Defining a Water-Soluble Formulation of Arachidonic Acid as a Novel Ferroptosis Inducer in Cancer Cells.

Here, we describe GS-9, a novel water-soluble fatty acid-based formulation comprising L-lysine and arachidonic acid, that we have shown to induce ferroptosis. GS-9 forms vesicle-like structures in solution and mediates lipid peroxidation, as evidenced by increased C11-BODIPY fluorescence and an accumulation of toxic malondialdehyde, a downstream product of lipid peroxidation. Ferroptosis inhibitors counteracted GS-9-induced cell death, whereas caspase 3 and 7 or MLKL knock-out cell lines are resistant to GS-9-induced cell death, eliminating other cell death processes such as apoptosis and necroptosis as the mechanism of action of GS-9. We also demonstrate that through their role of sequestering fatty acids, lipid droplets play a protective role against GS-9-induced ferroptosis, as inhibition of lipid droplet biogenesis enhanced GS-9 cytotoxicity. In addition, Fatty Acid Transport Protein 2 was implicated in GS-9 uptake. Overall, this study identifies and characterises the mechanism of GS-9 as a ferroptosis inducer. This formulation of arachidonic acid offers a novel tool for investigating and manipulating ferroptosis in various cellular and anti-cancer contexts.

Heparanase promotes the onset and progression of atherosclerosis in apolipoprotein E gene knockout mice.

BACKGROUND AND AIMS: Atherosclerosis is the primary underlying cause of myocardial infarction and stroke, which are the major causes of death globally. Heparanase (Hpse) is a pro-inflammatory extracellular matrix degrading enzyme that has been implicated in atherogenesis. However, to date the precise roles of Hpse in atherosclerosis and its mechanisms of action are not well defined. This study aims to provide new insights into the contribution of Hpse in different stages of atherosclerosis in vivo. METHODS: We generated Hpse gene-deficient mice on the atherosclerosis-prone apolipoprotein E gene knockout (ApoE-/-) background to investigate the impact of Hpse gene deficiency on the initiation and progression of atherosclerosis after 6 and 14 weeks high-fat diet feeding, respectively. Atherosclerotic lesion development, blood serum profiles, lesion composition and aortic immune cell populations were evaluated. RESULTS: Hpse-deficient mice exhibited significantly reduced atherosclerotic lesion burden in the aortic sinus and aorta at both time-points, independent of changes in plasma cholesterol levels. A significant reduction in the necrotic core size and an increase in smooth muscle cell content were also observed in advanced atherosclerotic plaques of Hpse-deficient mice. Additionally, Hpse deficiency reduced circulating and aortic levels of VCAM-1 at the initiation and progression stages of disease and circulating MCP-1 levels in the initiation but not progression stage. Moreover, the aortic levels of total leukocytes and dendritic cells in Hpse-deficient ApoE-/- mice were significantly decreased compared to control ApoE-/-mice at both disease stages. CONCLUSIONS: This study identifies Hpse as a key pro-inflammatory enzyme driving the initiation and progression of atherosclerosis and highlighting the potential of Hpse inhibitors as novel anti-inflammatory treatments for cardiovascular disease.

Effectiveness of an anti-inflammatory diet versus low-fat diet for knee osteoarthritis: the FEAST randomised controlled trial protocol.

