Botulinum toxin type A ameliorates adjuvant-arthritis pain by inhibiting microglial activation-mediated neuroinflammation and intracellular molecular signaling

Botulinum toxin effects on biochemical biomarkers related to inflammation-associated head and neck chronic conditions: a systematic review of clinical research

Botulinum toxin type A (BoNT) has emerged as a potential alternative to conventional therapies to many debilitating chronic diseases characterised by inflammatory states. However, the biological rationale remains ambiguous. Our review aimed to systematically assessed which biochemical biomarkers have been reported in clinical research to evaluate BoNT analgesic and mood-lifting effects in head and neck chronic conditions related to inflammation. We searched databases and registries between inception and September 29, 2023. Of the nine included studies, there were concerns about risk of bias for six studies. The leading biomarker with five studies was the calcitonin gene-related peptide (CGRP), followed by serotonin with two studies. Oxidative stress biomarkers were only reported in one study. Several important players in inflammatory processes and different immune cell classes have been evaluated in four studies. There was only one trial measuring changes in beta Tubulin and SNAP-25, and another study evaluating cutaneous neuropeptide substance-P. After BoNT, a significant effect was reported in six studies, including decrease in plasma levels of CGRP in chronic migraine and trigeminal neuralgia; serotonin decrease when collected from human tears in refractory intractable dry eye disease and increase in peripheral blood platelets in painful cervical dystonia associated to depression and anxiety; decrease in plasma concentration of markers of oxidative damage to proteins and increase in biomarkers for antioxidant power; decrease in expression of gene sets involved in inflammatory pathways and immune cells classes in the periosteum and metalloproteinase-9 molecule in the tears. BoNT seems to affect some biomarkers present in chronic inflammatory conditions. However, the certainty evidence found was very low to moderate. This study is registered on PROSPERO (CRD42023432131).

Botulinum toxin A dampened inflammatory response in BV-2 microglial cells

Our previous studies have demonstrated the analgesic effects of botulinum toxin type A (BoNT/A) in a pre-clinical model of rheumatoid arthritis of the temporomandibular joint, where we proposed that BoNT/A decreases the neurogenic milieu after reaching the subnucleus caudalis. However, it is unknown whether BoNT/A directly regulates microglial cell activity. Therefore, the present study investigates the effects of BoNT/A on a microglial murine cell lineage (BV-2) in different inflammatory conditions. Cellular viability and proliferation were carried out with different concentrations of BoNT/A (ranging from 0.3125 to 20 U/mL) for 24 h. Cells were primed with carrageenan (300 μg/mL) or Lipopolysaccharides (LPS) (20 ng/mL). The gene expression of IL-1β, IL-6, IL-18, TNF-α, Ikkβ, p65, Iba1 were quantified using PCR-RT. The supernatant was used to determine IL-1β, IL-6, and TNF-α levels. For all data, the significance level was set at 5%. Overall, data analysis revealed that BoNT/A 1.25 U/mL exhibited the greatest effect cell viability and proliferation. In addition, genes associated with inflammatory response in both stimuli (carrageenan and LPS) were downregulated in the presence of BoNT/A. Lastly, BoNT/A mitigates the protein levels of IL-1β and TNF-α in a time and dose-dependent manner. In conclusion, our results revealed that BoNT/A directly modulates the microglial cells' activities in an inflammatory context, opening new perspectives for using BoNT/A, considering its potential immunomodulatory effect.

Botulinum Toxin Treatment of Psoriasis-A Comprehensive Review

A literature search on the subject of botulinum toxin treatment in psoriasis found 15 relevant articles, 11 on human subjects and 4 on animal studies. Of the human data, eight were clinical trials and three were single case reports. Seven out of eight clinical trials, all open-label, reported improvement in psoriasis following intradermal or subcutaneous botulinum toxin injections. One double-blind, placebo-controlled study, which used a smaller dose than the open-label studies, did not note a healing effect. Animal studies have shown that injection of botulinum toxins in the skin heals psoriatic skin lesions and can reduce the level of interleukins (ILs) and cytokines as well as inflammatory cells in psoriatic plaques. There is a need for controlled, blinded studies conducted in larger numbers of patients with doses that have shown promise in open-label studies.

Botulinum toxin type A is a potential therapeutic drug for chronic orofacial pain

BACKGROUND

Botulinum toxin type A (BTX-A), produced by the gram-positive anaerobic bacterium Clostridium botulinum, acts by cleaving synaptosome-associated protein-25 (SNAP-25), an essential component of the presynaptic neuronal membrane that is necessary for fusion with the membrane proteins of neurotransmitter-containing vesicles. Recent studies have highlighted the efficacy of BTX-A in treating chronic pain conditions, including lower back pain, chronic neck pain, neuropathic pain, and trigeminal neuralgia, particularly when patients are unresponsive to traditional painkillers. This review focuses on the analgesic effects of BTX-A in various chronic pain conditions, with a particular emphasis on the orofacial region.

