Antipsoriatic anthrones with modulated redox properties. 4. Synthesis and biological activity of novel 9,10-dihydro-1,8-dihydroxy-9-oxo-2-anthracenecarboxylic and -hydroxamic acids

Copper-Catalyzed Remote Asymmetric Yne-Allylic Substitution of Yne-Allylic Esters with Anthrones

Anthrones are key structural motifs in many natural products and pharmaceutical chemicals. However, due to its unique tricyclic aromatic structure, the synthetic space for the development of chiral anthrone derivatives is largely limited. By utilizing the potential of the copper-catalyzed remote asymmetric yne-allylic substitution reaction, we describe the first example of copper-catalyzed highly regio- and enantioselective remote yne-allylic substitution on various yne-allylic esters with anthrones under a mild reaction condition, which afforded a range of enantioenriched 1,3-enynes with exhibiting broad functional group tolerance across 51 examples.

Straightforward Access to Anthrone Functionalized Benzylic Amines via Organocatalytic 1,2-Addition of Anthrones to Imines at Ambient Temperature

Activation of anthrone via benzylic deprotonation in the presence of triethylamine paves the way for the 1,2-addition reaction with imines to provide the desired functionalized anthrones in good to excellent yields under mild and operationally simple reaction conditions with a broad range of substrate scopes without using any external additives or toxic stoichiometric reagents.

Indium-Mediated Barbier allylations of Hydroxyanthraquinones: An Expedient synthesis of Novel 10-Alkenyl-10-Hydroxy-9(10H)-Anthracenones

Indium-mediated allylations of 1,8-dihydroxy-9,10-anthraquinone with allyl, cinnamyl and crotonyl bromides/ chlorides and 1,4- and 1,5- dihydroxy derivatives with allyl bromide in THF–MeOH–H2O gave the respective 10-alkenyl-10-hydroxy-9(10H)-anthracenones in excellent yields.

Substituent Effects on Regioselectivity of the Diels-Alder Reactions: Reactions of 10-Allyl-1,8-dichloroanthracene with 2-Chloroacrylonitrile, 1-Cyanovinyl Acetate and Phenyl Vinyl Sulfone

Diels-Alder reaction of 10-allyl-1,8-dichloroanthracene (3) with 2-chloroacrylonitrile (4) and 1-cyanovinyl acetate (5) gives exclusively theorthoisomer while its reaction with phenyl vinyl sulfone (10) yields a mixture of two isomeric adducts with priority toorthoisomer. The reactions proceeded under microwave condition in xylene. Configurations of these isomers have been assigned with the help of NMR spectra. The results indicated that the steric effect is dominating toward the isomer regioselectivity in the Diels-Alder reaction of the present compounds.

Expanding the scope of Metal-Free enantioselective allylic substitutions: Anthrones

The highly enantioselective asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with anthrones is presented. The reaction is simply catalyzed by cinchona alkaloid derivatives affording the final alkylated products in good yields and excellent enantioselectivities.

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.

Metformin inhibits proliferation of human keratinocytes through a mechanism associated with activation of the MAPK signaling pathway

In the present study, the effects of metformin on the proliferation of human immortalized keratinocytes (HaCaTs) and the underlying mechanisms were investigated. HaCaT cells in the logarithmic growth phase were treated with 50 mM metformin for 24, 48 and 72 h. Cell morphology after 24 h of treatment was observed under a microscope. Cell proliferation was detected using a colorimetric cell proliferation and cytotoxicity assay kit. Western blot analyses were performed to detect the protein phosphorylation levels of adenosine monophosphate-activated protein kinase (AMPK) and extracellular signal-related kinase 1/2 (ERK1/2). Metformin treatment resulted in morphological changes of the HaCaT cells. The survival rates of HaCaT cells treated with metformin were 36.18, 12.70 and 10.12% at 24, 48 and 72 h, respectively. As the treatment time extended, the survival rates of HaCaT cells decreased. Western blot analysis results showed that the mean level of phosphorylated (p)-AMPK in the HaCaT cells without metformin treatment was 2.856±0.323. However, the mean p-AMPK level following metformin treatment for 24 h increased to 5.198±0.625, indicating a significant difference between these two groups (P<0.05). The mean absorbance ratio of p-ERK1/2 was 7.550±1.087 for the untreated cells, but the levels in cells following metformin treatment for 24 h increased to 10.430±1.217, indicating a significant difference between the two groups (P<0.05). In conclusion, metformin treatment upregulated the levels of p-AMPK and p-ERK1/2 in HaCaT cells, and significantly inhibited HaCaT cell proliferation in vitro by a mechanism associated with activation of the mitogen-activated protein kinase signaling pathway.

