Browsing by Author "Mthethwa, Mashudu"

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    Fenofibrate protects endothelial cells against the harmful effects of TNF-alpha
    (South African Heart Association, 2017) Westcott, Corli; Genis, Amanda; Mthethwa, Mashudu; Graham, Roxanne; Van Vuuren, Derick; Huisamen, Barbara; Strijdom, Hans
    Introduction: Fenofibrate exerts pleiotropic effects on endothelial cells (ECs) by, amongst others, increasing nitric oxide (NO) production. We aimed to investigate fenofi brate’s putative beneficial actions in healthy or TNF-alpha-induced dysfunctional ECs. Methods: Fenofi brate-induced pro-vasodilatory responses were assessed in aortic rings (50 - 125μM; 30min) with and without L-NMMA (100μM). Rat cardiac microvascular ECs were treated with fenofibrate (30 and 50μM; 1h). In the pre-treatment experiments, fenofibrate (50μM) was administered one hour before TNFalpha treatment (20ng/ml; 24h). NO-production (DAF-2/DA or Griess assay), mitochondrial ROS-production (MitoSox™), cell viability (propidium iodide staining), and changes in the expression/phosphorylation of critical endothelial proteins were measured by Western blotting. Results: Fenofibrate increased NO-production ˜2-fold in healthy ECs (p<0.05 vs. vehicle). A ˜23% pro-vasodilatory response was induced in aortic rings, which was reversed by L-NMMA (p<0.05 vs. fenofibrate). Fenofibrate pretreatment ameliorated TNF-alpha-induced endothelial dysfunction by reversing the loss of NO, improving oxidative stress, restoring cell viability and preventing caspase-3 activation. Protective effects were underpinned by ˜47% and ˜49% up-regulation of activated eNOS and AMP-kinase, respectively (p<0.05 vs. TNFalpha). Conclusions: Fenofibrate protects TNF-alpha-induced dysfunctional ECs via up-regulated eNOS-NO, reduced oxidative stress and improved cell viability. These novel findings warrant further investigations to explore the potential use of fenofibrate as an anti-endothelial dysfunction therapeutic agent.
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    Personal NO2 and volatile organic compounds exposure levels are associated with markers of cardiovascular risk in women in the Cape Town region of South Africa
    (MDPI, 2019) Everson, Frans; De Boever, Patrick; Nawrot, Tim S.; Goswami, Nandu; Mthethwa, Mashudu; Webster, Ingrid; Martens, Dries S.; Mashele, Nyiko; Charania, Sana; Kamau, Festus; Strijdom, Hans
    ENGLISH ABSTRACT: Exposure to ambient NO2 and benzene, toluene ethyl-benzene and m+p- and o-xylenes (BTEX) is associated with adverse cardiovascular effects, but limited information is available on the effects of personal exposure to these compounds in South African populations. This 6-month follow-up study aims to determine 7-day personal ambient NO2 and BTEX exposure levels via compact passive diffusion samplers in female participants from Cape Town, and investigate whether exposure levels are associated with cardiovascular risk markers. Overall, the measured air pollutant exposure levels were lower compared to international standards. NO2 was positively associated with systolic and diastolic blood pressure (SBP and DBP), and inversely associated with the central retinal venular equivalent (CRVE) and mean baseline brachial artery diameter. o-xylene was associated with DBP and benzene was strongly associated with carotid intima media thickness (cIMT). Our findings showed that personal air pollution exposure, even at relatively low levels, was associated with several markers of cardiovascular risk in women residing in the Cape Town region.
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    The responses of endothelium to insult : does endothelial heterogeneity play a role in in vitro cell models
    (Stellenbosch : Stellenbosch University, 2015-12) Mthethwa, Mashudu; Strijdom, Hans; Engelbrecht, Anna-Mart; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Medical Physiology.
    ENGLISH ABSTRACT: Endothelial injury and dysfunction precede the development of cardiovascular diseases. The endothelium may be regarded as the first line of defence against inflammation / obesity-induced vascular injury, therefore gaining more information on the mechanisms of injury and response to injury, as well as modulating endothelial function may be key in the prevention of cardiovascular diseases. Endothelial cells differ in structure and function, therefore endothelial heterogeneity may be relevant when investigating endothelial function and dysfunction. Understanding endothelial heterogeneity in response to pathophysiological stimuli may be of significance in the prevention of cardiovascular diseases. Oleanolic acid (OA), a plant-derived triterpenoid, has been shown to possess endothelio-protective properties; however, its role in reversing endothelial injury is poorly understood. This study investigated endothelial heterogeneity between aortic endothelial cells (AECs) and cardiac microvascular endothelial cells (CMECs) at baseline and in response to an inflammatory insult via the cytokine, tumour necrosis factor-alpha (TNF-α). An in vitro model of endothelial injury was developed by treating AECs and CMECs with 20 ng/ml TNF-α for 24 hours. Endothelial heterogeneity was investigated by comparing intracellular nitric oxide (NO) and reactive oxygen species (ROS) production, protein expression and phosphorylation, and large-scale protein expression and regulation in AECs and CMECs. The experimental techniques included flow cytometry, western blots and proteomic analyses. An ex vivo model of endothelial injury was included to investigate vascular function in aortic rings from lean and high fat diet (HFD) rats. The role of OA in reversing TNF-α-induced injury and modulating vascular function in the ex vivo model was investigated. Although baseline NO-levels were similar between AECs and CMECs, heterogeneity was observed with regards to the NO biosynthetic pathway in terms of increased eNOS expression in CMECs. Baseline ROS levels were heterogeneous between AECs and CMECs, interestingly CMECs possessed higher anti-oxidant capacity. An in vitro model of TNF-α-induced injury was confirmed by decreased NO-levels, increased ROS-levels and necrosis, up-regulation of apoptotic proteins and activation of inflammatory pathways in AECs and CMECs. Here, heterogeneity between AECs and CMECs was also observed: endothelial activation was mediated through different proteins in AECs (CD9 molecule, galectin) and CMECs (ICAM-1 and IL-36α). Apoptosis was mediated by caspase 3 in AECs and Bid in CMECs. AECs appeared to advance to a dysfunctional state shown by up-regulation of endothelin-converting enzyme and angiotensin II-converting enzyme, while CMECs maintained an activated state. OA reversed TNF-α-induced injury through restoring NO-production, decreasing ROS-production in both AECs and CMECs, and inhibiting necrosis in AECs. In the ex vivo model of injury, aortic rings from 16-week HFD rats showed a pro-contractile response to phenylephrine-induced contraction, a response that was reversed by OA. In conclusion, we demonstrated novel findings with regards to endothelial heterogeneity between AECs and CMECs under baseline and TNF-α-treated conditions. Although reduced NO-bioavailability may be the hallmark of endothelial dysfunction, signalling pathways mediating endothelial injury may differ between cell types as was shown in this study. We demonstrated that OA possess protective properties in AECs and CMECS, an observation which was translated to the ex vivo model.