Disease relevance of Mtt formazan

• An early indicator of A beta toxicity is the inhibition of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction to MTT formazan, a widely used assay for measuring cell viability [1].
• More strikingly, cellular MTT formazan exocytosis revealed the formation of bioactive amyloid species in prion-infected mouse N2a neuroblastoma cells [2].
• Ischemia of increasing time periods caused a progressive decrease in cellular and mitochondrial MTT reduction in enterocytes and reperfusion showed further decrease of MTT formazan formation [3].
• The growth and viability of glioma cells was evaluated by [3H]-thymidine incorporation and MTT (3(4,5-dimethylthiazol-2yl)-2,5-diphenyl-tetrazoliumbromi de) assay, resulted in a time dependent decrease in [3H]-thymidine incorporation into DNA and MTT formazan formation, respectively [4].
• Wolbachia contributed to the formation of MTT formazan in the MTT assay of viability and is therefore not exclusively a measure of worm viability and indicates that Wolbachia contributes directly to the metabolic activity of the nematode [5].

High impact information on Mtt formazan

• Treatments that change cellular free cholesterol levels also modulate the trafficking of the MTT formazan-containing vesicles, suggesting that the trafficking of these vesicles may be regulated by free cholesterol under physiological conditions [6].
• A correlation was established between the D-glucose concentration of the culture medium at the time of assay and the production of MTT formazan for cell lines representing seven tumor histologies [7].
• MTT formazan varied significantly among cell lines in both the kinetics of its formation and the degree of saturability exhibited [7].
• Decreases in the cellular concentration of the reduced pyridine nucleotides NADH and NADPH were accompanied by concomitant decreases in MTT formazan production [7].
• The absorption spectrum of MTT-formazan varies with cell number and with pH [8].

Chemical compound and disease context of Mtt formazan

• Colorectal tissues were exposed to microbicides overnight and either fixed in formalin to evaluate toxicity by histological analysis or placed in 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT) to quantitatively determine tissue viability [9].
• Cholesterol does not affect the toxicity of amyloid beta fragment but mimics its effect on MTT formazan exocytosis in cultured rat hippocampal neurons [10].
• Experiments have confirmed that MTT-formazan colorimetry in its simplest form (incubation of intact worms with MTT and direct visualisation of any formazan formed) can be readily applied to several species of filariae including Onchocerca volvulus [11].
• To determine the contribution of Wolbachia to the MTT assay, the MTT formazan formation of an insect cell-line (C6/36) with or without insect Wolbachia infection and treated or untreated with tetracycline was compared [5].

Biological context of Mtt formazan

• It can also be used for accurate determinations of drug sensitivity but only if a quantitative relationship is established between cell number and MTT-formazan production [8].
• The PI 3-kinase and Src pathways are known to promote cell survival in many systems; therefore, MTT (1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan) conversion was used to examine the effects of these inhibitors on cellular viability [12].
• These and other results suggest that MTT is taken up by cells through endocytosis and that reduced MTT formazan accumulates in the endosomal/lysosomal compartment and is then transported to the cell surface through exocytosis [13].
• These and other data suggest that MTT formazan exocytosis is a multistep process and that cytotoxic amyloid peptides enhance MTT formazan exocytosis through an intracellular signal transduction pathway [1].
• We have examined the effects of these MAbs on GH activity in two appropriate GH-responsive cell culture systems, investigating both acute signalling effects (Janus-activated kinase (Jak)-2 tyrosine phosphorylation -5 min) and longer-term (MTT-formazan production -24 h) effects of hormone-antibody complexes [14].

Anatomical context of Mtt formazan

• The present investigation was prompted, in part, by observations that reduction of MTT to its colored reaction product, MTT formazan, varied between cell lines and with culture age [7].
• Microscopic analysis of MTT-formazan product formation in PC12 and HeLa cells following beta 25-35 treatment revealed that it was the intracellular component of the reduction of this dye that was abolished [15].
• Endothelial cell viability was ascertained by colormetric measurement of mitochondrial reduction of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to purple 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan [16].
• Using the mouse myeloid cell line, FDC-P1, stably transfected with the full-length ovine GH receptor (oGHR), we demonstrate that rbGH causes a dose-dependent increase in MTT-formazan production by these cells [14].
• RESULTS: Only 25-45% of MTT-formazan was associated with mitochondria after 25 min of incubation [17].

Associations of Mtt formazan with other chemical compounds

• A decrease in the concentration of D-glucose from culture medium was accompanied by a decrease in MTT specific activity (MTT formazan/microgram cell protein) for a number of cell lines [7].
• Steroid hormones block amyloid fibril-induced 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) formazan exocytosis: relationship to neurotoxicity [18].
• (c) Many sterol sex hormones (e.g., estradiol and progesterone) block amyloid fibril-enhanced MTT formazan exocytosis as well as MTT formazan exocytosis in control cells by acting at a common late step in the exocytic pathway [18].
• Cell number decreased but MTT formazan formation increased, suggesting a direct interaction of kaempferol with the MTT tetrazolium reduction [19].
• Combining the rapid MTT formazan exocytosis assay and the MC65 protection assay led to the discovery of carbazole analogs as small molecule inhibitors of Abeta oligomer-induced cytotoxicity [20].

Gene context of Mtt formazan

• These findings suggest that cellular MTT formazan exocytosis can be useful for studying the roles of bioactive amyloid species in prion infectivity and prion-induced neurodegeneration [2].
• We recently demonstrated that cytotoxic amyloid peptides such as A beta and human amylin inhibit cellular MTT reduction by dramatically enhancing MTT formazan exocytosis [18].
• NAC35, an amyloidogenic fragment of alpha-synuclein (or NACP), also induces MTT formazan exocytosis [18].
• We now show the following: (a) Insulin and glucagon, when converted to fibrils with beta-pleated sheet structure, induce MTT formazan exocytosis that is indistinguishable from that induced by A beta [18].
• In the present study, we examined the effect of Abeta on the morphology of early endosomes, in which MTT is accumulated as MTT formazan after cellular reduction [21].

Analytical, diagnostic and therapeutic context of Mtt formazan

• METHODS: In order to establish the subcellular localization of the sites of reduction of MTT, we imaged the formation of MTT-formazan deposits using backscattered light confocal microscopy [17].
• We conclude that optimal detection of early stages of crystallization of MTT-formazan in living cells is possible using confocal microscopy of red, but not blue, scattered light [22].
• These motile worms were evaluated for viability using 4 measurements (long-term motility/survival in culture; [U-14C]adenine uptake and leakage; glucose utilization; MTT-formazan colorimetry) and were no different from unfrozen controls [23].
• Veratridine, a Na(+) channel opener that increases hindlimb oxygen uptake and lactate efflux without increases in perfusion pressure, also decreased MTT formazan production [24].
• The two quinonoids, namely menadione and co-enzyme Q0 markedly increased the MTT-formazan produced by hormone activated Nb2 cells and thereby amplified the response of our bioassay for human growth hormone (hGH) [25].

References