Pooi-Fong Wong

Reemergence of Endemic Chikungunya, Malaysia

Chikungunya virus infection recently reemerged in Malaysia after 7 years of nondetection. Genomic sequences of recovered isolates were highly similar to those of Malaysian isolates from the 1998 outbreak. The reemergence of the infection is not part of the epidemics in other Indian Ocean countries but raises the possibility that chikungunya virus is endemic in Malaysia.

Antiviral activity of four types of bioflavonoid against dengue virus type-2.

BackgroundDengue is a major mosquito-borne disease currently with no effective antiviral or vaccine available. Effort to find antivirals for it has focused on bioflavonoids, a plant-derived polyphenolic compounds with many potential health benefits. In the present study, antiviral activity of four types of bioflavonoid against dengue virus type -2 (DENV-2) in Vero cell was evaluated. Anti-dengue activity of these compounds was determined at different stages of DENV-2 infection and replication cycle. DENV replication was measured by Foci Forming Unit Reduction Assay (FFURA) and quantitative RT-PCR. Selectivity Index value (SI) was determined as the ratio of cytotoxic concentration 50 (CC50) to inhibitory concentration 50 (IC50) for each compound.ResultsThe half maximal inhibitory concentration (IC50) of quercetin against dengue virus was 35.7 μg mL-1 when it was used after virus adsorption to the cells. The IC50 decreased to 28.9 μg mL-1 when the cells were treated continuously for 5 h before virus infection and up to 4 days post-infection. The SI values for quercetin were 7.07 and 8.74 μg mL-1, respectively, the highest compared to all bioflavonoids studied. Naringin only exhibited anti-adsorption effects against DENV-2 with IC50 = 168.2 μg mL-1 and its related SI was 1.3. Daidzein showed a weak anti-dengue activity with IC50 = 142.6 μg mL-1 when the DENV-2 infected cells were treated after virus adsorption. The SI value for this compound was 1.03. Hesperetin did not exhibit any antiviral activity against DENV-2. The findings obtained from Foci Forming Unit Reduction Assay (FFURA) were corroborated by findings of the qRT-PCR assays. Quercetin and daidzein (50 μg mL-1) reduced DENV-2 RNA levels by 67% and 25%, respectively. There was no significant inhibition of DENV-2 RNA levels with naringin and hesperetin.ConclusionResults from the study suggest that only quercetin demonstrated significant anti-DENV-2 inhibitory activities. Other bioflavonoids, including daidzein, naringin and hesperetin showed minimal to no significant inhibition of DENV-2 virus replication. These findings, together with those previously reported suggest that select group of bioflavonoids including quercetin and fisetin, exhibited significant inhibitory activities against dengue virus. This group of flavonoids, flavonol, could be investigated further to discover the common mechanisms of inhibition of dengue virus replication.

Emergence of dengue virus type 4 genotype IIA in Malaysia.

Phylogenetic analyses of the envelope (E) gene sequence of five recently isolated dengue virus type 4 (DENV-4) suggested the emergence of a distinct geographical and temporal DENV-4 subgenotype IIA in Malaysia. Four of the isolates had direct ancestral lineage with DENV-4 Indonesia 1973 and showed evidence of intra-serotypic recombination with the other recently isolated DENV-4, MY01-22713. The E gene of isolate MY01-22713 had strong evidence of an earlier recombination involving DENV-4 genotype II Indonesia 1976 and genotype I Malaysia 1969. These results suggest that intra-serotypic recombination amongst DENV-4 from independent ancestral lineages may have contributed to the emergence of DENV-4 subgenotype IIA in Malaysia.

Novel antiviral activity of baicalein against dengue virus

BackgroundDengue is a serious arboviral disease currently with no effective antiviral therapy or approved vaccine available. Therefore, finding the effective compound against dengue virus (DENV) replication is very important. Among the natural compounds, bioflavonoids derived mainly from plants are of interest because of their biological and medicinal benefits.MethodsIn the present study, antiviral activity of a bioflavonoid, baicalein, was evaluated against different stages of dengue virus type 2 (DENV-2) replication in Vero cells using focus forming unit reduction assay and quantitative RT-PCR.ResultsBaicalein inhibited DENV-2 replication in Vero cells with IC50= 6.46 μg/mL and SI= 17.8 when added after adsorption to the cells. The IC50 against DENV-2 was 5.39 μg/mL and SI= 21.3 when cells were treated 5 hours before virus infection and continuously up to 4 days post infection. Baicalein exhibited direct virucidal effect against DENV-2 with IC 50= 1.55 μg/mL and showed anti-adsorption effect with IC50 = 7.14 μg/mL.ConclusionsFindings presented here suggest that baicalein exerts potent antiviral activity against DENV. Baicalein possesses direct virucidal activity against DENV besides its effects against dengue virus adsorption and intracellular replication of DENV-2. Baicalein, hence, should be considered for in vivo evaluation in the development of an effective antiviral compound against DENV.

