Abstract 13596: Effects of Plasminogen Activator Inhibitor-1 on the Circadian Clock in Liver

Abstract

Introduction: Plasminogen activator inhibitor-1 (PAI-1, encoded by Serpine1 ) plays a major role in the mammalian fibrinolytic system, but elevated PAI-1 activity contributes to other biological processes including the metabolic syndrome. Multiple studies suggest that disruption of circadian rhythms also promotes features of the metabolic syndrome including obesity, hypertension, and type 2 diabetes. While it has been long known that PAI-1 plasma levels exhibit a marked circadian variation, and that the expression of PAI-1 is strongly influenced by the clock, a reciprocal role for PAI-1 in regulating components of the clock itself has never been described. Hypothesis: We hypothesized that changes in PAI-1 activity influence the expression of core circadian clock genes and clock-controlled genes in the liver. Methods: We used two mouse models of reduced PAI-1 activity: oral PAI-1 inhibitor TM5614 (20 mg/kg/day) versus vehicle in C57BL/6J wild-type mice (n = 5 per group), and Serpine +/- heterozygous mice versus wild-type littermate control mice (n = 3 per group). Mice were maintained on a 14:10 light:dark cycle. Livers were collected between 3 and 4 hours after lights-on, which corresponds to Zeitgeber Time (ZT) 3-4. RNA was isolated for RNA-seq and downstream analyses. Results: Between ZT 3-4, we found that reduced PAI-1 activity led to marked changes in circadian gene expression in the liver. Both PAI-1 inhibition with TM5614 and PAI-1 haploinsufficiency significantly increased expression of the core circadian clock components Arntl (aka Bmal1) and Clock while significantly reducing expression of core clock components Per1, Per2, Per3, and clock output genes. Furthermore, we found that PAI-1 inhibition in aged transgenic mice overexpressing the stable variant of human SERPINE1 rescued two markers of impaired circadian function: 1) the premature onset of activity prior to lights-off, and 2) reduced feeding during the lights-off period. Conclusions: Taken together, these data support a reciprocal role for PAI-1 in regulating components of the circadian clock. Elevated PAI-1 activity may contribute to the metabolic syndrome through effects on the circadian clock and may provide a mechanistic link between PAI-1, the circadian clock, and aging.