INTRODUCTION: Chronic inflammation plays a key role in knee osteoarthritis pathophysiology and increases risk of comorbidities, yet most interventions do not typically target inflammation. Our study will investigate if an anti-inflammatory dietary programme is superior to a standard care low-fat dietary programme for improving knee pain, function and quality-of-life in people with knee osteoarthritis. METHODS AND ANALYSIS: The eFEct of an Anti-inflammatory diet for knee oSTeoarthritis study is a parallel-group, assessor-blinded, superiority randomised controlled trial. Following baseline assessment, 144 participants aged 45-85 years with symptomatic knee osteoarthritis will be randomly allocated to one of two treatment groups (1:1 ratio). Participants randomised to the anti-inflammatory dietary programme will receive six dietary consultations over 12 weeks (two in-person and four phone/videoconference) and additional educational and behaviour change resources. The consultations and resources emphasise nutrient-dense minimally processed anti-inflammatory foods and discourage proinflammatory processed foods. Participants randomised to the standard care low-fat dietary programme will receive three dietary consultations over 12 weeks (two in-person and one phone/videoconference) consisting of healthy eating advice and education based on the Australian Dietary Guidelines, reflecting usual care in Australia. Adherence will be assessed with 3-day food diaries. Outcomes are assessed at 12 weeks and 6 months. The primary outcome will be change from baseline to 12 weeks in the mean score on four Knee injury and Osteoarthritis Outcome Score (KOOS4) subscales: knee pain, symptoms, function in daily activities and knee-related quality of life. Secondary outcomes include change in individual KOOS subscale scores, patient-perceived improvement, health-related quality of life, body mass and composition using dual-energy X-ray absorptiometry, inflammatory (high-sensitivity C reactive protein, interleukins, tumour necrosis factor-α) and metabolic blood biomarkers (glucose, glycated haemoglobin (HbA1c), insulin, liver function, lipids), lower-limb function and physical activity. ETHICS AND DISSEMINATION: The study has received ethics approval from La Trobe University Human Ethics Committee. Results will be presented in peer-reviewed journals and at international conferences. TRIAL REGISTRATION NUMBER: ACTRN12622000440729.

The small molecule raptinal can simultaneously induce apoptosis and inhibit PANX1 activity.

Discovery of new small molecules that can activate distinct programmed cell death pathway is of significant interest as a research tool and for the development of novel therapeutics for pathological conditions such as cancer and infectious diseases. The small molecule raptinal was discovered as a pro-apoptotic compound that can rapidly trigger apoptosis by promoting the release of cytochrome c from the mitochondria and subsequently activating the intrinsic apoptotic pathway. As raptinal is very effective at inducing apoptosis in a variety of different cell types in vitro and in vivo, it has been used in many studies investigating cell death as well as the clearance of dying cells. While examining raptinal as an apoptosis inducer, we unexpectedly identified that in addition to its pro-apoptotic activities, raptinal can also inhibit the activity of caspase-activated Pannexin 1 (PANX1), a ubiquitously expressed transmembrane channel that regulates many cell death-associated processes. By implementing numerous biochemical, cell biological and electrophysiological approaches, we discovered that raptinal can simultaneously induce apoptosis and inhibit PANX1 activity. Surprisingly, raptinal was found to inhibit cleavage-activated PANX1 via a mechanism distinct to other well-described PANX1 inhibitors such as carbenoxolone and trovafloxacin. Furthermore, raptinal also interfered with PANX1-regulated apoptotic processes including the release of the 'find-me' signal ATP, the formation of apoptotic cell-derived extracellular vesicles, as well as NLRP3 inflammasome activation. Taken together, these data identify raptinal as the first compound that can simultaneously induce apoptosis and inhibit PANX1 channels. This has broad implications for the use of raptinal in cell death studies as well as in the development new PANX1 inhibitors.

Investigating the Role of Heparanase in Breast Cancer Development Utilising the MMTV-PyMT Murine Model of Mammary Carcinoma.

Breast cancer is the second most common human malignancy and is a major global health burden. Heparanase (HPSE) has been widely implicated in enhancing the development and progression of solid tumours, including breast cancer. In this study, the well-established spontaneous mammary tumour-developing MMTV-PyMT murine model was utilised to examine the role of HPSE in breast cancer establishment, progression, and metastasis. The use of HPSE-deficient MMTV-PyMT (MMTV-PyMTxHPSE-/-) mice addressed the lack of genetic ablation models to investigate the role of HPSE in mammary tumours. It was demonstrated that even though HPSE regulated mammary tumour angiogenesis, mammary tumour progression and metastasis were HPSE-independent. Furthermore, there was no evidence of compensatory action by matrix metalloproteinases (MMPs) in response to the lack of HPSE expression in the mammary tumours. These findings suggest that HPSE may not play a significant role in the mammary tumour development of MMTV-PyMT animals. Collectively, these observations may have implications in the clinical setting of breast cancer and therapy using HPSE inhibitors.

