Arginase 2 Research Articles

Linarin Identified as a Bioactive Compound of Lycii Cortex Ameliorates Insulin Resistance and Inflammation Through the c-FOS/ARG2 Signaling Axis.

Insulin resistance (IR) is a central pathophysiological process underlying numerous chronic metabolic disorders, including type 2 diabetes and obesity. Lycii Cortex, a widely used traditional Chinese herb, has demonstrated potential benefits in preventing and managing diabetes and IR. Whereas, the specific bioactive compounds responsible for these protective effects and their underlying mechanisms of action remain elusive. This study aimed to identify the bioactive components within Lycii Cortex that contribute to its anti-diabetic effects and to elucidate the molecular mechanisms underlying its beneficial actions on insulin resistance. Network pharmacology and molecular docking analyses were employed to identify the potential active compounds in Lycii Cortex and their corresponding target proteins. An invitro model of IR was established using palmitic acid (PA)-treated HepG2 cells. Cell viability was assessed using the CCK-8 assay, while glucose uptake was evaluated by 2-NBDG staining and extracellular glucose measurement. To validate the invitro findings, an invivo model of obesity-induced IR was established using high-fat diet (HFD)-fed mice. The network pharmacology analysis preliminarily identified 13 candidate chemicals and 10 hub LyC and IR-related genes (LIRRGs). Molecular docking analysis demonstrates that Linarin as the potential active component exhibits the greatest potential to target c-FOS for preventing obesity-induced IR. Enrichment analysis suggested that Linarin-targeted pathways are correlated with inflammation. Invitro experimental validation demonstrated that Linarin was capable of protecting against PA-induced IR in HepG2 cells evidenced by improving glucose uptake ability and reducing extracellular glucose content. Additionally, we found that Linarin ablated PA-induced increase in the expression of c-FOS and inflammatory cytokines. Furthermore, in PA-treated cells, silencing c-FOS markedly improved glucose consumption, and reduced inflammation and Arginase 2 (ARG2) expression. Similarly, as exposure to PA, silencing ARG2 also ameliorated glucose uptake and inflammation, while not affecting c-FOS expression. Invivo experiments further showed that Linarin administration remarkably improved glucose tolerance and insulin sensitivity, and reduced the fat mass and body weight in HFD-induced obese mice. In this study, Linarin has been identified as the bioactive compound of Lycii Cortex to ameliorate obesity-related IR and inflammation through the c-FOS/ARG2 signaling cascade. These findings underscore the therapeutic potential of Linarin and provide valuable insights into developing novel intervention strategies for type 2 diabetes therapy.

Pathophysiology of Arginases in Cancer and Efforts in Their Pharmacological Inhibition.

Arginases are key enzymes that hydrolyze L-arginine to urea and L-ornithine in the urea cycle. The two arginase isoforms, arginase 1 (ARG1) and arginase 2 (ARG2), regulate the proliferation of cancer cells, migration, and apoptosis; affect immunosuppression; and promote the synthesis of polyamines, leading to the development of cancer. Arginases also compete with nitric oxide synthase (NOS) for L-arginine, and their participation has also been confirmed in cardiovascular diseases, stroke, and inflammation. Due to the fact that arginases play a crucial role in the development of various types of diseases, finding an appropriate candidate to inhibit the activity of these enzymes would be beneficial for the therapy of many human diseases. In this review, based on numerous experimental, preclinical, and clinical studies, we provide a comprehensive overview of the biological and physiological functions of ARG1 and ARG2, their molecular mechanisms of action, and affected metabolic pathways. We summarize the recent clinical trials' advances in targeting arginases and describe potential future drugs.

Rapid profiling of fish cell nitrogen metabolism with single-cell Raman spectroscopy: Unveiling enzyme's role in ammonia detoxification

Ammonia is a prevalent aquatic pollutant that disrupts cellular functions and energy metabolism in fish, posing significant environmental and health threats. This research investigates the critical role of arginase 2 (ARG2) in mitigating ammonia toxicity in fish cells and its implications in adapting to nitrogen metabolism under high ammonia exposure. Through a CRISPR-Cas9 engineered ARG2 knockdown (KD) in the Epithelioma Papulosum Cyprini (EPC) cell line, we first investigated the biochemical responses of ARG2 KD and wild-type (WT) EPC cells to ammonia stress (NH4Cl treatment), showing diminished urea production and decreased cell viability in ARG2 KD cells. Subsequently, single-cell Raman spectroscopy analysis revealed that ARG2 KD cells exhibited profound metabolic shifts, including changes in protein, nucleic acids, lipid and sugar levels, showing the adjusting role of ARG2 in the balance of carbohydrate and nitrogen metabolism. Furthermore, the upregulated responses of various amino acids, such as glutamine, arginine, alanine, glutamic acid, glycine, histidine, phenylalanine and valine, in WT cells after NH4Cl treatment diminished in ARG2 KD cells except for the decrease in aspartic acid, indicating a switching effect of ARG2 in nitrogen metabolism under ammonia stress. This study highlights ARG2's essential role in ammonia detoxification and emphasizes ARG2's protective function and its importance in metabolism, shedding light on the adaptive mechanisms fish cells deploy against high ammonia environments. These insights contribute to deep understanding of aquatic organisms' molecular responses to environmental ammonia pollution, offering potential strategies for their protection.

