Resolvin D1 Improves the Resolution of Inflammation via Activating NF-κB p50/p50-Mediated Cyclooxygenase-2 Expression in Acute Respiratory Distress Syndrome.

Acute respiratory distress syndrome (ARDS) is a severe illness characterized by uncontrolled inflammation. The resolution of inflammation is a tightly regulated event controlled by endogenous mediators, such as resolvin D1 (RvD1). Cyclooxygenase-2 (COX-2) has been reported to promote inflammation, along with PGE2, in the initiation of inflammation, as well as in prompting resolution, with PGD2 acting in the later phase of inflammation. Our previous work demonstrated that RvD1 enhanced COX-2 and PGD2 expression to resolve inflammation. In this study, we investigated mechanisms underlying the effect of RvD1 in modulating proresolving COX-2 expression. In a self-limited ARDS model, an LPS challenge induced the biphasic activation of COX-2, and RvD1 promoted COX-2 expression during the resolution phase. However, it was significantly blocked by treatment of a NF-κB inhibitor. In pulmonary fibroblasts, NF-κB p50/p50 was shown to be responsible for the proresolving activity of COX-2. Additionally, RvD1 potently promoted p50 homodimer nuclear translocation and robustly triggered DNA-binding activity, upregulating COX-2 expression via lipoxin A4 receptor/formyl peptide receptor 2. Finally, the absence of p50 in knockout mice prevented RvD1 from promoting COX-2 and PGD2 expression and resulted in excessive pulmonary inflammation. In conclusion, RvD1 expedites the resolution of inflammation through activation of lipoxin A4 receptor/formyl peptide receptor 2 receptor and NF-κB p50/p50-COX-2 signaling pathways, indicating that RvD1 might have therapeutic potential in the management of ARDS.

Maresin 1 attenuates mitochondrial dysfunction through the ALX/cAMP/ROS pathway in the cecal ligation and puncture mouse model and sepsis patients.

Inflammation always accompanies infection during sepsis. Mitochondrial dysfunction and the role of reactive oxygen species (ROS) produced by mitochondria have been proposed in the pathogenesis of sepsis. Maresins have protective and resolving effects in experimental models of infection. In the present study, we investigated the effects of maresin 1 (MaR1) on mitochondrial function in cecal ligation and puncture (CLP)-induced sepsis and sepsis patients to identify mechanisms underlying maresin 1-mediated stimulation of ROS in mitochondria. We found that treatment with MaR1 significantly inhibited production of cytokines, decreased bacterial load in the peritoneal lavage fluid, reduced the number of neutrophils, decreased lactic acid level and upregulated cyclic AMP (cAMP) concentration, with the outcome of decreased lung injury in CLP-induced sepsis in mice. The effects of MaR1 on downregulation nitric oxide (NOX) activity, improvement CAT and SOD activity to inhibit ROS production in mitochondria was dependent on lipoxin receptor (ALX) and cAMP. Survival rates were significantly increased after the treatment of mice with MaR1. In BMDM stimulated with LPS, MaR1 inhibited the ROS production, downregulated enzyme activity, reduced mtO2 production, increased mitochondrial membrane potential, improved adenosine triphosphate (ATP) content and mitochondrial DNA (mtDNA) copy number. Finally, the effects of MaR1 on ROS production in the blood of healthy volunteers stimulated with LPS or sepsis patients were associated with ALX and cAMP. Taken together, these data suggest that treatment with MaR1 could attenuate mitochondrial dysfunction during sepsis through regulating ROS production.

Maresin 1 improves the Treg/Th17 imbalance in rheumatoid arthritis through miR-21.

