Atherosclerosis is an inflammatory disease involving the accumulation of macrophages in the intima. Wnt5a is a noncanonical member of the Wnt family of secreted glycoproteins. Recently, human macrophages have been shown to express Wnt5a upon stimulation with bacterial pathogens in vitro and in granulomatous lesions in the lung of Mycobacterium tuberculosis-infected patients. Wnt5a expression has also been liked to Toll-like receptor-4 (TLR-4), an innate immune receptor implicated in atherosclerosis. These observations, along with the fact that Wnt5a is involved in cell migration and proliferation, led us to postulate that Wnt5a plays a role in atherosclerosis. To investigate this hypothesis, we characterized Wnt5a expression in murine and human atherosclerotic lesions. Tissue sections derived from the aortic sinus to the aortic arch of apolipoprotein E-deficient mice and sections derived from the carotid arteries of patients undergoing endarterectomy were subjected to immunohistochemical analysis. All samples were found to be positive for Wnt5a with predominant staining in the areas of macrophage accumulation within the intima. In parallel, we probed for the presence of TLR-4 and found coincident TLR-4 and Wnt5a expression. For both the Wnt5a and TLR-4 staining, consecutive tissue sections treated with an isotype- and species-matched Ig served as a negative control and exhibited little, if any, reactivity. Quantitative RT-PCR revealed that Wnt5a mRNA expression in RAW264.7 murine macrophages can be induced by stimulation with LPS, a known ligand for TLR-4. Combined, these findings demonstrate for the first time Wnt5a expression in human and murine atherosclerotic lesions and suggest that cross talk between TLR-4 and Wnt5a is operative in atherosclerosis.

Deregulated innate immune responses that result in increased levels of type I interferons (IFNs) and stimulation of IFN-inducible genes are thought to contribute to chronic infl ammation and autoimmunity. One family of IFNinducible genes is the Ifi 200 family, which includes the murine (eg, Ifi 202a , Ifi 202b , Ifi 203 , Ifi 204 , Mndal , and Aim2 ) and human (eg, IFI16 , MNDA , IFIX , and AIM2 ) genes. Genes in the family encode structurally related proteins (the p200-family proteins), which share at least one partially conserved repeat of 200-amino acid (200-AA) residues. Consistent with the presence of 2 consecutive oligonucleotide/oligosaccharide-binding folds in the repeat, the p200-family proteins can bind to DNA. Additionally, these proteins (except the p202 proteins) also contain a pyrin (PYD) domain in the N-terminus. Increased expression of p202 proteins in certain strains of female mice is associated with lupus-like disease. Interestingly, only the Aim2 protein is conserved between the mouse and humans. Several recent studies have provided evidence that the Aim2 and p202 proteins can recognize DNA in cytoplasm and the Aim2 protein upon sensing DNA can form a caspase-1-activating infl ammasome. In this review, we discuss how the ability of p200-family proteins to sense cytoplasmic DNA may contribute to the development of chronic infl ammation and associated diseases.

Close links have been noted between chronic inflammation of the prostate and the development of human prostatic diseases such as benign prostate hyperplasia (BPH) and prostate cancer. However, the molecular mechanisms that contribute to prostatic inflammation remain largely unexplored. Recent studies have indicated that the IFN-inducible AIM2 protein is a cytosolic DNA sensor in macrophages and keratinocytes. Upon sensing DNA, AIM2 recruits the adaptor ASC and pro-CASP1 to assemble the AIM2 inflammasome. Activation of the AIM2 inflammasome cleaves pro-interleukin (IL)-1b and pro-IL-18 and promotes the secretion of IL-1b and IL-18 proinflammatory cytokines. Given that human prostatic infections are associated with chronic inflammation, the development of BPH is associated with an accumulation of senescent cells with a proinflammatory phenotype, and the development of prostate cancer is associated with the loss of IFN signaling, the role of AIM2 in mediating the formation of prostatic diseases was investigated. It was determined that IFNs (a, b, or g) induced AIM2 expression in human prostate epithelial cells and cytosolic DNA activated the AIM2 inflammasome. Steady-state levels of the AIM2 mRNA were higher in BPH than in normal prostate tissue. However, the levels of AIM2 mRNA were significantly lower in clinical tumor specimens. Accordingly, constitutive levels of AIM2 mRNA and protein were lower in a subset of prostate cancer cells as compared with BPH cells. Further, the cytosolic DNA activated the AIM2 inflammasome in the androgen receptor-negative PC3 prostate cancer cell line, suggesting that AIM2-mediated events are independent of androgen receptor status.

The interferon (IFN)-inducible IFI16 and AIM2 proteins act as innate immune sensors for cytosolic double-stranded DNA (dsDNA). Upon sensing dsDNA, the IFI16 protein induces the expression of IFN-β whereas the AIM2 protein forms an inflammasome, which promotes the secretion of IL-1β. Given that the knockdown of IFI16 expression in human diploid fibroblasts (HDFs) delays the onset of cellular senescence, we investigated the potential roles for the IFI16 and AIM2 proteins in cellular senescence. We found that increased IFI16 protein levels in old (versus young) HDFs were associated with the induction of IFN-β. In contrast, increased levels of the AIM2 protein in the senescent (versus old) HDFs were associated with increased production of IL-1β. The knockdown of type I IFN-receptor subunit-α, which reduced the basal levels of the IFI16, but not the AIM2, protein delayed the onset of cellular senescence. Accordingly, increased constitutive levels of IFI16 and AIM2 proteins in ataxia telangiectasia (AT) HDFs were associated with the activation of the IFN-signaling and increased levels of IL-1β. The IFN-β treatment of the young HDFs, which induced the expression of IFI16 and AIM2 proteins, activated a DNA-damage response and also increased basal levels of IL-1β. Interestingly, the knockdown of AIM2 expression in HDFs increased the basal levels of IFI16 protein and activated the IFN-signaling. In contrast, the knockdown of the IFI16 expression in HDFs decreased the basal and dsDNA-induced activation of the IFN-signaling. Collectively, our observations demonstrate differential roles for the IFI16 and AIM2 proteins in cellular senescence and associated secretory phenotype.