Arginase 2 attenuates ulcerative colitis by antioxidant effects of spermidine.

Spermidine suppress oxidative stress and is involved in various disease pathogenesis including ulcerative colitis (UC). Arginase 2 (ARG2) plays a central role in the synthesis of spermidine. This study aimed to clarify the effect of endogenously produced spermidine on colitis. The physiological role of ARG2 and spermidine was investigated using Arg2-deficient mice with reduced spermidine. Immunohistochemical staining of the rectum was used to analyze ARG2 expression and spermidine levels in healthy controls and UC patients. In mice with dextran sulfate sodium-induced colitis, ARG2 and spermidine levels were increased in the rectal epithelium. Spermidine protects colonic epithelial cells from oxidative stress and Arg2 knockdown cells reduced antioxidant activity. Organoids cultured from the small intestine and colon of Arg2-deficient mice both were more susceptible to oxidative stress. Colitis was exacerbated in Arg2-deficient mice compared to wild-type mice. Supplementation with spermidine result in comparable severity of colitis in both wild-type and Arg2-deficient mice. In the active phase of UC, rectal ARG2 expression and spermidine accumulation were increased compared to remission. ARG2 and spermidine levels were similar in healthy controls and UC remission patients. ARG2 produces spermidine endogenously in the intestinal epithelium and has a palliative effect on ulcerative colitis. ARG2 and spermidine are potential novel therapeutic targets for UC.

ARGINASE 2 AMELIORATES EXPERIMENTAL COLITIS THROUGH ANTIOXIDANT EFFECTS VIA SPERMIDINE PRODUCTION

Abstract BACKGROUND Spermidine which is a type of polyamine, shows elevated levels in patients with ulcerative colitis and is implicated in the pathogenesis of ulcerative colitis (UC). Arginase 2 (ARG2) plays a critical role in spermidine production. This study aimed to determine the role and mechanism of endogenous spermidine by using ARG2-deficient mice. METHODS The protective role of spermidine against oxidative stress was examined by intracellular reactive oxygen species levels and cell viability. The physiological role of spermidine was investigated using Arg2 knockdown cells with reduced spermidine. The importance of ARG2 in inflammation was examined in the dextran sulfate sodium-induced colitis model. Protein expression levels of ARG2 and accumulation of spermidine in patients with UC were evaluated by immunohistochemistry of the rectum. RESULTS ARG2 protein expression and the accumulation of spermidine were upregulated in the rectum of mice with dextran sulfate sodium colitis. Spermidine upregulated antioxidant genes in the cells. Arg2 knockdown cells showed reduced antioxidant activity. Dextran sulfate sodium colitis was more severe in Arg2-deficient mice, and organoids derived from Arg2-deficient mice showed diminished tolerance to oxidative stress. Furthermore, in the rectum of patients with UC, ARG2 and spermidine expression levels were higher in the active phase than in the remission phase. CONCLUSIONS Endogenous spermidine in the intestinal epithelium induced by ARG2 has a protective role in colitis. Spermidine may be a promising new therapeutic target for inflammatory bowel disease.

Molecular states associated with dysfunction and graft loss in heart transplants

PurposeWe explored the changes in gene expression correlating with dysfunction and graft failure in endomyocardial biopsies (EMBs). MethodsGenome-wide microarrays (19462 genes) were used to define mRNA changes correlating with dysfunction (LVEF≤55) and risk of graft loss within 3 years post biopsy. LVEF data was available for 1013 biopsies, and survival data for 779 patients (74 losses). Molecular classifiers were built for predicting dysfunction (LVEF≤55) and post-biopsy 3-year survival. ResultsDysfunction correlated with dedifferentiation - decreased expression of normal heart transcripts e.g., solute carriers, along with increased expression of inflammation genes. Many genes with reduced expression in dysfunction were matrix genes e.g., fibulin1 and decorin. Gene ontology (GO) categories suggested matrix remodeling and inflammation, not rejection.Genes associated with risk of failure post-biopsy overlapped dysfunction genes, but also included genes affecting microcirculation e.g., arginase 2 (ARG2), which reduces NO production, and endothelin 1 (EDN1). GO terms also reflected increased glycolysis and response to hypoxia, but decreased VEGF and angiogenesis pathways. TCMR was associated with reduced survival and ABMR with relatively good survival, but the main determinants of survival were features of parenchymal injury.Both dysfunction and graft loss correlated with increased biopsy expression of BNP (gene NPPB).Survival probability classifiers divided hearts into risk quintiles, with actuarial 3-year post-biopsy survival >95% for the highest vs. 50% for the lowest. ConclusionsDysfunction in transplanted hearts reflects dedifferentiation, decreased matrix genes, injury and inflammation. Risk of short-term loss includes these changes but is also associated with microcirculation abnormalities, glycolysis, and response-to-hypoxia.

