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Marine organism sulfated polysaccharides exhibiting significant antimalarial activity and inhibition of red blood cell invasion by Plasmodium.

Marques J, Vilanova E, Mourão PA, Fernàndez-Busquets X - Sci Rep (2016)

Bottom Line: The antimalarial activity of heparin, against which there are no resistances known, has not been therapeutically exploited due to its potent anticoagulating activity.Here, we have explored the antiplasmodial capacity of heparin-like sulfated polysaccharides from the sea cucumbers Ludwigothurea grisea and Isostichopus badionotus, from the red alga Botryocladia occidentalis, and from the marine sponge Desmapsamma anchorata.In one animal treated with I. badionotus fucan parasitemia was reduced from 10.4% to undetectable levels, and Western blot analysis revealed the presence of antibodies against P. yoelii antigens in its plasma.

View Article: PubMed Central - PubMed

Affiliation: Nanomalaria Group, Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain.

ABSTRACT
The antimalarial activity of heparin, against which there are no resistances known, has not been therapeutically exploited due to its potent anticoagulating activity. Here, we have explored the antiplasmodial capacity of heparin-like sulfated polysaccharides from the sea cucumbers Ludwigothurea grisea and Isostichopus badionotus, from the red alga Botryocladia occidentalis, and from the marine sponge Desmapsamma anchorata. In vitro experiments demonstrated for most compounds significant inhibition of Plasmodium falciparum growth at low-anticoagulant concentrations. This activity was found to operate through inhibition of erythrocyte invasion by Plasmodium, likely mediated by a coating of the parasite similar to that observed for heparin. In vivo four-day suppressive tests showed that several of the sulfated polysaccharides improved the survival of Plasmodium yoelii-infected mice. In one animal treated with I. badionotus fucan parasitemia was reduced from 10.4% to undetectable levels, and Western blot analysis revealed the presence of antibodies against P. yoelii antigens in its plasma. The retarded invasion mediated by sulfated polysaccharides, and the ensuing prolonged exposure of Plasmodium to the immune system, can be explored for the design of new therapeutic approaches against malaria where heparin-related polysaccharides of low anticoagulating activity could play a dual role as drugs and as potentiators of immune responses.

No MeSH data available.


Related in: MedlinePlus

Flow cytometry analysis of the inhibition of red blood cell invasion by P. falciparum in the presence of sulfated polysaccharides.The values indicate the corresponding absolute percentages (parasitemias) of rings and schizonts in the cultures, 20 h after treatment and at polysaccharide concentrations corresponding to the respective (a) IC50 and (b) IC90 reported in Table 1. The results are shown as the means of three independent experiments; the error bars represent standard deviations. Significant differences in the numbers of rings and schizonts relative to the respective non-treated controls as determined by t-tests are indicated by asterisks (*p<0.05, **p<0.005, ***p<0.001).
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f5: Flow cytometry analysis of the inhibition of red blood cell invasion by P. falciparum in the presence of sulfated polysaccharides.The values indicate the corresponding absolute percentages (parasitemias) of rings and schizonts in the cultures, 20 h after treatment and at polysaccharide concentrations corresponding to the respective (a) IC50 and (b) IC90 reported in Table 1. The results are shown as the means of three independent experiments; the error bars represent standard deviations. Significant differences in the numbers of rings and schizonts relative to the respective non-treated controls as determined by t-tests are indicated by asterisks (*p<0.05, **p<0.005, ***p<0.001).

Mentions: Since the antimalarial mechanism of heparin and related polysaccharides had been described to operate through inhibition of the invasion of RBCs by Plasmodium, we proceeded to investigate the invasion inhibition activity of the marine sulfated polysaccharides. Late-stage pRBC cultures that had been treated with the different structures revealed upon microscopic examination at 20 h post-treatment a clear decrease in ring stages relative to untreated samples (Fig. 4). Polysaccharide-treated samples thus showed a delay in P. falciparum development, as evidenced by the presence at 40 h within the intraerythrocytic cycle of a significant fraction of ring stages relative to untreated controls which contained, as expected, trophozoites and schizonts only. Quantitative microscopic counts evidenced a clear decrease in the invasion rate of all polysaccharide-treated samples (Table 2). Maturation rates, on the other hand, were not negatively affected, indicating that if rings are formed, their progression towards trophozoites and schizonts seems to proceed normally. The observation that some of the samples had maturation rates larger than the untreated control suggests that these cases reflected the presence of a significant number of parasites that either completed their invasion or started their differentiation into identifiable rings after the count of ring stages was made. A clear example of this is represented by L. grisea FucCS-treated samples, whose parasitemias at 40 h post-treatment were higher than those expected from the low invasion rate reported for this polysaccharide in Table 2. Likely, the reduced ring numbers observed in microscopic counts of in vitro assays indicates a slower invasion process of otherwise viable merozoites. These retarded invasions (therefore not detected as ring stages) eventually develop into trophozoites, which results in an apparently high maturation rate from rings to late forms. Indeed, when multiplying invasion by maturation rates, which gives an approximate comparative estimation of parasite viability, the values obtained (not shown) are in good agreement with the respective inhibitory effects on parasite growth (Fig. 3), with L. grisea FucCS exhibiting the highest antiplasmodial activity when all polysaccharides are tested at 4 μg/mL. Flow cytometry analyses of P. falciparum cultures treated at late stage with sulfated polysaccharides confirmed a clear dose-dependent invasion inhibition at their respective IC50 (Fig. 5a) and IC90 (Fig. 5b).


