siRNA targeted to p53 attenuates ischemic and cisplatin-induced acute kidney injury

An Activatable Near-Infrared Fluorescence Probe for in Vivo Imaging of Acute Kidney Injury by Targeting Phosphatidylserine and Caspase-3

Renal-clearable and target-responsive near-infrared (NIR) fluorescent imaging probes have been promising for in vivo diagnosis of acute kidney injury (AKI). However, designing an imaging probe that is renal-clearable and concurrently responsive toward multiple molecular targets to facilitate early detection of AKI with improved sensitivity and specificity is challenging. Herein, by leveraging the receptor-mediated binding and retention effect along with enzyme-triggered fluorescence activation, we design and synthesize an activatable small-molecule NIR fluorescent probe (1-DPA2) using a "one-pot sequential click reaction" approach. 1-DPA2 can target both the externalized phosphatidylserine (PS) and active caspase-3 (Casp-3), two essential biomarkers of apoptosis, producing enhanced 808 nm NIR fluorescence and a high signal-to-background ratio (SBR) amenable to detecting the onset of cisplatin-induced AKI in mice as early as 24 h post-treatment with cisplatin. We not only monitor the gradual activation of Casp-3 in the kidney of mice upon AKI progression but also can report on the progressive recovery of kidney functions in AKI mice following N-acetyl-l-cysteine (NAC) therapy via real-time fluorescence imaging by 1-DPA2. This study demonstrates the ability of 1-DPA2 for longitudinal monitoring of renal cell apoptosis by concurrently targeting PS externalization and Casp-3 activation, which is efficient for early diagnosis of AKI and useful for prediction of potential drug nephrotoxicity as well as in vivo screening of anti-AKI drugs' efficacy.

Tubular Cell Cycle Response upon AKI: Revising Old and New Paradigms to Identify Novel Targets for CKD Prevention

Acute kidney injury (AKI) is characterized by a rapid deterioration of kidney function, representing a global healthcare concern. In addition, AKI survivors frequently develop chronic kidney disease (CKD), contributing to a substantial proportion of disease burden globally. Yet, over the past 30 years, the burden of CKD has not declined to the same extent as many other important non-communicable diseases, implying a substantial deficit in the understanding of the disease progression. The assumption that the kidney response to AKI is based on a high proliferative potential of proximal tubular cells (PTC) caused a critical confounding factor, which has led to a limited development of strategies to prevent AKI and halt progression toward CKD. In this review, we discuss the latest findings on multiple mechanisms of response related to cell cycle behavior of PTC upon AKI, with a specific focus on their biological relevance. Collectively, we aim to (1) provide a new perspective on interpreting cell cycle progression of PTC in response to damage and (2) discuss how this knowledge can be used to choose the right therapeutic window of treatment for preserving kidney function while avoiding CKD progression.

Nucleic Acid Drugs-Current Status, Issues, and Expectations for Exosomes

Simple Summary

Nucleic acid drugs provide novel therapeutic modalities with characteristics that differ from those of small molecules and antibodies. In this review, I focus on the various mechanisms through which nucleic acid drugs act on, the status of their clinical development, and discuss several hurdles that need to be surmounted. In addition, by listing examples of how the progress in exosome biology can lead to the solution of problems in nucleic acid drug therapy, I hope that many more nucleic acid drugs including anticancer drugs will be developed in the future.

Abstract

Nucleic acid drugs are being developed as novel therapeutic modalities. They have great potential to treat human diseases such as cancers, viral infections, and genetic disorders due to unique characteristics that make it possible to approach undruggable targets using classical small molecule or protein/antibody-based biologics. In this review, I describe the advantages, classification, and clinical status of nucleic acid therapeutics. To date, more than 10 products have been launched, and many products have been tested in clinics. To promote the use of nucleic acid therapeutics such as antibodies, several hurdles need to be surmounted. The most important issue is the delivery of nucleic acids and several other challenges have been reported. Recent advanced delivery platforms are lipid nanoparticles and ligand conjugation approaches. With the progress of exosome biology, exosomes are expected to contribute to the solution of various problems associated with nucleic acid drugs.

Teprasiran, a Small Interfering RNA, for the Prevention of Acute Kidney Injury in High-Risk Patients Undergoing Cardiac Surgery: A Randomized Clinical Study

Supplemental Digital Content is available in the text.

Acute kidney injury (AKI) affects up to 30% of patients undergoing cardiac surgery, leading to increased in-hospital and long-term morbidity and mortality. Teprasiran is a novel small interfering RNA that temporarily inhibits p53-mediated cell death that underlies AKI.

Kim-1 Targeted Extracellular Vesicles: A New Therapeutic Platform for RNAi to Treat AKI

BACKGROUND

AKI is a significant public health problem with high morbidity and mortality. Unfortunately, no definitive treatment is available for AKI. RNA interference (RNAi) provides a new and potent method for gene therapy to tackle this issue.

METHODS

We engineered red blood cell-derived extracellular vesicles (REVs) with targeting peptides and therapeutic siRNAs to treat experimental AKI in a mouse model after renal ischemia/reperfusion (I/R) injury and unilateral ureteral obstruction (UUO). Phage display identified peptides that bind to the kidney injury molecule-1 (Kim-1). RNA-sequencing (RNA-seq) characterized the transcriptome of ischemic kidney to explore potential therapeutic targets.

RESULTS

REVs targeted with Kim-1-binding LTH peptide (REV_LTH) efficiently homed to and accumulated at the injured tubules in kidney after I/R injury. We identified transcription factors P65 and Snai1 that drive inflammation and fibrosis as potential therapeutic targets. Taking advantage of the established REV_LTH, siRNAs targeting P65 and Snai1 were efficiently delivered to ischemic kidney and consequently blocked the expression of P-p65 and Snai1 in tubules. Moreover, dual suppression of P65 and Snai1 significantly improved I/R- and UUO-induced kidney injury by alleviating tubulointerstitial inflammation and fibrosis, and potently abrogated the transition to CKD.

CONCLUSIONS

A red blood cell-derived extracellular vesicle platform targeted Kim-1 in acutely injured mouse kidney and delivered siRNAs for transcription factors P65 and Snai1, alleviating inflammation and fibrosis in the tubules.

Effective tools for RNA-derived therapeutics: siRNA interference or miRNA mimicry

The approval of the first small interfering RNA (siRNA) drug Patisiran by FDA in 2018 marks a new era of RNA interference (RNAi) therapeutics. MicroRNAs (miRNA), an important post-transcriptional gene regulator, are also the subject of both basic research and clinical trials. Both siRNA and miRNA mimics are ~21 nucleotides RNA duplexes inducing mRNA silencing. Given the well performance of siRNA, researchers ask whether miRNA mimics are unnecessary or developed siRNA technology can pave the way for the emergence of miRNA mimic drugs. Through comprehensive comparison of siRNA and miRNA, we focus on (1) the common features and lessons learnt from the success of siRNAs; (2) the unique characteristics of miRNA that potentially offer additional therapeutic advantages and opportunities; (3) key areas of ongoing research that will contribute to clinical application of miRNA mimics. In conclusion, miRNA mimics have unique properties and advantages which cannot be fully matched by siRNA in clinical applications. MiRNAs are endogenous molecules and the gene silencing effects of miRNA mimics can be regulated or buffered to ameliorate or eliminate off-target effects. An in-depth understanding of the differences between siRNA and miRNA mimics will facilitate the development of miRNA mimic drugs.

p53 Deacetylation Alleviates Sepsis-Induced Acute Kidney Injury by Promoting Autophagy

