Background-Angiotensin (Ang) II type 2 (AT 2 ) receptor stimulation results in coronary vasodilation in the rat heart. In contrast, AT 2 receptor-mediated vasodilation could not be observed in large human coronary arteries. We studied Ang II-induced vasodilation of human coronary microarteries (HCMAs). Methods and Results-HCMAs (diameter, 160 to 500 m) were obtained from 49 heart valve donors (age, 3 to 65 years).Ang II constricted HCMAs, mounted in Mulvany myographs, in a concentration-dependent manner (pEC 50 , 8.6Ϯ0.2; maximal effect [E max ], 79Ϯ13% of the contraction to 100 mmol/L K ϩ ). The Ang II type 1 receptor antagonist irbesartan prevented this vasoconstriction, whereas the AT 2 receptor antagonist PD123319 increased E max to 97Ϯ14% (PϽ0.05). The increase in E max was larger in older donors (correlation ⌬E max versus age, rϭ0.47, PϽ0.05). The PD123319-induced potentiation was not observed in the presence of the NO synthase inhibitor L-NAME, the bradykinin type 2 (B 2 ) receptor antagonist Hoe140, or after removal of the endothelium. Ang II relaxed U46619-preconstricted HCMAs in the presence of irbesartan by maximally 49Ϯ16%, and PD123319 prevented this relaxation. Finally, radioligand binding studies and reverse transcription-polymerase chain reaction confirmed the expression of AT 2 receptors in HCMAs. Conclusions-AT 2 receptor-mediated vasodilation in the human heart appears to be limited to coronary microarteries and is mediated by B 2 receptors and NO. Most likely, AT 2 receptors are located on endothelial cells, and their contribution increases with age.

Different types of NPs (nanoparticles) are currently under development for diagnostic and therapeutic applications in the biomedical field, yet our knowledge about their possible effects and fate in living cells is still limited. In the present study, we examined the cellular response of human brain-derived endothelial cells to NPs of different size and structure: uncoated and oleic acid-coated iron oxide NPs (8-9 nm core), fluorescent 25 and 50 nm silica NPs, TiO2 NPs (21 nm mean core diameter) and PLGA [poly(lactic-co-glycolic acid)]-PEO [poly(ethylene oxide)] polymeric NPs (150 nm). We evaluated their uptake by the cells, and their localization, generation of oxidative stress and DNA-damaging effects in exposed cells. We show that NPs are internalized by human brain-derived endothelial cells; however, the extent of their intracellular uptake is dependent on the characteristics of the NPs. After their uptake by human brain-derived endothelial cells NPs are transported into the lysosomes of these cells, where they enhance the activation of lysosomal proteases. In brain-derived endothelial cells, NPs induce the production of an oxidative stress after exposure to iron oxide and TiO2 NPs, which is correlated with an increase in DNA strand breaks and defensive mechanisms that ultimately induce an autophagy process in the cells.

The expression and function in growth and apoptosis of the renin -angiotensin system (RAS) was evaluated in human glioblastoma. Renin and angiotensinogen (AGT) mRNAs and proteins were found by in situ hybridisation and immunohistochemistry in glioblastoma cells. Angiotensinogen was present in glioblastoma cystic fluids. Thus, human glioblastoma cells produce renin and AGT and secrete AGT. Human glioblastoma and glioblastoma cells expressed renin, AGT, renin receptor, AT 2 and/or AT 1 mRNAs and proteins determined by RT -PCR and/or Western blotting, respectively. The function of the RAS in glioblastoma was studied using human glioblastoma cells in culture. Angiotensinogen, des(Ang I)AGT, tetradecapaptide renin substrate (AGT1 -14), Ang I, Ang II or Ang III, added to glioblastoma cells in culture, did not modulate their proliferation, survival or death. Angiotensin-converting enzyme inhibitors did not diminish glioblastoma cell proliferation. However, the addition of selective synthetic renin inhibitors to glioblastoma cells decreased DNA synthesis and viable tumour cell number, and induced apoptosis. This effect was not counterbalanced by concomitant addition of Ang II. In conclusion, the complete RAS is expressed by human glioblastomas and glioblastoma cells in culture. Inhibition of renin in glioblastoma cells may be a potential approach to control glioblastoma cell proliferation and survival, and glioblastoma progression in combination therapy.

USPIO-NP-loaded filopodia were observed to invade the polyester membrane, suggesting that they can be transported by migrating angiogenic brain-derived endothelial cells.