Marine organism sulfated polysaccharides exhibiting significant antimalarial activity and inhibition of red blood cell invasion by Plasmodium.

Marques J, Vilanova E, Mourão PA, Fernàndez-Busquets X - Sci Rep (2016)

Flow cytometry analysis of the inhibition of red blood cell invasion by P. falciparum in the presence of sulfated polysaccharides.The values indicate the corresponding absolute percentages (parasitemias) of rings and schizonts in the cultures, 20 h after treatment and at polysaccharide concentrations corresponding to the respective (a) IC50 and (b) IC90 reported in Table 1. The results are shown as the means of three independent experiments; the error bars represent standard deviations. Significant differences in the numbers of rings and schizonts relative to the respective non-treated controls as determined by t-tests are indicated by asterisks (*p<0.05, **p<0.005, ***p<0.001).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829872&req=5

f5: Flow cytometry analysis of the inhibition of red blood cell invasion by P. falciparum in the presence of sulfated polysaccharides.The values indicate the corresponding absolute percentages (parasitemias) of rings and schizonts in the cultures, 20 h after treatment and at polysaccharide concentrations corresponding to the respective (a) IC50 and (b) IC90 reported in Table 1. The results are shown as the means of three independent experiments; the error bars represent standard deviations. Significant differences in the numbers of rings and schizonts relative to the respective non-treated controls as determined by t-tests are indicated by asterisks (*p<0.05, **p<0.005, ***p<0.001).
Mentions: Since the antimalarial mechanism of heparin and related polysaccharides had been described to operate through inhibition of the invasion of RBCs by Plasmodium, we proceeded to investigate the invasion inhibition activity of the marine sulfated polysaccharides. Late-stage pRBC cultures that had been treated with the different structures revealed upon microscopic examination at 20 h post-treatment a clear decrease in ring stages relative to untreated samples (Fig. 4). Polysaccharide-treated samples thus showed a delay in P. falciparum development, as evidenced by the presence at 40 h within the intraerythrocytic cycle of a significant fraction of ring stages relative to untreated controls which contained, as expected, trophozoites and schizonts only. Quantitative microscopic counts evidenced a clear decrease in the invasion rate of all polysaccharide-treated samples (Table 2). Maturation rates, on the other hand, were not negatively affected, indicating that if rings are formed, their progression towards trophozoites and schizonts seems to proceed normally. The observation that some of the samples had maturation rates larger than the untreated control suggests that these cases reflected the presence of a significant number of parasites that either completed their invasion or started their differentiation into identifiable rings after the count of ring stages was made. A clear example of this is represented by L. grisea FucCS-treated samples, whose parasitemias at 40 h post-treatment were higher than those expected from the low invasion rate reported for this polysaccharide in Table 2. Likely, the reduced ring numbers observed in microscopic counts of in vitro assays indicates a slower invasion process of otherwise viable merozoites. These retarded invasions (therefore not detected as ring stages) eventually develop into trophozoites, which results in an apparently high maturation rate from rings to late forms. Indeed, when multiplying invasion by maturation rates, which gives an approximate comparative estimation of parasite viability, the values obtained (not shown) are in good agreement with the respective inhibitory effects on parasite growth (Fig. 3), with L. grisea FucCS exhibiting the highest antiplasmodial activity when all polysaccharides are tested at 4 μg/mL. Flow cytometry analyses of P. falciparum cultures treated at late stage with sulfated polysaccharides confirmed a clear dose-dependent invasion inhibition at their respective IC50 (Fig. 5a) and IC90 (Fig. 5b).

Bottom Line: The antimalarial activity of heparin, against which there are no resistances known, has not been therapeutically exploited due to its potent anticoagulating activity.Here, we have explored the antiplasmodial capacity of heparin-like sulfated polysaccharides from the sea cucumbers Ludwigothurea grisea and Isostichopus badionotus, from the red alga Botryocladia occidentalis, and from the marine sponge Desmapsamma anchorata.In one animal treated with I. badionotus fucan parasitemia was reduced from 10.4% to undetectable levels, and Western blot analysis revealed the presence of antibodies against P. yoelii antigens in its plasma.

View Article: PubMed Central - PubMed

Affiliation: Nanomalaria Group, Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain.

ABSTRACT
The antimalarial activity of heparin, against which there are no resistances known, has not been therapeutically exploited due to its potent anticoagulating activity. Here, we have explored the antiplasmodial capacity of heparin-like sulfated polysaccharides from the sea cucumbers Ludwigothurea grisea and Isostichopus badionotus, from the red alga Botryocladia occidentalis, and from the marine sponge Desmapsamma anchorata. In vitro experiments demonstrated for most compounds significant inhibition of Plasmodium falciparum growth at low-anticoagulant concentrations. This activity was found to operate through inhibition of erythrocyte invasion by Plasmodium, likely mediated by a coating of the parasite similar to that observed for heparin. In vivo four-day suppressive tests showed that several of the sulfated polysaccharides improved the survival of Plasmodium yoelii-infected mice. In one animal treated with I. badionotus fucan parasitemia was reduced from 10.4% to undetectable levels, and Western blot analysis revealed the presence of antibodies against P. yoelii antigens in its plasma. The retarded invasion mediated by sulfated polysaccharides, and the ensuing prolonged exposure of Plasmodium to the immune system, can be explored for the design of new therapeutic approaches against malaria where heparin-related polysaccharides of low anticoagulating activity could play a dual role as drugs and as potentiators of immune responses.

No MeSH data available.


Related in: MedlinePlus