Murine AML12 hepatocytes allow Salmonella Typhimurium T3SS1-independent invasion and intracellular fate

Numerous studies have demonstrated the key role of the Salmonella Pathogenicity Island 1-encoded type III secretion system (T3SS1) apparatus as well as its associated effectors in the invasion and intracellular fate of Salmonella in the host cell. Several T3SS1 effectors work together to control cytoskeleton networks and induce massive membrane ruffles, allowing pathogen internalization. Salmonella resides in a vacuole whose maturation requires that the activity of T3SS1 subverts early stages of cell signaling. Recently, we identified five cell lines in which Salmonella Typhimurium enters without using its three known invasion factors: T3SS1, Rck and PagN. The present study investigated the intracellular fate of Salmonella Typhimurium in one of these models, the murine hepatocyte cell line AML12. We demonstrated that both wild-type Salmonella and T3SS1-invalidated Salmonella followed a common pathway leading to the formation of a Salmonella containing vacuole (SCV) without classical recruitment of Rho-GTPases. Maturation of the SCV continued through an acidified phase that led to Salmonella multiplication as well as the formation of a tubular network resembling Salmonella induced filaments (SIF). The fact that in the murine AML12 hepatocyte, the T3SS1 mutant induced an intracellular fate resembling to the wild-type strain highlights the fact that Salmonella Typhimurium invasion and intracellular survival can be completely independent of T3SS1.

Discovering the Protective Effects of Resveratrol on Aflatoxin B1-Induced Toxicity: A Whole Transcriptomic Study in a Bovine Hepatocyte Cell Line

Aflatoxin B1 (AFB1) is a natural feed and food contaminant classified as a group I carcinogen for humans. In the dairy industry, AFB1 and its derivative, AFM1, are of concern for the related economic losses and their possible presence in milk and dairy food products. Among its toxic effects, AFB1 can cause oxidative stress. Thus, dietary supplementation with natural antioxidants has been considered among the strategies to mitigate AFB1 presence and its toxicity. Here, the protective role of resveratrol (R) has been investigated in a foetal bovine hepatocyte cell line (BFH12) exposed to AFB1, by measuring cytotoxicity, transcriptional changes (RNA sequencing), and targeted post-transcriptional modifications (lipid peroxidation, NQO1 and CYP3A enzymatic activity). Resveratrol reversed the AFB1-dependent cytotoxicity. As for gene expression, when administered alone, R induced neglectable changes in BFH12 cells. Conversely, when comparing AFB1-exposed cells with those co-incubated with R+AFB1, greater transcriptional variations were observed (i.e., 840 DEGs). Functional analyses revealed that several significant genes were involved in lipid biosynthesis, response to external stimulus, drug metabolism, and inflammatory response. As for NQO1 and CYP3A activities and lipid peroxidation, R significantly reverted variations induced by AFB1, mostly corroborating and/or completing transcriptional data. Outcomes of the present study provide new knowledge about key molecular mechanisms involved in R antioxidant-mediated protection against AFB1 toxicity.

Oxidative Stress Effects of Soluble Sulfide on Human Hepatocyte Cell Line LO2

Soluble sulfide is well known for its toxicity and corrosion for hundreds of years. However, recent studies have demonstrated that hydrogen sulfide (H2S)—a novel gasotransmitter—supports a critical role during neuromodulation, cell proliferation, and cardioprotection for organisms. In particular, soluble sulfide plays multifaceted signaling functions in mammals during oxidative stress processes. However, the specific molecular regulation of soluble sulfide during oxidative stress remains unclear. In this study, Na2S was implemented as a soluble sulfide donor to expose LO2 cells. The 3-(4,5-dimethylthiazolyl-2),-2,5-diphenyltetrazolium bromide (MTT) assay, hydroxyl radical assay, superoxide dismutase (SOD) assay, and glutathione peroxidase (GSH-PX) assay were applied to analyze cytotoxicity, hydroxyl radical levels, SOD and GSH-Px activities, respectively. Soluble sulfide at a concentration 0.01–1.0 mM/L resulted in a marked and concentration-dependent reduction of LO2 cell viability. At low concentrations, sulfide solutions increased SOD activity and GSH-Px activity of LO2 after 24 h exposure, exhibiting a clear hormesis-effect and indicating the protective ability of soluble sulfide against oxidative stress. The decline in SOD and GSH-Px and the increase in hydroxyl radical (0.08–1.0 mM/L) suggested that oxidative damage could be a possible mechanism for sulfide-induced cytotoxicity.