Extracellular carbonic anhydrase mediates hemorrhagic retinal and cerebral vascular permeability through prekallikrein activation


Excessive retinal vascular permeability contributes to the pathogenesis of proliferative diabetic retinopathy and diabetic macular edema, leading causes of vision loss in working-age adults. Using mass spectroscopy–based proteomics, we detected 117 proteins in human vitreous and elevated levels of extracellular carbonic anhydrase-I (CA-I) in vitreous from individuals with diabetic retinopathy, suggesting that retinal hemorrhage and erythrocyte lysis contribute to the diabetic vitreous proteome. Intravitreous injection of CA-I in rats increased retinal vessel leakage and caused intraretinal edema. CA-I–induced alkalinization of vitreous increased kallikrein activity and its generation of factor XIIa, revealing a new pathway for contact system activation. CA-I–induced retinal edema was decreased by complement 1 inhibitor, neutralizing antibody to prekallikrein and bradykinin receptor antagonism. Subdural infusion of CA-I in rats induced cerebral vascular permeability, suggesting that extracellular CA-I could have broad relevance to neurovascular edema. Inhibition of extracellular CA-I and kallikrein-mediated innate inflammation could provide new therapeutic opportunities for the treatment of hemorrhage-induced retinal and cerebral edema.

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Figure 1: Western blot analysis of proteins from vitreous samples.
Figure 2: Intravitreal CA-I induces retinal vascular permeability.
Figure 3: Intravitreal CA-I induces retinal vascular permeability (RVP) via the kallikrein-bradykinin receptor pathway.
Figure 4: Effect of CA-I on vitreous pH and effects of pH on RVP and activity of the components of the kallikrein system.
Figure 5: CA-I increases blood-brain barrier permeability to Evans blue dye.


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We thank X. Chen and D. Bursell for technical assistance. This work was supported in part by the US National Institutes of Health (grants DK 60165, DK 36836, EY011289 and EY014106), the Juvenile Diabetes Research Foundation (1-2005-1047), the Massachusetts Lions Eye Research Fund, the Adler Foundation and the Air Force Office of Scientific Research Medical Free Electron Laser Program (FA9550-040-1-0046).

Author information

B.-B.G. conducted the proteomic and bioinformatic analysis; performed all western blot and in vitro enzymatic analyses, and cerebral vascular permeability experiments; and contributed to manuscript writing. A.C. and S.-E.B. performed retinal permeability analyses, intravitreal injections, and vitreous pH analyses; and assisted in designing the in vivo experiments. S.R. assisted with retinal permeability experiments and coordinated vitreous collection. S.J.F. performed proteome statistical analysis and assisted in editing the manuscript. V.S., M.W. and J.G.F. conducted the OCT measurements, and analyzed and interpreted the results. R.L.A. and P.G.A. provided vitreous samples and conducted the clinical diagnoses. L.P.A. provided vitreous samples and clinical information, and contributed to manuscript writing. E.P.F. designed the entire study, supervised all components of the study, and wrote the manuscript.

Correspondence to Edward P Feener.

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Competing interests

J.G.F. receives royalties from intellectual property licensed by MIT to Carl Zeiss Meditec and LightLab Imaging. E.P.F. and L.P.A. have a pending patent application that includes data from this report.

Supplementary information

Supplementary Fig. 1

Effect of C1-INH on PK activation by FXII in the presence of HK. Kallikrein activity was measured as cleavage of synthetic fluorogenic kallikrein substrate (0.4 mM) on a microplate reader at 37 °C at 15 min. (PDF 23 kb)

Supplementary Fig. 2

Effect of anti-PK antibody on PK activation by FXII in the presence of HK. (PDF 22 kb)

Supplementary Fig. 3

Effect of pH, CA-I and HCO3 on PK activation by FXII in the presence of HK. (PDF 16 kb)

Supplementary Fig. 4

Effect of pH on PK activation by FXII in the presence of HK. **P < 0.01 vs pH 7.4. (PDF 17 kb)

Supplementary Fig. 5

Effect of pH on FXII autoactivation in the absence of PK and HK. (PDF 14 kb)

Supplementary Table 1

Demographics of Study Subjects (PDF 31 kb)

Supplementary Table 2

Vitreous proteome in individuals with NDM, noDR or PDR (PDF 317 kb)

Supplementary Methods (PDF 20 kb)

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Gao, B., Clermont, A., Rook, S. et al. Extracellular carbonic anhydrase mediates hemorrhagic retinal and cerebral vascular permeability through prekallikrein activation. Nat Med 13, 181–188 (2007). https://doi.org/10.1038/nm1534

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