No abstract

Several protozoan parasites have been shown to undergo a form of programmed cell death that exhibits morphological features associated with metazoan apoptosis. These include the rodent malaria parasite, Plasmodium berghei. Malaria zygotes develop in the mosquito midgut lumen, forming motile ookinetes. Up to 50% of these exhibit phenotypic markers of apoptosis; as do those grown in culture. We hypothesised that naturally occurring signals induce many ookinetes to undergo apoptosis before midgut traversal. To determine whether nitric oxide and reactive oxygen species act as such triggers, ookinetes were cultured with donors of these molecules. Exposure to the nitric oxide donor SNP induced a significant increase in ookinetes with condensed nuclear chromatin, activated caspase-like molecules and translocation of phosphatidylserine that was dose and time related. Results from an assay that detects the potential-dependent accumulation of aggregates of JC-1 in mitochondria suggested that nitric oxide does not operate via loss of mitochondrial membrane potential. L-DOPA (reactive oxygen species donor) also caused apoptosis in a dose and time dependent manner. Removal of white blood cells significantly decreased ookinetes exhibiting a marker of apoptosis in vitro. Inhibition of the activity of nitric oxide synthase in the mosquito midgut epithelium using L-NAME significantly decreased the proportion of apoptotic ookinetes and increased the number of oocysts that developed. Introduction of a nitric oxide donor into the blood meal had no effect on mosquito longevity but did reduce prevalence and intensity of infection. Thus, nitric oxide and reactive oxygen species are triggers of apoptosis in Plasmodium ookinetes. They occur naturally in the mosquito midgut lumen, sourced from infected blood and mosquito tissue. Up regulation of mosquito nitric oxide synthase activity has potential as a transmission blocking strategy.

Schistosoma mansoni is one of the parasites causing schistosomiasis, a disease which threatens millions of people all over the world. Traditional chemical drugs are not fully effective against schistosomaisis due to the evolving drug resistant worm strains, so exploring new remedies derived from natural products is a good way to fight schistosomiasis. In the present investigation two natural products, Nigella sativa oil and Chroococcus turgidus extract were used separately or in a combination to explore their effect on S. mansoni. The infected mice treated with Chroococcus turgidus extract or/and sativa seed oil showed a significant decrease in the total worm burden. The total number of deposited eggs by females of S. mansoni was significantly decreased in the liver of mice treated with Chroococcus turgidus extract or/and sativa seed oil. However, in the intestine, the number of eggs was significantly reduced in mice treated with algal extract and those treated with both algal extract and oil. Fecundity of female S. mansoni showed a significant decrease from mice treated with algal extract or/and sativa seed oil. According to SEM investigations the tegmental surface, oral and ventral suckers of worms also showed considerable changes; as the tubercles lost their spines, some are swollen and torn out. The suckers become edematous and enlarged while the tegmental surface is damaged due to the treatment with Chroococcus turgidus extract or/and sativa seed oil. In conclusion, the Nigella sativa oil and Chroococcus turgidus extract are promising natural compounds that can be used in fighting schistosomiasis.

Culex pipiens is the most abundant mosquito in Al-Madinah Al-Munawwarah region, Saudi Arabia, transmitting several diseases like elephantiasis, avian malaria, and arboviruses. It has become resistant to several insecticides worldwide, and the search for new alternatives should be prioritized. Because of their biological profile and eco-friendly nature, ionic liquids (ILs) have recently attracted the attention of biologists. The present study was carried out to evaluate the effect of six ILs against C. pipiens larvae. Larval mortality, LC 50 , LC 90 , LT 50 and residual activity of ILS were determined. Aqueous solutions of tested ILs showed up to 100% larval mortality 24 h after exposure. Significant concentration-and time-based differences in larval mortality were found for a given IL as well as between different ILs. Ultimately, the ILs tested in the current study could be arranged in descending order according to their toxicity against larvae as follows: IL7, IL5, IL4, IL1, IL2 and IL6.