Role of β-adrenergic signaling in masseter muscle

Allopurinol attenuates development of Porphyromonas gingivalis LPS-induced cardiomyopathy in mice

Oxidative stress is involved in the progression of periodontitis, independently of confounding factors such as smoking, and numerous studies suggest that periodontitis is associated with increased risk of cardiovascular disease. In this study, therefore, we examined the effects of the xanthine oxidase inhibitor allopurinol on cardiac dysfunction in mice treated with Porphyromonas gingivalis lipopolysaccharide (PG-LPS) at a dose (0.8 mg/kg/day) equivalent to the circulating level in patients with periodontal disease. Mice were divided into four groups: 1) control, 2) PG-LPS, 3) allopurinol, and 4) PG-LPS +  allopurinol. After1 week, we evaluated cardiac function by echocardiography. The left ventricular ejection fraction was significantly decreased in PG-LPS-treated mice compared to the control (from 68 ±  1.3 to 60 ±  2.7%), while allopurinol ameliorated the dysfunction (67 ±  1.1%). The area of cardiac fibrosis was significantly increased (approximately 3.6-fold) and the number of apoptotic myocytes was significantly increased (approximately 7.7-fold) in the heart of the PG-LPS-treated group versus the control, and these changes were suppressed by allopurinol. The impairment of cardiac function in PG-LPS-treated mice was associated with increased production of reactive oxygen species by xanthine oxidase and NADPH oxidase 4, leading to calmodulin kinase II activation with increased ryanodine receptor 2 phosphorylation. These changes were also suppressed by allopurinol. Our results suggest that oxidative stress plays an important role in the PG-LPS-promoted development of cardiac diseases, and further indicate that allopurinol ameliorates Porphyromonas gingivalis LPS-induced cardiac dysfunction.

β2-adrenergic receptor activation decreases the mechanical sensitivity of rat masticatory muscle afferent fibres

BACKGROUND

Activation of β2 adrenergic receptors reduces cutaneous mechanical pain thresholds in rats. While β2 adrenergic receptor activation may contribute to mechanisms that underlie temporomandibular joint pain, its effect on masticatory muscle pain sensitivity is uncertain.

OBJECTIVES

The current study sought to determine the extent to which β adrenergic receptors are expressed by masticatory muscle afferent fibres, and to assess the effect of local activation of these receptors on the mechanical sensitivity of masticatory muscle afferent fibres in rats.

METHODS

Trigeminal ganglion neurons that innervate the rat (n = 12) masseter muscle and lower lip were identified by tissue injection of fluorescent dyes and were then stained with antibodies against β1 or β2 adrenergic receptors. Extracellular recordings from 60 trigeminal ganglion neurons that innervate the masticatory muscle were undertaken in a second group of anaesthetised rats of both sexes (n = 37) to assess afferent mechanical activation thresholds. Thresholds were assessed before and after injection of the β adrenergic receptor agonists into masticatory muscle.

RESULTS

β1 and β2 adrenergic receptor expression was greater in labial skin than in masticatory muscle ganglion neurons (p < .05, one-way ANOVA, Holm-Sidak test). There was a higher expression of β2 adrenergic receptors in masticatory muscle ganglion neurons in males than in females. The mixed β agonist isoproterenol increased afferent mechanical activation threshold in male but not female rats (p < .05, Mann-Whitney test). In male rats, salbutamol, a β2 selective agonist, also increased afferent mechanical activation threshold but hydralazine, a vasodilator, did not (p < .05, Mann-Whitney test).

CONCLUSION

Activation of β2 adrenergic receptors decreases the mechanical sensitivity of masticatory muscle afferent fibres in a sex-related manner.

