Reaction of alantolactone, an allergenic sesquiterpene lactone, with some amino acids. Resultant loss of immunologic reactivity

Helenin from Stevia lucida. The first report of this natural eudesmanolide mixture in Eupatorieae tribe

From aerial parts of Stevia lucida Lagasca was isolated the natural mixture of isomeric eudesmanolides helenin. The identification and quantification of the constituents of helenin (alantolactone 1 and isoalantolactone 2, ratio 3:7) was performed through the quantitative analysis of its 1D and 2D NMR spectra.

Metabolism Analysis of Alantolactone and Isoalantolactone in Rats by Oral Administration

Alantolactone and isoalantolactone are the major active ingredients of Inulae Radix. Their metabolism in vivo and in vitro was investigated by UPLC-Q-TOF-MS for the first time. As a result, nine metabolites in vivo including cysteine conjugates, oxidates, dehydrogenates, and hydrates were detected in rat bile after oral administration. The metabolites produced in vitro by incubation with rat liver microsomes were found to be substantially identical to those detected in vivo. However, no metabolites were detected in the samples of plasma, feces, and urine or in the incubates of gastric juice, intestinal juice, and intestinal bacteria. These results reveal that the liver is the main metabolic organ for alantolactone and isoalantolactone, and the first pass effect of the liver appears to be the reason for the low oral bioavailability of the two lactones.

Alantolactone induces apoptosis of human cervical cancer cells via reactive oxygen species generation, glutathione depletion and inhibition of the Bcl-2/Bax signaling pathway

Alantolactone is the active ingredient in frankincense, and is extracted from the dry root of elecampane. It has a wide variety of uses, including as an insect repellent, antibacterial, antidiuretic, analgesic and anticancer agent. In addition, alantolactone induces apoptosis of human cervical cancer cells, however, its mechanism of action remains to be elucidated. Therefore, the present study investigated whether alantolactone was able to induce apoptosis of human cervical cancer cells, and its potential mechanisms of action were analyzed. Treatment of HeLa cells with alantolactone (0, 10, 20, 30, 40, 50 and 60 µM) for 12 h significantly inhibited growth in a dose-dependent manner. Cells treated with 30 µM of alantolactone for 0, 3, 6 and 12 h demonstrated marked induction of apoptosis in a time-dependent manner. Treatment of HeLa cells with 30 µM of alantolactone for 0, 3, 6 and 12 h significantly induced the generation of reactive oxygen species (ROS) and inhibited glutathione (GSH) production in HeLa cells in a dose-dependent manner. Alantolactone additionally markedly inhibited the Bcl-2/Bax signaling pathway in HeLa cells. Therefore, administration of alantolactone induced apoptosis of human cervical cancer cells via ROS generation, GSH depletion and inhibition of the Bcl-2/Bax signaling pathway.

Alpha-methylene-gamma-butyrolactones: versatile skin bioactive natural products

Natural products containing an alpha-methylene-gamma-butyrolactone moiety, mainly of the sesquiterpene type, are widely observed in plants, which upon coming into contact with skin, will induce major skin toxicological side effects or phytodermatitis. Indeed two main dermatological pathologies have been associated with a skin exposure to molecules containing an alpha-methylene-gamma-butyrolactone moiety: allergic contact dermatitis (ACD) and chronic actinic dermatitis (CAD). ACD is an immunologically based disease resulting from modifications of epidermal proteins by sensitizers or haptens. Indeed, alpha-methylene-gamma-butyrolactones are highly electrophilic structures that can act as Michael acceptors towards nucleophilic residues of proteins. Cysteine and lysine are the most modified residues leading, in the case of enantiomerically pure lactones, to the formation of diastereomeric adducts. This chemical enantioselectivity induces an enantiospecificity of the allergic reaction, i.e., an individual sensitized to one enantiomer will not develop clinical symptoms when exposed to the other enantiomer and vice versa. Sesquiterpene lactones have been also associated with another pathology that involves UV irradiation and DNA modifications. Interestingly, it was found that alpha-methylene-gamma-butyrolactones, in addition to their electrophilic properties, were highly photoreactive molecules able to react with thymine/thymidine to form [2 + 2] photoadducts in very high yields. In all cases a syn regioselectivity was observed, probably associated with the polarization of the exomethylenic bond. This high photoreactivity of alpha-methylene-gamma-butyrolactones towards thymidine could be an explanation of the progressive evolution of allergic contact dermatitis towards chronic actinic dermatitis.

