Hetero-Polysaccharides Secreted from Dunaliella salina Exhibit Immunomodulatory Activity Against Peripheral Blood Mononuclear Cells and RAW 264.7 Macrophages
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Several species of microalgae have been known to produce exopolysaccharides (EPS) with potential immune activity. In the present investigation, ethyl acetate fraction of crude EPS secreted by Dunaliella salina was explored for immunomodulatory activity against peripheral blood mononuclear cells (PBMC) and RAW 264.7 macrophages. Effect of EPS on cell growth and cytokines production were measured using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and ELISA respectively. Griess reagent was used for measuring the nitric oxide production in RAW 264.7 macrophages. FTIR analysis and mass spectroscopy were carried out for the characterization. Ethyl acetate fraction exhibited dose dependent increase in proliferative index and cytokines production (IFN-γ, TNF-α, TGF-β). At low concentration (250 and 500 µg/mL), it showed growth inhibition and at higher concentration (1000 and 1500 µg/mL), it enhanced the cell growth. Interestingly, the pronounced increased TNF-α production was observed in ethyl acetate fraction treated PBMC cells at higher concentration (750 and 1000 µg/mL) indicating the immunostimulatory effect. In RAW cells, concentration dependent diminished cell growth (IC50 = 691 µg/mL) and nitric oxide production (IC50 = 630 µg/mL) was observed. FTIR analysis showed the presence of polysaccharides due to the detection of hydroxyl (–OH), Carbonyl (C–O) and alkyl (C–H) groups. Mass spectroscopy results revealed ethyl acetate fraction as penta-saccharide (m/z = 887.56 and 886.54) which are confirmed to be hetero-polysaccharides consisting of hexoses and pentoses along with association of ions. These results suggest that penta-saccharide (ethyl acetate fraction) isolated from D. salina may have the potential to be used for therapeutic purpose as immunomodulatory agent.
KeywordsCell growth Exopolysaccharides PBMC RAW 264.7 Cytokines
The author would like to acknowledge Dr. M. Krishnamohan, Birla Institute of Scientific Research, Jaipur, India for providing the culture of Dunaliella salina and Dr. Akshey Jain from Nitin Nursing Home and Dr. Vandana Goyal, from Rajendra Hospital, Patiala for providing us the blood needed for carrying out the experiments. The authors also would like acknowledge Mr. Anoop Patiyal from SAIF, Punjab University, Chandigarh for mass spectroscopic analysis.
Compliance with Ethical Standards
Conflict of interest
No competing financial interests exist.
The informed consent was given by all the donors for the experiments.
Research Involving Human Participants and/or Animals
The study obtained the approval from the institutional ethical committee (IEC).
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