Oral angiotensin-converting enzyme inhibitor captopril protects the heart from Porphyromonas gingivalis LPS-induced cardiac dysfunction in mice

Although angiotensin converting enzyme (ACE) inhibitors are considered useful for the treatment of human heart failure, some experimental failing-heart models have shown little beneficial effect of ACE inhibitors in animals with poor oral health, particularly periodontitis. In this study, we examined the effects of the ACE inhibitor captopril (Cap; 0.1 mg/mL in drinking water) on cardiac dysfunction in mice treated with Porphyromonas gingivalis lipopolysaccharide (PG-LPS) at a dose (0.8 mg/kg/day) equivalent to the circulating level in patients with periodontal disease. Mice were divided into four groups: 1) Control, 2) PG-LPS, 3) Cap, and 4) PG-LPS + Cap. After1 week, we evaluated cardiac function by echocardiography. The left ventricular ejection fraction was significantly decreased in PG-LPS-treated mice compared to the control (from 66 ± 1.8 to 59 ± 2.5%), while Cap ameliorated the dysfunction (63 ± 1.1%). The area of cardiac fibrosis was significantly increased (approximately 2.9-fold) and the number of apoptotic myocytes was significantly increased (approximately 5.6-fold) in the heart of PG-LPS-treated group versus the control, and these changes were suppressed by Cap. The impairment of cardiac function in PG-LPS-treated mice was associated with protein kinase C δ phosphorylation (Tyr-311), leading to upregulation of NADPH oxidase 4 and xanthine oxidase, and calmodulin kinase II phosphorylation (Thr-286) with increased phospholamban phosphorylation (Thr-17). These changes were also suppressed by Cap. Our results suggest that the renin-angiotensin system might play an important role in the development of cardiac diseases induced by PG-LPS.

Effects of the angiotensin-converting enzyme inhibitor captopril on occlusal-disharmony-induced cardiac dysfunction in mice

Occlusal disharmony is known to affect not only the oral cavity environment, but also the autonomic nervous system in the heart. Since the renin-angiotensin system (RAS) inhibitor captopril (Cap) is one of the first-line drugs for preventing cardiac remodeling in patients with heart failure, we hypothesized that Cap might prevent cardiac dysfunction induced by occlusal disharmony. Here, to test this idea, we used our bite-opening (BO) mouse model, which was developed by cementing a suitable appliance onto the mandibular incisor. Mice were divided into four groups: (1) Control, (2) BO, (3) Cap, and (4) BO + Cap. After 2 weeks, we evaluated cardiac function by echocardiography and confirmed that cardiac function was significantly decreased in the BO group compared to the control, while Cap ameliorated the dysfunction. Cardiac fibrosis, myocyte apoptosis and oxidative stress-induced myocardial damage in the BO group were significantly increased versus the control, and these increases were suppressed by Cap. Cardiac dysfunction induced by BO was associated with dual phosphorylation on PKCδ (Tyr-311/Thr-505), leading to activation of CaMKII with increased phosphorylation of RyR2 and phospholamban. Our results suggest that the RAS might play an important role in the development of cardiac diseases induced by occlusal anomalies.

Vidarabine, an anti-herpes agent, improves Porphyromonas gingivalis lipopolysaccharide-induced cardiac dysfunction in mice

In this work, we examined the involvement of type 5 adenylyl cyclase (AC5) in cardiac dysfunction induced in mice given Porphyromonas gingivalis lipopolysaccharide (PG-LPS) at a dose equivalent to the circulating levels in periodontitis (PD) patients. Cardiac function was significantly decreased in mice given PG-LPS compared to the control, but treatment for 1 week with the AC5 inhibitor vidarabine ameliorated the dysfunction. Cardiac fibrosis and myocyte apoptosis were significantly increased in the PG-LPS group, but vidarabine blocked these changes. The PG-LPS-induced cardiac dysfunction was associated with activation of cyclic AMP/Ca2+-calmodulin-dependent protein kinase II signaling and increased phospholamban phosphorylation at threonine 17. These results suggest that pharmacological AC5 inhibition may be a promising approach to treat PD-associated cardiovascular disease.

