The effects of baicalin on piglets challenged with Glaesserella parasuis

Abstract

Glaesserella parasuis (G. parasuis) causes porcine vascular inflammation and damage. Baicalin is reported to have antioxidant and anti-inflammatory functions. However, whether baicalin protects piglets against G. parasuis challenge and the potential protective mechanism have not been investigated. Therefore, in this study, we comprehensively examined the protective efficacy of baicalin in piglets challenged with G. parasuis and the possible protective mechanism. Our results show that baicalin attenuated the release of the inflammation-related cytokines interleukin (IL) 1β, IL6, IL8, IL10, and tumour necrosis factor α (TNF-α) and reduced high mobility group box 1 (HMGB1) production and cell apoptosis in piglets infected with G. parasuis. Baicalin also inhibited the activation of the mitogen-activated protein kinase (MAPK) signalling pathway and protected piglets against G. parasuis challenge. Taken together, our data suggest that baicalin could protect piglets from G. parasuis by reducing HMGB1 release, attenuating cell apoptosis, and inhibiting MAPK signalling activation, thereby alleviating the inflammatory response induced by the bacteria. Our results suggest that baicalin has utility as a novel therapeutic drug to control G. parasuis infection.

Keywords: Glaesserella parasuis; baicalin; inflammatory response; piglets; protection.

Figure 1

Effects of baicalin on the protection of piglets against G. parasuis challenge. Before G. parasuis challenge, the piglets in the EP group were injected intraperitoneally with EP, and the piglets in the FM group were injected intramuscularly with FM. After pretreatment with baicalin at concentrations of 25–100 mg/kg BW for 30 min, the piglets were challenged with 1 × 10⁹ CFU of G. parasuis strain SH0165. The mortality of the piglets was recorded. G. parasuis: HPS (the infection group); 25–100: the piglets were injected intramuscularly with baicalin at 25 mg/kg BW (treatment group 1), 50 mg/kg BW (treatment group 2), or 100 mg/kg BW (treatment group 3).

Figure 2

Effects of baicalin on the release of cytokines into the serum of piglets challenged with G. parasuis. A Determination of cytokine IL1β, IL6, IL8, IL10, and TNF-α production by ELISA. B Determination of cytokine IL1β, IL6, IL8, IL10, and TNF-α expression levels by qPCR. Before G. parasuis challenge, the piglets in the EP group were injected intraperitoneally with EP, and the piglets in the FM group were injected intramuscularly with FM. At 48 h after G. parasuis challenge, blood samples were collected for analysis of the cytokines IL1β, IL6, IL8, IL10, and TNF-α. G. parasuis: HPS. 25–100: piglets were injected intramuscularly with baicalin at 25, 50, or 100 mg/kg BW. ^##p < 0.01 vs control. *p < 0.05 vs the infection group, and **p < 0.01 vs the infection group.

Figure 3

Effects of baicalin on the release of HMGB1 into the serum of piglets challenged with G. parasuis. A Determination of HMGB1 production by ELISA. B Determination of the HMGB1 expression level by qPCR. Before G. parasuis challenge, the piglets in the EP group were injected intraperitoneally with EP, and the piglets in the FM group were injected intramuscularly with FM. At 48 h after G. parasuis challenge, blood samples were collected to measure the HMGB1 levels. G. parasuis: HPS. 25–100: the piglets were injected intramuscularly with baicalin at 25, 50, or 100 mg/kg BW. ^##p < 0.01 vs control. *p < 0.05 vs the infection group, and **p < 0.01 vs the infection group.

Figure 4

Effects of baicalin on cell apoptosis induced by G. parasuis. Before G. parasuis challenge, the piglets in the EP group were injected intraperitoneally with EP, and the piglets in the FM group were injected intramuscularly with FM. Aortic vessels were collected, and the expression of caspase 3 was measured by western blotting. G. parasuis: HPS. 25–100: the piglets were injected intramuscularly with baicalin at 25, 50, or 100 mg/kg BW. ^##p < 0.01 vs control. *p < 0.05 vs the infection group and **p < 0.01 vs the infection group.

Figure 5

Effects of baicalin on the MAPK signalling pathway activated by G. parasuis. Before G. parasuis challenge, the piglets in the EP group were injected intraperitoneally with EP, and the piglets in the FM group were injected intramuscularly with FM. Aortic vessels were collected, and the protein expression levels of ERK (A), p-ERK (B), JNK (C), p-JNK (D), P38 (E) and p-P38 (F) were determined. G. parasuis: HPS. 25–100: the piglets were injected intramuscularly with baicalin at 25, 50, or 100 mg/kg BW. ^##p < 0.01 vs control. *p < 0.05 vs the infection group, and **p < 0.01 vs the infection group.

Figure 6

Histopathological analysis of piglet lungs in the negative control group, the infection group, and the EP, FM, and baicalin treatment groups. G. parasuis: HPS. 25–100: the piglets were injected intramuscularly with baicalin at 25, 50, or 100 mg/kg BW.

Figure 7

Histopathological analysis of piglet brains in the negative control group, the infection group, and the EP, FM, and baicalin treatment groups. G. parasuis: HPS. 25–100: the piglets were injected intramuscularly with baicalin at 25, 50, or 100 mg/kg BW.