Immolina, a high-molecular-weight polysaccharide fraction of spirulina, enhances chemokine expression in human monocytic THP-1 cells

Introduction: Spirulina (Spirulina platensis) is a dietary supplement valued for its immune-enhancing properties. We previously reported that the immunostimulatory effect of spirulina can be traced to a high-molecular-weight polysaccharide fraction. This fraction, labeled Immolina, activates nuclear factor kappa-B in human monocytic THP-1 cells and increases expression of proinflammatory cytokines. Objective: To characterize further the immunostimulatory effects of Immolina on THP-1 cells, we evaluated its effect on genes encoding the chemokines interleukin (IL)-8, MCP-1, MIP-1α, MIP-1β, IP-10, the cytokines tumor necrosis factor (TNF)-α, IL-1β, and the enzyme cyclo-oxygenase-2 (COX-2). Methods: THP-1 cells were exposed to concentrations of Immolina ranging from 1 ng/mL to 100 μg/mL and changes in gene expression were assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). For comparison, THP-1 cells were activated with 1 ng/mL of TNF-α, 10 ng/mL of IL-1β, or 10 ng/mL of lipopolysaccharide using the same assay conditions. To assess the response of THP-1 cells to Immolina at the protein level, we probed culture supernatants using a cytokine array immunoblot assay. Results: RT-PCR analysis revealed that Immolina dose-dependently increased the expression of all 5 chemokines tested as well as the expression of TNF-α, IL-1β, and COX-2. The cytokine array immunoblot assay revealed an increase in the chemokines IL-8 and MIP-1β. Thymidine uptake experiments verified that Immolina did not affect the viability and growth rate of THP-1 cells. Conclusions: The results of the experiments demonstrate that Immolina activates THP-1 cells in a manner that is consistent with the recruitment of diverse populations of leukocytes in response to inflammatory and infectious signals.