1. β-Arrestin-Biased Agonist Targeting the Brain AT1R (Angiotensin II Type 1 Receptor) Increases Aversion to Saline and Lowers Blood Pressure in Deoxycorticosterone Acetate-Salt Hypertension
Mario Zanaty, et al. Hypertension. 2021 Feb;77(2):420-431. doi: 10.1161/HYPERTENSIONAHA.120.15793. Epub 2020 Nov 30.
Activation of central AT1Rs (angiotensin type 1 receptors) is required for the increased blood pressure, polydipsia, and salt intake in deoxycorticosterone acetate (DOCA)-salt hypertension. TRV120027 (TRV027) is an AT1R-biased agonist that selectively acts through β-arrestin. We hypothesized that intracerebroventricular administration of TRV027 would ameliorate the effects of DOCA-salt. In a neuronal cell line, TRV027 induced AT1aR internalization through dynamin and clathrin-mediated endocytosis. We next evaluated the effect of chronic intracerebroventricular infusion of TRV027 on fluid intake. We measured the relative intake of water versus various saline solutions using a 2-bottle choice paradigm in mice subjected to DOCA with a concomitant intracerebroventricular infusion of either vehicle, TRV027, or losartan. Sham mice received intracerebroventricular vehicle without DOCA. TRV027 potentiated DOCA-induced water intake in the presence or absence of saline. TRV027 and losartan both increased the aversion for saline-an effect particularly pronounced for highly aversive saline solutions. Intracerebroventricular Ang (angiotensin) II, but not TRV027, increased water and saline intake in the absence of DOCA. In a separate cohort, blood pressure responses to acute intracerebroventricular injection of vehicle, TRV, or losartan were measured by radiotelemetry in mice with established DOCA-salt hypertension. Central administration of intracerebroventricular TRV027 or losartan each caused a significant and similar reduction of blood pressure and heart rate. We conclude that administration of TRV027 a selective β-arrestin biased agonist directly into the brain increases aversion to saline and lowers blood pressure in a model of salt-sensitive hypertension. These data suggest that selective activation of AT1R β-arrestin pathways may be exploitable therapeutically.
2. Selective peptide and nonpeptide ligands differentially bind to angiotensin II AT2 receptor and a non-angiotensin II CGP42112 binding site
G M Ciuffo, J M Saavedra J Pharmacol Exp Ther. 1995 Sep;274(3):1129-34.
[125I]CGP42112 [Nic-Tyr-(epsilon-CBZ (benzyloxycarbonyl)-Arg)Lys-His-Pro-Ile] does not only recognize angiotensin II AT2 receptors, but has also the capacity to label a high-affinity, non-angiotensin II binding site, selectively associated with macrophages and activated microglia. We have searched for the structural requirements of the novel CGP42112 binding site, and compared these with the requirements for binding to the angiotensin II AT2 site. We designed a series of CGP42112 analogs and evaluated the new compounds by using binding assays on rat spleen (CGP42112 site) and rat fetal (angiotensin II AT2 site) membranes. The non-peptidic analog Z-Arg(Pmc)OH (N alpha CBZ-NG-2,2,5,7,8-pentamethylchroman-6-sulphonyl-L-Arg), the side chain of CGP42112 substituted on the guanidinium group, was selective in recognizing the CGP42112 site, and did not displace binding from the angiotensin II AT2 site. This is a potential lead compound for development of CGP42112 site-selective analogs. Conversely, the CGP42112 analog lacking the CBZ-group (Nic-Tyr-(Ac-Arg)Lys-His-ProOH, III) and the peptide Nic-Tyr-Lys-His-Ala-HisOH (VI), were selective for the angiotensin II AT2 site, and recognized the CGP42112 site poorly. Our results demonstrate that the structural requirements for the nonangiotensin II CGP42112 and the angiotensin II AT2 binding sites are different. We propose that the CBZ group and the free carboxyl terminal group, together with their spatial orientation, are key components of the molecule for the interaction in the non-angiotensin CGP42112 binding pocket.
3. Hypocrellin A-based photodynamic action induces apoptosis in A549 cells through ROS-mediated mitochondrial signaling pathway
Shanshan Qi, Lingyuan Guo, Shuzhen Yan, Robert J Lee, Shuqin Yu, Shuanglin Chen Acta Pharm Sin B. 2019 Mar;9(2):279-293. doi: 10.1016/j.apsb.2018.12.004. Epub 2018 Dec 15.
Over recent decades, many studies have reported that hypocrellin A (HA) can eliminate cancer cells with proper irradiation in several cancer cell lines. However, the precise molecular mechanism underlying its anticancer effect has not been fully defined. HA-mediated cytotoxicity and apoptosis in human lung adenocarcinoma A549 cells were evaluated after photodynamic therapy (PDT). A temporal quantitative proteomics approach by isobaric tag for relative and absolute quantitation (iTRAQ) 2D liquid chromatography with tandem mass spectrometric (LC-MS/MS) was introduced to help clarify molecular cytotoxic mechanisms and identify candidate targets of HA-induced apoptotic cell death. Specific caspase inhibitors were used to further elucidate the molecular pathway underlying apoptosis in PDT-treated A549 cells. Finally, down-stream apoptosis-related protein was evaluated. Apoptosis induced by HA was associated with cell shrinkage, externalization of cell membrane phosphatidylserine, DNA fragmentation, and mitochondrial disruption, which were preceded by increased intracellular reactive oxygen species (ROS) generations. Further studies showed that PDT treatment with 0.08 µmol/L HA resulted in mitochondrial disruption, pronounced release of cytochrome c, and activation of caspase-3, -9, and -7. Together, HA may be a possible therapeutic agent directed toward mitochondria and a promising photodynamic anticancer candidate for further evaluation.
