Physicochemical, biological and β-haematin inhibiting activity of pyrido-dibemequines, pyrido[1,2-α]benzimidazoles and their derivatives

There is an urgent need for new antimalarials following the emergence of Plasmodium falciparum strains with reduced sensitivity to the currently used artemisinin combination therapies. Classical aminoquinoline-based drugs inhibit the formation of haemozoin (HZ) thereby causing parasite death from the cellular accumulation of toxic 'free' haem. Coincidentally, this immutable pathway also exists in Schistosoma mansoni, and presents a vulnerable target for drug design in these haematophagus organisms. Therefore, it would be of interest to explore novel scaffolds that can inhibit HZ formation as well as exploit the merits of established drugs via structural modifications that would harness their pharmacological and pharmacokinetic advantages while circumventing their therapeutic shortcomings. This project investigated the physicochemical, biological and mechanistic profiles of pyrido-dibemequine (pDBQ) and pyrido[1,2-α]benzimidazole (PBI) derivatives whose structural motifs were informed by previously synthesised prototype molecules. Specifically, the aqueous solubility, membrane permeability, lipophilicity, metabolic stability and potential for cardiotoxicity of seven pDBQs, their metabolites and ten PBIs were tested through computational and experimental methods. In addition, their antiplasmodial and antischistosomal activities were determined and correlated with their respective physicochemical properties. As regards mechanistic evaluation, their ability to inhibit formation of abiotic HZ, β-haematin (βH), was assessed and intracellular inhibition of HZ formation probed. The pDBQs constitute reversed chloroquines with a 4-aminoquinoline nucleus hybridised to a dibenzylmethylamine side group that serves as a chemosensitising moiety. The pDBQ derivatives showed moderate to high solubility (52 - 197 μM) and permeability (LogPₐₚₚ: -4.6 - -3.6) at pH 6.5. Their lipophilicity, indexed by cLogP, ranged between 3.7 and 5.6 while the mean LogD at both cytosolic (7.4) and vacuolar (5.0) pH was 3.15 and 0.93, respectively. The compounds also showed low-nanomolar range antiplasmodial activity against both chloroquine (CQ)-sensitive (CQS) and resistant (CQR) strains (IC₅₀ range CQS: 14.4 - 126.6 nM, CQRᴰᵈ²: 44.5 - 162 nM and CQR⁷ᴳ⁸: 69.6 - 307.1 nM), with no discernible cross-resistance with CQ and the antiplasmodial activity directly correlated with lipophilicity. Mechanistically, all the pDBQs inhibited βH formation (IC₅₀: 13 - 25 μM) and haem-pyridine fractionation profiles revealed they produced a CQ-like dose-dependent increase in toxic 'free' haem with corresponding decrease in HZ levels. Predicted human-Ether-a-Go-Go-Related Gene (hERG) channel inhibition pIC₅₀ ranged between 6.2 and 6.6, and correlated strongly with the cLogP and molecular weight. The derivatives were also highly susceptibility to microsomal metabolism, with N-dealkylation identified as the main biotransformation route. The pDBQ metabolites exhibited solubility and membrane permeability profiles similar to the parent compounds at pH 6.5, albeit with reduced lipophilicity (cLogP range: 2.3 - 3.5). Their βH inhibition activity (IC₅₀: 15 - 24 μM) was also comparable to the parent compounds as were the haem-pyridine fractionation profiles. However, they showed greater antiplasmodial activity, with 4/7 derivatives exhibiting IC₅₀ < 80 nM against PƒDd2 (CQR strain). The metabolites had reduced hERG channel inhibition potential (pIC₅₀: 5.0 - 5.7) and significantly improved metabolic stability upon incubation with mouse and human liver microsomes. The PBIs comprise molecules with structural likeness to CQ, including a planar heterocyclic moiety and a basic amine side group. PBI analogues showed low to moderate solubility (<5 - 80 μM) and were moderately lipophilic (mean LogD7.4: 3.04). Although most of the derivatives were stable in liver microsomes, their predicted hERG channel inhibition potential was higher (pIC₅₀: 6.11 - 7.50), presumably due to their high molecular weights. All but one derivative had submicromolar activity against CQS and CQR strains, with analogues bearing halo-substituents on the left of the PBI core showing the best antiplasmodial activity (mean IC₅₀: CQS = 26.7 nM and CQR = 30.0 nM), highest selectivity (188 - 341) as well as complete cures in P. berghei-infected mice. The PBIs also inhibited βH formation (IC₅₀: 6.8 - 120 μM) but did not all display intracellular inhibition of HZ formation. All derivatives were active against juvenile (mean IC₅₀: 1.97 μM) and adult (mean IC₅₀: 4.38 μM) schistosomes, with the 3, 4-dichloro-substituted analogue exhibiting 48% reduction of worm burden in vivo. In summary, the pDBQs evaluated in this project constitute potent antiplasmodial inhibitors of HZ formation but whose activity is compromised by metabolic and hERG liability while their metabolites seem to possess improved biological and physicochemical features. The observed activity of the PBIs against P. falciparum and S. mansoni complements the already-established broad antimicrobial potency of this chemotype

