Electroacupuncture Alleviates Pain in Rats with Knee Osteoarthritis by Modulating Autophagy via the PI3K/Akt/mTOR Signaling Pathway
This study demonstrates that electroacupuncture alleviates pain in rats with knee osteoarthritis by activating the PI3K/Akt/mTOR signaling pathway to suppress excessive autophagy in the brain, thereby reducing inflammation and structural joint damage.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Pain is often thought of as a simple signal: a damaged part of the body sends a warning to the brain, which then registers the sensation. However, for millions of people living with chronic conditions like knee osteoarthritis, the story is more complex. The pain does not always match the visible damage in the joint, and it often persists long after the initial injury has occurred. Scientists now understand that this lingering pain involves changes deep within the central nervous system, specifically in the brain. One area of growing interest is a cellular process called autophagy. In healthy cells, this process acts as a cleanup crew, removing damaged parts to keep the cell functioning. But when this cleanup system goes into overdrive, it can start to break down healthy components, leading to cell stress and death. Another key player in this cellular drama is a signaling pathway known as PI3K/Akt/mTOR, which acts like a master switch telling the cell when to stop cleaning and start surviving. When this switch is turned off, the cleanup crew runs wild. Understanding how to flip this switch back on could offer new ways to treat pain that does not respond to standard medications.
Researchers at Henan University of Chinese Medicine and the Henan Provincial Hospital of Traditional Chinese Medicine set out to explore whether a traditional therapy called electroacupuncture could influence these cellular mechanisms to relieve pain. They focused on a group of rats that had been surgically induced with knee osteoarthritis, a condition that caused them to feel significant pain and showed clear damage to their knee joints. The team wanted to see if applying gentle electrical stimulation to specific points on the rats' legs could calm the pain signals traveling to the brain. To do this, they divided sixty rats into six groups. Some received the actual treatment, where needles were inserted into specific points on the leg and connected to a device that delivered a mild electrical current. Others received a "sham" treatment, where needles were placed in non-acupoint locations nearby, serving as a control to ensure the effect came from the specific points and not just the sensation of the needles. A third group received a drug known to activate the PI3K/Akt/mTOR pathway, while a fourth group received both the drug and the acupuncture. The treatments were given three times a week for eight weeks, totaling twenty-four sessions.
The results showed a clear difference between the groups. The rats with knee osteoarthritis that received no treatment or the sham needle placement continued to show low pain thresholds, meaning they reacted to light touches and heat much more quickly than healthy rats. Their knee joints also showed severe structural damage, and their blood contained high levels of inflammatory markers. However, the rats that received the real electroacupuncture treatment, as well as those given the activating drug, showed a marked improvement. They tolerated touch and heat for much longer periods, indicating a significant reduction in pain. Their knee joints looked healthier, with smoother cartilage surfaces and more organized cells, and the levels of inflammation in their blood dropped. The group that received both the acupuncture and the drug showed the most robust improvement, suggesting the two methods worked well together.
Digging deeper into the brain tissue of these rats, the researchers found the biological explanation for this relief. In the rats with untreated knee pain, the hippocampus—a region of the brain involved in processing pain and emotion—was filled with an excessive number of autophagosomes, the tiny sacs that carry out the cellular cleanup. This indicated that the cells were overworking their cleanup systems. At the same time, the levels of the PI3K/Akt/mTOR pathway proteins were very low, meaning the "stop" signal for this cleanup was missing. The researchers also observed that the brain cells were under stress, with a drop in energy production and an increase in proteins that signal cell death. When the rats received electroacupuncture or the activating drug, the picture changed. The number of autophagosomes decreased, returning to levels closer to those of healthy rats. The levels of the PI3K/Akt/mTOR pathway proteins rose, effectively turning the "stop" signal back on. This shift was accompanied by a rise in energy levels within the brain cells and a reduction in the proteins that trigger cell death. The study suggests that the electrical stimulation did not just mask the pain; it helped restore a balance in the brain's cellular machinery.
The findings indicate that chronic pain from knee osteoarthritis is linked to a specific breakdown in how brain cells manage their internal waste, driven by a signaling pathway that has gone quiet. By using electroacupuncture, the researchers were able to reactivate this pathway, which in turn slowed down the excessive cellular cleanup and protected the brain cells from stress. This provides a concrete biological reason for why this ancient therapy works, moving beyond the idea of simple symptom relief to a mechanism that addresses the underlying cellular dysfunction. While the study was conducted on rats, the results offer a promising glimpse into how non-drug therapies might one day be used to target the central nervous system's role in chronic pain, providing a safer alternative for those who cannot tolerate long-term medication.
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