Antipsoriatic and proinflammatory action of anthralin. Implications for the role of oxygen radicals

Prototropy, Intramolecular Interactions, Electron Delocalization, and Physicochemical Properties of 1,8-dihydroxy-9-anthrone-DFT-D3 Study of Substituent Effects

1,8-dihydroxy-9-anthrone are tricyclic compounds with a ketone group in the middle ring and two hydroxyl groups substituted in the side-aromatic rings what results in formation of two intramolecular hydrogen bonds in which the oxygen atom from the ketone group is the proton acceptor. 1,8-dihydroxy-9-anthrones in which intramolecular proton transfer between C10 and CO in the middle ring occurs, can exist in a tautomeric keto-enol equilibrium. For anthralin, the most important representative of this group, this equilibrium has been studied previously, but it has not been studied for its derivatives. Substituents in the middle ring change the geometry of 1,8-dihydroxy-9-anthrones so they are also expected to affect the keto-enol equilibrium. It is also important to study the effect of intramolecular hydrogen bonds on the structure of both tautomeric forms. It was found that the nature of the substituent in the middle ring could affect the antioxidant properties of the investigated compound.

Dithranol: An Insight into its Novel Delivery Cargos for Psoriasis Management

OBJECTIVE

Dithranol (DTH) is a well-known moiety that has long been used promisingly to impede and treat skin disorders, particularly psoriasis. Nowadays, a rekindled interest in the use of DTH for this disorder has been observed. Side effects associated with conventional topical formulations of this moiety have aroused the interest of the scientific community in investigating novel cargos of DTH for psoriasis management.

RESULTS

Previous research has evidenced the anti-inflammatory and anti-proliferating potential of DTH. Numerous studies have indicated that DTH inhibits polymorphonuclear (PMN) leucocyte, modulates epidermal cell receptors and promotes anti-psoriatic action. However, some deterrent factors like poor solubility, stability, toxicity, staining and skin irritation hamper its use as a potential therapeutic agent. With the adoption of novel drug delivery technologies, the above mentioned inherent limitations of DTH have been compensated to reestablish this drug moiety.

CONCLUSION

This article reviews novel drug delivery aspects, safety concerns, clinical evidence, current status, and future opportunities of DTH in the management of psoriasis. Further, it will update researchers on this promising drug moiety, which is free from systemic adverse responses in comparison to other therapeutic molecules like steroids, for psoriasis treatment.

Monooxygenase Substrates Mimic Flavin to Catalyze Cofactorless Oxygenations

Members of the antibiotic biosynthesis monooxygenase family catalyze O2-dependent oxidations and oxygenations in the absence of any metallo- or organic cofactor. How these enzymes surmount the kinetic barrier to reactions between singlet substrates and triplet O2 is unclear, but the reactions have been proposed to occur via a flavin-like mechanism, where the substrate acts in lieu of a flavin cofactor. To test this model, we monitored the uncatalyzed and enzymatic reactions of dithranol, a substrate for the nogalamycin monooxygenase (NMO) from Streptomyces nogalater As with flavin, dithranol oxidation was faster at a higher pH, although the reaction did not appear to be base-catalyzed. Rather, conserved asparagines contributed to suppression of the substrate pKa The same residues were critical for enzymatic catalysis that, consistent with the flavoenzyme model, occurred via an O2-dependent slow step. Evidence for a superoxide/substrate radical pair intermediate came from detection of enzyme-bound superoxide during turnover. Small molecule and enzymatic superoxide traps suppressed formation of the oxygenation product under uncatalyzed conditions, whereas only the small molecule trap had an effect in the presence of NMO. This suggested that NMO both accelerated the formation and directed the recombination of a superoxide/dithranyl radical pair. These catalytic strategies are in some ways flavin-like and stand in contrast to the mechanisms of urate oxidase and (1H)-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase, both cofactor-independent enzymes that surmount the barriers to direct substrate/O2 reactivity via markedly different means.

