Photolytic depolymerization of alginate

A photochemical reaction has been developed for the partial de-polymerization of sodium alginate, a polysaccharide utilized in medicine, pharmacy, basic sciences and foods. An aqueous solution of sodium alginate was photochemically depolymerized to ∼40% of its average molecular weight using ultraviolet light in the presence of titanium dioxide catalyst at pH 7 over a period of 3 h. The products were separated giving four fractions all having an average molecular weight that was smaller than that of the starting material. Characterization of the guluronate (G) and mannuronate (M) contents, and determination of the M/G ratio of photochemically depolymerized alginate, were accomplished using ¹H NMR spectroscopy. The resulting M/G ratio was compared to that obtained for alginate fractions produced by acid hydrolysis. The M and G content, of each alginate fraction, was also assigned with regards to their occurrence in G-rich, M-rich or M/G heteropolymeric domains. This new depolymerization method might also be applicable in the preparation of alginate oligosaccharides for use in the food and pharmaceutical industries.     

Some properties of alginate gels derived from algal sodium alginate

Alginic acid in soluble sodium alginate turns to insoluble gel after contact with divalent metal ions, such as calcium ions. The sodium alginate character has an effect on the alginate gel properties. In order to prepare a suitable calcium alginate gel for use in seawater, the effects of sodium alginate viscosity and M/G ratio (the ratio of D-mannuronate to L-guluronate) on the gel strength were investigated. The wet tensile strengths of gel fibers derived from high viscosity sodium alginate were higher than those from low viscosity sodium alginate. The tensile strength increased with diminishing sodium alginate M/G ratio. Among the gel fibers tested, the gel fiber obtained from a sodium alginate I-5G (1% aqueous solution viscosity = 520 mPa·s, M/G ratio = 0.6) had the highest wet tensile strength. After 13 days treatment in seawater, the wet tensile strength of the gel fiber retained 36% of the original untreated gel strength. For sodium alginates with similar viscosities, the seawater tolerance of low M/G ratio alginate was greater than that of the high M/G ratio one. This study enables us to determine a suitable calcium alginate gel for use in seawater.     

Chemometric prediction of alginate monomer composition: A comparative spectroscopic study using IR, Raman, NIR and NMR

The potential of using infrared (IR), Raman and near infrared (NIR) spectroscopy combined with chemometrics for reliable and rapid determination of the ratio of mannuronic and guluronic acid (M/G ratio) in commercial sodium alginate powders has been investigated. The reference method for quantification of the M/G ratio was solution-state ¹H nuclear magnetic resonance (NMR) spectroscopy. For a set of 100 commercial alginate powders with a M/G ratio range of 0.5–2.1 quantitative calibrations using partial least squares regression (PLSR) were developed and compared for the three spectroscopic methods. All three spectroscopic methods yielded models with prediction errors (RMSEP) of 0.08 and correlation coefficients between 0.96 and 0.97. However, the model based on extended inverted signal corrected (EISC) Raman spectra stood out by only using one PLS component for the prediction. The results are comparable to that of the experimental error of the reference method estimated to be between 0.01 and 0.08.     

Development of a gradient elution high-performance liquid chromatography assay with ultraviolet detection for the determination in plasma of the anticancer peptide [Arg, -Trp, mePhe]-substance P (6–11) (antagonist G), its major metabolites and a C-terminal pyrene-labelled conjugate