Recent studies have shown that autophagy upregulation can attenuate sepsis-induced acute kidney injury (SAKI). The tumor suppressor p53 has emerged as an autophagy regulator in various forms of acute kidney injury (AKI). Our previous studies showed that p53 acetylation exacerbated hemorrhagic shock-induced AKI and lipopolysaccharide (LPS)-induced endothelial barrier dysfunction. However, the role of p53-regulated autophagy in SAKI has not been examined and requires clarification. In this study, we observed the dynamic changes of autophagy in renal tubular epithelial cells (RTECs) and verified the protective effects of autophagy activation on SAKI. We also examined the changes in the protein expression, intracellular distribution (nuclear and cytoplasmic), and acetylation/deacetylation levels of p53 during SAKI following cecal ligation and puncture (CLP) or LPS treatment in mice and in a LPS-challenged human RTEC cell line (HK-2 cells). After sepsis stimulation, the autophagy levels of RTECs increased temporarily, followed by a sharp decrease. Autophagy inhibition was accompanied by an increased renal tubular injury score. By contrast, autophagy agonists could reduce renal tubular damage following sepsis. Surprisingly, the expression of p53 protein in both the renal cortex and HK-2 cells did not significantly change following sepsis stimulation. However, the translocation of p53 from the nucleus to the cytoplasm increased, and the acetylation of p53 was enhanced. In the mechanistic study, we found that the induction of p53 deacetylation, due to either the resveratrol/quercetin -induced activation of the deacetylase Sirtuin 1 (Sirt1) or the mutation of the acetylated lysine site in p53, promoted RTEC autophagy and alleviated SAKI. In addition, we found that acetylated p53 was easier to bind with Beclin1 and accelerated its ubiquitination-mediated degradation. Our study underscores the importance of deacetylated p53-mediated RTEC autophagy in future SAKI treatments.

Renal Delivery of Pharmacologic Agents During Machine Perfusion to Prevent Ischaemia-Reperfusion Injury: From Murine Model to Clinical Trials

Donor organ shortage still remains a serious obstacle for the access of wait-list patients to kidney transplantation, the best treatment for End-Stage Kidney Disease (ESKD). To expand the number of transplants, the use of lower quality organs from older ECD or DCD donors has become an established routine but at the price of increased incidence of Primary Non-Function, Delay Graft Function and lower-long term graft survival. In the last years, several improvements have been made in the field of renal transplantation from surgical procedure to preservation strategies. To improve renal outcomes, research has focused on development of innovative and dynamic preservation techniques, in order to assess graft function and promote regeneration by pharmacological intervention before transplantation. This review provides an overview of the current knowledge of these new preservation strategies by machine perfusions and pharmacological interventions at different timing possibilities: in the organ donor, ex-vivo during perfusion machine reconditioning or after implementation in the recipient. We will report therapies as anti-oxidant and anti-inflammatory agents, senolytics agents, complement inhibitors, HDL, siRNA and H2S supplementation. Renal delivery of pharmacologic agents during preservation state provides a window of opportunity to treat the organ in an isolated manner and a crucial route of administration. Even if few studies have been reported of transplantation after ex-vivo drugs administration, targeting the biological pathway associated to kidney failure (i.e. oxidative stress, complement system, fibrosis) might be a promising therapeutic strategy to improve the quality of various donor organs and expand organ availability.

The Genomic Response to TGF-β1 Dictates Failed Repair and Progression of Fibrotic Disease in the Obstructed Kidney

Tubulointerstitial fibrosis is a common and diagnostic hallmark of a spectrum of chronic renal disorders. While the etiology varies as to the causative nature of the underlying pathology, persistent TGF-β1 signaling drives the relentless progression of renal fibrotic disease. TGF-β1 orchestrates the multifaceted program of kidney fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery or re-differentiation, capillary collapse and subsequent interstitial fibrosis eventually leading to chronic and ultimately end-stage disease. An increasing complement of non-canonical elements function as co-factors in TGF-β1 signaling. p53 is a particularly prominent transcriptional co-regulator of several TGF-β1 fibrotic-response genes by complexing with TGF-β1 receptor-activated SMADs. This cooperative p53/TGF-β1 genomic cluster includes genes involved in cellular proliferative control, survival, apoptosis, senescence, and ECM remodeling. While the molecular basis for this co-dependency remains to be determined, a subset of TGF-β1-regulated genes possess both p53- and SMAD-binding motifs. Increases in p53 expression and phosphorylation, moreover, are evident in various forms of renal injury as well as kidney allograft rejection. Targeted reduction of p53 levels by pharmacologic and genetic approaches attenuates expression of the involved genes and mitigates the fibrotic response confirming a key role for p53 in renal disorders. This review focuses on mechanisms underlying TGF-β1-induced renal fibrosis largely in the context of ureteral obstruction, which mimics the pathophysiology of pediatric unilateral ureteropelvic junction obstruction, and the role of p53 as a transcriptional regulator within the TGF-β1 repertoire of fibrosis-promoting genes.

Epithelial proliferation and cell cycle dysregulation in kidney injury and disease

Various cellular insults and injury to renal epithelial cells stimulate repair mechanisms to adapt and restore the organ homeostasis. Renal tubular epithelial cells are endowed with regenerative capacity, which allows for a restoration of nephron function after acute kidney injury. However, recent evidence indicates that the repair is often incomplete, leading to maladaptive responses that promote the progression to chronic kidney disease. The dysregulated cell cycle and proliferation is also a key feature of renal tubular epithelial cells in polycystic kidney disease and HIV-associated nephropathy. Therefore, in this review, we provide an overview of cell cycle regulation and the consequences of dysregulated cell proliferation in acute kidney injury, polycystic kidney disease, and HIV-associated nephropathy. An increased understanding of these processes may help define better targets for kidney repair and combat chronic kidney disease progression.

Role of indoleamine 2,3-dioxygenase in ischemia-reperfusion injury of renal tubular epithelial cells

The present study evaluated indoleamine 2,3-dioxygenase 1 (IDO) kinetics and how it affects cell survival during the two distinct phases of ischemia-reperfusion (I-R) injury. Primary renal proximal tubular epithelial cells (RPTECs) were cultured under anoxia or reoxygenation with or without the IDO inhibitor 1-DL-methyltryptophan, the aryl-hydrocarbon receptor (AhR) inhibitor CH223191 or the ferroptosis inhibitor α-tocopherol. Using cell imaging, colorimetric assays, PCR and western blotting, it was demonstrated that IDO was upregulated and induced apoptosis during anoxia. The related molecular pathway entails tryptophan degradation, general control non-derepressible-2 kinase (GCN2K) activation, increased level of phosphorylated eukaryotic translation initiation factor 2α, activating transcription factor (ATF)4, ATF3, C/EBP homologous protein, phosphorylated p53, p53, Bax, death receptor-5 and eventually activated cleaved caspase-3. Reoxygenation also upregulated IDO, which, in this case, induced ferroptosis. The related molecular pathway encompasses kynurenine production, AhR activation, cytochrome p450 enzymes increase, reactive oxygen species generation and eventually ferroptosis. In conclusion, in RPTECs, both anoxia and reoxygenation upregulated IDO, which in turn induced GCN2K-mediated apoptosis and AhR-mediated ferroptosis. Since both phases of I-R injury share IDO upregulation as a common point, its inhibition may prove a useful therapeutic strategy for preventing or attenuating I-R injury.

Safety pharmacology of self-assembled-micelle inhibitory RNA-targeting amphiregulin (SAMiRNA-AREG), a novel siRNA nanoparticle platform

The present safety pharmacology core battery studies (neurobehavior, respiratory, cardiovascular system, and human ether a-go-go (hERG) channel current) investigated the potential harmful effects of self-assembled-micelle inhibitory RNA-targeting amphiregulin (SAMiRNA-AREG). The SAMiRNA-AREG was administered by single intravenous injection at up to 300 mg/kg and 100 mg/kg in mice and monkeys, respectively. The hERG assay was performed in Chinese hamster ovary (CHO) cells at SAMiRNA-AREG concentrations of up to 200 μg/mL. In the evaluation on neurobehavior, a transient decrease in body temperature was found at 0.5 h (30 min) post-dose at both sexes in mice, with a single 300 mg/kg dose of SAMiRNA-AREG. However, these effects had returned to normal at 1 h post-dose. In the evaluation on hERG channel current, there were statistically significant differences in the inhibition of peak hERG potassium channel current between the 20, 100, and 200 μg/mL SAMiRNA-AREG treatment groups and the vehicle control group. However, these effects were less potent than that of E-4031, a positive control article. For the respiratory and cardiovascular systems, no treatment-related changes were observed in mice or monkeys. Thus, under these experimental conditions, these studies suggest that SAMiRNA-AREG showed no adverse effects on the neurobehavior, respiratory, and cardiovascular function.

