Recent developments in relaxin mimetics as therapeutics for cardiovascular diseases

Time-dependent specific molecular signatures of inflammation and remodelling are associated with trimethylamine-N-oxide (TMAO)-induced endothelial cell dysfunction

Endothelial dysfunction is a critical initiating factor contributing to cardiovascular diseases, involving the gut microbiome-derived metabolite trimethylamine N-oxide (TMAO). This study aims to clarify the time-dependent molecular pathways by which TMAO mediates endothelial dysfunction through transcriptomics and metabolomics analyses in human microvascular endothelial cells (HMEC-1). Cell viability and reactive oxygen species (ROS) generation were also evaluated. TMAO treatment for either 24H or 48H induces reduced cell viability and enhanced oxidative stress. Interestingly, the molecular signatures were distinct between the two time-points. Specifically, few Gene Ontology biological processes (BPs) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were modulated after a short (24H) compared to a long (48H) treatment. However, the KEGG signalling pathways namely "tumour necrosis factor (TNF)" and "cytokine-cytokine receptor interaction" were downregulated at 24H but activated at 48H. In addition, at 48H, BPs linked to inflammatory phenotypes were activated (confirming KEGG results), while BPs linked to extracellular matrix (ECM) structural organisation, endothelial cell proliferation, and collagen metabolism were repressed. Lastly, metabolic profiling showed that arachidonic acid, prostaglandins, and palmitic acid were enriched at 48H. This study demonstrates that TMAO induces distinct time-dependent molecular signatures involving inflammation and remodelling pathways, while pathways such as oxidative stress are also modulated, but in a non-time-dependent manner.

Pressurized Hot Water Extraction of Mangosteen Pericarp and Its Associated Molecular Signatures in Endothelial Cells

The mangosteen (Garcinia mangostana L.) pericarp is known to be rich in potent bioactive phytochemical compounds such as xanthones, which possess pharmacologically important antioxidant activity and beneficial cardiometabolic properties. Mangosteen pericarp is typically classified as unavoidable food waste and discarded, despite being rich in bioactive phytochemical compounds that therefore present an exciting opportunity for valorization. Thus, this study aims to extract phytochemical compounds from mangosteen pericarp using pressurized hot water extraction (PHWE) and determine its biological effects in endothelial cells using RNA sequencing. Liquid chromatography with MS/MS (LC/MSMS) and UV detection (LC/UV) was subsequently used to identify three key phytochemical compounds extracted from the mangosteen pericarp: α-Mangostin, γ-Mangostin, and Gartanin. Within the tested range of extraction temperatures by PHWE, our results demonstrated that an extraction temperature of 120 °C yielded the highest concentrations of α-Mangostin, γ-Mangostin, and Gartanin with a concomitant improvement in antioxidant capacity compared to other extraction temperatures. Using global transcriptomic profiling and bioinformatic analysis, the treatment of endothelial cells with mangosteen pericarp extracts (120 °C PHWE) for 48 h caused 408 genes to be differentially expressed. Furthermore, our results demonstrated that key biological processes related to "steroid biosynthesis and metabolism", likely involving the activation of the AMPK signaling pathway, were upregulated by mangosteen pericarp extract treatment. In conclusion, our study suggests a green extraction method to valorize phytochemical compounds from mangosteen pericarp as a natural product with potential beneficial effects on cardiometabolic health.

Recent advances in the combination of organic solvent-free extraction, chemical standardization, antioxidant assay, and cell culture metabolomics for functional food and its by-product

Functional foods and their by-products contain a wide range of bioactive components with an array of health benefits and were proposed to improve public health, well-being, and others. To achieve a circular economy, the processing and extraction of flavonoids, phenolic compounds, and others from functional food and agri-food wastes will require the use of environmentally friendly, sustainable, and a low-cost solution. Extraction methods that can eliminate the use of organic solvents, suitable for use in the laboratory and production of extracts will be covered. This will include subcritical water extraction (SBE), pressurized hot water extraction (PHWE), supercritical fluid extraction (SFE), and others. Based on the selected analytical methods, the determination of the marker or bioactive compounds and chemical fingerprints will provide the control measures to identify the batch-to-batch variation of the composition of the functional food products obtained. The combination of chemical standardization with antioxidant assay, such as DPPH and ABTS+ will provide further information on the quality of the extracts. Lastly, to ascertain the biological and physiological relevance of the antioxidant properties of the target sample, treatment of the antioxidant compounds or extracts was carried out using cellular models, and validated using other experimental endpoints, such as metabolomics.

