Combining angiotensin receptor blockade and enzyme replacement therapy for vascular disease in mucopolysaccharidosis type I

Abstract

Vascular involvement in the genetic disorder mucopolysaccharidosis type I (MPS I) has features of atherosclerotic disease near branch points of arterial vasculature, such as intimal thickening with disruption of the internal elastic lamina, and proliferation of macrophages and myofibroblasts. Inflammatory pathways are implicated in the pathogenesis of vascular disease in MPS I animal models, evidenced by cytokines like CD18 and TGF-β within arterial plaques. The angiotensin II-mediated inflammatory pathway is well studied in human atherosclerotic coronary artery disease. Recent work indicates treatment with the angiotensin receptor blocker losartan may improve vascular MPS I disease in mouse models. Here, we combined losartan with the standard therapy for MPS I, enzyme replacement therapy (ERT), to measure effects on cytokines in serum and aortic vasculature. Each treatment group (losartan, ERT, and their combination) equally normalized levels of cytokines that were largely differential between normal and mutant mice. Some cytokines, notably CD30 ligand, Eotaxin-2, LIX, IL-13, IL-15, GM-CSF, MCP-5, MIG, and CCL3 showed elevations in mice treated with ERT above normal or mutant levels; these elevations were reduced or absent in mice that received losartan or combination therapy. The observations suggest that losartan may impact inflammatory cascades due to MPS I and may also blunt inflammation in combination with ERT.

Keywords: Alpha-L-iduronidase; Hurler; Hurler-Scheie; Losartan; Lysosomal storage disease; Scheie.

Fig. 1

Anti-iduronidase antibodies in treated mice. Specific IgG against rhIDU in pooled serum were measured by ELISA at the 24-week timepoint (16-weeks post initial treatment).

Fig. 2

Cytokine levels are ameliorated when combining ERT and losartan. Across several cytokine measurements, there is a general trend of the ERT treated group having a higher spike in that cytokine at 24 weeks of age (16 weeks post initial treatment). The cytokine spikes in the ERT group generally are higher in males than in females. This is especially true in CD30, Eotaxin-2, IL-13, IL-15, GM-CSF, MCP-5, and MIP-1α.

Fig. 3

Identified improvement with combination treatment in some cytokines only in one sex. Many cytokines saw the same trend of the combination treatment leading to less inflammation in the combination treatment group at 24 weeks of age (16 weeks post treatment) only within one sex with the other sex being either an insignificant difference between the two groups or the combination group was higher in that cytokine at 24 weeks of age. (A) Cytokines where males had a significant decrease in response in the combination group when compared to the ERT alone group. (B) Cytokines where females had a significant decrease at 24 weeks of age in response in the combination treatment group when compared to the ERT alone group.

Fig. 4

Combination treatment in females led to an increase of eight cytokines in response when compared to the ERT alone or LXN alone groups. In females, there was a trend in eight cytokines that the combination treatment group (ERT + LXN) had elevated levels of the cytokines when compared to the ERT alone group at 24 weeks of age and 16 weeks post treatment initialization. This elevation of the combination treatment was also higher than the LXN alone group as well. These cytokines were G-CSF, IL-3, IL-5, IL-6, IL-17 A, Leptin, Fas Ligand, and RANTES.

Fig. 5

TGFβ and pERK1/2 levels are lowered with any of the treatment methods explored in this study. (A) Aortic valve sections stained for TGFβ (top row) and pERK1/2 (bottom row). All treatments showed less fluorescence than the untreated control groups (HET and MUT). (B) Graphs showing the level of intensity of TGFβ (left) and pERK1/2 (right) in each treatment group based on the immunohistochemistry. Number of mice per group evaluated via immunohistochemistry: Het – 6, MUT – 2, ERT – 6, LXN – 4, ERT + LXN – 5.