Maslinic acid modulates secreted phospholipase A2-IIA (sPLA2-IIA)-mediated inflammatory effects in macrophage foam cells formation

Maslinic Acid Suppresses High Glucose-induced Inflammation by Epigenetically Inhibiting TXNIP Expression

OBJECTIVE

Hyperglycemia-induced inflammation and subsequent endothelial injuries ultimately lead to the pathogenesis of cardiovascular diseases associated with high mortality, such as atherosclerosis. Maslinic acid (MA) is a phytochemical with anti-inflammatory activity. However, it remains unknown whether it can inhibit diabetes-associated cardiovascular inflammation. The present study aimed to determine the effect of MA on high glucose-induced endothelial inflammation and apoptosis in human umbilical vein endothelial cells (HUVECs) and to explore the underlying mechanism.

METHODS

HUVECs were treated with high glucose to induce inflammation and apoptosis. Apoptosis was determined by flow cytometry. CCK-8 assay was used to examine cell viability. Production levels of cytokines were detected by quantitative realtime PCR (qPCR) and ELISA. Protein expression levels and signaling pathways activation were detected by Western blotting. RNA immunoprecipitation and qPCR were used to determine the N⁶-methyladenosine (m6A) levels of target mRNAs.

RESULTS

MA promoted the recruitment of RNA demethylase ALKBH5 to TXNIP mRNA, and subsequently enhanced its m6A demethylation. By this means, MA decreased the stability of TXNIP mRNA and downregulated its expression level. Subsequently, reactive oxygen species (ROS) and production of pro-inflammatory cytokines, including TNF-α, IL-6 and IL-1β, were inhibited. And high glucose-induced apoptosis in HUVECs was inhibited by MA.

CONCLUSION

MA ameliorates high glucose-induced endothelial inflammation and injury, serving as a new potential therapeutic application for protecting against diabetes-associated atherosclerosis and other inflammatory diseases.

Novel Biotransformation of Maslinic Acid to MA-2-O-β-D-Glucoside by UDP-Glycosyltransferases from Bacillus subtilis

Maslinic acid (MA) is a pentacyclic triterpenoid which originates from olive and other plants. Though MA possesses multiple biological activities, it has limitations due to its poor water solubility. YojK, YjiC, and UGT109A3 UDP-glycosyltransferases (UGTs) from Bacillus subtilis (B. subtilis) were utilized to catalyze the conjugation of MA with UDP-Glucose to generate a new MA glycosylation product, MA-2-O-β-D-glucoside (MA-2-O-β-D-Glu). The experimental results indicated that the resultant water solubility of MA-2-O-β-D-Glu is 1.69 times higher than that of MA. In addition, the recombinant YojK showed maximum activity at 40 °C with a pH range of 8.0−10.0, while the recombinant YjiC showed maximum activity at 45 °C with a pH of 8.0, and the recombinant UGT109A3 showed maximum activity at 40 °C with a pH of 8.0. Mg2+ is an important factor for efficient catalysis by three recombinant glycosyltransferases. The chemical conversion rate of the recombinant YojK, YjiC, and UGT109A3 is nearly 100% at their optimum pH, temperature, and metal ions. Furthermore, eight essential residues of three UGTs for MA glycosylation modification were further determined by molecular docking and site-directed mutagenesis. Thus, efficient glycosylation modification improves the water solubility of MA and provides a new potential method for the glycosylation modification of other pentacyclic triterpenoids.

Human Group IIA Phospholipase A2-Three Decades on from Its Discovery

Phospholipase A₂ (PLA₂) enzymes were first recognized as an enzyme activity class in 1961. The secreted (sPLA₂) enzymes were the first of the five major classes of human PLA₂s to be identified and now number nine catalytically-active structurally homologous proteins. The best-studied of these, group IIA sPLA₂, has a clear role in the physiological response to infection and minor injury and acts as an amplifier of pathological inflammation. The enzyme has been a target for anti-inflammatory drug development in multiple disorders where chronic inflammation is a driver of pathology since its cloning in 1989. Despite intensive effort, no clinically approved medicines targeting the enzyme activity have yet been developed. This review catalogues the major discoveries in the human group IIA sPLA₂ field, focusing on features of enzyme function that may explain this lack of success and discusses future research that may assist in realizing the potential benefit of targeting this enzyme. Functionally-selective inhibitors together with isoform-selective inhibitors are necessary to limit the apparent toxicity of previous drugs. There is also a need to define the relevance of the catalytic function of hGIIA to human inflammatory pathology relative to its recently-discovered catalysis-independent function.

