Renal Integrin-Linked Kinase Depletion Induces Kidney cGMP-Axis Upregulation: Consequences on Basal and Acutely Damaged Renal Function.

Soluble guanylyl cyclase (sGC) is activated by nitric oxide (NO) and produces cGMP, which activates cGMP-dependent protein kinases (PKG) and is hydrolyzed by specific phosphodiesterases (PDE). The vasodilatory and cytoprotective capacity of cGMP-axis activation results in a therapeutic strategy for several pathologies. Integrin-linked kinase (ILK), a major scaffold protein between the extracellular matrix and intracellular signaling pathways, may modulate the expression and functionality of the cGMP-axis-related proteins. We introduce ILK as a novel modulator in renal homeostasis as well as a potential target for cisplatin (CIS)-induced acute kidney injury (AKI) improvement. We used an adult mice model of depletion of ILK (cKD-ILK), which showed basal increase of sGC and PKG expressions and activities in renal cortex when compared with wildtype (WT) littermates. Twenty-four h activation of sGC activation with NO enhanced the filtration rate in cKD-ILK. During AKI, cKD-ILK maintained the cGMP-axis upregulation with consequent filtration rates enhancement and ameliorated CIS-dependent tubular epithelial-to-mesenchymal transition and inflammation and markers. To emphasize the role of cGMP-axis upregulation due to ILK depletion, we modulated the cGMP axis under AKI in vivo and in renal cultured cells. A suboptimal dose of the PDE inhibitor ZAP enhanced the beneficial effects of the ILK depletion in AKI mice. On the other hand, CIS increased contractility-related events in cultured glomerular mesangial cells and necrosis rates in cultured tubular cells; ILK depletion protected the cells while sGC blockade with ODQ fully recovered the damage.

Contribución de las toxinas urémicas a la fibrosis vascular asociada a la enfermedad renal crónica / Contribution of uraemic toxins to the vascular fibrosis associated with chronic kidney disease

ANTECEDENTES: Los pacientes con enfermedad renal crónica presentan una acumulación de toxinas urémicas, las cuales han sido identificadas como agentes patogénicos asociados con la mortalidad cardiovascular, muy elevada en este grupo de enfermos. Un fenómeno común a la disfunción renal progresiva y al daño vascular asociado es la acumulación anormal de proteínas de la matriz extracelular (MEC) en las estructuras renales o vasculares. OBJETIVO: Estudiar la contribución de la uremia o las toxinas urémicas a la producción de citocinas y MEC en aortas de animales urémicos o células de músculo liso de aorta humana (HAOSMC). MATERIALES Y MÉTODOS: Se utilizaron ratones con uremia inducida por una dieta rica en adenina (0,2%) durante 2, 4 o 6 semanas. Se evaluó la función renal mediante la diuresis, los niveles plasmáticos de creatinina y nitrógeno ureico plasmático, y la excreción fraccional de sodio y el daño vascular mediante histología y expresión proteica por RT-qPCR. In vitro, las HAOSMC se incubaron con toxinas urémicas: p-cresol 10-100 (μg/ml) e indoxil-sulfato 25-100 (μg/ml), solas o simultáneamente. La expresión proteica se evaluó por Western blot y microscopia confocal. RESULTADOS: La administración de adenina produjo un progresivo daño renal en los ratones, un engrosamiento de la pared aórtica y un incremento de la expresión de TGF-Beta1 y proteínas de MEC. Las toxinas a dosis altas y combinadas también indujeron expresión de TGF-Beta1 y proteínas de MEC por las células HAOSMC. CONCLUSIONES: La uremia producida por una dieta rica en adenina o las dosis altas de toxinas urémicas indujeron el depósito anormal de proteínas de MEC en las paredes vasculares o su producción por HAOSMC. La comprensión de los mecanismos que subyacen a este proceso fisiopatológico puede resultar de utilidad en la prevención del daño cardiovascular asociado a la progresión de la enfermedad renal crónica, una dolencia, de momento, irreversible y, en ocasiones, silenciosa hasta su diagnóstico en etapas avanzadas

BACKGROUND: Patients with chronic kidney disease present with an accumulation of uraemic toxins, which have been identified as pathogenic agents associated with cardiovascular mortality, which is very high is this patient group. A phenomenon common to the progressive renal dysfunction and associated vascular damage, is the abnormal accumulation of extracellular matrix (ECM) proteins in the renal or vascular structures. OBJECTIVE: To determine the contribution of uraemia or the uraemic toxins to the production of cytokinins and ECM in aortas of uraemic animals or human aortic smooth muscle cells (HASMCs). MATERIALS AND METHODS: Mice were used with uraemia induced by a diet rich in adenine (0.2%) for 2, 4 or 6 weeks. Kidney function was evaluated by means of urine volume, plasma levels of creatinine, urea, fractional excretion of sodium, and vascular damage using histology, as well as protein expression using RT-qPCR. The HASMCs were incubated in vitro with uraemic toxins: p-cresol 10-100 (Mig/ml) and indoxyl-sulphate 25-100 (Mig/ml) alone or simultaneously. The protein expression was evaluated using Western blot and confocal microscopy. RESULTS: The administration of adenine produced progressive kidney damage in the mice, thickening of the aortic wall, and increasing the expression of TGF-Beta1 and ECM proteins. The toxins at high doses and combined also induced the expression of TGF-Beta1 and ECM proteins by the HASMCs. CONCLUSIONS: The uraemia produced by an adenine rich diet or high doses of uraemic toxins induced the abnormal deposit of ECM proteins in the vascular wall or its production by HASMCs. The understanding of the mechanisms that underlie this pathophysiological process may be useful in the prevention of cardiovascular damage associated with the progress of chronic kidney disease, a disease, at the moment that is irreversible and occasional silent until its diagnosis in advanced stages