Alterations in gut microbiota contribute to cognitive deficits induced by chronic infection of Toxoplasma gondii.

Chronic infection with Toxoplasma gondii (T. gondii) emerges as a risk factor for neurodegenerative diseases in animals and humans. However, the underlying mechanisms are largely unknown. We aimed to investigate whether gut microbiota and its metabolites play a role in T. gondii-induced cognitive deficits. We found that T. gondii infection induced cognitive deficits in mice, which was characterized by synaptic ultrastructure impairment and neuroinflammation in the hippocampus. Moreover, the infection led to gut microbiota dysbiosis, barrier integrity impairment, and inflammation in the colon. Interestingly, broad-spectrum antibiotic ablation of gut microbiota attenuated the adverse effects of the parasitic infection on the cognitive function in mice; cognitive deficits and hippocampal pathological changes were transferred from the infected mice to control mice by fecal microbiota transplantation. In addition, the abundance of butyrate-producing bacteria and the production of serum butyrate were decreased in infected mice. Interestingly, dietary supplementation of butyrate ameliorated T. gondii-induced cognitive impairment in mice. Notably, compared to the healthy controls, decreased butyrate production was observed in the serum of human subjects with high levels of anti-T. gondii IgG. Overall, this study demonstrates that gut microbiota is a key regulator of T. gondii-induced cognitive impairment.

Probiotic Clostridium butyricum ameliorates cognitive impairment in obesity via the microbiota-gut-brain axis.

Obesity is a risk factor for cognitive dysfunction and neurodegenerative disease, including Alzheimer's disease (AD). The gut microbiota-brain axis is altered in obesity and linked to cognitive impairment and neurodegenerative disorders. Here, we targeted obesity-induced cognitive impairment by testing the impact of the probiotic Clostridium butyricum, which has previously shown beneficial effects on gut homeostasis and brain function. Firstly, we characterized and analyzed the gut microbial profiles of participants with obesity and the correlation between gut microbiota and cognitive scores. Then, using an obese mouse model induced by a Western-style diet (high-fat and fiber-deficient diet), the effects of Clostridium butyricum on the microbiota-gut-brain axis and hippocampal cognitive function were evaluated. Finally, fecal microbiota transplantation was performed to assess the functional link between Clostridium butyricum remodeling gut microbiota and hippocampal synaptic protein and cognitive behaviors. Our results showed that participants with obesity had gut microbiota dysbiosis characterized by an increase in phylum Proteobacteria and a decrease in Clostridium butyricum, which were closely associated with cognitive decline. In diet-induced obese mice, oral Clostridium butyricum supplementation significantly alleviated cognitive impairment, attenuated the deficit of hippocampal neurite outgrowth and synaptic ultrastructure, improved hippocampal transcriptome related to synapses and dendrites; a comparison of the effects of Clostridium butyricum in mice against human AD datasets revealed that many of the genes changes in AD were reversed by Clostridium butyricum; concurrently, Clostridium butyricum also prevented gut microbiota dysbiosis, colonic barrier impairment and inflammation, and attenuated endotoxemia. Importantly, fecal microbiota transplantation from donor-obese mice with Clostridium butyricum supplementation facilitated cognitive variables and colonic integrity compared with from donor obese mice, highlighting that Clostridium butyricum's impact on cognitive function is largely due to its ability to remodel gut microbiota. Our findings provide the first insights into the neuroprotective effects of Clostridium butyricum on obesity-associated cognitive impairments and neurodegeneration via the gut microbiota-gut-brain axis.

Overexpression of forebrain PTP1B leads to synaptic and cognitive impairments in obesity.

Obesity has reached pandemic proportions and is a risk factor for neurodegenerative diseases, including Alzheimer's disease. Chronic inflammation is common in obese patients, but the mechanism between inflammation and cognitive impairment in obesity remains unclear. Accumulative evidence shows that protein-tyrosine phosphatase 1B (PTP1B), a neuroinflammatory and negative synaptic regulator, is involved in the pathogenesis of neurodegenerative processes. We investigated the causal role of PTP1B in obesity-induced cognitive impairment and the beneficial effect of PTP1B inhibitors in counteracting impairments of cognition, neural morphology, and signaling. We showed that obese individuals had negative relationship between serum PTP1B levels and cognitive function. Furthermore, the PTP1B level in the forebrain increased in patients with neurodegenerative diseases and obese cognitive impairment mice with the expansion of white matter, neuroinflammation and brain atrophy. PTP1B globally or forebrain-specific knockout mice on an obesogenic high-fat diet showed enhanced cognition and improved synaptic ultrastructure and proteins in the forebrain. Specifically, deleting PTP1B in leptin receptor-expressing cells improved leptin synaptic signaling and increased BDNF expression in the forebrain of obese mice. Importantly, we found that various PTP1B allosteric inhibitors (e.g., MSI-1436, well-tolerated in Phase 1 and 1b clinical trials for obesity and type II diabetes) prevented these alterations, including improving cognition, neurite outgrowth, leptin synaptic signaling and BDNF in both obese cognitive impairment mice and a neural cell model of PTP1B overexpression. These findings suggest that increased forebrain PTP1B is associated with cognitive decline in obesity, whereas inhibition of PTP1B could be a promising strategy for preventing neurodegeneration induced by obesity.

