Effects of Simulated Microgravity on Ultrastructure and Apoptosis of Choroidal Vascular Endothelial Cells

Abstract

BackgroundIt was confirmed that simulated microgravity (SMG) led to ultrastructural alterations and apoptosis in many types of microvascular endothelial cells. However, whether SMG would also affect choroidal vascular endothelial cells (CVECs) remains unknown. This study was designed to investigate the effects of SMG on ultrastructure and apoptosis of CVECs.MethodsThe rotary cell culture system (RCCS) was utilized to simulate microgravity condition. Human CVECs were cultured under normal gravity (NG) or SMG condition for 3 days. The ultrastructure was viewed under transmission electron microscopy, and the organization of F-actin was observed by immunofluorescence staining. Additionally, the apoptosis percentage was calculated using flow cytometry. Moreover, the mRNA and protein expression of BAX, Bcl-2, Caspase3, Cytochrome C, p-AKT, and p-PI3K were detected with quantitative PCR and Western blot at different exposure time.ResultsIn the SMG group, CVECs presented with a shrunk cell body, chromatin condensation and margination, mitochondria vacuolization, and apoptotic bodies. The amount of F-actin decreased, and the filaments of F-actin were sparse or even partly discontinuous after cultivation under SMG for 72 h. The proportions of apoptotic CVECs in SMG groups at 24 and 72 h were significantly higher than those in the NG group (P < 0.001). The mRNA and protein expression of Bax, Caspase3, and Cytochrome C of CVECs in SMG groups at 24 and 72 h significantly increased than those of the NG group, respectively (P < 0.001). The alterations of p-AKT and p-PI3K protein expression possessed similar trends. On the contrary, the mRNA and protein expression of Bcl-2 in CVECs under SMG at 24 and 72 h were significantly less than that of the NG group, respectively (P < 0.001).ConclusionSimulated microgravity conditions can lead the alterations of the F-actin structure and apoptosis of CVECs. The Bcl-2 apoptosis pathway and PI3K/AKT pathway may participate in the damage of CVECs caused by SMG.

Role of Apoptosis in Wound Healing and Apoptosis Alterations in Microgravity

“…Another cell type of the dermis which is affected by microgravity are endothelial cells. There are several reports that endothelial cells exposed to simulated microgravity can become apoptotic and show upregulations of apoptosis signaling, downregulation of the PI3K/Akt pathway, increased expression of NF-κB, depolymerization of F-actin and that miR-503-5p can induce apoptosis of human pulmonary microvascular endothelial cells through, at least in part, inhibiting the expression of Bcl-2 (Morbidelli et al, 2005;Infanger et al, 2006;Kang et al, 2011;Maier et al, 2015;Xu et al, 2018;Tang et al, 2019;Zhao et al, 2021). In addition, clinorotation for 48 h activated autophagy in vascular endothelial cells (Wang et al, 2013).…”

Evaluation of the Effects of Microgravity on Activated Primary Human Hepatic Stellate Cells

“…The PI3K/Akt pathway regulates cell survival, proliferation, and motility and is known to be involved in endothelial NO synthase production and the inhibition of apoptosis in cells exposed to SMG [32]. It has also been shown that p-AKT and p-PI3K increase under SMG and are involved in survival [33]. A novel regulatory mechanism of glycolysis through cytoskeletal regulation by PI3K [34] may be involved in the alteration of glycolysis due to mitochondrial dysfunction under SMG.…”

Genomic Changes Driven by Radiation-Induced DNA Damage and Microgravity in Human Cells

“…Changes in chromatin accessibility for the different proteins involved in the DDR pathway can induce differential activity of the OsaD response. Chromatin condensation and margination associated with expression changes for genes in the Bcl2-apoptosis pathway and for proteins in the PI3K/Akt pathway have been observed in human endothelial cells incubated for 72 h in simulated microgravity [ 110 ]. Moreover, genes whose expression is dependent on the linker of the nucleoskeleton and cytoskeleton (LINC) complex, connecting chromatin with the nuclear surface, were altered in human breast epithelial cells cultured under simulated microgravity [ 111 ].…”