Metabolic syndrome and heart failure: 40 years follow up results of the Seven Countries Study

Introduction

Metabolic syndrome (Met Sy) as a highly debatable cluster of traditional risk factors is known to promote cardiometabolic-related morbidity and mortality, but its precise mechanisms remain to be determined.

Purpose

We sought to determine influence of MetSy on heart failure (HF) morbidity and mortality in the Seven Countries' Study as one of the oldest epidemiological studies.

Methods

The Seven Countries Study encompassed 12,763 participants from 3 continents who were all healthy men of over 40 years at baseline and who underwent regular check ups every 5 years throughout over a 4 decades' span. Morbidity and mortality was adjudicated according to valid ICD and LPH coding.

Results

Using the IDF definition of the Metabolic Syndrome, 9,09% of participants were identified (Figure 1). HF was confirmed in 220 patients (16.4% alive at 40y follow up visit), while 8.2% died of HF as well in the same time-frame (Tables 1 & 2). Presence of MetSy has been shown to significantly influence HF mortality (Figures 2) with lowest survival of 22% for 300 months of follow up for patients with both MetSy and HF (Log rank test=4.405, p<0.0001).

Conclusion

Metabolic syndrome treatment remains in the realm of risk factors' control that now we know influence both ischemic heart disease and heart failure of other origins. Historically, just emerging biomarkers' and targeted imaging weren't available to determine such at the time of HF diagnosis. Also, the sample consisted of men only, mainly Caucasian and a modest proportion of Asian and African-American now known to carry ethnic-specific burden of cardiovascular disease. All of the above, emphasizes the importance of more diversity, equity and inclusion-dedicated long term both observational, as well as interventional research.

Funding Acknowledgement

Type of funding sources: None.

Structure-activity relationships of natural quinone vegfrecine analogs with potent activity against VEGFR-1 and -2 tyrosine kinases

A series of analogs of vegfrecine, a natural quinone vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor, was synthesized via oxidative amination of 2,5-dihydroxybenzamide with functionalized arylamine followed by ammonolysis and substitution of the quinone ring. The inhibitory activities of the analogs against the VEGFR-1 and -2 tyrosine kinases were assayed in vitro with the aim to identify a compound suitable to treat cancer and inflammatory diseases. Alterations of the functionality of the phenyl group, substitution of the quinone ring, and oxidative cyclization of the 1-carboxamide-2-aminoquinone moiety to form an isoxazole quinone ring were examined. Introduction of halo- and alkyl-substituents at the 5'-position of the phenyl ring resulted in potent inhibition of the VEGFR-1 and -2 tyrosine kinases. In particular, structural modification at C-5' on the phenyl ring was shown to significantly affect the selectivity of the inhibition between the VEGFR-1 and -2 tyrosine kinases. Compound 8, 5'-methyl-vegfrecine, showed superior selectivity toward the VEGFR-2 tyrosine kinase over the VEGFR-1 tyrosine kinase.

Human pancreatic cancer cells under nutrient deprivation are vulnerable to redox system inhibition

Large regions in tumor tissues, particularly pancreatic cancer, are hypoxic and nutrient-deprived because of unregulated cell growth and insufficient vascular supply. Certain cancer cells, such as those inside a tumor, can tolerate these severe conditions and survive for prolonged periods. We hypothesized that small molecular agents, which can preferentially reduce cancer cell survival under nutrient-deprived conditions, could function as anticancer drugs. In this study, we constructed a high-throughput screening system to identify such small molecules and screened chemical libraries and microbial culture extracts. We were able to determine that some small molecular compounds, such as penicillic acid, papyracillic acid, and auranofin, exhibit preferential cytotoxicity to human pancreatic cancer cells under nutrient-deprived compared with nutrient-sufficient conditions. Further analysis revealed that these compounds target to redox systems such as GSH and thioredoxin and induce accumulation of reactive oxygen species in nutrient-deprived cancer cells, potentially contributing to apoptosis under nutrient-deprived conditions. Nutrient-deficient cancer cells are often deficient in GSH; thus, they are susceptible to redox system inhibitors. Targeting redox systems might be an attractive therapeutic strategy under nutrient-deprived conditions of the tumor microenvironment.

