Based on hydrogen and disulfide-mediated bonds, l-lysine and l-arginine enhanced the gel properties of low-salt mixed shrimp surimi (Antarctic krill and Pacific white shrimp)

This study delved into the effects of l-lysine (Lys) and l-arginine (Arg) on the gel properties and intermolecular interactions of low-salt (NaCl, 1 g/100 g) mixed shrimp surimi (Antarctic krill and Pacific white shrimp). The addition of Lys and Arg improved the gel strength and water holding capacity of low-salt gels, which were superior to the properties of STPP and high-salt (NaCl, 2.25 g/100 g) gels. These results can be attributed to the role of Lys and Arg in enhancing hydrogen and disulfide bonds within the low-salt gel system, promoting the solubilization of myofibrillar proteins (MP) and consequently increasing the number of MP molecules participating in gel formation. Antarctic krill MP did not show gel-forming ability and exerted a diluting effect on low-salt mixed shrimp surimi gels. Molecular docking analysis indicated the stable binding of Lys and Arg to myosin.

Review of the evidence of radioprotective potential of creatine and arginine as dietary supplements

PURPOSE

Creatine (Cr) and l-arginine are naturally occurring guanidino compounds, commonly used as ergogenic dietary supplements. Creatine and l-arginine exhibit also a number of non-energy-related features, such as antioxidant, anti-apoptotic, and anti-inflammatory properties, which contribute to their protective action against oxidative stress (OS). In this regard, there are a number of studies emphasizing the protective effect of Cr against OS, which develops in the process of aging, increased physical loads as part of athletes' workouts, as well as a number of neurological diseases and toxic effects associated with xenobiotics and UV irradiation. Against this backdrop, and since ionizing radiation causes OS in cells, leading to radiotoxicity, there is an increasing interest to understand whether Cr has the full potential to serve as an effective radioprotective agent. The extensive literature search did not provide any data on this issue. In this narrative review, we have summarized some of our own experimental data published over the last years addressing the respective radioprotective effects of Cr. Next, we have additionally reviewed the existing data on the radiomodifying effects of l-arginine presented earlier by other research groups.

CONCLUSIONS

Creatine possesses significant radioprotective potential including: (1) radioprotective effect on the survival rate of rats subjected to acute whole-body X-ray irradiation in a LD70/30 dose of 6.5 Gy, (2) radioprotective effect on the population composition of peripheral blood cells, (3) radioprotective effect on the DNA damage of peripheral blood mononuclear cells, (4) radioprotective effect on the hepatocyte nucleus-nucleolar apparatus, and (5) radioprotective effect on the brain and liver Cr-Cr kinase systems of the respective animals. Taking into account these cytoprotective, gene-protective, hepatoprotective and energy-stimulating features of Cr, as well as its significant radioprotective effect on the survival rate of rats, it can be considered as a potentially promising radioprotector for further preclinical and clinical studies. The review of the currently available data on radiomodifying effects of l-arginine has indicated its significant potential as a radioprotector, radiomitigator, and radiosensitizer. However, to prove the effectiveness of arginine (Arg) as a radioprotective agent, it appears necessary to expand and deepen the relevant preclinical studies, and, most importantly, increase the number of proof-of-concept clinical trials, which are evidently lacking as of now.

Short-Term l-arginine Treatment Mitigates Early Damage of Dermal Collagen Induced by Diabetes

Changes in the structural properties of the skin due to collagen alterations are an important factor in diabetic skin complications. Using a combination of photonic methods as an optic diagnostic tool, we investigated the structural alteration in rat dermal collagen I in diabetes, and after short-term l-arginine treatment. The multiplex approach shows that in the early phase of diabetes, collagen fibers are partially damaged, resulting in the heterogeneity of fibers, e.g., "patchy patterns" of highly ordered/disordered fibers, while l-arginine treatment counteracts to some extent the conformational changes in collagen-induced by diabetes and mitigates the damage. Raman spectroscopy shows intense collagen conformational changes via amides I and II in diabetes, suggesting that diabetes-induced structural changes in collagen originate predominantly from individual collagen molecules rather than supramolecular structures. There is a clear increase in the amounts of newly synthesized proline and hydroxyproline after treatment with l-arginine, reflecting the changed collagen content. This suggests that it might be useful for treating and stopping collagen damage early on in diabetic skin. Our results demonstrate that l-arginine attenuates the early collagen I alteration caused by diabetes and that it could be used to treat and prevent collagen damage in diabetic skin at a very early stage.

Dual Strategy with Adipose-Derived Stem Cells and l-arginine Recovered Cavernosal Functions in a Rat Model of Radical Prostatectomy

As standard therapy for prostate cancer, radical prostatectomy causes cavernous nerve (CN) injury and increases fibrosis and hypoxia-induced penile structural alterations. This study aimed to determine the potential beneficial effects of adipose-derived stem cells (ADSCs) and l-arginine alone or in combination on the penile erection in a rat model of erectile dysfunction caused by bilateral cavernous nerve transection (CNT). Male rats (n = 35) were randomized into five groups: Sham-operated; CNT (4-weeks); CNT plus ADSCs (1 × 106 cells by intracavernosal injection); CNT plus l-arginine (4 weeks, 10 mg/kg/day, oral); and ADSCs combined with l-arginine in CNT. In vivo erectile responses and in vitro relaxant responses were measured. Western blot and immunohistochemistry analyses were used to determine the expression and localization of endothelial nitric oxide synthase, neuronal nitric oxide synthase, transforming growth factor-beta 1, hypoxia-inducible factor-1 alpha (HIF-1α), and apoptosis markers (Bax and Bcl-2). The ratio of smooth muscle to collagen and nerve regeneration were calculated using Masson's trichrome and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining. The combined treatment restored diminished erectile responses, endothelium-dependent acetylcholine, and electrical field stimulation-induced relaxation of the corpus cavernosum in rats with CNT, whereas either monotherapy produced only partial improvements. All treatment regimens restored increases in the protein expression of HIF-1 and Bax in rats with CNT. The decrease in smooth muscle mass and NADPH-diaphorase-positive nerve fibers was partially ameliorated by monotherapy, whereas combined therapy led to recovery. These findings indicate that combined treatment with ADSCs and l-arginine may restore erectile function in rats with CNT by inhibiting hypoxia-induced neurotoxicity and preserving endothelium function and smooth muscle content.

Modulatory effects of supplementation of Lentinula edodes mycelia extract and l-arginine on the therapeutic efficacy of immunogenic chemotherapy in colon cancer-bearing mice

Some chemotherapeutic drugs can induce cancer cell death and enhance antitumor T-cell immunity in cancer-bearing hosts. Immunomodulatory reagents could augment such chemotherapy-induced effects. We previously reported that oral digestion of Lentinula edodes mycelia (L.E.M.) extract or  l-arginine supplementation can augment antitumor T-cell responses in cancer-bearing mice. In this study, the effects of L.E.M. extract with or without  l-arginine on the therapeutic efficacy of immunogenic chemotherapy by 5-fluorouracil (5-FU)/oxaliplatin (L-OHP) and/or cyclophosphamide (CP) are examined using two mouse colon cancer models. In MC38 and CT26 cancer models, therapy with 5-FU/L-OHP/CP significantly suppressed tumor growth, and supplementation with L.E.M. extract halved the tumor volumes. However, the modulatory effect of L.E.M. extract was not significant. In the CT26 cancer model, supplementation with L.E.M. extract and  l-arginine had no clear effect on tumor growth. In contrast, their addition to chemotherapy halved the tumor volumes, although the effect was not significant. There was no difference in the cytotoxicity of tumor-specific cytotoxic T cells generated from CT26-cured mice treated by chemotherapy alone versus chemotherapy combined with L.E.M. extract/ l-arginine. These results indicate that the antitumor effects of immunogenic chemotherapy were too strong to ascertain the effects of supplementation of L.E.M. extract and  l-arginine, but these reagents nonetheless have immunomodulatory effects on the therapeutic efficacy of immunogenic chemotherapy in colon cancer-bearing mice.

Gastro-protective effect of l-arginine against nitric oxide deficiency-related mucosal injury induced by indomethacin: Does age matter?

Gastric ulcer is a common disease with increased prevalence in the aged population. Aged gastric mucosa has increased susceptibility to injury along with nonsteroidal anti-inflammatory drugs use due to impaired mucosal defense and decreased vasodilator release. We investigated whether l-arginine could protect against age-related gastric ulceration induced by indomethacin. Aged and adult male Wistar rats were administered sole and combined treatment of  l-arginine and Nω -nitro-l-arginine methyl ester ( l-NAME) before induction of gastric ulceration by indomethacin. The gastroprotective effect of  l-arginine was displayed only in adult rats with indomethacin-induced gastric ulceration, as evidenced by a significant decrease in ulcer index, oxidative stress parameters, and mucosal myeloperoxidase activity along with increased mucosal PGE2 levels. Interestingly, the mucosal gene expressions of NF-кB, iNOS, and COX-2 were significantly suppressed by  l-arginine pretreatment and aggregated upon pretreatment with  l-NAME in both adult and aged rats treated with indomethacin. In conclusion,  l-arginine protected the rats' gastric mucosa against indomethacin-induced gastric ulceration, possibly, at least in part, by enhancement of mucosal nitric oxide/PGE2 content along with suppressing gastric inflammation and oxidative stress. This study supposed that the gastroprotective effect of  l-arginine depends on aging, and even so, the adoption of a new approach to gastric ulcer treatment for the aged population is warranted.

