Inhibiting Oxidative Phosphorylation In Vivo Restrains Th17 Effector Responses and Ameliorates Murine Colitis

Integration of signaling and metabolic pathways enables and sustains lymphocyte function. Whereas metabolic changes occurring during T cell activation are well characterized, the metabolic demands of differentiated T lymphocytes are largely unexplored. In this study, we defined the bioenergetics of Th17 effector cells generated in vivo. These cells depend on oxidative phosphorylation (OXPHOS) for energy and cytokine production. Mechanistically, the essential role of OXPHOS in Th17 cells results from their limited capacity to increase glycolysis in response to metabolic stresses. This metabolic program is observed in mouse and human Th17 cells, including those isolated from Crohn disease patients, and it is linked to disease, as inhibiting OXPHOS reduces the severity of murine colitis and psoriasis. These studies highlight the importance of analyzing metabolism in effector lymphocytes within in vivo inflammatory contexts and suggest a therapeutic role for manipulating OXPHOS in Th17-driven diseases.

ETC-1002 regulates immune response, leukocyte homing, and adipose tissue inflammation via LKB1-dependent activation of macrophage AMPK

ETC-1002 is an investigational drug currently in Phase 2 development for treatment of dyslipidemia and other cardiometabolic risk factors. In dyslipidemic subjects, ETC-1002 not only reduces plasma LDL cholesterol but also significantly attenuates levels of hsCRP, a clinical biomarker of inflammation. Anti-inflammatory properties of ETC-1002 were further investigated in primary human monocyte-derived macrophages and in in vivo models of inflammation. In cells treated with ETC-1002, increased levels of AMP-activated protein kinase (AMPK) phosphorylation coincided with reduced activity of MAP kinases and decreased production of proinflammatory cytokines and chemokines. AMPK phosphorylation and inhibitory effects of ETC-1002 on soluble mediators of inflammation were significantly abrogated by siRNA-mediated silencing of macrophage liver kinase B1 (LKB1), indicating that ETC-1002 activates AMPK and exerts its anti-inflammatory effects via an LKB1-dependent mechanism. In vivo, ETC-1002 suppressed thioglycollate-induced homing of leukocytes into mouse peritoneal cavity. Similarly, in a mouse model of diet-induced obesity, ETC-1002 restored adipose AMPK activity, reduced JNK phosphorylation, and diminished expression of macrophage-specific marker 4F/80. These data were consistent with decreased epididymal fat-pad mass and interleukin (IL)-6 release by inflamed adipose tissue. Thus, ETC-1002 may provide further clinical benefits for patients with cardiometabolic risk factors by reducing systemic inflammation linked to insulin resistance and vascular complications of metabolic syndrome.

AMP-activated protein kinase and ATP-citrate lyase are two distinct molecular targets for ETC-1002, a novel small molecule regulator of lipid and carbohydrate metabolism

ETC-1002 (8-hydroxy-2,2,14,14-tetramethylpentadecanedioic acid) is a novel investigational drug being developed for the treatment of dyslipidemia and other cardio-metabolic risk factors. The hypolipidemic, anti-atherosclerotic, anti-obesity, and glucose-lowering properties of ETC-1002, characterized in preclinical disease models, are believed to be due to dual inhibition of sterol and fatty acid synthesis and enhanced mitochondrial long-chain fatty acid β-oxidation. However, the molecular mechanism(s) mediating these activities remained undefined. Studies described here show that ETC-1002 free acid activates AMP-activated protein kinase in a Ca(2+)/calmodulin-dependent kinase β-independent and liver kinase β 1-dependent manner, without detectable changes in adenylate energy charge. Furthermore, ETC-1002 is shown to rapidly form a CoA thioester in liver, which directly inhibits ATP-citrate lyase. These distinct molecular mechanisms are complementary in their beneficial effects on lipid and carbohydrate metabolism in vitro and in vivo. Consistent with these mechanisms, ETC-1002 treatment reduced circulating proatherogenic lipoproteins, hepatic lipids, and body weight in a hamster model of hyperlipidemia, and it reduced body weight and improved glycemic control in a mouse model of diet-induced obesity. ETC-1002 offers promise as a novel therapeutic approach to improve multiple risk factors associated with metabolic syndrome and benefit patients with cardiovascular disease.

