Identification of urinary microRNA profiles in rats that may diagnose hepatotoxicity

Human miRNome profiling identifies microRNAs differentially present in the urine after kidney injury

BACKGROUND

Extracellular microRNAs (miRNAs) have been proposed as potentially robust and stable biomarkers of various disease conditions. The primary objective of this study was to identify miRNAs differentially occurring in the urine that could serve as potential biomarkers of acute kidney injury (AKI), because traditional AKI markers have limitations with respect to sensitivity, specificity, and timeliness of diagnosis.

METHODS

We profiled 1809 miRNAs in pooled urine samples from 6 patients with AKI and from 6 healthy controls. We measured the 378 stably detectable miRNAs in the 12 samples individually and selected the top 7 miRNAs that were most different in the urine of patients with AKI compared with the non-AKI control individuals. These miRNAs were assessed in a larger cohort of patients with AKI (n = 98: 71 AKI patients in the intensive care unit (ICU) and 27 kidney transplantation patients with biopsy-proven tubular injury) and patients without AKI (n = 97: 74 healthy volunteers and 23 ICU patients without AKI).

RESULTS

We identified 4 miRNAs capable of significantly differentiating patients with AKI from individuals without AKI: miR-21 (P = 0.0005), miR-200c (P < 0.0001), miR-423 (P = 0.001), and miR-4640 (P = 0.0355). The combined cross-validated area under the ROC curve for these 4 miRNAs was 0.91. The imprecision with respect to miRNA isolation and reverse transcription efficiency was <9% across 224 samples.

CONCLUSIONS

In this study we determined the entire miRNome of human urine and identified a panel of miRNAs that are both detectable noninvasively and diagnostically sensitive indicators of kidney damage.

Hopes and challenges in using miRNAs as translational biomarkers for drug-induced liver injury

There is a need for better biomarkers of drug-induced liver injury (DILI) to guide risk assessment and patient management. Over the past 3 years, both animal and clinical studies have provided proof-of-concept data showing that a subset of miRNAs appear to offer unique advantages over the conventional DILI biomarkers, such as enhanced sensitivity and specificity, reduced inter-individual variations, the potential to differentiate lethal and nonlethal liver injury, and the ability to reflect the patterns and even the etiology of liver injury. Notably, many studies have demonstrated that level of miR-122, a liver-enriched miRNA accounting for approximately 70% of total hepatic miRNAs, was increased many fold in the blood when DILI occurred. However, currently available data are predominantly based on animal models and not human samples. Due to the lack of a standard quantification method for miRNAs and confirmatory studies using a comprehensive list of drugs and patients, the true value of all reported miRNA biomarkers remains to be carefully assessed. An outstanding challenge is to examine if miRNAs are also useful for idiosyncratic DILI, which constitutes the major part of clinical DILI cases but generally cannot be recapitulated in traditional animal models or in clinical trials (the latter due to its relative rarity).

Identification of endogenous reference genes for RT-qPCR analysis of plasma microRNAs levels in rats with acetaminophen-induced hepatotoxicity

Circulating microRNA (miRNA) expression profiles have been reported to be promising biomarkers for drug-induced liver injury in preclinical and clinical practice. Proper normalization is critical for accurate miRNAs expression analysis. Herein, using SYBR green quantitative real-time PCR (RT-qPCR), we evaluated the expression stability of six candidate reference genes including two commonly used small RNAs (U6, 5S) and four miRNAs (let-7a, miR-92a, miR-103 and miR-16) in plasma of rats with acetaminophen-induced hepatotoxicity. Data were analysed using geNorm, Normfinder, BestKeeper and comparative delta-Ct statistical models, and the results consistently show that miR-103 is the most stably expressed reference gene. Whereas the commonly used housekeeping genes 5S or U6 are all not suitable normalizers, because 5S exhibits extensive variability in expression and U6 has a low expression level across the plasma samples. Then the effect of reference genes on normalization of plasma miR-122 was assessed; when normalized to the most stable reference gene there were significant differences between the acetaminophen-treated group and the vehicle group. However, when the data were normalized to a less stably expressed gene, miR-16, a biased result was obtained. Therefore, we recommend that miR-103 as suitable reference gene for plasma miRNAs analysis for acetaminophen-induced liver injury. Data presented in this paper are crucial to successful biomarker discovery and validation for the diagnosis of the early stage of acetaminophen hepatotoxicity.

Diffuse and interstitial lung disease and childhood rheumatologic disorders

PURPOSE OF REVIEW

Advances in genetics and clinical diagnostics, along with recently described clinical entities and refined classification schemes, have improved our understanding of diffuse and interstitial lung diseases in children. This review presents recent updates in these disorders in the context of systemic inflammatory conditions.

RECENT FINDINGS

Classification of childhood diffuse lung disease (DLD) using adult paradigms is not useful. Distinct clinical-pathologic entities exist in children. Infants are more likely to present with genetic and developmental disorders, and older children with inflammatory and immune-mediated conditions. A combination of clinical evaluation, high-resolution computed tomography scanning, pulmonary function testing and serology, with bronchoscopy and surgical lung biopsy in selected cases, is most useful in the evaluation of DLD in the context of rheumatologic conditions. Common causes of DLD, such as infection, especially in the setting of immunodeficiency, must be ruled out. Optimal therapy for specific disorders will require careful analysis of data from national registries. Emerging use of biomarkers and high-throughput molecular analysis will yield novel insight into these disorders.

