Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA014

Poster Communications

Discrepant findings to angiotensin II-induced hypertension in Rag-1 knockout mice cannot be explained by dose effects and salt intake alone

A. Seniuk1, A. Stubbe1, J. Thiele1, P. Oser1, A. Rosendahl2, U. Wenzel2, H. Ehmke1

1. Department of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany. 2. Department of Nephrology, University Medical Center Hamburg, Hamburg, Germany.

Motivation: Several laboratories have found a resistance of Rag-1 knockout mice, lacking functional B- and T-cells, to angiotensin II mediated hypertension. Recently, however, Ji et al. have reported that their Rag-1 knockout mice strain, purchased in 2015/2016, lost the pressure resistant phenotype. Interestingly, we never observed any angiotensin II resistance of Rag-1 knockout mice, purchased in 2009. Here, we investigated whether dose effects or differences in salt intake might be responsible for these discrepant findings. Methods: Rag-1 knockout mice, directly imported from the Jackson Laboratory, and corresponding C57Bl/6J wildtype mice were analysed for blood pressure via radiotelemetry under different doses of angiotensin II (170 ng*kg-1*min-1, 490 ng*kg-1*min-1 or 1500 ng*kg-1*min-1) and under conditions of low- and high salt intake (modified special diet containing either 0.2 g Na+/kg or 30 g Na+/kg). Flow cytometry measurements of lymphocytes were performed in renal and aortic tissue. Results: We did not observe any difference in blood pressure response between Rag-1 knockout mice and C57Bl/6J wildtype mice to angiotensin II, neither under different doses of angiotensin II nor under different levels of salt intake (2-way ANOVA, all n.s.). Blood pressure increases in both mouse strains are very similar to those described for C57Bl/6J wildtype mice by other groups. As expected for Rag-1 knockout mice, no T-cells were detectable in aortic or renal tissue. In C57Bl/6J wildtype mice, levels of CD3-positive-, CD4-positive- or γδ-T-cells measured as percentage of infiltrating CD45+ cells, were not affected by angiotensin II treatment. Conclusions: Our findings indicate that Rag-1 knockout mice are not protected from angiotensin II-mediated hypertension by lack of functional T-cells alone, since Rag-1 knockout mice and C57Bl/6J wildtype mice showed identical blood pressure increases in response to angiotensin II treatment, independent of dose and sodium intake. Full development of the blood pressure resistant phenotype depends on the action of a yet unidentified modifier, which might be found in housing conditions or microbiome. The lack of a resistance of our Rag-1 knockout mice to angiotensin II induced hypertension comes along with an absence of an increased T cell infiltration in typical hypertensive end organs. Accordingly, the role of the adaptive immune system examined in Rag-1 knockout/C57Bl/6J mice has to be reviewed critical for investigation of angiotensin II-mediated immunological effects.

Where applicable, experiments conform with Society ethical requirements