Sex‐Specific Influence of Broad‐Spectrum Antibiotic Treatment on Dahl Salt‐Sensitive Hypertension

Abstract

Our laboratory has previously demonstrated through fecal microbiota transfer studies that the gut microbiota importantly contributes to the development of hypertension, renal damage, and renal inflammation in the Dahl Salt-Sensitive (SS) rat fed a 4.0% high salt diet (HS). We have furthermore provided evidence that female SS rats are significantly protected from salt-induced hypertension, renal injury, and renal immune cell infiltration compared to males. One potential explanation for this sex difference is the substantial divergence we have observed in gut microbiota composition between male and female SS rats. Given the established role of the gut microbiota, we hypothesized that gut microbiota ablation via broad-spectrum antibiotic treatment would modulate the hypertensive response to high salt in both male and female SS rats. SS rats were treated with a broad-spectrum antibiotic cocktail of bacitracin and streptomycin (Bac/Strep, 2 g/L in drinking water) throughout the 3-week duration of HS challenge. SS males treated with Bac/Strep resulted in a significant reduction in mean arterial pressure (170.8±5.1 vs 156.0±4.1 mmHg, Vehicle vs Bac/Strep, n=12-13/group, p=0.001), proteinuria (365.0±39.7 vs 254.1±23.2 mg/day, p=0.002), and albuminuria (207.6±24.4 vs 124.3±10.3 mg/day, p<0.001) compared to male vehicle-treated rats after 3 weeks of HS. Due to the immunological nature of Dahl SS hypertension, we analyzed the infiltrating immune cell profile in the kidneys of Bac/Strep-treated males and found a specific decrease in B cells (40.7% reduction, p=0.012) as compared to vehicle-treated male SS kidneys, with no change in the number of T cells or monocytes/macrophages. These data altogether indicate that Bac/Strep treatment eliminated gut bacteria responsible for driving the hypertensive and renal injury phenotype in male Dahl SS rats. However, these protective effects of Bac/Strep were not observed in female SS rats. There was no significant difference in mean arterial pressure (134.6±3.1 vs 134.7±2.7 mmHg, Vehicle vs Bac/Strep, n=7-9/group, p= 0.974), proteinuria (39.5±3.8 vs 45.6±8.5 mg/day, p=0.408), or albuminuria (16.7±2.3 vs 18.7±3.7 mg/day, p=0.572) between vehicle- and Bac/Strep-treated female SS rats after 3 weeks of HS. Interestingly, despite the lack of an effect on the salt-induced hypertensive phenotype in females, there was still a significant decrease in renal B cells (38.5% reduction, p=0.05) in Bac/Strep-treated female SS rats compared to vehicle, perhaps indicating a specific effect of antibiotic treatment as opposed to a consequence of reduced blood pressure and renal damage. In conclusion, broad-spectrum antibiotic treatment reduced hypertension, renal damage, and renal inflammation in male Dahl SS rats, providing further evidence for the contribution of the gut bacteria in the response to HS. However, it appears that salt-induced elevations in blood pressure in female rats occur independent of Bac/Strep-sensitive gut bacteria.