Calbindin 2-specific deletion of arginase 2 preserves visual function after optic nerve crush

We previously found that global deletion of the mitochondrial enzyme arginase 2 (A2) limits optic nerve crush (ONC)-induced neuronal death. Herein, we examined the cell-specific role of A2 in this pathology by studies using wild type (WT), neuronal-specific calbindin 2 A2 KO (Calb2cre/+ A2 f/f), myeloid-specific A2 KO (LysMcre/+ A2f/f), endothelial-specific A2 KO (Cdh5cre/+ A2f/f), and floxed controls. We also examined the impact of A2 overexpression on mitochondrial function in retinal neuronal R28 cells. Immunolabeling showed increased A2 expression in ganglion cell layer (GCL) neurons of WT mice within 6 h-post injury and inner retinal neurons after 7 days. Calb2 A2 KO mice showed improved neuronal survival, decreased TUNEL-positive neurons, and improved retinal function compared to floxed littermates. Neuronal loss was unchanged by A2 deletion in myeloid or endothelial cells. We also found increased expression of neurotrophins (BDNF, FGF2) and improved survival signaling (pAKT, pERK1/2) in Calb2 A2 KO retinas within 24-hour post-ONC along with suppression of inflammatory mediators (IL1β, TNFα, IL6, and iNOS) and apoptotic markers (cleavage of caspase3 and PARP). ONC increased GFAP and Iba1 immunostaining in floxed controls, and Calb2 A2 KO dampened this effect. Overexpression of A2 in R28 cells increased Drp1 expression, and decreased mitochondrial respiration, whereas ABH-induced inhibition of A2 decreased Drp1 expression and improved mitochondrial respiration. Finally, A2 overexpression or excitotoxic treatment with glutamate significantly impaired mitochondrial function in R28 cells as shown by significant reductions in basal respiration, maximal respiration, and ATP production. Further, glutamate treatment of A2 overexpressing cells did not induce further deterioration in their mitochondrial function, indicating that A2 overexpression or glutamate insult induce comparable alterations in mitochondrial function. Our data indicate that neuronal A2 expression is neurotoxic after injury, and A2 deletion in Calb2 expressing neurons limits ONC-induced retinal neurodegeneration and improves visual function.

Arginase2 mediates contrast-induced acute kidney injury via facilitating nitrosative stress in tubular cells

Contrast-induced acute kidney injury(CI-AKI) is the third cause of AKI. Although tubular injury has been regarded as an important pathophysiology of CI-AKI, the underlying mechanism remains elusive. Here, we found arginase2(ARG2) accumulated in the tubules of CI-AKI mice, and was upregulated in iohexol treated kidney tubular cells and in blood samples of CI-AKI mice and patients, accompanied by increased nitrosative stress and apoptosis. However, all of the above were reversed in ARG2 knockout mice, as evidenced by the ameliorated kidney dysfunction and the tubular injury, and decreased nitrosative stress and apoptosis. Mechanistically, HO-1 upregulation could alleviate iohexol or ARG2 overexpression mediated nitrosative stress. Silencing and overexpressing ARG2 was able to upregulate and downregulate HO-1 expression, respectively, while HO-1 siRNA had no effect on ARG2 expression, indicating that ARG2 might inhibit HO-1 expression at the transcriptional level, which facilitated nitrosative stress during CI-AKI. Additionally, CREB1, a transcription factor, bound to the promoter region of ARG2 and stimulated its transcription. Similar findings were yielded in cisplatin- or vancomycin-induced AKI models. Taken together, ARG2 is a crucial target of CI-AKI, and activating CREB1/ARG2/HO-1 axis can mediate tubular injury by promoting nitrosative stress, highlighting potential therapeutic strategy for treating CI-AKI.

Systemic Effects of Homoarginine Supplementation on Arginine Metabolizing Enzymes in Rats with Heart Failure with Preserved Ejection Fraction.

