Methaemoglobinaemia and the radical curative efficacy of 8-aminoquinoline antimalarials

Methaemoglobin results from the oxidation of ferrous to ferric iron in the centre of the haem moeity of haemoglobin. The production of dose-dependent methaemoglobinaemia by 8-aminoquinoline antimalarial drugs appears to be associated with, but is not directly linked to therapeutic efficacy against latent vivax and ovale malarias. Iatrogenic methaemoglobinaemia may be a useful pharmacodynamic measure in 8-aminoquinoline drug and dose optimization.

The Synthesis of Malonganenone Analogues for Antiparasitic Structure-Activity Relationship Analyses

<p>The most lethal causative species of malaria, Plasmodium falciparum, has been reported as developing resistance against current antimalarial drugs in South-East Asia. New antimalarial drugs, especially those with novel modes of action, need to be established before resistance spreads. The marine natural products malonganenones A, B, and C, isolated from the gorgonian Leptogorgia gilchristi, have recently been shown to inhibit P. falciparum parasite growth. Therefore, a library of malonganenone analogues were synthesised for structure activity relationship analysis. A range of purines, purinones, and pyrimidines were alkylated with simple terpenoid chains to generate malonganenone A and B analogues, while malonganenone C analogues were made by acetylation or formylation, then methylation of terpenoid amines. The compounds were moderately active against P. falciparum infected red blood cells, but exhibited significant activity against Trypanosoma brucei, the parasite responsible for African sleeping sickness. Off target activity was assessed by assay against Escherichia coli, Staphylococcus aureus, Steptococcus uberis and HeLa cells. The overall structureactivity relationship analysis resulted in the identification of lead candidate, geranylgeranyl imidazole (146), which had IC50 values of 10.2 μM and 3.4 μM against P. falciparum and T. brucei, respectively. In addition, the minimum inhibitory concentration of 146 against S. uberis and S. aureus was 16 – 32 μM and 128 μM, respectively. Compound 146 was inactive against E. coli and was also non-toxic to HeLa cells. In addition, a geometric mixture of E and Z isomers at the alkene closest to the imidazole head group was more active than just the E isomer as for 146, which suggested the Z isomer was more active than the E isomer. Therefore, the lead compound identified within this project was the 2Z isomer of geranylgeranyl imidazole.</p>

The Synthesis of Malonganenone Analogues for Antiparasitic Structure-Activity Relationship Analyses

<p>The most lethal causative species of malaria, Plasmodium falciparum, has been reported as developing resistance against current antimalarial drugs in South-East Asia. New antimalarial drugs, especially those with novel modes of action, need to be established before resistance spreads. The marine natural products malonganenones A, B, and C, isolated from the gorgonian Leptogorgia gilchristi, have recently been shown to inhibit P. falciparum parasite growth. Therefore, a library of malonganenone analogues were synthesised for structure activity relationship analysis. A range of purines, purinones, and pyrimidines were alkylated with simple terpenoid chains to generate malonganenone A and B analogues, while malonganenone C analogues were made by acetylation or formylation, then methylation of terpenoid amines. The compounds were moderately active against P. falciparum infected red blood cells, but exhibited significant activity against Trypanosoma brucei, the parasite responsible for African sleeping sickness. Off target activity was assessed by assay against Escherichia coli, Staphylococcus aureus, Steptococcus uberis and HeLa cells. The overall structureactivity relationship analysis resulted in the identification of lead candidate, geranylgeranyl imidazole (146), which had IC50 values of 10.2 μM and 3.4 μM against P. falciparum and T. brucei, respectively. In addition, the minimum inhibitory concentration of 146 against S. uberis and S. aureus was 16 – 32 μM and 128 μM, respectively. Compound 146 was inactive against E. coli and was also non-toxic to HeLa cells. In addition, a geometric mixture of E and Z isomers at the alkene closest to the imidazole head group was more active than just the E isomer as for 146, which suggested the Z isomer was more active than the E isomer. Therefore, the lead compound identified within this project was the 2Z isomer of geranylgeranyl imidazole.</p>

Can Good Products Drive Out Bad? A Randomized Intervention in the Antimalarial Medicine Market in Uganda

How can quality be improved in markets in developing countries, which are known to be plagued by substandard and counterfeit (“fake” , in short) products? We study the market for antimalarial drugs in Uganda, where we randomly assign entry of a retailer (NGO) providing a superior product - an authentic drug priced below the market - and investigate how incumbent firms and consumers respond. We find that the presence of the NGO had economically important effects. Approximately one year after the new market actor entered, the share of incumbent firms selling fake drugs dropped by more than 50% in the intervention villages, with higher quality drugs sold at significantly lower prices. Household survey evidence further shows that the quality improvements were accompanied by consumers expecting fewer fake drugs sold by drug stores. The intervention increased use of the antimalarial drugs overall. The results are consistent with a simple model where the presence of a seller committed to high quality, as opposed to an average firm, strengthens reputational incentives for competing firms to improve quality in order to not be forced out of the market, leading to ‘good driving out bad’.

