Realgar transforming solution-induced differentiation of NB4 cell by the degradation of PML/RARα partially through the ubiquitin–proteasome pathway

Various crystalline forms of realgar exhibit differentiated anti-abscess and anticancer effects based on a PXRD analysis and biological evaluation

ETHNOPHARMACOLOGICAL RELEVANCE

Realgar is a mineral medicine with a long history that can be used externally or internally. It is often used to treat skin diseases and leukemia in clinical practice. Realgar exhibits a polycrystalline phenomenon, and it remains unknown whether there is a difference in the efficacies of the different realgar crystalline forms.

PURPOSE

The aim of this study is to investigate the pharmacodynamic differences of the different realgar crystalline forms (α-As4S4 and β-As4S4) using in vivo and in vitro experiments.

MATERIAL AND METHODS

The in realgar crystalline patterns were initially identified using a powder x-ray diffractometer (PXRD). The antimicrobial activities of α-As4S4 and β-As4S4 were then assessed in vitro to elucidate their effectiveness against bacteria. Transdermal absorption and pharmacokinetic experiments were used to investigate the variances in the bioavailabilities between the in vitro and in vivo conditions. The effects of α-As4S4 and β-As4S4 for skin abscess healing were studied in mice using a subcutaneous injection of Staphylococcus aureus (S. aureus). HL-60 cells were exposed to a serum that contained different crystalline forms of realgar to evaluate the potential differences in the therapeutic effects of α-As4S4 and β-As4S4 on leukemia.

RESULTS

Realgar is composed of α-As4S4 and β-As4S4 crystalline forms. The soluble arsenic content in α-As4S4 generally exceeded that of β-As4S4, and the antimicrobial activity showed a positive correlation with the soluble arsenic content. α-As4S4 demonstrated a higher in vivo and in vitro bioavailability and a faster elimination rate in vivo compared to β-As4S4. The pharmacodynamic experimental investigations showed that α-As4S4 exhibited a superior healing effect on subcutaneous abscesses. Furthermore, serum pharmacology experiments revealed that α-As4S4 induced significantly higher membrane damage and apoptosis in HL-60 cells compared to β-As4S4.

CONCLUSION

The different realgar crystalline forms had distinct pharmacodynamics. α-As4S4 demonstrated higher bioavailability in vitro and in vivo and superior effects on skin abscess healing compared to β-As4S4. It also possessed anti-leukemia properties. It is the first time to report the differences in the efficacy between two crystalline forms of realgar, which is helpful to improve the knowledge of the real chemical substances for realgar.

Pharmacology, Toxicology, and Rational Application of Cinnabar, Realgar, and Their Formulations

Ethnopharmacological Relevance. Mineral medicines are widely used traditional Chinese medicines with curative effects. These medicines are used for many refractory diseases. Aim of the Review. In this review, cinnabar (HgS) and realgar (As₂S₂) serve as examples of mineral medicines, and their pharmacology, therapeutic toxicity, use in traditional medicine mixtures, and research perspectives are discussed. Materials and Methods. A search was performed for the literature on cinnabar and realgar in PubMed, the Chinese Pharmacopeia, Google, and other sources. The search included studies using single herbs, traditional formulations, or novel dosage forms. Results. Cinnabar and cinnabar formulas exhibit good efficacy for sedation, sleep improvement, anxiety alleviation, and brain protection. However, previous studies on neurotransmitters have reached different conclusions, and detailed pharmacological mechanisms are lacking. Realgar and its formulas exert promising antitumor activity through regulation of cell cycle arrest, intrinsic and extrinsic apoptosis, induction of differentiation, autophagy, metabolic reprogramming, matrix metalloproteinase-9 (MMP-9) signaling, and reactive oxygen species (ROS) generation. In addition, realgar can be used to treat a variety of refractory diseases by regulating immunity and exerting antibacterial, antiviral, and other effects. However, the existing pharmacological research on the use of realgar for epidemic prevention is insufficient, and animal experiments and research at the cellular level are lacking. Inappropriate applications of cinnabar and realgar can cause toxicity, including neurotoxicity, liver toxicity, kidney toxicity, and genotoxicity. The toxicological mechanism is complex, and molecular-level research is limited. For clinical applications, theory and clinical experience must be combined to guide scientific and rational drug use and to achieve reduced toxicity and increased efficacy through the use of modern preparation methods or combined drugs. Notably, when cinnabar and realgar are used to treat targeted diseases, these agents have a bidirectional effect of “treatment” and “toxicity” on the central nervous system in pathological and normal states. The pharmacological and toxicological mechanisms need to be elucidated in greater detail in the future. Overall, systematic research is needed to provide a basis for better promotion of the rational use of cinnabar and realgar in the clinic. Conclusion. Mineral medicines are multicomponent, multiactivity, and multitargeted substances. The pharmacology and mechanisms of the toxicity and action of realgar and cinnabar are extremely complex. A number of Chinese medicinal preparations of realgar and cinnabar have demonstrated unique efficacy in the treatment of refractory diseases.

