Colquhounia Root Tablet Protects Rat Pulmonary Microvascular Endothelial Cells against TNF‐α‐Induced Injury by Upregulating the Expression of Tight Junction Proteins Claudin‐5 and ZO‐1

Abstract

Background There are currently limited effective pharmacotherapy agents for acute lung injury (ALI). Inflammatory response in the lungs is the main pathophysiological process of ALI. Our preliminary data have shown that colquhounia root tablet (CRT), a natural herbal medicine, alleviates the pulmonary inflammatory responses and edema in a rat model with oleic acid-induced ALI. However, the potential molecular action mechanisms underlining its protective effects against ALI are poorly understood. This study aimed to investigate the effects and mechanism of CRT in rat pulmonary microvascular endothelial cells (PMEC) with TNF-α-induced injury. Methods PMECs were divided into 6 groups: normal control, TNF-α (10 ng/mL TNF-α), Dex (1×10−6 M Dex + 10 ng/mL TNF-α), CRT high (1000 ng/mL CRT + 10 ng/mL TNF-α), CRT medium (500 ng/mL CRT + 10 ng/mL TNF-α), and CRT low group (250 ng/mL CRT + 10 ng/mL TNF-α). Cell proliferation and apoptosis were detected by MTT assay and flow cytometry. Cell micromorphology was observed under transmission electron microscope. The localization and expression of tight junction proteins Claudin-5 and ZO-1 were analyzed by immunofluorescence staining and Western blot, respectively. Results TNF-a had successfully induced an acute endothelial cell injury model. Dex and CRT treatments had significantly stimulated the growth and reduced the apoptosis of PMECs (all p < 0.05 or 0.01) and alleviated the TNF-α-induced cell injury. The expression of Claudin-5 and ZO-1 in Dex and all 3 CRT groups was markedly increased compared with TNF-a group (all p < 0.05 or 0.01). Conclusion CRT effectively protects PMECs from TNF-α-induced injury, which might be mediated via stabilizing the structure of tight junction. CRT might be a promising, effective, and safe therapeutic agent for the treatment of ALI.

Propofol attenuated TNF-α-modulated occludin expression by inhibiting Hif-1α/ VEGF/ VEGFR-2/ ERK signaling pathway in hCMEC/D3 cells

“…Consistently, we found that TNF-α significantly decreased the expression of occludin and ZO-1 in hCMEC/D3 cells. Interestingly, TNF-α was shown to reduce claudin-5 expression in pulmonary microvascular endothelial cells [26,27], while we found TNF-α had no effect on claudin-5 expression in hCEMC/D3 cells. We inferred that TNF-α may exert different effects on occludin expression in different organs.…”

“…For example, TNF-α was shown to decrease occludin expression in glomerular endothelial cells of mice [25]. It has also been revealed that TNF-α induced rat pulmonary microvascular endothelial cells injury via downregulating the expression of ZO-1 [26]. A study revealed that TNF-α reduced occludin and ZO-1 expression in pulmonary microvascular endothelial cells [27].…”

Propofol attenuated the effect of TNF-α on occludin expression by inhibiting HIF-1α/VEGF/VEGFR-2/ERK signaling pathway in hCMEC/D3 cells

“…Consistently, we found that TNF-α could significantly decrease the expression of occludin and ZO-1 in hCMEC/D3 cells. Interestingly, TNF-α was shown to reduce claudin-5 expression in pulmonary microvascular endothelial cells [ 26,27], while we found TNF-α had no effect on claudin-5 expression in hCEMC/D3 cells. We inferred that TNF-α may exert different effects on occludin expression in different organs.…”

“…For example, TNF-α was shown to decrease occludin expression in glomerular endothelial cells of mice [ 25]. It has also been revealed that TNF-α can induce rat pulmonary microvascular endothelial cells injury via downregulating the expression of ZO-1 [ 26]. A study revealed that TNF-α could reduce occludin and ZO-1 expression in pulmonary microvascular endothelial cells [ 27].…”

Propofol attenuated the effect of TNF-α on occludin expression by inhibiting HIF-1α/VEGF/VEGFR-2/ERK signaling pathway in hCMEC/D3 cells

“…As shown in Fig. 2A, we pretreated hCMEC/D3 cells with different concentrations of propofol (5,10,25, 50 μM) for 2 h and followed by TNF-α (10 ng/ml, 4 h) treatment and found 25 μM propofol pretreatment could significantly inhibit the TNF-α-modulated occludin expression in hCMEC/D3 cells.…”