# Anti-Inflammatory Effects of Lipoxin A4 in Salmonella Typhimurium-Induced Enteritis in Wenchang Chickens

## TL;DR

Lipoxin A4 reduces inflammation caused by Salmonella in Wenchang chickens, suggesting a potential treatment for poultry health.

## Contribution

The study demonstrates LXA4's anti-inflammatory effects in both in vivo and in vitro models of Salmonella-induced enteritis in Wenchang chickens.

## Key findings

- LXA4 treatment reduced pro-inflammatory cytokines and COX-2 expression in infected chickens.
- LXA4 attenuated inflammation in chicken HD11 macrophages challenged with Salmonella.
- The anti-inflammatory effects of LXA4 were neutralized by the ALX/FPR2 antagonist Boc-2.

## Abstract

Salmonella Typhimurium (S. Typhimurium) is a widely distributed zoonotic enteric pathogen and the most frequently reported serovar associated with Salmonella infections. It is also one of the principal causative agents of salmonellosis in poultry. Infection with S. Typhimurium typically results in reduced growth rate, impaired feed conversion efficiency, and increased mortality in young chicks. Wenchang chicken, an indigenous and economically valuable meat-type breed from Hainan Province, is integral to elevating poultry product quality while fostering the progression of specialized poultry production systems. However, this breed is particularly susceptible to S. Typhimurium infection, which often leads to severe intestinal inflammation and diarrhea, thereby posing substantial risks to health status and growth performance. Serving as an archetypal specialized pro-resolving mediator (SPM), Lipoxin A4 (LXA4) modulates immune cell activation and facilitates the restoration of tissue homeostasis. Given its central role in actively orchestrating the resolution of inflammation, increasing attention has been directed toward its regulatory functions in intestinal inflammatory responses. Based on its well-documented pro-resolving activity, the current study seeks to determine the protective function of LXA4 during the alleviation of S. Typhimurium-induced intestinal inflammation in Wenchang chickens, thereby providing a foundation for establishing new anti-inflammatory strategies and contributing to the sustainable and healthy progression of the poultry sector.

S. Typhimurium infection has the capacity to elicit enteric inflammation and metabolic dysfunction among poultry. Prior research conducted by our laboratory observed an increase in LXA4 titers within the gut of Wenchang chickens following infection with S. Typhimurium. Based on this observation, the present study analyzed the changes in body weight, immune organ indices, the levels of intestinal inflammatory cytokines, as well as cyclooxygenase-2 (COX-2) expression in Wenchang chickens before and after infection. The findings indicated that S. Typhimurium infection led to reduced body weight and significantly decreased thymus and bursa indices. Furthermore, a significant elevation was observed in the transcript levels of pro-inflammatory mediators, including IL-1β, along with IL-6, and TNF-α, concurrently with an increase in the mRNA transcript levels of the enzyme COX-2. Treatment with LXA4 attenuated these alterations and effectively alleviated the inflammatory response. Additionally, an in vitro system was employed to validate the anti-inflammatory properties of LXA4 against S. Typhimurium-induced inflammation in chicken HD11 macrophages. The results demonstrated that LXA4 attenuated the transcript levels of IL-1β, as well as IL-6, TNF-α, and COX-2, at various intervals (2, 12, and 24 h), thereby alleviating inflammation elicited by S. Typhimurium challenge. We employed the LXA4 receptor antagonist Boc-2 to explore the ALX/FPR2 signaling axis and noted the successful neutralization of LXA4-mediated anti-inflammatory properties by this antagonist in S. Typhimurium–challenged HD11 macrophages. Collectively, these findings indicate that S. Typhimurium triggers pro-inflammatory reactions across both in vivo chicken models and in vitro HD11 macrophage systems, whereas LXA4 effectively mitigates this inflammatory process. This research establishes the conceptual underpinnings necessary to advance the design of therapeutic modalities aimed at counteracting S. Typhimurium challenges within poultry populations.