Study of Tissue-Specific Reactive Oxygen Species Formation by Cell Membrane Microarrays for the Characterization of Bioactive Compounds

The production of reactive oxygen species (ROS) increases considerably in situations of cellular stress, inducing lipid peroxidation and multiple alterations in proteins and nucleic acids. However, sensitivity to oxidative damage varies between organs and tissues depending on the triggering process. Certain drugs used in the treatment of diverse diseases such as malaria have side effects similar to those produced by oxidative damage, although no specific study has been conducted. For this purpose, cell membrane microarrays were developed and the superoxide production evoked by the mitochondrial activity was assayed in the presence of specific inhibitors: rotenone, antimycin A and azide. Once the protocol was set up on cell membrane isolated from rat brain areas, the effect of six antimalarial drugs (atovaquone, quinidine, doxycycline, mefloquine, artemisinin, and tafenoquine) and two essential oils (Rosmarinus officinalis and Origanum majoricum) were evaluated in multiple human samples. The basal activity was different depending on the type of tissue, the liver, jejunum and adrenal gland being the ones with the highest amount of superoxide. The antimalarial drugs studied showed specific behavior according to the type of human tissue analyzed, with atovaquone and quinidine producing the highest percentage of superoxide formation, and doxycycline the lowest. In conclusion, the analysis of superoxide production evaluated in cell membranes of a collection of human tissues allowed for the characterization of the safety profile of these antimalarial drugs against toxicity mediated by oxidative stress.

How Antimalarials and Antineoplastic Drugs can Interact in Combination Therapies: a Perspective on the Role of PPT1 Enzyme

: Antimalarial drugs from different classes have demonstrated anticancer effects in different types of cancer cells, but their complete mode of action in cancer remains unknown. Recently, several studies reported the important role of palmitoyl-protein thioesterase 1 (PPT1), a lysosomal enzyme, as the molecular target of chloroquine and its derivates in cancer. It was also found that PPT1 is overexpressed in different types of cancer, such as breast, colon, etc. Our group has found a synergistic interaction between antimalarial drugs, such as mefloquine, artesunate and chloroquine and antineoplastic drugs in breast cancer cells, but the mechanism of action was not determined. Here, we describe the importance of autophagy and lysosomal inhibitors in tumorigenesis and hypothesize that other antimalarial agents besides chloroquine could also interact with PPT1 and inhibit the mechanistic target of rapamycin (mTOR) signalling, an important pathway in cancer progression. We believe that PPT1 inhibition results in changes in the lysosomal metabolism that result in less accumulation of antineoplastic drugs in lysosomes, which increases the bioavailability of the antineoplastic agents. Taken together, these mechanisms help to explain the synergism of antimalarial and antineoplastic agents in cancer cells.

The Antimalaria Drug Artesunate Inhibits Porcine Reproductive and Respiratory Syndrome Virus Replication via Activating AMPK and Nrf2/HO-1 Signaling Pathways

Porcine Reproductive and Respiratory Syndrome virus (PRRSV) causes significant economic losses to the pork industry worldwide. Currently, vaccine strategies provide limited protection against PRRSV transmission, and no effective drug is commercially available. Therefore, there is an urgent need to develop novel antiviral strategies to prevent PRRSV pandemics. This study showed that artesunate (AS), one of the antimalarial drugs, potently suppressed PRRSV replication in Marc-145 cells and ex vivo primary porcine alveolar macrophages (PAMs) at micromolar concentrations. Furthermore, we demonstrated that this suppression was closely associated with AS-activated AMPK (energy homeostasis) and Nrf2/HO-1 (inflammation) signaling pathways. AS treatment promoted p-AMPK, Nrf2 and HO-1 expression, and thus inhibited PRRSV replication in Marc-145 and PAM cells in a time- and dose-dependent manner. These effects of AS were reversed when AMPK or HO-1 gene was silenced by siRNA. In addition, we demonstrated that AMPK works upstream of Nrf2/HO-1 as its activation by AS is AMPK-dependent. Adenosine phosphate analysis showed that AS activates AMPK via improving AMP/ADP:ATP ratio rather than direct interaction with AMPK. Altogether, our findings indicate that AS could be a promising novel therapeutics for controlling PRRSV and that its anti-PRRSV mechanism, which involves the functional link between energy homeostasis and inflammation suppression pathways, may provide opportunities for developing novel antiviral agents. Importance Porcine reproductive and respiratory syndrome virus (PRRSV) infections have been continuously threatened the pork industry worldwide. Vaccination strategies provide very limited protection against PRRSV infection, and no effective drug is commercially available. We show that artesunate (AS), one of the antimalarial drugs, is a potent inhibitor against PRRSV replication in Marc-145 cells and ex vivo primary porcine alveolar macrophages (PAMs). Furthermore, we demonstrate that AS inhibits PRRSV replication via activation of AMPK-dependent Nrf2/HO-1 signaling pathways, revealing a novel link between energy homeostasis (AMPK) and inflammation suppression (Nrf2/HO-1) during viral infection. Therefore, we believe that AS may be a promising novel therapeutics for controlling PRRSV, and its anti-PRRSV mechanism may provide a potential strategy to develop novel antiviral agents.

