Inhibitory Effects of Antimicrobial Peptide JH-3 on Salmonella enterica Serovar Typhimurium Strain CVCC541 Infection-Induced Inflammatory Cytokine Release and Apoptosis in RAW264.7 Cells.

Lei Wang,Shijun Chen,Gaiping Zhang,Yawei Sun,Xueqin Zhao,Jinqing Jiang,Huihui Zhang,Yanzhao Xu,Xiaojing Xia,Chunling Zhu,Bolin Hang,Jianhe Hu,Wanhai Qin

doi:10.3390/molecules24030596

Abstract

The antibiotic resistance of Salmonella has become increasingly serious due to the increased use of antibiotics, and antimicrobial peptides have been considered as an ideal antibiotic alternative. Salmonella can induce macrophage apoptosis and thus further damage the immune system. The antimicrobial peptide JH-3 has been shown to have a satisfactory anti-Salmonella effect in previous research, but its mechanism of action remains unknown. In this study, the effects of JH-3 on macrophages infected with Salmonella Typhimurium CVCC541 were evaluated at the cellular level. The results showed that JH-3 significantly alleviated the damage to macrophages caused by S. Typhi infection, reduced the release of lactic dehydrogenase (LDH), and killed the bacteria in macrophages. In addition, JH-3 decreased the phosphorylation level of p65 and the expression and secretion of interleukin 2 (IL-2), IL-6, and tumor necrosis factor-α (TNF-α) by inhibiting the activation of the mitogen-activated protein kinase (MAPK) (p38) signaling pathway and alleviating the cellular inflammatory response. From confocal laser scanning microscopy and flow cytometry assays, JH-3 was observed to inhibit the release of cytochrome c in the cytoplasm; the expression of TNF-αR2, caspase-9, and caspase-8; to further weaken caspase-3 activation; and to reduce the S.-Typhi-induced apoptosis of macrophages. In summary, the mechanism by which JH-3 inhibits Salmonella infection was systematically explored at the cellular level, laying the foundation for the development and utilization of JH-3 as a therapeutic alternative to antibiotics.

Highlights

Salmonella is a Gram-negative bacterium that primarily infects the gut and is an important zoonotic pathogen
The results indicated that JH-3 can significantly reduce the damage to macrophages caused by Salmonella CVCC541; shorten the survival time of Salmonella CVCC541 in macrophages; decrease the Salmonella-CVCC541-mediated release of the inflammatory cytokines interleukin 2 (IL-2), IL-6, and tumor necrosis factor-α (TNF-α); and inhibit apoptosis
We showed that JH-3 decreased the release of the inflammatory cytokines IL-2, IL-6, and TNF-α by inhibiting the mitogen-activated protein kinase (MAPK) (p38) signaling pathway, demonstrating that JH-3 had a satisfactory anti-inflammatory effect, which had been indicated in previous reports [16,18,20]

Summary

Introduction

Salmonella is a Gram-negative bacterium that primarily infects the gut and is an important zoonotic pathogen. With respect to animal husbandry, in 2015, up to a 29.2% isolation rate of Salmonella was observed in pig slaughterhouses in Hennan, China, among which Salmonella. The effective prevention and control of Salmonella infection is of great importance to the development of animal husbandry and public health [5]. AMPs are key components of the host innate immune system and possess excellent activities against disease, including antibacterial, antiviral, antifungal, antiparasitic, and anticancer activities [6,7] AMPs are widespread in organisms and have been isolated from a wide range of species, including single-celled microbes, insects, invertebrates, plants, amphibians, birds, fish, mammals, and humans. AMPs possess unique antibacterial mechanisms and have ideal antimicrobial activities against clinical multidrug-resistant strains without inducing bacterial resistance [9]. More than 2000 types of AMPs have been identified [10]

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