Sesquiterpene lactone parthenolide blocks lipopolysaccharide-induced osteolysis through the suppression of NF-kappaB activity

Effective treatment for bacteria-induced bone lytic diseases is not yet available. In this study, we showed that PAR, an NF-kappaB inhibitor found in medicinal herbs, can block LPS-induced osteolysis. PAR does this by inhibiting osteoclastogenesis and bone resorption and promoting apoptosis of osteoclasts through the suppression of NF-kappaB activity.

INTRODUCTION

Osteolysis induced by chronic gram-negative bacterial infection underlies many bone diseases such as osteomyelitis, septic arthritis, and periodontitis. Drugs that inhibit lipopolysaccharide (LPS)-induced osteolysis are critically needed for the prevention of bone destruction in infective bone diseases. In this study, we investigated the effect of parthenolide (PAR) on LPS-induced osteolysis in vivo and studied its role in osteoclastogenesis, bone resorption, apoptosis, and NF-kappaB activity.

MATERIALS AND METHODS

The LPS-induced osteolysis in the mouse calvarium model was used to examine the effect of PAR in vivo. RANKL-induced osteoclast differentiation from RAW264.7 cells and bone resorption assays were used to assess the effect of PAR in vitro. Assays for NF-kappaB activation, p65 translocation, and IkappaB-alpha degradation were used to determine the mechanism of action of PAR in osteoclasts and their precursors. Flow cytometry and confocal microscopic analysis were used to examine cell apoptosis. Semiquantitative RT-PCR was performed to examine the effect of PAR on gene expression of RANK and TRAF6.

RESULTS

We found that PAR (0.5 and 1 mg/kg), injected simultaneously with LPS (25 mg/kg) or 3 days later, blocked the LPS-induced osteolysis in the mouse calvarium model. In vitro studies showed that low concentrations of PAR (<1 microM) inhibited in vitro osteoclastogenesis and osteoclastic bone resorption, whereas higher concentrations (>5 microM) triggered apoptotic cell death of osteoclasts and their precursor cells in a dose-dependent manner. Furthermore, PAR inhibited LPS-induced NF-kappaB activation, p65 translocation, and IkappaB-alpha degradation both in mature osteoclasts and their precursors in a time- and dose-dependent manner. In addition, PAR inhibited NF-kappaB activation induced by osteoclastogenic factors RANKL, interleukin (IL)-1beta, or TNF-alpha to varying degrees and reduced the gene expression of RANK and TRAF6.

CONCLUSION

The NF-kappaB pathway is known to mediate both osteoclast differentiation and survival. These findings indicate that PAR blocks LPS-induced osteolysis through the suppression of NF-kappaB activity and suggest that it might have therapeutic value in bacteria-induced bone destruction.

