Molecular modeling of non-covalent binding of homochiral (3S,3′S)-astaxanthin to matrix metalloproteinase-13 (MMP-13)

Astaxanthin: A Marine Drug That Ameliorates Cerebrovascular-Damage-Associated Alzheimer's Disease in a Zebrafish Model via the Inhibition of Matrix Metalloprotease-13

Alzheimer's disease (AD) is a major type of dementia disorder. Common cognitive changes occur as a result of cerebrovascular damage (CVD) via the disruption of matrix metalloproteinase-13 (MMP-13). In diabetic cases, the progress of vascular dementia is faster and the AD rate is higher. Patients with type 2 diabetes are known to have a higher risk of the factor for AD progression. Hence, this study is designed to investigate the role of astaxanthin (AST) in CVD-associated AD in zebrafish via the inhibition of MMP-13 activity. CVD was developed through the intraperitoneal and intracerebral injection of streptozotocin (STZ). The AST (10 and 20 mg/L), donepezil (1 mg/L), and MMP-13 inhibitor (i.e., CL-82198; 10 μM) were exposed for 21 consecutive days in CVD animals. The cognitive changes in zebrafish were evaluated through light and dark chamber tests, a color recognition test, and a T-maze test. The biomarkers of AD pathology were assessed via the estimation of the cerebral extravasation of Evans blue, tissue nitrite, amyloid beta-peptide aggregation, MMP-13 activity, and acetylcholinesterase activity. The results revealed that exposure to AST leads to ameliorative behavioral and biochemical changes. Hence, AST can be used for the management of AD due to its multi-targeted actions, including MMP-13 inhibition.

In Vitro Evaluation of Skin-Related Physicochemical Properties and Biological Activities of Astaxanthin Isomers

Dietary astaxanthin exists predominantly as the all-E-isomer; however, certain amounts of the Z-isomers are universally present in the skin, whose roles remain largely unknown. The aim of this study was to investigate the effects of the astaxanthin E/Z-isomer ratio on skin-related physicochemical properties and biological activities using human dermal fibroblasts and B16 mouse melanoma cells. We revealed that astaxanthin enriched in Z-isomers (total Z-isomer ratio = 86.6%) exhibited greater UV-light-shielding ability and skin antiaging and skin-whitening activities, such as anti-elastase and anti-melanin formation activities, than the all-E-isomer-rich astaxanthin (total Z-isomer ratio = 3.3%). On the other hand, the all-E-isomer was superior to the Z-isomers in singlet oxygen scavenging/quenching activity, and the Z-isomers inhibited type I collagen release into the culture medium in a dose-dependent manner. Our findings help clarify the roles of astaxanthin Z-isomers in the skin and would help in the development of novel skin health-promoting food ingredients.

Effects of supplementing natural astaxanthin from Haematococcus pluvialis to laying hens on egg quality during storage at 4°C and 25°C

The objective of this study was to evaluate the effects of different levels of dietary natural astaxanthin (ASTA) (from the microalga Haematococcus pluvialis) and storage at 4°C and 25°C on the quality of eggs from laying hens. Nongda No. 3 laying hens (n = 450) were randomly allocated to 1 of 5 dietary treatments. Each treatment had 6 replicates of 15 hens each. All birds were assigned to a corn-soybean meal-based diet containing 0, 20, 40, 80, or 160 mg/kg natural ASTA for 4 wk. A total of 540 eggs were collected at the end of the 4-week feeding trial. Sixty fresh eggs were collected and measured for egg quality within 24 h after collection. The other 480 eggs were used in a factorial arrangement with 5 dietary ASTA levels, 4 storage times, and 2 storage temperatures. During the 8-week storage period at 4°C and 25°C, egg quality measurements were performed every 2 wk on 12 eggs per treatment. No significant effects (P > 0.05) on yolk index, yolk pH, Haugh units, weight loss, or eggshell strength were observed with increasing concentrations of dietary ASTA. Yolk color darkened linearly with increasing dose of ASTA (P < 0.05). During storage of eggs, yolk index and Haugh units decreased significantly (P < 0.05), whereas yolk pH and weight loss increased (P < 0.05). An interaction was observed between dietary ASTA level and storage time on yolk index, yolk color, and Haugh units (P < 0.05). These results demonstrated that dietary ASTA from H. pluvialis delayed the decrease in yolk index and yolk color during storage at 4°C and 25°C. Therefore, we speculate that there may be a combined effect of dietary ASTA level and storage time on egg internal quality; this information may provide additional options by which to extend the storage time of eggs.

