SERCA plays a crucial role in the toxicity of a betulinic acid derivative with potential antimalarial activity

Chemical Strategies towards the Synthesis of Betulinic Acid and Its More Potent Antiprotozoal Analogues

Betulinic acid (BA, 3β-hydroxy-lup-20(29)-en-28-oic acid) is a pentacyclic triterpene acid present predominantly in Betula ssp. (Betulaceae) and is also widely spread in many species belonging to different plant families. BA presents a wide spectrum of remarkable pharmacological properties, such as cytotoxic, anti-HIV, anti-inflammatory, antidiabetic and antimicrobial activities, including antiprotozoal effects. The present review first describes the sources of BA and discusses the chemical strategies to produce this molecule starting from betulin, its natural precursor. Next, the antiprotozoal properties of BA are briefly discussed and the chemical strategies for the synthesis of analogues displaying antiplasmodial, antileishmanial and antitrypanosomal activities are systematically presented. The antiplasmodial activity described for BA was moderate, nevertheless, some C-3 position acylated analogues showed an improvement of this activity and the hybrid models—with artesunic acid—showed the most interesting properties. Some analogues also presented more intense antileishmanial activities compared with BA, and, in addition to these, heterocycles fused to C-2/C-3 positions and amide derivatives were the most promising analogues. Regarding the antitrypanosomal activity, some interesting antitrypanosomal derivatives were prepared by amide formation at the C-28 carboxylic group of the lupane skeleton. Considering that BA can be produced either by isolation of different plant extracts or by chemical transformation of betulin, easily obtained from Betula ssp., it could be said that BA is a molecule of great interest as a starting material for the synthesis of novel antiprotozoal agents.

The Natural Compound Oblongifolin C Exhibits Anticancer Activity by Inhibiting HSPA8 and Cathepsin B In Vitro

PPAPs (Polycyclic polyprenylated acylphloroglucinols) are a class of compounds with diverse bioactivities, including anticancer effects. Oblongifolin C (OC) is a PPAP isolated from the plant of Garcinia yunnanensis Hu. We previously discovered that OC induces apoptosis, inhibits autophagic flux, and attenuates metastasis in cancer cells. However, the protein targets and the detailed mechanism of action of OC remain unclear. To identify protein targets of OC, a non-labeled protein fishing assay was performed, and it was found that OC may interact with several proteins, including the heat shock 70 kDa protein 8 (HSPA8). Expanding on our previous studies on protein cathepsin B, this current study applied Surface Plasmon Resonance (SPR) and Isothermal Titration Calorimetry (ITC) to confirm the potential binding affinity between OC and two protein targets. This study highlights the inhibitory effect of OC on HSPA8 in cancer cells under heat shock stress, by specifically inhibiting the translocation of HSPA8. OC also enhanced the interaction between HSPA8, HSP90, and p53, upregulated the expression of p53 and significantly promoted apoptosis in cisplatin-treated cells. Additionally, a flow cytometry assay detected that OC sped up the apoptosis rate in HSPA8 knockdown A549 cells, while overexpression of HSPA8 delayed the OC-induced apoptosis rate. In summary, our results reveal that OC potentially interacts with HSPA8 and cathepsin B and inhibits HSPA8 nuclear translocation and cathepsin B activities, altogether suggesting the potential of OC to be developed as an anticancer drug.

Sarco/Endoplasmic Reticulum Calcium ATPase Inhibitors: Beyond Anticancer Perspective

The sarco/endoplasmic reticulum calcium ATPase (SERCA), which plays a key role in the maintenance of Ca²⁺ ion homeostasis, is an extensively studied enzyme, the inhibition of which has a considerable impact on cell life and death decision. To date, several SERCA inhibitors have been thoroughly studied and the most notable one, a derivative of the sesquiterpene lactone thapsigargin, is gradually approaching a clinical application. Meanwhile, new compounds with SERCA-inhibiting properties of natural, synthetic, or semisynthetic origin are being discovered and/or developed; some of these might also be suitable for the development of new drugs with improved performance. This review brings an up-to-date comprehensive overview of recently discovered compounds with the potential of SERCA inhibition, discusses their mechanism of action, and highlights their potential clinical applications, such as cancer treatment.

