All-trans retinoic acid potentiates cisplatin-induced kidney injury in rats: impact of retinoic acid signaling pathway

All-trans retinoic acid in anticancer therapy: how nanotechnology can enhance its efficacy and resolve its drawbacks

Introduction: All-trans retinoic acid (ATRA, tretinoin) is the main drug used in the treatment of acute promyelocytic leukemia (APL). Despite its impressive activity against APL, the same could not be clinically observed in other types of cancer. Nanotechnology can be a tool to enhance ATRA anticancer efficacy and resolve its drawbacks in APL as well as in other malignancies.Areas covered: This review covers ATRA use in APL and non-APL cancers, the problems that were found in ATRA therapy and how nanoencapsulation can aid to circumvent them. Pre-clinical results obtained with nanoencapsulated ATRA are shown as well as the two ATRA products based on nanotechnology that were clinically tested: ATRA-IV® and Apealea®.Expert opinion: ATRA presents interesting properties to be used in anticancer therapy with a notorious differentiation and antimetastatic activity. Bioavailability and resistance limitations impair the use of ATRA in non-APL cancers. Nanotechnology can circumvent these issues and provide tools to enhance its anticancer activities, such as co-loading of multiple drug and active targeting to tumor site.

The yin and yang of retinoic acid signaling in kidney diseases

Retinoic acid (RA) signaling is involved in various physiological and pathological conditions, including development, tumorigenesis, inflammation, and tissue damage and repair. In kidneys, the beneficial effect of RA has been reported in multiple disease models, such as glomerulosclerosis, renal fibrosis, and acute kidney injury. In this issue of the JCI, Chen et al. report a pathway activated by RA signaling that is mediated by the retinoic acid receptor responder protein 1 (RARRES1). Specifically, RARRES1, which is proteolytically cleaved to release the extracellular domain, was endocytosed by podocytes to induce apoptosis and glomerular dysfunction kidney disease. These findings unveil the contrasting aspects, a Janus face, of RA signaling that may guide its therapeutic use.

Retinoic acid receptor-beta prevents cisplatin-induced proximal tubular cell death

Cisplatin's toxicity in renal tubular epithelial cells limits the therapeutic efficacy of this antineoplastic drug. In cultured human proximal tubular HK-2 cells (PTC) a prostaglandin uptake transporter (PGT)-dependent increase in intracellular prostaglandin E₂ (iPGE₂) mediates cisplatin's toxicity (i.e. increased cell death and loss of cell proliferation) so that it is prevented by PGT inhibitors. Here we found in cisplatin-treated PTC that 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), a PGT inhibitor, prevented cisplatin's toxicity but not the increase in iPGE₂. Because expression of retinoic acid receptor-β (RAR-β) is dependent on iPGE₂ and because RAR-β is a regulator of cell survival and proliferation, we hypothesized that RAR-β might mediate the protective effect of DIDS against cisplatin's toxicity in PTC. Our results confirmed this hypothesis because: i) protection of PTC by DIDS was abolished by RAR-β antagonist LE-135; ii) DIDS increased the expression of RAR-β in PTC and prevented its decrease in cisplatin-treated PTC but not in cisplatin-treated human cervical adenocarcinoma HeLa cells in which DIDS failed to prevent cisplatin's toxicity; iii) while RAR-β expression decreased in cisplatin-treated PTC, RAR-β over-expression prevented cisplatin's toxicity. RAR-β agonist CH55 or RAR pan-agonist all-trans retinoic acid did not prevent cisplatin's toxicity, which suggests that RAR-β does not protect PTC through activation of gene transcription. In conclusion, RAR-β might be a new player in cisplatin-induced proximal tubular injury and the preservation of its expression in proximal tubules through treatment with DIDS might represent a novel strategy in the prevention of cisplatin's nephrotoxicity without compromising cisplatin's chemotherapeutic effect on cancer cells.

Anti-PD-L1-modified and ATRA-loaded nanoparticles for immuno-treatment of oral dysplasia and oral squamous cell carcinoma

Aim: To develop nanomedicines for immuno-therapy of oral dysplasia and oral squamous cell carcinoma. Materials & methods: All-trans retinoic acid (ATRA)-poly(lactide-co-glycolide acid) (PLGA)-poly(ethylene glycol) (PEG)-programmed death-ligand 1 (PD-L1) nanomedicines were fabricated by loading ATRA into PLGA-PEG nanocarriers and modification using an anti-PD-L1 antibody. Results: ATRA-PLGA-PEG-PD-L1 nanoparticles showed fast cellular uptake, significantly inhibited proliferation and induced apoptosis in DOK and CAL27 cells. Moreover, in C3H tumor-bearing mice, ATRA-PLGA-PEG-PD-L1 nanoparticles more specifically targeted tumor cells, enhanced anticancer activity and reduced side effects when compared with free ATRA. Furthermore, CD8+ T cells were activated around PD-L1 positive cells in the tumor microenvironment after treatment. Conclusion: ATRA-PLGA-PEG-PD-L1 nanoparticles had low toxicity, high biocompatibility and specifically targeted oral dysplasia and squamous carcinoma cells both in vitro and in vivo.

