Acidity and lipolysis by group V secreted phospholipase A(2) strongly increase the binding of apoB-100-containing lipoproteins to human aortic proteoglycans

Local acidic areas characterize diffuse intimal thickening (DIT) and advanced atherosclerotic lesions. The role of acidity in the modification and extra- and intracellular accumulation of triglyceride-rich VLDL and IDL particles has not been studied before. Here, we examined the effects of acidic pH on the activity of recombinant human group V secreted phospholipase A(2) (sPLA(2)-V) toward small VLDL (sVLDL), IDL, and LDL, on the binding of these apoB-100-containing lipoproteins to human aortic proteoglycans, and on their uptake by human monocyte-derived macrophages. At acidic pH, the ability of sPLA(2)-V to lipolyze the apoB-100-containing lipoproteins was moderately, but significantly, increased while binding of the lipoproteins to proteoglycans increased >60-fold and sPLA(2)-V-modification further doubled the binding. Moreover, acidic pH more than doubled macrophage uptake of soluble complexes of sPLA(2)-V-LDL with aortic proteoglycans. Proteoglycan-affinity chromatography at pH 7.5 and 5.5 revealed that sVLDL, IDL, and LDL consisted of populations with different proteoglycan-binding affinities, and, surprisingly, the sVLDL fractions with the highest proteoglycan-affinity contained only low amounts of apolipoproteins E and C-III. Our results suggest that in atherosclerotic lesions with acidic extracellular pH, sPLA(2)-V is able to lipolyze sVLDL, IDL, and LDL, and increase their binding to proteoglycans. This is likely to provoke extracellular accumulation of lipids derived from these atherogenic lipoprotein particles and to increase the progression of the atherosclerotic lesions.     

Antibacterial properties of recombinant human non-pancreatic secretory phospholipase A2

Human non-pancreatic secretory phospholipase A₂ (hnpsPLA₂) is a group IIA phospholipase A₂ which plays an important role in the innate immune response. This enzyme was found to exhibit bactericidal activity toward Gram-positive bacteria, but not Gram-negative ones. Though native hnpsPLA₂ is active over a broad pH range, it is only highly active at alkaline conditions with the optimum activity pH of about 8.5. In order to make it highly active at neutral pH, we have obtained two hnpsPLA₂ mutants, Glu89Lys and Arg100Glu that work better at neutral pH in a previous study. In the present study, we tested the bactericidal effects of the native hnpsPLA₂ and the two mutants. Both native hnpsPLA₂ and the two mutants exhibit bactericidal activity toward Gram-positive bacteria. Furthermore, they can also kill Escherichia coli, a Gram-negative bacterium. The two mutants showed better bactericidal activity for E. coli at neutral pH than the native enzyme, which is consistent with the enzyme activities. As hnpsPLA₂ is highly stable and biocompatible, it may provide a promising therapy for bacteria infection treatment or other bactericidal applications.     

Effects of the propeptide of group X secreted phospholipase A2 on substrate specificity and interfacial activity on phospholipid monolayers

Group X secreted phospholipase A₂ (GX sPLA₂) plays important physiological roles in the gastrointestinal tract, in immune and sperm cells and is involved in several types of inflammatory diseases. It is secreted either as a mature enzyme or as a mixture of proenzyme (with a basic 11 amino acid propeptide) and mature enzyme. The role of the propeptide in the repression of sPLA₂ activity has been studied extensively using liposomes and micelles as model interfaces. These substrates are however not always suitable for detecting some fine tuning of lipolytic enzymes. In the present study, the monolayer technique is used to compare PLA₂ activity of recombinant mouse GX sPLA₂ (mGX) and its pro-form (PromGX) on monomolecular films of dilauroyl-phosphatidyl-ethanolamine (DLPE), -choline (DLPC) and -glycerol (DLPG). The PLA₂ activity and substrate specificity of mGX (PE ≈ PG > PC) were found to be surface pressure-dependent. mGX displayed a high activity on DLPE and DLPG but not on DLPC monolayers up to surface pressures corresponding to the lateral pressure of biological membranes (30–35 mN/m). Overall, the propeptide impaired the enzyme activity, particularly on DLPE whatever the surface pressure. However some conditions could be found where the propeptide had little effects on the repression of PLA₂ activity. In particular, both PromGX and mGX had similar activities on DLPG at a surface pressure of 30 mN/m. These findings show that PromGX can be potentially active depending on the presentation of the substrate (i.e., lipid packing) and one cannot exclude such an activity in a physiological context. A structural model of PromGX was built to investigate how the propeptide controls the activity of GX sPLA₂. This model shows that the propeptide is located within the interfacial binding site (i-face) and could disrupt both the interfacial binding of the enzyme and the access to the active site by steric hindrance.     

