From the Gut to the Brain: The Role of Enteric Glial Cells and Their Involvement in the Pathogenesis of Parkinson's Disease.

The brain-gut axis has been identified as an important contributor to the physiopathology of Parkinson's disease. In this pathology, inflammation is thought to be driven by the damage caused by aggregation of α-synuclein in the brain. Interestingly, the Braak's theory proposes that α-synuclein misfolding may originate in the gut and spread in a "prion-like" manner through the vagus nerve into the central nervous system. In the enteric nervous system, enteric glial cells are the most abundant cellular component. Several studies have evaluated their role in Parkinson's disease. Using samples obtained from patients, cell cultures, or animal models, the studies with specific antibodies to label enteric glial cells (GFAP, Sox-10, and S100ß) seem to indicate that activation and reactive gliosis are associated to the neurodegeneration produced by Parkinson's disease in the enteric nervous system. Of interest, Toll-like receptors, which are expressed on enteric glial cells, participate in the triggering of immune/inflammatory responses, in the maintenance of intestinal barrier integrity and in the configuration of gut microbiota; thus, these receptors might contribute to Parkinson's disease. External factors like stress also seem to be relevant in its pathogenesis. Some authors have studied ways to reverse changes in EGCs with interventions such as administration of Tryptophan-2,3-dioxygenase inhibitors, nutraceuticals, or physical exercise. Some researchers point out that beyond being activated during the disease, enteric glial cells may contribute to the development of synucleinopathies. Thus, it is still necessary to further study these cells and their role in Parkinson's disease.

Content Validity of the Spanish Adaptation of the Premature Infant Pain Profile Revised.

BACKGROUND: To the best of our knowledge, there are no validated neonatal pain assessment scales in Spanish. Given the need for such a scale, a study was undertaken to adapt and validate the Premature Infant Pain Profile-Revised (PIPP-R) scale. After translation and back-translation, content validity was addressed, a crucial phase in validation studies, in which researchers examine whether the items that make up the scale represent the content that the scale is intended to assess. AIMS: The aim was to provide evidence for the content validity of the Spanish adaptation of the PIPP-R scale. METHOD: The study used the Delphi technique with 10 experts. Data collection was anonymous and was conducted through an online platform. It was an ad hoc survey consisting of four questions, with a five-point Likert scale for each item on the scale and for the instruction table. An item-content validity index (I-CVI) and a scale-content validity index (S-CVI) were calculated for the analysis. RESULTS: After two rounds of the survey, all items exceeded an I-CVI of 0.9. The S-CVI value was 0.98 (±0.03) for the scale, and 1 for its instruction table. The kappa index yielded values indicating an excellent degree of agreement. CONCLUSIONS: The Spanish version of the PIPP-R obtained a high degree of content validity according to the expert group and the Delphi technique.

Effects of vincristine and monosodium glutamate on gastrointestinal motility and visceral sensitivity.

BACKGROUND: Chemotherapy-induced adverse effects are an unresolved nightmare. In preclinical studies in rats, the food additive monosodium glutamate (MSG) improved some of the side effects caused by cisplatin, but its effects in other models of chemotherapy-treated animals are not well known. The aim of this study was to test if MSG may improve some of the adverse effects induced by vincristine in rats. METHODS: Young male Wistar rats were exposed or not to MSG (4 g L-1 ) in drinking water from week 0 till 1 week after treatment (week 3). Rats received two cycles of five daily intraperitoneal (ip) injections (Monday to Friday, weeks 1 and 2) of either saline (2 mL kg-1 ) or vincristine (0.1 mg kg-1 ). Gastrointestinal motility was measured in vivo by radiological methods after the first and tenth ip administrations. On week 3, the threshold for mechanical somatic and colorectal sensitivity was recorded using Von Frey filaments applied to the paws and an intracolonic balloon, respectively. Finally, samples of the terminal ileum and distal colon were histologically evaluated in sections. KEY RESULTS: Vincristine reduced body weight gain, food intake, and upper gastrointestinal transit, caused somatic (but not visceral) hypersensitivity and increased the thickness of the submucosal and muscle layers of the small intestine. In vincristine-treated animals, MSG partially prevented gastrointestinal dysmotility and reduced visceral sensitivity but did not improve structural alterations of the small intestine. CONCLUSIONS & INFERENCES: MSG could be used as an adjuvant to conventional treatments to improve some gastrointestinal dysfunctions caused by chemotherapy.

