Skeletal muscle atrophy, which is induced by factors such as disuse, spaceflight, certain medications, neurological disorders, and malnutrition, is a global health issue that lacks effective treatment. Hindlimb unloading is a commonly used model of muscle atrophy. However, the underlying mechanism of muscle atrophy induced by hindlimb unloading remains unclear, particularly from the perspective of the myocyte proteome and metabolism. We first used mass spectrometry for proteomic sequencing and untargeted metabolomics to analyze soleus muscle changes in rats with hindlimb unloading. The study found 1052 proteins and 377 metabolites (with the MS2 name) that were differentially expressed between the hindlimb unloading group and the control group. Proteins like ACTN3, MYH4, MYBPC2, and MYOZ1, typically found in fast-twitch muscles, were upregulated, along with metabolism-related proteins GLUL, GSTM4, and NDUFS4. Metabolites arachidylcarnitine and 7,8-dihydrobiopterin, as well as pathways like histidine, taurine, and hypotaurine metabolism, were linked to muscle atrophy. Protein and metabolism joint analyses revealed that some pathways, such as glutathione metabolism, ferroptosis, and lysosome pathways, were likely to be involved in soleus atrophy. In this study, we have applied integrated deep proteomic and metabolomic analyses. The upregulation of proteins that are expressed in fast-twitch fibers indicates the conversion of slow-twitch fibers to fast-twitch fibers under hindlimb unloading. In addition, some differentially abundant metabolites and pathways revealed the important role of metabolism in muscle atrophy of the soleus. As shown in the graphical abstract, our study provides insights into the pathogenesis and treatment of muscle atrophy that results from unloading by integrating proteomics and metabolomics of the soleus muscles.

Exposure to microgravity during spaceflight induces the alterations in endothelial cell function associated with post-flight cardiovascular deconditioning. PIEZO1 is a major mechanosensitive ion channel that regulates endothelial cell function. In this study, we used a two-dimensional clinostat to investigate the expression of PIEZO1 and its regulatory mechanism on human umbilical vein endothelial cells (HUVECs) under simulated microgravity. Utilizing quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis, we observed that PIEZO1 expression was significantly increased in response to simulated microgravity. Moreover, we found microgravity promoted endothelial cells migration by increasing expression of PIEZO1. Proteomics analysis highlighted the importance of C-X-C chemokine receptor type 4(CXCR4) as a main target molecule of PIEZO1 in HUVECs. CXCR4 protein level was increased with simulated microgravity and decreased with PIEZO1 knock down. The mechanistic study showed that PIEZO1 enhances CXCR4 expression via Ca²⁺ influx. In addition, CXCR4 could promote endothelial cell migration under simulated microgravity. Taken together, these results suggest that the upregulation of PIEZO1 in response to simulated microgravity regulates endothelial cell migration due to enhancing CXCR4 expression via Ca²⁺ influx.

The adverse effects of weightlessness on the human cardiovascular system greatly hinder the process of long-term and long-distance space exploration. Succinylation is an important type of protein post-translational modification. However, whether succinylation modification is able to play a role in altered vascular endothelial cell function under microgravity or simulated microgravity has not been reported. This study aims to investigate the quantitative global proteome and the changes in lysine succinylation in related proteins, seeking to facilitate a better understanding of the protein post-translational modification in cardiovascular deconditioning under microgravity. LC-MS/MS combined with bioinformatics analysis were used to quantitatively detect the perspectives at the global protein level. Immunoprecipitation and Western blot analysis were conducted to further verify the alterations of related proteins and lysine succinylation. A total of 132 differentially expressed proteins and 164 differentially expressed lysine succinylation sites were identified in human umbilical vein endothelial cells (HUVECs). Bioinformatics analysis indicates that lysine succinylation may play a potential role in energy metabolism. In addition, desuccinylase SIRT5 was downregulated and regulated succinylation modification levels of HUVECs under simulated microgravity. Notably, the overexpression of SIRT5 effectively protected HUVECs from apoptosis induced by simulated microgravity. And the succinylation of Lys396 in ERO1A was significantly increased in HUVECs under simulated microgravity. Mechanistically, the knockdown of SIRT5 was found to induce the apoptosis of HUVECs through the succinylation of Lys396 in ERO1A. These results can provide new ideas for elucidating the molecular mechanism of cardiovascular dysfunction in microgravity environments, and provide key molecular targets for scientific protective measures against microgravity in space.

Simulated microgravity profoundly alters endothelial function, particularly cell migration. However, the mechanosensitive molecular pathways involved remain incompletely understood. In this study, we performed integrated transcriptomic and proteomic analyses of human umbilical vein endothelial cells exposed to simulated microgravity to identify key regulators of endothelial migration. RNA-seq and proteomic profiling identified 964 differentially expressed genes and 183 differentially expressed proteins, primarily enriched in stress response, signal transduction, and angiogenesis pathways. Combined analysis of both datasets revealed four key genes—TLR2, HSPB1, RBM3, and HSPA1B—with more than a twofold change. Protein–protein interaction analysis incorporating 48 endothelial migration—related genes further highlighted TLR2 as a central hub with strong interaction with CXCR4. Functional experiments demonstrated that simulated microgravity significantly enhanced endothelial migration through TLR2 upregulation, while TLR2 activation further promoted this response by increasing CXCR4 expression. These findings identify the TLR2–CXCR4 axis as a previously unrecognized mechanosensitive signaling pathway driving endothelial adaptation to simulated microgravity, offering potential molecular targets for therapeutic intervention against microgravity-induced vascular remodeling.

Exposure to microgravity results in cardiovascular deconditioning, with endothelial cell apoptosis recognized as a pivotal initiating event. However, the mechanosensitive mechanisms underlying this process remain poorly understood. Here, we demonstrate that the expression of mechanosensitive ion channel protein PIEZO1 is upregulated in human umbilical vein endothelial cells (HUVECs) under simulated microgravity. Functional studies revealed that PIEZO1 activation promotes endothelial apoptosis under simulated microgravity conditions. Proteomic analysis following PIEZO1 knockdown revealed extensive alterations in biological processes associated with apoptosis. Furthermore, we found that PIEZO1 activation triggers calcium influx, leading to elevated expression of the HMGA2. Moreover, we identify that PIEZO1 activation induces calcium influx, which subsequently elevates the expression of HMGA2. The knockdown of HMGA2 significantly mitigated microgravity-induced endothelial apoptosis, indicating its role in PIEZO1-mediated apoptosis. These findings reveal a novel PIEZO1–Ca²⁺–HMGA2 axis critical for microgravity-induced endothelial apoptosis, providing mechanistic insight into cardiovascular adaptation to spaceflight and potential therapeutic targets for countermeasure development.