Oligonucleotide-Based Therapies for Renal Diseases

The global burden of chronic kidney disease (CKD) is increasing every year and represents a great cost for public healthcare systems, as the majority of these diseases are progressive. Therefore, there is an urgent need to develop new therapies. Oligonucleotide-based drugs are emerging as novel and promising alternatives to traditional drugs. Their expansion corresponds with new knowledge regarding the molecular basis underlying CKD, and they are already showing encouraging preclinical results, with two candidates being evaluated in clinical trials. However, despite recent technological advances, efficient kidney delivery remains challenging, and the presence of off-targets and side-effects precludes development and translation to the clinic. In this review, we provide an overview of the various oligotherapeutic strategies used preclinically, emphasizing the most recent findings in the field, together with the different strategies employed to achieve proper kidney delivery. The use of different nanotechnological platforms, including nanocarriers, nanoparticles, viral vectors or aptamers, and their potential for the development of more specific and effective treatments is also outlined.

The Indiana O'Brien Center for Advanced Renal Microscopic Analysis

The Indiana O'Brien Center for Advanced Microscopic Analysis is a National Institutes of Health (NIH) P30-funded research center dedicated to the development and dissemination of advanced methods of optical microscopy to support renal researchers throughout the world. The Indiana O'Brien Center was founded in 2002 as an NIH P-50 project with the original goal of helping researchers realize the potential of intravital multiphoton microscopy as a tool for understanding renal physiology and pathophysiology. The center has since expanded into the development and implementation of large-scale, high-content tissue cytometry. The advanced imaging capabilities of the center are made available to renal researchers worldwide via collaborations and a unique fellowship program. Center outreach is accomplished through an enrichment core that oversees a seminar series, an informational website, and a biennial workshop featuring hands-on training from members of the Indiana O'Brien Center and imaging experts from around the world.

The growth of siRNA-based therapeutics: Updated clinical studies

More than two decades after the natural gene-silencing mechanism of RNA interference was elucidated, small interfering RNA (siRNA)-based therapeutics have finally broken into the pharmaceutical market. With three agents already approved and many others in advanced stages of the drug development pipeline, siRNA drugs are on their way to becoming a standard modality of pharmacotherapy. The majority of late-stage candidates are indicated for rare or orphan diseases, whose patients have an urgent need for novel and effective therapies. Additionally, there are agents that have the potential to meet the need of a broader population. Inclisiran, for instance, is being developed for hypercholesterolemia and has shown benefit in patients who are uncontrolled even after maximal statin therapy. This review provides a brief overview of mechanisms of siRNA action, physiological barriers to its delivery and activity, and the most common chemical modifications and delivery platforms used to overcome these barriers. Furthermore, this review presents comprehensive profiles of the three approved siRNA drugs (patisiran, givosiran, and lumasiran) and the seven other siRNA candidates in Phase 3 clinical trials (vutrisiran, nedosiran, inclisiran, fitusiran, teprasiran, cosdosiran, and tivanisiran), summarizing their modifications and delivery strategies, disease-specific mechanisms of action, updated clinical trial status, and future outlooks.

Kidney-Targeted Cytosolic Delivery of siRNA Using a Small-Sized Mirror DNA Tetrahedron for Enhanced Potency

A proper intracellular delivery method with target tissue specificity is critical to utilize the full potential of therapeutic molecules including siRNAs while minimizing their side effects. Herein, we prepare four small-sized DNA tetrahedrons (sTds) by self-assembly of different sugar backbone-modified oligonucleotides and screened them to develop a platform for kidney-targeted cytosolic delivery of siRNA. An in vivo biodistribution study revealed the kidney-specific accumulation of mirror DNA tetrahedron (L-sTd). Low opsonization of L-sTd in serum appeared to avoid liver clearance and keep its size small enough to be filtered through the glomerular basement membrane (GBM). After GBM filtration, L-sTd could be delivered into tubular cells by endocytosis. The kidney preference and the tubular cell uptake property of the mirror DNA nanostructure could be successfully harnessed for kidney-targeted intracellular delivery of p53 siRNA to treat acute kidney injury (AKI) in mice. Therefore, L-sTd could be a promising platform for kidney-targeted cytosolic delivery of siRNA to treat renal diseases.

Novel Fanconi renotubular syndromes provide insights in proximal tubule pathophysiology

The various forms of Fanconi renotubular syndromes (FRTS) offer significant challenges for clinicians and present unique opportunities for scientists who study proximal tubule physiology. This review will describe the clinical characteristics, genetic underpinnings, and underlying pathophysiology of the major forms of FRST. Although the classic forms of FRTS will be presented (e.g., Dent disease or Lowe syndrome), particular attention will be paid to five of the most recently discovered FRTS subtypes caused by mutations in the genes encoding for L-arginine:glycine amidinotransferase (GATM), solute carrier family 34 (type Ii sodium/phosphate cotransporter), member 1 (SLC34A1), enoyl-CoAhydratase/3-hydroxyacyl CoA dehydrogenase (EHHADH), hepatocyte nuclear factor 4A (HNF4A), or NADH dehydrogenase complex I, assembly factor 6 (NDUFAF6). We will explore how mutations in these genes revealed unexpected mechanisms that led to compromised proximal tubule functions. We will also describe the inherent challenges associated with gene discovery studies based on findings derived from small, single-family studies by focusing the story of FRTS type 2 (SLC34A1). Finally, we will explain how extensive alternative splicing of HNF4A has resulted in confusion with mutation nomenclature for FRTS type 4.

SIRT2 is involved in cisplatin-induced acute kidney injury through regulation of mitogen-activated protein kinase phosphatase-1

BACKGROUND

Activation of mitogen-activated protein kinase phosphatase-1 (MKP-1), a dual-specificity protein phosphatase, regulates mitogen-activated protein kinase signaling. C-Jun N-terminal kinase (JNK) and p38 are activated in cisplatin-induced renal injury. However, the change of MKP-1 expression in cisplatin-induced renal injury and the regulatory effect of sirtuin 2 (SIRT2), a nicotinamide adenine dinucleotide-dependent deacetylase, on MKP-1 remains unknown.

METHODS

To address these issues, we used constitutional Sirt2 knockout (KO) mice, transgenic (TG) mice with increased expression of SIRT2 specifically in proximal tubular epithelial cellsand wild-type (WT) mice. Cisplatin nephrotoxicity was induced by intraperitoneal injection of cisplatin.

RESULTS

MKP-1 expression in the kidney was decreased after cisplatin treatment. Cisplatin-induced downregulation of MKP-1 was reversed in Sirt2 KO mice kidney and further decreased in Sirt2 TG mice kidney. We observed similar phenomenon with SIRT2-knockdown or SIRT2-overexpressed tubular epithelial cells. Phosphorylation of p38 and JNK, a downstream signal pathway of MKP-1, increased in WT mice kidney following treatment with cisplatin. A decrease in SIRT2 suppressed cisplatin-induced phosphorylation of p38 and JNK in kidney and tubular epithelial cells. Overexpression of SIRT2 further increased phosphorylation of p38 and JNK in kidney and tubular epithelial cells. Acetylation of MKP-1 was significantly increased in SIRT2-knockdown cells and decreased in SIRT2-overexpressed cells after cisplatin stimulation. Sirt2 KO mice and Sirt2 TG mice showed amelioration and aggravation of renal injury, apoptosis, necroptosis and inflammation induced by cisplatin.

CONCLUSION

Our data show that SIRT2 is associated with cisplatin-induced renal injury through regulation of MKP-1 expression.