Abstract 465: ETC-1002, a Novel Dicarboxylic Fatty Acid Analog, Inhibits Inflammatory Response in Primary Human Monocyte-Derived Macrophages as Well as in Adipose Tissue of Insulin-Resistant Mice via AMPK-Dependent Mechanisms

ETC-1002, a small molecule regulator of imbalances in lipid and carbohydrate metabolism, is an investigational drug currently in Phase 2 development to treat dyslipidemia and other cardiometabolic risk factors. In hyperlipidemic LDL receptor-deficient mice, robust antiatherosclerotic activities of ETC-1002 coincided with reduced levels of inflammatory markers in mouse atheroma. To further investigate anti-inflammatory properties of ETC-1002, human monocyte-derived macrophages (MDMs) differentiated in autologous serum were stimulated with 100 ng/ml of LPS in the absence or presence of the 10 μM and 30 μM of ETC-1002. TLR4-mediated activation of downstream kinases as well as the production of pro-inflammatory mediators were assessed with phosphokinase and protein arrays. Lower levels of JNK, cJUN, p38 and ERK phosphorylation in cells treated with ETC-1002 were consistent with reduced production of pro-inflammatory cytokines (TNF-α, IL-6, IL-8 and MIP1α) and chemokines (CXCL10, CXCL1, CCL2 and CCL5). ETC-1002 at 30 mg/kg dose largely diminished thioglycolate-induced homing of neutrophils and macrophages into the mouse peritoneal cavity, supporting the inhibitory effect of ETC-1002 on leukocyte chemotactic and inflammatory activity. Furthermore, in a mouse model of diet-induced obesity and insulin resistance, epididymal fat pad mass and IL-6 release by inflamed adipose tissue were significantly attenuated (by 32% and 80% respectively) in animals treated with ETC-1002. Importantly, enhanced levels of AMPK phosphorylation, changes in intracellular energy charge coupled with reduced basal rates of sterol and fatty acid synthesis by human MDMs strongly supported AMPK-dependent anti-inflammatory effects of ETC-1002. Thus, our data suggest that ETC-1002, via stimulation of AMPK activity, may provide additional clinical benefits for patients with metabolic syndrome by reducing systemic inflammation and other cardiometabolic abnormalities linked to vascular disease.

Abstract 292: ETC-1002 Reduces Body Weight Gain and Hepatic Triglyceride Content and Improves Glycemic Control in a Mouse Model of Diet-Induced Obesity

ETC-1002 is an investigational drug currently in Phase 2 clinical development to treat dyslipidemia and other cardiometabolic risk factors. Previously, ETC-1002 prevented hyperlipidemia and atherosclerosis in rodent models; and improved hepatic triglycerides (TG) as well as fasting blood glucose and insulin in the KKA y insulin resistant mouse model via putative mechanisms including activation of AMP-activated protein kinase. In the present study we investigated the effect of ETC-1002 on body weight, hepatic TG and insulin sensitivity in a diet-induced obese (DIO) mouse model. C57BL/6 mice were fed a 60% high-fat diet beginning at 11 weeks of age. At 12 weeks of age mice were assigned to treatment groups and administered vehicle or ETC-1002 at 3, 10, or 30 mg/kg/day for 9 weeks. A separate cohort of mice was maintained on standard rodent chow diet throughout the study as a comparator. Food consumption, body weight, hepatic TG content, fasting blood glucose, fasting plasma insulin, insulin tolerance tests, and glucose tolerance tests were measured. Mice developed obesity, hyperinsulinemia, mild hyperglycemia and elevated hepatic triglycerides in response to the high-fat diet. ETC-1002 results were dose-dependent and statistically significant at doses of 10 and 30 mg/kg/day. ETC-1002 attenuated body weight gain 8% and 15% with no effect on food consumption. Body weight changes were associated with 12% and 32% decreases in epididymal fat pad mass. Hepatic TG content was also reduced with ETC-1002 by 34% and 46%; respectively. ETC-1002 treatment reduced fasting blood glucose 11% and 16%; plasma insulin 80% and 95%; and resulted in significant improvements in insulin tolerance tests (19% and 22% reduction in AUC) with modestly improved glucose tolerance (not significant). In an intervention study with a 12 week lead-in on high-fat diet, comparable effects on body weight, hepatic TG, and insulin sensitivity were observed. In summary, ETC-1002 reduced obesity and hepatic TG and improved glycemic parameters in a high-fat fed diet-induced mouse model of disease. The present data in the DIO mouse, combined with previously reported efficacy in rodent models supports ETC-1002 as a regulator of imbalances in lipid and carbohydrate metabolism.

