Different effect of glutamine on macrophage tumor necrosis factor-alpha release and heat shock protein 72 expression in vitro and in vivo.

Macrophage plays a vital role in sepsis. However, the modulatory effect of glutamine (Gln) on macrophage/ monocyte-mediate cytokines release is still controversial. Thus, we investigated the effect of Gln on macrophage tumor necrosis factor (TNF)-alpha release and heat shock protein (HSP) 72 expression in vivo and in vitro. Data from our study indicated that the increase of HSP72 expression was significant at 8 mM of Gln 4 h after lipopolysaccharide (LPS) stimulation and became independent of Gln concentrations at 24 h, whereas TNF-alpha release was dose- and time-dependent on Gln. Heat stress (HS) induced more HSP72 and less TNF-alpha production compared with the non-HS group. However, the production of TNF-alpha in cells pretreated with HS was increased with increasing concentrations of Gln. Treatment with various concentrations of Gln for 1 h and then 0.5 mM Gln for 4 h led to an increase in HSP72 expression, but not in TNF-alpha production. In sepsis model mice, Gln treatment led to a significantly lower intracellular TNF-alphalevel and an increase in HSP72 expression in mouse peritoneal macrophages. Our results demonstrate that Gln directly increases TNF-alpha release of LPS-stimulated RAW264.7 macrophages in a dose-dependent manner, and also decreases mouse peritoneal macrophages TNF-a release in the sepsis model. Taken together, our data suggest that there may be more additional pathways by which Gln modulates cytokine production besides HSP72 expression in macrophage during sepsis.

[The different effects of glutamine on macrophage cytokines release in vivo and in vitro].

OBJECTIVE: To evaluate the effects of glutamine (Gln) on macrophages cytokines release and heat shock protein 72 (HSP72) expression in vivo and in vitro, and explore the anti-inflammation mechanisms of Gln during sepsis. METHODS: In experiment one, mouse peritoneal macrophage cell line RAW264.7 cells were divided into 0, 0.5 and 8 mmol/L Gln groups, and cells and supernatants were harvested at 0, 1, 4, 12 and 24 hours after lipopolysaccharide (LPS) challenge. In experiment two, forty-five Kunming mice were randomized into sham-operation group (Sham), sepsis model group, and Gln group. Sepsis was induced by cecal ligation and puncture (CLP). Either Gln 0.75 g/kg (Gln group) or saline (Sham and model group) was administered immediately after CLP via tail-vein injection. Blood sample was collected at 6 hours, and macrophages were harvested by peritoneal lavage. Tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-10 contents in supernatant, serum and cell lysate were analyzed with enzyme-linked immunosorbent assay (ELISA), macrophages HSP72 expression was assessed with Western blotting. RESULTS: Gln promoted RAW264.7 cells to release TNF-alpha, IL-6 and IL-10 in a dose-dependent and time-dependent manner in vitro (P<0.05 or P<0.01), and significantly increased HSP72 expression in 8 mmol/L Gln group at 4 hours after LPS stimulation (both P<0.01). In vivo, in animals given Gln intracellular TNF-alpha and IL-6 levels were significantly lower than sepsis animals (P<0.01 and P<0.05), but there was no statistically significant difference in intracellular IL-10 levels among three groups. The serum levels of TNF-alpha in Gln group were significantly lower than in model group (P<0.05), while serum IL-6 and IL-10 levels were similar between two groups. Gln treatment led to significant HSP72 expression compared to model and Sham groups (both P<0.01). CONCLUSION: Gln can promote inflammatory cytokines release from macrophages in vitro, which cannot be attenuated by HSP72 expression induced by Gln in LPS challenged RAW264.7 macrophages. Gln treatment significantly decreases intracellular TNF-alpha and IL-6 levels in vivo during sepsis. HSP72 expression increases after Gln treatment both in vivo and in vitro. These data implicate that HSP72 may not play a major role in attenuating the inflammatory response after Gln administration in sepsis.

Angiotensin-converting enzyme 2 prevents lipopolysaccharide-induced rat acute lung injury via suppressing the ERK1/2 and NF-κB signaling pathways.

Acute respiratory distress syndrome (ARDS) caused by severe sepsis remains a major challenge in intensive care medicine. ACE2 has been shown to protect against lung injury. However, the mechanisms of its protective effects on ARDS are largely unknown. Here, we report that ACE2 prevents LPS-induced ARDS by inhibiting MAPKs and NF-κB signaling pathway. Lentiviral packaged Ace2 cDNA or Ace2 shRNA was intratracheally administrated into the lungs of male SD rats. Two weeks after gene transfer, animals received LPS (7.5 mg/Kg) injection alone or in combination with Mas receptor antagonist A779 (10 µg/Kg) or ACE2 inhibitor MLN-4760 (1 mg/Kg) pretreatment. LPS-induced lung injury and inflammatory response were significantly prevented by ACE2 overexpression and deteriorated by Ace2 shRNA. A779 or MLN-4760 pretreatment abolished the protective effects of ACE2. Moreover, overexpression of ACE2 significantly reduced the Ang II/Ang-(1-7) ratio in BALF and up-regulated Mas mRNA expression in lung, which was reversed by A779. Importantly, the blockade of ACE2 on LPS-induced phosphorylation of ERK1/2, p38 and p50/p65 was also abolished by A779. Whereas, only the ERK1/2 inhibitor significantly attenuated lung injury in ACE2 overexpressing rats pretreated with A779. Our observation suggests that AEC2 attenuates LPS-induced ARDS via the Ang-(1-7)/Mas pathway by inhibiting ERK/NF-κB activation.

Angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis prevents lipopolysaccharide-induced apoptosis of pulmonary microvascular endothelial cells by inhibiting JNK/NF-κB pathways.

ACE2 and Ang-(1-7) have important roles in preventing acute lung injury. However, it is not clear whether upregulation of the ACE2/Ang-(1-7)/Mas axis prevents LPS-induced injury in pulmonary microvascular endothelial cells (PMVECs) by inhibiting the MAPKs/NF-κB pathways. Primary cultured rat PMVECs were transduced with lentiviral-borne Ace2 or shRNA-Ace2, and then treated or not with Mas receptor blocker (A779) before exposure to LPS. LPS stimulation resulted in the higher levels of AngII, Ang-(1-7), cytokine secretion, and apoptosis rates, and the lower ACE2/ACE ratio. Ace2 reversed the ACE2/ACE imbalance and increased Ang-(1-7) levels, thus reducing LPS-induced apoptosis and inflammation, while inhibition of Ace2 reversed all these effects. A779 abolished these protective effects of Ace2. LPS treatment was associated with activation of the ERK, p38, JNK, and NF-κB pathways, which were aggravated by A779. Pretreatment with A779 prevented the Ace2-induced blockade of p38, JNK, and NF-κB phosphorylation. However, only JNK inhibitor markedly reduced apoptosis and cytokine secretion in PMVECs with Ace2 deletion and A779 pretreatment. These results suggest that the ACE2/Ang-(1-7)/Mas axis has a crucial role in preventing LPS-induced apoptosis and inflammation of PMVECs, by inhibiting the JNK/NF-κB pathways.