[Arg⁶, -Trp^7,9, mePhe⁸]-substance P (6–11), code-named antagonist G, is a novel peptide currently undergoing early clinical trials as an anticancer drug. A sensitive, high efficiency high-performance liquid chromatography (HPLC) method is described for the determination in human plasma of antagonist G and its three major metabolites, deamidated-G (M1), G-minus Met¹¹ (M2) and G[Met¹¹(O)] (M3). Gradient elution was employed using 40 mM ammonium acetate in 0.15% trifluoroacetic acid as buffer A and acetonitrile as solvent B, with a linear gradient increasing from 30 to 100% B over 15 min, together with a microbore analytical column (μBondapak C₁₈, 30 cm×2 mm I.D.). Detection was by UV at 280 nm and the column was maintained at 40°C. Retention times varied by <1% throughout the day and were as follows: G, 13.0 min; M1, 12.2 min; M2, 11.2 min; M3, 10.8 min, and 18.1 min for a pyrene conjugate of G (G–P). The limit of detection on column (LOD) was 2.5 ng for antagonist G, M1–3 and G–P and the limit of quantitation (LOQ) was 20 ng/ml for G and 100 ng/ml for M1–3. Sample clean-up by solid-phase extraction using C₂-bonded 40 μm silica particles (Bond Elut, 1 ml reservoirs) resulted in elimination of interference from plasma constituents. Within-day and between-day precision and accuracy over a broad range of concentrations (100 ng/ml–100 μg/ml) normally varied by <10%, although at the highest concentrations of M1 and M2 studied (50 μg/ml), increased variability and reduced recovery were observed. The new assay will aid in the clinical development of antagonist G.     

Direct quantification of M/G ratio from C CP-MAS NMR spectra of alginate powders by multivariate curve resolution

Multivariate curve resolution (MCR) was applied to ¹³C cross-polarisation (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of non-depolymerised alginate powders obtained from brown seaweed plus a pure mannuronate sample isolated from Pseudomonas fluorescens for estimation of the mannuronic acid/guluronic acid ratio (M/G ratio). An excellent MCR model with a correlation coefficient of r² = 0.99 was established between the estimated M/G ratios and the M/G ratios obtained from the traditional ¹H solution state NMR method. The new method allows for successful determination of the M/G ratio independent of the calcium content (at least up to 2.4%, which was the upper limit in this study) with a root mean square error of prediction of 0.05. It is thus concluded that ¹³C CP-MAS NMR in combination with multivariate curve resolution is a reliable, convenient (no sample preparation is required) and relatively rapid method for M/G ratio determinations of alginates and it may serve as a good alternative to the chemical techniques traditionally used.     

Effects of phorbol 12-myristate 13-acetate on potassium transport in the red blood cells of frog <Emphasis Type="Italic">Rana temporaria</Emphasis>

Phorbol 12-myristate 13-acetate (PMA), a stimulator of PKC, was examined for its influence on K⁺ (⁸⁶Rb) influx in the frog erythrocyte. PMA, 0.1 μM, was found to accelerate ouabain-sensitive K⁺ influx, which was suppressed by 73% with 1 mM amiloride, indicating secondary activation of the Na⁺–K⁺-pump due to stimulation of Na⁺ /H⁺ exchange. PMA-induced stimulation of the sodium pump was completely inhibited with 1 μM staurosporine and by ~50% with 20 μM chelerythrine. In contrast to Na⁺–K⁺-pump, an activity of Cl⁻-dependent K⁺ transport (K–Cl cotransport, KCC), calculated as the difference between K⁺ influxes in Cl⁻ and NO₃ ⁻-media, was substantially decreased under the influence of PMA. Staurosporine fully restored the PMA-induced inhibition of KCC, whereas chelerythrine did not exert any influence. Osmotic swelling of the frog erythrocytes was accompanied by approximately twofold stimulation of KCC. Swelling-activated KCC was inhibited by ~50 and ~83% in the presence of PMA and genistein, respectively, but not chelerythrine. Exposure of the frog erythrocytes to 5 mM fluoride (F⁻) also reduced the KCC activity in isotonic and hypotonic media, with maximal suppression of K⁺ influx in both media being observed upon simultaneous addition of PMA and F⁻. Furosemide and [(dihydronindenyl)oxy] alkanoic acid inhibited the K⁺ influx in both the media by ~50–60%. The results obtained show both the direct and indirect effects of PMA on the K⁺ transport in frog erythrocytes and a complicated picture of KCC regulation in frog erythrocytes with involvement of PKC, tyrosine kinase and protein phosphatase.     

