A new nitrobenzoate compound called X8 blocks blood vessel growth in zebrafish embryos. At a dose of 3 µM it causes malformed vessels, heart swelling, and circulation problems, likely by stopping cells from multiplying and moving and by lowering key vascular genes. The effect seems tied to interference with the VEGF/VEGFR2 pathway, which is a major driver of new blood vessel formation.

Proper growth and patterning of blood vessels are critical for embryogenesis. Chemicals or environmental hormones may interfere with vascular growth and cause developmental defects. Nitrobenzoate-based compounds have been demonstrated to have a wide range of biological and pharmacological functions, leading to the development of numerous 4-nitrobenzoate derivatives for clinical application. In this study, we tested a novel nitrobenzoate-derived compound, X8, and investigated its effects on vascular development using zebrafish as a model organism. We first determined the survival rate of embryos after the addition of exogenous X8 (0.5, 1, 3, 5, and 10 &#x3bc;M) to the fish medium and determined a sublethal dose of 3 &#x3bc;M for use in further assays. We used transgenic fish to examine the effects of X8 treatment on vascular development. At 25-32 h postfertilization (hpf), X8 treatment impaired the growth of intersegmental vessels (ISVs) and caudal vein plexuses (CVPs). Moreover, X8-treated embryos exhibited pericardial edema and circulatory defects at 60-72 hpf, suggesting the effects of X8 in vasculature. Apoptosis tests showed that the vascular defects were likely caused by the inhibition of proliferation and migration. To investigate the molecular impacts underlying the defects in the vasculature of X8-treated fish, the expression levels of vascular markers, including <i>ephrinb2</i>, <i>mrc1</i>, and <i>stabilin</i>, were assessed, and the decreased expression of those genes was detected, indicating that X8 inhibited the expression of vascular genes. Finally, we showed that X8 treatment disrupted exogenous GS4012-induced angiogenesis in <i>Tg(flk:egfp)</i> zebrafish embryos. In addition, vascular defects were enhanced during cotreatment with X8 and the VEGFR2 inhibitor SU5416, suggesting that X8 treatment causes vascular defects mediated by disruption of VEGF/VEGFR2 signaling. Collectively, our findings indicate that X8 could be developed as a novel antiangiogenic agent.