Alpha-tomatine induces apoptosis and inhibits nuclear factor-kappa B activation on human prostatic adenocarcinoma PC-3 cells.

Background Alpha-tomatine (α-tomatine) is the major saponin in tomato (Lycopersicon esculentum). This study investigates the chemopreventive potential of α-tomatine on androgen-independent human prostatic adenocarcinoma PC-3 cells. Methodology/Principal Findings Treatment of highly aggressive human prostate cancer PC-3 cells with α-tomatine resulted in a concentration-dependent inhibition of cell growth with a half-maximal efficient concentration (EC50) value of 1.67±0.3 µM. It is also less cytotoxic to normal human liver WRL-68 cells and normal human prostate RWPE-1 cells. Assessment of real-time growth kinetics by cell impedance-based Real-Time Cell Analyzer (RTCA) showed that α-tomatine exhibited its cytotoxic effects against PC-3 cells as early as an hour after treatment. The inhibitory effect of α-tomatine on PC-3 cancer cell growth was mainly due to induction of apoptosis as evidenced by positive Annexin V staining and decreased in mitochondrial membrane potential but increased in nuclear condensation, polarization of F-actin, cell membrane permeability and cytochrome c expressions. Results also showed that α-tomatine induced activation of caspase-3, -8 and -9, suggesting that both intrinsic and extrinsic apoptosis pathways are involved. Furthermore, nuclear factor-kappa B (NF-κB) nuclear translocation was inhibited, which in turn resulted in significant decreased in NF-κB/p50 and NF-κB/p65 in the nuclear fraction of the treated cells compared to the control untreated cells. These results provide further insights into the molecular mechanism of the anti-proliferative actions of α-tomatine. Conclusion/Significance α-tomatine induces apoptosis and inhibits NF-κB activation on prostate cancer cells. These results suggest that α-tomatine may be beneficial for protection against prostate cancer development and progression.

In vitro antiviral activity of Fisetin, Rutin and Naringenin against Dengue virus type-2

In vitro antiviral activities of three flavonoids; fisetin, naringenin and rutin against DENV-2 (NGC strain) were evaluated. Inhibitory effects of each compound at the different stages of DENV-2 infection were examined using foci forming unit reduction assay (FFURA) and quantitative real-time polymerase chain amplification (qRT-PCR). Fisetin, rutin and naringenin showed cytotoxic effects against Vero cells with 50% cytotoxicity (CC50 ) values of 247, >1000, and 87 µg/mL, respectively. Fisetin when added to Vero cells after virus adsorption inhibited DENV replication with a half maximal inhibition concentration (IC50 ) value of 55 µg/mL and selectivity index (SI) of 4.49. The IC50 value of fisetin was 43.12 µg/mL with SI=5.72 when Vero cells were treated for 5 h before virus infection and continuously up to 4 days postinfection. There was no direct virucidal activity or prophylactic activity of fisetin against DENV-2. Rutin and naringenin did not inhibit DENV-2 replication in Vero cells. Naringenin however, exhibited direct virucidal activity against DENV-2 with IC50 = 52.64 µg/mL but the SI was <1. The present study suggests that among the flavonoids examined, only fisetin showed significant in vitro anti dengue virus replication activity.

Eurycomanone suppresses expression of lung cancer cell tumor markers, prohibitin, annexin 1 and endoplasmic reticulum protein 28.

Bioactive compounds from the medicinal plant, Eurycoma longifolia Jack have been shown to promote anti-proliferative effects on various cancer cell lines. Here we examined the effects of purified eurycomanone, a quassinoid found in Eurycoma longifolia Jack extract, on the expression of selected genes of the A549 lung cancer cells. Eurycomanone inhibited A549 lung cancer cell proliferation in a dose-dependent manner at concentrations ranging from 5 to 20 μg/ml. The concentration that inhibited 50% of cell growth (GI(50)) was 5.1 μg/ml. The anti-proliferative effects were not fully reversible following the removal of eurycomanone, in which 30% of cell inhibition still remained (p<0.0001, T-test). At 8 μg/ml (GI(70)), eurycomanone suppressed anchorage-independent growth of A549 cells by >25% (p<0.05, T-test, n=8) as determined using soft agar colony formation assay. Cisplatin, a chemotherapy drug used for the treatment of non small cell lung cancer on the other hand, inhibited A549 cells proliferation at concentrations ranging from 0.2 μg/ml to 15 μg/ml with a GI(50) of 0.58 μg/ml. The treatment with eurycomanone reduced the abundance expression of the lung cancer markers, heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1, p53 tumor suppressor protein and other cancer-associated genes including prohibitin (PHB), annexin 1 (ANX1) and endoplasmic reticulum protein 28 (ERp28) but not the house keeping genes. The mRNA expressions of all genes with the exception of PHB were significantly downregulated, 72 h after treatment (p<0.05, T-test, n=9). These findings suggest that eurycomanone at viable therapeutic concentrations of 5-20 μg/ml exhibited significant anti-proliferative and anti-clonogenic cell growth effects on A549 lung cancer cells. The treatment also resulted in suppression of the lung cancer cell tumor markers and several known cancer cell growth-associated genes.