Benzylic Functionalization of Anthrones via the Asymmetric Ring Opening of Oxabicycles Utilizing a Fourth-Generation Rhodium Catalytic System

While anthrones exist as privileged scaffolds in bioactive molecules, the enantioselective functionalization of anthrones is surprisingly scarce in the literature, with no asymmetric transition metal catalyzed example to date. Herein, we report the first asymmetric transition metal catalyzed benzylic functionalization of anthrones through the rhodium(I) catalyzed desymmetrization of oxabicycles. As previously developed rhodium(I) systems were found to be unsuitable for this substrate, a new robust fourth-generation [Rh(cod)OH]2 based catalytic system was developed to address synthetic challenges in this protocol.

Upregulation of the sFas/sFasL system in psoriatic patients

PURPOSE

Psoriasis is a chronic, recurrent, inflammatory disease. Recent investigations indicate its autoimmune pathogenesis. Apoptosis plays an important role in the development of many autoimmune diseases. The aim of this study was to evaluate the influence of topical treatment of psoriasis on soluble Fas (sFas) and soluble Fas-ligand (sFasL).

MATERIAL/METHODS

Serum concentrations of sFas and sFasL were measured using ELISA in 40 psoriatic patients before and after topical treatment with dithranol and compared to the values obtained from 16 healthy subjects. Data were analyzed with respect to severity of psoriasis, duration of the disease and coexisting obesity, diabetes and hypertension.

RESULTS

We found that serum levels of sFas before (11.9±2.4ng/mL) and after treatment (12.2±2.5ng/mL) were significantly higher in patients with psoriasis as compared to the control group (6.4±1.8ng/mL). Concentrations of sFasL did not differ significantly from healthy subjects, but increased after treatment. The sFas/sFasL ratio was significantly higher in psoriasis (128±47) than in the control group and, even though it tended to decrease after treatment, it still remained higher than in the control group (65±22). Additionally we observed a positive correlation of sFas/sFasL ratio with the age of patients and duration of the disease. Psoriatic patients suffering from hypertension and overweight had significantly higher sFas/sFasL ratio than other psoriatic patients.

CONCLUSIONS

Our data indicate upregulation of the sFas/sFasL system in psoriatic patients. We demonstrate association of sFas/sFasL with commorbidities - components of metabolic syndrome.

Dissociative Electron Attachment to Anthralin to Model Its Biochemical Reactions

The antipsoriatic drug anthralin (dithranol) is known to be extensively accumulated inside mitochondria of keratinocytes and to interact with the electron flow of the respiratory chain. Primary products of the one-electron reduction of polyphenolic anthralin observed in vivo are its dehydrogenated anions, which are formed by H-atom abstraction. The same species are mainly generated at low electron energies by dissociative electron attachment (DEA) to anthralin molecules in vacuo. A likely mechanism for the biochemical transformations of anthralin under reductive conditions in vivo is hypothesized on the basis of its DEA properties. The involvement of excited electronic states generated by ultraviolet irradiation of skin is discussed.

Allergic contact dermatitis in psoriasis patients: typical, delayed, and non-interacting

Psoriasis is characterized by an apoptosis-resistant and metabolic active epidermis, while a hallmark for allergic contact dermatitis (ACD) is T cell-induced keratinocyte apoptosis. Here, we induced ACD reactions in psoriasis patients sensitized to nickel (n = 14) to investigate underlying mechanisms of psoriasis and ACD simultaneously. All patients developed a clinically and histologically typical dermatitis upon nickel challenge even in close proximity to pre-existing psoriasis plaques. However, the ACD reaction was delayed as compared to non-psoriatic patients, with a maximum intensity after 7 days. Whole genome expression analysis revealed alterations in numerous pathways related to metabolism and proliferation in non-involved skin of psoriasis patients as compared to non-psoriatic individuals, indicating that even in clinically non-involved skin of psoriasis patients molecular events opposing contact dermatitis may occur. Immunohistochemical comparison of ACD reactions as well as in vitro secretion analysis of lesional T cells showed a higher Th17 and neutrophilic migration as well as epidermal proliferation in psoriasis, while ACD reactions were dominated by cytotoxic CD8+ T cells and a Th2 signature. Based on these findings, we hypothesized an ACD reaction directly on top of a pre-existing psoriasis plaque might influence the clinical course of psoriasis. We observed a strong clinical inflammation with a mixed psoriasis and eczema phenotype in histology. Surprisingly, the initial psoriasis plaque was unaltered after self-limitation of the ACD reaction. We conclude that sensitized psoriasis patients develop a typical, but delayed ACD reaction which might be relevant for patch test evaluation in clinical practice. Psoriasis and ACD are driven by distinct and independent immune mechanisms.

