Neuroprotective Effects of a Novel Demeclocycline Derivative Lacking Antibiotic Activity: From a Hit to a Promising Lead Compound

Abstract

The antibiotic tetracycline demeclocycline (DMC) was recently reported to rescue α-synuclein (α-Syn) fibril-induced pathology. However, the antimicrobial activity of DMC precludes its potential use in long-term neuroprotective treatments. Here, we synthesized a doubly reduced DMC (DDMC) derivative with residual antibiotic activity and improved neuroprotective effects. The molecule was obtained by removal the dimethylamino substituent at position 4 and the reduction of the hydroxyl group at position 12a on ring A of DMC. The modifications strongly diminished its antibiotic activity against Gram-positive and Gram-negative bacteria. Moreover, this compound preserved the low toxicity of DMC in dopaminergic cell lines while improving its ability to interfere with α-Syn amyloid-like aggregation, showing the highest effectiveness of all tetracyclines tested. Likewise, DDMC demonstrated the ability to reduce seeding induced by the exogenous addition of α-Syn preformed fibrils (α-SynPFF) in biophysical assays and in a SH-SY5Y-α-Syn-tRFP cell model. In addition, DDMC rendered α-SynPFF less inflammogenic. Our results suggest that DDMC may be a promising drug candidate for hit-to-lead development and preclinical studies in Parkinson’s disease and other synucleinopathies.

Rescue of Dopamine Neurons from Iron-Dependent Ferroptosis by Doxycycline and Demeclocycline and Their Non-Antibiotic Derivatives

“…Although we are well aware that this model system cannot entirely recapitulate the complex and multifaceted nature of neurodegeneration in PD, we suggest that protective TCs, which lack antibiotic activity and reach the brain in relevant amounts may be of potential interest for PD treatment. This may be especially true for DDMC , which was also reported to inhibit αS aggregation [ 22 ], another important contributive mechanism to PD neurodegeneration.…”

“…DDMC was synthesized from DMC HCl by concomitant reduction of the dimethylamino group at position 4 and hydroxy group at position 12a, with the help of zinc dust in an acetic acid/water mixture [ 22 ]. DDOX was obtained through a similar protocol requiring a reduction step from DOX .…”

Design and Synthesis of New Non-Antibiotic Doxycyclin Derivatives Against alpha-Synuclein Aggregation with Anti-Inflammatory Properties

“…Surprisingly, the insertion of nitrogen containing heterocycles such as pyridine, quinoline, or pyrrole derivatives was ineffective in our hands. We were also pleased to enable the insertion of alkene derivatives (11)(12). (Scheme 2) Scheme 2.…”

“…6 Among these neuroprotective effects, DOX was able to prevent the aggregation of -Syn; 7 reduce oxidative stress, act as an anti-inflammatory agent, 8 induce cellular redistribution of aggregates in an animal model of Parkinson's disease 9 among other activities on inflammatory processes in ex vitro and in cellulo assays. 7,[10][11][12] These pieces of evidence make DOX a good candidate as a novel therapeutic agent of interest for Parkinson's disease treatment but also for Alzheimer disease. 13 Interestingly, in animal models of Parkinson's disease, DOX has been found to limit neurodegenerative effects (e.g., neuron death, neuro-inflammation) in hemiparkinsonian mice receiving intra-striatal injections of 6hydroxydopamine (6-OHDA) 14 and in mice expressing human α-Syn (A53T).…”

“…16 Recently, we showed that a new tetracycline derivative, a "reduced" demeclocycline derivative called DDMC, showed promising neuroprotective activity by interfering with α-Syn amyloid-like aggregation and without exhibiting significant antibiotic properties. 11 Moreover, demeclocycline (DMC), DOX, and their corresponding reduced analogs DDMC and DDOX have also shown neuroprotective properties through their ability to chelate iron, preventing oxidative stress. 17 (Figure 1) In continuation to these past studies, and motivated by these encouraging results, a series of original DOX derivatives was synthesized to increase the anti-aggregative properties towards α-Syn.…”