Realgar (As4S4), a traditional Chinese medicine, induces acute promyelocytic leukemia cell death via the Bcl-2/Bax/Cyt-C/AIF signaling pathway in vitro

Acute promyelocytic leukemia (APL) is a specific subtype of acute myelogenous leukemia (AML) characterized by the proliferation of abnormal promyelocytes. Realgar, a Chinese medicine containing arsenic, can be taken orally. Traditional Chinese medicine physicians have employed realgar to treat APL for over a thousand years. Therefore, realgar may be a promising candidate for the treatment of APL. Nevertheless, the underlying mechanism behind realgar therapy is largely unclear. The present study aimed to investigate the effect of realgar on cell death in the APL cell line (NB4) in vitro and to elucidate the underlying mechanism. In this study, after APL cells were treated with different concentrations of realgar, the cell survival rate, apoptotic assay, morphological changes, ATP levels and cell cycle arrest were assessed. The expression of Bcl-2, Bax, Cytochrome C (Cyt-C) and apoptosis-inducing factor (AIF) at the mRNA and protein levels were also measured by immunofluorescence, quantitative PCR (qPCR) and Western blotting. We found that realgar could significantly inhibit APL cell proliferation and cell death in a time- and dose-dependent manner. Realgar effectively decreased the ATP levels in APL cells. Realgar also induced APL cell cycle arrest at the S and G2/M phases. Following realgar treatment, the mRNA and protein levels of Bcl-2 were significantly downregulated, whereas the levels of Bax, Cyt-C, and AIF were significantly upregulated. In summary, realgar can induce APL cell death via the Bcl-2/Bax/Cyt-C/AIF signaling pathway, suggesting that realgar may be an effective therapeutic for APL.

Mineral medicine: from traditional drugs to multifunctional delivery systems

Mineral drugs are an important constituent of traditional Chinese medicine (TCM). Taking minerals that contain heavy metals as drugs is a very national characteristic part of TCM. However, the safety and scientific nature of mineral drugs are controversial owing to their heavy metals and strong toxicity. In 2000, the Food and Drug Administration (FDA) authorized arsenic trioxide (ATO) as first-line therapy for acute promyelocytic leukemia. This makes the development and utilization of mineral drugs become a research hotspot. The development of nanomedicine has found a great prospect of mineral drugs in nano-delivery carriers. And that will hold promise to address the numerous biological barriers facing mineral drug formulations. However, the studies on mineral drugs in the delivery system are few at present. There is also a lack of a detailed description of mineral drug delivery systems. In this review, the advanced strategies of mineral drug delivery systems in tumor therapy are summarized. In addition, the therapeutic advantages and research progress of novel mineral drug delivery systems are also discussed. Here, we hope that this will provide a useful reference for the design and application of new mineral drug delivery systems.

Mechanistic effects of arsenic trioxide on acute promyelocytic leukemia and other types of leukemias

Acute promyelocytic leukemia (APL), a subtype of acute myeloid leukemia characterized with a translocation between promyelocytic leukemia gene (PML) on chromosome 15 and retinoic acid receptor alpha gene (RARα) on chromosome 17. Transcription of this fusion gene results in PML/RARα fusion protein blocking expression of critical genes involved in differentiation of myeloid cells through interaction with RAR element. PML/RARα fusion protein prevents normal function of PML and RARα as well as inhibiting apoptosis. Arsenic trioxide (ATO) is an important agent for the treatment of relapsed and newly diagnosed APL. ATO induces apoptosis, autophagy, and partial cellular differentiation as well as inhibiting cell growth and angiogenesis. Recognition of signaling pathways and molecular mechanisms induced by ATO can be effective for discovering novel treatment strategies to target leukemia cells. Also, it can be developed for the treatment of a variety of cancer cells. This review provides a perspective on anticancerous effects of ATO on APL and leukemia cells.