Structural determinants of the intrinsic fluorescence emission in notexin and phospholipase A2 enzymes

Fluorescence measurements of the homologous proteins, notexin and PLA₂ enzymes fromNaja naja atra, Naja nigricollis, and Hemachatus haemachatus venoms, showed that the wavelength of maximum emission and the quantum yield of their intrinsic fluorescence emission spectra were different. To verify the factors which affected their fluorescence characteristics, the dynamics of tryptophan residues in those homologous proteins were studied by quenching with acrylamide, iodide, and cesium. The degrees of exposure of tryptophanyl groups in notexin and PLA₂ enzymes assessed by acrylamide quenching were found to be the major factor that determined their fluorescence characteristics. However, the positively charged groups surrounding tryptophan residues of PLA₂ enzymes fromN. naja atra andN. nigricollis venoms might affect the quantum yield of their fluorophores. Tryptophan residues of notexin were in an environment with less fluctuation, which did not allow free diffusion of ionic quencher. This might render its typtophan residues to fluoresce at a shorter wavelength. These results suggested that the structural determinants affecting the intrinsic fluorescence emission of homologous proteins can be easily assessed by quenching studies.     

Differential contributions of protein kinase C isoforms in the regulation of group IIA secreted phospholipase A2 expression in cytokine-stimulated rat fibroblasts

Protein kinase C (PKC) is a family of serine/threonine kinases involved in various signal transduction pathways. We investigated the roles of PKC in the regulation of group IIA secreted phospholipase A₂ (sPLA₂-IIA) expression in cytokine-stimulated rat fibroblastic 3Y1 cells. Here we show that the induction of sPLA₂-IIA by proinflammatory cytokines was under the control of both classical cPKCα and atypical aPKCλ/ι pathways by using PKC inhibitors, a PKC activator, and PKC knockdowns. Treatment of 3Y1 cells with PKC selective inhibitors having broad specificity, such as chelerythrine chloride and GF109203X, blocked IL-1β/TNFα-dependent induction of sPLA₂-IIA protein in a dose-dependent manner. Treatment with the PKC activator phorbol 12-myristate 13-acetate (PMA), which activates cPKC and novel nPKC isoforms, markedly attenuated the cytokine-dependent induction of sPLA₂-IIA expression. In comparison, 24-h pretreatment with PMA, which down-regulates these PKC isoforms, markedly enhanced sPLA₂-IIA expression. Results with short hairpin RNA (shRNA)-mediated knockdown of PKC isoforms revealed that the cytokine-induced sPLA₂-IIA expression was markedly enhanced in cPKCα knockdown cells compared to those in replicate control cells. In contrast, knockdown of the aPKCλ/ι isoform reduced the cytokine-induced expression of sPLA₂-IIA. These results suggest that the aPKCλ/ι pathway is required for the induction of sPLA₂-IIA expression and that the cPKCα pathway acts as a negative regulator of sPLA₂-IIA expression in cytokine-stimulated rat fibroblasts.     

In silico and in vitro characterization of phospholipase A2 isoforms from soybean (Glycine max)

At the present, no secreted phospholipase A₂ (sPLA₂) from soybean (Glycine max) was investigated in detail. In this work we identified five sequences of putative secreted sPLA₂ from soybean after a BLAST search in G. max database. Sequence analysis showed a conserved PA2c domain bearing the Ca²⁺ binding loop and the active site motif. All the five mature proteins contain 12 cysteine residues, which are commonly conserved in plant sPLA₂s. We propose a phylogenetic tree based on sequence alignment of reported plant sPLA₂s including the novel enzymes from G. max. According to PLA₂ superfamily, two of G. max sPLA₂s are grouped as XIA and the rest of sequences as XIB, on the basis of differences found in their molecular weights and deviating sequences especially in the N- and C-terminal regions of the isoenzymes. Furthermore, we report the cloning, expression and purification of one of the putative isoenzyme denoted as GmsPLA₂-XIA-1. We demonstrate that this mature sPLA₂ of 114 residues had PLA₂ activity on Triton:phospholipid mixed micelles and determine the kinetic parameters for this system. We generate a model based on the known crystal structure of sPLA₂ from rice (isoform II), giving first insights into the three-dimensional structure of folded GmsPLA₂-XIA-1. Besides describing the spatial arrangement of highly conserved pair HIS-49/ASP-50 and the Ca⁺² loop domains, we propose the putative amino acids involved in the interfacial recognition surface. Additionally, molecular dynamics simulations indicate that calcium ion, besides its key function in the catalytic cycle, plays an important role in the overall stability of GmsPLA₂-XIA-1 structure.     

