Denis Tsz-Ming Ip

Antiviral activities of whey proteins

Milk contains an array of proteins with useful bioactivities. Many milk proteins encompassing native or chemically modified casein, lactoferrin, alpha-lactalbumin, and beta-lactoglobulin demonstrated antiviral activities. Casein and alpha-lactalbumin gained anti-HIV activity after modification with 3-hydroxyphthalic anhydride. Many milk proteins inhibited HIV reverse transcriptase. Bovine glycolactin, angiogenin-1, lactogenin, casein, alpha-lactalbumin, beta-lactoglobulin, bovine lactoferrampin, and human lactoferrampin inhibited HIV-1 protease and integrase. Several mammalian lactoferrins prevented hepatitis C infection. Lactoferrin, methylated alpha-lactalbumin and methylated beta-lactoglobulin inhibited human cytomegalovirus. Chemically modified alpha-lactalbumin, beta-lactoglobulin and lysozyme, lactoferrin and lactoferricin, methylated alpha-lactalbumin, methylated and ethylated beta-lactoglobulins inhibited HSV. Chemically modified bovine beta-lactoglobulin had antihuman papillomavirus activity. Beta-lactoglobulin, lactoferrin, esterified beta-lactoglobulin, and esterified lactoferrindisplayed anti-avian influenza A (H5N1) activity. Lactoferrin inhibited respiratory syncytial virus, hepatitis B virus, adenovirus, poliovirus, hantavirus, sindbis virus, semliki forest virus, echovirus, and enterovirus. Milk mucin, apolactoferrin, Fe3+-lactoferrin, beta-lactoglobulin, human lactadherin, bovine IgG, and bovine kappa-casein demonstrated antihuman rotavirus activity.

Acetylshikonin, a Novel AChE Inhibitor, Inhibits Apoptosis via Upregulation of Heme Oxygenase-1 Expression in SH-SY5Y Cells.

Acetylcholinesterase inhibitors are prominent alternative in current clinical treatment for AD patients. Therefore, there is a continued need to search for novel AChEIs with good clinical efficacy and less side effects. By using our in-house natural product database and AutoDock Vina as a tool in docking study, we have identified twelve phytochemicals (emodin, aloe-emodin, chrysophanol, and rhein in Rhei Radix Et Rhizoma; xanthotoxin, phellopterin, alloisoimperatorin, and imperatorin in Angelicae dahuricae Radix; shikonin, acetylshikonin, isovalerylshikonin, and β,β-dimethylacrylshikonin in Arnebiae Radix) as candidates of AChEIs that were not previously reported in the literature. In addition to AChEI activity, a series of cell-based experiments were conducted for the investigation of their neuroprotective activities. We found that acetylshikonin and its derivatives prevented apoptotic cell death induced by hydrogen peroxide in human and rat neuronal SH-SY5Y and PC12 cells at 10 μM. We showed that acetylshikonin exhibited the most potent antiapoptosis activity through the inhibition of the generation of reactive oxygen species as well as protection of the loss of mitochondria membrane potential. Furthermore, we identified for the first time that the upregulation of heme oxygenase 1 by acetylshikonin is a key step mediating its antiapoptotic activity from oxidative stress in SH-SY5Y cells.

Crystallization and preliminary crystallographic analysis of a novel orange fluorescent protein from the Cnidaria tube anemone Cerianthus sp.

A novel orange fluorescent protein, with excitation and emission maxima at 548 and 565 nm, respectively, from the Cnidaria tube anemone Cerianthus sp. has been cloned and overexpressed in Escherichia coli. The orange fluorescent protein has been crystallized by the sitting-drop vapour-diffusion method at 290 K using polyethylene glycol 3350 as a precipitant. A complete set of diffraction data was collected to 2.0 A resolution at 100 K. The crystals belong to the space group R3, with hexagonal unit-cell parameters a = b = 216.947, c = 51.839 A. There are four protein molecules in the asymmetric unit, giving a Matthews coefficient of 2.3 A(3) Da(-1) and a solvent content of 47%.

Lack of allelic association of dopamine D4 receptor gene polymorphisms with Parkinson's disease in a chinese population

Parkinsons disease (PD) is a neurodegenerative disease caused by a multitude of environmental, neurochemical, and genetic factors. The gene for human dopamine D4 receptor (DRD4) has been considered as a plausible candidate for the pathogenesis of PD. Different dopamine D4 receptor allelic forms have variable affinity toward certain neuroleptics such as clozapine, suggesting a role for dopamine D4 receptors in neurologic disorders. To test the hypothesis that the DRD4 polymorphism is associated with the susceptibility to Parkinsons disease, we have examined differences in allele frequencies of different DRD4 polymorphisms in 101 Chinese patients with PD and in 105 age‐matched control subjects in Hong Kong. The DRD4 gene was analyzed by a non‐radioactive polymerase chain reaction‐based Southern hybridization with chemiluminescence detection. The number of polymorphic 48 base pair tandem repeats in exon 3 was identified in each study subject. The DRD4 alleles with high frequencies in the control subjects are 4‐repeat allele (72.4%), 2‐repeat allele (21.4%), and 7‐repeat allele (3.8%) which accounted for over 97% of the total alleles in the elderly Chinese population. The most prevalent genotype in the control subjects is the 4/4 (47.6%), followed by 4/2 (38.6), 4/7 (7.6%), and 2/2 (3.0%). None of the variable number tandem repeat polymorphism showed evidence for genetic association with Parkinsons disease.

