Ian G. C. Coutts

Transglutaminase Inhibition Reduces Fibrosis and Preserves Function in Experimental Chronic Kidney Disease

Progressive tissue fibrosis is involved in debilitating diseases that affect organs including the lungs, liver, heart, skin, and kidneys. Recent evidence suggests that tissue transglutaminase, an enzyme that crosslinks proteins, may be involved in tissue fibrosis by crosslinking and stabilizing the extracellular matrix or by recruiting and activating the large latent transforming growth factor (TGF)-β1 complex. We treated rats that had undergone 5/6-nephrectomy with two different irreversible inhibitors of transglutaminase and found that both prevented a decline in kidney function and reduced the development of glomerulosclerosis and tubulointerstitial fibrosis by up to 77% and 92%, respectively. Treatment reduced the accumulation of collagen I and collagen III, with the primary mechanism of action being direct interference with the crosslinking of extracellular matrix rather than altered regulation of TGFβ1. We conclude that inhibition of transglutaminase offers a potential therapeutic option for chronic kidney disease and other conditions that result from tissue fibrosis. Copyright

Transglutaminase inhibition ameliorates experimental diabetic nephropathy

Diabetic nephropathy is characterized by excessive extracellular matrix accumulation resulting in renal scarring and end-stage renal disease. Previous studies have suggested that transglutaminase type 2, by formation of its protein crosslink product epsilon-(gamma-glutamyl)lysine, alters extracellular matrix homeostasis, causing basement membrane thickening and expansion of the mesangium and interstitium. To determine whether transglutaminase inhibition can slow the progression of chronic experimental diabetic nephropathy over an extended treatment period, the inhibitor NTU281 was given to uninephrectomized streptozotocin-induced diabetic rats for up to 8 months. Effective transglutaminase inhibition significantly reversed the increased serum creatinine and albuminuria in the diabetic rats. These improvements were accompanied by a fivefold decrease in glomerulosclerosis and a sixfold reduction in tubulointerstitial scarring. This was associated with reductions in collagen IV accumulation by 4 months, along with reductions in collagens I and III by 8 months. This inhibition also decreased the number of myofibroblasts, suggesting that tissue transglutaminase may play a role in myofibroblast transformation. Our study suggests that transglutaminase inhibition ameliorates the progression of experimental diabetic nephropathy and can be considered for clinical application.

Synthesis of potent water-soluble tissue transglutaminase inhibitors

Dipeptide-based sulfonium peptidylmethylketones derived from 6-diazo-5-oxo-L-norleucine (DON) have been investigated as potential water-soluble inhibitors of extracellular transglutaminase. The lead compounds were prepared in four steps and exhibited potent activity against tissue transglutaminase.

An extracellular transglutaminase is required for apple pollen tube growth

An extracellular form of the calcium-dependent protein-cross-linking enzyme TGase (transglutaminase) was demonstrated to be involved in the apical growth of Malus domestica pollen tube. Apple pollen TGase and its substrates were co-localized within aggregates on the pollen tube surface, as determined by indirect immunofluorescence staining and the in situ cross-linking of fluorescently labelled substrates. TGase-specific inhibitors and an anti-TGase monoclonal antibody blocked pollen tube growth, whereas incorporation of a recombinant fluorescent mammalian TGase substrate (histidine-tagged green fluorescent protein: His6-Xpr-GFP) into the growing tube wall enhanced tube length and germination, consistent with a role of TGase as a modulator of cell wall building and strengthening. The secreted pollen TGase catalysed the cross-linking of both PAs (polyamines) into proteins (released by the pollen tube) and His6-Xpr-GFP into endogenous or exogenously added substrates. A similar distribution of TGase activity was observed in planta on pollen tubes germinating inside the style, consistent with a possible additional role for TGase in the interaction between the pollen tube and the style during fertilization.

Novel synthetic approaches to the palmarumycin skeleton

Abstract Oxidation of readily available aminonaphthols 7a and 7b with activated manganese dioxide gives palmarumycin analogues 8a and 8b in good yield. The related benzoquinone monoacetals 10a–c undergo cycloaddition with 3-methoxy-2-pyrone at high pressure to give adducts 12a–c, also possessing the palmarumycin framework.

The reaction of lithium trimethylsilyldiazomethane with pyroglutamates — a facile synthesis of 6-diazo-5-oxo-norleucine and derivatives

Abstract The reaction of carbamate derivatives of pyroglutamic acid esters with the lithium salt of trimethylsilyldiazomethane below −100°C gives good yields of the corresponding substituted 6-diazo-5-oxo-norleucine esters; cleavage of Fmoc-substituted products provides a safe, convenient route to the parent acid.

Spirodienones part 81. The direct preparation of spirodioxole — and spirobenzoxazole - cyclohexadienones by the oxidation of 4 - aryloxyanilines

Abstract Oxidation of 4(2 - hydroxyphenoxy)anilines 1b to 1d with active manganese dioxide leads directly to quinone mono - ketals 2b to 2d in reasonable yield. Similar reaction of 4 (2 - sulfonamidophenoxy)anilines 9a , 9b provides an efficient synthesis of spirobenzoxazolecyclohexadienones 10a and 10b but treatment with manganese dioxide of alcohol 3 and oxime 6 gives respectively azobenzene 4 and terphenyl 7 rather than spirodienones

Spirodienones. Part 5. The synthesis and reactions of N-sulphonylcyclohexadienimines

The anodic or chemical oxidation of para-substituted sulphonanilides gives 4,4-disubstituted N-sulphonylcyclohexadienimines, which, from appropriately substituted anilines, may be spirocyclic. The scope and limitations of the synthesis are described, and a mechanism proposed. The selective hydrolysis of the dienimines to the corresponding dienones provides a convenient route to the latter compounds. The reaction of some of the dienimines with dienes is discussed.