Application Of Botulinum Neurotoxin Research Articles

Therapy with botulinum neurotoxin for Parkinson's disease.

Botulinum neurotoxin (BoNT) has been in use since the 1970's. Its effect is reached mainly by inhibiting the release of acetylcholine in the synaptic gap of motor neurons or at the motor end plate and the parasympathetic ganglia. In the case of Parkinson's disease, it is used to treat several motor and non-motor symptoms. Within recent years increasingly numerous possible fields of application of BoNT have been found for the treatment of Parkinson's disease, and for some specific symptoms it has in fact become the therapy of choice, while for others it is but one of the therapeutic options that come into consideration when others are not sufficiently effective. In the following, we intend to outline the indications, the possible side effects and also the approvals for therapies with botulinum toxin in the primary and secondary symptoms of Parkinson's disease.

Mechanism and clinical use of botulinum neurotoxin in head and facial region.

Botulinum neurotoxin (BoNT) is a biological toxin produced by Clostridium botulinum. BoNT is a potent toxin extensively used in therapeutic interventions. This review provides an updated overview of the mechanisms of action and clinical applications of BoNT in head and facial region. MEDLINE/PubMed searches were conducted using the terms "botulinum neurotoxin" and "dentistry" along with a combination of other related terms. In addition, studies were manually selected from reference lists of the selected articles. The Food and Drug Administration in the United States initially approved BoNT to treat strabismus, blepharospasm, and hemifacial spasms. The use of BoNT in dermatology and cosmetics has been widely established and has created a revolution in these fields. Over the years, its applications in various medical specialties have expanded widely. Owing to its safety, efficacy, and long duration of action, it is well-accepted by patients. BoNT/A and BoNT/B are widely used in clinical practice. Several off-label uses of BoNT in the dental fraternity have yielded promising results. We have elaborated on the speculated mechanism of action, dosage, effective sites of injection, and adverse effects of each therapeutic application. The various clinical indications for BoNT include bruxism, myofascial pain, temporomandibular joint dislocation, hemifacial pain, orofacial dystonia, facial paralysis, chronic migraine, and trigeminal neuralgia. BoNT is a safe treatment that can be used effectively, provided that the clinician has adequate knowledge regarding the mechanism, injection techniques, and local and systemic side effects and that it is administered cautiously and purposefully.

The Effectiveness and Safety of Botulinum Neurotoxin in Obstetric Brachial Plexus Injury: A Systematic Review and Meta-Analysis.

Obstetric brachial plexus injury, also known as neonatal brachial plexus injury, is not unusual in newborns. Given the lack of a comprehensive synthesis of the available data on the effectiveness of botulinum neurotoxin (BoNT) in treating children with obstetric brachial plexus injury, we conducted a systematic review and meta-analysis. We searched PubMed, Embase, Web of Science, and Cochrane databases from inception to 25 November 2022. Outcomes were function of the shoulder and elbow joints, muscle power of the deltoid, biceps brachii and triceps brachii, and the recurrence rate of subluxation or dislocation after reduction of the shoulder joint after BoNT application. Meta-regression was conducted to assess the moderator effect of age. We included 11 case series and 2 cohort studies. Passive range of motion of shoulder external rotation (standardized mean difference [SMD], 0.678; 95% confidence interval [95%CI], 0.423 to 0.934), Active Movement Scale for shoulder external rotation (SMD, 0.47; 95%CI, 0.131 to 0.808), and active range of motion of elbow extension (SMD, 2.445; 95%CI, 1.556 to 3.334) increased significantly after BoNT. However, the modified Gilbert scale for shoulder abduction (SMD, 1.239; 95% CI, -0.2 to 2.678), the Toronto score for active elbow flexion (SMD, 1.099; 95% CI, -0.053 to 2.252), muscle power of deltoid (SMD, 0.675; 95% CI, -0.599 to 1.949), biceps brachii (SMD, 0.225; 95% CI, -0.633 to 1.083), and triceps brachii (SMD, 1.354; 95% CI, -1.493 to 4.202) did not reach statistical significance. The moderator effect of age was not significant (p = 0.88). Meta-analysis was not done for recurrence rate of subluxation or dislocation due to insufficient data. In conclusion, our data support BoNT use in patients with obstetric brachial plexus injury. However, definite conclusions cannot be drawn due to small sample size and the lack of randomized controlled trials. More research is warranted to clarify the effectiveness of BoNT in patients with obstetric brachial plexus injury by using standardized injection protocols and outcome measurements.

