Synthesis and Evaluation of Cleistanthin A Derivatives as Potent Vacuolar H+-ATPase Inhibitors

Alkylide derivatives of diphyllin: synthesis and preliminary anticancer evaluation

Fourteen diphyllin 4-C-substituted alkylide derivatives were designed and synthesized using a Heck coupling and subsequent hydrogenation reaction. Olefins 3g and 3i exhibited the highest cytotoxicity on breast cancer cell lines MCF-7 with IC50 values of 0.08 and 0.07 µM, and they showed weaker V-ATPase inhibitory potency compared to diphyllin.

Bioactivities and Mechanisms of Action of Diphyllin and Its Derivatives: A Comprehensive Systematic Review

Natural products are treasure houses for modern drug discovery. Diphyllin is a natural arylnaphthalene lignan lactone isolated from the leaf of Astilboides tabularis. Studies have found that it possesses plenty of bioactivity characteristics. In this paper, we reviewed the structure, bioactivity, and mechanism of action of diphyllin and its derivatives. The references were obtained from PubMed, Web of Science, and Science Direct databases up to August 2023. Papers without a bio-evaluation were excluded. Diphyllin and its derivatives have demonstrated V-ATPase inhibition, anti-tumor, anti-virus, anti-biofilm, anti-inflammatory, and anti-oxidant activities. The most studied activities of diphyllin and its derivatives are V-ATPase inhibition, anti-tumor activities, and anti-virus activities. Furthermore, V-ATPase inhibition activity is the mechanism of many bioactivities, including anti-tumor, anti-virus, and anti-inflammatory activities. We also found that the galactosylated modification of diphyllin is a common phenomenon in plants, and therefore, galactosylated modification is applied by researchers in the laboratory to obtain more excellent diphyllin derivatives. This review will provide useful information for the development of diphyllin-based anti-tumor and anti-virus compounds.

ECDD-S16 targets vacuolar ATPase: A potential inhibitor compound for pyroptosis-induced inflammation

BACKGROUND

Cleistanthin A (CA), extracted from Phyllanthus taxodiifolius Beille, was previously reported as a potential V-ATPase inhibitor relevant to cancer cell survival. In the present study, ECDD-S16, a derivative of cleistanthin A, was investigated and found to interfere with pyroptosis induction via V-ATPase inhibition.

OBJECTIVE

This study examined the ability of ECDD-S16 to inhibit endolysosome acidification leading to the attenuation of pyroptosis in Raw264.7 macrophages activated by both surface and endosomal TLR ligands.

METHODS

To elucidate the activity of ECDD-S16 on pyroptosis-induced inflammation, Raw264.7 cells were pretreated with the compound before stimulation with surface and endosomal TLR ligands. The release of lactate dehydrogenase (LDH) was determined by LDH assay. Additionally, the production of cytokines and the expression of pyroptosis markers were examined by ELISA and immunoblotting. Moreover, molecular docking was performed to demonstrate the binding of ECDD-S16 to the vacuolar (V-)ATPase.

RESULTS

This study showed that ECDD-S16 could inhibit pyroptosis in Raw264.7 cells activated with surface and endosomal TLR ligands. The attenuation of pyroptosis by ECDD-S16 was due to the impairment of endosome acidification, which also led to decreased Reactive Oxygen Species (ROS) production. Furthermore, molecular docking also showed the possibility of inhibiting endosome acidification by the binding of ECDD-S16 to the vacuolar (V-)ATPase in the region of V0.

CONCLUSION

Our findings indicate the potential of ECDD-S16 for inhibiting pyroptosis and prove that vacuolar H+ ATPase is essential for pyroptosis induced by TLR ligands.

Cleistanthins A and B Ameliorate Testosterone-Induced Benign Prostatic Hyperplasia in Castrated Rats by Regulating Apoptosis and Cell Differentiation

Background The aging male population is at higher risk for benign prostatic hyperplasia (BPH) wherein increased proliferation of stromal and epithelial cells of the prostate is observed. In this study, we investigated the effect of cleistanthins A and B on the inhibition of testosterone-induced BPH in castrated rats. Methodology Male Wistar rats were divided into eight groups (n = 6) and surgical castration was performed. BPH was induced by the administration of testosterone propionate in corn oil at 5 mg/kg for four weeks. The control group received corn oil, and the model group received testosterone propionate. The standard treatment group received finasteride orally along with testosterone. Cleistanthins A and B at 0.3, 1, and 3 mg/kg were administered by oral gavage along with testosterone. After four weeks, rats were sacrificed, and prostates were weighed and assessed for histomorphological, inflammatory, apoptotic, and proliferative markers. Results Cleistanthins A and B decreased prostatic enlargement and histopathological abnormalities. Elevated serum dihydrotestosterone levels were lowered significantly in both the cleistanthin A and cleistanthin B groups compared to the BPH model group. Cleistanthins A and B significantly lowered the serum interleukin (IL)-1β and tumor necrosis factor-alpha inflammatory markers in the test groups. Western blot analysis revealed cleistanthin A downregulated the IL-6, signal transducer and activator of transcription 3/cyclin D1 signaling pathway. Both cleistanthins A and B upregulated the apoptotic markers caspase-3 and cleaved caspase-3, whereas the cell proliferation markers cyclin D1 and proliferating cell nuclear antigen were found to be downregulated. Conclusions Both cleistanthins A and B inhibited BPH in a rat model by apoptotic induction and impeded cell proliferation.