SUMMARY

In the setting of known or suspected rheumatologic disorders, diagnosis and management of DLD are challenging, and require close collaboration among rheumatologists, pulmonologists, and other specialists.

microRNAs as mediators of drug toxicity

microRNAs (miRNAs) represent the most abundant class of gene expression regulators that bind complementarily to transcripts to repress their translation or mRNA degradation. These small ( 21-23 nucleotides in length) noncoding RNAs are derived through a multistep process by miRNA genes located in genomic DNA. Because miRNAs regulate fundamental cellular functions, their dysregulation affects a large range of physiological processes, such as development, immune responses, metabolism, and diseases as well as toxicological outcomes. Cancer-related miRNAs have been extensively studied; however, the roles of miRNAs in xenobiotic metabolism and in toxicology have only recently been explored. This review focuses on the current knowledge of miRNA-dependent regulation of drug-metabolizing enzymes and nuclear receptors and the associated potential toxicological implications. The potential modulation of toxicology-related changes in miRNA expression, the role of miRNA in immune-mediated drug-induced liver injuries, the use of circulating miRNAs in body fluids as potential toxicological biomarkers, and the link between miRNA-related pharmacogenomics and adverse drug reactions are highlighted.

Evaluation of miR-122 and other biomarkers in distinct acute liver injury in rats

The detection of drug-induced hepatotoxicity remains an important safety issue in drug development. A liver-specific microRNA species, microRNA-122 (miR-122), has recently shown potential for predicting liver injury in addition to the standard hepatic injury biomarkers. The objective of this study was to measure miR-122 together with several other liver markers in distinct settings of acute liver toxicity in rats to determine the value of miR-122 as a biomarker for liver injury in this species. Rats were exposed to 3 well-established liver toxicants (acetaminophen, allyl alcohol, and α-naphthyl isothiocyanate), a liver-enzyme inducer (phenobarbital), or a cardiotoxicant (doxorubicin). There was a clear increase in plasma miR-122 following administration of acetaminophen, allyl alcohol, and α-naphthyl isothiocyanate. The response of miR-122 paralleled that of other markers and was consistent with liver injury as indicated by histopathological evaluation. Furthermore, the changes in miR-122 were detected earlier than standard liver injury markers and exhibited a wide dynamic range. In contrast, miR-122 responses to phenobarbital and doxorubicin were low. Based on these findings, miR-122 shows significant promise and may provide added value for assessing liver toxicity in drug development.

Expression, circulation, and excretion profile of microRNA-21, -155, and -18a following acute kidney injury

MicroRNAs (miRNAs) are endogenous noncoding RNA molecules that are involved in post-transcriptional gene silencing. Using global miRNA expression profiling, we found miR-21, -155, and 18a to be highly upregulated in rat kidneys following tubular injury induced by ischemia/reperfusion (I/R) or gentamicin administration. Mir-21 and -155 also showed decreased expression patterns in blood and urinary supernatants in both models of kidney injury. Furthermore, urinary levels of miR-21 increased 1.2-fold in patients with clinical diagnosis of acute kidney injury (AKI) (n = 22) as compared with healthy volunteers (n = 25) (p < 0.05), and miR-155 decreased 1.5-fold in patients with AKI (p < 0.01). We identified 29 messenger RNA core targets of these 3 miRNAs using the context likelihood of relatedness algorithm and found these predicted gene targets to be highly enriched for genes associated with apoptosis or cell proliferation. Taken together, these results suggest that miRNA-21 and -155 could potentially serve as translational biomarkers for detection of AKI and may play a critical role in the pathogenesis of kidney injury and tissue repair process.

Frontiers in preclinical safety biomarkers: microRNAs and messenger RNAs

The measurement of plasma microRNAs (miRNAs) and messenger RNAs (mRNAs) is the most recent effort to identify novel biomarkers in preclinical safety. These genomic markers often display tissue-specific expression, may be released from the tissues into the plasma during toxic events, change early and with high magnitude in tissues and in the blood during specific organ toxicities, and can be measured using multiplex formats. Their validation as biomarkers has been challenged by the technical difficulties. In particular, the concentration of miRNAs in the plasma depends on contamination by miRNAs originating from blood cells and platelets, and the relative fraction of miRNAs in complexes with Argonaute 2, high-density lipoproteins, and in exosomes and microvesicles. In spite of these hurdles, considerable progress has recently been made in assessing the potential value of miRNAs in the clinic, especially in cancer patients and cardiovascular diseases. The future of miRNAs and mRNAs as biomarkers of disease and organ toxicity depends on our ability to characterize their kinetics and to establish robust collection and measurement methods. This review covers the basic biology of miRNAs and the published literature on the use of miRNAs and mRNAs as biomarkers of specific target organ toxicity.