Synthesis and Biological Evaluation of Novel Bufalin Derivatives

Bufalin and other cardiac steroids (CS) have been used for centuries for the treatment of congestive heart failure, arrhythmias, and other maladies. However, toxicity and the small therapeutic window of this family of steroids limit their use. Therefore, attempts to synthesize a potent, but less toxic, CS are of major importance. In the present study, two novel bufalin derivatives were synthesized and some of their pharmacological properties were characterized. The reaction of bufalin with Ishikawa's reagent resulted in the production of two novel bufalin derivatives: bufalin 2,3-ene and bufalin 3,4-ene. The compounds were purified with TLC and HPLC and their structure was verified with UV, NMR, and MS analyses. The biological activities of these compounds were evaluated by testing their ability to inhibit the Na⁺, K⁺-ATPase activity of the brain microsomal fraction to induce cytotoxic activity against the NCI-60 human tumor cell line panel and non-cancer human cells, and to increase the force of contraction of quail embryonic heart muscle cells in culture. The two steroids exhibited biological activities similar to those of other CS in the tested experimental systems, but with reduced cytotoxicity, advocating their development as drugs for the treatment of heart failure and arrhythmias.

Dimethyl fumarate attenuates lipopolysaccharide-induced mitochondrial injury by activating Nrf2 pathway in cardiomyocytes

AIMS

To determine whether dimethyl fumarate (DMF) can protect against lipopolysaccharide (LPS) -induced myocardial injury.

MAIN METHODS

H9c2 cells pretreated with or without DMF were stimulated with LPS. Cell viability and apoptosis were evaluated. Nrf2 and HO-1 expression were detected using Western blotting. Mitochondrial morphology, mitochondrial superoxide production were observed using confocal microscope. Mitochondrial respiration function was measured using Seahorse bioanalyzer.

KEY FINDINGS

(1) The cell viability decreased, LDH release and apoptosis increased in LPS- challenged H9c2 cells. DMF pretreatment brought a higher cell viability, and a lower LDH leakage and apoptosis than those of LPS group (P < 0.01). (2) DMF pretreatment resulted in an increased Nrf2 and HO-1 expression, and enhanced nuclear Nrf2 level in LPS-challenged cells (P < 0.01). (3) Nrf2-siRNA could inhibit DMF-induced enhancement of HO-1 expression and cell viability, and partly abolish DMF-induced reduction of LDH leakage and apoptosis. (4) ERK1/2 inhibitor PD98059 could not only prevent the DMF-induced enhancement of nuclear Nrf2 and HO-1, but also inhibit DMF-induced increase in cell viability. (5) Compared with LPS-challenged cells, DMF pretreatment caused a lower production of mitochondrial superoxide and a higher mitochondrial membrane potential, which could be abolished by Nrf2-siRNA. (6) DMF could attenuate LPS-induced mitochondrial fragmentation and improve mitochondrial respiration function by enhancement of the oxygen consumption rate of basal respiration and ATP production in LPS-challenged cells (P < 0.01).

SIGNIFICANCE

DMF protects cardiomyocytes against LPS-induced damage. ERK1/2-dependent activation of Nrf2/HO-1 pathway is responsible for DMF-induced cardioprotection via reduction of oxidative stress, improvement of mitochondrial morphology and energy metabolism.

Shengmai injection alleviates H2O2‑induced oxidative stress through activation of AKT and inhibition of ERK pathways in neonatal rat cardiomyocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Shengmai injection (SMI) is a classical traditional Chinese medicine (TCM) officially recorded in Pharmacopoeia of the People's Republic of China (version 2015) and has long been used to treat heart failure in China. However scientific evidence for the anti-oxidative stress potential of SMI used in traditional medicine is lacking.

