Synthesis of benzopyran derivatives as PPARα and/or PPARγ activators

We describe the synthesis of 26 compounds, small polycerasoidol analogs, that are Lipinski’s rule-of-five compliant. In order to confirm key structural features to activate PPARα and/or PPARγ, we have adopted structural modifications in the following parts: (i) the benzopyran core (hydrophobic nucleus) by benzopyran-4-one, dihydrobenzopyran or benzopyran-4-ol; (ii) the side chain at 2-position by shortening to C3, C4 and C5-carbons versus C-9-carbons of polycerasoidol; (iii) the carboxylic group (polar head) by oxygenated groups (hydroxyl, acetoxy, epoxide, ester, aldehyde) or non-oxygenated motifs (allyl and alkyl). Benzopyran-4-ones 6, 12, 13 and 17 as well as dihydrobenzopyrans 22, 24 and 25 were able to activate hPPARα, whereas benzopyran-4-one (7) with C5-carbons in the side chain exhibited hPPARγ agonism. According to our previous docking studies, SAR confirm that the hydrophobic nucleus (benzopyran-4-one or dihydrobenzopyran) is essential to activate PPARα and/or PPARγ, and the flexible linker (side alkyl chain) should containg at least C5-carbon atoms to activate PPARγ. By contrast, the polar head (“carboxylic group”) tolerated several oxygenated groups but also non-oxygenated motifs. Taking into account these key structural features, small polycerasoidol analogs might provide potential active molecules useful in the treatment of dyslipidemia and/or type 2 diabetes.     

Modulation of PPAR subtype selectivity. Part 2: Transforming PPARα/γ dual agonist into α selective PPAR agonist through bioisosteric modification

A novel series of oxime containing benzyl-1,3-dioxane-r-2-carboxylic acid derivatives (6a-k) were designed as selective PPARα agonists, through bioisosteric modification in the lipophilic tail region of PPARα/γ dual agonist. Some of the test compounds (6a, 6b, 6c and 6f) showed high selectivity towards PPARα over PPARγ in vitro. Further, highly potent and selective PPARα agonist 6c exhibited significant antihyperglycemic and antihyperlipidemic activity in vivo, along with its improved pharmacokinetic profile. Favorable in-silico interaction of 6c with PPARα binding pocket correlate its in vitro selectivity profile toward PPARα over PPARγ. Together, these results confirm discovery of novel series of oxime based selective PPARα agonists for the safe and effective treatment of various metabolic disorders.     

Skin-targeted inhibition of PPAR β/δ by selective antagonists to treat PPAR β/δ-mediated psoriasis-like skin disease in vivo

We have previously shown that peroxisome proliferator activating receptor ?/δ (PPAR β/δ is overexpressed in psoriasis. PPAR β/δ is not present in adult epidermis of mice. Targeted expression of PPAR β/δ and activation by a selective synthetic agonist is sufficient to induce an inflammatory skin disease resembling psoriasis. Several signalling pathways dysregulated in psoriasis are replicated in this model, suggesting that PPAR β/δ activation contributes to psoriasis pathogenesis. Thus, inhibition of PPAR β/δ might harbour therapeutical potential. Since PPAR β/δ has pleiotropic functions in metabolism, skin-targeted inhibition offer the potential of reducing systemic adverse effects. Here, we report that three selective PPAR β/δ antagonists, GSK0660, compound 3 h, and GSK3787 can be formulated for topical application to the skin and that their skin concentration can be accurately quantified using ultra-high performance liquid chromatography (UPLC)/mass spectrometry. These antagonists show efficacy in our transgenic mouse model in reducing psoriasis-like changes triggered by activation of PPAR β/δ. PPAR β/δ antagonists GSK0660 and compound 3 do not exhibit systemic drug accumulation after prolonged application to the skin, nor do they induce inflammatory or irritant changes. Significantly, the irreversible PPAR β/δ antagonist (GSK3787) retains efficacy when applied topically only three times per week which could be of practical clinical usefulness. Our data suggest that topical inhibition of PPAR β/δ to treat psoriasis may warrant further exploration.     

Scaffold-Based Pan-Agonist Design for the PPARα, PPARβ and PPARγ Receptors

As important members of nuclear receptor superfamily, Peroxisome proliferator-activated receptors (PPAR) play essential roles in regulating cellular differentiation, development, metabolism, and tumorigenesis of higher organisms. The PPAR receptors have 3 identified subtypes: PPARα, PPARβ and PPARγ, all of which have been treated as attractive targets for developing drugs to treat type 2 diabetes. Due to the undesirable side-effects, many PPAR agonists including PPARα/γ and PPARβ/γ dual agonists are stopped by US FDA in the clinical trials. An alternative strategy is to design novel pan-agonist that can simultaneously activate PPARα, PPARβ and PPARγ. Under such an idea, in the current study we adopted the core hopping algorithm and glide docking procedure to generate 7 novel compounds based on a typical PPAR pan-agonist {"type":"entrez-nucleotide","attrs":{"text":"LY465608","term_id":"1257853743","term_text":"LY465608"}}LY465608. It was observed by the docking procedures and molecular dynamics simulations that the compounds generated by the core hopping and glide docking not only possessed the similar functions as the original {"type":"entrez-nucleotide","attrs":{"text":"LY465608","term_id":"1257853743","term_text":"LY465608"}}LY465608 compound to activate PPARα, PPARβ and PPARγ receptors, but also had more favorable conformation for binding to the PPAR receptors. The additional absorption, distribution, metabolism and excretion (ADME) predictions showed that the 7 compounds (especially Cpd#1) hold high potential to be novel lead compounds for the PPAR pan-agonist. Our findings can provide a new strategy or useful insights for designing the effective pan-agonists against the type 2 diabetes.     

