How can (-)-epigallocatechin gallate from green tea prevent HIV-1 infection? Mechanistic insights from computational modeling and the implication for rational design of anti-HIV-1 entry inhibitors

A comprehensive review on targeting cluster of differentiation: An attractive strategy for inhibiting viruses through host proteins

Viral infections continue to pose a significant global public health threat. Targeting host proteins, such as cluster of differentiation (CD) macromolecules, may offer a promising alternative approach to developing antiviral treatments. CDs are cell-surface biological macromolecules mainly expressed on leukocytes that viruses can use to enter cells, thereby evading immune detection and promoting their replication. The manipulation of CDs by viruses may represent an effective and clever means of survival through the prolonged co-evolution of hosts and viruses. Targeting of CDs is anticipated to hinder the invasion of related viruses, modulate the body's immune system, and diminish the incidence of subsequent inflammation. They have become crucial for biomedical diagnosis, and some have been used as valuable tools for resisting viral infections. However, a summary of the structures and functions of CDs involved in viral infection is currently lacking. The development of drugs targeting these biological macromolecules is restricted both in terms of their availability and the number of compounds currently identified. This review provides a comprehensive analysis of the critical role of CD proteins in virus invasion and a list of relevant targeted antiviral agents, which will serve as a valuable reference for future research in this field.

Epigallocatechin Gallate: A Multifaceted Molecule for Neurological Disorders and Neurotropic Viral Infections

Epigallocatechin-3-gallate (EGCG), a polyphenolic moiety found in green tea extracts, exhibits pleiotropic bioactivities to combat many diseases including neurological ailments. These neurological diseases include Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. For instance, in the case of Alzheimer's disease, the formation of a β-sheet in the region of the 10th-21st amino acids was significantly reduced in EGCG-induced oligomeric samples of Aβ40. Its interference induces the formation of Aβ structures with an increase in intercenter-of-mass distances, reduction in interchain/intrachain contacts, reduction in β-sheet propensity, and increase in α-helix. Besides, numerous neurotropic viruses are known to instigate or aggravate neurological ailments. It exerts an effect on the oxidative damage caused in neurodegenerative disorders by acting on GSK3-β, PI3K/Akt, and downstream signaling pathways via caspase-3 and cytochrome-c. EGCG also diminishes these viral-mediated effects, such as EGCG delayed HSV-1 infection by blocking the entry for virions, inhibitory effects on NS3/4A protease or NS5B polymerase of HCV and potent inhibitor of ZIKV NS2B-NS3pro/NS3 serine protease (NS3-SP). It showed a reduction in the neurotoxic properties of HIV-gp120 and Tat in the presence of IFN-γ. EGCG also involves numerous viral-mediated inflammatory cascades, such as JAK/STAT. Nonetheless, it also inhibits the Epstein-Barr virus replication protein (Zta and Rta). Moreover, it also impedes certain viruses (influenza A and B strains) by hijacking the endosomal and lysosomal compartments. Therefore, the current article aims to describe the importance of EGCG in numerous neurological diseases and its inhibitory effect against neurotropic viruses.

Theaflavin Chemistry and Its Health Benefits

Huge epidemiological and clinical studies have confirmed that black tea is a rich source of health-promoting ingredients, such as catechins and theaflavins (TFs). Furthermore, TF derivatives mainly include theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), and theaflavin-3,3'-digallate (TF3). All of these TFs exhibit extensive usages in pharmaceutics, foods, and traditional medication systems. Various indepth studies reported that how TFs modulates health effects in cellular and molecular mechanisms. The available literature regarding the pharmacological activities of TFs has revealed that TF3 has remarkable anti-inflammatory, antioxidant, anticancer, antiobesity, antiosteoporotic, and antimicrobial properties, thus posing significant effects on human health. The current manuscript summarizes both the chemistry and various pharmacological effects of TFs on human health, lifestyle or aging associated diseases, and populations of gut microbiota. Furthermore, the biological potential of TFs has also been focused to provide a deeper understanding of its mechanism of action.

Nanotechnology Applications of Flavonoids for Viral Diseases

Recent years have witnessed the emergence of several viral diseases, including various zoonotic diseases such as the current pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Other viruses, which possess pandemic-causing potential include avian flu, Ebola, dengue, Zika, and Nipah virus, as well as the re-emergence of SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome) coronaviruses. Notably, effective drugs or vaccines against these viruses are still to be discovered. All the newly approved vaccines against the SARS-CoV-2-induced disease COVID-19 possess real-time possibility of becoming obsolete because of the development of ‘variants of concern’. Flavonoids are being increasingly recognized as prophylactic and therapeutic agents against emerging and old viral diseases. Around 10,000 natural flavonoid compounds have been identified, being phytochemicals, all plant-based. Flavonoids have been reported to have lesser side effects than conventional anti-viral agents and are effective against more viral diseases than currently used anti-virals. Despite their abundance in plants, which are a part of human diet, flavonoids have the problem of low bioavailability. Various attempts are in progress to increase the bioavailability of flavonoids, one of the promising fields being nanotechnology. This review is a narrative of some anti-viral dietary flavonoids, their bioavailability, and various means with an emphasis on the nanotechnology system(s) being experimented with to deliver anti-viral flavonoids, whose systems show potential in the efficient delivery of flavonoids, resulting in increased bioavailability.

An Overview on the Potential Roles of EGCG in the Treatment of COVID-19 Infection

Coronavirus disease-19 (COVID-19) pandemic is currently ongoing worldwide and causes a lot of deaths in many countries. Although different vaccines for the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection have been developed and are now available, there are no effective antiviral drugs to treat the disease, except for Remdesivir authorized by the US FDA to counteract the emergency. Thus, it can be useful to find alternative therapies based on the employment of natural compounds, with antiviral features, to circumvent SARS-CoV-2 infection. Pre-clinical studies highlighted the antiviral activities of epigallocatechin-3-gallate (EGCG), a catechin primarily found in green tea, against various viruses, including SARS-CoV-2. In this review, we summarize this experimental evidence and highlight the potential use of EGCG as an alternative therapeutic choice for the treatment of SARS-CoV-2 infection.

Antiviral Effects of Green Tea EGCG and Its Potential Application against COVID-19

(–)-Epigallocatechin-3-O-gallate (EGCG), the most abundant component of catechins in tea (Camellia sinensis (L.) O. Kuntze), plays a role against viruses through inhibiting virus invasiveness, restraining gene expression and replication. In this paper, the antiviral effects of EGCG on various viruses, including DNA virus, RNA virus, coronavirus, enterovirus and arbovirus, were reviewed. Meanwhile, the antiviral effects of the EGCG epi-isomer counterpart (+)-gallocatechin-3-O-gallate (GCG) were also discussed.

