Coelastrella sp. extract attenuates inflammatory responses and NF-κB p65 nuclear accumulation in LPS- stimulated RAW 264.7 macrophages

Inflammation is the body's urgent, necessary response to injury or infection, a biological alarm system that summons immune cells to fight off invaders and begin the work of repair. However, when this system stays switched on too long or reacts too strongly, it can damage healthy tissue and fuel chronic diseases ranging from heart trouble to arthritis. A key driver of this overreaction is a signaling pathway inside immune cells that acts like a master switch, turning on genes that produce inflammatory chemicals. Scientists have long known that natural substances found in plants and algae can sometimes calm this switch, offering a gentler alternative to powerful drugs that often carry heavy side effects. The challenge has been to identify exactly which natural sources work, how they work, and whether they can safely quiet the immune system without shutting it down entirely.

Researchers at Sun Moon University in South Korea turned their attention to a specific type of freshwater green microalga called Coelastrella sp., a tiny organism that has shown promise as a source of health-promoting compounds. They set out to see if an extract made from this algae could calm down an overactive immune response in a laboratory setting. To test this, they used a standard model of immune cells known as macrophages, which are the body's first responders. In the experiment, these cells were exposed to a bacterial trigger that forces them into a state of high alert, mimicking a severe infection. This trigger causes the cells to flood their surroundings with nitric oxide, a gas that helps fight bacteria but can be harmful in excess, and to produce reactive oxygen species, which are unstable molecules that cause oxidative stress. The researchers then introduced their algae extract to see if it could lower these dangerous levels without killing the cells themselves.

The team first prepared the extract by soaking freeze-dried algae powder in a mixture of water and ethanol, using sound waves to help pull out the active compounds. They found that the resulting liquid was rich in polyphenols and flavonoids, two classes of natural compounds known for their ability to neutralize harmful molecules. When they tested the extract on the immune cells, they discovered a safe window of concentration where the substance did not harm the cells but still had a powerful effect. At these safe levels, the extract significantly reduced the amount of nitric oxide the cells produced. It also lowered the levels of reactive oxygen species, the unstable molecules that can damage cell structures. The reduction in these harmful byproducts was clear and measurable, suggesting the extract was effectively dampening the cell's aggressive response to the bacterial trigger.

Beyond simply cleaning up the chemical mess, the extract appeared to stop the problem at its source by interfering with the cell's internal instructions. The researchers looked at the genetic messages inside the cells that tell them to build inflammatory proteins. They found that the extract lowered the production of messages for several key inflammatory markers, including a protein called iNOS, which makes nitric oxide, and various signaling molecules like interleukin-6 and tumor necrosis factor-alpha. The extract also reduced the amount of the actual proteins these genes build. The most significant drop was seen in the instructions for interleukin-1-beta and the master switch protein known as NF-κB p65. By lowering the levels of these proteins, the extract effectively told the cell to stand down, producing fewer inflammatory signals than it would have otherwise.

To understand exactly how the extract stopped the inflammatory signal, the scientists watched where the master switch protein, NF-κB p65, was located inside the cell. Under normal conditions, this protein sits quietly in the cell's main body, but when the cell is under attack, it moves into the nucleus, the control center, to turn on inflammatory genes. The researchers used a special glowing dye to track this movement and found that the algae extract kept a large portion of the protein out of the nucleus. Instead of rushing to the control center to start the alarm, the protein remained in the outer regions of the cell. This physical blockage prevented the inflammatory genes from being activated, which explains why the levels of inflammatory proteins dropped so sharply.

The study concludes that the Coelastrella sp. extract acts as a multi-layered defense against inflammation. It does not just neutralize harmful chemicals after they are made; it also stops the cell from making them in the first place by blocking the movement of the master switch protein. While the researchers noted that their work was limited to cells in a dish and that they have not yet identified the exact single molecule responsible for the effect, the results provide a strong foundation for further study. The extract successfully reduced oxidative stress, lowered nitric oxide production, and prevented the activation of inflammatory genes, all without harming the cells. This suggests that this specific microalga holds potential as a natural resource for developing new ways to manage inflammation, offering a path toward treatments that work with the body's own biology rather than overriding it.