Relaxin elicits renoprotective actions accompanied by increasing bile acid levels in streptozotocin-induced diabetic mice

BACKGROUND

The peptide hormone relaxin has potent anti-fibrotic and anti-inflammatory properties in various organs, including the kidneys. However, the protective effects of relaxin in the context of diabetic kidney complications remain controversial. Here, we aimed to evaluate the effects of relaxin treatment on key markers of kidney fibrosis, oxidative stress, and inflammation and their subsequent impact on bile acid metabolism in the streptozotocin-induced diabetes mouse model.

METHODS AND RESULTS

Male mice were randomly allocated to placebo-treated control, placebo-treated diabetes or relaxin-treated diabetes groups (0.5 mg/kg/d, final 2 weeks of diabetes). After 12 weeks of diabetes or sham, the kidney cortex was harvested for metabolomic and gene expression analyses. Diabetic mice exhibited significant hyperglycaemia and increased circulating levels of creatine, hypoxanthine and trimethylamine N-oxide in the plasma. This was accompanied by increased expression of key markers of oxidative stress (Txnip), inflammation (Ccl2 and Il6) and fibrosis (Col1a1, Mmp2 and Fn1) in the diabetic kidney cortex. Relaxin treatment for the final 2 weeks of diabetes significantly reduced these key markers of renal fibrosis, inflammation, and oxidative stress in diabetic mice. Furthermore, relaxin treatment significantly increased the levels of bile acid metabolites, deoxycholic acid and sodium glycodeoxycholic acid, which may in part contribute to the renoprotective action of relaxin in diabetes.

CONCLUSION

In summary, this study shows the therapeutic potential of relaxin and that it may be used as an adjunctive treatment for diabetic kidney complications.

Endothelium-dependent relaxation is impaired in Schlager hypertensive (BPH/2J) mice by region-specific mechanisms in conductance and resistance arteries

AIMS

Endothelial dysfunction and arterial stiffness are hallmarks of hypertension, and major risk factors for cardiovascular disease. BPH/2J (Schlager) mice are a genetic model of spontaneous hypertension, but little is known about the vascular pathophysiology of these mice and the region-specific differences between vascular beds. Therefore, this study compared the vascular function and structure of large conductance (aorta and femoral) and resistance (mesenteric) arteries of BPH/2J mice with their normotensive BPN/2J counterparts.

MAIN METHODS

Blood pressure was measured in BPH/2J and BPN/3J mice via pre-implanted radiotelemetry probes. At endpoint, vascular function and passive mechanical wall properties were assessed using wire and pressure myography, qPCR and histology.

KEY FINDINGS

Mean arterial blood pressure was elevated in BPH/2J mice compared to BPN/3J controls. Endothelium-dependent relaxation to acetylcholine was attenuated in both the aorta and mesenteric arteries of BPH/2J mice, but through different mechanisms. In the aorta, hypertension reduced the contribution of prostanoids. Conversely, in the mesenteric arteries, hypertension reduced the contribution of both nitric oxide and endothelium-dependent hyperpolarization. Hypertension reduced volume compliance in both femoral and mesenteric arteries, but hypertrophic inward remodelling was only observed in the mesenteric arteries of BPH/2J mice.

SIGNIFICANCE

This is the first comprehensive investigation of vascular function and structural remodelling in BPH/2J mice. Overall, hypertensive BPH/2J mice exhibited endothelial dysfunction and adverse vascular remodelling in the macro- and microvasculature, underpinned by distinct region-specific mechanisms. This highlights BPH/2J mice as a highly suitable model for evaluating novel therapeutics to treat hypertension-associated vascular dysfunction.

Gut-Derived Metabolite, Trimethylamine-N-oxide (TMAO) in Cardio-Metabolic Diseases: Detection, Mechanism, and Potential Therapeutics

Trimethylamine N-oxide (TMAO) is a biologically active gut microbiome-derived dietary metabolite. Recent studies have shown that high circulating plasma TMAO levels are closely associated with diseases such as atherosclerosis and hypertension, and metabolic disorders such as diabetes and hyperlipidemia, contributing to endothelial dysfunction. There is a growing interest to understand the mechanisms underlying TMAO-induced endothelial dysfunction in cardio-metabolic diseases. Endothelial dysfunction mediated by TMAO is mainly driven by inflammation and oxidative stress, which includes: (1) activation of foam cells; (2) upregulation of cytokines and adhesion molecules; (3) increased production of reactive oxygen species (ROS); (4) platelet hyperreactivity; and (5) reduced vascular tone. In this review, we summarize the potential roles of TMAO in inducing endothelial dysfunction and the mechanisms leading to the pathogenesis and progression of associated disease conditions. We also discuss the potential therapeutic strategies for the treatment of TMAO-induced endothelial dysfunction in cardio-metabolic diseases.

