Macrophages require distinct arginine catabolism and transport systems for proliferation and for activation.

In murine macrophages, as a result of arginine catabolism during activation, citruline isproduced under the effect of IFN-c and LPS, and ornithine and polyamines by IL-4 and IL-10. For proliferation, arginine is required from the extracellular medium and is used for protein synthesis. During activation, most arginine (>95% in 6 h) was metabolized, while under proliferation only half was incorporated into proteins. Under basal conditions, this amino acid was preferentially transported by y+L activity. During activation, arginine transport increased drastically (4–5-fold) through y+ cationic amino acid transporter (CAT) activity. By contrast, M-CSF induced only a modest increase in uptake (0.5-fold). The increase in arginine transport during activation, but not proliferation, was mediated by the SLC7A2/Cat2 gene. SLC7A1/Cat1 is constitutively expressed, and is not modified by proliferating or activating agents.M-CSF-dependent proliferation was not affected in the macrophages of SLC7A2 knockout mice; however, these cells showed a drastic reduction in the production of citruline or ornithine and polyamines during activation. The data show that a large increase in a specific transport system (CAT2) is necessary for activation-induced arginine metabolism, while arginine is in excess for the requirements of proliferation and a modest increase in transport occurs

Arginine transport is impaired in C57Bl/6 mouse macrophages as a result of a deletion in the promoter of slc7a2 (CAT2) and Leishmania infection is reduced

Host genetic factors play a crucial role in immune response. To determine whether the differences betweenC57Bl/6 and BALB-C mice are due only to the production of cytokines by T-helper 1 cells or T-helper 2 cells,we obtained bone marrow–derived macrophages from both strains and incubated them with these cytokines.Although the induction of Nos2 and Arg1 was similar in the 2 strains, infectivity to Leishmania major differed,as did macrophage uptake of arginine, which was higher in BALB-C macrophages. The levels of interferon γ–and interleukin 4–dependent induction of the cationic amino acid transporter SLC7A2 (also known as “cationicamino acid transporter 2,” or “CAT2”) were decreased in macrophages from C57Bl/6 mice. This reductionwas a result of a deletion in the promoter of one of the 4 AGGG repeats. These results demonstrate that theavailability of arginine controls critical aspects of macrophage activation and reveal a factor for susceptibility to Leishmania infection

Lipopolysaccharide-induced apoptosis of macrophages determines the up-regulation of concentrative nucleoside transporters Cnt1 and Cnt2 through tumor necrosis factor-alpha-dependent and -independent mechanisms

In murine bone marrow macrophages, lipopolysaccharide (LPS) induces apoptosis through the autocrine production of tumor necrosis factor-alpha (TNF-alpha), as demonstrated by the fact that macrophages from TNF-alpha receptor I knock-out mice did not undergo early apoptosis. In these conditions LPS up-regulated the two concentrative high affinity nucleoside transporters here shown to be expressed in murine bone marrow macrophages, concentrative nucleoside transporter (CNT) 1 and 2, in a rapid manner that is nevertheless consistent with the de novo synthesis of carrier proteins. This effect was not dependent on the presence of macrophage colony-stimulating factor, although LPS blocked the macrophage colony-stimulating factor-mediated up-regulation of the equilibrative nucleoside transport system es. TNF-alpha mimicked the regulatory response of nucleoside transporters triggered by LPS, but macrophages isolated from TNF-alpha receptor I knock-out mice similarly up-regulated nucleoside transport after LPS treatment. Although NO is produced by macrophages after LPS treatment, NO is not involved in these regulatory responses because LPS up-regulated CNT1 and CNT2 transport activity and expression in macrophages from inducible nitric oxide synthase and cationic amino acid transporter (CAT) 2 knock-out mice, both of which lack inducible nitric oxide synthesis. These data indicate that the early proapoptotic responses of macrophages, involving the up-regulation of CNT transporters, follow redundant regulatory pathways in which TNF-alpha-dependent- and -independent mechanisms are involved. These observations also support a role for CNT transporters in determining extracellular nucleoside availability and modulating macrophage apoptosis

Age-Related Alteration of Arginase Activity Impacts on Severity of Leishmaniasis

It is well documented that ageing alters many aspects of immune responses; however, a causal relation between impaired immune functions in ageing individuals and the response to infection has not been established. Experimental leishmaniasis is an excellent model to analyse protective and pathological immune responses. Leishmania parasites are obligate intracellular pathogens and invade mainly macrophages, which have dual function: they can kill the parasites or promote their growth. We have recently shown that arginase, an enzyme induced in infected macrophages, is a key factor for parasite survival. Here, we show that ageing reduces the expression levels of arginase in macrophages, resulting in more efficient control of parasite growth. Our results suggest that age-related differences in the metabolism of arginase in macrophages might contribute to the higher susceptibility of children to leishmaniasis

European Registry on Helicobacter pylori Management: Effectiveness of First and Second-Line Treatment in Spain