The small molecule ACM-001 improves cardiac function in a rat model of severe cancer cachexia

AIMS

Cachexia, a common manifestation of malignant cancer, is not only associated with weight loss, but also with severe cardiac atrophy and impaired cardiac function. Here, we investigated the effects of ACM-001 (0.3 or 3 mg/kg/day) in comparison to carvedilol (3 or 30 mg/kg/day), metropolol (50 or 100 mg/kg/day), nebivolol (1 or 10 mg/kg/day) and tertatolol (0.5 or 5 mg/kg/day) on cardiac mass and function in a rat cancer cachexia model.

METHODS AND RESULTS

Young male Wistar Han rats were inoculated i.p. with 108 Yoshida hepatoma AH-130 cells and treated once daily with verum or placebo by gavage. Cardiac function (echocardiography), body weight and body composition (nuclear magnetic resonance scans) were assessed. The hearts of animals were euthanized on day 11 (placebo and 3 mg/kg/day ACM-001) were used for signalling studies. Beta-blockers had no effect on tumour burden. ACM-001 reduced body weight loss (placebo: -34 ± 2.4 g vs. 3 mg/kg/day ACM-001: -14.8 ± 8.4 g, p = 0.033). Lean mass wasting was attenuated (placebo: -16.5 ± 2.34 g vs. 3 mg/kg/day ACM-001: -2.4 ± 6.7 g, p = 0.037), while fat loss was similar (p = 0.4) on day 11. Placebo animals lost left ventricular mass (-101 ± 14 mg), which was prevented only by 3 mg/kg/day ACM-001 (7 ± 25 mg, p < 0.01 vs. placebo). ACM-001 improved the ejection fraction (EF) (ΔEF: placebo: -24.3 ± 2.6 vs. 3 mg/kg/day ACM-001: 0.1 ± 2.9, p < 0.001). Cardiac output was 50% lower in the placebo group (-41 ± 4 ml/min) compared to baseline, while 3 mg/kg/day ACM-001 preserved cardiac output (-5 ± 8 ml/min, p < 0.01). The molecular mechanisms involved inhibition of protein degradation and activation of protein synthesis pathways.

CONCLUSION

This study shows that 3 mg/kg/day ACM-001 restores the anabolic/catabolic balance in cardiac muscle leading to improved function. Moreover, not all beta-blockers have similar effects.

The contribution of autonomic mechanisms to pain in temporomandibular disorders: A narrative review

BACKGROUND

Temporomandibular disorders (TMD) are diagnosed based on symptom presentation and, like other functional pain disorders, often lack definitive pathology. There is a strong association between elevated stress levels and the severity of TMD-related pain, which suggests that alterations in autonomic tone may contribute to this pain condition.

OBJECTIVES

This narrative review examines the association between altered autonomic function and pain in TMD.

METHODS

Relevant articles were identified by searching PubMed and through the reference list of those studies.

RESULTS

TMD sufferers report an increased incidence of orthostatic hypotension. As in other chronic musculoskeletal pain conditions, TMD is associated with increased sympathetic tone, diminished baroreceptor reflex sensitivity and decreased parasympathetic tone. It remains to be determined whether ongoing pain drives these autonomic changes and/or is exacerbated by them. To examine whether increased sympathetic tone contributes to TMD-related pain through β₂ adrenergic receptor activation, clinical trials with the beta blocker propranolol have been undertaken. Although evidence from small studies suggested propranolol reduced TMD-related pain, a larger clinical trial did not find a significant effect of propranolol treatment. This is consistent with human experimental pain studies that were unable to demonstrate an effect of β₂ adrenergic receptor activation or inhibition on masticatory muscle pain. In preclinical models of temporomandibular joint arthritis, β₂ adrenergic receptor activation appears to contribute to inflammation and nociception, whereas in masticatory muscle, α₁ adrenergic receptor activation has been found to induce mechanical sensitization. Some agents used to treat TMD, such as botulinum neurotoxin A, antidepressants and α₂ adrenergic receptor agonists, may interact with the autonomic nervous system as part of their analgesic mechanism.

