Thapsigargin-From Traditional Medicine to Anticancer Drug.

A sesquiterpene lactone, thapsigargin, is a phytochemical found in the roots and fruits of Mediterranean plants from Thapsia L. species that have been used for centuries in folk medicine to treat rheumatic pain, lung diseases, and female infertility. More recently thapsigargin was found to be a potent cytotoxin that induces apoptosis by inhibiting the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump, which is necessary for cellular viability. This biological activity encouraged studies on the use of thapsigargin as a novel antineoplastic agent, which were, however, hampered due to high toxicity of this compound to normal cells. In this review, we summarized the recent knowledge on the biological activity and molecular mechanisms of thapsigargin action and advances in the synthesis of less-toxic thapsigargin derivatives that are being developed as novel anticancer drugs.

Helenalin - A Sesquiterpene Lactone with Multidirectional Activity.

Sesquiterpene lactones, secondary metabolites of plants, present in a large number of species mostly from the Asteracea family, are used in the traditional medicine of many countries for the treatment of various pathological conditions. They exert a broad range of activities, including antiinflammatory, anti-bacterial and anti-cancer properties. The best-known sesquiterpene lactones which are already used as drugs or are used in clinical trials are artemisinin, thapsigargin and parthenolide. Yet another sesquiterpene lactone, helenalin, an active component of Arnica montana, known for its strong anti-inflammatory activity, has been used for centuries in folk medicine to treat minor injuries. Unfortunately, helenalin's ability to cause allergic reactions and its toxicity to healthy tissues prevented so far the development of this sesquiterpene lactone as an anticancer or anti-inflammatory drug. Recently, the new interest in the biological properties, as well as in the synthesis of helenalin analogs has been observed. This review describes helenalin's major biological activities, molecular mechanisms of action, its toxicity and potential for further research.

Antinociceptive potency of a fluorinated cyclopeptide Dmt-c[D-Lys-Phe-p-CF3-Phe-Asp]NH2.

Opioid peptides and opiate drugs such as morphine, mediate their analgesic effects, but also undesired side effects, mostly through activation of the mu opioid receptor. However, delta- and kappa-opioid receptors can also contribute to the analgesic effects of opioids. Recent findings showed that simultaneous activation of multiple opioid receptors may result in additional analgesia with fewer side effects. Here, we evaluated the pharmacological profile of our formerly developed mixed mu/kappa-opioid receptor ligands, Dmt-c[D-Lys-Phe-Phe-Asp]NH2 (C-36) and Dmt-c[D-Lys-Phe-p-CF3-Phe-Asp]NH2 (F-81). The ability of these peptides to cross the blood-brain barrier was tested in the parallel artificial membrane permeability (PAMPA) assay. On the basis of the hot-plate test in mice after central and peripheral administration, analog F-81 was selected for the anti-nociceptive and anti-inflammatory activity assessment after peripheral administration.

Anticancer activity and radiosensitization effect of methyleneisoxazolidin-5-ones in hepatocellular carcinoma HepG2 cells.

Parthenolide (PTL), a well-known sesquiterpene lactone of natural origin with α,ß-unsaturated carbonyl structure, has proven to show promising anti-cancer properties. In this report, anti-proliferative potential of two synthetic methyleneisoxazolidin-5-ones, MZ-6 and MZ-14, with the same structural motif, has been investigated in human hepatoma HepG2 cells. The effects on apoptosis induction and DNA damage were evaluated. All compounds decreased the number of live cells and increased the number of late apoptotic cells. However, only MZ-14 was able to induce DNA damage. Both synthetic compounds increased intracellular reactive oxygen species (ROS) generation and mitochondrial membrane potential changes at the same level as PTL. Additionally, cell survival was analyzed after a combined treatment, in which HepG2 cells were preincubated for 24 h with MZ-6, MZ-14 or PTL and irradiated with different doses of X-rays. The inhibition of cell survival was assessed by the clonogenic assay. We have shown that the clone formation was strongly inhibited by the combined treatment. The synergistic effect was observed for all three compounds but MZ-6 was significantly more effective. It is interesting to note that in HepG2 cells MZ-6 was the least cytotoxic of the tested compounds, did not induce DNA damage and was less active than the others in the clonogenic cell survival assay. It seems advantages from the point of view of the further in vivo studies that the compound with the lowest cytotoxic activity showed the strongest sensitizing effect.

