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Shimin Li, Tracy Nguyen, Joseph Bonanno; CD147 Knockdown Decreases Corneal Lactate Transport and Endothelial Cell Viability. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1658.
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The glycolytic cornea produces large quantities of lactate. Simultaneous export of catabolic lactate is crucial for the maintenance of corneal health, hydration and transparency. The corneal endothelium plays a pivotal role in lactate efflux through transmembrane monocarboxylate transporters (MCTs). Previously, we found that CD147, a multifunctional glycoprotein, is required to sustain the expression of basolateral MCT1 and MCT4. Reports show that CD147 is also involved in regulating cell apoptosis (Chen H, Hum Reprod. 27(6):1568-76, 2012). In this study, we asked if CD147 plays a role in lactate transport and corneal endothelial cell viability.
Fresh rabbit corneas were cultured ex vivo and transfected with 100 nM of CD147 siRNA or scrambled-sequence siRNA using HiperFect transfection reagent. 72 hours post-transfection, the endothelial monolayer was peeled and mounted in a double-sided perfusion chamber. Lactate induced cell acidification (LIA) was measured in response to 30 mM lactate in bicarbonate-free Ringer. In situ cell death elicited by CD147 knockdown was assessed using TUNEL assay.
Steady state endothelial pHi was significantly lower in CD147 knockdown (KD) corneas than control corneas (6.92 vs. 7.09, p<0.02, n=9). When the apical surface was perfused with lactate, the rate and amount of LIA were not significantly different in the KD corneas compared to the control corneas (p<0.06 and p<0.40, respectively). However, when lactate was perfused on the basolateral surface, the rate and amount of LIA in the KD corneas was 2.9 and 2.1 fold less, respectively, in the KD corneas than the control corneas (p<0.01 and p<0.03), consistent with the basolateral location of CD147, MCT1 and MCT4. TUNEL positive cell counts were 1.5% + 0.002 in control corneas and 19.2% + 0.008 in KD corneas respectively (p<0.01, n=6).
CD147 plays a crucial role in the transport of lactate across the corneal endothelium by regulating the expression and function of MCT1 and MCT4. CD147 is also involved in corneal endothelial cell viability.
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