The effect of intradermal botulinum toxin type A injection on healing of porcine full-thickness wounds.

Although botulinum toxin type A (BT-A) is approved for chronic migraine treatment, its site and mechanism of action are still elusive. Recently our group discovered that suppression of CGRP release from dural nerve endings might account for antimigraine action of pericranially injected BT-A. We demonstrated that central antinociceptive effect of BT-A in sciatic region involves endogenous opioid system as well. Here we investigated possible interaction of BT-A with endogenous opioid system within the trigeminal region. In orofacial formalin test we investigated the influence of centrally acting opioid antagonist naltrexone (2mg/kg, s.c.) versus peripherally acting methylnaltrexone (2mg/kg, s.c.) on BT-A's (5 U/kg, s.c. into whisker pad) or morphine's (6mg/kg, s.c.) antinociceptive effect and the effect on dural neurogenic inflammation (DNI). DNI was assessed by Evans blue-plasma protein extravasation. Naltrexone abolished the effect of BT-A on pain and dural plasma protein extravasation, whereas peripherally acting methylnaltrexone did not change either BT-A's effect on pain or its effect on dural extravasation. Naltrexone abolished the antinociceptive and anti-inflammatory effects of morphine, as well. However, methylnaltrexone decreased the antinociceptive effect of morphine only partially in the second phase of the test and had no significant effect on morphine-mediated reduction in DNI. Morphine acts on pain in trigeminal region both peripherally and centrally, whereas the effect on dural plasma protein extravasation seems to be only centrally mediated. However, the interaction of BT-A with endogenous opioid system, with consequent inhibition of nociceptive transmission as well as the DNI, occurs primarily centrally. Botulinum toxin type A (BT-A)'s axonal transport and potential transcytosis suggest that its antinociceptive effect might involve diverse neurotransmitters at different sites of trigeminal system. Here we discovered that the reduction in pain and accompanying DNI involves the interaction of BT-A with central endogenous opioid system (probably at the level of trigeminal nucleus caudalis).

Botulinum toxin type A (BTXA) can inhibit the growth of hypertrophic scars, but the molecular mechanism for this action is unknown. In addition to reducing the tension around the wound by stimulating temporary denervation, a growing body of evidence suggests that BTXA is involved in regulating the cell cycle and decreasing transforming growth factor-β1 (TGF-β1) expression in the fibroblasts of hypertrophic scars. Connective tissue growth factor (CTGF) is a downstream regulator of TGF-β1 function and an independent mediator of scarring and fibrosis. The effects of BTXA on CTGF in hypertrophic scar still are unknown. This study aimed to explore the effect of BTXA on CTGF in fibroblasts derived from hypertrophic scar and to elucidate its actual mechanism further. Fibroblasts isolated from tissue specimens of hypertrophic scar were treated with BTXA. The difference in proliferation between treated and nontreated fibroblasts was analyzed by flow cytometry. Proteins of CTGF were checked using Western blot in fibroblasts with and without BTXA. The proliferation of the fibroblasts treated with BTXA was slower than that of the fibroblasts that had no BTXA treatment (p<0.01), which showed that BTXA effectively inhibited the growth of fibroblasts. Compared with fibroblasts that received no BTXA treatment, BTXA at 1U/10(6) cells decreased the expression of CTGF by 49.2%±12.5% (p<0.01), and BTXA at 2.5U/10(6) cells decreased the expression of CTGF by 56.9% (p<0.01). These results suggest that BTXA effectively inhibited the growth of fibroblasts derived from hypertrophic scar and in turn caused a decrease in CTGF protein, providing theoretical support for the application of BTXA to control hypertrophic scarring.