A restoration of low homoarginine (hArg) levels in obese ZSF1 rats (O-ZSF1) before (S1-ZSF1) and after (S2-ZSF1) the manifestation of heart failure with preserved ejection fraction (HFpEF) did not affect the worsening of cardiac HFpEF characteristics. Here, potential regulation of key enzymes of arginine metabolism in other organs was analyzed. Arginase 2 (ARG2) was reduced >35% in the kidney and small intestine of hArg-supplemented rats compared to O-ZSF1. Glycine amidinotransferase (GATM) was 29% upregulated in the kidneys of S1-ZSF1. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) levels were reduced >50% in the livers of O-ZSF1 but restored in S2-ZSF1 compared to healthy rats (L-ZSF1). In the skeletal muscle, iNOS was lower in O-ZSF1 and further decreased in S1-ZSF1 and S2-ZSF1 compared to L-ZSF1. iNOS levels were lower in the liver of the S2-ZSF1 group but higher in the kidneys of S1-ZSF1 compared to L-ZSF1. Supplementation with hArg in an in vivo HFpEF model resulted in the inhibition of renal ARG2 and an increase in GATM expression. This supplementation might contribute to the stabilization of intestinal iNOS and ARG2 imbalances, thereby enhancing barrier function. Additionally, it may offer protective effects in skeletal muscle by downregulating iNOS. In the conceptualization of hArg supplementation studies, the current disease progression stage as well as organ-specific enzyme regulation should be considered.

Arginase 2 Promotes Cisplatin-Induced Acute Kidney Injury by the Inflammatory Response of Macrophages

Acute kidney injury (AKI) is a complex clinical syndrome with a rapid decrease in renal function caused by several different etiologies, including sepsis, ischemia, and the administration of nephrotoxic drugs. Tubular arginase 2 (ARG2), an arginine-metabolic enzyme, is a potential therapeutic target for AKI, but it has not been confirmed under various AKI conditions. The aim of this study was to investigate ARG2 as a therapeutic target for cisplatin-induced AKI. Cisplatin-treated mice with a genetic deficiency in Arg2 had significant amelioration of renal dysfunction, characterized by decreased acute tubular damage and apoptosis. In contrast, cisplatin-induced tubular toxicity was not ameliorated in proximal tubule cells derived from Arg2-deficient mice. Immunohistochemical analysis demonstrated the increased infiltration of ARG2-positive macrophages in kidneys damaged by cisplatin. Importantly, cisplatin-treated Arg2 knockout mice exhibited a significant reduction in kidney inflammation, characterized by the decreased infiltration of inflammatory macrophages and reduced gene expression of interleukin (IL)-6 and IL-1β. The secretion of IL-6 and IL-1β induced by lipopolysaccharides was decreased in bone marrow–derived macrophages isolated from Arg2-deficient mice. Furthermore, the lipopolysaccharide-induced elevation of mitochondrial membrane potential and production of reactive oxygen species were reduced in bone marrow–derived macrophages lacking Arg2. These findings indicate that ARG2 promotes the inflammatory responses of macrophages through mitochondrial reactive oxygen species, resulting in the exacerbation of AKI. Therefore, targeting ARG2 in macrophages may constitute a promising therapeutic approach for AKI.