Repurposed inhibitor of bacterial dihydrodipicolinate reductase exhibits effective herbicidal activity.

Herbicide resistance represents one of the biggest threats to our natural environment and agricultural sector. Thus, new herbicides are urgently needed to tackle the rise in herbicide-resistant weeds. Here, we employed a novel strategy to repurpose a 'failed' antibiotic into a new and target-specific herbicidal compound. Specifically, we identified an inhibitor of bacterial dihydrodipicolinate reductase (DHDPR), an enzyme involved in lysine biosynthesis in plants and bacteria, that exhibited no antibacterial activity but severely attenuated germination of the plant Arabidopsis thaliana. We confirmed that the inhibitor targets plant DHDPR orthologues in vitro, and exhibits no toxic effects against human cell lines. A series of analogues were then synthesised with improved efficacy in germination assays and against soil-grown A. thaliana. We also showed that our lead compound is the first lysine biosynthesis inhibitor with activity against both monocotyledonous and dicotyledonous weed species, by demonstrating its effectiveness at reducing the germination and growth of Lolium rigidum (rigid ryegrass) and Raphanus raphanistrum (wild radish). These results provide proof-of-concept that DHDPR inhibition may represent a much-needed new herbicide mode of action. Furthermore, this study exemplifies the untapped potential of repurposing 'failed' antibiotic scaffolds to fast-track the development of herbicide candidates targeting the respective plant enzymes.

Crocodile defensin (CpoBD13) antifungal activity via pH-dependent phospholipid targeting and membrane disruption.

Crocodilians are an order of ancient reptiles that thrive in pathogen-rich environments. The ability to inhabit these harsh environments is indicative of a resilient innate immune system. Defensins, a family of cysteine-rich cationic host defence peptides, are a major component of the innate immune systems of all plant and animal species, however crocodilian defensins are poorly characterised. We now show that the saltwater crocodile defensin CpoBD13 harbors potent antifungal activity that is mediated by a pH-dependent membrane-targeting action. CpoBD13 binds the phospholipid phosphatidic acid (PA) to form a large helical oligomeric complex, with specific histidine residues mediating PA binding. The utilisation of histidine residues for PA engagement allows CpoBD13 to exhibit differential activity at a range of environmental pH values, where CpoBD13 is optimally active in an acidic environment.

Novel Formulation of Undecylenic Acid induces Tumor Cell Apoptosis.

Undecylenic acid, a monounsaturated fatty acid, is currently in clinical use as a topical antifungal agent, however the potential for therapeutic application in other disease settings has not been investigated. In this study, we describe a novel platform for the solubilization of fatty acids using amino acids and utilize this approach to define a tumoricidal activity and underlying mechanism for undecylenic acid. We examined a novel formulation of undecylenic acid compounded with L-Arginine, called GS-1, that induced concentration-dependent tumor cell death, with undecylenic acid being the cytotoxic component. Further investigation revealed that GS-1-mediated cell death was caspase-dependent with a reduction in mitochondrial membrane potential, suggesting a pro-apoptotic mechanism of action. Additionally, GS-1 was found to localize intracellularly to lipid droplets. In contrast to previous studies where lipid droplets have been shown to be protective against fatty acid-induced cell death, we showed that lipid droplets could not protect against GS-1-induced cytotoxicity. We also found a role for Fatty Acid Transport Protein 2 (FATP2) in the uptake of this compound. Collectively, this study demonstrates that GS-1 has effective pro-apoptotic antitumor activity in vitro and, together with the novel platform of fatty acid solubilization, contributes to the re-emerging field of fatty acids as potential anti-cancer therapeutics.

Heparanase: A Novel Therapeutic Target for the Treatment of Atherosclerosis.

