(545.2) Angiotensin-(1-7) Restores Gut Barrier Integrity and Ameliorates Systemic Inflammation in Aging

Poster Board Number: B185

Kishore Chittimalli (North Dakota State University), Jesmin Jahan (North Dakota State University), Anil Sakamuri (North Dakota State University), Yagna Jarajapu (North Dakota State University)

Background: Advancing of age decreases the barrier properties of intestinal epithelium which leads to sterile systemic inflammation. Chronic low-grade chronic inflammation is an underlying cause for the age-related comorbidities such as cardiovascular disorders. Renin Angiotensin System (RAS) plays an important role in the homeostasis of cardiovascular functions however, the role of RAS in the aging gut is poorly studied. The protective axis of RAS, which constitutes Angiotensin converting enzyme-2 (ACE2)/ Angiotensin-(1-7) (Ang-(1-7))/Mas receptor (MasR) is known to be counter-regulatory to the classical axis, ACE/Ang II/AT1 receptor (AT1R). This study tested the hypothesis that leaky gut with aging is associated with ACE2/ACE imbalance and that activation of MasR with Ang-(1-7) would restore gut barrier integrity and ameliorates systemic inflammation.

Methods: Study was carried out in Young (3-4 months) and Old (20-24 months) male mice. ACE and ACE2 enzyme activities were evaluated in the colon. Gene and protein expressions of RAS components were determined by western blotting. Ang-(1-7) was administered by subcutaneous osmotic pump (1 µg/Kg/min) for four weeks and the gut permeability was evaluated by using FITC-dextran. Colon wall integrity was evaluated by immunohistochemistry of claudin 1 and occludin. Zonulin-1, IL-6, and TNFα were analyzed in the plasma. A779, MasR antagonist, was administered by an osmotic pump in selected experiments (1 µg/Kg/min, subcutaneous).

Results: ACE2 protein and activity were decreased in Old group while that of ACE were increased (n=6) (n=8) in the colon of the Old mice compared to the Young. Protein expression of both AT1R and MasR was higher while that of AT2R was lower in the Old (Plt;0.05, n=8). Protein expression of ACE2, ACE AT1R and MasR in the Old colons were restored to Young levels by treatment with Ang-(1-7). Gut permeability was higher in Old mice (Plt;0.01 vs Young, n=6) that was reversed by Ang-(1-7). The beneficial effect of Ang-(1-7) was abolished by concurrent administration of A779. Hematoxylin amp; Eosin staining revealed that aging was associated with atrophied villi in the gut wall that was normalized by Ang-(1-7). Gene expression of claudin 1 and occludin were lower in the Old colon wall that were restored by Ang-(1-7) and similar observations were made by immunohistochemistry. Importantly, plasma levels of Zonulin-1, (Plt;0.01) IL-6 and TNFα (Plt;0.05) (n=8) were higher in the Old group compared to the Young, which were lowered by Ang-(1-7) (n=5).

Conclusion: These results suggest that activation of MasR ameliorates aging-associated systemic inflammation by restoring gut barrier integrity, which at least in part contributes to the cardiovascular-protective functions.

This study is partly supported by the National Institute of Aging AG056881.