Rapid preparative isolation of cleistanthin a from the leaves of Cleistanthus collinus Using reverse-phase flash chromatography

Introduction:

Cleistanthin A (CA) is an aryl naphthalene lignan, which has a potent anticancer activity by regulating the tumor microenvironment. The objective was to develop a new technique for the isolation of cleistanthin A from the acetone extract of Cleistanthus collinus utilizing reverse phase flash chromatography.

Materials and Methods:

Cleistanthus collinus leaves were shade dried, defatted using n-hexane and then macerated to obtain acetone extract which was further subjected to reverse phase flash chromatography for the isolation of cleistanthin A using the gradient mobile phase of 0.1% formic acid (v/v) in water and acetonitrile. Gradient elution of chromatographic run was performed for 80 min. The separated peaks that showed absorbance at λ_max 254 nm were collected for the chemical characterization. Cell viability of the isolated cleistanthin A was studied on hepatocellular cancer cell line HePG2 and prostate cancer cell line PC3 using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

Results:

The chemical characteristics of the isolated compound cleistanthin A was further characterized using spectral techniques such as ¹H and ¹³C nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), and electron spray ionization-tandem mass spectrometry (ESI-MS/MS). Cleistanthin A has decreased the cell viability of the HePG2 cell line to 52.25% at 32 μg/ml and PC3 cell line to 51.82% at 16 μg/ml in a dose-dependent manner.

Conclusion:

Cleistanthin A was successfully isolated from the natural source using reverse phase flash chromatography and the MTT assay has shown that cleistanthin A has decreased the cell viability in both the HePG2 and PC3 cell lines in a dose-dependent manner.

Elusive Toxin in Cleistanthus collinus Causing Vasoconstriction and Myocardial Depression: Detailed NMR Analyses and Biological Studies of Cleistanthoside A

Cleistanthus collinus leaf extracts are consumed for suicidal purposes in southern India. The boiled decoction is known to be more toxic than the fresh leaf juice. Although several compounds have been isolated and their toxicity tested, controversy remains as to which compounds are responsible for the high level of toxicity of C. collinus. We report herein that cleistanthoside A is the major toxin in the boiled aqueous extract of fresh leaves and causes death in rats in small doses. The toxicity of the boiled extract prepared in the manner described can be attributed entirely to cleistanthoside A. Cleistanthin A could also be isolated from the boiled extract, albeit in trace amounts. As hypotension not responding to vasoconstrictors is the cause of death in patients who have consumed the boiled extract, effects of cleistanthoside A on the determinants of blood pressure, namely, force of cardiac contraction and vascular resistance, were tested in isolated organ experiments. Cleistanthoside A has a direct vasoconstrictor effect; however, it inhibits ventricular contractility. Therefore, the notion that the shock in C. collinus poisoning is of vascular origin must be considered carefully, and the possibility of cardiogenic shock must be studied. We present the crystal structure of cleistanthin A and show the potency of fast NMR methods (NOAH4-BSCN-NUS) in the full spectral assignment of cleistanthoside A as a real-world sample of a natural product. We also compare the results of the NOAH4-BSCN-NUS NMR experiments with conventional NMR methods.

Synthesis and evaluation of diphyllin β-hydroxyl amino derivatives as novel V-ATPase inhibitors

Natural diphyllin glycosides were identified as potent vacuolar H⁺ -ATPase (V-ATPase) inhibitors. A series of diphyllin β-hydroxyl amino derivatives were designed and synthesized as novel diphyllin derivatives. Most of these derivatives displayed potent cytotoxicity against six cancer cell lines with IC₅₀ values in the submicromolar to nanomolar concentration range. Compounds 2b, 2c, 2l, 2m, and 2n showed similar V-ATPase inhibitory potency to Bafilomycin A1. Compound 2l exhibited potent activity of modulation of lysosomal pH and cytoplasmic pH.

