Arginase Inhibition Restores Peroxynitrite-Induced Endothelial Dysfunction via L-Arginine-Dependent Endothelial Nitric Oxide Synthase Phosphorylation

Metabolic reprogramming in skin wound healing

Metabolic reprogramming refers to the ability of a cell to alter its metabolism in response to different stimuli and forms of pressure. It helps cells resist external stress and provides them with new functions. Skin wound healing involves the metabolic reprogramming of nutrients, such as glucose, lipids, and amino acids, which play vital roles in the proliferation, differentiation, and migration of multiple cell types. During the glucose metabolic process in wounds, glucose transporters and key enzymes cause elevated metabolite levels. Glucose-mediated oxidative stress drives the proinflammatory response and promotes wound healing. Reprogramming lipid metabolism increases the number of fibroblasts and decreases the number of macrophages. It enhances local neovascularization and improves fibrin stability to promote extracellular matrix remodelling, accelerates wound healing, and reduces scar formation. Reprogramming amino acid metabolism affects wound re-epithelialization, collagen deposition, and angiogenesis. However, comprehensive reviews on the role of metabolic reprogramming in skin wound healing are lacking. Therefore, we have systematically reviewed the metabolic reprogramming of glucose, lipids, and amino acids during skin wound healing. Notably, we identified their targets with potential therapeutic value and elucidated their mechanisms of action.

Downregulation of inflammatory erectile dysfunction by Mantisa religiosa egg-cake through NO-cGMP-PKG dependent NF-kB signaling cascade activated by mixture of salt intake

We hypothesized whether 10% praying-mantis-egg-cake (10% PMEC) can be applied against inflammatory-erectile-dysfunction and whether it could be linked to NO-cGMP-dependent PKG signaling cascade. Ninety male albino-rats were randomly distributed into nine (n = 10) groups. Group I was given distilled water. Group II and III were pre-treated with 80 mg/kg NaCl and 75 mg/kg MSG, respectively. Group IV was pre-treated with 80 mg/kg NaCl + 75 mg/kg MSG. Group V was administered with 80 mg/kg NaCl+ 3 mg/kg Amylopidin. Group VI was given 80 mg/kg NaCl + 10% PMEC. Group VII was treated with 75 mg/kg MSG + 10% PMEC. Group VIII was treated with 80 mg/kg NaCl+ 75 mg/kg MSG + 10% PMEC. Group IX was post-treated with 10% PMEC for 14 days. Penile PDE-5¹, arginase, ATP hydrolytic, cholinergic, dopaminergic (MAO-A) and adenosinergic (ADA) enzymes were hyperactive on intoxication with NaCl and MSG. The erectile dysfunction caused by inflammation was linked to alteration of NO-cGMP-dependent PKG signaling cascade via up-regulation of key cytokines and chemokine (MCP-1). These lesions were prohibited by protein-rich-cake (10% PMEC). Thus, protein-rich-cake (10% PMEC) by a factor of 4 (25%) inhibited penile cytokines/MCP-1 on exposure to mixture of salt-intake through NO-cGMP-PKG dependent-NF-_KB signaling cascade in rats.

Study of the effect of acetylsalicylic acid and a selective arginase II inhibitor KUD 975 on the correction of hemostatic disorders in experimental preeclampsia

Introduction: The disruption of the functional state of the vascular endothelium is among the main causes of preeclampsia, which is one of the most common causes of maternal and perinatal mortality. It can be enhanced by the humoral factors secreted by the activated platelets. The use of acetylsalicylic acid is an effective way to prevent preeclampsia. However, its ability to activate eNOS is a prerequisite for researching its ability to correct the disorders in developing preeclampsia, including by reducing the platelet activity. In this case its effect can be enhanced through increasing the bioavailability of L-arginine by using a selective arginase II inhibitor KUD 975. These facts were the prerequisite for conducting this study.

Materials and methods: The study was conducted on 180 female Wistar rats weighing 250–300 g. Acetylsalicylic acid was used at a dose of 7 mg/kg/day and 10 mg/kg/day, KUD 975 – at a dose of 1 mg/kg/day and 3 mg/kg/day. Adenosine diphosphate (ADP, 6.5 microns), arachidonic acid (ASPI, 0.5 mM), and collagen (3.2 mcg/ml) were used as aggregation inducers.