Cysteine 38 in p65/NF-kappaB plays a crucial role in DNA binding inhibition by sesquiterpene lactones

Sesquiterpene lactones (SLs) have potent anti-inflammatory properties. We have shown previously that they exert this effect in part by inhibiting activation of the transcription factor NF-kappaB, a central regulator of the immune response. We have proposed a molecular mechanism for this inhibition based on computer molecular modeling data. In this model, SLs directly alkylate the p65 subunit of NF-kappaB, thereby inhibiting DNA binding. Nevertheless, an experimental evidence for the proposed mechanism was lacking. Moreover, based on experiments using the SL parthenolide, an alternative mode of action has been proposed by other authors in which SLs inhibit IkappaB-alpha degradation. Here we report the construction of p65/NF-kappaB point mutants that lack the cysteine residues alkylated by SLs in our model. In contrast to wild type p65, DNA-binding of the Cys(38) --> Ser and Cys(38,120) --> Ser mutants is no longer inhibited by SLs. In addition, we provide evidence that parthenolide uses a similar mechanism to other SLs in inhibiting NF-kappaB. Contrary to previous reports, we show that parthenolide, like other SLs, inhibits NF-kappaB most probably by alkylating p65 at Cys(38). Although a slight inhibition of IkappaB degradation was detected for all SLs, the amount of remaining IkappaB was too low to explain the observed NF-kappaB inhibition.

The influence of glutathione and cysteine levels on the cytotoxicity of helenanolide type sesquiterpene lactones against KB cells

The biological activities of sesquiterpene lactones have been attributed to their reactivity with the cysteine residues of functional proteins forming covalent bonds via Michael type addition. In the present study we investigated the influence of different L-cysteine (cys) and glutathione (GSH) concentrations on the cytotoxicity of the sesquiterpene lactones (STLs) helenalin, 11alpha,13-dihydrohelenalin acetate and chamissonolide against KB cells. Due to the significantly higher reactivity of the alpha-methylene-gamma-lactone (ML) towards cys as compared with the cyclopentenone (CP) site at physiological pH, addition of 20, 50 and 100 molar equivalents of cys decreased the cytotoxicity of helenalin and chamissonolide, whereas the cytotoxicity of 11alpha,13-dihydrohelenalin acetate remained unaffected. In contrast, the influence of GSH addition on the cytotoxicity of 11alpha,13-dihydrohelenalin acetate depends on the concentration of GSH added. Concentration-effect curves obtained for chamissonolide and GSH resembled the decline in cytotoxicity after cys addition. Helenalin showed a biphasic shape of the concentration-effect curve for the 100:1 GSH/helenalin ratio resembling at higher doses the chamissonolide and in lower doses the 11alpha,13-dihydrohelenalin acetate curve at 50-fold excess. These results can be explained by the different reactivity and equilibrium conditions for thiol addition of the two reactive centers of bifunctional STLs in cellular test systems and verified a clear correlation between the different reactivity of their electrophilic centers and the observed biological effects in in-vitro cell systems.

Synergistic insecticidal mode of action between sesquiterpene lactones and a phototoxin, alpha-terthienyl

The synergistic insecticidal action of characteristic defensive substances produced by the plant family Asteraceae was investigated under controlled laboratory conditions. Sesquiterpene lactones isolated from Asteraceae that may form, through a Michael addition process, conjugates with glutathione were administered in a meridic diet to a herbivorous insect, Manduca sexta. By administering sesquiterpenes, variable in vivo reduced glutathione levels were observed in the insect larvae. When the Asteraceae-derived photooxidant alpha-terthienyl was co-administered, lipid peroxidation and larval mortality were significantly enhanced in the treated groups of insects with lowered in vivo glutathione levels.

Helenanolide type sesquiterpene lactones. Part 5: the role of glutathione addition under physiological conditions

Sesquiterpene lactones (STLs) are known to exert most of their numerous biological activities through inhibition of enzymes and other functional proteins by forming covalent bonds with free cysteine residues in these macromolecules. The question arises how these drugs can alkylate such vital target structures instead of being quickly deactivated by reaction with the cysteine group of glutathione (GSH) which is present in high concentrations in all cells. We have measured in this study the pH dependent kinetics of GSH addition to the cyclopentenone and alpha-methylene-gamma-lactone group of helenanolide type sesquiterpene lactones using UV-spectrophotometry. The reaction with GSH at physiological pH proceeds very quickly but is reversible so that a fraction of STL molecules will always be available for reaction with protein targets. In agreement with these chemical data, helenalin-mono- and -bis-glutathionyl adducts were demonstrated to inhibit the nuclear transcription factor NF-kappaB at concentrations similar to the free sesquiterpene lactone.