Anthrone and related hydroxyarenes: tautomerization and hydrogen bonding

The keto-enolization of hydroxyl-substituted naphthols and 9-anthrols has been investigated by means of CBS-QB3 calculations. An excellent agreement between experiment and theory is found for the energetics for the anthrone (5) ⇌ anthrol (6) equilibrium, with an enthalpy of tautomerization, Δ(t)H, of 3.8 kcal mol(-1). In contrast, 1-naphthol is the preferred tautomer with a Δ(t)H = -9.0 kcal mol(-1). Substitution of the hydrogens at the adjacent carbons by hydroxyl groups leads to the formation of strong intramolecular hydrogen bonds within a six-membered ring in the enones and the enols. Due to the difference in the intramolecular hydrogen bond enthalpy, Δ(HB)H(intra), the equilibrium shifts further to the enone. Thus, for 1,8-dihydroxy-anthrone (anthralin, dithranol) Δ(t)H increases to 12.7 kcal mol(-1) with an enol/enone ratio of 10(-10). The solvent effect on the 5 ⇌ 6 equilibrium has been quantified by considering the formation of intermolecular hydrogen bond(s), leading to an acidity parameter α₂(H) for anthrol of 0.42. It is shown that the hydrogen bond donating ability of bulk methanol is greatly attenuated through the formation of cyclic oligomers. The benzylic and phenolic bond dissociation enthalpies for anthrone up to anthralin suggest some antioxidant potency but the precise (radical) mechanism of action remains uncertain.

Structure-activity relationship studies of acridones as potential antipsoriatic agents. 2. Synthesis and antiproliferative activity of 10-substituted hydroxy-10H-acridin-9-ones against human keratinocyte growth

A series of 10-substituted hydroxy-10H-acridin-9-ones were synthesized and studied as potential antipsoriatic agents. The antiproliferative activity of the novel derivatives, which can be considered as aza-analogues of the antipsoriatic drug anthralin, was determined using the human keratinocyte cell line HaCaT. Structure-activity relationships with respect to the nature of the N-substituent at the acridone scaffold were delineated. Release of lactate dehydrogenase (LDH) was used to exclude non-specific cytotoxic effects. As compared to anthralin, N-substitution of the acridone scaffold in the target compounds provided agents devoid of radical producing properties, which was documented by their ineffectiveness to interact with the free radical 2,2-diphenyl-1-picrylhydrazyl. This was in excellent agreement with the data obtained from the LDH assay in which the novel compounds did not induce membrane damage. Benzyl substitution at the 10-position yielded keratinocyte growth inhibitory activity in the low micromolar range. The most potent inhibitor of keratinocyte hyperproliferation was compound 8a having an N-methyl group and a 1,3-dihydroxy arrangement at the acridone scaffold, with an IC(50) value comparable to that of anthralin.

A randomized, double‐blind, vehicle‐controlled study of a novel liposomal dithranol formulation in psoriasis

Dithranol is infrequently used in psoriasis in spite of excellent efficacy due to its local adverse effects. We have synthesized a novel formulation of dithranol in which the drug is entrapped in phospholipid liposomes. This formulation has shown markedly low irritation and minimal staining of skin and clothes in preliminary studies. Twenty patients with bilaterally symmetrical stable plaque psoriasis applied 0.5% dithranol lipogel to lesions over one side of the body. On the other side, 10 patients were randomized to apply pure liposomal base and 10 applied a conventional cream containing 1.15% dithranol, 1.15% salicylic acid and 5.3% coal tar in a 30-minute, short contact regimen for 6 weeks. Patients were assessed for disease severity, perilesional erythema and skin staining, pruritus and any other adverse effects at baseline, 2, 4 and 6 weeks. Both lipogel and the cream significantly reduced the total severity score compared to the liposomal base at 4 (p = 0.004) and 6 (p = 0.01) weeks. There was no significant difference in the clinical response of dithranol cream and lipogel. Markedly low incidence and severity of perilesional erythema (p<0.001) and skin staining (p<0.05) was seen with the lipogel in comparison with the cream.

