P0102 Isatin: An indole alkaloid with intestinal anti-inflammatory activity in the trinitrobenzene sulfonic acid colitis model
Authors: Socca E A R , de Almeida A C A , Dunder R J , Manzo L P , de-Faria F M , Souza-Brito A R M , Luiz-Ferreira A 
Published: January 2025

Abstract

Background
Inflammatory bowel disease (IBD) is a complex and recurring inflammatory disorder that affects the gastrointestinal tract.1 Various drugs have been developed for treating IBD, but there are still limitations due to adverse effects experienced by patients.2 Plant-derived molecules with anti-inflammatory properties represent a valuable alternative as a complementary therapy for IBD.3 Isatin is a compound found in several medicinal plant species with various biological activities, including a modulatory effect on pro-inflammatory mediators. This study aimed to evaluate the effect of isatin in experimental colitis.

Methods
Rats were divided into three groups (10 animals/group): Saline (non-colitic control), TNBS (colitic untreated), and isatin (colitic treated with isatin 6 mg/kg). After anesthesia with ketamine (50 mg/kg) and xylazine (10 mg/kg), the TNBS and isatin groups received a single dose of TNBS (10 mg) dissolved in 0.25 mL of 50% ethanol (v/v) by rectal administration. To evaluate the intestinal anti-inflammatory activity of isatin, animals were treated 2, 24, and 48 hours after the TNBS challenge and euthanized after 72 hours by CO2 overdose. The colons were removed, the macroscopic inflammation and the colon weight/length ratio were measured and the cytokines IL-1β, IL-12, IFN-γ, and TNF-α were quantified by ELISA. Median (minimum-maximum) or mean ± SEM values were compared through the Kruskal-Wallis test (Dunn’s test) or two-way ANOVA (Tukey’s test). The experiments were approved by the Ethics Commission in Animal Use (Protocol number 2773-1).

Results
The TNBS group showed increased colonic wall thickness and inflammatory cell infiltration. Isatin reduced the macroscopic inflammation score [Isatin: 6 (6-7) versus TNBS: 9 (8-10); p &lt; 0.01] promoted by TNBS instillation. Oral administration of isatin prevented the increase in the colon weight/length ratio (0.151 ± 0.017 versus 0.192 ± 0.015; p &lt; 0.01). The colonic damage caused by TNBS instillation was also characterised by an increase in the levels of pro-inflammatory cytokines compared to the Saline group. In contrast, isatin reduced the levels of TNF-α (2.42 ± 0.72 versus 6.32 ± 1.91; p&lt;0.001), IFN-γ (4.26 ± 1.15 versus 7.34 ± 0.48; p&lt;0.01), IL-1β (16.54 ± 4.76 versus 35.91 ± 4.11; p&lt;0.001), and IL-12 (13.38 ± 3.65 versus 28.87 ± 8.39; p&lt;0.01) while increased the levels of IL-10 (6.41 ± 0.60 versus 4.82 ± 0.26; p&lt;0.01) when compared with TNBS group.

Conclusion
Isatin decreased the macroscopic inflammation score and the colon weight/length ratio. The action of isatin on colitis involves the reduction of pro-inflammatory mediators such as TNF-α and IL-1β and increase of the anti-inflammatory cytokine IL-10, suggesting a potential curative role of isatin in colitis therapy.

References
1.Luiz-Ferreira A, Stolfi C. Pharmaceuticals. 2023;17:59. doi: 10.3390/ph17010059.
2.Jauregui-Amezaga A, Smet A. J Clin Med. 2024;13:4622. doi: 10.3390/jcm13164622.
3.de Almeida, de-Faria FM, Dunder RJ, et al. Evid Based Complement Alternat Med. 2017;2017:8528210. doi: 10.1155/2017/8528210.