Results and discussion: ADMA-like preeclampsia simulation led to an increase in platelet aggregation ability when using all aggregation inducers. This is evidenced by an increase in a degree, rate of aggregation, and a shortened time of thrombus formation. The use of acetylsalicylic acid and a selective arginase II inhibitor KUD 975 led to a decrease in the aggregation ability of platelets and an increase in thrombosis time, while the combined administration of the studied agents showed a more pronounced effect.

Conclusion: The data obtained while performing a series of experiments strongly indicate a promising outlook for using acetylsalicylic acid and a selective arginase II inhibitor KUD 975 in order to correct emerging disorders in preeclampsia.

Virus-Induced Membrane Fusion in Neurodegenerative Disorders

A growing body of epidemiological and research data has associated neurotropic viruses with accelerated brain aging and increased risk of neurodegenerative disorders. Many viruses replicate optimally in senescent cells, as they offer a hospitable microenvironment with persistently elevated cytosolic calcium, abundant intracellular iron, and low interferon type I. As cell-cell fusion is a major driver of cellular senescence, many viruses have developed the ability to promote this phenotype by forming syncytia. Cell-cell fusion is associated with immunosuppression mediated by phosphatidylserine externalization that enable viruses to evade host defenses. In hosts, virus-induced immune dysfunction and premature cellular senescence may predispose to neurodegenerative disorders. This concept is supported by novel studies that found postinfectious cognitive dysfunction in several viral illnesses, including human immunodeficiency virus-1, herpes simplex virus-1, and SARS-CoV-2. Virus-induced pathological syncytia may provide a unified framework for conceptualizing neuronal cell cycle reentry, aneuploidy, somatic mosaicism, viral spreading of pathological Tau and elimination of viable synapses and neurons by neurotoxic astrocytes and microglia. In this narrative review, we take a closer look at cell-cell fusion and vesicular merger in the pathogenesis of neurodegenerative disorders. We present a "decentralized" information processing model that conceptualizes neurodegeneration as a systemic illness, triggered by cytoskeletal pathology. We also discuss strategies for reversing cell-cell fusion, including, TMEM16F inhibitors, calcium channel blockers, senolytics, and tubulin stabilizing agents. Finally, going beyond neurodegeneration, we examine the potential benefit of harnessing fusion as a therapeutic strategy in regenerative medicine.

Protein tyrosine nitration in atherosclerotic endothelial dysfunction

Accumulation of reactive oxygen species (ROS) can induce both protein tyrosine nitration and endothelial dysfunction in atherosclerosis. Endothelial dysfunction refers to impaired endothelium-dependent vasorelaxation that can be triggered by an imbalance in nitric oxide (NO) production and consumption. ROS reacts with NO to generate peroxynitrite, decreasing NO bioavailability. Peroxynitrite also promotes protein tyrosine nitration in vivo that can affect protein structure and function and further damage endothelial function. In this review, we discuss the process of protein tyrosine nitration, increased expression of nitrated proteins in cardiovascular disease and their association with endothelial dysfunction, and the interference of tyrosine nitration with antioxidants and the protective role in endothelial dysfunction. These may lead us to the conception that protein tyrosine nitration may be one of the causes of endothelial dysfunction, and help us gain information about the mechanism of endothelial dysfunction underlying atherosclerosis.

Changes in arginase isoforms in a murine model of neonatal brain hypoxia-ischemia

BACKGROUND

Arginases (ARG isoforms, ARG-1/ARG-2) are key regulatory enzymes of inflammation and tissue repair; however, their role after neonatal brain hypoxia (H) and hypoxia-ischemia (HI) remains unknown.

METHODS

C57BL/6 mice subjected to the Vannucci procedure on postnatal day (P9) were sacrificed at different timepoints. The degree of brain damage was assessed histologically. ARG spatiotemporal localization was determined via immunohistochemistry. ARG expression was measured by Western blot and activity spectrophotometrically.