Fluorescence remission spectroscopy of psoriatic lesions and the effect of topical anthralin therapy

BACKGROUND

Psoriatic lesions are characterized by induration, scaling and erythema. Erythema is a result of inflammation and increased microvascular blood flow. Anthralin is the strongest topical antipsoriatic drug that causes clearing of psoriatic lesions and temporary remission.

OBJECTIVE

The objective evaluation of skin perfusion might be a suitable way to gain a better insight in the pathophysiological process of this disease and to evaluate the response to antipsoriatic anthralin therapy.

METHODS

We evaluated 21 psoriatic lesions (plaques, patches and pinpoint lesions) including 4 lesions in remission with anthralin induced erythema and 4 controls of healthy, uninvolved skin. We performed the measurements with a combined fluorescence and remission imaging (FRIS). The FRIS sensor is coupled with a touch screen industrial computer. The equipment consists of a white-light halogen lamp (20 W), two VIS-spectrometer modules (Zeiss) for remission detection and references. Imaging is realized by CCD-colour camera module and white light ring-lighting. Fluorescence emission was realized using an ultraviolet LED with a wavelength of 370 nm. The fluorescence detector is a highly sensitive MCS CCD (Zeiss) with an integration time of 2.5 sec.

RESULTS

Spectral remission of psoriatic skin is characterized by a pronounced decrease (60-80%) of the haemoglobin double-peak compared to uninvolved skin. The NADH-fluorescence is diminished in lesional psoriatic skin including anthralin-treated areas with clinical remission.

CONCLUSIONS

Vascular perfusion is increased in psoriatic lesions as demonstrated by remission spectroscopy. NADH-fluorescence is reduced in lesional psoriatic skin and in anthralin-induced erythema. FRIS is a suitable tool for objective evaluation of the cutaneous response to antipsoriatic treatment.

The C3H/HeJ mouse and DEBR rat models for alopecia areata: review of preclinical drug screening approaches and results

The C3H/HeJ inbred mouse strain and the Dundee Experimental Bald Rat (DEBR) strain spontaneously develop adult onset alopecia areata (AA), a cell-mediated disease directed against actively growing hair follicles. The low frequency of AA and the inability to predict the stage of AA as it evolves in the naturally occuring C3H/HeJ model of AA can be converted into a highly predictable system by grafting full thickness skin from AA-affected mice to normal haired mice of the same strain. The rat DEBR model develops spontaneous AA at a higher frequency than in the mouse model but they are more expensive to use in drug studies owing to their larger size. Regardless of the shortcomings of either model, these rodent models can be used succesfully to screen novel or approved drugs for efficacy to treat human AA. As the pathogenesis of AA follows the canonical lymphocytic co-stimulatory cascade in the mouse AA model, it can be used to screen compounds potentially useful to treat a variety of cell-mediated diseases. Efficacy of various agents can easily be screened by simply observing the presence, rate, and cosmetic acceptability of hair regrowth. More sophisticated assays can refine how the drugs induce hair regrowth and evaluate the underlying pathogenesis of AA. Some drugs commonly used to treat human AA patients work equally as well in both rodent models validating their usefulness as models for drug efficacy and safety for humanAA.

