Protection by dexamethasone from a lethal infection with Listeria monocytogenes in mice

Ethanol Extracts from the Aerial Parts of Inula japonica and Potentilla chinensis Alleviate Airway Inflammation in Mice That Inhaled Particulate Matter 10 and Diesel Particulate Matter

Air pollution causes various airway diseases. However, many commonly used treatments can have high risks of side effects or are costly. To examine the anti-inflammatory properties of Inula japonica Thunb. and Potentilla chinensis Ser., a mouse model was generated via inhalation of both particulate matter 10 and diesel particulate matter, and 30% ethanol extracts of either I. japonica (IJ) or P. chinensis (PC) and a mixture of both ethanol extracts (IP) were orally administered to BALB/c mice for 12 days. IJ, PC, and IP inhibited immune cell numbers and their regulation in both the bronchoalveolar lavage fluid (BALF) and lungs. These agents suppressed the levels of interleukin (IL)-1α, IL-17, tumor necrosis factor (TNF)-α, C-X-C motif chemokine ligand (CXCL)-1, and CXCL-2 in BALF, and also inhibited F4/80 and IL-1 receptor-associated kinase (IRAK)-1 in lungs. They reduced the gene expression of TNF-α, CXCL-1, inducible NOS, COX-2, Mucin 5AC, and transient receptor potential cation channel subfamily V member 1 in lungs. These extracts also reduced histopathological changes and inflammatory progression, manifested as decreased cell infiltration, collagen deposition, and respiratory epithelial cell thickness. I. japonica and P. chinensis show potential for development as pharmaceuticals that suppress inflammatory progression and alleviate airway inflammation diseases caused by air pollutants.

[Host responses to bacterial infections]

Pathogenic bacteria and host defense system have been evolved by their offense and defense. In vivo research is crucial for elucidation of interactions between them. I have investigated their offence and defense by various standpoints using mouse models of Listeria monocytogenes and Staphylococcus aureus infections. Herein, the results of my research including the roles of endogenous cytokines in host defense, the attenuation of host defense mechanism in obesity and diabetes, the development of vaccines against S. aureus infection by staphylococcal enterotoxin (SE) family molecules, and the emesis-inducing mechanism of SEA are described.

The role of macrophage migration inhibitory factor in lethal Listeria monocytogenes infection in mice

Macrophage migration inhibitory factor (MIF) has been characterized as a proinflammatory cytokine. Previous studies have indicated that MIF may play a beneficial role or a detrimental role in microbial infections, depending on pathogens. In this study, we investigated the role of MIF in Listeria monocytogenes infection. The MIF titers increased 6h after lethal L. monocytogenes infection but not in the sublethal infection. The elimination of bacteria from the spleens and livers was not affected by anti-MIF antibody (Ab) injection in the sublethal infection, whereas anti-MIF Ab treatment rescued mice from the lethal infection, suggesting that MIF plays a deteriorating role in lethal L. monocytogenes infection. Anti-MIF Ab treatment significantly augmented interleukin (IL)-10 production in the spleens and livers 24h after infection, suggesting that MIF might down-regulate IL-10 production. Although the administration of anti-IL-10 monoclonal Ab showed no significant effect on the bacterial growth in the organs, the bacterial infection was deteriorated by the combined administration of Abs against MIF and IL-10. On the other hand, anti-MIF Ab treatment also increased in the serum cortisol titer 6h after infection compared with the control immunoglobulin G-injected group. Depletion of endogenous IL-10 decreased serum cortisol titers. These results suggested that IL-10 and cortisol might be involved in the deteriorating effect of MIF on lethal L. monocytogenes infection.

Dexamethasone effects on group B streptococcal infection in newborn rats

BACKGROUND

We previously published that human neutrophil-mediated bacterial killing of group B Streptococcus (GBS) in vitro was dependent on the timing and concentration of dexamethasone exposure.

HYPOTHESIS

Dexamethasone treatment would affect neutrophil mediated killing of GBS in an animal model.

METHODS

Wistar rat pups were randomly allocated to receive placebo or dexamethasone before, early or late after GBS infection. Suckling rats were infected with 104 or 105 colony-forming units of GBS or nothing. Pups were followed for survival, quantitative bacteremia, growth and neutrophil-mediated bacterial killing. Neutrophils for bacterial killing were obtained via cardiac puncture before infection. Statistics included chi square for survival, Mann-Whitney U test for bacteremia, analysis of variance for growth and paired Student's t test for bacterial killing analyses.

RESULTS

Dexamethasone treatment before invasive GBS infection decreases quantitative bacteremia, improves survival and improves neonatal neutrophil-mediated bacterial killing in suckling rats, whereas dexamethasone treatment after infection increases bacteremia and decreases survival. Regardless of timing of dexamethasone treatment, before or after invasive GBS infection, growth was significantly impaired in all suckling rats receiving dexamethasone compared with controls.

CONCLUSION

Treatment with dexamethasone before invasive GBS infection improves survival and decreases bacteremia in suckling rats; this appears in part to be mediated by improved neonatal neutrophil-mediated bacterial killing. We speculate that this improvement in outcome may be a result of improved number or function of neutrophil cell surface receptors.

Relationships between IFNgamma, IL-6, corticosterone, and Listeria monocytogenes pathogenesis in BALB/c mice

The relationships between Listeria monocytogenes (LM) pathogenesis, based on bacterial load, and serum levels of IL-6, IFNgamma, and corticosterone (CORT) were quantified. Serum IFNgamma levels increased along with the LM burden; however, with LM burdens > or =3 x 10(6) CFU per spleen, the serum IFNgamma level decreased along with a decrease in splenic weight. Serum IL-6 levels exponentially increased with increases of LM, and the CORT level positively correlated with the increase in IL-6 and LM. The serum level of IFNgamma appeared to be a good biomarker of the host's ability to combat the infection only when the LM burden did not exceed a critical level (>3 x 10(6) CFU per spleen). Interestingly, the LM load at which the IFNgamma level began to decline was near the dose at which the IL-6 concentration exponentially increased, suggesting a transition point shift from stress (assessed as CORT level) being immunoenhancing to becoming immunosuppressive. The IL-6:IFNgamma ratio may be a good indicator of disease severity and/or the ability to cope with an infection.