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Objective: To investigate the protective effect of agmatine (AGM) against peritoneal inflammatory response and neutrophil (PMN) infiltration induced by zymosan (ZYM) in mice., Methods: Thirty-six adult male C57BL/6 mice were randomly divided into sham group, model group, and AGM treatment group. Peritonitis model was reproduced by intra-peritoneal injection of 1 mg/mL ZYM (0.5 mL), while equivalent phosphate buffer saline (PBS) was given to sham group. 200 mg/kg AGM was injected into peritoneal cavity after ZYM challenge in AGM treatment group. Six mice in each group were sacrificed at 2 hours and 6 hours, respectively, after reproduction of the model. Blood sample and peritoneal lavage fluid (PLF) were collected. The levels of keratinocyte-derived chemokine (KC), macrophage inflammatory protein 2 (MIP-2), tumor necrosis factor-α (TNF-α), interleukins-6 (IL-6) in serum and PLF were determined by enzyme linked immunosorbent assay (ELISA). The number of leukocytes and PMN in PLF were determined by hemocytometer and flow cytometry, respectively., Results: Compared with sham group, all serum and PLF levels of KC, MIP-2, TNF-α and IL-6 were greatly elevated at 2 hours after ZYM injection in model group, while AGM treatment could dramatically reduce the levels of the above-mentioned cytokines in serum and PLF as compared with those of the model group [serum KC (ng/L): 990.7±137.9 vs. 2 053.2±262.7, MIP-2 (ng/L): 642.2±124.4 vs. 1 369.7±146.5, TNF-α (ng/L): 608.6±38.1 vs. 1 044.7±101.0, IL-6 (ng/L): 1 058.2±129.1 vs. 1 443.3±190.1; PLF KC (ng/L): 7 462.3±839.6 vs. 12 723.5±1 515.7, MIP-2 (ng/L): 1 570.8±193.4 vs. 3 471.4±384.7, TNF-α (ng/L): 1 115.8±156.7 vs. 1 499.2±231.2, IL-6 (ng/L): 2 646.5±223.2 vs. 3 126.7±291.4; all P < 0.05]. The expressions of KC, MIP-2 and TNF-α at 6 hours were significantly lower than those at 2 hours in model group and AGM treatment group, but IL-6 levels were further increased. The levels of KC and MIP-2 in serum and PLF at 6 hours were decreased to the levels of sham group. At 6 hours after the reproduction of the model, the number of total inflammatory cells and PMN of PLF in the model group was significantly higher than those of the sham group. In contrast, AGM notably lowered the number of inflammatory cells and PMN in peritoneal fluid after ZYM attack [total inflammatory cells (×109/L): 14.7±1.1 vs. 2.0±0.4, 10.1±1.2 vs. 14.7±1.1; PMN (×109/L): 11.37±1.22 vs. 0.18±0.05, 7.69±0.57 vs. 11.37±1.22, all P < 0.05]., Conclusion: AGM can effectively alleviate acute peritoneal inflammatory injury induced by ZYM, mainly through reducing the secretion of inflammatory mediators and chemokines, and inhibiting the infiltration of leukocytes and neutrophils.

Objective: To observe protective effects of agmatine (AGM) on inflammatory response and spleen immune function in mice with trauma., Methods: Forty-eight adult male C57BL/6 mice were randomly divided into three groups (n = 16 each), including control group, model group (bilateral femoral fracture and removal of 35% of the total blood volume), and AGM group (trauma/hemorrhage and AGM 200 mg/kg). Eight mice in each group were sacrificed at 3 hours and 24 hours, respectively, after modeling, and blood samples and tissue homogenate of spleen and liver were collected. The contents of tumor necrosis factor-α (TNF-α), interleukins (IL-6, IL-1β) in serum and liver tissue were determined with enzyme linked immunosorbent assay (ELISA). Serum aspartate transaminase (AST), alanine aminotransferase (ALT) and lactic dehydrogenase (LDH) were determined with automatic biochemistry analyzer. Spleen proliferation response stimulated with concanavalin A (ConA) was evaluated with methyl thiazolyl tetrazolium colourimetry (MTT). γ-interferon (IFN-γ) and IL-2 releases were determined with ELISA., Results: Compared with control group, 3 hours after trauma/hemorrhage, the levels of serum TNF-α, IL-6, and IL-1β in model group were significantly elevated [TNF-α (ng/L): 145.38±31.50 vs. 23.06±11.14, IL-6 (ng/L): 496.94±50.76 vs. 47.13±17.47, IL-1β (ng/L): 321.31±43.02 vs. 29.25±16.24,all P < 0.01]. It was found that AGM treatment could alleviate the increase in serum pro-inflammatory mediators induced by trauma/hemorrhage, such as TNF-α (ng/L: 111.56±25.47 vs. 145.38±31.50), IL-6 (ng/L: 412.56±44.33 vs. 496.94±50.76), IL-1β (ng/L: 273.38±45.25 vs. 321.31±43.02, P < 0.05 or P < 0.01). Twenty-four hours after trauma/hemorrhage, serum pro-inflammatory mediators were recovered to the levels in control group. There was no significant difference in TNF-α and IL-6 levels at 3 hours after trauma/hemorrhage among groups. Compared with control group, the expressions of liver TNF-α and IL-6 in model group were increased at 24 hours following trauma [TNF-α (ng/mg): 32.93±4.90 vs. 26.58±2.33,IL-6 (ng/mg): 11.20±1.66 vs. 8.38±0.89,both P < 0.01]. However, AGM inhibited the level of TNF-α (ng/mg: 28.92±3.16 vs. 32.93±4.90) and IL-6 (ng/mg: 9.03±1.28 vs. 11.20±1.66) in the liver as induced by trauma/hemorrhage (P < 0.05 and P < 0.01). At 24 hours after modeling, model group and AGM group had distinctly higher serum AST, ALT, LDH levels than those of control group [AST (U/L): 405.9±31.2, 245.7±22.1 vs. 128.2±15.9; ALT (U/L): 92.1±6.3, 51.6±5.0 vs. 30.1±3.2; LDH (U/L): 606.7±36.3, 478.7±25.3 vs. 384.0±16.6, all P < 0.01]. Nevertheless,the increase in serum AST, ALT and LDH was alleviated in AGM group (all P < 0.01). Meantime, trauma/hemorrhage produced a noticeable depression of proliferation of splenic cells and IFN-γ and IL-2 release stimulated with ConA compared with control group [proliferation rate: (40.97±4.13)% vs. (89.99±7.76)%, IFN-γ (ng/L): 91.6±12.3 vs. 353.2±21.5,IL-2 (ng/L): 53.4±6.4 vs. 91.0±12.2,all P < 0.01]. In contrast, AGM notably restored the capacity of proliferation response of splenic cells [proliferation rate: (74.86±5.75)% vs. (40.97±4.13)%,P < 0.01],enhanced the release of IFN-γ and IL-2 stimulated with ConA [IFN-γ (ng/L): 327.8±23.6 vs. 91.6±12.3, IL-2 (ng/L): 74.8±10.4 vs. 53.4±6.4, both P < 0.01]., Conclusions: AGM can dramatically alleviate spleen immunosuppression, excessive inflammation and organ damage induced by trauma/hemorrhage.

Macrophages are key responders of inflammation and are closely related with oxidative stress. Activated macrophages can enhance oxygen depletion, which causes an overproduction of reactive oxygen species (ROS) and leads to further excessive inflammatory response and tissue damage. Agmatine, an endogenous metabolite of L-arginine, has recently been shown to have neuroprotective effects based on its antioxidant properties. However, the antioxidant effects of agmatine in peripheral tissues and cells, especially macrophages, remain unclear. In this study we explored the role of agmatine in mediating antioxidant effects in RAW 264.7 cells and studied its antioxidant mechanism. Our data demonstrate that agmatine is an activator of Nrf2 signaling that markedly enhances Nrf2 nuclear translocation, increases nuclear Nrf2 protein level, up-regulates the expression of the Nrf2 downstream effector HO-1, and attenuates ROS generation induced by Lipopolysaccharide (LPS). We further demonstrated that the agmatine-induced activation of Nrf2 is likely through the PI3K/Akt pathway. LY294002, a specific PI3K/Akt inhibitor, abolished agmatine-induced HO-1 up-regulation and ROS suppression significantly. Inhibiting HO-1 pathway significantly attenuated the antioxidant effect of agmatine which the products of HO-1 enzymatic activity contributed to. Furthermore, the common membrane receptors of agmatine were evaluated, revealing that α2-adrenoceptor, I1-imidazoline receptor or I2-imidazoline receptor are not required by the antioxidant properties of agmatine. Taken together, our findings revealed that agmatine has antioxidant activity against LPS-induced ROS accumulation in RAW 264.7 cells involving HO-1 expression induced by Nrf2 via PI3K/Akt pathway activation. [ABSTRACT FROM AUTHOR]