Anthralin: Primary Products of Its Redox Reactions

One-electron reduction significantly enhances the ability of anthralin, 1, to act as a hydrogen atom donor. On annealing of an MTHF glass in which the radical anion of anthralin, 1*-, is generated radiolytically, this species decays mainly by loss of H* to give the anthralyl anion, 2- . On the other hand, radicals formed on radiolysis of matrices that are suitable for the generation of radical anions or cations are capable to abstract H* from anthralin to give the anthralyl radical, 2* . Both 2- and 2* are obtained simultaneously by mesolytic cleavage of the radical anion of the anthralin dimer. Contrary to general assumptions, the anthralyl radical is found to be much more reactive toward oxygen than the anion. All intermediates are characterized spectroscopically and by reference to quantum chemical calculations. Attempts to generate the radical cation of anthralin by X-irradiation of an Ar matrix containing anthralin led also to significant formation of its radical anion, i.e., anthralin acts apparently as an efficient electron trap in such experiments.

Antipsoriatic drug anthralin induces EGF receptor phosphorylation in keratinocytes: requirement for H(2)O(2) generation

Even though anthralin is a well-established topical therapeutic agent for psoriasis, little is known about its effects and biochemical mechanisms of signal transduction. In contrast to a previous report, we found that anthralin induced time- and concentration-dependent phosphorylation of epidermal growth factor receptor in primary human keratinocytes. Four lines of evidence show that this process is mediated by reactive oxygen species. First, we found that anthralin induces time-dependent generation of H(2)O(2). Second, there is a correlation between a time-dependent increase in anthralin-induced epidermal growth factor receptor phosphorylation and H(2)O(2) generation. Third, the structurally different antioxidants n-propyl gallate and N-acetylcysteine inhibited epidermal growth factor receptor phosphorylation induced by anthralin. Fourth, overexpression of catalase inhibited this process. The epidermal growth factor receptor-specific tyrosine kinase inhibitor PD153035 abrogated anthralin-induced epidermal growth factor receptor phosphorylation and activation of extracellular-regulated kinase 1/2. These findings establish the following sequence of events: (1) H(2)O(2) generation, (2) epidermal growth factor receptor phosphorylation, and (3) extracellular-regulated kinase activation. Our data identify anthralin-induced reactive oxygen species and, more specifically, H(2)O(2) as an important upstream mediator required for ligand-independent epidermal growth factor receptor phosphorylation and downstream signaling.

Restoration of hair growth in mice with an alopecia areata-like disease using topical anthralin

Anthralin is a widely used topical anti-psoriatic drug that may have an immunomodulating effect on alopecia areata (AA) as it does in psoriasis. The aims of the present study were to investigate the effects of anthralin on hair growth in balding C3H/HeJ mice affected by an AA-like disease and to study the underlying mechanisms. Affected C3H/HeJ mice were treated daily for 10 weeks on half of the dorsal skin with 0.2% anthralin and the contra-lateral side was treated with the vehicle ointment. The percentage of surface hair coverage and hair density was graded weekly for both sides and hair growth indices were calculated using these two variables. Hair regrowth was observed in 9/14 mice on the treated sides. Four mice displayed near complete replacement of normal density and length hairs. All the vehicle-treated sides showed either no change or continued hair loss. An RNase protection assay (RPA) showed that expression of tumor necrosis factor-alpha (TNF-alpha) and -beta were inhibited by anthralin upon successful treatment. It appears that anthralin may be an effective therapy for C3H/HeJ mice with AA and certain cytokines may be involved in the therapeutic effects of anthralin on restoring hair regrowth in AA-affected C3H/HeJ mice.

Cytokines and signal transduction pathways mediated by anthralin in alopecia areata-affected Dundee experimental balding rats

Although many therapeutic modalities have been tested on alopecia areata, patient outcomes have been disappointing. Use of animal models would help to develop more efficient therapies as well as understanding therapeutic mechanisms. We have demonstrated that 0.1% topical anthralin ointment is 100% effective in restoring follicular activity in Dundee experimental balding rats. This is the most promising topical treatment for Dundee experimental balding rats among the therapeutic agents tested on this model. Various cytokines have been shown to be associated with the pathogenesis of alopecia areata. To test whether any of these cytokines might be modulated by anthralin, an RNase protection assay and the real-time polymerase chain reaction were performed to compare their expression between anthralin-treated and control skins. These experiments showed that expression of tumor necrosis factor-alpha and interferon-gamma was inhibited by anthralin, whereas expression of interleukin-1alpha/beta and their receptor antagonist, interleukin-1Ra, and interleukin-10 was stimulated by anthralin. In addition, using an antibody-based multi-immunoblotting technique, we found that certain signaling regulatory proteins were modulated by anthralin. Their potential roles in reversing the autoimmune-arrested follicular activity in Dundee experimental balding rats are discussed.

