Researchers made several new versions of a tiny three‑amino‑acid peptide that was previously shown to boost blood‑vessel growth. In lab tests, three of the new peptides (called 5‑7) helped human endothelial cells multiply, move, and invade more than the original peptide, and one of them even repaired damaged vessels in zebrafish at very low concentrations.

In our previous studies, tripeptide <b>1</b> was found to induce angiogenesis in zebrafish embryos and in HUVECs. Based on the lead compound <b>1</b>, seven new marine tripeptide analogues <b>2</b>&#x207b;<b>8</b> have been designed and synthesized in this paper to evaluate the effects on promoting cellular proliferation in human endothelial cells (HUVECs) and zebrafish. Among them, compounds <b>5</b>&#x207b;<b>7</b> possessed more remarkable increasing proliferation effects than other compounds, and the EC₅₀ values of these and the leading compound <b>1</b> were 1.0 &#xb1; 0.002 &#x3bc;M, 1.0 &#xb1; 0.0005 &#x3bc;M, 0.88 &#xb1; 0.0972 &#x3bc;M, and 1.31 &#xb1; 0.0926 &#x3bc;M, respectively. Furthermore, <b>5</b>&#x207b;<b>7</b> could enhance migrations (58.5%, 80.66% and 60.71% increment after culturing 48 h, respectively) and invasions (49.08%, 47.24% and 56.24% increase, respectively) in HUVECs compared with the vehicle control. The results revealed that the tripeptide including l-Tyrosine or d-Proline fragments instead of l-Alanine of leading compound <b>1</b> would contribute to HUVECs' proliferation. Taking the place of the original (l-Lys-l-Ala) segment of leading compound <b>1</b>, a new fragment (l-Arg-d-Val) expressed higher performance in bioactivity in HUVECs. In addition, compound <b>7</b> could promote angiogenesis in zebrafish assay and it was more interesting that it also could repair damaged blood vessels in PTK787-induced zebrafish at a low concentration. The above data indicate that these peptides have potential implications for further evaluation in cytothesis studies.