Design and synthesis of new homo and hetero bis-piperazinyl-1-propanone derivatives as 5-HT7R selective ligands over 5-HT1AR

Benzoxazolone-arylpiperazinyl scaffold-based PET ligand for 5-HT7 : Synthesis and biological evaluation

Efforts are underway to improve the diagnosis and treatment for neurological disorders like depression, anxiety, epilepsy, and schizophrenia. The G-protein-coupled receptors (GPCRs) 5-HT₇   receptor, the most recently identified member of 5-HT receptor family dysregulation has an association with various central nervous system (CNS) disorders and its ligands have an edge as potential therapeutics. Here, we report the synthesis, characterization, and biological evaluation of diversely substituted methoxy derivatives of 2-benzoxazolone arylpiperazine for targeting 5-HT₇  receptors. Out of all derivatives, only C-2 substituted derivative, 3-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butyl)benzoxazol-2(3H)-one/ABO demonstrate a high affinity for human 5-HT₇ receptors. [¹¹ C]ABO was obtained by O-methylation of desmethyl-precursor using [¹¹ C]CH₃ OTf in the presence of NaOH giving a high radiochemical yield of 25 ± 12% (decay-corrected, n = 7) with stability up to 1.5 h postradiolabeling. In vitro autoradiography displays binding of [¹¹ C]ABO in accordance with 5-HT₇ distribution with a decrease of approximately 80% and 40% activity in the hippocampus and cerebellum brain region when administered with 10 µM cold ligand. Prefatory positron emission tomography scan results in Sprague-Dawley (SD) rat brain revealed fast and high radioactivity build-up in 5-HT₇ receptor-rich regions, namely, the hippocampus (2.75 ± 0.16 SUV) and the cerebral cortex (2.27 ± 0.02 SUV) establishing selective targeting of [¹¹ C]ABO. In summary, these pieces of data designate [¹¹ C]ABO as a promising 5-HT₇  receptor ligand that can have possible roles in clinics after its further optimization on different animal models.

Examination of the Novel Sigma-1 Receptor Antagonist, SI 1/28, for Antinociceptive and Anti-allodynic Efficacy against Multiple Types of Nociception with Fewer Liabilities of Use

Neuropathic pain is a significant problem with few effective treatments lacking adverse effects. The sigma-1 receptor (S1R) is a potential therapeutic target for neuropathic pain, as antagonists for this receptor effectively ameliorate pain in both preclinical and clinical studies. The current research examines the antinociceptive and anti-allodynic efficacy of SI 1/28, a recently reported benzylpiperazine derivative and analog of the S1R antagonist SI 1/13, that was 423-fold more selective for S1R over the sigma-2 receptor (S2R). In addition, possible liabilities of respiration, sedation, and drug reinforcement caused by SI 1/28 have been evaluated. Inflammatory and chemical nociception, chronic nerve constriction injury (CCI) induced mechanical allodynia, and adverse effects of sedation in a rotarod assay, conditioned place preference (CPP), and changes in breath rate and locomotor activity were assessed after i.p. administration of SI 1/28. Pretreatment with SI 1/28 produced dose-dependent antinociception in the formalin test, with an ED50 (and 95% C.I.) value of 13.2 (7.42-28.3) mg/kg, i.p. Likewise, SI 1/28 produced dose-dependent antinociception against visceral nociception and anti-allodynia against CCI-induced neuropathic pain. SI 1/28 demonstrated no impairment of locomotor activity, conditioned place preference, or respiratory depression. In summary, SI 1/28 proved efficacious in the treatment of acute inflammatory pain and chronic neuropathy without liabilities at therapeutic doses, supporting the development of S1R antagonists as therapeutics for chronic pain.

Chemical update on the potential for serotonin 5-HT6 and 5-HT7 receptor agents in the treatment of Alzheimer's disease

Despite the better understanding of the mechanisms underlying Alzheimer's Disease (AD) and launched clinical trials, no AD-modifying treatment based on a synthetic drug has been introduced for almost twenty years. The serotonin 5-HT₆ and 5-HT₇ receptors turned out to be promising biological targets for modulation of central nervous system dysfunctions including cognitive impairment. Within this paper, we evaluate the pharmacological potency of both, 5-HT₆R and 5-HT₇R, agents in search for novel AD treatment. An overview of chemical structures of the 5-HTRs ligands with simultaneous procognitive action which have undergone preclinical and clinical studies within the last 10 years has been performed.