Synthesis and biological characterisation of ester and amide derivatives of fusidic acid as antiplasmodial agents

A series of novel fusidic acid (FA) derivatives was synthesized by replacing the carboxylic acid group with various ester and amide groups and evaluated in vitro for their antiplasmodial activity against the chloroquine-sensitive NF54 and multidrug-resistant K1 strains of the malarial parasite Plasmodium falciparum. Most of these derivatives showed a 4-49 and 5-17-fold increase in activity against NF54 and KI strains, respectively, as compared to FA and had a good selectivity index. These derivatives are stable over the incubation period and do not appear to be prodrugs of fusidic acid

Racial Ethnic Health Disparities: A Phenomenological Exploration of African American Adults with Diabetes Complications.

Racial/ethnic minority groups experience a higher mortality rate, a lower life expectancy, and worse mental health outcomes than non-Hispanic in the United States. There is a scarcity of qualitative studies on racial/ethnic health disparities. The purpose of this hermeneutic phenomenological study was to explore the personal experiences, attitudes, and perspectives of 6 African American adults with chronic health issues related to diabetes through a face-to-face interview. Social cognitive theory and health belief model guided the study. The participants were recruited through purposeful sampling. The data were coded using axial and thematic coding and subsequently analyzed through phenomenological interpretive inquiry. The participants\u27 perceived experiences were summarized in 7 themes (Beliefs and perceptions, denial, attitudes, treatment cost, neighborhood effect, juggling work and family related stress, and need for positive motivation and support). The participants\u27 experiences with their health outcomes were influenced by internal and some external factors that were beyond their control. Social change implications include public policy makers integrating health policies that are designed for socioeconomic inequality in the neighborhood and improving health insurance company policies on treatment copays. Public health and other human services professionals can develop health intervention to assist minorities with chronic health issues to manage their disease and overcome barriers related to the disease

Stereotypes, advertising and social identity : a theoretical study with reference to the university as a space of cultural negotiation

This study is an investigation into the stereotypes used in advertisements designed to appeal to university students’ sense of having a social identity, taking the situation at Nelson Mandela Metropolitan University (NMMU) as being representative of university campuses as, among other things, social and cultural space. The study assumes that a university is a site of cultural negotiation, and as such may be viewed as a place where identities are formed and readjusted to conform to stereotypes popularised by influential social models as portrayed in the media. Moreover, with the process of globalization, which distributes stereotypical images globally, one would assume that advertising at NMMU functions in a similar way to its mode of functioning in most parts of the world. Although such media (advertisements) exist in various forms, the scope of the research for this study was limited to print advertisements. Advertisements relevant to the concerns of this study are found everywhere at South African universities. Today, the latest trend for companies like Mr. Price, Standard Bank, Truworths, Red Bull, and Axe, among others, is to sponsor university events, that way creating the opportunity to advertise their products or services to students. Moreover, the notice boards of South African universities are filled with posters advertising new products in the market. In addition to all this, the general South African goods and services market is flooded with magazines that contain stereotype-promoting advertisements targeting students or, in general, young adults. For the purposes of this study, a ‘stereotype’ is understood as an iconic site of identification which functions as a generalized model for social behaviour. In this sense, a ‘stereotype’ may also be understood as a representation of an ‘ideal self’. The purpose of this study is threefold: firstly, to show how and why students may be vulnerable to the stereotypes identified in terms of Lacan’s theory of the ‘mirror stage’; secondly, to identify and categorize the various stereotypes used in advertising to appeal to the student’s sense of social identity, and thirdly, to show that advertisements can be misleading in so far as stereotyping ignores the specificity of every student’s personal social situation and creates false expectations on the part of the target students

Safety of Artemether-Lumefantrine Exposure in First Trimester of Pregnancy: An Observational Cohort.

