tetracycline and Alzheimer-Disease

The novel antibiotic-exploiting strategy in the treatment of Alzheimer's (AD) and Parkinson's (PD) disease has emerged as a potential breakthrough in the field. The research in animal AD/PD models provided evidence on the antiamyloidogenic, anti-inflammatory, antioxidant and antiapoptotic activity of tetracyclines, associated with cognitive improvement. The neuroprotective effects of minocycline and doxycycline in animals initiated investigation of their clinical efficacy in AD and PD patients which led to inconclusive results and additionally to insufficient safety data on a long-standing doxycycline and minocycline therapy in these patient populations. The safety issues should be considered in two levels; in AD/PD patients (particularly antibiotic-induced alteration of gut microbiota and its consequences), and as a world-wide threat of development of bacterial resistance to these antibiotics posed by a fact that AD and PD are widespread incurable diseases which require daily administered long-lasting antibiotic therapy. Recently proposed subantimicrobial doxycycline doses should be thoroughly explored for their effectiveness and long-term safety especially in AD/PD populations. Keeping in mind the antibacterial activity-related far-reaching undesirable effects both for the patients and globally, further work on repurposing these drugs for a long-standing therapy of AD/PD should consider the chemically modified tetracycline compounds tailored to lack antimicrobial but retain (or introduce) other activities effective against the AD/PD pathology. This strategy might reduce the risk of long-term therapy-related adverse effects (particularly gut-related ones) and development of bacterial resistance toward the tetracycline antibiotic agents but the therapeutic potential and desirable safety profile of such compounds in AD/PD patients need to be confirmed.

Topics: Alzheimer Disease; Animals; Anti-Bacterial Agents; Doxycycline; Drug Repositioning; Humans; Minocycline; Parkinson Disease; Tetracycline

The misfolding of amyloid proteins is closely correlated with the pathogenesis of protein conformation-related diseases, such as Alzheimer's disease (AD), prion disease, and type 2 diabetes mellitus (T2DM). The deposition of human islet amyloid polypeptide (hIAPP) and amyloid-β (Aβ) protein is entangled in AD and diabetes mellitus. The development of potential inhibitors is a feasible therapeutic strategy to treat these diseases by resisting peptide aggregation. Doxycycline is a typical clinical antibiotic that has been utilized in neurodegenerative studies. However, the roles of tetracyclines in hIAPP aggregation remain unclear. Herein, we studied the inhibitory effects of three tetracycline derivatives, namely, minocycline hydrochloride (1), methacycline hydrochloride (2), and doxycycline (3), on the fibril formation and cytotoxicity of hIAPP and compared with that of Aβ. The well-known 3 was selected and compared with 1 and 2. Tetracycline derivatives acted as effective inhibitors to reverse the self-assembly of hIAPP and Aβ, and disaggregate the aged peptides fibrils into mostly monomers. Tetracycline derivatives also reduced the cytotoxicity induced by amyloid peptide oligomerization. Further molecular mechanism studies revealed hydrophobic and hydrogen bond interactions as the primary binding pattern between tetracycline derivatives and peptides. A good bioactivity against amyloidosis was demonstrated by three tetracyclines. This work provided a basis for using tetracycline antibiotics as potential inhibitors against hIAPP aggregation.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Diabetes Mellitus, Type 2; Humans; Islet Amyloid Polypeptide; Protein Aggregation, Pathological; Tetracycline

Topics: Alzheimer Disease; Animals; Doxycycline; Escherichia coli; Genetic Vectors; Glycogen Synthase Kinase 3 beta; Hippocampus; Mice; Mice, Transgenic; Neurodegenerative Diseases; Neurogenesis; Neurons; Promoter Regions, Genetic; Repressor Proteins; Retroviridae; Tetracycline; Transcriptional Activation