To What Extent Does Arginine Reduce the Risk of Developing Necrotizing Enterocolitis?

Necrotizing enterocolitis (NEC) and neonatal sepsis are polar opposite diseases that are commonly encountered in the NICU. Concerning the frequency of these pathologies, NEC is regarded as being a much rarer condition, whereas neonatal sepsis is slightly more commonly encountered. However, neonatal sepsis can present with varying clinical presentations and, if caught late, can be detrimental to the patient. Many different modes of therapies have been studied for both conditions at different levels of pathologies, from a microscopic to a macroscopic level, leading to an assessment of treatment approaches. With the different ongoing treatment protocols being studied, one such therapy under investigation that does stand out is the use of L-arginine in both conditions. The L-arginine, being an essential amino acid, has many basic biological roles in developing neonates. It mainly involves the production of nitric oxide (NO), a potent vasodilator, which is particularly important in the development of vasculature in almost every organ. In premature infants, poorly developed vasculature makes them more susceptible to injury, therefore increasing the risk of diseases such as NEC and the severity of diseases such as neonatal sepsis. By assessing the uses of L-arginine and its application towards treating conditions like NEC and neonatal sepsis, we aim to identify its potential benefits as a treatment and its potential applications in clinical practice by understanding its basic functions and role in the pathophysiology of NEC and neonatal sepsis.

Thermal stability and interfacial rheology of whey protein-corn oil emulsions: The effect of l-arginine fortification

The effect of l-arginine (Arg) on the thermal stability of whey protein-corn oil emulsions was investigated to determine its role in improving emulsion stability. The results indicated that with an increase in Arg concentration, the emulsion stability index, emulsification activity index, and absolute ζ-potential increased initially and decreased after high-temperature sterilization. However, the mean particle size, apparent viscosity, creaming indices, and dynamic interfacial pressure of the emulsions first decreased and then increased, and the performance of samples that only showed an increase in pH could also improve the emulsification stability. These results clarify the mechanism by which Arg increases the thermal stability of emulsions.

Crystal Structure and Functional Characterization of Acetylornithine Aminotransferase from Corynebacterium glutamicum

The amino acids l-arginine and l-ornithine are widely used in animal feed and as health supplements and pharmaceutical compounds. In arginine biosynthesis, acetylornithine aminotransferase (AcOAT) uses pyridoxal-5'-phosphate (PLP) as a cofactor for amino group transfer. Here, we determined the crystal structures of the apo and PLP complex forms of AcOAT from Corynebacterium glutamicum (CgAcOAT). Our structural observations revealed that CgAcOAT undergoes an order-to-disorder conformational change upon binding with PLP. Additionally, we observed that unlike other AcOATs, CgAcOAT exists as a tetramer. Subsequently, we identified the key residues involved in PLP and substrate binding based on structural analysis and site-directed mutagenesis. This study might provide structural insights on CgAcOAT, which can be utilized for the development of improved l-arginine production enzymes.

L-arginine and aged garlic extract for the prevention of migraine: a study protocol for a randomised, double-blind, placebo-controlled, phase-II trial (LARGE trial)

Background

Migraine is a common and distressing neurological condition characterised by recurrent throbbing headaches, nausea and heightened sensitivity to light and sound. Accumulating evidence suggests that cerebral arteries dilate during migraine, causing distal microvessels to constrict, which could activate nociceptors and cause onset of headache pain. If so, preventing or attenuating chronic microvascular constriction, and promoting a dilatory phenotype, may reduce frequency and/or severity of migraines. The primary aim of the L-Arginine and Aged Garlic Extract (LARGE) trial is to investigate whether oral treatment with dietary nutraceuticals, L-arginine and aged garlic extract (AGE), both systemic vasodilatory agents, will alleviate migraine frequency, duration and severity in adults with chronic frequent episodic migraines.

Methods

The study is a randomised double-blind placebo-controlled phase-II single-site clinical trial conducted in Perth, Australia. The target sample is to recruit 240 participants diagnosed with chronic frequent episodic migraines between 18 and 80 years of age. Participants will be randomised to one of four treatment groups for 14 weeks (placebo induction for 2 weeks, followed by 12 weeks on one of the respective treatment arms): placebo, L-arginine, AGE, or a combination of L-arginine and AGE. The doses of L-arginine and AGE are 1.5 g and 1 g daily, respectively. The primary outcome is to assess migraine response using change in migraine frequency and intensity between baseline and 12 weeks. Secondary outcomes include the impact of L-arginine and/or AGE on photosensitivity, retinal vessel changes, and blood biomarker concentrations of vascular tone, following a 12-week intervention.

Discussion

The protocol describes the oral administration of 2 nutraceutical-based interventions as possible prophylactic treatments for chronic frequent episodic migraines, with potential for direct clinical translation of outcomes. Potential limitations of the study include the fixed-dose design of each treatment arm and that in vivo neuroimaging methods, such as magnetic resonance imaging (MRI), will not be conducted to determine putative cerebro-vasodilatory changes to coincide with the outcome measures. Dose-response studies may be indicated.

Trial registration

The trial was retrospectively registered with the Australian New Zealand Clinical Trials Registry ACTRN12621001476820 (Universal Trial Number: U1111-1268-1117) on 04/08/2021. This is protocol version 1, submitted on 25/11/2022.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-023-03149-y.

Cystatin-c May Indicate Subclinical Renal Involvement, While Orosomucoid Is Associated with Fatigue in Patients with Long-COVID Syndrome

Long-COVID syndrome is associated with high healthcare costs, but its pathophysiology is not yet fully understood. Inflammation, renal impairment or disturbance of the NO system emerge as potential pathogenetic factors. We aimed to investigate the relationship between symptoms of long-COVID syndrome and serum levels of cystatin-c (CYSC), orosomucoid (ORM), l-arginine, symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA). A total of 114 patients suffering from long-COVID syndrome were included in this observational cohort study. We found that serum CYSC was independently associated with the anti-spike immunoglobulin (S-Ig) serum level (OR: 5.377, 95% CI: 1.822-12.361; p = 0.02), while serum ORM (OR: 9.670 (95% CI: 1.34-9.93; p = 0.025) independently predicted fatigue in patients with long-COVID syndrome, both measured at baseline visit. Additionally, the serum CYSC concentrations measured at the baseline visit showed a positive correlation with the serum SDMA levels. The severity of abdominal and muscle pain indicated by patients at the baseline visit showed a negative correlation with the serum level of L-arginine. In summary, serum CYSC may indicate subclinical renal impairment, while serum ORM is associated with fatigue in long-COVID syndrome. The potential role of l-arginine in alleviating pain requires further studies.

Intramuscular administration of l-arginine boosts testicular hemodynamics, plasma concentrations of testosterone and nitric oxide in heat-stressed rams

The current study aimed to assess, for the first time, the effects of intramuscular injection of l-arginine (L-arg) on testicular hemodynamics, echogenicity, and plasma concentrations of testosterone, total antioxidant capacity, and nitric oxide (NO) in Ossimi rams. Twelve sexually matured heat-stressed rams were randomly assigned to one of two groups: the L-arg group (n = 6) received 5 mg/kg L-arg dissolved in 2 ml normal saline 0.9%, or the control group (n = 6) received merely 2 ml of normal saline 0.9%. Blood sampling, B-mode ultrasound assessment of the testicular parenchyma, and pulsed-wave Doppler ultrasound of the testicular artery for both right and left testis were performed immediately before 0 min and 1, 4, 24, 48, 72, and 168 h after L-arg or saline administration. In the L-arg group, resistive index (RI) and pulsatility index (PI) means were significantly lower compared to the control group at 4-168 h post-treatment. Plasma testosterone concentrations were higher (P < 0.05) at 4 h and onward in the L-arg treated compared to the control rams, the same for NO levels however its increase (P < 0.05) was observed as soon as 1 h post-treatment. In L-arg treated rams, NO concentrations were positively correlated to plasma testosterone concentrations (r = 0.7, p < .01), but negatively correlated to both RI and PI (r = -0.8 and -0.6, respectively, p < .01). In conclusion, l-arginine administration enhanced testicular blood flow and increased plasma testosterone and nitric oxide concentrations in heat-stressed rams.

Analysis of a maternal health medicines pipeline database 2000-2021: New candidates for the prevention and treatment of fetal growth restriction

OBJECTIVE

The Accelerating Innovation for Mothers project established a new database of candidate medicines under development between 2000 and 2021 for five pregnancy-related conditions, including fetal growth restriction. The objective was to assess medicines for fetal growth restriction and their potential for clinical use globally.

DESIGN

Landscape analysis.

SETTING

Global (focus on low- and middle-income countries, LMICs).

SAMPLE

Drugs, dietary supplements and biologics under investigation for prevention or treatment of fetal growth restriction.

METHODS

A research pipeline database of medicines was created through searching AdisInsight, PubMed and various grant and clinical trial databases. Analysis of clinical and preclinical candidates were descriptive.

MAIN OUTCOMES MEASURES

Fetal growth restriction candidates in clinical development were identified and ranked as high, medium or low potential based on prespecified criteria, including efficacy, safety and accessibility.