There is limited data available regarding safety profile of artemisinins in early pregnancy. They are, therefore, not recommended by WHO as a first-line treatment for malaria in first trimester due to associated embryo-foetal toxicity in animal studies. The study assessed birth outcome among pregnant women inadvertently exposed to artemether-lumefantrine (AL) during first trimester in comparison to those of women exposed to other anti-malarial drugs or no drug at all during the same period of pregnancy. Pregnant women with gestational age <20 weeks were recruited from Maternal Health clinics or from monthly house visits (demographic surveillance), and followed prospectively until delivery. 2167 pregnant women were recruited and 1783 (82.3%) completed the study until delivery. 319 (17.9%) used anti-malarials in first trimester, of whom 172 (53.9%) used (AL), 78 (24.4%) quinine, 66 (20.7%) sulphadoxine-pyrimethamine (SP) and 11 (3.4%) amodiaquine. Quinine exposure in first trimester was associated with an increased risk of miscarriage/stillbirth (OR 2.5; 1.3-5.1) and premature birth (OR 2.6; 1.3-5.3) as opposed to AL with (OR 1.4; 0.8-2.5) for miscarriage/stillbirth and (OR 0.9; 0.5-1.8) for preterm birth. Congenital anomalies were identified in 4 exposure groups namely AL only (1/164[0.6%]), quinine only (1/70[1.4%]), SP (2/66[3.0%]), and non-anti-malarial exposure group (19/1464[1.3%]). Exposure to AL in first trimester was more common than to any other anti-malarial drugs. Quinine exposure was associated with adverse pregnancy outcomes which was not the case following other anti-malarial intake. Since AL and quinine were used according to their availability rather than to disease severity, it is likely that the effect observed was related to the drug and not to the disease itself. Even with this caveat, a change of policy from quinine to AL for the treatment of uncomplicated malaria during the whole pregnancy period could be already envisaged.\u

The Age Factor in Linguistic Variation: A Reference to the Use of Kiswahili at Busia Border Town in East Africa

This paper deals with age as a linguistic variable in the use of Kiswahili among ordinary citizens in Busia town at the Kenya-Uganda border. I chose age over other possible factors because it emerged as a salient ground for variation in the use of Kiswahili among ordinary citizens in my PhD research on language as a lived practice. Thus, the paper is intended to demonstrate how the ordinary citizens in Busia use Kiswahili across three different age categories: the youth, the adults, and the elderly, and what this variation reveals about how Kiswahili is socially construed and constructed by its speakers. Specifically, three objectives are embedded in the discussions of the paper, 1) to ascertain the age-related patterns of the use of Kiswahili in Busia town, 2) to explore the salient age-related linguistic forms of Kiswahili used by each age category, and 3) to provide a sociolinguistic account for the patterns and forms that emerge. The findings reveal several complex age-based patterns of the use of Kiswahili, but generally show that the youth prefer slang-like and other “sub-standard” forms of Kiswahili, the adults employ some standard forms of Kiswahili but with extensive code-mixing between Kiswahili and English, and the elderly prefer their vernaculars to Kiswahili, which (vernaculars) influence the forms of Kiswahili that they sporadically speak. The paper concludes that Kiswahili, just like any other language, is dynamic and prone to variations based on various contextual and social factors. With this conclusion, the paper recommends further extensive studies that can shade more light on other linguistic variables such as level of education and gender, and how these complement the age variable in the use of Kiswahili within the context of this study

The nanosyntax of spatial deixis

This paper provides a fine-grained morphosyntactic analysis of spatial deixis. We propose that the universal core of spatial deixis is a three-way contrast: Proximal close to speaker', Medial close to hearer', and Distal far from speaker and hearer'. This system arises from three features merged as heads in a single universal functional sequence: Dx(3) > Dx(2) > Dx(1). The hierarchy is understood in terms of superset-subset relations, such that Proximal [Dx(1)] is a subset of Medial [Dx(2) [Dx(1)]], which in turn is a subset of Distal [Dx(3) [Dx(2) [Dx(1)]]]. Evidence comes from patterns of syncretism and morphological containment in the demonstrative systems of a number of genetically diverse languages. Regarding syncretisms, languages can show a transparent three-way morphological contrast, or some sort of syncretism: Medial/Proximal vs. Distal, Distal/Medial vs. Proximal, or a totally syncretic Distal/Medial/Proximal (i.e. a neutral demonstrative). These syncretisms entail that the features responsible for the Proximal and Medial readings be adjacent and that the features responsible for the Distal and Medial readings be adjacent in the fseq. Regarding containment, we show that Proximal can be structurally contained within Medial and that Medial can be structurally contained within Distal, meaning that Medial structures are larger than Proximal structures, and that Distal structures are larger than Medial structures, confirming our hierarchy. We show that these facts are naturally accounted for by nanosyntactic principles of spellout. We end the paper by accounting for potential counterexamples and other issues