A Highly Active Triterpene Derivative Capable |of Biofilm Damage to Control Cryptococcus spp

Cryptococcus neoformans is an encapsulated yeast responsible for more than 180,000 deaths per year. The standard therapeutic approach against cryptococcosis is a combination of amphotericin B with flucytosine. In countries where cryptococcosis is most prevalent, 5-fluorocytosine is rarely available, and amphotericin B requires intravenous administration. C. neoformans biofilm formation is related to increased drug resistance, which is an important outcome for hospitalized patients. Here, we describe new molecules with anti-cryptococcal activity. A collection of 66 semisynthetic derivatives of ursolic acid and betulinic acid was tested against mature biofilms of C. neoformans at 25 µM. Out of these, eight derivatives including terpenes, benzazoles, flavonoids, and quinolines were able to cause damage and eradicate mature biofilms. Four terpene compounds demonstrated significative growth inhibition of C. neoformans. Our study identified a pentacyclic triterpenoid derived from betulinic acid (LAFIS13) as a potential drug for anti-cryptococcal treatment. This compound appears to be highly active with low toxicity at minimal inhibitory concentration and capable of biofilm eradication.

Deep insights into the response of human cervical carcinoma cells to a new cyano enone-bearing triterpenoid soloxolone methyl: a transcriptome analysis

Semisynthetic triterpenoids, bearing cyano enone functionality in ring A, are considered now as novel promising anti-tumor agents. However, despite the large-scale studies, their effects on cervical carcinoma cells and, moreover, mechanisms underlying cell death activation by such compounds in this cell type have not been fully elucidated. In this work, we attempted to reconstitute the key pathways and master regulators involved in the response of human cervical carcinoma KB-3-1 cells to the novel glycyrrhetinic acid derivative soloxolone methyl (SM) by a transcriptomic approach. Functional annotation of differentially expressed genes, analysis of their cis^- regulatory sequences and protein-protein interaction network clearly indicated that stress of endoplasmic reticulum (ER) is the central event triggered by SM in the cells. A range of key ER stress sensors and transcription factor AP-1 were identified as upstream transcriptional regulators, controlling the response of the cells to SM. Additionally, by using Gene Expression Omnibus data, we showed the ability of SM to modulate the expression of key genes involved in regulation of the high proliferative rate of cervical carcinoma cells. Further Connectivity Map analysis revealed similarity of SM's effects with known ER stress inducers thapsigargin and geldanamycin, targeting SERCA and Grp94, respectively. According to the molecular docking study, SM could snugly fit into the active sites of these proteins in the positions very close to that of both inhibitors. Taken together, our findings provide a basis for the better understanding of the intracellular processes in tumor cells switched on in response to cyano enone-bearing triterpenoids.

Betulinic acid attenuates liver fibrosis by inducing autophagy via the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway

The present study was designed to investigate the effects of betulinic acid on human hepatic stellate cells in vitro and C57BL/6 mice in vivo, as well as the signaling pathways involved. In this study, we explored the effects of betulinic acid on expression of alpha smooth muscle actin and autophagy-related proteins. Betulinic acid reduced pathological damage associated with liver fibrosis, as well as serum platelet-derived growth factor and serum hydroxyproline levels. Furthermore, betulinic acid downregulated the expression of alpha smooth muscle actin and type I collagen in mouse liver and upregulated the expression of microtubule-associated protein light chain 3B and autophagy-related gene 7 at the gene and protein levels. LC3II expression was increased and alpha smooth muscle actin expression was decreased in betulinic acid-treated hepatic stellate cells. Interventions with bafilomycin A1 and mCherry-GFP-LC3 adenoviruses promoted the formation of autophagosomes in hepatic stellate cells and the development of autophagic flow. Our study found that mitogen-activated protein kinase/extracellular signal-regulated kinase may be involved in the effects of betulinic acid on liver fibrosis. The present study suggests that betulinic acid has anti-hepatic fibrosis activity by inducing autophagy and could serve as a promising new agent for treating hepatic fibrosis.

β-eudesmol inhibits thymic stromal lymphopoietin through blockade of caspase-1/NF-κB signal cascade in allergic rhinitis murine model

Allergic rhinitis (AR) is a global health problem because of its steadily increasing incidence and prevalence that currently affects about 30% of people worldwide. β-eudesmol has various beneficial effects, including anti-cancer and anti-allergic activities. However, the effects of β-eudesmol on AR have not yet been clarified; thus, we investigated the effects of β-eudesmol in an ovalbumin-induced AR animal model using enzyme-linked immunosorbent assay, histamine assay, Western blotting, and hematoxylin and eosin staining methods. β-eudesmol reduced the nasal rubs score and levels of histamine and immunoglobulin E in serum of AR mouse. In addition, the levels of thymic stromal lymphopoietin, interleukin-1β, tumor necrosis factor-α, and macrophage inflammatory protein-2 were down-regulated and infiltration of eosinophils and the level of intercellular adhesion molecule-1 were inhibited by β-eudesmol administration. β-eudesmol administration also reduced active caspase-1 and nuclear factor-κB DNA binding activity in nasal mucosa tissues of AR mice. Taken together, these results indicate that β-eudesmol would be effective for the treatment of allergic and inflammatory diseases, such as AR.