Botulinum toxin type A (BoNT-A) therapy has gained wide acceptance in the management of spasticity in cerebral palsy (CP). Clinical experience from numerous case reports and series, retrospective and prospective open label cohort studies, and randomized controlled trials (RCT) has grown over the past 10 years. Several independent systematic reviews on the role of BoNT-A for upper and lower limb spasticity have been written by various authors. The objective of this paper is to summarize past systematic reviews and recent RCT not yet included in the systematic reviews that assess the effectiveness of BoNT-A in upper and lower limb spasticity in children with CP. We reviewed four Class II RCT discussed in five independent systematic reviews and two new Class II trials on the use of BoNT-A alone or with occupational therapy compared to placebo or occupational therapy alone in children with upper limb spasticity. There were 229 children recruited in these six trials and of those, 115 children received BoNT-A in the upper limbs. Five of six RCT showed a time limited decrease in muscle tone most especially at the wrist. Four of six trials showed improvement of hand function on a few specific functional tests. Four systematic reviews concluded that there is insufficient and inconsistent evidence to support or refute the effectiveness of BoNT-A in upper limb spasticity but one recent review recommended that BoNT-A should be considered as a treatment option in upper limb spasticity. For lower limb spasticity, we reviewed 13 RCT discussed in six systematic reviews and two new trials comparing BoNT-A with placebo or other rehabilitation modalities such as physiotherapy, occupational therapy, casting or electrical stimulation. In these studies, 617 children were recruited and of those, 360 children received BoNT-A in the lower limbs. There were six Class I and nine Class II trials. Three Class I trials documented significant improvement in gait pattern in children with gastrocnemius spasticity and one Class I study showed significant reduction in tone in the hip adductors. The most recent review establishes BoNT-A as an effective treatment for equinovarus deformity. Adverse events in these trials were mild and self-limited. The most common complaints were pain in the injection sites and transient weakness. BoNT-A is considered safe for use in children. In conclusion, there is now growing convincing evidence for the time limited beneficial effect of BoNT-A in decreasing muscle tone in children with upper and lower limbs spasticity associated with CP. Decrease muscle tone in the lower limbs translates to improved gait in CP children with spastic equinovarus however more systematic studies are necessary to show sufficient evidence for improved hand function from BoNT-A injection in the upper limbs.

Scar contracture (SC) is one of the most common complications resulting from major burn injuries. Numerous treatments are currently available but they do not always yield excellent therapeutic results. Recent reports suggest that botulinum toxin type A (BTXA) is effective at reducing SC clinically, but the molecular mechanism for this action is unknown. α-Smooth muscle actin (α-SMA) and myosin II are the main components of stress fibers, which are the contractile structures of fibroblasts. The effects of BTXA on α-SMA and myosin II in SC are still unknown. This study aimed to explore the effect of BTXA on α-SMA and myosin II expression in fibroblasts derived from SC and to elucidate its actual mechanism further. Fibroblasts were isolated from tissue specimens of SC. Fibroblasts were cultured in Dulbecco modified Eagle medium with different concentrations of BTXA and their proliferation was analyzed through the tetrazolium-based colorimetric method at 1, 4, and 7 days. Proteins of α-SMA and myosin II were checked using Western blot in fibroblasts treated with different concentrations of BTXA at 1, 4, and 7 days. Fibroblasts without BTXA treatment had a higher proliferation than that in other groups, which indicated that the proliferation of fibroblasts was significantly inhibited by BTXA (P < 0.05). Proteins of α-SMA and myosin II between fibroblasts with BTXA and fibroblasts without BTXA are statistically significant (P < 0.05). These results suggest that BTXA effectively inhibited the growth of fibroblasts derived from SC and reduced the expression of α-SMA and myosin II, which provided theoretical support for the application of BTXA to control SC.

Botulinum toxin type A (BTXA) is a neurotoxic protein produced by Clostridium botulinum. Our previous studies demonstrated that BTXA inhibits the secretory function of submandibular gland (SMG) and changes its structure. Several studies reported that SMG damage and repair often occur with autophagy in the rat. However, no studies reported whether secretory inhibition and structural changes of SMG after BTXA injection is related with autophagy. The present study was carried out to explore the association between BTXA injection and autophagy in rat SMG. Western blotting and immunofluorescence were used to detect the expression and distribution of light chain 3 (LC3) in rat SMG. MTS was used to detect the toxicity of BTXA on rat SMG-C6 cell line. GFP-LC3 and Lyso-Tracker Red fluorescence probe were used to assess the levels of autophagosomes and lysosome fusion and the effect of BTXA on autophagic flux in SMG-C6. Western blotting and immunofluorescence results showed that BTXA temporarily increased autophagosomes in rat SMG. MTS results showed that BTXA exerted its toxicity on SMG-C6 in a dose-dependent manner. BTXA increased the number of autophagosomes in SMG-C6; however, most autophagosomes did not colocalize with lysosome. Therefore, we presume that BTXA can change autophagic flux of SMG cells, the mechanism of which might relate with BTXA’s disturbing autophagosome-lysosome fusion.

