Botulinum toxin for gastrointestinal disorders: therapy and mechanisms

Role of Endoscopy in Motility Disorders of Upper Gastrointestinal Tract

Gastrointestinal motility disorders have a wide range of symptoms and affect patients' quality of life. With the advancement of endoscopy, the diagnostic and therapeutic roles of endoscopy in motility disorders is becoming more significant. Endoscopy is necessary to rule out possible organic diseases in patients with suspected motility disorders and provide significant clues for their diagnosis. Moreover, interventional endoscopy may be a primary or alternative treatment option for selected patients with motility disorders, and it is becoming a promising field as new therapeutic applications are developed and utilized for various motility disorders. This review may provide suitable indications for the use of endoscopy in diagnosing and treating motility disorders of the upper gastrointestinal tract.

[Endoscopic intragastric injection of botulinum toxin in the treatment of patients with morbid obesity: opportunities and prospects]

The authors consider modern epidemiological and demographic data on morbid obesity. Literature review is devoted to non-surgical treatment of patients with morbid obesity. The authors analyze the results of experimental and clinical studies on endoscopic intragastric injection of botulinum toxin and bariatric efficacy of this approach. The indications for endoscopic intragastric injection of botulinum toxin and advantages of this technique are clearly formulated. The authors identified the most significant criteria for objective assessment of clinical effectiveness of endoscopic intragastral injection of botulinum toxin, as well as scientific and methodological principles necessary for this technique. Clinical efficacy of intragastric injection of botulinum toxin including overweight loss, anorexigenic and gastroparetic effects indicates inconsistent results and certain unresolved problems. Thus, large-scale multiple-center randomized controlled trials and multivariate analysis are required to determine the role of endoscopic intragastric injection of botulinum toxin in complex treatment of patients with morbid obesity.

Gastric ulcer induced changes in substance P and Nk1, Nk2, Nk3 receptors expression in different stomach localizations with regard to intrinsic neuronal system

Gastric ulceration, a focal tissue damage accompanied by inflammation, can influence other parts of the stomach. Substance P and its receptors are strongly involved in regulation of gastrointestinal motility, secretion and inflammation. The enteric nervous system is one of the regulators of gastrointestinal functioning and contributes to tissue response to the pathology. The pig, an omnivorous animal, is a valuable species for gastrointestinal experiments. Thus, the objective of the study was to verify whether the antral ulceration induces changes in the expression of substance P and tachykinin receptors in the neighboring (antrum) and distanced (corpus, pylorus) porcine gastric tissues and therein localized myenteric and submucosal perikarya as well as in the intrinsic descending neurons supplying pyloric sphincter. The experiment was performed on healthy pigs and pigs with experimentally induced gastric ulcers. Stomach samples from the corpus, antrum (adjacent to the ulcer in experimental pigs) and pylorus were analyzed by: (1) double immunofluorescence for changes in the number of SP-positive myenteric and submucosal neurons (2) Real-Time PCR for changes in expression of mRNA encoding SP and Nk1, Nk2, Nk3 receptors. Additionally, gastric descending neurons supplying pyloric sphincter were immunostained for SP. In experimental animals, only the number of SP-positive myenteric perikarya significantly increased in all stomach localizations studied. Q-PCR revealed increased expression for: SP, Nk1, Nk3 in the corpus; Nk2 and Nk3 in the pylorus; In the antrum, expression of Nk3 was increased but Nk2-decreased. Antral ulcers induced significant changes in the expression of SP and tachykinin receptors in the wide stomach area indicating sophisticated tissue reaction.

Botulinum Toxin A for Controlling Obesity

Rapid growth of the overweight population and the number of obese individuals in recent decades suggests that current strategies based on diet, exercise, and pharmacological knowledge are not sufficient to address this epidemic. Obesity is the result of a high caloric intake and energy storage, not counterbalanced by an equally important energy expense. Botulinum toxin type A (BoNT-A) use is rapidly expanding to include treatment of a variety of ophthalmological, gastrointestinal, urological, orthopedic, dermatological, secretory, painful, and cosmetic disorders. Many studies evaluating the effect of BoNT-A in gastric antrum e/o fundus for the treatment of obesity have been published. This treatment modality was based on the observation that gastric injection of BoNT-A in laparatomized rats induced a significant reduction of food intake and body weight. These studies have been published yielding debated results. Differences in the selection of patients, the doses of BoNT-A, the method of administration of the toxin, and the instruments of evaluation of some parameters among these studies may be the cause. In this review, it will study the state-of-the-art use of BoNT-A in obesity basic science models and review the clinical evidence on the therapeutic applications of BoNT-A for obesity.

