Effects Of Fucoidan On Helicobacter Pylori Colonization On The Surface Of Gastric Mucosa

Objective:Establishing the mouse model of Helicobacter pylori（HP）infection to investigate how HP colonization was influenced by fucoidan extracted from the brown alga on the surface of gastric mucosa,and to explore whether fucoidan has a protective effect on the gastric mucosa after HP infection.Methods:22 male C57BL/6 mice were at 8 weeks of age,and they were randomly divided into four groups,including A（Control group）,B（HP group）,C（Fucoidan group）,D（HP+Fucoidan group）,E（Fucoidan+HP group）,the whole experiment lasted 5 weeks.The control group received an equal volume of sterilized double distilled water（dd H₂O）,mice in the B group were gavaged with HP,the C group received fucoidan in an equal volume with other groups,the D group was mice firstly gavaged with fucoidan for 2 weeks followed by HP infection for 3 weeks,and the E group were infected with HP firstly for 3weeks followed by fucoidan intake for another 2 weeks.Mice in each group were sacrificed by cervical dislocation after the experiment,gastric tissue hematoxylin-eosin staining（HE）scores and gastric tissue immunohistochemical scores were subsequently calculated.Discrepancies between gastric tissues in four groups were analyzed by sequencing and analysis of 16S ribosomal RNA gene.Result:（1）Comparison of body weight growth rate across the four groups.Compared with group A,the body weight growth rate in group B and group D was significantly lower（P<0.05）.Compared to group B,the mice in group C and group E had a significantly higher body weight growth rate.In Group C,with a lower growth rate compared to group D（P<0.05）,however,there was no difference between group C and E（P>0.05）.And the results also showed that the body weight growth rate was significantly higher in the E group compared with the D group（P<0.05）.（2）Disc diffusion method.No Bacteriostatic ring is around the filter paper disks with water or fucoidan.A bacteriostatic ring that reached a diameter of approximately 3.5-cm was shown around the levofloxacin filter paper disks.（3）Inflammation scores in gastric mucosa through Hematoxylin-eosin staining（HE）method.As compared to group A,inflammation histological scores for individual mice in the other 4 groups were higher（P<0.01）.Compared with group B,mice in the C and the D group showed lower inflammatory levels（P<0.05）,while in the E group,no significant statistical difference was seen（P>0.05）.Compared to group E,the mice in group D showed a higher inflammatory level（P<0.05）.（4）（1）Haematoxylin and eosin stained sections under high magnification microscope to assess HP colonization scores in the stomach:Compared with group A,the HP colonization score showed higher in group B,D and E（P<0.05）.In Group D,with a lower colonization score compared to group B（P<0.05）and there was a lower colonization score in group E（P<0.01）compared to group B.（2）Immunohistochemical staining stained sections under high magnification microscope to assess HP colonization scores in the stomach:Compared with group A,the score showed higher in groups B,D and E（P<0.05）.Compared with group B,the immunohistochemical staining score was significantly lower in the D and E groups（P<0.05）.（5）The microbiota on the surface of gastric mucosa was analyzed by using 16S rRNA gene sequencing.In the B（HP）group,the relative abundance of Gardnerella was significantly higher compared with the other four groups（P<0.05）.As compared to the other four groups,the relative abundance of Chryseobacterium in group D was significantly higher（P<0.05）.In the C,D and E group,with a lower relative abundance of two harmful bacteria（Alistipe,Erysipelatoclostridium）compared to group A and B（P<0.05）.The relative abundance of Alistipe was significantly higher in the B and E group than in the C group（P<0.05）.Statistically significant lower relative abundance of Lachnospiraceae＿NK4A136＿group was observed in Groups C in comparison to Group B（P<0.05）,while the lower relative abundance of Bifidobacterium was seen in Groups C compared to Group E（P<0.05）.The relative abundance of Faecalibaculum in samples D and E was much higher than those in either sample A or B（P<0.05）.Conclusion:（1）Fucoidan intervention could significantly promote the increase of body mass of mice;（2）Fucoidan intervention could significantly prevent HP colonization and lower inflamma-tion levels in the stomach;（3）With the intervention of fucoidan,the abundance of beneficial bacteria were increased while the abundance of pathogenic bacteria were decreased;（4）Results also indicated that fucoidan had no bacteriostatic effect with the dose range used at a specific period of timein the present study.