#4542 L-ARGININE-NITRIC OXIDE MOLECULAR PATHWAY IN AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE

Abstract Background and Aims Autosomal Dominant Polycystic Kidney Disease (ADPKD) is an inherited, complex disease, cystogenesis and phenotypic changes in this disorder being not yet fully understood. Recently, arginine, important for renal cells metabolism, was proved to play an important role in ADPKD physiopathology (1). The inability of cells to recycle or synthesize intracellular arginine through the urea cycle is defined as arginine auxotrophy. Arginine auxotrophy in ADPKD induces cell hyperproliferation, and cysts formation (2). We aimed to explore L-Arginine (Arg) - Nitric Oxide (NO) molecular pathway in ADPKD, a multisystemic, arginine auxotrophe disease. Method We developed a prospective, case control study, in Carol Davila Clinical Hospital of Nephrology, Bucharest, Romania. The study included a group of 62 subjects with ADPKD (mean age -54.3years old, men:women 34:28, with 1A and 1B Mayo ADPKD risk classes) and a group of 37 healthy subjects, similar as sex, mean age. ADPKD diagnosis was based on familial history, clinical exam and CT or MRI scan. We excluded from the study subjects that presented cysts in other organs except the kidney, with eGFR<60mL/min/1.73mp, with history of hematuria, cysts infection, urinary tract infection, renal lithiasis, with unstable blood pressure and hypertensive treatment for less than 6 months; metabolic disorders (carbamoyl phosphate synthase 1 and N-acetyl glutamate synthase deficiencies, lack of ornithine transcarbamilase, hyperargininemia, phenylketonuria). Laboratory tests: serum level of arginine, enzymatic activity of arginase 2 (ARG-2) and nitric oxide inducible synthase (NOS-2), serum levels of stable metabolites of nitric oxide (nitrate, direct nitrite, total nitrite), endogenous inhibitors of nitric oxide synthesis (Asymmetric Dimethylarginine -ADMA, Symmetric Dimethylarginine SDMA). Results In ADPKD patients, the serum levels of arginine and of the stable metabolites of nitric oxide had statistically significant lower levels compared with control group (Table 1). The levels of the principal enzymes that metabolizes arginine – arginase 2 and nitric oxide inducible synthase, respectively the endogenous inhibitors of nitric oxide synthesis were statistically significant higher in ADPKD group when compared with control group (Table 1). The ARG2/Arg, NOS2/Arg, Nitrite/Arg, Nitrate/Arg, ADMA/Arg and SDMA/Arg ratios were statistically significant overexpressed in ADPKD group when compared with control group. Conclusion ADPKD is a metabolic kidney disease, auxotrophic for arginine. The metabolic ADPKD phenotype of renal cells with low risk of progression (1A and 1B Mayo) is defined by the alteration of L-Arginine-NO molecular pathway, the significant reduction of systemic arginine, moderately increased enzymatic activities of ARG2 and NOS2, the reduction of the synthesis and bioactivity of NO. Exploring arginine reprogramming and related molecular L-Arg-NO pathways disturbances could offer more information about ADPKD physiopathology.

Macrophage-derived Osteopontin (SPP1) Protects From Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is characterized by steatosis, lobular inflammation, hepatocyte ballooning degeneration, and fibrosis, all of which increase the risk of progression to end-stage liver disease. Osteopontin (OPN, SPP1) plays an important role in macrophage (MF) biology, but whether MF-derived OPN affects NASH progression is unknown. We analyzed publicly available transcriptomic datasets from patients with NASH, and used mice with conditional overexpression or ablation of Spp1 in myeloid cells and liver MFs, and fed them a high-fat, fructose, and cholesterol diet mimicking the Western diet, to induce NASH. This study demonstrated that MFs with high expression of SPP1 are enriched in patients and mice with nonalcoholic fatty liver disease (NAFLD), and show metabolic but not pro-inflammatory properties. Conditional knockin of Spp1 in myeloid cells (Spp1KI Mye) or in hepatic macrophages (Spp1KILvMF) conferred protection, whereas conditional knockout of Spp1 in myeloid cells (Spp1ΔMye) worsened NASH. The protective effect was mediated by induction of arginase-2 (ARG2), which enhanced fatty acid oxidation (FAO) in hepatocytes. Induction of ARG2 stemmed from enhanced production of oncostatin-M (OSM) in MFs from Spp1KI Mye mice. OSM activated STAT3 signaling, which upregulated ARG2. In addition to hepatic effects, Spp1KI Mye also protected through sex-specific extrahepatic mechanisms. MF-derived OPN protects from NASH, by upregulating OSM, which increases ARG2 through STAT3 signaling. Further, the ARG2-mediated increase in FAO reduces steatosis. Therefore, enhancing the OPN-OSM-ARG2 crosstalk between MFs and hepatocytes may be beneficial for patients with NASH.

Abstract 3678: Rewiring of amino acid metabolism in neurofibromatosis type 1-related tumors

Abstract Neurofibromatosis type 1 (NF1) is a tumor-predisposing genetic disorder caused by heterozygous mutations in the NF1 gene encoding for the tumor suppressor Neurofibromin. Biallelic NF1 inactivation in Schwann cells leads to the onset of neurofibromas, benign neoplasms that can cause severe medical complications and give rise to malignant peripheral nerve sheath tumors (MPNSTs), for which no treatment exists. Neurofibroma cells undergo bioenergetic changes required to sustain their malignant transformation. Our group has shown that inhibition of the mitochondrial chaperone TRAP1, a master metabolic regulator, hampers MPNST cell tumorigenicity. A growing number of evidence indicates that urea cycle (UC) dysregulation can redirect metabolic substrates to specific biosynthetic routes in many tumor cell types. We have found that a complete UC is absent in MPNST cell models, as they lack ornithine transcarbamylase (OTC), a key UC enzyme that converts ornithine into citrulline. In the absence of TRAP1, MPNST cells strongly reduce arginine levels and accumulate ornithine through the activity of the mitochondrial enzymes arginase 2 (ARG2) and ornithine aminotransferase (OAT). These changes can reverberate on glutamine and proline levels ultimately affecting extracellular matrix deposition, motility and ROS homeostasis, as well as on ornithine-dependent polyamine biosynthesis that can regulate cell growth and proliferation. Surprisingly, in the absence of TRAP1 MPNST cells also accumulate citrulline, even though they do not express either OTC or any nitric oxide synthase (NOS) isoform that converts arginine into citrulline. We ascribe citrulline production to the activity of dimethylarginine dimethylaminohydrolase (DDAH) enzymes, involved in the catabolism of asymmetric dimethylarginines. Induction of DDAHs indicates an elevated protein catabolism that could contribute to tune MPNST cell tumorigenicity. A thorough comprehension of the amino acid metabolism rewiring in NF1-related tumors may unveil new targetable liabilities of cancer cells to be exploited for the design of new effective therapeutic approaches. Citation Format: Martina La Spina. Rewiring of amino acid metabolism in neurofibromatosis type 1-related tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3678.

