Localized tissue hypoxia is a feature of infection and inflammation, resulting in the upregulation of the transcription factors HIF-1α and NF-κB via inhibition of oxygen sensing hydroxylase enzymes. Previous studies have demonstrated a beneficial role for the hydroxylase inhibitor dimethyloxallyl glycine (DMOG) in inflammatory conditions, including experimental colitis, by regulating the activity of HIF-1 and NF-κB. We have demonstrated in vivo that pre-treatment with DMOG attenuates systemic LPS-induced activation of the NF-κB pathway. Furthermore, mice treated with DMOG had significantly increased survival in LPS-induced shock. Conversely, in models of polymicrobial sepsis, DMOG exacerbates disease severity. DMOG treatment of mice promotes M2 polarization in macrophages within the peritoneal cavity, resulting in the downregulation of pro-inflammatory cytokines such as TNFα. In addition, in vivo DMOG treatment upregulates IL-10 expression, specifically in the peritoneal B-1 cell population. This study demonstrates cell type specific roles for hydroxylase inhibition in vivo and provides insight into the mechanism underlying the protection conveyed by DMOG in models of endotoxic shock.

Streptococcus pneumoniae cause considerable morbidity and mortality, with persistent neurological sequelae, particularly in young children and the elderly. It is widely assumed that carriage occurs through direct mucosal colonization from the environment whereas meningitis results from invasion from the blood. However, the results of published studies can be interpreted that pneumococci may enter the brain directly from the nasal cavity by axonal transport through olfactory nerves. This hypothesis is based on findings that (i) teichoic acid of the pneumococcal cell wall interact with gangliosides (GLS), (ii) the interaction of GLS with cholera toxin leads to axonal transport through the olfactory nerves into the brain, and (iii) viruses enter the brain through axonal transport into olfactory nerves. After nasal inoculation, we observe high numbers of pneumococci in nasal washes and the olfactory nerves and epithelium. Significant numbers of pneumococci also infected the olfactory bulbs, brain, and the trigeminal ganglia. The absence of bacteremia in this model makes it unlikely that the bacteria entered the brain from the blood stream. Recovery of colony-forming units from the brain, lungs, olfactory nerves, and epithelium and nasal washes was inhibited by incubating pneumococci with GLS before nasal inoculation. These findings, confirmed by PCR and immunohistochemistry, support a GLSmediated process of infection and are consistent with pneumococci reaching the brain through retrograde axonal transport.

Pro-inflammatory cytokines have been implicated in the precipitation of depression and related disorders, and the antidepressant sensitive serotonin transporter (SERT) may be a major target for immune regulation in these disorders. Here, we focus on astrocytes, a major class of immune competent cells in the brain, to examine the effects of pro-longed treatment with tumor necrosis factoralpha (TNF-a) on SERT activity. We first established that high-affinity serotonin uptake into C6 glioma cells occurs through a SERT-dependent mechanism. Functional SERT expression is also confirmed for primary astrocytes. In both cell types, exposure to TNF-a resulted in a dose-and timedependent increase in SERT-mediated 5-HT uptake, which was sustained for at least 48 h post-stimulation. Further analysis in primary astrocytes revealed that TNF-a enhanced the transport capacity (V max ) of SERT-specific 5-HT uptake, suggesting enhanced transporter expression, consistent with our observation of an increase in SERT mRNA levels. We confirmed that in both, primary astrocytes and C6 glioma cells, treatment with TNF-a activates the p38 mitogen-activated protein kinase (MAPK) signaling pathway. Pre-treatment with the p38 MAPK inhibitor SB203580 attenuated the TNF-a mediated stimulation of 5-HT transport in both, C6 glioma and primary astrocytes. In summary, we show that SERT gene expression and activity in astrocytes is subject to regulation by TNF-a, an effect that is at least in part dependent on p38 MAPK activation.

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