AIM OF STUDY

The present study aimed to evaluate the efficacy of SMI in alleviating H₂O₂‑induced Oxidative Stress the underlying mechanisms MATERIALS AND METHODS: H₂O₂-induced oxidative stress model of cardiomyocytes was established with primary cultured neonatal rat cardiomyocytes. CCK8 cell viability assay and lacatate dehydrogenase cytotoxicity assay were performed to ensure the safety dose and lowest effective dose for the mode employing CCK-8 cell viability assay kit and lactate dehydrogenase cytotoxicity assay kit. ROS levels were determined using CM-H2DCFDA fluorescent probe in cardiomyocytes with H₂O₂-induced oxidative stress. The change of NAD(P)H level in cardiomyocytes was evaluated during the process of oxidative stress. The content of myocardial cytosolic Ca²⁺ and Ca²⁺ was determined using Fura-2/AM and Rhod 2-AM fluorescent probe in mitochondrial in the process of oxidative stress. Annexin V-FITC/PI double staining was applied to examine the apoptotic cells in cardiomyocytes with oxidative stress. To identify the apoptosis after oxidative stress myocardial cells with the application of Annexin V-FITC/PI double staining apoptosis detection kit. Quantitative polymerase chain reaction (RT-PCR) was applied to measure the expression of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GSR). Western blot was performed to observe the phosphorylation of AKT and ERK1/2.

RESULTS

SMI was shown to significantly attenuate oxidative stress-induced cell proliferation arrest and apoptosis in neonatal rat cardiomyocytes. In addition, SMI treatment could decrease the production of reactive oxygen species (ROS), nicotinamide adenine dinucleotide (NADH) and malondialdehyde (MDA), and reduce the overloads of cytoplasmic Ca²⁺ and mitochondrial Ca²⁺ induced by H₂O₂. SMI could also restore the mRNA expression and activities of SOD, GSR, and CAT suppressed by H₂O₂. Mechanistically, SMI upregulated intracellular AKT phosphorylation and downregulate ERK1/2 phosphorylation in H₂O₂-treated cardiomyocytes. Pretreatment with LY294002, an AKT phosphorylation inhibitor, suppressed the protective role of SMI in cardiomyocytes, while pretreatment with PD98059, an ERK1/2 phosphorylation inhibitor, enhanced the effect of SMI.

CONCLUSIONS

In conclusion, SMI may attenuate oxidative stress-induced damage in cardiomyocytes potentially through the AKT and ERK1/2 pathway and can function as a promising injectable traditional Chinese medicine to treat oxidative stress-induced injury.

The pro- and anti-tumor roles of mesenchymal stem cells toward BRCA1-IRIS-overexpressing TNBC cells

Background

To evaluate the cross-talk between BRCA1-IRIS (IRIS)-overexpressing (IRISOE) TNBC cells and tumor-resident mesenchymal stem cells (MSCs) that triggers the aggressiveness or elimination of IRISOE TNBC tumors.

Methods

We analyzed the effect of silencing or inactivating IRIS on the bi-directional interaction between IRISOE TNBC cells and MSCs on tumor formation and progression. We analyzed the downstream signaling in MSCs induced by IL-6 secreted from IRISOE TNBC cells. We compared the effect of MSCs on the formation and progression of IRIS-proficient and deficient-TNBC cells/tumors using in vitro and in vivo models. Finally, we analyzed the association between IL-6, PTGER2, and PTGER4 overexpression and breast cancer subtype; hormone receptor status; and distant metastasis-free or overall survival.

