Diphenyleneiodonium

That the oxidative burst is directly involved in the chemical defense of these algae is clear. This reaction can be inhibited by diphenyleneiodonium, a suicide inhibitor of NADPH-oxidase which suppresses both the production of reactive oxygen species and the natural resistance to epiphytic bacteria. In addition a role in the defense against endophytes was indicated, since pre-treatment with oligomeric guluronates resulted in decreased infection of L. digitata with the pathogen Laminariocolax tomentosoides [141]. 

McGuire, J., Anderson, D. J., MacDonald, B. J., Narayanasami, R., Bennett, B. M., Inhibition of NADPH-cytochrome P450 reductase and glyceryl trinitrate biotransformation by diphenyleneiodonium sulfate. 

Rashid R, Langfinger D, Wagner R, Schuchmann H-P, von Sonntag C (1999) Bleomycin vs. OH-radi-cal-induced malonaldehydic-product formation in DNA. Int J Radiat Biol 75 110-109 Razskazovskiy Y (2003) Radiation-activated nuclease activity of o,o -diphenyleneiodonium cations (DPI) a reductively initiated chain reaction involving the Cl chemistry. Radiat Res... 

Fig. 1.5 Effect of iV-acetyl-L-cysteine (NAC) and diphenyleneiodonium (DPI) on Gia-2 and Gioc-3 protein expression in vascular smooth muscle cells (VSMC) from 12 week-old SHR and age-matched WKY rats. Confluent VSMC from SHR and WKY rats were treated with 20 mM NAC (A) or 10 pM DPI (B) for 24 hours at 37 °C. Membrane proteins (30 pg) were separated and transferred to nitrocellulose, which was immunoblotted with antibodies AS/7 and EC/1 against Gioc-2 (A) and Gioc-3 (B), respectively, as described earlier (Lappas et al. 2005). The blots are representative of five separate experiments. The graphs in the lower panel show quantification of protein bands by densitometric scanning. The results are expressed as percentage of WKY control which has been taken as 100%. Values are mean S.E.M of five separate experiments. P < 0.05 versus WKY, < 0.01 versus SHR.

Using the cyt P450 substrate, 7-ethoxyresorufm (7-ER) and the flavoprotein inhibitor diphenyleneiodonium (DPI), it was reported that a substantial inhibition of GTN-induced relaxation occurred and these compounds also reduced cGMP accumulation and inhibited transformation of GTN to 1,2-GDN [63,65]. 

Weir, E., Wyatt, CN, Reeve, HL, Huang, J, Archer, SL, and Peers, C (1994). Diphenyleneiodonium inhibits both potassium and calcium currents in isolated pulmonary artery smooth muscle cells. J Appl Physiol 76(6) 2611-2615. 

The most important representative of cyclic iodonium salts, the dibenziodolium or diphenyleneiodonium (DPI) cation 238, known in the form of iodide, chloride, hydrosulfate, hexafluorophosphate, or tetrafluoroborate salts, can be obtained by three different procedures (A, B and C) summarized in Scheme 2.71. Method A, originally developed by Mascarelli and Benati in 1909 [355], uses 2,2 -diaminodiphenyl (235) as the starting material, which upon diazotization with sodium nitrite in a hydrochloric acid solution followed by potassium iodide addition, gives DPI 238 as iodide salt. A similar reaction starting from 2-amino-2 -iododiphenyl 236 affords DPI as hexafluorophosphate or tetrafluoroborate in excellent yields (Method B) [356]. The third method involves the peracetic oxidation of 2-iodobiphenyl (237) to an iodine(III) intermediate that then cyclizes in acidic solution (Method C) [357]. More recently, these methods were used to prepare the tritium labeled DPI and of its 4-nitro derivative [358]. 

Exposure of foetal sheep pulmonary artery smooth muscle cells to endothelin-1 resulted in increases in superoxide production and viable foetal pulmonary artery smooth muscle cells after 72 h (Wedgwood et al. 2001). These increases were prevented by pre-treatment with the ETa receptor agonist PD-156707 (1 /iM). Treatment with pertussis toxin blocked the effects of endothelin-1. Wortman-nin, LY-294002, diphenyleneiodonium, 4-(2-amino-ethyl)benzenesulphonyl fluoride, and apocynin also prevented the endothelin-1-mediated increases in superoxide production and viable cell numbers. Exposure to H2O2 or diethyldithiocarbamate increased viable cell number by 37 % and 50 %, respectively. 

Diaryliodonium salts are industrially employed as photoinitiators in cationic polymerizations [8-10]. They have been employed as Lewis acids [11], as oxidants (via formation of phenyl radicals) [12, 13], and in the area of macromolecular chemistry [14, 15]. Furthermore, diaryliodonium salts show biological activity in various applications, usually because of their ability to act as radical initiators [3, 16]. Diphenyleneiodonium chloride (DPI) is a cyclic diaryliodonium salt which has found numerous biological applications, often as a NADPH oxidase inhibitor ([17] see also [20 0] in [18]). The applications outlined above do not involve arylations and are hence not covered in this chapter. 

Thomas H III, Carson R, Fried E, Novitch R. Inhibition of hypoxic pulmonary vasoconstriction by diphenyleneiodonium. Biochem Pharmacol 1991 42 R9-R12. 

Gatley S, Sherratt H. The effects of diphenyleneiodonium on mitochondrial reactions. Biochem J 1976 158 307-315. 

The most important representatives of stable cycHc iodonium salts, dibenziodohum or diphenyleneiodonium (DPI) salts, have been prepared as the iodide 26, the hexafluorophosphate 28, the tetrafiuoroborate 29, and the chloride 31, and can be obtained by three different procedures... 

Watling-Payne AS and Selwyn MJ (1974) Inhibition and uncoupling of photophosphorylation in isolated chloroplasts by organotin, organomercury and diphenyleneiodonium compounds, Biochem. J. 142, 65-74. 

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