There is strong experimental evidence, obtained using both pharmacological inhibitors and genetically modified animals, that NO production by the microvascular endothelium plays a critical role in NVC responses and that cerebromicrovascular endothelial dysfunction significantly contributes to age-related neurovascular dysfunction (Toth et al. in aging, similar to the recently demonstrated protective effects of treatment with the NAD+ precursor nicotinamide mononucleotide (NMN). To test this hypothesis, 24-month-old C57BL/6 mice were treated with PJ-34, a potent PARP Ywhaz inhibitor, for 2?weeks. NVC was assessed by measuring CBF responses (laser speckle contrast imaging) in the somatosensory whisker barrel cortex evoked by contralateral whisker stimulation. FGH10019 We found that NVC responses were significantly impaired in aged mice. Treatment with PJ-34 improved NVC responses by increasing endothelial NO-mediated vasodilation, which was associated with significantly improved spatial working memory. PJ-34 treatment also improved endothelium-dependent acetylcholine-induced relaxation of aorta rings. Thus, PARP-1 activation, likely by decreasing NAD+ availability, contributes to age-related endothelial dysfunction and neurovascular uncoupling, exacerbating cognitive decline. The cerebromicrovascular protective effects of pharmacological inhibition of PARP-1 highlight the preventive and therapeutic potential of treatments that restore NAD+ homeostasis as effective interventions in patients at risk for vascular cognitive impairment (VCI). value less than 0.05 was considered statistically significant. Data are expressed as mean??S.E.M. Results PJ-34 treatment rescues NVC responses in aged mice by restoring endothelial NO mediation NVC responses measured in the somatosensory whisker barrel cortex elicited by contralateral whisker stimulation were significantly decreased in 24-month-old mice compared to young animals indicating impaired functional hyperemia in old age (Fig.?1) (Park et al. 2007). Two-week treatment with PJ-34 significantly increased CBF responses induced by contralateral whisker stimulation in aged mice, restoring NVC to levels observed in young mice (Fig.?1). There is strong experimental evidence, obtained using both pharmacological inhibitors and genetically modified animals, that NO production by the microvascular endothelium plays a critical role in NVC responses and that cerebromicrovascular endothelial dysfunction significantly contributes to age-related neurovascular dysfunction (Toth et al. 2014, 2015a). Accordingly, in untreated aged animals, administration of the NO synthase inhibitor L-NAME was without FGH10019 effect, whereas in young mice, it significantly decreased NVC responses, eliminating the differences between the age groups (Fig.?1c). In PJ-34-treated aged mice, L-NAME significantly decreased CBF responses elicited by whisker stimulation (Fig.?1c), suggesting that PARP-1 inhibition improves NO mediation of NVC responses in aged animals. Open in a separate window Fig. 1 Treatment with the PARP-1 inhibitor PJ-34 improves NO mediation of neurovascular coupling responses in aged mice. a Representative pseudocolor laser speckle flowmetry maps of baseline CBF (upper row; shown for orientation purposes) and CBF changes in the whisker barrel field relative to baseline during contralateral whisker stimulation (bottom row, right oval, 30?s, 5?Hz) in young (3?months old), aged (24?months old), and PJ-34-treated aged mice. Color bar represents CBF as percent change from baseline. b The time-course of CBF changes after the start of contralateral whisker stimulation (horizontal bars). Summary data are shown in c. Data are mean??S.E.M. ( em n /em ?=?6C8 in each group), * em P /em ? ?0.05 vs. young; # em P /em ? ?0.05 vs. aged. (one-way ANOVA with post hoc Tukeys tests). n.s., not significant Our results show that treatment with PJ-34 treatment also restores acetylcholine-induced, endothelium-dependent relaxation of aged mouse aortas (Fig.?2), extending previous findings obtained with a structurally different PARP inhibitor (Pacher FGH10019 et al. 2004). To assess the role of endothelium-derived NO, L-NAME was applied. L-NAME abolished acetylcholine-induced vasorelaxation, eliminating the differences between the three groups (data not shown). These finding provide additional evidence that PARP inhibition significantly improves endothelial function by restoring endothelial NO mediation in aged vessels. Open in a separate window Fig. 2 Treatment with PJ-34 improves NO-mediated, endothelium-dependent vasorelaxation in aged mice. Shown are acetylcholine (ACh)-induced relaxations in the absence and presence of the NO synthase inhibitor L-NAME (3??10?4?mol/L) in aortic ring preparations isolated from young (4?months old), aged (24?months old), and PJ-34-treated aged mice. Age-related declines in endothelial function were reversed by PJ-34 treatment. Data are mean??S.E.M. ( em n /em ?=?5C8 for each data point).* em P /em ? ?0.05 vs. young; # em P /em ? ?0.05 vs. aged Restoration of cerebromicrovascular function is associated with improved cognitive function in aged mice treated with PJ-34 Experimental studies provide proof-of-concept that pharmacologically induced neurovascular uncoupling is associated with detectable cognitive impairment (Tarantini et al. 2015). To determine how rescue of cerebromicrovascular function by PJ-34 treatment impacts cognitive performance in aged mice, animals were tested in the radial arms water maze (Fig.?3). We compared the learning performance of mice in each experimental group by analyzing the day-to-day changes in the combined error rate and successful escape rate..