Regulatory mechanism of NOV/CCN3 in the inflammation and apoptosis of lung epithelial alveolar cells upon lipopolysaccharide stimulation

by Selleckchem | Dec 12 2023

Lipopolysaccharide (LPS) induces stress inflammation and apoptosis. Pulmonary epithelial cell apoptosis, which accelerates the progression of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), is the leading cause of mortality in patients with ALI/ARDS. The nephroblastoma overexpressed protein (CCN3), an inflammatory modulator, is reported to be a biomarker in ALI. Using the LPS-induced ALI model, this study investigated the expression of CCN3 and its possible molecular mechanism in lung alveolar epithelial cell inflammation and apoptosis. Our data revealed that LPS treatment greatly increased the level of CCN3 in A549 cells. The A549 cells were transfected with specific CCN3 small interfering RNA (siRNA) using transfection reagent. CCN3 siRNA not only largely attenuated the expressions of the inflammatory cytokines interleukin (IL)-1β and transforming growth factor (TGF)-β1, but also reduced the apoptotic rate of the AEC II cells and affected the expressions of the apoptosis-associated proteins (Bcl-2 and caspase-3). Furthermore, CCN3 knockdown greatly inhibited the activation of nuclear factor-κB p65 in A549 cells. In addition, TGF-β/p-Smad inhibitor (TP0427736) and NF-κB inhibitor (PDTC) significantly attenuated the expression level of CCN3 in A549 cells. In conclusion, our data indicated that CCN3 siRNA affected downstream signal through TGF-β/ p-Smad or NF-κB pathway, leading to the inhibition of cell inflammation and apoptosis in human alveolar epithelial cells.

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The provided text describes a study conducted to investigate the role of nephroblastoma overexpressed protein (CCN3) in the context of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Here's a breakdown of the key findings and the study's conclusions:

### Background Information:
- **LPS-induced Stress:** Lipopolysaccharide (LPS) triggers stress inflammation and apoptosis.
- **ALI/ARDS:** ALI and its severe form, ARDS, are characterized by pulmonary epithelial cell apoptosis, a major contributor to patient mortality.
- **CCN3:** CCN3, an inflammatory modulator, is considered a biomarker in ALI.

### Study Objective:
The study aimed to understand how CCN3 influences inflammation and apoptosis in lung alveolar epithelial cells under LPS-induced ALI conditions.

### Methodology and Findings:
- **LPS Effect on CCN3:** LPS treatment significantly increased CCN3 levels in A549 cells (a type of human alveolar epithelial cell line).
- **CCN3 Knockdown:** Using specific CCN3 small interfering RNA (siRNA), the researchers reduced CCN3 expression in A549 cells.
- **Inflammatory Response:** CCN3 siRNA reduced the expressions of inflammatory cytokines IL-1β and TGF-β1.
- **Apoptosis Regulation:** CCN3 siRNA decreased the apoptotic rate of alveolar epithelial cells (AEC II cells) and influenced apoptosis-associated proteins (Bcl-2 and caspase-3).
- **Pathway Analysis:** CCN3 knockdown inhibited the activation of nuclear factor-κB p65 in A549 cells.
- **Inhibitor Effects:** Inhibitors targeting TGF-β/p-Smad and NF-κB pathways reduced CCN3 expression in A549 cells.

### Conclusion:
The study's data suggested that CCN3 siRNA influenced downstream signals via the TGF-β/p-Smad or NF-κB pathway. This influence led to the inhibition of inflammation and apoptosis in human alveolar epithelial cells under LPS-induced ALI conditions. In summary, CCN3 appears to play a crucial role in the progression of ALI/ARDS by modulating inflammatory responses and apoptosis, possibly through the TGF-β/p-Smad and NF-κB pathways.