Sex differences are a well-known phenomenon in Alzheimer's disease (AD), with women having a higher risk for AD than men. Many AD mouse models display a similar sex-dependent pattern, with females showing earlier cognitive deficits and more severe neuropathology than males. However, whether those differences are relevant to human disease is unclear. Here we show that in AD mouse models that overexpress amyloid precursor protein (APP) under control of the prion protein promoter (PrP), female transgenic mice have higher APP expression than males, complicating interpretations of the role of sex-related factors in such models. By contrast, in a tTa:APPsi model, in which APP expression is driven by the tetracycline transactivator (tTa) from the CaMKIIα promoter, there are no sex-related differences in expression or processing of APP. In addition, the levels of Aβ dimers and tetramers, as well as Aβ peptide accumulation, are similar between sexes. Behavioral testing demonstrated that both male and female tTa:APPsi mice develop age-dependent deficits in spatial recognition memory and conditional freezing to context. These cognitive deficits were accompanied by habituation-associated hyperlocomotion and startle hyper-reactivity. Significant sex-related dimorphisms were observed, due to females showing earlier onsets of the deficits in conditioned freezing and hyperlocomotion. In addition, tTa:APPsi males but not females demonstrated a lack of novelty-induced activation. Both males and females showed atrophy of the dentate gyrus (DG) of the dorsal hippocampus, associated with widening of the pyramidal layer of the CA1 area in both sexes. Ventral DG was preserved. Sex-related differences were limited to the DG, with females showing more advanced degeneration than males. Collectively, our data show that the tTa:APPsi model is characterized by a lack of sex-related differences in APP expression, making this model useful in deciphering the mechanisms of sex differences in AD pathogenesis. Sex-related dimorphisms observed in this model under conditions of equal APP expression between sexes suggest a higher sensitivity of females to the effects of APP and/or Aβ production.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Atrophy; Conditioning, Psychological; Dentate Gyrus; Disease Models, Animal; Fear; Female; Humans; Locomotion; Male; Mice; Mice, Transgenic; Models, Biological; Mutation; Presenilin-1; Recognition, Psychology; Sex Factors; Tetracycline

Amyloid plaques composed of β-amyloid (Aβ) protein are a pathological hallmark of Alzheimer's disease. We here report the generation and characterization of a novel transgenic mouse model of Aβ toxicity. The rTg9191 mice harbor a transgene encoding the 695 amino-acid isoform of human amyloid precursor protein (APP) with the Swedish and London mutations (APPNLI) linked to familial Alzheimer's disease, under the control of a tetracycline-response element, as well as a transgene encoding the tetracycline transactivator, under the control of the promoter for calcium-calmodulin kinase IIα. In these mice, APPNLI is expressed at a level four-fold that of endogenous mouse APP and its expression is restricted to forebrain regions. Transgene expression was suppressed by 87% after two months of doxycycline administration. Histologically, we showed that (1) Aβ plaques emerged in cerebral cortex and hippocampus as early as 8 and 10.5-12.5 months of age, respectively; (2) plaque deposition progressed in an age-dependent manner, occupying up to 19% of cortex at ~25 months of age; and (3) neuropathology--such as abnormal neuronal architecture, tau hyperphosphorylation and misfolding, and neuroinflammation--was observed in the vicinity of neuritic plaques. Biochemically, we determined total Aβ production at varied ages of mice, and we showed that mice produced primarily fibrillar Aβ assemblies recognized by conformation-selective OC antibodies, but few non-fibrillar oligomers (e.g., Aβ*56) detectable by A11 antibodies. Finally, we showed that expression of the tetracycline transactivator resulted in reduced brain weight and smaller dentate-gyrus size. Collectively, these data indicate that rTg9191 mice may serve as a model for studying the neurological effects of the fibrillar Aβ assemblies in situ.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cerebral Cortex; Disease Models, Animal; Doxycycline; Female; Hippocampus; Humans; Male; Mice; Mice, Transgenic; Plaque, Amyloid; Prosencephalon; Tetracycline

Combined results of theoretical molecular dynamic simulations and in vitro spectroscopic (circular dichroism and fluorescence) studies are presented, providing the atomistic and secondary structure details of the process by which a selected small molecule may destabilize the β-sheet ordered "amyloid" oligomers formed by the model undecapeptide of amyloid β-peptide 25-35 [Aβ(25-35)]. Aβ(25-35) was chosen because it is the shortest fragment capable of forming large β-sheet fibrils and retaining the toxicity of the full length Aβ(1-40/42) peptides. The conformational transition, that leads to the formation of β-sheet fibrils from soluble unordered structures, was found to depend on the environmental conditions, whereas the presence of myricetin destabilizes the self-assembly and antagonizes this conformational shift. In parallel, we analyzed several molecular dynamics trajectories describing the evolution of five monomer fragments, without inhibitor as well as in the presence of myricetin. Other well-known inhibitors (curcumin and (-)-tetracycline), found to be stronger and weaker Aβ(1-42) aggregation inhibitors, respectively, were also studied. The combined in vitro and theoretical studies of the Aβ(25-35) self-assembly and its inhibition contribute to understanding the mechanism of action of well-known inhibitors and the peptide amino acid residues involved in the interaction leading to a rational drug design of more potent new molecules able to antagonize the self-assembly process.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Circular Dichroism; Curcumin; Flavonoids; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Models, Molecular; Peptide Fragments; Protein Structure, Secondary; Spectrometry, Fluorescence; Temperature; Tetracycline