Synthesis of 5-trifluoromethyl-2-sulfonylpyridine PPARβ/δ antagonists: Effects on the affinity and selectivity towards PPARβ/δ

The covalent modification of peroxisome-proliferator activated receptor β/δ (PPARβ/δ) is part of the mode of action of 5-trifluoromethyl-2-sulfonylpyridine PPARβ/δ antagonists such as GSK3787 and CC618. Herein, the synthesis and in vitro biological evaluation of a range of structural analogues of the two antagonists are reported. The new ligands demonstrate that an improvement in the selectivity of 5-trifluoromethyl-2-sulfonylpyridine antagonists towards PPARβ/δ is achievable at the expense of their immediate affinity for PPARβ/δ. However, their putatively covalent and irreversible mode of action may ensure their efficacy over time, as observed in time-resolved fluorescence resonance energy transfer (TR-FRET)-based ligand displacement assays.     

Structure-Based Virtual Screening and Discovery of New PPARδ/γ Dual Agonist and PPARδ and γ Agonists

Peroxisome proliferator-activated receptors (PPARs) are involved in the control of carbohydrate and lipid metabolism and are considered important targets to treat diabetes mellitus and metabolic syndrome. The available PPAR ligands have several side effects leading to health risks justifying the search for new bioactive ligands to activate the PPAR subtypes, in special PPARδ, the less studied PPAR isoform. Here, we used a structure-based virtual screening protocol in order to find out new PPAR ligands. From a lead-like subset of purchasable compounds, we identified 5 compounds with potential PPAR affinity and, from preliminary in vitro assays, 4 of them showed promising biological activity. Therefore, from our in silico and in vitro protocols, new PPAR ligands are potential candidates to treat metabolic diseases.     

PPARα、PPARγ及其双激动剂与动脉粥样硬化

过氧化物酶体增殖物激活受体（peroxisome proliferator-activated receptors,PPARs）是核受体超家族中的一类配体依赖的核转录因子,其中两种重要的亚型PPARα和PPARγ在脂肪细胞分化、能量代谢和炎症过程中都发挥重要作用。研究显示,PPARα和PPARγ的配体激动剂不仅可以改善包括糖尿病、高血压和肥胖等在内的胰岛素抵抗综合征,而且还可以通过作用于血管壁从而减缓动脉粥样硬化的进程。本文将就PPARα和PPARγ及其双激动剂与动脉粥样硬化发病机制和治疗的相关研究进展进行概括介绍。     

激活PPARα缓解PPARγ诱导的小鼠脂肪肝

目的研究PPARα激活后对PPARγ诱导小鼠脂肪肝的影响。方法以4~5周龄C57BL/6J小鼠为模型,实验分为4组:正常饮食组;0.125%Wy-14,643处理组;PPARγ腺病毒(Ad/PPARγ)注射组;先给予0.125%Wy-14,643饮食再注射Ad/PPARγ组。实验结束时,收集肝脏组织称重、照相,HE、油红O染色观察PPARα激活后对PPARγ诱导肝脏脂肪变性的影响。结果野生型小鼠给予PPARα激动剂Wy-14,643处理8 d,与对照组相比,处理组小鼠肝脏明显增大,呈现过氧化物酶体增殖反应;野生型小鼠给予Ad/PPARγ5 d,小鼠肝脏显著增大,出现脂肪肝;给予PPARα激动剂Wy-14,643 3 d,再给予Ad/PPARγ5 d,小鼠肝脏增大更加显著,HE染色、油红O染色结果显示小鼠肝脏脂肪变性明显减轻。结论激活PPARα能够缓解PPARγ诱导的小鼠肝脏脂肪变,为脂肪肝的预防和治疗提供了新的研究思路和靶点。     

全脑缺血/再灌注大鼠海马PPARα表达变化

目的观察全脑缺血/再灌注损伤大鼠海马组织中PPARα mRNA和蛋白表达的动态变化.方法采用夹闭两侧颈总动脉,颈静脉抽血再回输建立大鼠全脑缺血/再灌注模型(I/R).RT-PCR和Western Blot分别检测PPARα mRNA和蛋白在缺血再灌注不同时间的表达.结果大鼠海马PPARα mRNA表达在缺血/再灌注30 min后升高,24 h时达峰,而后降低,再灌注30 d仍略高于正常水平.PPARα蛋白表达变化与PPARα mRNA表达相似.结论全脑缺血/再灌注损伤可诱导PPARα mRNA及蛋白表达,升高时限为30 d.     