Vasoactive intestinal peptide induces vascular endothelial growth factor production in human HaCaT keratinocytes via MAPK pathway

Psoriasis is a chronic skin disease characterized by abnormal keratinocyte proliferation and differentiation, inflammation, and angiogenesis. Although dysfunction of the immune system is known to be an important factor in the pathogenesis of psoriasis, there is also strong evidence that psychological stresses are involved. Neuropeptides are thought to be main mediators of neurogenic inflammation, presumably involved in the pathogenesis of psoriasis. Vasoactive intestinal peptide (VIP) is one of the major neuropeptides in human and rodent skin. In the present study, we examined the effect and mechanism of VIP on vascular endothelial growth factor (VEGF) production by HaCaT cells which is a spontaneous, immortalized, human keratinocyte cell line. Our data indicate the mRNA and protein levels of VEGF by VIP were increased in a concentration-dependent manner. However, this increase was abrogated by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor PD98059 or p38MAPK inhibitor SB203580; pretreatment with c-Jun N-terminal kinase (JNK) inhibitor SP600125 did not attenuate the effects of VIP on the expression of VEGF. In addition, VIP treatment induced rapid phosphorylation of ERK1/2 and p38MAPK, and PD98059 and SB203580 were able to inhibit VIP-induced phosphorylation of ERK1/2 and p38MAPK, respectively. These results suggest that VIP increases the expression of VEGF through the ERK1/2 and p38MAPK signaling pathway in human HaCaT cells.

Corticotropin-releasing hormone attenuates vascular endothelial growth factor release from human HaCaT keratinocytes

OBJECTIVES

Corticotropin-releasing hormone (CRH) is a central component of the local hypothalamic-pituitary-adrenal (HPA) axis, which has a functional equivalent in the skin. To determine whether CRH and its receptor, CRH-R1, modulate the expression of vascular endothelial growth factor (VEGF), which is overexpressed in psoriatic epidermis and plays a causal role in the pathogenesis of psoriasis, we investigated the effect of CRH on the expression of VEGF in a human keratinocyte cell line (HaCaT) and whether this effect is via the mitogen-activated protein kinase (MAPK) signal transduction pathways.

METHODS

Real-time RT-PCR, ELISA assay and western blot were used in the present study to investigate the expression of VEGF in CRH-treated HaCaT cells.

RESULTS

The mRNA and protein levels of VEGF in CRH-treated HaCaT cells were significantly attenuated. However, this downregulation was abrogated by pretreatment with antalarmin, SB203580 and SP600125; pretreatment with PD98059 did not attenuate the effects of CRH on the expression of VEGF. In addition, CRH treatment induced rapid phosphorylation of p38 MAPK and JNK1/2, and antalarmin, SB203580 and SP600125 inhibited CRH-induced phosphorylation of p38 MAPK and JNK1/2.

CONCLUSIONS

CRH might downregulate the expression of VEGF through the CRH-R1 and MAPK (p38 MAPK and JNK1/2) signaling pathways in human HaCaT cells.

Calcitonin gene-related peptide regulates the expression of vascular endothelial growth factor in human HaCaT keratinocytes by activation of ERK1/2 MAPK

Psoriasis is a chronic disease characterized by abnormal epidermal proliferation, inflammation and angiogenesis. The pathogenetic process resulting in hypervascularity remains to be further investigated. It has been reported that a potent angiogenic factor, vascular endothelial growth factor (VEGF) is overexpressed in psoriatic epidermis and that the level of calcitonin gene-related peptide (CGRP) is elevated in psoriasis lesions and CGRP-containing neuropeptide nerve fibers are denser in the psoriatic epidermis. We hypothesized that CGRP might regulate the expression of VEGF by human keratinocytes. VEGF expression in the CGRP-treated human keratinocytes was investigated and the CGRP signaling pathways were examined with respect to VEGF expression. The mRNA and protein levels of VEGF by CGRP were increased in a concentration-dependent manner. However, this increase was abrogated by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor PD98059. The CGRP-mediated VEGF induction was also effectively inhibited by a pretreatment with the CGRP receptor antagonist CGRP 8-37. In addition, CGRP treatment induced rapid phosphorylation of ERK1/2, PD98059 and CGRP 8-37 were able to inhibit CGRP-induced ERK1/2 phosphorylation. These results suggest that CGRP regulates the expression of VEGF through the CGRP receptor and ERK1/2 MAPK signaling pathway in human HaCaT keratinocytes.

