👤 R A Johns

A novel class of nonpeptide melanocortin type 2 receptor (MC2R) antagonists was discovered through modification of known nonpeptide MC4R ligands. Structure-activity relationship (SAR) studies led to the discovery of Show less

Cholesteryl ester transfer protein (CETP) represents one of the key regulators of the homeostasis of lipid particles, including high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles. Epidemiological evidence correlates increased HDL and decreased LDL to coronary heart disease (CHD) risk reduction. This relationship is consistent with a clinical outcomes trial of a CETP inhibitor (anacetrapib) combined with standard of care (statin), which led to a 9% additional risk reduction compared to standard of care alone. We discuss here the discovery of MK-8262, a CETP inhibitor with the potential for being the best-in-class molecule. Novel in vitro and in vivo paradigms were integrated to drug discovery to guide optimization informed by a critical understanding of key clinical adverse effect profiles. We present preclinical and clinical evidence of MK-8262 safety and efficacy by means of HDL increase and LDL reduction as biomarkers for reduced CHD risk. Show less

Cholesteryl ester transfer protein (CETP) inhibitors reduce the transfer of cholesteryl esters from the high-density lipoprotein (HDL-C) to apolipoprotein such as VLDL/LDL, with exchange of triglycerides. Thus, this inhibition increases the HDL-C levels, which is believed to lower the risk for heart disease and stroke. We report here a series of CETP inhibitors based on the cyclic, bicyclic urea and sulfamide cores. These CETP inhibitors exemplified by 15, 31, and 45 demonstrated in vitro potency in inhibiting the CETP transfer activity, and 15, 31 showing in vivo efficacy to increase HDL-C levels in cynomolgus-CETP transgenic mice. The synthesis and biological evaluations of these CETP inhibitors are described. Show less

Anacetrapib is an inhibitor of cholesteryl ester transfer protein (CETP) previously under development as a lipid-modifying agent that reduces LDL-cholesterol and increases HDL-cholesterol in hypercholesterolemic patients. Anacetrapib demonstrates a long terminal half-life and accumulates in adipose tissue, which contributes to a long residence time of anacetrapib. Given our previous report that anacetrapib distributes into the lipid droplet of adipose tissue, we sought to understand whether anacetrapib affected adipose function, using a diet-induced obese (DIO) mouse model. Following 20 weeks of treatment with anacetrapib (100 mg/kg/day), levels of the drug increased to approximately 0.6 mmol/L in white adipose tissue. This level of anacetrapib was not associated with any impairment in adipose functionality as evidenced by a lack of any reduction in biomarkers of adipose functionality (plasma adiponectin, leptin, insulin; adipose adiponectin, leptin mRNA). In DIO wild-type (WT) mice treated with anacetrapib for 2 weeks and then subjected to 30% food restriction during washout to induce weight loss (18%) and fat mass loss (7%), levels of anacetrapib in adipose and plasma were not different between food restricted and ad lib-fed mice. These data indicate that despite deposition and long-term residence of ~0.6 mmol/L levels of anacetrapib in adipose tissue, adipose tissue function appears to be unaffected in mice. In addition, these data also indicate that even with severe caloric restriction and acute loss of fat mass, anacetrapib does not appear to be mobilized from the fat depot, thereby solidifying the role of adipose as a long-term storage site of anacetrapib. Show less