Perturbation of glutathione status and generation of oxidative stress in mouse skin following application of contact allergenic sesquiterpene lactones and isothiocyanates

1. The sensitizing or non-sensitizing status of selected sesquiterpene lactones and isothiocyanates was confirmed in mouse by open epicutaneous application. 2. Glutathione status of mouse skin was determined 12 h after lactone/isothiocyanate application; glutathione S-transferase activity also was determined 12 h after lactone application. 3. NAD(P)H utilization by rat liver microsomal preparations exposed to the sesquiterpene lactones and isothiocyanates was measured. 4. A correlation was observed between sensitizing status and the ability to perturb glutathione status, to induce glutathione S-transferase activity, and to stimulate NAD(P)H utilization. 5. It was concluded that sensitizing sesquiterpene lactones and isothiocyanates could induce oxidative stress in mouse skin, possibly as a result of their reductive metabolism.

Plant-induced dermatitis

Patients with plant-induced dermatitis frequently present to the emergency department. The range of responses varies from irritant to allergic to photo or granulomatous. To a certain extent the clinical presentations will vary; it is important to determine causation because appropriate emergency therapy treatment also will vary. This review considers the most common forms of plant dermatitis and emphasizes advances in the understanding of pathomechanisms and recommended therapy for each type.

Treatment of dermatitis from parthenin

Composites and some other plants containing sesquiterpene lactones, frequently cause allergic contact dermatitis in man. No treatment is available to control this disease successfully. We have used an amino acid, cysteine, to treat allergic contact dermatitis in guinea pigs sensitized to parthenin, a major sesquiterpene lactone of an allergenic weed, Parthenium hysterophorus L. Cysteine treatment of the allergic reaction induced by parthenin resulted in (a) reduced time of recovery and (b) reduced intensity of the skin reaction.

Formation of adducts of parthenin and related sesquiterpene lactones with cysteine and glutathione

Parthenin, the major sesquiterpene lactone of Parthenium hysterophorus, a weed responsible for dermatitis in man is primarily restricted to leaf and stem trichomes. Parthenin forms a monoadduct with L-cysteine through the alpha-methylene group of the gamma-lactone and a biadduct with the endocyclic double bond on the cyclopentenone ring. Studies with other sesquiterpene lactones support the view that the types of adducts formed are correlated with the biological activity of the sesquiterpene lactones.

Allergic contact dermatitis due to sesquiterpene lactones. A comparative study of human and animal sensitivity to alpha-methylene-gamma-butyrolactone and derivatives

Several compounds containing the alpha-methylene-gamma-butyrolactone moiety have been tested on human volunteers and on guinea-pigs; the animals were experimentally sensitized by alantolactone, isoalantolactone and laurel oil. Of the two new lactones, spirolactone was the more reactive: this was confirmed by both animal and human testing. The synthetic lactones are less reactive than natural ones. alpha-Methylene-gamma-butyrolactone itself does not elicit cross-reactions in guinea pigs sensitive either to alantolactone or to isoalantolactone, or in patients sensitive to sesquiterpene lactones. The alpha-methylene-gamma-butyrolactone group is necessary for cross-reaction, but to be active, it has first to be substituted. It was also found that isoalantolactone, allegedly not allergenic, is in fact a sensitizer and cross-reacts with alantolactone. The cross-reaction between laurel and Frullania, found in man, also occurs in guinea-pigs. It is more evident when sesquiterpene lactone is the sensitizer and laurel used to elicit reaction.

