Evidence for inflammatory and secretagogue lipids in cyst fluids from patients with autosomal dominant polycystic kidney disease.

Advanced autosomal dominant polycystic kidney disease (ADPKD) is characterized morphologically by massive cyst enlargement, moderate interstitial infiltration with mononuclear cells, and extensive fibrosis. In patients affected by a common genotype (PKD1), it has been suggested that the progressive decline in renal function that transpires over a highly variable time course may be due to endogenous or exogenous epigenetic factors. We have postulated that a neutral lipid, discovered in human cyst fluid and stimulating the rates of transepithelial fluid secretion and cellular proliferation of renal epithelial cells in vitro may have a potential role in cyst growth and the progressive decline of kidney function. In this study, we used thin-layer chromatography (TLC) and high-performance TLC (HPTLC) to determine whether lipid extracts of human cyst fluid stimulated monocyte chemotaxis in vitro. Monocyte chemotactic activity, determined by the transmembrane migration of murine RAW 264.7 cells, was stimulated (delta 26.0 +/- 1.5 optical density units) by a lipid fraction less polar than sphingosine but more polar by TLC and HPTLC than 1-monooleoylglycerol. A high level of secretagogue activity was detected in this fraction (delta 0.336 +/- 0.022 microliter/cm2 1 hr) and to a lesser extent (delta 0.253 +/- 0.022 microliter/cm2/hr) in a neighboring fraction that encompassed the 1-monooleoylglycerol standard. Cyst fluid with undetectable secretagogue activity had a monocyte chemotactic-activity level only 18% as great as fluids with high levels of secretagogue activity. The secretagogue and chemotactic activities in TLC-HPTLC fractions were resistant to treatment with KOH, but both were diminished by HCl, borohydride, or periodate. Rat proximal tubule cultures incubated with oleate complexed with albumin elaborated secretagogue and chemotactic activities in the conditioned medium, with TLC-HPTLC mobility characteristics similar to the biologically active cyst fluid lipids. On the basis of these studies, we conclude that human cyst fluids harbor potent secretagogue and chemotactic lipids that may have a role in determining the functional course of ADPKD. On the basis of preliminary chemical characterizations, we suggest that the secretatogue and monocyte chemotactic activities of cyst fluid may reflect the action of lipid molecules of similar structure, the source of which may be renal epithelial cells.