Red blood cell Rpl13a small noncoding nucleolar RNAs guides 2'-O-methylation on peroxidasin messenger RNA promoting venous thrombosis in aging.

Background: Oxidative stress is one of the aging hallmarks. Small noncoding nucleolar RNAs (snoRNAs) of the ribosomal protein L13a (Rpl13a) locus are master regulators of reactive oxygen species (ROS) and oxidative stress, and their loss protects mice from diabetes. Yet, whether excess ROS in red blood cells (RBCs) is regulated by Rpl13a snoRNAs in aging and mediate venous thrombosis (VT)/thromboembolism (VT/E) is unknown.

Objectives: We investigated if RBCs retain Rpl13a snoRNAs and contribute to RBC ROS-mediated VT in a mid-life stage population.

Methods: Blood samples were collected from healthy mid-life stage (55-68 years old) and young (21-30 years old) adults, VT/E patients, and young wild-type mice at 12 to 24 weeks of age, and aged wild-type and aged Rpl3a snoRNA knockout mice at 72 to 96 weeks of age (equivalent to humans 21-30 and 55-68 years old, respectively).

Results: RBCs from mid-life stage adults and VT/E patients showed higher ROS production and prothrombotic potential than that in those from the younger cohort. RBC ROS levels and prothrombotic potential were associated with abnormal Rpl13a snoRNAs levels. In aging, Rpl13a snoRNAs regulated human and murine RBC ROS levels and prothrombotic activation by modulating peroxidase activity. This was due largely to Rpl13a snoRNAs-guided 2'-O-methylation on RBC peroxidasin (Pxdn) messenger RNA, a modification that inhibited the messenger RNA translation and Pxdn activity. In vivo Rpl13a snoRNA knockout in aged mice blunted RBC ROS generation and decreased thrombi size, thrombi RBC content, and RBCs-triggering prothrombin activation.

Conclusion: These findings point out to a novel role of RBC Rpl13a snoRNAs in VT by dysregulating Pxdn expression in aging.