Interrogating alkyl and arylalkylpolyamino (bis)urea and (bis)thiourea isosteres as potent antimalarial chemotypes against multiple lifecycle forms of Plasmodium falciparum parasites

A new series of potent potent aryl/alkylated (bis)urea- and (bis)thiourea polyamine analogues were synthesized and evaluated in vitro for their antiplasmodial activity. Altering the carbon backbone and terminal substituents increased the potency of analogues in the compound library 3-fold, with the most active compounds, 15 and 16, showing half-maximal inhibitory concentrations (IC50 values) of 28 and 30 nM, respectively, against various Plasmodium falciparum parasite strains without any cross-resistance. In vitro evaluation of the cytotoxicity of these analogues revealed marked selectivity towards targeting malaria parasites compared to mammalian HepG2 cells (>5000-fold lower IC50 against the parasite). Preliminary biological evaluation of the polyamine analogue antiplasmodial phenotype revealed that (bis)urea compounds target parasite asexual proliferation, whereas (bis)thiourea compounds of the same series have the unique ability to block transmissible gametocyte forms of the parasite, indicating pluripharmacology against proliferative and non-proliferative forms of the parasite. In this manuscript, we describe these results and postulate a refined structure–activity relationship (SAR) model for antiplasmodial polyamine analogues. The terminally aryl/alkylated (bis)urea- and (bis)thiourea–polyamine analogues featuring a 3-5-3 or 3-6-3 carbon backbone represent a structurally novel and distinct class of potential antiplasmodials with activities in the low nanomolar range, and high selectivity against various lifecycle forms of P. falciparum parasites.South African National Research Foundation (FA2007050300003 & UID: 84627), the University of Pretoria and the South African Medical Research Council Strategic Health Initiatives Partnerships with the Medicines for Malaria Venture.http://www.elsevier.com/locate/bmc2016-08-31hb201

Stable isotopic composition of fossil mammal teeth and environmental change in southwestern South Africa during the Pliocene and Pleistocene

The past 5 million years mark a global change from the warmer, more stable climate of the Pliocene to the initiation of glacial-interglacial cycles during the Pleistocene. Marine core sediment records located off the coast of southwestern Africa indicate aridification and intensified upwelling in the Benguela Current over the Pliocene and Pleistocene. However, few terrestrial records document environmental change in southwestern Africa over this time interval. Here we synthesize new and published carbon and oxygen isotope data of the teeth from large mammals (>6 kg) at Langebaanweg (~5 million years ago, Ma), Elandsfontein (1.0 – 0.6 Ma), and Hoedjiespunt (0.35 – 0.20 Ma), to evaluate environmental change in southwestern Africa between the Pliocene and Pleistocene. The majority of browsing and grazing herbivores from these sites yield enamel 13 C values within the range expected for animals with a pure C3 diet, however some taxa have enamel 13C values that suggest the presence of small amounts C4 grasses at times during the Pleistocene. Considering that significant amounts of C4 grasses require a warm growing season, these results indicate that the winter rainfall zone, characteristic of the region today, could have been in place for the past 5 million years. The average 18O value of the herbivore teeth increases ~4.4‰ between Langebaanweg and Elandsfontein for all taxa except suids. This increase may solely be a function of a change in hydrology between the fluvial system at Langebaanweg and the spring-fed environments at Elandsfontein, or a combination of factors that include depositional context, regional circulation and global climate. However, an increase in regional aridity or global cooling between the early Pliocene and mid-Pleistocene cannot explain the entire increase in enamel 18O values. Spring-fed environments like those at Elandsfontein may have 75 provided critical resources for mammalian fauna in the mid-Pleistocene within an increasingly arid southwestern Africa ecosystem

Pseudoscience : a case study of a South African lifestyle magazine, and a survey of its usage