CONCLUSION

Even if dysautonomia turns out to be a consequence rather than a causative factor of painful TMD, the study of its role has opened up a greater understanding of the pathogenesis of this condition.

Role of TLR4 signaling on Porphyromonas gingivalis LPS-induced cardiac dysfunction in mice

Oral infections, particularly periodontitis, are a well-established risk factor for cardiovascular diseases, although the molecular mechanisms involved remain elusive. The aims of the present study were to investigate the effects of lipopolysaccharide derived from Porphyromonas gingivalis (PG-LPS) on cardiac function in mice, and to elucidate the underlying mechanisms. Mice (C57BL/6) were injected with PG-LPS (0.8 mg/kg/day) with or without an inhibitor of Toll-like receptor 4 (TLR4) signaling (TAK-242, 0.8 mg/kg/day) for 4 weeks. Left ventricular ejection function was significantly decreased at 1 week (from 67 ± 0.5 to 58 ± 1.2%) and remained low at 4 weeks (57 ± 1.0%). The number of apoptotic myocytes was increased (approximately 7.4-fold), the area of fibrosis was increased (approximately 3.3-fold) and the number of 8-hydroxydeoxyguanosine-positive myocytes, a sensitive indicator of oxidative DNA damage, was increased (approximately 7.6-fold) at 4 weeks in the heart of PG-LPS treated mice. However, levels of various serum pro-inflammatory cytokines in PG-LPS-treated mice were similar to those in control mice. The impairment of cardiac function in PG-LPS-treated mice appears to involve activation of TLR4-NADPH oxidase (NOX) 4 signaling, leading to abundant production of reactive oxygen species and Ca²⁺ leakage from sarcoplastic reticulumn induced by calmodulin kinase II (CaMKII)-mediated phosphorylation of phospholamban (at Thr-17) and ryanodine receptor 2 (at Ser-2448). Pharmacological inhibition of TLR4 with TAK-242 attenuated the changes in cardiac function in PG-LPS-treated mice. Our results indicate that TLR4-NOX4 signaling may be a new therapeutic target for treatment of cardiovascular diseases in patients with periodontitis.

Driving an Oxidative Phenotype Protects Myh4 Null Mice From Myofiber Loss During Postnatal Growth

Postnatal muscle growth is accompanied by increases in fast fiber type compositions and hypertrophy, raising the possibility that a slow to fast transition may be partially requisite for increases in muscle mass. To test this hypothesis, we ablated the Myh4 gene, and thus myosin heavy chain IIB protein and corresponding fibers in mice, and examined its consequences on postnatal muscle growth. Wild-type and Myh4^–/– mice had the same number of muscle fibers at 2 weeks postnatal. However, the gastrocnemius muscle lost up to 50% of its fibers between 2 and 4 weeks of age, though stabilizing thereafter. To compensate for the lack of functional IIB fibers, type I, IIA, and IIX(D) fibers increased in prevalence and size. To address whether slowing the slow-to-fast fiber transition process would rescue fiber loss in Myh4^–/– mice, we stimulated the oxidative program in muscle of Myh4^–/– mice either by overexpression of PGC-1α, a well-established model for fast-to-slow fiber transition, or by feeding mice AICAR, a potent AMP kinase agonist. Forcing an oxidative metabolism in muscle only partially protected the gastrocnemius muscle from loss of fibers in Myh4^–/– mice. To explore whether traditional means of stimulating muscle hypertrophy could overcome the muscling deficits in postnatal Myh4^–/– mice, myostatin null mice were bred with Myh4^–/– mice, or Myh4^–/– mice were fed the growth promotant clenbuterol. Interestingly, both genetic and pharmacological stimulations had little impact on mice lacking a functional Myh4 gene suggesting that the existing muscle fibers have maximized its capacity to enlarge to compensate for the lack of its neighboring IIB fibers. Curiously, however, cell signaling events responsible for IIB fiber formation remained intact in the tissue. These findings further show disrupting the slow-to-fast transition of muscle fibers compromises muscle growth postnatally and suggest that type IIB myosin heavy chain expression and its corresponding fiber type may be necessary for fiber maintenance, transition and hypertrophy in mice. The fact that forcing muscle metabolism toward a more oxidative phenotype can partially compensates for the lack of an intact Myh4 gene provides new avenues for attenuating the loss of fast-twitch fibers in aged or diseased muscles.

