From Plant to Chemistry: Sources of Antinociceptive Non-Opioid Active Principles for Medicinal Chemistry and Drug Design.

Pain is associated with many health problems and a reduced quality of life and has been a common reason for seeking medical attention. Several therapeutics are available on the market, although side effects, physical dependence, and abuse limit their use. As the process of pain transmission and modulation is regulated by different peripheral and central mechanisms and neurotransmitters, medicinal chemistry continues to study novel ligands and innovative approaches. Among them, natural products are known to be a rich source of lead compounds for drug discovery due to their chemical structural variety and different analgesic mechanisms. Numerous studies suggested that some chemicals from medicinal plants could be alternative options for pain relief and management. Previously, we conducted a literature search aimed at identifying natural products interacting either directly or indirectly with opioid receptors. In this review, instead, we have made an excursus including active ingredients derived from plants whose mechanism of action appears from the literature to be other than the modulation of the opioid system. These substances could, either by themselves or through synthetic and/or semi-synthetic derivatives, be investigated in order to improve their pharmacokinetic characteristics and could represent a valid alternative to the opioid approach to pain therapy. They could also be the basis for the study of new mechanisms of action in the approach to this complex and disabling pathology.

Designing drugs optimized for both blood-brain barrier permeation and intra-cerebral partition.

INTRODUCTION: With the increasing incidence and prevalence of neurological disorders globally, there is a paramount need for new pharmacotherapies. BBB effectively protects the brain but raises a profound challenge to drug permeation, with less than 2% of most drugs reaching the CNS. AREAS COVERED: This article reviews aspects of the most recent design strategies, providing insights into ideas and concepts in CNS drug discovery. An overview of the products available on the market is given and why clinical trials are continuously failing is discussed. EXPERT OPINION: Among the available CNS drugs, small molecules account for most successful CNS therapeutics due to their ability to penetrate the BBB through passive or carrier-mediated mechanisms. The development of new CNS drugs is very difficult. To date, there is a lack of effective drugs for alleviating or even reversing the progression of brain diseases. Particularly, the use of artificial intelligence strategies, together with more appropriate animal models, may enable the design of molecules with appropriate permeation, to elicit a biological response from the neurotherapeutic target.

Sigma-1 Receptor Inhibition Reduces Mechanical Allodynia and Modulate Neuroinflammation in Chronic Neuropathic Pain.

Neuropathic pain is one of the most debilitating forms of chronic pain, resulting from an injury or disease of the somatosensory nervous system, which induces abnormal painful sensations including allodynia and hyperalgesia. Available treatments are limited by severe side-effects and reduced efficacy in the chronic phase of the disease. Sigma-1 receptor (σ1R) has been identified as a chaperone protein, which modulate opioid receptors activities and the functioning of several ion channels, exerting a role in pain transmission. As such, it represents a druggable target to treat neuropathic pain. This study aims at investigating the therapeutic potential of the novel compound (+)-2R/S-LP2, a σ1R antagonist, in reducing painful behaviour and modulating the neuroinflammatory environment. We showed that repeated administration of the compound significantly inhibited mechanical allodynia in neuropathic rats, increasing the withdrawal threshold as compared to CCI-vehicle rats. Moreover, we found that (+)-2R/S-LP2-mediated effects resolve the neuroinflammatory microenvironment by reducing central gliosis and pro-inflammatory cytokines expression levels. This effect was coupled with a significant reduction of connexin 43 (Cx43) expression levels and gap junctions/hemichannels mediated microglia-to-astrocyte communication. These results suggest that inhibition of σ1R significantly attenuates neuropathic pain chronicization, thus representing a viable effective strategy.

From Plant to Chemistry: Sources of Active Opioid Antinociceptive Principles for Medicinal Chemistry and Drug Design.

Pain continues to be an enormous global health challenge, with millions of new untreated or inadequately treated patients reported annually. With respect to current clinical applications, opioids remain the mainstay for the treatment of pain, although they are often associated with serious side effects. To optimize their tolerability profiles, medicinal chemistry continues to study novel ligands and innovative approaches. Among them, natural products are known to be a rich source of lead compounds for drug discovery, and they hold potential for pain management. Traditional medicine has had a long history in clinical practice due to the fact that nature provides a rich source of active principles. For instance, opium had been used for pain management until the 19th century when its individual components, such as morphine, were purified and identified. In this review article, we conducted a literature survey aimed at identifying natural products interacting either directly with opioid receptors or indirectly through other mechanisms controlling opioid receptor signaling, whose structures could be interesting from a drug design perspective.

Discovery of AD258 as a Sigma Receptor Ligand with Potent Antiallodynic Activity.