Green Extraction of Orange Peel Waste Reduces TNFα-Induced Vascular Inflammation and Endothelial Dysfunction

Orange peel waste (OPW) is known to contain an abundant amount of polyphenols compounds such as flavonoids, well-reported for their antioxidant and anti-inflammatory properties. While OPW is generally regarded as a food waste, the opportunity to extract bioactive compounds from these “wastes” arises due to their abundance, allowing the investigation of their potential effects on endothelial cells. Hence, this study aims to use a green extraction method and pressurized hot water extraction (PHWE) to extract bioactive compounds from OPW. Liquid chromatography with UV detection (LC/UV) and liquid chromatography mass spectrometry (LC/MS) were subsequently used to identify the bioactive compounds present. Through the optimization of the extraction temperature for PHWE, our results demonstrated that extraction temperatures of 60 °C and 80 °C yield distinct bioactive compounds and resulted in better antioxidant capacity compared to other extraction temperatures or organic solvent extraction. Despite having similar antioxidant capacity, their effects on endothelial cells were distinct. Specifically, treatment of endothelial cells with 60 °C OPW extracts inhibited TNFα-induced vascular inflammation and endothelial dysfunction in vitro, suggesting that OPW possess vasoprotective effects likely mediated by anti-inflammatory effects.

Valorization of avocado seeds with antioxidant capacity using pressurized hot water extraction

The pulp of avocado (Persea Americana) is widely consumed as the primary food source, while the seed is often discarded as food waste. Increased consumption of avocado would inevitably results in production of waste by-products such as avocado seeds, hence the ability to extract phytochemicals from such waste, and upcycling to potential nutraceutical products is of great interest. The overall aim of this study is to explore avocado seeds as potential functional food through the combined use of a green extraction method, chemical standardization and pattern recognition tools, and biological characterization assays. Specifically, this study utilized an organic solvent-free extraction method, pressurized hot water extraction (PHWE) to extract phytochemicals from avocado seeds and liquid chromatography mass spectrometry (LCMS) was used to identify the phytochemicals present in the avocado seeds. Our results demonstrated that avocado seed extracts have antioxidant activity and inhibited oxidative stress-induced metabolomics changes in endothelial cells, suggesting that avocado seed extracts have vasoprotective actions.

Gallic acid-mitochondria targeting sequence-H3R9 induces mitochondria-targeted cytoprotection

The development of selective targeting of drug molecules towards the mitochondria is an important issue related to therapy efficacy. In this study, we report that gallic acid (GA)-mitochondria targeting sequence (MTS)-H₃R₉ exhibits a dual role as a mitochondria-targeting vehicle with antioxidant activity for disease therapy. In viability assays, GA-MTS-H₃R₉ showed a better rescue action compared to that of MTS-H₃R₉. GA-MTS-H₃R₉ dramatically exhibited cell penetration and intercellular uptake compared to MTS and fit escape from lysosome release to the cytosol. We demonstrated the useful targeting of GA-MTS-H₃R₉ towards mitochondria in AC16 cells. Also, we observed that the antioxidant properties of mitochondrial-accrued GA-MTS-H₃R₉ alleviated cell damage by reactive oxygen species production and disrupted mitochondrial membrane potential. GA-MTS-H₃R₉ showed a very increased cytoprotective effect against anticancer activity compared to that of MTS-H₃R₉. We showed that GA-MTS-H₃R₉ can act as a vehicle for mitochondria-targeting and as a reagent for therapeutic applications intended for cardiovascular disease treatment.

Relaxin exerts a protective effect during ischemia-reperfusion in the rat model

BACKGROUND

Testicular torsion, which causes ischemia-reperfusion (IR) injury, is a serious urological emergency that can lead to testicular dysfunction, including infertility, primarily among newborn and pubertal males; thus, effective drugs should be administered during or after ischemia.

OBJECTIVES

Using a rat model of testicular IR injury, the present study investigated the protective effects of relaxin (RLN) against oxidative stress, testicular dysfunction, inflammation, histological damage, arrested spermatogenesis, and germ cell apoptosis as well as explored the usefulness of RLN as a potential protective drug for IR injury combined with surgical treatment.

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to left testicular ischemia for 2 h, followed by 24 h of reperfusion. They were subsequently divided into three groups: sham, IR, and IR + RLN groups. Porcine RLN (500 ng/h) or saline was infused using an implanted osmotic mini-pump 90 min after inducing ischemia. The RLN dose used herein was that which resulted in serum RLN levels comparable to those in mid-pregnant rats based on previous studies.