Neuro-Gastro-Cannabinology: A Novel Paradigm for Regulating Mood and Digestive Health.

The maintenance of homeostasis in the gastrointestinal (GI) tract is ensured by the presence of the endocannabinoid system (ECS), which regulates important physiological activities, such as motility, permeability, fluid secretion, immunity, and visceral pain sensation. Beside its direct effects on the GI system, the ECS in the central nervous system indirectly regulates GI functions, such as food intake and energy balance. Mounting evidence suggests that the ECS may play an important role in modulating central neurotransmission which affects GI functioning. It has also been found that the interaction between the ECS and microbiota affects brain and gut activity in a bidirectional manner, and a number of studies demonstrate that there is a strong relationship between GI dysfunctions and mood disorders. Thus, microbiota can regulate the tone of the ECS. Conversely, changes in intestinal ECS tone may influence microbiota composition. In this mini-review, we propose the concept of neuro-gastro-cannabinology as a novel and alternative paradigm for studying and treating GI disorders that affect mood, as well as mood disorders that imbalance GI physiology. This concept suggests the use of prebiotics or probiotics for improving the tone of the ECS, as well as the use of phytocannabinoids or endocannabinoid-like molecules, such as palmitoylethanolamide, to restore the normal intestinal microbiota. This approach may be effective in ameliorating the negative effects of GI dysfunctions on mood and/or the effects of mood disorders on digestive health.

Effect of the Cannabinoid Agonist WIN 55,212-2 on Neuropathic and Visceral Pain Induced by a Non-Diarrheagenic Dose of the Antitumoral Drug 5-Fluorouracil in the Rat.

5-fluorouracil (5-FU) is an antineoplastic drug used to treat colorectal cancer, but it causes, among other adverse effects, diarrhea and mucositis, as well as enteric neuropathy, as shown in experimental animals. It might also cause neuropathic pain and alterations in visceral sensitivity, but this has not been studied in either patients or experimental animals. Cannabinoids have antimotility and analgesic effects and may alleviate 5-FU-induced adverse effects. Our aim was to evaluate the effects of the cannabinoid agonist WIN 55,212-2 on neuropathic and visceral pain induced by a non-diarrheagenic dose of 5-FU. Male Wistar rats received a dose of 5-FU (150 mg/kg, ip) and gastrointestinal motility, colonic sensitivity, gut wall structure and tactile sensitivity were evaluated. WIN 55,212-2 (WIN) was administered to evaluate its effect on somatic (50-100 µg ipl; 1 mg/kg, ip) and visceral (1 mg/kg, ip) sensitivity. The cannabinoid tetrad was used to assess the central effects of WIN (1 mg/kg, ip). 5-FU decreased food intake and body weight gain, produced mucositis and thermal hyperalgesia, but these effects were reduced afterwards, and were not accompanied by diarrhea. Tactile mechanical allodynia was also evident and persisted for 15 days. Interestingly, it was alleviated by WIN. 5-FU tended to increase colonic sensitivity whereas WIN reduced the abdominal contractions induced by increasing intracolonic pressure in both control and 5-FU-treated animals. Importantly, the alleviating effects of WIN against those induced by 5-FU were not accompanied by any effect in the cannabinoid tetrad. The activation of the peripheral cannabinoid system may be useful to alleviate neuropathic and visceral pain associated with antitumoral treatment.

Probiotics and Probiotic-like Agents against Chemotherapy-Induced Intestinal Mucositis: A Narrative Review.

