A dimeric thymosin beta 4 with novel bio-activity protects post-ischemic cardiac function by accelerating vascular endothelial cell proliferation.

ABSTRACT

BACKGROUND: Thymosin beta 4 (Tß4) is a 43-amino-acid peptide with protective properties in myocardium injury. Previously, we produced a recombinant human dimeric Tß4 (DTß4). Here, the cardioprotective effects of DTß4 and the molecular mechanisms underlying its enhanced activity were investigated. METHODS AND RESULTS: Echocardiography measurements showed that the cardioprotective effect of DTß4 in myocardial infarction mice was significantly higher than that of wild-type Tß4. Corresponding in vitro analyses demonstrated that the enhanced cardioprotection provided by DTß4 was largely due to increased stimulation of angiogenesis. HPLC analysis, western blotting and qRT-PCR indicated that the enhanced pro-angiogenesis activity of DTß4 was independent of the protein half-life and the known downstream pathways of wild-type Tß4. Transcriptome deep sequencing (RNA-seq), BrdU incorporation assays, flow cytometry analysis and RNA interference demonstrated that the enhanced angiogenic activity of DTß4 depended on MALAT1 (metastasis-associated lung adenocarcinoma transcript 1)-induced proliferation of vascular endothelial cells, which has not been reported for wild-type Tß4. Moreover, transcription factor activation screening, luciferase promoter reporter assay and immunoprecipitation assay demonstrated that DTß4 enhanced MALAT1 transcription by inhibiting the degradation of prospero-related homeobox 1 (PROX1). CONCLUSION: This study demonstrates the potential applications and the novel bioactivity of the Tß4 dimer. Moreover, to construct the dimer represents a new method for production of bioactive peptides that may have novel activities.