The effect of JV-GL1 in normotensive mice
As JV-GL1 is an EP2 agonist (Coleman et al., 2018; Woodward et al., 2019a), our first aim was to measure the IOP-lowering effect of JV-GL1 in normotensive mice that express EP2(Ptger2 +/+) versus mice that lack EP2 (Ptger2 -/-). BetweenPtger2 +/+ andPtger2 -/-, there was no significant difference in baseline IOP nor outflow facility (Supplemental Figure 1). Three hours after unilateral treatment with JV-GL1 (0.01%, 10 µl), IOP was reduced in Ptger2 +/+ mice (ΔIOP =-3.1 [-4.1, -2.1] mmHg; mean [95% CI]; P <0.0001; n=9 mice) with respect to the vehicle-treated contralateral eye (Fig. 1A). InPtger2 -/- mice, however, there was no significant IOP reduction following treatment with JV-GL1 after 3 hrs (ΔIOP = 0.8 [-0.4, 2.0] mmHg; P =1, n=7). By 24 hours, IOP in the treated eye of Ptger2 +/+ mice had returned to baseline and was not statistically different from IOP in the control eye (ΔIOP = 0.0 [-1.0, 1.0] mmHg, P =1, n=9). Thus, the IOP-lowering effect of JV-GL1 requires Ptger2 and lasts for less than 24 hrs, at least in normotensive mice.
We also compared the effects of JV-GL1 against the archetypical EP2 agonist butaprost (Fig. 1A). Like JV-GL1, butaprost lowered IOP in the Ptger2 +/+ mice at 3 hrs relative to the contralateral vehicle-treated eye (∆IOP = -2.4 [‑4.2, ‑0.6]  mmHg; P <0.01; n=7), but butaprost did not affect IOP in the Ptger2 -/- littermates (∆IOP = 0.4 [-0.7, 1.5]  mmHg; P =1; n=7). The IOP reduction in response to butaprost was not significantly different from that of JV-GL1 at 3 hrs (P =1), and neither drug had an observable effect on IOP at 24 hrs. Thus, the magnitude and duration of IOP-lowering in response to JV-GL1 appears to be similar to that of butaprost in ocular normotensive mice.
To investigate the physiological mechanism of IOP reduction, we then examined the effect of JV-GL1 on pressure-dependent outflow. We observed no significant effect of de-esterified JV-GL1 (100 nM) on outflow facility when perfused directly into enucleated eyes of C57BL/6J mice (relative to contralateral vehicle-perfused eyes), which expressPtger2 (-6% [-22, 13], P =0.4, n=5 pairs; Fig. 1B). Thus, consistent with other EP2 agonists that are thought to lower IOP primarily by increasing unconventional outflow (Nilsson et al. ,2006; Woodward, et al. , 2019b), JV-GL1 does not appear to have an acute effect on outflow facility.