Recent Advances on Nanomaterials to COVID-19 Management: A Systematic Review on Antiviral/Virucidal Agents and Mechanisms of SARS-CoV-2 Inhibition/Inactivation

The current pandemic of coronavirus disease 2019 (COVID-19) is recognized as a public health emergency of worldwide concern. Nanomaterials can be effectively used to detect, capture/inactivate or inhibit coronavirus cell entry/replication in the human host cell, preventing infection. Their potential for nanovaccines, immunoengineering, diagnosis, repurposing medication, and disinfectant surfaces targeting the novel coronavirus (SARS-CoV-2) is highlighted. In this systematic review the aim is to present an unbiased view of which and how nanomaterials can reduce the spread of COVID-19. Herein, the focus is on SARS-CoV-2, analyzing 46 articles retrieved before December 31, 2020. The interface between nanomaterials is described, and the main mechanisms to inhibit SARS-CoV-2 pathogenesis and viral inactivation are also discussed. Nanocarbons, biopolymeric, copper, and silver nanoparticles are potential antiviral and virucidal agents toward self-cleaning and reusable filter media and surfaces (e.g., facial masks), drug administration, vaccines, and immunodiagnostic assays. Trends in toxicology research and safety tests can help fill the main gaps in the literature and overcome health surveillance's challenges. Phytochemicals delivery by nanocarriers also stand out as candidates to target and bio-friendly therapy. Nanocellulose might fill in the gaps. Future research using nanomaterials targeting novel therapies/prophylaxis measures to COVID-19 and future outbreaks is discussed.

A Review on the Biological Activity of Camellia Species

Medicinal plants have been used since antiquity to cure illnesses and injuries. In the last few decades, natural compounds extracted from plants have garnered the attention of scientists and the Camellia species are no exception. Several species and cultivars are widespread in Asia, namely in China, Japan, Vietnam and India, being also identified in western countries like Portugal. Tea and oil are the most valuable and appreciated Camellia subproducts extracted from Camellia sinensis and Camellia oleifera, respectively. The economic impact of these species has boosted the search for additional information about the Camellia genus. Many studies can be found in the literature reporting the health benefits of several Camellia species, namely C. sinensis, C. oleifera and Camellia japonica. These species have been highlighted as possessing antimicrobial (antibacterial, antifungal, antiviral) and antitumoral activity and as being a huge source of polyphenols such as the catechins. Particularly, epicatechin (EC), epigallocatechin (EGC), epicatechin-3-gallate (ECG), and specially epigallocatechin-3-gallate (EGCG), the major polyphenols of green tea. This paper presents a detailed review of Camellia species’ antioxidant properties and biological activity.

Current concepts in the development of therapeutics against human and animal coronavirus diseases by targeting NP

The coronavirus (CoV) infects a broad range of hosts including humans as well as a variety of animals. It has gained overwhelming concerns since the emergence of deadly human coronaviruses (HCoVs), severe acute respiratory syndrome coronavirus (SARS-CoV) in 2003, followed by Middle East respiratory syndrome coronavirus (MERS-CoV) in 2015. Very recently, special attention has been paid to the novel coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 due to its high mobility and mortality. As the COVID-19 pandemic continues, despite vast research efforts, the effective pharmaceutical interventions are still not available for clinical uses. Both expanded knowledge on structure insights and the essential function of viral nucleocapsid (N) protein are key basis for the development of novel, and potentially, a broad-spectrum inhibitor against coronavirus diseases. This review aimed to delineate the current research from the perspective of biochemical and structural study in cell-based assays as well as virtual screen approaches to identify N protein antagonists targeting not only HCoVs but also animal CoVs.

Antileishmanial Activity of Lignans, Neolignans, and Other Plant Phenols

Secondary metabolites (SM) from organisms have served medicinal chemists over the past two centuries as an almost inexhaustible pool of new drugs, drug-like skeletons, and chemical probes that have been used in the "hunt" for new biologically active molecules with a "beneficial effect on human mind and body." Several secondary metabolites, or their derivatives, have been found to be the answer in the quest to search for new approaches to treat or even eradicate many types of diseases that oppress humanity. A special place among SM is occupied by lignans and neolignans. These phenolic compounds are generated biosynthetically via radical coupling of two phenylpropanoid monomers, and are known for their multitarget activity and low toxicity. The disadvantage of the relatively low specificity of phenylpropanoid-based SM turns into an advantage when structural modifications of these skeletons are made. Indeed, phenylpropanoid-based SM previously have proven to offer great potential as a starting point in drug development. Compounds such as Warfarin^® (a coumarin-based anticoagulant) as well as etoposide and teniposide (podophyllotoxin-based anticancer drugs) are just a few examples. At the beginning of the third decade of the twenty-first century, the call for the treatment of more than a dozen rare or previously "neglected" diseases remains for various reasons unanswered. Leishmaniasis, a neglected disease that desperately needs new ways of treatment, is just one of these. This disease is caused by more than 20 leishmanial parasites that are pathogenic to humans and are spread by as many as 800 sandfly species across subtropical areas of the world. With continuing climate changes, the presence of Leishmania parasites and therefore leishmaniasis, the disease caused by these parasites, is spreading from previous locations to new areas. Thus, leishmaniasis is affecting each year a larger proportion of the world's population. The choice of appropriate leishmaniasis treatment depends on the severity of the disease and its form of manifestation. The success of current drug therapy is often limited, due in most cases to requiring long hospitalization periods (weeks to months) and the toxicity (side effects) of administered drugs, in addition to the increasing resistance of the parasites to treatment. It is thus important to develop new drugs and treatments that are less toxic, can overcome drug resistance, and require shorter periods of treatment. These aspects are especially important for the populations of developing countries. It was reported that several phenylpropanoid-based secondary metabolites manifest interesting antileishmanial activities and are used by various indigenous people to treat leishmaniasis. In this chapter, the authors shed some light on the various biological activities of phenylpropanoid natural products, with the main focus being on their possible applications in the context of antileishmanial treatment.