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide, and its management places a huge burden on healthcare systems through hospitalisation and treatment. Atherosclerosis is a chronic inflammatory disease of the arterial wall resulting in the formation of lipid-rich, fibrotic plaques under the subendothelium and is a key contributor to the development of CVD. As such, a detailed understanding of the mechanisms involved in the development of atherosclerosis is urgently required for more effective disease treatment and prevention strategies. Heparanase is the only mammalian enzyme known to cleave heparan sulfate of heparan sulfate proteoglycans, which is a key component of the extracellular matrix and basement membrane. By cleaving heparan sulfate, heparanase contributes to the regulation of numerous physiological and pathological processes such as wound healing, inflammation, tumour angiogenesis, and cell migration. Recent evidence suggests a multifactorial role for heparanase in atherosclerosis by promoting underlying inflammatory processes giving rise to plaque formation, as well as regulating lesion stability. This review provides an up-to-date overview of the role of heparanase in physiological and pathological processes with a focus on the emerging role of the enzyme in atherosclerosis.

GS-2: A Novel Broad-Spectrum Agent for Environmental Microbial Control.

The environmental control of microbial pathogens currently relies on compounds that do not exert long-lasting activity on surfaces, are impaired by soil, and contribute to the growing problem of antimicrobial resistance. This study presents the scientific development and characterization of GS-2, a novel, water-soluble ammonium carboxylate salt of capric acid and L-arginine that demonstrates activity against a range of bacteria (particularly Gram-negative bacteria), fungi, and viruses. In real-world surface testing, GS-2 was more effective than a benzalkonium chloride disinfectant at reducing the bacterial load on common touch-point surfaces in a high-traffic building (average 1.6 vs. 32.6 CFUs recovered from surfaces 90 min after application, respectively). Toxicology testing in rats confirmed GS-2 ingredients were rapidly cleared and posed no toxicities to humans or animals. To enhance the time-kill against Gram-positive bacteria, GS-2 was compounded at a specific ratio with a naturally occurring monoterpenoid, thymol, to produce a water-based antimicrobial solution. This GS-2 with thymol formulation could generate a bactericidal effect after five minutes of exposure and a viricidal effect after 10 min of exposure. Further testing of the GS-2 and thymol combination on glass slides demonstrated that the compound retained bactericidal activity for up to 60 days. Based on these results, GS-2 and GS-2 with thymol represent a novel antimicrobial solution that may have significant utility in the long-term reduction of environmental microbial pathogens in a variety of settings.

Neurotoxic amyloidogenic peptides in the proteome of SARS-COV2: potential implications for neurological symptoms in COVID-19.

COVID-19 is primarily known as a respiratory disease caused by SARS-CoV-2. However, neurological symptoms such as memory loss, sensory confusion, severe headaches, and even stroke are reported in up to 30% of cases and can persist even after the infection is over (long COVID). These neurological symptoms are thought to be produced by the virus infecting the central nervous system, however we don't understand the molecular mechanisms triggering them. The neurological effects of COVID-19 share similarities to neurodegenerative diseases in which the presence of cytotoxic aggregated amyloid protein or peptides is a common feature. Following the hypothesis that some neurological symptoms of COVID-19 may also follow an amyloid etiology we identified two peptides from the SARS-CoV-2 proteome that self-assemble into amyloid assemblies. Furthermore, these amyloids were shown to be highly toxic to neuronal cells. We suggest that cytotoxic aggregates of SARS-CoV-2 proteins may trigger neurological symptoms in COVID-19.

An Ultrasound-Responsive Theranostic Cyclodextrin-Loaded Nanoparticle for Multimodal Imaging and Therapy for Atherosclerosis.

