Alteration of tight junctions during botulinum toxin type A-inhibited salivary secretion

Cellular Senescence Contributes to the Dysfunction of Tight Junctions in Submandibular Glands of Aging Mice

The current mechanism by which aging reduces salivary secretion is unknown. This study investigates the mechanism of aging-related submandibular (SMG) dysfunction and evaluates the therapeutic potential of dental pulp stem cell-derived exosomes (DPSC-exos). We found that the stimulated salivary flow rate was significantly reduced in naturally aging and D-galactose-induced aging mice (D-gal mice) compared to control mice. Acinar atrophy and periductal fibrosis in SMGs and parotid glands (PGs) were observed in naturally aging and D-gal mice, whereas sublingual glands (SLGs) had no notable alterations. We observed the accumulation of senescent cells in the SMGs, along with a decrease in claudin-3 (Cldn-3) expression and alterations in the distribution of Cldn1 and Cldn3. Additionally, after D-gal-induced senescence of SMG-C6 cells, there was a decrease in paracellular pathway permeability, reduced expression of Cldn3 and occludin, and changes in the distribution of Cldn1, 3, 4, and 7. Furthermore, injecting DPSC-exos into the SMGs of D-gal mice improved stimulated salivary flow rate, reduced acinar atrophy, and decreased SA-β-gal activity. Our study identified that increased senescence of SMGs in aging mice can cause a decrease in salivary secretion by disrupting the expression and distribution of tight junction molecules, and injection of DPSC-exos ameliorates SMG secretory dysfunction. These findings may provide new clues to novel therapeutic targets for aging-related dysfunction of SMGs.

Staggered botulinum toxin-a injections into parotid and submandibular glands prior to four-duct ligation for pediatric sialorrhea

OBJECTIVES

This study aimed to assess the effectiveness of four-duct ligation following Botulinum toxin-A injections into the parotid and submandibular glands in pediatric patients with sialorrhea resistant to nonsurgical treatments. Prior research has individually explored either surgical or Botulinum toxin interventions; however, the safety and efficacy of the combined approach to these treatments have yet to be documented.

METHODS

Patients were assessed before surgery and 6, 12, and 24 months post-operatively. Evaluations involved interviews with parents and caregivers, conducted face-to-face or by telephone, using the Drooling Severity and Frequency Scales. Additionally, metrics such as the daily count of bib changes and the hourly frequency of saliva wiping were recorded. Quality-of-life assessments were performed before and after the surgical procedures. All complications associated with the interventions were carefully recorded.

RESULTS

The study group consisted of 25 participants, with a median age of 6 years (range 2-17 years). Each participant was diagnosed with a neurological, metabolic, or genetic disorder. Evaluations were conducted periodically, culminating in a final follow-up at 24 months. The treatment demonstrated a 100% success rate at six months post-operation (25/25 patients), which slightly decreased to 96% at the 12-month mark (24/25 patients) and further to 84% by the 24-month follow-up (21/25 patients). Major complications were not observed. However, minor complications were reported in six patients (24%): three exhibited temporary facial swelling (12%), two encountered minor bleeding (8%), and one experienced excessive dryness (4%).

CONCLUSIONS

The combination of Botulinum toxin-A injection 3 weeks prior to the four-duct ligation procedure demonstrated high success rates and substantially reduced the incidence of infectious and cosmetic complications. Consequently, this staggered approach to combination treatment is recommended for managing pediatric sialorrhea cases that are resistant to non-surgical interventions.

