Chronically Hypertensive Transgenic Mice Expressing Human AT1R Haplotype‐I Exhibit Increased Susceptibility To Francisella Tularensis

Abstract

Angiotensin receptor type 1 (AT1R), a G-protein coupled receptor mediates the effect of angiotensin-II and contributes to the pathophysiological consequences of metabolic disorders leading to vascular remodeling, hypertension, and end-organ damage. Genetic variations that increase human AT1R (hAT1R) expression can cause above pathological outcomes due to renin-angiotensin system overactivity. Previously we have shown that transgenic (TG) mice containing haplotype-I (Hap-I, hypertensive genotype) of human AT1R gene are more prone to develop the metabolic syndrome (MetS) related disorders as compared to the TG mice containing haplotype-II (Hap-II, normotensive genotype). We have also shown that as compared to Hap-II, the aged Hap-I TG mice overexpress the hAT1R gene resulting in an increase in blood pressure, inflammatory molecules, and renal dysfunction. Aging together with an increased risk of hypertension, can affect multiple organ systems in a complex manner, including susceptibility to various infections. The current study, therefore, was designed to examine the potential effect of aging and associated MetS disorders in our hAT1R containing TG mice model, in response to the infection by Francisella tularensis live vaccine strain (LVS) inhalation. Our results show that Hap-I TG mice have a significantly high mortality rate two weeks post-infection as compared to the Hap-II animals. Histochemical analysis of lung tissues from adult and aged animals show a comparatively elevated pathology in mice containing Hap-I of hAT1R. The lung tissue and plasma from Hap-I TG mice also show a relatively higher bacterial load five days post-infection. Preliminary RT-PCR experiments show increased inflammatory markers like IL-6, TGF-β, TNF-α, CRP and redox markers like NOX1, NOX4 in lung tissues of Hap-I TG mice. These studies suggest that haplotype dependent over-expression of hAT1R gene, leads to an enhanced mortality and lung pathology to F. tularensis LVS infection, which gets aggravated in aged animals. Clinically, our results may help in exploring the role of AT1R induced hypertension in pulmonary infections.