Modified Zhenwu Decoction suppresses chronic colitis via targeting macrophage CCR2/Fyn/p38 MAPK signaling axis.

Background: Ulcerative colitis (UC) is associated with intestinal macrophage infiltration due to disruption of the mucosal barrier and bacterial invasion. Therefore, it is crucial to identify therapeutic agents capable of attenuating the macrophage-induced inflammatory response to preserve mucosal homeostasis and immune tolerance. The modified Zhenwu decoction (CDD-2103) is a novel herbal formulation developed based on the principles of Traditional Chinese medicine. To date, there are no clinically approved herbal formulations for UC with a well-known mechanism of action on macrophages.

Purpose: The objective of this study was to systematically investigate the inhibitory effect of the active fraction of CDD-2103 in a mouse model of chronic colitis and delineate the mechanisms underlying its inhibitory action.

Methods: CDD-2103 was extracted into four fractions using organic solvents with increasing polarity. A chronic 49-day dextran sulfate sodium (DSS)-induced colitis mice model, closely resembling human clinical conditions, was used to examine the effect of CDD-2103 on chronic colitis. To confirm the effect of CDD-2103 on macrophages in this chronic colitis model, adoptive macrophage transfer and CCL2 supplementation were conducted. The mechanisms of action of CDD-2103 were further elucidated utilizing bone marrow-derived macrophages (BMDMs). Transcriptome analysis was conducted to gain insights into the underlying mechanism of action of CDD-2103 in BMDMs.

Results: Our in vitro and in vivo findings demonstrated that the ethanol-enriched fraction of CDD-2103 exhibited significant anti-inflammatory effects, leading to the suppression of colitis severity. This effect was associated with diminished accumulation of colonic macrophages in the lamina propria of CDD-2103-intervened colitis mice. Specifically, CDD-2103 inhibited CCR2/L2-mediated proinflammatory macrophage infiltration into the colon without affecting macrophage proliferation. Mechanistically, CDD-2103 inhibited Fyn expression-mediated p38 MAPK activation and subsequently suppressed CCR2 expression in BMDMs.

Conclusions: Collectively, our study supports the potential use of CDD-2103 to limit macrophage infiltration, thereby reducing inflammation during UC treatment. CDD-2103 and the components in the ethanolic fraction are promising candidates for the development of novel drugs for UC management. Additionally, our study underscores Fyn-mediated CCR2 expression as a potential therapeutic target for the management of UC.