Inhibitors of lipoprotein(a) assembly

Compounds of the general structure A and B were investigated for their activity as lipoprotein(a), [Lp(a)], assembly (coupling) inhibitors. SAR around the amino acid derivatives (structure A) gave compound 14-6 as a potent coupling inhibitor. Oral dosing of compound 14-6 to Lp(a) transgenic mice and cymologous monkeys resulted in a>30% decrease in plasma Lp(a) levels after 1-2 weeks of treatment at 100 mg/kg/day.

Recombinant adenovirus vector mediated expression of lipoprotein (a) [Lp(a)] in rabbit plasma

Lipoprotein (a) [Lp(a)] is a heterodimer of apolipoprotein (a) [apo(a)] and apolipoprotein B-100 (apoB-100) of low density lipoprotein linked by a disulfide bond. Apo(a) and apoB-100 are synthesized by the liver and covalently associate or couple to form Lp(a) extracellularly. Elevated plasma Lp(a) is an independent risk factor for vascular injury disorders such as restenosis after balloon angioplasty and accelerated graft atherosclerosis following heart transplantation. Lp(a) is not expressed in laboratory animals making studies of its pathophysiology difficult. To overcome this problem, we explored the possibility of generating Lp(a) in rabbit plasma using replication-deficient adenovirus vector mediated gene delivery. Rabbits were chosen because of their large vessels and unlike mouse or rat, rabbit apoB-100 could interact with apo(a) to generate Lp(a). The recombinant (r) adenovirus vector construct used encoded a 200 kDa apo(a) [Ad-apo(a)]. Ad-apo(a) injection into the rabbit marginal vein caused the appearance of plasma rLp(a). Injection of a r adenovirus vector expressing the bacterial LacZ gene (Ad-LacZ) or PBS (vehicle) did not result in detectable plasma rLp(a). These are the first results to demonstrate plasma expression of rLp(a) in rabbits using adenovirus vector mediated gene transfer. Therefore, this system may be suitable for investigating Lp(a)'s role in the development of vascular injury diseases in a rabbit model.

Bacterial expression and characterization of human recombinant apolipoprotein(a) kringle IV type 9

Elevated plasma lipoprotein(a) [Lp(a)] is an independent risk factor for several vascular diseases. Lp(a) particles are generated through the formation of a disulfide bond between Cys4057 of kringle IV type 9, (KIVt9), of the multikringle apolipoprotein(a) [apo(a)] and a cysteine in apoB-100 low-density lipoprotein (LDL). To better understand this interaction, we have expressed and purified KIVt9 from Escherichia coli as a His-Tag fusionprotein. Dithiothreitol (DTT)-treated purified KIVt9 migrated as a single approximately 17. 3-kDa band on SDS-PAGE gels. Without DTT, an additional band twice the molecular weight of KIVt9 was observed. The double-size band presumably resulted from dimerization of individual kringles, through their unpaired cysteine residues, since a mutation Cys4057 --> Ser ([Ser4057]KIVt9) abolished dimer formation. Using a gel-shift assay, we showed that KIVt9 could couple to 14-amino-acid apoB-100 synthetic peptides (apoB3732-3745 and apoB4319-4332) containing Cys3734 or Cys4326. Both of these apoB-100 cysteines have been reported to associate with apo(a) to generate Lp(a). In the presence of either apoB-100 peptide, KIVt9 was shifted to a higher molecular weight that was consistent with the covalent addition of a 1.2-kDa apoB-100 peptide. Identical apoB-100 peptides in which the cysteine residues were replaced by alanine ([Ala3734]apoB3732-3745 and [Ala4326]apoB4319-4332) had no effect in the gel-shift assay. Furthermore, [Ser4057]KIVt9 did not covalently interact with apoB3732-3745 or apoB4319-4332. These results indicated that KIVt9 couples to the Cys-apoB-100 peptides through a disulfide linkage. This system may be suitable for further investigating the apo(a)/apoB-100 coupling reaction and the structure of KIVt9 through X-ray crystallographic studies.

