The effect of a novel, dual function histamine H1 receptor antagonist/5-lipoxygenase enzyme inhibitor on in vivo dermal inflammation and extravasation

Inhibitory effects of the ethyl acetate extract from bulbs of Scilla scilloides on lipoxygenase and hyaluronidase activities

CONTEXT

Scilla scilloides Druce (Liliaceae) is a folk medicine to treat dermal inflammation; however, the medicinal properties of this plant have not been completely established.

OBJECTIVE

The current study investigates the potent anti-inflammatory effects of S. scilloides bulbs for its traditional usage using lipoxygenase and hyaluronidase as the inflammation model. To gain insight into the active constituents, nine homoisoflavones (1-9) were subsequently tested.

MATERIALS AND METHODS

Lipoxygenase and hyaluronidase inhibition of ethyl acetate extract from the bulbs of this plant within 2000 µg/mL or homoisoflavones within 1000 µM were determined by colorimetric methods. RAW264.7 cells were incubated with 10 or 50 µM homoisoflavones plus lipopolysaccharide (LPS) for 24 h. The culture media were collected and analyzed for determination of the nitric oxide (NO) level by the colorimetric Griess method to measure the extent of inflammation.

RESULTS

The extract exhibited inhibitory effects on lipoxygenase and hyaluronidase activities with IC50 values 31.5 and 169 µg/mL, respectively. Among the nine homoisoflavones tested, four (1 and 3-5) resulted in 79.3-97.9% higher lipoxygenase inhibition than 6.7-32.7% of the others at 500 µM. Calculated IC50 values indicated 5 as the compound responsible for strong lipoxygenase inhibition with 15.8 µM as the IC50 value. In the hyaluronidase assay, all homoisoflavones tested at 1000 µM demonstrated 16.2-58.0% inhibition. Incubating the cells in the presence of all nine homoisoflavones tested at 50 µM significantly suppressed the NO production, downward to 1.5-66.0%, in the LPS-activated macrophage cells as a model.

DISCUSSION AND CONCLUSION

These results may indicate a potential role of S. scilloides for anti-inflammatory purposes.

Anti-inflammatory and antioxidative effects of a methanol extract from bulbs of Scilla scilloides

The extract from bulbs of Scilla scilloides exhibited inhibitory effects in lipoxygenase and hyaluronidase assays and various oxidation models in vitro. Incubating the cells in the presence of this extract ameliorated t-butyl hydroperoxide-induced cytotoxicity from 27% to 57% in a macrophage model. The results may indicate the potential role of S. scilloides for its anti-inflammatory and antioxidative effects.

Fullerene nanomaterials inhibit phorbol myristate acetate-induced inflammation

Inflammation is a natural biological response that occurs when vascular tissues are subjected to harmful stimuli. This process may be beneficial to the host during wound healing and infections but can be detrimental if left unchecked. Oxidative stress, the generation of reactive oxygen species, is thought to be one component of this response. Fullerenes can counteract reactive oxygen species due to their potent antioxidant capabilities. Thus, we hypothesized that these molecules may inhibit inflammation. To test this hypothesis we used an in vivo model of phorbol 12-myristate 13-acetate (PMA)-induced inflammation and examined the effects fullerenes have on mitigating this response. We show that PMA-induced inflammation and oedema is dramatically inhibited when fullerenes are given prior to challenge. Thus, fullerene derivatives may be a novel way to blunt certain inflammatory conditions and facilitate faster recovery of damaged tissue.

Histamine H4 receptors modulate dendritic cell migration through skin--immunomodulatory role of histamine

BACKGROUND

Dendritic cells (DC) are the major antigen-presenting cells and play a key role in adaptive immunity as they are able to activate naive T cells. It was recently described, that the histamine H(4) receptor (H4R) is present on human monocyte-derived DC and that chemotaxis and T-helper (Th)1-Th2 polarization is mediated by this receptor. However, the distribution of histamine receptors on murine DC has not been studied yet.

METHODS

The histamine receptor expression on murine bone marrow (BM)-derived DC and effects of histamine and H4R agonism on DC migration through skin were studied. As it was demonstrated in scratching experiments that NMRI mice are more susceptible to H4R-mediated itch than BALB/c mice, DC function of NMRI and BALB/c mice was compared.

RESULTS

The mRNA of the H1R, H2R and H4R could be detected in murine BM-derived DC, while mRNA of the H3R was found to be low or undetectable. There were no distinct differences in mRNA expression and in H4R protein level (flow cytometry) between NMRI compared with BALB/c mice indicating, that a higher susceptibility is not associated with a generally higher H4R expression in all cell types. Histamine as well as the H4R agonist clobenpropit induced an enhanced chemotaxis in the skin DC migration assay. The enhanced chemotaxis was blocked by the H4R antagonist JNJ7777120. This finding was confirmed by in vitro migration experiments with BM-derived DC.

CONCLUSION

Referring to DC migration, blocking the H4R on inflammatory cells might be a promising anti-inflammatory, immunomodulatory strategy.

Therapeutic options for 5-lipoxygenase inhibitors

5-Lipoxygenase (5-LO) catalyzes the conversion of arachidonic acid (AA) into leukotriene (LT) A(4) and 5-hydroperoxyeicosatetraenoic acid. LTA(4) can then be converted into LTB(4) by LTA(4) hydrolase or into LTC(4) by LTC(4) synthase and the LTC(4) synthase isoenzymes MGST2 and MGST3. LTB(4) is a potent chemoattractant for neutrophils, eosinophils and monocytes leading to adherence of phagocytes to vessel walls, neutrophil degranulation and release of superoxide anions. LTC(4) and its metabolite, LTD(4), are potent bronchoconstrictors that increase vascular permeability and stimulate mucus secretion from airways. Recent data also suggest that LT have an immunomodulatory role. Due to these properties, the increased biosynthesis of LT in asthma, and based upon clinical data obtained with CysLT(1) receptor antagonists in asthma patients, there is a consensus that CysLT play a prominent role in asthma. In this review, we summarize the knowledge on possible functions of the 5-LO pathway in various diseases like asthma, cancer and cardiovascular events and review the corresponding potential therapeutic roles of 5-LO inhibitors.

Effects of anti-inflammatory biflavonoid, ginkgetin, on chronic skin inflammation

Ginkgetin, a biflavonoid from Ginkgo biloba leaves (Ginkgoaceae), was previously demonstrated to inhibit phospholipase A2 and to suppress proinflammatory gene expression such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase. In this study, the effects of ginkgetin were examined on an animal model of chronic skin inflammation and proinflammatory gene expression. When topically applied to ICR mouse ear, ginkgetin (20-80 microg/ear/treatment) inhibited ear edema (22.8-30.5%) and prostaglandin E2 production (30.2-31.1%) induced by multiple treatment of 12-O-tetradecanoylphorbol-13-acetate (TPA) for 7 consecutive days. By histological comparison, ginkgetin was also found to reduce epidermal hyperplasia. The expression of proinflammatory gene, interleukin-1beta, was suppressed by ginkgetin. From the results, it is suggested that ginkgetin may be beneficial against chronic skin inflammatory disorders like atopic dermatitis.