIPK1 inhibitors or repurposing of multiple kinase inhibitors such as dabrafenib may facilitate clinical development of the RIPK3 inhibition concept for diverse inflammatory diseases, including kidney diseases (AU)

La proteína quinasa 3 que interactúa con el receptor (RIPK3) es una quinasa intracelular que se encuentra a medio camino entre la muerte celular y la inflamación. La RIPK3 contiene un dominio motivo de interacción homotípica de RIP (RHIM), que permite las interacciones con otras proteínas que contienen RHIM, y un dominio de quinasa que permite la fosforilación de las proteínas diana. La RIPK3 puede ser activada a través de la interacción con las proteínas que contienen RHIM tales como RIPK1, TRIF y DAI (ZBP1, DLM-1), o a través de mecanismos independientes de RHIM en un pH intracelular alcalino. La RIPK3 media en la necroptosis y promueve la inflamación, independientemente de la necroptosis, bien a través de la activación de NFκB, o del inflamasoma. Existe evidencia preclínica in vivo de la contribución de RIPK3 a la insuficiencia renal aguda (IRA) y la enfermedad renal crónica (ERC), así como a la transición IRA-ERC derivada de ratones con deficiencia de RIPK3 o del uso de pequeñas moléculas inhibidoras de RIPK3. En dichos estudios, el tener a RIPK3 como objetivo redujo la inflamación, pero la nefropatía mejoró solo en algunos contextos. La traducción clínica de estos hallazgos se ha demorado debido al potencial de ciertas pequeñas moléculas inhibidoras de la actividad de la quinasa RIPK3 para activar la muerte celular induciendo cambios conformacionales de la proteína. Comprender mejor los cambios conformacionales de RIPK3 activadores de la apoptosis, los inhibidores duales RIPK3/RIPK1 o la reconversión de múltiples inhibidores de la quinasa tales como dabrafenib podría facilitar el desarrollo clínico del concepto de la inhibición de RIPK3 para diversas enfermedades inflamatorias, incluyendo las enfermedades renales (AU)

RIPK3 and kidney disease.

Receptor interacting protein kinase 3 (RIPK3) is an intracellular kinase at the crossroads of cell death and inflammation. RIPK3 contains a RIP homotypic interaction motif (RHIM) domain which allows interactions with other RHIM-containing proteins and a kinase domain that allows phosphorylation of target proteins. RIPK3 may be activated through interaction with RHIM-containing proteins such as RIPK1, TRIF and DAI (ZBP1, DLM-1) or through RHIM-independent mechanisms in an alkaline intracellular pH. RIPK3 mediates necroptosis and promotes inflammation, independently of necroptosis, through either activation of NFκB or the inflammasome. There is in vivo preclinical evidence of the contribution of RIPK3 to both acute kidney injury (AKI) and chronic kidney disease (CKD) and to the AKI-to-CKD transition derived from RIPK3 deficient mice or the use of small molecule RIPK3 inhibitors. In these studies, RIPK3 targeting decreased inflammation but kidney injury improved only in some contexts. Clinical translation of these findings has been delayed by the potential of some small molecule inhibitors of RIPK3 kinase activity to trigger apoptotic cell death by inducing conformational changes of the protein. A better understanding of the conformational changes in RIPK3 that trigger apoptosis, dual RIPK3/RIPK1 inhibitors or repurposing of multiple kinase inhibitors such as dabrafenib may facilitate clinical development of the RIPK3 inhibition concept for diverse inflammatory diseases, including kidney diseases.

Tubular Mitochondrial Dysfunction, Oxidative Stress, and Progression of Chronic Kidney Disease.

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected conditions, and CKD is projected to become the fifth leading global cause of death by 2040. New therapeutic approaches are needed. Mitochondrial dysfunction and oxidative stress have emerged as drivers of kidney injury in acute and chronic settings, promoting the AKI-to-CKD transition. In this work, we review the role of mitochondrial dysfunction and oxidative stress in AKI and CKD progression and discuss novel therapeutic approaches. Specifically, evidence for mitochondrial dysfunction in diverse models of AKI (nephrotoxicity, cytokine storm, and ischemia-reperfusion injury) and CKD (diabetic kidney disease, glomerulopathies) is discussed; the clinical implications of novel information on the key role of mitochondria-related transcriptional regulators peroxisome proliferator-activated receptor gamma coactivator 1-alpha, transcription factor EB (PGC-1α, TFEB), and carnitine palmitoyl-transferase 1A (CPT1A) in kidney disease are addressed; the current status of the clinical development of therapeutic approaches targeting mitochondria are updated; and barriers to the clinical development of mitochondria-targeted interventions are discussed, including the lack of clinical diagnostic tests that allow us to categorize the baseline renal mitochondrial dysfunction/mitochondrial oxidative stress and to monitor its response to therapeutic intervention. Finally, key milestones for further research are proposed.

Bone Marrow-Derived RIPK3 Mediates Kidney Inflammation in Acute Kidney Injury.

