Type II Fatty Acid Biosynthesis Is Essential for Plasmodium falciparum Sporozoite Development in the Midgut of Anopheles Mosquitoes

The prodigious rate at which malaria parasites proliferate during asexual blood-stage replication, midgut sporozoite production, and intrahepatic development creates a substantial requirement for essential nutrients, including fatty acids that likely are necessary for parasite membrane formation. Plasmodium parasites obtain fatty acids either by scavenging from the vertebrate host and mosquito vector or by producing fatty acids de novo via the type two fatty acid biosynthesis pathway (FAS-II). Here, we study the FAS-II pathway in Plasmodium falciparum, the species responsible for the most lethal form of human malaria. Using antibodies, we find that the FAS-II enzyme FabI is expressed in mosquito midgut oocysts and sporozoites as well as liver-stage parasites but not during the blood stages. As expected, FabI colocalizes with the apicoplast-targeted acyl carrier protein, indicating that FabI functions in the apicoplast. We further analyze the FAS-II pathway in Plasmodium falciparum by assessing the functional consequences of deleting fabI and fabB/F. Targeted deletion or disruption of these genes in P. falciparum did not affect asexual blood-stage replication or the generation of midgut oocysts; however, subsequent sporozoite development was abolished. We conclude that the P. falciparum FAS-II pathway is essential for sporozoite development within the midgut oocyst. These findings reveal an important distinction from the rodent Plasmodium parasites P. berghei and P. yoelii, where the FAS-II pathway is known to be required for normal parasite progression through the liver stage but is not required for oocyst development in the Anopheles mosquito midgut.     

In Vitro Culture,Drug Sensitivity,and Transcriptome of Plasmodium Vivax Hypnozoites

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2-Hexadecynoic acid inhibits plasmodial FAS-II enzymes and arrests erythrocytic and liver stage Plasmodium infections

Acetylenic fatty acids are known to display several biological activities, but their antimalarial activity has remained unexplored. In this study, we synthesized the 2-, 5-, 6-, and 9-hexadecynoic acids (HDAs) and evaluated their in vitro activity against erythrocytic (blood) stages of Plasmodium falciparum and liver stages of Plasmodium yoelii infections. Since the type II fatty acid biosynthesis pathway (PfFAS-II) has recently been shown to be indispensable for liver stage malaria parasites, the inhibitory potential of the HDAs against multiple P. falciparum FAS-II (PfFAS-II) elongation enzymes was also evaluated. The highest antiplasmodial activity against blood stages of P. falciparum was displayed by 5-HDA (IC₅₀ value 6.6 μg/ml), whereas the 2-HDA was the only acid arresting the growth of liver stage P. yoelii infection, in both flow cytometric assay (IC₅₀ value 2-HDA 15.3 μg/ml, control drug atovaquone 2.5 ng/ml) and immunofluorescence analysis (IC₅₀ 2-HDA 4.88 μg/ml, control drug atovaquone 0.37 ng/ml). 2-HDA showed the best inhibitory activity against the PfFAS-II enzymes PfFabI and PfFabZ with IC₅₀ values of 0.38 and 0.58 μg/ml (IC₅₀ control drugs 14 and 30 ng/ml), respectively. Enzyme kinetics and molecular modeling studies revealed valuable insights into the binding mechanism of 2-HDA on the target enzymes. All HDAs showed in vitro activity against Trypanosoma brucei rhodesiense (IC₅₀ values 3.7–31.7 μg/ml), Trypanosoma cruzi (only 2-HDA, IC₅₀ 20.2 μg/ml), and Leishmania donovani (IC₅₀ values 4.1–13.4 μg/ml) with generally low or no significant toxicity on mammalian cells. This is the first study to indicate therapeutic potential of HDAs against various parasitic protozoa. It also points out that the malarial liver stage growth inhibitory effect of the 2-HDA may be promoted via PfFAS-II enzymes. The lack of cytotoxicity, lipophilic nature, and calculated pharmacokinetic properties suggests that 2-HDA could be a useful compound to study the interaction of fatty acids with these key P. falciparum enzymes.     

A rapid technique to predict malting quality in barley prior to harvest

Samples of grain from three spring barley cultivars of differing malting quality were collected at regular intervals during four weeks prior to harvest. The samples were dried, then assessed for relative grain hardness using the "Milling Energy" test. Ranking order of the cultivars for this character, which relates strongly to malting quality, was unaltered throughout. In a further experiment, it was demonstrated that selection for milling energy could be successfully practised on oven-dried grain collected six weeks after ear emergence.     

DSC — A Valuable Tool in Heterocyclic Synthesis

Many decomposition and ring closure reactions in the azide series (e.g. a cyclization and rearrangement reaction sequence from the azido ester 1 via the ethoxy oxazole 2 to the oxazolone 3), intramolecular rearrangement reactions (e.g. via a-oxoketenes), self condensation of p-octopamine and also reactions with two reactants and the influence of solvents at the reaction conditions were studied using DSC (Differential Scanning Calorimetry).     

Elevated adiponectin and sTNFRII serum levels can predict progression to hepatocellular carcinoma in patients with compensated HCV1 cirrhosis

Background and aims

An obesity-related altered adipose tissue secretion is suggested as a risk factor for hepatocellular carcinoma (HCC) in patients with hepatitis C virus (HCV) cirrhosis. However, no prospective study has yet examined the predictive value of circulating adipokines and immuno-inflammatory biomarkers regarding this risk.

Methods

This was a case-control study nested in a prospective French national cohort of HCV-infected patients with biopsy-proven compensated cirrhosis.We selected 56 HCV1-infected patients who subsequently developed HCC (cases), and 96 controls matched for age, gender and diabetes, not developing HCC after a similar period. Adipokines and immuno-inflammatory biomarkers were determined on baseline frozen serum samples. Their influence on the occurrence of HCC was assessed using a mixed logistic regression model under univariate analysis and a backward stepwise procedure under multivariate analysis.

Results

The patients were mostly male (62.5%) with active HCV replication (83%) and had been followed for a median duration of 6.3 years during which 44.4% achieved a sustained viral response. Higher adiponectinemia levels were found in cases than in controls (P = 0.01). Levels of the immuno-inflammatory markers were similar in both groups except sTNFRII >5,000 pg/mL (52% cases versus 24% controls; P = 0.001). No marker was associated with histological steatosis. Under multivariate analysis, baseline adiponectin and sTNFRII levels were independently associated with the occurrence of HCC,alongside previous excessive alcohol intake and HCV viral load.

Conclusions

High baseline circulating adiponectin and sTNFRII levels were associated with an increased risk of HCC in patients with HCV1 cirrhosis, independently of their HCV replication status.