Effectiveness of Botulinum Neurotoxin in Treatment of Scoliosis among Children and Adolescents: A Systematic Review and Meta-Analysis.

Scoliosis refers to a three-dimensional deviation in the axis of the spine. Muscle imbalance is believed to play a role in scoliosis. Botulinum neurotoxin (BoNT) can reduce muscle overactivity and may have the potential to ameliorate spinal scoliosis. This study investigated the effectiveness of intramuscular BoNT injection in vertebral curve correction and reviewed the possible influencing factors. PubMed, Medline, Cochrane Central Register of Controlled Trials, Web of Science, Airiti Library, and Index of the Taiwan Periodical Literature System databases were searched from inception until 7 September 2022 for eligible studies. The main outcome was the change in Cobb angle after BoNT application. Subgroup analysis was conducted according to differences in study designs, etiology of scoliosis, and methods used for target muscle selection. We enrolled three studies including 31 participants aged between 2 and 18 years. The meta-analysis revealed no significant reduction in the Cobb angle after BoNT injection (standardized mean difference, −0.783, 95% CI, −2.142 to 0.576). Study designs (p = 0.011) and methods used for target muscle selection (p = 0.017) but not etiology of scoliosis (p = 0.997) reached statistical significance between subgroups. In conclusion, the current meta-analysis does not support the application of BoNT in children and adolescents with scoliosis. However, a decisive conclusion could not be made due to high between-study heterogeneity and small sample size. More randomized controlled trials with appropriate target muscle selection and standard outcome measurement should be conducted to examine the efficacy of botulinum neurotoxin in treating scoliosis. INPLASY ID: INPLASY202290031.

Dramatic neurological and biological effects by botulinum neurotoxin type A on SH-SY5Y neuroblastoma cells, beyond the blockade of neurotransmitter release

BackgroundGene expression profile analysis on mammalian cell lines and animal models after exposure to botulinum neurotoxin (BoNT) has been investigated in several studies in recent years. Microarray analysis provides a powerful tool for identifying critical signaling pathways involved in the biological and inflammatory responses to BoNT and helps determine the mechanism of the function of botulinum toxins.One of the pivotal clinical characteristics of BoNT is its prolonged on-site effects. The role of BoNT on the blockage of neurotransmitter acetylcholine release in the neuromuscular junction has been well established. However, the effects of the treatment time of BoNT on the human cellular model and its potential mechanism remain to be defined.MethodsThis study aimed to use gene microarray technology to compare the two physiological critical time points of BoNT type A (BoNT/A) treatment of human neuroblastoma cells and to advance our understanding of the profound biological influences that toxin molecules play in the neuronal cellular system. SH-SY5Y neuroblastoma cells were treated with BoNT/A for 4 and 48 h, which represent the time needed for the entrance of toxin into the cells and the time necessary for the initial appearance of the on-site effects after BoNT application, respectively.ResultsA comparison of the two time points identified 122 functional groups that are significantly changed. The top five groups are alternative splicing, phosphoprotein, nucleus, cytoplasm, and acetylation. Furthermore, after 48 h, there were 744 genes significantly up-regulated, and 624 genes significantly down-regulated (p‹ 0.01). These genes fell into the following neurological and biological annotation groups: Nervous system development, proteinaceous extracellular matrix, signaling pathways regulating pluripotency of stem cells, cellular function and signal transduction, and apoptosis.We have also noticed that the up-regulated groups contained neuronal cell development, nervous system development, and metabolic processes. In contrast, the down-regulated groups contained many chromosomes and cell cycle categories.ConclusionsThe effects of BoNT/A on neuronal cells extend beyond blocking the neurotransmitter release, and that BoNT/A is a multifunctional molecule that can evoke profound cellular responses which warrant a more in-depth understanding of the mechanism of the toxin’s effects after administration.

Application of Botulinum Neurotoxin in Male Sexual Dysfunction: Where Are We Now?