Results

We show high-level IL-6 secreted from IRISOE TNBC cells that enhances expression of its receptor (IL-6R) in MSCs, their proliferation, and migration toward IRISOE, in vitro, and recruitment into IRISOE TNBC tumors, in vivo. In serum-free medium, recombinant IL-6 and the IL-6-rich IRISOE TNBC cell condition media (CM) decreased STAT3^Y705 phosphorylation (p-STAT3^Y705) in MSCs. Inhibiting IRIS expression or activity prolonged STAT3^Y705 phosphorylation in MSCs. The interaction with IRISOE TNBC cells skewed MSC differentiation toward prostaglandin E₂ (PGE₂)-secreting pro-aggressiveness cancer-associated fibroblasts (CAFs). Accordingly, co-injecting human or mouse MSCs with IRISOE TNBC tumor cells promoted the formation of aggressive mammary tumors, high circulating IL-6 and PGE₂ levels, and reduced overall survival. In contrast, IRIS-silenced or inactivated cells showed reduced tumor formation ability, limited MSC recruitment into tumors, reduced circulating IL-6 and PGE₂ levels, and prolonged overall survival. A positive correlation between IL-6, PTGER2, and PTGER4 expression and basal phenotype; ER-negativity; distant metastasis-free and overall survival in basal; or BRCA^mutant carriers was observed. Finally, the bi-directional interaction with MSCs triggered death rather than growth of IRIS-silenced TNBC cells, in vitro and in vivo.

Conclusions

The IL-6/PGE₂-positive feedback loop between IRISOE TNBC tumor cells and MSCs enhances tumor aggressiveness. Inhibiting IRIS expression limits TNBC tumor growth and progression through an MSC-induced death of IRIS-silenced/inactivated TNBC cells.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1131-2) contains supplementary material, which is available to authorized users.

The Na,K-ATPase in vascular smooth muscle cells

The Na,K-ATPase is an enzyme essential for ion homeostasis in all cells. Over the last decades, it has been well-established that in addition to the transport of Na⁺/K⁺ over the cell membrane, the Na,K-ATPase acts as a receptor transducing humoral signals intracellularly. It has been suggested that ouabain-like compounds serve as endogenous modulators of this Na,K-ATPase signal transduction. The molecular mechanisms underlying Na,K-ATPase signaling are complicated and suggest the confluence of divergent biological pathways. This review discusses recent updates on the Na,K-ATPase signaling pathways characterized or suggested in vascular smooth muscle cells. The conventional view on this signaling is based on a microdomain structure where the Na,K-ATPase controls the Na,Ca-exchanger activity via modulation of intracellular Na⁺ in the spatially restricted submembrane space. This, in turn, affects intracellular Ca²⁺ and Ca²⁺ load in the sarcoplasmic reticulum leading to modulation of contractility as well as gene expression. An ion-transport-independent signal transduction from the Na,K-ATPase is based on molecular interactions. This was primarily characterized in other cell types but recently also demonstrated in vascular smooth muscles. The downstream signaling from the Na,K-ATPase includes Src and phosphatidylinositol-4,5-bisphosphate 3 kinase signaling pathways and generation of reactive oxygen species. Moreover, in vascular smooth muscle cells the interaction between the Na,K-ATPase and proteins responsible for Ca²⁺ homeostasis, e.g., phospholipase C and inositol triphosphate receptors, contributes to an integration of the signaling pathways. Recent update on the Na,K-ATPase dependent intracellular signaling and the significance for physiological functions and pathophysiological changes are discussed in this review.

Na⁺, K⁺-ATPase Signaling and Bipolar Disorder

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Although in past decades the "monoamine hypothesis" has dominated our understanding of both the pathophysiology of depressive disorders and the action of pharmacological treatments, recent studies focus on the involvement of additional neurotransmitters/neuromodulators systems and cellular processes in BD. Here, evidence for the participation of Na⁺, K⁺-ATPase and its endogenous regulators, the endogenous cardiac steroids (ECS), in the etiology of BD is reviewed. Proof for the involvement of brain Na⁺, K⁺-ATPase and ECS in behavior is summarized and it is hypothesized that ECS-Na⁺, K⁺-ATPase-induced activation of intracellular signaling participates in the mechanisms underlying BD. We propose that the activation of ERK, AKT, and NFκB, resulting from ECS-Na⁺, K⁺-ATPase interaction, modifies neuronal activity and neurotransmission which, in turn, participate in the regulation of behavior and BD. These observations suggest Na⁺, K⁺-ATPase-mediated signaling is a potential target for drug development for the treatment of BD.