Rapid clearance of Plasmodium yoelii-infected erythrocytes after exposure to the ionophore A23187

Comprehensive Strategies for Metabolic Syndrome: How Nutrition, Dietary Polyphenols, Physical Activity, and Lifestyle Modifications Address Diabesity, Cardiovascular Diseases, and Neurodegenerative Conditions

Several hallmarks of metabolic syndrome, such as dysregulation in the glucose and lipid metabolism, endothelial dysfunction, insulin resistance, low-to-medium systemic inflammation, and intestinal microbiota dysbiosis, represent a pathological bridge between metabolic syndrome and diabesity, cardiovascular, and neurodegenerative disorders. This review aims to highlight some therapeutic strategies against metabolic syndrome involving integrative approaches to improve lifestyle and daily diet. The beneficial effects of foods containing antioxidant polyphenols, intestinal microbiota control, and physical activity were also considered. We comprehensively examined a large body of published articles involving basic, animal, and human studie, as well as recent guidelines. As a result, dietary polyphenols from natural plant-based antioxidants and adherence to the Mediterranean diet, along with physical exercise, are promising complementary therapies to delay or prevent the onset of metabolic syndrome and counteract diabesity and cardiovascular diseases, as well as to protect against neurodegenerative disorders and cognitive decline. Modulation of the intestinal microbiota reduces the risks associated with MS, improves diabetes and cardiovascular diseases (CVD), and exerts neuroprotective action. Despite several studies, the estimation of dietary polyphenol intake is inconclusive and requires further evidence. Lifestyle interventions involving physical activity and reduced calorie intake can improve metabolic outcomes.

Calcium homeostasis and signaling in the blood-stage malaria parasite

The nature of the mechanisms underlying Ca2+ homeostasis in malaria parasites has puzzled investigators for almost two decades. This review summarizes the current knowledge about Ca2+ homeostasis in Plasmodium spp and highlights some key aspects of this process that are specific to this parasite. Plasmodium spp are exposed, during their intracellular stage, not to the usual millimolar concentrations of Ca2+ found in body fluids, but rather to the very low Ca2+ environment of the host cell cytoplasm. Two crucial questions then arise: (1) how is Ca2+ homeostasis achieved by these protozoa; and (2) do they use Ca2+-based signaling pathways? By critically reviewing the recent literature in the field, Célia Garcia here provides at least some partial answers to these questions.

Differential in vitro activities of ionophore compounds against Plasmodium falciparum and mammalian cells

Twenty-two ionophore compounds were screened for their antimalarial activities. They consisted of true ionophores (mobile carriers) and channel-forming quasi-ionophores with different ionic specificities. Eleven of the compounds were found to be extremely efficient inhibitors of Plasmodium falciparum growth in vitro, with 50% inhibitory concentrations of less than 10 ng/ml. Gramicidin D was the most active compound tested, with 50% inhibitory concentration of 0.035 ng/ml. Compounds with identical ionic specificities generally had similar levels of antimalarial activity, and ionophores specific to monovalent cations were the most active. Compounds were further tested to determine their in vitro toxicities against mammalian lymphoblast and macrophage cell lines. Nine of the 22 compounds, i.e., alborixin, lonomycin, nigericin, narasin, monensin and its methylated derivative, lasalocid and its bromo derivative, and gramicidin D, most specific to monovalent cations, were at least 35-fold more active in vitro against P. falciparum than against the two other mammalian cell lines. The enhanced ability to penetrate the erythrocyte membrane after infection could be a factor that determines ionophore selectivity for infected erythrocytes.

Initial extracellular development in vitro of erythrocytic stages of malaria parasites (Plasmodium falciparum)

Merozoites of Plasmodium falciparum placed in culture medium with a 50% erythrocyte extract and supplemented with ATP and pyruvate differentiated extracellularly into early trophic forms. Erythrocyte extract prepared by sonication was found superior to extract prepared by freezing and thawing. Under the best conditions, up to 30% of the merozoites showed some development after 16 hr of incubation and approximately 5% developed into larger forms, often ring-shaped and occasionally showing pigment. The small as well as the larger forms took up the fluorescent dye rhodamine 123. Under similar conditions, partial further development was also obtained of young rings freed from their host cells. Again, the sonicated erythrocyte extract gave better development than the frozen-thawed extract, and ATP with pyruvate had a marked favorable effect. These parasites had both a plasma membrane and a surrounding closely apposed parasitophorous membrane, whereas the forms derived by extracellular development of merozoites had only their plasma membrane. We conclude that initial development requires neither an intact erythrocyte nor a parasitophorous membrane.

Possible roles of Ca2+ and cGMP as mediators of the exflagellation of Plasmodium berghei and Plasmodium falciparum

The roles of Ca2+ and cyclic nucleotides as secondary, intracellular messengers for exflagellation of Plasmodium berghei and Plasmodium falciparum were investigated. Treatment with Ca2+ antagonists such as TMB-8 (an inhibitor of intracellular Ca2+ release) or W-7 (a calmodulin inhibitor) strongly inhibited exflagellation induced by alkaline medium at pH 8.0 whereas EGTA (a Ca2+ chelator) or nicardipine and nifedipine (Ca2+ channel inhibitors) had no effect. These results may indicate that mobilization of parasites' internal resources of Ca2+ is a prerequisite for exflagellation. Agents which increase cAMP levels did not induce exflagellation at the non-permissive pH of 7.3, and had no significant inhibitory effect at the permissive pH of 8.0. IBMX (cAMP/cGMP-phosphodiesterase inhibitor), however, enhanced exflagellation at pH 7.3, indicating the possibility that cGMP, but not cAMP, may be involved in the induction of exflagellation. Furthermore, cGMP or agents which increase cGMP levels such as nitroprusside (a potent activator of guanylate cyclase), enhanced exflagellation at pH 7.3, whereas N-methyl-hydroxylamine (guanylate cyclase inhibitor) inhibited the exflagellation at pH 8.0. From these results, it may be concluded that the induction of exflagellation requires both Ca2+ mobilization and an increase in cGMP levels.