Botulinum neurotoxin (BoNT) is a recognized therapeutic agent of modern medical care, routinely used to treat medical conditions affecting a variety of organ systems including the musculoskeletal, integumentary, and urological domains. Ongoing research is exploring BoNT's potential role as a therapeutic agent for a variety of male sexual pathologies. To review and analyze the literature regarding BoNT as a treatment option for male sexual dysfunction. A PubMed search was performed for English-language articles in peer-reviewed journals between 1970 and 2019 (with one article from 1897). Relevant articles referenced within these texts were also included. One article did not have an accompanied English full-text available. The following search terms were used: "Botox", "Botulinum toxin", "Botulinum toxin A", "Onabotulinum A", "Abobutlinum A", "BoNT", "BoNT-A", "Male sexual health", "Male sexual pathology", "Peyronie's disease", "Premature ejaculation", "Scrotal Pain", "Penile Retraction", "Scrotox", "Erectile Dysfunction", and "Botox in Urology". There is interest in the potential role of BoNT in the treatment of male sexual pathologies. We identified studies that used BoNT to treat chronic scrotal content pain, premature ejaculation, erectile dysfunction, Peyronie's disease, penile retraction, and more. However, despite preclinical/clinical data indicating some potential efficacy and safety in these settings, a lack of robust clinical trial data has resulted in no current Food and Drug Administration-approved indications for the use of BoNT in the treatment of male sexual pathology. As a result, much of the current use of BoNT by today's providers is "off-label," and ongoing clinical trials aim to further elucidate the potential role of this therapeutic agent. Current data suggest that BoNT could have a potential role as a treatment option for certain types of male sexual pathologies. However, more randomized controlled trial data regarding its long-term safety and efficacy are necessary before a widespread clinical adoption can take place. Reddy AG, Dick BP, Natale C, etal. Application of Botulinum Neurotoxin in Male Sexual Dysfunction: Where Are We Now?. J Sex Med 2021;9:320-330.

Application of Botulinum Neurotoxin in Female Sexual and Genitourinary Dysfunction: A Review of Current Practices.

The past 2decades have witnessed an increased amount of research into botulinum neurotoxin (BoNT) as a treatment for various forms of sexual dysfunction and pain syndromes refractory to other medical therapy. BoNT is postulated to reduce pain sensation by inhibiting neuropeptide release in the presynaptic neuron. Dyspareunia, vaginismus, vestibulodynia, and persistent genital arousal disorder are female sexual dysfunctions with cryptic pathophysiology and limited treatment options. BoNT has emerged as a potential treatment for many of these afflictions in women. To review the literature regarding BoNT as a treatment for female sexual and genitourinary dysfunction. A PubMed search for English-language articles was performed using the following terms: "Botox," "botulinum toxin," "botulinum toxin A," "Onabotulinum A," "Abobutlinum A," "BoNT," and "BoNT-A." The main outcomes measured by each study were resolution of dysfunction. This entailed reduction of pain with intercourse for dyspareunia, reduction of pain for vestibulodynia, decreased arousal for persistent genital arousal disorder, and ability to tolerate penetration for vaginismus. A total of 12 human studies that evaluated BoNT as a treatment for female sexual disorders were included. Study types included prospective, retrospective, cohort, pilot, and open-label. There is growing evidence suggesting that BoNT is a safe and efficacious treatment option for female patients suffering from various sexual and genitourinary disorders. However, more research is needed to develop a better understanding of the mechanisms through which BoNT treats these disorders. Dick B, Natale C, Reddy A, etal. Application of Botulinum Neurotoxin in Female Sexual and Genitourinary Dysfunction: A Review of Current Practices. Sex Med 2021;9:57-63.

Novel Native and Engineered Botulinum Neurotoxins.

Botulinum neurotoxins (BoNTs), produced by Clostridia and other bacteria, are the most potent toxins known. Their cleavage of the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins in neurons prevents the release of neurotransmitters, thus resulting in the muscle paralysis that is characteristic of botulism. This mechanism of action has been exploited for a variety of therapeutic and cosmetic applications of BoNTs. This chapter provides an overview of the native BoNTs, including the classical serotypes and their clinical use, mosaic BoNTs, and novel BoNTs that have been recently identified in clostridial and non-clostridial strains. In addition, the modular structure of native BoNTs, which are composed of a light chain and a heavy chain, is amenable to a multitude of novel fusions and mutations using molecular biology techniques. These novel recombinant BoNTs have been used or are being developed to further characterize the biology of toxins, to assist in vaccine production, to serve as delivery vehicles to neurons, and to be utilized as novel therapeutics for both neuronal and non-neuronal cells.

