Monocyte Phagocytosis of Viable Staphylococcus aureus is Impaired by Barbiturates, but not by Propofol

Propofol specifically suppresses IL-1β secretion but increases bacterial survival in Staphylococcus aureus-infected RAW264.7 cells

Anesthetics have immunomodulatory effects, but the use of different assay systems has contributed to inconsistent results in the literature. IL-1β and reactive oxygen species (ROS) secreted by phagocytes are important factors that protect against Staphylococcus aureus infection. In this study, the effects of four intravenous anesthetics (propofol, thiamylal sodium, midazolam, and ketamine) on IL-1β secretion, ROS, and bacterial survival in S. aureus-infected RAW264.7 cells were evaluated. S. aureus-infected RAW264.7 cells with or without intravenous anesthetic treatment were established as the experimental model. Cell supernatants were subjected to ELISAs to measure secreted IL-1β. Cell pellets were subjected to qPCR and western blot analyses to analyze IL-1β mRNA and protein levels. Luminol chemiluminescence assays were used to detect ROS, and bacterial survival was determined by counting the colony forming units at the beginning and end of the infection. Compared with the levels after treatment with the other intravenous anesthetics, secreted IL-1β levels were lowest in the supernatant of S. aureus-infected RAW264.7 cell cultures after propofol treatment, but propofol did not decrease IL-1β mRNA or protein expression. However, thiamylal sodium and midazolam decreased IL-1β mRNA and protein expression in a dose-dependent manner. Additionally, propofol substantially decreased S. aureus-stimulated ROS and phagocytosis. Bacterial survival was strongly increased by propofol treatment. Of the four intravenous anesthetics, propofol was the most potent inhibitor of IL-1β secretion and ROS level in S. aureus-infected RAW264.7 cells; moreover, propofol resulted in an increase in bacterial survival by inhibiting ROS and phagocytosis.

Mesenchyme-derived factors enhance preneoplastic growth by non-genotoxic carcinogens in rat liver

Many frequently prescribed drugs are non-genotoxic carcinogens (NGC) in rodent liver. Their mode of action and health risks for humans remain to be elucidated. Here, we investigated the impact of two model NGC, the anti-epileptic drug phenobarbital (PB) and the contraceptive cyproterone acetate (CPA), on intrahepatic epithelial–mesenchymal crosstalk and on growth of first stages of hepatocarcinogenesis. Unaltered hepatocytes (HC) and preneoplastic HC (HC_PREN) were isolated from rat liver for primary culture. DNA replication of HC and HC_PREN was increased by in vitro treatment with 10 µM CPA, but not 1 mM PB. Next, mesenchymal cells (MC) obtained from liver of rats treated with either PB (50 mg/kg bw/day) or CPA (100 mg/kg bw/day), were cultured. Supernatants from both types of MC raised DNA synthesis of HC and HC_PREN. This indicates that PB induces replication of HC and HC_PREN only indirectly, via growth factors secreted by MC. CPA, however, acts on HC and HC_PREN directly as well as indirectly via mesenchymal factors. Transcriptomics and bio-informatics revealed that PB and CPA induce extensive changes in the expression profile of MC affecting many growth factors and pathways. MC from PB-treated rats produced and secreted enhanced levels of HBEGF and GDF15, factors found to suppress apoptosis and/or induce DNA synthesis in cultured HC and HC_PREN. MC from CPA-treated animals showed enhanced expression and secretion of HGF, which strongly raised DNA replication of HC and HC_PREN. In conclusion, our findings reveal profound effects of two prototypical NGC on the hepatic mesenchyme. The resulting release of factors, which suppress apoptosis and/or enhance cell replication preferentially in cancer prestages, appears to be crucial for tumor promotion by NGC in the liver.

Proinflammatory mesenchymal effects of the non-genotoxic hepatocarcinogen phenobarbital: a novel mechanism of antiapoptosis and tumor promotion

Many environmental pollutants and drugs, including steroid hormones, hypolipidemics and antiepileptics, are non-genotoxic carcinogens (NGC) in rodent liver. The mechanism of action and the risk for human health are still insufficiently known. Here, we study the effects of phenobarbital (PB), a widely used model NGC, on hepatic epithelial-mesenchymal crosstalk and the impact on hepatic apoptosis. Mesenchymal cells (MC) and hepatocytes (HC) were isolated from control and PB-treated rat livers. PB induced extensive changes in gene expression in MC and much less in HC as shown by transcriptomics with oligoarrays. In MC only, transcript levels of numerous proinflammatory cytokines were elevated. Correspondingly, ELISA on the supernatant of MC from PB-treated rats revealed enhanced release of various cytokines. In cultured HC, this supernatant caused (i) nuclear translocation and activation of nuclear factor-κB (shown by immunoblots of nuclear extracts and reporter gene assays), (ii) elevated expression of proinflammatory genes and (iii) protection from the proapoptotic action of transforming growth factor beta 1 (TGFß1). PB treatment in vivo or in vitro elevated the production and release of tumor necrosis factor alpha from MC, which was identified as mainly responsible for the inhibition of apoptosis in HC. In conclusion, our findings reveal profound proinflammatory effects of PB on hepatic mesenchyme and mesenchymal-epithelial interactions. The resulting release of cytokines acts antiapoptotic in HC, an effect crucial for tumor promotion and carcinogenesis by NGC.

Immunological modifications induced from products used during the perioperative period

Anesthetics and other products used during the perioperative period may influence immune function not only merely by reducing the HPA-axis stress response but also by directly modulating innate and adaptive immune responses. Most of the literature on the immune effects of anesthetics has been derived from in vitro or animal studies, due to the number of confounding variables in real life surgical settings. These immunosuppressive effects might not normally have clinical consequences for an immune-competent patient, but may act as important modifiers in postoperative morbidity and mortality. Furthermore, some inhibitory effects on neutrophil functions may provide a therapeutically beneficial effect under specific surgical clinical conditions, such as ischemia-reperfusion injury.