A leading role for the immune system in the pathophysiology of preeclampsia.

Preeclampsia syndrome is characterized by inadequate placentation, because of deficient trophoblastic invasion of the uterine spiral arteries, leading to placental hypoxia, secretion of proinflammatory cytokines, the release of angiogenic and antiangiogenic factors and miRNAs. Although immune-system alterations are associated with the origin of preeclampsia, other factors, including proinflammatory cytokines, neutrophil activation, and endothelial dysfunction, are also related to the pathophysiology of this syndrome. The pathophysiology of preeclampsia may involve several factors, including persistent hypoxia at the placental level and the release of high amounts of STBMs. DAMP molecules released under hypoxic conditions and STBMs, which bind TLRs, may activate monocytes, DCs, NK cells, and neutrophils, promoting persistent inflammatory conditions in this syndrome. The development of hypertension in preeclamptic women is also associated with endothelial dysfunction, which may be mediated by various mechanisms, including neutrophil activation and NET formation. Furthermore, preeclamptic women have higher levels of nonclassic and intermediate monocytes and lower levels of lymphoid BDCA-2(+) DCs. The cytokines secreted by these cells may contribute to the inflammatory process and to changes in adaptive-immune system cells, which are also modulated in preeclampsia. The changes in T cell subsets that may be seen in preeclampsia include low Treg activity, a shift toward Th1 responses, and the presence of Th17 lymphocytes. B cells can participate in the pathophysiology of preeclampsia by producing autoantibodies against adrenoreceptors and autoantibodies that bind the AT1-R.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor.

BACKGROUND AND OBJECTIVE: Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process. MATERIAL AND METHODS: Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period. RESULTS: After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations. CONCLUSION: Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Angiogenic and antiangiogenic balance regulates concomitant antitumoral resistance.

Concomitant antitumoral resistance (CAR), the phenomenon by which the growth of distant secondary tumor implants or metastases in some tumor-bearing hosts is inhibited by the presence of a primary tumor, has been previously ascribed to an antiangiogenic process. Here, we investigated vascular endothelial growth factor (VEGF) and endostatin serum levels in nude or BALB/c mice bearing human lung tumors (Calu-6 and H460) or murine mammary tumors (M3MC, M-234p and M-234m), respectively. In these experimental models we previously found an association between in vivo generation of CAR and in vitro conversion of plasminogen into angiostatin. Serum endostatin level in CAR+ Calu-6-bearing mice was significantly higher than in CAR- H460 counterpart. Sera from mammary tumor-bearing mice showed similar levels of endostatin, regardless of their ability to induce CAR. Conversely, serum VEGF levels in mice bearing CAR+ tumors were lower than those found in CAR- tumor-bearing hosts. Immunostaining with an anti-CD31 antibody revealed that secondary tumors subjected to CAR were significantly less vascularized than primary tumors, while this difference was not observed in CAR- tumors. In vitro studies showed an inhibitory effect of sera from CAR-inducing tumors on endothelial cell proliferation as compared to normal sera, whereas sera from non-CAR-inducing tumors did not alter endothelial proliferation and, in some instances, even caused stimulation of endothelial proliferation. These data suggest that the antiangiogenic mechanism operating in concomitant antitumoral resistance is the result of an increase in the ratio of antiangiogenic/proangiogenic regulators. The levels of the factors involved in this phenomenon can vary in the different tumor models, but the trend favoring the inhibition of angiogenesis is always conserved.