Refolding and purification of the human secreted group IID phospholipase A2 expressed as inclusion bodies in Escherichia coli

The secreted phospholipases A₂ (sPLA₂s) are water-soluble enzymes that bind to the surface of both artificial and biological lipid bilayers and hydrolyze the membrane phospholipids. The tissue expression pattern of the human group IID secretory phospholipase A₂ (hsPLA₂-IID) suggests that the enzyme is involved in the regulation of the immune and inflammatory responses. With an aim to establish an expression system for the hsPLA₂-IID in Escherichia coli, the DNA-coding sequence for hsPLA₂-IID was subcloned into the vector pET3a, and expressed as inclusion bodies in E. coli (BL21). A protocol has been developed to refold the recombinant protein in the presence of guanidinium hydrochloride, using a size-exclusion chromatography matrix followed by dilution and dialysis to remove the excess denaturant. After purification by cation-exchange chromatography, far ultraviolet circular dichroism spectra of the recombinant hsPLA₂-IID indicated protein secondary structure content similar to the homologous human group IIA secretory phospholipase A₂. The refolded recombinant hsPLA₂-IID demonstrated Ca²⁺-dependent hydrolytic activity, as measuring the release free fatty acid from phospholipid liposomes. This protein expression and purification system may be useful for site-directed mutagenesis experiments of the hsPLA₂-IID which will advance our understanding of the structure–function relationship and biological effects of the protein.     

A possible role of lysophospholipids produced by calcium-independent phospholipase A2 in membrane-raft budding and fission

Phospholipase A₂ (PLA₂) not only plays a role in the membrane vesiculation system but also mediates membrane-raft budding and fission in artificial giant liposomes. This study aimed to demonstrate the same effects in living cells. Differentiated Caco-2 cells were cultured on filter membranes. MDCK cells were challenged with Influenza virus. The MDCK cultures were harvested for virus titration with a plaque assay. Alkaline phosphatase (ALP), a membrane-raft associated glycosylphosphatidylinositol (GPI)-anchored protein, was 70% released by adding 0.2 mmol/l lysophosphatidylcholine, which was abolished by treatment with a membrane-raft disrupter, methyl-β-cyclodextrin. Activation of calcium-independent PLA₂ (iPLA₂) by brefeldin A increased the apical release of ALP by approximately 1.5-fold (p < 0.01), which was blocked by PLA₂ inhibitor bromoenol lactone (BEL). BEL also reduced Influenza virus production into the media (< 10%) in the MDCK culture. These results suggest that cells utilize inverted corn-shaped lysophospholipids generated by PLA₂ to modulate plasma membrane structure and assist the budding of raft-associated plasma membrane particles, which virus utilizes for its budding. Brush borders are enriched with membrane-rafts and undergo rapid turnover; thus, PLA₂ may be involved in the regulatory mechanism in membrane dynamism. Further, iPLA₂ may provide a therapeutic target for viral infections.     

Intracellular- and extracellular-derived Ca influence phospholipase A2-mediated fatty acid release from brain phospholipids

Docosahexaenoic acid (DHA) and arachidonic acid (AA) are found in high concentrations in brain cell membranes and are important for brain function and structure. Studies suggest that AA and DHA are hydrolyzed selectively from the sn-2 position of synaptic membrane phospholipids by Ca²⁺-dependent cytosolic phospholipase A₂ (cPLA₂) and Ca²⁺-independent phospholipase A₂ (iPLA₂), respectively, resulting in increased levels of the unesterified fatty acids and lysophospholipids. Cell studies also suggest that AA and DHA release depend on increased concentrations of Ca²⁺, even though iPLA₂ has been thought to be Ca²⁺-independent. The source of Ca²⁺ for activation of cPLA₂ is largely extracellular, whereas Ca²⁺ released from the endoplasmic reticulum can activate iPLA₂ by a number of mechanisms. This review focuses on the role of Ca²⁺ in modulating cPLA₂ and iPLA₂ activities in different conditions. Furthermore, a model is suggested in which neurotransmitters regulate the activity of these enzymes and thus the balanced and localized release of AA and DHA from phospholipid in the brain, depending on the primary source of the Ca²⁺ signal.     