Vidarabine, an anti-herpes agent, prevents occlusal-disharmony-induced cardiac dysfunction in mice

We recently reported a positive relationship between occlusal disharmony and cardiovascular disease via activation of β-adrenergic signaling in mice. Furthermore, inhibition of type 5 adenylyl cyclase (AC5), a major cardiac subtype in adults, protects the heart against oxidative stress. Here, we examined the role of AC5 in the development of occlusal-disharmony-induced cardiovascular disease in bite-opening (BO) mice, prepared by cementing a suitable appliance onto the mandibular incisor. We first examined the effects of BO treatment on cardiac function in mice treated or not treated for 2 weeks with vidarabine, which we previously identified as an inhibitor of cardiac AC. Cardiac function was significantly decreased in the BO group compared to the control group, but vidarabine ameliorated the dysfunction. Cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage were significantly increased in the BO group, but vidarabine blocked these changes. The BO-induced cardiac dysfunction was associated with increased phospholamban phosphorylation at threonine-17 and serine-16, as well as increased activation of the Ca2+-calmodulin-dependent protein kinase II/receptor-interacting protein 3 signaling pathway. These data suggest that AC5 inhibition with vidarabine might be a new therapeutic approach for the treatment of cardiovascular disease associated with occlusal disharmony.

Chronic treatment with terbutaline increases glucose and oleic acid oxidation and protein synthesis in cultured human myotubes

Objective

In vivo studies have reported several beneficial metabolic effects of β-adrenergic receptor agonist administration in skeletal muscle, including increased glucose uptake, fatty acid metabolism, lipolysis and mitochondrial biogenesis. Although these effects have been widely studied in vivo, the in vitro data are limited to mouse and rat cell lines. Therefore, we sought to discover the effects of the β₂-adrenergic receptor agonist terbutaline on metabolism and protein synthesis in human primary skeletal muscle cells.

Methods

Human cultured myotubes were exposed to terbutaline in various concentrations (0.01–30 ​μM) for 4 or 96 ​h. Thereafter uptake of [¹⁴C]deoxy-D-glucose, oxydation of [¹⁴C]glucose and [¹⁴C]oleic acid were measured. Incorporation of [¹⁴C]leucine, gene expression by qPCR and proteomics analyses by mass spectrometry by the STAGE-TIP method were performed after 96 ​h exposure to 1 and 10 ​μM of terbutaline.

Results

The results showed that 4 ​h treatment with terbutaline in concentrations up to 1 ​μM increased glucose uptake in human myotubes, but also decreased both glucose and oleic acid oxidation along with oleic acid uptake in concentrations of 10–30 ​μM. Moreover, administration of terbutaline for 96 ​h increased glucose uptake (in terbutaline concentrations up to 1 ​μM) and oxidation (1 ​μM), as well as oleic acid oxidation (0.1–30 ​μM), leucine incorporation into cellular protein (1–10 ​μM) and upregulated several pathways related to mitochondrial metabolism (1 ​μM). Data are available via ProteomeXchange with identifier PXD024063.

Conclusion

These results suggest that β₂-adrenergic receptor have direct effects in human skeletal muscle affecting fuel metabolism and net protein synthesis, effects that might be favourable for both type 2 diabetes and muscle wasting disorders.

