The liver X receptor agonist TO901317 protects mice against cisplatin-induced kidney injury

Nuclear receptors in renal health and disease

As a major social and economic burden for the healthcare system, kidney diseases contribute to the constant increase of worldwide deaths. A deeper understanding of the underlying mechanisms governing the etiology, development and progression of kidney diseases may help to identify potential therapeutic targets. As a superfamily of ligand-dependent transcription factors, nuclear receptors (NRs) are critical for the maintenance of normal renal function and their dysfunction is associated with a variety of kidney diseases. Increasing evidence suggests that ligands for NRs protect patients from renal ischemia/reperfusion (I/R) injury, drug-induced acute kidney injury (AKI), diabetic nephropathy (DN), renal fibrosis and kidney cancers. In the past decade, some breakthroughs have been made for the translation of NR ligands into clinical use. This review summarizes the current understanding of several important NRs in renal physiology and pathophysiology and discusses recent findings and applications of NR ligands in the management of kidney diseases.

Liver X Receptor α in Sciatic Nerve Exerts an Alleviating Effect on Neuropathic Pain Behaviors Induced by Crush Injury

Peripheral nerve injury often leads to neuropathic pain. In the present study, we assessed the role of liver x receptor alpha (LXRα), an oxysterol regulated nuclear transcription factor that promotes reverse cholesterol transport and alternative (M2) macrophage activation, in the development of neuropathic pain. We found that compared to WT mice, in LXRα knockout mice the development of mechanical allodynia following sciatic nerve crush was accelerated and the duration was prolonged. Furthermore, the expression of M1-like macrophage marker iNOS and M1-like macrophages inducer hydrogen peroxide (H2O2) was increased, whereas expression of M2 macrophage marker arginase-1 (Arg-1) and interleukin-10 (IL-10) was reduced in the sciatic nerve of LXRα knockout mice. Moreover, peri-sciatic administration of LXRs agonist GW3965, immediately after the nerve crush, into wild type mice, suppressed the mechanical allodynia induced by crush injury. GW3965 also suppressed the expression of iNOS and production of H2O2 in the injured nerve and enhanced the expression of IL-10 and Arg-1. Importantly, peri-sciatic administration of IL-10 neutralization antibody prevented the alleviating effect of GW3965 on mechanical allodynia. Altogether, these results indicates that the lack of LXRα in the sciatic nerve results in an augmented inflammatory profile of macrophages, which ultimately speed up the development of neuropathic pain and dampen its recovery following nerve injury. Activation of LXRα by its agonist might rebalance the neuroprotective and neurotoxic macrophage phenotypes, and thus alleviate the neuropathic pain behavior.

MDM2 inhibition improves cisplatin-induced renal injury in mice via inactivation of Notch/hes1 signaling pathway

OBJECTIVE

To explore the potential function of MDM2-mediated Notch/hes1 signaling pathway in cisplatin-induced renal injury.

METHODS

The acute renal injury models of mice after intraperitoneal injection of cisplatin in vivo, and the apoptotic models of human renal tubular epithelial (HK-2) cells induced by cisplatin in vitro, were conducted respectively. The renal function-related parameters were measured. The renal tissue pathological changes and apoptosis were observed by PAS staining and TUNEL staining, respectively. Cell viability and apoptosis were detected by MTT and flow cytometry. Notch/hes1 pathway-related proteins were tested by Western blotting.

RESULTS

After mice injected by cisplatin, the levels of Cr, BUN, urine cystatin C, urine NGAL and urine ACR were increased and GFR was decreased with the elevation of renal tubular injury scores, the upregulation of the expressions of MDM2, N1ICD, Hes1 and Cleaved caspase-3, as well as the enhancement of cell apoptosis accompanying decreased ratio of Bcl-2/Bax. However, these cisplatin-induced renal injuries of mice have been improved by MDM2 inhibition. Besides, the declined viability, increased cytotoxicity, and enhanced apoptosis were observed in cisplatin-induced HK-2 cells, with the activated Notch/hes1 pathway. Notably, the phenomenon was alleviated in cisplatin-induced HK-2 cells transfected with MDM2 shRNA, but was severer in those co-treated with AdMDM2. Moreover, Notch1 siRNA can reverse the injury of AdMDM2 on HK-2 cells.

CONCLUSION

Inhibiting MDM2 could reduce cell apoptosis through blocking Notch/hes1 signaling pathway, thus alleviating the acute renal injury caused by cisplatin.