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

Pes cavus in Charcot-Marie-Tooth disease type 1A (CMT1A) is thought to be due to muscle imbalance of the lower leg. Botulinum toxin type A (BoNT-A) can modify foot deformity in other conditions of muscle imbalance. We tested the safety and effectiveness of BoNT-A on pes cavus progression in pediatric CMT1A. A 24-month, randomized, single-blind trial of BoNT-A was undertaken in 10 affected children (20 legs), aged 3-14 years. The treated leg received intramuscular BoNT-A injections at 6-month intervals in the tibialis posterior and peroneus longus. The control leg received no injections. Primary outcome was radiographic alignment at 24 months. Secondary outcomes were foot posture, ankle flexibility, and strength, assessed every 6 months. Radiographically, BoNT-A produced a small non-significant reduction in cavus progression. There was no effect of BoNT-A on secondary outcomes. There were no serious adverse events. At 24 months, the intramuscular BoNT-A injections proved safe and well-tolerated but did not affect the progression of pes cavus in CMT1A.

Botulinum toxin type A (BoNT-A) is an established preventive therapy for chronic migraines; however, uncertainty remains regarding its comparative efficacy and safety. Thus, we aimed to summarize current evidence from high-quality systematic reviews of the therapeutic effects of BoNT-A in migraine management. An umbrella review was conducted following PRISMA guidelines and registered in PROSPERO. High-quality systematic reviews with meta-analysis evaluating BoNT-A efficacy were identified through five databases up to August 2024. Primary outcomes included monthly headache frequency and severity. Methodological quality and risk of bias were assessed using the umbrella review checklist. Fourteen articles were included. Overall, quantitative evidence indicated favorable effects of BoNT-A compared with placebo for chronic migraines, across headache frequency, headache severity, and acute medication use, but less efficacy than topiramate and the CGRP monoclonal antibodies (CGRPmAbs) galcanezumab and fremanezumab. Though the adverse events were frequent, BoNT-A was generally well-tolerated. Comparative data suggested superior tolerability versus topiramate and a safety profile like CGRPmAbs. Although botulinum toxin type A is widely used as a preventive treatment for chronic migraines, the available evidence supports its efficacy at a moderate level. Further head-to-head and long-term analyses are needed to clarify its comparative role alongside newer biologic treatments.

Botulinum toxin type A (BTX-A) is a potent neurotoxin that causes relaxation of striated muscle by inhibiting the release of acetylcholine at the neuromuscular junction. Some studies have suggested that BTX-A treatment for Raynaud syndrome is safe and effective with few adverse reactions. However, the underlying mechanism remains unclear. In the present study, we used both arterial rings isolated from rabbits and human microvascular endothelial cells (HMEC-1) to evaluate the mechanism underlying the effects of BTX-A on arterial vasoconstriction induced by 5-hydroxytryptamine. The roles of calcium sensitization and the endothelial nitric oxide synthase (eNOS)/soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway were investigated. BTX-A caused a concentration-dependent decrease in the contraction of endothelium-intact arteries and significantly reduced calcium sensitization in the arteries. Inhibitors of eNOS (L-NAME) and sGC (methylene blue) both significantly abolished the vasodilatory action of BTX-A. Furthermore, BTX-A increased eNOS activity and the cGMP level in dose- and time-dependent manners and increased eNOS and sGC protein levels in a time-dependent manner in HMEC-1. Taken together, these findings indicate that BTX-A suppresses arterial vasoconstriction by regulating smooth muscle calcium sensitization and the eNOS/sGC/cGMP pathway. Impact statement Raynaud syndrome (RS), usually caused by cold or mental stress, may lead to cyanosis and reactive hyperemia accompanied by pain or paresthesia. Although a variety of drugs have been used to alleviate the symptoms, the effects have not been satisfactory, so there is an urgent need to explore new alternative treatments. The present study investigated the mechanism underlying the effects of botulinum toxin type A (BTX-A) on arterial vasoconstriction, which may provide new approaches for RS. We found that BTX-A suppresses arterial vasoconstriction by regulating smooth muscle calcium sensitization and the endothelial nitric oxide synthase (eNOS)/soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway. These findings clarify the underlying mechanism of the effects of BTX-A on arterial vasoconstriction and provide new theoretical support for the use of BTX-A on RS. It may also help us to develop new medicines which regulate calcium sensitization and the eNOS/sGC/cGMP pathway against RS.