Alteration of the expression of Bcl-2, Bcl-x, Bax, Fas, and Fas ligand in the involved skin of psoriasis vulgaris following topical anthralin therapy

Anthralin (dithranol) is frequently used for the treatment of psoriasis. However, the mode of action of anthralin has not been completely elucidated as yet. Recent findings suggest that psoriatic keratinocytes are resistant to the apoptotic process. In this study, we examined the immunohistochemical expression of apoptosis-regulated protein in the involved psoriatic skin following topical anthralin therapy. Biopsy specimens were obtained from back skins treated with topical anthralin or white petrolatum (control) in 4 patients with psoriasis vulgaris. Immunohistochemical examination revealed that psoriatic keratinocytes expressed high levels of Bcl-x, which was significantly reduced after anthralin treatment. Bax was not detected in the epidermal keratinocytes in the petrolatum-treated skin, while it was present in the upper keratinocytes after anthralin therapy. Bcl-2 was detected only in basal layers of psoriatic epidermis following both petrolatum and anthralin application. Psoriatic keratinocytes expressed higher levels of Fas in the lower epidermis, while only weak expression was detected in anthralin-treated plaques. On the other hand, hyperproliferative keratinocytes strongly expressed Fas ligand (FasL) on their plasma membranes as well as infiltrating lymphocytes in the upper dermis. Furthermore, anthralin-treated psoriatic epidermis did not express FasL. In normal skin, keratinocytes expressed low to absent levels of Bcl-x and Bax, while Bcl-2 was detected only in melanocytes in basal layers. Neither Fas nor FasL were detected in the epidermis of normal skin. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining revealed positive labeling on the majority of psoriatic keratinocytes through the epidermis in petrolatum-treated skin, whereas anthralin treatment markedly reduced TUNEL-positive keratinocytes. These in vivo results may reflect improvement of the psoriatic skin following effective anthralin therapy.

The combined effect of topical CX-659S, a novel diaminouracil derivative, with topical corticosteroid on the three types of allergic responses in mice or guinea pigs

CX-659S ((S)-6-amino-5-(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxamido)-3-methyl-1-phenyl-2,4(1H,3H)-pyrimidinedione), a newly discovered anti-inflammatory compound, exerts inhibitory effects against picryl chloride-, oxazolone-, and dinitrochlorobenzene-induced acute contact hypersensitivity responses (CHRs) characterized by Th1-type reactions. Furthermore, this compound suppressed chronic CHRs characterized by Th2-type reactions, which is well known to mimic many, if not all, events occurring within the lesional skin of patients with atopic dermatitis (AD). The present study was conducted to determine the combined effect of topical CX-659S with topical corticosteroid on immediate type (ITR), late type (LTR), and delayed type hypersensitivity (DTHR) allergic reactions that are involved in AD. An ineffective dose of CX-659S (0.03 mg/ear) combined with betamethasone valerate (BV) significantly potentiated inhibitory activity of BV alone (0.1 micro g/ear and 0.3Shizuokag/ear) on both the ITR and the LTR in mice with the ovalbumin (OVA)-induced biphasic cutaneous reaction. Furthermore, the combined effect of CX-659S with BV was also observed on dinitrochlorobenzene (DNCB)-induced DTHR in guinea pigs. These results indicate that CX-659S has a combined effect with corticosteroids on every ITR, LTR, and DTHR. Proper treatment with corticosteroids for a safe and effective treatment of AD is needed. Thus, the combination therapy of topical CX-659S with topical corticosteroid would be one of the potential approaches for devising a proper treatment with corticosteroids.

Frequent use of tobacco and alcohol in Chinese psoriasis patients

BACKGROUND

This study aimed to explore smoking and drinking as risk factors in psoriasis.

