Cardiovascular

PTBP1 promotes coronary artery calcification by regulating CARD8 alternative splicing and NLRP3 inflammasome activation.

Hu H, Zhang F, Wu J, Ma L • Archives of biochemistry and biophysics • 2026

PubMed 42208669 DOI 10.1016/j.abb.2026.110884

TL;DR

PTBP1 promotes coronary artery calcification by directly binding to CARD8 pre-mRNA to regulate its alternative splicing, which activates the NLRP3 inflammasome and drives osteogenic-like transdifferentiation of human aortic smooth muscle cells.

Key Findings

Results

RNA sequencing analysis identified decreased skipping of exon 4 in CARD8 within a human aortic smooth muscle cell (HASMC) calcification model.

The finding was identified through RNA sequencing analysis of HASMCs under calcification conditions.
Decreased exon 4 skipping in CARD8 was a notable splicing change associated with the calcification phenotype.
This observation prompted investigation into the upstream regulator of CARD8 alternative splicing.

Results

PTBP1 directly bound to CARD8 pre-mRNA and regulated its alternative splicing process in vitro.

RNA immunoprecipitation assays were used to validate the direct binding of PTBP1 to CARD8 pre-mRNA.
Minigene reporter assays were employed to confirm the effect of PTBP1 on CARD8 splicing patterns.
PTBP1 is described as an RNA-binding protein with profound regulatory functions in post-transcriptional regulation.

Results

Knockdown of PTBP1 significantly inhibited the calcification of HASMCs in vitro.

RNA interference techniques were utilized to knock down PTBP1 expression in HASMCs.
The protective effect of PTBP1 knockdown on calcification was reversed by concurrent knockdown of CARD8.
These results indicate that PTBP1's pro-calcific function is dependent on CARD8 expression.

Results

CARD8 deficiency promoted NLRP3 inflammasome assembly, enhanced Caspase-1 activation, and increased IL-1β and IL-18 secretion in HASMCs.

Loss of CARD8 was mechanistically linked to enhanced NLRP3 inflammasome assembly.
Downstream effects included enhanced Caspase-1 activation and increased secretion of the pro-inflammatory cytokines IL-1β and IL-18.
These inflammasome-driven changes drove osteogenic-like transdifferentiation and the calcification process of HASMCs.
Functional studies were conducted to untangle the regulatory role of CARD8 in HASMCs calcification.

Results

PTBP1 knockdown significantly alleviated the degree of coronary artery calcification in a mouse model, in a manner dependent on CARD8 expression levels.

A CAC mouse model was established to verify the in vitro findings in vivo.
Both RNA interference and overexpression techniques were utilized in the animal experiments.
The alleviation of CAC by PTBP1 knockdown was confirmed to be dependent on the expression level of CARD8, consistent with in vitro findings.

Conclusions

The PTBP1/CARD8 axis represents a novel mechanism promoting coronary artery calcification through NLRP3 inflammasome activation.

The study describes 'a novel mechanism whereby PTBP1 promotes CAC by regulating CARD8 alternative splicing to activate the NLRP3 inflammasome.'
The pathway proceeds from PTBP1-mediated splicing of CARD8 pre-mRNA, to reduced CARD8 function, to NLRP3 inflammasome activation, to osteogenic transdifferentiation.
The authors suggest this axis provides 'potential targets for developing novel therapeutic strategies' for CAC.
Coronary artery calcification is described as 'a significant predictor of cardiovascular events.'

What This Means

This research suggests that a protein called PTBP1 plays a key role in driving coronary artery calcification — the buildup of calcium deposits in the arteries of the heart, which is a known risk factor for heart attacks and other cardiovascular events. The study found that PTBP1 acts by binding to the genetic blueprint (pre-mRNA) of another protein called CARD8 and altering how that blueprint is read, a process known as alternative splicing. This change in CARD8 reduces its normal function, which in turn activates an inflammatory alarm system in the cell called the NLRP3 inflammasome, releasing signals that cause smooth muscle cells in blood vessel walls to transform into bone-like cells and deposit calcium. The researchers demonstrated this mechanism using both laboratory cell models (human aortic smooth muscle cells) and a mouse model of coronary artery calcification. When PTBP1 was silenced, calcification was significantly reduced — but this protective effect disappeared when CARD8 was also silenced at the same time, confirming that CARD8 is a critical link in this pathway. The inflammasome activation triggered by loss of CARD8 led to increased levels of inflammatory molecules (IL-1β and IL-18) that promote the harmful transformation of vascular smooth muscle cells. This research suggests that the PTBP1-CARD8-NLRP3 inflammasome pathway is a previously unrecognized molecular chain of events that contributes to artery calcification. These findings could point toward new therapeutic targets — such as PTBP1 or components of this pathway — that might one day be used to slow or prevent coronary artery calcification and reduce associated cardiovascular risk.

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Citation

Hu H, Zhang F, Wu J, Ma L. (2026). PTBP1 promotes coronary artery calcification by regulating CARD8 alternative splicing and NLRP3 inflammasome activation.. Archives of biochemistry and biophysics. https://doi.org/10.1016/j.abb.2026.110884

Key Findings

What This Means

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