Abstract 035: Early Depletion Of Activated Neutrophils Ameliorates Ang Ii-induced Hypertension In Gstm1 Deficient Mice

Abstract

Background: Glutathione-S-transferase Mu1( Gstm1 ) gene encodes an enzyme that functions in the detoxification of electrophilic compounds. The common GSTM1 deletion variant in humans is associated with increased risks of chronic kidney disease progression. We reported that deletion of Gstm1 in mice increases oxidative stress, kidney inflammation and injury in angiotensin II induced hypertension (Ang II-HTN). Bone marrow cross-transplantation suggested a chemotaxis signal originating from the kidney. Moreover, we recently found that global deletion of Gstm1 significantly increased neutrophil chemotaxis response to CXCL1 and CXCL2 in vitro and kidney neutrophil populations early in Ang II-HTN by day 4. To test whether early activation of neutrophil mediates inflammation and kidney injury in Gstm1 KO mice, we depleted neutrophils using Ly6G antibody. Methods: Gstm1 KO male mice (12 weeks old) on 129S6 background were used for the study. After a 2-week training period, baseline systolic blood pressure (SBP) was measured by tail cuff daily for 2 weeks. For neutrophil depletion, Ly6G antibody (1A8, BioXcell ) (n=3) or control IgG (2A3)(n=2) were injected IP (200 μg/mouse) at 48hr and 24hr before Ang II mini-osmotic pump was implanted (1000 ng/kg/minute). A third IP injection was performed at day 4 after the Ang II. SBP was measured for 8 days during Ang II-HTN. FACS analysis was performed at day 8 post Ang II to determine the efficiency of neutrophil depletion. Results: Compared to control IgG, Ly6G antibody significantly depleted neutrophil populations in the kidney, bone marrow, and spleen by 95%, 97%, and 93%, respectively. Baseline SBP was similar between the two groups (129.5 ± 6.7 vs 128.3 ± 0.8 mm Hg, p = 0.9). In Ang II-HTN, depletion of neutrophils with Ly6G antibody in Gstm1 KO mice resulted in a trend in decrease in SBP compared to control antibody (154.7 ± 17.9 vs 182.6 ± 2.6 mm Hg; p = 0.13). Conclusion: Loss of Gstm1 activates neutrophils early in Ang II-HTN. Successful depletion of neutrophils in Gstm1 KO mice decreased blood pressure in response to Ang II. Further studies are underway to confirm the pressor response and to determine whether depletion of neutrophils early in Ang II-HTN can ameliorate kidney inflammation and injury in GSTM1 deficiency.