Pyloric sphincter therapy: botulinum toxin, stents, and pyloromyotomy

Gastroparesis is a syndrome characterized by delayed gastric emptying with associated symptoms. Gastric emptying is a complex process and pyloric dysfunction may play a key role in select subsets of patients with gastroparesis. Diagnostic tests to measure pyloric physiology are now available and have the potential to be more widely used in clinical practice. Targeted therapies including botulinum toxin, transpyloric stent placement, surgical pyloroplasty and endoscopic pyloromyotomy have been developed. Data are emerging regarding efficacy and durability, but these therapies may play a prominent role in select patients with gastroparesis and pyloric dysfunction.

Current diagnosis and management of achalasia

Achalasia is the best characterized primary esophageal motility disorder of the esophagus and typically presents with absent peristalsis of the esophageal body and a failure of the lower esophageal sphincter to relax upon swallowing on manometry, associated with progressively severe dysphagia, regurgitation, aspiration, chest pain, and weight loss. The diagnosis is suggested by barium swallow and endoscopy, and confirmed by manometry. As there is no curative treatment for achalasia, treatment is confined to disruption of the lower esophageal sphincter to improve bolus passage. Treatment modalities available for this purpose include pneumatic dilation, laparoscopic Heller myotomy and since recently peroral endoscopic myotomy or POEM. In this review, we will discuss the current diagnosis, management, and treatment options of achalasia.

Substance P is essential for maintaining gut muscle contractility: a novel role for coneurotransmission revealed by botulinum toxin

Substance P (SP) is commonly coexpressed with ACh in enteric motor neurons, and, according to the classical paradigm, both these neurotransmitters excite smooth muscle via parallel pathways. We hypothesized that, in addition, SP was responsible for maintaining the muscular responsiveness to ACh. We tested this hypothesis by using botulinum toxin (BoNT/A), a known blocker of vesicular release of neurotransmitters including ACh and neuropeptides. BoNT/A was injected into rat pyloric sphincter in different doses; as control we used boiled BoNT/A. At the desired time point, pylorus was dissected out and pyloric contractility was measured ex vivo in an organ bath and by measuring phosphorylation of myosin light chain 20 (MLC20). BoNT/A (10 IU) significantly reduced the response of pyloric muscle to exogenous ACh, an effect that was accompanied by reduced MLC20 phosphorylation in the muscle. Both effects were reversed by exogenous SP. CP-96345, a NK1 receptor antagonist, blocked the ability of exogenous SP to reverse the cholinergic hyporesponsiveness as well as the reduction in MLC20 phosphorylation induced by BoNT/A. In conclusion, we have identified a novel role for SP as a coneurotransmitter that appears to be important for the maintenance of muscular responsiveness to the principal excitatory neurotransmitter, ACh. These results also provide new insight into the effects of botulinum toxin on the enteric nervous system and gastrointestinal smooth muscle.

Management of achalasia

Achalasia is a rare motility disorder of the esophagus characterized by the absence of peristalsis and defective relaxation of the lower esophageal sphincter. Patients present at all ages with dysphagia and regurgitation as main symptoms. The diagnosis is suggested by barium swallow and endoscopy and confirmed by manometry. Because there is no curative treatment for achalasia, treatment is confined to disruption of the lower esophageal sphincter to improve bolus passage. The most successful therapies are pneumodilation and laparoscopic Heller myotomy, with comparable short-term clinical rates of success. The prognosis of achalasia patients is good, but re-treatment is often necessary.

Clinical uses of botulinum neurotoxins: current indications, limitations and future developments

Botulinum neurotoxins (BoNTs) cause flaccid paralysis by interfering with vesicle fusion and neurotransmitter release in the neuronal cells. BoNTs are the most widely used therapeutic proteins. BoNT/A was approved by the U.S. FDA to treat strabismus, blepharospam, and hemificial spasm as early as 1989 and then for treatment of cervical dystonia, glabellar facial lines, axillary hyperhidrosis, chronic migraine and for cosmetic use. Due to its high efficacy, longevity of action and satisfactory safety profile, it has been used empirically in a variety of ophthalmological, gastrointestinal, urological, orthopedic, dermatological, secretory, and painful disorders. Currently available BoNT therapies are limited to neuronal indications with the requirement of periodic injections resulting in immune-resistance for some indications. Recent understanding of the structure-function relationship of BoNTs prompted the engineering of novel BoNTs to extend therapeutic interventions in non-neuronal systems and to overcome the immune-resistance issue. Much research still needs to be done to improve and extend the medical uses of BoNTs.

Endoscopy in the diagnosis and management of motility disorders

BACKGROUND

Gastrointestinal illness may result from either an underlying structural abnormality (e.g. neoplastic obstruction), or a functional disorder (e.g. motor diarrhea), or both (e.g. achalasia with squamous esophageal cancer).