The design and synthesis of a series of 2,7-diazaspiro[4.4]nonane derivatives as potent sigma receptor (SR) ligands, associated with analgesic activity, are the focus of this work. In this study, affinities at S1R and S2R were measured, and molecular modeling studies were performed to investigate the binding pose characteristics. The most promising compounds were subjected to in vitro toxicity testing and subsequently screened for in vivo analgesic properties. Compound 9d (AD258) exhibited negligible in vitro cellular toxicity and a high binding affinity to both SRs (KiS1R = 3.5 nM, KiS2R = 2.6 nM), but not for other pain-related targets, and exerted high potency in a model of capsaicin-induced allodynia, reaching the maximum antiallodynic effect at very low doses (0.6-1.25 mg/kg). Functional activity experiments showed that S1R antagonism is needed for the effects of 9d and that it did not induce motor impairment. In addition, 9d exhibited a favorable pharmacokinetic profile.

New Insights into the Opioid Analgesic Profile of cis-(-)-N-Normetazocine-derived Ligands.

In this work, we report on the in vitro and in vivo pharmacological properties of LP1 analogs to complete the series of structural modifications aimed to generate compounds with improved analgesia. To do that, the phenyl ring in the N-substituent of our lead compound LP1 was replaced by an electron-rich or electron-deficient ring and linked through a propanamide or butyramide spacer at the basic nitrogen of the (-)-cis-N-normetazocine skeleton. In radioligand binding assays, compounds 3 and 7 were found to display nanomolar binding affinity for the µ opioid receptor (MOR) (Ki = 5.96 ± 0.08 nM and 1.49 ± 0.24 nM, respectively). In the mouse vas deferens (MVD) assay, compound 3 showed an antagonist effect against DAMGO ([D-Ala2, N-MePhe4, Gly-ol]-enkephalin), a highly selective MOR prototype agonist, whereas compound 7 produced naloxone reversible effect at MOR. Moreover, compound 7, as potent as LP1 and DAMGO at MOR, was able to reduce thermal and inflammatory pain assessed by the mouse tail-flick test and rat paw pressure thresholds (PPTs) measured by a Randall-Selitto test.

Design, synthesis, in vitro evaluation, and molecular modeling studies of N-substituted benzomorphans, analogs of LP2, as novel MOR ligands.

6,7-Benzomorphans have been investigated in medicinal chemistry for developing new drugs. This nucleus could be considered a versatile scaffold. The physicochemical properties of benzomorphan N-substituent are crucial in achieving a definite pharmacological profile at opioid receptors. Thus, the dual-target MOR/DOR ligands LP1 and LP2 were obtained through N-substituent modifications. Specifically, LP2, bearing as N-substituent the (2R/S)-2-methoxy-2- phenylethyl group, is a dual-target MOR/DOR agonist and is successful in animal models of inflammatory and neuropathic pain. To obtain new opioid ligands, we focused on the design and synthesis of LP2 analogs. First, the 2-methoxyl group of LP2 was replaced by an ester or acid functional group. Then, spacers of different lengths were introduced at N-substituent. In-vitro, their affinity profile versus opioid receptors has been performed through competition binding assays. Molecular modeling studies were conducted to deeply analyze the binding mode and the interactions between the new ligands and all opioid receptors.

Novel N-normetazocine Derivatives with Opioid Agonist/Sigma-1 Receptor Antagonist Profile as Potential Analgesics in Inflammatory Pain.

Although opioids and nonsteroidal anti-inflammatory drugs (NSAIDs) are the most common drugs used in persistent pain treatment; they have shown many side effects. The development of new analgesics endowed with mu opioid receptor/delta opioid receptor (MOR/DOR) activity represents a promising alternative to MOR-selective compounds. Moreover, new mechanisms, such as sigma-1 receptor (σ1R) antagonism, could be an opioid adjuvant strategy. The in vitro σ1R and σ2R profiles of previous synthesized MOR/DOR agonists (-)-2R/S-LP2 (1), (-)-2R-LP2 (2), and (-)-2S-LP2 (3) were assayed. To investigate the pivotal role of N-normetazocine stereochemistry, we also synthesized the (+)-2R/S-LP2 (7), (+)-2R-LP2 (8), and (+)-2S-LP2 (9) compounds. (-)-2R/S-LP2 (1), (-)-2R-LP2 (2), and (-)-2S-LP2 (3) compounds have Ki values for σ1R ranging between 112.72 and 182.81 nM, showing a multitarget opioid/σ1R profile. Instead, (+)-2R/S-LP2 (7), (+)-2R-LP2 (8), and (+)-2S-LP2 (9) isomers displayed a nanomolar affinity for σ1R, with significative selectivity vs. σ2R and opioid receptors. All isomers were evaluated using an in vivo formalin test. (-)-2S-LP2, at 0.7 mg/kg i.p., showed a significative and naloxone-reversed analgesic effect. The σ1R selective compound (+)-2R/S-LP2 (7), at 5.0 mg/kg i.p., decreased the second phase of the formalin test, showing an antagonist σ1R profile. The multitarget or single target profile of assayed N-normetazocine derivatives could represent a promising pharmacological strategy to enhance opioid potency and/or increase the safety margin.