Cancer chemotherapy has allowed many patients to survive, but not without risks derived from its adverse effects. Drugs, such as 5-fluorouracil, irinotecan, oxaliplatin, methotrexate, and others, as well as different drug combinations trigger intestinal mucositis that may cause or contribute to anorexia, pain, diarrhea, weight loss, systemic infections, and even death. Dysbiosis is a hallmark of chemotherapy-induced intestinal mucositis and diarrhea, and, therefore, strategies aimed at modulating intestinal microbiota may be useful to counteract and prevent those dreadful effects. This narrative review offers an overview of the studies performed to test the efficacy of probiotics and probiotic-like agents against chemotherapy-induced intestinal mucositis and its consequences. Microbiota modulation through the oral administration of different probiotics (mainly strains of Lactobacillus and Bifidobacterium), probiotic mixtures, synbiotics, postbiotics, and paraprobiotics has been tested in different animal models and in some clinical trials. Regulation of dysbiosis, modulation of epithelial barrier permeability, anti-inflammatory effects, modulation of host immune response, reduction of oxidative stress, or prevention of apoptosis are the main mechanisms involved in their beneficial effects. However, the findings are limited by the great heterogeneity of the preclinical studies and the relative lack of studies in immunocompromised animals, as well as the scarce availability of results from clinical trials. Despite this, the results accumulated so far are promising. Hopefully, with the aid of these agents, intestinal mucositis will be less impactful to the cancer patient in the near future.

Radiographic and histopathological study of gastrointestinal dysmotility in lipopolysaccharide-induced sepsis in the rat.

BACKGROUND: Sepsis is a highly incident condition in which a cascade of proinflammatory cytokines is involved. One of its most frequent consequences is ileus, which can increase mortality. Animal models such as that induced by systemic administration of lipopolysaccharide (LPS) are useful to deeply evaluate this condition. The effects of sepsis on the gastrointestinal (GI) tract have been explored but, to our knowledge, in vivo studies showing the motor and histopathological consequences of endotoxemia in an integrated way are lacking. Our aim was to study in rats the effects of sepsis on GI motility, using radiographic methods, and to assess histological damage in several organs. METHODS: Male rats were intraperitoneally injected with saline or E. coli LPS at 0.1, 1, or 5 mg kg-1 . Barium sulfate was intragastrically administered, and X-rays were performed 0-24 h afterwards. Several organs were collected for organography, histopathology, and immunohistochemistry studies. KEY RESULTS: All LPS doses caused gastroparesia, whereas changes in intestinal motility were dose-and time-dependent, with an initial phase of hypermotility followed by paralytic ileus. Lung, liver, stomach, ileum, and colon (but not spleen or kidneys) were damaged, and density of neutrophils and activated M2 macrophages and expression of cyclooxygenase 2 were increased in the colon 24 h after LPS 5 mg kg-1 . CONCLUSIONS AND INFERENCES: Using radiographic, noninvasive methods for the first time, we show that systemic LPS causes dose-, time-, and organ-dependent GI motor effects. Sepsis-induced GI dysmotility is a complex condition whose management needs to take its time-dependent changes into account.

New Pieces for an Old Puzzle: Approaching Parkinson's Disease from Translatable Animal Models, Gut Microbiota Modulation, and Lipidomics.

Parkinson's disease (PD) is a severe neurodegenerative disease characterized by disabling motor alterations that are diagnosed at a relatively late stage in its development, and non-motor symptoms, including those affecting the gastrointestinal tract (mainly constipation), which start much earlier than the motor symptoms. Remarkably, current treatments only reduce motor symptoms, not without important drawbacks (relatively low efficiency and impactful side effects). Thus, new approaches are needed to halt PD progression and, possibly, to prevent its development, including new therapeutic strategies that target PD etiopathogeny and new biomarkers. Our aim was to review some of these new approaches. Although PD is complex and heterogeneous, compelling evidence suggests it might have a gastrointestinal origin, at least in a significant number of patients, and findings in recently developed animal models strongly support this hypothesis. Furthermore, the modulation of the gut microbiome, mainly through probiotics, is being tested to improve motor and non-motor symptoms and even to prevent PD. Finally, lipidomics has emerged as a useful tool to identify lipid biomarkers that may help analyze PD progression and treatment efficacy in a personalized manner, although, as of today, it has only scarcely been applied to monitor gut motility, dysbiosis, and probiotic effects in PD. Altogether, these new pieces should be helpful in solving the old puzzle of PD.

Maternal Supplementation with N-Acetylcysteine Modulates the Microbiota-Gut-Brain Axis in Offspring of the Poly I:C Rat Model of Schizophrenia.