AIMS

The purpose of this study was to highlight the potential value and role of endoscopy in the recognition and management of patients with functional and motility disorders.

METHODS

We performed a literature review in PubMed.

RESULTS

Diagnostic and therapeutic endoscopy may be under-used by motility-oriented gastroenterologists; in contrast, motility and other functional studies may be under-used by endoscopists. Yet, many areas of cross-exchange exist.

CONCLUSIONS

This review aims to guide the appropriate indications for the use of endoscopy in diagnosing and treating functional GI and motility disorders and serve as a bridge and a forum of exchange between endoscopists and motility specialists.

Multiple preoperative endoscopic interventions are associated with worse outcomes after laparoscopic Heller myotomy for achalasia

BACKGROUND

The effect of preoperative pneumatic dilation or botulinum toxin injection on outcomes after laparoscopic Heller myotomy (LHM) for achalasia is unclear. We compared outcomes in patients with and without multiple preoperative endoscopic interventions.

METHODS

This cohort study categorized achalasia patients undergoing first-time LHM by the number of preoperative endoscopic interventions: zero or one intervention vs. two or more interventions. Outcomes of interest included surgical failure (defined as the need for re-intervention), gastrointestinal symptoms, and health-related quality of life. Logistic regression modeling was performed to determine the independent effect of multiple preoperative endoscopic interventions on the likelihood of surgical failure.

RESULTS

One hundred thirty-four patients were included; 88 (66%) had zero to one preoperative intervention, and 46 (34%) had multiple (more than one) interventions. The incidence of surgical failure was 7% in the zero to one intervention group and 28% in the more than one intervention group (p < 0.01). Greater improvements in gastrointestinal symptoms and health-related quality of life were seen in the zero to one intervention group. On logistic regression modeling, the likelihood of surgical failure was significantly higher in the more than one intervention group (odds ratio = 5.1, 95% confidence interval 1.6-15.8, p = 0.005).

CONCLUSIONS

Multiple endoscopic treatments are associated with poorer outcomes and should be limited to achalasia patients who fail surgical therapy.

Advances in the treatment of achalasia

Achalasia is a rare motor disorder of the oesophagus. As its etiology and pathogenesis are still unclear, the treatment nowadays is focused on relief of symptoms. At present, treatment options for achalasia include pharmacotherapy, endoscopic botulinum toxin injection, endoscopic dilation, endoscopic microwave therapy and surgery therapy. In this article, we will review the recent advances in the treatment of achalasia.

Evolution of neurotoxins: from research modalities to clinical realities

In the 1950s, the discovery of anti-nerve growth factor, an immunotoxin stunting sympathetic neural development, signaled the advent of neurotoxins as research modalities. Other selective neurotoxins were discovered in rapid succession. In the 1960s, 6-hydroxydopamine and 6-hydroxydopa were shown to destroy noradrenergic and dopaminergic nerves. Excitotoxins (glutamate, aspartate, and analogs) were discovered in the 1970s. DSP-4 [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine] proved to be selective for noradrenergic destruction, while 5,6- and 5,7-dihydroxytryptamines were relatively selective for serotonin neurons. Additional neurotoxins were discovered, but it was MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) that predominated neurotoxicity research in the 1980s. Eventually, Clostridium botulinum neurotoxin (BoNT), discovered as a "poisonous" principle in the late 1800s, resurfaced in purified and standardized forms as a clinically useful drug. Neurotoxins represent chemical tools, useful not only for discerning neuronal mechanisms and animal modeling of neurological disorders, but also for their use in medicine and potential as treatments for medical disorders. This unit reviews the early discovery of neurotoxins, describes categories of neurotoxins, and finally characterizes their usefulness--first as research tools, and eventually as clinical therapeutic agents.

Endoscopic pyloric injection of botulinum toxin-A for the treatment of postvagotomy gastroparesis

OBJECTIVES

To evaluate the efficacy of botulinum toxin-A in the treatment of postvagotomy gastroparesis.

METHODS

This open-labeled trial identified and recruited 11 subjects who developed symptomatic gastroparesis after a vagotomy (9 fundoplication, 1 trauma, and 1 exploratory laparotomy). Gastroparesis was defined as an abnormal solid-phase gastric emptying test using the standardized 4-hour radionuclide eggbeater meal method and vagotomy was confirmed with a sham meal challenge test. To complete the study, subjects should have completed the 6-month follow-up visit after their pylorus was injected with botulinum toxin-A injection in a 4-quadrant manner. Patients either received 100 (n = 2) or 200 (n = 9) units of botulinum toxin. Questionnaires recorded symptom severity of gastroparesis at baseline and at monthly intervals for 6 months after the therapy was completed by the patients.

