Tadahiko Mashino

Anti-inflammatory activity of structurally related flavonoids, Apigenin, Luteolin and Fisetin

Flavonoids are widely distributed in many fruits and plants, and it has been shown that most flavonoids have anti-inflammatory activity; however, the mechanisms of how the flavonoids exhibit their anti-inflammatory activity have not been clarified. We therefore focus on flavonoids Apigenin, Luteolin and Fisetin because of their related structure. We found that these compounds significantly inhibited TNFα-induced NF-κB transcriptional activation; however, they had no effect on the degradation of IκB proteins and the nuclear translocation and DNA binding activity of NF-κB p65. Interestingly, the suppression of NF-κB activation by these flavonoids is due to inhibition of the transcriptional activation of NF-κB, since the compounds markedly inhibited the transcriptional activity of GAL4-NF-κB p65 fusion protein. In addition, while Apigenin and Luteolin slightly inhibited TNFα-induced JNK activation, they had no effect on TNFα-induced activation of ERK and p38. Unexpectedly, Fisetin enhanced and sustained activation of ERK and JNK but not p38 in response to TNFα. Strikingly, TNFα-induced expression of CCL2/MCP-1 and CXCL1/KC was significantly inhibited by Apigenin and Luteolin but not Fisetin. Furthermore, the administration of Apigenin and Luteolin markedly inhibited acute carrageenan-induced paw edema in mice; however, Fisetin failed to have an effect. These observations strongly suggest that the slight structural difference in flavonoids may cause a defective effect of Fisetin on these inflammatory responses, and this may be due to the differences in their direction of the effect on the activation pathways of MAP kinases.

In vitro free radical scavenging activity of platinum nanoparticles

A polyacrylic acid (PAA)-protected platinum nanoparticle species (PAA-Pt) was prepared by alcohol reduction of hexachloroplatinate. The PAA-Pt nanoparticles were well dispersed and homogeneous in size with an average diameter of 2.0 +/- 0.4 nm (n = 200). We used electron spin resonance to quantify the residual peroxyl radical ([Formula: see text]) generated from 2,2-azobis (2-aminopropane) dihydrochloride (AAPH) by thermal decomposition in the presence of O(2) and a spectrophotometric method to quantify the residual 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. PAA-Pt scavenged these two radicals in a dose-dependent manner. Platinum was the functional component. PAA-Pt reduced the rate of oxygen consumption required for linoleic acid peroxidation initiated by [Formula: see text] generated from AAPH, indicating inhibition of the propagation of linolate peroxidation. A thiobarbituric acid test also revealed dose-dependent inhibition of the linolate peroxidation by PAA-Pt. Fifty micromolar platinum, as PAA-Pt, completely quenched 250 microM DPPH radical for 5 min. Even when twice diluted in half, the PAA-Pt still quenched 100% of the 250 microM DPPH radical. The scavenging activity of PAA-Pt is durable. These observations suggest that PAA-Pt is an efficient scavenger of free radicals.

Licochalcone A significantly suppresses LPS signaling pathway through the inhibition of NF-κB p65 phosphorylation at serine 276

Licorice root, Glycyrrhiza inflata, has been used as a traditional medicine for the treatment of bronchial asthma and inflammation; however, the mechanism of its anti-inflammatory activity has not been clarified. Here, we investigated the effect of Licochalcone A, a major component of G. inflata, on the LPS signaling pathway. We found that Licochalcone A remarkably inhibited LPS-induced NO production, and TNFalpha expression and MCP-1 expression in both RAW264.7 cells and primary macrophages. Furthermore, when injected with Licochalcone A prior to injection of LPS, the serum level of TNFalpha and MCP-1 in C57BL/6 mice was clearly decreased, indicating that Licochalcone A has a potent anti-inflammatory effect both in vitro and in vivo. Strikingly, Licochalcone A significantly inhibited LPS-induced NF-kappaB transcriptional activation; however, it had no effect on not only the phosphorylation and degradation of IkappaBalpha but also nuclear translocation and DNA binding activity of NF-kappaB p65. Interestingly, Licochalcone A markedly inhibited the phosphorylation of p65 at serine 276. As a result, it reduced NF-kappaB transactivation by preventing the interaction of p65 with p300. Taken together, Licochalcone A might contribute to the potent anti-inflammatory effect of G. inflata through the unique mechanism of NF-kappaB inhibition.