Event-related potential evidence for tactile orientation processing in the human brain.

It is well known that information on stimulus orientation plays an important role in sensory processing. However, the neural mechanisms underlying somatosensory orientation perception are poorly understood. Adaptation has been widely used as a tool for examining sensitivity to specific features of sensory stimuli. Using the adaptation paradigm, we measured event-related potentials (ERPs) in response to tactile orientation stimuli presented pseudo-randomly to the right-hand palm in trials with all the same or different orientations. Twenty participants were asked to count the tactile orientation stimuli. The results showed that the adaptation-related N60 component was observed around contralateral central-parietal areas, possibly indicating orientation processing in the somatosensory regions. Conversely, the adaptation-related N120 component was identified bilaterally across hemispheres, suggesting the involvement of the frontoparietal circuitry in further tactile orientation processing. P300 component was found across the whole brain in all conditions and was associated with task demands, such as attention and stimulus counting. These findings help provide an understanding of the mechanisms of tactile orientation processing in the human brain.

Gold-Catalyzed Cascade Reaction of Diynamides with Allylic Alcohols: A Versatile Platform to Allenamide, 2-Aminofuran and Bridged [2.2.2]Octadiene Derivatives.

Transition metal-catalyzed divergent synthesis through alternation of the catalyst is appealing, as it provides an operationally simple way to access different valuable products, while using the same reactants as starting materials. Herein, a gold-catalyzed cascade reaction of conjugated diynamides with allylic alcohols is described. By variation of the catalysts, substituted allenes and furans could be obtained selectively. Mechanistic studies indicate that, after the addition of allylic alcohol to gold-activated diynamide, a [3,3]-sigmatropic rearrangement would take place and lead to the formation of a common reactive intermediate, which would further convert to the final products selectively. Further variation of the structure of diynamides has unveiled an additional reaction sequence involving intramolecular Himbert arene/allene Diels-Alder cycloaddition to afford a series of dearomatized products bearing bicyclo[2,2,2]octadiene core.

Polyene phosphatidylcholine ameliorates synovial inflammation: involvement of PTEN elevation and glycolysis suppression.

BACKGROUND: Synovial inflammation, characterized by the activation of synovial fibroblasts (SFs), is a crucial factor to drive the progression of rheumatoid arthritis (RA). Polyene phosphatidylcholine (PPC), the classic hepatoprotective drug, has been reported to ameliorate arthritis in animals. However, the molecular mechanism remains poorly understood. METHODS AND RESULTS: Using in vitro primary synovial fibroblast (SFs) culture system, we revealed that phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, mediates the anti-inflammatory effect of PPC in lipopolysaccharide (LPS)-stimulated primary SFs. PPC decreased the production of TNF-α and IL-6 production while elevating the level of IL-10 and TGF-ß. Furthermore, PPC up-regulated the expression of PTEN, but inhibited the expression of p-AKT (ser473) and PI3K-p85α. Moreover, pre-treatment of SF1670 (the inhibitor of PTEN) or 740Y-P (the agonist of AKT/PI3K pathways) partially abrogated the anti-inflammatory effect of PPC. In addition, PPC could inhibit the expression of GLUT4, a key transporter of glucose that fuels the glycolysis, which is accompanied by the expression downregualtion of glycolytic enzymes PFKFB3 and PKM2. Furthermore, PPC could reduce ROS production and mitochondrial membrane potential in LPS-stimulated SFs and MH7A cell line. CONCLUSION: The present study supported that PPC can alleviate synovial inflammation, which involves in the elevation of PTEN and blockage of glycolysis.

Alkyne Insertion Enabled Vinyl to Acyl 1,5-Palladium Migration: Rapid Access to Substituted 5-Membered-Dihydrobenzofurans and Indolines.

"Through space" palladium/hydrogen shift is an efficient strategy to achieve selective functionalization of a specific remote C-H bond. Compared with relatively extensive exploited 1,4-palladium migration process, the relevant 1,5-Pd/H shift was far less investigated. We herein report a novel 1,5-Pd/H shift pattern between a vinyl and an acyl group. Through the pattern, rapid access to 5-membered-dihydrobenzofuran and indoline derivatives has been achieved. Further studies have unveiled an unprecedented trifunctionalization (vinylation, alkynylation and amination) of a phenyl ring through 1,5-palladium migration relayed decarbonylative Catellani type reaction. A series of mechanistic investigations and DFT calculations have provided insights into the reaction pathway. Notably, it was unveiled that the 1,5-palladium migration in our case prefers a stepwise mechanism involving a PdIV intermediate.

Post-Assembly Modification of Homochiral Titanium-Organic Cages for Recognition and Separation of Molecular Isomers.