New trends in botulinum toxin use in dermatology

Background: Recent studies have highlighted new botulinum neurotoxin (BoNT) applications in the field of dermatology. Objective: To review current knowledge of BoNT use in dermatology. Methods: The literature of the last 5 years has been reviewed. Results: We describe interesting protocols of BoNT treatment for hyperhidrosis (HH), hypertrophic scars and keloids, Raynaud phenomenon, facial flushing, oily skin, psoriasis, Hailey-Hailey disease, and cutaneous lesions like painful lesions and periorbital syringomas. Conclusions: Several skin conditions eligible for BoNT treatment have been described. After the wide application for HH treatment, scars as well as vascular and inflammatory skin disorders, oily skin and cutaneous lesions represent fields of application of BoNT.

New trends in botulinum toxin use in dermatology.

BackgroundRecent studies have highlighted new botulinum neurotoxin (BoNT) applications in the field of dermatology.ObjectiveTo review current knowledge of BoNT use in dermatology.MethodsThe literature of the last 5 five years has been reviewed.ResultsWe describe interesting protocols of BoNT treatment for hyperhidrosis (HH), hypertrophic scars and keloids, Raynaud phenomenon, facial flushing, oily skin, psoriasis, Hailey-Hailey disease, and cutaneous lesions like painful lesions and periorbital syringomas.ConclusionsSeveral skin conditions eligible for BoNT treatment have been described. After the wide application for HH treatment, scars as well as vascular and inflammatory skin disorders, oily skin and cutaneous lesions represent fields of application of BoNT.

Botulinum Neurotoxin Application to the Severed Femoral Nerve Modulates Spinal Synaptic Responses to Axotomy and Enhances Motor Recovery in Rats.

Botulinum neurotoxin A (BoNT) and brain-derived neurotrophic factor (BDNF) are known for their ability to influence synaptic inputs to neurons. Here, we tested if these drugs can modulate the deafferentation of motoneurons following nerve section/suture and, as a consequence, modify the outcome of peripheral nerve regeneration. We applied drug solutions to the proximal stump of the freshly cut femoral nerve of adult rats to achieve drug uptake and transport to the neuronal perikarya. The most marked effect of this application was a significant reduction of the axotomy-induced loss of perisomatic cholinergic terminals by BoNT at one week and two months post injury. The attenuation of the synaptic deficit was associated with enhanced motor recovery of the rats 2–20 weeks after injury. Although BDNF also reduced cholinergic terminal loss at 1 week, it had no effect on this parameter at two months and no effect on functional recovery. These findings strengthen the idea that persistent partial deafferentation of axotomized motoneurons may have a significant negative impact on functional outcome after nerve injury. Intraneural application of drugs may be a promising way to modify deafferentation and, thus, elucidate relationships between synaptic plasticity and restoration of function.

Light Chain Diversity among the Botulinum Neurotoxins.

Botulinum neurotoxins (BoNT) are produced by several species of clostridium. There are seven immunologically unique BoNT serotypes (A–G). The Centers for Disease Control classifies BoNTs as ‘Category A’ select agents and are the most lethal protein toxins for humans. Recently, BoNT-like proteins have also been identified in several non-clostridia. BoNTs are di-chain proteins comprised of an N-terminal zinc metalloprotease Light Chain (LC) and a C-terminal Heavy Chain (HC) which includes the translocation and receptor binding domains. The two chains are held together by a disulfide bond. The LC cleaves Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). The cleavage of SNAREs inhibits the fusion of synaptic vesicles to the cell membrane and the subsequent release of acetylcholine, which results in flaccid paralysis. The LC controls the catalytic properties and the duration of BoNT action. This review discusses the mechanism for LC catalysis, LC translocation, and the basis for the duration of LC action. Understanding these properties of the LC may expand the applications of BoNT as human therapies.

The non-neuronal and nonmuscular effects of botulinum toxin: an opportunity for a deadly molecule to treat disease in the skin and beyond.