Ipso substitution of bisphenol A catalyzed by microsomal cytochrome P450 and enhancement of estrogenic activity

Bisphenol A (BPA), an industrial chemical with estrogenic activity, was investigated as a substrate for the ipso-metabolism catalyzed by microsomal cytochrome P450 (P450). BPA was expected to be transformed to a quinol via an ipso-addition reaction; however, hydroquinone (HQ) was detected as a metabolite via an ipso-substitution reaction. Isopropenylphenol (IPP) and hydroxycumyl alcohol (HCA) were also produced as eliminated metabolites by C-C bond scission via ipso-substitution. Incorporation of the ¹⁸O atom to HCA from H₂¹⁸O suggested the presence of a carbocation intermediate. Bulkiness of p-substituted group of BPA and/or stability of the eliminated carbocation intermediate may cause ipso-substitution of BPA. CYP3A4 and CYP3A5 showed higher activity for ipso-substitution. CYP2D6*1 also showed the activity; however, the other 9 isozymes did not. IPP showed ER-binding activity in the same degree of BPA. Furthermore, the ER-binding activity of HCA was about a hundred times greater than that of BPA. These results suggested that this new metabolic pathway contributes to the activation of the estrogenic activity of BPA.

Licochalcone A Potently Inhibits Tumor Necrosis Factor α-Induced Nuclear Factor-κB Activation through the Direct Inhibition of IκB Kinase Complex Activation

Glycyrrhiza inflata has been used as a traditional medicine with anti-inflammatory activity; however, its mechanism has not been fully understood. Licochalcone A is a major and biogenetically characteristic chalcone isolated from G. inflata. Here, we found that licochalcone A strongly inhibited tumor necrosis (TNF)-α-induced nuclear localization, DNA binding activity, and the transcriptional activity of nuclear factor-κB (NF-κB). Whereas licochalcone A had no effect on the recruitment of receptor-interacting protein 1 and IκB kinase β (IKKβ) to TNF receptor I by TNF-α, it significantly inhibited TNF-α-induced IκB kinase complex (IKK) activation and inhibitor of nuclear factor-κB degradation. It is interesting that we found that the cysteine residue at position 179 of IKKβ is essential for licochalcone A-induced IKK inhibition, because licochalcone A failed to affect the kinase activity of the IKKβ (C179A) mutant. In contrast, a structurally related compound, echinatin, failed to inhibit TNF-α-induced IKK activation and NF-κB activation, suggesting that the 1,1-dimethy-2-propenyl group in licochalcone A is important for the inhibition of NF-κB. In addition, TNF-α-induced expression of inflammatory cytokines CCL2/monocyte chemotactic protein-1and CXCL1/KC was clearly inhibited by licochalcone A but not echinatin. Taken together, licochalcone A might contribute to the potent anti-inflammatory effect of G. inflata through the inhibition of IKK activation.

The fixed structure of Licochalcone A by α, β-unsaturated ketone is necessary for anti-inflammatory activity through the inhibition of NF-κB activation

Glycyrrhiza inflata has been used as a traditional medicine with anti-inflammatory activity. Previously, we reported that a major component, Licochalcone A, potently inhibited TNFalpha-induced NF-kappaB activation by inhibiting IKKbeta activation. In this study, we investigated whether the fixed structure of Licochalcone A by alpha, beta-unsaturated ketone is required for its inhibitory effect of NF-kappaB activation. Interestingly, reduced Licochalcone A, which lacks a double bond, failed to inhibit TNFalpha-induced NF-kappaB activation. Whereas Licochalcone A potently inhibited TNFalpha-induced IKK activation, IkappaBalpha degradation, nuclear localization of NF-kappaB and its DNA binding activity, no inhibitory effect was observed by reduced Licochalcone A. In addition, TNFalpha-induced expression of inflammatory cytokines, CCL2/MCP-1 and CXCL1/KC, was clearly inhibited by Licochalcone A but not reduced Licochalcone A. As a result, culture media pretreated with Licochalcone A but not reduced Licochalcone A following TNFalpha stimulation significantly inhibited the chemotactic activity of neutrophils. Furthermore, acute carrageenan-induced paw edema in mice was markedly inhibited by administration of Licochalcone A but not reduced Licochalcone A. Taken together, it is suggested that Licochalcone A is a promising anti-inflammatory drug in vivo and its fixed structure is critical for anti-inflammatory activity.

Pyrrolidinium-type fullerene derivative-induced apoptosis by the generation of reactive oxygen species in HL-60 cells

The biological activities of C(60)-bis(N,N-dimethylpyrrolidinium iodide), a water-soluble cationic fullerene derivative, on human promyeloleukaemia (HL-60) cells were investigated. The pyrrolidinium fullerene derivative showed cytotoxicity in HL-60 cells. The characteristics of apoptosis, such as DNA fragmentation and condensation of chromatin in HL-60 cells, were observed by exposure to the pyrrolidinium fullerene derivative. Caspase-3 and -8 were activated and cytochrome c was also released from mitochondria. The generation of reactive oxygen species (ROS) by the pyrrolidinium fullerene derivative was observed by DCFH-DA, a fluorescence probe for the detection of ROS. Pre-treatment with alpha-tocopherol suppressed cell death and intracellular oxidative stress caused by the pyrrolidinium fullerene derivative. The apoptotic cell death induced by the pyrrolidinium fullerene derivative was suggested to be mediated by ROS generated by the pyrrolidinium fullerene derivative.

