RESUMO
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.
Assuntos
Neuroblastoma , Fármacos Neuroprotetores , Sinucleinopatias , Antibacterianos/farmacologia , Demeclociclina , Bactérias Gram-Negativas , Bactérias Gram-Positivas , Humanos , Chumbo , Fármacos Neuroprotetores/farmacologiaRESUMO
Tauopathies are neurodegenerative disorders with increasing incidence and still without cure. The extensive time required for development and approval of novel therapeutics highlights the need for testing and repurposing known safe molecules. Since doxycycline impacts α-synuclein aggregation and toxicity, herein we tested its effect on tau. We found that doxycycline reduces amyloid aggregation of the 2N4R and K18 isoforms of tau protein in a dose-dependent manner. Furthermore, in a cell free system doxycycline also prevents tau seeding and in cell culture reduces toxicity of tau aggregates. Overall, our results expand the spectrum of action of doxycycline against aggregation-prone proteins, opening novel perspectives for its repurposing as a disease-modifying drug for tauopathies.
RESUMO
On the French West Indian island of Guadeloupe, atypical parkinsonian patients represent two-thirds of all cases of parkinsonism, which is exceptionally frequent compared to epidemiological data from European countries where atypical parkinsonism accounts for only approximately 5% of all cases. The clinical entity was a unique combination of levodopa-resistant parkinsonism, tremor, myoclonus, hallucinations, REM sleep behavior disorder and fronto-subcortical dementia. Based on the presence or the absence of supranuclear gaze palsy, two subgroups of patients were distinguished. In patients with oculomotor signs that came to autopsy, neuronal loss was found to predominate in the substantia nigra and the striatum but other brain areas were also affected, including the frontal cortex. In addition, tau-containing lesions were detected throughout the brain. Epidemiological data suggested a close association of the disease with the regular consumption of soursop, a tropical annonaceous plant. Experimental studies performed in midbrain cell cultures identified annonacin, a selective mitochondrial complex I inhibitor contained in the fruit and leaves of soursop, as a probable etiological factor. Consistent with this view, chronic administration of annonacin to rats through Alzet osmotic minipumps showed that annonacin was able to reproduce the brain lesions characteristic of the human disease.
Assuntos
Complexo I de Transporte de Elétrons/antagonistas & inibidores , Furanos/administração & dosagem , Lactonas/administração & dosagem , Mitocôndrias/efeitos dos fármacos , Transtornos Parkinsonianos/etiologia , Transtornos Parkinsonianos/patologia , Animais , Guadalupe/epidemiologia , Humanos , Mitocôndrias/metabolismo , Transtornos Parkinsonianos/epidemiologiaRESUMO
In Guadeloupe, epidemiological data have linked atypical parkinsonism with fruit and herbal teas from plants of the Annonaceae family, particularly Annona muricata. These plants contain a class of powerful, lipophilic complex I inhibitors, the annonaceous acetogenins. To determine the neurotoxic potential of these substances, we administered annonacin, the major acetogenin of A. muricata, to rats intravenously with Azlet osmotic minipumps (3.8 and 7.6 mg per kg per day for 28 days). Annonacin inhibited complex I in brain homogenates in a concentration-dependent manner, and, when administered systemically, entered the brain parenchyma, where it was detected by matrix-associated laser desorption ionization-time of flight mass spectrometry, and decreased brain ATP levels by 44%. In the absence of evident systemic toxicity, we observed neuropathological abnormalities in the basal ganglia and brainstem nuclei. Stereological cell counts showed significant loss of dopaminergic neurones in the substantia nigra (-31.7%), and cholinergic (-37.9%) and dopamine and cyclic AMP-regulated phosphoprotein (DARPP-32)-immunoreactive GABAergic neurones (-39.3%) in the striatum, accompanied by a significant increase in the number of astrocytes (35.4%) and microglial cells (73.4%). The distribution of the lesions was similar to that in patients with atypical parkinsonism. These data are compatible with the theory that annonaceous acetogenins, such as annonacin, might be implicated in the aetiology of Guadeloupean parkinsonism and support the hypothesis that some forms of parkinsonism might be induced by environmental toxins.
Assuntos
Corpo Estriado/efeitos dos fármacos , Complexo I de Transporte de Elétrons/antagonistas & inibidores , Furanos/toxicidade , Lactonas/toxicidade , Doenças Neurodegenerativas/induzido quimicamente , Extratos Vegetais/toxicidade , Substância Negra/efeitos dos fármacos , Trifosfato de Adenosina/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Contagem de Células , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Furanos/administração & dosagem , Gliose/induzido quimicamente , Gliose/patologia , Guadalupe , Infusões Intravenosas , Lactonas/administração & dosagem , Masculino , Mitocôndrias/enzimologia , Doenças Neurodegenerativas/enzimologia , Doenças Neurodegenerativas/patologia , Neurônios/efeitos dos fármacos , Neurônios/patologia , Transtornos Parkinsonianos/etiologia , Extratos Vegetais/administração & dosagem , Ratos , Ratos Endogâmicos Lew , Substância Negra/metabolismo , Substância Negra/patologiaRESUMO
In the French West Indies there is an abnormally high frequency of levodopa-resistant parkinsonism, suggested to be caused by consumption of fruit and infusions of tropical plants, especially Annona muricata (corossol, soursop). To determine whether toxic substances from this plant can cause the neuronal degeneration or dysfunction underlying the syndrome, we exposed mesencephalic dopaminergic neurons in culture to the total extract (totum) of alkaloids from Annona muricata root bark and to two of the most abundant subfractions, coreximine and reticuline. After 24 hours, 50% of dopaminergic neurons degenerated with 18 microg/ml totum, 4.3 microg/ml (13 microM) coreximine, or 100 microg/ml (304 microM) reticuline. The effects of the alkaloid totum were not restricted to the population of dopaminergic cells since GABAergic neurons were also affected by the treatment. Nuclei in dying neurons showed DNA condensation or fragmentation, suggesting that neuronal death occurred by apoptosis. Cell death was not excitotoxic and did not require toxin uptake by the dopamine transporter. Neurodegeneration was attenuated by increasing the concentration of glucose in the culture medium, which also reduced the effect of the dopaminergic neurotoxin MPP+, a mitochondrial respiratory chain inhibitor. Toxin withdrawal after short-term exposure arrested cell death. Acute treatment with totum, coreximine, or reticuline reversibly inhibited dopamine uptake by a mechanism that was distinct from that causing neuronal death. GABA uptake was not reduced under the same conditions. This study suggests that alkaloids from A. muricata can modulate the function and the survival of dopaminergic nerve cells in vitro. It is therefore conceivable that repeated consumption could cause the neuronal dysfunction and degeneration underlying the West Indian parkinsonian syndrome.