A Microdialysis Assay for Assessing sGC Stimulator Target Engagement in the Rat Liver

Abstract

Dysfunction of the nitric oxide (NO)‐soluble guanylate cyclase (sGC)‐cyclic guanosine monophosphate (cGMP) pathway has been implicated in numerous cardiovascular, metabolic, and fibrotic diseases. sGC stimulators are small molecules that bind sGC and synergize with NO to increase the enzymatic formation of cGMP and amplify downstream signaling. In preclinical models of liver disease, sGC stimulators have been shown to attenuate liver steatosis, inflammation, and fibrosis. To demonstrate their engagement in the sGC‐cGMP pathway in vivo, a unique microdialysis assay was developed to directly measure changes in cGMP levels in the rat liver.A midline laparotomy was performed on anesthetized male, Sprague Dawley rats (225–250 g) to expose the liver. A 25‐gauge needle was used to place a dialysis probe within the right medial lobe. The probe was perfused with saline at a rate of 2.5 μL/min and dialysate collected in one‐hour periods. Following baseline collection, test compound was administered intravenously, and dialysate collected for the following 2 hours. The NO donor sodium nitroprusside (SNP, 300 nM) was dosed via retrodialysis at study's end as a positive control. cGMP in the dialysate was measured using an enzyme immunoassay.In a study investigating our clinical‐stage sGC stimulator, praliciguat, an oral 3‐mg/kg dose produced a 3.9 ± 1.7‐fold increase (p<.0001) in cGMP from baseline levels of 0.8 ± 0.1 nM. A 1‐mg/kg dose caused a 1.7 ± 0.1‐fold increase in cGMP (p<.001), while the effect of a 0.3‐mg/kg dose was not significant. On average, SNP induced a 4.7 ± 1‐fold increase in cGMP (p<.0001).In summary, our microdialysis assay enabled in vivo monitoring of sGC stimulation in the rat liver. Beyond demonstrating the effects of praliciguat, this method can be used to evaluate and characterize other sGC stimulators for their capacity to amplify liver cGMP production. Further, this assay helps to link previously observed hepatic effects of sGC stimulators in disease models with an enhancement of sGC signaling.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.