Cleistanthin A induces apoptosis and suppresses motility of colorectal cancer cells

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Here, we investigated the molecular mechanisms that underpin the anticancer effects of cleistanthin A (CA) in two CRC cell lines, HCT 116, and SW480. At 48 h, CA exhibited apoptotic cytotoxic effects in both CRC cell lines, concomitant with reduction of an anti-apoptotic protein, survivin. Mechanistically, CA treatment significantly reduced the expression levels of β-catenin and active-β-catenin in a dose-dependent manner in both CRC cell lines. Moreover, CA suppressed the Wnt/β-catenin signaling pathway by decreasing β-catenin-mediated transcriptional activity and expression of β-catenin target genes, AXIN2, CCND1, and survivin. Furthermore, CA also inhibited transcriptional activity in cells overexpressing a constitutively active β-catenin S33Y, indicating a GSK-3β-independent mechanism underlying the observed CA effects on CRC cells. Although cytotoxic activity was not observed with CA treatment at 24 h, cell migration and invasion were significantly reduced. In addition, CA suppressed V-type ATPase activity and focal adhesion kinase (FAK) phosphorylation. Collectively, our study reveals that CA has time-dependent effects on CRC cell phenotypes. First, short-term CA treatment inhibited CRC cell migration and invasion partly through the suppression of V-type ATPase activity. This suppression resulted in reduced FAK activation. Second, longer-term CA treatment decreased cell viability which correlated with the suppression of Wnt/β-catenin signaling induced transcriptional activity. Altogether, our data suggest that CA has the potential to develop as an effective and novel therapeutic drug for CRC patients.

Effects of diphyllin as a novel V-ATPase inhibitor on TE-1 and ECA-109 cells

Diphyllin is a natural component of traditional Chinese medicine, which effectively inhibits V-ATPase activity and affects the progression of cancer. However, few studies have been conducted on esophageal cancer, and the mechanisms remain to be elucidated. The present study revealedthat diphyllin inhibited proliferation and induced S arrest in esophageal cancer cell lines TE-1 and ECA-109. Further experiments revealed that diphyllin inhibited V-ATPase activity and decreased the mRNA expression of mammalian target of rapamycin complex 1 (mTORC1), hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial growth factor (VEGF). The present study also revealed that diphyllin inhibited proliferation and reduced the formation of new blood vessels. Diphyllin inhibited blood metastasis by regulating the mTORC1/HIF-1α-/VEGF pathway, therefore it could be considered as a new V-ATPase inhibitor to treat esophageal cancer.

Vacuolar H+-ATPases (V-ATPases) as therapeutic targets: a brief review and recent developments

Vacuolar H⁺-ATPases (V-ATPases) are multi-subunit enzymes that play housekeeping roles in eukaryotic cells by acidifying lysosomes, late endosomes, Golgi, and other membrane-bounded compartments. Beyond that, V-ATPases have specialized functions in certain cell types linked to diseases including osteoporosis and cancer. Efforts to identify strategies to develop inhibitors selective for V-ATPases that are involved in disease progression have been ongoing for more than two decades, but so far have not yielded a therapeutic agent that has been translated to the clinic. Recent basic science studies have identified unexpected roles for V-ATPases in nutrient and energy sensing, and renin/angiotensin signaling, which offer additional incentives for considering V-ATPases as therapeutic targets. This article briefly reviews efforts to utilize inhibitors of V-ATPases as drugs. Primary focus is on recent "rational" efforts to identify small molecule inhibitors of the V-ATPases that are selectively expressed in osteoclasts and cancer cells. Enoxacin and bis-enoxacin are two molecules that emerged from these efforts. These molecules block a binding interaction between V-ATPases and microfilaments that occurs in osteoclasts, but not most other cell types, which relates to the specialized function of V-ATPases in bone resorption. Enoxacin and bis-enoxacin have proven useful in the treatment of bone diseases and cancer in animal models and display therapeutic effects that are different, and perhaps better, than current drugs. These results provide evidence that agents targeting subsets of V-ATPases may prove useful in the clinic.

Lysosomal Biology in Cancer

Cells depend on the lysosome for sequestration and degradation of macromolecules in order to maintain metabolic homeostasis. These membrane-enclosed organelles can receive intracellular and extracellular cargo through endocytosis, phagocytosis, and autophagy. Lysosomes establish acidic environments to activate enzymes that are able to break down biomolecules engulfed through these various pathways. Recent advances in methods to study the lysosome have allowed the discovery of extended roles for the lysosome in various diseases, including cancer, making it an attractive and targetable node for therapeutic intervention. This review focuses on key aspects of lysosomal biology in the context of cancer and how these properties can be exploited for the development of new therapeutic strategies. This will provide a contextual framework for how advances in methodology could be applied in future translational research.

Targeting the lysosome in cancer

Lysosomes are membrane-bound intracellular organelles that receive macromolecules delivered by endocytosis, phagocytosis, and autophagy for degradation and recycling. Over the last decade, advances in lysosome research have established a broad role for the lysosome in the pathophysiology of disease. In this review, we highlight the recent discoveries in lysosome biology, with an emphasis on their implications for cancer therapy. We focus on targeting the lysosome in cancer by exploring lysosomal biogenesis and its role in the crosstalk between apoptosis and autophagy. We also discuss how lysosomal inhibition could emerge as a new therapeutic strategy to overcome drug resistance in cancer.