Roxatidine Attenuates Degradation of Extracellular Matrix

Degradation of extracellular matrix such as type II collagen and aggrecan induced by proinflammatory cytokines has been considered as an important hallmark of Osteoarthritis (OA). Roxatidine is a licensed specific competitive H (2) -receptor antagonist used for the treatment of gastric and duodenal ulcers. The pharmacological function of roxatidine on Osteoarthritis (OA) remains unknown. In the current study, we report that roxatidine attenuated TNF-α- induced degradation of type II collagen by suppressing the expression of MMP-3 and MMP-13 in human chondrosarcoma cell line SW1353 cells. In addition, roxatidine ameliorated TNF-α- induced reduction of aggrecan by inhibiting the expression of ADAMTS-4 and ADAMTS-5. Notably, results indicate that roxatidine ameliorated TNF-α- induced the phosphorylations of IKK, IκBα, and NF-κB p65 as well as nuclear translocation of NF-κB p65 and the transcriptional activity of NF-κB, suggesting that roxatidine abolished the activation of NF-κB signaling pathway. Our findings implicate that roxatidine might be considered as an anti-osteoarthritic agent.

Discovery of potent inhibitor for matrix metalloproteinase-9 by pharmacophore based modeling and dynamics simulation studies

Matrix metalloproteinase-9 (MMP-9) is an attractive target for anticancer therapy. In the present study ligand based pharmacophore modeling was performed to elucidate the structural elements for a diverse class of MMP-9 inhibitors. The pharmacophore model was validated through Güner-Henry (GH) scoring method. The final pharmacophore model consisted of three hydrogen bond acceptors (HBA), and two ring aromatic regions (RA). This model was utilized to screen the natural compound database to seek novel compounds as MMP-9 inhibitors. The identified hits were validated using molecular docking and molecular dynamics simulation studies. Finally, one compound named Hinokiflavone from Juniperus communis had high binding free energy of -26.54kJ/mol compared with the known inhibitors of MMP-9. Cytotoxicity for hinokiflavone was evaluated by MTT assay. Inhibition of MMP-9 in the presence of hinokiflavone was detected by gelatin zymography and gelatinolytic inhibition assay. Results revealed that the natural compounds derived based on the developed pharmacophore model would be useful for further design and development of MMP-9 inhibitors.

Epigallocatechin-3-gallate prevents tumor cell implantation/growth in an experimental rat bladder tumor model

The aim of this study was to determine the efficacy of epigallocatechin-3-gallate (EGCG) (Polyphenon E®) in comparison with mitomycin C (MMC) to prevent tumor cell implantation/growth in an animal model of superficial bladder cancer and search for possible mechanism(s) of action. Female Fisher 344 rats were used to study the effects of EGCG and mitomycin C for the prevention of transitional cell tumor implantation (AY-27). Twenty rats served as a control, tumor implantation and saline wash only. Sixty rats were treated with EGCG (100, 200 and 400 µM) intravesically for 60 or 120 min after tumor implantation. Thirty other rats were divided equally and pretreated with 400 µM EGCG or saline for 120 min before tumor initiation. In a separate series of experiments, 30 rats were treated 2 weeks after tumor initiation with saline or EGCG (400 µM). In a different experiment 39 rats were treated with: saline (n=10) EGCG (n=9) 400 µM, MMC (n=10) 0.5 µM, MMC (n=10) 400 µM. Rats were sacrificed 3 weeks following treatment. Gross and histological analyses were performed on the bladders. EGCG and mitomycin C prevented intravesical tumor growth in a concentration- and time-dependent manner. EGCG pretreatment or treatment 2 weeks post tumor implantation did not have therapeutic effects. Molecular modeling suggests that EGCG inhibits urokinase and matrix metalloproteinase-9. EGCG prevents intravesical tumor implantation/growth with a slightly better efficacy than mitomycin C in this experimental model. The data suggest that EGCG lowers proteolytic activity and lowers probability of cancer cell implantation rather than direct cancer cell killing.

