Effects Of Diammonium Glycyrrhizinate On Ulcerative Colitis In Rats

Background Ulcerative colitis (UC) is chronic non-specific intestinal inflammation and ulcerative lesions, which usually occurs in the rectum and the colon. The exact pathogenesis in UC is poorly understood. Its incidence has increased year by year at home and abroad. In recent years, it has made progress in the etiology of UC (including infection, genetics, immunology and so on), also in the pharmacotherapy, and some remedy have been used in experimental research and clinical treatment,such as the new 5-ASA praeparatums, immune response regulation agent (anti-CD3 antibody, visilizumab) and cytokine-control agent (anti-TNF-αmonoclonal antibody, infliximab), etc.The clinical applications of traditional drugs have been restricted, due to high incidence rate of adverse effect and higher cost. Therefore, it is important to seek for the safer and cheaper medication to treat UC effectively.Diammonium Glycyrrhizinate (DG), the third generation extract from the active ingredient of licorice, has many biological activities such as protecting membrane structure, anti-biological oxidation, regulating immune function and effecting endogenous steroid hormone. Because of its hormonelike anti-inflammatory effects, DG may be an effective treatment for UC, especially for the patients with hormonal resistance, corticoids dependent and with contraindication. So far, the research of the treatment of hepatitis by DG is widely reported. But the treatment of UC by DG is rarely reported and the mechanism is unknown. The topic is to investigate the effects of DG on UC in rats, to probe into its underlying mechanisms and to provide a theoretical basis for clinical application for treatment of UC.Objective To investigate the effects of diammonium glycyrrhizinate (DG) on ulcerative colitis (UC) in rats and to probe into its underlying mechanisms.Methods The rat colitis model was induced by 2,4-dinitrochlorobenzene (DNCB) and acetic acid. UC rats were randomly divided into one model group and four treatment groups (n=10 in each group).The rats in 5-aminosalicylic acid (5-ASA) group were given an enema with 5-ASA (100 mg/kg).The rats in DG group were given an enema with DG (40 mg/kg). The rats in combination of 5-ASA and DG group were given an enema with 5-ASA (100 mg/kg) (8:00) and DG (40 mg/kg) (16:00). The rats in combination of 5-ASA and dexamethasone group were given an enema with 5-ASA (100 mg/kg) (8:00) and dexamethasone (0.2 mg/kg) (16:00). Symptom of bowel complaint, hemafecia and the change of body weight were observed. After 7 days, blood were collected for serum level of interleukin-6 (IL-6), IL-4 analysis by radioimmunoassay and colon homogenate MPO, SOD analysis by colorimetric method. The colon histopathologies were explored with HE staining. The expression of nuclear factor (NF)-κB and iNOS in colonic mucosa were determined by immunohistochemistry.Results 1.Compared with normal control group, disease activity index (DAI), lesions of colonic mucosa, MPO activity, serum level of IL-6, NF-κB p65 expression and iNOS expression in colonic mucosa increased significantly, and serum level of IL-4, SOD activity decreased in model group (P<0.05). 2.After 7 days of treatment, compared with model group, DAI, lesions of colonic mucosa, MPO activity, serum level of IL-6, NF-κB p65 expression and iNOS expression in colonic mucosa decreased significantly, and serum level of IL-4, SOD activity increased in 5-ASA and DG group (P<0.05). 3. Compared with 5-ASA group or DG group, the above changes were more significant in combination of 5-ASA and DG group and in combination of 5-ASA and dexamethasone group (P<0.05), and there was no significant difference between normal control group and combination of 5-ASA and DG group (P>0.05), also between normal control group and combination of 5-ASA and dexamethasone group. 4. There was no significant difference between 5-ASA group and DG group (P>0.05), also between combination of 5-ASA and DG group and combination of 5-ASA and dexamethasone group.Conclusion DG and 5-ASA could effectively treat experimental colitis in rats by suppressing the activity of NF-κB p65 and iNOS, increasing the expression of IL-4 in serum and SOD activity and decreasing the expression of IL-6 in serum. DG had similar effect as 5-ASA to reduce the inflammation of UC rats. The combination treatment of DG and 5-ASA has a better effect than either of individual treatment alone. The combination of 5-ASA and DG group had similar effect as the combination of 5-ASA and dexamethasone group to reduce the inflammation of UC rats without the hormonelike side effects.