Background/Purpose: Alternative pre-mRNA splicing of Vascular Endothelial Growth Factor-A (VEGF-A) produces pro-angiogenic (VEGF-Axxxa) or anti-angiogenic (VEGF-Axxxb) isoforms that contribute to angiogenesis in inflammatory arthritis. Isoform expression is regulated by post-translational modification of serine-arginine-rich splicing factor-1 (SRSF-1) by Serine Arginine Protein Kinase 1 (SRPK-1). Increased expression of the anti-angiogenic VEGF-A isoform (VEGF-Axxxb) could be a potential therapeutic target for inflammation and pain in inflammatory arthritis. We therefore tested the hypothesis that VEGF-A165b is expressed, and VEGF splicing is regulated in synovial fibroblasts in culture. 

Methods: Normal human fibroblast-like synoviocytes (HFLS) were stimulated with Tumour necrosis factor alpha(TNF-a) and interleukin-1 beta (IL-1b) and with an SRPK-1 inhibitor in-vitro. The effect of TNF-a and IL-1b on VEGF-A splice variant expression, with and without SRPK1 inhibition, was measured using RT-PCR and ELISA. Normal HFLS were fixed and immuno-stained for SRSF-1 and SRSF-2.  

Results: Treatment with TNF-a and IL-1b (20ng/ml) caused the early nuclear translocation of SRSF-1 after 2h. Treatment with IL-1b led to a switch in splicing to the pro-angiogenic VEGF-A165a isoform at mRNA level after 24h. Increased association of SRSF-1 and CLK-1 was observed within nuclear speckles, indicating that this splicing is regulated by an SRSF-1-CLK-1–SRSF-2 interaction. Co-incubation with the SRPK-1 Inhibitor decreased the association of SRSF-1 to nuclear speckles and reversed the early nuclear translocation of SRSF-1. 

Conclusion: Tumour necrosis factor- alpha and interleukin-1 beta regulate the alternative splicing pathway of VEGF-A in fibroblast-like synoviocytes via SRPK-1

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/investigating-the-srpk-1-vegf-a-alternative-splicing-pathway-asatherapeutic-target-in-arthritis/