PPARγ up-regulates TGFβ/smad signal pathway repressor c-Ski

TGFβ/smad pathway is recognized as an important signal pathway to promote the pathogenesis of atherosclerosis (AS). Peroxisome proliferator-activated receptor γ (PPARγ) activation is considered to be important in modulating AS. Herein, we investigated the regulation of PPARγ on c-Ski, the repressor of TGFβ/smad pathway, in rat AS model and cultured vascular smooth muscle cells (VSMCs). c-Ski mRNA and protein expression were detected by real-time PCR and Western blot, respectively, in vivo and in vitro with treatment of PPARγ agonist rosiglitazone and antagonist GW9662. The proliferation and collagen secretion of VSMCs after c-Ski transfection were investigated. The underlying mechanism was further investigated by online program NUBIScan and luciferase reporter gene analysis. Results showed that both mRNA and protein expressions of c-Ski in the AS lesions was down-regulated in vivo, while in cultured VSMCs, c-Ski transfection significantly suppressed the proliferation and collagen secretion of rat VSMCs. Rosiglitazone significantly up-regulated mRNA and protein levels of c-Ski in VSMCs, which could be blocked by GW9662. Online NUBIScan analysis suggested possible PPARγ binding sites in the promoter region of c-Ski. In addition, luciferase activity of c-Ski reporter gene was also increased obviously in the presence of rosiglitazone. These results indicate that c-Ski is one of the newly found target genes of PPARγ and thus involved in the anti-AS effect of PPARγ.     

SAR studies of acidic dual γ-secretase/PPARγ modulators

A novel set of dual γ-secretase/PPARγ modulators characterized by a 2-benzyl hexanoic acid scaffold is presented. Synthetic efforts were focused on the variation of the substitution pattern of the central benzene. Finally, we obtained a new class of 2,5-disubstituted 2-benzylidene hexanoic acid derivatives, which act as dual γ-secretase/PPARγ modulators in the low micromolar range. We have explored broad SAR and successfully improved the dual pharmacological activity and the selectivity profile against potential off-targets such as NOTCH and COX. Compound 17 showed an IC(50) Aβ42=2.4 μM and an EC(50) PPARγ=7.2 μM and could be a valuable tool to further evaluate the concept of dual γ-secretase/PPARγ modulators in animal models of Alzheimer's disease.     

PPARα and PPARγ regulate the nucleoside transporter hENT1

Human equilibrative nucleoside transporter 1 (hENT1) is an important determinant for nucleoside analog based chemotherapy success. Preliminary data suggest hENT1 regulation by PPARs. Using A2780 cells, we investigated the role of PPARs on hENT1 expression and activity. PPARα and PPARγ agonists, Wy14,643 and RGZ, increased hENT1 expression, but only PPARα activation or overexpression resulted in higher hENT1 transport activity. On the other hand, promoter analysis showed two putative PPRE in hENT1 promoter and luciferase-coupled promoter constructs were generated and analyzed. Our results suggest that PPARα-but not PPARγ-mediated expression regulation of hENT1 is PPRE-dependent. In conclusion, PPARα and PPARγ activation modulate hENT1 expression.     

Signal transduction pathways involved in PPARβ/δ-induced neuronal differentiation

Neuroblastomas are pediatric tumors originating from neuroblasts in the developing peripheral nervous system. The neurotrophin brain-derived neurotrophic factor (BDNF) is a key regulator of survival and differentiation of specific neuronal populations in the central and peripheral nervous system. Patients whose neuroblastoma tumors express high levels of BDNF and TrkB have an unfavorable prognosis. We have previously reported on the neuronal differentiating activity of peroxisome proliferator-activated receptors (PPAR)β/δ natural and synthetic ligands by modulating BDNF/TrkB pathway, suggesting their potential use as new therapeutic strategies for neuroblastoma. The validation of new therapeutic agents implies the understanding of their mechanisms of action. Herein, we report the effects of activated-PPARβ/δ on signal transduction pathways known to be involved in neuronal differentiation, such as ERK1,2 and BDNF pathways. The results obtained, using also PPARβ/δ silencing, indicating a neuronal differentiating effect PPARβ/δ-dependent through BDNF-P75-ERK1,2 pathways, further support a role for PPARβ/δ in neuronal differentiation and pointing towards PPARβ/δ as a modulator of pathways crucial for neuronal differentiation. These findings open new perspectives in the formulation of potential therapeutic approaches to be used as adjuvant treatment with the standard therapies.     

Synthesis and pharmacological evaluation of novel benzoylazole-based PPAR α/γ activators

In our search for new PPARα/γ agonists, we designed and synthesized a series of benzoylazole-based carboxylic acids. Compound 9 showed potent PPARγ partial agonistic activity with modest PPARα agonistic activity. The sodium salt of 9 (9Na) demonstrated potent efficacy in lowering both blood glucose and lipids in an animal model without causing significant body weight gain, a well-known side effect associated with PPARγ full agonists.