The microbiota-gut-brain axis is a complex interconnected system altered in schizophrenia. The antioxidant N-acetylcysteine (NAC) has been proposed as an adjunctive therapy to antipsychotics in clinical trials, but its role in the microbiota-gut-brain axis has not been sufficiently explored. We aimed to describe the effect of NAC administration during pregnancy on the gut-brain axis in the offspring from the maternal immune stimulation (MIS) animal model of schizophrenia. Pregnant Wistar rats were treated with PolyI:C/Saline. Six groups of animals were studied according to the study factors: phenotype (Saline, MIS) and treatment (no NAC, NAC 7 days, NAC 21 days). Offspring were subjected to the novel object recognition test and were scanned using MRI. Caecum contents were used for metagenomics 16S rRNA sequencing. NAC treatment prevented hippocampal volume reduction and long-term memory deficits in MIS-offspring. In addition, MIS-animals showed lower bacterial richness, which was prevented by NAC. Moreover, NAC7/NAC21 treatments resulted in a reduction of proinflammatory taxons in MIS-animals and an increase in taxa known to produce anti-inflammatory metabolites. Early approaches, like this one, with anti-inflammatory/anti-oxidative compounds, especially in neurodevelopmental disorders with an inflammatory/oxidative basis, may be useful in modulating bacterial microbiota, hippocampal size, as well as hippocampal-based memory impairments.

Radiographic assessment of the impact of sex and the circadian rhythm-dependent behaviour on gastrointestinal transit in the rat.

Relatively little is known about the influence of sex and the circadian rhythm on gastrointestinal transit. However, these factors could have an important impact on aspects such as digestion, oral absorption of drugs or the clinical manifestation of gastrointestinal diseases, among others. Remarkably, preclinical models have scarcely taken these factors into consideration. In this study, we assessed the gastrointestinal transit of young adult Wistar Han rats of both sexes, under normal and inverted light cycle. To do this, serial radiographs were taken for 24 h (T0-T24) after intragastric barium administration and subsequently analysed to construct transit curves for each gastrointestinal region. Under a normal light cycle, transit curves were similar, except for a slower transit in females compared with males from T8 to T24. Under the inverted cycle, there was a significant acceleration in stomach emptying (similar in both sexes), emptying of the small intestine (even faster in females) and filling of the caecum and colon (which was also even faster in females). This study confirms, using X-ray non-invasive methods for the first time, that both sex and circadian rhythm (probably through its effect on behaviour) influence gastrointestinal transit in laboratory animals.

Evaluation of the Effects of Instant Cascara Beverage on the Brain-Gut Axis of Healthy Male and Female Rats.

Instant cascara (IC) is a sustainable beverage obtained from dried coffee cherry pulp, rich in nutrients and bioactive compounds. The present research aimed to determine the effects of IC on general health and brain-gut axis parameters of healthy female and male rats. Wistar rats were exposed to IC (10 mg/mL) in their drinking water for 3 weeks. Body weight and solid and liquid intakes were monitored as indicators of food safety. Gastrointestinal transit was radiographically evaluated one day (acute) and 3 weeks (chronic) after the start of IC exposure. Locomotor activity, anxiety, and anhedonia of the animals after 3 weeks of treatment was also studied. Overall, compared to water-exposed animals, IC significantly increased food intake in males (p < 0.0001) and liquid intake in females (p < 0.05) without changes in body weight in either case. IC did not significantly modify gastrointestinal motility parameters after its acute or repeated intake and did not cause any significant behavioral alterations in males or females (p > 0.05). In conclusion, repeated intake of IC at the studied concentration did not negatively affect brain-gut axis functions of healthy male and female rats. Anxiety behavior, diarrhea, constipation, abnormal weight modifications, or other typical effects of toxicity were not observed in animals treated with the new powdered beverage, suggesting its food safety under the studied conditions.

Contractility of isolated colonic smooth muscle strips from rats treated with cancer chemotherapy: differential effects of cisplatin and vincristine.