Metabolic syndrome and mortality prediction in the seven countries' study: single or multifactorial

Introduction

The metabolic syndrome (Met Sy) is a known cluster of risk factors (HTA, HLP, DM, BMI) that promotes overall vascular disease, however its real impact on overall, ischemic heart disease (IHD) and cerebrovascular disease (CVD) mortality remains debated.

Material and methods

The Seven Countries Study encompassed 12,763 participants who were healthy men over 40y at baseline and who underwent regular check ups every 5 years throughout over a 4 decades' span. Morbidity and mortality was adjudicated according to valid ICD and LPH coding.

Results

Using the IDF definition of the Metabolic Syndrome, 9,09% of participants were identified. In a multivariate analysis predictors for overall Mt were hypertension (p<0.0001) and BMI (p<0.029), while HLP had a weak prediction value (p=0.083), where as MetSy and DM had not at all. Hypertension (p<0.0001) remained a strong predictor for IHD mortality together with HLP (p<0.0001), while diabetes was of weak predictive value (p=0.065), whereas MetSy failed to. Although HTA was a strong predictor for CVD mortality, so did MetSy (p<0.050), while DM and HLP haven't while BMI had a low impact (p=0.070).

Conclusion

Metabolic syndrome's role in atherosclerotic burden remains important, however whether its power is due to its respective components or their interactions remains to be an issue. The described results belong to an era where both IHD and CVD were considered a “male disease” women were spared of, so, further validation in the described cohorts is needed in an offspring fashion, however hypertension remains the driving force of both overall mortality as well as specific IHD and CVD ones, also previously demonstrated in the very same cohort to be more important in the setting of maternal family history of hypertension, than paternal one.

MetSy in the SCS

Funding Acknowledgement

Type of funding source: None

Predictors of Cerebral Aneurysm Rupture after Coil Embolization: Single-Center Experience with Recanalized Aneurysms

BACKGROUND AND PURPOSE

Recanalization after coil embolization is widely studied. However, there are limited data on how recanalized aneurysms rupture. Herein, we describe our experience with the rupture of recanalized aneurysms and discuss the type of recanalized aneurysms at greatest rupture risk.

MATERIALS AND METHODS

A total of 426 unruptured aneurysms and 169 ruptured aneurysms underwent coil embolization in our institution between January 2009 and December 2017. Recanalization occurred in 38 (8.9%) of 426 unruptured aneurysms (unruptured group) and 37 (21.9%) of 169 ruptured aneurysms (ruptured group). The Modified Raymond-Roy classification on DSA was used to categorize the recanalization type. Follow-up DSA was scheduled until 6 months after treatment, and follow-up MRA was scheduled yearly. If recanalization was suspected on MRA, DSA was performed.

RESULTS

In the unruptured group, the median follow-up term was 74.0 months. Retreatment for recanalization was performed in 18 aneurysms. Four of 20 untreated recanalized aneurysms (0.94% of total coiled aneurysms) ruptured. In untreated recanalized aneurysms, class IIIb aneurysms ruptured significantly more frequently than class II and IIIa (P = .025). In the ruptured group, the median follow-up term was 28.0 months. Retreatment for recanalization was performed in 16 aneurysms. Four of 21 untreated recanalized aneurysms (2.37% of total coiled aneurysms) ruptured. Class IIIb aneurysms ruptured significantly more frequently than class II and IIIa (P = .02).

CONCLUSIONS

The types of recanalization after coil embolization may be predictors of rupture. Coiled aneurysms with class IIIb recanalization should undergo early retreatment because of an increased rupture risk.

Leucinostatin Y: A Peptaibiotic Produced by the Entomoparasitic Fungus Purpureocillium lilacinum 40-H-28

Leucinostatin Y, a new peptaibiotic, was isolated from the culture broth of the entomoparasitic fungus Purpureocillium lilacinum 40-H-28. The planar structure was elucidated by detailed analysis of its NMR and MS/MS data. The absolute configurations of the amino acids were partially determined by an advanced Marfey's method. The biological activities of leucinostatin Y were assessed using human pancreatic cancer cells, revealing the importance of the C-terminus of leucinostatins for preferential cytotoxicity to cancer cells under glucose-deprived conditions and inhibition of mitochondrial function.