Optimization of citric acid treatment for the sequential extraction of fucoidan and alginate from Sargassum latifolium and their potential antioxidant and Fe(III) chelation properties

In this study, citric acid was applied as a safe organic acid for the treatment of the brown macroalga Sargassum latifolium to facilitate the sequential extraction of fucoidan and alginate without cross contamination. Box-Behnken experimental design was used to investigate the effects of citric acid concentration, temperature, and time on fucoidan yield, its fucose and sulfate contents, and molecular weight (MW), while the investigated responses of the sequentially extracted alginate were yield, mannuronic/guluronic acid ratio (M/G) and MW. Under the optimized conditions, the fucoidan yield, fucose content, sulfate content, and MW were 6.55%, 21.01%, 30.92% and 7.12 × 10³ Da, respectively, while alginate yield, M/G, and MW were 28.81%, 0.36, and 1.50 × 10⁵ Da, respectively. The optimized products showed good Fe(III) chelating properties and the iron contents were 509.82 mg g^?1 for fucoidan-Fe and 406.71 ± 5.18 mg g^?1 for alginate-Fe. Under simulated gastrointestinal conditions, fucoidan-Fe and alginate-Fe complexes released 46 and 57% iron, respectively, which are nutritionally relevant amounts. Both fucoidan and alginate showed potent antioxidant properties, but their Fe complexes exhibited a reduced activity. The results of the present study indicated that citric acid could support the basis for an economical biorefinery process for the sequential extraction of fucoidan and alginate. Additionally, these polysaccharides could be good candidates for the preparations of iron supplements.

     

Polar Constituents of Brown Seaweed Colpomenia peregrina (Sauv.) Hamel from the Black Sea

GC-MS of trimethylsilyl derivatives of the compounds present in the butanolic extract of biomass of brown seaweed Colpomenia peregrina from the Black Sea aided in identification of 24 components, including aliphatic hydroxy and keto and aromatic acids, glycerol, mannitol, floridoside, and monosaccharides. The polysaccharide composition of the biomass was also studied, with high sodium alginate and laminaran contents and a comparatively low level of fucoidan being revealed. The polysaccharides were isolated from the biomass by fractional extraction and purified by precipitation or ion exchange chromatography. The structures of alginic acid and laminaran were deduced from ¹³C NMR spectra and confirmed, in the case of laminaran, by methylation analysis. The sodium alginate was shown to contain more guluronic (G) than mannuronic acid (M) residues, the M/G ratio being 0.48. Laminaran was demonstrated to be a -glucan with 1 3 linkages in its backbone and 1 6 linkages in its branching points, which is characteristic of brown algae. Fucoidan turned out to be a complex heteropolysaccharide containing, in addition to fucose and sulfate, other neutral monosaccharides and uronic acids.     

Effect of molecular weight on the antioxidant property of low molecular weight alginate from Laminaria japonica

In this study, three alginate fractions with different molecular weights and ratios of mannuronic acid (M) to guluronic acid (G) were prepared by enzymatic hydrolysis and ultrafiltration to assess the antioxidant property of alginates from Laminaria japonica with molecular weight below 10 kDa. The antioxidant properties of different molecular weight alginates were evaluated by determining the scavenging abilities on superoxide, hydroxyl, and hypochlorous acid and inhibitory effect on Fe²⁺-induced lipid peroxidation in yolk homogenate. The results showed that low molecular weight alginates exhibited high scavenging capacities on superoxide, hydroxyl, and hypochlorous acid radicals and good inhibition of Fe²⁺-induced lipid peroxidation in yolk. By comparison, alginate A1 with molecular weight below 1 kDa and M/G of 1.84 had better scavenging activity on superoxide, hydroxyl, and hypochlorous acid radicals in vitro than A2 (1–6 kDa), A3 (6–10 kDa), ascorbic acid, and carnosine. With similar M/G ratio, A2 exhibited better antioxidant activity on superoxide and hypochlorous acid radicals than A3. However, fraction A3 with molecular weight of 6–10 kDa exhibited higher inhibitory ability on lipid peroxidation in yolk in vitro than A1 and A2. The results indicated that molecular weight played a more important role than M/G ratio on alginate to determine the antioxidant ability. By comparison, low molecular weight alginates composed of guluronic acid and mannuronic acid exhibited better antioxidant ability on oxygen free radicals than sulfated polysaccharides from L. japonica in our previous study and represent a good source of marine polysaccharide with potential application as natural antioxidant.     