In Vitro Antioxidant and Anti-Glycation Activity of Resveratrol and Its Novel Triester with Trolox

Resveratrol (RSV) is well known for its many beneficial activities, but its unfavorable physicochemical properties impair its effectiveness after systemic and topical administration; thus, several strategies have been investigated to improve RSV efficacy. With this aim, in this work, we synthesized a novel RSV triester with trolox, an analogue of vitamin E with strong antioxidant activity. The new RSV derivative (RSVTR) was assayed in vitro to evaluate its antioxidant and anti-glycation activity compared to RSV. RSVTR chemical stability was assessed at pH 2.0, 6.8, and 7.2 and different storage temperatures (5 °C, 22 °C, and 37 °C). An influence of pH stronger than that of temperature on RSVTR half-life values was pointed out, and RSVTR greatest stability was observed at pH 7.2 and 5 °C. RSVTR showed a lower antioxidant ability compared to RSV (determined by the oxygen radical absorbance capacity assay) while its anti-glycation activity (evaluated using the Maillard reaction) was significantly greater than that of RSV. The improved ability to inhibit the glycation process was attributed to a better interaction of RSVTR with albumin owing to its increased topological polar surface area value and H-bond acceptor number compared to RSV. Therefore, RSVTR could be regarded as a promising anti-glycation agent worthy of further investigations.

Strategies to Improve Resveratrol Systemic and Topical Bioavailability: An Update

In recent years, a great deal of attention has been paid to natural compounds due to their many biological effects. Polyphenols are a class of plant derivatives that have been widely investigated for preventing and treating many oxidative stress-related pathological conditions, such as neurodegenerative and cardiovascular diseases, cancer, diabetes mellitus and inflammation. Among these polyphenols, resveratrol (RSV) has attracted considerable interest owing to its high antioxidant and free radical scavenging activities. However, the poor water solubility and rapid metabolism of RSV lead to low bioavailability, thus limiting its clinical efficacy. After discussing the main biochemical mechanisms involved in RSV biological activities, this review will focus on the strategies attempted to improve RSV effectiveness, both for systemic and for topical administration. In particular, technological approaches involving RSV incorporation into different delivery systems such as liposomes, polymeric and lipid nanoparticles, microemulsions and cyclodextrins will be illustrated, highlighting their potential clinical applications. In addition, chemical modifications of this antioxidant aimed at improving its physicochemical properties will be described along with the results of in vitro and in vivo studies.

Synthesis, in vitro and in vivo characterization of new benzoxazole and benzothiazole-based sigma receptor ligands

A new set of 5-chlorobenzoxazole- and 5-chlorobenzothiazole-based derivatives containing the azepane ring as a basic moiety was designed, synthesized and evaluated through binding assays to measure their affinity and selectivity towards σ₁ and σ₂ receptors. Compounds 19, 22 and 24, with a four units spacer between the bicyclic scaffold and the azepane ring, showed nanomolar affinity towards both receptor subtype and the best K_i values (K_i σ₁ = 1.27, 2.30, and 0.78 and K_i σ₂ = 7.9, 3.8, and 7.61 nM, respectively). Evaluation of cytotoxic and apoptotic effects in MCF-7 human cancer cells was useful to assess σ₂ receptor activity, while an in vivo mice model of inflammatory pain allowed to analyze σ₁ receptor pharmacological properties. In vitro and in vivo results suggested that compound 19 is a σ₁/σ₂ agonist, compound 24 a σ₁ antagonist/σ₂ agonist, whereas compound 22 might act as σ₁ antagonist/σ₂ partial agonist. Due to their pharmacological profile, a potential therapeutic application in cancer of aforesaid novel σ₁/σ₂ receptor ligands, especially 22 and 24, is proposed.

Pharmacology and Therapeutic Potential of the 5-HT7 Receptor

It is well-documented that serotonin (5-HT) exerts its pharmacological effects through a series of 5-HT receptors. The most recently identified member of this family, 5-HT₇, was first identified in 1993. Over the course of the last 25 years, this receptor has been the subject of intense investigation, and it has been demonstrated that 5-HT₇ plays an important role in a wide range of pharmacological processes. As a result of these findings, modulation of 5-HT₇ activity has been the focus of numerous drug discovery and development programs. This review provides an overview of the roles of 5-HT₇ in normal physiology and the therapeutic potential of this interesting drug target.