Activation of phospholipase A2 by temporin B: Formation of antimicrobial peptide-enzyme amyloid-type cofibrils

Phospholipases A2 have been shown to be activated in a concentration dependent manner by a number of antimicrobial peptides, including melittin, magainin 2, indolicidin, and temporins B and L. Here we used fluorescently labelled bee venom PLA2 (PLA2D) and the saturated phospholipid substrate 1,2-dipalmitoyl-glycero-sn-3-phosphocholine (L-DPPC), exhibiting a lag-burst behaviour upon the initiation of the hydrolytic reaction by PLA2. Increasing concentrations of Cys-temporin B and its fluorescent Texas red derivative (TRC-temB) caused progressive shortening of the lag period. TRC-temB/PLA2D interaction was observed by Förster resonance energy transfer (FRET), with maximum efficiency coinciding with the burst in hydrolysis. Subsequently, supramolecular structures became visible by microscopy, revealing amyloid-like fibrils composed of both the activating peptide and PLA2. Reaction products, palmitic acid and 1-palmitoyl-2-lyso-glycero-sn-3-phosphocholine (lysoPC, both at > 8 mol%) were required for FRET when using the non-hydrolysable substrate enantiomer 2,3-dipalmitoyl-glycero-sn-1-phosphocholine (D-DPPC). A novel mechanism of PLA2 activation by co-fibril formation and associated conformational changes is suggested.     

B2 receptor-mediated dual effect of bradykinin on proximal tubule Na-ATPase: Sequential activation of the phosphoinositide-specific phospholipase Cβ/protein kinase C and Ca-independent phospholipase A2 pathways

In a previous paper we showed that bradykinin (BK), interacting with its B₂ receptor, inhibits proximal tubule Na⁺-ATPase activity but does not change (Na⁺ + K⁺)ATPase activity. The aim of this paper was to investigate the molecular mechanisms involved in B₂-mediated modulation of proximal tubule Na⁺-ATPase by BK. To abolish B₁ receptor-mediated effects, all experiments were carried out in the presence of (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Leu), des-Arg⁹-[Leu⁸]-BK (DALBK), a specific antagonist of B₁ receptor. A dual effect on the Na⁺-ATPase activity through the B₂ receptor was found: short incubation times (1-10 min) stimulate the enzyme activity; long incubation times (10-60 min) inhibit it. The stimulatory effect of BK is mediated by activation of phosphoinositide-specific phospholipase C β (PI-PLCβ)/protein kinase C (PKC); its inhibitory action is mediated by Ca²⁺-independent phospholipase A₂ (iPLA₂). Prior activation of the PI-PLCβ/PKC pathway is required to activate the iPLA₂-mediated inhibitory phase. These results reveal a new mechanism by which BK can modulate renal sodium excretion: coupling between B₂ receptor and activation of membrane-associated iPLA₂.     

Molecular cloning of the 31 kDa cytosolic phospholipase A2, as an antigen recognized by the lung cancer-specific human monoclonal antibody, AE6F4

The human monoclonal antibody AE6F4 specifically reacts with human lung cancer tissues but does not with normal tissues. This monoclonal antibody recognizes a cytosolic 31 kDa antigen in the cancer cells. In a previous study, we elucidated that the 31 kDa antigen belonged to a family of proteins collectively designated as 14-3-3 proteins, which were known as protein kinase-dependent activators of tyrosine/trytophan hydroxylases, or protein kinase C inhibitor proteins. Here we report molecular cloning of the 31 kDa antigen from the human lung adenocarcinoma cell line, A549. Sequencing analysis indicates that the cloned cDNA is identical to that of previously reported human placental cytosolic phospholipase A₂ (cPLA₂), which is also a member of the 14-3-3 protein family. Western analysis demonstrated that a 31 kDa recombinant cPLA₂ expressed in monkey COS cells was recognized by the AE6F4 monoclonal antibody. Binding of the monoclonal antibody to the recombinant cPLA₂ was abolished when treated with sodium periodate, suggesting that not only are carbohydrate chains associated with the cPLA₂, but they also play a crucial role in antigen recognition by the monoclonal antibody.     

