Small bowel changes associated with vincristine sulfate treatment: an experimental study in the guinea pig

Protective effect of oxytocin on vincristine-induced gastrointestinal dysmotility in mice

Aims: Vincristine (VCR), an antineoplastic drug, induces peripheral neuropathy characterized by nerve damage, limiting its use and reducing the quality of life of patients. VCR causes myenteric neuron damage, inhibits gastrointestinal motility, and results in constipation or paralytic ileus in patients. Oxytocin (OT) is an endogenous neuropeptide produced by the enteric nerve system, which regulates gastrointestinal motility and exerts neuroprotective effects. This study aimed to investigate whether OT can improve VCR-induced gastrointestinal dysmotility and evaluate the underlying mechanism. Methods: Mice were injected either with saline or VCR (0.1 mg/kg/d, i. p.) for 14 days, and OT (0.1 mg/kg/d, i.p.) was applied 1 h before each VCR injection. Gastrointestinal transit and the contractile activity of the isolated colonic segments were assessed. The concentration of OT in plasma was measured using ELISA. Immunofluorescence staining was performed to analyze myenteric neurons and reactive oxygen species (ROS) levels. Furthermore, the indicators of oxidative stress were detected. The protein expressions of Nrf2, ERK1/2, P-ERK1/2, p38, and P-p38 in the colon were tested using Western blot. Results: VCR reduced gastrointestinal transit and the responses of isolated colonic segments to electrical field stimulation and decreased the amount of neurons. Furthermore, VCR reduced neuronal nitric oxide synthase and choline acetyltransferase immunopositive neurons in the colonic myenteric nerve plexus. VCR increased the concentration of OT in plasma. Exogenous OT pretreatment ameliorated the inhibition of gastrointestinal motility and the injury of myenteric neurons caused by VCR. OT pretreatment also prevented the decrease of superoxide dismutase activity, glutathione content, total antioxidative capacity, and Nrf2 expression, the increase of ROS levels, and the phosphorylation of ERK1/2 and p38 MAPK following VCR treatment. Conclusion: Our results suggest that OT pretreatment can protect enteric neurons from VCR-induced injury by inhibiting oxidative stress and MAPK pathways (ERK1/2, p38). This may be the underlying mechanism by which it alleviates gastrointestinal dysmotility.

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.

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.

Impact of chemotherapy-induced enteric nervous system toxicity on gastrointestinal mucositis

PURPOSE OF REVIEW

Chemotherapy is a first-line treatment for many cancers; however, its use is hampered by a long list of side-effects. Gastrointestinal mucositis is a common and debilitating side-effect of anticancer therapy contributing to dose reductions, delays and cessation of treatment, greatly impacting clinical outcomes. The underlying pathophysiology of gastrointestinal mucositis is complex and likely involves several overlapping inflammatory, secretory and neural mechanisms, yet research investigating the role of innervation in gastrointestinal mucositis is scarce. This review provides an overview of the current literature surrounding chemotherapy-induced enteric neurotoxicity and discusses its implications on gastrointestinal mucositis.

RECENT FINDINGS

Damage to the intrinsic nervous system of the gastrointestinal tract, the enteric nervous system (ENS), occurs following chemotherapeutic administration, leading to altered gastrointestinal functions. Chemotherapeutic drugs have various mechanisms of actions on the ENS. Oxidative stress, direct toxicity and inflammation have been identified as mechanisms involved in chemotherapy-induced ENS damage. Enteric neuroprotection has proven to be beneficial to reduce gastrointestinal dysfunction in animal models of oxaliplatin-induced enteric neuropathy.

SUMMARY

Understanding of the ENS role in chemotherapy-induced mucositis requires further investigation and might lead to the development of more effective therapeutic interventions for prevention and treatment of chemotherapy-induced gastrointestinal side-effects.

Neuropathology of paediatric chronic intestinal pseudo-obstruction and related animal models

Chronic intestinal pseudo-obstruction (CIP) in paediatric patients is due to heterogeneous aetiologies that include primary disorders of the enteric nervous system. These conditions are poorly delineated by contemporary diagnostic approaches, in part because the complex nature of the enteric nervous system may shelter significant physiological defects behind subtle or quantitative anatomical changes. Until recently, relatively few experimental animal models existed for paediatric CIP. However, the availability of rodent models, particularly novel mutants created in the last few years by genetic manipulations, has brought unprecedented opportunities to investigate molecular, cellular, physiological, and histological details of enteric neuropathology. Information gleaned from studies of these animals is likely to change diagnostic and therapeutic approaches to paediatric CIP and related conditions.

Effect of erythromycin on L-threonine transport in rabbit jejunum in vitro

Several antibiotics characterized by different molecular structures are known to affect some intestinal activities. Some of them have been described as inhibitors of the intestinal sugar and amino acid transport with different mechanisms. Erythromycin (EM) is a macrolide antibiotic acting as a motilin agonist and thus stimulating the gastrointestinal motor activity. Since several substances which increase the motor activity of the gastrointestinal tract may produce effects on the intestinal absorption of nutrients, the present study has been carried out to determine whether erythromycin affects the L-threonine intestinal absorption. The results obtained indicate that erythromycin diminishes the L-threonine intestinal transport, probably at the mucosal border level. Two groups of experiments carried out, with Na(+)-deprived medium and ouabain-enriched medium, might indicate that erythromycin action could be due to either a direct or an indirect action on the Na(+)-dependent L-threonine transport located in the brush border.

