ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: PO0652

Blocking the ACE N-Domain Prevents Salt Sensitivity in Diabetes

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Veiras, Luciana C., Cedars-Sinai Medical Center, Los Angeles, California, United States
  • Bernstein, Ellen A., Cedars-Sinai Medical Center, Los Angeles, California, United States
  • Bernstein, Kenneth E., Cedars-Sinai Medical Center, Los Angeles, California, United States
  • Giani, Jorge F., Cedars-Sinai Medical Center, Los Angeles, California, United States
Background

Angiotensin converting enzyme (ACE) can regulate inflammation independently of angiotensin II production. Specifically, blocking the ACE N-domain results in the accumulation of the anti-inflammatory peptide AcSDKP. We showed that interleukin-6 (IL-6) induces salt sensitivity through an upregulation of the epithelial sodium channel (ENaC) in diabetic mice. Here, we hypothesize that blocking the ACE N-domain reduces renal IL-6 levels and prevents salt sensitivity in diabetes.

Methods

7-mo-old diabetic db/db mice lacking a functional ACE N-domain (db-nko) and db/db controls (db) were exposed to a high salt diet (HS, NaCl 4%w/w) for 4 weeks (n=6).

Results

Despite similar hyperglycemia and body weight, after HS, db-nko displayed lower mean arterial pressure (MAP) (107±5 vs. 123±4 mmHg, P<0.01), less expression of αENaC subunit (0.8±0.3 vs. 1.4±0.3 A.U., P<0.05), and lower renal IL-6 levels (112±16 vs. 270±17 pg/mg kidney, P<0.01) compared to db mice. Flow cytometry analysis of renal macrophages showed that db-nko mice have lower M1 (CD45+F4/80+CD80+) to M2 (CD45+F4/80+CD206+) ratio compared to db (2.4±0.6 vs. 4.8±0.7, P<0.05). Further, renal macrophages (3x104) were isolated by flow cytometry cell sorting, cultured for 16h, and IL-6 assessed in the culture media by ELISA. Macrophages from db-nko release significantly less IL-6 compared to db macrophages (2±1 vs. 7±2 pg/ml, P<0.01). To evaluate the role of AcSDKP, an additional group of db-nko were treated for 8 weeks with S17092, an inhibitor of prolyl-oligopeptidase that forms AcSDKP. After HS, MAP, renal αENaC expression, IL-6, and the macrophage M1/M2 ratio of db-nko+S17092 were similar to db mice. Finally, to evaluate whether the absence of the ACE N-domain affects immune or non-immune renal cells, db mice were transplanted with a bone marrow (BM) of db-nko while db-nko received a db BM. Strikingly, db-nko with db BM developed salt sensitivity but db with db-nko BM remained salt resistant (MAP after HS: 121±8 vs. 107±4 mmHg, P<0.05). The absence of salt sensitivity in db with db-nko BM was associated with less IL-6 levels and lower M1/M2 macrophage ratio in the kidney.

Conclusion

Thus, blocking the ACE N-domain and the consequent AcSDKP accumulation in immune cells, polarize macrophages towards an M2 phenotype resulting in less renal inflammation and no salt sensitivity in diabetes.

Funding

  • Other NIH Support