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The metabolic effects of terbutaline were studied in human primary myotubes.

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Acute treatment with terbutaline increased glucose uptake.

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Chronic treatment with terbutaline increased glucose and oleic acid oxidation.

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Chronic treatment with terbutaline increased protein synthesis.

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Proteomics analysis revealed an increase in mitochondrial proteins.

Effects of chronic Porphylomonas gingivalis lipopolysaccharide infusion on cardiac dysfunction in mice

OBJECTIVE

Periodontitis (PD) is a chronic inflammatory disease of tooth-supportive tissue. An association between PD and cardiovascular disease (CVD) has been established. Although PD is generally accepted as a risk factor for CVD, the existence of a relationship remains debatable. Possible mechanisms include the release of inflammatory mediators such as lipopolysaccharide (LPS), which may spread systemically and promote CVD.

METHODS

To compare the effects of lipopolysaccharide derived from Porphylomonas gingivalis (PG-LPS) on cardiac muscle in mice, mice were treated for 1 week with/without PG-LPS at a dose equivalent to the circulating level in PD patients (0.8 mg/kg/day).

RESULTS

Cardiac function in terms of left ventricular ejection function was significantly decreased at 1 week compared to that in the control (from 66 ± 0.5% to 57 ± 1.1%). Compared to the controls, the number of apoptotic myocytes and the area of fibrosis were significantly increased by approximately 2.7-fold and 14-fold, respectively. The impairment of cardiac function appeared to involve the activation of cAMP/PKA signaling and cAMP/calmodulin kinase II signaling (CaMKII), leading to cardiac fibrosis, myocyte apoptosis and heart failure.

CONCLUSIONS

Our results indicate that cAMP/PKA and cAMP/CaMKII signaling may be a new therapeutic target for the treatment of cardiovascular diseases in patients with periodontitis.

Integrative analysis of miRNA-mRNA expression profiles in esophageal fibrosis after ESD

The incidence of esophageal fibrosis and benign esophageal stricture (BES) has increased in recent years due to the curative therapy for early-stage esophageal carcinoma, including partial esophagectomy and esophageal endoscopic submucosal dissection (ESD). The aim of the present study was to identify key genes and associated pathways of esophageal fibrosis after the ESD procedure. During the esophageal ESD procedure, the esophageal tissue in the remaining submucosal layer, referred to as normal esophageal (NE) tissue, was collected, and 1 week thereafter, post-operative esophageal (PE) tissue was obtained. High-throughput sequencing was used to identify dysregulated microRNAs (miRNAs/miRs) between NE and PE tissues. According to the differentially expressed (DE) miRNAs, putative target genes were predicted. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes enrichment analysis and DEmiRNA interaction network analysis were performed. Reverse transcription-quantitative PCR (RT-qPCR) was performed to validate the RNA-sequencing results. A total of 199 miRNAs were determined to be DE between NE and PE tissues. Compared with the expression in the NE group, 83 miRNAs were significantly upregulated, while 116 miRNAs were significantly downregulated. According to these DE miRNAs, forkhead box O1 (FOXO1), paired box 6 (PAX6), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and adrenoceptor β1 (ADRB1) were DE genes regulated by five DE miRNAs, including miR-223-3p, miR-142-5p, miR-582-5p, miR-21-3p and miR-218-5p. The results suggested that certain pathways were markedly dysregulated, including FOXO, MAPK, AMP-activated protein kinase and signaling pathways regulating the pluripotency of stem cells and proteoglycans in cancer. According to the RT-qPCR results, the expression levels of FOXO1, PAX6, ADRB1, miR-223-3p, miR-582-5p, miR-21-3p and miR-218-5p were consistent with the integrated analysis. In conclusion, FOXO1, PAX6, PIK3CA and ADRB1 may have a role in esophageal fibrosis, regulated by miR-223-3p, miR-142-5p, miR-582-5p, miR-21-3p and miR-218-5p. The present results provided an improved understanding of the changes in the microenvironment during the process of esophageal fibrosis, as well as novel potential targets for the treatment of esophageal fibrosis and BES.