Thesis (MA)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Across the globe scientists are taking issue with pseudoscience, as well as the role of the media in promoting it. Articles based on pseudoscience, especially those relating to Complementary and Alternative Medicine (CAM) that fall outside the realms of orthodox medicine, are common in all forms of media, but especially in women’s health and lifestyle magazines. Scientists are quite vociferous in their condemnation of CAM for both ethical and safety reasons, since neither the therapies nor the remedies associated with CAM practices have been proven to be efficacious, or even safe. In fact, some of the therapies and advice offered by CAM practitioners are dangerous and, in some instances, may even be life threatening. Nevertheless, the media continue to promote CAM, and the public continues to support it – despite the warnings and denunciation by scientists. This is an exploratory study to determine the prevalence of pseudoscience, generally, in South African women’s health and lifestyle magazines, and to uncover the reasons the public supports it. The magazine Longevity is used as an example of this type of publication, and a content analysis is used to illustrate the prevalence of pseudoscience articles and adverts in South African media, while field research, in the form of personal interviews, attempts to determine the reasons people support CAM in spite of its denunciation, as well as the media’s role in fostering this support. Both mainstream science and pseudoscience are described, while a literature review reveals the scientific perspective of CAM, provides examples of the more popular forms of CAM and the dangers inherent in them, as well as the ways in which science and pseudoscience in general, are handled by the media. Using the hypodermic needle theory, plus the results of the content analysis and field research, this study shows that media promote pseudoscience because it pays; the public support CAM because they believe it works; and that that belief is primarily the result of public disillusionment with the practice of orthodox medicine, rather than the result of media’s promotion of CAM, as scientists contend.AFRIKKANSE OPSOMMING: Wetenskaplikes van regoor die wêreld het ’n probleem met pseudowetenskap, sowel as die rol wat die media speel om dit bevorder. Artikels gebaseer op pseudowetenskap, veral dié met betrekking tot Aanvullende en Alternatiewe Medisyne (AAM), wat buite die grense van ortodokse medisyne val, is algemeen in alle vorme van media, maar veral in gesondheid-en lewenstyltydskrifte vir vroue. Wetenskaplikes is baie uitgesproke in hul veroordeling van AAM om beide etiese en veiligheidsredes, omdat nóg die terapie nóg die middels wat verband hou met AAM praktyke bewys is om doeltreffend, of selfs veilig te wees. Trouens, sommige van die terapieë en advies wat aangebied word deur AAM beoefenaars is gevaarlik, en in sommige gevalle selfs lewensgevaarlik. Tog hou die media aan om AAM te bevorder, en die publiek om dit te ondersteun – ten spyte van die waarskuwings en veroordeling deur wetenskaplikes. Hierdie narvorsing is ’n verkennende studie om die voorkoms van pseudowetenskap in Suid-Afrikaanse vroue se gesondheid- en lewenstyltydskrifte te bepaal, en die redes te ontbloot waarom die publiek dit ondersteun. Die tydskrif Longevity word gebruik as ’n voorbeeld van hierdie tipe publikasie, en ’n inhoudsanalise word gebruik om die voorkoms van pseudowetenskaplike artikels en advertensies in die Suid-Afrikaanse media te illustreer, terwyl navorsing in die veld, in die vorm van persoonlike onderhoude, poog om die redes te bepaal waarom mense AAM ondersteun, ten spyte van veroordeling, sowel as die rol wat die media speel in die bevordering van hierdie ondersteuning. Beide hoofstroom wetenskap en pseudowetenskap word beskryf, terwyl ’n literatuuroorsig die wetenskaplike perspektief van AAM ontbloot, voorbeelde van die meer populêre vorme van AAM word verskaf asook van die gevare daaraan verbonde, sowel as die maniere waarop wetenskap en pseudowetenskap in die algemeen, hanteer word deur die media. Met behulp van die spuitnaald teorie, plus die resultate van die inhoudsanalise en navorsing in die veld, bewys hierdie studie dat die media pseudowetenskap bevorder, want dit betaal; die publiek ondersteun AAM omdat hulle glo dit werk; en dat daardie geloof primêr die gevolg is van openbare ontnugtering met die beoefening van ortodokse medisyne, eerder as die gevolg van die media se bevordering van AAM, soos wetenskaplikes beweer

Synthesis structure-activity relationships and biological evaluation of optimised terminally alkylated (bis)urea and (bis)thiourea polyamine analogues as antiplasmodial agents