Exploring the multiple roles of guardian of the genome: P53

Background

Cells have evolved balanced mechanisms to protect themselves by initiating a specific response to a variety of stress. TheTP53gene, encoding P53 protein, is one of the many widely studied genes in human cells owing to its multifaceted functions and complex dynamics. The tumour-suppressing activity of P53 plays a principal role in the cellular response to stress. The majority of the human cancer cells exhibit the inactivation of the P53 pathway. In this review, we discuss the recent advancements in P53 research with particular focus on the role of P53 in DNA damage responses, apoptosis, autophagy, and cellular metabolism. We also discussed important P53-reactivation strategies that can play a crucial role in cancer therapy and the role of P53 in various diseases.

Main body

We used electronic databases like PubMed and Google Scholar for literature search. In response to a variety of cellular stress such as genotoxic stress, ischemic stress, oncogenic expression, P53 acts as a sensor, and suppresses tumour development by promoting cell death or permanent inhibition of cell proliferation. It controls several genes that play a role in the arrest of the cell cycle, cellular senescence, DNA repair system, and apoptosis. P53 plays a crucial role in supporting DNA repair by arresting the cell cycle to purchase time for the repair system to restore genome stability. Apoptosis is essential for maintaining tissue homeostasis and tumour suppression. P53 can induce apoptosis in a genetically unstable cell by interacting with many pro-apoptotic and anti-apoptotic factors.

Furthermore, P53 can activate autophagy, which also plays a role in tumour suppression. P53 also regulates many metabolic pathways of glucose, lipid, and amino acid metabolism. Thus under mild metabolic stress, P53 contributes to the cell’s ability to adapt to and survive the stress.

Conclusion

These multiple levels of regulation enable P53 to perform diversified roles in many cell responses. Understanding the complete function of P53 is still a work in progress because of the inherent complexity involved in between P53 and its target proteins. Further research is required to unravel the mystery of this Guardian of the genome “TP53”.

Review: Ischemia Reperfusion Injury-A Translational Perspective in Organ Transplantation

Thanks to the development of new, more potent and selective immunosuppressive drugs together with advances in surgical techniques, organ transplantation has emerged from an experimental surgery over fifty years ago to being the treatment of choice for many end-stage organ diseases, with over 139,000 organ transplants performed worldwide in 2019. Inherent to the transplantation procedure is the fact that the donor organ is subjected to blood flow cessation and ischemia during harvesting, which is followed by preservation and reperfusion of the organ once transplanted into the recipient. Consequently, ischemia/reperfusion induces a significant injury to the graft with activation of the immune response in the recipient and deleterious effect on the graft. The purpose of this review is to discuss and shed new light on the pathways involved in ischemia/reperfusion injury (IRI) that act at different stages during the donation process, surgery, and immediate post-transplant period. Here, we present strategies that combine various treatments targeted at different mechanistic pathways during several time points to prevent graft loss secondary to the inflammation caused by IRI.

Acute kidney injury pathology and pathophysiology: a retrospective review

Acute kidney injury (AKI) is the clinical term used for decline or loss of renal function. It is associated with chronic kidney disease (CKD) and high morbidity and mortality. However, not all causes of AKI lead to severe consequences and some are reversible. The underlying pathology can be a guide for treatment and assessment of prognosis. The Kidney Disease: Improving Global Outcomes guidelines recommend that the cause of AKI should be identified if possible. Renal biopsy can distinguish specific AKI entities and assist in patient management. This review aims to show the pathology of AKI, including glomerular and tubular diseases.

Targeting acute kidney injury in COVID-19

As of 15 August 2020, Coronavirus disease 2019 (COVID-19) has been reported in >21 million people world-wide and is responsible for more than 750,000 deaths. The occurrence of acute kidney injury (AKI) in patients hospitalized with COVID-19 has been reported to be as high as 43%. This is comparable to AKI in other forms of pneumonia requiring hospitalization, as well as in non-infectious conditions like cardiac surgery. The impact of AKI on COVID-19 outcomes is difficult to assess at present but, similar to other forms of sepsis, AKI is strongly associated with hospital mortality. Indeed, mortality is reported to be very low in COVID-19 patients without AKI. Given that AKI contributes to fluid and acid-base imbalances, compromises immune response and may impair resolution of inflammation, it seems likely that AKI contributes to mortality in these patients. The pathophysiologic mechanisms of AKI in COVID-19 are thought to be multifactorial including systemic immune and inflammatory responses induced by viral infection, systemic tissue hypoxia, reduced renal perfusion, endothelial damage and direct epithelial infection with Severe Acute Respiratory Syndrome Coronavirus 2. Mitochondria play a central role in the metabolic deregulation in the adaptive response to the systemic inflammation and are also found to be vital in response to both direct viral damage and tissue reperfusion. These stress conditions are associated with increased glycolysis and reduced fatty acid oxidation. Thus, there is a strong rationale to target AKI for therapy in COVID-19. Furthermore, many approaches that have been developed for other etiologies of AKI such as sepsis, inflammation and ischemia-reperfusion, have relevance in the treatment of COVID-19 AKI and could be rapidly pivoted to this new disease.

Advances in fluorescence microscopy techniques to study kidney function

Fluorescence microscopy, in particular immunofluorescence microscopy, has been used extensively for the assessment of kidney function and pathology for both research and diagnostic purposes. The development of confocal microscopy in the 1950s enabled imaging of live cells and intravital imaging of the kidney; however, confocal microscopy is limited by its maximal spatial resolution and depth. More recent advances in fluorescence microscopy techniques have enabled increasingly detailed assessment of kidney structure and provided extraordinary insights into kidney function. For example, nanoscale precise imaging by rapid beam oscillation (nSPIRO) is a super-resolution microscopy technique that was originally developed for functional imaging of kidney microvilli and enables detection of dynamic physiological events in the kidney. A variety of techniques such as fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS) and Förster resonance energy transfer (FRET) enable assessment of interaction between proteins. The emergence of other super-resolution techniques, including super-resolution stimulated emission depletion (STED), photoactivated localization microscopy (PALM), stochastic optical reconstruction microscopy (STORM) and structured illumination microscopy (SIM), has enabled functional imaging of cellular and subcellular organelles at ≤50 nm resolution. The deep imaging via emission recovery (DIVER) detector allows deep, label-free and high-sensitivity imaging of second harmonics, enabling assessment of processes such as fibrosis, whereas fluorescence lifetime imaging microscopy (FLIM) enables assessment of metabolic processes.

Improving Molecular Therapy in the Kidney

Mutations in approximately 80 genes have been implicated as the cause of various genetic kidney diseases. However, gene delivery to kidney cells from the blood is inefficient because of the natural filtering functions of the glomerulus, and research into and development of gene therapy directed toward kidney disease has lagged behind as compared with hepatic, neuromuscular, and ocular gene therapy. This lack of progress is in spite of numerous genetic mouse models of human disease available to the research community and many vectors in existence that can theoretically deliver genes to kidney cells with high efficiency. In the past decade, several groups have begun to develop novel injection techniques in mice, such as retrograde ureter, renal vein, and direct subcapsular injections to help resolve the issue of gene delivery to the kidney through the blood. In addition, the ability to retarget vectors specifically toward kidney cells has been underutilized but shows promise. This review discusses how recent advances in gene delivery to the kidney and the field of gene therapy can leverage the wealth of knowledge of kidney genetics to work toward developing gene therapy products for patients with kidney disease.

Ginsenoside Rh1 Alleviates HK-2 Apoptosis by Inhibiting ROS and the JNK/p53 Pathways

Background

Cisplatin is widely used in the treatment of malignant patients; however, its adverse nephrotoxic effects limit its clinical use. Ginsenoside Rh1 is a main component of ginseng and has many pharmaceutical effects, including immunomodulatory effects.

Objective

The objective of this research is to assess the effects of ginsenoside Rh1 on a cisplatin-induced HK-2 injury model and to study its potential effect mechanisms.