The role of oxidative stress in anticancer activity of sesquiterpene lactones.

Sesquiterpene lactones (SLs) are plant-derived compounds that are abundant in plants of the Asteraceae family and posses a broad spectrum of biological activities, ranging from anti-inflammatory, phytotoxic, antibacterial, and antifungal to cytotoxic/anticancer. In recent years, anticancer properties of these compounds and molecular mechanisms of their action have been studied extensively on numerous cell lines and also on experimental animals. SLs have been shown to disrupt cellular redox balance and induce oxidative stress in cancer cells. Oxidative stress is associated with increased production of reactive oxygen species (ROS) which in turn can promote many aspects of cancer development and progression. On the other hand, ROS, which initiate apoptosis via the mitochondrial-dependent pathway, can also be used to kill cancer cells, if they can be generated in cancer. One of the most important regulators of the redox equilibrium in the cells is reduced glutathione (GSH). In cancer cells, GSH levels are higher than in normal cells. Therefore, SL can induce apoptosis of cancer cells by decreasing intracellular GSH levels. The use of SL which can affect intracellular redox signaling pathways can be considered an interesting approach for cancer treatment. In this review, we give a brief description of the mechanisms and pathways involved in oxidative stress-induced anticancer activity of SL.

α-Methylene-γ-lactones as a novel class of anti-leukemic agents.

Natural products are important leads in drug discovery. In recent years, the anti-leukemic properties of natural compounds isolated from plants, containing an α-Methylene-γ-lactones skeleton, have attracted a lot of attention. Extensive research has been carried out to characterize their molecular mechanisms of action and potential chemotherapeutic application in different types of cancer, including leukemias. Sesquiterpene lactones, a group of α-Methylene-γ-lactones are plant-derived compounds, mostly of the Compositae family, used in traditional medicine especially for the treatment of inflammation. However, they exhibit a broad spectrum of other biological effects, including cytotoxic, anti-bacterial, anti-helminthic, and anti-tumor activity. Recently, a sesquiterpene lactone, parthenolide, and several other compounds containing an α-methylene-γ-lactone skeleton have become topics of interest as potential antileukemic agents. The recent research emphasizes their selective activity against leukemia cells while the normal hematopoietic cells remain unaffected. In this review, we give a brief description of natural α-Methylene-γ-lactones isolated from plants and their derivates with minor chemical modifications that possess anti-leukemic activity. We also discuss molecular mechanisms of action of these compounds, in particular, their selectivity against leukemia cells.

Pharmacological characterization of endomorphin-2-based cyclic pentapeptides with methylated phenylalanine residues.

As part of our continuing studies on the structure-activity relationships of cyclic pentapeptides based on the structure of endomorphin-2, we report here the synthesis and biological activities of a new series of analogs incorporating 2', 3' or 4'-methylphenylalanine (MePhe) residues into positions 3 or 4 of the parent cyclopeptide, Dmt-c[d-Lys-Phe-Phe-Asp]NH2 (Dmt=2',6'-dimethyltyrosine). Analogs with MePhe in position 4 showed a row of magnitude increased µ-opioid receptor (MOP receptor) affinity as compared with a parent compound. The in vitro potencies of the new analogs were determined in calcium mobilization assay performed in Chinese Hamster Ovary (CHO) cells expressing human recombinant opioid receptors and chimeric G proteins. All analogs were strong µ/κ (MOP/KOP) receptor agonists and weak δ (DOP) receptor agonists. In the in vivo hot-plate test in mice, the MePhe(4)-modified peptides showed remarkable antinociceptive activity after intracerebroventricular (i.c.v.) administration which was most likely due to the concomitant activation of more than one opioid receptor type.

Overview of metabolism and bioavailability enhancement of polyphenols.