Botulinum toxin type A inhibits M1 macrophage polarization by deactivation of JAK2/STAT1 and IκB/NFκB pathway and contributes to scar alleviation in aseptic skin wound healing

The non-neuronal and non-muscular effects of botulinum toxin type A (BTXA) on scar reduction has been discovered. This study was designed to investigate the effects of BTXA on macrophages polarization during the early stage of skin repair. A skin defect model was established on the dorsal skin of SD rats. BTXA was intracutaneous injected into the edge of wound immediately as the model was established. Histological examinations were performed on scar samples. Raw 264.7 was selected as the cell model of recruited circulating macrophages, and was induced for M1 polarization by LPS. Identify the signaling pathways that primarily regulated M1 polarization and respond to BTXA treatment. Application of BTXA at early stage of injury significantly reduced the scar diameter without delaying wound closure. BTXA treatment improved fiber proliferation and arrangement, and inhibited angiogenesis in scar granular tissue. The number of M1 macrophages and the levels of pro-inflammation were decreased after treated with BTXA in scar tissues. LPS activated JAK2/STAT1 and IκB/NFκB pathways were downregulated by BTXA, as well as LPS induced M1 polarization. At early stage of skin wound healing, injection of BTXA effectively reduced the number of M1 macrophages and the levels of pro-inflammatory mediators which contributes to scar alleviation. BTXA resisted the M1 polarization of macrophages induced by LPS via deactivating the JAK2/STAT1 and IκB/NFκB pathways.

The role and mechanism of tight junctions in the regulation of salivary gland secretion

Tight junctions (TJs) are cell-cell interactions that localize at the most apical portion of epithelial/endothelial cells. One of the predominant functions of TJs is to regulate material transport through paracellular pathway, which serves as a selective barrier. In recent years, the expression and function of TJs in salivary glands has attracted great interest. The characteristics of multiple salivary gland TJ proteins have been identified. During salivation, the activation of muscarinic acetylcholine receptor and transient receptor potential vanilloid subtype 1, as well as other stimuli, promote the opening of acinar TJs by inducing internalization of TJs, thereby contributing to increased paracellular permeability. Besides, endothelial TJs are also redistributed with leakage of blood vessels in cholinergic-stimulated submandibular glands. Furthermore, under pathological conditions, such as Sjögren's syndrome, diabetes mellitus, immunoglobulin G4-related sialadenitis, and autotransplantation, the integrity and barrier function of TJ complex are impaired and may contribute to hyposalivation. Moreover, in submandibular glands of Sjögren's syndrome mouse model and patients, the endothelial barrier is disrupted and involved in hyposecretion and lymphocytic infiltration. These findings enrich our understanding of the secretory mechanisms that link the importance of epithelial and endothelial TJ functions to salivation under both physiological and pathophysiological conditions.

The effectiveness of ultrasound-guided injection of BTX-A in the management of sialorrhea in neurogenic dysphagia patients

Objective

To evaluate the effectiveness of ultrasound-guided injection of botulinum toxin type A (BTX-A) in treating sialorrhea.

Methods

We recruited 32 sialorrhea subjects and they received an ultrasound-guided injection of BTX-A. The extent of salivation was evaluated according to the Visual Analog Scale (VAS), Drooling Severity and Frequency Scale (DSFS), and Saliva Flow Rate (SFR). Laryngeal secretions were evaluated based on Fiberoptic Endoscopic Evaluation of Swallowing (FEES) rated according to the Murray Secretion Scale (MSS). We assessed the extent of salivation and laryngeal secretions before injection and at 1, 2, and 4 weeks after injection.

Results

The scores for the VAS, DSFS-S, DSFS-F, and DSFS-T decreased significantly at 1, 2, and 4 weeks after injection compared with before injection (p < .05). Based on VAS, the efficacy was substantially higher at 2 and 4 weeks after injection than at 1 week after injection (p < .05). According to DSFS-S and DSFS-T, the efficacy was significantly higher at 4 weeks than at 1 week after injection (p < .05). The SFR and MSS scores at 1 and 2 weeks after injection were superior to those before injection (p < .05). Meanwhile, the SFR score 2 weeks after injection was superior to that 1 week after injection (p < .05).

Conclusion

The ultrasound-guided injection of BTX-A can effectively reduce saliva secretion in patients with neurogenic dysphagia. Furthermore, it has the advantages of early onset time and lasting curative effects, which indicates that clinical promotion and application of this technique are justified.

Level of Evidence

Level 3.