Methods

HK-2 cell vitality was assessed via Cell Counting Kit-8 (CCK-8) assay. Carboxyfluorescein succinimidyl ester/propidium iodide (CFSF/PI) staining was used to detect the apoptosis of HK-2 cells. ROS expression was detected by DCFDA. The expressions of JNK, p53, caspase-3, Bax, and NGAL were detected by western blot.

Results

Ginsenoside Rh1 was found to increase the vitality of HK-2 cells and inhibit ROS production and the apoptosis of HK-2 cells in a cisplatin-induced injury model. Ginsenoside Rh1 was found to inhibit the expression of JNK, p53, caspase-3, Bax, and NGAL in a cisplatin-induced injury model.

Conclusion

Ginsenoside Rh1 alleviated HK-2 apoptosis in a cisplatin-induced injury model by inhibiting ROS production and the JNK/p53 pathway. Ginsenoside Rh1 may be a promising drug for the alleviation of cisplatin-induced nephrotoxicity in malignant patients.

Therapeutic siRNA: state of the art

RNA interference (RNAi) is an ancient biological mechanism used to defend against external invasion. It theoretically can silence any disease-related genes in a sequence-specific manner, making small interfering RNA (siRNA) a promising therapeutic modality. After a two-decade journey from its discovery, two approvals of siRNA therapeutics, ONPATTRO® (patisiran) and GIVLAARI™ (givosiran), have been achieved by Alnylam Pharmaceuticals. Reviewing the long-term pharmaceutical history of human beings, siRNA therapy currently has set up an extraordinary milestone, as it has already changed and will continue to change the treatment and management of human diseases. It can be administered quarterly, even twice-yearly, to achieve therapeutic effects, which is not the case for small molecules and antibodies. The drug development process was extremely hard, aiming to surmount complex obstacles, such as how to efficiently and safely deliver siRNAs to desired tissues and cells and how to enhance the performance of siRNAs with respect to their activity, stability, specificity and potential off-target effects. In this review, the evolution of siRNA chemical modifications and their biomedical performance are comprehensively reviewed. All clinically explored and commercialized siRNA delivery platforms, including the GalNAc (N-acetylgalactosamine)-siRNA conjugate, and their fundamental design principles are thoroughly discussed. The latest progress in siRNA therapeutic development is also summarized. This review provides a comprehensive view and roadmap for general readers working in the field.

Acute Kidney Injury: From Diagnosis to Prevention and Treatment Strategies

Acute kidney injury (AKI) is characterized by an acute decrease in renal function that can be multifactorial in its origin and is associated with complex pathophysiological mechanisms. In the short term, AKI is associated with an increased length of hospital stay, health care costs, and in-hospital mortality, and its impact extends into the long term, with AKI being associated with increased risks of cardiovascular events, progression to chronic kidney disease (CKD), and long-term mortality. Given the impact of the prognosis of AKI, it is important to recognize at-risk patients and improve preventive, diagnostic, and therapy strategies. The authors provide a comprehensive review on available diagnostic, preventive, and treatment strategies for AKI.

Mistimed H2S upregulation, Nrf2 activation and antioxidant proteins levels in renal tubular epithelial cells subjected to anoxia and reoxygenation

Ischemia-reperfusion (I-R) injury is involved in the pathogenesis of several human diseases. In the present study, the kinetics of the H₂S producing enzymes-nuclear factor erythroid 2-like 2 (Nrf2)-antioxidant proteins axis under anoxia or reoxygenation was evaluated, as well as its effects on survival of mouse renal proximal tubular epithelial cells (RPTECs). In RPTECs subjected to anoxia and subsequent reoxygenation, reactive oxygen species (ROS) production, lipid peroxidation, ferroptotic cell death, the levels of the H₂S producing enzymes and H₂S, the expression of Nrf2 and its transcriptional targets superoxide dismutase-3, glutathione reductase, ferritin H and cystine-glutamate antiporter, as well as apoptosis, and the levels of p53, Bax and phosphorylated p53 were assessed. When needed, the H₂S producing enzyme inhibitor aminooxyacetate, or the ferroptosis inhibitor α-tocopherol, were used. Reoxygenation induced ferroptosis, whereas anoxia activated the p53-Bax pathway and induced apoptosis. The H₂S producing enzymes-Nrf2-antioxidant proteins axis was activated only during anoxia and not during reoxygenation, when cellular viability is threatened by ROS overproduction and the ensuing ferroptosis. The activation of the above axis during anoxia ameliorated the effects of the apoptotic p53-Bax pathway, but did not adequately protect against apoptosis. In conclusion, the H₂S-Nrf2 axis is activated by anoxia, and although it reduces apoptosis, it does not completely prevent apoptotic cell death. Additionally, following reoxygenation, the above axis was not activated. This mistimed activation of the H₂S producing enzymes-Nrf2-antioxidant proteins axis contributes to reoxygenation-induced cell death. Determining the exact molecular mechanisms involved in reoxygenation-induced cell death may assist in the development of clinically relevant interventions for preventing I-R injury.

Safety Considerations for Humans and Other Vertebrates Regarding Agricultural Uses of Externally Applied RNA Molecules

The potential of double-stranded RNAs (dsRNAs) for use as topical biopesticides in agriculture was recently discussed during an OECD (Organisation for Economic Co-operation and Development) Conference on RNA interference (RNAi)-based pesticides. Several topics were presented and these covered different aspects of RNAi technology, its application, and its potential effects on target and non-target organisms (including both mammals and non-mammals). This review presents information relating to RNAi mechanisms in vertebrates, the history of safe RNA consumption, the biological barriers that contribute to the safety of its consumption, and effects related to humans and other vertebrates as discussed during the conference. We also review literature related to vertebrates exposed to RNA molecules and further consider human health safety assessments of RNAi-based biopesticides. This includes possible routes of exposure other than the ingestion of potential residual material in food and water (such as dermal and inhalation exposures during application in the field), the implications of different types of formulations and RNA structures, and the possibility of non-specific effects such as the activation of the innate immune system or saturation of the RNAi machinery.

Pharmacological inhibition of ataxia-telangiectasia mutated exacerbates acute kidney injury by activating p53 signaling in mice

The DNA damage response after kidney injury induces cell cycle arrest in renal tubular epithelial cells, resulting in the secretion of pro-fibrotic cytokines, thereby promoting interstitial fibrosis in a paracrine manner. Phosphorylation of ataxia-telangiectasia mutated (ATM) is the initial step in the DNA damage response and subsequent cell cycle arrest; however, the effects of ATM inhibition on the injured kidney have not been explored. Pharmacological ATM inhibition by KU55933 in cisplatin-treated mice did not ameliorate, but instead exacerbated cisplatin-induced DNA damage and tubular injury, thereby increasing mortality. Analysis of isolated tubular epithelia by FACS from bigenic SLC34a1-CreERt2; R26tdTomato proximal tubular-specific reporter mice revealed that KU55933 upregulated p53 and subsequent pro-apoptotic signaling in tubular epithelia of cisplatin-treated mice, leading to marked mitochondrial injury and apoptosis. In addition, KU55933 attenuated several DNA repair processes after cisplatin treatment, including single-strand DNA repair and Fanconi anemia pathways, suggesting that DNA repair after dual treatment of cisplatin and KU55933 was not sufficient to prevent the cisplatin-induced tubular injury. Our study suggested that ATM inhibition does not increase DNA repair after cisplatin-induced DNA damage and exacerbates tubular injury through the upregulation of p53-dependent pro-apoptotic signaling. Acute kidney injury must be carefully monitored when ATM inhibitors become available in clinical practice in the future.