METHODS

Data collected from 789 psoriasis patients and 789 healthy controls were analyzed to determine whether there was an association between smoking/drinking and psoriasis.

RESULTS

The proportion of male psoriasis patients using tobacco and alcohol was much higher than that of the control group (P < 10(-6)), whereas no statistical differences were found between female smokers and the control group. In general, heavy smokers were more likely to have severe psoriasis.

CONCLUSION

Tobacco use in patients is correlated with psoriasis.

CX-659S: a novel diaminouracil derivative that has antioxidative and acute anti-inflammatory activities

We investigated the antioxidative activities and the effects on acute inflammation in mice of a novel diaminouracil derivative, CX-659S ((S)-6-amino-5-(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxamido)-3-methyl-1-phenyl-2,4(1H,3H)-pyrimidinedione). CX-659S showed potent scavenging activities against the hydroxyl radical and peroxynitrite and inhibited lipid peroxidation in rat brain homogenates in vitro. Topically applied CX-659S dose-dependently inhibited arachidonic acid- and 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear edema in mice. Consistent with its antioxidative properties in vitro, CX-659S dramatically attenuated the accumulation of lipid peroxides in the mouse ear elicited by repeated application of TPA. Previously, we reported the effectiveness of CX-659S against contact hypersensitivity reactions in both mouse and guinea pig models. These present results further suggest the therapeutic potential of CX-659S for acute skin inflammation that may involve oxidative tissue damage.

Studies on anthracenes. 3. Synthesis, lipid peroxidation and cytotoxic evaluation of 10-substituted 1,5-dichloro-9(10H)-anthracenone derivatives

The synthesis of a series of 1,5-dichloro-9(10H)-anthracenones bearing O-linked and N-linked substituents in the 10-position are described. Previous studies have shown that 9-acyloxy 1,5-dichloroanthracenes and 9-acyloxy 1,8-dichloroanthracenes displayed a potential cytotoxic effect. These results have encouraged us in further investigation of potential anthracenone derivatives. Therefore, a series of 10-substituted 1,8-dichloro-9(10H)-anthracenone derivatives were synthesized. These compounds were evaluated for their ability to inhibit the growth of human oral epidermoid carcinoma cells (KB cell line), human cervical carcinoma cells of ME 180 (GBM 8401) and Chinese hamster ovary (CHO) cells, respectively. Compounds 3c and 4c of this series compare favorably in the KB cellular assay with mitoxantrone. Compound 4c showed combined inhibitory action against KB, GBM and CHO cell growth, respectively. In addition, redox property of the compounds for the inhibition of lipid peroxidation in model membranes was determined. Compounds 4b and 4d exhibited stronger antioxidant activity than ascorbic acid, (+)-alpha-tocopherol and mitoxantrone, respectively.

Cornified envelope formation by anthralin, simple analogues, and related anthracenones

The ability of the antipsoriatic anthralin to induce HaCaT keratinocyte differentiation was investigated and correlated with its potency to inhibit proliferation of keratinocytes. To determine the structural requirements for this effect, anthralin and seventeen simple analogues or related anthracenones were examined for their ability to induce the formation of cornified envelope as a marker of terminal differentiation. Covalently cross-linked protein was measured as a key feature of this process. Induction of keratinocyte differentiation was significant at a concentration of 0.5 microM anthralin after 48 h exposure. The presence of the 1,8-dihydroxy groups is a critical determinant of cross-linking activity, since removing or exchanging these groups prevented the induction of keratinocyte differentiation. Furthermore, at least one hydrogen atom at the 10-position of anthralin is required. Moreover, anthralin, anthralin dimer, and anthralin triacetate exhibited antiproliferative and antirespiratory activity at concentrations required to induce keratinocyte differentiation, suggesting a causality between these effects. In addition, cornified envelope formation was observed for a number of related anthracenones at concentrations as low as 1-5 microM. In general, compounds containing benzoyl substituents, independent of the position in the anthralin nucleus, were more potent than those having benzyl substituents. Only marginal differences in cross-linking potency were observed within a number of phenylpropionyl substituted analogues, suggesting that the ability to induce keratinocyte differentiation is independent of the nature of substituents at the side chain.