Expression of calcium-binding protein regucalcin mRNA in the cloned rat hepatoma cells (Hr-II-E) is stimulated through Ca2+ signaling factors: Involvement of protein kinase C

The expression of hepatic Ca²⁺-binding protein regucalcin in the cloned rat hepatoma cells (H4-II-E) was investigated. The change in regucalcin mRNA levels was analyzed by Northern blotting using rat liver regucalcin complementary DNA (0.9 kb of open reading frame). Regucalcin mRNA was expressed in H4-II-E hepatoma cells. This expression was clearly stimulated in the presence of serum (10% fetal bovine serum). Bay K 8644 (2. 5 × 10^-6 M), a Ca²⁺ channel agonist, significantly stimulated regucalcin mRNA expression in the absence or presence of 10% serum. Dibutyryl cyclic AMP (10^-3 M) did not have a stimulatory effect on the regucalcin mRNA expression. The presence of phorbol 12-myristate 13-acetate (PMA; 10^-6 M) or estrogen (10^-8 M) caused a significant increase in regucalcin mRNA levels in the hepatoma cells cultured in serum-free medium, while insulin (5 × 10^-9 M) or dexamethasone (10^-6 M) had no effect. Bay K 8644-stimulated regucalcin mRNA expression in the hepatoma cells was completely blocked in the presence of trifluoperazine (10^-5 M), an antagonist of calmodulin, or staurosporine (10^-7 M), an inhibitor of protein kinase C. The stimulatory effect of PMA was clearly inhibited in the presence of stauroporine. The present study demonstrates that regucalcin mRNA is expressed in the transformed H4-II-E hepatoma cells, and that the expression is stimulated through Ca²⁺-dependent signaling factors.     

Alginate films for delivery of root-knot nematode inoculum and evaluation of microbial interactions

A method was developed for utilizing alginate films to deliver inoculum into soil and evaluate microbial antagonistic activity against nematode eggs. Eggs of Meloidogyne incognita were harvested from galled tomato roots (Lycopersicon esculentum), surface disinfested, suspended in 2% (w/v) aqueous sodium alginate, and applied to 2.5 × 5.0 cm polyvinyl chloride coated fiberglass screens (1.5 mm² mesh size) at a uniform thickness of 0.5 mm. The alginate solution was gelled by dipping in 0.25 M CaCl₂. Films containing eggs were observed in vitro and egg development was evaluated. The number of immature eggs and eggs with first stage juveniles declined linearly over time while the number of empty eggs shells, and hatched juveniles increased over time, indicating that the alginate gel did not inhibit development and motility of M. incognita juveniles. In a greenhouse experiment using cucumber (Cucumis sativus) the number of galls g^-1 root was correlated with the number of eggs in alginate films placed in each pot at planting. Films containing M. incognita eggs were buried in field soil containing organic amendments, incubated, removed from soil, rinsed with water, and observed. The number of immature eggs in grids from soil amended with chitin or flax seed meal were lower than in untreated soil; percent parasitized eggs was also greater in films from amended soil than from untreated soil.     

Pilot plant scale extraction of alginates from Macrocystis pyrifera 3. Precipitation, bleaching and conversion of calcium alginate to alginic acid

Three steps of the alginate production process were studied at pilot plantlevel. The effect of the amount of calcium chloride used during theprecipitation was measured in terms of filtration time of the precipitatedcalcium alginate. Three different proportions of calcium chloride per gramof alginate were tested. The best proportion used was 2.2 parts ofcalcium chloride per one part of alginate, yielding a filtration rate of 97.9L min^-1 on a screen area of 1.32 m². The method ofadding the solutions and the degree of mixing are discussed as other factorsaffecting the precipitation step. The effect of bleaching the calciumalginate with sodium hypochlorite (5%) was studied. Seven proportions,ranging from 0 to 0.77 mL of sodium hypochlorite per gram of sodiumalginate were tested. The effect of hypochlorite was compared foralginates with three different viscosities. Using alginates with mediumviscosity (300–500 mPa s), the best proportion was 0.4 mL hypochloriteper gram of alginate, yielding an alginate of light cream color with 20%less viscosity than the control. Alginates with lower viscosity showed asmaller loss of viscosity. The effect of pH during conversion of calciumalginate to alginic acid was determined using four combinations of pH,ranging from 2.2 to 1.6, in three acid washings. The extent of conversionwas determined by measuring the percent reduction of the alginate viscosity(RV) in 1% solution before and after adding a sequestrant of calcium. When a pH 1.8 or 1.6 was used for each washing, only two washings werenecessary to produce a RV lower than 40% (maximum recommended). The use of pH 2 required three acid washings to produce the same effect. The pH 2.2 did not remove enough calcium, even with three washings,the RV of the resulting sodium alginate being greater that 40%. Theresults of these experiments provide the information that producers needwhen deciding the best parameters to obtain a product with the desiredcharacteristics.     

