Sleep disorders are great problems in modern society. Even minimal changes of sleep can affect health. Especially, patients with pulmonary diseases complain of sleep problems such as sleep disturbance and insomnia. Recent studies have shown an association between sleep deprivation (SD) and inflammation, however, the underlying mechanisms remain unclear. In the present study, we investigated whether melatonin protects against acute lung inflammation in SD. Male ICR mice were deprived sleep using modified multiplatform water bath for 3 days. Acute lung inflammation was induced by lipopolysaccharide (LPS; 5 mg/kg). Melatonin (5 mg/kg) and LPS was administered in SD mice at day 2. Mice were divided into five groups as control, SD, LPS, LPS + SD, and LPS + SD + melatonin (each group, n = 11). Mice were killed on day 3 after treatment of melatonin and LPS for 24 hr. Lung tissues were collected for histological examination and protein analysis. The malondialdehyde (MDA) level was determined for the effect of oxidative stress. Melatonin restored weight loss in LPS + SD. Histological findings revealed alveolar damages with inflammatory cell infiltration in LPS + SD. Melatonin remarkably attenuated the alveolar damages. In western blot analysis, LPS reduced the levels of Bcl-XL and procaspase-3 in SD mice. After treatment with melatonin, the levels of Bcl-XL and procaspase-3 increased when compared with LPS + SD. LPS treatment showed an increase of TUNEL-positive cells, whereas melatonin prevented the increase of cell death in LPS + SD animals. In lipid peroxidation assay, melatonin significantly reduced the elevated MDA level in LPS + SD. Our results suggest that melatonin attenuates acute lung inflammation during SD via anti-apoptotic and anti-oxidative actions.

Abstract. Sleep disturbance has become an endemic behavior in modern countries, and its prevalence has also increased. Even a subtle sleep deficiency is related to health problems. Particularly, patients with pulmonary disease often complain of insomnia. We recently showed that sleep deprivation (SD) exacerbates existing acute lung inflammation, and that melatonin treatment attenuates it via anti-apoptotic and anti-oxidant action. In order to reinforce our previous report, the present study was designed to evaluate pro-inflammatory mediators in acute lung inflammation in SD mice. In addition, we investigated the infiltration of inflammatory cells into the lungs. Twenty-five ICR mice were divided into 5 groups (n=5/ group): control, SD, lipopolysaccharide (LPS), LPS + SD and LPS + SD + melatonin. The SD mice were deprived of sleep for 96 h in a multiplatform water bath. LPS (5 mg/kg) and melatonin (5 mg/kg) were administered on day 2. The mice were sacrificed on day 3, and serum and bronchoalveolar lavage (BAL) fluid were collected. The serum levels of inflammatory cytokines were increased in the LPS + SD group. Interleukin-6, tumor necrosis factor-α and interferon-γ levels were also increased in BAL fluid in the LPS + SD group. Melatonin reduced inflammatory mediators in the serum and BAL fluid. The accumulation of leukocytes in the LPS and LPS + SD mice was elevated, however, melatonin inhibited the recruitment of inflammatory cells (p<0.05). Lymphocytes in the BAL fluid of the LPS + SD group were increased, and macrophage levels were decreased; however, the increment was attenuated by melatonin administration (p<0.05). In conclusion, this study indicates that melatonin has a protective effect against lung inflammation associated with SD.