Sex Differences in the Response to Viral Infections: TLR8 and TLR9 Ligand Stimulation Induce Higher IL10 Production in Males

BACKGROUND: Susceptibility to viral infections as well as their severity are higher in men than in women. Heightened antiviral responses typical of women are effective for rapid virus clearance, but if excessively high or prolonged, can result in chronic/inflammatory pathologies. We investigated whether this variability could be in part attributable to differences in the response to the Toll-Like Receptors (TLR) more involved in the virus recognition. METHODS: Cytokine production by peripheral blood mononuclear cells (PBMCs) from male and female healthy donors after stimulation with Toll-like receptors (TLR) 3, 7, 8, 9 ligands or with viruses (influenza and Herpes-simplex-1) was evaluated. RESULTS: Compared to females, PBMCs from males produced not only lower amounts of IFN-α in response to TLR7 ligands but also higher amounts of the immunosuppressive cytokine IL10 after stimulation with TLR8 and TLR9 ligands or viruses. IL10 production after TLR9 ligands or HSV-1 stimulation was significantly related with plasma levels of sex hormones in both groups, whereas no correlation was found in cytokines produced following TLR7 and TLR8 stimulation. CONCLUSIONS: Given the role of an early production of IL10 by cells of innate immunity in modulating innate and adaptive immune response to viruses, we suggest that sex-related difference in its production following viral nucleic acid stimulation of TLRs may be involved in the sex-related variability in response to viral infections

APP Processing Induced by Herpes Simplex Virus Type 1 (HSV-1) Yields Several APP Fragments in Human and Rat Neuronal Cells

Lifelong latent infections of the trigeminal ganglion by the neurotropic herpes simplex virus type 1 (HSV-1) are characterized by periodic reactivation. During these episodes, newly produced virions may also reach the central nervous system (CNS), causing productive but generally asymptomatic infections. Epidemiological and experimental findings suggest that HSV-1 might contribute to the pathogenesis of Alzheimer's disease (AD). This multifactorial neurodegenerative disorder is related to an overproduction of amyloid beta (Aβ) and other neurotoxic peptides, which occurs during amyloidogenic endoproteolytic processing of the transmembrane amyloid precursor protein (APP). The aim of our study was to identify the effects of productive HSV-1 infection on APP processing in neuronal cells. We found that infection of SH-SY5Y human neuroblastoma cells and rat cortical neurons is followed by multiple cleavages of APP, which result in the intra- and/or extra-cellular accumulation of various neurotoxic species. These include: i) APP fragments (APP-Fs) of 35 and 45 kDa (APP-F35 and APP-F45) that comprise portions of Aβ; ii) N-terminal APP-Fs that are secreted; iii) intracellular C-terminal APP-Fs; and iv) Aβ1-40 and Aβ1-42. Western blot analysis of infected-cell lysates treated with formic acid suggests that APP-F35 may be an Aβ oligomer. The multiple cleavages of APP that occur in infected cells are produced in part by known components of the amyloidogenic APP processing pathway, i.e., host-cell β-secretase, γ-secretase, and caspase-3-like enzymes. These findings demonstrate that HSV-1 infection of neuronal cells can generate multiple APP fragments with well-documented neurotoxic potentials. It is tempting to speculate that intra- and extracellular accumulation of these species in the CNS resulting from repeated HSV-1 reactivation could, in the presence of other risk factors, play a co-factorial role in the development of AD

The Luminescent Conjugated Oligothiophene h-FTAA Attenuates the Toxicity of Different A beta Species

The prevailing opinion is that prefibrillar beta-amyloid (A beta) species, rather than end-stage amyloid fibrils, cause neuronal dysfunction in Alzheimers disease, although the mechanisms behind A beta neurotoxicity remain to be elucidated. Luminescent conjugated oligothiophenes (LCOs) exhibit spectral properties upon binding to amyloid proteins and have previously been reported to change the toxicity of A beta(1- 42) and prion protein. In a previous study, we showed that an LCO, pentamer formyl thiophene acetic acid (p-FTAA), changed the toxicity of A beta(1-42). Here we investigated whether an LCO, heptamer formyl thiophene acetic acid (h-FTAA), could change the toxicity of A beta(1-42) by comparing its behavior with that of p-FTAA. Moreover, we investigated the effects on toxicity when A ss with the Arctic mutation (A beta Arc) was aggregated with both LCOs. Cell viability assays on SH-SY5Y neuroblastoma cells demonstrated that h-FTAA has a stronger impact on A beta(1-42) toxicity than does p-FTAA. Interestingly, h-FTAA, but not p-FTAA, rescued the A beta(Arc)-mediated toxicity. Aggregation kinetics and binding assay experiments with A beta(1-42) and A beta(Arc) when aggregated with both LCOs showed that h-FTAA and p-FTAA either interact with different species or affect the aggregation in different ways. In conclusion, h-FTAA protects against A beta(1-42) and A beta(Arc) toxicity, thus showing h-FTAA to be a useful tool for improving our understanding of the process of A beta aggregation linked to cytotoxicity.Funding Agencies|Torsten Soderberg Foundation; Apotekare Hedbergs Foundation; Stohnes stiftelse</p