Redox-modulated pathways in inflammatory skin diseases

Inflammatory skin diseases account for a large proportion of all skin disorders and constitute a major health problem worldwide. Contact dermatitis, atopic dermatitis, and psoriasis represent the most prevalent inflammatory skin disorders and share a common efferent T-lymphocyte mediated response. Oxidative stress and inflammation have recently been linked to cutaneous damage in T-lymphocyte mediated skin diseases, particularly in contact dermatitis. Insights into the pathophysiology responsible for contact dermatitis can be used to better understand the mechanism of other T-lymphocyte mediated inflammatory skin diseases, and may help to develop novel therapeutic approaches. This review focuses on redox sensitive events in the inflammatory scenario of contact dermatitis, which comprise for example, several kinases, transcription factors, cytokines, adhesion molecules, dendritic cell surface markers, the T-lymphocyte receptor, and the cutaneous lymphocyte-associated antigen (CLA). In vitro and animal studies clearly point to a central role of several distinct but interconnected redox-sensitive pathways in the pathogenesis of contact dermatitis. However, clinical evidence that modulation of the skin's redox state can be used therapeutically to modulate the inflammatory response in contact dermatitis is presently not convincing. The rational for this discrepancy seems to be multi-faceted and complex and will be discussed.

10-Phenylbutyryl-substituted anthracenones as inhibitors of keratinocyte growth and LTB(4) biosynthesis

A recent observation that phenylbutyryl anthracenone 2, an analogue of the antipsoriatic anthralin, is a potent inhibitor of leukotriene B(4) (LTB(4)) biosynthesis has prompted a search of other anthracenones with improved antiproliferative activity. In that direction, a limited number of analogues related to 2 have been prepared and evaluated in the HaCaT keratinocytes proliferation and in the polymorphonuclear leukocyte LTB(4) assay. The 4-methoxy analogue 2a and the side chain methylated 2l retain the full inhibitory activity of 1 against LTB(4) biosynthesis while their antiproliferative activity is markedly enhanced and comparable to that of the antipsoriatic anthralin. In contrast to anthralin, cytotoxic effects against cell membranes are strongly reduced as documented by the LDH activity released from cytoplasm of keratinocytes.

Anti-psoriatic drug anthralin activates JNK via lipid peroxidation: mononuclear cells are more sensitive than keratinocytes

Anthralin is a widely used, topical therapy for psoriasis. Anti-proliferative and anti-inflammatory properties of anthralin have been identified. Little is known, however, about differential sensitivities of targeted cell types and specific mechanisms of signaling pathway activation. We demonstrate that anthralin exerts potent effects on keratinocytes and mononuclear cells through strong induction of lipid peroxidation and JNK activation, a stress-induced signal transduction pathway. Lipid peroxidation was observed rapidly and half-maximal levels of lipid peroxidation were reached at a 10-fold lower concentration of anthralin for peripheral blood mononuclear cells vs normal keratinocytes. JNK activation was detected in peripheral blood mononuclear cells at a 40-fold lower anthralin dose compared with keratinocytes. For both cell types, selected inhibitors of lipid peroxidation prevented JNK activation. This study demonstrates that mononuclear leukocytes are markedly more sensitive than keratinocytes to anthralin-induced lipid peroxidation and JNK activation. We identify anthralin as a novel and potent inducer of JNK activation and demonstrate that this process is mediated, at least in part, by lipid peroxidation which is among the earliest and most proximate, membrane-related responses to anthralin yet described.

10-omega-phenylalkyl-9(10H)-anthracenones as inhibitors of keratinocyte growth with reduced membrane damaging properties

Work aimed at further improving the benefit to risk ratio of the antipsoriatic agent anthralin has led to 10-omega-phenylalkyl-9(10H)-anthracenones, members of which are equally potent as inhibitors of the growth of HaCaT keratinocytes. In contrast to anthralin, induction of membrane injury is strongly reduced as documented by the release of LDH activity from cytoplasm of keratinocytes.