Solid Lipid Nanoparticles Loading Idebenone Ester with Pyroglutamic Acid: In Vitro Antioxidant Activity and In Vivo Topical Efficacy

Idebenone (IDE), a strong antioxidant widely investigated for the treatment of neurodegenerative diseases and skin disorders, shows low oral and topical bioavailability due to its unfavorable physico-chemical properties. In this work, to improve IDE topical effectiveness, we explored a two-steps approach: (1) we synthesized an IDE ester (IDEPCA) with pyroglutamic acid, a molecule whose hydrating effects are well known; (2) we loaded IDEPCA into solid lipid nanocarriers (SLN). We evaluated in vitro antioxidant and anti-glycation activity and in vivo hydrating effects after topical application in human volunteers from gel vehicles of IDEPCA SLN in comparison to IDE SLN. All SLN showed good technological properties (mean particle size < 25 nm, polydispersity index < 0.300, good stability). The oxygen radical absorbance capacity assay showed that IDEPCA SLN and IDE SLN had similar antioxidant activity while IDEPCA SLN were more effective in the in vitro NO scavenging assay. Both IDEPCA and IDE SLN showed the same effectiveness in inhibiting the formation of advanced glycation end products. In vivo experiments pointed out a better hydrating effect of IDEPCA SLN in comparison to IDE SLN. These results suggest that the investigated approach could be a promising strategy to obtain topical formulations with increased hydrating effects.

Structure-Activity Relationships and Therapeutic Potentials of 5-HT7 Receptor Ligands: An Update

Serotonin 5-HT₇ receptor (5-HT₇R) has been the subject of intense research efforts because of its presence in brain areas such as the hippocampus, hypothalamus, and cortex. Preclinical data link the 5-HT₇R to a variety of central nervous system processes including the regulation of circadian rhythms, mood, cognition, pain processing, and mechanisms of addiction. 5-HT₇R blockade has antidepressant effects and may ameliorate cognitive deficits associated with schizophrenia. 5-HT₇R has been recently shown to modulate neuronal morphology, excitability, and plasticity, thus contributing to shape brain networks during development and to remodel neuronal wiring in the mature brain. Therefore, the activation of 5-HT₇R has been proposed as a therapeutic approach for neurodevelopmental and neuropsychiatric disorders associated with abnormal neuronal connectivity. This Perspective celebrates the silver jubilee of the discovery of 5-HT₇R by providing a survey of recent studies on the medicinal chemistry of 5-HT₇R ligands and on the neuropharmacology of 5-HT₇R.

Pharmacophore Comparison and Development of Recently Discovered Long Chain Arylpiperazine and Sulfonamide Based 5-HT7 Ligands

The serotonin system exerts its effects on the CNS and many peripheral systems. Of the 14 serotonin receptors, the 5-HT7 receptor is the most recently discovered. The 5-HT7 receptor has been shown to be involved in stress reduction, depression, and nociceptive control. Despite the 20 years since the discovery of 5-HT7R, there are still few truly selective ligands. Two of the common scaffolds for 5-HT7R ligands are long chain arylpiperazines (LCAPs) and sulfonamide containing compounds. This review focuses on recently developed (2014-2016) 5-HT7R ligands, their selectivity for the receptor, and suggests the possible new pharmacophore models for these ligands.

In Vitro Antioxidant Activity of Idebenone Derivative-Loaded Solid Lipid Nanoparticles

Idebenone (IDE) has been proposed for the treatment of neurodegenerative diseases involving mitochondria dysfunctions. Unfortunately, to date, IDE therapeutic treatments have not been as successful as expected. To improve IDE efficacy, in this work we describe a two-step approach: (1) synthesis of IDE ester derivatives by covalent linking IDE to other two antioxidants, trolox (IDETRL) and lipoic acid (IDELIP), to obtain a synergic effect; (2) loading of IDE, IDETRL, or IDELIP into solid lipid nanoparticles (SLN) to improve IDE and its esters’ water solubility while increasing and prolonging their antioxidant activity. IDE and its derivatives loaded SLN showed good physico-chemical and technological properties (spherical shape, mean particle sizes 23–25 nm, single peak in the size distribution, ζ potential values −1.76/−2.89 mV, and good stability at room temperature). In vitro antioxidant activity of these SLN was evaluated in comparison with free drugs by means of oxygen radical absorbance capacity (ORAC) test. IDETRL and IDELIP showed a greater antioxidant activity than IDE and encapsulation of IDE and its derivatives into SLN was able to prolong their antioxidant activity. These results suggest that loading IDETRL and IDELIP into SLN could be a useful strategy to improve IDE efficacy.