Dominant negative effect of TGF-beta1 and TNF-alpha on basal and IL-6-induced lipoprotein(a) and apolipoprotein(a) mRNA expression in primary monkey hepatocyte cultures

Lipoprotein(a) [Lp(a)] consists of apolipoprotein(a) [apo(a)] disulfide linked to apolipoprotein B-100 of LDL. Elevated plasma Lp(a) is an independent risk factor for a variety of vascular diseases. Lp(a) has been reported to be an acute-phase reactant, suggesting that cytokines may regulate its levels. To determine whether Lp(a) expression was subject to modulation by cytokines, primary monkey hepatocytes that endogenously express Lp(a) were used. Hepatocytes were treated with interleukin (IL)-6, the major mediator of the acute-phase response, and several other cytokines. IL-6 treatment (0.3 to 10 ng/mL) resulted in a marked, dose-dependent, 2- to 4-fold enhancement of Lp(a) accumulation in the hepatocyte culture media that was highly correlated with changes in apo(a) mRNA levels (r>0.9). Several other cytokines, such as IL-2, IL-8, and hepatocyte growth factor, had no significant effect on Lp(a) levels; however, transforming growth factor-beta1 (TGF-beta1) and tumor necrosis factor-alpha (TNF-alpha) were very active in inhibiting Lp(a) accumulation in the culture media, with IC50s of approximately 0.3 and 1 ng/mL, respectively. Both TGF-beta1 and TNF-alpha also decreased the apo(a) transcript. Mixing experiments, in which hepatocytes were treated with 10 ng/mL of IL-6 and 0.3 to 10 ng/mL of TGF-beta1 or TNF-alpha, demonstrated that the IL-6-mediated induction of Lp(a) and apo(a) mRNA was ablated with very low levels of either inhibitory cytokine, suggesting a dominant negative effect of TGF-beta1 and TNF-alpha. These results show that Lp(a) and apo(a) mRNA expression in primary monkey hepatocytes is subject to both positive (IL-6) and negative (TGF-beta1 and TNF-alpha) regulation by physiological levels of cytokines. Thus, in vivo Lp(a) levels may be dependent on the balance between stimulatory and inhibitory cytokines.

The apolipoprotein(a) promoter contains a retinoid response element

Retinoids were previously shown to lower apolipoprotein(a) [apo(a)] mRNA levels, suggesting that the apo(a) promoter contains a retinoid response element (RRE). Scanning the apo(a) promoter for sequences related to the consensus RRE half-site (5'-PuG(G/T)TCA-3') uncovered four sites that could potentially function as RREs at -2915, -1875, -1036, and -407. The activity of these sites was assessed by their ability to compete with a very strong consensus DR5 RRE for binding to retinoic acid receptor (RARalpha) and retinoid X receptor (RXRalpha) heterodimers using electrophoretic mobility-shift assays. Only the -1036 site (5'-TGACCTTGTGATCC-'3) was an effective competitor of the DR5 RRE; therefore, it was designated as apo(a) RRE. Apo(a) RRE competed with DR5 RRE for RARalpha/RXRalpha binding with 1/10 the affinity of DR5 RRE, while a scrambled apo(a) RRE was inactive. These results suggested that apo(a) RRE is a potential candidate for mediating the effect retinoids have on apo(a) mRNA expression.

CI-1011 lowers lipoprotein(a) and plasma cholesterol concentrations in chow-fed cynomolgus monkeys