The accumulation and deposition of amyloid beta (Aβ) peptide in extracellular dense plaques in the brain is a key phase in Alzheimer's disease (AD). Small oligomeric forms of Aβ are responsible for the toxicity and the early cognitive impairment observed in patients before the amyloid plaque deposits appear. It is essential for the development of an efficient cure for AD to identify compounds that interfere with Aβ aggregation, counteracting the molecular mechanisms involved in conversion of the monomeric amyloid protein into oligomeric and fibrillar forms. Tetracyclines have been proposed for AD therapy, although their effects on the aggregation of Aβ protein, particularly their ability to interact in vivo with the Aβ oligomers and/or aggregates, remain to be understood. Using transgenic Caenorhabditis elegans as a simplified invertebrate model of AD, we evaluated the ability of tetracyclines to interfere with the sequence of events leading to Aβ proteotoxicity. The drugs directly interact with the Aβ assemblies in vivo and reduce Aβ oligomer deposition, protecting C. elegans from oxidative stress and the onset of the paralysis phenotype. These effects were specific, dose-related and not linked to any antibiotic activity, suggesting that the drugs might offer an effective therapeutic strategy to target soluble Aβ aggregates.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Caenorhabditis elegans; Disease Models, Animal; Dose-Response Relationship, Drug; Oxidative Stress; Protein Synthesis Inhibitors; Tetracycline

Cell cycle proteins are elevated in the brain of patients and in transgenic models of Alzheimer's disease (AD), suggesting that aberrant cell cycle re-entry plays a key role in this disorder. However, the precise relationship between cell cycle reactivation and the hallmarks of AD, amyloid-beta (Abeta) plaques and tau-laden neurofibrillary tangles, remains unclear. We sought to determine whether cell cycle reactivation initiates in direct response to Abeta and tau accumulation or whether it occurs as a downstream consequence of neuronal death pathways. Therefore, we used a triple transgenic mouse model of AD (3xTg-AD) that develops plaques and tangles, but does not exhibit extensive neuronal loss, whereas to model hippocampal neuronal death a tetracycline-regulatable transgenic model of neuronal ablation (CaM/Tet-DT(A) mice) was used. Cell-cycle protein activation was determined in these two models of neurodegeneration, using biochemical and histological approaches. Our findings indicate that Cdk4, PCNA and phospho-Rb are significantly elevated in CaM/Tet-DT(A) mice following neuronal death. In contrast, no significant activation of cell-cycle proteins occurs in 3xTg-AD mice versus non-transgenic controls. Taken together, our data indicate that neuronal cell cycle reactivation is not a prominent feature induced by Abeta or tau pathology, but rather appears to be triggered by acute neuronal loss.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cell Cycle Proteins; Cell Death; Cyclin-Dependent Kinase 4; Denervation; Disease Models, Animal; Histones; Mice; Mice, Transgenic; Neurons; Proliferating Cell Nuclear Antigen; Retinoblastoma Protein; tau Proteins; Tetracycline

Inhibition of the accumulation of amyloid beta-peptide (Abeta) and the formation of beta-amyloid fibrils (fAbeta) from Abeta, as well as the destabilization of preformed fAbeta in the CNS would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We previously reported that nordihydroguaiaretic acid (NDGA) and wine-related polyphenols inhibit fAbeta formation from Abeta(1-40) and Abeta(1-42) as well as destabilizing preformed fAbeta(1-40) and fAbeta(1-42) dose-dependently in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of polymeric polyphenol, tannic acid (TA) on the formation, extension, and destabilization of fAbeta(1-40) and fAbeta(1-42) at pH 7.5 at 37 degrees C in vitro. We next compared the anti-amyloidogenic activities of TA with myricetin, rifampicin, tetracycline, and NDGA. TA dose-dependently inhibited fAbeta formation from Abeta(1-40) and Abeta(1-42), as well as their extension. Moreover, it dose-dependently destabilized preformed fAbetas. The effective concentrations (EC50) of TA for the formation, extension and destabilization of fAbetas were in the order of 0-0.1 microM. Although the mechanism by which TA inhibits fAbeta formation from Abeta as well as destabilizes preformed fAbeta in vitro is still unclear, it could be a key molecule for the development of therapeutics for AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Flavonoids; Kinetics; Masoprocol; Microscopy, Electron; Rifamycins; Tannins; Tetracycline; Thermodynamics