Immunological activity of parthenin and its diasteriomer in persons sensitized by Parthenium hysterophorus L

Persons suffering from allergic dermatitis caused by direct contact with Parthenium hysterophorus (Compositae) showed delayed immunologic reaction to the sesquiterpene lactone parthenin but not to its diasteriomer, hymenin.

Alantolactone sensitivity in chrysanthemum contact dermatitis

A case of occupational chrysanthemum contact dermatitis is reported. Patch tests showed the patient to be sensitized to Chrysanthemum morifolium (Chr M) leaves, flowers, and stems (alcoholic extracts) and to alantolactone. An attempt at desensitization appears to have been successful. Gas chromatography indicated the presence of alantolactone in all the various parts of Chr M, mostly in the flowers. The "maximization test" succeeded in sensitizing guinea pigs to alantolactone.

The sensitizing capacity of Compositae plants. I. Occupational contact dermatitis from Arnica longifolia Eaton

Three patients with occupational contact dermatitis due to Arnica longifolia Eaton and Arnica montana L. are reported. During cultivation, harvesting of the flower heads, chemical investigation of the sesquiterpene lactone constituents and preparation of therapeutic tinctures, they had frequent contact with the plant materials. Patch tests with the two sesquiterpene lactones carabron and helenalin, isolated during investigation from A. longifolia Eaton, were positive in all three patients, though the second patient had never shown visible allergic reactions of the skin. Sensitization experiments with carabron in five guinea pigs were successful. The investigation results revealed that carabron, helenalin and the acetyl derivative of helenalin must be considered as the sensitizers of A. longifolia, and helenalin acetate and properly arnifolin as sensitizers of A. montana. Studies on cross reactivity in the sensitized animals with six related sesquiterpene lactones showed that only those compounds gave a positive test response which contain an alpha-methylene gamma-lactone group. Cross reactions were obtained with a crude extract of Chrysanthemum indicum L. The case reports supported by the patch test and investigation results demonstrate that persons handling a new drug from the Compositae family run a risk of developing an allergy after intensive contact with the plant and its constituents.

Toxic effect of alantolactone and dihydroalantolactone in in vitro cultures of leukocytes

Alantolactone, an allergenic sesquiterpene lactone, is toxic to leukocytes in in vitro cultures. Cell (1 X 10(6) cells/ml of culture) stimulation by pokeweed mitogen (PWM) decreases with increasing amounts of terpene. A concentration of 1 mug/ml of culture decreases stimulation by 50%. The reduced terpene, dihydro-11,13-alantolactone (DHA) is also toxic. A concentration of 1.7 mug/ml of culture of DHA brings about a 50% decrease in stimulation. Both compounds affect cell viability as measured by dye exclusion. It is suggested that the toxicity of alantolactone is not due to the presence of the alpha-methylene group conjugated to the carbonyl function of the gamma-lactone system.

An antigen from Parthenium hysterophorus Linn

The increasing incidence of contact dermatitis due to the wild growth of the weed Partheium hysterophorus Linn. in many parts of India has prompted chemical analysis coupled with clinical testing to isolate the offending agent. Results are present to show that parthenin, a sesquiterpene lactone, is the major antigen which produces contact dermatitis in sensitive human beings.

Contact hypersensitivity to sesquiterpene lactones in Chyrsanthemum dermatitis

In six persons with contact allergy to chrysanthemum of florists, patch tests were performed with 25 sequiterpene lactones. Positive responses were observed to 15 lactones. The most frequently encountered positive responses were to alantolactone (positive in all cases) and to arbusculin A, 8-deoxycumambrin, ambrosin, damsin and psilostachynin. The findings corroborate the assumption that an alpha-methylene group attached to the gamma-lactone ring is an essential prerequisite for allergenic activity of sesquiterpene lactones. Pyrethrum produced a positive reaction in one of the patients, pyrethrins gave negative reactions in all. Some of the chrysanthemum patients were also hypersensitive to turpentine and colophony and to garlic, primin and tars.