RESULTS

Testicular IR increased germ cell apoptosis and histological damage as well as promoted disorganized and arrested spermatogenesis, accompanied by a significant increase in oxidative stress and inflammation. However, RLN administration ameliorated the adverse consequences associated with IR injury by attenuating oxidative stress and mitigating apoptosis and inflammation.

DISCUSSION AND CONCLUSION

The study findings clearly demonstrated that RLN exerts a protective effect against IR-induced testicular injury by attenuating oxidative stress, apoptosis, and inflammation, suggesting that RLN together with surgical treatment is a potentially efficacious approach toward ameliorating testicular dysfunction following testicular torsion.

Pressurized Hot Water Extraction of Okra Seeds Reveals Antioxidant, Antidiabetic and Vasoprotective Activities

Abelmoschus esculentus L. Moench (okra) is a commonly consumed vegetable that consists of the seeds and peel component which are rich in polyphenolic compounds. The aim of this study is to utilize pressurized hot water extraction (PHWE) for the extraction of bioactive phytochemicals from different parts of okra. A single step PHWE was performed at various temperatures (60 °C, 80 °C, 100 °C and 120 °C) to determine which extraction temperature exhibits the optimum phytochemical profile, antioxidant and antidiabetic activities. The optimum temperature for PHWE extraction was determined at 80 °C and the biological activities of the different parts of okra (Inner Skin, Outer Skin and Seeds) were characterized using antioxidant (DPPH and ABTS), α-glucosidase and vasoprotective assays. Using PHWE, the different parts of okra displayed distinct phytochemical profiles, which consist of primarily polyphenolic compounds. The okra Seeds were shown to have the most antioxidant capacity and antidiabetic effects compared to other okra parts, likely to be attributed to their higher levels of polyphenolic compounds. Similarly, okra Seeds also reduced vascular inflammation by downregulating TNFα-stimulated VCAM-1 and SELE expression. Furthermore, metabolite profiling by LC/MS also provided evidence of the cytoprotective effect of okra Seeds in endothelial cells. Therefore, the use of PHWE may be an alternative approach for the environmentally friendly extraction and evaluation of plant extracts for functional food applications.

The Physiology of Reproduction - Quo vadis?

The reproductive system in males and females reflects a highly dynamic underlying physiology. Yet our current understanding of this system is still largely based upon relatively simplistic snapshots of individual component cells and tissues. Gamete production as well as gonadal hormone synthesis and its influence are the manifestations of dynamic and redundant informational networks and processes, whose qualitative and quantitative dimensions, especially through development from embryo through puberty and adulthood into ageing, are still largely uncharted. Whilst the recent huge advances in molecular science have helped to describe the components of the reproductive system in ever greater detail, how these interact and function in space and time dimensions is still largely obscure. Recent developments in microfluidics, stem cell biology, and the integration of single-cell transcriptomics with tissue dynamics are offering possible methodological solutions to this issue. Such knowledge is essential if we are to understand not only the normal healthy functioning of this system, but also how and why it is affected in disease or by external impacts such as those from environmental endocrine disruptors, or in ageing. Moreover, operating within a complex network of other physiological systems, its integrational capacity is much more than the generation of male and female gametes and their roles in fertility and infertility; rather, it represents the underpinning support for health and well-being across the lifespan, through pregnancy, puberty, and adulthood, into old age.

Hydrophobic interactions of relaxin family peptide receptor 3 with ligands identified using a NanoBiT-based binding assay

Relaxin family peptide receptor 3 (RXFP3) is a G protein-coupled receptor implicated in the regulation of food intake and stress response upon activation by the neuropeptide relaxin-3. In recent studies, interactions of RXFP3 with some natural or synthetic ligands have been investigated. In the present study, we identified the hydrophobic interactions of human RXFP3 with the chimeric agonist R3/I5 and the chimeric antagonist R3(ΔB23-27)R/I5 using a newly developed NanoBiT-based homogenous binding assay. We first demonstrated that the conserved large aliphatic B15Ile and B19Ile were important for the binding of the agonist and antagonist to RXFP3, because alanine replacement significantly decreased their receptor-binding potency. Thereafter, we demonstrated that the conserved large aliphatic Leu246 and Leu248 in extracellular loop 2 were important for RXFP3 binding to the agonist and antagonist, because alanine replacement significantly decreased the binding affinity of RXFP3 for both ligands. Finally, we deduced probable hydrophobic interactions based on the ability of RXFP3 mutants to distinguish the wild-type and mutant ligands: Leu246 of RXFP3 interacted with B15Ile of both ligands, while Leu248 of RXFP3 interacted with both B15Ile and B19Ile of the agonist and antagonist. The present results not only provided new insights into the interaction mechanism of RXFP3 with agonists and antagonists, but also demonstrated usefulness of the NanoBiT-based homogenous binding assay to study the interaction mechanism of certain receptors with their ligands.