Background A suitable pharmacological substitute for the well-established surgical delay technique for random skin flaps to increase viability has been elusive. Objective To evaluate the effects of nitroglycerin and botulinum toxin type A on random flap survival in a rat model. Methods The present controlled experimental study was performed in the four groups of rats. One week after intervention in each group, the flap was raised and kept in situ, and flap necrosis was evaluated through follow-up. Group 1 received intradermal botulinum toxin type A (BTX-A) and topical nitroglycerin 2%; group 2 received BTX-A and topical Vaseline (Unilever, USA); group 3 received topical nitroglycerin and intradermal normal saline; and group 4 received topical Vaseline and intradermal normal saline. Results BTX-A reduced the area of necrosis compared with control (24% versus 56% respectively; P&lt;0.001). Nitroglycerin application was associated with a trend toward improved flap viability (42% versus 56%; P=0.059). The combination of topical nitroglycerin and BTX-A, compared with Vaseline and BTX-A, was associated with decreased flap necrosis (16.1% versus 24%, respectively), although it was not statistically significant (P=0.45). Conclusions BTX-A was effective in reducing distal flap necrosis. The effect of BTX-A was significantly more pronounced than nitroglycerin ointment.

A suitable pharmacological substitute for the well-established surgical delay technique for random skin flaps to increase viability has been elusive. To evaluate the effects of nitroglycerin and botulinum toxin type A on random flap survival in a rat model. The present controlled experimental study was performed in the four groups of rats. One week after intervention in each group, the flap was raised and kept in situ, and flap necrosis was evaluated through follow-up. Group 1 received intradermal botulinum toxin type A (BTX-A) and topical nitroglycerin 2%; group 2 received BTX-A and topical Vaseline (Unilever, USA); group 3 received topical nitroglycerin and intradermal normal saline; and group 4 received topical Vaseline and intradermal normal saline. BTX-A reduced the area of necrosis compared with control (24% versus 56% respectively; P<0.001). Nitroglycerin application was associated with a trend toward improved flap viability (42% versus 56%; P=0.059). The combination of topical nitroglycerin and BTX-A, compared with Vaseline and BTX-A, was associated with decreased flap necrosis (16.1% versus 24%, respectively), although it was not statistically significant (P=0.45). BTX-A was effective in reducing distal flap necrosis. The effect of BTX-A was significantly more pronounced than nitroglycerin ointment.

BackgroundHypertrophic scar formation may be related to cutaneous neurogenic inflammation (CNI) through the substance P-neurokinin 1 receptor (SP-NK1R) signaling pathway. As a widely used drug in aesthetic clinical work, botulinum toxin type A (BTX-A) has a therapeutic effect on scars, but the actual mechanism remains unclear. This study aimed to clarify the potential mechanism by which BTX-A inhibits CNI in hypertrophic scars both in vitro and in vivo.MethodsTissue samples were obtained from surgical excisions. Immunohistological analysis was used to locate SP in human hypertrophic scars and normal skin. RT-PCR and western blot analysis were used to evaluate the expression of collagens after SP/BTX-A treatment. A rabbit ear scar model was used to explore the in vivo effect of BTX-A on scar treatment.ResultsSP and NK-1R were overexpressed in hypertrophic scars compared to normal skin tissues. Collagen secretion of hypertrophic scar-derived fibroblasts increased with increasing doses of SP. However, BTX-A may downregulate collagen expression through SP-NK1R pathway with or without the presence of SP inducing agent capsaicin. Meanwhile, SP inhibited the expression of NK-1R, and this inhibition was blocked by pretreatment with BTX-A. In vivo, intralesional BTX-A injection can also reduce the volume of scars and inhibit collagen secretion. Capsaicin may cause more severe scar manifestations, while the therapeutic effect of BTX-A remains.ConclusionOur research confirms that CNI stimulates fibroblasts during scar formation, while BTX-A can reduce collagen secretion by inhibiting the SP-NK1R signaling pathway, thus identifying a novel therapeutic target for this benign solid skin tumor.