Cerebral deposition of beta-amyloid is a major neuropathological feature in Alzheimer's disease. Here we show that tetracyclines, tetracycline and doxycycline, classical antibiotics, exhibit anti-amyloidogenic activity. This capacity was determined by the exposure of beta 1-42 amyloid peptide to the drugs followed by the electron microscopy examination of the amyloid fibrils spontaneously formed and quantified with thioflavine T binding assay. The drugs reduced also the resistance of beta 1-42 amyloid fibrils to trypsin digestion. Tetracyclines not only inhibited the beta-amyloid aggregates formation but also disassembled the pre-formed fibrils. The results indicate that drugs with a well-known clinical profile, including activity in the central nervous system, are potentially useful for Alzheimer's therapy.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Benzothiazoles; Doxycycline; Fluorescent Dyes; Humans; Hydrolysis; In Vitro Techniques; Macromolecular Substances; Microscopy, Electron; Peptide Fragments; Tetracycline; Tetracyclines; Thiazoles; Trypsin

Most cases of early onset familial Alzheimer's disease (FAD) involve mutations in presenilins (PS1 and PS2) genes. The C-terminal portion of PS2 is a homologue with an apoptosis-linked gene (ALG-3). To characterise the role of PS1 in apoptosis, we overexpressed the corresponding C-terminal fragment of PS1 (PS1-f) under the control of the tetracycline-responsive transactivator in Jurkat cells. The tight regulation of the expression of the 11 kDa PS1-f peptide was verified. A 50% inhibition of anti-Fas induced apoptosis was observed upon PS1-f transient overexpression compared to the repressed state. Stable transfectants selectively overexpressing PS1-f revealed a transient protective effect of 30% after apoptosis induction.

Topics: Alzheimer Disease; Antibodies, Monoclonal; Apoptosis; Base Sequence; DNA Primers; fas Receptor; Gene Expression Regulation; Green Fluorescent Proteins; Humans; Jurkat Cells; Luminescent Proteins; Membrane Proteins; Molecular Sequence Data; Peptide Fragments; Polymerase Chain Reaction; Presenilin-1; Recombinant Fusion Proteins; Tetracycline; Transfection

The beta amyloid peptide which accumulates within the brains of patients with Alzheimer's disease (AD) is proteolytically derived from a precursor protein (beta PP). We established and characterized four stably transformed human neuroblastoma cell lines which conditionally expressed a partial beta PP fusion protein (amino-17 residues+carboxyl-99 residues; S beta C). Conditional expression of S beta C was achieved using a tetracycline-responsive promoter system. Expression of this fusion protein in one of the cell lines resulted in pronounced cytotoxicity. Addition of n6,O2'-dibutyryl adenosine 3',5'-cyclic monophosphate and/or fetal bovine serum to the culture medium of this cell line further elevated the level of S beta C expression and enhanced the associated cytotoxicity. Conditioned medium, acquired from cells expressing S beta C, was not cytotoxic. These findings suggest that modulation of beta PP expression and/or metabolism can have cytotoxic consequences. This is the first report of cytotoxic effects mediated by conditional expression of a beta PP derivative. This immortal cell line provides a unique opportunity to screen for complementary DNAs which suppress this toxicity. Such cDNAs could help elucidate the processes underlying S beta C mediated cytotoxicity which in turn could further our understanding of the pathogenesis of AD and could also provide additional candidate genes for various forms of familial AD.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Brain; Bucladesine; Cell Line; Cell Survival; Flow Cytometry; Gene Expression; Humans; Neuroblastoma; Promoter Regions, Genetic; Recombinant Fusion Proteins; Restriction Mapping; Tetracycline; Transfection; Tumor Cells, Cultured