Proteomics of the red alga, Gracilaria changii (Gracilariales, Rhodophyta)

The application of proteomics in alga research is still quite limited. The present report describes the establishment of the proteome of a red alga of economic importance, Gracilaria changii (Xia et Abbott) Abbott, Zhang et Xia. Initially, four protein extraction methods including direct precipitation by trichloroacetic acid/acetone, direct lysis using urea buffer, Tris buffer, and phenol/chloroform extraction were compared for their suitability to generate G. changii proteins for two‐dimensional gel electrophoresis (2‐DE). The phenol/chloroform protein extraction method gave the best 2‐DE resolution of the proteins. Using these 2‐DE gels and mass spectrometry, several proteins including pigment proteins, metabolic enzymes, and ion transporters were identified. These findings highlight the potential of using proteomic approaches for the investigation of G. changii protein function.

In Vitro and In Vivo Anti-Angiogenic Activities of Panduratin A

Background Targeting angiogenesis has emerged as an attractive and promising strategy in anti-cancer therapeutic development. The present study investigates the anti-angiogenic potential of Panduratin A (PA), a natural chalcone isolated from Boesenbergia rotunda by using both in vitro and in vivo assays. Methodology/Principal Findings PA exerted selective cytotoxicity on human umbilical vein endothelial cells (HUVECs) with IC50 value of 6.91±0.85 µM when compared to human normal fibroblast and normal liver epithelial cells. Assessment of the growth kinetics by cell impedance-based Real-Time Cell Analyzer showed that PA induced both cytotoxic and cytostatic effects on HUVECs, depending on the concentration used. Results also showed that PA suppressed VEGF-induced survival and proliferation of HUVECs. Furthermore, endothelial cell migration, invasion, and morphogenesis or tube formation demonstrated significant time- and dose-dependent inhibition by PA. PA also suppressed matrix metalloproteinase-2 (MMP-2) secretion and attenuated its activation to intermediate and active MMP-2. In addition, PA suppressed F-actin stress fiber formation to prevent migration of the endothelial cells. More importantly, anti-angiogenic potential of PA was also evidenced in two in vivo models. PA inhibited neo-vessels formation in murine Matrigel plugs, and angiogenesis in zebrafish embryos. Conclusions/Significance Taken together, our study demonstrated the distinctive anti-angiogenic properties of PA, both in vitro and in vivo. This report thus reveals another biological activity of PA in addition to its reported anti-inflammatory and anti-cancer activities, suggestive of PA’s potential for development as an anti-angiogenic agent for cancer therapy.

Paeonol protects against premature senescence in endothelial cells by modulating Sirtuin 1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE Paeonol is a phenolic compound isolated mainly from Moutan cortex, root bark of Chinese Peony tree. Moutan cortex holds a significant value in traditional Chinese medicine for alleviating various oxidative stress-related diseases mainly atherosclerosis and myocardial infarction. The present study seeks to identify the protective mechanisms of paeonol in oxidative stress-induced premature senescence in endothelial cells. MATERIALS AND METHODS HUVECs were pretreated with paeonol or DMSO control at different doses for 24h prior to an exposure of 200μM of reactive oxygen species (ROS) inducer, hydrogen peroxide (H2O2). The protective effects of paeonol against H2O2-induced senescence were evaluated and the activation of Sirtuin 1 pathway by paeonol pretreatment was investigated in HUVECs. RESULTS Paeonol attenuated H2O2-induced cell growth arrest at G0/G1 phase, reduced the percentage of SA-β-Gal positive cells and increased BrdU incorporation. In addition, enzymatic Sirt1 activation assay indicated that paeonol significantly increased lysyl deactylase activity of Sirt1 enzyme with a fold change of 2.4±0.195 (p<0.05). Furthermore, pretreatment with paeonol significantly decreased the levels of p53, acetyl H3K14 and H4K16 protein expression upregulated by H2O2 stimulation. The changes in the histone protein levels were accompanied with an increase in Sirt1 protein expression level. CONCLUSION These findings suggest that paeonol protects endothelial cells against oxidative stress-induced premature senescence by modulating the expressions of Sirt1 protein and its substrates.