Species differences in expression pattern of arginase isoenzymes and differential effects of arginase inhibition on collagen synthesis in human and rat pulmonary fibroblasts

Immunosuppressive tumor microenvironment and uterine fibroids: Role in collagen synthesis

Uterine fibroids (UF), also called uterine leiomyoma, is one of the most prevalent uterine tumors. UF represents a serious women's health global problem with a significant physical, emotional, and socioeconomic impact. Risk factors for UF include racial disparities, age, race, hormonal factors, obesity, and lifestyle (diet, physical activity, and stress. There are several biological contributors to UF pathogenesis such as cellular proliferation, angiogenesis, and extracellular matrix (ECM) accumulation. This review addresses tumor immune microenvironment as a novel mediator of ECM deposition. Polarization of immune microenvironment towards the immunosuppressive phenotype has been associated with ECM deposition. Immunosuppressive cells include M2 macrophage, myeloid-derived suppressor cells (MDSCs), and Th17 cells, and their secretomes include interleukin 4 (IL-4), IL-10, IL-13, IL-17, IL-22, arginase 1, and transforming growth factor-beta (TGF-β1). The change in the immune microenvironment not only increase tumor growth but also aids in collagen synthesis and ECM disposition, which is one of the main hallmarks of UF pathogenesis. This review invites further investigations on the change in the UF immune microenvironment as well as a novel targeting approach instead of the traditional UF hormonal and supportive treatment.

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.

Arginase impedes the resolution of colitis by altering the microbiome and metabolome

Arginase 1 (Arg1), which converts l-arginine into ornithine and urea, exerts pleiotropic immunoregulatory effects. However, the function of Arg1 in inflammatory bowel disease (IBD) remains poorly characterized. Here, we found that Arg1 expression correlated with the degree of inflammation in intestinal tissues from IBD patients. In mice, Arg1 was upregulated in an IL-4/IL-13- and intestinal microbiota-dependent manner. Tie2-Cre Arg1fl/fl mice lacking Arg1 in hematopoietic and endothelial cells recovered faster from colitis than Arg1-expressing (Arg1fl/fl) littermates. This correlated with decreased vessel density, compositional changes in intestinal microbiota, diminished infiltration by myeloid cells, and an accumulation of intraluminal polyamines that promote epithelial healing. The proresolving effect of Arg1 deletion was reduced by an l-arginine-free diet, but rescued by simultaneous deletion of other l-arginine-metabolizing enzymes, such as Arg2 or Nos2, demonstrating that protection from colitis requires l-arginine. Fecal microbiota transfers from Tie2-Cre Arg1fl/fl mice into WT recipients ameliorated intestinal inflammation, while transfers from WT littermates into Arg1-deficient mice prevented an advanced recovery from colitis. Thus, an increased availability of l-arginine as well as altered intestinal microbiota and metabolic products accounts for the accelerated resolution from colitis in the absence of Arg1. Consequently, l-arginine metabolism may serve as a target for clinical intervention in IBD patients.

Long-term usability and bio-integration of polyimide-based intra-neural stimulating electrodes

Stimulation of peripheral nerves has transiently restored lost sensation and has the potential to alleviate motor deficits. However, incomplete characterization of the long-term usability and bio-integration of intra-neural implants has restricted their use for clinical applications. Here, we conducted a longitudinal assessment of the selectivity, stability, functionality, and biocompatibility of polyimide-based intra-neural implants that were inserted in the sciatic nerve of twenty-three healthy adult rats for up to six months. We found that the stimulation threshold and impedance of the electrodes increased moderately during the first four weeks after implantation, and then remained stable over the following five months. The time course of these adaptations correlated with the progressive development of a fibrotic capsule around the implants. The selectivity of the electrodes enabled the preferential recruitment of extensor and flexor muscles of the ankle. Despite the foreign body reaction, this selectivity remained stable over time. These functional properties supported the development of control algorithms that modulated the forces produced by ankle extensor and flexor muscles with high precision. The comprehensive characterization of the implant encapsulation revealed hyper-cellularity, increased microvascular density, Wallerian degeneration, and infiltration of macrophages within the endoneurial space early after implantation. Over time, the amount of macrophages markedly decreased, and a layer of multinucleated giant cells surrounded by a capsule of fibrotic tissue developed around the implant, causing an enlargement of the diameter of the nerve. However, the density of nerve fibers above and below the inserted implant remained unaffected. Upon removal of the implant, we did not detect alteration of skilled leg movements and only observed mild tissue reaction. Our study characterized the interplay between the development of foreign body responses and changes in the electrical properties of actively used intra-neural electrodes, highlighting functional stability of polyimide-based implants over more than six months. These results are essential for refining and validating these implants and open a realistic pathway for long-term clinical applications in humans.