Analysis of the anticancer activity of curcuminoids, thiotryptophan and 4-phenoxyphenol derivatives

Curcumin, a non-nutritive yellow pigment derived from the rhizome of Curcuma longa (turmeric), is considered to be an established nutraceutical with anticancer activity. Turmeric contains three principal components, curcumin, demethoxycurcumin and bisdemethoxycurcumin, of which curcumin is most abundant and potent. The concurrence of a high consumption of turmeric and a low incidence of prostate cancer in Asian countries may suggest a role for curcumin in chemoprevention. Curcumin has been identified to exhibit anti-inflammatory, anti-oxidative and anticarcinogenic properties. Since the compound does not exhibit side effects, curcumin has been designated for several clinical trials as a treatment for human cancers. The pro-apototic, antioxidant and anti-inflammatory characteristics of curcumin are implicated in its anticancer activity, yet the mechanism of action of curcumin remains unknown. To achieve an effective pharmacological outcome, curcumin must reach and sustain appropriate levels at the site of action. However, the main disadvantage of curcumin is its high metabolic instability and poor aqueous solubility that limits its systemic bioavailability. To overcome this difficulty, the present study tested the anticancer activity of new curcumin-like compounds (E21cH and Q012095H). Also, the use of new medicaments requires an understanding of their pharmacokinetic profiles and targets. Thus, molecular modeling methods were used to identify the targets of curcumin and curcumin-like compounds compared with other anticancer drugs (Q012138 and Q012169AT), which were used as the controls. The present study identified several enzymes that are targeted by curcumin, aldo-keto reductase family 1 member B10 (AKR1B10), serine/threonine-protein kinase, protein kinase C, matrix metalloproteinase (MMP), cyclooxygenase and epidermal growth factor receptor, which were tested as targets for these anticancer chemicals. All the examined small compounds demonstrated anticancer activity in the in vitro experiments and may impact cancer cells by acting on AKR1B10, MMP-9 and their targets.

Analysis of the inhibition of PAI-1 by metal theaflavin complexes and their degradation products

The inhibition of elements of the plasminogen activator system [urokinase (uPA), tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1)] plays an important role in human diseases. PAI-1 is overexpressed in obesity and diabetes, and the inhibition of this protein has been postulated to alleviate the symptoms of both disorders. We found that two theaflavins (TFs) from black tea inhibit PAI-1 and we suggest that the beneficial effects of drinking tea may be associated with the suppression of PAI-1 activity by theaflavins. Epidemiological studies are controversial; some studies show the beneficial effects of drinking black tea on obesity and diabetes, while others do not. TFs, a family of compounds that can comprise up to 40% the dry weight of black tea, are responsible for the characteristic color, and they are known to chelate metals. We hypothesized that the content/variety of metals present in drinking water may be one of the reasons for such controversies in the population studies. TFs are excellent chelating compounds by trapping metals into complexes; thus, the quality of water used for tea preparation may influence changes in the formation of new products according to TF affinity for different metals, as well as their high molecular weight oxidation products. Our modeling and docking studies suggest that TF/metal complexes have similar affinity to PAI-1 as native TFs. However, analyses using liquid chromatography-mass spectroscopy (LC-MS) revealed the presence of TF degradation products in tea brewed using water containing metal salts. These can further form high molecular weight oxidation products. Thus, metals present in tea could diminish the beneficial effects of black tea by reducing TF concentration via metal-induced degradation and precipitation.

