| background and objectiveIn recent years, with the development of modern medicine ,the survival rates for childhood cancer have risen from 10% to almost 80%. Outcome in acute lymphoblastic leukemia (ALL) has gone from a 6-month median survival to an 80% overall cure rate. The result should be attributed to the improvement of treatment and the development of new drugs.High-methotrexate(HD-MTX) program is not only effective to prevent out-myeloid leukemia but also improved the rate of event-free survival in ALL. Compare with radiotherapy,HDMTX has a good long-term effect and takes no impacts on children's intelligence and mental growth.So it has been a component of extramedullary prevention and systemic chemotherapy.MTX is an anti-metabolite that attacks the cell in its S phase and disrupts DNA synthesis. It not only inhibits the leukemia cells,but also the epithelial cell which located in gastrointestinal mucosa and skin .It inhibits epithelial proliferation and enterocyte function and increases the risk of gut-associated sepsis. It is reported that there is 40% incidence of mucositis which increases with the number of treatment cycles and who receive high doses of chemotherapy have a 76% chance of getting mucositis. Mucositis not only increases with the pain and cost,but also affect the progress of chemotherapy or mortality. So how to relieve the degree and the incidence of mucositis has been becoming a major problem.Probiotics is a kind of beneficial bacteria on human body,including Lactobacillus,Bifidobacterium and Gram-positive coccus. As the major component of human gut microflora, probiotics is generally applied to treat disease of digestive system.,such as diarrhoea induced by pneumonia of newborn,neonatal jaundice, irritable bowel syndrome and so on. It has been found that probiotics can enhance the defense function of gastrointestinal tract and play the anti-infective and anti-inflammatory roles by immune rejection and immunoregulation. Recently researchers found probiotics can prevent the inflammation obviously by degrading the inflammatory cytokines such as tumour necrosis factor(TNF-α),interleukin-6(IL-1β) level in the early of Ulcerative colitis and necrotizing enterocolitis. Besides probiotics can increase the secrets of SIgA,enhance immunological function.,and maintain the enteric mucosal barrier .The mechanism of chemotherapy-induced mucositis is the activation of transcription factors,in particular nuclear factor-κB (NF-κB) ,which results in the production of pro-inflammatory cytokines,including TNF-α,IL-1β,IL-6 and so on. And this results in original cell death,apoptosis and tissue damage. There are rarely reports about weather administration of probiotics can enhance local immunologic barrier and mitigate mucositis induced by chemotherapy. So we develop the animal model for gastrointestinal mucositis in rats induced by MTX and investigate weather the administration of probiotics is effective to the mucositis.MethodsRats were randomly assigned to three groups (n = 18 /group): normal control (group A), MTX +saline (group B), MTX+ probiotics (group C). Mucositis was induced by intraperitoneal injection of a single dose of MTX (100 mg/kg) on day 0, with saline as control. Probiotics was administered twice daily by orogastric gavage 2 days prior to MTX injection and continued until day 4, with saline as placebo. Probiotics is Live Combined Bifidobacterium Lactobacillus and Streptococcus thermophilus Tablets'Oral, containing Bifidobacterium longum of 0.5×10~7CFU, Bacillus bulgaricus and Streptococcus thermophilus of 0.5×10~6CFU). 6 rats of each group were sacrificed on experimental day 1,3,5. And the following indexes were observed. Specimens from the proximal jejunum were collected and were stained withhaematoxylin and eosin (H&E) and immunohistochemical staining.Observation:1. The morphological change of jejunum. Proximal jejunum were stained with haematoxylin and eosin (H&E).Quantitative histological analyses were also utilized to measure the changes of crypt depth and villus height at the time course.2.Observation the expression of TNF-αin jejunum by immunohistochemistry. To the cell membrane and(or) the cytoplasm appeared brown particles for positive expression.3. Detection the content of SIgA on intestinal mucosal fluid by Elisa.4. Bacterial translocdtion from intestine was detected by bacterial culture of mesenteric lymph node.5. The survival of the experimented rats.Results1. MTX group shows the performance of small intestinal mucositis,and it is the most mucositis in the third day. It shows organizational structure with intestinal disorders,shorter villus,necrosis and shedding partly,crypt shallowing even disappearing. and substantial inflammatory cell infiltration. And the pathological changes reduce slightly on the fifth day. Probiotics can improve mucositis. The villous height and crypt depth at MTX group are lower than that of normal control. Probiotics can enhance the villous height and crypt depth obviously.2. Areas of staining corresponded with areas of surface epithelium and lamina propria. The jejunum of rat which received MTX group presented intense immunostaining for TNF-αon the surface epithelium. The treatment with probiotics reduced the immunostaining.3.MTX can reduce the content of SIgA on intestinal mucosal fluid. The content of SIgA in probiotics group is higher than MTX group.4. Bacterial translocdtion from intestine by bacterial culture of mesenteric lymph node in probiotics group was less than MTX group.5. Probiotics administration is associated with significantly increased survival of the rats.Conclusion1. HDMTX can induce typical mucositis. It appear obvious damage on the first day,and it is the most serious on the third day,appearing the shorten and coarsen villus, epithelial cell fallen off,and inflammatory cell infiltrated.2. Probiotics can mitigate mucositis by reducing the expression of TNF-αon the surface epithelium. increasing SIgA,and reducing bacterial culture.3. The administration of Probiotics can shorten the course of mucositis,lessen the death rate. It provided a theoretical basis for the administration of probiotics to prevent the side effect in chemotherapy. |
PDF Full Text Request