Monotherapy with a novel intervenolin derivative, AS-1934, is an effective treatment for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H. pylori) infection causes various gastrointestinal diseases including gastric cancer. Hence, eradication of this infection could prevent these diseases. The most popular first-line treatment protocol to eradicate H. pylori is termed "triple therapy" and consists of a proton pump inhibitor (PPI), clarithromycin, and amoxicillin or metronidazole. However, the antibiotics used to treat H. pylori infection are hindered by the antibiotics-resistant bacteria and by their antimicrobial activity against intestinal bacteria, leading to side effects. Therefore, an alternative treatment with fewer adverse side effects is urgently required to improve the overall eradication rate of H. pylori.

OBJECTIVE

The aim of this study was to assess the effectiveness and mechanism of action of an antitumor agent, intervenolin, and its derivatives as an agent for the treatment of H. pylori infection.

RESULTS

We demonstrate that intervenolin, and its derivatives showed selective anti-H. pylori activity, including antibiotic-resistant strains, without any effect on intestinal bacteria. We showed that dihydroorotate dehydrogenase, a key enzyme for de novo pyrimidine biosynthesis, is a target and treatment with intervenolin or its derivatives decreased the protein and mRNA levels of H. pylori urease, which protects H. pylori against acidic conditions in the stomach. Using a mouse model of H. pylori infection, oral monotherapy with the intervenolin derivative AS-1934 had a stronger anti-H. pylori effect than the triple therapy commonly used worldwide to eradicate H. pylori.

CONCLUSION

AS-1934 has potential advantages over current treatment options for H. pylori infection.

Microbial metabolites and derivatives targeted at inflammation and bone diseases therapy: chemistry, biological activity and pharmacology

Microbial metabolites have attracted increasing interest as a source of therapeutics and as probes for biological mechanisms. New microbial metabolites and derivatives targeted at inflammation and bone disease therapy have been identified by focusing on prostaglandin release, osteoblast differentiation and immune cell functions. These modulators of inflammatory processes and bone disease contribute to our understanding of biological mechanisms and support identification of the therapeutic potential of drug lead candidates. The present review describes recent advances in the chemistry and analysis of inhibitors of prostaglandin release or other functional molecules of immune cells, as well as inducers of osteoblast differentiation, including biological and pharmacological activities.The Journal of Antibiotics advance online publication, 1 November 2017; doi:10.1038/ja.2017.138.

Phenazine carboxylic acid and its derivative induce osteoblast differentiation in preosteoblastic MC3T3-E1 cells but adipocyte differentiation in pluripotent mesenchymal C3H10T1/2 cells

Osteoblast and adipocyte are differentiated from mesenchymal stem cells and dysregulation of the differentiation might result in disease, such as osteoporosis and diabetes. To find small compounds that induce osteoblast differentiation, we screened an in-house natural compounds library with mouse preosteoblastic MC3T3-E1 cells using alkaline phosphatase (ALP) expression as an early osteoblast marker. We found that phenazine-1-carboxylic acid (PCA), one of the major phenazine derivatives produced by Pseudomonas, induced osteoblast differentiation in the cells at micromolar concentrations. PCA acted synergistically with an agonist of hedgehog signaling in inducing ALP activity in the cells. We also found that 2-hydroxy-PCA (2H-PCA) induced osteoblast differentiation in the cells but 2-methoxy-PCA and 1-hydroxy-phenazine did not. Unexpectedly, treatment of mouse pluripotent mesenchymal C3H10T1/2 cells with PCA or 2H-PCA induced an obvious morphological change. Oil Red O staining and real-time reverse-transcription PCR analysis revealed that PCA induced not osteoblast differentiation but adipocyte differentiation in C3H10T1/2 cells. These compounds could allow us to investigate the mechanism of osteoblast and adipocyte differentiation in the two model cell systems through a chemical biology approach.