RESULTS

ARG isoform expression increased during neurodevelopment (P9-P17) in the cortex and hippocampus. This was suppressed with H and HI only in the hippocampus. In the cortex, both isoforms increased with H alone and only ARG-2 increased with HI at 3 days. ARG activity during neurodevelopment remained unchanged, but increased at 1 day with H and not HI. ARG-1 localized with microglia at the injury site as early as 4 h after injury, while ARG-2 localized with neurons.

CONCLUSIONS

ARG isoform expression increases with age from P9 to P17, but is suppressed by injury specifically in the hippocampus and not in the cortex. Both levels and activity of ARG isoforms increase with H, while ARG-1 immunolabelling is upregulated in the HI cortex. Evidently, ARG isoforms in the brain differ in spatiotemporal localization, expression, and activity during neurodevelopment and after injury.

IMPACT

Arginase isoforms change during neurodevelopment and after neonatal brain HI. This is the first study investigating the key enzymes of inflammation and tissue repair called arginases following murine neonatal brain HI. The highly region- and cell-specific expression suggests the possibility of specific functions of arginases. ARG-1 in microglia at the injury site may regulate neuroinflammation, while ARG-2 in neurons of developmental structures may impact neurodevelopment. While further studies are needed to describe the exact role of ARGs after neonatal brain HI, our study adds valuable data on anatomical localization and expression of ARGs in brain during development and after stroke.

Arginase-1 deficiency in neural cells does not contribute to neurodevelopment or functional outcomes after sciatic nerve injury

Arginase-1 (Arg1) is an enzyme controlling the final step of the urea cycle, with highest expression in the liver and lower expression in the lungs, pancreas, kidney, and some blood cells. Arg1 deficiency is an inherited urea cycle disorder presenting with neurological dysfunction including spastic diplegia, intellectual and growth retardation, and encephalopathy. The contribution of Arg1 expression in the central and peripheral nervous system to the development of neurological phenotypes remains largely unknown. Previous studies have shown prominent arginase-1 expression in the nervous system and post-peripheral nerve injury in mice, but very low levels in the naïve state. To investigate neurobiological roles of Arg1, we created a conditional neural (n)Arg1 knockout (KO) mouse strain, with expression eliminated in neuronal and glial precursors, and compared them to littermate controls. Long-term analysis did not reveal any major differences in blood amino acid levels, body weight, or stride gait cycle from 8 to 26-weeks of age. Brain structure measured by magnetic resonance imaging at 16-weeks of age observed only a significant decrease in the volume of the mammillary bodies. We also assessed whether nArg1, which is expressed by sensory neurons after injury, may play a role in regeneration following sciatic nerve crush. Only subtle differences were observed in locomotor and sensory recovery between nArg1 KO and control mice. These results suggest that arginase-1 expression in central and peripheral neural cells does not contribute substantially to the phenotypes of this urea cycle disorder, nor is it likely crucial for post-injury regeneration in this mouse model.

The Nitric Oxide Pathway in Pulmonary Arterial Hypertension: Pathomechanism, Biomarkers and Drug Targets

The altered Nitric Oxide (NO) pathway in the pulmonary endothelium leads to increased vascular smooth muscle tone and vascular remodelling, and thus contributes to the development and progression of pulmonary arterial hypertension (PAH). The pulmonary NO signalling is abrogated by the decreased expression and dysfunction of the endothelial NO synthase (eNOS) and the accumulation of factors blocking eNOS functionality. The NO deficiency of the pulmonary vasculature can be assessed by detecting nitric oxide in the exhaled breath or measuring the degradation products of NO (nitrite, nitrate, S-nitrosothiol) in blood or urine. These non-invasive biomarkers might show the potential to correlate with changes in pulmonary haemodynamics and predict response to therapies. Current pharmacological therapies aim to stimulate pulmonary NO signalling by suppressing the degradation of NO (phosphodiesterase- 5 inhibitors) or increasing the formation of the endothelial cyclic guanosine monophosphate, which mediates the downstream effects of the pathway (soluble guanylate cyclase sensitizers). Recent data support that nitrite compounds and dietary supplements rich in nitrate might increase pulmonary NO availability and lessen vascular resistance. This review summarizes current knowledge on the involvement of the NO pathway in the pathomechanism of PAH, explores novel and easy-to-detect biomarkers of the pulmonary NO.