Acute subjective morbidity after cisplatin-based combination chemotherapy in patients with testicular cancer: a prospective study

In a randomized trial, 22 patients with metastatic testicular cancer used low-fibre diet during and after their first cycle of cisplatin and vinblastine containing combination chemotherapy, in order to reduce the acute gastrointestinal post-treatment morbidity (Group 1). Their subjective morbidity, including aspects of general well-being, was compared to 23 comparable patients having no diet restrictions (Group 2). A third similarly composed group consisted of 10 testicular cancer patients without diet restrictions, who received etoposide (VP-16) instead of vinblastine. Low-fibre diet did not reduce the frequency or severity of the acute post-treatment gastrointestinal morbidity. Severe constipation and/or paralytic ileus was observed in 23 patients in Groups 1 and 2 and necessitated short-term hospitalization in 14. The substitution of vinblastine by etoposide resulted in a significant reduction of the acute gastrointestinal morbidity and in a considerable improvement of the patients' general well-being. It is concluded that VP-16 should be given instead of vinblastine to patients receiving cisplatin-based combination chemotherapy in order to maintain an optimal quality of life during cytostatic treatment. This study also indicates that the frequency and severity of subjective treatment-related morbidity often is underestimated by retrospective routine clinical assessment, and should preferably be assessed prospectively by frequently applied patients' questionnaires.

Small bowel function in acute lymphoblastic leukaemia

Small bowel function before, during, and after treatment for acute lymphoblastic leukaemia was studied in 26 children. A significant impairment of D-xylose absorption was found during treatment. Permeability studies showed a significant decrease in mannitol and a significant increase in lactulose concentrations; five of 20 children tested had evidence of lactose malabsorption, three of whom were symptomatic. Intestinal function abnormalities were greater in children whose methotrexate treatments were separated by 7 day than by 16 day intervals. Only five (19%) children had no abnormal tests. Abnormalities of small bowel function may be treatment induced and this has implications for morbidity from gastrointestinal symptoms, impairment of the mucosal barrier, and malabsorption of both nutrients and drugs leading to malnutrition and suboptimal drug concentrations.

Jejunal crypt cell abnormalities associated with methotrexate treatment in children with acute lymphoblastic leukaemia

Jejunal mucosal crypts were examined in jejunal biopsies from eight children with acute lymphoblastic leukaemia who had recently received methotrexate treatment. By comparison with biopsies from children under investigation for suspected malabsorption crypt mitosis was significantly reduced and showed a negative correlation with the dose of methotrexate given prior to biopsy. The three major cell types were studied under light and transmission electron microscopy. Gut endocrine cells were unaffected by therapy and immature crypt enterocytes showed only patchy degenerative abnormalities. By contrast a number of Paneth cells showed striking structural alterations with vacuolar dilatation of the cytoplasm. The extent of this correlated with the time since methotrexate treatment rather than its dose and may have been a functional response rather than of a toxic nature.

[Cytostatica and small intestine (author's transl)]

Cytostatica not only suppress proliferation in tumor cells but it also checks proliferation in small intestinal epithelium. The consequence is cell reduction and damage resulting in a diminished function. Because of the high reserve capacity of the small intestinal epithelium, clinical signs of diminished function are mostly seen after repeated high doses or one extremely high doses of Cytostatica. Although there is abundant information on the effect of Cytostatica on the small intestinal epithelium (cell turnover, morphology, digestive enzymes and absorption) there are other areas that are as urgent for the interested clinician to work on: 1. Would it be possible to coincide the dose and dosage rate with the cell cycles to reduce the chance of damage to small intestinal epithelium? 2. Which role has the luminal content when there is damage from Cytostatica? Is it possible to concentrate on changing the luminal contents (antibiotics, "elemental diet", cultivate desirable microflora, etc.) Therefore diminishing the damage from Cytostatica? 3. How would Cytostatica influence the barrier function on the intestinal wall? Should the patient on Cytostatica therapy receive special protection against intestinal infection? 4. Does Cytostatica affect the biotransformation in the small intestinal epithelium, especially when taken orally? How important is this biotransformation in small intestinal epithelium damaged by Cytostatica therapy? 5. What factors determine the regeneration of the small intestinal epithelium after Cytostatica damage?

Toxicology of vindesine (desacetyl vinblastine amide) in mice, rats, and dogs

Comparative acute intravenous toxicity studies of vinblastine sulfate (VLB), vincristine sulfate (VCR), and vindesine in mice and rats indicated that vindesine was more toxic than VLB and less toxic than VCR. Rats were able to tolerate larger repeated doses of vindesine than dogs. Rats given intravenous doses totaling 0.15 mg/kg-wk vindesine for 3 months developed no remarkable signs of toxicity. Doses of 0.3 mg/kg-wk or greater produced anorexia, depressed blood cell counts, atrophic intestinal mucosa, inhibition of spermatogenesis, extramedullary hematopoiesis, and infections. Dogs were given total weekly intravenous doses of 0.04, 0.08, 0.1, or 0.16 mg/kg vindesine for 3 months. The only observed effect in the two lower dose groups was inhibition of spermatogenesis. Groups receiving 0.1 or 0.16 mg/kg developed leukopenia, slight erythropenia, inhibition of spermatogenesis, focal skeletal muscle degeneration, elevated lactic dehydrogenase, and an increase in bone marrow myeloid: erythroid ratio. No evidence of functional or structural changes in neural tissues was found. The above effects are common to animals given VCR at lower doses and for a shorter test period. It is therefore concluded that vindesine is less toxic in animals than VCR.