Abstract
Study 1: Nuclear factor erythroid 2 (NFE2)-related factor 2 (NRF2) antioxidant gene expression and its role in combatting, inflammation and oxidative stress in patients with ST-elevation myocardial infarction.Introduction: The aim of this study is to provide evidence that reduction in NRF2 (master regulator of the body’s redox status) activity is associated with increased oxidative stress, inflammation and poor endothelial function in patient with ST-elevated myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI).
Methods: The STEMI single time point study recruited 40 STEMI-patients that had undergone PCI and compared against 30 healthy volunteer controls (HVs). The STEMI multiple time point sub-study recruited a further 29 STEMI patients and 20 HVs. Gene expression assays (using RT-PCR), cytokine analysis (using ELISAs) and vascular tests (using SphygmoCor, flow mediated dilation (FMD), EndoPAT and full-field laser perfusion imaging (FLPI2) were done to determine intergroup differences in expression of an array of genes, cytokines associated with inflammation and oxidative stress and its impact on endothelial function.
Results: The post-occlusive reactive hyperaemia (PORH) and glyceryl trinitrate (GTN) responses in FMD assessment were notably better in the healthy volunteers than STEMI patients in the single-time point study. STEMI patients displayed greater arterial stiffness i.e., higher augmentation index (AIx and AIx @HR75) and increased carotid-femoral-PWV compared to HVs in the multiple time point study. Many inflammatory genes MSK1, MSK2, CREB1, SIK1, SIK3, NOS2, NOS3 and HLA-1 were significantly downregulated in STEMI patients compared to HVs (p<0.001). The results from the multiple time point study showed a similar decrease in expression of inflammatory genes with time after PCI. Levels of inflammatory cytokines including IL-4, IL-9, FGF basic, MCP-1 were all found to be lower in STEMI patients than HVs (p=<0.001), while, anti-inflammatory cytokine, IL-10, was found to be higher in STEMI population than HVs (p=0.002). Interestingly, serum IL-6 levels was significantly raised in STEMI patients compared to HVs. No intergroup differences were identified in terms of Nrf2 expression or the expression of its downstream target genes. However, STEMI patients exhibited compromised temporal expression of antioxidant genes, specifically the GCLC and GCLM genes, and demonstrated an inability to mount a robust antioxidant response. This was evident as the transcription levels of both genes significantly decreased between the 2-hour post-PCI and 24-hour post-PCI time points.
Conclusions: Aside for elevated IL-6 levels in ST-elevation myocardial infarction (STEMI) patients, these patients were seen to be in an anti-inflammatory state post-PCI. This anti-inflammatory state might be a result of an innate compensatory response to revascularisation therapy and/or due to prescribed medications such as unfractionated heparin which is a potent inhibitor of p38/MAPK and NFkB mediated inflammation. The heightened levels of IL-6 may, to some extent, contribute to the observed decline in flow-mediated dilation (FMD) response observed in patients with STEMI. Moreover, our data implies a distinct necessity for pre-percutaneous coronary intervention (PCI) blood samples, which should be conducted prior to the administration of heparin to patients. These assessments are essential for gaining a more comprehensive understanding of how inflammation and oxidative stress evolve throughout the course of revascularization therapies.
Study 2: Focused longitudinal observational study to improve knowledge of covid-19 (FOLLOW-COVID19).
Introduction: COVID-19 is a complex multisystemic disease. Many studies have described the multifaceted role of the endothelium in the pathophysiology of COVID-19. Emerging evidence suggests that endotheliitis in arteries may be a contributing factor of morbidity and mortality in COVID-19.
Methods: In this study 89 participants infected with COVID-19 were categorised into two groups: non-hospitalised patients (N=33, mean age = 49+/-9.7yrs) and hospitalised patients (N=55, mean age = 60+/-12.2yrs). All participants underwent arterial stiffness assessment, endothelial function tests and microvascular function tests using non-invasive techniques such as SphygmoCor, EndoPAT and FLPI2 respectively. These tests were performed at visit 1 (>3 months after infection) and visit 2 (>6 months after infection).
Results: The Carotid-Femoral Pulse Wave Velocity (cfPWV, a measure of arterial stiffness) was significantly higher in hospitalised patients than non-hospitalised patients at both visit 1 (hospitalised cfPWV: 8.1+/-1.3m/s vs non-hospitalised cfPWV: 7.0+/-1.3m/s, p=0.03) and visit 2 (hospitalised cfPWV: 8.7+/-1.4m/s vs non-hospitalised cfPWV: 7.3+/-1.4m/s, p=0.012). EndoPAT analysis revealed that hospitalised patients demonstrated poorer endothelial function compared to non-hospitalised patients (hospitalised: RHI = 2.0+/-0.8 vs non-hospitalised: RHI =2.4+/-0.7, p=0.028). Furthermore, FLPI2 tests showed that hospitalised patients had higher baseline skin perfusion (p=0.035) and decreased responses to endothelium-dependent (acetylcholine (ACh), visit 1 p= 0.019 and visit 2 p<0.001) and endothelial-independent (sodium nitroprusside (SNP), visit 1, p=0.026) vasodilators. Interestingly, hospitalised patients also displayed a progressive deterioration in vasodilatory response to ACh between visit 1 and visit 2 (p=0.036). Elevated gene expression of SIK 2 and high serum levels of inflammatory and coagulative markers were seen in hospitalised COVID-19 patients compared to non-hospitalised COVID-19 patients.
Conclusion: The results from this study illustrate that severe COVID-19 infections which require hospitalisation are associated with arterial stiffness and poor endothelial function. A limitation of this study which was considered when interpreting the results was age-matching as the hospitalised patients were significantly older compared to non-hospitalised patients. Nonetheless, microvascular dysfunction (seen as attenuation of ACh and heat response in hospitalised patients) and progressive deterioration of microvascular function seen in severely affected patients between visits was independent of baseline characteristic such as age, BMI and pre-COVID-19 PMHx. This microvascular impairment seen in hospitalised COVID-19 patients was postulated to be governed by elevated gene expression of SIK 2 and high serum levels of inflammatory and coagulative markers seen in these patients.
| Date of Award | 2024 |
|---|---|
| Original language | English |
| Sponsors | The Cunningham Trust & Chief Scientist Office |
| Supervisor | Faisel Khan (Supervisor) & John Hayes (Supervisor) |