PIGF Involved In Regulation Of The Flt 1/STAT3/ SOCS3 Signaling Pathway In The Pathogenesis Of Preeclampsia

Preeclampsia (PE) is a multisystem disorder associated with maternal hypertension, proteinuria, placental abnormalities and adverse fetal outcomes. However, the pathogenesis of PE is not clear.As a problem that originates from the placenta, Preeclampsia is characterized by an impaired invasion of placenta trophoblasts, which causes a reduced remodeling of the maternal spiral arteries eventually leading to a decrease in blood flow to the placenta. Therefore, endothelial and vascular dysfunction are the key events in the development of preeclampsia, and oxidative stress play an important role in disease development of preeclampsia during different pathological stage.Persistent activation of cell transduction pathway mediates the cascade reaction of downstream signal, and finally induce cellular adaptive changes. Increasing studies have shown that as a direct transcriptional activator of the VEGF gene, STAT3 can upregulate VEGF expression and contribute to tumor angiogenesis, moreover, after combining with Flt-1 receptor, VEGF could stimulate the activator of STAT3.PIGF is a glycoprotein which have a highly homologous with VEGF,so we deduce that PIGF involve the pathogenesis of PE through STAT3 signaling pathways. SOCS3 can attenuates proinflammatory signaling mediated by STAT3 pathway, and it is also showed that SOCS3 is involved in the process of placental vascular remodeling during gestation. Therefore, we speculate that STAT3 pathway play an important role in the process of placental vascular remodeling during gestation, and it is also involved in the pathological development of Preeclampsia. A series of experiments were designed for the study of regulation of STAT 3 and SOCS3 on placental vascular factors in the pathogenesis of PE. Meanwhile, we discussion the regulation of PIGF on Flt-1/STAT3/SOCS3 signaling pathway in onset of preeclampsia.It will enrich and improve the molecular pathogenesis of preeclampsia,and would provide novel targets for prevention and treating of the disease.Method:In this study, PIGF, sFlt-1, MDA and IL-6 content were detected in serum and placenta of PE and control group. The expression and location of Flt-1, STAT3, p-STAT3 and SOCS3 in the placenta were examined by immunochemistry and western-blot. To evaluated the effects of chronic hypoxia on expression of Flt-1、 STAT3、p-STAT3 and SOCS3, primary trophoblast cells from PE and control group were cultivated and exposed to 2.0% O2 to establish the chronic hypoxia cell model. After 48 h’s treatment, cells were collected and subjected to western-blot to detect the expression of Flt-1、STAT3、p-STAT3 and SOCS3. PIGF and sFlt-1 concentration in cultured medium were determined by ELISA. To evaluate the effects of PIGF overexpression on Flt-1/STAT3/SOCS3 pathway, Lentiviras which contains PIGF and GFP recombinant (LV-PIGF-GFP) or only GFP gene (LV-GFP) was used to infect primary trophoblast cells from PE group, respectively, which were defined as experimental group (EG) and negative control (NC). The infection efficiency of lentivirus was measured by GFP fluorescence expression observed under the microscope. Expression of SOCS-3, Flt-1、STAT3、p-STAT3 were analyzed by western blot.Results:1) Compared with the control group, the content of sFlt-1, IL-6 and MDA in the serum and placenta of PE group were significantly increased, but the PIGF level were decreased (P<0.05); The apoptosis of trophoblast cells in PE group was significantly higher than control group (P<0.05); furthermore the increased ROS production and lowered membrane potential were also observed in the mitochondrial of PE group.2) The expression of Flt-1, STAT3 and p-STAT3 in the placenta were observed using Immunofluorescence technique. Flt-1 was mainly distributed in the membrane of trophoblasts,fluorescence intensity of Flt-1 in patients with preeclampsia was decreased significantly.The expression of SOCS3 was found in the membrane of trophoblasts of placenta, fluorescence intensity of SOCS3 in preeclampsia was decreased significantly.The expression of STAT3 was found in the cytoplasm and nucleus of trophoblasts of placenta, and there was no significant difference between PE and control group. Distribution of p-STAT3 was apparently in the nucleus of trophoblasts. Compared with the control group, the reduction of p-STAT3 expression was observed in PE group.3) PIGF level were significantly decreased in PE primary trophoblast cells under hypoxia, and also the expression of Flt-1, p-STAT3 and SOCS3 (P<0.05). But there was no significantly change of STAT3 expression in both group under hypoxia.4) Establishment of PIGF overexpressed primary trophoblast cell models and the expression of Flt-1, STAT3, p-STAT3 and SOCS3 in the cells under hypoxia were examined by western-blot method. Compared with LV-GFP group, the expression of STAT3, Flt-1 and p-STAT3 were upregulated in LV-PIGF-GFP group under hypoxia.Conclusion1) Inflammatory and oxidative stress damage are detected in the serum and placenta of PE patient, and finally induced maternal multisystem dysfunction.2) A similar trend is found in the expression of Flt-1, p-STAT3 and SOCS3 in PE group, and they may get involved in the pathological process of PE.3) Hypoxia can inhibit the activation of STAT3, induce the reduction of PIGF,Flt-l contents, and finally aggravate apoptosis of primary trophoblast cells in PE group. Over-expression of PIGF can stimulate the expression of F1M/STAT3/SOCS3 signal pathway and enhance anti-hypoxia ability of primary trophoblast cells.Conclusively, low levels of P1GF/Flt-1 in maternal circulation are associated with impaired vasculogenesis and angiogenesis, failure of trophoblast invasion, and inappropriate placental development, which induces pregnancy complications. PIGF/Flt-1/STAT 3pathway get involved in the pathogenesis of PE, and the decreased level of PIGF and Flt-1 can interfere with the activation of STAT/SOCS3 pathway, which may induce the overexpression of inflammatory cytokines and exacerbate PE progression. Moreover, the inhibition of STAT/SOCS3 pathway can directly influence the expression of VEGF and Flt-1, and aggravate vasculogenesis dysfunction. PIGF works as the regulator of Flt-1/STAT3/SOCS3 pathway and play an important role in PE disease.