Restoration of mitophagy by crebanine suppresses sevoflurane-induced microglial activation and cognitive deficits by blocking mitochondrial DNA-triggered cGAS–STING pathway

Every year, millions of people undergo surgery, and for many, the recovery involves more than just healing a wound. A significant number of older adults experience a foggy, lingering confusion after anesthesia wears off, a condition known as postoperative cognitive dysfunction. This state can rob patients of their sharp memory and ability to think clearly, sometimes for weeks or even longer. While doctors have long suspected that the inflammation caused by the body's immune cells in the brain plays a major role in this decline, the exact chain of events that turns a routine anesthetic into a brain injury has remained a mystery. Specifically, scientists have been searching for the initial spark that sets off this inflammatory fire, hoping to find a way to stop it before it starts.

In a new study, researchers from Henan Provincial People's Hospital in China have traced this spark to a breakdown in the cellular recycling system of the brain's immune cells. They focused on a natural compound called crebanine, found in a climbing plant, to see if it could repair this system. The team discovered that a common anesthetic gas called sevoflurane damages the tiny power plants inside brain immune cells, causing them to leak their internal contents. This leakage triggers a false alarm that convinces the brain it is under attack, leading to the inflammation that harms memory. By restoring the cell's ability to clean out these damaged power plants, the researchers found that crebanine could stop the alarm from sounding, effectively protecting the brain from the cognitive decline usually seen after surgery.

The story begins with the brain's immune cells, known as microglia. These cells act as the brain's security guards, constantly scanning for trouble. Under normal conditions, they are calm and watchful. However, when exposed to sevoflurane, a gas widely used to keep patients asleep during surgery, these guards become agitated. They swell up and start releasing toxic chemicals that damage nearby nerve cells. The researchers wanted to know why this happens. They suspected the problem started with the mitochondria, the structures inside cells that generate energy. When mitochondria get damaged, they need to be removed and recycled, a process called mitophagy. If this recycling fails, the damaged mitochondria pile up and begin to leak their genetic material, known as mitochondrial DNA, into the main part of the cell.

To test this theory, the scientists worked with microglial cells in a lab dish. They exposed these cells to sevoflurane and watched what happened. As they suspected, the gas disrupted the recycling process. The cells could no longer clear out their broken mitochondria, leading to a buildup of waste and a surge in harmful oxygen molecules. This chaos caused the mitochondria to rupture, spilling their DNA into the cell's interior. The cell's sensors, which are designed to detect foreign invaders like bacteria, mistook this leaked DNA for an attack. This triggered a powerful defense pathway, causing the microglia to switch into a highly aggressive mode and release a flood of inflammatory signals.

The researchers then introduced crebanine to the mix. This natural compound, which has been studied for its ability to reduce inflammation, acted as a repair crew. When added to the cells before the gas exposure, it restored the recycling process. The damaged mitochondria were cleared away efficiently, preventing the DNA from leaking out. Because the genetic material stayed locked inside the mitochondria, the false alarm never went off. The microglia remained calm, and the inflammatory cascade was stopped before it could begin. To be certain that this was the only way crebanine worked, the scientists blocked the recycling process with a chemical inhibitor. When they did this, crebanine lost its power to protect the cells, proving that the drug's success depended entirely on fixing the recycling system.

To see if these findings held true in a living animal, the team moved to an experiment with older rats. They divided the animals into groups, exposing some to the anesthetic gas and others to a control environment. The rats that breathed the gas showed clear signs of brain trouble: their brain tissue became inflamed, nerve cells began to die, and they struggled to learn and remember in a water maze test. However, the rats that received crebanine before the gas exposure fared much better. Their brains showed far less inflammation, their nerve cells survived, and they navigated the maze with the same ease as healthy animals. The drug did not just reduce the damage; it preserved the animals' ability to think and learn, effectively shielding them from the cognitive fog that usually follows anesthesia.

The study provides a clear map of how a common anesthetic can harm the aging brain and offers a potential way to prevent it. It shows that the damage is not a random accident but a specific chain reaction starting with a failure to clean up cellular waste. By fixing the cleanup crew, the researchers were able to stop the chain reaction at its source. While crebanine is not yet a treatment for humans, the work suggests that targeting the cell's recycling machinery could be a powerful strategy to protect patients from the cognitive side effects of surgery. The findings offer a glimmer of hope that one day, the fog of postoperative confusion could be lifted before it ever forms.