Vibrio japonicus sp. nov., a novel member of the Nereis clade in the genus Vibrio isolated from the coast of Japan

A novel Vibrio strain, JCM 31412^T, was isolated from seawater collected from the Inland Sea (Setonaikai), Japan, and characterized as a Gram-negative, oxidase-positive, catalase-negative, facultatively anaerobic, motile, ovoid-shaped bacterium with one polar flagellum. Based on 16S rDNA gene identity, strain JCM 31412^T showed a close relationship with type strains of Vibrio brasiliensis (LMG 20546^T, 98.2% identity), V. harveyi (NBRC 15634^T, 98.2%), V. caribbeanicus (ATCC BAA-2122^T, 97.8%) and V. proteolyticus (NBRC 13287^T, 97.8%). The G+C content of strain JCM 31412^T DNA was 46.8%. Multi-locus sequence analysis (MLSA) of eight loci (ftsZ, gapA, gyrB, mreB, pyrH, recA, rpoA and topA; 5535bp) further clustered strain JCM 31412^T in the Nereis clade, genus Vibrio. Phenotypically, strain JCM 31412^T differed from the closest related Vibrio species in its utilization of melibiose and raffinose, and its lack of casein and gelatin hydrolysis. It was further differentiated based on its fatty acid composition, specifically properties of C_12:03OH and summed features, which were significantly different from those of V. brasiliensis, V. nigripulchritudo and V. caribbeanicus type strains. Overall, the results of DNA-DNA hybridization, and physiological and biochemical analysis differentiated strain JCM 31412^T from other described species of the genus Vibrio. Based on these polyphasic taxonomic findings, it was therefore concluded that JCM 31412^T was a novel Vibrio species, for which the name Vibrio japonicus sp. nov. was proposed, with JCM 31412^T (= LMG 29636^T = ATCC TSD-62^T) as the type strain.

New anti-cancer chemicals Ertredin and its derivatives, regulate oxidative phosphorylation and glycolysis and suppress sphere formation in vitro and tumor growth in EGFRvIII-transformed cells

BACKGROUND

EGFRvIII is a mutant form of the epidermal growth factor receptor gene (EGFR) that lacks exons 2-7. The resulting protein does not bind to ligands and is constitutively activated. The expression of EGFRvIII is likely confined to various types of cancer, particularly glioblastomas. Although an anti-EGFRvIII vaccine is of great interest, low-molecular-weight substances are needed to obtain better therapeutic efficacy. Thus, the purpose of this study is to identify low molecular weight substances that can suppress EGFRvIII-dependent transformation.

METHODS

We constructed a new throughput screening system and searched for substances that decreased cell survival of NIH3T3/EGFRvIII spheres under 3-dimensional (3D)-culture conditions, but retained normal NIH3T3 cell growth under 2D-culture conditions. In vivo activity was examined using a mouse transplantation model, and derivatives were chemically synthesized. Functional characterization of the candidate molecules was investigated using an EGFR kinase assay, immunoprecipitation, western blotting, microarray analysis, quantitative polymerase chain reaction analysis, and measurement of lactate and ATP synthesis.

RESULTS

In the course of screening 30,000 substances, a reagent, "Ertredin" was found to inhibit anchorage-independent 3D growth of sphere-forming cells transfected with EGFRvIII cDNA. Ertredin also inhibited sphere formation in cells expressing wild-type EGFR in the presence of EGF. However, it did not affect anchorage-dependent 2D growth of parental NIH3T3 cells. The 3D-growth-inhibitory activity of some derivatives, including those with new structures, was similar to Ertredin. Furthermore, we demonstrated that Ertredin suppressed tumor growth in an allograft transplantation mouse model injected with EGFRvIII- or wild-type EGFR-expressing cells; a clear toxicity to host animals was not observed. Functional characterization of Ertredin in cells expressing EGFRvIII indicated that it stimulated EGFRvIII ubiquitination, suppressed both oxidative phosphorylation and glycolysis under 3D conditions, and promoted cell apoptosis.

CONCLUSION

We developed a high throughput screening method based on anchorage-independent sphere formation induced by EGFRvIII-dependent transformation. In the course of screening, we identified Ertredin, which inhibited anchorage-independent 3D growth and tumor formation in nude mice. Functional analysis suggests that Ertredin suppresses both mitochondrial oxidative phosphorylation and cytosolic glycolysis in addition to promoting EGFRvIII degradation, and stimulates apoptosis in sphere-forming, EGFRvIII-overexpressing cells.