Atherosclerosis is a major cause of mortality and morbidity worldwide. Left undiagnosed and untreated, atherosclerotic plaques can rupture and cause cardiovascular complications such as myocardial infarction and stroke. Atherosclerotic plaques are composed of lipids, including oxidized low-density lipoproteins and cholesterol crystals, and immune cells, including macrophages. 2-Hydroxypropyl-beta-cyclodextrin (CD) is FDA-approved for capturing, solubilizing, and delivering lipophilic drugs in humans. It is also known to dissolve cholesterol crystals and decrease atherosclerotic plaque size. However, its low retention time necessitates high dosages for successful therapy. This study reports CD delivery via air-trapped polybutylcyanoacrylate nanoparticles (with diameters of 388 ± 34 nm) loaded with CD (CDNPs). The multimodal contrast ability of these nanoparticles after being loaded with IR780 dye in mice is demonstrated using ultrasound and near-infrared imaging. It is shown that CDNPs enhance the cellular uptake of CD in murine cells. In an ApoE-/- mouse model of atherosclerosis, treatment with CDNPs significantly improves the anti-atherosclerotic efficacy of CD. Ultrasound triggering further improves CD uptake, highlighting that CDNPs can be used for ultrasound imaging and ultrasound-responsive CD delivery. Thus, CDNPs represent a theranostic nanocarrier for potential application in patients with atherosclerosis.

Cytotoxic properties of rhenium(I) tricarbonyl complexes of N-heterocyclic carbene ligands.

A family of eight rhenium(I) tricarbonyl complexes bearing pyridyl-imidazolylidene or bis-imidazolylidene ligands in combination with a series of N-acetyl amino acids ligands (glycine, isoleucine, and proline) and an acetate have been synthesised and characterised. These complexes are of interest as potential anticancer agents, where the oxygen bound carboxylate ligand can exchange with water giving rise to cytotoxic cationic complexes. The pseudo-first-order aquation rate constants for the complexes were evaluated using 1H NMR time-course experiments and for the complexes of the bis-imidazolylidene ligand the average k1 value was 6.22 × 10-5 s-1 while for the pyridyl-imidazolylidene ligand the aquation rate was slower with the average k1 value being 3.00 × 10-5 s-1. Cytotoxicity studies in three cancer cell lines (MDA-MB-231, PC3 and HEPG2) showed that the Re(I) complexes of the bis-imidazolylidene ligand were significantly more toxic than those of the pyridyl-imidazolylidene ligand.

Human ß-Defensin 2 (HBD-2) Displays Oncolytic Activity but Does Not Affect Tumour Cell Migration.

Defensins form an integral part of the cationic host defence peptide (HDP) family, a key component of innate immunity. Apart from their antimicrobial and immunomodulatory activities, many HDPs exert multifaceted effects on tumour cells, notably direct oncolysis and/or inhibition of tumour cell migration. Therefore, HDPs have been explored as promising anticancer therapeutics. Human ß-defensin 2 (HBD-2) represents a prominent member of human HDPs, being well-characterised for its potent pathogen-killing, wound-healing, cytokine-inducing and leukocyte-chemoattracting functions. However, its anticancer effects remain largely unknown. Recently, we demonstrated that HBD-2 binds strongly to phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2), a key mediator of defensin-induced cell death and an instructional messenger during cell migration. Hence, in this study, we sought to investigate the lytic and anti-migratory effects of HBD-2 on tumour cells. Using various cell biological assays and confocal microscopy, we showed that HBD-2 killed tumour cells via acute lytic cell death rather than apoptosis. In addition, our data suggested that, despite the reported PI(4,5)P2 interaction, HBD-2 does not affect cytoskeletal-dependent tumour cell migration. Together, our findings provide further insights into defensin biology and informs future defensin-based drug development.

Defensin-lipid interactions in membrane targeting: mechanisms of action and opportunities for the development of antimicrobial and anticancer therapeutics.

Defensins are a class of host defence peptides (HDPs) that often harbour antimicrobial and anticancer activities, making them attractive candidates as novel therapeutics. In comparison with current antimicrobial and cancer treatments, defensins uniquely target specific membrane lipids via mechanisms distinct from other HDPs. Therefore, defensins could be potentially developed as therapeutics with increased selectivity and reduced susceptibility to the resistance mechanisms of tumour cells and infectious pathogens. In this review, we highlight recent advances in defensin research with a particular focus on membrane lipid-targeting in cancer and infection settings. In doing so, we discuss strategies to harness lipid-binding defensins for anticancer and anti-infective therapies.

