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Background: Transglutaminase 2 (TG2) is an enzyme involved in the pathogenesis of vascular remodeling in conditions of chronic over-nutrition and activation of the renin angiotensin aldosterone system (RAAS). Furthermore, it has been shown that pharmacologic inhibition of TG2 significantly reduces blood pressure in male rodents. However, the cell-specific role of TG2 activation in vascular smooth muscle cells (VSMC) in mediating the hypertensive response to RAAS overactivation has not been explored. Methods: We generated a novel inducible model (tamoxifen dose: 50 mg/kg/d oral for 6 weeks) of TG2 deletion in VSMC (VSMCTG2KO) by sequentially crossing Tgm2t/t floxed mice (loxP sites flanking exons 6-8 of the TG2, C polypeptide [Tgm2] gene) with male Myh11-CreERT2 positive mice. Effectiveness of the TG2 deletion was evaluated by immunohistochemistry and TG2 activity was determined by incorporation of Alexa Fluor488 Cadaverine.A cohort of fifteen-month-old wild-type and VSMC TG2KO male mice were implanted with deoxycorticosterone (DOCA; 50 mg, 21-day releasing pellets) and 1 % salt added to the drinking water. Systolic blood pressure was assessed by tail-cuff method prior to sacrifice. Ex vivo aortic stiffness was determined by atomic force microscopy. Student t-test or two-way ANOVA were used for statistical analysis as appropriate. The results were considered significant when p Results: administration of DOCA/salt induced increases in systolic blood pressure, augmented expression of TG2 in aorta, as well as increased aortic stiffness in wild-type mice (10.47±1.27kPA DOCA/salt vs. 3.91 + 1.01 kPa placebo). The VSMCTG2KO model exhibited 77% downregulation of TG2 expression in VSMC. VSMC TG2 KO suppressed DOCA/salt induced TG2 activity (29.13 + 2.22 arbitrary units (AU) in DOCA/salt vs 14.10 + 2.90 AU in KO cohort). This was accompanied by a significant improvement in DOCA/ salt-induced hypertension (SBP 142 ± 5.4 mmHg in DOCA/salt treated mice vs. 111.8 ± 6.2 mmHg in VSMCTG2KO). Conclusions: Our data demonstrate for the first-time the key role of TG2 activation in VSMC, in the regulation of hypertensive responses in in a male rodent model of RAAS activation.

Obesity and insulin resistance stiffen the vasculature, with females appearing to be more adversely affected. As augmented arterial stiffness is an independent predictor of cardiovascular disease (CVD), the increased predisposition of women with obesity and insulin resistance to arterial stiffening may explain their heightened risk for CVD. However, the cellular mechanisms by which females are more vulnerable to arterial stiffening associated with obesity and insulin resistance remain largely unknown. In this study, we provide evidence that female mice are more susceptible to Western diet–induced endothelial cell stiffening compared with age-matched males. Mechanistically, we show that the increased stiffening of the vascular intima in Western diet–fed female mice is accompanied by enhanced epithelial sodium channel (ENaC) activity in endothelial cells (EnNaC). Our data further indicate that: (i) estrogen signaling through estrogen receptor α (ERα) increases EnNaC activity to a larger extent in females compared with males, (ii) estrogen-induced activation of EnNaC is mediated by the serum/glucocorticoid inducible kinase 1 (SGK-1), and (iii) estrogen signaling stiffens endothelial cells when nitric oxide is lacking and this stiffening effect can be reduced with amiloride, an ENaC inhibitor. In aggregate, we demonstrate a sexual dimorphism in obesity-associated endothelial stiffening, whereby females are more vulnerable than males. In females, endothelial stiffening with obesity may be attributed to estrogen signaling through the ERα–SGK-1–EnNaC axis, thus establishing a putative therapeutic target for female obesity-related vascular stiffening.