A proper diet is one of major factors contributing to good health and is directly related to general condition of the organism. Phenolic compounds are abundant in foods and beverages (fresh and processed fruits and vegetables, leguminous plants, cereals, herbs, spices, tea, coffee, wine, beer) and their pleiotropic biological activities result in numerous health beneficial effects. On the other hand, high reactivity and very large diversity in terms of structure and molecular weight renders polyphenols one of the most difficult groups of compounds to investigate, as evidenced by ambiguous and sometimes contradictory results of many studies. Furthermore, phenolics undergo metabolic transformations, which significantly change their biological activities. Here, we discuss some aspects of metabolism and absorption of phenolic compounds. On the basis of information reported in the literature as well as in summaries of clinical trials and patent applications, we also give an overview of strategies for enhancing their bioavailability.

Natural and synthetic α-methylenelactones and α-methylenelactams with anticancer potential.

α-Methylene-γ- and δ-lactones, as well as α-methylene-γ- and δ-lactams, are plant-derived compounds often used in traditional medicine for the treatment of inflammatory diseases. In recent years, the anticancer properties of these compounds and the molecular mechanisms of their action have been studied extensively. In the search for modern anticancer drugs, various synthetic analogs of α-methylene-γ- and δ-lactones and lactams have been synthesized and tested for their cytotoxic activity. In this review, we give a brief description of the occurrence and biological activity of such compounds isolated from plants and their diverse synthetic analogs.

[Salvinorin A and related diterpenes--biological activity and potential therapeutic uses]. / Salwinoryna A i jej pochodne--aktywnosc biologiczna i potencjalne zastosowanie terapeutyczne.

Salvinorin A (SA) is the main active ingredient of Salvia divinorum, a naturally occurring hallucinogen plant from Mexico. Traditionally, herbal preparations obtained from Salvia were used by the Mazatec Indians for their divination rites and the treatment of gastrointestinal disorders. SA is a selective K-opioid receptor agonist, producing antinociception in animals and humans and displaying regulatory effect on colonic function. Studies in humans demonstrated potent hallucinogenic effect of SA. The extensive research on SA and related neoclerodane diterpenes over the past few years resulted in a number of reports on their isolation, synthesis, and pharmacological characterization. In this review we try to summarize, from the pharmacological and synthetic point of view, the structure-activity relationship studies of SA and discuss the possible use of SA and its derivatives as therapeutics.

Salvinorin A has antiinflammatory and antinociceptive effects in experimental models of colitis in mice mediated by KOR and CB1 receptors.

BACKGROUND: Salvinorin A (SA) has a potent inhibitory action on mouse gastrointestinal (GI) motility and ion transport, mediated primarily by kappa-opioid receptors (KOR). The aim of the present study was to characterize possible antiinflammatory and antinociceptive effects of SA in the GI tract of mice. METHODS: Colonic damage scores and myeloperoxidase activity were determined after intraperitoneal (i.p.), intracolonic (i.c.), and oral (p.o.) administration of SA using the trinitrobenzene sulfonic acid (TNBS) and dextran sodium sulfate (DSS) models of colitis in mice. Additionally, KOR, cannabinoid (CB)1, and CB2 western blot analysis of colon samples was performed. The antinociceptive effect of SA was examined based on the number of behavioral responses to i.c. instillation of mustard oil (MO). RESULTS: The i.p. (3 mg/kg, twice daily) and p.o. (10 mg/kg, twice daily) administration of SA significantly attenuated TNBS and DSS colitis in mice. The effect of SA was blocked by KOR antagonist nor-binaltorphimine (10 mg/kg, i.p.). Western blot analysis showed no influence of SA on KOR, CB1, or CB2 levels. SA (3 mg/kg, i.p. and 10 mg/kg, i.c.) significantly decreased the number of pain responses after i.c. instillation of MO in the vehicle- and TNBS-treated mice. The antinociceptive action of SA was blocked by KOR and CB1 antagonists. The analgesic effect of i.c. SA was more potent in TNBS-treated mice compared to controls. CONCLUSIONS: Our results suggest that the drugs based on the structure of SA have the potential to become valuable antiinflammatory or analgesic therapeutics for the treatment of GI diseases.

Effect of tooth pulp and periaqueductal central gray stimulation on the expression of genes encoding the selected neuropeptides and opioid receptors in the mesencephalon, hypothalamus and thalamus in rats.

