Acupuncture Analgesia - The anti-inflammatory effect of acupuncture and its significance in analgesia

Authors: Bonnie Xia Jin, Louis Lei Jin, Guan-Yuan Jin  - International Institute of Systems Medicine, Milwaukee, WI 53222 USA

World Journal of Acupuncture - Moxibustion - Volume 29, Issue 1, March 2019, Pages 1-6

https://doi.org/10.1016/j.wjam.2019.03.003

In the mechanisms of acupuncture analgesia, an important aspect often overlooked is the anti-inflammatory effect of acupuncture, which is mainly attained through the self-limiting inflammatory response-inflammatory reflex and its regulation of hypothalamic-pituitary-adrenal(HPA) axis and autonomic nerve system (the vagus nerve and the sympathetic postganglionic fiber). The significance of anti-inflammatory effect of acupuncture in analgesia is manifested twofold: The first, inflammatory nociceptive pain is a major type of chronic pain. The second, neurogenic inflammation is the mechanism by which certain acupoints or acu-reflex points (ARPs) are formed at the body surface and have short-cut connections to the pathological focus. Selecting ARPs and applying appropriate sensory stimulation or local microtrauma (affected by different needling means or stimulation parameters), combined with low-frequency electrical stimulation or the vagus stimulation in the concha region, are helpful to strengthen the anti-inflammatory and analgesic effect of acupuncture.

In the study for the mechanisms of acupuncture analgesia, the release of endogenous opioids is already well understood. However, with new discoveries of inflammatory reflex and the affirmation of the anti-inflammatory effect of acupuncture in the past few decades, acupuncture's anti-inflammatory effect in reducing pain plays an important part in its analgesic mechanisms. By reviewing the anti-inflammatory and analgesic effect of acupuncture and its mechanisms, this paper presents the significance of anti-inflammatory effect for acupuncture analgesia, and explores ways how to improve the analgesic effect of acupuncture by enhancing the anti-inflammatory effect, including the optimal selection of stimulation points, means or methods of acupuncture.

The anti-inflammatory effect of acupuncture has been thoroughly studied and affirmed in many inflammatory diseases, especially in the treatment of inflammatory pain. The following are some examples related to somatic pain and visceral pain .In a randomized controlled study, 63 patients with rheumatoid arthritis (RA) were split into two groups. One group received electroacupuncture (EA) and the other received non-EA. Acupuncture points were selected on specific points or locations related to pain. 

To clarify the anti-inflammatory mechanisms of acupuncture, we must first review the mechanism of self-limiting inflammatory response in tissue injury. Inflammation is a self-protection response of the body. Once invasion and tissue injury occur, they are sensed by pattern recognition receptors that activate innate immune cells. This early response gives rise to a cascade of events, including the release of proinflammatory cytokines and recruitment of leukocytes, aimed to clear pathogens and other inflammatory factors.

First, and foremost, the reason why anti-inflammation is crucial for acupuncture analgesia is because inflammatory nociceptive pain is a major type of chronic pain. Generally, commonly seen pain in the clinic can be roughly divided into inflammatory nociceptive (tissue-injury), neuropathic (nerve-injury), cancer-related and visceral pain [9]. In fact, any exogenous or endogenous injuries will eventually lead to inflammatory responses, which itself serves as the direct cause of pain.

Once the anti-inflammatory mechanisms of acupuncture is well-understood and the significance of anti-inflammation for analgesia is beyond doubt, it is now time to explore strategies on how to select proper stimulus targets (acupoints or ARPs), as well as means of needling and their stimulus parameters improve the treatment methods in line with the purpose of anti-inflammatory and analgesic effect.