Arginine and Endothelial Function

Arginine (L-arginine), is an amino acid involved in a number of biological processes, including the biosynthesis of proteins, host immune response, urea cycle, and nitric oxide production. In this systematic review, we focus on the functional role of arginine in the regulation of endothelial function and vascular tone. Both clinical and preclinical studies are examined, analyzing the effects of arginine supplementation in hypertension, ischemic heart disease, aging, peripheral artery disease, and diabetes mellitus.

Antunes I, Dömling A, H. Elsinga P. Arginase as a Potential Biomarker of Disease Progression: A Molecular Imaging Perspective

Arginase is a widely known enzyme of the urea cycle that catalyzes the hydrolysis of L-arginine to L-ornithine and urea. The action of arginase goes beyond the boundaries of hepatic ureogenic function, being widespread through most tissues. Two arginase isoforms coexist, the type I (Arg1) predominantly expressed in the liver and the type II (Arg2) expressed throughout extrahepatic tissues. By producing L-ornithine while competing with nitric oxide synthase (NOS) for the same substrate (L-arginine), arginase can influence the endogenous levels of polyamines, proline, and NO•. Several pathophysiological processes may deregulate arginase/NOS balance, disturbing the homeostasis and functionality of the organism. Upregulated arginase expression is associated with several pathological processes that can range from cardiovascular, immune-mediated, and tumorigenic conditions to neurodegenerative disorders. Thus, arginase is a potential biomarker of disease progression and severity and has recently been the subject of research studies regarding the therapeutic efficacy of arginase inhibitors. This review gives a comprehensive overview of the pathophysiological role of arginase and the current state of development of arginase inhibitors, discussing the potential of arginase as a molecular imaging biomarker and stimulating the development of novel specific and high-affinity arginase imaging probes.

Correction of morphofunctional disorders of the cardiovascular system with asialized erythropoietin and arginase II selective inhibitors KUD 974 and KUD 259 in experimental preeclampsia

Introduction: Preeclampsia remains one of the most common causes of maternal and perinatal mortality worldwide. A significant role in the pathogenesis of this pathology is assigned to placental ischemia and endothelial dysfunction. Therefore, the aim of the present study was to study the effectiveness of asialized erythropoietin and arginase II selective inhibitors: KUD-259 and KUD-974 in the correction of morphofunctional disorders of the cardiovascular system in experimental preeclampsia.

Materials and methods: The study was performed in 260 female Wistar rats, each weighing 250–300 g. An ADMA-like preeclampsia was reproduced in the experiment. To assess the emerging morphofunctional disorders, the following parameters were used: blood pressure, coefficient of endothelial dysfunction, microcirculation in the placenta, proteinuria, fluid content in the omentum, concentration of terminal metabolites in the blood plasma, and morphometric parameters of fetuses.

Results and discussion: The administration of arginase II selective inhibitor KUD-974 in combination with asialized erythropoietin leads to a pronounced correction of emerging changes: a decrease in systolic and diastolic blood pressure in 1.5 and 1.7 times, a decrease in proteinuria in 3.6 times and a decrease in fluid content in the omentum. When arginase II selective inhibitor KUD 974 and asialized erythropoietin are used with methyldopa, the positive effects of the former are enhanced.

Conclusion: Arginase II selective inhibitors KUD-259 and KUD-974 and asialized erythropoietin have a pronounced positive effect on the correction of morphofunctional disorders in animals with ADMA-like preeclampsia.

Naringin protects against Bisphenol-A induced oculopathy as implication of cataract in hypertensive rat model