BACKGROUND: Receptor-interacting protein kinase 3 (RIPK3), a component of necroptosis pathways, may have an independent role in inflammation. It has been unclear which RIPK3-expressing cells are responsible for the anti-inflammatory effect of overall Ripk3 deficiency and whether Ripk3 deficiency protects against kidney inflammation occurring in the absence of tubular cell death. METHODS: We used chimeric mice with bone marrow from wild-type and Ripk3-knockout mice to explore RIPK3's contribution to kidney inflammation in the presence of folic acid-induced acute kidney injury AKI (FA-AKI) or absence of AKI and kidney cell death (as seen in systemic administration of the cytokine TNF-like weak inducer of apoptosis [TWEAK]). RESULTS: Tubular and interstitial cell RIPK3 expressions were increased in murine AKI. Ripk3 deficiency decreased NF-κB activation and kidney inflammation in FA-AKI but did not prevent kidney failure. In the chimeric mice, RIPK3-expressing bone marrow-derived cells were required for early inflammation in FA-AKI. The NLRP3 inflammasome was not involved in RIPK3's proinflammatory effect. Systemic TWEAK administration induced kidney inflammation in wild-type but not Ripk3-deficient mice. In cell cultures, TWEAK increased RIPK3 expression in bone marrow-derived macrophages and tubular cells. RIPK3 mediated TWEAK-induced NF-κB activation and inflammatory responses in bone marrow-derived macrophages and dendritic cells and in Jurkat T cells; however, in tubular cells, RIPK3 mediated only TWEAK-induced Il-6 expression. Furthermore, conditioned media from TWEAK-exposed wild-type macrophages, but not from Ripk3-deficient macrophages, promoted proinflammatory responses in cultured tubular cells. CONCLUSIONS: RIPK3 mediates kidney inflammation independently from tubular cell death. Specific targeting of bone marrow-derived RIPK3 may limit kidney inflammation without the potential adverse effects of systemic RIPK3 targeting.

Nicotinamide and acute kidney injury.

In a recent issue of ckj, Piedrafita et al. reported that urine tryptophan and kynurenine are reduced in cardiac bypass surgery patients that develop acute kidney injury (AKI), suggesting reduced activity of the kynurenine pathway of nicotinamide (NAM) adenine dinucleotide (NAD+) synthesis from tryptophan. However, NAM supplementation aiming at repleting NAD+ did not replete kidney NAD+ and did not improve glomerular filtration or reduce histological injury in ischaemic-reperfusion kidney injury in mice. The lack of improvement of kidney injury is partially at odds with prior reports that did not study kidney NAD+, glomerular filtration or histology in NAM-treated wild-type mice with AKI. We now present an overview of research on therapy with vitamin B3 vitamers and derivate molecules {niacin, Nicotinamide [NAM; niacinamide], NAM riboside [Nicotinamide riboside (NR)], Reduced nicotinamide riboside [NRH] and NAM mononucleotide} in kidney injury, including an overview of ongoing clinical trials, and discuss the potential explanations for diverging reports on the impact of these therapeutic approaches on pre-clinical acute and chronic kidney disease.

Urinary Cyclophilin A as Marker of Tubular Cell Death and Kidney Injury.

Background: Despite the term acute kidney injury (AKI), clinical biomarkers for AKI reflect function rather than injury and independent markers of injury are needed. Tubular cell death, including necroptotic cell death, is a key feature of AKI. Cyclophilin A (CypA) is an intracellular protein that has been reported to be released during necroptosis. We have now explored CypA as a potential marker for kidney injury in cultured tubular cells and in clinical settings of ischemia-reperfusion injury (IRI), characterized by limitations of current diagnostic criteria for AKI. Methods: CypA was analyzed in cultured human and murine proximal tubular epithelial cells exposed to chemical hypoxia, hypoxia/reoxygenation (H/R) or other cell death (apoptosis, necroptosis, ferroptosis) inducers. Urinary levels of CypA (uCypA) were analyzed in patients after nephron sparing surgery (NSS) in which the contralateral kidney is not disturbed and kidney grafts with initial function. Results: Intracellular CypA remained unchanged while supernatant CypA increased in parallel to cell death induction. uCypA levels were higher in NSS patients with renal artery clamping (that is, with NSS-IRI) than in no clamping (NSS-no IRI), and in kidney transplantation (KT) recipients (KT-IRI) even in the presence of preserved or improving kidney function, while this was not the case for urinary Neutrophil gelatinase-associated lipocalin (NGAL). Furthermore, higher uCypA levels in NSS patients were associated with longer surgery duration and the incidence of AKI increased from 10% when using serum creatinine (sCr) or urinary output criteria to 36% when using high uCypA levels in NNS clamping patients. Conclusions: CypA is released by kidney tubular cells during different forms of cell death, and uCypA increased during IRI-induced clinical kidney injury independently from kidney function parameters. Thus, uCypA is a potential biomarker of kidney injury, which is independent from decreased kidney function.