A PF‐3845‐induced novel lipid fraction in mouse medullary interstitial cells causes diuresis and natriuresis via a CB1‐mediated pathway

Abstract

The relationship between the endocannabinoid system in the renal medulla and the long‐term regulation of blood pressure is not understood. To investigate the possible role of the endocannabinoid system in renomedullary interstitial cells, mouse medullary interstitial cells (MMICs) were obtained, cultured and characterized for their responses to treatment with a selective inhibitor of fatty acid amide hydrolase (FAAH), PF‐3845. Treatment of MMICs with PF‐3845 increased cytoplasmic lipid granules detected by Sudan Black B staining and multilamellar bodies identified by transmission electron microscopy. HPLC analyses of lipid extracts of MMIC culture medium revealed a 205nm‐absorbing peak that showed responsiveness to PF‐3845 treatment. The biologic activities of the PF‐3845‐induced product (PIP) isolated by HPLC were investigated in anesthetized, normotensive surgically‐instrumented mice. Intravenous and intramedullary infusions of PIP at low doses resulted in a vasodepressor, diuretic and natriuretic effects. Pharmacological and genetic ablation of cannabinoid 1 receptors resulted in the loss of the vasodepressor, diuretic and natriuretic effect of PIP. Radioactive binding assays showed that PIP competes for binding to CB1 receptors in the presence of a full agonist (CP 55,940). PIP did not elevate urine and sodium excretion in a genetic knockout mouse model of FAAH. A PIP‐induced decrease in blood pressure at high doses of PIP was similar between FAAH WT and FAAH KO mice. These data support a model whereby PF‐3845 treatment of MMICs results in increased secretion of a neutral lipid which acts directly to promote diuresis and natriuresis via a CB1‐mediated mechanism. The diuretic and natriuretic responses to PIP are eliminated by inhibition of FAAH, suggesting an undergoing sensitization to PIP in FAAH KO mice. Efforts to identify the structure of the PF‐3845‐induced lipid and its relationship to the previously proposed renomedullary antihypertensive lipids are ongoing.Support or Funding InformationThis work was supported by the National Institute of Diabetes and Digestive and Kidney Disorders grant [grant R01DK102539] and the National Institute on Drug Abuse [grant P30DA033934]. S.D. was supported by the National Institute on Drug Abuse [training grant T32DA007027].This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.