Delayed Contralateral Nephrectomy Halted Post-Ischemic Renal Fibrosis Progression and Inhibited the Ischemia-Induced Fibromir Upregulation in Mice

Mitigating off-target effects of small RNAs: conventional approaches, network theory and artificial intelligence

Three types of highly promising small RNA therapeutics, namely, small interfering RNAs (siRNAs), microRNAs (miRNAs) and the RNA subtype of antisense oligonucleotides (ASOs), offer advantages over small-molecule drugs. These small RNAs can target any gene product, opening up new avenues of effective and safe therapeutic approaches for a wide range of diseases. In preclinical research, synthetic small RNAs play an essential role in the investigation of physiological and pathological pathways as silencers of specific genes, facilitating discovery and validation of drug targets in different conditions. Off-target effects of small RNAs, however, could make it difficult to interpret experimental results in the preclinical phase and may contribute to adverse events of small RNA therapeutics. Out of the two major types of off-target effects we focused on the hybridization-dependent, especially on the miRNA-like off-target effects. Our main aim was to discuss several approaches, including sequence design, chemical modifications and target prediction, to reduce hybridization-dependent off-target effects that should be considered even at the early development phase of small RNA therapy. Because there is no standard way of predicting hybridization-dependent off-target effects, this review provides an overview of all major state-of-the-art computational methods and proposes new approaches, such as the possible inclusion of network theory and artificial intelligence (AI) in the prediction workflows. Case studies and a concise survey of experimental methods for validating in silico predictions are also presented. These methods could contribute to interpret experimental results, to minimize off-target effects and hopefully to avoid off-target-related adverse events of small RNA therapeutics. LINKED ARTICLES: This article is part of a themed issue Non-coding RNA Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.2/issuetoc.

Focus on oliguria during renal replacement therapy

Oliguria is a clinical symptom characterized by decreased urine output, which can occur at any stage of acute kidney injury and also during renal replacement therapy. In some cases, oliguria may resolve with adjustment of blood purification dose or fluid management, while in others, it may suggest a need for further evaluation and intervention. It is important to determine the underlying cause of oliguria during renal replacement therapy and to develop an appropriate treatment plan. This review looks into the mechanisms of urine production to investigate the mechanism of oliguria during renal replacement therapy from two aspects: diminished glomerular filtration rate and tubular abnormalities. The above conditions all implying a renal oxygen supply-demand imbalance, which is the signal of worsening kidney injury. It also proposes a viable clinical pathway for the treatment and management of patients with acute kidney injury receiving renal replacement therapy.

Development of a Model of Tubulointerstitial Fibrosis Using Transient Unilateral Renal Ischemia and Delayed Contralateral Nephrectomy in Domesticated Cats

Tubulointerstitial fibrosis is a classic histologic feature of chronic kidney disease (CKD) in cats and a final common pathway toward end-stage renal disease. Domesticated cats have been used in models of ischemia-induced renal fibrosis. The objective of this study was to evaluate the performance of 2 variations of a transient unilateral renal ischemia and delayed contralateral nephrectomy model of tubulointerstitial fibrosis in cats. Purpose-bred, young adult, domesticated cats underwent 90 min of surgically induced ischemia to the right kidney followed by delayed contralateral nephrectomy performed 21 d (RI-CN21d group; n = 10) or 90 d postischemia (RI-CN90d group; n = 12). Control cats underwent sham surgery followed by left nephrectomy 21 d after (sham-CN group; n = 3). Renal functional parameters, including glomerular filtration rate and serum creatinine concentration, were evaluated before and after surgeries. The right kidneys were harvested 120 d postischemia/ sham. Renal histology with lesion scoring and histomorphometry for quantification of smooth muscle actin immunolabeling and collagen staining were performed on harvested kidneys. Severe acute kidney injury prompted euthanasia after left nephrectomy in 5/10 (50.0%), 2/12 (16.7%), and 0/3 (0%) of cats in the RI-CN21d, RI-CN90d, and sham-CN groups, respectively. A significant decrease in glomerular filtration rate by day 120, relative to baseline, occurred in cats in the RI-CN21d group (P < 0.001) and RI-CN90d group (P < 0.001) but not the sham-CN group (P = 0.76). All but one cat in the ischemia groups were azotemic at the study end. Kidneys subjected to ischemia had higher interstitial inflammation, tubular atrophy, and fibrosis scores compared with sham-operated kidneys. There were significant increases in smooth muscle actin immunolabeling and collagen staining in these kidneys, relative to the contralateral kidneys. In summary, 90 min of unilateral renal ischemia and delayed contralateral nephrectomy induced histologic and biochemical changes consistent with CKD in cats. A 90-d period between ischemia and nephrectomy resulted in improved survivability of the model.

YB-1 Is a Novel Target for the Inhibition of α-Adrenergic-Induced Hypertrophy

Cardiac hypertrophy resulting from sympathetic nervous system activation triggers the development of heart failure. The transcription factor Y-box binding protein 1 (YB-1) can interact with transcription factors involved in cardiac hypertrophy and may thereby interfere with the hypertrophy growth process. Therefore, the question arises as to whether YB-1 influences cardiomyocyte hypertrophy and might thereby influence the development of heart failure. YB-1 expression is downregulated in human heart biopsies of patients with ischemic cardiomyopathy (n = 8), leading to heart failure. To study the impact of reduced YB-1 in cardiac cells, we performed small interfering RNA (siRNA) experiments in H9C2 cells as well as in adult cardiomyocytes (CMs) of rats. The specificity of YB-1 siRNA was analyzed by a miRNA-like off-target prediction assay identifying potential genes. Testing three high-scoring genes by transfecting cardiac cells with YB-1 siRNA did not result in downregulation of these genes in contrast to YB-1, whose downregulation increased hypertrophic growth. Hypertrophic growth was mediated by PI3K under PE stimulation, as well by downregulation with YB-1 siRNA. On the other hand, overexpression of YB-1 in CMs, caused by infection with an adenovirus encoding YB-1 (AdYB-1), prevented hypertrophic growth under α-adrenergic stimulation with phenylephrine (PE), but not under stimulation with growth differentiation factor 15 (GDF15; n = 10-16). An adenovirus encoding the green fluorescent protein (AdGFP) served as the control. YB-1 overexpression enhanced the mRNA expression of the Gq inhibitor regulator of G-protein signaling 2 (RGS2) under PE stimulation (n = 6), potentially explaining its inhibitory effect on PE-induced hypertrophic growth. This study shows that YB-1 protects cardiomyocytes against PE-induced hypertrophic growth. Like in human end-stage heart failure, YB-1 downregulation may cause the heart to lose its protection against hypertrophic stimuli and progress to heart failure. Therefore, the transcription factor YB-1 is a pivotal signaling molecule, providing perspectives for therapeutic approaches.

Permissive azotemia during acute kidney injury enables more rapid renal recovery and less renal fibrosis: a hypothesis and clinical development plan

Preclinical models of acute kidney injury (AKI) consistently demonstrate that a uremic milieu enhances renal recovery and decreases kidney fibrosis. Similarly, significant decreases in monocyte/macrophage infiltration, complement levels, and other markers of inflammation in the injured kidney are observed across multiple studies and species. In essence, decreased renal clearance has the surprising and counterintuitive effect of being an effective treatment for AKI. In this Perspective, the author suggests a hypothesis describing why the uremic milieu is kidney protective and proposes a clinical trial of 'permissive azotemia' to improve renal recovery and long-term renal outcomes in critically ill patients with severe AKI.