Inhibition of macrophage proliferation dominates plaque regression in response to cholesterol lowering.

Statins induce plaque regression characterized by reduced macrophage content in humans, but the underlying mechanisms remain speculative. Studying the translational APOE*3-Leiden.CETP mouse model with a humanized lipoprotein metabolism, we find that systemic cholesterol lowering by oral atorvastatin or dietary restriction inhibits monocyte infiltration, and reverses macrophage accumulation in atherosclerotic plaques. Contrary to current believes, none of (1) reduced monocyte influx (studied by cell fate mapping in thorax-shielded irradiation bone marrow chimeras), (2) enhanced macrophage egress (studied by fluorescent bead labeling and transfer), or (3) atorvastatin accumulation in murine or human plaque (assessed by mass spectrometry) could adequately account for the observed loss in macrophage content in plaques that undergo phenotypic regression. Instead, suppression of local proliferation of macrophages dominates phenotypic plaque regression in response to cholesterol lowering: the lower the levels of serum LDL-cholesterol and lipid contents in murine aortic and human carotid artery plaques, the lower the rates of in situ macrophage proliferation. Our study identifies macrophage proliferation as the predominant turnover determinant and an attractive target for inducing plaque regression.

Distribution of perfluorooctanesulfonate and perfluorooctanoate into human plasma lipoprotein fractions.

Some cross-sectional epidemiological studies have reported positive associations of serum concentrations of non-high density lipoprotein cholesterol with serum perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA). However, the strength of the reported associations is inconsistent for exposure-response across three orders of magnitude of serum PFOS and/or PFOA concentrations. These positive associations are unexpected based on toxicological/mechanistic studies, suggesting that the associations may have a biological, rather than a causal, basis. This study tested the hypothesis that PFOS and PFOA distribute into serum lipoprotein fractions such that increases in serum lipoproteins would result in corresponding increases in serum concentrations of PFOS and PFOA. Based on observed binding of PFOS and PFOA to isolated ß-lipoproteins in physiological saline (96% and 40% bound, respectively) in preliminary experiments using ultrafiltration and LC-MS/MS methods, binding to human donor plasma lipoprotein fractions was investigated by two density gradient methods. The majority of PFOS and PFOA recovered masses were found in lipoprotein-depleted plasma. Plasma density gradient fractionation data suggested that maximally 9% of PFOS distributes to lipoprotein-containing fractions, yet only 1% or less of PFOA is so distributed. These data do not support a strong role for plasma lipoprotein fractions in explaining the inconsistent dose-response associations reported in cross-sectional epidemiological studies.

A combinatorial approach toward the generation of ambiphilic peptide-based inhibitors of protein:geranylgeranyl transferase-1.

A combinatorial synthesis of oligopeptide analogues and their evaluation as protein:geranylgeranyl transferase inhibitors is presented. The combinatorial strategy is based on the random mutation, in each new generation, of one of any of the four amino acid building blocks of which the most effective compounds of the previous generation are assembled. In this way, a progressive improvement of the average inhibitory activity was observed until the fifth generation. The most active inhibitors were found to inhibit PGGT-1 in the low micromolar range (IC(50): 3.8-8.1 microM).