Druggable targets from coronaviruses for designing new antiviral drugs

Severe respiratory infections were highlighted in the SARS-CoV outbreak in 2002, as well as MERS-CoV, in 2012. Recently, the novel CoV (COVID-19) has led to severe respiratory damage to humans and deaths in Asia, Europe, and Americas, which allowed the WHO to declare the pandemic state. Notwithstanding all impacts caused by Coronaviruses, it is evident that the development of new antiviral agents is an unmet need. In this review, we provide a complete compilation of all potential antiviral agents targeting macromolecular structures from these Coronaviruses (Coronaviridae), providing a medicinal chemistry viewpoint that could be useful for designing new therapeutic agents.

Study on the interaction between catechin and cholesterol by the density functional theory

Catechin – a natural polyphenol substance – has excellent antioxidant properties for the treatment of diseases, especially for cholesterol lowering. Catechin can reduce cholesterol content in micelles by forming insoluble precipitation with cholesterol, thereby reducing the absorption of cholesterol in the intestine. In this study, to better understand the molecular mechanism of catechin and cholesterol, we studied the interaction between typical catechins and cholesterol by the density functional theory. Results show that the adsorption energies between the four catechins and cholesterol are obviously stronger than that of cholesterol themselves, indicating that catechin has an advantage in reducing cholesterol micelle formation. Moreover, it is found that the molecular interactions of the complexes are mainly due to charge transfer of the aromatic rings of the catechins as well as the hydrogen bond interactions. Unlike the intuitive understanding of a complex formed by hydrogen bond interaction, which is positively correlated with the number of hydrogen bonds, the most stable complexes (epicatechin–cholesterol or epigallocatechin–cholesterol) have only one but stronger hydrogen bond, due to charge transfer of the aromatic rings of catechins.

HIV-1 Entry Inhibitors: A Review of Experimental and Computational Studies

The HIV-1 life cycle consists of different events, such as cell entry and fusion, virus replication, assembly and release of the newly formed virions. The more logical way to inhibit HIV transmission among individuals is to inhibit its entry into the immune host cells rather than targeting the intracellular viral enzymes. Both viral and host cell surface receptors and co-receptors are regarded as potential targets in anti-HIV-1 drug design process. Because of the importance of this topic it was decided to summarize recent reports on small-molecule HIV-1 entry inhibitors that have not been considered in the latest released reviews. All the computational studies reported in the literature regarding HIV-1 entry inhibitors since 2014 was also considered in this review.

Computational Molecular Docking and X-ray Crystallographic Studies of Catechins in New Drug Design Strategies

Epidemiological and laboratory studies have shown that green tea and green tea catechins exert beneficial effects on a variety of diseases, including cancer, metabolic syndrome, infectious diseases, and neurodegenerative diseases. In most cases, (-)-epigallocatechin gallate (EGCG) has been shown to play a central role in these effects by green tea. Catechins from other plant sources have also shown health benefits. Many studies have revealed that the binding of EGCG and other catechins to proteins is involved in its action mechanism. Computational docking analysis (CMDA) and X-ray crystallographic analysis (XCA) have provided detailed information on catechin-protein interactions. Several of these studies have revealed that the galloyl moiety anchors it to the cleft of proteins through interactions with its hydroxyl groups, explaining the higher activity of galloylated catechins such as EGCG and epicatechin gallate than non-galloylated catechins. In this paper, we review the results of CMDA and XCA of EGCG and other plant catechins to understand catechin-protein interactions with the expectation of developing new drugs with health-promoting properties.

Epigallocatechin-3-gallate local pre-exposure application prevents SHIV rectal infection of macaques

Epigallocatechin-3-gallate (EGCG), a natural and major ingredient of green tea, has been shown to have anti-inflammation and anti-HIV-1 properties. We demonstrated that the intrarectal administration of EGCG could protect rhesus macaques from repetitive, intrarectal challenges with low-dose SHIV_SF162P3N. This protection has a per-exposure risk reduction of 91.5% (P = 0.0009; log-rank test) and a complete protection of 87.5% (P < 0.001; Fisher's exact test). All protected animals showed no evidence of systemic and mucosal SHIV infection as demonstrated by the absence of viral RNA, DNA and antibodies. In contrast, all controls became infected after repeated SHIV challenges (a median of 2.5 times, range of 1-8 times). Mechanistically, EGCG could block the binding of HIV-1 gp120 to CD4 receptor and suppress the macrophage infiltration/activation in the rectal mucosa of macaques. These data support further clinical evaluation and development of EGCG as a novel, safe and cost-effective microbicide for preventing sexual transmission of HIV-1.

A Review of the Antiviral Role of Green Tea Catechins

Over the centuries, infectious diseases caused by viruses have seriously threatened human health globally. Viruses are responsible not only for acute infections but also many chronic infectious diseases. To prevent diseases caused by viruses, the discovery of effective antiviral drugs, in addition to vaccine development, is important. Green tea catechins (GTCs) are polyphenolic compounds from the leaves of Camelliasinensis. In recent decades, GTCs have been reported to provide various health benefits against numerous diseases. Studies have shown that GTCs, especially epigallocatechin-3-gallate (EGCG), have antiviral effects against diverse viruses. The aim of this review is to summarize the developments regarding the antiviral activities of GTCs, to discuss the mechanisms underlying these effects and to offer suggestions for future research directions and perspectives on the antiviral effects of EGCG.

Salts Influence Cathechins and Flavonoids Encapsulation in Liposomes: A Molecular Dynamics Investigation

Cathechins and flavonoids are responsible of numerous health benefits. Two of the most representatives' compounds for their antioxidant and therapeutic effects are Epigallocatechin 3-Gallate (EGCG), from green tea extracts, and morelloflavone (MF), from Garcinia dulcis. Here we explore, by atomistic Molecular Dynamics simulations, how EGCG and MF interact with lipid bilayers and we show the salts' influence on their encapsulation degree in neutral liposomes. As a result, we found out that EGCGs naturally bind to the hydrophilic regions of phospholipids, positioning themselves mostly at the interface between water and lipid phases. The presence of a salt clearly influences the EGCG molecules' absorption and the total effect depends strongly on the salt nature and concentration. Beside, for MF, we observed a high stability of the intermolecular MFs aggregates in water that strongly penalizes the flavonoid's interaction with the lipid polar heads. However, salts can influence MF's liposomal penetration, even if they are not able to promote completely its absorption inside the bilayer. For both compounds, the increase of penetration is more marked in presence of magnesium chloride, whilst calcium chloride showed the opposite effect.