RESULTS

Of the 444 unique candidates in the database across all five pregnancy-related conditions, 63 were for fetal growth restriction. Of these, 31 were in clinical development (phases I, II or III) and 32 were in preclinical development. Three candidates, aspirin, l-arginine and vitamin D, were ranked as having high potential as preventive agents. There were no high-potential candidates for treating fetal growth restriction, although five candidates were ranked as having medium potential: allylestrenol, dalteparin, omega-3 fatty acids, tadalafil, and United Nations International Multiple Micronutrient Antenatal Preparation (UNIMMAP).

CONCLUSIONS

l-Arginine, aspirin and vitamin D are promising, high-potential preventative agents for fetal growth restriction. Based on the medicines pipeline, new pharmacological agents for fetal growth restriction are unlikely to emerge in the near future.

Taste Masking of Promethazine Hydrochloride Using l-Arginine Polyamide-Based Nanocapsules

Promethazine hydrochloride (PMZ), a potent H1-histamine blocker widely used to prevent motion sickness, dizziness, nausea, and vomiting, has a bitter taste. In the present study, taste masked PMZ nanocapsules (NCs) were prepared using an interfacial polycondensation technique. A one-step approach was used to expedite the synthesis of NCs made from a biocompatible and biodegradable polyamide based on l-arginine. The produced NCs had an average particle size of 193.63 ± 39.1 nm and a zeta potential of −31.7 ± 1.25 mV, indicating their stability. The NCs were characterized using differential scanning calorimetric analysis and X-ray diffraction, as well as transmission electron microscopy that demonstrated the formation of the NCs and the incorporation of PMZ within the polymer. The in vitro release study of the PMZ-loaded NCs displayed a 0.91 ± 0.02% release of PMZ after 10 min using artificial saliva as the dissolution media, indicating excellent taste masked particles. The in vivo study using mice revealed that the amount of fluid consumed by the PMZ-NCs group was significantly higher than that consumed by the free PMZ group (p < 0.05). This study confirmed that NCs using polyamides based on l-arginine and interfacial polycondensation can serve as a good platform for the effective taste masking of bitter actives.

TRAUMA INDUCES INTRAVASCULAR HEMOLYSIS, EXACERBATED BY RED BLOOD CELL TRANSFUSION AND ASSOCIATED WITH DISRUPTED ARGININE-NITRIC OXIDE METABOLISM

ABSTRACT

Background: Severe injury can provoke systemic processes that lead to organ dysfunction, and hemolysis of both native and transfused red blood cells (RBCs) may contribute. Hemolysis can release erythrocyte proteins, such as hemoglobin and arginase-1, the latter with the potential to disrupt arginine metabolism and limit physiologic NO production. We aimed to quantify hemolysis and arginine metabolism in trauma patients and measure association with injury severity, transfusions, and outcomes. Methods: Blood was collected from injured patients at a level I trauma center enrolled in the COMBAT (Control of Major Bleeding After Trauma) trial. Proteomics and metabolomics were performed on plasma fractions through liquid chromatography coupled with mass spectrometry. Abundances of erythrocyte proteins comprising a hemolytic profile as well as haptoglobin, l -arginine, ornithine, and l -citrulline (NO surrogate marker) were analyzed at different timepoints and correlated with transfusions and adverse outcomes. Results: More critically injured patients, nonsurvivors, and those with longer ventilator requirement had higher levels of hemolysis markers with reduced l -arginine and l -citrulline. In logistic regression, elevated hemolysis markers, reduced l -arginine, and reduced l -citrulline were significantly associated with these adverse outcomes. An increased number of blood transfusions were significantly associated with elevated hemolysis markers and reduced l -arginine and l -citrulline independently of New Injury Severity Score and arterial base excess. Conclusions: Severe injury induces intravascular hemolysis, which may mediate postinjury organ dysfunction. In addition to native RBCs, transfused RBCs can lyse and may exacerbate trauma-induced hemolysis. Arginase-1 released from RBCs may contribute to the depletion of l -arginine and the subsequent reduction in the NO necessary to maintain organ perfusion.

Arginine for the Treatment of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes: A Systematic Review

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a mitochondrial disease that lacks a definitive treatment. Lately, there has been an increased interest in the scientific community about the role of arginine in the short and long-term settings of the disease. We aim to conduct a systematic review of the clinical use of arginine in the management of MELAS and explore the role of arginine in the pathophysiology of the disease. We used PubMed advanced-strategy searches and only included full-text clinical trials on humans written in the English language. After applying the inclusion/exclusion criteria, four clinical trials were reviewed. We used the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol for this systematic review. We used the Cochrane Collaboration risk-of-bias tool to assess the bias encountered in each study. Overall, IV arginine seems to be effective in improving symptoms during acute attacks of MELAS, while oral arginine supplementation increases endothelial function, preventing further stroke-like episodes.

The Role of L-Arginine-NO System in Female Reproduction: A Narrative Review

Accumulating evidence are available on the involvement of l-arginine-nitric oxide (NO) system in complex biological processes and numerous clinical conditions. Particular attention was made to reveal the association of l-arginine and methylarginines to outcome measures of women undergoing in vitro fertilization (IVF). This review attempts to summarize the expression and function of the essential elements of this system with particular reference to the different stages of female reproduction. A literature search was performed on the PubMed and Google Scholar systems. Publications were selected for evaluation according to the results presented in the Abstract. The regulatory role of NO during the period of folliculogenesis, oocyte maturation, fertilization, embryogenesis, implantation, placentation, pregnancy, and delivery was surveyed. The major aspects of cellular l-arginine uptake via cationic amino acid transporters (CATs), arginine catabolism by nitric oxide synthases (NOSs) to NO and l-citrulline and by arginase to ornithine, and polyamines are presented. The importance of NOS inhibition by methylated arginines and the redox-sensitive elements of the process of NO generation are also shown. The l-arginine-NO system plays a crucial role in all stages of female reproduction. Insufficiently low or excessively high rates of NO generation may have adverse influences on IVF outcome.

l-Arginine as Bio-Based Curing Agent for Epoxy Resins: Temperature-Dependence of Mechanical Properties

The precise characterization of new bio-based thermosets is imperative for the correct assessment of their potential as matrix material in fiber-reinforced polymer composites. Therefore, the mechanical properties of diglycidyl ether of bisphenol a (DGEBA) cured with l-arginine were investigated to determine whether the bio-based thermoset possesses the required mechanical properties for application as a matrix material. The cured thermoset is called Argopox. The mixture of amino acid and epoxy resin was prepared via three-roll milling and cured in the presence of an urea-based accelerator. The tensile, compression, flexural and toughness properties of Argopox were characterized at T=−40 ∘C, 22 ∘C and 80 ∘C to determine the temperature-dependence of the thermoset’s mechanical properties in its service temperature range. The glass transition temperature Tg was analyzed via dynamic mechanical analysis (DMA) and is approximately 119 ∘C. The tensile, compression and flexural strength at 22 ∘C are about 56 MPa, 98 MPa and 85 MPa, respectively. The critical stress intensity factor KIC and fracture energy GIC at 22 ∘C are roughly 1.1 MPam0.5 and 510 Jm−, respectively. Consequently, Argopox possesses mechanical properties that reach performance levels similar to that of materials which are already used as matrix for fiber reinforced composites.

Genomics and transcriptomics-guided metabolic engineering Corynebacterium glutamicum for l-arginine production

l-arginine is a semi-essential amino acid that is broadly used as food additives and pharmaceutical intermediates. The synthesis of l-arginine is restricted by complex metabolic mechanisms and suboptimal fermentation conditions. Initially, a mutant strain that accumulated 19.4 g/L l-arginine was generated by random mutagenesis. Subsequently, a mutation of the repressor protein (argRG159D) in the l-arginine operon and glutamate synthase (gltD) with 532-fold upregulation were identified to be vital for l-arginine production by multi-omic analysis. Systematic metabolic engineering was used to modify the strain, which included interfering with α-ketoglutarate dehydrogenase complex (ODHC) activity by knocking out serine/threonine-protein kinase (pknG), enhancing the expression of multiple key enzymes in the l-arginine synthesis pathway, and increasing the availability of intracellular cofactor (NADPH) and energy (ATP). Finally, C. glutamicum ARG12 produced 71.3 g/L l-arginine, with a yield of 0.43 g/g glucose by fermentation optimization. This study provides new ideas to boost l-arginine production.

l-Arginine as a Bio-Based Curing Agent for Epoxy Resins: Glass Transition Temperature, Rheology and Latency

The need for sustainable practices in the processing chain of fiber-reinforced thermosets has led to the development of bio-based epoxy resins and curing agents. As a contribution to sustainable composites, this study focuses on the glass transition temperature (Tg), viscosity and latency of diglycidyl ether of bisphenol a (DGEBA) cured with l-arginine in the presence of a urea-based accelerator. These characteristics are decisive features for application as a matrix in fiber-reinforced polymer composites produced via prepreg technology in which low viscosity and sufficient latency, meaning low reactivity of the one-component system, are necessary. The homogeneous mixture of amino acid and epoxy resin was prepared via three-roll milling. Two formulations, Argopox-1 with 1 wt.% accelerator and Argopox-2.5 with 2.5wt.% accelerator, were prepared and parts of each formulation were stored at 22 °C and -18 °C, respectively. Both formulations were tested via differential scanning calorimetry (DSC) and small amplitude oscillatory shear rheology (SAOS) after 0 d, 30 d, 60 d, 90 d and 180 d of storage to determine the influence of accelerator weight fraction, storage temperature and storage period on the glass transition temperature of the uncured resin system Tg0, and their viscosity. The Tg of the thermosets is about 100 °C. The DSC and SAOS measurements show that the Tg0 of Argopox-1 shifts about 5 °C in 60 d, while its viscosity is still low enough to be processed in a prepreg production line. Furthermore, Argopox-1 is storable for at least 180 d at -18 °C without significant changes in its Tg0 and viscosity. Consequently, Argopox-1 possesses a sufficiently high Tg and adequate latency, as well as a low viscosity for application as prepreg matrix material.