The β3 Adrenergic Receptor Agonist CL316243 Ameliorates the Metabolic Abnormalities of High-Fat Diet-Fed Rats by Activating AMPK/PGC-1α Signaling in Skeletal Muscle

PURPOSE

Skeletal muscle has a major influence on whole-body metabolic homeostasis. In the present study, we aimed to determine the metabolic effects of the β3 adrenergic receptor agonist CL316243 (CL) in the skeletal muscle of high-fat diet-fed rats.

METHODS

Sprague-Dawley rats were randomly allocated to three groups, which were fed a control diet (C) or a high-fat diet (HF), and half of the latter were administered 1 mg/kg CL by gavage once weekly (HF+CL), for 12 weeks. At the end of this period, the serum lipid profile and glucose tolerance of the rats were evaluated. In addition, the phosphorylation and protein and mRNA expression of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ coactivator (PGC)-1α, and carnitine palmitoyl transferase (CPT)-1b in skeletal muscle were measured by Western blot analysis and qPCR. The direct effects of CL on the phosphorylation (p-) and expression of AMPK, PGC-1α, and CPT-1b were also evaluated by Western blotting and immunofluorescence in L6 myotubes.

RESULTS

CL administration ameliorated the abnormal lipid profile and glucose tolerance of the high-fat diet-fed rats. In addition, the expression of p-AMPK, PGC-1α, and CPT-1b in the soleus muscle was significantly increased by CL. CL (1 µM) also increased the protein expression of p-AMPK, PGC-1α, and CPT-1b in L6 myotubes. However, the effect of CL on PGC-1α protein expression was blocked by the AMPK antagonist compound C, which suggests that CL increases PGC-1α protein expression via AMPK.

CONCLUSION

Activation of the β3 adrenergic receptor in skeletal muscle ameliorates the metabolic abnormalities of high-fat diet-fed rats, at least in part via activation of the AMPK/PGC-1α pathway.

Pharmacological Strategy for Congenital Myasthenic Syndrome with CHRNE Mutations: A Meta-Analysis of Case Reports

BACKGROUND

Congenital myasthenic syndromes (CMSs) are a heterogeneous group of neuromuscular disorders. Mutations of the nicotinic acetylcholine receptor epsilon subunit gene (CHRNE) are the most common causes of these disorders. CMSs are gaining increasing recognition by clinicians. However, pharmacological treatment of CMS with CHRNE mutations has only been discussed in a small number of case reports.

OBJECTIVE

This study aims to determine how to choose an appropriate pharmacological strategy for CMS with CHRNE mutations.

METHODS

A meta-analysis was performed. PubMed, MEDLINE, Web of Science, and Cochrane Library databases were searched for studies published in English prior to June 1, 2020. The extracted data included clinical information, gene mutations, pharmacological treatment, and treatment effects.

RESULTS

A total of 48 studies and 208 CMS patients with CHRNE mutations were included in our meta-analysis. Ten different pharmacological strategies were used in these patients. Our research found that β2-adrenergic receptor agonists had the best treatment effect for CMS patients with CHRNE mutations, especially in patients with primary AChR deficiency. In addition, our analysis found no evidence that age at disease onset influences the treatment results.

CONCLUSION

This meta-analysis provides evidence that (1) β2-adrenergic receptor agonist therapy could be the first choice of pharmacological strategy for treating CMS with CHRNE mutations; (2) a single-drug-regime, rather than a combination therapy, should be the first choice of treatment; and (3) it is never too late to initiate pharmacological treatment.

