Tolonium chloride is a phenothiazine that has been used as a hemostatic, a biological stain, and a dye for wool and silk. Tolonium chloride has also been used as a diagnostic aid for oral and gastric neoplasms and in the identification of the parathyroid gland in thyroid surgery
Title: Toluidine blue O modifies hippocampal amyloid pathology in a transgenic mouse model of Alzheimer's disease Yuksel M, Biberoglu K, Onder S, Akbulut KG, Tacal O Ref: Biochimie, 146:105, 2018 : PubMed
Recently, we have demonstrated that toluidine blue O (TBO), a phenothiazine dye, shows inhibitory effects on both cholinesterases and amyloid pathology in Alzheimer's disease (AD) cellular model. In the present study, we aimed to determine the effects of TBO (in a purity of 85%) on amyloid and tau pathologies in a triple transgenic mouse model of AD (3xTg-AD). Beginning at 7.5 (mild pathology) or 13 (severe pathology) months of age, 3xTg-AD mice were treated intraperitoneally with 4mg/kg TBO or vehicle daily for 30 days. TBO treatment significantly reduced the levels of insoluble Abeta40 and Abeta42 in the hippocampi of mild and severe pathology groups compared to vehicle-treated counterparts. When the levels of full-length amyloid precursor protein (APP) and beta-site APP-cleaving enzyme 1 (BACE1) were assessed in 3xTg-AD mice at late pathological stage, no significant changes were observed after TBO treatment. Similarly, TBO did not recover hyperphosphorylation of tau at residues Thr181 and Ser202/Thr205 significantly in soluble and insoluble hippocampal fractions of 3xTg-AD mice. Taken together, the current study is the first in vivo report, to our knowledge, demonstrating that TBO mitigates amyloid pathology in 3xTg-AD mice with no apparent change on tau phosphorylation. Overall, the preliminary data presented here support the possible use of TBO as a disease-modifying drug for AD treatment.
Title: Toluidine blue O is a potent inhibitor of human cholinesterases Biberoglu K, Tek MY, Ghasemi ST, Tacal O Ref: Archives of Biochemistry & Biophysics, 604:57, 2016 : PubMed
In this study, the inhibitory effects of three phenothiazines [toluidine blue O (TBO), thionine (TH) and methylene violet (MV)] were tested on human plasma butyrylcholinesterase (BChE) and their inhibitory mechanisms were studied in detail. MV acted as a linear mixed type inhibitor of human BChE with Ki = 0.66 +/- 0.06 muM and alpha = 13.6 +/- 3.5. TBO and TH caused nonlinear inhibition of human BChE, compatible to double occupancy. Ki values estimated by nonlinear regression analysis for TBO and TH were 0.008 +/- 0.003 muM and 2.1 +/- 0.42 muM, respectively. The inhibitory potential of TBO was also tested on human erythrocyte AChE. TBO acted as a linear mixed type inhibitor of human AChE with Ki = 0.041 +/- 0.005 muM and alpha = 1.6 +/- 0.007. Using four site-directed BChE mutants, the role of peripheral anionic site residues of human BChE was also investigated in the binding of TBO to BChE. The peripheral anionic site mutants of BChE caused 16-69-fold increase in Ki value of TBO, compared to recombinant wild-type, suggesting that peripheral anionic site residues are involved in the binding of TBO to human BChE. In conclusion, TBO which is a potent inhibitor of human cholinesterases, may be a potential drug candidate for the treatment of Alzheimer's disease.