1,4-Bis(5-(naphthalen-1-yl)thiophen-2-yl)naphthalene, a small molecule, functions as a novel anti-HIV-1 inhibitor targeting the interaction between integrase and cellular Lens epithelium-derived growth factor

Translocation of viral integrase (IN) into the nucleus is a critical precondition of integration during the life cycle of HIV, a causative agent of Acquired Immunodeficiency Syndromes (AIDS). As the first discovered cellular factor to interact with IN, Lens epithelium-derived growth factor (LEDGF/p75) plays an important role in the process of integration. Disruption of the LEDGF/p75-IN interaction has provided a great interest for anti-HIV agent discovery. In this work, we reported that one small molecular compound, 1,4-bis(5-(naphthalen-1-yl)thiophen-2-yl)naphthalene(Compound 15), potently inhibit the IN-LEDGF/p75 interaction and affect the HIV-1 IN nuclear distribution at 1 μM. The putative binding mode of Compound 15 was constructed by a molecular docking simulation to provide structural insights into the ligand-binding mechanism. Compound 15 suppressed viral replication by measuring p24 antigen production in HIV-1IIIB acute infected C8166 cells with EC50 value of 11.19 μM. Compound 15 might supply useful structural information for further anti-HIV agent discovery.

Differential gene expression profiling on the muscle of acetylcholinesterase knockout mice: a preliminary analysis.

Acetylcholinesterase (AChE) (EC. 3.1.1.7) is the acetylcholine-hydrolyzing enzyme that plays an essential role on cholinergic neurotransmission at the synapses of the brain and at the neuromuscular junctions. In order to gain insight into the molecular mechanisms of neuromuscular dysfunction associated with AChE deficiency, we have compared the RNA expression profiles of the muscles of AChE knockout mice with those of the wild-type siblings. Total RNA from the leg muscle of the mice of the wild-type and the AChE nullizygous mice were subjected to microarray analyses with Affymetrix GeneChip((R)) Mouse Gene 1.0 ST Array. The pair-wise comparison of gene expression levels of the 28,853 mRNA transcripts showed that 303 genes were either up- or down-regulated by more than 2.0 folds in the AChE knockout mice. The interaction study of these differentially regulated genes indicated that some of these genes are clustered in biological functions that are related to lipid metabolism and the skeletal-muscular functions.

Silibinin, a novel chemokine receptor type 4 antagonist, inhibits chemokine ligand 12-induced migration in breast cancer cells.

PURPOSE C-X-C chemokine receptor type 4 (CXCR4) signaling has been demonstrated to be involved in cancer invasion and migration; therefore, CXCR4 antagonist can serve as an anti-cancer drug by preventing tumor metastasis. This study aimed to identify the CXCR4 antagonists that could reduce and/or inhibit tumor metastasis from natural products. METHODS AND RESULTS According to the molecular docking screening, we reported here silibinin as a novel CXCR4 antagonist. Biochemical characterization showed that silibinin blocked chemokine ligand 12 (CXCL12)-induced CXCR4 internalization by competitive binding to CXCR4, therefore inhibiting downstream intracellular signaling. In human breast cancer cells MDA-MB-231, which expresses high levels of CXCR4, inhibition of CXCL12-induced chemomigration can be found under silibinin treatment. Overexpression of CXCL12 sensitized MDA-MB-231 cells to the inhibition of silibinin, which was abolished by CXCR4 knockdown. The inhibition of silibinin was also observed in MCF-7/CXCR4 cells rather than MCF-7 cells that express low level of CXCR4. CONCLUSIONS Our work demonstrated that silibinin is a novel CXCR4 antagonist that may have potential therapeutic use for prevention of tumor metastasis.

Discovery of a novel HIV-1 integrase inhibitor from natural compounds through structure based virtual screening and cell imaging

The interaction between HIV‐1 integrase and LEDGF/P75 has been validated as a target for anti‐HIV drug development. Based on the crystal structure of integrase in complex with LEDGF/P75, a library containing 80 thousand natural compounds was filtered with virtual screening. 11 hits were selected for cell based assays. One compound, 3‐(1,3‐benzothiazol‐2‐yl)‐8‐{[bis(2‐hydroxyethyl)amino]methyl}‐7‐hydroxy‐2H‐chromen‐2‐one (D719) inhibited integrase nuclear translocation in cell imaging. The binding mode of D719 was analyzed with molecular simulation. The anti‐HIV activity of D719 was assayed by measuring the p24 antigen production in acute infection. The structure characteristics of D719 may provide valuable information for integrase inhibitor design.

Bovine Lactoferrampin, Human Lactoferricin, and Lactoferrin 1-11 Inhibit Nuclear Translocation of HIV Integrase.

This study aimed to investigate fragments derived from human and bovine lactoferrins for ability to inhibit nuclear translocation of HIV-1 integrase. It was shown that human lactoferricin, human lactoferrin 1-11, and bovine lactoferrampin reduced nuclear distribution of HIV-1 integrase. Bovine lactoferrampin could inhibit both the activity and nuclear translocation of HIV-1 integrase. Human lactoferrampin, bovine lactoferricin, and bovine lactoferrin 1-11 had no effect on HIV-1 integrase nuclear translocation. Human lactoferrampin which inhibited the activity of integrase did not prevent its nuclear translocation. Human lactoferricin and lactoferrin 1-11 did not inhibit HIV-1 integrase nuclear translocation despite their ability to attenuate the enzyme activity. The discrepancy between the findings on reduction of HIV-1 activity and inhibition of nuclear translocation of HIV-1 integrase was due to the different mechanisms involved. A similar reasoning can also be applied to the different inhibitory potencies of the milk peptides on different HIV enzymes, i.e., nuclear translocation.