Chemogenetics Modulation of Electroacupuncture Analgesia in Mice Spared Nerve Injury-Induced Neuropathic Pain through TRPV1 Signaling Pathway.

Neuropathic pain, which is initiated by a malfunction of the somatosensory cortex system, elicits inflammation and simultaneously activates glial cells that initiate neuroinflammation. Electroacupuncture (EA) has been shown to have therapeutic effects for neuropathic pain, although with uncertain mechanisms. We suggest that EA can reliably cure neuropathic disease through anti-inflammation and transient receptor potential V1 (TRPV1) signaling pathways from the peripheral to the central nervous system. To explore this, we used EA to treat the mice spared nerve injury (SNI) model and explore the underlying molecular mechanisms through novel chemogenetics techniques. Both mechanical and thermal pain were found in SNI mice at four weeks (mechanical: 3.23 ± 0.29 g; thermal: 4.9 ± 0.14 s). Mechanical hyperalgesia was partially attenuated by 2 Hz EA (mechanical: 4.05 ± 0.19 g), and thermal hyperalgesia was fully reduced (thermal: 6.22 ± 0.26 s) but not with sham EA (mechanical: 3.13 ± 0.23 g; thermal: 4.58 ± 0.37 s), suggesting EA's specificity. In addition, animals with Trpv1 deletion showed partial mechanical hyperalgesia and no significant induction of thermal hyperalgesia in neuropathic pain mice (mechanical: 4.43 ± 0.26 g; thermal: 6.24 ± 0.09 s). Moreover, we found increased levels of inflammatory factors such as interleukin-1 beta (IL1-ß), IL-3, IL-6, IL-12, IL-17, tumor necrosis factor alpha, and interferon gamma after SNI modeling, which decreased in the EA and Trpv1-/- groups rather than the sham group. Western blot and immunofluorescence analysis showed similar tendencies in the dorsal root ganglion, spinal cord dorsal horn, somatosensory cortex (SSC), and anterior cingulate cortex (ACC). In addition, a novel chemogenetics method was used to precisely inhibit SSC to ACC activity, which showed an analgesic effect through the TRPV1 pathway. In summary, our findings indicate a novel mechanism underlying neuropathic pain as a beneficial target for neuropathic pain.

Acupoint Catgut Embedding Diminishes Fibromyalgia Pain through TRPV1 in the Mouse Brain.

BACKGROUND: Chronic pain refers to pain that persists for over three months. Chronic pain may restrict activities of daily living, including work, learning, social life, and can lead to anxiety, depression, and sleep disturbance. Imaging data have demonstrated that central sensitization often occurs in the brain of patients with chronic pain, which arises from imbalanced neurotransmission in the central nervous system. Transient receptor potential vanilloid 1 (TRPV1) is an ion channel to serve as an inflammatory detector in the brain. We aim to determine the properties of acupoint catgut embedding (ACE) on cold stress-induced mice fibromyalgia (FM) and surveyed the character of TRPV1 and linked molecules in chronic FM pain. METHODS: Intermittent cold stress (ICS) was used to induce mice FM model. Mice were subgrouped into normal mice, ICS-induced FM group, FM mice with ACE, and FM in Trpv1-⁣/- group. ACE is a novel acupuncture technique that provides convenience and continuous nerve stimulation that has been reported effective on pain management. RESULTS: Our behavioral experiments showed similar levels of pain response among all groups before treatment. After ICS, prolonged mechanical and thermal pain was initiated (mechanical threshold: 1.96 ± 0.12 g; thermal latency: 4.86 ± 0.21 s) and were alleviated by ACE treatment and TRPV1 gene deletion. Inflammatory mediators were increased in the plasma of FM mice, while TRPV1 and related kinases were amplified in the hypothalamus and cerebellum. These changes were ameliorated in the ACE-treated and Trpv1-⁣/- groups. CONCLUSIONS: These novel findings suggest that chronic FM pain can be modulated by ACE or TRPV1 gene deletion. The analgesic effect of ACE through the TRPV1 pathway may reflect its potential as a therapeutic target for FM treatment.

Paper-Based Detection Device for Microenvironment Examination: Measuring Neurotransmitters and Cytokines in the Mice Acupoint.