Characterization of Catechins in Water by Photoemission Yield Spectroscopy in Air

Photoemission yield spectroscopy in air (PYSA) was applied for the characterization of catechins in water in ambient conditions. According to the results of measurements on aqueous solutions of epigallocatechin gallate (EGCg) of various concentrations, the photoemission yield is almost proportional to the concentration of EGCg. Contrarily, the threshold energy of photoemission, EPET, is almost constant at 5.46 ± 0.02 eV. Moreover, we measured aqueous solutions of epicatechin (EC), epigallocatechin (EGC), and epicatechin gallate (ECg). The values of EPET of EC, EGC, ECg were estimated to be 5.72 ± 0.02, 5.68 ± 0.01, and 5.45 ± 0.02 eV, respectively, and a dependence on the molecular structure was found. Furthermore, changes in the photoemission yield spectra of heated EGCg were well explained by molecular orbital calculations on the basis of an assumption of epimerization.

DYRK1A inhibition as potential treatment for Alzheimer's disease

In total, 47,500,000 people worldwide are affected by dementia and this number is estimated to double by 2030 and triple within 2050 resulting in a huge burden on public health. Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia, accounting for 60-70% of all the cases. The cause of AD is still poorly understood but several brain abnormalities (e.g., loss of neuronal connections and neuronal death) have been identified in affected patients. In addition to the accumulation of β-amyloid plaques in the brain tissue, aberrant phosphorylation of tau proteins has proved to increase neuronal death. DYRK1A phosphorylates tau on 11 different Ser/Thr residues, resulting in the formation of aggregates called 'neurofibrillary tangles' which, together with amyloid plaques, could be responsible for dementia, neuronal degeneration and cell death. Small molecule inhibition of DYRK1A could thus represent an interesting approach toward the treatment of Alzheimer's and other neurodegenerative diseases. Herein we review the current progress in the identification and development of DYRK1A inhibitors.

The Effect of Green Tea Extract Supplementation on Liver Enzymes in Patients with Nonalcoholic Fatty Liver Disease

Background:

Green tea is one of the most popular beverages in the world. It is believed to have beneficial effects in the prevention and treatment of many diseases, one of which is nonalcoholic fatty liver disease (NAFLD). The present study investigated the effects of consumption of green tea in NAFLD patients.

Methods:

This study was a double-blind, placebo-controlled, randomized clinical trial. Ultrasonography was used to diagnose fatty liver in patients with alanine aminotransferase (ALT) >31 mg/dl and 41 mg/dl and aspartate aminotransferase (AST) >31 mg/dl and 47 g/dl in women and men, respectively and without other hepatic diseases. A total of 80 participants (20–50 years) with NAFLD were randomly allocated into two groups to receive either green tea extract (GTE) supplement (500 mg GTE tablet per day) or placebo for 90 days. At baseline and at the end of the intervention weight, serum ALT, AST, and alkaline phosphatase (ALP) were measured in fasting state, and dietary data were collected at baseline and end of the study.

Results:

Green tea group showed significant reductions in ALT and AST levels after 12 weeks period (P < 0.001). The placebo group showed a reduction in ALT and AST levels at the end of the study, but it was no significant. ALP levels showed significant reductions in both groups after 12 weeks period (P < 0.001).

Conclusions:

According to the findings of this study, GTE supplementation decrease liver enzymes in patients with NAFLD. It can be claimed that GTE prescribed can be considered as a treatment to improve serum levels of liver enzymes in NAFLD patients.

Quantification of total polyphenols, catechin, caffeine, L-theanine, determination of antioxidant activity and effect on antileishmanial drugs of ethiopian tea leaves extracts

Objective:

In this study four tea samples Gumero black, Wushwush black and Wushwush green from Agri- Ceft Plc and East Africa black tea leaves from East African Agribusiness Plc were investigated for total polyphenols, caffeine, catechin and L-theanine content.

Materials and Methods:

The aqueous extracts were investigated for their antioxidant and antileishmanial property and effect on amphotericin B, miltefocine and sodium stibogluconate, the commonly used antileishmanial drugs. Antileishmanial studies were conducted on L. aethiopica.

Results:

Wushwush green tea had the highest content of polyphenol (19.98 ± 1.15 mg gallic acid equivalent /100 g dry leaf weight), catechin (37.06 mg/g) and L-theanine (48.54 mg/g but the lowest caffeine content). It exhibited the highest antioxidant activity. The highest antioxidant effect of Wushwush green tea may be attributed to the highest polyphenol content. East African black tea had the lowest L-theanine (20.72 mg/g) and antioxidant activity but the highest caffeine (16.60 mg/g) content.

Conclusion:

Wushwush green tea showed slight inhibitory effect on L. aethiopica while the lack tea extracts (Gumero, East Africa and Wushwush) exhibited no antileishmanial activity. Wushwush green tea did not show any synergistic or antagonistic effect on the antileishmanial drugs used in this study while Gumero, East Africa and Wushwush black tea extracts exhibited dose dependant inhibitory activity to the commonly used antileishmanial drugs included in this study.

Interaction of dietary compounds, especially polyphenols, with the intestinal microbiota: a review

The intestinal microbiome plays an important role in the metabolism of chemical compounds found within food. Bacterial metabolites are different from those that can be generated by human enzymes because bacterial processes occur under anaerobic conditions and are based mainly on reactions of reduction and/or hydrolysis. In most cases, bacterial metabolism reduces the activity of dietary compounds; however, sometimes a specific product of bacterial transformation exhibits enhanced properties. Studies on the metabolism of polyphenols by the intestinal microbiota are crucial for understanding the role of these compounds and their impact on our health. This review article presents possible pathways of polyphenol metabolism by intestinal bacteria and describes the diet-derived bioactive metabolites produced by gut microbiota, with a particular emphasis on polyphenols and their potential impact on human health. Because the etiology of many diseases is largely correlated with the intestinal microbiome, a balance between the host immune system and the commensal gut microbiota is crucial for maintaining health. Diet-related and age-related changes in the human intestinal microbiome and their consequences are summarized in the paper.