Coronary artery bypass grafting is among the most commonly performed of all cardiovascular surgical procedures. However, graft failure due to stenosis reduces the long-term benefit of the intervention. This study asks if elevating plasma high density lipoprotein cholesterol (HDL-C) levels by inhibition of cholesteryl ester transfer protein (CETP) activity with des-fluoro-anacetrapib, an analog of the CETP inhibitor anacetrapib, prevents vein bypass-induced neointimal hyperplasia. NZW rabbits were placed on a normal chow diet or chow containing 0.14% (wt/wt) des-fluoro-anacetrapib for 6 weeks. Bypass grafting of the jugular vein to the common carotid artery was performed 2 weeks after starting dietary des-fluoro-anacetrapib supplementation. The animals were euthanised 4 weeks post-bypass grafting. Relative to control, dietary supplementation with des-fluoro-anacetrapib reduced plasma CETP activity by 89 ± 6.9%, increased plasma apolipoprotein A-I levels by 24 ± 5.5%, increased plasma HDL-C levels by 93 ± 26% and reduced intimal hyperplasia in the grafted vein by 38 ± 6.2%. Des-fluoro-anacetrapib treatment was also associated with decreased bypass grafting-induced endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), endothelial dysfunction, and smooth muscle cell (SMC) proliferation in the grafted vein. In conclusion, increasing HDL-C levels by inhibiting CETP activity is associated with inhibition of intimal hyperplasia in grafted veins, reduced inflammatory responses, improved endothelial function, and decreased SMC proliferation. Show less

Anacetrapib is an inhibitor of cholesteryl ester transfer protein (CETP), associated with reduction in LDL cholesterol and increase in HDL cholesterol in hypercholesterolemic patients. Anacetrapib was not taken forward into filing/registration as a new drug for coronary artery diease, despite the observation of a ∼9% reduction in cardiovascular risk in a large phase III cardiovascular outcomes trial (REVEAL). Anacetrapib displayed no adverse effects throughout extensive preclinical safety evaluation, and no major safety signals were observed in clinical trials studying anacetrapib, including REVEAL. However, anacetrapib demonstrated a long terminal half-life in all species, thought to be due, in part, to distribution into adipose tissue. We sought to understand the dependence of anacetrapib's long half-life on adipose tissue and to explore potential mechanisms that might contribute to the phenomenon. In mice, anacetrapib localized primarily to the lipid droplet of adipocytes in white adipose tissue; in vitro, anacetrapib entry into cultured human adipocytes depended on the presence of a mature adipocyte and lipid droplet but did not require active transport. In vivo, the entry of anacetrapib into adipose tissue did not require lipase activity, as the distribution of anacetrapib into adipose was-not affected by systemic lipase inhibition using poloaxamer-407, a systemic lipase inhibitor. The data from these studies support the notion that the entry of anacetrapib into adipose tissue/lipid droplets does not require active transport, nor does it require mobilization or entry of fat into adipose via lipolysis. Show less

Apolipoprotein A5 (APOA5) 1131 is one of the most investigated gene polymorphisms in association with cardiovascular diseases (CVD) for its roles in epigenetics pathways. The major objective of this metaprediction study was to comprehensively examine the association of polymorphism risk subtypes of APOA5 1131 gene and potential contributing factors of CVD risks in global populations. This study is a meta-analysis to determine APOA5 gene polymorphisms as risk factors for CVDs. Following the guidelines of meta-analyses, we applied big data analytics including the recursive partition tree, nonlinear association curve fit, and heat maps for data visualization-in addition to the conventional pooled analyses. A total of 17,692 CVD cases and 23,566 controls from 50 study groups were included. The frequency of APOA5 1131 CC and TC polymorphisms in Asian populations (22.2%-52.6%) were higher than that in other populations, including Caucasians and Eurasians (10.0%-25.0%). The homozygous CC and heterozygous TC genotypes (both p < .0001) were associated with increased risks for CVD and were higher in many Western nations, including Canada, Spain, the Czech Republic, Hungary, Turkey, Egypt, France, and Iran. The CC genotype was associated with greater risks (RR > 2.00, p < .0001) for dyslipidemia and myocardial infarction, whereas RR > 1.00 was associated with metabolic syndrome, coronary artery disease, and stroke. Air pollution was significantly associated with APOA5 1131 CC and TC polymorphisms. The findings of this study provided novel insight to further understand the associations among APOA5 1131 polymorphisms, air pollution, and the development of CVDs. Methylation studies are needed to examine epigenetic factors associated with APOA5 1131 polymorphisms and CVD and to suggest potential prevention strategies for CVD. Show less