Background: Certain antineoplastic drugs cause gastrointestinal disorders even after the end of treatment. Enteric neuropathy has been associated with some of these alterations. Our goal was to assess the impact of repeated treatment with cisplatin and vincristine on the contractility of circular and longitudinal muscle strips isolated from the rat colon. Methods: Two cohorts of male rats were used: in cohort 1, rats received one intraperitoneal (ip) injection of saline or cisplatin (2 mg kg-1 week-1) on the first day of weeks 1-5; in cohort 2, rats received two cycles of five daily ip injections (Monday to Friday, weeks 1-2) of saline or vincristine (0.1 mg kg-1 day-1). Body weight and food and water intake were monitored throughout the study. One week after treatment, responses of colonic smooth muscle strips to acetylcholine (10-9-10-5 M) and electrical field stimulation (EFS, 0.1-20 Hz), before and after atropine (10-6 M), were evaluated in an organ bath. Results: Both drugs decreased body weight gain. Compared to saline, cisplatin significantly decreased responses of both longitudinal and circular smooth muscle strips to EFS, whereas vincristine tended to increase them, although in a non-significant manner. No differences were observed in the muscle response to acetylcholine. Atropine abolished the contractile responses induced by acetylcholine, although those induced by EFS were only partially reduced in the presence of atropine. Conclusion: The findings suggest that although both drugs cause the development of enteric neuropathy, this seems to have a functional impact only in cisplatin-treated animals. Understanding the effects of chemotherapy on gastrointestinal motor function is vital for enhancing the quality of life of cancer patients.

Molecular Targets to Alleviate Enteric Neuropathy and Gastrointestinal Dysfunction.

Enteric neuropathy underlies long-term gastrointestinal (GI) dysfunction associated with several pathological conditions. Our previous studies have demonstrated that structural and functional changes in the enteric nervous system (ENS) result in persistent alterations of intestinal functions long after the acute insult. These changes lead to aberrant immune response and chronic dysregulation of the epithelial barrier. Damage to the ENS is prognostic of disease progression and plays an important role in the recurrence of clinical manifestations. This suggests that the ENS is a viable therapeutic target to alleviate chronic intestinal dysfunction. Our recent studies in preclinical animal models have progressed into the development of novel therapeutic strategies for the treatment of enteric neuropathy in various chronic GI disorders. We have tested the anti-inflammatory and neuroprotective efficacy of novel compounds targeting specific molecular pathways. Ex vivo studies in human tissues freshly collected after resection surgeries provide an understanding of the molecular mechanisms involved in enteric neuropathy. In vivo treatments in animal models provide data on the efficacy and the mechanisms of actions of the novel compounds and their combinations with clinically used therapies. These novel findings provide avenues for the development of safe, cost-effective, and highly efficacious treatments of GI disorders.

The Enteric Glia and Its Modulation by the Endocannabinoid System, a New Target for Cannabinoid-Based Nutraceuticals?

The enteric nervous system (ENS) is a part of the autonomic nervous system that intrinsically innervates the gastrointestinal (GI) tract. Whereas enteric neurons have been deeply studied, the enteric glial cells (EGCs) have received less attention. However, these are immune-competent cells that contribute to the maintenance of the GI tract homeostasis through supporting epithelial integrity, providing neuroprotection, and influencing the GI motor function and sensation. The endogenous cannabinoid system (ECS) includes endogenous classical cannabinoids (anandamide, 2-arachidonoylglycerol), cannabinoid-like ligands (oleoylethanolamide (OEA) and palmitoylethanolamide (PEA)), enzymes involved in their metabolism (FAAH, MAGL, COX-2) and classical (CB1 and CB2) and non-classical (TRPV1, GPR55, PPAR) receptors. The ECS participates in many processes crucial for the proper functioning of the GI tract, in which the EGCs are involved. Thus, the modulation of the EGCs through the ECS might be beneficial to treat some dysfunctions of the GI tract. This review explores the role of EGCs and ECS on the GI tract functions and dysfunctions, and the current knowledge about how EGCs may be modulated by the ECS components, as possible new targets for cannabinoids and cannabinoid-like molecules, particularly those with potential nutraceutical use.

Cultural Adaptation and Validation of the Premature Infant Pain Profile-Revised (PIPP-R) Pain Measurement Scale: Research Protocol.

INTRODUCTION: The main objective of this study is to validate the PIPP-R scale (Premature Infant Pain Profile-Revised) for measuring neonatal pain in the Spanish hospital setting. MATERIALS AND METHODS: The original scale will be translated from English into Spanish and a consensus translation will be prepared by the research team, which will be back-translated from Spanish into English. The content validity of the Spanish version of the scale will be measured using the Delphi method. Subsequently, a multicenter observational study will be conducted to assess construct validity, internal consistency, and intra-observer and inter-observer agreement. Pain will be assessed by comparing scores for a specific non-painful procedure with those for a specific painful procedure. The sample will include 300 subjects in intensive care and intermediate care units, who will be equally distributed among the participating hospitals. The subjects will be stratified into three groups by gestational age. DISCUSSION: The original version of the PIPP-R scale is useful for objectively assessing neonatal acute and procedural pain from a gestational age of 25 weeks and over. It is important to culturally adapt the original validated scale and to test its validity and reliability in the Spanish healthcare context. The results of this study may represent significant progress in pain management.

