RAMP2

As the most common subtype of lung cancer, non-small cell lung cancer (NSCLC)is responsible for a large proportion of global cancer-caused deaths. The implication of long non-coding RNAs (lncRNAs) as tumor-suppressor or carcinogenic genes in NSCLC has been widely documented. Our study sought to investigate the performance of lncRNA RAMP2 antisense RNA1 (RAMP2-AS1) in NSCLC. GEPIA bioinformatics tool and RT-qPCR were applied for assessing the expression of RAMP2-AS1 and its neighboring gene receptor activity-modifying protein 2 (RAMP2) in NSCLC. Functional assays including CCK-8 assay, colony formation assay as well as caspase-3 activity analysis and Transwell invasion assays were applied for detecting the biological phenotypes of NSCLC cells. Interaction among RAMP2-AS1, RAMP2 and T-cell intracellular antigen 1cytotoxic granule associated RNA binding protein (TIA1) was evaluated by RNA immunoprecipitation and pulldown assays. We found that RAMP2-AS1 and RAMP2 were downregulated in NSCLC. Overexpression of RAMP2-AS1 hampered proliferation and invasion, whereas induced apoptosis of NSCLC cells. Mechanistically, RAMP2-AS1 interacted with TIA1 to stabilize the mRNA of RAMP2. In conclusion, we first uncovered that RAMP2-AS1 stabilized RAPM2 mRNA through TIA1 to inhibit the progression of NSCLC, providing new insight to improve the treatment efficacy of NSCLC.

Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition characterized by widespread inflammation and pulmonary edema. Adrenomedullin (AM), a bioactive peptide with various functions, is expected to be applied in treating ARDS. Its functions are regulated primarily by two receptor-activity-modifying proteins, RAMP2 and RAMP3, which bind to the AM receptor calcitonin-receptor-like receptor (CLR). However, the roles of RAMP2 and RAMP3 in ARDS remain unclear. We generated a mouse model of ARDS via intratracheal administration of lipopolysaccharide (LPS), and analyzed the pathophysiological significance of RAMP2 and RAMP3. RAMP2 expression declined with LPS administration, whereas RAMP3 expression increased at low doses and decreased at high doses of LPS. After LPS administration, drug-inducible vascular endothelial-cell-specific RAMP2 knockout mice (DI-E-RAMP2^-/-) showed reduced survival, increased lung weight, and had more apoptotic cells in the lungs. DI-E-RAMP2^-/- mice exhibited reduced expression of Epac1 (which regulates vascular endothelial cell barrier function), while RAMP3 was upregulated in compensation. In contrast, after LPS administration, RAMP3^-/- mice showed no significant changes in survival, lung weight, or lung pathology, although they exhibited significant downregulation of iNOS, TNF-α, and NLRP3 during the later stages of inflammation. Based on transcriptomic analysis, RAMP2 contributed more to the circulation-regulating effects of AM, whereas RAMP3 contributed more to its inflammation-regulating effects. These findings indicate that, while both RAMP2 and RAMP3 participate in ARDS pathogenesis, their functions differ distinctly. Further elucidation of the pathophysiological significance and functional differences between RAMP2 and RAMP3 is critical for the future therapeutic application of AM in ARDS.

Post-hepatectomy liver failure (PHLF) leads to poor prognosis in patients receiving hepatectomy, where hepatic-vascular reconstitution plays a critical role. However, the regulators of hepatic-vascular reconstitution remain unclear. This study aimed to investigate the regulatory mechanisms of hepatic-vascular reconstitution and identify biomarkers predicting PHLF in patients underwent hepatectomy.

Candidate genes that were associated with hepatic vascular reconstitution were screened in adeno-associated virus 8 (AAV8) combining Alb-Cre-CRISPR/Cas9 mice underwent partial hepatectomy. The biological activities of candidate genes were estimated using endothelial precursors transfusion and an associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) model. The level of candidates was detected in biopsies from ALPPS patients. Risk factors of PHLF were also screened using retrospective data.

The downregulation of Gata3 and upregulation of Ramp2 in hepatocytes promoted the proliferation of liver sinusoidal endothelial cells (LSECs) and hepatic revascularization. Pigment epithelium-derived factor (PEDF) and vascular endothelial growth factor A (VEGFA) played opposite roles in regulating the migration of endothelial precursors from bone marrow and the formation of new sinusoids after hepatectomy. Gata3 restricted endothelial cell function in patient-derived hepatic-organoids, which was abrogated by Gata3 inhibitor. Moreover, overexpression of Gata3 led to higher mortality in ALPPS mice, which was improved by PEDF-neutralizing antibody. The expression of Gata3/Ramp2 and PEDF/VEGFA tended to have negative correlation in ALPPS patients. A nomogram model incorporating multiple factors such as serum PEDF/VEGF index (SPVI) was constructed and could efficiently predict the risk of PHLF.

The balance of Gata3 and Ramp2 in hepatocytes regulated the proliferation of LSECs and hepatic revascularization via shifting PEDF to VEGFA, which provided potential targets for the prevention and treatment of PHLF.

In this study, we revealed a novel mechanism that the balance of Gata3 and Ramp2 in hepatocyte regulated hepatic vascular reconstitution via shifting PEDF to VEGFA during hepatectomy- or ALLPS-induced liver regeneration. We also identified serum PEDF/VEGFA index (SPVI) as a potential predictor for post-hepatectomy liver failure (PHLF) in patients who underwent hepatectomy. This study will provide a better understanding on how hepatocytes contribute to liver regeneration and new targets for the prevention and treatment of PHLF.