Angioplasty and stent implantation, the most common treatment for atherosclerotic lesions, have a significant failure rate because of restenosis. This study asks whether increasing plasma high-density lipoprotein (HDL) levels by inhibiting cholesteryl ester transfer protein activity with the anacetrapib analog, des-fluoro-anacetrapib, prevents stent-induced neointimal hyperplasia. New Zealand White rabbits received normal chow or chow supplemented with 0.14% (wt/wt) des-fluoro-anacetrapib for 6 weeks. Iliac artery endothelial denudation and bare metal steel stent deployment were performed after 2 weeks of des-fluoro-anacetrapib treatment. The animals were euthanized 4 weeks poststent deployment. Relative to control, dietary supplementation with des-fluoro-anacetrapib reduced plasma cholesteryl ester transfer protein activity and increased plasma apolipoprotein A-I and HDL cholesterol levels by 53±6.3% and 120±19%, respectively. Non-HDL cholesterol levels were unaffected. Des-fluoro-anacetrapib treatment reduced the intimal area of the stented arteries by 43±5.6% ( Inhibiting cholesteryl ester transfer protein activity in New Zealand White rabbits with iliac artery balloon injury and stent deployment increases HDL levels, inhibits vascular smooth muscle cell proliferation, and reduces neointimal hyperplasia in an scavenger receptor-B1, PDZ domain-containing protein 1- and phosphatidylinositol-3-kinase/Akt-dependent manner. Show less

Cholesteryl ester transfer protein (CETP) inhibitors are a new class of therapeutics for dyslipidemia that simultaneously improve two major cardiovascular disease (CVD) risk factors: elevated low-density lipoprotein (LDL) cholesterol and decreased high-density lipoprotein (HDL) cholesterol. However, the detailed molecular mechanisms underlying their efficacy are poorly understood, as are any potential mechanistic differences among the drugs in this class. Herein, we used electron microscopy (EM) to investigate the effects of three of these agents (Torcetrapib, Dalcetrapib and Anacetrapib) on CETP structure, CETP-lipoprotein complex formation and CETP-mediated cholesteryl ester (CE) transfer. We found that although none of these inhibitors altered the structure of CETP or the conformation of CETP-lipoprotein binary complexes, all inhibitors, especially Torcetrapib and Anacetrapib, increased the binding ratios of the binary complexes (e.g., HDL-CETP and LDL-CETP) and decreased the binding ratios of the HDL-CETP-LDL ternary complexes. The findings of more binary complexes and fewer ternary complexes reflect a new mechanism of inhibition: one distal end of CETP bound to the first lipoprotein would trigger a conformational change at the other distal end, thus resulting in a decreased binding ratio to the second lipoprotein and a degraded CE transfer rate among lipoproteins. Thus, we suggest a new inhibitor design that should decrease the formation of both binary and ternary complexes. Decreased concentrations of the binary complex may prevent the inhibitor was induced into cell by the tight binding of binary complexes during lipoprotein metabolism in the treatment of CVD. Show less

Intraplaque hemorrhage (IPH) drives atherosclerosis through the dual metabolic stresses of cholesterol-enriched erythrocyte membranes and pro-oxidant heme/iron. When clearing tissue hemorrhage, macrophages are typically seen storing either iron or lipid. We have recently defined hemorrhage-associated macrophages (HA-mac) as a plaque macrophage population that responds adaptively to IPH. This study aimed to define the key transcription factor(s) involved in HO-1 induction by heme. To address this question, we used microarray analysis and transfection with siRNA and plasmids. To maintain physiological relevance, we focused on human blood-derived monocytes. We found that heme stimulates monocytes through induction of activating transcription factor 1 (ATF-1). ATF-1 coinduces heme oxygenase-1 (HO-1) and Liver X receptor beta (LXR-β). Heme-induced HO-1 and LXR-β were suppressed by knockdown of ATF-1, and HO-1 and LXR-β were induced by ATF-1 transfection. ATF-1 required phosphorylation for full functional activity. Expression of LXR-β in turn led to induction of other genes central to cholesterol efflux, such as LXR-α and ABCA1. This heme-directed state was distinct from known macrophage states (M1, M2, Mox) and, following the same format, we have designated them Mhem. These results show that ATF-1 mediates HO-1 induction by heme and drives macrophage adaptation to intraplaque hemorrhage. Our definition of an ATF-1-mediated pathway for linked protection from foam cell formation and oxidant stress may have therapeutic potential. Show less