Nuclear receptors in the kidney during health and disease

Over the last 30 years, nuclear receptors (NRs) have been increasingly recognized as key modulators of systemic homeostasis and as contributing factors in many diseases. In the kidney, NRs play numerous important roles in maintaining homeostasis-many of which continue to be unraveled. As "master regulators", these important transcription factors integrate and coordinate many renal processes such as circadian responses, lipid metabolism, fatty acid oxidation, glucose handling, and inflammatory responses. The use of recently-developed genetic tools and small molecule modulators have allowed for detailed studies of how renal NRs contribute to kidney homeostasis. Importantly, while NRs are intimately involved in proper kidney function, they are also implicated in a variety of renal diseases such as diabetes, acute kidney injury, and other conditions such as aging. In the last 10 years, our understanding of renal disease etiology and progression has been greatly shaped by knowledge regarding how NRs are dysregulated in these conditions. Importantly, NRs have also become attractive therapeutic targets for attenuation of renal diseases, and their modulation for this purpose has been the subject of intense investigation. Here, we review the role in health and disease of six key renal NRs including the peroxisome proliferator-activated receptors (PPAR), estrogen-related receptors (ERR), the farnesoid X receptors (FXR), estrogen receptors (ER), liver X receptors (LXR), and vitamin D receptors (VDR) with an emphasis on recent findings over the last decade. These NRs have generated a wealth of data over the last 10 years that demonstrate their crucial role in maintaining normal renal homeostasis as well as their capacity to modulate disease progression.

A meta-analysis of preclinical studies using antioxidants for the prevention of cisplatin nephrotoxicity: implications for clinical application

Cisplatin is an effective chemotherapeutic drug whose clinical use and efficacy are limited by its nephrotoxicity, which affects mainly the renal tubules and vasculature. It accumulates in proximal and distal epithelial tubule cells and causes oxidative stress-mediated cell death and malfunction. Consequently, many antioxidants have been tested for their capacity to prevent cisplatin nephrotoxicity. In this study, we made a systematic review of the literature and meta-analyzed 152 articles, which tested the nephroprotective effect of isolated compounds or mixtures of natural origin on cisplatin nephrotoxicity in preclinical models. This meta-analysis identified the most effective candidates and examined the efficacy obtained by antioxidants administered by the oral and intraperitoneal routes. By comparing with a recent, similar meta-analysis performed on clinical studies, this article identifies a disconnection between preclinical and clinical research, and contextualizes, discusses, and integrates the existing preclinical information toward the optimized selection of candidates to be further explored (clinical level). Despite proved efficacy, this article discusses the barriers limiting the clinical development of natural mixtures, such as those in extracts from Calendula officinalis flowers and Heliotropium eichwaldii roots. On the contrary, isolated compounds are more straightforward candidates, among which arjunolic acid and quercetin stand out in this meta-analysis.

The organic ester O,O'-diethyl-(S,S)-ethylenediamine-N,N'-di-2-(3-cyclohexyl)propanoate dihydrochloride attenuates murine breast cancer growth and metastasis

Pharmacological treatment of cancer is mostly limited by drug-toxicity and resistance. It has been noticed that new organic ester ligand, O,O’-diethyl-(S,S)-ethylenediamine-N,N’-di-2-(3-cyclohexyl)propanoate dihydrochloride (named DE-EDCP) showed effective cytotoxic capacities against several human and mouse cancer cell lines. However, its effects on tumor growth and metastasis are unexplored. The aim of present study was to examine the ability of DE-EDCP to inhibit 4T1 murine breast cancer growth and progression and to explore possible molecular mechanisms. DE-EDCP exhibited significant tumoricidal activity on human and murine breast cancer cell lines. Further, marked reduction of murine breast cancer growth and progression by DE-EDCP was shown. DE-EDCP exhibits fewer side-effects compared to cisplatin as a conventional chemotherapeutic. Results obtained from in vivo and in vitro experiments indicate that DE-EDCP induces apoptosis and inhibits proliferation of 4T1 cells. DE-EDCP increases percentage of 4T1 cells in late apoptosis, expression of pro-apoptotic Bax and caspase-3, while decreases expression of anti-apoptotic Bcl-2. DE-EDCP treatment increased the percentage of TUNEL-positive nuclei and reduced Ki-67 expression in breast cancer tissue. DE-EDCP decreased expression of cyclin D3 and Ki-67, increased expression of cyclin-dependent kinase inhibitors p16, p21 and p27 and arrested 4T1 cells in G0/G1 cell cycle phase. Expression of STAT3 and downstream regulated molecules, NANOG and SOX2, was reduced in 4T1 cells after DE-EDCP treatment.

In conclusion, DE-EDCP impairs breast cancer growth and progression by triggering cancer cell death and inhibition of cancer cell proliferation. DE-EDCP might be of interest in the development of the new anticancer agent.

