Abstract
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.
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.