HIGHLIGHT

This review focuses on the mechanisms by which BTX-A induces analgesia in patients with inflammatory and temporomandibular joint pain. This review also highlights the fact that BTX-A can effectively manage neuropathic pain and trigeminal neuralgia, which are difficult-to-treat chronic pain conditions. Herein, we present a comprehensive assessment of the central analgesic effects of BTX-A and a discussion of its various applications in clinical dental practice.

CONCLUSION

BTX-A is an approved treatment option for various chronic pain conditions. Although there is evidence of axonal transport of BTX-A from peripheral to central endings in motor neurons, the precise mechanism underlying its pain-modulating effects remains unclear. This review discusses the evidence supporting the effectiveness of BTX-A in controlling chronic pain conditions in the orofacial region. BTX-A is a promising therapeutic agent for treating pain conditions that do not respond to conventional analgesics.

Platelet-rich plasma alleviates neuropathic pain in osteoarthritis by downregulating microglial activation

BACKGROUND

The development of neuropathic pain (NP) is one of the reasons why the pain is difficult to treat, and microglial activation plays an important role in NP. Recently, platelet-rich plasma (PRP) has emerged as a novel therapeutic method for knee osteoarthritis (KOA). However, it's unclarified whether PRP has analgesic effects on NP induced by KOA and the underlying mechanisms unknown.

PURPOSE

To observe the analgesic effects of PRP on NP induced by KOA and explore the potential mechanisms of PRP in alleviating NP.

METHODS

KOA was induced in male rats with intra-articular injections of monosodium iodoacetate (MIA) on day 0. The rats received PRP or NS (normal saline) treatment at days 15, 17, and 19 after modeling. The Von Frey and Hargreaves tests were applied to assess the pain-related behaviors at different time points. After euthanizing the rats with deep anesthesia at days 28 and 42, the corresponding tissues were taken for subsequent experiments. The expression of activating transcription factor 3 (ATF3) in dorsal root ganglia (DRG) and ionized-calcium-binding adapter molecule-1(Iba-1) in the spinal dorsal horn (SDH) was detected by immunohistochemical staining. In addition, the knee histological assessment was performed by hematoxylin-eosin (HE) staining.

RESULTS

The results indicated that injection of MIA induced mechanical allodynia and thermal hyperalgesia, which could be reversed by PRP treatment. PRP downregulated the expression of ATF3 within the DRG and Iba-1 within the SDH. Furthermore, an inhibitory effect on cartilage degeneration was observed in the MIA + PRP group only on day 28.

CONCLUSION

These results indicate that PRP intra-articular injection therapy may be a potential therapeutic agent for relieving NP induced by KOA. This effect could be attributed to downregulation of microglial activation and reduction in nerve injury.

Cellular and molecular mechanisms involved in the analgesic effects of botulinum neurotoxin: A literature review

Botulinum neurotoxins (BoNTs), derived from Clostridium botulinum, have been employed to treat a range of central and peripheral neurological disease. Some studies indicate that BoNT may be beneficial for pain conditions as well. It has been hypothesized that BoNTs may exert their analgesic effects by preventing the release of pain-related neurotransmitters and neuroinflammatory agents from sensory nerve endings, suppressing glial activation, and inhibiting the transmission of pain-related receptors to the neuronal cell membrane. In addition, there is evidence to suggest that the central analgesic effects of BoNTs are mediated through their retrograde axonal transport. The purpose of this review is to summarize the experimental evidence of the analgesic functions of BoNTs and discuss the cellular and molecular mechanisms by which they can act on pain conditions. Most of the studies reviewed in this article were conducted using BoNT/A. The PubMed database was searched from 1995 to December 2022 to identify relevant literature.

Botox for the prevention of radiation-induced Sialadenitis and xerostomia in head and neck cancer patients: A pilot study

BACKGROUND

To determine the safety of Botox and its potential effect on alleviating radiation therapy (RT)-induced sialadenitis in head and neck cancer patients.

METHODS

Twenty patients with stage III/IV head and neck cancer were randomized to receive Botox or saline injections into both submandibular glands (SMG). There were three visits: one before RT (V1); 1 week after RT (V2); and 6 weeks after RT (V3), each of which included saliva collection, a 24-h dietary recall, and a quality-of-life survey.

RESULTS

No adverse events were observed. While the control group was much older, the Botox group more commonly underwent induction chemotherapy compared with controls. From V1 to V2, salivary flow decreased in both groups, but only in the control group from V1 to V3. CXCL-1 (GRO), a neutrophil chemoattractant, was lower in the Botox group compared with the control group at V3.

CONCLUSION

Botox can be safely administered to the salivary glands prior to external beam radiation without observed complications or side-effects. After an initial reduction in salivary flow following RT, the Botox group showed lack of further flow reduction compared with controls. The inflammatory marker CXCL 1, which was reduced in the in Botox group at V3, may be a candidate for further studies of radiation-induced sialadenitis.

