DGLA from the Microalga Lobosphaera Incsa P127 Modulates Inflammatory Response, Inhibits iNOS Expression and Alleviates NO Secretion in RAW264.7 Murine Macrophages

Abstract

Microalgae have been considered as a renewable source of nutritional, cosmetic and pharmaceutical compounds. The ability to produce health-beneficial long-chain polyunsaturated fatty acids (LC-PUFA) is of high interest. LC-PUFA and their metabolic lipid mediators, modulate key inflammatory pathways in numerous models. In particular, the metabolism of arachidonic acid under inflammatory challenge influences the immune reactivity of macrophages. However, less is known about another omega-6 LC-PUFA, dihomo-γ-linolenic acid (DGLA), which exhibits potent anti-inflammatory activities, which contrast with its delta-5 desaturase product, arachidonic acid (ARA). In this work, we examined whether administrating DGLA would modulate the inflammatory response in the RAW264.7 murine macrophage cell line. DGLA was applied for 24 h in the forms of carboxylic (free) acid, ethyl ester, and ethyl esters obtained from the DGLA-accumulating delta-5 desaturase mutant strain P127 of the green microalga Lobosphaera incisa. DGLA induced a dose-dependent increase in the RAW264.7 cells’ basal secretion of the prostaglandin PGE1. Upon bacterial lipopolysaccharide (LPS) stimuli, the enhanced production of pro-inflammatory cytokines, tumor necrosis factor alpha (TNFα) and interleukin 1β (IL-1β), was affected little by DGLA, while interleukin 6 (IL-6), nitric oxide, and total reactive oxygen species (ROS) decreased significantly. DGLA administered at 100 µM in all forms attenuated the LPS-induced expression of the key inflammatory genes in a concerted manner, in particular iNOS, IL-6, and LxR, in the form of free acid. PGE1 was the major prostaglandin detected in DGLA-supplemented culture supernatants, whose production prevailed over ARA-derived PGE2 and PGD2, which were less affected by LPS-stimulation compared with the vehicle control. An overall pattern of change indicated DGLA’s induced alleviation of the inflammatory state. Finally, our results indicate that microalgae-derived, DGLA-enriched ethyl esters (30%) exhibited similar activities to DGLA ethyl esters, strengthening the potential of this microalga as a potent source of this rare anti-inflammatory fatty acid.

Algal Lipids as Modulators of Skin Disease: A Critical Review

“…Other studies have observed that the fractions enriched in phospholipids classes (PC and PG) isolated from the macroalga P. palmata, and the glycolipids classes (MGDG, DGDG, and SQDG) isolated from the macroalgae P. palmata and Chondrus crispus [97,98], and the microalgae Nannochloropsis granulata and T. chui [99,100] had a strong suppression of NO production in LPS-activated Raw 264.7 cells, this effect mainly being due to the decreased expression of iNOS. Similar trends were detected when these cells were exposed to other classes of lipids, such as free and ethyl esterified dihomo-γ-linolenic acid (DGLA, 20:3 omega-6) from a mutant strain (P127) of the microalga Lobosphaera incisa [101], DGTS from N. granulata [102], and MGMG from Chlorella sorokiniana [103].…”

“…The authors observed a decrease in the production of prostaglandin E2 (PGE2) as well as a downregulation of the expression of COX-2. Interestingly, one study reported increased base levels of PGE1, a prostaglandin associated with an anti-inflammatory response, in Raw 264.7 cells stimulated with free and ethyl-esterified DGLA [101].…”

Microalgal Lipid Extracts Have Potential to Modulate the Inflammatory Response: A Critical Review

“…Oxylipins resulting from the enzymatical oxidation of PUFAs, isolated from Chlamydomonas debaryana and Nannochloropsis gaditana , and LPC(16:0), isolated from Cylindrotheca Closterium, showed the capacity to downregulate LPS-triggered TNF-α production in THP-1 macrophages [ 72 , 73 ]. The induction of IL-6 in LPS-activated Raw264.7 cells was decreased with free and esterified DGLA from a mutant strain of the microalga Lobosphaera incisa P127 [ 74 ]. Another study observed a reduction in TNF-α, IL-6, and IL-1β expression in peritoneal blood mononuclear cells (PBMC) treated with ergosterol and 7-dehydroporiferasterol isolated from the microalga Dunaliella tertiolecta [ 75 ].…”

“…The following are available online at https://www.mdpi.com/article/10 .3390/ijms22189825/s1, Supplementary Table S1: Anti-inflammatory activity of microalgae lipids [19][20][21][22][23][24][25]32,33,[50][51][52]56,57,[59][60][61][62][63][64][65][66][67][71][72][73][74][75][77][78][79]98].…”

“…The following are available online at , Supplementary Table S1: Anti-inflammatory activity of microalgae lipids [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 32 , 33 , 50 , 51 , 52 , 56 , 57 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 71 , 72 , 73 , 74 , 75 , 77 , 78 , 79 , 98 ].…”