A large percentage of redox-responsive gene promoters contain evolutionarily conserved guanine-rich clusters; guanines are the bases most susceptible to oxidative modification(s). Consequently, 7,8-dihydro-8-oxoguanine (8-oxoG) is one of the most abundant base lesions in promoters and is primarily repaired via the 8-oxoguanine DNA glycosylase-1 (OOG1)-initiated base excision repair pathway. In view of a prompt cellular response to oxidative challenge, we hypothesized that the 8-oxoG lesion and the cognate repair protein OGG1 are utilized in transcriptional gene activation. Here, we document TNFα-induced enrichment of both 8-oxoG and OGG1 in promoters of pro-inflammatory genes, which precedes interaction of NF-κB with its DNA-binding motif. OGG1 bound to 8-oxoG upstream from the NF-κB motif increased its DNA occupancy by promoting an on-rate of both homodimeric and heterodimeric forms of NF-κB. OGG1 depletion decreased both NF-κB binding and gene expression, whereas Nei-like glycosylase-1 and -2 had a marginal effect. These results are the first to document a novel paradigm wherein the DNA repair protein OGG1 bound to its substrate is coupled to DNA occupancy of NF-κB and functions in epigenetic regulation of gene expression.

Beclin 1 was originally identified as a novel Bcl-2-interacting protein, but co-immunoprecipitation studies suggest that the major physiological partner for Beclin 1 is the mammalian class III phosphatidylinositol 3-kinase (PI 3-kinase) Vps34. Beclin 1 has been proposed to function as a tumor suppressor by promoting cellular macroautophagy, a process that is known to depend on Vps34. However, an alternative role for Beclin 1 in modulating normal Vps34-dependent protein trafficking pathways has not been ruled out. This possibility was examined in U-251 glioblastoma cells. Immunoprecipitates of endogenous Beclin 1 contained human Vps34 (hVps34), but not Bcl-2. Suppression of Beclin 1 expression by short interfering (si)RNA-mediated gene silencing blunted the autophagic response of the cells to nutrient deprivation or C2-ceramide. However, other PI 3-kinase-dependent trafficking pathways, such as the post-endocytic sorting of the epidermal growth factor receptor (EGFR) or the proteolytic processing of procathepsin D en route from the trans-Golgi network (TGN) to lysosomes, were not affected. Depletion of Beclin 1 did not reduce endocytic internalization of a fluid phase marker (horseradish peroxidase, HRP) or cause swelling of late endosomal compartments typically seen in cells where the function of hVps34 is impaired. These findings argue against a role for Beclin 1 as an essential chaperone or adaptor for hVps34 in normal vesicular trafficking, and they support the hypothesis that Beclin 1 functions mainly to engage hVps34 in the autophagic pathway.

Among the insidious DNA base lesions, 8-oxo-7,8-dihydroguanine (8-oxoG) is one of the most abundant, a lesion that arises through the attack by reactive oxygen species on guanine, especially when located in cis-regulatory elements. 8-oxoG is repaired by the 8-oxoguanine glycosylase 1 (OGG1)-initiated DNA base excision repair (BER) pathway. Here we investigated whether 8-oxoG repair by OGG1 in promoter regions is compatible with a prompt gene expression and a host innate immune response. For this purpose, we utilized a mouse model of airway inflammation, supplemented with cell cultures, chromatin immunoprecipitation, siRNA knockdown, real-time PCR, Comet and reporter transcription assays. Our data show that exposure of cells to tumor necrosis factor alpha (TNF-α) altered cellular redox, increased the 8-oxoG level in DNA, recruited OGG1 to promoter sequences and transiently inhibited BER of 8-oxoG. Promoter-associated OGG1 then enhanced NF-êB/RelA binding to cis-elements and facilitated recruitment of Specificity Protein 1 (SP1), transcription initiation factor II-D (TFIID), and phospho-RNA polymerase II, resulting in the rapid expression of chemokines/cytokines and inflammatory cell accumulation in mouse airways. siRNA depletion of OGG1 or prevention of guanine oxidation significantly decreased TNF-α-induced inflammatory responses. Together, these results show that non-productive binding of OGG1 to 8-oxoG in promoter sequences could be an epigenetic mechanism to modulate gene expression for a prompt innate immune response.