Comparative study of the effects of fetal bovine serum versus horse serum on growth and differentiation of primary equine bronchial fibroblasts

BACKGROUND

Airway fibroblasts have become a critical addition to all facets of structural lung tissue changes such as in human asthma and chronic obstructive pulmonary disease, but little is known about their role in the equine recurrent airway obstruction, a disease that resembles to the human asthma. Since the equine bronchial fibroblasts (EBF) have not been isolated and characterized yet, the use of defined medium was investigated.

RESULTS

Primary EBF were cultured on non-collagen coated flasks without serum or in the presence of fetal bovine serum (FBS) or horse serum (HS) or in serum depleted medium. EBF cultured in serum-free basal media and those serum deprived were not able to proliferate and even exhibited considerable cell death. In media containing FBS or HS, proliferation of the cells was reproducible between different primary cultures and cells demonstrated expression of vimentin. Large variations were found in the ability of FBS and HS to support growth and differentiation of EBF in monolayer culture. Indications of growth-promoting actions, increasing passage number as well as maintaining fibroblast morphology were found rather in FBS than in HS. EBF culturing in HS needed longer doubling and confluence time. The protein content of the cell pellets was higher in EBF cultured in medium containing HS than FBS. Alpha-smooth muscle actin seemed to be less expressed in EBF cultured in medium containing FBS than those in HS.

CONCLUSIONS

In sum, serum addition to basal EBF medium enhanced EBF differentiation into myofibroblasts, and these findings are useful to develop in vitro fibroblast culture models that mimic in vivo physiological processes and to study airway disease mechanisms and remodeling.

Arginase inhibition prevents inflammation and remodeling in a guinea pig model of chronic obstructive pulmonary disease

Airway inflammation and remodeling are major features of chronic obstructive pulmonary disease (COPD), whereas pulmonary hypertension is a common comorbidity associated with a poor disease prognosis. Recent studies in animal models have indicated that increased arginase activity contributes to features of asthma, including allergen-induced airway eosinophilia and mucus hypersecretion. Although cigarette smoke and lipopolysaccharide (LPS), major risk factors for COPD, may increase arginase expression, the role of arginase in COPD is unknown. This study aimed to investigate the role of arginase in pulmonary inflammation and remodeling using an animal model of COPD. Guinea pigs were instilled intranasally with LPS or saline twice weekly for 12 weeks and pretreated by inhalation of the arginase inhibitor 2(S)-amino-6-boronohexanoic acid (ABH) or vehicle. Repeated LPS exposure increased lung arginase activity, resulting in increased l-ornithine/l-arginine and l-ornithine/l-citrulline ratios. Both ratios were reversed by ABH. ABH inhibited the LPS-induced increases in pulmonary IL-8, neutrophils, and goblet cells as well as airway fibrosis. Remarkably, LPS-induced right ventricular hypertrophy, indicative of pulmonary hypertension, was prevented by ABH. Strong correlations were found between arginase activity and inflammation, airway remodeling, and right ventricular hypertrophy. Increased arginase activity contributes to pulmonary inflammation, airway remodeling, and right ventricular hypertrophy in a guinea pig model of COPD, indicating therapeutic potential for arginase inhibitors in this disease.