Irreversible inactivation of glutathione S-transferase-π by a low concentration of naphthoquinones

π-Class glutathione S-transferase (GST-π) was very potently inactivated by oxidants such as H2O2, xanthine-xanthine oxidase and naphthoquinones. Thiols and glutathione analogs including dithiothreitol, reduced gluta-thione, cysteine, cysteamine, S-methyl-SG, S-hexyl-SG and S-decyl-SG protected GST-π from the inactivation, but a substrate analog (2,4-dinitrophenol), superoxide dismutase and catalase did not, suggesting that the cysteinyl residue(s) in/nearby the glutathione binding site (G-site) may be oxidatively modified by these oxidants. Many reductants and radical scavengers including butylated hydoxytoluene, α-tocopherol, ascorbate, uric acid, mannitol, tyrosine, tryptophan, histidine, quercitrin and bilirubin had no effect on the inactivation. GST-π pretreated with cystamine was reactivated very efficiently by 50 mM DTT following incubation with 1,2-naphthoquinone, whereas cystamine-untreated GST-π was not reactivated.

An iminosugar-based heparanase inhibitor heparastatin (SF4) suppresses infiltration of neutrophils and monocytes into inflamed dorsal air pouches

Local infiltration of inflammatory cells is regulated by a number of biological steps during which the cells likely penetrate through subendothelial basement membranes that contain heparan sulfate proteoglycans. In the present study, we examined whether administration of heparastatin (SF4), an iminosugar-based inhibitor of heparanase, could suppress local inflammation and degradation of heparan sulfate proteoglycans in basement membranes. In a carrageenan- or formyl peptide-induced dorsal air pouch inflammation model, the number of infiltrated neutrophils and monocytes was significantly lower in mice after topical administration of heparastatin (SF4). The concentration of chemokines MIP-2 and KC in pouch exudates of drug-treated mice was similar to control. In a zymosan-induced peritonitis model, the number of infiltrated cells was not altered in drug-treated mice. To further test how heparastatin (SF4) influences transmigration of inflammatory neutrophils, its suppressive effect on migration and matrix degradation was examined in vitro. In the presence of heparastatin (SF4), the number of neutrophils that infiltrated across a Matrigel-coated polycarbonate membrane was significantly lower, while the number of neutrophils passing through an uncoated membrane was not altered. Lysate of bone marrow-derived neutrophils released sulfate-radiolabeled macromolecules from basement membrane-like extracellular matrix, which was suppressed by heparastatin (SF4). Heparan sulfate degradation activity was almost completely abolished after incubation of lysate with protein G-conjugated anti-heparanase monoclonal antibody, strongly suggesting that the activity was due to heparanase-mediated degradation. Taken together, in a dorsal air pouch inflammation model heparastatin (SF4) potentially suppresses extravasation of inflammatory cells by impairing the degradation of basement membrane heparan sulfate.

Heparanase augments inflammatory chemokine production from colorectal carcinoma cell lines

To explore possible roles of heparanase in cancer-host crosstalk, we examined whether heparanase influences expression of inflammatory chemokines in colorectal cancer cells. Murine colorectal carcinoma cells incubated with heparanase upregulated MCP-1, KC, and RANTES genes and released MCP-1 and KC proteins. Heparanase-dependent production of IL-8 was detected in two human colorectal carcinoma cell lines. Addition of a heparanase inhibitor Heparastatin (SF4) did not influence MCP-1 production, while both latent and mature forms of heparanase augmented MCP-1 release, suggesting that heparanase catalytic activity was dispensable for MCP-1 production. In contrast, addition of heparin to the medium suppressed MCP-1 release in a dose-dependent manner. Similarly, targeted suppression of Ext1 by RNAi significantly suppressed cell surface expression of heparan sulfate and MCP-1 production in colon 26 cells. Taken together, it is concluded that colon 26 cells transduce the heparanase-mediated signal through heparan sulfate binding. We propose a novel function for heparanase independent of its endoglycosidase activity, namely as a stimulant for chemokine production.

