MicroRNAs Predict and Regulate Heme Oxygenase-1 Expression

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The shortage of organs available for donation has resulted in the increased use of organs from deceased donors. These organs endure a relatively prolonged period without an adequate blood supply and subsequently become injured (ischaemia reperfusion injury (IRI)). IRI is associated with reduced function of the transplanted kidney immediately following transplantation and long term is associated with increased rates of transplant loss. The drug heme arginate (HA) increases the natural protective enzyme heme oxygenase-1 (HO-1), resulting in a wide range of beneficial effects in studies examining inflammation and IRI. In particular, increases in HO-1 in the white blood immune cells 'monocytes' and their derived tissue cells 'macrophages' appear to be important for protection. There are now a number of registered clinical trials assessing the use of HA in the treatment of inflammatory conditions including pancreatitis, diabetes and renal transplantation (HOT1 study). In the upcoming multicentre 'HOT2' trial, the effect of HA on kidney transplant function in the early post-operative period will be determined.In the HOT1 study, we noted that individuals responded variably to HA treatment, with some individuals generating higher levels of in HO-1 in blood monocytes. We have found that multiple small RNA molecules 'microRNAs' (miRs) are strongly associated with individual HO-1 response to treatment. As differences in blood miRs are evident prior to treatment, we believe that this 'miR signature' may predict treatment response and therefore could be used to personalise treatment to the individual. We also hypothesise that these miRs may regulate drug effects by interfering with the molecular pathway of HO-1 in monocytes and macrophages. By unpicking the action of these miRs, we may identify novel therapeutic targets in the regulation of HO-1. In this study, we plan to investigate the role of miRs in a subset of kidney transplant patients recruited to the 'HOT2' clinical trial. We will determine whether our miR signature can predict HO-1 upregulation following HA treatment in the monocytes of kidney transplant patients. We will determine whether our miR signature is applicable to other populations by examining stored samples from 2 previous clinical trials where HA was given to patients undergoing liver and cardiac surgery. Determining this may allow us to personalise HA treatment to those likely to respond in future. MiRs are known to suppress gene expression. We will use cell culture experiments using human macrophages to examine the mechanism in which these miRs regulate HO-1 expression following HA treatment. We will both increase and block the expression of key miRs before HA treatment, to see if this influences HO-1 response. We will also test factors which may regulate the expression of these miRs. This may allow us to identify novel regulators of HO-1 which could potentially be exploited as therapeutic targets in future. This research will be conducted in the internationally renowned Queens Margaret Research Institute (QMRI) in Edinburgh which is adjacent to the Royal Infirmary of Edinburgh (RIE). The RIE is the lead centre for the HOT2 study and is supported by the Edinburgh Clinical Trials Unit. This will allow us to recruit patients and analyse samples on the same site. The QMRI is home to experts in macrophages, microRNAs, HO-1 and has supported 3 clinical trials using HA to completion previously. The local expertise available, will assist us in delivering this proposal. This is a novel and exiting area of research with potential benefits to both renal transplant patients and the wider population. Determining if this miR signature can be used to personalise medicine is of potential immediate benefit to patients, whilst unpicking the mechanism in which miRs regulate HO-1 may allow the development new treatments that can upregulate HO-1 in all patients.