CC chemokine receptor 5 influences late-stage atherosclerosis.

Members of the chemokine system, play a central role in inflammatory processes that underlie the pathogenesis of atherosclerosis and possibly, aortic valve sclerosis. Here we show that genetic inactivation of CC chemokine receptor 5 (CCR5) in the atherosclerosis-prone Apoe-/- mice (Apoe-/- Ccr5-/-) fed a normal chow or a high-fat diet (HFD) are protected against advanced atherosclerosis as well as age-associated aortic valve thickening (AAAVT)--a murine correlate of aortic valve sclerosis. Notably, human sclerotic valves contained CCR5+ cells. We confirm that Apoe-/- Ccr5-/- mice does not influence early-atherosclerotic stage. Adoptive transfer studies showed that the atheroprotective effect of CCR5 inactivation resided in the bone marrow compartment, but was not dependent on T-cells. The CCR5-null state was associated with phenotypes postulated to be atheroprotective such as reduced macrophage accumulation in the plaque, and lower circulating levels of IL-6 and MCP-5. The lack of CCR5 expression in Apoe-/- mice was also associated with higher numbers of endothelial progenitor cells (EPCs)--another postulated athero-protective factor. Compared with controls, carriers of a polymorphism in the Ccr5 gene that leads to the lack of CCR5 in the cell surface had an increased mean percentage of EPCs, but this difference did not reach statistical significance. Collectively, these findings underscore a critical role of CCR5 in age-associated cardiovascular diseases, and highlight that the effects of the chemokine system can be temporally constrained to distinct stages of these disease processes.

CC chemokine receptor (CCR)-2 prevents arthritis development following infection by Mycobacterium avium.

The host factors that influence autoimmune arthritides such as rheumatoid arthritis have not been fully elucidated. We previously found that genetic inactivation of CC chemokine receptor 2 (CCR2) in the arthritis-prone DBA/1j mouse strain significantly increases the susceptibility of this strain to autoimmune arthritis induced by immunization with collagen type II (CII) and complete Freund's adjuvant (CFA). Here, we show that following intradermal infection with Mycobacterium avium, a similar arthritis phenotype was detected in Ccr2-null mice in the DBA/1j, but not in the BALB/c background. The failure to develop arthritis in Ccr2-null BALB/c mice occurred in the face of high bacterial burdens and low interferon gamma (IFNgamma) production. By contrast, Ccr2-null DBA/1j mice had low bacterial burdens, produced normal amounts of IFNgamma, and had high titers of autoantibodies against CII. Thus, the Ccr2-null state in an arthritic-prone genetic background leads to increased arthritis susceptibility following infectious (M. avium) and noninfectious (CII/CFA) challenges. Because CCR2 serves as a negative regulator of murine arthritis, caution might need to be exercised while testing CCR2 blockers in human arthritis or other diseases. These findings also indicate that Ccr2-null DBA/1j mice might serve as a valuable model system to uncover the immunological determinants of arthritis and to test novel antiarthritic agents.

Characterization of metal ligand mutants of tyrosine hydroxylase: insights into the plasticity of a 2-histidine-1-carboxylate triad.

The amino acid ligands to the active site iron in the aromatic amino acid hydroxylase tyrosine hydroxylase are two histidines and a glutamate. This 2-histidine-1-carboxylate motif has been found in a number of other metalloenzymes which catalyze a variety of oxygenase reactions. As a probe of the plasticity of this metal binding site, each of the ligands in TyrH has been mutated to glutamine, glutamate, or histidine. The H336E and H336Q enzymes show dramatic decreases in iron affinity but retain substantial activity for both tyrosine hydroxylation and tetrahydropterin oxidation. The H331E enzyme shows a lesser decrease in iron affinity and is unable to hydroxylate tyrosine. Instead, this enzyme oxidizes tetrahydropterin in the absence of added tyrosine. The E376H enzyme has no significant activity, while the E376Q enzyme hydroxylates tyrosine at about 0.4% the wild-type rate. When dopamine is bound to either the H336Q or H331E enzymes, the position of the long wavelength charge-transfer absorbance band is consistent with the change in the metal ligand. In contrast, the H336E enzyme does not form a stable binary complex with dopamine, while the E376H and E376Q enzymes catalyze dopamine oxidation.