Effect of PAO (phenylarsine oxide) on the Inhibitory Effect of Insulin and IGF-1 on Insulin Release from INS-1 Cells

Abstract

Abstract. Phenylarsine oxide (PAO) which complexes vicinal thiol groups is a valuable pharmacological tool to investigate the interaction of peptides such as insulin with their receptors and the signal transduction from the receptor to the cell interior. This tool was now used to elucidate the inhibitory effects of insulin and IGF-1 on insulin secretion via their receptors. Insulin and IGF-1 inhibited insulin release from INS-1 cells, an insulin secreting cell line. PAO was able to reverse this inhibitory effect of both hormones. Dimercaptopropanol (DMP), which is well known to antagonize PAO effects, inhibited the abolishment of PAO effect on the inhibitory effect of insulin and IGF-1 regarding insulin release. Membrane bound GLUT2 in INS-1 cells was increased by either insulin and IGF-1 which is counteracted by PAO. Thus the inhibitory effect of insulin and IGF-1 on insulin release is operative and can be disturbed by a thiol interacting compound such as PAO. This may happen at the receptor level or at the sub-receptor level. [6][7][8] e.g. in the presence of vanadate; PAO thereby probably bypasses the direct effects on the insulin receptor and will interact with the components of insulin signal transduction [9,10]. With respect to biological effects there is an (a) Inhibition of insulin effect on various parameters and enzymes (fructose 2,6-biphosphate, phosphofructokinase, glucokinase, glycolysis, glycogen synthesis, amino acid transport, glycogenolysis, proteolysis) (b) Inhibition of glucose transport even under conditions when insulin receptor binding/autophosphorylation is not influenced [11][12][13]; inhibition of IGF-1 -induced glucose transport (c) Decrease in GLUT4 [14], albeit no down-regulation of the GLUT1 transporter and inhibition of the insulin-induced dephosphorylation of GLUT4 (d) Increase in amino acid uptake [15] (e) Inhibition of the insulin-induced PP-1 activation and inhibition of phosphotyrosine phosphatase (GAP-phosphorylation on tyrosine (p21 ras-GTPase activation protein), increased GAP-association with the insulin receptor, inhibition of insulininduced p21 ras activation) [16] (f) inhibition of PI3-kinase a which is recruited from IRS-1 (insulin receptor substrate 1) tyrosine phosphorylation [17].

Central Nervous System Delivery of Intranasal Insulin: Mechanisms of Uptake and Effects on Cognition

“…These included agents such as phenylarsine oxide, which has effects on N-type Ca 2+ channel currents and phosphatidylinositol 4-kinase, an important component of the 4,5-biphosphate signal pathway that blocks receptor-mediated transcytosis. Phenylarsine oxide has also been shown to inhibit insulin-stimulated glucose transport without affecting insulin binding and tyrosine kinase activity of the insulin receptor, and it is capable of promoting insulin secretion from INS-1 cells in the presence of insulin or IGF-1, factors known to inhibit insulin release [36]. Verapamil, the L- and T-type Ca 2+ channel blocker, which also inhibits P-glycoprotein, the ATP-dependent drug transport protein, also increased 125 I-insulin uptake.…”

Posttranslational Modification of Human Glyoxalase 1 Indicates Redox-Dependent Regulation

“…Due to the conserved tertiary structure of the vicinal disulfide turn and the dramatic change that can be expected upon reduction of it, this structural element was suggested to act as a redox-activated conformational switch [45]. Disruption of such thiols was shown to inactivate the redox-sensitive protein phosphatase [47] as well as squalene monooxygenase [48] and affected the function of many other proteins [45], [49], [50].…”

Role of Disulfide Bonds in Activity and Stability of Tigerinin-1R

“…None of the peptides exhibited hemolysis against human red blood cells at a concentration of 250 μM after 2 h of incubation at 37 °C, as the calculated hemolysis rate was less than 2% ( Figure 2 A). The rat insulinoma INS-1 cell line, which is widely used in insulin secretion studies, has been used as a model for the in vitro study of biological activities of tigerinin analogs [ 25 , 26 , 27 ]. As shown in Figure 2 B, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tests confirmed that no tigerinin peptide exhibited obvious cytotoxicity against INS-1 cells at concentrations of 10 −8 , 10 −6 , and 10 −4 M after incubation for 24 h at 37 °C.…”