Endovascular Treatment of Unruptured Paraclinoid Aneurysms: Single-Center Experience with 400 Cases and Literature Review

BACKGROUND AND PURPOSE

Paraclinoid aneurysms have been increasingly treated endovascularly. The natural history of these aneurysms has gradually been elucidated. The purpose of this study was to assess the safety and efficacy of endovascular treatment for these aneurysms.

MATERIALS AND METHODS

We performed a retrospective review of 377 patients with 400 paraclinoid aneurysms treated between January 2006 and December 2012. Their clinical records, endovascular reports, and radiologic and clinical outcomes were analyzed. Because aneurysms ≥7 mm are at higher risk of rupture, we classified aneurysms as small (<7 mm) or large (≥7 mm).

RESULTS

Overall, 115 of the 400 aneurysms (28.8%) were large (≥7 mm). Thromboembolic complications were found significantly more often with large aneurysms than with small ones (7.4% vs 1.0%, P = .001). Hemorrhagic complications were found only with small aneurysms (0.7%). The 6-month morbidity rates were similar for small (1.0%) and large (0.8%) aneurysms. Immediate angiographic outcomes were similar (P = .37), whereas recurrences and retreatment occurred more frequently with large aneurysms (P = .001 and P = .007, respectively). Multivariate analysis showed that aneurysm size was the only independent predictor for recurrence (P = .005). Most recurrences (81%) were detected by scheduled angiography at 6 months.

CONCLUSIONS

Aneurysm size influenced the type of complication (thromboembolic or hemorrhagic) and the recurrence rate. Given the approximately 1% annual rupture rate for aneurysms ≥7 mm, analysis of our data supports the rationale of using prophylactic endovascular treatment for unruptured paraclinoid aneurysms ≥7 mm.

Resonance effect in white X-ray magnetic diffraction of GdAl2

Using elliptically polarized white synchrotron radiation and an energy-sensitive detector, the 444 reflection from a single-crystal sample of the ferromagnetic compound GdAl2magnetized along the scattering vector has been measured, and the asymmetry of the diffraction intensity upon the magnetization reversal has been studied in the X-ray energy range across the GdLIIedge. The dependence of the magnetic asymmetry on the scattering angle or on the X-ray energy is understood as the superposition of the sharp near-edge structure and the much broader component arising from the interference between the electric scattering and the resonant and nonresonant magnetic scattering, respectively. To interpret the experimental results, an analytical treatment of the magnetic asymmetry is developed, and in the course of the analysis it is pointed out that in general the pseudo-extinction of the Bragg reflection due to the dispersion effects can be utilized as a technique to raise the magnetic sensitivity in the X-ray scattering from ferromagnetic materials. The potential of an unconventional approach to the resonant X-ray scattering using a white beam, as is clearly demonstrated by the present experiment, is also discussed.

Asteltoxins from the Entomopathogenic Fungus Pochonia bulbillosa 8-H-28

New asteltoxins C (3) and D (4) were found in the extract of the entomopathogenic fungus Pochonia bulbillosa 8-H-28. Compound 2, which was spectroscopically identical with the known asteltoxin B, was isolated, and structural analysis led to a revision of the structure of asteltoxin B. Compounds 2 and 4 have a novel tricyclic ring system connected to a dienyl α-pyrone structure. Compound 3 has a 2,8-dioxabicyclo[3.3.0]octane ring similar to that of asteltoxin (1). Compound 3 showed potent antiproliferative activity against NIAS-SL64 cells derived from the fat body of Spodoptera litura larvae, while 2 and 4 were inactive.

Generation of spin currents by surface plasmon resonance

Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light–electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY₂Fe₅O₁₂ bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY₂Fe₅O₁₂ interface. This spin-current generation cannot be explained by conventional heating effects, requiring us to introduce nonequilibrium magnons excited by surface-plasmon-induced evanescent electromagnetic fields in BiY₂Fe₅O₁₂. This plasmonic spin pumping integrates surface plasmons with spin-current physics, opening the door to plasmonic spintronics.

Optical methods allow for the excitation of diverse magnetic phenomena in nanostructured materials. Here, Uchida et al. demonstrate how pure spin current may be generated across a Pt/BiY₂Fe₅O₁₂ thin film interface by optically exciting surface plasmon resonance in embedded gold nanoparticles.