Role of oxidative stress in the control of the TRPP2 channel polycystin-2 in the human syncytiotrophoblast

MONTALBETTI, N., DALGHI, M., REPETTO, M. AND H.F. CANTIELLO

Santiago, Chile

Simposio; 2nd Latino-American Symposium on Placenta & Materno-Fetal Interaction: From Basic to Clinical Research; 2005

Pregnancy is susceptible to oxidative stress (OS) and antioxidant defenses can be altered in response to elevated levels of OS such as gestational diabetes mellitus (GDM), where products of lipid peroxidation may be increased. Growing evidence implicates OS in the pathophysiology of preeclampsia, hydatidiform mole, and free radical-induced birth defects and abortions. TRP channels such as TRPM2, is directly gated by OS agents, including, hydrogen peroxide (H2O2), which stimulates TRPM2 channel activity, in a phenomenon which may be associated with NADH to NAD+ conversion. The human syncytiotrophoblast (hST) expresses abundant polycystin-2 (PC2, TRPP2), a TRP-type Ca2+-permeable non-selective cation channel. Here, we explored the effect of OS in PC2 channel activity of term hST apical membranes. Methods: hST apical membranes were prepared by ultra-centrifugation, and reconstituted lipid bilayer assay chamber to assess cation channel activity. Results: Addition of H2O2 or terbutylic peroxide, rapidly and completely inactivated PC2 channel activity in hST vesicles. To explore whether this effect was mediated by a direct interaction the oxygen reactive species with the channel, or was it mediated by lipid peroxidation, membrane phospholipids were first peroxidized and then channel activity explored in their absence. Conclusions: The data are consistent with a regulatory effect by lipid peroxidation of the PC2 channel, suggesting its potential role as a target of OS in such pathological conditions as GDM, known to induce lipid peroxidation. The study further supports the hypothesis that OS in human pregnancy may be linked to dysregulation of Ca2+ transport by channels such as PC2. Whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus may be required to assess whether PC2 channel function can be restored.defects and abortions. TRP channels such as TRPM2, is directly gated by OS agents, including, hydrogen peroxide (H2O2), which stimulates TRPM2 channel activity, in a phenomenon which may be associated with NADH to NAD+ conversion. The human syncytiotrophoblast (hST) expresses abundant polycystin-2 (PC2, TRPP2), a TRP-type Ca2+-permeable non-selective cation channel. Here, we explored the effect of OS in PC2 channel activity of term hST apical membranes. Methods: hST apical membranes were prepared by ultra-centrifugation, and reconstituted lipid bilayer assay chamber to assess cation channel activity. Results: Addition of H2O2 or terbutylic peroxide, rapidly and completely inactivated PC2 channel activity in hST vesicles. To explore whether this effect was mediated by a direct interaction the oxygen reactive species with the channel, or was it mediated by lipid peroxidation, membrane phospholipids were first peroxidized and then channel activity explored in their absence. Conclusions: The data are consistent with a regulatory effect by lipid peroxidation of the PC2 channel, suggesting its potential role as a target of OS in such pathological conditions as GDM, known to induce lipid peroxidation. The study further supports the hypothesis that OS in human pregnancy may be linked to dysregulation of Ca2+ transport by channels such as PC2. Whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus may be required to assess whether PC2 channel function can be restored.