Pulmonary Arteriovenous Malformations (PAVMs) and Pregnancy: A Rare Case of Hemothorax and Review of the Literature.

Pulmonary arteriovenous malformations (PAVMs) are anatomical abnormalities consisting in a direct connection between pulmonary arteries and veins. Most of PAVMs are related to Hereditary Hemorrhagic Teleangiectasia, whereas only 10 to 20% are isolated sporadic cases. PAVMs tend to increase in size naturally; however, several factors can influence their growth such as pulmonary arterial hypertension, puberty, and pregnancy. Clinical manifestations are related to the right-to-left shunting and include dyspnoea, hypoxia, and pulmonary hypertension. The presence of PAVMs during pregnancy is associated with an increased risk of complications such as their rupture, haemothorax, and hypovolemic shock. The treatment reserved to PAVMs was the surgical resection of the lung lobe involving the malformation. Due to the worldwide acceptance of endovascular technique, the transcatheter embolization (TCE) is today considered as the mainstay of treatment. Recent studies reported the safeness of the TCE during pregnancy if performed by an experienced radiologist, at second or third trimesters when radiation exposure is believed to have minimal effect on the foetus. However, although the TCE during pregnancy represents an option, the treatment prior to pregnancy has to be considered the auspicial solution. Our study reports the case of a dyspnoeic pregnant woman with unknown pAVM causing hemothorax and simultaneously treated for pAVM reparation, left lower lobe resection, and hysterectomy. Postoperative treatment of embolization was performed to definitively close the pAVM.

Thyroid adenolipoma: a case report.

Generally, small quantities of adipose tissue is present in the thyroid gland. The adenolipoma of the thyroid gland is considered a rare finding. It consists in a benign, encapsulated neoplasm composed of mature adipose tissue and glandular elements. We report a case of a 71 year-old female patient presenting with swelling of the anterior neck and history of airway obstruction. Ultrasound (US) examination showed a bulky multinodular goiter which caused dislocation and compression of the trachea. The scans performed at the level of the isthmic region showed the presence of a hyperechoic oval formation with a homogeneous echostructure and regular contours; these characteristics suggested the lipomatous nature of the nodule. The patient was subsequently subjected to a Computer Tomography (CT) of the neck for a pre-operative balance of the goitre and to exclude extra-thyroid pathologies. The CT scan confirmed the sonographic findings, and the probable adipose nature of the isthmic formation. After the patient has been subjected to total thyroidectomy and histological examination confirmed the diagnosis of adenolipoma.

Wilkie's syndrome.

Superior mesenteric artery syndrome, also known as Wilkie's syndrome, is a rare vascular disease caused by the anomalous course of the superior mesenteric artery arising from the abdominal aorta with a smaller angle than the norm (<22°). The reduced angle compresses the structures situated between the aorta and the superior mesenteric artery, such as the duodenum and left renal vein; this can determine painful crises, intestinal subocclusions, and left varicocele. This syndrome can be congenital or acquired. The acquired type is more common and is generally caused by reduced perivascular fat surrounding the abdominal aorta and the superior mesenteric artery; this form is common among anorexic patients that have had a rapid weight loss. We present the case of a female patient who suffered from repeated postprandial vomiting and who lost 12 kg in 4 months. B-mode ultrasound imaging revealed evidence of a reduced angle between the aorta and the superior mesenteric artery, as found in Wilkie's syndrome. After diagnosis, the patient followed a high-calorie diet, and 2 months later an ultrasound scan proved the restoration of the aorto-mesenteric angle as a consequence of increased perivascular fat with regression of symptoms.

Copeman nodule: a case report.

The Copeman nodule is a disease of the subcutaneous soft tissue consisting in subcutaneous adipose tissue herniation through the superficial muscular fascia. A 30-year-old female patient presented with chronic left pain just above the iliac crest. Ultrasound examination showed subcutaneous adipose tissue herniation through the superficial muscular fascia with a hernia gap of 15.9 mm in diameter. Then the patient underwent surgery under local anesthesia with suturing of the hernia gap and immediate regression of chronic pain. Ultrasound can accurately highlight or exclude the presence of Copeman nodule and, in our view, should be used as first examination in patients with superficial chronic pain to the right or left side.