Paeonol protects against acute pancreatitis by Nrf2 and NF-κB pathways in mice

OBJECTIVES

Paeonol (PAE) is an active ingredient with anti-inflammatory and antioxidant properties. This study was designed to investigate the effect of PAE on acute pancreatitis (AP).

METHODS

AP was induced by the intraperitoneal injection of 20% l-arginine (4 g/kg) for 6 h. Mice were pretreated with PAE (25, 50 or 100 mg/kg) intragastrically for 5 days. The histological damage and alterations of biochemical indicators, inflammatory cytokines and oxidative stress factors in AP mice were detected. The Nrf2 and NF-κB pathways were examined to illustrate the potential mechanism.

KEY FINDINGS

In AP model, we found that PAE attenuated histological injury of pancreatic tissues, reduced the serum levels of α-amylase and increased Ca2+ contents in a dose-dependent manner. The white blood cell content, and IL-1β, IL-6 and TNF-α levels in the serum of AP mice were reduced by PAE. Furthermore, PAE caused a reduction of MPO and MDA levels, accompanied by an increase in SOD activity in the pancreas of AP mice. We also demonstrated that the alterations of Nrf2 and NF-κB pathways in AP mice were reversed by PAE.

CONCLUSIONS

PAE attenuates inflammation and oxidative stress in the development of AP by the regulation of Nrf2 and NF-κB pathways.

Effect of the variation in the extracellular concentration of l-arginine in the physiology of Leishmania (Viannia) braziliensis and its susceptibility to some antileishmanial drugs

The knowledge about amino acid metabolism in trypanosomatids is a valuable source of new therapeutic targets. l-arginine is an essential amino acid for Leishmania parasites, and it participates in the synthesis of polyamines, a group of essential nutrients used for nucleic acids, proteins biosynthesis, and redox modulation necessary for proliferation. In the present study, we evaluated the effect of changes in the availability of this amino acid on promastigotes and intracellular amastigotes on U937 macrophages and showed that the absence of l-arginine in culture medium negatively influences the growth and infectivity of Leishmania (Viannia) braziliensis, causing a decrease in the percentage of the infected cells and parasite load tested through light microscopy. In addition, the absence of l-arginine resulted in the parasite's inability to regulate its reactive oxygen species (ROS) production, which persisted for up to 24 h by flow cytometry following the probe H2DCF-DA dye. Moreover, the differentiation of promastigote to amastigote in axenic culture was more significant at low concentrations of l-arginine suggesting that this depletion induces a stress environment to increase this transformation under axenic conditions. No association was established between the availability of l-arginine and the effectiveness of antileishmanial drugs. All these results confirm the importance of l-arginine in L. braziliensis life cycle vital processes, such as its replication and infectivity, as documented in other Leishmania species. Based on these results, we proposed that the l-arginine uptake/metabolism route is possible in exploring new antileishmanial drugs.

Interval training and Crataegus persica ameliorate diabetic nephropathy via miR-126/Nrf-2 mediated inhibition of stress oxidative in rats with diabetes after myocardial ischemia-reperfusion injury

Myocardial disorders are the most common cause of renal failure and mortality in diabetic patients, but the molecular mechanism of this process is not yet clear. The reduction of nuclear Erythroid2-related factor-2 (Nrf-2) and positive regulators of Nrf-2 proteins, such as DJ-1 and microRNA-126 (miR-126), after hypoxia and the promotion of reactive oxygen species, might be an intervention indicator in renal failure after myocardial ischemia-reperfusion. Therefore, this study evaluates the renoprotective effect of exercise training and Crataegus persica extract (CE) on myocardial ischemia-reperfusion-induced kidney injury in diabetic rats. Fifty rats were divided into five groups: healthy sedentary control (Con), sedentary diabetic (D), interval trained diabetic (TD), diabetic plus Crataegus persica extract treatment (CD), and interval trained diabetic plus Crataegus persica extract treatment (TCD) groups. The rats in the exercise groups were subjected to moderate-intensity interval training five days per week for ten weeks. The rats in CD and TCD groups received 300 mg/kg of Crataegus persica through gavage for ten weeks. Then, the subjects underwent 30 min of myocardial ischemia and subsequently reperfusion for 24 h. At the end of the experiment, insulin sensitivity, oxidative stress, renal function, histopathology of the kidney, Nrf-2, miR-126, and DJ-1 gene expression levels were evaluated. The results show that the treatments decreased elevated levels of renal oxidative stress, glomerular filtration rate, insulin sensitivity, and pathological score in diabetic rats. Also, the expression of Nrf-2 and miR-126, unlike DJ-1, decreased in diabetic rats due to interval training. Due to the results, diabetes aggravates acute myocardial ischemia-reperfusion-induced kidney injury, while moderate-intensity interval training and Crataegus persica treatment simultaneously ameliorate myocardial ischemia-reperfusion-induced renal injury via miR-126/Nrf-2 pathway and improve insulin sensitivity and renal function in type 1 diabetic rats.

Arginine Supplementation Targeting Tumor-Killing Immune Cells Reconstructs the Tumor Microenvironment and Enhances the Antitumor Immune Response

The tumor microenvironment (TME) is characterized by several immunosuppressive factors, of which weak acidity and l-arginine (l-arg) deficiency are two common features. A weak acidic environment threatens the survival of immune cells, and insufficient l-arg will severely restrain the effect of antitumor immune responses, both of which affect the efficiency of cancer treatments (especially immunotherapy). Meanwhile, l-arg is essential for tumor progression. Thus, two strategies, l-arg supplementation and l-arg deprivation, are developed for cancer treatment. However, these strategies have the potential risk of promoting tumor growth and impairing immune responses, which might lead to a paradoxical therapeutic effect. It is optimal to limit the l-arg availability of tumor cells from the microenvironment while supplying l-arg for immune cells. In this study, we designed a multivesicular liposome technology to continuously supply alkaline l-arg, which simultaneously changed the acidity and l-arg deficiency in the TME, and by selectively knocking down the CAT-2 transporter, l-arg starvation of tumors was maintained while tumor-killing immune cells were enriched in the TME. The results showed that our strategy promoted the infiltration and activation of CD8+ T cells in tumor, increased the proportion of M1 macrophages, inhibited melanoma growth, and prolonged survival. In combination with anti-PD-1 antibody, our strategy reversed the low tumor response to immune checkpoint blockade therapy, showing a synergistic antitumor effect. Our work provided a reference for improving the TME combined with regulating nutritional competitiveness to achieve the sensitization of immunotherapy.

Systems metabolic engineering of Corynebacterium glutamicum eliminates all by-products for selective and high-yield production of the platform chemical 5-aminovalerate

5-aminovalerate (AVA) is a platform chemical of substantial commercial value to derive nylon-5 and five-carbon derivatives like δ-valerolactam, 1,5-pentanediol, glutarate, and 5-hydroxyvalerate. De-novo bio-production synthesis of AVA using metabolically engineered cell factories is regarded as exemplary route to provide this chemical in a sustainable way. So far, this route is limited by low titers, rates and yields and suffers from high levels of by-products. To overcome these limitations, we developed a novel family of AVA producing C. glutamicum cell factories. Stepwise optimization included (i) improved AVA biosynthesis by expression balancing of the heterologous davAB genes from P. putida, (ii) reduced formation of the by-product glutarate by disruption of the catabolic y-aminobutyrate pathway (iii), increased AVA export, and (iv) reduced AVA re-import via native and heterologous transporters to account for the accumulation of intracellular AVA up to 300 mM. Strain C. glutamicum AVA-5A, obtained after several optimization rounds, produced 48.3 g L^-1 AVA in a fed-batch process and achieved a high yield of 0.21 g g^-1. Surprisingly in later stages, the mutant suddenly accumulated glutarate to an extent equivalent to 30% of the amount of AVA formed, tenfold more than in the early process, displaying a severe drawback toward industrial production. Further exploration led to the discovery that ArgD, naturally aminating N-acetyl-l-ornithine during l-arginine biosynthesis, exhibits deaminating side activity on AVA toward glutarate formation. This promiscuity became relevant because of the high intracellular AVA level and the fact that ArgD became unoccupied with the gradually stronger switch-off of anabolism during production. Glutarate formation was favorably abolished in the advanced strains AVA-6A, AVA-6B, and AVA-7, all lacking argD. In a fed-batch process, C. glutamicum AVA-7 produced 46.5 g L^-1 AVA at a yield of 0.34 g g^-1 and a maximum productivity of 1.52 g L^-1 h^-1, outperforming all previously reported efforts and stetting a milestone toward industrial manufacturing of AVA. Notably, the novel cell factories are fully genome-based, offering high genetic stability and requiring no selection markers.

l-Arginine Induces White Adipose Tissue Browning-A New Pharmaceutical Alternative to Cold

The beneficial effects of l-arginine supplementation in obesity and type II diabetes involve white adipose tissue (WAT) reduction and increased substrate oxidation. We aimed to test the potential of l-arginine to induce WAT browning. Therefore, the molecular basis of browning was investigated in retroperitoneal WAT (rpWAT) of rats exposed to cold or treated with 2.25% l-arginine for 1, 3, and 7 days. Compared to untreated control, levels of inducible nitric oxide (NO) synthase protein expression and NO signaling increased in both cold-exposed and l-arginine-treated groups. These increases coincided with the appearance of multilocular adipocytes and increased expression levels of uncoupling protein 1 (UCP1), thermogenic and beige adipocyte-specific genes (Cidea, Cd137, and Tmem26), mitochondriogenesis markers (peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α, mitochondrial DNA copy number), nuclear respiratory factor 1, PPARα and their respective downstream lipid oxidation enzymes after l-arginine treatment. Such browning phenotype in the l-arginine-treated group was concordant with end-course decreases in leptinaemia, rpWAT mass, and body weight. In conclusion, l-arginine mimics cold-mediated increases in NO signaling in rpWAT and induces molecular and structural fingerprints of rpWAT browning. The results endorse l-arginine as a pharmaceutical alternative to cold exposure, which could be of great interest in obesity and associated metabolic diseases.

