Sensing Cytosolic DNA Lowers Blood Pressure by Direct cGAMP-Dependent PKGI Activation

Abstract

BACKGROUND: The major cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) has emerged as a key mediator of inflammation that underlies cardiovascular disease. On interaction with double-stranded DNA, cGAS generates the second messenger 2′,3′-cyclic GMP-AMP (cGAMP) that directly binds to and activates the stimulator of interferon genes, which in turn leads to enhanced expression of genes encoding interferons and proinflammatory cytokines. Here, we show that cGAMP generated by cGAS also directly activates PKGI (cGMP-dependent protein kinase 1), a mechanism that underlies crosstalk between inflammation and blood pressure regulation. METHODS: The ability of cGAS and cGAMP to activate PKGI was assessed using molecular, cellular, and biochemical analyses, and in myography experiments, as well. The release of cGAMP from the endothelium was measured using an ELISA, and its uptake into the vascular smooth muscle was assessed using molecular and biochemical approaches, including the identification and targeting of specific cGAMP transporters. The blood pressure of wild-type and cGAS –/– mice was assessed using implanted telemetry probes. cGAS was activated by in vivo transfection with G3-YSD or mice were made septic by administration of lipopolysaccharide. RESULTS: The detection of cytosolic DNA by cGAS within the vascular endothelium leads to formation of cGAMP that was found to be actively extruded by MRP1 (multidrug resistance protein 1). Once exported, this cGAMP is then imported into neighboring vascular smooth muscle cells through the volume-regulated anion channel, where it can directly activate PKGI. The activation of PKGI by cGAMP mediates vasorelaxation that is dependent on the activity of MRP1 and volume-regulated anion channel, but independent of the canonical nitric oxide pathway. This mechanism of PKGI activation mediates lowering of blood pressure and contributes to hypotension and tissue hypoperfusion during sepsis. CONCLUSIONS: The activation of PKGI by cGAMP enables the coupling of blood pressure to cytosolic DNA sensing by cGAS, which plays a key role during sepsis by mediating hypotension and tissue hypoperfusion.