The root extract of the medicinal plant Pelargonium sidoides is a potent HIV-1 attachment inhibitor

Global HIV-1 treatment would benefit greatly from safe herbal medicines with scientifically validated novel anti-HIV-1 activities. The root extract from the medicinal plant Pelargonium sidoides (PS) is licensed in Germany as the herbal medicine EPs®7630, with numerous clinical trials supporting its safety in humans. Here we provide evidence from multiple cell culture experiments that PS extract displays potent anti-HIV-1 activity. We show that PS extract protects peripheral blood mononuclear cells and macrophages from infection with various X4 and R5 tropic HIV-1 strains, including clinical isolates. Functional studies revealed that the extract from PS has a novel mode-of-action. It interferes directly with viral infectivity and blocks the attachment of HIV-1 particles to target cells, protecting them from virus entry. Analysis of the chemical footprint of anti-HIV activity indicates that HIV-1 inhibition is mediated by multiple polyphenolic compounds with low cytotoxicity and can be separated from other extract components with higher cytotoxicity. Based on our data and its excellent safety profile, we propose that PS extract represents a lead candidate for the development of a scientifically validated herbal medicine for anti-HIV-1 therapy with a mode-of-action different from and complementary to current single-molecule drugs.

Tea: A native source of antimicrobial agents

Tea (Camellia sinensis) is one of the most popular nonalcoholic beverages, consumed by over two-thirds of the world's population because of its refreshing, mild stimulant and medicinal properties. It is processed in different ways in different parts of the world to give green, black, oolong, and pu-erh tea. Among all tea polyphenols, epigallocatechin-3-gallate has been responsible for much of the health promoting abilities of tea including anti-inflammatory, antimicrobial, antitumour, anti-oxidative, protection from cardiovascular disease, anti-obesity, and anti-aging properties. In the present review, the antibacterial, antiviral, and antifungal activities of different types of tea and their polyphenols are reported, highlighting their mechanisms of action and structure–activity relationship. Moreover, considering that the changing patterns of infectious diseases and the emergence of microbial strains resistant to current antibiotics, there is an urgent need to find out new potent antimicrobial agents as adjuvants to antibiotic therapy. The synergistic effect of tea polyphenols in combination with conventional antimicrobial agents against clinical multidrug-resistant microorganisms has also been discussed in this review.

Green tea with high-density catechins improves liver function and fat infiltration in non-alcoholic fatty liver disease (NAFLD) patients: a double-blind placebo-controlled study

Catechins, a major component of green tea extract, have anti-hyperlipidemic effects. The present study investigated the effects of consumption of green tea with high-density catechins in non-alcoholic fatty liver disease (NAFLD) patients. Seventeen patients with NAFLD consumed green tea with high-density catechins, low-density catechins or a placebo for 12 weeks in a randomized double-blind study. Ultrasonography and computed tomography (CT) were performed at baseline and after 12 weeks. Serum alanine aminotransferase (ALT) levels and urine 8-isoprostane were monitored and compared to baseline at 4, 8 and 12 weeks. Body fat was significantly decreased in the high-density catechin group compared with the placebo and low-density catechin groups after 12 weeks of consumption. All the patients in the high-density catechin group showed a significantly improved liver-to-spleen CT attenuation ratio compared with the placebo and low-density catechin groups after 12 weeks of consumption. The high-density catechin group significantly decreased serum ALT levels and reduced urinary 8-isoprostane excretion compared with the placebo and low-density catechin group after 12 weeks of consumption. Based on a reduced proportion of body fat as estimated by bioimpedance measurement, increased liver-to-spleen CT attenuation ratio, decreased serum ALT levels and reduced urinary 8-isoprostane excretion, we concluded that 12 weeks of 700 ml per day of green tea containing >1 g catechin improved liver fat content and inflammation by reducing oxidative stress in patients with NAFLD.

Microscopic Modes and Free Energies for Topoisomerase I-DNA Covalent Complex Binding with Non-campothecin Inhibitors by Molecular Docking and Dynamics Simulations

Topoisomerase I (Topo1) has been identified as an attractive target for anticancer drug development due to its central role in facilitating the nuclear process of the DNA. It is essential for rational design of novel Topo1 inhibitors to reliably predict the binding structures of the Topo1 inhibitors interacting with the Topo1-DNA complex. The detailed binding structures and binding free energies for the Topo1-DNA complex interacting with typical non-camptothecin (CPT) Topo1 inhibitors have been examined by performing molecular docking, molecular dynamic (MD) simulations, and binding free energy calculations. The computational results provide valuable insights into the binding modes of the inhibitors binding with the Topo1-DNA complex and the key factors affecting the binding affinity. It has been demonstrated that the - stacking interaction with the DNA base pairs and the hydrogen bonding with Topo1 have the pivotal contributions to the binding structures and binding free energies, although the van der Waals and electrostatic interactions also significantly contribute to the stabilization of the binding structures. The calculated binding free energies are in good agreement with the available experiment activity data. The detailed binding modes and the crucial factors affecting the binding free energies obtained from the present computational studies may provide valuable insights for future rational design of novel, more potent Topo1 inhibitors.

A computational exploration of the interactions of the green tea polyphenol (-)-Epigallocatechin 3-Gallate with cardiac muscle troponin C

Thanks to its polyphenols and phytochemicals, green tea is believed to have a number of health benefits, including protecting from heart disease, but its mechanism of action at the molecular level is still not understood. Here we explore, by means of atomistic simulations, how the most abundant of the green tea polyphenols, (-)-Epigallocatechin 3-Gallate (EGCg), interacts with the structural C terminal domain of cardiac muscle troponin C (cCTnC), a calcium binding protein that plays an important role in heart contractions. We find that EGCg favourably binds to the hydrophobic cleft of cCTnC consistently with solution NMR experiments. It also binds to cCTnC in the presence of the anchoring region of troponin I (cTnI(34-71)) at the interface between the E and H helices. This appears to affect the strength of the interaction between cCTnC and cTnI(34-71) and also counter-acts the effects of the Gly159Asp mutation, related to dilated cardiomyopathy. Our simulations support the picture that EGCg interacting with the C terminal domain of troponin C may help in regulating the calcium signalling either through competitive binding with the anchoring domain of cTnI or by affecting the interaction between cCTnC and cTnI(34-71).

Role of green tea as an antioxidant in periodontal disease: The Asian paradox

Green tea is a popular beverage nowadays and intake of green tea polyphenols has shown preventive effect against cancer and cardiovascular disease in experimental and epidemiologic studies. Several studies have suggested that green tea catechins, such as epigallocatechin gallate, inhibit periodontal pathogens and reduce the destruction of periodontal tissue. This paper aims to review the role of green tea in inflammatory diseases, especially in periodontal diseases.

