Alzheimer's disease is a chronic neurodegenerative disease with two main pathological features, amyloid β plaques and neurofibrillary tangles. Neuroinflammation also plays an important role in its development and progression. Various harmful stimuli activate the NLRP3 inflammasome, leading to the conversion of pro-caspase-1 into active caspase-1. The latter links NLRP3 inflammasome activation to the release of inflammatory cytokines IL-1β and IL-18, as well as pyroptotic cell death. Persistent activation of innate immune system cells results in excessive release of pro-inflammatory molecules, an intensified immune response, and neuronal loss. By inhibiting caspase-1, it is possible to interrupt inflammatory signaling, slow down neurodegeneration, and mitigate cognitive decline.
The aim of the master's thesis was to synthesize compounds with a carbamoyl fluoride warhead that would inhibit caspase-1. We synthesized analogs of the caspase-1 inhibitors, the indoline-1-carbamoyl fluorides MMZ-20B and KZK-49-3D, thereby expanding the chemical space of indoline-1-carbamoyl fluorides. The synthesis started from substituted indoles, which were reduced to indolines, from which carbamoyl fluorides were prepared following a reported procedure. The inhibitory potencies of the synthesized compounds on recombinant human caspase-1 were evaluated using an enzymatic assay, and molecular modeling was performed to explain the binding of the derivatives to the enzyme's active site. Seven of the synthesized carbamoyl fluorides inhibited caspase-1, with the most potent inhibitor being compound 18 with residual activity of 6.9 % at a concentration of 100 µM in the presence of 1 mM dithiothreitol and comparable 3.1 % in its absence. Based on the results, we conclude that the substituents at position 7 of indoline-1-carbamoyl fluorides have a major impact on the inhibitory potency. The negative mesomeric effect of nitro group (analogue 23) increases the reactivity of carbamoyl fluoride, while the amino group of 33, with its positive mesomeric effect, is likely responsible for the inactivity of the latter. The finding that the linker at position 3 of indoline is too short to allow the introduced aromatic chains to form interactions with the S4 binding pocket of caspase-1 thus improving binding to the active site and inhibiting the enzyme provides a strong starting point for further fragment growth development and its optimization.
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