(1) Background: The medical practice of acupuncture involves the insertion of a specialized stainless needle into a specific body point, often called an acupoint, to initiate a perceived phenomenon of de-qi sensation. Therefore, the term "de-qi" describes bodily sensations experienced by the recipient during acupuncture, which may include feelings of soreness, heaviness, fullness, numbness, and migration. However, while acupuncture treatments reportedly result in acupoint activation and an increased release of neurotransmitters or cytokines, detecting these substances released into the acupoint microenvironment is often missed or delayed in clinical and basic practice. (2) Methods: To address this situation, we employed a paper-based enzyme-linked immunosorbent assay method to examine acupoint environmental changes using minute volumes of easily accessible acupoint fluids. (3) Results: Our results indicated that while levels of adenosine triphosphate (ATP), interleukin-1ß, interleukin-6, glutamate, substance P, and histamine were all increased in the experimental group following electroacupuncture (EA) treatment, contrary results were observed in the sham EA and transient receptor potential vanilloid 1 (Trpv1-/-) groups. Subsequently, TRPV1 and its associated molecules were augmented in mouse dorsal root ganglion, spinal cord, thalamus, and the somatosensory cortex, then examined by Western blotting and immunofluorescence techniques. Investigations revealed that these elevations were still unobserved in the sham EA or EA in the Trpv1-/- groups. Furthermore, results showed that while administering ATP could mimic EA function, it could be reversed by the ATP P2 receptor antagonist, suramin. (4) Conclusions: Our data provide novel information, indicating that changes in neurotransmitter and cytokine levels can offer insight into acupuncture mechanisms and clinical targeting.

Optogenetic modulation of electroacupuncture analgesia in a mouse inflammatory pain model.

Peripheral tissue damage and associated inflammation can trigger neuroplastic changes in somatic pain pathways, such as reduced neuronal firing thresholds and synaptic potentiation, that ultimately lead to peripheral sensitization and chronic pain. Electroacupuncture (EA) can relieve chronic inflammatory pain, but the underlying mechanisms are unknown, including the contributions of higher pain centers such as somatosensory cortex (SSC). We investigated these mechanisms using optogenetic modulation of SSC activity in a mouse inflammatory pain model. Injection of Complete Freund's Adjuvant into the hind paw reliably induced inflammation accompanied by reduced mechanical and thermal pain thresholds (hyperalgesia) within three days (mechanical: 1.54 ± 0.13 g; thermal: 3.94 ± 0.43 s). Application of EA produced significant thermal and mechanical analgesia, but these responses were reversed by optogenetic activation of SSC neurons, suggesting that EA-induced analgesia involves modulation of central pain pathways. Western blot and immunostaining revealed that EA also attenuated CaMKIIα signaling in the dorsal root ganglion, central spinal cord, SSC, and anterior cingulate cortex (ACC). In contrast, optogenetic activation of the SSC induced CaMKIIα signaling in SSC and ACC. These findings suggest that AE can relieve inflammatory pain by suppressing CaMKIIα-dependent plasticity in cortical pain pathways. The SSC and ACC CaMKIIα signaling pathways may be valuable therapeutic targets for chronic inflammatory pain treatment.

Electroacupuncture Reduces Fibromyalgia Pain by Attenuating the HMGB1, S100B, and TRPV1 Signalling Pathways in the Mouse Brain.

Fibromyalgia is characterized by chronic and persistent widespread pain and generalized muscle tenderness, and it is refractory to treatment. The central nervous system (CNS) plays an important role, pain signalling, in fibromyalgia subjects. Electroacupuncture (EA) has been practiced for thousand years to treat many diseases that involve pain. We established fibromyalgia-like pain in mice using intermittent cold stress and investigated therapeutic effects and modes of action with EA. EA of 2 Hz and 1 mA was performed for 20 min at the ST36 acupoint in mice from Day 3 to Day 5. Our results showed that mechanical and thermal hyperalgesia were induced by intermittent cold stress (Day 5: mechanical: 1.43 ± 0.34 g; thermal: 3.98 ± 0.73 s) and were subsequently reversed by EA (Day 5: mechanical: 4.62 ± 0.48 g; thermal: 7.68 ± 0.68 s) or Trpv1 -/- (Day 5: mechanical: 4.38 ± 0.51 g; thermal: 7.48 ± 0.98 s). Activity in the HMGB1, S100B, and TRPV1 pathways was increased in the mouse prefrontal cortex, somatosensory cortex, thalamus, and amygdala with the stress treatment. This increase was attenuated by EA or Trpv1 -/-. These results suggest potential targets for the treatment of TRPV1-dependant fibromyalgia pain.