Green tea phenolic epicatechins inhibit hepatitis C virus replication via cycloxygenase-2 and attenuate virus-induced inflammation

Chronic hepatitis C virus (HCV) infection is the leading risk factor for hepatocellular carcinoma (HCC) and chronic liver disease worldwide. Green tea, in addition to being consumed as a healthy beverage, contains phenolic catechins that have been used as medicinal substances. In the present study, we illustrated that the epicatechin isomers (+)-epicatechin and (−)-epicatechin concentration-dependently inhibited HCV replication at nontoxic concentrations by using in vitro cell-based HCV replicon and JFH-1 infectious systems. In addition to significantly suppressing virus-induced cyclooxygenase-2 (COX-2) expression, our results revealed that the anti-HCV activity of the epicatechin isomers occurred through the down-regulation of COX-2. Furthermore, both the epicatechin isomers additively inhibited HCV replication in combination with either interferon-α or viral enzyme inhibitors [2′-C-methylcytidine (NM-107) or telaprevir]. They also had prominent anti-inflammatory effects by inhibiting the gene expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and inducible nitrite oxide synthase as well as the COX-2 in viral protein-expressing hepatoma Huh-7 cells. Collectively, (+)-epicatechin and (−)-epicatechin may serve as therapeutic supplements for treating HCV-related diseases.

Recent advances in the design, synthesis, and biological evaluation of selective DYRK1A inhibitors: a new avenue for a disease modifying treatment of Alzheimer's?

With 24.3 million people affected in 2005 and an estimated rise to 42.3 million in 2020, dementia is currently a leading unmet medical need and costly burden on public health. Seventy percent of these cases have been attributed to Alzheimer's disease (AD), a neurodegenerative pathology whose most evident symptom is a progressive decline in cognitive functions. Dual specificity tyrosine phosphorylation regulated kinase-1A (DYRK1A) is important in neuronal development and plays a variety of functional roles within the adult central nervous system. The DYRK1A gene is located within the Down syndrome critical region (DSCR) on human chromosome 21 and current research suggests that overexpression of DYRK1A may be a significant factor leading to cognitive deficits in people with Alzheimer's disease (AD) and Down syndrome (DS). Currently, treatment options for cognitive deficiencies associated with Down syndrome, as well as Alzheimer's disease, are extremely limited and represent a major unmet therapeutic need. Small molecule inhibition of DYRK1A activity in the brain may provide an avenue for pharmaceutical intervention of mental impairment associated with AD and other neurodegenerative diseases. We herein review the current state of the art in the development of DYRK1A inhibitors.

A facile inhibitor screening of SARS coronavirus N protein using nanoparticle-based RNA oligonucleotide

Hundreds of million people worldwide have been infected with severe acute respiratory syndrome (SARS), and the rate of global death from SARS has remarkably increased. Hence, the development of efficient drug treatments for the biological effects of SARS is highly needed. We have previously shown that quantum dots (QDs)-conjugated RNA oligonucleotide is sensitive to the specific recognition of the SARS-associated coronavirus (SARS-CoV) nucleocapsid (N) protein. In this study, we found that a designed biochip could analyze inhibitors of the SARS-CoV N protein using nanoparticle-based RNA oligonucleotide. Among the polyphenolic compounds examined, (-)-catechin gallate and (-)-gallocatechin gallate demonstrated a remarkable inhibition activity on SARS-CoV N protein. (-)-catechin gallate and (-)-gallocatechin gallate attenuated the binding affinity in a concentrated manner as evidenced by QDs-conjugated RNA oligonucleotide on a designed biochip. At a concentration of 0.05 μg mL(-1), (-)-catechin gallate and (-)-gallocatechin gallate showed more than 40% inhibition activity on a nanoparticle-based RNA oligonucleotide biochip system.

Adsorption characteristics of (-)-epigallocatechin gallate and caffeine in the extract of waste tea on macroporous adsorption resins functionalized with chloromethyl, amino, and phenylamino groups

According to the Friedel-Crafts and amination reaction, a series of macroporous adsorption resins (MARs) with novel structures were synthesized and identified by the Brunauer-Emmett-Teller (BET) method and Fourier transform infrared (FTIR) spectra, and corresponding adsorption behaviors for (-)-epigallocatechin gallate (EGCG) and caffeine (CAF) extracted from waste tea were systemically investigated. Based on evaluation of adsorption kinetics, the kinetic data were well fitted by pseudo-second-order kinetics. Langmuir, Freundlich, Temkin-Pyzhev, and Dubinin-Radushkevich isotherms were selected to illustrate the adsorption process of EGCG and CAF on the MARs. Thermodynamic parameters were adopted to explain in-depth information of inherent energetic changes associated with the adsorption process. The effect of temperature on EGCG and CAF adsorption by D101-3 was further expounded. Van der Waals force, hydrogen bonding, and electrostatic interaction were the main driving forces for the adsorption of EGCG and CAF on the MARs. This study might provide a scientific reference point to aid the industrial large-scale separation and enrichment of EGCG from the extracts of waste tea using modified MARs.

Novel human mPGES-1 inhibitors identified through structure-based virtual screening

Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible prostaglandin E synthase after exposure to pro-inflammatory stimuli and, therefore, represents a novel target for therapeutic treatment of acute and chronic inflammatory disorders. It is essential to identify mPGES-1 inhibitors with novel scaffolds as new leads or hits for the purpose of drug design and discovery that aim to develop the next-generation anti-inflammatory drugs. Herein we report novel mPGES-1 inhibitors identified through a combination of large-scale structure-based virtual screening, flexible docking, molecular dynamics simulations, binding free energy calculations, and in vitro assays on the actual inhibitory activity of the computationally selected compounds. The computational studies are based on our recently developed three-dimensional (3D) structural model of mPGES-1 in its open state. The combined computational and experimental studies have led to identification of new mPGES-1 inhibitors with new scaffolds. In particular, (Z)-5-benzylidene-2-iminothiazolidin-4-one is a promising novel scaffold for the further rational design and discovery of new mPGES-1 inhibitors. To our best knowledge, this is the first time a 3D structural model of the open state mPGES-1 is used in structure-based virtual screening of a large library of available compounds for the mPGES-1 inhibitor identification. The positive experimental results suggest that our recently modeled trimeric structure of mPGES-1 in its open state is ready for the structure-based drug design and discovery.