People who have experienced high blood pressure are at greater risk of susceptibility to other health problems including oculopathy. The patients with these experiences do not have adequate treatment and those who do; spend much funds on the drug purchase. The study examines the protective effect of naringin (NRG) against ocular impairment in _L-NAME induced hypertensive rat on exposure to a cellular disruptor. Fifty-six adult male albino rats were randomly distributed into eight (n = 7) groups. Group I: control animals, Group II was treated with Nω-nitro-L-arginine methyl ester hydrochloride (_L-NAME), Group III was treated with 50 mg/kg Bisphenol-A, Group IV was treated with _L-NAME +50 mg/kg Bisphenol-A. Group V was administered with _L-NAME +80 mg/kg NRG. Group VI was administered with 50 Mg/kg BPA + 80 mg/kg NRG. Group VII was administered with _L-NAME+50 mg/kg Bisphenol-A +80 mg/kg NRG. Lastly, group VIII was treated with 80 mg/kg NRG alone for 14 days. Naringin prevented hypertension and ocular dysfunction by depleting the activities of angiotensin-converting enzymes, arginase, aldose-reductase and phosphodiesterase-5¹ (PDE-5¹) with corresponding down-regulation of inflammatory markers including TNF-α and IL-B. Moreover, ocular impairment was remarkably reduced by NRG as manifested by the decreased activities of AChE, BuChE, MAO-A and enzymes of ATP hydrolysis (ATPase, ADPase, AMPase) and adenosine deaminase with resultant increased NO level. Also, ocular expression of CD43 transcript, caspaace-9 and tumor suppressor P53 proteins were suppressed on treatment with NRG. This study corroborates the view that NRG may be a useful therapy in alleviating inflammatory markers, apoptosis and metabolic nucleotides disorders via the NOS/cGMP/PKG signaling pathways in hypertensive rat model on exposure to a cellular disruptor.

Semen Cuscutae Administration Improves Hepatic Lipid Metabolism and Adiposity in High Fat Diet-Induced Obese Mice

Since arginase has been shown to compete with nitric oxide (NO) synthase, emerging evidence has reported that arginase inhibition improves obesity by increasing NO production. Semen cuscutae (SC), which is a well-known Chinese medicine, has multiple biological functions such as anti-oxidant function and immune regulation. In this study, we investigated whether the SC as a natural arginase inhibitor influences hepatic lipid abnormalities and whole-body adiposity in high-fat diet (HFD)-induced obese mice. The lipid accumulation was significantly reduced by SC treatment in oleic acid-induced hepatic steatosis in vitro. Additionally, SC supplementation substantially lowered HFD-induced increases in arginase activity and weights of liver and visceral fat tissue, while increasing hepatic NO. Furthermore, elevated mRNA expressions of sterol regulatory element-binding transcription factor 1 (SREBP-1c), fatty-acid synthase (FAS), peroxisome proliferator-activated receptor-gamma (PPAR-γ)1, and PPAR-γ2 in HFD-fed mice were significantly attenuated by SC supplementation. Taken together, SC, as a novel natural arginase inhibitor, showed anti-obesity properties by modulating hepatic arginase and NO production and metabolic pathways related to hepatic triglyceride (TG) metabolism.

Arginase Inhibition Suppresses Native Low-Density Lipoprotein-Stimulated Vascular Smooth Muscle Cell Proliferation by NADPH Oxidase Inactivation

PURPOSE

Vascular smooth muscle cell (VSMC) proliferation induced by native low-density lipoprotein (nLDL) stimulation is dependent on superoxide production from activated NADPH oxidase. The present study aimed to investigate whether the novel arginase inhibitor limonin could suppress nLDL-induced VSMC proliferation and to examine related mechanisms.

MATERIALS AND METHODS

Isolated VSMCs from rat aortas were treated with nLDL, and cell proliferation was measured by WST-1 and BrdU assays. NADPH oxidase activation was evaluated by lucigenin-induced chemiluminescence, and phosphorylation of protein kinase C (PKC) βII and extracellular signal-regulated kinase (ERK) 1/2 was determined by western blot analysis. Mitochondrial reactive oxygen species (ROS) generation was assessed using MitoSOX-red, and intracellular L-arginine concentrations were determined by high-performance liquid chromatography (HPLC) in the presence or absence of limonin.

RESULTS

Limonin inhibited arginase I and II activity in the uncompetitive mode, and prevented nLDL-induced VSMC proliferation in a p21Waf1/Cip1-dependent manner without affecting arginase protein levels. Limonin blocked PKCβII phosphorylation, but not ERK1/2 phosphorylation, and translocation of p47phox to the membrane was decreased, as was superoxide production in nLDL-stimulated VSMCs. Moreover, mitochondrial ROS generation was increased by nLDL stimulation and blocked by preincubation with limonin. Mitochondrial ROS production was responsible for the phosphorylation of PKCβII. HPLC analysis showed that arginase inhibition with limonin increases intracellular L-arginine concentrations, but decreases polyamine concentrations. L-Arginine treatment prevented PKCβII phosphorylation without affecting ERK1/2 phosphorylation.