Effects of occlusal disharmony on susceptibility to atrial fibrillation in mice

Tooth loss or incorrect positioning causes occlusal disharmony. Furthermore, tooth loss and atrial fibrillation (AF) are both risk factors for ischemic stroke and coronary heart disease. Therefore, we hypothesized that occlusal disharmony-induced stress increases susceptibility to AF, and we designed the present study to test this idea in mice. Bite-opening (BO) was done by cementing a suitable appliance onto the mandibular incisor to cause occlusal disharmony by increasing the vertical height of occlusion by 0.7 mm for a period of 2 weeks. AF susceptibility, evaluated in terms of the duration of AF induced by transesophageal burst pacing, was significantly increased concomitantly with atrial remodeling, including fibrosis, myocyte apoptosis and oxidative DNA damage, in BO mice. The BO-induced atrial remodeling was associated with increased calmodulin kinase II-mediated ryanodine receptor 2 phosphorylation on serine 2814, as well as inhibition of Akt phosphorylation. However, co-treatment with propranolol, a non-selective β-blocker, ameliorated these changes in BO mice. These data suggest that improvement of occlusal disharmony by means of orthodontic treatment might be helpful in the treatment or prevention of AF.

Effects of occlusal disharmony on cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage in mice

Occlusal disharmony leads to morphological changes in the hippocampus and osteopenia of the lumbar vertebra and long bones in mice, and causes stress. Various types of stress are associated with increased incidence of cardiovascular disease, but the relationship between occlusal disharmony and cardiovascular disease remain poorly understood. Therefore, in this work, we examined the effects of occlusal disharmony on cardiac homeostasis in bite-opening (BO) mice, in which a 0.7 mm space was introduced by cementing a suitable applicance onto the mandibular incisior. We first examined the effects of BO on the level of serum corticosterone, a key biomarker for stress, and on heart rate variability at 14 days after BO treatment, compared with baseline. BO treatment increased serum corticosterone levels by approximately 3.6-fold and the low frequency/high frequency ratio, an index of sympathetic nervous activity, was significantly increased by approximately 4-fold by the BO treatment. We then examined the effects of BO treatment on cardiac homeostasis in mice treated or not treated with the non-selective β-blocker propranolol for 2 weeks. Cardiac function was significantly decreased in the BO group compared to the control group, but propranolol ameliorated the dysfunction. Cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage were significantly increased in the BO group, but propranolol blocked these changes. The BO-induced cardiac dysfunction was associated with increased phospholamban phosphorylation at threonine-17 and serine-16, as well as inhibition of Akt/mTOR signaling and autophagic flux. These data suggest that occlusal disharmony might affect cardiac homeostasis via alteration of the autonomic nervous system.

The determination of β-agonist residues in bovine tissues using liquid chromatography-tandem mass spectrometry

We aimed to develop a rapid, simple and reproducible method based on LC-tandem mass spectrometry (LC-MS/MS) to analyze β-agonist residues (clenbuterol, zilpaterol, ractopamine and isoxsuprine) in bovine tissues. The method was validated in accordance with the European Council Decision 2002/657/EC. The samples were homogenized, and then 10 mL of an acetate buffer was added to a 5-g sample. The sample was then centrifuged at 12,000 rpm and filtered. Sodium hydroxide (2 m) was added to adjust pH of the sample that was centrifuged again. The extract was filtered through a solid-phase extraction column. The residue was re-dissolved in 250 μL acetonitrile and then subjected to LC-MS/MS. The separation was done on a C₁₈ column. The mobile phase consisted of 0.1% formic acid in deionized water and 0.1% formic acid in methanol. The mean recoveries of β-agonists were in the range of 84.3%-119.1% with relative standard deviations (%RSDs) of 0.683%-4.05%. Decision limits and detection capabilities of the analytes ranged from 0.0960 to 4.9349 μg/kg and from 0.0983 to 5.0715, respectively. This method was used to detect four β-agonists in 100 bovine muscle, 100 liver and 100 kidney tissues from a slaughterhouse. No residue was found above the maximum residue limit level.