Short-term stress significantly decreases morphine analgesia in trigeminal but not in spinal innervated areas in rats.

Plenty information exists regarding the effects of chronic stress, although few data exist on the effects of short-lasting stressors, which would mimic daily challenges. Differences in craniofacial and spinal nociception have been observed, thus those observations obtained in spinally innervated areas cannot be directly applied to the orofacial region. Although, opioids are considered amongst the most effective analgesics, their use is sometimes hampered by the constipation they induce. Thus, our aims were to study if a short-lasting stressor, forced swim stress (FSS), modifies nociception, morphine antinociception and constipation in rats. Animals were submitted to 10-20 min of FSS for three days, nociception and gastrointestinal transit were studied 24 h after the last swimming session. Nociception and morphine (0.6-5 mg/kg) antinociception were evaluated in the formalin and hypertonic saline tests in the orofacial area and limbs. Morphine-induced modifications in the GI transit were studied through radiographic techniques. Naloxone was administered, before each swimming session, to analyse the involvement of the endogenous opioid system on the effect of stress. Overall, stress did not alter nociception, although interestingly it reduced the effect of morphine in the orofacial tests and in the inflammatory phase of the formalin tests. Naloxone antagonized the effect of stress and normalized the effect of morphine. Stress did not modify the constipation induced by morphine. Opioid treatment may be less effective under a stressful situation, whilst adverse effects, such as constipation, are maintained. The prevention of stress may improve the level of opioid analgesia.

Effects of Commercial Probiotics on Colonic Sensitivity after Acute Mucosal Irritation.

Gastrointestinal pathologies associated with abdominal pain, such as irritable bowel syndrome or inflammatory bowel disease, lack sufficiently effective treatments. In our study we have used a rat model of visceral pain (72 animals; n = 8-13 per experimental group) to analyze the consequences of intracolonic administration of the irritant acetic acid on visceral sensitivity, histology of the colonic wall, and inflammatory response. Moreover, we have studied the possible beneficial effects of a pretreatment with a commercial probiotic (Actimel®). Contrary to expectations, acetic acid application (7 cm proximal to the anus) decreased the nociceptive response to intracolonic mechanical stimulation, with a slight increase in the histological damage of colonic mucosa. The intensity of these changes depended on the concentration (4% or 0.6%) and the time of application (30 or 60 min). Pretreatment with probiotics (by daily gavage, for 1 week) normalized the values obtained in the visceral sensitivity test but revealed an increase in the number of macrophages. These results suggest a possible activation of inhibitory mechanisms early after colonic irritation, not previously described (which need further experimental confirmation), and the ability of probiotics to normalize the effects of acetic acid. In addition, pretreatment with probiotics has a direct effect on immune functions, stimulating macrophagic activity.

Mechanisms of Chemotherapy-Induced Neurotoxicity.

Since the first clinical trials conducted after World War II, chemotherapeutic drugs have been extensively used in the clinic as the main cancer treatment either alone or as an adjuvant therapy before and after surgery. Although the use of chemotherapeutic drugs improved the survival of cancer patients, these drugs are notorious for causing many severe side effects that significantly reduce the efficacy of anti-cancer treatment and patients' quality of life. Many widely used chemotherapy drugs including platinum-based agents, taxanes, vinca alkaloids, proteasome inhibitors, and thalidomide analogs may cause direct and indirect neurotoxicity. In this review we discuss the main effects of chemotherapy on the peripheral and central nervous systems, including neuropathic pain, chemobrain, enteric neuropathy, as well as nausea and emesis. Understanding mechanisms involved in chemotherapy-induced neurotoxicity is crucial for the development of drugs that can protect the nervous system, reduce symptoms experienced by millions of patients, and improve the outcome of the treatment and patients' quality of life.