The essentiality of His-47 and the N-terminal region for the binding of 8-anilinonaphthalene-1-sulfonate with Taiwan cobra phospholipase A2

The binding of the apolar fluorescent dye 8-anilinonaphthalene-1-sulfonate (ANS) toNaja naja atra phospholipase A₂ (PLA₂) as well as the enhancement of ANS fluorescence of the PLA₂-ANS complex decreased with increasing pH in a pH range from 3 to 9. These pH-dependent curves can be well interpreted as the perturbation of an ionizable group with pK value of 5.8, which was assigned as His-47 in the active site of PLA₂. The ionizable group with pK 5.8 was no longer observed after methylation of His-47, supporting the idea that thepH dependence of ANS binding arose from an electrostatic interaction between His-47 and the bound ANS. Removal of the N-terminal octapeptide of PLA₂ caused a precipitous drop in the capability of PLA₂ for binding with ANS and enhancing ANS fluorescence, reflecting that the integrity of the N-terminal region was essential for maintaining the hydrophobic character of the ANS-binding site. However, the nonpolarity of the ANS-binding site in the N-terminus-removed derivative was still partially retained at lowpH, but was completely lost at highpH. Evidently, the N-terminal region plays a more crucial role in ANS binding at highpH than at lowpH. These results indicate that hydrophobic interaction as well as electrostatic interaction are involved in the binding of ANS to PLA₂, and that the relative contributions of both interactions in ANS fluorescence enhancement may be different under differentpH.     

Specific binding of three neurotoxins with phospholipase A2 activity to synaptosomal membrane preparations from the guinea pig brain

Snake presynaptic toxins such as crotoxin, -bungarotoxin and taipoxin block neuromuscular transmission through inhibiting the release of acetylcholine by their phospholipase A₂ activities. On the other hand, many other phospholipase A₂s show little neurotoxicity. It is likely that the difference lies in whether high affinity binding to nerve cell membranes exists or not. To test this idea, crotoxin, -bungarotoxin and taipoxin were first radioactively labeled with Na(¹²⁵I) without loss of their neurotoxicity. Using the radioactive toxins we have found that each of the three showed specific binding to synaptosomal membranes from guinea pig brain. In contrast, we could not detect specific binding of a non-neurotoxic pancreatic phospholipase A₂. Crotoxin and taipoxin, but not -bungarotoxin, also bound specifically to membrane preparation from other tissues. The binding of each toxin was not greatly affected by the other two toxins. The photoaffinity labeling technique has been used to obtain further information about the components which bind crotoxin. For this purpose, (¹²⁵I) crotoxin was derivatized with N-hydroxysuccinimidyl-4-azidobenzoate. Autoradiographic analysis of the membranes following photoirradiation in the presence of the modified crotoxin revealed that an 85K dalton component was preferentially covalently conjugated with the crotoxin analogue in a specific manner.On leave from Department of Biochemistry and Biophysics, University of Hawaii, School of Medicine, Honolulu, Hawaii.     

An examination of structural interactions presumed to be of importance in the stabilization of phospholipase A2 dimers based upon comparative protein sequence analysis of a monomeric and dimeric enzyme from the venom ofAgkistrodon p. piscivorus

Phospholipases A₂ may exist in solution both as monomers and dimers, but enzymes that form strong dimers (K _D approximately 10^–9 M) have been found, thus far, only in venoms of the snake family Crotilidae. The complete amino acid sequences of a basic monomeric and an acidic dimeric phospholipase A₂ fromAgkistrodon piscivorus piscivorus (American cotton-mouth water moccasin) venom have been determined by protein sequencing methods as part of a search for aspects of structure contributing to formation of stable dimers. Both the monomeric and dimeric phospholipases A₂ are highly homologous to the dimeric phospholipases A₂ fromCrotalus atrox andCrotalus adamanteus venoms, and both have the seven residue carboxy-terminal extension characteristic of the crotalid and viperid enzymes. Thus, it is clear that the extension is not a prerequisite for dimerization. Studies to date have revealed two characteristic features of phosphilipases A₂ that exist in solution as strong dimers. One is the presence in the dimers of a Pro-Pro sequence at position 112 and 113 which just precedes the seven residue carboxy-terminal extension (residues 116–122). The other is a low isoelectric point; only the acidic phospholipases A₂ have been observed, thus far, to form stable dimers. These, alone or together, may be necessary, though not sufficient conditions for phospholipase A₂ dimer formation. Ideas regarding subunit interactions based upon crystallographic data are evaluated relative to the new sequence information on the monomeric and dimeric phospholipases A₂ fromA. p. piscivorus venom.     