Insight into the binding of the wild type and mutated alginate lyase (AlyVI) with its substrate: a computational and experimental study

The homology model of the wild type alginate lyase (AlyVI) marine bacterium Vibrio sp. protein, was built using the crystal structure of the Family 7 alginate lyase from Sphingomonas sp. A1. To rationalize the observed structure-affinity relationships of aliginate lyase alyVI with its (GGG) substrate, molecular docking, MD imulations and binding free energy calculations followed by site-directed mutagenesis and alyVI activity assays were carried out. Per-residue decomposition of the (GGG) binding energy revealed that the most important contributions were from polar and charged residues, such as Asn138, Arg143, Asn217, and Lys308, while van der Waals interactions were responsible for binding with the catalytic His200 and Tyr312 residues. The mutants H200A, K308A, Y312A, Y312F, and W165A were found to be inactive or almost inactive. However, the catalytic efficiency (k(cat)/K(m)) of the double mutant L224V/D226G increased by two-fold compared to the wild type enzyme. This first structural model with its substrate binding mode and the agreement with experimental results provide a suitable base for the future rational design of new mutated alyVI structures with improved catalytic activity.

Freeze-drying of mononuclear cells derived from umbilical cord blood followed by colony formation

BACKGROUND

We recently showed that freeze-dried cells stored for 3 years at room temperature can direct embryonic development following cloning. However, viability, as evaluated by membrane integrity of the cells after freeze-drying, was very low; and it was mainly the DNA integrity that was preserved. In the present study, we improved the cells' viability and functionality after freeze-drying.

METHODOLOGY/PRINCIPAL FINDINGS

We optimized the conditions of directional freezing, i.e. interface velocity and cell concentration, and we added the antioxidant EGCG to the freezing solution. The study was performed on mononuclear cells (MNCs) derived from human umbilical cord blood. After freeze-drying, we tested the viability, number of CD34(+)-presenting cells and ability of the rehydrated hematopoietic stem cells to differentiate into different blood cells in culture. The viability of the MNCs after freeze-drying and rehydration with pure water was 88%-91%. The total number of CD34(+)-presenting cells and the number of colonies did not change significantly when evaluated before freezing, after freeze-thawing, and after freeze-drying (5.4 x 10(4)+/-4.7, 3.49 x 10(4)+/-6 and 6.31 x 10(4)+/-12.27 cells, respectively, and 31+/-25.15, 47+/-45.8 and 23.44+/-13.3 colonies, respectively).

CONCLUSIONS

This is the first report of nucleated cells which have been dried and then rehydrated with double-distilled water remaining viable, and of hematopoietic stem cells retaining their ability to differentiate into different blood cells.

A novel Hsp90 inhibitor to disrupt Hsp90/Cdc37 complex against pancreatic cancer cells

Pancreatic cancer is an aggressive disease with multiple biochemical and genetic alterations. Thus, a single agent to hit one molecular target may not be sufficient to treat this disease. The purpose of this study is to identify a novel Hsp90 inhibitor to disrupt protein-protein interactions of Hsp90 and its cochaperones for down-regulating many oncogenes simultaneously against pancreatic cancer cells. Here, we reported that celastrol disrupted Hsp90-Cdc37 interaction in the superchaperone complex to exhibit antitumor activity in vitro and in vivo. Molecular docking and molecular dynamic simulations showed that celastrol blocked the critical interaction of Glu33 (Hsp90) and Arg167 (Cdc37). Immunoprecipitation confirmed that celastrol (10 micromol/L) disrupted the Hsp90-Cdc37 interaction in the pancreatic cancer cell line Panc-1. In contrast to classic Hsp90 inhibitor (geldanamycin), celastrol (0.1-100 micromol/L) did not interfere with ATP binding to Hsp90. However, celastrol (1-5 micromol/L) induced Hsp90 client protein degradation (Cdk4 and Akt) by 70% to 80% and increased Hsp70 expression by 12-fold. Celastrol induced apoptosis in vitro and significantly inhibited tumor growth in Panc-1 xenografts. Moreover, celastrol (3 mg/kg) effectively suppressed tumor metastasis by more than 80% in RIP1-Tag2 transgenic mouse model with pancreatic islet cell carcinogenesis. The data suggest that celastrol is a novel Hsp90 inhibitor to disrupt Hsp90-Cdc37 interaction against pancreatic cancer cells.

Modeling the catalysis of anti-cocaine catalytic antibody: competing reaction pathways and free energy barriers

The competing reaction pathways and the corresponding free energy barriers for cocaine hydrolysis catalyzed by an anti-cocaine catalytic antibody, mAb15A10, were studied by using a novel computational strategy based on the binding free energy calculations on the antibody binding with cocaine and transition states. The calculated binding free energies were used to evaluate the free energy barrier shift from the cocaine hydrolysis in water to the antibody-catalyzed cocaine hydrolysis for each reaction pathway. The free energy barriers for the antibody-catalyzed cocaine hydrolysis were predicted to be the corresponding free energy barriers for the cocaine hydrolysis in water plus the calculated free energy barrier shifts. The calculated free energy barrier shift of -6.87 kcal/mol from the dominant reaction pathway of the cocaine benzoyl ester hydrolysis in water to the dominant reaction pathway of the antibody-catalyzed cocaine hydrolysis is in good agreement with the experimentally derived free energy barrier shift of -5.93 kcal/mol. The calculated mutation-caused shifts of the free energy barrier are also reasonably close to the available experimental activity data. The good agreement suggests that the protocol for calculating the free energy barrier shift from the cocaine hydrolysis in water to the antibody-catalyzed cocaine hydrolysis may be used in future rational design of possible high-activity mutants of the antibody as anti-cocaine therapeutics. The general strategy of the free energy barrier shift calculation may also be valuable in studying a variety of chemical reactions catalyzed by other antibodies or proteins through noncovalent bonding interactions with the substrates.

Epigallocatechin gallate inactivates clinical isolates of herpes simplex virus

In the absence of a fully effective herpes simplex virus (HSV) vaccine, topical microbicides represent an important strategy for preventing HSV transmission. (-)-Epigallocatechin gallate (EGCG) (molecular weight, 458.4) is the primary catechin in green tea. The present study shows that EGCG has greater anti-HSV activity than other green tea catechins and inactivates multiple clinical isolates of HSV type 1 (HSV-1) and HSV-2. EGCG reduced HSV-2 titers by >or=1,000-fold in 10 to 20 min and reduced HSV-1 titers by the same amount in 30 to 40 min. The anti-HSV activity of EGCG is due to a direct effect on the virion, and incubating Vero and CV1 cells with EGCG for 48 h prior to infection with HSV-1 and HSV-2, respectively, does not reduce HSV production. Electron microscopic (EM) studies showed that purified virions exposed to EGCG were damaged, and EM immunogold labeling of the envelope glycoproteins gB and gD was significantly reduced following EGCG treatment while capsid protein labeling was unchanged. When purified HSV-1 envelope glycoproteins gB and gD were incubated with EGCG and then examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, lower-molecular-weight gB and gD bands decreased and new higher-molecular-weight bands appeared, indicating the EGCG-dependent production of macromolecular complexes. gB and gD are essential for HSV infectivity, and these results suggest that EGCG could inactivate HSV virions by binding to gB, gD, or another envelope glycoprotein. EGCG is stable in the pH range found in the vagina and appears to be a promising candidate for use in a microbicide to reduce HSV transmission.