Ecdysterone treatment restores constitutive NO synthesis and alleviates oxidative damage in heart tissue and mitochondria of streptozotocin-induced diabetic rats

Constitutive NO synthases (cNOS) are the primary targets of diabetes mellitus and the impairment of cNOS functioning in cardiovascular system is one of the hallmarks of this disease. The aim of this work was to study the effect of a plant sterol ecdysterone (20-β-hydroxyecdysterone) on the NO synthases functioning and RNS metabolism in heart mitochondria and the heart tissue in the rat model of streptozotocin-induced type I diabetes. Diabetes development resulted in cNOS dysfunction both in heart mitochondria and heart tissue. cNOS activity was dramatically suppressed, but 3-fold and 6-fold rise of iNOS activity was observed in mitochondria and heart tissue respectively. Also, in mitochondria there was ~2.5 time’s increase in urea content and the activity of arginase 2 (ARG2), which could compete with NOS for the common substrate L-arginine. Total RNS production was dramatically elevated in mitochondria of diabetic animals, which well agreed with iNOS activation. Unlike this, in heart tissue dramatic increase of iNOS activity increased the content of nitrosothiols (RSNO), while total RNS production remained close to control. Both in the heart tissue and mitochondria, there was dramatic augmentation of superoxide production that correlated with sharp elevation of iNOS activity and steep rise of diene conjugates (DC) content, which indicated strong lipid oxidation. Ecdysterone treatment resulted in the reduction of iNOS activity and twofold elevation of mtNOS activity as compared to control. However, in the whole heart tissue eNOS was restored only by half of control level, which indicated specific action of ecdysterone on mtNOS isoform. RNS production returned to control in mitochondria, and was by half reduced in the heart tissue, which indicated the abolition of nitrosative stress. Correlation dependence between iNOS activity and superoxide production was found in mitochondria, which could indicate iNOS uncoupling. The restoration of cNOS activity and the reduction of iNOS activity to control level after ecdysterone treatment well correlated with the reduction of superoxide production and indicated possible ‘iNOS re-coupling‘, which resulted in the reduction of DC formation to control level. So, STZ-induced type I diabetes dramatically up-regulated iNOS activity and suppressed cNOS activity. Ecdysterone treatment reduced iNOS activity and restored constitutive NO biosynthesis to control level, which abolished oxidative and nitrosative stress in cardiac mitochondria and heart tissue of STZ-induced diabetic animals. Possible pathways involved in ecdysterone action on constitutive NO biosynthesis were discussed.

Tubular Elabela-APJ axis attenuates ischemia-reperfusion induced acute kidney injury and the following AKI-CKD transition by protecting renal microcirculation.

Rationale: Ischemia-reperfusion injury (I/R) is a common cause of acute kidney injury (AKI). Post-ischemic recovery of renal blood supply plays an important role in attenuating injury. Exogenous application of elabela (ELA) peptides has been demonstrated by us and others to alleviate AKI, partly through its receptor APJ. However, the endogenous role of ELA in renal I/R remains unclear. Methods: Renal tubule specific ELA knockout (ApelaKsp KO) mice challenged with bilateral or unilateral I/R were used to investigate the role of endogenous ELA in renal I/R. RNA-sequencing analysis was performed to unbiasedly investigate altered genes in kidneys of ApelaKsp KO mice. Injured mice were treated with ELA32 peptide, Nω-hydroxy-nor-L-arginine (nor-NOHA), prostaglandin E2 (PGE2), Paricalcitol, ML221 or respective vehicles, individually or in combination. Results: ELA is mostly expressed in renal tubules. Aggravated pathological injury and further reduction of renal microvascular blood flow were observed in ApelaKsp KO mice during AKI and the following transition to chronic kidney disease (AKI-CKD). RNA-seq analysis suggested that two blood flow regulators, arginine metabolizing enzyme arginase 2 (ARG2) and PGE2 metabolizing enzyme carbonyl reductases 1 and 3 (CBR1/3), were altered in injured ApelaKsp KO mice. Notably, combination application of an ARG2 inhibitor nor-NOHA, and Paricalcitol, a clinically used activator for PGE2 synthesis, alleviated injury-induced AKI/AKI-CKD stages and eliminated the worst outcomes observed in ApelaKsp KO mice. Moreover, while the APJ inhibitor ML221 blocked the beneficial effects of ELA32 peptide on AKI, it showed no effect on combination treatment of nor-NOHA and Paricalcitol. Conclusions: An endogenous tubular ELA-APJ axis regulates renal microvascular blood flow that plays a pivotal role in I/R-induced AKI. Furthermore, improving renal blood flow by inhibiting ARG2 and activating PGE2 is an effective treatment for AKI and prevents the subsequent AKI-CKD transition.

