Limits...
Plasma Kallikrein-Kinin System as a VEGF-Independent Mediator of Diabetic Macular Edema

View Article: PubMed Central - PubMed

ABSTRACT

This study characterizes the kallikrein-kinin system in vitreous from individuals with diabetic macular edema (DME) and examines mechanisms contributing to retinal thickening and retinal vascular permeability (RVP). Plasma prekallikrein (PPK) and plasma kallikrein (PKal) were increased twofold and 11.0-fold (both P < 0.0001), respectively, in vitreous from subjects with DME compared with those with a macular hole (MH). While the vascular endothelial growth factor (VEGF) level was also increased in DME vitreous, PKal and VEGF concentrations do not correlate (r = 0.266, P = 0.112). Using mass spectrometry–based proteomics, we identified 167 vitreous proteins, including 30 that were increased in DME (fourfold or more, P < 0.001 vs. MH). The majority of proteins associated with DME displayed a higher correlation with PPK than with VEGF concentrations. DME vitreous containing relatively high levels of PKal and low VEGF induced RVP when injected into the vitreous of diabetic rats, a response blocked by bradykinin receptor antagonism but not by bevacizumab. Bradykinin-induced retinal thickening in mice was not affected by blockade of VEGF receptor 2. Diabetes-induced RVP was decreased by up to 78% (P < 0.001) in Klkb1 (PPK)-deficient mice compared with wild-type controls. B2- and B1 receptor–induced RVP in diabetic mice was blocked by endothelial nitric oxide synthase (NOS) and inducible NOS deficiency, respectively. These findings implicate the PKal pathway as a VEGF-independent mediator of DME.

No MeSH data available.


Effects of intravitreal injection of human DME vitreous on RVP in diabetic rats. Human vitreous samples, including DME patient ID #12 with relatively PK↑ vit (PPK 91.6 nmol/L [18.1-fold increase in PKal], VEGF 114 pg/mL), DME patient ID #13 with VEGF↑ vit (PPK 25.2 nmol/L [2.3-fold increase in PKal], VEGF 2,864 pg/mL), and control MH vitreous with low levels of both PKal and VEGF, were injected into rat vitreous. Coinjections were performed with Hoe140/desArg10-Hoe140 (desHoe140) and bevacizumab (Bev), as indicated, and RVP was measured by vitreous fluorophotometry at 40 min (A) and 48 h (B) postinjection. a.u., arbitrary units.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4587649&req=5

Figure 4: Effects of intravitreal injection of human DME vitreous on RVP in diabetic rats. Human vitreous samples, including DME patient ID #12 with relatively PK↑ vit (PPK 91.6 nmol/L [18.1-fold increase in PKal], VEGF 114 pg/mL), DME patient ID #13 with VEGF↑ vit (PPK 25.2 nmol/L [2.3-fold increase in PKal], VEGF 2,864 pg/mL), and control MH vitreous with low levels of both PKal and VEGF, were injected into rat vitreous. Coinjections were performed with Hoe140/desArg10-Hoe140 (desHoe140) and bevacizumab (Bev), as indicated, and RVP was measured by vitreous fluorophotometry at 40 min (A) and 48 h (B) postinjection. a.u., arbitrary units.

Mentions: The potential effects of VEGF and BK peptides in human vitreous on the RVP were examined in the rat model of RVP described above. We selected two human vitreous DME samples, as indicated in Fig. 1H, patient ID #12, with relatively high PKal and low VEGF (PK↑ vit; PPK 91.6 nmol/L [18.1-fold increase in PKal], VEGF 114 pg/mL) and patient ID #13, with low PKal and high VEGF (VEGF↑ vit; PPK 25.2 nmol/L [2.3-fold increase in PKal], VEGF 2,864 pg/mL), and a control MH vitreous with low levels of both PKal and VEGF. Ten microliters of human vitreous fluid was injected into the vitreous of DM rats in the presence or absence of coinjections with bevacizumab or the combination of Hoe140 and des-Arg10-Hoe140. At 40 min postinjection, PK↑ vit did not increase RVP, whereas VEGF↑ vit significantly enhanced RVP (1.41-fold, P < 0.05) compared with vitreous from the MH patient. The VEGF↑ vit–induced response was blocked by bevacizumab (P < 0.01) but not affected by Hoe140/des-Arg10-Hoe140 (Fig. 4A). In contrast, at 48 h, RVP was increased by intravitreal injection of PKal↑ vit (1.6-fold, P < 0.01), which was suppressed by Hoe140/des-Arg10-Hoe140 (P < 0.01), but not by bevacizumab (P = not significant [NS]). RVP that was increased at 40 min by intravitreal injection of VEGF↑ vit returned to baseline at 48 h postinjection (P = NS vs. MH) (Fig. 4B).