The sustained control and elimination of malaria requires novel approaches to combat the emergence of drug resistance. Plasmodium falciparum causes the most lethal form of human malaria. Current therapeutics have shown decreased efficacy as a result of P. falciparum developing resistance to them. Consequently, novel antimalarial agents with new mechanisms of action are urgently needed to aid in the control and ultimate eradication of this disease and should display low resistance indices and high selectivity indices. Polyamines are involved in a variety of cellular functions including cell differentiation and proliferation and have been shown to be essential to malaria parasites in vitro. However, these analogues lacked drug-like properties, negating their use in malaria disease models in vivo. The objective of this study was to develop novel polyamine analogues based on a previous generation of compounds and to determine their antiplasmodial activity in vitro. Consequently, a novel series of (bis)urea and (bis)thiourea polyamine analogues were designed and synthesised with moderately high yields and purity. In silico evaluation of drug-likeness of these compounds indicated low oral bioavailability overall, although the predicted values were improved over the parent series. The antiplasmodial activity of the novel analogues indicated that halogenation generally decreases activity except for bromination, which did improve in vitro activity. Cheminformatics analysis enabled in-depth analysis of the structure-activity relationships (SAR) of this class of compounds, allowing structural features to be identified that are important for activity. Complementing the SAR with quantitative structure-activity relationships (QSAR) allowed the determination of a descriptor that weakly correlates with the analogues’ activities. The structural requirements for activity were found to be based on representations of the polyamine analogues molecular structures by means of circular atom neighbourhood’s. This work therefore contributed to the further development of the polyamine analogues as potential antimalarial drugs.Dissertation (MSc)--University of Pretoria, 2017.National Research Foundation (NRF)South African Research Chair (SARChI) programmeBiochemistryMScUnrestricte

Global proteome response of human cancer cell lines to low dose eIF4E/eIF4G inhibition

Cachexia is a debilitating muscle wasting disease and co-morbidity strongly associated with chronic inflammatory conditions such as cancer, chronic heart failure, chronic obstructive pulmonary disease and sepsis. Cachexia has a strong negative impact on quality of life and research suggests that 20% of cancer patients will die of cachexia. Translation initiation is the most highly regulated step of protein synthesis and the eukaryotic initiation factor 4F (eIF4F) translation initiation complex is the gatekeeper of this process; the eIF4F complex is composed of eIFG, a scaffolding protein, eIF4E, an mRNA cap-recognition protein and eIF4A, an RNA helicase. Inhibition of eIF4A by pateamine A has been shown to rescue muscle wasting in vitro and in vivo, this result has been reproduced with other eIF4A inhibitors. Pateamine A is a sponge-derived natural product with nanomolar toxicity to cancer cells. Surprisingly, at doses well below its anti-neoplastic activity it exerts distinct effects on cachexia. The research in this thesis follows on from previous work in our laboratory with pateamine A in human cell lines. Work on the effects of pateamine A on the proteome suggests that not all the proteins changing in expression are explainable by stressing the translation initiation complex. A model by which motifs in the 5’ UTRs of transcripts are a recognised and removed from the system in a selective manner could help explain these effects. We aimed to target eIF4E, another component of the eIF4F system, with two compounds to see if a comparable dose of eIF4E inhibitors could elicit a pateamine-like response. DMSO, a solvent used extensively in this thesis, had unexpected effects on translation. We conclude that 4E1RCat, a compound developed as a selective inhibitor of eIF4E, is not likely to be useable in further work, due to its window of activity coinciding with an unacceptable concentration of DMSO. Ribavirin, our second compound, showed a proteomic response consistent with its classification as an eIF4E translation initiation inhibitor. The proteome response seen with our eIF4E inhibitors is consistent with disruption of translation initiation. However, the data for 4E1RCat was deemed untrustworthy in the wake of revelations that DMSO, the vehicle in which it is dissolved, exerts an almost identical response. From the results obtained, it was not possible to confidently test whether protein downregulation occurred in response to a 5’UTR sequence motif, as seen for inhibitors of eIF4A. Coupled with the uncertainty associated with the 4E1Rcat results, there were relatively few downregulated proteins from the treatments, and many of these could be explained by the direct biological response to the function of the compound in the treatment. All in all, we have obtained new insights into the effects of DMSO on the proteome which will aid further experimentation. This thesis has laid the groundwork for further investigation of the effects of eIF4F inhibition in the context of better understanding the remediation of cachexia through the eIF4F system