There is growing evidence that botulinum neurotoxins (BoNTs) exhibit biological effects on various human cell types with a host of associated clinical implications. This review aims to provide an update on the non-neuronal and nonmuscular effects of botulinum toxin. We critically analysed recent reports on the structure and function of cellular signalling systems subserving biological effects of BoNTs. The BoNT receptors and intracellular targets are not unique for neurotransmission. They have been found in both neuronal and non-neuronal cells, but there are differences in how BoNT binds to, and acts on, neuronal vs. non-neuronal cells. The non-neuronal cells that express one or more BoNT/A-binding proteins, and/or cleavage target synaptosomal-associated protein 25, include: epidermal keratinocytes; mesenchymal stem cells from subcutaneous adipose; nasal mucosal cells; urothelial cells; intestinal, prostate and alveolar epithelial cells; breast cell lines; neutrophils; and macrophages. Serotype BoNT/A can also elicit specific biological effects in dermal fibroblasts, sebocytes and vascular endothelial cells. Nontraditional applications of BoNT have been reported for the treatment of the following dermatological conditions: hyperhidrosis, Hailey-Hailey disease, Darier disease, inversed psoriasis, aquagenic palmoplantar keratoderma, pachyonychia congenita, multiple eccrine hydrocystomas, eccrine angiomatous hamartoma, eccrine sweat gland naevi, congenital eccrine naevus, Raynaud phenomenon and cutaneous leiomyomas. Experimental studies have demonstrated the ability of BoNT/A to protect skin flaps, facilitate wound healing, decrease thickness of hypertrophic scars, produce an anti-ageing effect, improve a mouse model of psoriasiform dermatitis, and have also revealed extracutaneous effects of BoNT arising from its anti-inflammatory and anticancer properties. BoNTs have a much wider range of applications than originally understood, and the individual cellular responses to the cholinergic impacts of BoNTs could provide fertile ground for future studies.

Botulinum Toxin in Paediatric Neuro-Rehabilitation

Background: Botulinum neurotoxin (BoNT) is a frequently used therapeutic agent in the field of movement disorders, especially in spastic cerebral palsy (CP) and focal dystonias. While there are many studies concerning the therapy of CP with BoNT, little is known about the effectiveness and efficacy of this agent in children in rehabilitation, for example, after traumatic brain injury or other acquired brain injuries. Nevertheless, BoNT is often used for tonus modulation, also in combination with other pharmacological interventions, for the facilitation of therapeutic, orthopedic, and caring procedures, as well as the reduction of drooling. Methods: The application of BoNT in rehabilitation was evaluated with the help of questionnaires for the upper and lower extremities and the head–neck area. The evaluation was performed after 4 and 8 weeks, respectively, by internal physical or occupational therapists. Overall, 45 questionnaires of patients aged 1.3 to 18.5 years were analyzed. Results: In 61.5% (lower extremities) and 62% (upper extremities) of cases, the local efficacy of BoNT at the individual muscle was evaluated as being “good.” Side effects were only observed in one case. Fortunately, in 85.7%, the therapy with BoNT facilitated therapeutic procedures. This leads to the recommendation of further application of BoNT in similar situations in 81% of the cases for the lower extremities. Conclusion: Even if the local effect at the individual muscle seems not to be always in an optimal range, the overall therapeutic effect facilitates physical and occupational therapies and therefore is an important component in rehabilitation.

Botulinum Toxin for Neuropathic Pain: A Review of the Literature.

Botulinum neurotoxin (BoNT), derived from Clostridium botulinum, has been used therapeutically for focal dystonia, spasticity, and chronic migraine. Its spectrum as a potential treatment for neuropathic pain has grown. Recent opinions on the mechanism behind the antinociceptive effects of BoNT suggest that it inhibits the release of peripheral neurotransmitters and inflammatory mediators from sensory nerves. There is some evidence showing the axonal transport of BoNT, but it remains controversial. The aim of this review is to summarize the experimental and clinical evidence of the antinociceptive effects, mechanisms, and therapeutic applications of BoNT for neuropathic pain conditions, including postherpetic neuralgia, complex regional pain syndrome, and trigeminal neuralgia. The PubMed and OvidSP databases were searched from 1966 to May 2015. We assessed levels of evidence according to the American Academy of Neurology guidelines. Recent studies have suggested that BoNT injection is an effective treatment for postherpetic neuralgia and is likely efficient for trigeminal neuralgia and post-traumatic neuralgia. BoNT could also be effective as a treatment for diabetic neuropathy. It has not been proven to be an effective treatment for occipital neuralgia or complex regional pain syndrome.

