# p16INK4a promotes myocardial ischemia-reperfusion injury by regulating bile acid transport via Slco1a4

## TL;DR

The protein p16INK4a worsens heart damage after blood flow is restored by affecting bile acid transport in heart cells.

## Contribution

This study reveals a new regulatory pathway involving p16INK4a, CUGBP1, Npas2, and Slco1a4 in cardiac ischemia-reperfusion injury.

## Key findings

- p16INK4a is upregulated in I/R injury and promotes cardiomyocyte apoptosis.
- p16INK4a inhibition reduces cell death in I/R models.
- p16INK4a regulates Npas2 via CUGBP1, leading to increased Slco1a4 and bile acid transport.

## Abstract

Myocardial ischemia-reperfusion (I/R) injury remains a significant challenge in cardiovascular medicine, with its molecular mechanisms still not fully understood. Screening the GEO and Comparative Toxicogenomics Database as well as spatial multi-omics data, we identify Cdkn2a, encoding p16INK4a, as a determinant in I/R injury. Cdkn2a expression is elevated in the myocardium of ischemic cardiomyopathy patients and p16INK4a protein is enriched in cardiomyocytes within ischemic zones of myocardial infarction tissues. We find that p16INK4a is consistently upregulated in both in vivo and in vitro I/R models, promoting apoptosis in neonatal rat cardiomyocytes (NRCMs) and human embryonic stem cell-derived cardiomyocytes (hESC-CMs) exposed to oxygen-glucose deprivation/reperfusion (OGD/R). p16INK4a inhibition confers cellular protection, an effect also observed in in vivo I/R injury models. Mechanistically, p16INK4a promotes binding of the RNA-binding protein CUGBP1 to the GRE sequence of Npas2 mRNA reducing its stability and translation, likely by inhibiting CDK4. This regulation impairs transcription of the Nasp2 target Slco1a4 and consequently bile acid transport, resulting in accumulation of intracellular bile acids and apoptosis. These findings identify p16INK4a-regulated bile acid transport as a driver of cardiac I/R injury.

In myocardial I/R injury, p16INK4a facilitates CUGBP1 binding to the GRE sequence within the 3′UTR of Npas2, thereby reducing Npas2 mRNA stability, translational efficiency, and protein expression, which in turn enhances Slco1a4 transcription and bile acid transport.

p16INK4a is upregulated in myocardial ischemia-reperfusion (I/R) injury, and its inhibition attenuates cardiomyocyte apoptosis in both in vitro and in vivo models.p16INK4a, in conjunction with CDK4, regulates CUGBP1, which binds to the GRE sequence within the 3′UTR of Npas2, thereby reducing its mRNA stability, translational efficiency, and protein expression.Downregulation of Npas2 subsequently induces transcriptional upregulation of Slco1a4 and enhances bile acid transport, establishing a novel p16INK4a-Npas2-Slco1a4 regulatory axis in cardiac I/R injury.

p16INK4a is upregulated in myocardial ischemia-reperfusion (I/R) injury, and its inhibition attenuates cardiomyocyte apoptosis in both in vitro and in vivo models.

p16INK4a, in conjunction with CDK4, regulates CUGBP1, which binds to the GRE sequence within the 3′UTR of Npas2, thereby reducing its mRNA stability, translational efficiency, and protein expression.

Downregulation of Npas2 subsequently induces transcriptional upregulation of Slco1a4 and enhances bile acid transport, establishing a novel p16INK4a-Npas2-Slco1a4 regulatory axis in cardiac I/R injury.

In myocardial I/R injury, p16INK4a facilitates CUGBP1 binding to the GRE sequence within the 3′UTR of Npas2, thereby reducing Npas2 mRNA stability, translational efficiency, and protein expression, which in turn enhances Slco1a4 transcription and bile acid transport.