Disulfides from the Brown Alga Dictyopteris membranacea Suppress M1 Macrophage Activation by Inducing AKT and Suppressing MAPK/ERK Signaling Pathways

Inflammation is part of the organism's response to deleterious stimuli, such as pathogens, damaged cells, or irritants. Macrophages orchestrate the inflammatory response obtaining different activation phenotypes broadly defined as M1 (pro-inflammatory) or M2 (homeostatic) phenotypes, which contribute to pathogen elimination or disease pathogenesis. The type and magnitude of the response of macrophages are shaped by endogenous and exogenous factors and can be affected by nutrients or therapeutic agents. Multiple studies have shown that natural products possess immunomodulatory properties and that marine algae contain products with such action. We have previously shown that disulfides isolated from Dictyopteris membranacea suppress nitric oxide (NO) production from activated macrophages, suggesting potential anti-inflammatory actions. In this study, we investigated the anti-inflammatory mechanism of action of bis(5-methylthio-3-oxo-undecyl) disulfide (1), 5-methylthio-1-(3-oxo-undecyl) disulfanylundecan-3-one (2) and 3-hexyl-4,5-dithiocycloheptanone (3). Our results showed that all three compounds inhibited M1 activation of macrophages by down regulating the production of pro-inflammatory cytokines TNFα, IL-6 and IL-12, suppressed the expression of the NO converting enzyme iNOS, and enhanced expression of the M2 activation markers Arginase1 and MRC1. Moreover, disulfides 1 and 2 suppressed the expression of glucose transporters GLUT1 and GLUT3, suggesting that compounds 1 and 2 may affect cell metabolism. We showed that this was due to AKT/MAPK/ERK signaling pathway modulation and specifically by elevated AKT phosphorylation and MAPK/ERK signal transduction reduction. Hence, disulfides 1-3 can be considered as potent candidates for the development of novel anti-inflammatory molecules with homeostatic properties.

Evaluation of the Genotoxicity and Cytotoxicity of Semipurified Fractions from the Mediterranean Brown Algae, Dictyopteris membranacea

Dictyopteris membranacea, a species of Mediterranean brown algae, is believed to have potential pharmacological and nutritional applications. However, such potentials only make sense when devoid of any adverse health consequences. The present study should be seen in this context. It aimed at evaluating the genotoxicity and cytoxicity of its organic extract (F₀) and semi purified fractions (F₄, F₅, and F₆). Extracts were tested using the bacterial Vitotox^® test and micronucleus assay in different concentrations (from 1.25 μg/mL up to 100 μg/mL, depending on the test and the extract). Applied concentrations were based on a preliminary dose-finding test with the neutral red uptake assay. The results show that all extracts were not genotoxic in the presence or absence of a rat metabolic enzyme fraction (S9). This is encouraging and justifies further investigations on the therapeutic and other values of this algae.

Water soluble polysaccharides extracted from Pterocladia capillacea and Dictyopteris membranacea and their biological activities

Cold and hot water extracts (CWE, HWE) of both the red alga Pterocladia capillacea (P. capillacea) and the brown alga Dictyopteris membranacea (D. membranacea) were studied for their polysaccharide contents. In both (CWE) and (HWE) extracts. Relatively higher yields were obtained in case of P. capillacea pillacea (2.87 and 6.46%, respectively). The polysaccharide contents of the CWE hydrolyzate of both studied algae analyzed by HPLC were found to be enriched with glucuronic acid, arabinose and glucose, whereas, HWE hydrolyzate were found to be rich in glucuronic acid and fructose. The polysaccharide contents of the CWE and HWE extracts of (D. membranacea) showed appreciable antimicrobial activity in addition to a moderate antitumor activity against HELA (Cervix carcinoma cell line) at IC50 = 9.83 μg/dl, respectively. Whereas the polysaccharide contents of the CWE and HWE extracts of (P. capillacea) exhibited a promising anticoagulant activity.