Plasma Kallikrein-Kinin System as a VEGF-Independent Mediator of Diabetic Macular Edema
Effects of intravitreal injection of human DME vitreous on RVP in diabetic rats. Human vitreous samples, including DME patient ID #12 with relatively PK↑ vit (PPK 91.6 nmol/L [18.1-fold increase in PKal], VEGF 114 pg/mL), DME patient ID #13 with VEGF↑ vit (PPK 25.2 nmol/L [2.3-fold increase in PKal], VEGF 2,864 pg/mL), and control MH vitreous with low levels of both PKal and VEGF, were injected into rat vitreous. Coinjections were performed with Hoe140/desArg10-Hoe140 (desHoe140) and bevacizumab (Bev), as indicated, and RVP was measured by vitreous fluorophotometry at 40 min (A) and 48 h (B) postinjection. a.u., arbitrary units.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4587649&req=5

Figure 4: Effects of intravitreal injection of human DME vitreous on RVP in diabetic rats. Human vitreous samples, including DME patient ID #12 with relatively PK↑ vit (PPK 91.6 nmol/L [18.1-fold increase in PKal], VEGF 114 pg/mL), DME patient ID #13 with VEGF↑ vit (PPK 25.2 nmol/L [2.3-fold increase in PKal], VEGF 2,864 pg/mL), and control MH vitreous with low levels of both PKal and VEGF, were injected into rat vitreous. Coinjections were performed with Hoe140/desArg10-Hoe140 (desHoe140) and bevacizumab (Bev), as indicated, and RVP was measured by vitreous fluorophotometry at 40 min (A) and 48 h (B) postinjection. a.u., arbitrary units.
Mentions: The potential effects of VEGF and BK peptides in human vitreous on the RVP were examined in the rat model of RVP described above. We selected two human vitreous DME samples, as indicated in Fig. 1H, patient ID #12, with relatively high PKal and low VEGF (PK↑ vit; PPK 91.6 nmol/L [18.1-fold increase in PKal], VEGF 114 pg/mL) and patient ID #13, with low PKal and high VEGF (VEGF↑ vit; PPK 25.2 nmol/L [2.3-fold increase in PKal], VEGF 2,864 pg/mL), and a control MH vitreous with low levels of both PKal and VEGF. Ten microliters of human vitreous fluid was injected into the vitreous of DM rats in the presence or absence of coinjections with bevacizumab or the combination of Hoe140 and des-Arg10-Hoe140. At 40 min postinjection, PK↑ vit did not increase RVP, whereas VEGF↑ vit significantly enhanced RVP (1.41-fold, P < 0.05) compared with vitreous from the MH patient. The VEGF↑ vit–induced response was blocked by bevacizumab (P < 0.01) but not affected by Hoe140/des-Arg10-Hoe140 (Fig. 4A). In contrast, at 48 h, RVP was increased by intravitreal injection of PKal↑ vit (1.6-fold, P < 0.01), which was suppressed by Hoe140/des-Arg10-Hoe140 (P < 0.01), but not by bevacizumab (P = not significant [NS]). RVP that was increased at 40 min by intravitreal injection of VEGF↑ vit returned to baseline at 48 h postinjection (P = NS vs. MH) (Fig. 4B).

View Article: PubMed Central - PubMed

ABSTRACT

This study characterizes the kallikrein-kinin system in vitreous from individuals with diabetic macular edema (DME) and examines mechanisms contributing to retinal thickening and retinal vascular permeability (RVP). Plasma prekallikrein (PPK) and plasma kallikrein (PKal) were increased twofold and 11.0-fold (both P &lt; 0.0001), respectively, in vitreous from subjects with DME compared with those with a macular hole (MH). While the vascular endothelial growth factor (VEGF) level was also increased in DME vitreous, PKal and VEGF concentrations do not correlate (r = 0.266, P = 0.112). Using mass spectrometry&ndash;based proteomics, we identified 167 vitreous proteins, including 30 that were increased in DME (fourfold or more, P &lt; 0.001 vs. MH). The majority of proteins associated with DME displayed a higher correlation with PPK than with VEGF concentrations. DME vitreous containing relatively high levels of PKal and low VEGF induced RVP when injected into the vitreous of diabetic rats, a response blocked by bradykinin receptor antagonism but not by bevacizumab. Bradykinin-induced retinal thickening in mice was not affected by blockade of VEGF receptor 2. Diabetes-induced RVP was decreased by up to 78% (P &lt; 0.001) in Klkb1 (PPK)-deficient mice compared with wild-type controls. B2- and B1 receptor&ndash;induced RVP in diabetic mice was blocked by endothelial nitric oxide synthase (NOS) and inducible NOS deficiency, respectively. These findings implicate the PKal pathway as a VEGF-independent mediator of DME.

No MeSH data available.