Activation of the cholinergic anti-inflammatory pathway by GTS-21 attenuates cisplatin-induced acute kidney injury in mice

Acute kidney injury (AKI) is the most common side effect of cisplatin, a widely used chemotherapy drug. Although AKI occurs in up to one third of cancer patients receiving cisplatin, effective renal protective strategies are lacking. Cisplatin targets renal proximal tubular epithelial cells leading to inflammation, reactive oxygen species, tubular cell injury, and eventually cell death. The cholinergic anti-inflammatory pathway is a vagus nerve-mediated reflex that suppresses inflammation via α7 nicotinic acetylcholine receptors (α7nAChRs). Our previous studies demonstrated the renoprotective and anti-inflammatory effects of cholinergic agonists, including GTS-21. Therefore, we examined the effect of GTS-21 on cisplatin-induced AKI. Male C57BL/6 mice received either saline or GTS-21 (4mg/kg, i.p.) twice daily for 4 days before cisplatin and treatment continued through euthanasia; 3 days post-cisplatin mice were euthanized and analyzed for markers of renal injury. GTS-21 significantly reduced cisplatin-induced renal dysfunction and injury (p<0.05). GTS-21 significantly attenuated renal Ptgs2/COX-2 mRNA and IL-6, IL-1β, and CXCL1 protein expression, as well as neutrophil infiltration after cisplatin. GTS-21 blunted cisplatin-induced renal ERK1/2 activation, as well as renal ATP depletion and apoptosis (p<0.05). GTS-21 suppressed the expression of CTR1, a cisplatin influx transporter and enhanced the expression of cisplatin efflux transporters MRP2, MRP4, and MRP6 (p<0.05). Using breast, colon, and lung cancer cell lines we showed that GTS-21 did not inhibit cisplatin’s tumor cell killing activity. GTS-21 protects against cisplatin-AKI by attenuating renal inflammation, ATP depletion and apoptosis, as well as by decreasing renal cisplatin influx and increasing efflux, without impairing cisplatin-mediated tumor cell killing. Our results support further exploring the cholinergic anti-inflammatory pathway for preventing cisplatin-induced AKI.

Mesenchymal Stem Cells Attenuate Cisplatin-Induced Nephrotoxicity in iNOS-Dependent Manner

Mesenchymal stem cells (MSCs) are, due to their immunomodulatory characteristics, utilized in therapy of immune-mediated diseases. We used murine model of cisplatin nephrotoxicity to explore the effects of MSCs on immune cells involved in the pathogenesis of this disease. Intraperitoneal application of MSCs significantly attenuated cisplatin nephrotoxicity, decreased inflammatory cytokines TNF-α and IL-17, and increased anti-inflammatory IL-10, IL-6, nitric oxide (NO), and kynurenine in sera of cisplatin-treated mice. MSC treatment significantly attenuated influx of leukocytes, macrophages, dendritic cells (DCs), neutrophils, CD4+ T helper (Th), and CD8+ cytotoxic T lymphocytes (CTLs) in damaged kidneys and attenuated the capacity of renal-infiltrated DCs, CD4+ Th, and CD8+ CTLs to produce TNF-α and IL-17. Similar effects were observed after intraperitoneal injection of MSC-conditioned medium (MSC-CM) indicating that MSCs exert their beneficial effects in paracrine manner. Inhibition of inducible nitric oxide synthase (iNOS) in MSC-CM resulted with increased number of TNF-α-producing DCs and IL-17-producing CTLs, decreased number of IL-10-producing tolerogenic DCs and regulatory CD4+FoxP3+ T cells, and completely diminished renoprotective effects of MSC-CM. In conclusion, MSCs, in iNOS-dependent manner, attenuated inflammation in cisplatin nephrotoxicity by reducing the influx and capacity of immune cells, particularly DCs and T lymphocytes, to produce inflammatory cytokines.

Physiology and Pathophysiology of the Intrarenal Renin-Angiotensin System: An Update

The renin-angiotensin system (RAS) has a pivotal role in the maintenance of extracellular volume homeostasis and blood pressure through complex mechanisms. Apart from the well known systemic RAS, occurrence of a local RAS has been documented in multiple tissues, including the kidney. A large body of recent evidence from pharmacologic and genetic studies, particularly those using various transgenic approaches to manipulate intrarenal levels of RAS components, has established the important role of intrarenal RAS in hypertension. Recent studies have also begun to unravel the molecular mechanisms that govern intrarenal RAS activity. This local system is under the control of complex regulatory networks consisting of positive regulators of (pro)renin receptor, Wnt/β-catenin signaling, and PGE₂/PGE₂ receptor EP₄ subtype, and negative regulators of Klotho, vitamin D receptor, and liver X receptors. This review highlights recent advances in defining the regulation and function of intrarenal RAS as a unique entity separate from systemic angiotensin II generation.