Arginase activity is associated with fibrosis in experimental infection with Taenia crassiceps, but does not play a major role in resistance to infection

Murine infection with Taenia crassiceps cysticerci is used as an experimental model for human and animal cysticercosis. In this infection parasites can be found associated with an inflammatory infiltrate enriched with macrophages. Experimental evidence exists supporting a role for either NO-producing classically activated (CAMΦ) or arginase- and CD301-expressing alternatively activated macrophages (AAMΦ) in T. crassiceps resistance. In both cell types, arginine is utilized as an important mediator in macrophage effector functions. To investigate whether there is an association between arginine availability, susceptibility to T. crassiceps and other parameters such as fibrosis, BALB/c mice were infected intraperitoneally with cysticerci and treated daily with the arginase inhibitor nor-NOHA or supplemented with l-arginine and followed for eight weeks. The numbers and developmental stages of parasites were evaluated as well as the presence of CD301+ AAMΦ, arginase activity and collagen deposition in the peritoneal membrane. Treatment with the arginase inhibitor or supplementation with l-arginine did not change the parasitic load or profile of the infection. However, the arginase inhibitor significantly decreased the deposition of collagen. These results suggest that arginase activity does not interfere with parasite control during experimental infection with T. crassiceps, but it is important for fibrosis in cysticercosis.

Comparative pharmacokinetics of N(ω)-hydroxy-nor-L-arginine, an arginase inhibitor, after single-dose intravenous, intraperitoneal and intratracheal administration to brown Norway rats

1.  Rodent studies have documented that N(ω)-hydroxy-nor-L-arginine (nor-NOHA), an arginase inhibitor, has therapeutic potential in the treatment of cardiovascular and obstructive airway diseases. However, its bioavailability and pharmacokinetics have not been described so far. 2.  Anesthetized brown Norway rats were administered single doses of nor-NOHA (10, 30 or 90 mg/kg) intravenously (i.v.), intraperitonealy (i.p.) or via intratracheal (i.t.) instillation of aerosol. Plasma nor-NOHA was assayed using a validated HPLC method. 3.  Upon i.v. administration, the mean concentration showed a biphasic decline and its value dropped below 10% of the maximum after 20 min. The pharmacokinetics were linear with the total and inter-compartmental clearances of 33 and 17 mL/min/kg, central and peripheral volumes of distribution of 0.19 and 0.43 L/kg and terminal half-life of 30 min. 4.  The average absolute bioavailability of nor-NOHA after i.p. and i.t. delivery was 98% and 53%, respectively. The absorption from the airways was rate-limiting and its extent decreased with the dose. 5.  In conclusion, nor-NOHA is rapidly cleared from the plasma in concordance with the short time window of its in vivo inhibitory activity reported in the literature. I.t. instillation of aerosol for topical effects of nor-NOHA in the airways is characterized with significant systemic availability.

The acute-phase protein serum amyloid A induces endothelial dysfunction that is inhibited by high-density lipoprotein

The acute-phase protein serum amyloid A (SAA) is elevated during inflammation and may be deposited in atheroma where it promotes atherosclerosis. We investigated the proatherogenic effects of SAA on the vascular endothelium and their regulation by high-density lipoprotein (HDL). Exposure of human aortic endothelial cells (HAEC) to SAA (0.25-25μg/ml) decreased nitric oxide ((•)NO) synthesis/bioavailability, although the endothelial NO synthase monomer-to-dimer ratio was unaffected. SAA (10μg/ml) stimulated a Ca(2+) influx linked to apocynin-sensitive superoxide radical anion (O(2)(•-)) production. Gene expression for arginase-1, nuclear factor κB (NF-κB), interleukin-8, and tissue factor (TF) increased within 4h of SAA stimulation. Enzymatically active Arg-1/2 was detected in HAEC cultured with SAA for 24h. Therefore, in addition to modulating (•)NO bioavailability by stimulating O(2)(•-) production in the endothelium, SAA modulated vascular l-Arg bioavailability. SAA also diminished relaxation of preconstricted aortic rings induced by acetylcholine, and added superoxide dismutase restored the vascular response. Preincubation of HAEC with HDL (100 or 200, but not 50, μg/ml) before (not after) SAA treatment ameliorated the Ca(2+) influx and O(2)(•-) production; decreased TF, NF-κB, and Arg-1 gene expression; and preserved overall vascular function. Thus, SAA may promote endothelial dysfunction by modulating (•)NO and l-Arg bioavailability, and HDL pretreatment may be protective. The relative HDL to SAA concentrations may regulate the proatherogenic properties of SAA on the vascular endothelium.