Pragmatic strategies in the use of Kiswahili demonstratives

This paper focuses on two spatial Kiswahili demontratives. In Kiswahili, demonstratives have been traditionally treated as morphosyntactic elements that modulate various elements and realize emphatic function. Demonstratives have also been studied as elements that express and facilitate cohesive relations and elements that realize deictic functions in discourse. In this paper we look at Kiswahili demonstratives as used in the standard Kiswahili language in Nairobi city. We argue that besides the traditionally recognized functions, demonstratives in standard Kiswahili are also used to pass subtle discourse messages which can only be explained by taking into account the pragmatic strategies employed in the use of demonstratives in specific discourse settings

Quinine Treatment Selects the pfnhe-1 ms4760-1 Polymorphism in Malian Patients with Falciparum Malaria

Background. The mechanism of Plasmodium falciparum resistance to quinine is not known. In vitro quantitative trait loci mapping suggests involvement of a predicted P. falciparum sodium-hydrogen exchanger (pfnhe-1) on chromosome 13. Methods. We conducted prospective quinine efficacy studies in 2 villages, Kolle and Faladie, Mali. Cases of clinical malaria requiring intravenous therapy were treated with standard doses of quinine and followed for 28 days. Treatment outcomes were classified using modified World Health Organization protocols. Molecular markers of parasite polymorphisms were used to distinguish recrudescent parasites from new infections. The prevalence of pfnhe-1 ms4760-1 among parasites before versus after quinine treatment was determined by direct sequencing. Results. Overall, 163 patients were enrolled and successfully followed. Without molecular correction, the mean adequate clinical and parasitological response (ACPR) was 50.3% (n = 163). After polymerase chain reaction correction to account for new infections, the corrected ACPR was 100%. The prevalence of ms4760-1 increased significantly, from 26.2% (n = 107) before quinine treatment to 46.3% (n = 54) after therapy (P = .01). In a control sulfadoxine-pyrimethamine study, the prevalence of ms4760-1 was similar before and after treatment. Conclusions. This study supports a role for pfnhe-1 in decreased susceptibility of P. falciparum to quinine in the field.Howard Hughes Medical Institute [55005502]; Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health; European and Developing Countries Clinical Trials Partnership [EDCTP IP_07_31060_002]info:eu-repo/semantics/publishedVersio

Quinoxaline-based anti-schistosomal compounds have potent anti-plasmodial activity

The human pathogens Plasmodium and Schistosoma are each responsible for over 200 million infections annually, especially in low- and middle-income countries. There is a pressing need for new drug targets for these diseases, driven by emergence of drug-resistance in Plasmodium and an overall dearth of drug targets against Schistosoma. Here, we explored the opportunity for pathogen-hopping by evaluating a series of quinoxaline-based anti-schistosomal compounds for their activity against P. falciparum. We identified compounds with low nanomolar potency against 3D7 and multidrug-resistant strains. In vitro resistance selections using wildtype and mutator P. falciparum lines revealed a low propensity for resistance. Only one of the series, compound 22, yielded resistance mutations, including point mutations in a non-essential putative hydrolase pfqrp1, as well as copy-number amplification of a phospholipid-translocating ATPase, pfatp2, a potential target. Notably, independently generated CRISPR-edited mutants in pfqrp1 also showed resistance to compound 22 and a related analogue. Moreover, previous lines with pfatp2 copy number variations were similarly less susceptible to challenge with the new compounds. Finally, we examined whether the predicted hydrolase activity of PfQRP1 underlies its mechanism of resistance, showing that both mutation of the putative catalytic triad and a more severe loss of function mutation elicited resistance. Collectively, we describe a compound series with potent activity against two important pathogens and their potential target in P. falciparum.</p