Terpenoid and lipid profiles vary in different Phytophthora cactorum - strawberry interactions

Specialized metabolites are essential components in plant defence systems, serving as signalling molecules and chemical weapons against pathogens. The manipulation of plant defence metabolome or metabolites can thus be an important virulence strategy for pathogens. Because of their central role, metabolites can give valuable insights into plant-pathogen interactions. Here, we have conducted nontargeted metabolite profiling with UPLC-ESI-qTOF-MS to investigate the metabolic changes that have taken place in the crown tissue of Fragaria vesca L. (woodland strawberry) and Fragaria × ananassa (Weston) Duchesne ex Rozier (garden strawberry) during 48 h after Phytophthora cactorum challenge. Two P. cactorum isolates were compared: Pc407 is highly virulent to F. × ananassa and causes crown rot, whereas Pc440 is mildly virulent. In total, 45 metabolites differentially accumulated between the treatment groups were tentatively identified. Triterpenoids and various lipid compounds were highly represented. The levels of several triterpenoids increased upon inoculation, some of them showing distinct accumulation patterns in different interactions. Triterpenoids could either inhibit or stimulate P. cactorum growth and, therefore, triterpenoid profiles might have significant impact on disease progression. Of the lipid compounds, lysophospholipids, linoleic acid and linolenic acid were highly accumulated in the most compatible Pc407 - F. × ananassa interaction. As lysophospholipids promote cell death and have been linked to susceptibility, these compounds might be involved in the pathogenesis of crown rot disease. This metabolite analysis revealed potential factors contributing to the outcome of P. cactorum - strawberry interactions. The information is highly valuable, as it can help to find new breeding strategies and new solutions to control P. cactorum in strawberry.

Advances in Research on the Preparation and Biological Activity of Maslinic Acid

Maslinic acid, a pentacyclic triterpene acid, is mainly isolated from olives. Maslinic acid and its derivatives exhibit a broad range of biological properties, such as anti-inflammatory, anticancer, anti-diabetic, antimicrobial, neuroprotective and hepatoprotective activities. In this minireview, the progress of research on maslinic acid with regard to its bioactivities, extraction, semisynthetic preparation and patents is reported. The relationships between the structure and the activity of maslinic acid and its derivatives are also discussed.

Phospholipase A2 Drives Tumorigenesis and Cancer Aggressiveness through Its Interaction with Annexin A1

Phospholipids are suggested to drive tumorigenesis through their essential role in inflammation. Phospholipase A₂ (PLA₂) is a phospholipid metabolizing enzyme that releases free fatty acids, mostly arachidonic acid, and lysophospholipids, which contribute to the development of the tumor microenvironment (TME), promoting immune evasion, angiogenesis, tumor growth, and invasiveness. The mechanisms mediated by PLA₂ are not fully understood, especially because an important inhibitory molecule, Annexin A1, is present in the TME but does not exert its action. Here, we will discuss how Annexin A1 in cancer does not inhibit PLA₂ leading to both pro-inflammatory and pro-tumoral signaling pathways. Moreover, Annexin A1 promotes the release of cancer-derived exosomes, which also lead to the enrichment of PLA₂ and COX-1 and COX-2 enzymes, contributing to TME formation. In this review, we aim to describe the role of PLA₂ in the establishment of TME, focusing on cancer-derived exosomes, and modulatory activities of Annexin A1. Unraveling how these proteins interact in the cancer context can reveal new strategies for the treatment of different tumors. We will also describe the possible strategies to inhibit PLA₂ and the approaches that could be used in order to resume the anti-PLA₂ function of Annexin A1.

Recent advances in chemistry and bioactivity of Sargentodoxa cuneata

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Sargentodoxa comprises only one species, Sargentodoxa cuneata (Oliv.) Rehd et al., widely distributed in the subtropical zone of China. The plant is extensively used in traditional medicine for treating arthritis, joint pains, amenorrhea, acute appendicitis and inflammatory intestinal obstruction. Pharmacological studies show anti-inflammatory, antioxidant, antitumor, antimicrobial, and anti-sepsis activities.

AIM OF THE REVIEW

This review aims to summarize the information about distribution, traditional uses, chemical constituents and pharmacological activities of S. cuneata, as an attempt to provide a scientific basis for its traditional uses and to support its application and development for new drug development.

