The incidence of cardiovascular disease is predicted to increase as the population ages. There is accumulating evidence that arginase upregulation is associated with impaired endothelial function. Here, we demonstrate that arginase II (ArgII) is upregulated in aortic vessels of aged mice and contributes to decreased nitric oxide (NO) generation and increased reactive oxygen species (ROS) production via endothelial nitric oxide synthase (eNOS) uncoupling. Inhibiting ArgII with small interfering RNA technique restored eNOS coupling to that observed in young mice and increased NO generation and decreased ROS production. Furthermore, enhanced vasoconstrictor responses to U46619 and attenuated vasorelaxation responses to acetylcholine in aged vasculature were markedly improved following siRNA treatment against ArgII. These results might be associated with increased L-arginine bioavailability. Collectively, these results suggest that ArgII may be a valuable target in age-dependent vascular diseases.
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology ; Aging ; Animals ; Aorta/enzymology/physiopathology ; Arginase/genetics/*metabolism ; Endothelium, Vascular/*enzymology/physiopathology ; Enzyme Induction ; Gene Knockdown Techniques ; Mice ; Mice, Inbred C57BL ; Nitric Oxide/metabolism ; Nitric Oxide Synthase Type III/*metabolism ; RNA, Small Interfering/genetics ; Reactive Oxygen Species/metabolism ; Up-Regulation ; Vasoconstriction/drug effects

BACKGROUNDHemorrhagic shock is usually associated with complicated immune and inflammatory responses, which are sometimes crucial for the prognosis. As regulators of the immune and inflammatory system; proliferation, migration, distribution and activation of myeloid-derived suppressor cells (MDSCs) are intimately linked to the inflammation cascade.

METHODSIn a model of severe hemorrhagic shock, thirty-five rats were randomly divided into control, sham, normal saline resuscitation (NS), hypertonic saline resuscitation (HTS), and hydroxyethyl starch resuscitation (HES), with seven in each group. MDSCs were analyzed by flow cytometric staining of CD11b/c(+)Gra(+) in peripheral blood mononuclear cells (PBMC), spleen cell suspensions, and bone marrow nucleated cells (BMNC). Simultaneously, the expressions of arginase-1 (ARG-1) and inducible nitric oxide synthase (iNOS) mRNA in MDSCs were evaluated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTSIn the early stage after hemorrhagic shock, fluid resuscitation and emergency treatment, the MDSCs in the PBMC of NS, HTS and HES groups markedly increased, and MDSCs in BMNC of these groups decreased accordingly, significantly different to the control group. In hemorrhagic shock rats infused with HTS at the early resuscitation stage, MDSCs in PBMC increased about 2 and 4 folds, and MDSCs in BMNC decreased about 1.3 and 1.6 folds, as compared to the sham group respectively, with statistically significant difference. Furthermore, compared to the NS and HES groups, the MDSCs in PBMC of HTS group increased 1.6 and 1.8 folds with statistically significant differences; the MDSCs decrease in BMNC was not significant. However, there was no statistically significant difference in MDSCs of spleen among the five groups. In addition, compared to the control, sham, NS and HES groups, the ARG-1 and iNOS mRNA of MDSCs in PBMC, spleen and BMNC in the HTS group had the highest level of expression, but no statistically significant differences were noted.

CONCLUSIONSIn this model of rat with severe and controlled hemorrhagic shock, small volume resuscitation with HTS contributes to dramatically early migration and redistribution of MDSCs from bone marrow to peripheral circulation, compared to resuscitation with NS or HES.

Animals ; Arginase ; genetics ; metabolism ; Blood Pressure ; physiology ; Disease Models, Animal ; Flow Cytometry ; Fluid Therapy ; methods ; Leukocytes, Mononuclear ; metabolism ; Male ; Nitric Oxide Synthase Type II ; metabolism ; Rats ; Rats, Sprague-Dawley ; Real-Time Polymerase Chain Reaction ; Saline Solution, Hypertonic ; therapeutic use ; Shock, Hemorrhagic ; immunology ; metabolism ; therapy

Myeloid-derived suppressor cells (MDSCs) play a crucial role in T cell dysfunction, which is related to poor outcome in patients with severe trauma. Cyclooxygenase-2 (Cox-2) contributes to immune disorder in trauma and infection via production of prostaglandin E2. However, the role of Cox-2 in the accumulation and function of MDSCs after traumatic stress has not been fully elucidated. In the present study, we treated murine trauma model with NS398, a selective Cox-2 inhibitor. Then the percentages of CD11b+/Gr-1+ cells, proliferation and apoptosis of CD4+ T cells were determined. Arginase activity and arginase-1 (Arg-1) protein expression of splenic CD11b+/Gr-1+ cells, and delayed-type hypersensitivity (DTH) response were analyzed. The results showed that Cox-2 blockade significantly decreased the percentages of CD11b+/Gr-1+ cells in the spleen and bone marrow 48 and 72 h after traumatic stress. NS398 inhibited arginase activity and down-regulated the Arg-1 expression of splenic CD11b+/Gr-1+ cells. Moreover, NS398 could promote proliferation and inhibit apoptosis of CD4+ T cells. It also restored DTH response of traumatic mice. Taken together, our data revealed that Cox-2 might play a pivotal role in the accumulation and function of MDSC after traumatic stress.
Animals ; Apoptosis ; drug effects ; Arginase ; biosynthesis ; CD11b Antigen ; biosynthesis ; CD4-Positive T-Lymphocytes ; drug effects ; metabolism ; Cell Proliferation ; drug effects ; Cyclooxygenase 2 ; biosynthesis ; Cyclooxygenase 2 Inhibitors ; administration & dosage ; Gene Expression Regulation ; drug effects ; Humans ; Mice ; Myeloid Progenitor Cells ; metabolism ; pathology ; Nitrobenzenes ; administration & dosage ; Stress Disorders, Traumatic ; drug therapy ; genetics ; pathology ; Sulfonamides ; administration & dosage