Immunoregulatory CD71+ Erythroid Cells (CECs) Expand in Multiple Myeloma and Impair Control of L. Monocytogenes Infection

Introduction Although the clinical management of multiple myeloma (MM) patients has significantly improved over recent years, MM remains a largely incurable disease. One of the most common complication of MM, which correlates with the worse clinical outcome, is anemia. Moreover, MM patients are prone to develop life-threatening infections mainly due to the disease-related impairment of the immune system function. Recently, CD71+ erythroid progenitor and precursor cells (CECs) arose as a relevant immunomodulatory population. CECs have been shown to create an immunosuppressive microenvironment via multiple mechanisms including arginase 2 (ARG2), PDL-1, and TGF-beta. It was recently observed in our laboratory that mice bearing late-stage tumors are characterized by the presence of an increased percentage of CECs in their blood and spleens. Moreover, the tumor-associated CECs show elevated levels of arginases. The abovementioned facts may suggest an important role of CECs and their related mechanisms in compromising the immune response in MM. Methods Vk*MYC MM model Recipient C57BL/6 (wild type or ARG2 KO) mice were injected via tail vein with 1 × 106 Vk*MYC cells. M-spike levels were evaluated with serum protein electrophoresis. Five weeks later they were challenged with L. monocytogenes. L.monocytogenes infection and bacterial burden evaluation Mice were injected intraperitoneally with 1 x 103L. monocytogenes cells (strain EGDe). Bacterial burden was analyzed 72h and 7 days post infection. Briefly, spleens and livers of sacrificed mice were isolated, weighed, and homogenized. The homogenates were serially diluted and plated on culture plates. Bacterial burden was calculated using the number of colonies and the dilution factor. Flow cytometry analysis Flow cytometry analyses (immunophenotyping of spleen and bone marrow (BM) cells as well as cytokine beads arrays, Legenplex, BioLegend) were performed using BD Fortessa X-20 flow cytometer operated by BD FACSDiva Software ver. 8.0. The acquired data were re-analyzed using FlowJo™ ver. 10 software. Arginase inhibitor OAT-1746 arginase inhibitor (Molecure SA) was administered intraperitoneally at doses of 5 or 20 mg/kg twice daily, starting from the second or the fifth day before the bacterial challenge, respectively. The treatment was continued until the end of the experiment. Results In Vk*MYC-bearing mice we observed an accumulation of CECs in the blood and spleen in time, correlating with the development of anemia. At the late stage of the disease MM-associated CECs showed less differentiated phenotype and increased expression of arginase-1 (ARG1) and ARG2. MM-associated CECs inhibited T cells activation and proliferation in an ARG and reactive oxygen species-dependent manner. Interestingly, MM development was delayed in ARG2 KO vs WT mice. In the BM aspirates of MM patients we observed increased percentage of CECs expressing high levels of both ARG1 and ARG2 comparing with healthy controls. Moreover, MM impaired control of L. monocytogenes infection as we observed an elevated bacterial burden in the livers and spleens of Vk*MYC-bearing vs control mice. Infected MM-bearing mice had fewer NK cells and activated CD4+ and CD8+ T cells in the spleen than infected control mice. Furthermore, MM altered the dynamics of cytokines involved in the control of intracellular infection. 24h post Listeria challenge we observed their significant decrease followed by an increase at 72h comparing to infected non-MM mice. These results indicate that MM-bearing mice have delayed initial immune response leading to increased bacterial burden followed by excessive cytokines response resulting in sepsis-like condition leading to increased mice mortality. Finally, ARG inhibitor decreased L. monocytogenes burden in MM-bearing mice. Altogether, our results show that accumulation of CECs during MM progression leads to impaired bacterial infection control, at least partially dependent on ARG2 activity. Funding: National Science Centre in Poland [grants No 2017/25/B/NZ6/01139 and 2019/35/B/NZ6/00540]; Polish Ministry of Education and Science [grant No 013/RID/2018/19 (Regional Initiative for Excellence, project budget 12,000,000 PLN)].

