Neointimal lesions are characterized by accumulation of cells within the arterial wall and are a prelude to atherosclerotic disease. Here we report that a brief exposure to either alkyl ether analogs of the growth factor–like phospholipid lysophosphatidic acid (LPA), products generated during the oxidative modification of low density lipoprotein, or to unsaturated acyl forms of LPA induce progressive formation of neointima in vivo in a rat carotid artery model. This effect is completely inhibited by the peroxisome proliferator-activated receptor (PPAR)γ antagonist GW9662 and mimicked by PPARγ agonists Rosiglitazone and 1-O-hexadecyl-2-azeleoyl-phosphatidylcholine. In contrast, stearoyl-oxovaleryl phosphatidylcholine, a PPARα agonist and polypeptide epidermal growth factor, platelet-derived growth factor, and vascular endothelial growth factor failed to elicit neointima. The structure-activity relationship for neointima induction by LPA analogs in vivo is identical to that of PPARγ activation in vitro and disparate from that of LPA G protein–coupled receptor activation. Neointima-inducing LPA analogs up-regulated the CD36 scavenger receptor in vitro and in vivo and elicited dedifferentiation of cultured vascular smooth muscle cells that was prevented by GW9662. These results suggest that selected LPA analogs are important novel endogenous PPARγ ligands capable of mediating vascular remodeling and that activation of the nuclear transcription factor PPARγ is both necessary and sufficient for neointima formation by components of oxidized low density lipoprotein.

Vaccination represents the most effective form of protection against influenza infection. While neutralizing antibodies are typically measured as a correlate of vaccine-induced protective immunity against influenza, nonneutralizing antibodies may contribute to protection or amelioration of disease. The goal of this study was to dissect the individual contributions of the immunoglobulin G1 (IgG1) and IgG2a antibody isotypes to vaccine-induced immunity against influenza virus. To accomplish this, we utilized an influenza vaccine regimen that selectively enhanced IgG1 or IgG2a antibodies by using either DNA or viral replicon particle (VRP) vectors expressing influenza virus hemagglutinin (HA) (HA-DNA or HA-VRP, respectively). After HA-DNA vaccination, neutralizing antibodies were detected by both in vitro (microneutralization) and in vivo (lung viral titer) methods and were associated with increased IgG1 expression by enzyme-linked immunosorbent assay (ELISA). Vaccination with HA-VRP did not strongly stimulate either neutralizing or IgG1 antibodies but did induce IgG2a antibodies. Expression of IgG2a antibodies in this context correlated with clearance of virus and increased protection against lethal influenza challenge. Increased induction of both antibody isotypes as measured by ELISA was a better correlate for vaccine efficacy than neutralization alone. This study details separate but important roles for both IgG1 and IgG2a expression in vaccination against influenza and argues for the development of vaccine regimens that stimulate and measure expression of both antibody isotypes.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-regulated chloride channel localized primarily at the apical or luminal surfaces of epithelial cells that line the airway, gut, and exocrine glands; it is well established that CFTR plays a pivotal role in cholera toxin (CTX)-induced secretory diarrhea. Lysophosphatidic acid (LPA), a naturally occurring phospholipid present in blood and foods, has been reported to play a vital role in a variety of conditions involving gastrointestinal wound repair, apoptosis, inflammatory bowel disease, and diarrhea. Here we show, for the first time, that type 2 LPA receptors (LPA2) are expressed at the apical surface of intestinal epithelial cells, where they form a macromolecular complex with Na+/H+ exchanger regulatory factor–2 and CFTR through a PSD95/Dlg/ZO-1–based interaction. LPA inhibited CFTR-dependent iodide efflux through LPA2-mediated Gi pathway, and LPA inhibited CFTR-mediated short-circuit currents in a compartmentalized fashion. CFTR-dependent intestinal fluid secretion induced by CTX in mice was reduced substantially by LPA administration; disruption of this complex using a cell-permeant LPA2-specific peptide reversed LPA2-mediated inhibition. Thus, LPA-rich foods may represent an alternative method of treating certain forms of diarrhea.

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Here we showed that a naturally occurring ether analog of lysophosphatidic acid, 1-O-octadecenyl-2-hydroxy-sn-glycero-3-phosphate (AGP), is a high affinity partial agonist of the peroxisome proliferator-activated receptor ␥ (PPAR␥ The peroxisome proliferator-activated receptors (PPARs) 2 are members of the nuclear receptor superfamily that are involved in the regulation of lipid metabolism, glucose homeostasis, cell differentiation, and motility (1-4). The nuclear receptor superfamily consists of several ligand-regulated transcription factors that include the steroid and thyroid hormone receptors, vitamin D 3 receptor, retinoic acid receptors, and the PPARs (5-7). The PPAR subfamily consists of three isoforms, PPAR␣, PPAR␤/␦, and PPAR␥. PPAR␥ has two isotypes, ␥ 1 and ␥ 2 , that differ by a 30-amino acid extension on the N terminus of PPAR␥ 2 . Genetic deletion of PPAR␥ 1 is embryonic lethal (8); however, deletion of PPAR␥ 2 causes minimal alterations in lipid metabolism (9). The effects of ligands on PPAR␥ and retinoid X receptor are mediated through their ligand binding domains (LBD), conserved regions of ϳ250 amino acids within the C-terminal half of the receptors (10). PPAR␥, like other PPAR isoforms, undergoes a conformational change that stabilizes the AF-2 helix upon binding of agonist. Upon activation, these isoforms heterodimerize with the retinoid X receptor and bind to the peroxisome proliferator-response element (PPRE) in the promoters of target genes (5-7, 11, 12).A number of natural ligands for PPAR␥ have been identified and include two main groups of compounds, fatty acids and phospholipids. PPAR␥ exhibits a modest preference for essential polyunsaturated fatty acids, including linoleic (13), linolenic (14), arachidonic (15), and eicosapentaenoic acids (16). PPAR␥ is also activated by the monounsaturated fatty acid oleic acid (17). Several oxidatively modified lipids bind to and activate PPAR␥, including 15-deoxy-⌬-prostaglandin J 2 (18, 19), 9-hydroxy-10,12-octadecadienoic acid, 13-hydroxy-10,12-octadecadienoic acid (20), the oxidized alkyl phospholipid hexadecyl azelaoyl phosphatidylcholine (21), and nitrolinoleic acid (22). Many of these endogenous molecules require high concentrations and are weak activators of PPAR␥, casting doubt about their physiological relevance as bona fide agonists. The thiozolidinedione (TZD) class of anti-diabetics, including rosiglitazone (Rosi), troglitazone, and pioglitazone, are full agonists with

Quail have emerged as a potential intermediate host in the spread of avian influenza A viruses in poultry in Hong Kong. To better understand this possible role, we tested the replication and transmission in quail of influenza A viruses of all 15 HA subtypes. Quail supported the replication of at least 14 subtypes. Influenza A viruses replicated predominantly in the respiratory tract. Transmission experiments suggested that perpetuation of avian influenza viruses in quail requires adaptation. Swine influenza viruses were isolated from the respiratory tract of quail at low levels. There was no evidence of human influenza A or B virus replication. Interestingly, a human-avian recombinant containing the surface glycoprotein genes of a quail virus and the internal genes of a human virus replicated and transmitted readily in quail; therefore, quail could function as amplifiers of influenza virus reassortants that have the potential to infect humans and/or other mammalian species.

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