The Luminescent Oligothiophene p-FTAA Converts Toxic A beta(1-42) Species into Nontoxic Amyloid Fibers with Altered Properties

Aggregation of the amyloid-(beta) peptide (A beta) in the brain leads to the formation of extracellular amyloid plaques, which is one of the pathological hallmarks of Alzheimer disease (AD). It is a general hypothesis that soluble prefibrillar assemblies of the A beta peptide, rather than mature amyloid fibrils, cause neuronal dysfunction and memory impairment in AD. Thus, reducing the level of these prefibrillar species by using molecules that can interfere with the A beta fibrillation pathway may be a valid approach to reduce A beta cytotoxicity. Luminescent-conjugated oligothiophenes (LCOs) have amyloid binding properties and spectral properties that differ when they bind to protein aggregates with different morphologies and can therefore be used to visualize protein aggregates. In this study, cell toxicity experiments and biophysical studies demonstrated that the LCO p-FTAA was able to reduce the pool of soluble toxic A beta species in favor of the formation of larger insoluble nontoxic amyloid fibrils, there by counteracting A beta-mediated cytotoxicity. Moreover, p-FTAA bound to early formed A beta species and induced a rapid formation of beta-sheet structures. These p-FTAA generated amyloid fibrils were less hydrophobic and more resistant to proteolysis by proteinase K. In summary, our data show that p-FTAA promoted the formation of insoluble and stable A beta species that were nontoxic which indicates that p-FTAA might have therapeutic potential.Funding Agencies|Swedish Research Council; Torsten Soderberg Foundation; Alzheimer Foundation; Dementia Foundation; Linkoping University Neurobiology Center</p

Inhibition of nSMase2 Reduces the Transfer of Oligomeric alpha-Synuclein Irrespective of Hypoxia

Recently, extracellular vesicles (EVs), such as exosomes, have been proposed to play an influential role in the cell-to-cell spread of neurodegenerative diseases, including the intercellular transmission of alpha-synuclein (alpha-syn). However, the regulation of EV biogenesis and its relation to Parkinson's disease (PD) is only partially understood. The generation of EVs through the ESCRT-independent pathway depends on the hydrolysis of sphingomyelin by neutral sphingomyelinase 2 (nSMase2) to produce ceramide, which causes the membrane of endosomal multivesicular bodies to bud inward. nSMase2 is sensitive to oxidative stress, a common process in PD brains; however, little is known about the role of sphingomyelin metabolism in the pathogenesis of PD. This is the first study to show that inhibiting nSMase2 decreases the transfer of oligomeric aggregates of alpha-syn between neuron-like cells. Furthermore, it reduced the accumulation and aggregation of high-molecular-weight alpha-syn. Hypoxia, as a model of oxidative stress, reduced the levels of nSMase2, but not its enzymatic activity, and significantly altered the lipid composition of cells without affecting EV abundance or the transfer of alpha-syn. These data show that altering sphingolipids can mitigate the spread of alpha-syn, even under hypoxic conditions, potentially suppressing PD progression

The number of vertebrate repeats can be regulated at yeast telomeres by Rap1-independent mechanisms

The number of telomeric DNA repeats at chromosome ends is maintained around a mean value by a dynamic balance between elongation and shortening. In particular, proteins binding along the duplex part of telomeric DNA set the number of repeats by progressively limiting telomere growth. The paradigm of this counting mechanism is the Rap1 protein in Saccharomyces cerevisiae. We demonstrate here that a Rap1-independent mechanism regulates the number of yeast telomeric repeats (TG(1–3)) and of vertebrate repeats (T(2)AG(3)) when TEL1, a yeast ortholog of the human gene encoding the ATM kinase, is inactivated. In addition, we show that a T(2)AG(3)-only telomere can be formed and maintained in humanized yeast cells carrying a template mutation of the gene encoding the telomerase RNA, which leads to the synthesis of vertebrate instead of yeast repeats. Genetic and biochemical evidences indicate that this telomere is regulated in a Rap1-independent manner, both in TEL1 and in tel1Δ humanized yeast cells. Altogether, these findings shed light on multiple repeat-counting mechanisms, which may share critical features between lower and higher eukaryotes