Christopher J. Lewis

Identification and Expression of Mammalian Long-Chain PUFA Elongation Enzymes

In mammalian cells, Sprecher has proposed that the synthesis of long-chain PUFA from the 20-carbon substrates involves two consecutive elongation steps, a Δ6-desaturation step followed by retroconversion (Sprecher, H., Biochim. Biophys. Acta 1486, 219–231, 2000). We searched the database using the translated sequence of human elongase ELOVL5, whose encoded enzyme elongates monounsaturated and polyunsaturated FA, as a query to identify the enzyme(s) involved in elongation of very long chain PUFA. The database search led to the isolation of two cDNA clones from human and mouse. These clones displayed deduced amino acid sequences that had 56.4 and 58% identity, respectively, to that of ELOVL5. The open reading frame of the human clone (ELOVL2) encodes a 296-amino acid peptide, whereas the mouse clone (Elovl2) encodes a 292-amino acid peptide. Expression of these open reading frames in bakers yeast, Saccharomyces cerevisiae, demonstrated that the encoded proteins were involved in the elongation of both 20-and 22-carbon long-chain PUFA, as determined by the conversion of 20∶4n−6 to 22∶4n−6, 22∶4n−6 to 24∶4n−6, 20∶5n−3 to 22∶5n−3, and 22∶5n−3 to 24∶5n−3. The elongation activity of the mouse Elovl2 was further demonstrated in the transformed mouse L cells incubated with long-chain (C20-and C22-carbon) n−6 and n−3 PUFA substrates by the significant increase in the levels of 24∶4n−6 and 24∶5n−3, respectively. This report demonstrates the isolation and identification of two mammalian genes that encode very long chain PUFA specific elongation enzymes in the Sprecher pathway for DHA synthesis.

Wnt5a is expressed in murine and human atherosclerotic lesions

Atherosclerosis is an inflammatory disease involving the accumulation of macrophages in the intima. Wnt5a is a noncanonical member of the Wnt family of secreted glycoproteins. Recently, human macrophages have been shown to express Wnt5a upon stimulation with bacterial pathogens in vitro and in granulomatous lesions in the lung of Mycobacterium tuberculosis-infected patients. Wnt5a expression has also been liked to Toll-like receptor-4 (TLR-4), an innate immune receptor implicated in atherosclerosis. These observations, along with the fact that Wnt5a is involved in cell migration and proliferation, led us to postulate that Wnt5a plays a role in atherosclerosis. To investigate this hypothesis, we characterized Wnt5a expression in murine and human atherosclerotic lesions. Tissue sections derived from the aortic sinus to the aortic arch of apolipoprotein E-deficient mice and sections derived from the carotid arteries of patients undergoing endarterectomy were subjected to immunohistochemical analysis. All samples were found to be positive for Wnt5a with predominant staining in the areas of macrophage accumulation within the intima. In parallel, we probed for the presence of TLR-4 and found coincident TLR-4 and Wnt5a expression. For both the Wnt5a and TLR-4 staining, consecutive tissue sections treated with an isotype- and species-matched Ig served as a negative control and exhibited little, if any, reactivity. Quantitative RT-PCR revealed that Wnt5a mRNA expression in RAW264.7 murine macrophages can be induced by stimulation with LPS, a known ligand for TLR-4. Combined, these findings demonstrate for the first time Wnt5a expression in human and murine atherosclerotic lesions and suggest that cross talk between TLR-4 and Wnt5a is operative in atherosclerosis.

Phenyl methimazole inhibits TNF-α-induced VCAM-1 expression in an IFN regulatory factor-1-dependent manner and reduces monocytic cell adhesion to endothelial cells

Proinflammatory cytokine (e.g., TNF-α)-induced expression of endothelial cell adhesion molecules (ECAMs) on the lumenal surface of the vascular endothelium and a consequent increase in leukocyte adhesion are key aspects of pathological inflammation. A promising therapeutic approach to diminish aberrant leukocyte adhesion is, therefore, to inhibit cytokine-induced ECAM expression at the transcription level. Several studies suggest that methimazole, a compound used clinically to treat autoimmune diseases, such as Graves’ disease, may also diminish pathological inflammation by suppressing ECAM expression. In this study we probed the hypothesis that a derivative of methimazole, phenyl methimazole (compound 10), can reduce cytokine-induced ECAM expression and consequent leukocyte adhesion. We found that compound 10 1) dramatically inhibits TNF-α-induced VCAM-1 mRNA and protein expression in human aortic endothelial cells (HAEC), has a relatively modest inhibitory effect on TNF-α induced E-selectin expression and has no effect on ICAM-1 expression; 2) significantly reduces TNF-α-induced monocytic (U937) cell adhesion to HAEC under in vitro flow conditions similar to that present in vivo; 3) inhibits TNF-α-induced IFN regulatory factor-1 binding to VCAM-1 promoter; and 4) reduces TNF-α-induced IRF-1 expression in HAEC. Combined, the results indicate that phenyl methimazole can reduce TNF-α-induced VCAM-1 expression in an IFN regulatory factor-1-dependent manner and that this contributes significantly to reduced monocytic cell adhesion to TNF-α-activated HAEC.

