Pharmaceutical, Biomedical and Veterinary Sciences

Pauline Lempens

• 12 April 2023, 4pm - 6pm
• Aula Janssens, ITG
• Promoters: Leen Rigouts, Bouke de Jong

Daniel Mukadi

• 27 March 2023, 4pm - 6pm
• Aula P.G. Janssens, ITG
• Promoters: Kevin Ariën, Johan van Griensven

Abstract

The Democratic Republic of the Congo has faced fifteen Ebola virus disease (EVD) outbreaks, among which the 2018-2020 was the most widespread and deadliest so far. During that outbreak associated with chronic insecurity, community mistrust and resistance, thirteen field laboratories were deployed to support the EVD diagnosis with the GeneXpert®. As this latter cannot be used everywhere in remote areas due to its additional requirements, rapid diagnostic tests (RDTs) were proposed as an alternative tool to support quick decision-making at the point-of-care. However, questions regarding RDTs diagnostic performance and usability were raised due to their disparate performances.

In the first part of this PhD thesis, we showed how decentralized and strategically positioned diagnostic laboratories quickly helped to mitigate the risk of Ebola virus spread through rapid, efficient, accurate and well-structured response. Quick hand over of competences and capacities to local teams led to successful management of further health emergencies (EVD flare-ups and Covid-19 pandemic), as those laboratories had dedicated equipment and well-trained local personnel. Sequencing data guided public health decision-making, helped understanding the outbreak dynamics, at risk populations and exposed health zones.

In the second part of this PhD, QuickNaviTM RDT had high specificity and quite good sensitivity than OraQuick® and Coris® tests in outbreaks conditions. QuickNavi-EbolaTM was less impressive compared to previous studies; OraQuick® test was almost in line with previous findings, although it performed better for the middle and lower Ct-values in laboratory conditions. None of the four Ebola RDTs evaluated throughout our studies, achieved the desired (sensitivity >98%, specificity >99%) or acceptable (sensitivity >95%, specificity >99%) levels of performance as stated by the WHO Target Product Profile for EBOV tests. However, respective specificities of the QuickNaviTM (>99%) and OraQuick® Ebola (98%) in most our studies were close to the acceptable level of performance (>99%).

Based on overall performances, QuickNaviTM and Oraquick® Ebola RDTs were proposed as a screening panel at the point-of-care to triage and isolate suspect-cases waiting for the RT-qPCR results. RDTs results expectancy will be done separately i.e. individuals with at least one positive RDT isolated in the high-risk area and those with negative RDTs results in low-risk area.

For postmortem surveillance, OraQuick® RDT effectively complemented the response efforts, improved the community engagement, and decreased the number of systematic safe and dignified burials (SDBs) in corpses with non-reactive test. Trust towards postmortem testing led families to voluntarily request for SDBs despite OraQuick® non-reactive results.

​​Raphaëlle Corremans

• 23 February 2023, 4:30pm - 6:30pm
• Promotiezaal (CDE)
• Promoters: Anja Verhulst, Benjamin Vervaet

Abstract

Chronic kidney disease (CKD) is a major renal health issue, which has a high socio-economic impact by its far-reaching health consequences. This often results in the need for renal replacement therapy (dialysis or transplantation). Currently, disease management remains mainly supportive in nature due to the lack of efficient treatments that directly act on the kidney and improve its outcome upon injury. However, recent research on the antidiabetic drug metformin revealed a consistent beneficial effect of this drug on the challenged kidney. This PhD thesis further explores the renoprotective effects of metformin and compares these effects to that of canagliflozin, an antidiabetic drug that was recently approved by the US Food and Drug Administration (FDA, 2021) to treat CKD.

