Hiroki Sekine

Nrf2 (NF-E2-related factor-2) transcription factor regulates oxidative/xenobiotic stress response and also represses inflammation. However, the mechanisms how Nrf2 alleviates inflammation are still unclear. Here, we demonstrate that Nrf2 interferes with lipopolysaccharide-induced transcriptional upregulation of proinflammatory cytokines, including IL-6 and IL-1β. Chromatin immunoprecipitation (ChIP)-seq and ChIP-qPCR analyses revealed that Nrf2 binds to the proximity of these genes in macrophages and inhibits RNA Pol II recruitment. Further, we found that Nrf2-mediated inhibition is independent of the Nrf2-binding motif and reactive oxygen species level. Murine inflammatory models further demonstrated that Nrf2 interferes with IL6 induction and inflammatory phenotypes in vivo. Thus, contrary to the widely accepted view that Nrf2 suppresses inflammation through redox control, we demonstrate here that Nrf2 opposes transcriptional upregulation of proinflammatory cytokine genes. This study identifies Nrf2 as the upstream regulator of cytokine production and establishes a molecular basis for an Nrf2-mediated anti-inflammation approach.

Aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, is known to mediate a wide variety of pharmacological and toxicological effects caused by polycyclic aromatic hydrocarbons. Recent studies have revealed that AhR is involved in the normal development and homeostasis of many organs. Here, we demonstrate that AhR knockout (AhR KO) mice are hypersensitive to lipopolysaccharide (LPS)-induced septic shock, mainly due to the dysfunction of their macrophages. In response to LPS, bone marrow-derived macrophages (BMDM) of AhR KO mice secreted an enhanced amount of interleukin-1beta (IL-1beta). Since the enhanced IL-1beta secretion was suppressed by supplementing Plasminogen activator inhibitor-2 (Pai-2) expression through transduction with Pai-2-expressing adenoviruses, reduced Pai-2 expression could be a cause of the increased IL-1beta secretion by AhR KO mouse BMDM. Analysis of gene expression revealed that AhR directly regulates the expression of Pai-2 through a mechanism involving NF-kappaB but not AhR nuclear translocator (Arnt), in an LPS-dependent manner. Together with the result that administration of the AhR ligand 3-methylcholanthrene partially protected mice with wild-type AhR from endotoxin-induced death, these results raise the possibility that an appropriate AhR ligand may be useful for treating patients with inflammatory disorders.

Erythropoietin (Epo) is produced by renal Epo-producing cells (REPs) in a hypoxia-inducible manner. The conversion of REPs into myofibroblasts and coincident loss of Epo-producing ability are the major cause of renal fibrosis and anemia. However, the hypoxic response of these transformed myofibroblasts remains unclear. Here, we used complementary in vivo transgenic and live imaging approaches to better understand the importance of hypoxia signaling in Epo production. Live imaging of REPs in transgenic mice expressing green fluorescent protein from a modified Epo-gene locus revealed that healthy REPs tightly associated with endothelium by wrapping processes around capillaries. However, this association was hampered in states of renal injury-induced inflammation previously shown to correlate with the transition to myofibroblast-transformed renal Epo-producing cells (MF-REPs). Furthermore, activation of hypoxia-inducible factors (HIFs) by genetic inactivation of HIF-prolyl hydroxylases (PHD1, PHD2, and PHD3) selectively in Epo-producing cells reactivated Epo production in MF-REPs. Loss of PHD2 in REPs restored Epo-gene expression in injured kidneys but caused polycythemia. Notably, combined deletions of PHD1 and PHD3 prevented loss of Epo expression without provoking polycythemia. Mice with PHD-deficient REPs also showed resistance to LPS-induced Epo repression in kidneys, suggesting that augmented HIF signaling counterbalances inflammatory stimuli in regulation of Epo production. Thus, augmentation of HIF signaling may be an attractive therapeutic strategy for treating renal anemia by reactivating Epo synthesis in MF-REPs.

PURPOSE: To examine the brain damage of solvent abusers in Japan, where pure industrial toluene is frequently abused. METHODS: Twenty solvent abusers 17 to 33 years of age with 7.2 +/- 4.0 years of abuse were examined with a 1.5-T MR imaging system. RESULTS: White matter hyperintensities in cerebrum, brain stem, and cerebellum on T2-weighted images were found in seven cases. The extent of white matter change was most clearly shown on proton density-weighted images. The patients with restricted white matter change and intermediate white matter change showed white matter hyperintensities in the brain stem and cerebellum on T2-weighted images, in some cases, with additional hypointensities in the corresponding T1-weighted images. These patients had mainly abused pure toluene. The patients with diffuse white matter change showed obvious brain atrophy, including hippocampal atrophy and thinning of the corpus callosum. These patients had mainly abused lacquer thinner. CONCLUSION: There are some patients with restricted but severe enough change to cause the neurologic symptoms in specific regions, such as the brain stem and/or cerebellum, before the brain atrophy becomes apparent. This suggests that the restricted white matter change represents not only an early change of diffuse white matter change, but at least in some cases also represents a qualitatively different change than that of diffuse white matter change. We suggest that pure toluene has a possible relation to this qualitative difference.