#1181 The relationship between renal ischaemia-reperfusion injury and circadian rhythm

Abstract Background and Aims Kidney disease is a global health problem in which various aetiologies contribute to renal injury and dysfunction. Renal ischaemia-reperfusion injury (IRI) is a condition caused by early oxidative stress due to renal tissue ischaemia and a rapid immune response after reperfusion. Circadian rhythms are important regulators of metabolism and their disruption can lead to heart disease and fibrosis in various organs. Although recent reports have shed light on the impact of renal injury and disease on the renal circadian clock, the exact mechanisms by which circadian rhythm genes contribute to the progression of renal dysfunction in IRI and the onset of chronic kidney disease (CKD) are not fully understood. Method Male Wistar rats (8-9 weeks old, 250-280 g body weight) were used to establish the I/R model. To induce renal I/R injury, the left renal artery was clamped for 30 or 45 min and then removed to restore blood flow. Simultaneously, nephrectomy of the right kidney was performed; renal tissue and blood were collected 14 days after I/R. HE staining, Sirius red staining and immunostaining (F4/80 staining) were performed. Kidney tissue was RNA-seq'd and qPCR'd for circadian rhythm genes and fibrosis genes involved in kidney failure that were altered by I/R. Kidney tissue was also RNA-seq'd and qPCR'd for circadian rhythm genes and fibrosis genes involved in kidney failure. We also established an in vitro hypoxia-reoxygenation (H/R) model using single cell RPTECs and performed qPCR and Western blotting. Results In the IRI rat group, the expression of circadian repressor genes Nr1d1 and Nr1d2, which are important for reducing inflammation, decreased, while the expression of Bmal1 and Cry1, which regulate renal deterioration, increased. Using RNA-seq, we also identified the involvement of the TGFβ pathway in linking the circadian clock to kidney injury and fibrosis, and observed similar results in the H/R group using RPTEC cells in vivo. Conclusion Fibrosis and circadian rhythms were found to be closely related in renal IRI. The findings described here may help in the development of new therapeutic approaches to ameliorate the effects of renal IRI and improve the outcome of kidney disease, including kidney transplantation, offering hope to patients worldwide.