Objective: To study the influence and mechanism of hypoxia on the expression of angiotensin-converting enzyme 2 (ACE2) in human umbilical vein endothelial cells (HUVECs).
Methods: HUVECs were cultured as adherent cells and identified by immunohistochemical study of Factor VIII. Then the cells were cultured in 37 degrees C incubators under hypoxia condition (1% O2 + 94% N2 + 5%C O2) or regular 5% CO2 condition for 3 h, 6 h, 12 h, 24 h, respectively, and the culture medium and cells were collected at each time point. ACE2 protein was measure by immunohistochemical assay, ACE2 mRNA was quantified by real-time RT-PCR.
Results: (1) ACE2 protein expression decreased after hypoxia treatment for 3 h, 6 h, 12 h, and 24 hour compared with regular oxygen condition (chi2 = 825.078, 768.141, 623.931, 350.260, P < 0.00625), the maximum reduction came at 3 h after hypoxia exposure, then raised gradually after 6 h, 12 h, and 24 h exposure; (2) ACE2 mRNA expression show a similar tendency to ACE2 protein. After hypoxia disposal, its relative expression rate reduced to 0.281 at 3 h (P = 0.031), then increased gradually at 6 h (0.445, P = 0.034), 12 h (0.794, P = 0.434), 24 h (0.891, P = 0.692).
Conclusion: Our study show hypoxia down-regulate the protein and gene expression of ACE2 in HUVECs in 24 hours. The down-regulation effect of hypoxia reached maximum level at 3 h, and then attenuated gradually at 6 h, 12 h and 24 h, which indicate that ACE2 might play an important role in the regulation of RAS in HUVECs after hypoxia injury.