Efficacy of Intra-Articular Injection of Botulinum Toxin Type A (IncobotulinumtoxinA) in Temporomandibular Joint Osteoarthritis: A Three-Arm Controlled Trial in Rats

Temporomandibular disorders (TMD) are complex pathologies responsible for chronic orofacial pain. Intramuscular injection of botulinum toxin A (BoNT/A) has shown effectiveness in knee and shoulder osteoarthritis, as well as in some TMDs such as masticatory myofascial pain, but its use remains controversial. This study aimed to evaluate the effect of intra-articular BoNT/A injection in an animal model of temporomandibular joint osteoarthritis. A rat model of temporomandibular osteoarthritis was used to compare the effects of intra-articular injection of BoNT/A, placebo (saline), and hyaluronic acid (HA). Efficacy was compared by pain assessment (head withdrawal test), histological analysis, and imaging performed in each group at different time points until day 30. Compared with the rats receiving placebo, those receiving intra-articular BoNT/A and HA had a significant decrease in pain at day 14. The analgesic effect of BoNT/A was evident as early as day 7, and lasted until day 21. Histological and radiographic analyses showed decrease in joint inflammation in the BoNT/A and HA groups. The osteoarthritis histological score at day 30 was significantly lower in the BoNT/A group than in the other two groups (p = 0.016). Intra-articular injection of BoNT/A appeared to reduce pain and inflammation in experimentally induced temporomandibular osteoarthritis in rats.

Evaluation of Recombinant Botulinum Neurotoxin Type A1 Efficacy in Peripheral Inflammatory Pain in Mice

Well-established efficacy of botulinum neurotoxin type A (BoNT/A) in aesthetic dermatology and neuromuscular hyperactivity disorders relies on canonical interruption of acetylcholine neurotransmission at the neuromuscular junction at the site of the injection. The mechanisms and the site of activity of BoNT/A in pain, on the other hand, remain elusive. Here, we explored analgesic activity of recombinant BoNT/A1 (rBoNT/A1; IPN10260) in a mouse model of inflammatory pain to investigate the potential role of peripheral sensory afferents in this activity. After confirming analgesic efficacy of rBoNT/A1 on CFA-induced mechanical hypersensitivity in C57Bl6J mice, we used GCaMP6s to perform in vivo calcium imaging in the ipsilateral dorsal root ganglion (DRG) neurons in rBoNT/A1 vs. vehicle-treated mice at baseline and following administration of a range of mechanical and thermal stimuli. Additionally, immunohisochemical studies were performed to detect cleaved SNAP25 in the skin, DRGs and the spinal cord. Injection of CFA resulted in reduced mechanical sensitivity threshold and increased calcium fluctuations in the DRG neurons. While rBoNT/A1 reduced mechanical hypersensitivity, calcium fluctuations in the DRG of rBoNT/A1- and vehicle-treated animals were similar. Cleaved SNAP25 was largely absent in the skin and the DRG but present in the lumbar spinal cord of rBoNT/A1-treated animals. Taken together, rBoNT/A1 ameliorates mechanical hypersensitivity related to inflammation, while the signal transmission from the peripheral sensory afferents to the DRG remained unchanged. This strengthens the possibility that spinal, rather than peripheral, mechanisms play a role in the mediation of analgesic efficacy of BoNT/A in inflammatory pain.

A Novel Progress: Glial Cells and Inflammatory Pain

Inflammatory pain is the perception of noxious stimuli that occurs during inflammation or an immune response. Glial cells are widespread in the central and peripheral nervous systems, supporting and guiding the migration of neurons, participating in the immune response, forming the myelin sheath and blood-brain barrier, and maintaining the concentration of potassium ions outside nerve cells. Recent studies have shown that glial cells have a significant connection with the production and development of inflammatory pain. This article reviews the relationship, mechanisms, therapeutic targets between five types of glial cells and inflammatory pain, and the medicine composition that can effectively inhibit inflammatory pain. It expands the study on the mechanism of glial cells regulating pain and provides new ideas for the therapy of inflammatory pain.

BoNT/A alleviates neuropathic pain in osteoarthritis by down-regulating the expression of P2X4R in spinal microglia

Neuropathic pain in osteoarthritis is one of the reasons why the pain is difficult to treat, and P2X4R plays an important role in neuropathic pain. In addition, BoNT/A has been proven to have analgesic effects on both neuropathic pain and osteoarthritis, but its exact mechanism is still unknown. This study aims to investigate the relationship between the analgesic effect of BoNT/A on osteoarthritis and the expression of P2X4R in spinal cord microglia. The analgesic effect was compared between BoNT/A and compound betamethasone. Western blot analysis was used to examine the expression of P2X4R and BDNF proteins in the spinal cord. Immunohistochemistry was used to determine the cellular location of P2X4R. Mechanical allodynia and weight asymmetry were identified using the hind paw withdrawal threshold and weight bearing test. The results showed that intra-articular injection of MIA induced persistent mechanical allodynia and weight asymmetry in rats. Both BoNT/A and betamethasone could relieve pain behavior in rats, but BoNT/A had a more obvious effect and lasted longer. Furthermore, BoNT/A could reverse the MIA-induced overexpression of BDNF and P2X4R in the spinal dorsal horn. To sum up, BoNT/A is more effective than betamethasone in relieving MIA-induced osteoarthritis pain in rats, and its analgesic effect may be related to the regulation of P2X4R-mediated BDNF release in spinal microglia and the relief of neuropathic pain in osteoarthritis.