Heparanase is a regulator of natural killer cell activation and cytotoxicity.

Heparanase is the only mammalian enzyme capable of cleaving heparan sulfate, a glycosaminoglycan of the extracellular matrix and cell surfaces. Most immune cells express heparanase that contributes to a range of functions including cell migration and cytokine expression. Heparanase also promotes natural killer (NK) cell migration; however, its role in other NK cell functions remains to be defined. In this study, heparanase-deficient (Hpse-/- ) mice were used to assess the role of heparanase in NK cell cytotoxicity, activation, and cytokine production. Upon challenge with the immunostimulant polyinosinic:polycytidylic acid (poly(I:C)), NK cells isolated from Hpse-/- mice displayed impaired cytotoxicity against EO771.LMB cells and reduced levels of activation markers CD69 and NKG2D. However, in vitro cytokine stimulation of wild-type and Hpse-/- NK cells resulted in similar CD69 and NKG2D expression, suggesting the impaired NK cell activation in Hpse-/- mice results from elements within the in vivo niche. NK cells are activated in vivo by dendritic cells (DCs) in response to poly(I:C). Poly(I:C)-stimulated Hpse-/- bone marrow DCs (BMDCs) expressed less IL-12, and when cultured with Hpse-/- NK cells, less MCP-1 mRNA and protein was detected. Although cell-cell contact is important for DC-mediated NK cell activation, co-cultures of Hpse-/- BMDCs and NK cells showed similar levels of contact to wild-type cells, suggesting heparanase contributes to NK cell activation independently of cell-cell contact with DCs. These observations define a role for heparanase in NK cell cytotoxicity and activation and have important implications for how heparanase inhibitors currently in clinical trials for metastatic cancer may impact NK cell immunosurveillance.

The Heparanase Regulatory Network in Health and Disease.

The extracellular matrix (ECM) is a structural framework that has many important physiological functions which include maintaining tissue structure and integrity, serving as a barrier to invading pathogens, and acting as a reservoir for bioactive molecules. This cellular scaffold is made up of various types of macromolecules including heparan sulfate proteoglycans (HSPGs). HSPGs comprise a protein core linked to the complex glycosaminoglycan heparan sulfate (HS), the remodeling of which is important for many physiological processes such as wound healing as well as pathological processes including cancer metastasis. Turnover of HS is tightly regulated by a single enzyme capable of cleaving HS side chains: heparanase. Heparanase upregulation has been identified in many inflammatory diseases including atherosclerosis, fibrosis, and cancer, where it has been shown to play multiple roles in processes such as epithelial-mesenchymal transition, angiogenesis, and cancer metastasis. Heparanase expression and activity are tightly regulated. Understanding the regulation of heparanase and its downstream targets is attractive for the development of treatments for these diseases. This review provides a comprehensive overview of the regulators of heparanase as well as the enzyme's downstream gene and protein targets, and implications for the development of new therapeutic strategies.

Towards novel herbicide modes of action by inhibiting lysine biosynthesis in plants.

Weeds are becoming increasingly resistant to our current herbicides, posing a significant threat to agricultural production. Therefore, new herbicides with novel modes of action are urgently needed. In this study, we exploited a novel herbicide target, dihydrodipicolinate synthase (DHDPS), which catalyses the first and rate-limiting step in lysine biosynthesis. The first class of plant DHDPS inhibitors with micromolar potency against Arabidopsis thaliana DHDPS was identified using a high-throughput chemical screen. We determined that this class of inhibitors binds to a novel and unexplored pocket within DHDPS, which is highly conserved across plant species. The inhibitors also attenuated the germination and growth of A. thaliana seedlings and confirmed their pre-emergence herbicidal activity in soil-grown plants. These results provide proof-of-concept that lysine biosynthesis represents a promising target for the development of herbicides with a novel mode of action to tackle the global rise of herbicide-resistant weeds.