Synthesis and structure–activity correlations of the cytotoxic bifunctional 1,4-diamidoanthraquinone derivatives

Anthraquinone-based compounds are attractive target for the design of new anticancer drugs. We have previously described a series of 1,5- and 1,4-difunctionalized anthraquinones, which exhibit different spectra of potency, together with human telomerase evaluation. The present study details the preparation of further, distinct series of regioisomeric difunctionalized amidoanthraquinone and examines their in vitro cytotoxicity in C6, Hepa G2, and 2.2.15 cell lines. Two structurally related compounds, mitoxantrone and adriamycin, were tested in parallel as positive controls. The structure-activity relationships indicated amido substitution may lead to a different mechanism of cytotoxicity. Compounds, which have -(CH2)n- side chains terminating in basic groups such as aminoalkyl-substituted, showed cytotoxic activity in several cell lines. The exact mode of intercalative binding may be dictated by the positional placement of substituent side chains. Implications for amidoanthraquinone cytotoxicity as potential anticancer agents are discussed. In addition, we further delineate the nature of the pharmacophore for this class of compounds, which provides a rational basis for the structure-activity relationships.

Differential regulation of IGF-II-induced IL-8 by extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinases in human keratinocytes

In order to study the relationship between insulin like growth factor-II (IGF-II) and interleukin-8 (IL-8) that are upregulated in psoriasis, we monitored IL-8 expression in IGF-II-treated human keratinocytes and explored the signaling pathways of IL-8 expression by IGF-II. IGF-II increased the IL-8 mRNA and protein levels in human keratinocytes. The upregulation of IL-8 expression by IGF-II was reduced by pretreatment with inhibitors of tyrosine kinase, Src, PI3-kinase, and ERK, but not by p38. Furthermore, IGF-II remarkably increased the DNA binding activities of NF-kappaB and AP-1, and the IL-8 promoter activity. However, cotransfection with IkappaB mutant blocked the IGF-II-induced IL-8 promoter activity. In addition, cotransfection with dominant negative MEK1 mutant, but not with dominant negative p38 mutant, blocked the IGF-II-induced IL-8 promoter activity. These results suggest that IGF-II is involved in the pathogenesis of psoriasis by inducing IL-8 gene expression through the tyrosine kinase-Src-ERK1/2-AP-1 pathway, and the PI3-kinase and NF-kappaB pathway.

2-Arylalkyl-substituted anthracenones as inhibitors of 12-lipoxygenase enzymes. 2. Structure-activity relationships of the linker chain

A series of 2-arylalkyl-substituted anthracenones were tested as inhibitors of three types of 12-lipoxygenase isoforms in epidermal homogenate of mice, bovine platelets and porcine leukocytes. Their inhibitory activities were compared with those to inhibit the 5-lipoxygenase enzyme in bovine leukocytes. The compounds were synthesised by Marschalk, Wittig or Horner-Emmons reaction at the anthracenedione stage and then reduced to the anthracenones. Structure-activity relationship for the chain linking the anthracenone nucleus and the phenyl ring terminus was investigated. The 2-phenylethyl analogues were among the most potent inhibitors, and 3,4-dimethoxy-substituted 10f was identified as a selective inhibitor of the 12-LO enzymes over 5-LO. Selectivity for 12-LO isoforms was observed with an increase in the overall lipophilicity of the inhibitors. However, none of the linker chains of the 2-substituted anthracenones provided inhibitors that were able to discriminate between the 12-LO isoforms.

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.

Reversal of epidermal hyperproliferation in psoriasis by insulin-like growth factor I receptor antisense oligonucleotides

Epidermal hyperplasia is a key feature of the common skin disorder psoriasis. Stimulation of epidermal keratinocytes by insulin-like growth factor I (IGF-I) is essential for cell division, and increased sensitivity to IGF-I may occur in psoriasis. We hypothesized that inhibition of IGF-I receptor expression in the psoriasis lesion would reverse psoriatic epidermal hyperplasia by slowing the rate of keratinocyte cell division. Here we report the use of C5-propynyl-dU,dC-phosphorothioate antisense oligonucleotides to inhibit IGF-I receptor expression in keratinocytes. We identified several inhibitory antisense oligonucleotides and demonstrated IGF-I receptor inhibition in vitro through an mRNA targeting mechanism. Repeated injection of these oligonucleotides into human psoriasis lesions, grafted onto nude mice, caused a dramatic normalization of the hyperplastic epidermis. The findings indicate that IGF-I receptor stimulation is a rate-limiting step in psoriatic epidermal hyperplasia and that IGF-I receptor targeting by cutaneous administration of antisense oligonucleotides forms the basis of a potential new psoriasis therapy.

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.