Flow of 14C-methanol via assimilatory and dissimilatory sequences with yeast in presence of glucose

Experiments were performed to reveal the extent to which individual heterotrophic substrates of a mixture contribute to the overall carbon and energy metabolism. For this reason Hansenula polymorpha MH 20 was chemostatically (C-limited) cultivated at different growth rates on mixtures of methanol and glucose fed at proportions of 3:1 and 1:3 (in weight units), respectively. The distributions of ¹⁴C-carbon from methanol in biomass as well as carbon dioxide (and supernatant) fractions were determined. From these results it followed, firstly, that energy derived from methanol dissimilation was used in part for the incorporation of glucose carbon, resulting in carbon conversion efficiencies for this substrate equivalent to yield coefficients of 0.61–0.69 g/g. Secondly, the growth yield data revealed that the efficiency of methanol conversion had to be increased in order to account for the experimentally determined yield figures. This was further confirmed by theoretical treatment of the growth yield data which showed that these could only be obtained if P/O-quotients for methanol conversion similar to those for glucose, i.e. 2.0–2.5, were considered. The latter property was regarded as the main reason for the observed improvement of growth yield accompanying the simultaneous utilization of methanol and glucose in this yeast.Abbreviations ATP_M,a ATP required for incorporation of assimilated methanol at a given P/O-quotient - ATP_M,d ATP generated from dissimilated methanol at a given P/O-quotient - G and M glucose and methanol; respectively (the indices u, a, d and e mean utilized, assimilated, dissimilated and incorporated by excess energy, respectively) - PGA 3-phosphoglyceric acid - Y _G ^app apparent growth yield on glucose in presence of methanol - Y _G ^P/O theoretical growth yield on glucose at a given P/O-quotient     

Alginic acids in Lessonia vadosa: Partial hydrolysis and elicitor properties of the polymannuronic acid fraction

Extraction of Lessonia vadosa(Laminariales, Phaeophyta) collectedin three different localities near PuntaArenas in the south of Chile, with 3%aqueous sodium carbonate solutions gave asodium alginate yield in the range3.0–17.7% dry weight. There were markeddifferences in the mannuronic acid toguluronic acid ratio (M/G) (0.21–1.69) inthe alginic acids, samples collected inPuerto del Hambre in winter were composedmainly of mannuronic acid residues. Thealginate samples were characterized bypartial hydrolysis and FT-IR spectroscopy.No relationship was found between tissuetype and polyguluronic acid content. Theelicitor activity of the polymannuronicacid enriched fraction from alginic acid ofblades from Puerto del Hambre was assayedin wheat plants. The polymannuronic acidenriched fraction induced substancialelicitation of phenylalanine ammonia-lyase(PAL) and peroxidase (POD) activities.     

Response surface design for the optimization of enzymatic detection of mercury in aqueous solution using immobilized urease from vegetable waste

