Effect of prorenin peptide vaccine on the early phase of diabetic retinopathy in a murine model of type 2 diabetes.

Harumasa Yokota,Satoru Yamagami,Hiroki Hayashi,Hironori Nakagami,Taiji Nagaoka,Akifumi Kushiyama,Junya Hanaguri,Alfred S Lewin

doi:10.1371/journal.pone.0262568

Harumasa Yokota, Satoru Yamagami + Show 6 more

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https://doi.org/10.1371/journal.pone.0262568

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Abstract

Prorenin is viewed as an ideal target molecule in the prevention of diabetic retinopathy. However, no drugs are available for inhibiting activation of prorenin. Here, we tested the effect of a prorenin peptide vaccine (VP) in the retina of a murine model of type 2 diabetes (T2D). To choose the optimal vaccine, we selected three different epitopes of the prorenin prosegment (E1, E2, and E3) and conjugated them to keyhole limpet hemocyanin (KLH). We injected C57BL/6J mice twice with KLH only (as a control vaccine), E1 conjugated with KLH (E1-KLH), E2-KLH, or E3-KLH and compared antibody titers. E2-KLH showed the highest antibody titer and specific immunoreactivity of anti-sera against prorenin, so we used E2-KLH as VP. Then, we administered injections to the non-diabetic db/m and diabetic db/db mice, as follows: db/m + KLH, db/db + KLH, and db/db + VP. Retinal blood flow measurement with laser speckle flowgraphy showed that the impaired retinal circulation response to both flicker light and systemic hyperoxia in db/db mice improved with VP. Furthermore, the prolonged implicit time of b-wave and oscillatory potentials in electroretinography was prevented, and immunohistochemical analysis showed reduced microglial activation, gliosis, and vascular leakage. The enzyme-linked immunosorbent spot assay confirmed vaccinated mice had no auto-immune response against prorenin itself. The present data suggest that vaccination against prorenin is an effective and safe measure against the early pathological changes of diabetic retinopathy in T2D.

Highlights

Prorenin is the most upstream protein in the renin-angiotensin system (RAS)
To evaluate the specific reactivity of prorenin peptide vaccine with the full length of prorenin, we performed immunoblotting analysis by using sera obtained from the mice immunized with E2-keyhole limpet hemocyanin (KLH) (Fig 2B)
We found no difference in the amplitude of sum of the OPs (SOPs), the implicit time of SOPs was significantly longer in db/db + KLH than in db/m + KLH but was significantly shorter in db/db + VP than in db/db + KLH (Fig 6E)

Summary

Introduction

Prorenin is the most upstream protein in the renin-angiotensin system (RAS). Until the early 2000s, prorenin was viewed as an inactive form of renin; the findings of two studies on prorenin published in 2003 and 2004 [1, 2] greatly changed the situation.

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