# Liver Transcriptome Analysis Reveals a Potential Mechanism of Heat Stress Increasing Susceptibility to Salmonella Typhimurium in Chickens

## TL;DR

Heat stress makes chickens more vulnerable to Salmonella infection by causing inflammation and weakening defenses, as shown by liver gene activity and key immune genes.

## Contribution

Identified three key genes (PTGDS, SLC6A9, WISP2) linking heat stress to increased Salmonella susceptibility in chickens.

## Key findings

- Heat stress reduced weight gain, increased inflammation, and raised mortality in Salmonella-infected chickens.
- Transcriptome analysis showed heat stress caused excessive inflammation and antioxidant imbalance in the liver.
- Three genes (PTGDS, SLC6A9, WISP2) were validated as critical in immune response under heat stress and Salmonella infection.

## Abstract

Salmonella infection causes severe disease in chickens and major economic losses for the poultry industry. Heat stress, which is becoming more common with global warming, makes chickens more vulnerable to infections, but how it does so remains incompletely understood. This study investigated how heat stress affects the ability of chickens to resist Salmonella infection. We compared healthy chickens to those infected with Salmonella Typhimurium, and to chickens exposed to both heat stress and Salmonella Typhimurium. The results showed that heat stress caused infected chickens to gain less weight, develop stronger inflammation, and experience higher mortality. Transcriptome analysis of the liver revealed that heat stress triggered excessive inflammatory responses and impaired antioxidant defenses. By integrating differential expression analysis, weighted gene co-expression network analysis, and cellular-level validation, we identified three key candidate genes (PTGDS, SLC6A9, and WISP2) that may play important roles in the host immune response during Salmonella Typhimurium infection under heat stress. These findings are important for disease-resistant poultry breeding and improving prevention strategies for poultry farming during hot weather.

Salmonella infection poses a serious threat to the poultry industry, causing significant economic losses. Under global warming conditions, the underlying molecular mechanisms by which heat stress affects bacterial infections in poultry remain unclear. This study conducted a Salmonella Typhimurium infection under heat stress in Guang Ming broilers. A total of 100 chickens were randomly divided into three groups: control group (CTL), Salmonella Typhimurium (ST) infection group, and heat stress and Salmonella Typhimurium (HS + ST) co-stimulation group. By integrating inflammatory phenotypes, liver transcriptome profiles, and weighted gene co-expression network analysis (WGCNA), we systematically investigated the key regulatory factors through which heat stress affects host susceptibility to Salmonella. The results demonstrated that heat stress reduced body weight gain, exacerbated Salmonella Typhimurium-induced inflammatory responses, and increased mortality. Transcriptome results revealed that heat stress led to excessive inflammatory responses and antioxidant defense imbalances. Combined differential expression analysis and WGCNA identified three hub regulatory genes: PTGDS and WISP2 showed significant correlations with the heterophil/lymphocyte ratio, while SLC6A9 was significantly correlated with serum IL-8 levels. Validation in HD11 cell infection models confirmed the differential expression of these genes under heat stress and Salmonella Typhimurium co-stimulation, indicating their critical roles in host immune regulation. This study elucidates the intrinsic regulatory relationships through which heat stress promotes Salmonella pathogenicity and inflammatory responses, providing important insights for disease-resistant poultry breeding and prevention strategies.