Protective effects of ginsenoside-Rg2 and -Rh1 on liver function through inhibiting TAK1 and STAT3-mediated inflammatory activity and Nrf2/ARE-mediated antioxidant signaling pathway

Systemic or hepatic inflammation is caused by intraperitoneal application of lipopolysaccharide (LPS). In this study, we investigated anti-inflammatory and antioxidant properties of combination of ginsenoside-Rg2 (G-Rg2) and -Rh1 (G-Rh1) on liver function under LPS challenging. We first confirmed that G-Rg2 and -Rh1 at 100 μg/ml did not show cytotoxicity in HepG2 cells. G-Rg2 and -Rh1 treatment significantly inhibited activation of STAT3 and TAK1, and inflammatory factors including iNOS, TNF-α, and IL-1β in peritoneal macrophages. In HepG2 cells, G-Rg2 and -Rh1 treatment inhibited activation of STAT3 and TAK1/c-Jun N-terminal kinase, and down-regulated nuclear translocation of NF-κB transcription factor. In addition, LPS-induced mitochondrial dysfunction was restored by treatment with G-Rg2 and -Rh1. Interestingly, pretreatment with G-Rg2 and -Rh1 effectively inhibited mitochondrial damage-mediated ROS production induced by LPS stimulation, and alterations of Nrf2 nuclear translocation and ARE promotor activity were involved in G-Rg2 and -Rh1 effects on balancing ROS levels. In liver tissues of LPS-treated mice, G-Rg2 and -Rh1 treatment protected liver damages and increased Nrf2 expression while reducing CD45 expression. Taken together, G-Rg2 and -Rh1 exerts a protective effect on liver function by increasing antioxidant through Nrf2 and anti-inflammatory activities through STAT3/TAK1 and NF-κB signaling pathways in liver cells and macrophages.

Nuclear import of NLS- RARα is mediated by importin α/β

The promyelocytic leukemia-retinoic acid receptor α (PML/RARα) is hypothesized to play a vital role in the pathogenesis of acute promyelocytic leukemia (APL). A previous study has demonstrated that PML/RARα is cleaved by neutrophil elastase (NE) in early myeloid cells, which leads to an increase in the nuclear localization signal (NLS) in RARα and in the incidence of APL. In this study, we explored the effects of NLS-RARα on acute myeloid leukemia (AML) cells and studied the mechanism of its localization. LV-NLS-RARα recombinant lentivirus and negative control LV-NC lentivirus were transfected into HL-60 cells and U937 cells while mutant NLS-RARα were transfected into U937 cells, and all groups were treated with 1α, 25-dihydroxyvitamin D3(1,25D3). The results showed that NLS-RARα was located mainly in the nucleus while mutant NLS-RARα was located in the cytoplasm. Overexpression of NLS-RARα downregulated the expression of CD11b, CD11c, CD14, and three forms of CEBPβ compared to the overexpression of NC and mutant NLS-RARα. It was speculated that the abnormal localization of NLS-RARα was mediated via importin-α/β in the pathogenesis of APL. By producing point mutations in the two NLSs in NLS-RARα, we showed that the nuclear import of NLS-RARα was mainly dependent on the NLS of the RARα portion. Subsequently, we found that importin-α1 (KPNA2)/importin-β1 (KPNB1) participates in the nuclear transport of NLS-RARα. Taken together, abnormal localization of NLS-RARα blocks the differentiation of APL cells, and nuclear localization of NLS-RARα depends on NLS of the RARα portion and is mediated via binding with importin-α/β.

Serum Proteomic Profiling Analysis of Rats Chronically Exposed to Arsenic

Background

Arsenic (As) is an environmental contaminant, and As pollution in water and soil is a public health issue worldwide. As exposure is associated with the incidence of many disorders, such as arteriosclerosis, diabetes, neurodegenerative diseases, and renal dysfunction. However, the mechanism of As toxicity remains unclear.

Material/Methods

We investigated the changes in serum protein profiles of rats chronically exposed to As. Twenty healthy rats were randomly divided into 4 groups, and sodium arsenite of varying final concentrations (0, 2, 10, and 50 mg/L, respectively) was add into the drinking water for each group. The administration lasted for 3 months. Two proteomic strategies, isobaric tags for relative and absolute quantitation (iTRAQ), and 2-dimensional gel electrophoresis (2-DE), were employed to screen the differential serum proteins between control and arsenite exposure groups.

Results

We identified a total of 27 differentially-expressed proteins, among which 9 proteins were significantly upregulated and 18 were downregulated by As exposure. Many of the differentially-expressed proteins were related to fat digestion and absorption, including 5 apolipoproteins, which indicated lipid metabolism may be the most affected by As exposure.

Conclusions

This study revealed the influence of As on lipid metabolism, suggesting an increased potential risk of relevant diseases in subjects chronically exposed to As.