Objective To detect the expression of single immunoglobin IL-1 receptor related protein ( SIGIRR) in normal human lung tissues, and study its changes in alveolar epithelial cell acutely injured by lipopolysaccharide ( LPS) . Methods Twenty samples of human normal lung tissue were collected during the lobectomies. The expression of SIGIRR was detected by immunohistochemistry, western blot and RT-PCR. The human type II alveolar epithelial cell acute injury model was established by stimulating A549 cells with LPS of a final concentration of 10 μg/mL. The cells were collected at 0, 3, 6, 12, and 24 hours after the stimulation. The changes of SIGIRR expression at the same time points were observed by western blot. The expression vector containing full-length SIGIRR cDNA was transfected transiently into A549 cells to induce SIGIRR overexpression. MTT assay was performed to measure the injury of A549 cells caused by LPS. Results The immunohistochemistry, western blot and RT-PCR showed that there was a high expression of SIGIRR in normal human lung tissues. The expression of SIGIRR was located in alveolar epithelial cells by immunohistochemistry. The expression of SIGIRR at 3, 6, and 12 hours was down-regulated after LPSstimulation and raised again at 24 hours to the baseline. MTT assay showed that SIGIRR overexpression substantially reduced the growth inhibition ratio of A549 cells after LPS stimulation. Conclusions Expression of SIGIRR in normal human lung tissues was confirmed by different detection methods. SIGIRR alleviates the injury of alveolar epithelial cells caused by LPS, implying SIGIRR might be involved in the regulationof acute lung injury mediated by LPS.
Objective To identify the effects of single immunoglobin IL-1 receptor related protein （SIGIRR） on inflammation induced by high mobility group box 1 （HMGB1） in A549 derived from human alveolar epithelial cells. Methods Eukaryotic expression vectors pCDNA3.1（+） constructed with SIGIRR cDNA were transiently transfected into A549 cells，in which SIGIRR was forced to be over-expressed. Western blot and RT-PCR were applied to detect the expression level of SIGIRR after transfection. After the stimulation by HMGB1，the transcriptional activity of NF-κB in A549 cells was detected by dual-luciferase reporter assay system，and the protein levels of inflammatory cytokine TNF-α and IL-1β were measured by ELISA. Results The expression level of SIGIRR increased significantly in A549 cells transfected with SIGIRR vectors. The transcriptional activity of NF-κB was enhanced obviously after HMGB1 treatment in A549 cells by dual-luciferase reporter assay system，while the transfection of SIGIRR vectors decreased the activity. The protein levels of TNF-α and IL-1β were down-regulated in A549 cells over-expressing SIGIRR after HMGB1 stimulation compared with the non-transfected cells. Conclusions Up-regulated SIGIRR expression can inhibit HMGB1-induced proinlammatory cytokine release in A549 cells such as TNF-α and IL-1β. The transcriptional activity of NF-κB is dampened by SIGIRR transfection，implying that the anti-inflammatory effects of SIGIRR may be involved in the regulation of NF-κB.
ObjectiveTo investagte the effects of single immunoglobin IL-1 receptor related protein (SIGIRR) on inflammation induced by cigarette smoke extract (CSE) in A549 cells derived from mouse alveolar epithelial cells. MethodsA549 cells were divided into a control group and an over-expressed SIGIRR group. Eukaryotic expression vectors pcDNA3.1(+) constructed with SIGIRR cDNA were transiently transfected into A549 cells, in which SIGIRR was forced to be over-expressed. The expression level of SIGIRR after transfection was detected with Western blot and RT-PCR method. After stimulated by CSE in both groups, the protein level of IL-6 was detected by ELISA, the transcriptional activity of cyclooxygenase-2(COX-2) was detected by dual-luciferase reporter assay system, and the release of reactive oxygen species (ROS) was measured by chemiluminescence method. ResultsThe expression level of SIGIRR increased significantly in A549 cells transfected with SIGIRR vectors. The COX-2 expression and the levels of ROS and IL-6 were significantly increased in the control group after CSE stimulation. Nevertheless, in the over-expressed SIGIRR group, the COX-2 expression and the release of ROS was reduced while the protein level of IL-6 was down-regulated compared with the control group(P < 0.05). ConclusionsUp-regulated SIGIRR expression can suppress the levels of ROS, COX-2 and IL-6 in A549 cells stimulated by CSE. It suggests that SIGIRR can inhibit airway inflammation caused by smoking.