Long‐term Gut Microbiota Depletion Exacerbates Hypertension and Renal Injury in an Experimental Model of Autoimmune Disease

Abstract

The gut microbiota plays an indispensable role in the development and maintenance of both the innate and adaptive immune systems. Alterations in the gut microbiota, or gut dysbiosis, is associated with many autoimmune disorders, including those without gastrointestinal manifestations, such as rheumatoid arthritis and systemic lupus erythematosus (SLE). SLE is a multisystem autoimmune disorder that primarily affects women and is characterized by high rates of hypertension, renal injury, and cardiovascular disease. Recent studies in several animal models have also posited a possible causative role of the gut dysbiosis in the development of hypertension. In the present study, we hypothesized that the gut dysbiosis in SLE may play a role in the development of immune system dysfunction and hypertension in an experimental model of SLE, the NZBWF1 mouse. To test this hypothesis, we treated 18‐week‐old female control (NZW, n=14) and SLE (NZBWF1, n=14) mice with broad spectrum antibiotics (Abx: 0.4 g/L ampicillin, 0.4 g/L neomycin sulfate, 0.4 g/L metronidazole, and 0.2 g/L vancomycin) in drinking water for 16 weeks. Additional groups of control and SLE mice received normal drinking water (control, n=14; SLE, n=14) over the course of the study. At the conclusion of the treatment, we confirmed successful gut microbiome depletion in the feces of control and SLE mice by qPCR of 16S rRNA. Mean arterial pressure (MAP; mmHg), measured in conscious mice by carotid artery catheter, was higher in SLE mice than in control mice (110±4 mmHg control vs. 131±6 mmHg SLE, p<0.01). Unexpectedly, treatment with antibiotics further increased blood pressure in SLE mice (SLE‐Abx: 151±4 mmHg, p<0.01 vs. SLE), but had no impact on blood pressure in control animals (110±4 mmHg control vs. 106±4 mmHg control‐Abx, p=0.91). Urinary albumin excretion, a marker of renal injury, was assessed by ELISA at the conclusion of the study. Albumin excretion was increased in SLE mice (0.22±0.08 mg/day control vs. 25.1±15.7 mg/day SLE, p=0.08), and urinary albumin remained elevated in SLE mice administered antibiotics (43.6±17.3 mg/day, p=0.68 vs. SLE‐Abx). Additionally, renal immune cell infiltration was assessed using flow cytometry. SLE mice had significantly higher levels of renal CD4+ T cells as compared to control mice (0.46±0.04% control vs. 0.84±0.1% SLE, p<0.05), but treatment with antibiotics elevated renal CD4+ T cells further (2.9±0.5%, p<0.001 vs. SLE). An additional pilot study (n=7‐9 mice/group) of short‐term antibiotic treatment from 26‐32 weeks of age had no impact on blood pressure in SLE mice (120±4 mmHg SLE vs. 122±3 mmHg SLE‐Abx, p=0.97). These data suggest that a long‐term loss of the microbiome in SLE actually further exacerbate disease progression and the development of hypertension.