PTPRO inhibits LPS-induced apoptosis in alveolar epithelial cells.

Acute lung injury (ALI) and its severe manifestation, acute respiratory distress syndrome (ARDS), represent critical clinical syndromes with multifactorial origins, notably stemming from sepsis within intensive care units (ICUs). Despite their high mortality rates, no selective cure is available beside ventilation support. Apoptosis plays a complex and pivotal role in the pathophysiology of acute lung injury. Excessive apoptosis of alveolar epithelial and microvascular endothelial cells can lead to disruption of lung epithelial barrier integrity, impairing the body's ability to exchange blood and gas. At the same time, apoptosis of damaged or dysfunctional cells, including endothelial and epithelial cells, can help maintain tissue integrity and accelerate recovery from organ pro-inflammatory stress. The balance between pro-survival and pro-apoptotic signals in lung injury determines patient outcomes, making the modulation of apoptosis an area of intense research in the quest for more effective therapies. Here we found that protein tyrosine phosphatase receptor type O (PTPRO), a poorly understood receptor-like protein tyrosine phosphatase, is consistently upregulated in multiple tissue types of mice under septic conditions and in the lung alveolar epithelial cells. PTPRO reduction by its selective short-interfering RNA (siRNA) leads to excessive apoptosis in lung alveolar epithelial cells without affecting cell proliferation. Consistently PTPRO overexpression by a DNA construct attenuates apoptotic signaling induced by LPS. These effects of PTPTO on cellular apoptosis are dependent on an ErbB2/PI3K/Akt/NFκB signaling pathway. Here we revealed a novel regulatory pathway of cellular apoptosis by PTPRO in lung alveolar epithelial cells during sepsis.

[CXCL1 induces the contraction of endothelial cytoskeleton and increases permeability in mouse cerebral endothelium bEND.3 cells by promoting protein kinase B phosphorylation].

Objective To investigate the effects of C-X-C motif chemokine ligand 1 (CXCL1) and its receptor CXCR2 on the cerebral endothelial cytoskeleton rearrangement and permeability in the inflammation of septic encephalopathy. Methods The murine model of septic encephalopathy was established by intraperitoneal injection of LPS (10 mg/kg). The levels of TNF-α and CXCL1 in the whole brain tissue were detected by ELISA. The expression of CXCR2 was detected by Western blot analysis after bEND.3 cells were stimulated with 500 ng/mL LPS and 200 ng/mL TNF-α. After treated with CXCL1(150 ng/mL), the changes of endothelial filamentous actin (F-actin) rearrangement in bEND.3 cells were observed by immuno-fluorescence staining. In the cerebral endothelial permeability test, bEND.3 cells were randomly divided into PBS control group, CXCL1 group, and CXCL1 combined with CXCR2 antagonist SB225002 group. Then endothelial transwell permeability assay kit was used to detect the endothelial permeability changes. After stimulated with CXCL1 in bEND.3 cells, Western blot analysis was used to detect the expression of protein kinase B (AKT) and phosphorylated-AKT (p-AKT). Results Intraperitoneal injection of LPS significantly increased the levels of TNF-α and CXCL1 in the whole brain. LPS and TNF-α both upregulated the expression of CXCR2 protein in bEND.3 cells. CXCL1 stimulation induced the endothelial cytoskeleton contraction, increased paracellular gap formation and elevated endothelial permeability in bEND.3 cells, which was inhibited by the pretreatment with SB225002(CXCR2 antagonist). Furthermore, CXCL1 stimulation also enhanced the phosphorylation of AKT in bEND.3 cells. Conclusion CXCL1 induces the cytoskeleton contraction and increased permeability through AKT phosphorylation in bEND.3 cells, which can be effectively inhibited by CXCR2 antagonist SB225002.

[Protein tyrosine phosphatase receptor type O (PTPRO) promotes phagocytic activity of alveolar epithelial cells via activating AKT signal pathway in LPS induced acute lung injury].

Objective To investigate the effect of protein tyrosine phosphatase receptor type O (PTPRO) on the phagocytic activity of alveolar epithelial cells in LPS-induced acute lung injury. Methods Mice were randomly divided into the normal control group and LPS stimulation group. The infiltration of inflammatory cells was detected by HE staining. The cytokine TNF-α level in lung was analyzed by ELISA. Western blotting was performed to detect the effect of LPS on PTPRO protein expression in lung. After the expression of PTPRO in MLE-12 cells was silenced by siRNA in vitro, flow cytometry was used to detect the effects of LPS and PTPRO siRNA on the phagocytic activity of MLE-12 cells, and the effects of LPS and PTPRO siRNA on the expression of PTPRO, AKT and phosphorylated AKT protein were measured by Western blotting. Results After the establishment of murine acute lung injury model by LPS injection(1 mg/kg), the infiltrated polymorphonuclear leukocytes were markedly increased. The level of TNF-α in lung tissue and the expression of PTPRO in MLE-12 cells were both significantly increased after LPS stimulation. However, the activity of MLE-12 cells to phagocytose fluorescent microbeads was evidently decreased after silencing PTPRO. Furthermore, silencing PTPRO induced a remarkable decrease in the phosphorylation of AKT in MLE-12 cells. Conclusion PTPRO can promote phagocytic activity of MLE-12 cells via activating AKT signaling pathway.