Ischemia and Reperfusion Injury in Kidney Transplantation: Relevant Mechanisms in Injury and Repair

Ischemia and reperfusion injury (IRI) is a complex pathophysiological phenomenon, inevitable in kidney transplantation and one of the most important mechanisms for non- or delayed function immediately after transplantation. Long term, it is associated with acute rejection and chronic graft dysfunction due to interstitial fibrosis and tubular atrophy. Recently, more insight has been gained in the underlying molecular pathways and signalling cascades involved, which opens the door to new therapeutic opportunities aiming to reduce IRI and improve graft survival. This review systemically discusses the specific molecular pathways involved in the pathophysiology of IRI and highlights new therapeutic strategies targeting these pathways.

p53-cyclophilin D mediates renal tubular cell apoptosis in ischemia-reperfusion-induced acute kidney injury

Ischemia-reperfusion (I/R)-induced acute kidney injury (I/R-AKI) favors mitochondrial permeability transition pore (mPTP) opening and subsequent cell death. Cyclophilin D (CypD) is an essential component of the mPTP, and recent findings have implicated the p53-CypD complex in cell death. To evaluate the role of p53-CypD after I/R-AKI, we tested the hypothesis that the p53-CypD complex mediates renal tubular cell apoptosis in I/R-AKI via mPTP opening. Expression of p53 and cleaved caspase-3 was significantly increased in rats subjected to I/R-AKI compared with normal controls and sham-operated controls. The underlying mechanisms were determined using an in vitro model of ATP depletion. Inhibition of mPTP opening using the CypD inhibitor cyclosporin A or siRNA for p53 in ATP-depleted HK-2 cells prevented mitochondrial membrane depolarization and reduced apoptosis. Furthermore, p53 bound to CypD in ATP-depleted HK-2 cells. These results suggest that the p53-CypD complex mediates renal tubular cell apoptosis in I/R-AKI via mPTP opening.

Meclofenamic acid promotes cisplatin-induced acute kidney injury by inhibiting fat mass and obesity-associated protein-mediated m6A abrogation in RNA

The role of RNA methylation on the sixth N atom of adenylate (m⁶A) in acute kidney injury (AKI) is unknown. FTO (fat mass and obesity-associated protein) reverses the m⁶A modification in cisplatin-induced AKI. Here, we aimed to determine FTO's role in AKI. We induced AKI in c57BL/6 mice by intraperitoneal cisplatin injection and treated the animal with vehicle or an FTO inhibitor meclofenamic acid (MA) for 3 days. Moreover, as an in vitro model, human kidney proximal tubular cells (HK2 cells) were treated with cisplatin. We found that the cisplatin treatment reduces FTO expression and increases m⁶A levels in vivo and in vitro MA aggravated renal damage and increased apoptosis in cisplatin-treated kidneys, phenotypes that were correlated with reduced FTO expression and increased m⁶A levels. Moreover, MA promoted apoptosis in cisplatin-treated HK2 cells, which was correlated with the reduced FTO expression and increased m⁶A in HK2 cells. FTO protein overexpression reduced m⁶A levels and inhibited apoptosis in cisplatin-treated HK2 cells and also blocked the MA-induced increase in m⁶A levels and apoptosis rates. In agreement, overexpression of the m⁶A-generating methyltransferase-like 3 and 14 (METTL3 and METTL14) or siRNA-mediated FTO knockdown promoted apoptosis and enhanced m⁶A levels in cisplatin-treated HK2 cells. MA increased p53 mRNA and protein levels in AKI both in vitro and in vivo, and FTO overexpression reduced p53 expression and reversed the MA-induced p53 increase in AKI. In conclusion, reduced renal FTO expression in cisplatin-induced AKI increases RNA m⁶A levels and aggravates renal damages.

TGF-β1-p53 cooperativity regulates a profibrotic genomic program in the kidney: molecular mechanisms and clinical implications

Chronic kidney disease affects >15% of the U.S. population and >850 million individuals worldwide. Fibrosis is the common outcome of many chronic renal disorders and, although the etiology varies (i.e., diabetes, hypertension, ischemia, acute injury, and urologic obstructive disorders), persistently elevated renal TGF-β1 levels result in the relentless progression of fibrotic disease. TGF-β1 orchestrates the multifaceted program of renal fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery and redifferentiation, and subsequent tubulointerstitial fibrosis, eventually leading to chronic renal disease. Recent findings implicate p53 as a cofactor in the TGF-β1-induced signaling pathway and a transcriptional coregulator of several TGF-β1 profibrotic response genes by complexing with receptor-activated SMADs, which are homologous to the small worms (SMA) and Drosophilia mothers against decapentaplegic (MAD) gene families. The cooperative p53-TGF-β1 genomic cluster includes genes involved in cell growth control and extracellular matrix remodeling [e.g., plasminogen activator inhibitor-1 (PAI-1; serine protease inhibitor, clade E, member 1), connective tissue growth factor, and collagen I]. Although the molecular basis for this codependency is unclear, many TGF-β1-responsive genes possess p53 binding motifs. p53 up-regulation and increased p53 phosphorylation; moreover, they are evident in nephrotoxin- and ischemia/reperfusion-induced injury, diabetic nephropathy, ureteral obstructive disease, and kidney allograft rejection. Pharmacologic and genetic approaches that target p53 attenuate expression of the involved genes and mitigate the fibrotic response, confirming a key role for p53 in renal disorders. This review focuses on mechanisms whereby p53 functions as a transcriptional regulator within the TGF-β1 cluster with an emphasis on the potent fibrosis-promoting PAI-1 gene.-Higgins, C. E., Tang, J., Mian, B. M., Higgins, S. P., Gifford, C. C., Conti, D. J., Meldrum, K. K., Samarakoon, R., Higgins, P. J. TGF-β1-p53 cooperativity regulates a profibrotic genomic program in the kidney: molecular mechanisms and clinical implications.

Polyamine Catabolism in Acute Kidney Injury

Acute kidney injury (AKI) refers to an abrupt decrease in kidney function. It affects approximately 7% of all hospitalized patients and almost 35% of intensive care patients. Mortality from acute kidney injury remains high, particularly in critically ill patients, where it can be more than 50%. The primary causes of AKI include ischemia/reperfusion (I/R), sepsis, or nephrotoxicity; however, AKI patients may present with a complicated etiology where many of the aforementioned conditions co-exist. Multiple bio-markers associated with renal damage, as well as metabolic and signal transduction pathways that are involved in the mediation of renal dysfunction have been identified as a result of the examination of models, patient samples, and clinical data of AKI of disparate etiologies. These discoveries have enhanced our ability to diagnose AKIs and to begin to elucidate the mechanisms involved in their pathogenesis. Studies in our laboratory revealed that the expression and activity of spermine/spermidine N1-acetyltransferase (SAT1), the rate-limiting enzyme in polyamine back conversion, were enhanced in kidneys of rats after I/R injury. Additional studies revealed that the expression of spermine oxidase (SMOX), another critical enzyme in polyamine catabolism, is also elevated in the kidney and other organs subjected to I/R, septic, toxic, and traumatic injuries. The maladaptive role of polyamine catabolism in the mediation of AKI and other injuries has been clearly demonstrated. This review will examine the biochemical and mechanistic basis of tissue damage brought about by enhanced polyamine degradation and discuss the potential of therapeutic interventions that target polyamine catabolic enzymes or their byproducts for the treatment of AKI.

Hydrophobicity drives the systemic distribution of lipid-conjugated siRNAs via lipid transport pathways

Efficient delivery of therapeutic RNA beyond the liver is the fundamental obstacle preventing its clinical utility. Lipid conjugation increases plasma half-life and enhances tissue accumulation and cellular uptake of small interfering RNAs (siRNAs). However, the mechanism relating lipid hydrophobicity, structure, and siRNA pharmacokinetics is unclear. Here, using a diverse panel of biologically occurring lipids, we show that lipid conjugation directly modulates siRNA hydrophobicity. When administered in vivo, highly hydrophobic lipid-siRNAs preferentially and spontaneously associate with circulating low-density lipoprotein (LDL), while less lipophilic lipid-siRNAs bind to high-density lipoprotein (HDL). Lipid-siRNAs are targeted to lipoprotein receptor-enriched tissues, eliciting significant mRNA silencing in liver (65%), adrenal gland (37%), ovary (35%), and kidney (78%). Interestingly, siRNA internalization may not be completely driven by lipoprotein endocytosis, but the extent of siRNA phosphorothioate modifications may also be a factor. Although biomimetic lipoprotein nanoparticles have been explored for the enhancement of siRNA delivery, our findings suggest that hydrophobic modifications can be leveraged to incorporate therapeutic siRNA into endogenous lipid transport pathways without the requirement for synthetic formulation.