76. Controversies on unresolved issues in the use of botulinum neurotoxins: the application of botulinum neurotoxin for hemiparetic gait

76. Controversies on unresolved issues in the use of botulinum neurotoxins: the application of botulinum neurotoxin for hemiparetic gait

Anti-apoptotic activity of hemagglutinin-33 and botulinum neurotoxin and its implications to therapeutic and countermeasure issues

Botulinum neurotoxins (BoNTs), produced by Clostridium botulinum are the most toxic substances known to the mankind. BoNTs (seven serotypes, A–G) are produced along with a group of neurotoxin associated proteins (NAPs) in a physiologically coordinated manner, regulated by a common transcription factor for the gene cluster that encodes for the BoNT and NAPs. Hemagglutinin-33 (Hn-33) is a 33kDa subcomponent of NAPs, which is resistant to protease digestion, and accounts for about half of the NAPs molecules in the BoNT/A complex. Natural exposures to BoNT in food poisoning cases as well as in the medical applications of BoNT as a therapeutic agent, humans are exposed to the BoNT/A complex. The toxin itself is known to block neurotransmitter release from presynaptic nerves, but the effect of NAPs is unexplored. In this article, we report an important observation of the anti-apoptotic effect of Hn-33 in Hn-33-preincubated human neuroblastoma SH-SY5Y cells. Activity of caspases, which are the central executioners of apoptosis, was substantially (78%) reduced by Hn-33. Degradation of chromosomal DNA, another biochemical hallmark of apoptosis, was blocked in Hn-33 incubated SH-SY5Y cells. Interestingly, purified BoNT/A also showed substantial anti-apoptotic activity. These findings may have significant implications to the use of BoNT as a therapeutic agent, and to devise counter measures to botulinum poisoning.

Sensing the deadliest toxin: technologies for botulinum neurotoxin detection.

Sensitive and rapid detection of botulinum neurotoxins (BoNTs), the most poisonous substances known to date, is essential for studies of medical applications of BoNTs and detection of poisoned food, as well as for response to potential bioterrorist threats. Currently, the most common method of BoNT detection is the mouse bioassay. While this assay is sensitive, it is slow, quite expensive, has limited throughput and requires sacrificing animals. Herein, we discuss and compare recently developed alternative in vitro detection methods and assess their ability to supplement or replace the mouse bioassay in the analysis of complex matrix samples.

Lokale Botulinumneurotoxin-A-Therapie bei tardiver Dyskinesie der Zunge

Tardive dyskinesia syndromes in the head and neck region may appear as adverse effects of psychopharmacotherapy. They are caused by blockage of central dopamine receptors. Oftentimes, these disorders persist even after discontinuation of the antipsychotic medication, and they are disabling the patients functionally and psychosocially. Medical therapeutic efforts with different psychopharmaceuticals, benzodiazepines or vitamin-E-preparations are frequently unsuccessful. Local application of botulinum neurotoxin A offers a new treatment modality, which can target the overshooting dysfunction directly at the peripheral muscle.

High glucose changes extracellular adenosine triphosphate levels in rat retinal cultures

Diabetic retinopathy (DR) is the leading cause of blindness in adults. In diabetes, there is activation of microglial cells and a concomitant release of inflammatory mediators. However, it remains unclear how diabetes triggers an inflammatory response in the retina. Activation of P2 purinergic receptors by adenosine triphosphate (ATP) may contribute to the inflammatory response in the retina, insofar as it has been shown to be associated with microglial activation and cytokine release. In this work, we evaluated how high glucose, used as a model of hyperglycemia, considered the main factor in the development of DR, affects the extracellular levels of ATP in retinal cell cultures. We found that basal extracellular ATP levels were not affected by high glucose or mannitol, but the extracellular elevation of ATP, after a depolarizing stimulus, was significantly higher in retinal cells cultured in high glucose compared with control or mannitol-treated cells. The increase in the extracellular ATP was prevented by application of botulinum neurotoxin A or by removal of extracellular calcium. In addition, degradation of exogenously added ATP was significantly lower in high-glucose-treated cells. It was also observed that, in retinal cells cultured under high-glucose conditions, the changes in the intracellular calcium concentrations were greater than those in control or mannitol-treated cells. In conclusion, in this work we have shown that high glucose alters the purinergic signaling system in the retina, by increasing the exocytotic release of ATP and decreasing its extracellular degradation. The resulting high levels of extracellular ATP may lead to inflammation involved in the pathogenesis of DR.