Downregulation of eNOS and preserved endothelial function in endothelial-specific arginase 1-deficient mice

Arginase 1 (Arg1) is a ubiquitous enzyme belonging to the urea cycle that catalyzes the conversion of l-arginine into l-ornithine and urea. In endothelial cells (ECs), Arg1 was proposed to limit the availability of l-arginine for the endothelial nitric oxide synthase (eNOS) and thereby reduce nitric oxide (NO) production, thus promoting endothelial dysfunction and vascular disease. The role of EC Arg1 under homeostatic conditions is in vivo less understood. The aim of this study was to investigate the role of EC Arg1 on the regulation of eNOS, vascular tone, and endothelial function under normal homeostatic conditions in vivo and ex vivo. By using a tamoxifen-inducible EC-specific gene-targeting approach, we generated EC Arg1 KO mice. Efficiency and specificity of the gene targeting strategy was demonstrated by DNA recombination and loss of Arg1 expression measured after tamoxifen treatment in EC only. In EC Arg1 KO mice we found a significant decrease in Arg1 expression in heart and lung ECs and in the aorta, however, vascular enzymatic activity was preserved likely due to the presence of high levels of Arg1 in smooth muscle cells. Moreover, we found a downregulation of eNOS expression in the aorta, and a fully preserved systemic l-arginine and NO bioavailability, as demonstrated by the levels of l-arginine, l-ornithine, and l-citrulline as well as nitrite, nitrate, and nitroso-species. Lung and liver tissues from EC Arg1 KO mice showed respectively increase or decrease in nitrosyl-heme species, indicating that the lack of endothelial Arg1 affects NO bioavailability in these organs. In addition, EC Arg1 KO mice showed fully preserved acetylcholine-mediated vascular relaxation in both conductance and resistant vessels but increased phenylephrine-induced vasoconstriction. Systolic, diastolic, and mean arterial pressure and cardiac performance in EC Arg1 KO mice were not different from the wild-type littermate controls. In conclusion, under normal homeostatic conditions, lack of EC Arg1 expression is associated with a down-regulation of eNOS expression but a preserved NO bioavailability and vascular endothelial function. These results suggest that a cross-talk exists between Arg1 and eNOS to control NO production in ECs, which depends on both L-Arg availability and EC Arg1-dependent eNOS expression.

Integrated Metabolomics and Transcriptomics Analyses Reveal Metabolic Mechanisms in Porcine Intestinal Epithelial Cells under Zearalenone Stress

Zearalenone (ZEA) is a mycotoxin that frequently occurs in agricultural crops and related products and seriously threatens both animal feed and human food safety. To identify key metabolites and regulators involved in ZEA toxicological processes, we performed metabolomic and transcriptomic analyses of porcine IPEC-J2 intestinal epithelial cells upon ZEA exposure using liquid chromatography-mass spectrometry (LC-MS)/MS and RNA-seq techniques. A total of 325 differential metabolites and 5646 differentially expressed genes were detected. Integrated analyses of metabolomic and transcriptomic data indicated that metabolic processes including lipid metabolism, amino acid metabolism, and carbohydrate metabolism were most affected. Exogenous addition of the key metabolite l-arginine significantly facilitated ZEA metabolism and ameliorated ZEA-induced reactive oxygen species levels and cell apoptosis. Furthermore, l -arginine contributed to the expression of phase II detoxification genes (SULT2B1, GSTA1, GSTM3, and GPX4). l-Arginine addition also increased the protein levels of LC3-II and Beclin 1, and downregulated p62/SQSTM1 levels, indicating its regulatory roles in autophagic flux activation upon ZEA exposure. This study provided global insights into metabolic and transcriptional changes as well as key metabolites and regulators underlying the cellular response to ZEA exposure, and paved the way for the identification of metabolic and molecular targets for biomonitoring and controlling contamination by ZEA.

l-Arginine prevents 4-hydroxy-2-nonenal accumulation and depresses inflammation via inhibiting NF-κB activation

4-Hydroxy-2-nonenal (HNE) is an inducer of inflammation. The aim of this study was to elicit the link between the inhibition of HNE accumulation and the depression of inflammation whether dependent onl-arginine availability in growing rats. Male Wistar rats were fed with different levels of l-arginine at 250, 500, and 1000 mg/kg body weight for 14 days. The control group was fed with commercial pellets. After 14 days of oral administration, l-arginine significantly reduced hepatic accumulation of HNE and depressed inflammation in rats as compared with the control group. Compared to the control group, the anti-inflammatory action of l-arginine is reflected by upregulation of hepatic interleukin-10 (IL-10) and the suppression of hepatic cyclooxygenase-2, tumor necrotic factor α, IL-1β, and IL-6 expressions in growing rats. With l-arginine administration, the activation of nuclear factor-κB (NF-κB) was efficaciously inhibited through the upregulation of inhibitory κBα, and the depression of phosphoinositide 3-kinase/protein kinase B (PI3K/Akt). In conclusion, this study demonstrated that l-arginine could reduce hepatic HNE levels and depress inflammation in growing rats, revealing a link between the inhibition of HNE accumulation with the depression of inflammation, which was attributed to the availability of l-arginine. A significant finding of this study was that the anti-inflammatory mechanism exerted by l-arginine was to inhibit NF-κB activation via downregulating PI3K/Akt.

l-Arginine and Beetroot Extract Supplementation in the Prevention of Sarcopenia

Aging is associated with a significant decline in neuromuscular function, leading to a reduction in muscle mass and strength. The aim of the present report was to evaluate the effect of supplementation with nitric oxide precursors (l-arginine and beetroot extract) in muscular function during a training period of 6 weeks in elderly men and women. The study (double-blind, placebo-controlled) involved 66 subjects randomly divided into three groups: placebo, arginine-supplemented and beetroot extract-supplemented. At the end of this period, no changes in anthropometric parameters were observed. Regarding other circulating parameters, urea levels were significantly (p < 0.05) lower in women of the beetroot-supplemented group (31.6 ± 5.9 mg/dL) compared to placebo (41.3 ± 8.5 mg/dL) after 6 weeks of training. In addition, the circulating creatine kinase activity, as an index of muscle functionality, was significantly (p < 0.05) higher in women of the arginine- (214.1 ± 162.2 mIU/L) compared to the beetroot-supplemented group (84.4 ± 36.8 mIU/L) at the end of intervention. No significant effects were noticed with l-arginine or beetroot extract supplementation regarding strength, endurance and SPPB index. Only beetroot extract supplementation improved physical fitness significantly (p < 0.05) in the sprint exercise in men after 6 weeks (2.33 ± 0.59 s) compared to the baseline (2.72 ± 0.41 s). In conclusion, beetroot seems to be more efficient during short-term training while supplementing, preserving muscle functionality in women (decreased levels of circulating creatine kinase) and with modest effects in men.

Histological and biochemical apoptosis changes of female rats' ovary by Zinc oxide nanoparticles and potential protective effects of l-arginine: An experimental study

Background

This research aims to investigate the adverse effects of ZnO NP on ovarian tissue and the follicular and menstrual cycle and the protective effects of l-arginine on the aforementioned tissues.

Material and methods

30 rats were divided into five groups. The first group was the control group. The second and fourth groups received 100 mg/kg and 200 mg/kg ZnO NP, respectively. The third and fifth groups received the same doses of ZnO NP as the second and fourth groups, respectively. However, the third and fifth groups received an additional dose of 1.3 gr/kg of LA amino acid. ZnO NP and LA are given intraperitoneal for 21 days. Blood samples from each rat and a part of the ovarium were collected to test for gene expression and histological analysis.

Results

Compared to levels of housekeeping gene β-actine, levels of apoptosis effectors such as Bax, Bcl, Caspase 3, and Caspase 9 were significantly increased in all groups. In groups that received doses of LA (three and five), atretic follicle size was smaller compared to groups that did not receive LA (two and four). In addition, in the third group, the secondary and primordial follicle's generated oocytes were smaller compared with groups two, four, and five. Compared with the control group, all groups experienced morphological degeneration of follicles and tissue.

Conclusion

ZnO NP has inevitable, morphological, and physiological effects on the ovary and can detrimentally impact the tissue. LA can aid in the regeneration of the tissue and block damage induced by stress and toxicity.

•

Zinc oxide nanoparticles are widely used in various everyday products, such as food packaging, additives, cosmetics, and bioimaging.