Role of 57-72 loop in the allosteric action of bile salts on pancreatic IB phospholipase A2: Regulation of fat and cholesterol homeostasis

Mono- and biphasic kinetic effects of bile salts on the pancreatic IB phospholipase A2 (PLA2) catalyzed interfacial hydrolysis are characterized. This novel phenomenon is modeled as allosteric action of bile salts with PLA2 at the interface. The results and controls also show that these kinetic effects are not due to surface dilution or solubilization or disruption of the bilayer interface where in the mixed-micelles substrate replenishment becomes the rate-limiting step. The PLA2-catalyzed rate of hydrolysis of zwitterionic dimyristoylphosphatidylcholine (DMPC) vesicles depends on the concentration and structure of the bile salt. The sigmoidal rate increase with cholate saturates at 0.06 mole fraction and changes little at the higher mole fractions. Also, with the rate-lowering bile salts (B), such as taurochenodeoxycholate (TCDOC), the initial sigmoidal rate increase at lower mole fraction is followed by nearly complete reversal to the rate at the pre-activation level at higher mole fractions. The rate-lowering effect of TCDOC is not observed with the (62-66)-loop deleted ΔPLA2, or with the Naja venom PLA2 that is evolutionarily devoid of the loop. The rate increase is modeled with the assumption that the binding of PLA2 to DMPC interface is cooperatively promoted by bile salt followed by allosteric k_cat^?-activation of the bound enzyme by the anionic interface. The rate-lowering effect of bile salts is attributed to the formation of a specific catalytically inert E^?B complex in the interface, which is noticeably different than the 1:1 EB complex in the aqueous phase. The cholate-activated rate of hydrolysis is lowered by hypolidemic ezetimibe and guggul extract which are not interfacial competitive inhibitors of PLA2. We propose that the biphasic modulation of the pancreatic PLA2 activity by bile salts regulates gastrointestinal fat metabolism and cholesterol homeostasis.     

Lysoglycerophospholipids in chronic inflammatory disorders: The PLA2/LPC and ATX/LPA axes

Lysophosphatidylcholine (LPC) and lysophosphatidic acid (LPA), the most prominent lysoglycerophospholipids, are emerging as a novel class of inflammatory lipids, joining thromboxanes, leukotrienes and prostaglandins with which they share metabolic pathways and regulatory mechanisms. Enzymes that participate in LPC and LPA metabolism, such as the phospholipase A₂ superfamily (PLA₂) and autotaxin (ATX, ENPP2), play central roles in regulating LPC and LPA levels and consequently their actions. LPC/LPA biosynthetic pathways will be briefly presented and LPC/LPA signaling properties and their possible functions in the regulation of the immune system and chronic inflammation will be reviewed. Furthermore, implications of exacerbated LPC and/or LPA signaling in the context of chronic inflammatory diseases, namely rheumatoid arthritis, multiple sclerosis, pulmonary fibrosis and hepatitis, will be discussed. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.     

Cytokines, macrophage lipid metabolism and foam cells: implications for cardiovascular disease therapy

Cardiovascular disease is the biggest killer globally and the principal contributing factor to the pathology is atherosclerosis; a chronic, inflammatory disorder characterized by lipid and cholesterol accumulation and the development of fibrotic plaques within the walls of large and medium arteries. Macrophages are fundamental to the immune response directed to the site of inflammation and their normal, protective function is harnessed, detrimentally, in atherosclerosis. Macrophages contribute to plaque development by internalizing native and modified lipoproteins to convert them into cholesterol-rich foam cells. Foam cells not only help to bridge the innate and adaptive immune response to atherosclerosis but also accumulate to create fatty streaks, which help shape the architecture of advanced plaques. Foam cell formation involves the disruption of normal macrophage cholesterol metabolism, which is governed by a homeostatic mechanism that controls the uptake, intracellular metabolism, and efflux of cholesterol. It has emerged over the last 20 years that an array of cytokines, including interferon-γ, transforming growth factor-β1, interleukin-1β, and interleukin-10, are able to manipulate these processes. Foam cell targeting, anti-inflammatory therapies, such as agonists of nuclear receptors and statins, are known to regulate the actions of pro- and anti-atherogenic cytokines indirectly of their primary pharmacological function. A clear understanding of macrophage foam cell biology will hopefully enable novel foam cell targeting therapies to be developed for use in the clinical intervention of atherosclerosis.