Licochalcone A is a potent inhibitor of TEL-Jak2-mediated transformation through the specific inhibition of Stat3 activation.

Aberrant activation of Jak/Stat signaling causes a number of hematopoietic disorders and oncogenesis, and therefore the effective inhibitors of the Jak/Stat signaling pathway may be therapeutically useful. TEL-Jak2 gene fusion, which has been identified in human leukemia, encodes a chimeric protein endowed with constitutive tyrosine kinase activity. Expression of TEL-Jak2 protects Ba/F3 cells from IL-3 withdrawal-induced apoptotic cell death and leads to IL-3-independent growth. However, its mechanisms remain to be only partially understood. Here, we first found that Licochalcone A, one of the flavonoids isolated from the root of Glycyrrhiza inflate, inhibited TEL-Jak2-mediated cell proliferation and survival in the absence of IL-3. Licochalcone A failed to inhibit the activity of TEL-Jak2, however, this induced apoptosis of TEL-Jak2-transformed cells with a much lower concentration in the absence of IL-3 than in the presence of IL-3. Interestingly, Licochalcone A significantly inhibited the phosphorylation and nuclear localization of Stat3, which is essential for TEL-Jak2-induced cell transformation. These data suggest that Licochalcone A is a specific inhibitor for Stat3 and would be employed for the treatment of various diseases caused by disorders of the Jak/Stat pathway.

Synthesis of Keap1-phosphorylated p62 and Keap1-Nrf2 protein-protein interaction inhibitors and their inhibitory activity

The Keap1-Nrf2 system is involved not only in biological defense but also in malignancy progression and chemoresistance. The ubiquitin-binding protein p62/Sqstm1 (p62), which is highly expressed in several cancers, competes with Nrf2 for Keap1 binding, leading to activation of Nrf2-mediated gene expression and survival of cancer cells. We had previously identified an inhibitor for the Keap1-phosphorylated-p62 (p-p62) protein-protein interaction (PPI), the acetonyl naphthalene derivative K67. In this study, we established facile synthetic routes for K67 and derivatives with various side chains on the C-2 position of naphthalene ring. K67 possessed high selectivity in the inhibition of Keap1-p-p62. Other derivatives showed potent Keap1-Nrf2 and Keap1-p-p62 PPI inhibitory activities, though the selectivity between the two activities was lower than K67.

Pyrrolidinium fullerene induces apoptosis by activation of procaspase-9 via suppression of Akt in primary effusion lymphoma

Primary effusion lymphoma (PEL) is a subtype of non-Hodgkins B-cell lymphoma and is an aggressive neoplasm caused by Kaposis sarcoma-associated herpesvirus (KSHV) in immunosuppressed patients. In general, PEL cells are derived from post-germinal center B-cells and are infected with KSHV. To evaluate potential novel anti-tumor compounds against KSHV-associated PEL, seven water-soluble fullerene derivatives were evaluated as potential drug candidates for the treatment of PEL. Herein, we discovered a pyrrolidinium fullerene derivative, 1,1,1,1-tetramethyl [60]fullerenodipyrrolidinium diiodide, which induced apoptosis of PEL cells via a novel mechanism, the caspase-9 activation by suppressing the caspase-9 phosphorylation, causing caspase-9 inactivation. Pyrrolidinium fullerene treatment reduced significantly the viability of PEL cells compared with KSHV-uninfected lymphoma cells, and induced the apoptosis of PEL cells by activating caspase-9 via procaspase-9 cleavage. Pyrrolidinium fullerene additionally reduced the Ser473 phosphorylation of Akt and Ser196 of procaspase-9. Ser473-phosphorylated Akt (i.e., activated Akt) phosphorylates Ser196 in procaspase-9, causing inactivation of procaspase-9. We also demonstrated that Akt inhibitors suppressed the proliferation of PEL cells compared with KSHV-uninfected cells. Our data therefore suggest that Akt activation is essential for cell survival in PEL and a pyrrolidinium fullerene derivative induced apoptosis by activating caspase-9 via suppression of Akt in PEL cells. In addition, we evaluated whether pyrrolidinium fullerene in combination with the HSP90 inhibitor (geldanamycin; GA) or valproate, potentiated the cytotoxic effects on PEL cells. Compared to treatment with pyrrolidinium fullerene alone, the addition of low-concentration GA or valproate enhanced the cytotoxic activity of pyrrolidinium fullerene. These results indicate that pyrrolidinium fullerene could be used as a novel therapy for the treatment of PEL.