Lipoprotein(a) (Lp(a)), which is generated through the covalent association of apolipoprotein(a) (apo(a)) and apo B-100-LDL, is an independent risk factor for several vascular diseases. Therefore, there is interest in developing therapies for lowering Lp(a). This investigation was carried out to determine the effect of CI-1011, a potent lipid regulator in rodents, on Lp(a) and other lipid parameters in cynomolgus monkeys (Macaca fascicularis). Nine healthy male monkeys on a normal chow diet were orally treated with CI-1011 at 30 mg/kg per day for 3 weeks. Lp(a) and total cholesterol levels were significantly decreased after 1 week and maximally reduced to 68 and 73% of control levels, respectively, after 3 treatment weeks. The decreases in total cholesterol were mainly due to changes in low density lipoprotein (LDL). The LDL:HDL ratio decreased by 30%. Triglycerides were unaffected by treatment. Lp(a) and total cholesterol levels returned to pretreatment values after stopping treatment suggesting a direct effect of the compound on their inhibition. Further studies demonstrated that CI-1011 was effective at a low dose of 3 mg/kg per day after 1 week of administration. CI-1011 also decreased apo B-100 to 80% of control levels, but this change was not sufficient to account for the Lp(a) lowering. There was also no correlation between the changes in Lp(a) and apo B-100 levels. Treatment of cynomolgus monkey primary hepatocyte cultures with CI-1011 resulted in a dose-dependent inhibition of Lp(a) levels suggesting a direct hepatic effect of the compound. Western blot analysis of the samples showed that changes in Lp(a) were associated mainly with decreased apo(a) (47%), but not apo B-100 (17%). These results demonstrate that CI-1011 effectively decreases Lp(a) levels both in vivo and in vitro.

Retinoids inhibit primary cynomolgus monkey hepatocyte lipoprotein(a) levels

Elevated plasma lipoprotein(a) [Lp(a)] independently contributes to a variety of vascular diseases; consequentially, factors that modulate its levels are of interest. Since Lp(a) is produced by a disulfide linkage between apolipoprotein(a) [apo(a)] and apolipoproteinB-100 (apoB-100) of low density lipoprotein (LDL) on the hepatocyte surface, modulation of either particle may be useful in lowering Lp(a). Using primary cynomolgus monkey hepatocyte cultures that endogenously express apo(a) and apoB-100, we showed that all-trans (retinol, retinal, retinoic acid) and 9-cis (retinal, retinoic acid) retinoids lower Lp(a) accumulation in the cell media, with the 9-cis derivatives being > 10-fold more potent than the all-trans stereoisomers. Lp(a) Towering was related to decreases in apo(a) and its cognate transcript, but not to apoB-100. These results demonstrate that retinoids lower Lp(a) levels by decreasing apo(a) through its cognate mRNA.

Localization of lipoprotein(a) in a monkey model of rapid neointimal growth

Lipoprotein(a) [Lp(a)] has been proposed as a restenosis risk factor, but it is not known if Lp(a) is present in the injured arterial wall during the initial neointimal growth. The purpose of this study was to determine if Lp(a) is incorporated into the vessel wall during rapid neointimal formation after arterial injury in primates. In this model, distention of the iliac artery with an angioplasty catheter caused focal breaks in the internal elastic lamina (IEL) in 80% of the vessels and extensive IEL fragmentation with medial disruption in 20% of the vessels. Neointimal growth was noted in all injured arteries; thrombus formation was noted in 40% of the vessels. Based on morphometric measurements, injured arteries had neointimal areas of 0.41 +/- 0.05 (n = 4) and 0.83 +/- 0.23 (n = 6) mm2 at 14 and 28 days after injury, respectively. Control arteries had an intact IEL and a monolayer of intimal cells. Lp(a) localization was examined histologically by using a mouse monoclonal anti-Lp(a) antibody. Lp(a), found in all injured arteries, was localized primarily in the neointima in 50% of the vessels. In the subset of vessels with evidence of thrombus formation, intense Lp(a) immunostaining was associated with the thrombus. Lp(a) was specific to injured arteries as uninjured vessels did not stain. In addition, staining was not seen with a negative control, a nonspecific mouse IgG1 antibody. The presence of Lp(a) at the site of rapid neointimal growth supports a role for this lipoprotein in the response to vascular injury after balloon angioplasty.