The tumor inhibitor and antiangiogenic agent withaferin A targets the intermediate filament protein vimentin

The natural product withaferin A (WFA) exhibits antitumor and antiangiogenesis activity in vivo, which results from this drug's potent growth inhibitory activities. Here, we show that WFA binds to the intermediate filament (IF) protein, vimentin, by covalently modifying its cysteine residue, which is present in the highly conserved alpha-helical coiled coil 2B domain. WFA induces vimentin filaments to aggregate in vitro, an activity manifested in vivo as punctate cytoplasmic aggregates that colocalize vimentin and F-actin. WFA's potent dominant-negative effect on F-actin requires vimentin expression and induces apoptosis. Finally, we show that WFA-induced inhibition of capillary growth in a mouse model of corneal neovascularization is compromised in vimentin-deficient mice. These findings identify WFA as a chemical genetic probe of IF functions, and illuminate a potential molecular target for withanolide-based therapeutics for treating angioproliferative and malignant diseases.

Theoretical calculation of the binding free energies for pyruvate dehydrogenase E1 binding with ligands

We have tested a computational protocol based on molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) free-energy calculations to examine the detailed microscopic structures and binding free energies for the pyruvate dehydrogenase multienzyme complex (PDHc) E1 binding with its ligands (cofactor and inhibitors). The calculated binding free energies are all in good agreement with available experimental data, with an average absolute deviation of approximately 0.7 kcal/mol, suggesting that the computational protocol tested may be valuable in future rational design of new, more potent inhibitors of PDHc E1.

Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas

Tea leaves produce organic compounds that may be involved in the defense of the plants against invading pathogens including insects, bacteria, fungi, and viruses. These metabolites include polyphenolic compounds, the six so-called catechins, and the methyl-xanthine alkaloids caffeine, theobromine, and theophylline. Postharvest inactivation of phenol oxidases in green tea leaves prevents oxidation of the catechins, whereas postharvest enzyme-catalyzed oxidation (fermentation) of catechins in tea leaves results in the formation of four theaflavins as well as polymeric thearubigins. These substances impart the black color to black teas. Black and partly fermented oolong teas contain both classes of phenolic compounds. A need exists to develop a better understanding of the roles of polyphenolic tea compounds in food and medical microbiology. This overview surveys and interprets our present knowledge of activities of tea flavonoids and teas against foodborne and other pathogenic bacteria, virulent protein toxins produced by some of the bacteria, virulent bacteriophages, pathogenic viruses and fungi. Also covered are synergistic, mechanistic, and bioavailability aspects of the antimicrobial effects. Further research is suggested for each of these categories. The herein described findings are not only of fundamental interest, but also have practical implications for nutrition, food safety, and animal and human health.

Modeling Subtype-Selective Agonists Binding with α4β2 and α7 Nicotinic Acetylcholine Receptors: Effects of Local Binding and Long-Range Electrostatic Interactions

The subtype-selective binding of 14 representative agonists with alpha4beta2 and alpha7 nicotinic acetylcholine receptors (nAChRs) has been studied by performing homology modeling, molecular docking, geometry optimizations, and microscopic and phenomenological binding free energy calculations. All of the computational results demonstrate that the subtype selectivity of the agonists binding with alpha4beta2 and alpha7 7 nAChRs is affected by both local binding and long-range electrostatic interactions between the receptors and the protonated structures of the agonists. The effects of the long-range electrostatic interactions are mainly due to the distinct difference in the net charge of the ligand-binding domain between the two nAChR subtypes. For the alpha4beta2-selective agonists examined, the microscopic binding modes with the alpha4beta2 nAChR are very similar to the corresponding modes with the alpha7 nAChR, and therefore, the subtype selectivity of these agonists binding with alpha4beta2 and alpha7 nAChRs is dominated by the long-range electrostatic interactions. For the alpha7-selective agonists, their microscopic binding modes with the alpha7 nAChR are remarkably different from those with the alpha4beta2 nAChR so that the local binding (including the hydrogen bonding and cation-pi interactions) with the alpha7 nAChR is much stronger than that with the alpha4beta2 nAChR. The calculated phenomenological binding free energies are in good agreement with available experimental data for the relative binding free energies concerning the subtype selectivity of agonists binding with the two different nAChR subtypes. The fundamental insights obtained in the present study should be valuable for future rational design of potential therapeutic agents targeted to specific nAChR subtypes.

Microscopic Modes and Free Energies of 3-Phosphoinositide-Dependent Kinase-1 (PDK1) Binding with Celecoxib and Other Inhibitors

Celecoxib, also known as Celebrex (approved by FDA in 1998) and remembered as the fastest-selling drug in history, was used as a cyclooxygenase-2 (COX-2) selective inhibitor having both anti-inflammatory and anticancer activities. Most recent studies have revealed that the apoptotic activity of celecoxib (and its derivatives) is actually independent of the COX-2 inhibitory activity and that celecoxib also inhibits the kinase activity of 3-phosphoinositide-dependent protein kinase-1 (PDK1), suggesting that the well-known anticancer activity of celecoxib is not due to the inhibition of COX-2, but possibly is due to the inhibition of PDK1. It is highly desirable to develop new celecoxib derivatives as PDK1-specifc inhibitors to avoid the side effects of COX-2 inhibitors. To understand how PDK1 binds with celecoxib and its derivatives, we have performed extensive molecular docking and combined molecular dynamics (MD) simulations and molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) binding free energy calculations on eight representative PDK1 inhibitors, leading to the finding of a new, more favorable binding mode which is remarkably different from the previously proposed binding mode. Based on the determined most stable binding structures, the calculated binding free energies are all in good agreement with the corresponding experimental data, and the biological activity data available for celecoxib and its derivatives can be better interpreted. The obtained new insights, concerning both the binding mode and computational protocol, will be valuable not only for future rational design of novel, more potent PDK1-specific inhibitors as promising anticancer therapeutics, but also for rational design of drugs targeting other proteins.