Phenylmethimazole blocks palmitate-mediated induction of inflammatory cytokine pathways in 3T3L1 adipocytes and RAW 264.7 macrophages

Visceral adipocytes and associated macrophages produce and release excessive amounts of biologically active inflammatory cytokines via the portal and systemic vascular system, which induce insulin resistance in insulin target tissues such as fat, liver, and muscle. Free fatty acids (FFAs) absorbed via the portal system or released from adipocytes also induce insulin resistance. In this report, we show that phenylmethimazole (C10) blocks basal IL6 and leptin production as well as basal Socs-3 expression in fully differentiated 3T3L1 cells (3T3L1 adipocytes) without affecting insulin-stimulated AKT signaling. In addition, C10 inhibits palmitate-induced IL6 and iNos up-regulation in both 3T3L1 adipocytes and RAW 264.7 macrophages, LPS-induced NF-κB and IFN-β activation in 3T3L1 cells, and LPS-induced iNos, Ifn-β, Il1β, Cxcl10, and Il6 expression in RAW 264.7 macrophages. C10 also blocks palmitate-induced Socs-3 up-regulation and insulin receptor substrate-1 (IRS-1) serine 307 phosphorylation in 3T3L1 adipocytes. Additionally, we show for the first time that although palmitate increases IRS-1 serine 307 phosphorylation in 3T3L1 adipocytes, AKT serine 473 phosphorylation is enhanced, not reduced, by palmitate. These results suggest that through inhibition of FFA-mediated signaling in adipocytes and associated macrophages, as well as possibly other insulin target cells/tissues (i.e. non-immune cells), C10 might be efficacious to prevent or reverse cytokine-induced insulin resistance seen in obesity-related insulin resistance and type 2 diabetes mellitus.

Increased Wnt5a mRNA Expression in Advanced Atherosclerotic Lesions, and Oxidized LDL Treated Human Monocyte-Derived Macrophages

Objective Wnt5a is a secreted glycoprotein highly present in atherosclerotic lesions. Uptake of oxidized-low density lipoprotein (ox-LDL) by monocytes/macrophages plays a critical role in atherosclerosis. The objective of this study was to determine if Wnt5a mRNA expression correlates with the severity of atherosclerotic lesions, and if, ox-LDL can induce Wnt5a mRNA in macrophages. Methods Wnt5a mRNA in tissue sections from carotid arteries of patients undergoing endarterectomy was quantified via RT-PCR and correlated with plaque severity. Human monocyte-derived macrophages and differentiated THP-1 cells, a human monocytic cell line, were treated with ox-LDL or native-LDL. Subsequently, Wnt5a transcripts were quantified by RT-PCR. Results Regions of the arteries with more severe plaques had detectable and significant levels of Wnt5a mRNA, while regions of the arteries containing less vulnerable plaques had low or non-detectable Wnt5a. Ox-LDL, but not native-LDL, induced Wnt5a mRNA in both human monocyte-derived macrophages and differentiated THP-1 cells. Conclusion Our results demonstrate that the expression of Wnt5a correlates with the severity of atherosclerotic lesions, and that ox-LDL induces Wnt5a mRNA expression in human macrophages. These findings are consistent with the hypothesis that Wnt5a plays a critical role in atherosclerosis progression and that a source of Wnt5a is ox-LDL stimulated macrophages.

Phenyl methimazole suppresses dextran sulfate sodium-induced murine colitis

Ulcerative colitis is an autoimmune-inflammatory disease characterized by abnormally increased expression of Toll-like receptor-4 (TLR4) in colonic epithelial cells, increased production of pro-inflammatory cytokines (e.g., TNF-alpha, IL-1beta, IL-6, IL-12), chemokines (e.g., IP-10), and endothelial cell adhesion molecules (e.g., VCAM-1), plus enhanced leukocyte infiltration into colonic interstitium. Previously, we have shown that phenyl methimazole (C10) markedly decreases virally-induced TLR-3 expression and signaling and potently inhibits both TNF-alpha-induced VCAM-1 expression and the resultant leukocyte-endothelial cell adhesion. In this study we probed the hypothesis that C10 is efficacious in a TLR-4- and VCAM-1-associated murine model [the dextran sulfate sodium (DSS) model] of human colitis. C10 was administered intraperitoneally coincident with or after DSS treatment was initiated. Macroscopic colon observations revealed that C10 significantly reversed DSS-induced shortening of the colon (P<0.05) and reduced the presence of blood in the colon. Histological analyses of colonic tissues revealed that C10 distinctly attenuated both DSS-induced edema as well as leukocyte infiltration in the colonic mucosa and resulted in pronounced protection against DSS-induced crypt damage (P<0.001). Northern blot analyses and immunohistochemistry of colonic tissue revealed that C10 markedly diminished DSS-induced expression of pertinent inflammatory mediators: TNF-alpha, IL-1beta, IL-6, IL-12, IP-10, TLR-4 and VCAM-1. Most importantly, C10 significantly improved survival and protected mice against DSS-induced colitic-death: 75% by comparison to 12.5% with identical treatment with DMSO-control (log rank test: P=0.005). These results provide direct evidence that C10 suppresses DSS-induced colitis by inhibiting expression of key inflammatory mediators and leukocyte infiltration, and is a potentially attractive therapeutic for colitis.

