Julia Liang

Primary aldosteronism (PA) is the most common cause of secondary hypertension and accounts for 5–15% of hypertensive patients. Familial hyperaldosteronism, a monogenic cause of PA, accounts for ~1–5% of cases. Familial hyperaldosteronism type III results from mutations in the KCNJ5 gene, which lead to excessive aldosterone production and hypertension due to dysfunction of the GIRK4 channel in the adrenal gland. Despite the importance of KCNJ5 in PA pathogenesis, little is known about the molecular mechanisms underlying germline KCNJ5 mutations and their functional consequences. This study explored the structural changes in KCNJ5 pathogenic variant c.452G>A (p.Gly151Glu or GIRK4^G151E). Homology modeling and molecular dynamics simulations of the mutant GIRK4 channel showed that structural rearrangements occur in GIRK4^G151E when compared to GIRK4^WT, displaying higher RMSD and SASA, which may be attributed to differences in residue fluctuations in the cytosolic and extracellular domains, and ligands may bind with a stronger affinity to GIRK4^G151E. Given that the mutation is located within or proximal to the selectivity filter of GIRK4, we expect that the primary mechanism of dysfunction involves altered ion selectivity, leading to membrane depolarization. Our novel findings highlight the importance of understanding the molecular mechanisms underlying KCNJ5 mutations in PA and hypertension pathogenesis. This knowledge could inform the development of more targeted and effective treatments for this condition.

The mineralocorticoid receptor (MR) is a steroid hormone receptor that plays a key role in regulating sodium and water homeostasis and blood pressure. MR antagonists are a guideline recommended for therapy for the treatment of hypertension and cardiovascular disease but can cause hyperkalaemia. Modelling was performed for binding of the endogenous ligands aldosterone and cortisol and MR antagonist spironolactone to the ligand binding domain (LBD) of the MR. A molecular docking screen of compounds that were structurally similar to known antagonists was performed, leading to the identification of two novel compounds, C79 and E67. Molecular dynamics (MD) assessed the dynamic interactions with C79, E76, endogenous ligands, and spironolactone with the MR ligand binding domain (LBD). Analysis of the protein backbone showed modest changes in the overall structure of the MR LBD in response to binding of antagonists, with movement in helix 12 consistent with previous observations. All ligands tested maintained stable binding within the MR LBD throughout the simulations. Hydrogen bond formation played a more prominent role in the binding of endogenous ligands compared to antagonists. MM-PBSA binding free energy calculations showed that all ligands had similar binding affinities, with binding facilitated by key residues within the binding site. The novel antagonists demonstrated similar binding properties to spironolactone, warranting further evaluation. This study provides insights into the molecular mechanisms of MR activation and inhibition, which can aid in the development of novel therapeutic strategies for cardiovascular diseases.

Primary aldosteronism is characterised by the excessive production of aldosterone, which is a key regulator of salt metabolism, and is the most common cause of secondary hypertension. Studies have investigated the association between primary aldosteronism and genetic alterations, with pathogenic mutations being identified. This includes a glycine-to-arginine substitution at position 151 (G151R) of the G protein-activated inward rectifier potassium (K⁺) channel 4 (GIRK4), which is encoded by the KCNJ5 gene. Mutations in GIRK4 have been found to reduce the selectivity for K⁺ ions, resulting in membrane depolarisation, the activation of voltage-gated Ca²⁺ channels, and an increase in aldosterone secretion. As a result, there is an interest in identifying and exploring the mechanisms of action of small molecule modulators of wildtype (WT) and mutant channels. In order to investigate the potential modulation of homotetrameric GIRK4^WT and GIRK4^G151R channels, homology models were generated. Molecular dynamics (MD) simulations were performed, followed by a cluster analysis to extract starting structures for molecular docking. The central cavity has been previously identified as a binding site for small molecules, including natural compounds. The OliveNet^TM database, which consists of over 600 compounds from Olea europaea, was subsequently screened against the central cavity. The binding affinities and interactions of the docked ligands against the GIRK4^WT and GIRK4^G151R channels were then examined. Based on the results, luteolin-7-O-rutinoside, pheophorbide a, and corosolic acid were identified as potential lead compounds. The modulatory activity of olive-derived compounds against the WT and mutated forms of the GIRK4 channel can be evaluated further in vitro.

In a landmark study, oleocanthal (OLC), a major phenolic in extra virgin olive oil (EVOO), was found to possess anti-inflammatory activity similar to ibuprofen, involving inhibition of cyclooxygenase (COX) enzymes. EVOO is a rich source of bioactive compounds including fatty acids and phenolics; however, the biological activities of only a small subset of compounds associated with Olea europaea have been explored. Here, the OliveNet^TM library (consisting of over 600 compounds) was utilized to investigate olive-derived compounds as potential modulators of the arachidonic acid pathway. Our first aim was to perform enzymatic assays to evaluate the inhibitory activity of a selection of phenolic compounds and fatty acids against COX isoforms (COX-1 and COX-2) and 15-lipoxygenase (15-LOX). Olive compounds were found to inhibit COX isoforms, with minimal activity against 15-LOX. Subsequent molecular docking indicated that the olive compounds possess strong binding affinities for the active site of COX isoforms, and molecular dynamics (MD) simulations confirmed the stability of binding. Moreover, olive compounds were predicted to have favorable pharmacokinetic properties, including a readiness to cross biological membranes as highlighted by steered MD simulations and umbrella sampling. Importantly, olive compounds including OLC were identified as non-inhibitors of the human ether-à-go-go-related gene (hERG) channel based on patch clamp assays. Overall, this study extends our understanding of the bioactivity of Olea-europaea-derived compounds, many of which are now known to be, at least in part, accountable for the beneficial health effects of the Mediterranean diet.