Cleft lip repair (CLR) can be complicated by hypertrophic scar or keloid. Botulinum toxin type A (BTA) may improve postoperative scarring by reducing muscle tension and cytokine activity at the scar site. This systematic review analyzes the available evidence regarding the effect of BTA on scar quality after CLR. The search was conducted in 6 different databases in accordance with PRISMA guidelines (PubMed, Scielo, Embase, Scopus, Web of Science, and Cochrane) using "botulinum toxin" and "cleft lip" as keywords. Academic hospital. Exclusive to patients who underwent CLR and BTA injection. Mean visual analog scores (VAS), mean Vancouver scar scale (VSS), scar width, and BTA or CLR-related complications. Five studies for a total of 216 patients met inclusion criteria. Four studies reported on primary CLR during infancy while 1 study recruited older patients seeking revision. All patients had BTA (range: 1-2 units/kg) injected in the orbicularis oris muscle. One study documented BTA injections in additional perioral muscles. All 4 studies that measured scar width and had a saline control arm found a significant decrease in width with BTA injection. Improvement of VAS and VSS with BTA was reported in 3 of 5 studies and 2 of 5 studies, respectively. There were no reports of complications associated with BTA or CLR. The existing studies support the use of BTA injection to improve scar quality following CLR with low concern for complication. Further investigations with a greater number of patients are necessary.

Botulinum toxin type A (BoNT-A) is widely employed for cosmetic purposes and in the treatment of certain diseases such as strabismus, hemifacial spasm and focal dystonia among others. BoNT-A effect mainly acts at the muscular level by inhibiting the release of acetylcholine at presynaptic levels consequently blocking the action potential in the neuromuscular junction. Despite the great progress in approval and pharmaceutical usage, improvement in displacing BoNT-A to other pathologies has remained very limited. Patients under diagnosis of several types of cancer experience pain in a myriad of ways; it can be experienced as hyperalgesia or allodynia, and the severity of the pain depends, to some degree, on the place where the tumor is located. Pain relief in patients diagnosed with cancer is not always optimal, and as the disease progresses, transition to more aggressive drugs, like opioids is sometimes unavoidable. In recent years BoNT-A employment in cancer has been explored, as well as an antinociceptive drug; experiments in neuropathic, inflammatory and acute pain have been carried out in animal models and humans. Although its mechanism has not been fully known, evidence has shown that BoNT-A inhibits the secretion of pain mediators (substance P, Glutamate, and calcitonin gene related protein) from the nerve endings and dorsal root ganglion, impacting directly on the nociceptive transmission through the anterolateral and trigeminothalamic systems. The study aimed to collect available literature regarding molecular, physiological and neurobiological evidence of BoNT-A in cancer patients suffering from acute, neuropathic and inflammatory pain in order to identify possible mechanisms of action in which the BoNT-A could impact positively in pain treatment. BoNT-A could be an important neo-adjuvant and coadjuvant in the treatment of several types of cancer, to diminish pro-tumor activity and secondary pain.

To determine whether the use of topical anesthesia has an impact on botulinum toxin type A (BTX-A) efficacy. Forty patients (20 receiving BTX-A for facial cosmetic rhytid reduction and 20 for benign essential blepharospasm) were evaluated in a double-blind, randomized, triple-crossover study at 2.5- to 4.5-month intervals. The discomfort and efficacy of BTX-A injections after betacaine application to half the face (random assignment) were compared against the discomfort and efficacy of a placebo ointment on the other half of the face. This was followed by cryoanalgesia to the entire face. Patients ranged from 27 to 81 years of age (mean, 53 years), and 34 were female. Of the 120 total injection comparisons, a better BTX-A effect on one side of the face was reliably identified by 80% and 77% of blepharospasm and cosmetic patients, respectively, with the placebo-treated side providing better BTX-A effect approximately 90% of the time (p < 0.001). Patients reported a more painful side during injection in just 18 of the 120 trials, and only 1 of 40 patients believed the administration of analgesia was worth the trouble. Pretreatment with topical betacaine followed by skin cooling seems to have a deleterious impact on BTX-A effect without a significantly beneficial patient-perceived reduction in injection discomfort.