Antiinflammatory effect of phytosterols in experimental murine colitis model: prevention, induction, remission study

Abstract

Phytosterols, besides hypocholesterolemic effect, present anti-inflammatory properties. Little information is available about their efficacy in Inflammatory Bowel Disease (IBD). Therefore, we have evaluated the effect of a mixture of phytosterols on prevention/induction/remission in a murine experimental model of colitis. Phytosterols were administered x os before, during and after colitis induction with Dextran Sodium Sulfate (DSS) in mice. Disease Activity Index (DAI), colon length, histopathology score, 18F-FDG microPET, oxidative stress in the intestinal tissue (ileum and colon) and gallbladder ileum and colon spontaneous and carbachol (CCh) induced motility, plasma lipids and plasma, liver and biliary bile acids (BA) were evaluated. A similar longitudinal study was performed in a DSS colitis control group. Mice treated with DSS developed severe colitis as shown by DAI, colon length, histopathology score, 18F-FDG microPET, oxidative stress. Both spontaneous and induced ileal and colonic motility were severely disturbed. The same was observed with gallbladder. DSS colitis resulted in an increase in plasma cholesterol, and a modification of the BA pattern. Phytosterols feeding did not prevent colitis onset but significantly reduced the severity of the disease and improved clinical and histological remission. It had strong antioxidant effects, almost restored colon, ileal and gallbladder motility. Plasmatic levels of cholesterol were also reduced. DSS induced a modification in the BA pattern consistent with an increase in the intestinal BA deconjugating bacteria, prevented by phytosterols. Phytosterols seem a potential nutraceutical tool for gastrointestinal inflammatory diseases, combining metabolic systematic and local anti-inflammatory effects.

Figure 1. Overview of experimental design.

Since at time points indicated by arrows 3–5 animals of each group were sacrificed, a total of 10 mice in the Ph group and 6 mice in the CD group (4 died) for each group completed the study. Mice receiving Ph for 14 days (day 0–14) were used to examine the Prevention of DSS induced colitis by Ph and compared with mice consuming CD. Mice receiving DSS from day 14 to day 24 and Ph were used to examine the response to Ph during the acute phase. Mice receiving Ph over 10 days after DSS was stopped and substituted for with water were used to evaluate the remission induced by Ph.

Figure 2. Assessment of acute colitis and evaluation of the response to Ph. Disease Activity Index.

DAI evaluation throughout the study in prevention (days 0–14), induction (days 14–24) and remission (days 24–38) in CD and Ph mice respectively (*P<.05. **P<.01). DSS (5% v/w) was added to tap water. DAI was evaluated: from day 1 to day 14 on 27 CD and 27 Ph mice respectively; since at day 14, 9 mice of the CD group and 9 mice of the Ph group were sacrificed, from day 14 to day 24, DAI was evaluated on 18 mice of each group; since at day 24, 9 mice of the CD group and 9 mice of the Ph group were sacrificed, from day 24 to day 38, it was evaluated on 9 mice of the CD group and 9 mice of the Ph group.

Figure 3. Assessment of acute colitis and evaluation of the response to Ph. ¹⁸F-FDG micro PET.

A. Quantification of ¹⁸F-FDG uptake (SUV) in the distal colon of Balb/c mice fed with CD and Ph. Analysis were repeated on the same mice at day 14^th, after CD and Ph (respectively n = 5; n = 5, **P = .0014), at day 24^th, the last of the ten days of DSS colitis induction (CD n = 5; Ph n = 5, ns), at day 38^th, fourteen days after the end of the DSS administration (CD n = 4; Ph n = 5, * P<.05). B. Representative PET image showing different ¹⁸F-FDG accumulation in the distal colon (yellow arrows) of Balb/c mice fed with CD (left image) and Ph (right image) at the end of induction. On the left of each images the SUV chromatic scale, from 0.00 to 6.19, is reported.

Figure 4. Assessment of acute colitis and evaluation of the response to Ph. Oxydative stress.

MDA equivalents in ileum (A) and colon homogenates (B) White bars refer to CD and black bars refer to Ph treatment in the prevention, induction and remission period. In both ileum and colon, a strong oxidative stress is observed in the CD group in the induction phase, shown by a significant increase in MDA equivalents, prevented by Ph treatment (n = 4, *P<.001). The increase is significantly higher than in the prevention and remission phases (n = 4, *P<.001). C. Coenzyme Q₉ levels in colon homogenate measured by HPLC. The ubiquinone content is not significantly different in all experimental conditions. Each tissue was analyzed in triplicate. Statistical analysis was performed by one way ANOVA test.

Figure 5. Assessment of acute colitis and evaluation of the response to Ph. Histology.

Prevention: normal ileum (Left) and colon (Right) in CD and Ph mice. (H&E,4x). Induction: colonic sections from ileum and colon from CD and Ph. The ileum is normal in both groups. Colon. Upper panel. Left: mucosal ulceration with linfoplasmacytic and neutrophils infiltrate extending to the entire mucosa (H&E, 20 x). Right: cryptic abscess (H&E, 10 x). Lower panel: colonic sections from Ph mice at the end of the induction period. Left: The mucosa and sub-mucosa show a moderate inflammatory infiltrate with lymphocytes and neutrophils (H&E, 10 x). Right: follicular inflammation. (H&E, 10 x). Remission. Upper panel: colonic mucosa specimens. Left: inflammatory infiltrate (H&E, 4x). Right: inflammatory infiltrate with lymphocytes and neutrophils (H&E, 20 x). Lower panel: colonic mucosa specimens. Left: minimal focal lymphocytes infiltration (H&E, 4x). The same at higher magnification (H&E, 10x).

Figure 6. Plasma, liver and biliary BA.

A. Plasma free and taurine-conjugated BA. B. Biliary BA. C. Liver BA. BA were evaluated after 14 days either Ph or CD and at the end of the study (day38). Since the CD group from day 0 to day 14 went on assuming the same usual commercial diet as before, day 14 was considered as the control value with respect to Ph. Plasma, liver and bile were collected from the same animal. The results were expressed as mean ± SD (n = 3–4 animals) CA: cholic acid; CDCA: chenodeoxycholic acid; DCA: deoxycholic acid; LCA: lithocholic acid; UDCA: ursodeoxycholic acid; muCA: muricholic acid; T-: Taurine conjugated-.

Figure 7. Gallbladder Spontaneous and Induced motility.

Amplitude (A) and Frequency (B) of spontaneous phasic contractions and (C) response to CCh and Atropine in mice gallbladder. Data are mean ± SEM values (n = 3–5) (*P>.01) (**P>.05).

Figure 8. Ileum Spontaneous and Induced motility.

Amplitude (A) and Frequency (B) of spontaneous phasic contractions and (C) response to CCh and Atropine in mice ileum. Data are mean ± SEM values (n = 3–5) (*P>.01) (**P>.05).

Figure 9. Colon Spontaneous and Induced motility.

Amplitude (A) and Frequency (B) of spontaneous phasic contractions and (C) response to CCh and Atropine in mice colon. Data are mean ± SEM values (n = 3–5) (*P>.01) (**P>.05).