Phenylmethimazole inhibits production of proinflammatory mediators and is protective in an experimental model of endotoxic shock

Background:One form of sepsis, or endotoxic shock, is a hyperactivated systemic response caused by excessive expression of proinflammatory mediators, which results from Gram-negative bacterial lipopolysaccharide-stimulated Toll-like receptor-4 signaling. This lipopolysaccharide signaling is known to consist of a MyD88-dependent nuclear factor-&kgr;B-mediated pathway that results in production of proinflammatory mediators (tumor necrosis factor-&agr;, interleukin-6, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, inducible nitric oxide synthase, cyclooxygenase-2) and a MyD88-independent interferon regulatory factor-mediated pathway that regulates production of Type 1 interferon-inducible proteins (interferon &ggr;-induced protein-10, monocyte chemotactic protein-1). In prior studies, phenylmethimazole markedly decreased virally induced Toll-like receptor-3 expression and signaling and significantly suppressed murine colitis in an experimental model wherein lipopolysaccharide is known to play an important role. Objective:In this study, we probed the hypothesis that phenylmethimazole inhibits lipopolysaccharide-mediated Toll-like receptor-4 signaling and is efficacious in attenuating inflammatory changes and improving survival in an in vivo murine model of endotoxic shock. Design:Experimental animal model. Setting:University laboratory. Subjects:Male C57BL/6J mice weighing 18–22 g. Interventions:Phenylmethimazole (1 mg/kg) was administered intraperitoneally to mice before a lethal lipopolysaccharide challenge (25 mg/kg). RAW264.7 mouse macrophage cells were pretreated with phenylmethimazole followed by lipopolysaccharide stimulation. Measurements and Main Results:Macroscopic observations revealed that phenylmethimazole was significantly protective in controlling clinical manifestations of endotoxic shock and death under conditions wherein flunixin of meglumine and prednisolone were marginally effective. A combination of enzyme-linked immunosorbent assay, Northern blot, reverse transcriptase-polymerase chain reaction, immunohistochemistry, and Western blot analyses showed that phenylmethimazole attenuated lipopolysaccharide-induced increases in production of proinflammatory cytokines (tumor necrosis factor-&agr;, interleukin-6, interferon-&ggr;), endothelial cell adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1), inducible nitric oxide synthase and cyclooxygenase-2, interferon regulatory factor-1, interferon-inducible proteins (interferon &ggr;-induced protein-10, monocyte chemotactic protein-1), and signal transducer and activator of transcription-1 phosphorylation in multiple tissues in mice. Consistent with these observations, electrophoretic mobility shift assay demonstrated that phenylmethimazole inhibited in vitro lipopolysaccharide-induced nuclear factor-&kgr;B and interferon regulatory factor-1 activation in RAW 264.7 mouse macrophages. Conclusions:Collectively, these results provide direct evidence that phenylmethimazole diminishes lipopolysaccharide-induced MyD88-dependent as well as MyD88-independent signaling pathways and is protective in an experimental model of endotoxic shock.

A Quantitative Real-Time PCR Approach for the Detection and Characterization of Endothelial Cells in Whole Blood

Pathological inflammation and endothelial dysfunction in atherosclerosis causes endothelial cell detachment from affected vasculature giving rise to circulating endothelial cells (CECs). A blood-based assay that can detect and characterize CECs in atherosclerosis could serve as a valuable diagnostic. Thus, we sought to develop a prototypic assay that detects and characterizes the inflammatory state of endothelial cells present in blood. For this purpose, we spiked resting and inflamed human umbilical vein endothelial cells (HUVEC) into separate samples of whole blood. RNA was harvested and analyzed via quantitative real-time PCR (qPCR) using melanoma cell adhesion molecule (MCAM), as an endothelial marker, and vascular cell adhesion molecule (VCAM-1), which is increased on inflamed endothelium. We found that MCAM mRNA levels correlated with the number of HUVEC spiked into the blood. VCAM-1 mRNA levels were elevated, and correlated with the number of HUVEC, in blood spiked with inflamed HUVEC but not in blood spiked with resting HUVEC. VCAM-1 and MCAM mRNA levels were converted into numerical indices that indicate the inflammatory state of the HUVEC. Combined, the blood spiking studies demonstrate that a VCAM-1/MCAM qPCR assay can successfully detect inflamed endothelial cells in whole blood thus providing proof-of-concept for a diagnostic based on a coupled-phenotypic qPCR assay.