RESULTS

Of the 11 subjects initially recruited, 10 finished the 6-month follow-up visit (7 women). Mean age was 51 years (range, 31-84 years). Mean symptom score at baseline was 16 (95% CI 13-19) and showed a numerical decline to 9 (P > 0.05) over the 6-month period after the procedure (95% CI 5-13). Seven (70%) patients observed >30% improvement in the total symptom score. No complications were recorded.

CONCLUSIONS

In conclusion, this open-label study in patients with postvagotomy gastroparesis patients reveals a reduction of gastroparetic symptoms at 1 and 3 months after treatment with pyloric injection of botulinum toxin-A, with return of symptoms by 6 months. Thus, botulinum toxin treatment does not produce a sustained reduction in gastroparetic symptoms in this clinical setting.

Botulinum neurotoxin: evolution from poison, to research tool--onto medicinal therapeutic and future pharmaceutical panacea

Botulinum neurotoxin (BoNT), for more than a hundred years, has been a recognized poisonous principle in spoiled food. As its chemical structure became unraveled, and as more knowledge was gained over its mechanism of toxicity, it became clear that BoNT had the potential to act therapeutically as a targeted toxin that could inactivate specific nerve populations, and thus achieve a therapeutic goal. BoNT has evolved over the past 25 years into a viable therapeutic, now being a first line treatment for dystonia, overtly altering the course of progression of this disorder. BoNT is used for hyperhidrosis and gustatory sweating syndrome, alleviation of pain, as a treatment for overactive bladder, achalasia and anal fissure; and it has gained popularity as a cosmetic aid. Many other possible uses are being explored. The greatest potential for BoNT may lie in its being a molecular Trojan Horse - able to carry a specific enzyme or specific drug to the inside of a cancer or other type of cell while bypassing other cells and thereby having little or no ill effect. BoNT's pharmaceutical potential is boundless.

Botulinum toxin A for the treatment of delayed gastric emptying

BACKGROUND

Observational data suggest that intrapyloric injection of botulinum toxin A (BoTN/A) reduces symptoms and accelerates gastric emptying in idiopathic and diabetic gastroparesis. Our purpose was to determine whether botulinum toxin improves symptoms to a significantly greater extent than placebo. An additional objective was to determine whether there is an acceleration of gastric emptying after injection.

METHODS

A single-institution, randomized, double-blind, placebo-controlled trial* was done. Eligible patients had a Gastroparesis Cardinal Symptom Index score > or = 27 with randomization to intrapyloric botulinum toxin, 200 U (units), or saline placebo. Reassessment of symptoms and repeat gastric emptying scan at 1-month follow-up were done.

RESULTS

Thirty-two patients were randomized to botulinum toxin (N = 16) and placebo (N = 16). At 1-month follow-up, 37.5% randomized to botulinum toxin and 56.3% randomized to placebo achieved improvement as defined by this study. There were no identifiable clinical predictors of response. The botulinum toxin group demonstrated improvement in gastric emptying; however, this was not superior to placebo. No serious adverse events were attributable to botulinum toxin.

CONCLUSIONS

Intrapyloric injection of botulinum toxin improves gastric emptying in patients with gastroparesis, although this benefit was not superior to placebo at 1 month. Also, in comparison to placebo, symptoms do not improve significantly by 1 month after injection. Overall, we are unable to recommend botulinum toxin therapy for widespread use in the treatment of delayed gastric emptying until more data are available.

Beyond gastric emptying: a "toxic" lesson about gastroparesis

The first published controlled trial of intrapyloric botulinum toxin for gastroparesis failed to demonstrate a significant effect of treatment on symptoms, despite an improvement in gastric emptying. In this editorial, I discuss the limitations and implications of this study, with particular emphasis on what the use of botulinum toxin can teach us about the pathophysiology of gastroparesis and other gastrointestinal smooth muscle disorders.

Achalasia

Achalasia is a rare motor disorder of the oesophagus, characterised by the absence of peristalsis and impaired swallow-induced relaxation. These motor abnormalities result in stasis of ingested food in the oesophagus, leading to clinical symptoms, such as dysphagia, regurgitation of food, retrosternal pain and weight loss. Although it is well demonstrated that loss of myenteric oesophageal neurons is the underlying problem, it still remains unclear why these neurons are preferentially attacked and destroyed by the immune system. This limited insight into pathophysiology explains the fact that treatment is limited to interventions aimed at reducing the pressure of the lower oesophageal sphincter. The most successful therapies are clearly pneumatic dilatation and Heller myotomy with short-term success rates of 70-90%, declining to 50-65% after more than 15 years. The challenge for the coming years will undoubtedly be to get more insight into the underlying disease mechanisms and to develop a treatment to restore function.