Abstract 016: GRN Gene Mutation Leads To Vascular Abnormalities Via Mitochondrial Dysfunction And Oxidative Stress

Abstract

Background: Cardiovascular disease (CVD) is the leading cause of death worldwide. Loss of contractility of vascular smooth muscle cells (VSMC) is a major factor of CVD. The GRN gene encodes the glycoprotein progranulin (PGRN). Ubiquitously expressed, PGRN is implicated in anti-inflammation and cell proliferation. However, the role of PGRN in CVD remains to be elucidated. Herein, we tested the hypothesis that PGRN influences VSMC contraction via regulating mitochondria quality. Methods: We used aortae from wildtype (PGRN +/+ ) and PGRN global knockout (PGRN -/- ) mice to study vascular contraction via wire myograph and isolate primary aVSMCs to elucidate mechanisms. Results: We observed a significantly suppressed contractile profile in PGRN -/- aVSMC characterized by reduced α smooth muscle actin expression and impaired VSMC contractility, analyzed by collagen disc assay. PGRN -/- aortae demonstrated diminished vascular contractility to KCl (maximal response in mN, PGRN +/+ 5.3±0.3 vs PGRN -/- 4.0±0.4*, *P<0.05) and thromboxane A2 analog, U46619 (maximal response in mN, PGRN +/+ 6.0±0.5 vs PGRN -/- 4.7±0.3*, *P<0.05). RNA-sequencing in aortae revealed a suppression in oxidative phosphorylation in PGRN -/- . Furthermore, PGRN -/- VSMC and aortae displayed a suppressed mitochondrial oxygen consumption rate (OCR) analyzed by Seahorse and Oroboros followed by attenuated ATP levels and elevated mitochondrial oxidative stress. No difference was observed for mitochondria DNA number or biogenesis. To rescue the PGRN levels, we incubated aortae from PGRN -/- mice with lentivirus (LV) encoding PGRN for 48h, which elevated the vascular contractility to KCl (maximal response in mN, PGRN -/- 4.8 ± 0.4 vs PGRN -/-LV 7.1 ± 0.3*, *P<0.05) and U46619 (maximal response in mN, PGRN -/- 8.0 ± 0.2 vs PGRN -/-LV 16.0 ± 0.2*, *P<0.05), increased OCR, and controlled the oxidative stress, whereas inhibiting mitochondria with rotenone prevented the LV effects. Conclusion: Collectively, we demonstrated that PGRN is essential to maintain vascular contractility via regulating mitochondrial function. Our results show that loss-of-function of PGRN is a risk factor for developing CVD and places PGRN as a potential alternative therapeutic target for high-risk CVD populations.