Role of nitric oxide and metallothionein in cytotoxic activity of cadmium in CACO-2 cells
Acta Medica Iranica
سال 2018 شماره 56
Malekmarzban, F., Seyedabadi, M., Ghahremani, M.H., Aliebrahimi, S., Habibollahi, P., Tavajohi, S., Ostad, S.N.
2 از 7
Cadmium (Cd) induces carcinogenicity and cytotoxicity through a variety of mechanisms. Metallothioneins (MTs) play critical roles in metal detoxification and radical scavenging. Here we evaluated the possible involvement of NO and MT in Cd-induced toxicity and resistance development. By utilizing Cd-resistant Caco-2 cells as a model of chronic exposure to Cadmium, we observed that Cd decreased Caco-2 cell proliferation, whereas Cd-resistant cells showed a lower sensitivity to Cd cytotoxicity. L-NAME as an iNOS inhibitor and cPTIO as an NO scavenger induced a significant reduction in Cd-mediated toxicity of parent Caco-2 in spite of resistant cells. In resistant cells, iNOS mRNA expression was declined; however, MT protein synthesis was increased following acute and chronic Cd exposure. It seems that NO synthesis involves in Cd-induced cytotoxicity, while elevated MT expression is associated with Cd detoxification and resistance. © 2018 Tehran University of Medical Sciences. All rights reserved.
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Formation of nanosuspensions in bottom-up approach: theories and optimization
DARU Journal of Pharmaceutical Sciences
2019 شماره 235
Ali Ahmadi TehraniMohammad Mahdi OmranpoorAlireza VatanaraMohammad SeyedabadiVahid Ramezani
4 از 5
Nanosuspensions, liquid dispersions with nanometer size distribution, are becoming trendy in pharmaceutical practice to formulate poorly water-soluble drugs and to enhance their bioavailability. Generally, nanosuspensions are produced in two main approaches; top-down or bottom-up. The former is based on size-reduction of large particles via milling or high pressure homogenization. The latter is focused on the mechanisms of nucleation and particle growth.
In this review, the critical factors influencing the kinetics or dynamics of nucleation and growth are discussed. Subsequently, the mechanisms of nanosuspension instability as well as strategies for stabilization are elaborated. Furthermore, the effects of stabilizers on key parameters of instability as well as the process of choosing an appropriate stabilizer is discussed.
Steric and electrostatic stabilizations or combination of them is essential for nanosuspensions formulation to prevent coagulation. Accordingly, some characteristics of stabilizers play critical role on stability and optimization of nanosuspensions; i.e., HLB and concentration. Nevertheless, after reviewing various articles, it is ascertained that each formulation requires individual selection of surfactants according to the parameters of the particle surface and the medium.
Based on the results, application of excipients such as stabilizers requires proper optimization of type and concentration. This implies that each formulation requires its own optimization process.
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Biased signaling of G protein coupled receptors (GPCRs): Molecular determinants of GPCR/transducer selectivity and therapeutic potential
Pharmacology & Therapeutics
Mohammad Seyedabadi, Mohammad Hossein Ghahremani, Paul R. Albert
1 از 3
G protein coupled receptors (GPCRs) convey signals across membranes via interaction with G proteins. Originally, an individual GPCR was thought to signal through one G protein family, comprising cognate G proteins that mediate canonical receptor signaling. However, several deviations from canonical signaling pathways for GPCRs have been described. It is now clear that GPCRs can engage with multiple G proteins and the line between cognate and non-cognate signaling is increasingly blurred. Furthermore, GPCRs couple to non-G protein transducers, including β-arrestins or other scaffold proteins, to initiate additional signaling cascades.
Receptor/transducer selectivity is dictated by agonist-induced receptor conformations as well as by collateral factors. In particular, ligands stabilize distinct receptor conformations to preferentially activate certain pathways, designated ‘biased signaling’. In this regard, receptor sequence alignment and mutagenesis have helped to identify key receptor domains for receptor/transducer specificity. Furthermore, molecular structures of GPCRs bound to different ligands or transducers have provided detailed insights into mechanisms of coupling selectivity. However, receptor dimerization, compartmentalization, and trafficking, receptor-transducer-effector stoichiometry, and ligand residence and exposure times can each affect GPCR coupling. Extrinsic factors including cell type or assay conditions can also influence receptor signaling. Understanding these factors may lead to the development of improved biased ligands with the potential to enhance therapeutic benefit, while minimizing adverse effects.
In this review, evidence for ligand-specific GPCR signaling toward different transducers or pathways is elaborated. Furthermore, molecular determinants of biased signaling toward these pathways and relevant examples of the potential clinical benefits and pitfalls of biased ligands are discussed.
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