The core fucosylation (α1,6-fucosylation) of glycoproteins is widely distributed in mammalian tissues, and is altered under pathological conditions. To investigate physiological functions of the core fucose, we generated α1,6-fucosyltransferase ( Fut8 )-null mice and found that disruption of Fut8 induces severe growth retardation and death during postnatal development. Histopathological analysis revealed that Fut8 ^-/- mice showed emphysema-like changes in the lung, verified by a physiological compliance analysis. Biochemical studies indicated that lungs from Fut8 ^-/- mice exhibit a marked overexpression of matrix metalloproteinases (MMPs), such as MMP-12 and MMP-13, highly associated with lung-destructive phenotypes, and a down-regulation of extracellular matrix (ECM) proteins such as elastin, as well as retarded alveolar epithelia cell differentiation. These changes should be consistent with a deficiency in TGF-β1 signaling, a pleiotropic factor that controls ECM homeostasis by down-regulating MMP expression and inducing ECM protein components. In fact, Fut8 ^-/- mice have a marked dysregulation of TGF-β1 receptor activation and signaling, as assessed by TGF-β1 binding assays and Smad2 phosphorylation analysis. We also show that these TGF-β1 receptor defects found in Fut8 ^-/- cells can be rescued by reintroducing Fut8 into Fut8 ^-/- cells. Furthermore, exogenous TGF-β1 potentially rescued emphysema-like phenotype and concomitantly reduced MMP expression in Fut8 ^-/- lung. We propose that the lack of core fucosylation of TGF-β1 receptors is crucial for a developmental and progressive/destructive emphysema, suggesting that perturbation of this function could underlie certain cases of human emphysema.

Disruption of the circadian rhythm is a contributory factor to clinical and pathophysiological conditions, including cancer, the metabolic syndrome, and inflammation. Chronic and systemic inflammation are a potential trigger of type 2 diabetes and cardiovascular disease and are caused by the infiltration of large numbers of inflammatory macrophages into tissue. Although recent studies identified the circadian clock gene Rev-erbα, a member of the orphan nuclear receptors, as a key mediator between clockwork and inflammation, the molecular mechanism remains unknown. In this study, we demonstrate that Rev-erbα modulates the inflammatory function of macrophages through the direct regulation of Ccl2 expression. Clinical conditions associated with chronic and systemic inflammation, such as aging or obesity, dampened Rev-erbα gene expression in peritoneal macrophages from C57BL/6J mice. Rev-erbα agonists or overexpression of Rev-erbα in the murine macrophage cell line RAW264 suppressed the induction of Ccl2 following an LPS endotoxin challenge. We discovered that Rev-erbα represses Ccl2 expression directly through a Rev-erbα–binding motif in the Ccl2 promoter region. Rev-erbα also suppressed CCL2-activated signals, ERK and p38, which was recovered by the addition of exogenous CCL2. Further, Rev-erbα impaired cell adhesion and migration, which are inflammatory responses activated through the ERK- and p38-signaling pathways, respectively. Peritoneal macrophages from mice lacking Rev-erbα display increases in Ccl2 expression. These data suggest that Rev-erbα regulates the inflammatory infiltration of macrophages through the suppression of Ccl2 expression. Therefore, Rev-erbα may be a key link between aging- or obesity-associated impairment of clockwork and inflammation.

Pulmonary collectins, hydrophilic surfactant proteins A and D (SP-A and SP-D), have been implicated in the regulation of pulmonary host defence and inflammation. SP-A and SP-D directly interact with a variety of microorganisms including bacteria and viruses, and attenuate the growth of Gram-negative bacteria, Histoplasma capsulatum and Mycoplasma pneumoniae. The collectins are thought to contribute to bacterial clearance. These lectins augment the phagocytosis of the bacteria by macrophages. SP-A serves as an opsonin and stimulates the uptake of bacteria and bacillus Calmette-Guérin through a C1q receptor- and an SP-R210-mediated processes. The collectin also stimulates FcR- and CR1-mediated phagocytosis by activating the macrophages. In addition, SP-A and SP-D directly interact with macrophages and enhance the phagocytosis of Streptococcus pneumoniae and Mycobacterium by increasing cell surface localization of the phagocytic receptors, scavenger receptor A and mannose receptor. The collectins also modulate pulmonary inflammation. SP-A and SP-D bind to cell surface receptors including Toll-like receptors, SIRPalpha and calreticulin/CD91, and attenuate or enhance inflammation in a microbial ligand-specific manner. In this article we review the immunomodulatory functions of SP-A and SP-D and their possible mechanisms in direct actions on microbes, macrophage phagocytosis and modulation of inflammation.

The enzyme β1,4-N-acetylglucosaminyltransferase III (GnT-III) catalyzes the addition of a bisecting GlcNAc residue to glycoproteins, resulting in a modulation in biological function. Our previous studies showed that the transfection of the GnT-III gene into B16 melanoma cells results in a suppression of invasive ability and lung colonization. The suppression has been postulated to be due to an increased level of E-cadherin expression on the cell surface, which in turn leads to the up-regulation of cell-cell adhesion. In this study, we report on the effects of overexpression of GnT-III on cell-matrix adhesion. The overexpression of GnT-III, but not that of an enzymatic inactive GnT-III (D323A), inhibits cell spreading and migration on fibronectin, a specific ligand for integrin α₅β₁, and the focal adhesion kinase phosphorylation. E₄-PHA lectin blot analyses showed that the levels of bisecting GlcNAc structures on the integrin α₅ subunit as well as α₂ and α₃ subunits immunoprecipitated from GnT-III transfectants were substantially increased. In addition, the affinity of the binding of integrin α₅β₁ to fibronectin was significantly reduced by the introduction of the bisecting GlcNAc, to the α₅ subunit. These findings suggest that the modification of N-glycan of integrin by GnT-III inhibits its ligand binding ability, subsequently leading to the down-regulation of integrin-mediated signaling.