•

Using Zinc oxide nanoparticles in daily life may cause infertility by reducing the number of follicles in the ovary.

•

L-Arginine may be a beneficial daily supplement to prevent damage to the ovaries induced by Zinc oxide nanoparticles.

Contributions of endothelin-1 and l-arginine to blunted cutaneous microvascular function in young, black women

Non-Hispanic black (BL) individuals have the greatest prevalence of cardiovascular disease (CVD), relative to other racial/ethnic groups (e.g., non-Hispanic white population; WH), which may be secondary to blunted vascular function. Although women typically present with reduced CVD relative to men of the same racial/ethnic group, the prevalence is similar between BL women and men though the mechanisms differ. This study hypothesized that reduced microvascular function in young, BL women is associated with endothelin-1 (ET-1) overactivity or insufficient l-arginine bioavailability. Nine BL and nine WH women participated (age: 20 ± 2 vs. 22 ± 2 yr). Cutaneous microvascular function was assessed during 39°C local heating, whereas lactated Ringer's (control), BQ-123 (ET-1 receptor type A antagonist), BQ-788 (ET-1 receptor type B antagonist), or l-arginine were infused via intradermal microdialysis to modify cutaneous vascular conductance (CVC). Subsequent infusion of N^ω-nitro-l-arginine methyl ester allowed for quantification of the nitric oxide (NO) contribution to vasodilation, whereas combined sodium nitroprusside and 43°C heating allowed for normalization to maximal CVC (%CVC_max). BL women had blunted %CVC_max and NO contribution to dilation during the 39°C plateau (P < 0.027 for both). BQ-123 improved this response through augmented NO-mediated dilation (P < 0.048 for both). BQ-788 and l-arginine did not alter the CVC responses (P > 0.835 for both) or the NO contribution (P > 0.371 for both). Cutaneous microvascular function is reduced in BL women, and ET-1 receptor type A may contribute to this reduced function. Further research is needed to better characterize these mechanisms in young, BL women.NEW & NOTEWORTHY Cardiovascular disease remains a burden in the United States non-Hispanic black (BL) population, although its manifestation through blunted vasodilation in this population is different between men and women. Accordingly, this study determined that reduced microvascular function in young, BL women may be partially controlled by endothelin-1 (ET-1) type A receptors, although neither type B receptors nor insufficient l-arginine bioavailability seems to contribute to this response. Accordingly, further research is needed to better characterize these ET-1 related mechanisms and illuminate other pathways that may contribute to this disparate vascular function in young, BL women.

Therapeutic effect of rupatadine against l-arginine-induced acute pancreatitis in rats: role of inflammation

Acute pancreatitis (AP) is an abrupt inflammatory disorder causing high morbidity and mortality. As AP is an insidious medical emergency, a curative modality is required instead of a preventive measure. Thus, we investigated the possible curative effect of rupatadine on a rat model of AP. Rupatadine is a potent histamine receptor 1 (H1R) and platelet-activating factor (PAF) blocker. We used four groups of six Wistar rats as follows: the control group received vehicle; the rupatadine control group received rupatadine as 6 mg/kg orally; the AP group received l-arginine intraperitoneally, and the treatment group received rupatadine at 1, 6, and 24 h after l-arginine injection. The levels of serum amylase, pancreatic oxidative parameters, and pancreatic cytokines were measured. PAF, histamine, and myeloperoxidase levels were determined in the pancreas. Histopathological and immunohistochemical examinations were performed to determine nuclear factor kappa-B (NF-κB) and caspase 3 expressions. Oxidative damage and severe inflammation were detected in the pancreas of the AP group. Rupatadine reduced the oxidative damage and the levels of proinflammatory cytokines, PAF, histamine, myeloperoxidase, NF-κB, and caspase 3 expressions. It restored the pancreatic acini to almost normal condition. Rupatadine induced important anti-inflammatory and antiapoptotic effects against l-arginine-induced AP.

Arginine-mediated gut microbiome remodeling promotes host pulmonary immune defense against nontuberculous mycobacterial infection

Nontuberculous mycobacterial pulmonary diseases (NTM-PDs) are emerging as global health threats with issues of antibiotic resistance. Accumulating evidence suggests that the gut-lung axis may provide novel candidates for host-directed therapeutics against various infectious diseases. However, little is known about the gut-lung axis in the context of host protective immunity to identify new therapeutics for NTM-PDs. This study was performed to identify gut microbes and metabolites capable of conferring pulmonary immunity to NTM-PDs. Using metabolomics analysis of sera from NTM-PD patients and mouse models, we showed that the levels of l-arginine were decreased in sera from NTM-PD patients and NTM-infected mice. Oral administration of l-arginine significantly enhanced pulmonary antimicrobial activities with the expansion of IFN-γ-producing effector T cells and a shift to microbicidal (M1) macrophages in the lungs of NTM-PD model mice. Mice that received fecal microbiota transplants from l-arginine-treated mice showed increased protective host defense in the lungs against NTM-PD, whereas l-arginine-induced pulmonary host defense was attenuated in mice treated with antibiotics. Using 16S rRNA sequencing, we further showed that l-arginine administration resulted in enrichment of the gut microbiota composition with Bifidobacterium species. Notably, oral treatment with either Bifidobacterium pseudolongum or inosine enhanced antimicrobial pulmonary immune defense against NTM infection, even with multidrug-resistant clinical NTM strains. Our findings indicate that l-arginine-induced gut microbiota remodeling with enrichment of B. pseudolongum boosts pulmonary immune defense against NTM infection by driving the protective gut-lung axis in vivo.

l-Arginine Alleviates LPS-Induced Oxidative Stress and Apoptosis via Activating SIRT1-AKT-Nrf2 and SIRT1-FOXO3a Signaling Pathways in C2C12 Myotube Cells

l-arginine (l-Arg) has been reported to possess a wide range of functions, including anti-inflammatory, anti-oxidative, and anti-apoptosis. However, the role of l-Arg in LPS-induced muscle injury and its potential protective mechanism has not been well elucidated. This study aimed to investigate the effects of l-Arg on the LPS-induced oxidative stress and apoptosis in differentiated C2C12 myotube cells. Our results demonstrated that myotube cells treated with 0.2 mg/mL LPS significantly decreased cell viability. l-Arg treatment significantly suppressed LPS induced ROS accumulation and cell apoptosis. Furthermore, l-Arg improved antioxidant-related enzymes’ activities; increased antioxidant ability via Akt-Nrf2 signaling pathway; maintained the mitochondrial membrane potential (MMP); and enhanced FOXO3a expression, leading to a decrease in the mitochondrial-associated apoptotic proteins. In addition, l-Arg exposure dramatically increased the mRNA and protein expressions of SIRT1. The cytoprotective effect of l-Arg was restricted by the SIRT1 inhibitor EX527, which led to an increase in ROS level, apoptosis rate, and decreased cell MMP. The results also demonstrated that EX527 treatment significantly eliminated the effect of l-Arg on LPS-induced oxidative damage and mitochondria-mediated cell apoptosis. Our findings revealed that l-Arg could be used as a potential nutraceutical in reducing muscle injury via regulating SIRT1-Akt-Nrf2 and SIRT1-FOXO3a-mitochondria apoptosis signaling pathways.

l-Arginine Improves Solubility and ANTI SARS-CoV-2 Mpro Activity of Rutin but Not the Antiviral Activity in Cells

The COVID-19 pandemic outbreak prompts an urgent need for efficient therapeutics, and repurposing of known drugs has been extensively used in an attempt to get to anti-SARS-CoV-2 agents in the shortest possible time. The glycoside rutin shows manifold pharmacological activities and, despite its use being limited by its poor solubility in water, it is the active principle of many pharmaceutical preparations. We herein report our in silico and experimental investigations of rutin as a SARS-CoV-2 Mpro inhibitor and of its water solubility improvement obtained by mixing it with l-arginine. Tests of the rutin/l-arginine mixture in a cellular model of SARS-CoV-2 infection highlighted that the mixture still suffers from unfavorable pharmacokinetic properties, but nonetheless, the results of this study suggest that rutin might be a good starting point for hit optimization.

Nitric Oxide Releasing Delivery Platforms: Design, Detection, Biomedical Applications, and Future Possibilities

Gasotransmitters belong to the subfamily of endogenous gaseous signaling molecules, which find a wide range of biomedical applications. Among the various gasotransmitters, nitric oxide (NO) has an enormous effect on the cardiovascular system. Apart from this, NO showed a pivotal role in neurological, respiratory, and immunological systems. Moreover, the paradoxical concentration-dependent activities make this gaseous signaling molecule more interesting. The gaseous NO has negligible stability in physiological conditions (37 °C, pH 7.4), which restricts their potential therapeutic applications. To overcome this issue, various NO delivering carriers were reported so far. Unfortunately, most of these NO donors have low stability, short half-life, or low NO payload. Herein, we review the synthesis of NO delivering motifs, development of macromolecular NO donors, their advantages/disadvantages, and biological applications. Various NO detection analytical techniques are discussed briefly, and finally, a viewpoint about the design of polymeric NO donors with improved physicochemical characteristics is predicted.