Pharmacological Activation of Sirt1 Ameliorates Cisplatin-Induced Acute Kidney Injury by Suppressing Apoptosis, Oxidative Stress, and Inflammation in Mice

Sirtuin 1 (Sirt1) is an essential modulator of cellular metabolism and has pleiotropic effects. It was recently reported that Sirt1 overexpression in kidney tubule ameliorates cisplatin-induced acute kidney injury (AKI). However, whether pharmacological activation of Sirt1 also has a beneficial effect against the disease remains unclear. In this study, we aimed to evaluate whether SRT1720, a potent and specific activator of Sirt1, could ameliorate cisplatin-induced AKI. We found that SRT1720 treatment ameliorated cisplatin-induced acute renal failure and histopathological alterations. Increased levels of tubular injury markers in kidneys were significantly attenuated by SRT1720. SRT1720 treatment also suppressed caspase-3 activation and apoptotic cell death. Increased expression of 4-hydroxynonenal, elevated malondialdehyde level, and decreased ratio of reduced glutathione/oxidized glutathione after cisplatin injection were significantly reversed by SRT1720. In addition, SRT1720 treatment decreased renal expression of pro-inflammatory cytokines and prevented macrophage infiltration into damaged kidneys. We also showed that the therapeutic effects of SRT1720 were associated with reduced acetylation of p53 and nuclear factor kappa-B p65 and preservation of peroxisome function, as evidenced by recovered expression of markers for number and function of peroxisome. These results suggest that Sirt1 activation by SRT1720 would be a useful therapeutic option for cisplatin-induced AKI.

Advances in Toxicological Research of the Anticancer Drug Cisplatin

Cisplatin is one of the most widely used chemotherapeutic agents for various solid tumors in the clinic due to its high efficacy and broad spectrum. The antineoplastic activity of cisplatin is mainly due to its ability to cross-link with DNA, thus blocking transcription and replication. Unfortunately, the clinical use of cisplatin is limited by its severe, dose-dependent toxic side effects. There are approximately 40 specific toxicities of cisplatin, among which nephrotoxicity is the most common one. Other common side effects include ototoxicity, neurotoxicity, gastrointestinal toxicity, hematological toxicity, cardiotoxicity, and hepatotoxicity. These side effects together reduce the life quality of patients and require lowering the dosage of the drug, even stopping administration, thus weakening the treatment effect. Few effective measures exist clinically against these side effects because the exact mechanisms of various side effects from cisplatin remain still unclear. Therefore, substantial effort has been made to explore the complicated biochemical processes involved in the toxicology of cisplatin, aiming to identify effective ways to reduce or eradicate its toxicity. This review summarizes and reviews the updated advances in the toxicological research of cisplatin. We anticipate to provide insights into the understanding of the mechanisms underlying the side effects of cisplatin and designing comprehensive therapeutic strategies involving cisplatin.

Magnesium lithospermate B attenuates renal injury in 5/6 renal ablation/infarction rats by mitochondrial pathway of apoptosis

Apoptosis is closely interconnected with the severity of renal injury. Magnesium lithospermate B (MLB) extracted from Salviae miltiorrhizae radix showed a wide range of renoprotective effects. However, the underlying mechanisms under beneficial effects have not been elucidated. This study was conducted to investigate whether MLB could mediate renal protection and attenuate apoptosis by mitochondrial pathway. In the present study, the rat model of chronic renal failure (CRF) was established by the 5/6 renal ablation/infarction (A/I) operation. 28 days after the surgery, 30 rats were randomly divided into three groups: sham group, 5/6 (A/I) group and 5/6 (A/I) + MLB group. After 56 days of treatment, we detected the severity of kidney injury, the degree of mitochondrial bax oligomerization and cytochrome c release along with the expression of P53 protein. Our results showed that MLB markedly attenuated kidney injury and apoptosis in 5/6 (A/I) model rats with CRF. MLB effectively inhibited mitochondrial bax accumulation and release of cytochrome c into the cytosol and down-regulated the levels of p53 phosphorylation and acetylation. These data showed that MLB could contribute to renal protection by inhibiting mitochondrial pathway of apoptosis.

Inhibition of the H3K4 methyltransferase MLL1/WDR5 complex attenuates renal senescence in ischemia reperfusion mice by reduction of p16INK4a

Renal function declines with aging and is pathologically characterized by chronic inflammation and fibrosis. Renal senescence is induced not only by aging but also by various stimuli, including ischemia reperfusion injury. Recently, the accumulation of p16^INK4a-positive cells in the kidney has been considered a molecular feature of renal senescence, with the p16^INK4a gene reportedly regulated by mixed-lineage leukemia 1 (MLL1)/WD-40 repeat protein 5 (WDR5)-mediated histone 3 lysine 4 trimethylation (H3K4me3). Here, we determined whether inhibition of MLL1/WDR5 activity attenuates renal senescence, inflammation, and fibrosis in mice with ischemia reperfusion injury and in cultured rat renal fibroblasts. MM-102 or OICR-9429, both MLL1/WDR5 protein-protein interaction inhibitors, and small interfering RNA (siRNA) for MLL1 or WDR5 suppressed the expression of p16^INK4a in mice with ischemia reperfusion injury, accompanied by downregulation of H3K4me3 expression. MM-102 attenuated renal fibrosis and inflammation in the kidney of mice with ischemia reperfusion injury. Moreover, in vitro study showed that transforming growth factor-β1 induced the expression of MLL1, WDR5, H3K4me3, and p16^INK4a. Finally, chromatin immunoprecipitation identified the p16^INK4a promoter at an H3K4me3 site in renal fibroblasts. Thus, our findings show that H3K4me3 inhibition ameliorates ischemia reperfusion-induced renal senescence along with fibrosis and inflammation.

Drugs in Development for Acute Kidney Injury

The care of patients with acute kidney injury (AKI) has been limited due to the lack of effective therapeutics that can either prevent AKI during high-risk situations or treat AKI once established. A revolution in the scientific understanding of the pathogenesis of AKI has led to the identification of potential therapeutic targets. These targets include pathways involved in inflammation, cellular repair and fibrosis, cellular metabolism and mitochondrial function, oxidative stress, apoptosis, and hemodynamics and oxygen delivery. Many compounds are entering early-phase clinical trials. In addition, efforts to better describe sub-categories of AKI (through endo-phenotyping) hold promise to target therapies more effectively based upon pathways that are operative in the pathogenesis. These advances bring optimism that the care of patients with AKI will be transformed with the hope of better outcomes.

Cellular Senescence and the Kidney: Potential Therapeutic Targets and Tools

Chronic kidney disease (CKD) is an increasing health burden (affecting approximately 13.4% of the population). Currently, no curative treatment options are available and treatment is focused on limiting the disease progression. The accumulation of senescent cells has been implicated in the development of kidney fibrosis by limiting tissue rejuvenation and through the secretion of pro-fibrotic and pro-inflammatory mediators termed as the senescence-associated secretory phenotype. The clearance of senescent cells in aging models results in improved kidney function, which shows promise for the options of targeting senescent cells in CKD. There are several approaches for the development of “senotherapies”, the most rigorous of which is the elimination of senescent cells by the so-called senolytic drugs either newly developed or repurposed for off-target effects in terms of selectively inducing apoptosis in senescent cells. Several chemotherapeutics and checkpoint inhibitors currently used in daily oncological practice show senolytic properties. However, the applicability of such senolytic compounds for the treatment of renal diseases has hardly been investigated. A serious concern is that systemic side effects will limit the use of senolytics for kidney fibrosis. Specifically targeting senescent cells and/or targeted drug delivery to the kidney might circumvent these side effects. In this review, we discuss the connection between CKD and senescence, the pharmacological options for targeting senescent cells, and the means to specifically target the kidney.

