Identification and Cytotoxic Evaluation of Pregnane Saponins from the Twigs and Leaves of Dregea volubilis

Four new polyhydroxy pregnane glycosides, named volubilosides G-K (3, 5-7), along with three known secondary metabolites, dregeoside Da1 (1), dregeoside Ka1 (2), and volubiloside E (4) were isolated from the twigs and leaves of Dregea volubilis (DV). The chemical structures of these compounds (1-7) were elucidated using spectroscopic techniques (1D and 2D NMR and HR-ESI-MS analyses) and compared with those in the published literature. Compounds (1-7) were evaluated for cytotoxicity against eight cancer cell lines (MB49, K562, MKN-7, HT29, A549, MCF-7, MDA-MB-231, and HepG2), revealing varying levels of cytotoxic effects with IC50 values ranging from 4.29 to 21.05 μM. The results indicated that compounds 1-7 may serve as potential lead compounds for the discovery and development of novel anti-cancer drugs.

AhR Activation Leads to Attenuation of Murine Autoimmune Hepatitis: Single-Cell RNA-Seq Analysis Reveals Unique Immune Cell Phenotypes and Gene Expression Changes in the Liver

The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed ligand-activated transcription factor. While initially identified as an environmental sensor, this receptor has been shown more recently to regulate a variety of immune functions. AhR ligands vary in structure and source from environmental chemicals such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and indoles found in cruciferous vegetables to endogenous ligands derived from tryptophan metabolism. In the current study, we used TCDD, a high affinity AhR ligand to study the impact of AhR activation in the murine model of autoimmune hepatitis (AIH). Primarily, we used single-cell RNA-sequencing (scRNA-seq) technology to study the nature of changes occurring in the immune cells in the liver at the cellular and molecular level. We found that AhR activation attenuated concanavalin A (ConA)-induced AIH by limiting chemotaxis of pro-inflammatory immune cell subsets, promoting anti-inflammatory cytokine production, and suppressing pro-inflammatory cytokine production. scRNA-seq analysis showed some unusual events upon ConA injection such as increased presence of mature B cells, natural killer (NK) T cells, CD4+ or CD8+ T cells, Kupffer cells, memory CD8+ T cells, and activated T cells while TCDD treatment led to the reversal of most of these events. Additionally, the immune cells showed significant alterations in the gene expression profiles. Specifically, we observed downregulation of inflammation-associated genes including Ptma, Hspe1, and CD52 in TCDD-treated AIH mice as well as alterations in the expression of migratory markers such as CXCR2. Together, the current study characterizes the nature of inflammatory changes occurring in the liver during AIH, and sheds light on how AhR activation during AIH attenuates liver inflammation by inducing phenotypic and genotypic changes in immune cells found in the liver.

Anti-leukemic activity of Wattakaka volubilis leaf extract against human myeloid leukemia cell lines

ETHNOPHARMACOLOGICAL RELEVANCE

Wattakaka volubilis has been traditionally used in Ayurvedic medicine in India for treatment of several ailments such as bronchial asthma, inflammations, tumors, piles, leucoderma, application to boils, rat bite etc.

AIM OF THE STUDY

The present study was designed to investigate anti-leukemic activity of the crude aqueous methanolic extract and to identify active compounds from the leaves of Wattakaka volubilis.

MATERIALS AND METHODS

The leaves of Wattakaka volubilis were extracted with aqueous methanol. Liquid-liquid fractionation of the crude methanolic extract with different organic solvents was done and the fractions were screened for in vitro anti-leukemic activity using different leukemic cell lines. The active fractions were then subjected to chromatographic separation for isolation of bioactive compounds. Structure of isolated compound was elucidated by spectroscopic methods. The in vitro anti-leukemic activities of different extracts of the leaves and isolated compound WVP were studied in U-937, HL-60 and K-562 cell-lines by using cell count, MTT [(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide] and DNA laddering assays, flow-cytometric and confocal microscopic techniques.