OBJECTIVE: Treg/Th17 imbalance plays an important role in rheumatoid arthritis (RA). Maresin 1 (MaR1) prompts inflammation resolution and regulates immune responses. We explored the effect of MaR1 on RA progression and investigated the correlation between MaR1 and Treg/Th17 balance. METHODS: Both patients with RA and healthy controls were recruited into the study. Collagen-induced arthritis (CIA) model was constructed to detect the clinical score, histopathological changes and Treg/Th17 ratio. Purified naive CD4+ T-cells were used to study the effect of MaR1 on its differentiation process and microRNA microarray studies were performed to investigate MaR1 downstream microRNAs in this process. MicroRNA transfection experiments were conducted by lentivirus to verify the mechanism of MaR1 on Treg/Th17 balance. RESULTS: Compared with controls, the MaR1 concentration was higher in the patients with inactive RA and lower in the patients with active RA. Expression of the Treg transcription factor FoxP3 was the highest in inactive RA and the lowest in active RA, while the Th17 transcription factor RORc showed a reverse trend. An inverse correlation was observed between the FoxP3/RORc ratio and Disease Activity Score 28. Intervention of MaR1 in the CIA model reduced joint inflammation and damage, and improved the imbalanced Treg/Th17 ratio. MaR1 increased Treg cells proportion while reduced Th17 cells proportion under specific differentiation conditions. Furthermore, miR-21 was verified as MaR1 downstream microRNA, which was upregulated by MaR1, modulating the Treg/Th17 balance and thus ameliorating the RA progression. CONCLUSIONS: MaR1 is a therapeutic target for RA, likely operating through effects on the imbalanced Treg/Th17 ratio found in the disease.

Specialized Pro-resolving Mediators Regulate Alveolar Fluid Clearance during Acute Respiratory Distress Syndrome.

OBJECTIVE: Acute respiratory distress syndrome (ARDS) is an acute and lethal clinical syndrome that is characterized by the injury of alveolar epithelium, which impairs active fluid transport in the lung, and impedes the reabsorption of edema fluid from the alveolar space. This review aimed to discuss the role of pro-resolving mediators on the regulation of alveolar fluid clearance (AFC) in ARDS. DATA SOURCES: Articles published up to September 2017 were selected from the PubMed, with the keywords of "alveolar fluid clearance" or "lung edema" or "acute lung injury" or "acute respiratory distress syndrome", and "specialized pro-resolving mediators" or "lipoxin" or "resolvin" or "protectin" or "maresin" or "alveolar epithelial cells" or "aspirin-triggered lipid mediators" or "carbon monoxide and heme oxygenase" or "annexin A1". STUDY SELECTION: We included all relevant articles published up to September 2017, with no limitation of study design. RESULTS: Specialized pro-resolving mediators (SPMs), as the proinflammatory mediators, not only upregulated epithelial sodium channel, Na,K-ATPase, cystic fibrosis transmembrane conductance regulator (CFTR), and aquaporins levels, but also improved Na,K-ATPase activity to promote AFC in ARDS. In addition to the direct effects on ion channels and pumps of the alveolar epithelium, the SPMs also inhibited the inflammatory cytokine expression and improved the alveolar epithelial cell repair to enhance the AFC in ARDS. CONCLUSIONS: The present review discusses a novel mechanism for pulmonary edema fluid reabsorption. SPMs might provide new opportunities to design "reabsorption-targeted" therapies with high degrees of precision in controlling ALI/ARDS.

Protectin DX increases alveolar fluid clearance in rats with lipopolysaccharide-induced acute lung injury.

Acute respiratory distress syndrome is a life-threatening critical syndrome resulting largely from the accumulation of and the inability to clear pulmonary edema. Protectin DX, an endogenously produced lipid mediator, is believed to exert anti-inflammatory and pro-resolution effects. Protectin DX (5 µg/kg) was injected i.v. 8 h after LPS (14 mg/kg) administration, and alveolar fluid clearance was measured in live rats (n = 8). In primary rat ATII epithelial cells, protectin DX (3.605 × 10-3 mg/l) was added to the culture medium with LPS for 6 h. Protectin DX improved alveolar fluid clearance (9.65 ± 1.60 vs. 15.85 ± 1.49, p < 0.0001) and decreased pulmonary edema and lung injury in LPS-induced lung injury in rats. Protectin DX markedly regulated alveolar fluid clearance by upregulating sodium channel and Na, K-ATPase protein expression levels in vivo and in vitro. Protectin DX also increased the activity of Na, K-ATPase and upregulated P-Akt via inhibiting Nedd4-2 in vivo. In addition, protectin DX enhanced the subcellular distribution of sodium channels and Na, K-ATPase, which were specifically localized to the apical and basal membranes of primary rat ATII cells. Furthermore, BOC-2, Rp-cAMP, and LY294002 blocked the increased alveolar fluid clearance in response to protectin DX. Protectin DX stimulates alveolar fluid clearance through a mechanism partly dependent on alveolar epithelial sodium channel and Na, K-ATPase activation via the ALX/PI3K/Nedd4-2 signaling pathway.