The first part of this PhD project compared the therapeutic efficacy of metformin and canagliflozin, on the progression of CKD in the non-diabetic rat model with adenine-induced CKD. Metformin, but not canagliflozin, therapeutically halted functional renal decline of established CKD, as well as progressive expansion of the interstitium and interstitial inflammation. Proteomic analyses revealed that metformin’s renoprotective effect was associated with the activation of the Hippo signaling pathway. In the future, this might open up new perspectives for the development of novel, uncontested, more effective and safe targeted treatment strategies which can serve as interventions in CKD.

Since diabetes is one of the most important risk factors to develop CKD, the second part of the PhD project focused on diabetic kidney disease (DKD). Therefore, a suitable rat model of DKD, that develops the clinical and pathological features of human DKD within an acceptable experimental time frame, was optimized. We discovered that L-NAME-induced NO-deficiency in diabetic rats importantly contributed to the development of all desired characteristic features of human DKD. Additionally, also in this preclinical model the ability of metformin and canagliflozin to prevent or slow down the progression of DKD was compared. Metformin exerted renoprotective effects beyond its capacity to reduce blood glucose. Metformin was able to protect renal proximal tubular cells, reduce tubular damage and prevent collagen accumulation. Canagliflozin exerted similar protective actions, which however, could clearly be linked to its blood glucose lowering activity. In this preclinical model, both metformin and canagliflozin were able to protect the kidney, in a non-synergistic way, against DKD development by, at least in part, inhibiting the NF-κB signaling pathway.

Joey De Backer

• 6 February 2023, 4pm - 6pm
• Promotiezaal (CDE)
• Promoters: Wim Vanden Berghe, Annemie Bogaerts, David Hoogewijs

Abstract

Since its discovery 20 years ago, many studies have been performed to gain insight into the functional role of cytoglobin (Cygb). However, Cygb has been proven to be a promiscuous protein. Yet, there is a consensus that Cygb is a cytoprotective protein involved in redox homeostasis. CYGB is a ubiquitously expressed hexacoordinated globin that is highly expressed in melanocytes and is often found to be downregulated during melanocyte-to-melanoma transition.

In Chapter III, we investigated the molecular mechanism through which CYGB could be involved in redox regulation. Here, we showed that CYGB contains two redox-sensitive cysteine residues and that the formation of an intramolecular disulfide bridge resulted in the heme group becoming more accessible to external ligands. This supports the hypothesis that Cys38 and Cys83 serve as sensitive redox sensors. In Chapter IV we showed that CYGB mRNA and protein levels were elevated upon exposure to hypoxia. Interestingly, this upregulation was most likely HIF-2α-dependent. We propose that in melanoma, HIF-2α, rather than HIF-1α, positively regulates CYGB under hypoxic conditions in a cell type specific way. In Chapter V, the cytotoxic effect of indirect NTP treatment in two melanoma cell lines with divergent endogenous CYGB expression levels was investigated. We confirmed that NTP endows cytotoxicity that induces cell death through apoptosis and that this was mediated through the production of ROS. Moreover, we showed that CYGB protects melanoma cells from ROS-induced apoptosis by the scavenging of ROS. Interestingly, CYGB expression influenced the expression of NRF2 and HO-1. We identified the lncRNA MEG3 as a possible mechanism through which NRF2 expression and its downstream target HO-1 can be regulated by CYGB. In chapter VI, increased basal ROS levels and higher degree of lipid peroxidation upon RSL3 treatment contributed to the increased sensitivity of CYGB knockdown G361 cells to ferroptosis. Furthermore, transcriptome analysis demonstrates the enrichment of multiple cancer malignancy pathways upon CYGB knockdown, supporting a tumor-suppressive role for CYGB. Remarkably, CYGB expression regulation was identified as a critical determinant of the ferroptosis–pyroptosis therapy response. This suggests that CYGB is involved in the regulation of multiple modes of programmed cell death. FInally, we sought to delineate the RONS that are responsible for plasma-induced ICD. Our results highlight the importance of the short-lived species. Furthermore, we are first to demonstrate that NTP-created vaccine is safely prepared and offers complete protection. Moreover, we provide conclusive evidence that direct application of NTP induces ICD in melanoma.