Anti-inflammatory effects of acacia and guar gum in 5-amino salicylic acid formulations in experimental colitis

Abstract

Findings from recent studies revealed a significant anti-inflammatory effect of polysaccharide-based excipients when formulated with classical drugs in experimental inflammatory bowel disease models. In this study, acacia and guar gum were investigated beyond their typical functionality for a possible additive anti-inflammatory effect when administered with 5-amino salicylic acid (5ASA) in murine experimental colitis. Anti-inflammatory effects of acacia and guar gum-based aqueous suspensions of 5ASA were evaluated in a murine experimental colitis. Acacia or guar gum (30 or 300 mg/kg) were administered via rectal administration alone or in combination with 5ASA (30 mg/kg). Disease activity, myeloperoxidase activity (MPO) and intratissue concentrations of various cytokines were assessed. Both acacia and guar gum separately showed significant effects in reducing the inflammatory markers in murine colitis model in vivo. When combined with the anti-inflammatory drug 5ASA, acacia showed a stronger therapeutic effect than guar gum, especially at the higher dose of acacia (300 mg/kg) which significantly reduced the inflammation in vivo compared to 5ASA alone (MPO, 5ASA: 5743 ± 1334, 5ASA + 30 mg/kg acacia: 3762 ± 2342; 5ASA + 30 mg/kg guar gum: 7373 ± 2115, 5ASA + 300 mg/kg acacia: 3131 ± 1012, 5ASA + 300 mg/kg guar gum: 6358 ± 2379; all U/g tissue). Acacia and guar gum separately showed significant anti-inflammatory effects in murine colitis, and furthermore, high dose acacia led to an additional therapeutic benefit when co-administered with 5ASA. These results indicate that further investigations are surely warranted in the search of better colitis therapy.

Keywords: 5-Amino salicylic acid; Acacia; Colitis; Guar gum; Inflammatory bowel disease.

Graphical abstract

Fig. 1

NF-κB activity from LPS-activated RAW-Blue™ cells after incubation with 30 and 300 μg/ml of acacia (AG), 30 and 300 μg/ml of guar gum (GG) and 30 μg/ml of 5ASA for 24 h in serum-free medium (mean ± SD; n = 6). * indicates p < 0.05 compared to 5ASA 30 μg/ml. All treatments were significantly different from LPS (+) control (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from LPS-free control (p > 0.05).

Fig. 2

Disease activity index during experimental period (5 days) determined for n = 8 animals after treatment of severe colitis (120 mg/kg TNBS) with acacia (AG) or guar gum (GG) at a dose of 30 or 300 mg/kg and in combination with 5ASA at a dose of 30 mg/kg. Error bars were omitted for clarity reasons.

Fig. 3

Photographs representative of the mouse colon show tissue sections from the healthy control (I) colitis group (II), group treated with 30 mg/kg 5ASA (III), 30 mg/kg acacia and 30 mg/kg 5ASA (IV) and 30 mg/kg guar gum and 30 mg/kg 5ASA (V). The scale shown indicates the length in cm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

Determination of colon weight to length ratio after treatment of severe colitis (120 mg/kg TNBS) with acacia (AG) or guar gum (GG) at a dose of 30 or 300 mg/kg and in combination with 5ASA at a dose of 30 mg/kg (mean ± SD; n = 6). * indicates p < 0.05 compared to 5ASA 30 mg/kg. All treatments were significantly different from untreated colitis controls (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from healthy controls (p > 0.05).

Fig. 5

MPO activity after treatment of severe colitis (120 mg/kg TNBS) with acacia (AG) or guar gum (GG) at a dose of 30 or 300 mg/kg and in combination with 5ASA at a dose of 30 mg/kg (mean ± SD; n = 6). * indicates p < 0.05 compared to 5ASA 30 mg/kg. All treatments were significantly different from untreated colitis controls (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from healthy controls (p > 0.05).

Fig. 6

IL-1β (A), TNF-α (B) and IL-6 (C) secretion in colonic tissue homogenates after treatment of severe colitis (120 mg/kg TNBS) with acacia (AG) or guar gum (GG) at a dose of 30 or 300 mg/kg and in combination with 5ASA at a dose of 30 mg/kg (mean ± SD; n = 6). * indicates p < 0.05 compared to 5ASA 30 mg/kg. All treatments were significantly different from untreated colitis controls (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from healthy controls (p > 0.05).

Fig. 6

IL-1β (A), TNF-α (B) and IL-6 (C) secretion in colonic tissue homogenates after treatment of severe colitis (120 mg/kg TNBS) with acacia (AG) or guar gum (GG) at a dose of 30 or 300 mg/kg and in combination with 5ASA at a dose of 30 mg/kg (mean ± SD; n = 6). * indicates p < 0.05 compared to 5ASA 30 mg/kg. All treatments were significantly different from untreated colitis controls (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from healthy controls (p > 0.05).

Fig. 7

NF-κB activity in colonic tissue homogenates after treatment of severe colitis (120 mg/kg TNBS) with acacia (AG) or guar gum (GG) at a dose of 30 or 300 mg/kg in combination with 5ASA at a dose of 30 mg/kg (mean ± SD; n = 6). * indicates p < 0.05 compared to 5ASA 30 mg/kg. All treatments were significantly different from untreated colitis controls (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from healthy controls (p > 0.05).

Fig. 8

CLSM images obtained after administration of labeled acacia (AG) and guar gum (GG) to healthy and inflamed colonic tissue in mice.

Fig. 9

Relative fluorescence intensity (relative FI) in inflamed tissue for acacia and guar gum measured using Image J. Pictures were taken using the same settings and thresholding tool settings were duplicated in every image compared. (mean ± SD; n = 3; * indicates p < 0.05 compared to healthy tissue compared to inflamed tissue for each gum).

Fig. 10

Normalized index over all in-vivo inflammatory indicators expressed as a relative change compared to untreated colitis controls. * indicates p < 0.05 compared to 5ASA 30 mg/kg. All treatments were significantly different from untreated colitis controls (p < 0.05), while ▲ below the respective columns indicates treatment is not significantly different from healthy controls (p > 0.05).