Immune Modulating Brevetoxins: Monocyte Cytotoxicity, Apoptosis, and Activation of M1/M2 Response Elements Is Dependent on Reactive Groups

Effects of marine biotoxins on drug-metabolizing cytochrome P450 enzymes and their regulation in mammalian cells

Marine biotoxins are a heterogenous group of natural toxins, which are able to trigger different types of toxicological responses in animals and humans. Health effects arising from exposure to marine biotoxins are ranging, for example, from gastrointestinal symptoms to neurological effects, depending on the individual toxin(s) ingested. Recent research has shown that the marine biotoxin okadaic acid (OA) can strongly diminish the expression of drug-metabolizing cytochrome P450 (CYP) enzymes in human liver cells by a mechanism involving proinflammatory signaling. By doing so, OA may interfere with the metabolic barrier function of liver and intestine, and thus alter the toxico- or pharmacokinetic properties of other compounds. Such effects of marine biotoxins on drug and xenobiotic metabolism have, however, not been much in the focus of research yet. In this review, we present the current knowledge on the effects of marine biotoxins on CYP enzymes in mammalian cells. In addition, the role of CYP-regulating nuclear receptors as well as inflammatory signaling in the regulation of CYPs by marine biotoxins is discussed. Strong evidence is available for effects of OA on CYP enzymes, along with information about possible molecular mechanisms. For other marine biotoxins, knowledge on effects on drug metabolism, however, is scarce.

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of NP structure class diversity in relation to biota source and biome is discussed.

Karenia brevis Extract Induces Cellular Entry through Distinct Mechanisms in Phagocytic RAW 264.7 Macrophages versus Non-Phagocytic Vero Cells

Marine algae extracts are an important area of potential drug discovery; however, nearly all studies to date have used non-fluorescent-based methods to determine changes in target cell activity. Many of the most robust immunological and cellular analyses rely on fluorescent probes and readouts, which can be problematic when the algae extract is fluorescent itself. In this study, we identified the fluorescent spectrum of an isolated extract from the marine dinoflagellate Karenia brevis, which included two fluorescing components: chlorophyll α and pheophytin α. When excited at 405 nm and 664 nm, the extract emitted fluorescence at 676 nm and 696 nm, respectively. The extract and its fluorescing components, chlorophyll α and pheophytin α, entered phagocytic RAW 264.7 macrophages and non-phagocytic Vero kidney cells through distinct mechanisms. When incubated with the extract and its main components, both the RAW 264.7 macrophages and the Vero cells accumulated fluorescence as early as 30 min and continued through 48 h. Vero kidney cells accumulated the K. brevis fluorescent extract through a dynamin-independent and acidified endosomal-dependent mechanism. RAW 264.7 macrophages accumulated fluorescent extract through a dynamin-independent, acidified endosomal-independent mechanism, which supports accumulation through phagocytosis. Furthermore, RAW 264.7 macrophages downregulated cell-surface expression of CD206 in response to extract stimulation indicating activation of phagocytic responses and potential immunosuppression of these immune cells. This study represents the first characterization of the cellular update of K. brevis extracts in phagocytic versus non-phagocytic cells. The data suggest the importance of understanding cellular uptake of fluorescing algae extracts and their mechanism of action for future drug discovery efforts.

Application of a Cholesterol-Based Stationary Phase for the Analysis of Brevetoxins

A high-performance liquid chromatography protocol for the analysis of brevetoxins has been developed using a silica hydride-based cholesterol column. Brevetoxins are neurotoxins produced by harmful algae that have additional potential as drugs for a number of illnesses/diseases. To develop the optimum conditions, a number of different experimental approaches were tested. These include isocratic and gradient elution, different organic mobile phase components, and temperature variations. A separate protocol was developed for the compounds brevenal and brevenol, also produced by the same algae that make brevetoxins. Brevenal is a natural product under investigation as a therapy for chronic respiratory diseases, such as cystic fibrosis or asthma. The goal of this study was to provide a protocol for the analysis of these compounds that could be further developed into a validated method depending on a particular laboratory's capabilities and to highlight some of the unique features of the cholesterol stationary phase.