The authors have previously shown that the clinically relevant concentrations of inhalational anesthetics dose-dependently inhibit the postsynaptic density protein (PSD)-95, Dlg, and ZO-1 domain-mediated protein interactions between N-methyl-d-aspartate receptors and PSD-95/synaptic-associated protein (SAP) 90 or PSD-93/Chapsyn-110 and that the knockdown of spinal PSD-95/SAP90 significantly reduces the minimum alveolar concentration (MAC) for isoflurane in rats. The authors designed antisense oligodeoxynucleotides based on the mouse PSD-95/SAP90 and PSD-93/Chapsyn-110 messenger RNAs that correspond to their PSD-95, Dlg, and ZO-1 domain nucleotides and can specifically knock down the respective proteins. The authors intrathecally injected antisense oligodeoxynucleotides into wild-type and PSD-93/Chapsyn-110 knockout mice to investigate the effect of PSD-95/SAP90 and/or PSD-93/Chapsyn-110 deficiency on halothane anesthesia. Both PSD-95/SAP90 and PSD-93/Chapsyn-110 antisense oligodeoxynucleotides caused a dose-dependent and significant reduction in the MAC of halothane in wild-type mice. The intrathecal injection of PSD-95/SAP90 antisense oligodeoxynucleotide at different doses (25 and 50 microg) reduced halothane MAC by 40 and 55%, respectively, and intrathecal injection of PSD-93/Chapsyn-110 antisense oligodeoxynucleotide at different doses (12 and 24 microg) reduced halothane MAC by 25 and 53%, respectively. The PSD-95/SAP90 antisense oligodeoxynucleotide showed similar effect on halothane MAC in wild-type and PSD-93/Chapsyn-110 knockout mice, suggesting that the combination of PSD-95/SAP90 knockdown with PSD-93/Chapsyn-110 deletion did not have an additive effect on halothane anesthesia. The current results indicate that PSD-95/SAP90 and PSD-93/Chapsyn-110 are involved in the molecular mechanisms of halothane anesthesia and that the functional role of PSD-95/SAP90 in halothane anesthesia is not enhanced after PSD-93/Chapsyn-110 deletion. Show less

Postsynaptic density (PSD)-93, a neuronal scaffolding protein, binds to and clusters N-methyl-D-aspartate receptor (NMDAR) subunits NR2A and NR2B at cellular membranes in vitro. However, the roles of PSD-93 in synaptic NR2A and NR2B targeting in the central nervous system and NMDAR-dependent physiologic and pathologic processes are still unclear. We report here that PSD-93 deficiency significantly decreased the amount of NR2A and NR2B in the synaptosomal membrane fractions derived from spinal cord dorsal horn and forebrain cortex but did not change their levels in the total soluble fraction from either region. However, PSD-93 deficiency did not markedly change the amounts of NR2A and NR2B in either synaptosomal or total soluble fractions from cerebellum. In mice deficient in PSD-93, morphine dose-dependent curve failed to shift significantly rightward as it did in wild type (WT) mice after acute and chronic morphine challenge. Unlike WT mice, PSD-93 knockout mice also showed marked losses of NMDAR-dependent morphine analgesic tolerance and associated abnormal sensitivity in response to mechanical, noxious thermal, and formalin-induced inflammatory stimuli after repeated morphine injection. In addition, PSD-93 knockout mice displayed dramatic loss of jumping activity, a typical NMDAR-mediated morphine withdrawal abstinence behavior. These findings indicate that impaired NMDAR-dependent neuronal plasticity following repeated morphine injection in PSD-93 knockout mice is attributed to PSD-93 deletion-induced alterations of synaptic NR2A and NR2B expression in dorsal horn and forebrain cortex neurons. The selective effect of PSD-93 deletion on synaptic NMDAR expression in these two major pain-related regions might provide the better strategies for the prevention and treatment of opioid tolerance and physical dependence. Show less