Soluble and alginate immobilized urease was utilized for detection and quantitation of mercury in aqueous samples. Urease from the seeds of pumpkin, being a vegetable waste, was extracted and purified to apparent homogeneity (sp. activity 353 U/mg protein; A₂₈₀/A₂₆₀ = 1.12) by heat treatment at 48 ± 0.1 °C and gel filtration through Sephadex G-200. Homogeneous enzyme preparation was immobilized in 3.5% alginate leading to 86% immobilization, no leaching of enzyme was found over a period of 15 days at 4 °C. Urease catalyzed urea hydrolysis by soluble and immobilized enzyme revealed a clear dependence on the concentration of Hg²⁺. Inhibition caused by Hg²⁺ was non-competitive (K_i = 1.2 × 10⁻¹ μM for soluble and 1.46 × 10⁻¹ μM for alginate immobilized urease.). Time-dependent inhibition both in presence and in absence of Hg²⁺ ion revealed a biphasic inhibition in activity. For optimization of this process response surface methodology (RSM) was utilized where two-level-two-full factorial (2²) central composite design (CCD) has been employed. The regression equation and analysis of variance (ANOVA) were obtained using MINITAB^® 15 software. Predicted values thus obtained were closed to experimental value indicating suitability of the model. 3D response surface plot, iso-response contour plot and process optimization curve were helpful to predict the results by performing only limited set of experiments.     

Effects of morphine-3-glucuronide on the antinociceptive activity of peptide and nonpeptide opioid receptor agonists in mice

The effects of morphine-3-glucuronide (M3G), a metabolite of morphine, were determined on the antinociceptive actions, as measured by the tail flick test, of morphine, a μ-opioid receptor agonist, of U-50,488H, a κ-opioid receptor agonist, of [ -Pen², -Pen⁵]enkephalin (DPDPE), a δ₁-opioid receptor agonist, and of [ -Ala²,Glu⁴]deltorphin II (deltorphin II), a δ₂-opioid receptor agonist in mice. Morphine administered ICV (2.5 μg/mouse) or SC (10 mg/kg), U-50,488H (25 mg/kg, IP), DPDPE (15 μg/mouse; ICV), and deltorphin II (15 μg/mouse, ICV) produced antinociception in mice. Intraperitoneal or ICV injections of M3G did not produce any effect on the tail flick latency nor did it affect the antinociception-induced by morphine, U-50,488H, DPDPE, or deltorphin II. Previously M3G has been shown to antagonize the antinociceptive effects of morphine in the rat. It is concluded that in the mouse, M3G neither produces hyperalgesia nor modifies the actions of μ-, κ-, δ₁-, or δ₂-opioid receptor agonists.     

The acid-base transport proteins NHE1 and NBCn1 regulate cell cycle progression in human breast cancer cells

Precise acid-base homeostasis is essential for maintaining normal cell proliferation and growth. Conversely, dysregulated acid-base homeostasis, with increased acid extrusion and marked extracellular acidification, is an enabling feature of solid tumors, yet the mechanisms through which intra- and extracellular pH (pH_i, pH_e) impact proliferation and growth are incompletely understood. The aim of this study was to determine the impact of pH, and specifically of the Na⁺/H⁺ exchanger NHE1 and Na⁺, HCO₃^? transporter NBCn1, on cell cycle progression and its regulators in human breast cancer cells. Reduction of pH_e to 6.5, a common condition in tumors, significantly delayed cell cycle progression in MCF-7 human breast cancer cells. The NHE1 protein level peaked in S phase and that of NBCn1 in G2/M. Steady state pH_i changed through the cell cycle, from 7.1 in early S phase to 6.8 in G2, recovering again in M phase. This pattern, as well as net acid extrusion capacity, was dependent on NHE1 and NBCn1. Accordingly, knockdown of either NHE1 or NBCn1 reduced proliferation, prolonged cell cycle progression in a manner involving S phase prolongation and delayed G2/M transition, and altered the expression pattern and phosphorylation of cell cycle regulatory proteins. Our work demonstrates, for the first time, that both NHE1 and NBCn1 regulate cell cycle progression in breast cancer cells, and we propose that this involves cell cycle phase-specific pH_i regulation by the two transporters.     

Seasonal studies on the alginate and its biochemical composition I: Sargassum polycystum (Fucales), Phaeophyceae

Investigations were made on the brown seaweed Sargassum polycystum C. Agardh collected from Rameswaram Coast, Tamil Nadu. The alginates extracted from ‘leaf’, ‘stem’ and entire thallus of S. polycystum were investigated for their viscosity and chemical constituents, namely β‐D‐mannuronic acid (M‐block), α‐L‐guluronic acid (G‐block) and alternating sequences of β‐D‐mannuronic acid and α‐L‐guluronic acid (MG‐block) for six different seasons between August 1998 and November 1999. Significant seasonal variation (P< 0.05) was observed with high yield of alginate in February. The alginate extracted from the ‘leaf’ region showed a maximum yield whereas the ‘stem’ region exhibited maximum viscosity. The amount of G‐block was found to be more than M‐ and MG‐blocks in all the samples tested. The amount of G‐block was high in ‘stem’ followed by leaf and entire thallus. A positive correlation was recorded between viscosity and G‐block. Among the three alginates, the ratio of M/G was low in the ‘stem’ followed by ‘leaf’ and entire thallus.     

