Remote liver injury following acute renal ischaemia-reperfusion: involvement of circulating exosomal miR-687 and regulation by thymoquinone.

NEW FINDINGS: What is the central question of this study? What is the role of circulating exosomal miR-687 in remote hepatic injury following renal ischaemia-reperfusion injury (IRI) and does thymoquinone have a modulatory impact? What is the main finding and its importance? Exosomal miR-687 was expressed in renal IRI, entered the circulation and was deposited in the liver. Liver exosomal miR-687 was correlated with liver inflammation and apoptosis. Thymoquinone aborted the renal production of exosomal miR-687 and its further circulation to the liver. ABSTRACT: The pathophysiology of remote hepatic injury following acute renal ischaemia-reperfusion injury (IRI) is of particular clinical interest. Secreted small non-coding microRNA (miRs) are thought to exist in exosome-encapsulated form. Thymoquinone (TQ) is the main bioactive ingredient of Nigella sativa and has several renoprotective actions. We expected exosomal miR-687 to be relevant as it could act as a humoral mediator, with possible modulation by TQ. Thirty adult male Wister albino rats were assigned to three groups (n = 10); (1) sham-operated, (2) renal ischaemia-reperfusion injury (IRI), and (3) renal IRI pre-treated with TQ 10 mg/kg/day i.v. (TQ-IRI) for 10 days in addition to a dose administered at reperfusion onset. Following 24 h of reperfusion, the IRI group showed renal tissue hypoxia-inducible factor upregulation (P < 0.001). Electron microscopy images of exosomes and analysis of miR-687 revealed elevated levels, which appeared in the circulation. Large amounts of exosomal miR-687 were transmitted to the liver tissue. In the IRI group, liver transaminases (alanine aminotransferase, aspartate aminotransferase) were markedly (P < 0.001) elevated. The hepatic tissue inflammatory markers (vascular cell adhesion molecule-1, myeloperoxidase, monocyte chemotactic protein-1 and nuclear factor-κB) were upregulated (P < 0.001) accompanied with elevated caspase-3. TQ suppressed (P < 0.001) the renal expression and release of exosomal miR-687 into the circulation and its further deposition in the liver tissue; consequently, TQ diminished (P < 0.001) liver tissue inflammation and cellular apoptosis. The results were confirmed by histological tissue assessment. In conclusion, exosomal miR-687 liberated from injured renal tissues into the circulation may be an important factor in inducing remote hepatic injury. Exosomal miR-687 inhibition by TQ protected both renal and hepatic tissues from injury.

Thymoquinone ameliorates acute kidney injury induced by renal ischemia-reperfusion / La timoquinona mejora la lesión renal aguda inducida por isquemia-reperfusión renal

SUMMARY: Renal ischemia-reperfusion injury (IRI)is an unavoidable consequence in renal transplantation and multiple clinical settings. A debate has been raised about the particular role of hypoxia-inducible factor (HF-1α) in the renal injury pathogenesis and the renal cortex ultrastructural alterations. Also, we investigated the antioxidant/anti-inflammatory effect of thymoquinone and its modulatory role on HIF-1α in protection against renal IRI.Adult male Wister albino rats were assigned into 3 groups (n=16); 1) Sham-operated, 2) IRI model and 3) renal IRI pre-treated with thymoquinone 10 mg.kg-1.day-1 (TQ-IRI) for 10 days and at the reperfusion onset. Following the operation, 8 rats from each group were euthanized after 3 hours and the remaining 8 rats at 24 hours. Renal injury was assessed by the increased blood urea nitrogen, creatinine level, and the EGTI histological injury scoreat both 3 and 24h. HIF-1α was upregulated (p<0.01) and was correlated with renal tissue reactive oxygen species (ROS) production and total oxidant capacity (TAC) consumption. Elevated inflammatory markers (NFkB, MCP-1 and VCAM-1) were associated with renal IRI.Thymoquinone treatment inhibited the accumulation of HIF-1α (p<0.01), reduced renal oxidation/inflammation process and markedly diminished renal injury.

RESUMEN: La lesión por isquemia-reperfusión renal (IRR) es una consecuencia inevitable en el trasplante renal como también en múltiples contextos clínicos. Se ha suscitado una discusión referente a la relación particular del factor inducible por hipoxia (HF- 1α) en la patogénesis de la lesión renal y las alteraciones ultraestructurales de la corteza renal. Además, investigamos el efecto antioxidante / antiinflamatorio de la timoquinona y su papel modulador sobre HIF-1α en la protección contra IRR. Se utilizaron ratas albinas Wister macho adultas divididas en 3 grupos (n = 16); 1) Intervención simulada, 2) modelo IRR y 3) IRR pretratado con timoquinona 10 mg/kg-1. día-1 (TQ-IRR) durante 10 días y al inicio de la reperfusión. Posterior a la operación, 8 ratas de cada grupo fueron sacrificadas después de 3 horas y las 8 ratas restantes a las 24 horas. La lesión renal se evaluó por el aumento de nitrógeno ureico en sangre, el nivel de creatinina y la puntuación de lesión histológica EGTI tanto a las 3 como a las 24 horas. HIF-1α se incrementó (p <0,01) y se correlacionó con la producción de especies de oxígeno reactivo (ROS) del tejido renal y el consumo de capacidad oxidante total. Los marcadores inflamatorios elevados (NFkB, MCP-1 y VCAM-1) se asociaron con IRR. El tratamiento con timoquinona inhibió la acumulación de HIF-1α (p <0,01), redujo el proceso de oxidación / inflamación renal y disminuyó notablemente la lesión renal.