VEGF-A from Granuloma Macrophages Regulates Granulomatous Inflammation by a Non-angiogenic Pathway during Mycobacterial Infection

Abstract

Summary: Many autoimmune and infectious diseases are characterized by the formation of granulomas which are inflammatory lesions that consist of spatially organized immune cells. These sites protect the host and control pathogens like Mycobacterium tuberculosis (Mtb), but are highly inflammatory and cause pathology. Using bacille Calmette-Guerin (BCG) and Mtb infection in mice that induce sarcoid or caseating granulomas, we show that a subpopulation of granuloma macrophages produces vascular endothelial growth factor (VEGF-A), which recruits immune cells to the granuloma by a non-angiogenic pathway. Selective blockade of VEGF-A in myeloid cells, combined with granuloma transplantation, shows that granuloma VEGF-A regulates granulomatous inflammation. The severity of granuloma-related inflammation can be ameliorated by pharmaceutical or genetic inhibition of VEGF-A, which improves survival of mice infected with virulent Mtb without altering host protection. These data show that VEGF-A inhibitors could be used as a host-directed therapy against granulomatous diseases like tuberculosis and sarcoidosis, thereby expanding the value of already existing and approved anti-VEGF-A drugs. : Harding et al. show that VEGF-A inhibitors reduce granuloma-associated pathologies, including mycobacterial-based infections. Granulomas contain a heterogeneous inflammatory cell population, including macrophages that produce VEGF-A during periods of cell death. VEGF-A potentiates excessive inflammation by recruiting macrophages to the granuloma. FDA-approved VEGF-A inhibitors exist and could help limit tuberculosis-associated inflammation. Keywords: mycobacterium, tuberculosis, granuloma, VEGF-A, sarcoidosis, inflammation, P2RX7, monocyte recruitment