Distribution of Pfmdr 1 and Kelch 13 Genes Among the Children 5 Years and Below Attending a Secondary Health Facility, South-West, Nigeria.

Background: Malaria is a major public health concern in some part of the world especially in the tropical Africa where children are more vulnerable. The occurrence of resistant gene in Plasmodium falciparum to some antimalarial drugs could increase the malaria morbidity and mortality among the children. The study evaluates the distribution of P. falciparum resistant kelch protein gene on chromosome 13 (PfKelch 13) and multidrug resistant (Pfmdr1) mutant genes among children aged five years and below who attended Mother and Child Hospital, Akure, Nigeria. Methods: Thin and thick smears were prepared from the blood collected aseptically through venepuncture from five hundred (500) children (age 5years and below). Two hundred (200) malaria positive samples were randomly selected from the 500 samples for PCR analysis to detect Pfmdr1 and Kelch 13 mutant genes from the positive samples. Discussion: The results showed that of the 500 respondents who gave their consent to participate in the study, 288 (57.6%) were males while 212 (42.4%) were females. The distribution of Pfmdr1 are; mixed group (mutant/wild) 38.5% (77/200), mutant gene 35.5% (71/200), wild gene 20.5% (41/200) and the resistant genes were absent in 5.5% (11/200) of the infected children. The mixed group of Pfmdr1 gene was higher among infants (51.9%), male (44.3%), children with birth order 4 (60.0%) and children that have blood group B (51.3%), however, there is no significant difference in the distribution of Pfmdr1 between gender (χ2 = 0.634, df = 1, p>0.05). There was a point mutation in the codon position 557 where the amino acid Alanine was replaced by Serine in the PfK13. The research revealed high prevalence of Pfmdr1 mutant genes and point mutation in the PfK13 gene of P. falciparum among children which may be as a result of treatment of malaria with different antimalarial drugs which the parasite has developed resistance against. It is therefore important to administer other malaria drugs apart from the drugs the parasite has developed resistance against.

Molecular Surveillance and Ex Vivo Drug Susceptibilities of Plasmodium vivax Isolates From the China–Myanmar Border

Drug resistance in Plasmodium vivax may pose a challenge to malaria elimination. Previous studies have found that P. vivax has a decreased sensitivity to antimalarial drugs in some areas of the Greater Mekong Sub-region. This study aims to investigate the ex vivo drug susceptibilities of P. vivax isolates from the China–Myanmar border and genetic variations of resistance-related genes. A total of 46 P. vivax clinical isolates were assessed for ex vivo susceptibility to seven antimalarial drugs using the schizont maturation assay. The medians of IC50 (half-maximum inhibitory concentrations) for chloroquine, artesunate, and dihydroartemisinin from 46 parasite isolates were 96.48, 1.95, and 1.63 nM, respectively, while the medians of IC50 values for piperaquine, pyronaridine, mefloquine, and quinine from 39 parasite isolates were 19.60, 15.53, 16.38, and 26.04 nM, respectively. Sequence polymorphisms in pvmdr1 (P. vivax multidrug resistance-1), pvmrp1 (P. vivax multidrug resistance protein 1), pvdhfr (P. vivax dihydrofolate reductase), and pvdhps (P. vivax dihydropteroate synthase) were determined by PCR and sequencing. Pvmdr1 had 13 non-synonymous substitutions, of which, T908S and T958M were fixed, G698S (97.8%) and F1076L (93.5%) were highly prevalent, and other substitutions had relatively low prevalences. Pvmrp1 had three non-synonymous substitutions, with Y1393D being fixed, G1419A approaching fixation (97.8%), and V1478I being rare (2.2%). Several pvdhfr and pvdhps mutations were relatively frequent in the studied parasite population. The pvmdr1 G698S substitution was associated with a reduced sensitivity to chloroquine, artesunate, and dihydroartemisinin. This study suggests the possible emergence of P. vivax isolates resistant to certain antimalarial drugs at the China–Myanmar border, which demands continuous surveillance for drug resistance.