Protective Effect of All-Trans Retinoic Acid in Cisplatin-Induced Testicular Damage in Rats

PURPOSE

To investigate the effects of all-trans retinoic acid (ATRA) in cisplatin (CP)-induced testicular damage in rats.

MATERIALS AND METHODS

Twenty-eight male Wistar rats were divided into four groups: Control, ATRA alone, ATRA+CP, and CP alone. Body weight, testicular weight, sperm count, sperm motility, percentage of abnormal sperm, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI) in testicular tissue, and testicular histopathology were compared among groups.

RESULTS

The sperm count and motility significantly decreased and the percentage of abnormal sperm significantly increased in the CP group compared to the control and ATRA groups. CP+ATRA administration significantly increased the sperm count and motility, but reduced the abnormal sperm count. CP administration significantly increased TOS and OSI compared to the control group and the other groups. Administering CP+ATRA significantly decreased TOS and the OSI in testicular tissue and reduced spermatogenesis, but increased the Johnsen score.

CONCLUSIONS

The destructive effects of CP treatment on testicular tissue and spermatogenesis were reduced by administering ATRA.

All-trans retinoic acid prevents cisplatin-induced nephrotoxicity in rats

The aim of this study is to investigate the effects of all-trans retinoic acid (ATRA) use on cisplatin (CP)-induced nephrotoxicty. Twenty-eight rats were randomly divided into four groups. The rats in the control group were injected a single dose of 1 ml/kg saline intra-peritoneally (IP) during 10 days. The rats in the ATRA group were injected a single dose of ATRA during 10 days. The rats in the ATRA+CP group were injected a single dose of CP on the fourth day of the 10 days of ATRA treatment. The rats in the CP group were injected a single dose of CP on the fourth day of 10 days without administering a treatment. After treatment, the groups were compared with regard to total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) levels in renal tissue and renal histopathology. The serum creatinine and urea values were statistically significantly higher in the CP group compared to the other groups. The serum creatinine and urea values were statistically significantly lower in the ATRA+CP group when compared to the CP group. Although the TOS and OSI levels were found to be lower in the ATRA+CP group compared to the CP group, the difference was not statistically significant. Administration of ATRA together with CP was observed to reduce the histopathologic destruction in the kidney and lead to mild tubular degeneration, vacuolization, and necrosis (57.1% grade 1; 28.6% grade2, and 14.3% grade 3 necrosis). The results of the present study have revealed that ATRA administration ameliorates CP-induced nephrotoxicity; however, further studies are required to identify this issue before clinical application.

All-trans-retinoic acid-mediated cytoprotection in LLC-PK1 renal epithelial cells is coupled to p-ERK activation in a ROS-independent manner

Although all-trans-retinoic acid (ATRA) provides protection against a variety of conditions in vivo, particularly ischemia, the molecular mechanisms underpinning these effects remain unclear. The present studies were designed to assess potential mechanisms by which ATRA affords cytoprotection against renal toxicants in LLC-PK₁ cells. Pretreatment of LLC-PK₁ cells with ATRA (25 μM) for 24 h afforded cytoprotection against oncotic cell death induced by p-aminophenol (PAP), 2-(glutathion-S-yl)hydroquinone (MGHQ), and iodoacetamide but not against apoptotic cell death induced by cisplatin. Inhibition of protein synthesis with cycloheximide blunted ATRA protection, indicating essential cell survival pathways must be engaged before toxicant exposure to provide cytoprotection. Interestingly, ATRA did not prevent the PAP-induced generation of reactive oxygen species (ROS) nor did it alter glutathione levels. Moreover, ATRA had no significant effect on Nrf2 protein expression, and the Nrf2 inducers sulforaphane and MG132 did not influence ATRA cytoprotection, suggesting cytoprotective pathways beyond those that influence ROS levels contribute to ATRA protection. In contrast, ATRA rapidly (15 min) induced levels of the cellular stress kinases p-ERK and p-AKT at concentrations of ATRA (10 and 25 μM) required for cytoprotection. Consistent with a role for p-ERK in ATRA-mediated cytoprotection, inhibition of p-ERK with PD98059 reduced the ability of ATRA to afford protection against PAP toxicity. Collectively, these data suggest that p-ERK and its downstream targets, independent of ROS and antioxidant signaling, are important contributors to the cytoprotective effects of ATRA against oncotic cell death.

[Research advances in the protective effect of all-trans retinoic acid against podocyte injury]

All-trans retinoic acid (ATRA) is a vitamin A derivative and plays an important role in the regulation of cell aggregation, differentiation, apoptosis, proliferation, and inflammatory response. In recent years, some progress has been made in the role of ATRA in renal diseases, especially its protective effect on podocytes. This article reviews the research advances in podocyte injury, characteristics of ATRA, podocyte differentiation and regeneration induced by ATRA, and the protective effect of ATRA against proliferation, deposition of fibers, and apoptosis.