26 September 2007
Background: Hypertension is associated with inward remodeling of small arteries and decreased erythrocyte deformability, both impairing proper tissue perfusion. We hypothesized that these alterations depend on transglutaminases, cross-linking enzymes present in the vascular wall, monocytes/macrophages and erythrocytes. Methods and Results: Wild-type (WT) mice and tissue-type transglutaminase (tTG) knockout (KO) mice received the nitric oxide inhibitor Nω-nitro- L-arginine methyl ester hydrochloride ( L-NAME) to induce hypertension. After 1 week, mesenteric arteries from hypertensive WT mice showed a smaller lumen diameter (–6.9 ± 2.0%, p = 0.024) and a larger wall-to-lumen ratio (11.8 ± 3.5%, p = 0.012) than controls, whereas inward remodeling was absent in hypertensive tTG KO mice. After 3 weeks, the wall-to-lumen ratio was increased in WT (20.8 ± 4.8%, p = 0.005) but less so in tTG KO mice (11.7 ± 4.6%, p = 0.026), and wall stress was normalized in WT but not in tTG KO mice. L-NAME did not influence expression of tTG or an alternative transglutaminase, coagulation factor XIII (FXIII). Suppression of FXIII by macrophage depletion was associated with increased tTG in the presence of L-NAME. L-NAME treatment decreased erythrocyte deformability in the WT mice (–15.3% at 30 dynes/cm<sup>2</sup>, p = 0.014) but not in the tTG KO mice. Conclusion: Transglutaminases are involved in small artery inward remodeling and erythrocyte stiffening associated with nitric oxide inhibition-related hypertension.