The Functional DNA Methylation Signatures Relevant to Altered Immune Response of Neonatal T Cells with l-Arginine Supplementation

l-Arginine is an important nutrient in the infant diet that significantly regulates the maturation of the immune system in neonates, including the maturation of CD4⁺ T cells. The biological activities of CD4⁺ T cells differ substantially between neonates and adults, and these differences may be governed by epigenetic processes. Investigating these differences and the causative processes may help understand neonatal and developmental immunity. In this study, we compared the functional DNA methylation profiles in CD4⁺ T cells of neonates and adults, focusing on the role of l-arginine supplementation. Umbilical cord blood and adult CD4⁺ T cells were cultured with/without l-arginine treatment. By comparing DNA methylation in samples without l-arginine treatment, we found that CD4⁺ T cells of neonatal cord blood generally showed higher DNA methylation than those of adults (average CpG methylation percentage 0.6305 for neonate and 0.6254 for adult, t-test p-value < 0.0001), suggesting gene silencing in neonates. By examining DNA methylation patterns of CpG dinucleotides induced by l-arginine treatment, we found that more CpG dinucleotides were hypomethylated and more genes appeared to be activated in neonatal T-cells as compared with adult. Genes activated by l-arginine stimulation of cord blood samples were more enriched regarding immune-related pathways. CpG dinucleotides at IL-13 promoter regions were hypomethylated after l-arginine stimulation. Hypomethylated CpG dinucleotides corresponded to higher IL-13 gene expression and cytokine production. Thus, DNA methylation partially accounts for the mechanism underlying differential immune function in neonates. Modulatory effects of l-arginine on DNA methylation are gene-specific. Nutritional intervention is a potential strategy to modulate immune function of neonates.

Thymol regulates the functions of immune cells in the rat peritoneal cavity after l-arginine-induced pancreatitis

AIMS

The present study aimed to evaluate the protective action of thymol towards l-arginine-induced acute pancreatitis (AP) by studying the function of rat peritoneal immune cells.

MAIN METHODS

Rat peritoneal exudate cells (PECs), obtained 24 h after the injection of l-arginine (350 mg/100 g of b.w.), were evaluated for mitochondrial activity (MTT assay), adherence capacity (methylene-blue assay), and phagocyte enzyme activity (myeloperoxidase, MPO, assay). The activity of α-amylase and free MPO, as well as the concentration of reactive oxygen species (ROS, i.e. O₂^-), were determined in the peritoneal exudate fluid. Also, serum α-amylase activity determination and pancreatic tissue pathohistological analysis were performed.

KEY FINDING

The administered thymol (50 and 100 mg/kg, per os) caused a significant decrease in the PEC mitochondrial activity and adherence capacity when compared with these functions of PECs isolated from rats with AP. A decrease in cellular MPO activity, as well as in the levels of ROS, α-amylase, and free MPO in peritoneal exudates was found in animals treated with thymol compared to the control animals with AP. Additionally, thymol administration prevented an increase in serum α-amylase activity, accompanied by the decrease in pancreatic tissue damage that follows l-arginine application.

SIGNIFICANCE

The present results showed that thymol exerts significant immunomodulatory properties and a potential to silence PEC functions in inflammatory conditions such as the AP induced by l-arginine.

Nitric Oxide-cGMP Pathway Modulation in an Experimental Model of Hypoxic Pulmonary Hypertension

Manipulation of nitric oxide (NO) may enable control of progression and treatment of pulmonary hypertension (PH). Several approaches may modulate the NO-cGMP pathway in vivo. Here, we investigate the effectiveness of 3 modulatory sites: (i) the amount of l-arginine; (ii) the size of plasma NO stores that stimulate soluble guanylate cyclase; (iii) the conversion of cGMP into inactive 5′-GMP, with respect to hypoxia, to test the effectiveness of the treatments with respect to hypoxia-induced PH. Male rats (n = 80; 10/group) maintained in normoxic (21% O₂) or hypoxic chambers (10% O₂) for 14 days were subdivided in 4 sub-groups: placebo, l-arginine (20 mg/ml), the NO donor molsidomine (15 mg/kg in drinking water), and phoshodiesterase-5 inhibitor sildenafil (1.4 mg/kg in 0.3 ml saline, i.p.). Hypoxia depressed homeostasis and increased erythropoiesis, heart and right ventricle hypertrophy, myocardial fibrosis and apoptosis inducing pulmonary remodeling. Stimulating anyone of the 3 mechanisms that enhance the NO-cGMP pathway helped rescuing the functional and morphological changes in the cardiopulmonary system leading to improvement, sometimes normalization, of the pressures. None of the treatments affected the observed parameters in normoxia. Thus, the 3 modulatory sites are essentially similar in enhancing the NO-cGMP pathway, thereby attenuating the hypoxia-related effects that lead to pulmonary hypertension.

Quality of frozen porcine Longissimus lumborum muscles injected with l-arginine and l-lysine solution

This study investigated the effects of l-arginine and l-lysine on the water holding capacity, shear force, color, and protein denaturation of frozen porcine Longissimus lumborum. Four batches were prepared, each corresponding to samples of an experimental treatment: without a cryoprotective solution, injecting a 0.3% sodium tripolyphosphate and 0.5% NaCl solution, a 0.5% l-arginine solution, or a 0.5% l-lysine solution. The results showed that both l-arginine and l-lysine decreased thawing loss, cooking loss, shear force, L^⁎ values, b^⁎ values, and surface hydrophobicity, but they increased pH values, a^⁎ values, percentages of peak areas for T₂₁ relaxation times, and Ca²⁺-ATPase activity. Additionally, both histological and transmission electron microscopy images showed that l-lysine, and especially l-arginine could inhibit the formation of gaps between fiber bundles, alleviate the disruption of intracellular spaces, and maintain the structural integrity of sarcomeres. Overall, the results showed that both l-arginine and l-lysine hindered the structural damage of muscle fibers during freezing and protected myofibrillar proteins from denaturation, ultimately contributing to superior quality attributes.

Endothelial-transcytosed myeloperoxidase activates endothelial nitric oxide synthase via a phospholipase C-dependent calcium signaling pathway

During vascular inflammation, the leukocyte-derived enzyme myeloperoxidase (MPO) is transcytosed across the endothelium and into the sub-endothelial extracellular matrix, where it promotes endothelial dysfunction by catalytically consuming nitric oxide (NO) produced by endothelial NO synthase (eNOS). In the presence of chloride ions and hydrogen peroxide (H2O2), MPO forms the oxidant hypochlorous acid (HOCl). Here we examined the short-term implications of HOCl produced by endothelial-transcytosed MPO for eNOS activity. Incubation of MPO with cultured aortic endothelial cells (ECs) resulted in its transport into the sub-endothelium. Exposure of MPO-containing ECs to low micromolar concentrations of H2O2 yielded enhanced rates of H2O2 consumption that correlated with HOCl formation and increased eNOS enzyme activity. The MPO-dependent activation of eNOS occurred despite reduced cellular uptake of the eNOS substrate l-arginine, which involved a decrease in the maximal activity (Vmax), but not substrate affinity (Km), of the major endothelial l-arginine transporter, cationic amino acid transporter-1. Activation of eNOS in MPO-containing ECs exposed to H2O2 involved a rapid elevation in cytosolic calcium and increased eNOS phosphorylation at Ser-1179 and de-phosphorylation at Thr-497. These signaling events were attenuated by intracellular calcium chelation, removal of extracellular calcium and inhibition of phospholipase C. This study shows that stimulation of endothelial-transcytosed MPO activates eNOS by promoting phospholipase C-dependent calcium signaling and altered eNOS phosphorylation at Ser-1179 and Thr-497. This may constitute a compensatory signaling response of ECs aimed at maintaining eNOS activity and NO production in the face of MPO-catalyzed oxidative stress.

Long lasting protective effects of early l-arginine treatment on endothelium in an in vitro study

BACKGROUND & AIMS

Excess nutrient supply, such as high fat and high glucose intake, promotes oxidative stress and advanced glycation end products accumulation. Oxidative stress and AGE accumulation cause pathological elevation of arginase activity and pro-inflammatory signaling implicated in endothelial dysfunction. Several studies showed positive effects of l-arginine supplementation in endothelial function but little is currently known about the role of l-arginine as prevention of endothelial dysfunction caused by excessive nutrient supply (overfeeding). Our aim was to evaluate a possible protective effect of l-arginine on endothelial dysfunction caused by excessive nutrient supply (overfeeding), using human endothelial cells line in an in vitro study.

METHODS

Endothelial EA.hy926 cells were pre-treated with 1.72 mM of l-arginine for 24 h and afterwards subjected to nutritional stress (high lipid, high insulin and high glucose concentrations) for further 24 h. After treatment discontinuation, the cells were kept in culture for 48 h, in physiological condition, to evaluate the effects of treatments after normalization.

RESULTS

Excess nutrient supply in EA.hy926 cell line showed an increase of oxidative and nitrosative stress, a rise of AGEs production, high arginase activity, leading the cells to acidosis and to cell death. l-arginine pretreatment protects the cells by reducing apoptosis, acidosis, oxidative and nitrosative stress, arginase activity and AGE accumulation. l-arginine pretreatment reduces AGEs generation and accumulation by regulating STAB1 and RAGE gene expression levels. STAB1, acting as receptor scavenger of AGEs, interferes with AGE-RAGE binding and thus prevents activation of intracellular signaling pathways leading to cell damage. Moreover the reduction of oxidative stress promotes a decrease of excessive activation of arginase involved in endothelial dysfunction. The effects of pretreatment with l-arginine last even in the absence of stimuli and despite after treatment discontinuation.

