Cerebral cavernous malformations (CCMs) are common neurovascular lesions caused by loss-of-function mutations in one of three genes, including KRIT1 (CCM1), CCM2, and PDCD10 (CCM3), and generally regarded as an endothelial cell-autonomous disease. Here we reported that proliferative astrocytes played a critical role in CCM pathogenesis by serving as a major source of VEGF during CCM lesion formation. An increase in astrocyte VEGF synthesis is driven by endothelial nitric oxide (NO) generated as a consequence of KLF2 and KLF4-dependent elevation of eNOS in CCM endothelium. The increased brain endothelial production of NO stabilized HIF-1a in astrocytes, resulting in increased VEGF production and expression of a “hypoxic” program under normoxic conditions. We showed that the upregulation of cyclooxygenase-2 (COX-2), a direct HIF-1a target gene and a known component of the hypoxic program, contributed to the development of CCM lesions because the administration of a COX-2 inhibitor significantly prevented the progression of CCM lesions. Thus, non-cell-autonomous crosstalk between CCM endothelium and astrocytes propels vascular lesion development, and components of the hypoxic program represent potential therapeutic targets for CCMs.
Miguel Alejandro Lopez-Ramirez, Catherine Chinhchu Lai, Shady Ibrahim Soliman, Preston Hale, Angela Pham, Esau J. Estrada, Sara McCurdy, Romuald Girard, Riya Verma, Thomas Moore, Rhonda Lightle, Nicholas Hobson, Robert Shenkar, Orit Poulsen, Gabriel G. Haddad, Richard Daneman, Brendan Gongol, Hao Sun, Frederic Lagarrigue, Issam A. Awad, Mark H. Ginsberg