The purpose of this blog is to provide you with information on the study titled “Chemical Characterization and Immunomodulatory Activity of Fucoidan from Sargassum hemiphyllum (SHF)” conducted by Rui Li, et al. The study proved a theoretical basis for further development of SHF as a functional food ingredient or nutraceutical to enhance the human body’s immune system. The positive immune-enhancing effect of Sargassum hemiphyllum Fucoidan (SHF) is evident from its ability to significantly promote NO secretion in RAW 264.7 macrophages. This indicates the potential of SHF as an immune-boosting agent. The immune system of RAW 264.7 macrophages was strengthened by SHF, as evidenced by the upregulation of cyclooxygenase-2 (COX-2) and nitric oxide synthase (iNOS) levels. This increase was observed at both the gene expression and protein abundance levels.

The production of nitric oxide is a characteristic feature of activated macrophages, providing protection against rapidly dividing cancer cells and invading pathogens. In order to investigate the activation of macrophages by SHF, RAW 264.7 cells, which are mouse macrophages, were cultured with SHF. The NO production of it was quantified and then compared to the NO production of three commercially available Fucoidans, as illustrated in Figure 1. None of the three commercially available Fucoidans (See Figures 1A-C) increased NO production, and decreased NO production compared to the control group, whereas RAW 264.7 medium showed a dose-dependent increase in NO production. Activation of the cells was achieved by treating them with SHF at various test concentrations, specifically between 25 and 100 μg/mL, as shown in Figure 3A–C. In comparison to the control group, the release of NO in RAW 264.7 cells was significantly higher when exposed to SHF at concentrations of 50 and 100 μg/mL. (See Figure 1D) Hence, the results obtained from this study strongly suggest that SHF has the potential to enhance the release of NO, thereby potentially facilitating the activation of macrophages and their active participation in the immune response, ultimately playing a crucial role in immunomodulation.

There is a consistent connection between immunomodulatory activity and functional factors derived from macrophages. iNOS is a necessary controller responsible for the incorporation of large amounts of NO in macrophages, and both COX-2 and iNOS are pro-inflammatory mediators. Therefore, to identify Fucoidan-mediated macrophage activation, we decided to study the effects of SHF on COX-2 and iNOS mRNA expression in macrophages using qRT-PCR analysis. According to the results, there was no clear elevation in the expression of COX-2 mRNA when the concentration of SHF was 25 μg/mL, but a significant upregulation in COX-2 mRNA expression was observed at 50 μg/mL of SHF.

On the other hand, the results from Figure 2A reveal that there was no significant difference observed between these two groups. Figure 2B demonstrates that the expression of iNOS mRNA closely resembled that of COX-2. These results are consistent with NO production, indicating that SHF can increase target gene expression levels and promote NO secretion, and the conclusion that macrophages can be activated by SHF at concentrations of 50 and 100 μg/mL. This further corroborated this. In addition, SHF induces the release of NO by upregulating the expression of COX-2 and iNOS.

They used immunofluorescence to further determine whether SHF increases protein expression of both COX-2 and iNOS. The group treated with SHF showed an increase in the brightness of the blue and green fluorescence of COX-2 and iNOS proteins, which correlated with the concentration of SHF. The higher fluorescence intensity suggested that SHF enhanced the activation of these proteins.

In the study on the activation of COX-2 and iNOS proteins in RAW 264.7 cells, the researchers employed Western blot analysis to measure their protein expression. When stimulated, the cells treated with SHF showed decreased levels of COX-2 and iNOS, as stated in the results. All three groups tested (25, 50, and 100 μg/mL) had significantly higher levels of COX-2 and iNOS compared to the control group. The protein level analysis revealed that the immune system can be enhanced by SHF, with concentrations between 25 and 100 μg/mL showing positive effects.

The expression of several common immunoregulatory regulators correlates with the production of various macrophage-derived functional factors. The activation of the innate immune response is widely considered to be the primary means by which Fucoidan secures cells. This has great potential for controlling immunomodulatory signaling.

The results of the study showed that the administration of SHF led to a significant increase in NO secretion in RAW 264.7 macrophages, suggesting that SHF has a beneficial effect on immune enhancement. Additionally, SHF was found to strengthen the immune system of RAW 264.7 macrophages by increasing the levels of COX-2 and iNOS. This effect was observed at both the gene expression and protein abundance levels. Hence, the results indicate that SHF is a potential nutraceutical for immune system activation.

Source: Mar. Drugs 2023, 21(1), 18; https://doi.org/10.3390/md21010018