Anti-Inflammatory Effects of Acupuncture at ST36 Point: A Literature Review in Animal Studies

Acupuncture at the ST-36 point, known as Zusanli in traditional Chinese medicine, has been widely studied as a promising alternative therapy for the treatment of inflammatory conditions. This specific point, located in the anterior part of the leg, has aroused great scientific interest due to its consistent anti-inflammatory effects demonstrated in different experimental models. Although many studies have individually investigated the mechanisms by which acupuncture at ST-36 modulates inflammation, a comprehensive analysis that systematically organized all these findings to provide a complete picture of the anti-inflammatory effects of this ancient technique did not yet exist.

To fill this gap in scientific knowledge, researchers at Dongguk University in South Korea conducted a systematic review of the scientific literature published through July 2021. The main objective was to investigate how acupuncture at the ST-36 point regulates inflammation and which biological mechanisms underlie these effects. The researchers conducted a comprehensive search in the PubMed database using specific keywords such as "animal," "acupuncture," "ST36," "inflammation," and "immune," initially identifying 292 relevant studies. After applying rigorous selection criteria, which included studies conducted exclusively in animal models with a focus on the anti-inflammatory effects of acupuncture at ST-36, the authors selected 69 high-quality studies for detailed analysis.

These studies were then organized according to the anatomical regions investigated, allowing for a clearer understanding of how acupuncture affects different body systems.

The analysis revealed fascinating findings about the multiple mechanisms through which acupuncture at ST-36 exerts its anti-inflammatory effects. Forty-three studies examined changes in body fluids such as blood and plasma, demonstrating that acupuncture can significantly reduce levels of pro-inflammatory cytokines such as tumor necrosis factor alpha, interleukin-6, and interleukin-1 beta. Twenty-seven studies focused on the digestive system, showing that acupuncture can protect the intestinal barrier, reduce inflammatory cell infiltration, and modulate the composition of the gut microbiota. Seventeen studies investigated the nervous system, revealing that acupuncture can reduce neuroinflammation and modulate glial cell activity.

Additionally, thirty studies examined other tissues and organs, including liver, lungs, joints, and muscle tissues, demonstrating consistent anti-inflammatory effects throughout the body.

The identified mechanisms include activation of the vagus nerve, which is a crucial neural pathway for the regulation of the systemic inflammatory response. Acupuncture at ST-36 demonstrated activation of what scientists call the "cholinergic anti-inflammatory pathway," in which neural signals can rapidly suppress the production of pro-inflammatory cytokines in organs such as the spleen. Another important mechanism involves modulation of the TLR4/NF-kB signaling pathway, which is central to the regulation of the innate immune response. Acupuncture also influences macrophage polarization, favoring the anti-inflammatory M2 phenotype over the pro-inflammatory M1 phenotype.

Additionally, the technique affects signaling pathways such as MAPK and the activation of cannabinoid receptors, contributing to its therapeutic effects.

These findings have significant clinical implications for both patients and healthcare professionals. For patients suffering from chronic inflammatory conditions such as rheumatoid arthritis, inflammatory bowel diseases, or chronic pain, acupuncture at ST-36 offers a promising therapeutic option with the potential to reduce dependence on conventional anti-inflammatory medications. Nonsteroidal anti-inflammatory drugs, although effective, can cause significant side effects in the gastrointestinal, cardiovascular, and renal systems, especially with prolonged use. Acupuncture has a favorable safety profile, serving as a valuable alternative or complementary therapy.

For healthcare professionals, these findings provide a robust scientific basis for incorporating acupuncture into treatment protocols for inflammatory conditions, offering an integrative approach that can improve therapeutic outcomes.

It is important to recognize some limitations of this review. First, all analyzed studies were conducted in animal models, mainly rodents, which may limit the direct extrapolation of results to humans due to physiological differences between species. Second, there was considerable variability in the acupuncture protocols used among the studies, including different frequencies of electrical stimulation, duration of treatment, and application techniques, which can influence the results obtained. Third, although the identified mechanisms are biologically plausible, many studies investigated only specific aspects of the inflammatory response, not providing a complete view of how all these mechanisms interact in real clinical conditions.

Controlled clinical studies in humans are necessary to confirm these findings and establish optimized treatment protocols. Despite these limitations, this review represents a significant advance in understanding the anti-inflammatory mechanisms of acupuncture at ST-36, providing a solid foundation for future clinical investigations and offering valuable insights into how this ancient practice can be effectively integrated into modern medicine for the management of inflammatory conditions.