MiR-424 is over-expressed and attenuates ischemia-reperfusion kidney injury via p53 and death receptor 6 pathway

BACKGROUND

Ischemic reperfusion injury of kidney is major cause for renal failure, however the involved pathogenesis remains unclear creating an void for its effective treatment. Here we studied involvement of microRNA-424 in renal injury.

METHODS

For the study, p53 or HIF-1α mice were used, ischemic renal injury was induced using clamping of renal pedicles bilateraly. Proximal kidney tubular cells were used for in vitro studies. Hoechst 33342 analysis was done for apoptosis. Blood urea nitrogen (BUN) and serum creatinine was done for renal function, Hematoxylin-eosin tissue damage and Terminal transferase-dUTP nick-end labeling assay for apoptosis. RT-PCR was done for miRNA and ChIP assay to identify the binding of p53 to miR-424. TargetScan and miRanda data base were scanned to find targets of miR-424. Protein expression was done by western blot analysis.

RESULTS

We discovered that, miR-424 was over-expressed in ischemic renal injury mice and in hypoxia exposed renal cells. In cells, miR-424 suppressed the expression levels of death receptor 6 (DR6) and halted the apoptosis mediated by hypoxia. Blocking of miR-424 halted the inhibition of DR6 and caused apoptosis and activation of caspase. In mice, miR-424 mimic inhibited expression of DR6 and attenuated ischemic renal injury. We established that, up-regulation of miR-424 in ischemic reperfusion injury was p53 dependent, also inhibition of p53 caused repression of miR-424 levels in hypoxia induced cells in vitro. The p53 knockout mice showed attenuation in levels of miR-424 confirming role of p53 behind up-regulation of miR-424 in vivo.

CONCLUSION

The study confirmed p53/miR-424/DR6 as a protective cascade during ischemic-reperfusion injury.

Time-dependent p53 inhibition determines senescence attenuation and long-term outcome after renal ischemia-reperfusion

Inhibition of p53 has been shown to be an efficient strategy for ameliorating kidney ischemia-reperfusion (I/R) injury in experimental models. The therapeutic value of p53 siRNA-based inhibition for I/R in renal transplantation is currently being evaluated in clinical studies. While the major rationale for these studies is the suppression of proapoptotic properties, there are more equally important injury response pathways regulated by p53. A p53-dependent pathway shown to be crucial for renal long-term outcome is cellular senescence. In this study, we tested the hypothesis that p53 siRNA reduces I/R-induced senescence and thereby improves kidney outcome. By comparing the impact of different treatment durations in a mouse model of renal I/R, we found that repetitive administration of p53 siRNA during the first 14 days after I/R reduced the senescence load and ameliorated the postischemic phenotype. Prolonged application of p53 siRNA over a 26-day period after I/R, however, did not provide any additional benefit for senescence reduction but reversed some of the renoprotective effects of the early treatment. These data suggest a time-dependent role of p53 activity supporting the current therapeutic concept of a short-term inhibition, while advocating against a prolonged treatment after I/R.

MDM2 inhibitor ameliorates cisplatin-induced nephropathy via NFκΒ signal inhibition

Cisplatin is a platinum-containing chemotherapeutic drug, which is widely used and highly effective. While effective against tumors, its use is limited by severe side effects such as nephrotoxicity and bone marrow suppression. Murine double minute 2 (MDM2) is the E3 ubiquitin ligase of the tumor suppressor gene, p53, and inhibition of MDM2 can suppress tumor cell growth. However, independent of p53, MDM2 acts as a co-transcription factor for nuclear factor-κB (NFκB), whose signaling can be involved in cisplatin-induced tubular injury. We therefore examined the effects of MDM2 inhibitor on cisplatin cytotoxicity. In order to induce acute kidney injury and to investigate MDM2 inhibitory effects, we injected cisplatin into rats with or without the MDM2 inhibitor, DS-5272, and analyzed kidney physiology/histology and NFκB signaling. Serum creatinine was significantly lower in the DS-5272 group than in the vehicle group on day 3 (0.55 ± 0.069 vs 0.70 ± 0.072 mg/dL, P < 0.05). DS-5272 also significantly decreased kidney injury molecule-1 (KIM-1) expression, improved tubular injury, and decreased apoptotic cells. Western blotting showed that cisplatin increased NFκB phosphorylation in kidneys, which was significantly suppressed by DS-5272. In vitro, we treated HEK 293 cells with cisplatin, in the absence or presence of DS-5272, and examined cytotoxicity and NFκB transcriptional activity. DS-5272 co-treatment reduced both cisplatin-induced cell death and NFκB transcriptional activity. Collectively, these findings suggest that DS-5272 can ameliorate cisplatin nephrotoxicity via NFκB signal inhibition.

Gene Silencing With siRNA (RNA Interference): A New Therapeutic Option During Ex Vivo Machine Liver Perfusion Preservation

RNA interference (RNAi) is a natural process of posttranscriptional gene regulation that has raised a lot of attention culminating with the Nobel Prize in Medicine in 2006. RNAi-based therapeutics have been tested in experimental transplantation to reduce ischemia/reperfusion injury (IRI) with success. Modulation of genes of the innate immune system, as well as apoptotic genes, and those involved in the nuclear factor kappa B pathways can reduce liver injury in rodent liver pedicle clamping and transplantation models of IRI. However, in vivo use of RNAi faces limitations regarding the method of administration, uptake, selectivity, and stability. Machine perfusion preservation, a more recent alternative approach for liver preservation showing superior results to static cold preservation, could be used as a platform for gene interference therapeutics. Our group was the first to demonstrate uptake of small interfering RNA (siRNA) during liver machine preservation under both normothermic and hypothermic perfusion. Administering siRNA in the perfusion solution during ex vivo machine preservation has several advantages, including more efficient delivery, lower doses and cost-saving, and none/fewer side effects to other organs. Recently, the first RNAi drug was approved by the US Food and Drug Administration for clinical use, opening a new avenue for new drugs with different clinical applications. RNAi has the potential to have transformational therapeutic applications in several areas of medicine including transplantation. We believe that machine preservation offers great potential to be the ideal delivery method of siRNA to the liver graft, and future studies should be initiated to improve the clinical applicability of RNAi in solid organ transplantation.

Cell Death Patterns Due to Warm Ischemia or Reperfusion in Renal Tubular Epithelial Cells Originating from Human, Mouse, or the Native Hibernator Hamster

Ischemia–reperfusion injury contributes to the pathogenesis of many diseases, with acute kidney injury included. Hibernating mammals survive prolonged bouts of deep torpor with a dramatic drop in blood pressure, heart, and breathing rates, interspersed with short periods of arousal and, consequently, ischemia–reperfusion injury. Clarifying the differences under warm anoxia or reoxygenation between human cells and cells from a native hibernator may reveal interventions for rendering human cells resistant to ischemia–reperfusion injury. Human and hamster renal proximal tubular epithelial cells (RPTECs) were cultured under warm anoxia or reoxygenation. Mouse RPTECs were used as a phylogenetic control for hamster cells. Cell death was assessed by both cell imaging and lactate dehydrogenase (LDH) release assay, apoptosis by cleaved caspase-3, autophagy by microtubule-associated protein 1-light chain 3 B II (LC3B-II) to LC3B-I ratio, necroptosis by phosphorylated mixed-lineage kinase domain-like pseudokinase, reactive oxygen species (ROS) fluorometrically, and lipid peroxidation, the end-point of ferroptosis, by malondialdehyde. Human cells died after short periods of warm anoxia or reoxygenation, whereas hamster cells were extremely resistant. In human cells, apoptosis contributed to cell death under both anoxia and reoxygenation. Although under reoxygenation, ROS increased in both human and hamster RPTECs, lipid peroxidation-induced cell death was detected only in human cells. Autophagy was observed only in human cells under both conditions. Necroptosis was not detected in any of the evaluated cells. Clarifying the ways that are responsible for hamster RPTECs escaping from apoptosis and lipid peroxidation-induced cell death may reveal interventions for preventing ischemia–reperfusion-induced acute kidney injury in humans.