The Mediterranean diet well known for its beneficial health effects, including mood enhancement, is characterised by the relatively high consumption of extra virgin olive oil (EVOO), which is rich in bioactive phenolic compounds. Over 200 phenolic compounds have been associated with Olea europaea, and of these, only a relatively small fraction have been characterised. Utilising the OliveNet^TM library, phenolic compounds were investigated as potential inhibitors of the epigenetic modifier lysine-specific demethylase 1 (LSD1). Furthermore, the compounds were screened for inhibition of the structurally similar monoamine oxidases (MAOs) which are directly implicated in the pathophysiology of depression. Molecular docking highlighted that olive phenolics interact with the active site of LSD1 and MAOs. Protein–peptide docking was also performed to evaluate the interaction of the histone H3 peptide with LSD1, in the presence of ligands bound to the substrate-binding cavity. To validate the in silico studies, the inhibitory activity of phenolic compounds was compared to the clinically approved inhibitor tranylcypromine. Our findings indicate that olive phenolics inhibit LSD1 and the MAOs in vitro. Using a cell culture model system with corticosteroid-stimulated human BJ fibroblast cells, the results demonstrate the attenuation of dexamethasone- and hydrocortisone-induced MAO activity by phenolic compounds. The findings were further corroborated using human embryonic stem cell (hESC)-derived neurons stimulated with all-trans retinoic acid. Overall, the results indicate the inhibition of flavin adenine dinucleotide (FAD)-dependent amine oxidases by olive phenolics. More generally, our findings further support at least a partial mechanism accounting for the antidepressant effects associated with EVOO and the Mediterranean diet.

Genetic abnormalities have been associated with primary aldosteronism, a major cause of secondary hypertension. This includes mutations in the KCNJ5 gene, which encodes G protein-gated inwardly rectifying K⁺ channel 4 (GIRK4). For example, the substitution of glycine with glutamic acid gives rise to the pathogenic GIRK4^G151E mutation, which alters channel selectivity, making it more permeable to Na⁺ and Ca²⁺. While tertiapin and tertiapin-Q are well-known peptide inhibitors of the GIRK4^WT channel, clinically, there is a need for the development of selective modulators of mutated channels, including GIRK4^G151E. Using in silico methods, including homology modeling, protein–peptide docking, ligand-binding site prediction, and molecular docking, we aimed to explore potential modulators of GIRK4^WT and GIRK4^G151E. Firstly, protein–peptide docking was performed to characterize the binding site of tertiapin and its derivative to the GIRK4 channels. In accordance with previous studies, the peptide inhibitors preferentially bind to the GIRK4^WT channel selectivity filter compared to GIRK4^G151E. A ligand-binding site analysis was subsequently performed, resulting in the identification of two potential regions of interest: the central cavity and G-loop gate. Utilizing curated chemical libraries, we screened over 700 small molecules against the central cavity of the GIRK4 channels. Flavonoids, including luteolin-7-O-rutinoside and rutin, and the macrolides rapamycin and troleandomycin bound strongly to the GIRK4 channels. Similarly, xanthophylls, particularly luteoxanthin, bound to the central cavity with a strong preference towards the mutated GIRK4^G151E channel compared to GIRK4^WT. Overall, our findings suggest potential lead compounds for further investigation, particularly luteoxanthin, that may selectively modulate GIRK4 channels.

Announced on December 31, 2019, the novel coronavirus arising in Wuhan City, Hubei Province resulted in millions of cases and lives lost. Following intense tracking, coronavirus disease 2019 (COVID-19) was declared a pandemic by the World Health Organization (WHO) in 2020. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified as the cause of COVID-19 and the continuous evolution of the virus has given rise to several variants. In this review, a comprehensive analysis of the response to the pandemic over the first three-year period is provided, focusing on disease management, development of vaccines and therapeutics, and identification of variants. The transmissibility and pathogenicity of SARS-CoV-2 variants including Alpha, Beta, Gamma, Delta, and Omicron are compared. The binding characteristics of the SARS-CoV-2 spike protein to the angiotensin-converting enzyme 2 (ACE2) receptor and reproduction numbers are evaluated. The effects of major variants on disease severity, hospitalisation, and case-fatality rates are outlined. In addition to the spike protein, open reading frames mutations are investigated. We also compare the pathogenicity of SARS-CoV-2 with SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV). Overall, this study highlights the strengths and weaknesses of the global response to the pandemic, as well as the importance of prevention and preparedness. Monitoring the evolution of SARS-CoV-2 is critical in identifying and potentially predicting the health outcomes of concerning variants as they emerge. The ultimate goal would be a position in which existing vaccines and therapeutics could be adapted to suit new variants in as close to real-time as possible.