The management of Helicobacter pylori infection has to rely on previous local effectiveness due to the geographical variability of antibiotic resistance. The aim of this study was to evaluate the effectiveness of first and second-line H. pylori treatment in Spain, where the empirical prescription is recommended. A multicentre prospective non-interventional registry of the clinical practice of European gastroenterologists concerning H. pylori infection (Hp-EuReg) was developed, including patients from 2013 until June 2019. Effectiveness was evaluated descriptively and through a multivariate analysis concerning age, gender, presence of ulcer, proton-pump inhibitor (PPI) dose, therapy duration and compliance. Overall, 53 Spanish hospitals were included, and 10,267 patients received a first-line therapy. The best results were obtained with the 10-day bismuth single-capsule therapy (95% cure rate by intention-to-treat) and with both the 14-day bismuth-clarithromycin quadruple (PPI-bismuth-clarithromycin-amoxicillin, 91%) and the 14-day non-bismuth quadruple concomitant (PPI-clarithromycin-amoxicillin-metronidazole, 92%) therapies. Second-line therapies were prescribed to 2448 patients, with most-effective therapies being the triple quinolone (PPI-amoxicillin-levofloxacin/moxifloxacin) and the bismuth-levofloxacin quadruple schemes (PPI-bismuth-levofloxacin-amoxicillin) prescribed for 14 days (92%, 89% and 90% effectiveness, respectively), and the bismuth single-capsule (10 days, 88.5%). Compliance, longer duration and higher acid inhibition were associated with higher effectiveness. "Optimized" H. pylori therapies achieve over 90% success in Spain

Local Increase of Arginase Activity in Lesions of Patients with Cutaneous Leishmaniasis in Ethiopia

The leishmaniases are a complex of diseases caused by Leishmania parasites. Currently, the diseases affect an estimated 12 million people in 88 countries, and approximately 350 million more people are at risk. The leishmaniases belong to the most neglected tropical diseases, affecting the poorest populations, for whom access to diagnosis and effective treatment are often not available. Leishmania parasites infect cells of the immune system called macrophages, which have the capacity to eliminate the intracellular parasites when they receive the appropriate signals from other cells of the immune system. In nonhealing persistent leishmaniasis, lymphocytes are unable to transmit the signals to macrophages required to kill the intracellular parasites. The local upregulation of the enzyme arginase has been shown to impair lymphocyte effector functions at the site of pathology. In this study, we tested the activity of this enzyme in skin lesions of patients presenting with localized cutaneous leishmaniasis. Our results show that arginase is highly upregulated in these lesions. This increase in arginase activity coincides with lower expression of a signalling molecule in lymphocytes, which is essential for efficient activation of these cells. These results suggest that increased arginase expression in the localized cutaneous lesions might contribute to persistent disease in patients presenting with cutaneous leishmaniasis

Local Suppression of T Cell Responses by Arginase-Induced L-Arginine Depletion in Nonhealing Leishmaniasis

The balance between T helper (Th) 1 and Th2 cell responses is a major determinant of the outcome of experimental leishmaniasis, but polarized Th1 or Th2 responses are not sufficient to account for healing or nonhealing. Here we show that high arginase activity, a hallmark of nonhealing disease, is primarily expressed locally at the site of pathology. The high arginase activity causes local depletion of L-arginine, which impairs the capacity of T cells in the lesion to proliferate and to produce interferon-γ, while T cells in the local draining lymph nodes respond normally. Healing, induced by chemotherapy, resulted in control of arginase activity and reversal of local immunosuppression. Moreover, competitive inhibition of arginase as well as supplementation with L-arginine restored T cell effector functions and reduced pathology and parasite growth at the site of lesions. These results demonstrate that in nonhealing leishmaniasis, arginase-induced L-arginine depletion results in impaired T cell responses. Our results identify a novel mechanism in leishmaniasis that contributes to the failure to heal persistent lesions and suggest new approaches to therapy

In Vitro and In Vivo Efficacy of Ether Lipid Edelfosine against Leishmania spp. and SbV-Resistant Parasites

Leishmaniasis represents a major international health problem, has a high morbidity and mortality rate, and is classified as an emerging and uncontrolled disease by the World Health Organization. The migration of population from endemic to nonendemic areas, and tourist activities in endemic regions are spreading the disease to new areas. Unfortunately, treatment of leishmaniasis is far from satisfactory, with only a few drugs available that show significant side-effects. Here, we show in vitro and in vivo evidence for the antileishmanial activity of the ether phospholipid edelfosine, being effective against a wide number of Leishmania spp. causing cutaneous, mucocutaneous and visceral leishmaniasis. Our experimental mouse and hamster models demonstrated not only a significant antileishmanial activity of edelfosine oral administration against different wild-type Leishmania spp., but also against parasites resistant to pentavalent antimonials, which constitute the first line of treatment worldwide. In addition, edelfosine exerted a higher antileishmanial activity and a lower proneness to generate drug resistance than miltefosine, the first drug against leishmaniasis that can be administered orally. These data, together with our previous findings, showing an anti-inflammatory action and a very low toxicity profile, suggest that edelfosine is a promising orally administered drug for leishmaniasis, thus warranting clinical evaluation