Efficacy of relaxin for cisplatin-induced testicular dysfunction and epididymal spermatotoxicity

Background

Cisplatin (CP) is an extremely effective anticancer agent widely used to treat various cancer types, however, the potential side effects include testicular dysfunction. This study was to investigate, using a rat model of CP-induced testicular dysfunction, the protective effects of relaxin (RLN) against oxidative stress, testicular function, histological damage, spermatogenesis, germ-cell apoptosis, and sperm output, and to explore the usefulness of RLN as a potential protective drug for use with CP in chemotherapeutic treatments.

Methods

Sprague-Dawley male rats were used, which were divided into three groups: sham control, CP, and CP + RLN. Porcine RLN (500 ng/h) or saline was infused for 5 days using an implanted osmotic mini-pump following intraperitoneal injection of CP (6 mg/kg). RLN dose was chosen based on previous studies showing that it resulted in serum relaxin levels comparable to those in rats at the middle of pregnancy. At 5 days after CP administration, samples were collected and assessment of testicular histopathology, germ-cell apoptosis, oxidative stress, lipid peroxidation, and sperm quality was performed as main measures.

Results

The testicular CP model showed reduced testis weight and significantly decreased spermatogenesis scores. Additionally, CP administration induced a 4.6-fold increase in the apoptotic index associated with a significant increase in oxidative stress and upregulation of pro-apoptotic Casp3 and downregulation of anti-apoptotic Bcl2 levels, resulting in a marked reduction in sperm concentration. However, RLN administration caused a significant reduction in CP-mediated damage by attenuating oxidative stress and cell apoptosis. RLN administration efficiently scavenged ROS via the activation of SOD, CAT, and GPx and upregulation of GSH to prevent lipid peroxidation and decreased apoptosis by altering Bcl2 and Casp3 expression, thereby reducing histopathological damage and restoring spermatogenesis. Furthermore, RLN ameliorated attenuated sperm motility in the cauda epididymis resulting from CP treatment.

Conclusions

This study clearly indicates that RLN exerts a protective effect against CP-induced testicular damage through attenuation of oxidative stress and suppression of apoptosis. Our findings suggest RLN as a potentially efficacious drug for use with cisplatin chemotherapy in order to ameliorate CP-induced side effects and testicular injury adversely affecting spermatogenesis, sperm quality, and oxidative-stress parameters.

Relaxin reduces endothelium-derived vasoconstriction in hypertension: Revealing new therapeutic insights

BACKGROUND AND PURPOSE

Endothelium-derived vasoconstriction is a hallmark of vascular dysfunction in hypertension. In some cases, an overproduction of endothelium-derived prostacyclin (PGI₂ ) can cause contraction rather than relaxation. Relaxin is well known for its vasoprotective actions, but the possibility that this peptide could also reverse endothelium-derived vasoconstriction has never been investigated. We tested the hypothesis that short-term relaxin treatment mitigates endothelium-derived vasoconstriction in spontaneously hypertensive rats (SHR).

EXPERIMENTAL APPROACH

Male Wistar Kyoto rats (WKY) and SHR were subcutaneously infused with either vehicle (20 mmol·L^-1 sodium acetate) or relaxin (13.3 μg·kg^-1 ·hr^-1 ) using osmotic minipumps for 3 days. Vascular reactivity to the endothelium-dependent agonist ACh was assessed in vitro by wire myography. Quantitative PCR and LC-MS were used to identify changes in gene expression of prostanoid pathways and PG production, respectively.

KEY RESULTS

Relaxin treatment ameliorated hypertension-induced endothelial dysfunction by increasing NO-dependent relaxation and reducing endothelium-dependent contraction. Notably, short-term relaxin treatment up-regulated mesenteric PGI₂ receptor (IP) expression, permitting PGI₂ -IP-mediated vasorelaxation. In the aorta, reversal of contraction was accompanied by suppression of the hypertension-induced increase in prostanoid-producing enzymes and reduction in PGI₂ -evoked contractions.

CONCLUSIONS AND IMPLICATIONS

Relaxin has region-dependent vasoprotective actions in hypertension. Specifically, relaxin has distinct effects on endothelium-derived contracting factors and their associated vasoconstrictor pathways in mesenteric arteries and the aorta. Taken together, these observations reveal the potential of relaxin as a new therapeutic agent for vascular disorders that are associated with endothelium-derived vasoconstriction including hypertension.