CONCLUSIONS

An early l-arginine treatment is able to prevent oxidative stress and AGEs accumulation caused by overfeeding in human endothelial cell line by regulating STAB1/RAGE gene expression and by reducing excess arginase activity. The positive effects of l-arginine pretreatment continue even after treatment discontinuation in normal conditions.

l-Arginine and l-Lysine Alleviate Myosin from Oxidation: Their Role in Maintaining Myosin's Emulsifying Properties

This study investigated the alleviative effects of l-arginine and l-lysine on the emulsifying properties and structural changes of myosin under hydroxyl radical (·OH) stress. The results showed that ·OH decreased the emulsifying activity index and emulsifying stability index but increased the creaming index and droplet size of a soybean oil-myosin emulsion (SOME). Confocal laser scanning microscopy demonstrated that ·OH caused larger and more inhomogeneous SOME droplets. l-Arginine and l-lysine effectively alleviated ·OH-induced destructive effects on the emulsifying properties of myosin. In addition, ·OH increased the extent of protein carbonylation and dityrosine formation, surface hydrophobicity, and β-sheet content, but decreased the tryptophan fluorescence intensity, solubility, total sulfhydryl, and α-helix content of myosin. Although l-lysine increased dityrosine fluorescence intensity, l-arginine and l-lysine effectively alleviated the aforementioned structural changes of myosin. Therefore, l-arginine and l-lysine could mitigate ·OH-induced structural changes of myosin, which enabled myosin to maintain its emulsifying capacity under oxidative stress.

Effect of l-arginine on cardiac reverse remodeling and quality of life in patients with heart failure

BACKGROUND & AIMS

Heart failure (HF), as a major cardiac disease, is associated with considerable mortality, morbidities and poor quality of life. The aim of this study was to investigate the effect of l-arginine supplementation on cardiac outcomes and quality of life in patients with ischemic HF.

METHODS

This double-blind randomized controlled clinical trial was conducted in 50 patients with ischemic HF. Patients were randomly assigned to receive either 3 gr/d l-arginine or placebo, for 10 weeks. Cardiac function (based on echocardiography and six-minute walk test), blood pressure, and quality of life (based on the Minnesota living with heart failure questionnaire) were assessed.

RESULTS

The results showed significant improvements in ejection fraction (-6.5 ± 8.7 vs. -0.7 ± 7.8%, P = 0.037), left ventricular function (P = 0.043), diastolic dysfunction (P = 0.01) and marginally improvement in changes of left ventricular dimension during diastole (LVDd) (4 ± 6 vs. 0.3 ± 6.9 mm, P = 0.065) in the l-arginine compared to the placebo group. At the end of the study, physical aspect (5.7 ± 3.3 vs. 1.2 ± 6.1, P = 0.002) and total score (10 ± 6.7 vs. 4.1 ± 9.4, P = 0.011) of quality of life improved significantly in the l-arginine compared with the placebo group. Additionally, pre-to post-values of diastolic blood pressure, mean arterial pressure, LVDd, LV ejection fraction, left ventricular function, diastolic dysfunction as well as physical and total scores of quality of life improved significantly within the intervention, but not the placebo, group (all P < 0.05).

CONCLUSION

This study showed that 3 gr/d l-arginine supplementation for 10 weeks could improve cardiac recovery and function, and quality of life in patients with HF. This study was registered at the Iranian Clinical Trial Registration Center (www.irct.ir) with IRCT20170202032367N4 code.

Interactions of l-arginine with Langmuir monolayers of common phospholipids at the air-water interface

The interactions of l-arginine (l-arg) with Langmuir monolayers of three most common phospholipids, which are sodium salt of dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE), have been investigated at the air-water interface. The surface pressure-area (π-A) isotherms of these monolayers have been measured with a film balance and monolayer morphology has been observed by a Brewster angle microscopy (BAM). The DPPG monolayers on pure water do not show any phase transition but show irregular shaped condensed phases formed just after evaporation of the solvent at 20 °C. However, this monolayer on l-arg solution subphase indicates a first-order phase transition from liquid expanded to liquid condensed (LE-LC) phases and forms LC domains at the same temperature. With an increase in the l-arg concentration in the subphase up to 5.0 × 10^-4 M, the π-A shows an overall increasingly greater expansion in the molecular area. All of the π-A isotherms recorded on ≥5.0 × 10^-4 M l-arg solution subphases almost coincide with each other. These changes in the phase behavior have been explained by the fact that l-arg having guanidinium cationic group undergoes strong hydrogen bonding interaction with the anionic phosphatidylglycerol (PG-) head group. The bonding between two molecules is further strengthened by electrostatic attraction between cationic l-arg and anionic PG- ions. The BAM observation of the monolayer morphology supports this explanation. On the other hand, a very negligible interaction has been observed between l-arg and DPPC or DPPE monolayers. The π-A isotherms in the presence of l-arg for both the amphiphiles show a very little expansion only in the LE phase region, but coincide in the so called solid phase region. The monolayer morphology of both the monolayers also supports these results. This little effect of expansion in the LE region may be explained by the ion-pair formation between cationic l-arg and anionic head groups in the monolayers at lower pressures. However, due to compression at high pressure, the l-arg molecules are squeezed out from the amphiphile head groups.

Determining the cardiovascular effects of nitric oxide in the dorsolateral Periaqueductal Gray (dlPAG) in anaesthetised rats

OBJECTIVE

The dorsolateral periaqueductal gray (dlPAG) is an area located in the brain stem that performs a host of functions including cardiovascular regulation. Owing to the presence of nitric oxide (NO) in this area, we investigated its effect on the cardiovascular system.

METHODS

We divided rats into four groups: 1) control; 2) l-arginine (L-Arg, a precursor for nitric oxide, 60 nmol); 3) l-NAME (N omega-nitro-l-arginine methyl ester, a nitric oxide synthase inhibitor, 90 nmol); and 4) sodium nitroprusside (SNP, a nitric oxide donor, 27 nmol). After anaesthesia, the rats were mounted on a stereotaxic apparatus and the drugs were microinjected into the dlPAG. Cardiovascular parameters were continuously recorded by a PowerLab system connected to the cannulated femoral artery via a pressure transducer. The changes (Δ) of systolic blood pressure (SBP), mean arterial pressure (MAP), and heart rate (HR) were calculated at different times as compared to the control group.

RESULTS

In the l-NAME group, the ΔSBP, ΔMAP, and ΔHR were not significantly affected compared to the control group. In the L-Arg group, ΔSBP and ΔMAP increased; however, only SBP showed a significant increase compared to the control group. In the SNP group, SBP and MAP were significantly affected in comparison to the controls. Additionally, ΔHR decreased in both L-Arg and SNP, but was only significant in L-Arg.

CONCLUSION

Our study showed that NO of dlPAG has a pressor effect and attenuates baroreflex bradycardia. However, its pressor effect is more significant.

L-Arginine Enhances Intracellular Killing of Carbapenem-Resistant Klebsiella pneumoniae ST258 by Murine Neutrophils

Carbapenem-resistant Klebsiella pneumoniae ST258 (CRKP-ST258) are a global concern due to their rapid dissemination, high lethality, antibiotic resistance and resistance to components of the immune response, such as neutrophils. Neutrophils are major host mediators, able to kill well-studied and antibiotic-sensitive laboratory reference strains of K. pneumoniae. However, CRKP-ST258 are able to evade neutrophil phagocytic killing, persisting longer in the host despite robust neutrophil recruitment. Here, we show that neutrophils are unable to clear a CRKP-ST258 isolate (KP35). Compared to the response elicited by a prototypic K. pneumoniae ATCC 43816 (KPPR1), the neutrophil intracellular response against KP35 is characterized by equivalent production of reactive oxygen species (ROS) and myeloperoxidase content, but impaired phagosomal acidification. Our results ruled out that this phenomenon is due to a phagocytosis defect, as we observed similar efficiency of phagocytosis by neutrophils infected with KP35 or KPPR1. Genomic analysis of the cps loci of KPPR1 and KP35 suggest that the capsule composition of KP35 explain the high phagocytosis efficiency by neutrophils. Consistent with other reports, we show that KP35 did not induce DNA release by neutrophils and KPPR1 only induced it at 3 h, when most of the bacteria have already been cleared. l-arginine metabolism has been identified as an important modulator of the host immune response and positively regulate T cells, macrophages and neutrophils in response to microbes. Our data show that l-arginine supplementation improved phagosome acidification, increased ROS production and enhanced nitric oxide consumption by neutrophils in response to KP35. The enhanced intracellular response observed after l-arginine supplementation ultimately improved KP35 clearance in vitro. KP35 was able to dysregulate the intracellular microbicidal machinery of neutrophils to survive in the intracellular environment. This process, however, can be reversed after l-arginine supplementation.

l-arginine production in Corynebacterium glutamicum: manipulation and optimization of the metabolic process

As an important semi-essential amino acid, l-arginine is extensively used in the food and pharmaceutical fields. At present, l-arginine production depends on cost-effective, green, and sustainable microbial fermentation by using a renewable carbon source. To enhance its fermentative production, various metabolic engineering strategies have been employed, which provide valid paths for reducing the cost of l-arginine production. This review summarizes recent advances in molecular biology strategies for the optimization of l-arginine-producing strains, including manipulating the principal metabolic pathway, modulating the carbon metabolic pathway, improving the intracellular biosynthesis of cofactors and energy usage, manipulating the assimilation of ammonia, improving the transportation and membrane permeability, and performing biosensor-assisted high throughput screening, providing useful insight into the current state of l-arginine production.