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Histamine is a potent mediator of inflammation and a regulator of innate and adaptive immune responses. However, the influence of histamine on microglia, the resident immune cells in the brain, remains uninvestigated. In the present study, we found that microglia can constitutively express all four histamine receptors (H1R, H2R, H3R, and H4R), and the expression of H1R and H4R can be selectively upregulated in primary cultured microglia in a dose-dependent manner by histamine. Histamine can also dose-dependently stimulate microglia activation and subsequently production of proinflammatory factors tumor necrosis factor (TNF)-alpha and interleukin-6 (IL-6). The antagonists of H1R and H4R but not H2R and H3R reduced histamine-induced TNF-alpha and IL-6 production, MAPK and PI3K/AKT pathway activation, and mitochondrial membrane potential loss in microglia, suggesting that the actions of histamine are via H1R and H4R. On the other hand, inhibitors of JNK, p38, or PI3K suppressed histamine-induced TNF-alpha and IL-6 release from microglia. Histamine also activated NF-kappa B and ammonium pyrrolidinedithiocarbamate, an inhibitor of NF-kappa B, and reduced histamine-induced TNF-alpha and IL-6 release. In summary, the present study identifies the expression of histamine receptors on microglia. We also demonstrate that histamine induced TNF-alpha and IL-6 release from activated microglia via H1R and H4R-MAPK and PI3K/AKT-NF-kappa B signaling pathway, which will deepen the understanding of microglia-mediated neuroinflammatory symptoms of chronic neurodegenerative disease.

Lung cancer is the leading cause of cancer death, and it is widely accepted that chronic inflammation is an important risk for the development of lung cancer. Now, it is recognized that the nucleotide-binding and oligomerization domain (NOD) like receptors (NLRs)-containing inflammasomes are involved in cancer-related inflammation. This study was designed to investigate the effects of NLR family pyrin domain containing protein 3 (NLRP3) inflammasome on the proliferation and migration of lung adenocarcinoma cell line A549. Using 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, scratch assay, and Transwell migration assay, we showed that activation of the NLRP3 inflammasome by LPS+ATP enhanced the proliferation and migration of A549 cells. Western blot analysis showed that activation of phosphorylation of Akt, ERK1/2, CREB and the expression of Snail increased, while the expression of E-cadherin decreased after the activation of NLRP3 inflammasome. Moreover, these effects were inhibited by the following treatments: i) downregulating the expression of NLRP3 by short hairpin RNA (shRNA) interference, ii) inhibiting the activation of NLRP3 inflammasome with a caspase-1 inhibitor, iii) blocking the interleukin-1β (IL-1β) and IL-18 signal transduction with IL-1 receptor antagonist (IL-1Ra) and IL-18 binding protein (IL-18BP). Collectively, these results indicate that NLRP3 inflammasome plays a vital role in regulating the proliferation and migration of A549 cells and it might be a potential target for the treatment of lung cancer.

The functions of platelets and fibrinogen in protecting tumor cells from natural killer cytotoxicity have been discussed for more than 20 years. However, their exact roles and relationships in the process are still not clear. In this study, we show that tumor cells prefer to adhere to fibrinogen than to platelets, and fibrinogen can enhance the adhesion of tumor cells to platelets. Beta3 integrin plays an important role in the adhesion of B16F10 to platelets enhanced by fibrinogen. In the presence of thrombin, fibrinogen forms dense fibrin(ogen) layers around tumor cells. Tumor cells can induce platelets to aggregate and form thrombin. Platelets, as well as thrombin, can help fibrinogen protect tumor cells from lethal contact with natural killer cells and natural killer cytotoxicity. Hirudin, a specific inhibitor of thrombin, can reverse the effect of platelets on fibrinogen in blocking natural killer cytotoxicity. Our results suggest that fibrinogen helps platelets to adhere to tumor cells, and platelets in turn promote more fibrinogen to aggregate around tumor cells by forming thrombin. They facilitate each other in protecting tumor cells from natural killer cytotoxicity.

In recent years, it is recognized that acquired immunity is controlled by regulatory T cell (Treg). Since fundamental pathophysiological changes of allergy are mainly caused by hyperresponsiveness of immune system to allergens that acquires after birth, Tregs likely play key roles in the pathogenesis of allergy, particularly during the sensitization phase. However, accumulated information indicate that there are several distinctive subtypes of Tregs in man, and each of them seems to play different role in controlling immune system, which complicates the involvement of Tregs in allergy. The aim of the present study is to attempt to classify subtypes of Tregs and summarize their roles in allergy. Tregs should include natural Tregs (nTreg) including inducible costimulator (ICOS)(+) Tregs, inducible/adaptive Tregs (iTreg), interleukin (IL)-10-producing type 1 Tregs (Tr1 cells), CD8(+) Tregs and IL-17-producing Tregs. These cells share some common features including expression of Foxp3 (except for Tr1 cells), and secretion of inhibitory cytokine IL-10 and/or TGF-β. Furthermore, it is noticeable that Tregs likely contribute to allergic disorders such as dermatitis and airway inflammation, and play a crucial role in the treatment of allergy through their actions on suppression of effector T cells and inhibition of activation of mast cells and basophils. Modulation of functions of Tregs may provide a novel strategy to prevent and treat allergic diseases.