Arginase: Biological and Therapeutic Implications in Diabetes Mellitus and Its Complications.

Arginase is a ubiquitous enzyme in the urea cycle (UC) that hydrolyzes L-arginine to urea and L-ornithine. Two mammalian arginase isoforms, arginase1 (ARG1) and arginase2 (ARG2), play a vital role in the regulation of β-cell functions, insulin resistance (IR), and vascular complications via modulating L-arginine metabolism, nitric oxide (NO) production, and inflammatory responses as well as oxidative stress. Basic and clinical studies reveal that abnormal alterations of arginase expression and activity are strongly associated with the onset and development of diabetes mellitus (DM) and its complications. As a result, targeting arginase may be a novel and promising approach for DM treatment. An increasing number of arginase inhibitors, including chemical and natural inhibitors, have been developed and shown to protect against the development of DM and its complications. In this review, we discuss the fundamental features of arginase. Next, the regulatory roles and underlying mechanisms of arginase in the pathogenesis and progression of DM and its complications are explored. Furthermore, we review the development and discuss the challenges of arginase inhibitors in treating DM and its related pathologies.

Arginase-2-specific cytotoxic T cells specifically recognize functional regulatory T cells

BackgroundHigh expression of the metabolic enzyme arginase-2 (ARG2) by cancer cells, regulatory immune cells, or cells of the tumor stroma can reduce the availability of arginine (L-Arg) in the tumor...

Modulation of Arginase-2 mRNA Levels by ω-3 PUFAs and Aspirin in Asthmatic Human Lung Fibroblasts.

Airway remodeling (AR) increases disease severity, and morbidity of asthmatic patients by contributing to irreversible airflow obstruction and progressive declines in lung function. Arginase isoenzymes and the downstream enzymes ornithine decarboxylase (ODC) and ornithine aminotransferase (OAT) have been implicated in the hyperplastic and fibrotic changes of AR, respectively. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) and resolvin metabolites have anti-AR effects, but whether they are mediated through the arginase pathway is unclear. Our study intended to determine the effects of the ω-3 PUFAs eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), resolvin D1 (RvD1), TH1 cytokines, acetylsalicylic acid (ASA), cAMP, and dexamethasone (DEX) on the expression of arginase isoenzymes arginase 1 (ARG1) and arginase 2 (ARG2), ODC, and OAT in human lung fibroblasts (HLF) from normal (NHLF) and diseased (DHLF) asthmatic donors using reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR). Our data showed that EPA and EPA+DHA downregulated ARG2 mRNA 2-fold in both types of HLF. DHA, RvD1, and DEX did not alter mRNA levels for any of the genes studied. EPA lowered the ARG2 protein levels in DHLF, but did not affect those levels in NHLF. ASA upregulated ARG2 mRNA 5-fold and 7-fold in NHLF and DHLF, respectively, TH1 cytokines downregulated ARG2, ODC, and OAT mRNA in DHLF 10-fold, 2-fold, and 2.5-fold, respectively, and cAMP downregulated ARG2 mRNA 2-fold in DHLF. These results are the first to show a direct effect of ω-3 PUFAs on ARG2 mRNA levels and provide further evidence for a role of ω-3 PUFAs in AR.

Invariant NKT cells metabolically adapt to the acute myeloid leukaemia environment

Acute myeloid leukaemia (AML) creates an immunosuppressive environment to conventional T cells through Arginase 2 (ARG2)-induced arginine depletion. We identify that AML blasts release the acute phase protein serum amyloid A (SAA), which acts in an autocrine manner to upregulate ARG2 expression and activity, and promote AML blast viability. Following in vitro cross-talk invariant natural killer T (iNKT) cells become activated, upregulate mitochondrial capacity, and release IFN-γ. iNKT retain their ability to proliferate and be activated despite the low arginine AML environment, due to the upregulation of Large Neutral Amino Acid Transporter-1 (LAT-1) and Argininosuccinate Synthetase 1 (ASS)-dependent amino acid pathways, resulting in AML cell death. T cell proliferation is restored in vitro and in vivo. The capacity of iNKT cells to restore antigen-specific T cell immunity was similarly demonstrated against myeloid-derived suppressor cells (MDSCs) in wild-type and Jα18−/− syngeneic lymphoma-bearing models in vivo. Thus, stimulation of iNKT cell activity has the potential as an immunotherapy against AML or as an adjunct to boost antigen-specific T cell immunotherapies in haematological or solid cancers.