No abstract

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.

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.

The development of acute lung injury (ALI) during sepsis almost doubles the mortality rate of patients. The efficacy of current treatment strategies is low as treatment is usually initiated following the onset of symptoms. Inflammation is one of the main mechanisms of autoimmune disorders and is a common feature of sepsis. The suppression of inflammation is therefore an important mechanism for the treatment of sepsis. Sirtuin 1 (Sirt1) has been demonstrated to play a role in the regulation of inflammation. Resveratrol, a potent Sirt1 activator, exhibits anti‑inflammatory properties. However, the role of resveratrol for the treatment of ALI during sepsis is not fully understood. In the present study, the anti‑inflammatory role of Sirt1 in the lipopolysaccharide (LPS)‑induced TC‑1 cell line and its therapeutic role in ALI was investigated in a mouse model of sepsis. The upregulation of matrix metalloproteinase-9, interleukin (IL)‑1β, IL‑6 and inducible nitric oxide synthase was induced by LPS in the mouse model of sepsis and the TC‑1 cell line, and resveratrol suppressed the overexpression of these proinflammatory molecules in a dose‑dependent manner. Resveratrol decreased pulmonary edema in the mouse model of sepsis induced by LPS. In addition, resveratrol improved lung function and reduced pathological alterations in the mouse model of sepsis. Knockdown of Sirt1 by RNA interference resulted in an increased susceptibility of TC‑1 cells to LPS stimulation and diminished the anti‑inflammatory effect of resveratrol. These results demonstrated that resveratrol inhibits LPS‑induced ALI and inflammation via Sirt1, and indicated that Sirt1 is an efficient target for the regulation of LPS‑induced ALI and inflammation. The present study provides insights into the treatment of ALI during sepsis.

Abstract. Acute lung injury (ALI) and the more severe acute respiratory distress syndrome (ARDS) are common and complex inflammatory lung diseases. MicroRNAs (miRNAs), a type of non-coding RNA molecule that regulate gene expression at the post-transcriptional level, have emerged as a novel class of gene regulators, which have critical roles in a wide range of human disorders and diseases, including ALI.