CONCLUSION

Increased L-arginine levels following limonin-dependent arginase inhibition prohibited NADPH oxidase activation in a PKCβII-dependent manner, and blocked nLDL-stimulated VSMC proliferation.

Endogenous Regulators of the Immune System (sCD100, Malonic Dialdehyde, and Arginase)

Tissue damage in various diseases, hypoxic conditions, and some pathologies are associated with production of endogenous factors such as the soluble form of the surface receptor CD100, malonic dialdehyde, and arginase and their release into circulation. These factors modulate functional state of lymphocytes in the immune system: potentiate activation of B lymphocytes, activate synthesis and secretion of IL-25 and IL-17 cytokines, and suppress proliferative activity of T lymphocytes, thus modulating immunological reactivity of the organism. Reactions of innate and adaptive immunity develop against the background of changed immunological reactivity, which should be taken into account in the development of pathogenetically substantiated therapy.

Peroxynitrite induces apoptosis of mouse cochlear hair cells via a Caspase-independent pathway in vitro

Peroxynitrite (ONOO-) is a potent and versatile oxidant implicated in a number of pathophysiological processes. The present study was designed to investigate the effect of ONOO- on the cultured cochlear hair cells (HCs) of C57BL/6 mice in vitro as well as the possible mechanism underlying the action of such an oxidative stress. The in vitro primary cultured cochlear HCs were subjected to different concentrations of ONOO-, then, the cell survival and morphological changes were examined by immunofluorescence and transmission electron microscopy (TEM), the apoptosis was determined by Terminal deoxynucleotidyl transferase dUNT nick end labeling (TUNEL) assay, the mRNA expressions of Caspase-3, Caspase-8, Caspase-9, Apaf1, Bcl-2, and Bax were analyzed by RT-PCR, and the protein expressions of Caspase-3 and AIF were assessed by immunofluorescence. This work demonstrated that direct exposure of primary cultured cochlear HCs to ONOO- could result in a base-to-apex gradient injury of HCs in a concentration-dependent manner. Furthermore, ONOO- led to much more losses of outer hair cells than inner hair cells mainly through the induction of apoptosis of HCs as evidenced by TEM and TUNEL assays. The mRNA expressions of Caspase-8, Caspase-9, Apaf1, and Bax were increased and, meanwhile, the mRNA expression of Bcl-2 was decreased in response to ONOO- treatment. Of interesting, the expression of Caspase-3 had no significant change, whereas, the expression alteration of AIF was observed. These results suggested that ONOO- can effectively damage the survival of cochlear HCs via triggering the apoptotic pathway. The findings from this work suggest that ONOO--induced apoptosis is mediated, at least in part, via a Caspase-independent pathway in cochlear HCs.

Hybrid Nitric Oxide Donor and its Carrier for the Treatment of Peripheral Arterial Diseases

Nitric oxide (NO) has been known to promote physiological angiogenesis to treat peripheral arterial diseases (PAD) by increasing the vascular endothelial growth factor (VEGF) level in endothelial cells (ECs) and preventing platelet adherence and leukocyte chemotaxis. However, the ongoing ischemic event during peripheral ischemia produces superoxide and diminishes the NO bioavailability by forming toxic peroxynitrite anion. Here we disclose an efficacious hybrid molecule 4-(5-Amino-1,2,3-oxadiazol-3-yl)-2,2,6,6-tetramethyl-1-piperidinol (SA-2) containing both antioxidant and NO donor functionalities that provide a therapeutic level of NO necessary to promote angiogenesis and to protect ECs against hydrogen peroxide-induced oxidative stress. Compound SA-2 scavenged reactive oxygen species, inhibited proliferation and migration of smooth muscle cells (SMCs) and promoted the tube formation from ECs. Copolymer poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with SA-2 provided a sustained release of NO over days, improved aqueous stability in serum, protected ECs against oxidative stress, and enhanced angiogenesis under stress conditions as compared to that of the control in the in vitro matrigel tube formation assay. These results indicated the potential use of SA-2 nanoparticles as an alternative therapy to treat PAD.