N-acetylcysteine Alleviates the Meconium-Induced Acute Lung Injury

GPR84 regulates pulmonary inflammation by modulating neutrophil functions

Acute lung injury (ALI) is an acute, progressive hypoxic respiratory failure that could develop into acute respiratory distress syndrome (ARDS) with very high mortality rate. ALI is believed to be caused by uncontrolled inflammation, and multiple types of immune cells, especially neutrophils, are critically involved in the development of ALI. The treatment for ALI/ARDS is very limited, a better understanding of the pathogenesis and new therapies are urgently needed. Here we discover that GPR84, a medium chain fatty acid receptor, plays critical roles in ALI development by regulating neutrophil functions. GPR84 is highly upregulated in the cells isolated from the bronchoalveolar lavage fluid of LPS-induced ALI mice. GPR84 deficiency or blockage significantly ameliorated ALI mice lung inflammation by reducing neutrophils infiltration and oxidative stress. Further studies reveal that activation of GPR84 strongly induced reactive oxygen species production from neutrophils by stimulating Lyn, AKT and ERK1/2 activation and the assembly of the NADPH oxidase. These results reveal an important role of GPR84 in neutrophil functions and lung inflammation and strongly suggest that GPR84 is a potential drug target for ALI.

What is a Therapeutic Potential of N-Acetylcysteine in Lung Silicosis?

Lung silicosis is a serious pulmonary disease caused by an exposure of lung to inhaled silicon dioxide (SiO2) or silica. Although pathomechanisms of the disease have not been fully elucidated, oxidative stress has been recognized as a fundamental factor triggering a fibrotizing inflammation leading to irreversible changes in lung tissue. Based on this knowledge, therapeutic potential of various antioxidants has been intensively discussed. Among them, N-acetylcysteine with its multiple anti-inflammatory and antioxidant actions and a long-term experience with its clinical use in various diseases appears as a very promising choice. The purpose of this article is to review the therapeutic effects of N-acetylcysteine particularly in relation to a lung injury and to point out a potential of N-acetylcysteine in the treatment of lung silicosis.

Friend or Foe? The Roles of Antioxidants in Acute Lung Injury

Acute lung injury (ALI) is an acute hypoxic respiratory insufficiency caused by various intra- and extra-pulmonary injury factors. The oxidative stress caused by excessive reactive oxygen species (ROS) produced in the lungs plays an important role in the pathogenesis of ALI. ROS is a "double-edged sword", which is widely involved in signal transduction and the life process of cells at a physiological concentration. However, excessive ROS can cause mitochondrial oxidative stress, leading to the occurrence of various diseases. It is well-known that antioxidants can alleviate ALI by scavenging ROS. Nevertheless, more and more studies found that antioxidants have no significant effect on severe organ injury, and may even aggravate organ injury and reduce the survival rate of patients. Our study introduces the application of antioxidants in ALI, and explore the mechanisms of antioxidants failure in various diseases including it.

Co-administration of N-acetylcysteine and dexmedetomidine plays a synergistic effect on protection of LPS-induced acute lung injury via correcting Th1/Th2/Th17 cytokines imbalance

Recently both N-acetylcysteine (NAC) and Dexmedetomidine (DEX) have shown emerging roles in protection of acute lung injury (ALI). However, how their protective roles work and whether they can provide synergistic effects in ALI remain unknown. Here we explored it from the hot research viewpoint of Th1/Th2/Th17 cytokines balance. Lipopolysaccharide (LPS)-induced ALI was established and treated with NAC and/or DEX. Mice were divided into Sham group, ALI group, NAC group, DEX group and NAC+DEX group. Mice were sampled at 6, 12 and 24 hours after the model construction. Histopathology, wet to dry ratio and myeloperoxidase (MPO) activity were assessed in lung tissues. Protein concentration and cell count were assessed in bronchoalveolar lavage fluid (BALF). Th1/Th2/Th17 cytokines were assessed in plasma, BALF and lung homogenate. ALI-induced lung morphological damage, edema and aberrant MPO activity can be attenuated by NAC or DEX and mostly by NAC+DEX. NAC with DEX significantly reduced ALI-induced protein leakage and cell infiltration in BALF. Th1/Th2/Th17 cytokines imbalance aggravated with ALI progression. NAC, DEX and especially NAC+DEX can effectively correct these unbalanced cytokines. Galectin-9 and Tim-3 were transcriptionally up-regulated in ALI. Combination of NAC with DEX obtained a maximum effect on decreasing Galectin-9/Tim-3 expression. In summary, Th1/Th2/Th17 cytokines imbalance is newly found to participate in LPS-induced ALI. NAC or DEX administration can attenuate ALI by rebalancing Th1/Th2/Th17 cytokines. Their protective roles can be enhanced when co-administration, because DEX may relieve the Galectin-9/Tim-3 axis-mediated immune suppression.

Natural Antioxidants as Potential Therapy, and a Promising Role for Melatonin Against Pulmonary Hypertension

Plasma and serum samples, and lung/heart tissue of pulmonary hypertension (PH) patients and animal models of PH display elevated oxidative stress. Moreover, the severity of PH and levels of oxidative stress increase concurrently, which suggests that oxidative stress could be utilized as a biomarker for PH progression. Accumulating evidence has well established that oxidative stress is also key role player in the development of PH. Preclinical studies have demonstrated that natural antioxidants improved PH condition, and, therefore, antioxidant therapy has been proposed as a potential therapeutic strategy against PH. These natural antioxidants include medicinal plant extracts and compounds such as resveratrol and melatonin. Recent studies suggest that melatonin provides health benefit against PH, by enhancing antioxidant capacity, increasing vasodilation, counteracting lung and cardiac fibrosis, and stunting right ventricular (RV) hypertrophy/failure. This chapter comprehensively reviews and discusses a variety of natural antioxidants and their efficacy in modulating experimental PH. This chapter also demonstrates that antioxidant therapy remains a therapeutic strategy for PH, and particularly identifies melatonin as a safe, cost-effective, and promising antioxidant therapy.