Electroacupuncture reduces inflammation via specific neural pathways, study says

Stimulating the nervous system using small electric current by acupuncture could tamp down systemic inflammation in the body, according to a new research in mice published in the journal Neuron.

Previous studies have shown direct vagal nerve stimulations in the neck region can help reduce inflammation, but these experimental approaches require invasive procedures. The researchers set out to investigate whether and how electric stimulation using acupuncture can modulate inflammation.

The researchers began by giving mice a 15-minute electroacupuncture at 3 mA at a specific site on the abdomen. This acupoint, dubbed ST25, has been associated with nerves of the spleen, which is a major organ involved in immune responses, according to the study.

The team then simulated a life-threatening inflammatory condition that is often seen in patients suffering severe bacterial or virus infections by injecting mice with a compound called lipopolysaccharide (LPS). After injecting the treated mice with LPS, researchers found the serum levels of pro-inflammatory molecules in these animals was significantly lower than that of the control group. The mice's survival rates also more than doubled. However, when the researchers gave mice the electroacupuncture after the LPS shot, the treated mice had much greater inflammation than those that were untreated and did not survive.

By comparing the effect of electroacupuncture in mice with an altered nervous system, the team determined that high intensity stimulation at the abdomen could excite norepinephrine-producing nerves that connect the spine and spleen. The norepinephrine then activated a particular type of receptors in the spleen that suppressed pro-inflammatory molecules. When LPS was introduced first, another type of splenic receptors, pro-inflammatory in this case, became highly expressed, and the subsequent electroacupuncture therapy further enhanced inflammation.

The team then conducted electroacupuncture at a different acupoint, this time on mice's hindlegs. They found stimulation at a low intensity of 0.5 mA for 15 minutes could significantly reduce pro-inflammatory molecule levels either before or after LPS-injection. Mice's survival rate after electroacupuncture also increased by 1-fold or more. A genetically modified mice model suggests that low-level electroacupuncture at hindlegs reduced inflammation not though the spleen, but a different neural pathway involving the vagus nerves and the adrenal glands.

“Our study illustrated that electroacupuncture has neuroanatomic basis, but its efficacy and safety on humans need to be validated in clinical trials,” said Qiufu Ma, PhD, senior author of the study and a researcher at Harvard Medical School, in a statement. “There's still many questions unanswered about this medical practice and thus a lot of room to do more research.”