Nociceptive stimulation has been considered to affect the expression of genes encoding endogenous neuropeptides and their receptors. The effect of electric stimulation of the tooth pulp and/or periaqueductal gray (PAG) in rats on mRNA levels of the selected neuropeptides and opioid receptors (ORs) was investigated in comparison with control group, without stimulation. The levels of mRNA for the selected neuropeptides: galanin (GAL), vasopressin (AVP), oxytocin (OT), substance P (SP), somatostatin (SOM), vasoactive intestinal peptide (VIP), endomorphin-2 (EM-2), and opioid receptors: MOR, DOR and KOR in mesencephalic, hypothalamic and thalamic tissues were determined by real-time PCR. It was demonstrated that in the control group expression of the tested neuropeptides was at a very low level in the mesencephalon and thalamus, but at the higher level in the hypothalamus. The highest expression of ORs was observed in the mesencephalon. Nociceptive tooth pulp stimulation had the strongest effect in the hypothalamus, elevating mRNA levels of all tested neuropeptides except SOM. Electric stimulation of PAG either did not change or down-regulated mRNA levels of the neuropeptides in the cerebral structures. Simultaneous stimulation of PAG and tooth pulp either did not affect mRNA levels of the investigated neuropeptides or caused their slight decrease versus tooth pulp stimulation. The noxious stimulation of tooth pulp increased also the levels of OR mRNAs, while stimulation of PAG had the opposite effect. The above results demonstrated that tooth pulp stimulation significantly up-regulated the mRNA levels for a number of neuropeptides and all three types of ORs in the rat brain, which would result in more potent antinociception. In contrast, PAG stimulation down-regulated the mRNA levels of several neuropeptides and ORs in the cerebral tissues, which would cause decreased synthesis of ORs. The obtained results represent a new insight into the mechanism of orofacial pain.

Selective natural kappa opioid and cannabinoid receptor agonists with a potential role in the treatment of gastrointestinal dysfunction.

Salvinorin A is the major active ingredient of Salvia divinorum, a plant used by the Mazatec Indians of Mexico for spiritual and medical purposes. Different preparations from S. divinorum are also used in traditional healing practices to treat gastrointestinal disorders, including diarrhea. The recent extensive research on salvinorin A and other neoclerodane diterpenoids derived from S. divinorum resulted in a large number of reports describing their isolation, synthesis and structure-activity relationship. This review summarizes the present knowledge on salvinorin A and its analogues, with a focus on the effects on gastrointestinal tissues. We furthermore discuss structural changes in salvinorin A that may facilitate future use of its derivatives in human disease.

[D-1-Nal4]endomorphin-2 is a potent micro-opioid receptor antagonist in the aequorin luminescence-based calcium assay.

A functional assay, based on aequorin-derived luminescence triggered by receptor-mediated changes in Ca(2+) levels, was used to examine relative potency and efficacy of the micro-opioid receptor antagonists. A series of position 3- and 4-substituted endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2)) analogues containing D-3-(1-naphthyl)-alanine (D-1-Nal) or D-3-(2-naphthyl)-alanine (D-2-Nal), which were previously shown to reverse antinociception induced by endomorphin-2 in the in vivo hot-plate test in mice, was tested in the aequorin luminescence-based calcium assay to examine their micro-opioid antagonist potency in vitro. A recombinant mammalian cell line expressing the micro-opioid receptor together with a luminescent reporter protein, apoaequorin, was used in the study. The results obtained in this functional assay indicated that analogues with D-1-Nal or D-2-Nal substitutions in position 4 of endomorphin-2 are strong micro-opioid receptor antagonists, while those substituted in position 3 are partial agonists. Exceptional antagonist potency in the calcium assay was observed for [D-1-Nal(4)]endomorphin-2. The pA(2) value for this analogue was 7.95, compared to the value of 8.68 obtained for the universal, non-selective opioid antagonist of the alkaloid structure, naloxone. The obtained results were compared with the data from the hot-plate test in mice. In that in vivo assay [D-1-Nal(4)]endomorphin-2 was also the most potent analogue of the series.