Src family protein kinases (SFKs) -mediated tyrosine-phosphorylation regulates N-methyl-D-aspartate (NMDA) receptor synaptic function. Some members of the membrane-associated guanylate kinase (MAGUK) family of proteins bind to both SFKs and NMDA receptors, but it is unclear whether the MAGUK family of proteins is required for SFKs-mediated tyrosine-phosphorylation of the NMDA receptors. Here, we showed by co-immunoprecipitation that post-synaptic density (PSD) -93, a member of the MAGUK family of proteins, interacts with the NMDA receptor subunits NR2A and NR2B as well as with Fyn, a member of the SFKs, in mouse cerebral cortex. Using a biochemical fractionation approach to isolate subcellular compartments revealed that the expression of Fyn, but not of other members of the SFKs (Lyn, Src, and Yes), was significantly decreased in synaptosomal membrane fractions derived from the cerebral cortex of PSD-93 knockout mice. Interestingly, we found that PSD-93 disruption causes reduction of tyrosine-phosphorylated NR2A and NR2B in the same fraction. Moreover, PSD-93 deletion markedly blocked the SFKs-mediated increase in tyrosine-phosphorylated NR2A and NR2B through the protein kinase C pathway after induction with 4-phorbol 12-myristate 13-acetate in cultured cortical neurons. Our findings indicate that PSD-93 appears to mediate tyrosine-phosphorylation of the NMDA receptors and synaptic localization of Fyn. Show less

PSD-93, a molecular adaptive protein, binds to and clusters the N-methyl-D-aspartate (NMDA) receptor and assembles a specific set of signaling proteins (for example neuronal nitric oxide synthase, nNOS) around the NMDA receptor at synapses in the central nervous system. This suggests that PSD-93 might mediate many NMDA receptor-dependent physiological and pathophysiological functions. We report here that PSD-93 colocalizes and interacts with the NMDA receptor and neuronal nitric oxide synthase in cultured cortical neurons. Targeted disruption of PSD-93 gene significantly prevented NMDA receptor-nitric oxide signaling-dependent neurotoxicity triggered via platelet-activating factor (PAF) receptor activation. In addition, the deficiency of PSD-93 markedly attenuated platelet-activating factor-induced increase in cyclic guanosine 3',5'-monophosphate (cGMP) and prevented platelet-activating factor-promoted formation of NMDA receptor-neuronal nitric oxide synthase complex. These findings indicate that PSD-93 is involved in the NMDA receptor--nitric oxide-mediated pathological processing of neuronal damage triggered via platelet--activating factor receptor activation. Since platelet-activating factor is a potent neuronal injury mediator during the development of brain trauma, seizures, and ischemia, the present work suggests that PSD-93 might contribute to molecular mechanisms of neuronal damage in these brain disorders. Show less

Modification of synaptic NMDA receptor (NMDAR) expression influences NMDAR-mediated synaptic function and associated persistent pain. NMDARs directly bind to a family of membrane-associated guanylate kinases (MAGUKs) that regulate surface and synaptic NMDAR trafficking in the CNS. We report here that postsynaptic density-93 protein (PSD-93), a postsynaptic neuronal MAGUK, is expressed abundantly in spinal dorsal horn and forebrain, where it colocalizes and interacts with NMDAR subunits NR2A and NR2B. Targeted disruption of the PSD-93 gene reduces not only surface NR2A and NR2B expression but also NMDAR-mediated excitatory postsynaptic currents and potentials, without affecting surface AMPA receptor expression or its synaptic function, in the regions mentioned above. Furthermore, mice lacking PSD-93 exhibit blunted NMDAR-dependent persistent pain induced by peripheral nerve injury or injection of Complete Freund's Adjuvant, although they display intact nociceptive responsiveness to acute pain. PSD-93 appears to be important for NMDAR synaptic targeting and function and to be a potential biochemical target for the treatment of persistent pain. Show less