Expression of apolipoprotein[a] and plasminogen mRNAs in cynomolgus monkey liver and extrahepatic tissues

The apolipoprotein[a] (apo[a]) and plasminogen (PLG) genes share a high degree of sequence identity, suggesting that both genes may be coordinately expressed. To address this possibility, hepatic apo[a], PLG, and glyceraldehyde-3-phosphate dehydrogenase (G3PDH) mRNAs in 11 cynomolgus monkeys that express plasma Lp[a] over a 10-fold range (5.3-69.3 mg/dl) were measured. This analysis demonstrated a 13-fold variation in apo[a] mRNA. PLG mRNA levels ranged only 3-fold, which was similar to the deviation in G3PDH mRNA expression. Lp[a] and PLG plasma levels were also not related in the animals. To further define expression of the latter mRNAs, they were measured in liver and 13 extrahepatic tissues from 5 monkeys. Apo[a] transcript was detected for the first time in adrenal, lung, and pituitary in addition to brain and testes. PLG mRNA was detected extrahepatically only in testes while G3PDH mRNA was ubiquitously expressed. In individual animals, there was no relationship between hepatic and extrahepatic apo[a] mRNA levels suggesting tissue-dependent expression of the transcript. These results demonstrate that although the apo[a] and PLG genes are highly homologous, their mRNA expression differs markedly.

Gemfibrozil significantly lowers cynomolgus monkey plasma lipoprotein[a]-protein and liver apolipoprotein[a] mRNA levels

Eight male cynomolgus monkeys (Macaca fascicularis) on a normal chow diet were orally administered gemfibrozil daily using a weekly rising dose protocol for 3 weeks (50, 125, and 200 mg/kg per day). At these drug doses, Lp[a] levels were reduced: 83.7% +/- 3.2 (SEM), (P < 0.024); 63.7% +/- 4.1 (P < 0.013); and 36.2% +/- 1.1 (P < 0.002), respectively, of pretreatment values. Lp[a] reduction was directly related to blood gemfibrozil concentration (range 36-428 microM, r = 0.969) and occurred without concomitant changes in apolipoprotein B. Three weeks posttreatment Lp[a] levels returned to pretreatment values. A specific ribonuclease protection assay demonstrated that liver apolipoprotein[a] (apo[a]) mRNA expression was decreased in all animals to an average of 19.1% +/- 3.0 (P < 0.0026), of pretreatment values after the 200 mg/kg treatment, whereas, albumin, apolipoprotein A-I, apolipoprotein E, and glyceraldehyde-3-phosphate dehydrogenase mRNAs were unchanged. Lp[a] levels were unaffected by gemfibrozil in HepG2 cells permanently transfected with an apo[a] 10-kringle cDNA construct containing partial 5'- and 3'-untranslated sequences and under control of a constitutive CMV promoter. However, both Lp[a] and apo[a] mRNA in primary cynomolgus monkey hepatocytes were coordinately lowered in a dose-dependent fashion by gemfibrozil. Thus, Lp[a] can be regulated by gemfibrozil at the level of apo[a] mRNA expression.

Alveolar epithelial cells block lymphocyte proliferation in vitro without inhibiting activation

In the face of constant exposure to inhaled antigens, precise local regulation of immune responses in the pulmonary alveolar space is essential to achieve a delicate balance between host defense and excessive immune responses that are incompatible with the primary physiologic function of the lung. We postulated that the cells of the alveolar epithelium may have an immunoregulatory role in the lung. Therefore, we have examined the effects of primary cultures of rat type II alveolar epithelial cells on lymphocyte proliferation and on the expression of a number of markers of T-cell activation. Monolayers of alveolar epithelial cells suppressed proliferation and DNA synthesis by concanavalin A-stimulated rat splenocytes. Suppression of [3H]thymidine incorporation was independent of the dose of mitogen and was also apparent when lymphocytes were stimulated with phorbol esters and calcium ionophore, suggesting that the effect was independent of cell surface binding of the lectin. Suppression was reversed 48 h after lectin-stimulated splenocytes were removed from co-culture with alveolar epithelial cells. Despite inhibition of lymphocyte proliferation, other markers of T-cell activation were induced normally in lymphocytes cultured with alveolar epithelial cells. Culture with alveolar epithelial cells did not inhibit the the production of interleukin-2 by stimulated lymphocytes. Furthermore, by fluorescence-activated cell sorter analysis, equal proportions of stimulated lymphocytes in culture alone or with alveolar epithelial cell monolayers were induced to express receptors for interleukin-2 and for transferrin.(ABSTRACT TRUNCATED AT 250 WORDS)