Protective effects of topical application of a poorly soluble antioxidant astaxanthin liposomal formulation on ultraviolet-induced skin damage

Astaxanthin (Asx) would be expected to prevent ultraviolet (UV)-induced skin damage, as it is regarded as a potent antioxidative carotenoid in biological membranes. However, it is difficult to administer Asx topically to skin because of its poor water solubility. In this study, we attempted to solve this problem by preparing liposomes containing Asx (Asx-lipo), which were dispersible in the water phase, and therefore, suitable for topical application to the skin. Asx-lipo was shown to have potent scavenging ability against chemiluminescence-dependent singlet oxygen production in the water phase. When Asx-lipo was applied to skin before UV exposure, UV-induced skin thickening was prevented. Interestingly, collagen reduction induced by UV exposure was also prevented by preadministration of Asx-lipo. In addition, topical administration of Asx-lipo containing cationic lipid inhibited melanin production in skin exposed to UV. Consequently, we succeeded in preventing UV-induced skin damage using a topical application of a liposomal formulation containing Asx.

Advances in studies on collagenase inhibitors

Matrix metalloproteinases (MMPs) play an important role in many physiological and pathological processes. Development of MMP inhibitors, in particular collagenase inhibitors, for the treatment of arthritis has been more challenging, undoubtedly. Small-molecular-weight collagenase inhibitors may be classified into several different arbitrary structural classes, depending on the catalytic zinc-binding function as well as other structural elements of the inhibitors. This chapter tries to make an attempt in providing the reader with an overall flavor of the type of scaffolds reported in the past few years along with the molecular modeling studies.

Blind Dockings of Benzothiazoles to Multiple Receptor Conformations of Triosephosphate Isomerase from Trypanosoma cruzi and Human

We aim to uncover the binding modes of benzothiazoles, which have been reported as specific inhibitors of triosephosphate isomerase from the parasite Trypanosoma cruzi (TcTIM), by performing blind dockings on both TcTIM and human TIM (hTIM). Detailed analysis of binding sites and specific interactions are carried out based on ensemble dockings to multiple receptor conformers obtained from molecular dynamics simulations. In TcTIM dimer dockings, the inhibitors preferentially bind to the tunnel-shaped cavity formed at the interface of the subunits, whereas non-inhibitors mostly choose other sites. In contrast, TcTIM monomer binding interface and hTIM dimer interface do not present a specific binding site for the inhibitors. These findings point to the importance of the tunnel and of the dimeric form for inhibition of TcTIM. Specific interactions of the inhibitors and their sulfonate-free derivatives with the receptor residues indicate the significance of sulfonate group for binding affinity and positioning on the TcTIM dimer interface. One of the inhibitors also binds to the active site, which may explain its relatively higher inhibition effect on hTIM.

Molecular modeling of lanthionine synthetase component C-like protein 2: a potential target for the discovery of novel type 2 diabetes prophylactics and therapeutics

The rates of type 2 diabetes (T2D) are rising to epidemic proportions in the US and worldwide. While current T2D medications are efficacious, significant side effects have limited their use and availability. Our laboratory has discovered that abscisic acid (ABA) exerts anti-diabetic effects, in part, by activating peroxisome proliferator-activated receptor γ (PPAR γ). However, since ABA does not bind to the ligand-binding domain (LBD) of PPAR γ, the mechanism of activation of PPAR γ by ABA remains unknown. Lanthionine synthetase component C-like protein 2 (LANCL2) was predicted to be a novel target for the binding and signaling of ABA in human granulocytes and rat insulinoma cells. The goal of this study was to determine whether LANCL2 is a molecular target of ABA and other PPAR γ agonists. To this end we performed homology modeling to construct a three-dimensional structure of LANCL2 using the crystal structure of LANCL1 as a template. Our molecular docking studies predicted that ABA and other PPAR γ agonists (e.g., rosiglitazone and pioglitazone) share a binding site on the surface of LANCL2. The identification of a binding site for PPAR γ agonists will facilitate the high-throughput virtual screening of large compound libraries and may shed new light on alternative mechanisms of PPAR γ activation.