Bioenergetic programming of macrophages by the apolipoprotein A-I mimetic peptide 4F.

The apoA-I (apolipoprotein A-I) mimetic peptide 4F favours the differentiation of human monocytes to an alternatively activated M2 phenotype. The goal of the present study was to test whether the 4F-mediated differentiation of MDMs (monocyte-derived macrophages) requires the induction of an oxidative metabolic programme. 4F treatment induced several genes in MDMs that play an important role in lipid metabolism, including PPARγ (peroxisome-proliferator-activated receptor γ) and CD36. Addition of 4F was associated with a significant increase in FA (fatty acid) uptake and oxidation compared with vehicle treatment. Mitochondrial respiration was assessed by measurement of the OCR (oxygen-consumption rate). 4F increased basal and ATP-linked OCR as well as maximal uncoupled mitochondrial respiration. These changes were associated with a significant increase in ΔΨm (mitochondrial membrane potential). The increase in metabolic activity in 4F-treated MDMs was attenuated by etomoxir, an inhibitor of mitochondrial FA uptake. Finally, addition of the PPARγ antagonist T0070907 to 4F-treated MDMs reduced the expression of CD163 and CD36, cell-surface markers for M2 macrophages, and reduced basal and ATP-linked OCR. These results support our hypothesis that the 4F-mediated differentiation of MDMs to an anti-inflammatory phenotype is due, in part, to an increase in FA uptake and mitochondrial oxidative metabolism.

Oral amphipathic peptides as therapeutic agents.

Cholesterol can promote inflammation by its ability to stimulate the production of reactive oxygen species that result in the formation of pro-inflammatory oxidised phospholipids. High-density lipoproteins (HDLs) are part of the innate immune response and can be either pro- or anti-inflammatory independently of plasma HDL-cholesterol levels. During systemic inflammation as occurs with atherosclerosis, Apolipoprotein A-I can be altered, reducing its ability to promote reverse cholesterol transport and HDL can become pro-inflammatory. Amphipathic peptides with either a class A amphipathic helix (D-4F) or a class G* amphipathic helix (D-[113-122]apoJ), or even those that are too small to form a helix (KRES and FREL) have some similar characteristics. Their interaction with lipids leads to a reduction in lipoprotein-lipid hydroperoxides that releases HDL-associated antioxidant enzymes, such as paraoxonase, therefore providing antiatherosclerosis and anti-inflammatory activity. In addition, the peptide D-4F stimulates the formation and cycling of pre-beta HDL. These amphipathic peptides appear to have therapeutic potential as oral agents.

Oral D-4F causes formation of pre-beta high-density lipoprotein and improves high-density lipoprotein-mediated cholesterol efflux and reverse cholesterol transport from macrophages in apolipoprotein E-null mice.

BACKGROUND: These studies were designed to determine the mechanism of action of an oral apolipoprotein (apo) A-I mimetic peptide, D-4F, which previously was shown to dramatically reduce atherosclerosis in mice. METHODS AND RESULTS: Twenty minutes after 500 microg of D-4F was given orally to apoE-null mice, small cholesterol-containing particles (CCPs) of 7 to 8 nm with pre-beta mobility and enriched in apoA-I and paraoxonase activity were found in plasma. Before D-4F, both mature HDL and the fast protein liquid chromatography fractions containing the CCPs were proinflammatory. Twenty minutes after oral D-4F, HDL and CCPs became antiinflammatory, and there was an increase in HDL-mediated cholesterol efflux from macrophages in vitro. Oral D-4F also promoted reverse cholesterol transport from intraperitoneally injected cholesterol-loaded macrophages in vivo. In addition, oral D-4F significantly reduced lipoprotein lipid hydroperoxides (LOOH), except for pre-beta HDL fractions, in which LOOH increased. CONCLUSIONS: The mechanism of action of oral D-4F in apoE-null mice involves rapid formation of CCPs, with pre-beta mobility enriched in apoA-I and paraoxonase activity. As a result, lipoprotein LOOH are reduced, HDL becomes antiinflammatory, and HDL-mediated cholesterol efflux and reverse cholesterol transport from macrophages are stimulated.