METHODOLOGY

Scientific information of S. cuneata was retrieved from the online bibliographic databases, including Web of Science, Google Scholar, PubMed, Springer Link, the Wiley online library, SciFinder, Baidu Scholar, China national knowledge infrastructure (CNKI) and WANFANG DATA (up to March 2020). We also search doctoral dissertations, master dissertations conference papers and published books. The keywords were used: "Sargentodoxa", "Da Xue Teng", "Hong Teng", "Xue Teng", "secondary metabolites", "chemical components", "biological activity", "pharmacology", "traditional uses".

OBSERVATIONS AND RESULTS

S. cuneata is utilized as valuable herbal medicines to treat various diseases in China. Over 110 chemical constituents have been isolated and identified from the stem of S. cuneata, including phenolic acids, phenolic glycosides, lignans, flavones, triterpenoids and other compounds. The extract and compounds of S. cuneata have a wide spectrum of pharmacological activities, including antitumor, anti-inflammatory, antioxidant, antimicrobial, anti-sepsis and anti-arthritis effects, as well as protective activity against cerebrovascular diseases.

CONCLUSION

S. cuneata has a rich legacy for the treatment of many diseases, especially arthritis and sepsis, which is reinforced by current investigations. However, the present studies about bioactive chemical constituents and detail pharmacological mechanisms of S. cuneata were insufficient. Further studies should focus on these aspects in relation to its clinical applications. This review has systematically summarized the traditional uses, phytochemical constituents and pharmacological effects of S. cuneata, providing references for the therapeutic potential of new drug development.

Maslinic acid prevents IL-1β-induced inflammatory response in osteoarthritis via PI3K/AKT/NF-κB pathways

Osteoarthritis (OA) is a degenerative joint disease characterized by destruction of articular cartilage. The inflammatory response is the most important factor affecting the disease process. As interleukin-1β (IL-1β) stimulates several key mediators in the inflammatory response, it plays a major role in the pathogenesis of OA. Maslinic acid (MA) is a natural compound distributed in olive fruit. Previous studies have found that maslinic acid has an inhibitory effect on inflammation, but its specific role in the progression of OA disease has not been studied so far. In this study, we aim to assess the protective effect of MA on OA progression by in vitro and in vivo experiments. Our results indicate that, in IL-1β-induced inflammatory response, MA is effective in attenuating some major inflammatory mediators such as nitric oxide (NO) and prostaglandin E2, and inhibits the expression of IL-6, inducible nitric oxide synthase, cyclooxygenase-2, and tumor necrosis factor-α (TNF-α) in a concentration-dependent manner. Also, MA downregulated the expression levels of thrombospondin motif 5 (ADAMTS5) and matrix metalloproteinase 13 in chondrocytes, resulting in reduced degradation of its extracellular matrix. Mechanistically, MA exhibits an anti-inflammatory effect by inactivating the PI3K/AKT/NF-κB pathway. In vivo, the protective effect of MA on OA development can be detected in a surgically induced mouse OA model. In summary, these findings suggest that MA can be used as a safe and effective potential OA therapeutic strategy.

Maslinic acid alleviates ischemia/reperfusion-induced inflammation by downregulation of NFκB-mediated adhesion molecule expression

Ischemia/reperfusion (I/R)-induced inflammation is associated with enhanced leukocyte rolling, adhesion and transmigration within the microcirculation. These steps are mediated by hypoxia-triggered signaling pathways, which upregulate adhesion molecule expression on endothelial cells and pericytes. We analyzed whether these cellular events are affected by maslinic acid (MA). Mitochondrial activity and viability of MA-exposed endothelial cells and pericytes were assessed by water-soluble tetrazolium (WST)-1 and lactate dehydrogenase (LDH) assays as well as Annexin V/propidium iodide (PI) stainings. Effects of MA on hypoxia and reoxygenation-induced expression of E-selectin, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 were determined by flow cytometry. The subcellular localization of the NFκB subunit p65 was analyzed by immunofluorescence and Western blot. I/R-induced leukocytic inflammation was studied in MA- and vehicle-treated mouse dorsal skinfold chambers by intravital fluorescence microscopy and immunohistochemistry. MA did not affect viability, but suppressed the mitochondrial activity of endothelial cells. Furthermore, MA reduced adhesion molecule expression on endothelial cells and pericytes due to an inhibitory action on NFκB signaling. Numbers of adherent and transmigrated leukocytes were lower in post-ischemic tissue of MA-treated mice when compared to vehicle-treated controls. In addition, MA affected reactive oxygen species (ROS) formation, resulting in a diminished oxidative DNA damage. Hence, MA represents an attractive compound for the establishment of novel therapeutic approaches against I/R-induced inflammation.