RESULTS

Kaempferol-3-O-[α-l-rhamnopyranosyl-(1→4)-O-α-l-rhamnopyranosyl-(1→6)-O]-β-d-glucopyranoside (WVP) was isolated from crude leaves extract of Wattakaka volubilis. Both the n-butanolic extract (WVB) of Wattakaka volubilis and its isolate WVP were found to be responsible for in vitro anti-leukemic activity. The IC(50) values of WVB were found be 120, 100 and 50(μg/ml) in U937, K562, and HL-60 cell lines, respectively. Whereas, the pure isolate WVP exhibited anti-leukemic activity with IC(50) values of 13.5, 10.8, and 13.2(μg/ml) in U937, K562, and HL-60 cell lines, respectively. The flow-cytometric analysis confirms that the cell cycle arrest occurs at G1 phase in case of U937 and K562 cell lines and G2/M phase in case of HL60 cell lines. Similarly both confocal microsocopic analysis and DNA laddering assay confirm the apoptosis and cell cycle arrests of leukemic cells.

CONCLUSION

The overall results provide evidence for the ethnopharmacological relevance for use of the plant Wattakaka volubilis in developing novel agents for the treatment of leukemia.

Mitochondria-dependent apoptosis of con A-activated T lymphocytes induced by asiatic acid for preventing murine fulminant hepatitis

Selectively facilitating apoptosis of activated T cells is essential for the clearance of pathogenic injurious cells and subsequent efficient resolution of inflammation. However, few chemicals have been reported to trigger apoptosis of activated T cells for the treatment of hepatitis without affecting quiescent T cells. In the present study, we found that asiatic acid, a natural triterpenoid, selectively triggered apoptosis of concanavalin A (Con A)-activated T cells in a mitochondria-dependent manner indicated by the disruption of the mitochondrial transmembrane potential, release of cytochrome c from mitochondria to cytosol, caspases activation, and cleavage of PARP. In addition, asiatic acid also induced the cleavage of caspase 8 and Bid and augmented Fas expression in Con A-activated T cells. However, following activation of T cells from MRL^lpr/lpr mice with mutation of Fas demonstrated a similar susceptibility to asiatic acid-induced apoptosis compared with normal T cells, suggesting that Fas-mediated death-receptor apoptotic pathway does not mainly contribute to asiatic acid-induced cell death. Furthermore, asiatic acid significantly alleviated Con A-induced T cell-dependent fulminant hepatitis in mice, as assessed by reduced serum transaminases, pro-inflammatory cytokines, and pathologic parameters. Consistent with the in vitro results, asiatic acid also induced apoptosis of activated CD4⁺ T cells in vivo. Taken together, our results demonstrated that the ability of asiatic acid to induce apoptosis of activated T cells and its potential use in the treatment of T-cell-mediated inflammatory diseases.

Immunosuppressive resveratrol aneuploids from Hopea chinensis

Two novel resveratrol aneuploids, hopeachinols A (1) and B (2), as well as a potent immunosuppressive polyphenol diptoindonesin G (3) were characterized from the ethanol extract of Hopea chinensis stem barks. The structure of the polyphenols was accommodated by comprehensive spectroscopic analysis with the absolute stereochemistry determined by the CD approach coupled with theoretical ECD spectra computer-generated through the Gaussian 03 program. The distinct structure and biological profile of 3 recommended it as a starting molecule for the relevant drug discovery.

Saikosaponin a inhibits the proliferation and activation of T cells through cell cycle arrest and induction of apoptosis

In the present study, we aimed at examining the immunosuppressive activity of saikosaponin a, a triterpene saponin derived from Bupleurum falcatum L. (Umbelliferae), and the underlying mechanisms. Saikosaponin a significantly inhibited the proliferation and activation of T cells activated by concanavalin A (Con A) in a concentration-dependent manner. Additionally, it potently suppressed Con A-stimulated IL-2, IFN-gamma and TNF-alpha production in mouse T cells. Saikosaponin a also caused G0/G1 arrest of activated T cells through down-regulating the protein levels of CDK6 and Cyclin D3 and up-regulating the protein level of p27(kip). Furthermore, the compound dose-dependently induced apoptosis of Con A-activated T cells rather than those non-activated, as determined by Annexin V/PI staining. Besides, it induced a remarkable collapse of mitochondrial membrane potential and caused significant release of cytochrome c from mitochondria to cytosol. In summary, these results suggest that the G0/G1 arrest as well as the induction of apoptosis via mitochondrial pathway are involved in the immunosuppressive activity of saikosaponin a against activated T cells. This may herald a novel approach for further studies of saikosaponin a as a candidate for the treatment of inflammatory and autoimmune diseases.