The Xanthine Derivative KMUP-1 Attenuates Serotonin-Induced Vasoconstriction and K+-Channel Inhibitory Activity via the PKC Pathway in Pulmonary Arteries

Serotonin (5-hydroxytryptamine, 5-HT) is a potent pulmonary vasoconstrictor that promotes pulmonary artery smooth muscle cell (PASMC) proliferation. 5-HT-induced K⁺ channel inhibition increases [Ca²⁺]_i in PASMCs, which is a major trigger for pulmonary vasoconstriction and development of pulmonary arterial hypertension (PAH). This study investigated whether KMUP-1 reduces pulmonary vasoconstriction in isolated pulmonary arteries (PAs) and attenuates 5-HT-inhibited K⁺ channel activities in PASMCs. In endothelium-denuded PA rings, KMUP-1 (1 μM) dose-dependently reduced 5-HT (100 μM) mediated contractile responses. Responses to KMUP-1 were reversed by K⁺ channel inhibitors (TEA, 10 mM, 4-aminopyridine, 5 mM, and paxilline, 10 μM). In primary PASMCs, KMUP-1 also dose-dependently restored 5-HT-inhibited voltage-gated K⁺-channel (Kv1.5 and Kv2.1) and large-conductance Ca²⁺-activated K⁺-channel (BK_Ca) proteins, as confirmed by immunofluorescent staining. Furthermore, 5-HT (10 μM)-inhibited Kv1.5 protein was unaffected by the PKA inhibitor KT5720 (1 μM) and the PKC activator PMA (1 μM), but these effects were reversed by KMUP-1 (1 μM), 8-Br-cAMP (100 μM), chelerythrine (1 μM), and KMUP-1 combined with a PKA/PKC activator or inhibitor. Notably, KMUP-1 reversed 5-HT-inhibited Kv1.5 protein and this response was significantly attenuated by co-incubation with the PKC activator PMA, suggesting that 5-HT-mediated PKC signaling can be modulated by KMUP-1. In conclusion, KMUP-1 ameliorates 5-HT-induced vasoconstriction and K⁺-channel inhibition through the PKC pathway, which could be valuable to prevent the development of PAH.     

The invasive brown seaweed Sargassum muticum as new resource for alginate in Morocco: Spectroscopic and rheological characterization

The Japanese brown seaweed Sargassum muticum, recently invaded several shorelines worldwide including the Atlantic coast of Morocco with large well‐established populations. Within the framework of a sustainable strategy to control this invasive seaweed, we report on extraction yield, spectroscopic characterization and rheological properties of alginate, a commercially valuable colloid, from harvested biomass of S. muticum. Extraction yield was about 25.6% on dry weight basis. Infrared spectroscopy analysis shows that the obtained Fourier transform infrared spectra of the extracted biopolymer exhibit strong similarities with that of the commercial alginate. Furthermore, Proton nuclear magnetic resonance spectroscopy revealed that S. muticum alginate has almost equal amounts of β‐D‐mannuronic acid (M; 49%) and α‐L‐guluronic acid (G; 51%) with an M/G ratio of 1.04 and a high content of heteropolymeric MG GM diads suggesting a sequence distribution of an alternated polymer type. Rheological measurements were performed at different sodium alginate concentrations, temperatures and shear rates. The hydrocolloid exhibited pseudoplastic behavior and showed shear thinning, particularly at high solution concentration and low temperature which is consistent with the rheological behavior reported for commercial alginates. Considering the abundance of S. muticum in the Northwestern Atlantic coast of Morocco and the quality of the extracted hydrogel, this invasive species could be considered as a potential source of alginates.