A chiral metal-organic cage (MOC) was extended and fixed into a porous framework using a post-assembly modification strategy, which made it easier to study the host-guest chemistry of the solid-state MOC using a single-crystal diffraction technique. Anionic Ti4 L6 (L=embonate) cage can be used as a 4-connecting crystal engineering tecton, and its optical resolution was achieved, thus homochiral ΔΔΔΔ- and ΛΛΛΛ-[Ti4 L6 ] cages were obtained. Accordingly, a pair of homochiral cage-based microporous frameworks (PTC-236(Δ) and PTC-236(Λ)) were easily prepared by a post-assembly reaction. PTC-236 has rich recognition sites provided by the Ti4 L6 moieties, chiral channels and high framework stability, affording a single-crystal-to-single-crystal transformation for guest structure analyses. Thus it was successfully utilized for the recognition and separation of isomeric molecules. This study provides a new approach for the orderly combination of well-defined MOCs into functional porous frameworks.

Layer-specific activation in human primary somatosensory cortex during tactile temporal prediction error processing.

The human brain continuously generates predictions of incoming sensory input and calculates corresponding prediction errors from the perceived inputs to update internal predictions. In human primary somatosensory cortex (area 3b), different cortical layers are involved in receiving the sensory input and generation of error signals. It remains unknown, however, how the layers in the human area 3b contribute to the temporal prediction error processing. To investigate prediction error representation in the area 3b across layers, we acquired layer-specific functional magnetic resonance imaging (fMRI) data at 7T from human area 3b during a task of index finger poking with no-delay, short-delay and long-delay touching sequences. We demonstrate that all three tasks increased activity in both superficial and deep layers of area 3b compared to the random sensory input. The fMRI signal was differentially modulated solely in the deep layers rather than the superficial layers of area 3b by the delay time. Compared with the no-delay stimuli, activity was greater in the deep layers of area 3b during the short-delay stimuli but lower during the long-delay stimuli. This difference activity features in the superficial and deep layers suggest distinct functional contributions of area 3b layers to tactile temporal prediction error processing. The functional segregation in area 3b across layers may reflect that the excitatory and inhibitory interplay in the sensory cortex contributions to flexible communication between cortical layers or between cortical areas.

Tactile angle discriminability improvement: contributions of working memory training and continuous attended sensory input.

Perceptual learning is commonly assumed to enhance perception through continuous attended sensory input. However, learning is generalizable to performance in untrained stimuli and tasks. Although previous studies have observed a possible generalization effect across tasks as a result of working memory (WM) training, comparisons of the contributions of WM training and continuous attended sensory input to perceptual learning generalization are still rare. Therefore, we compared which factors contributed most to perceptual generalization and investigated which skills acquired during WM training led to tactile generalization across tasks. Here, a Braille-like dot pattern matching n-back WM task was used as the WM training task, with four workload levels (0, 1, 2, and 3-back levels). A tactile angle discrimination (TAD) task was used as a pre- and posttest to assess improvements in tactile perception. Between tests, four subject groups were randomly assigned to four different workload n-back tasks to consecutively complete three sessions of training. The results showed that tactile n-back WM training could enhance TAD performance, with the 3-back training group having the highest TAD threshold improvement rate. Furthermore, the rate of WM capacity improvement on the 3-back level across training sessions was correlated with the rate of TAD threshold improvement. These findings suggest that continuous attended sensory input and enhanced WM capacity can lead to improvements in TAD ability, and that greater improvements in WM capacity can predict greater improvements in TAD performance.NEW & NOTEWORTHY Perceptual learning is not always specific to the trained task and stimuli. We demonstrate that both continuous attended sensory input and improved WM capacity can be used to enhance tactile angle discrimination (TAD) ability. Moreover, WM capacity improvement is important in generalizing the training effect to the TAD ability. These findings contribute to understanding the mechanism of perceptual learning generalization across tasks.

Noise Induced Depression-Like Behavior, Neuroinflammation and Synaptic Plasticity Impairments: The Protective Effects of Luteolin.

Noise is a kind of sound that causes agitation and harms human health. Studies have shown that noise can lead to neuroinflammation, damage to synaptic plasticity and altered levels of neurotransmitters that may result in depression. The present study demonstrated that luteolin exerted antidepressant-like effects by improving neuroinflammation in a mouse model of noise-induced depression. Luteolin significantly alleviated noise-induced depression-like behavior. Notably, luteolin treatment not only remarkably ameliorated noise-induced inflammation in the hippocampus and prefrontal cortex, but also increased synapsin. Furthermore, luteolin treatment significantly increased the contents of serum 5-hydroxytryptamine and norepinephrine in noise-induced mice. In sum, luteolin exerts antidepressant effects indepression-like mice caused by noise, which can serve as a potential agent for the treatment of chronic noise-induced depression.

Global surface features contribute to human haptic roughness estimations.

Previous studies have paid special attention to the relationship between local features (e.g., raised dots) and human roughness perception. However, the relationship between global features (e.g., curved surface) and haptic roughness perception is still unclear. In the present study, a series of roughness estimation experiments was performed to investigate how global features affect human roughness perception. In each experiment, participants were asked to estimate the roughness of a series of haptic stimuli that combined local features (raised dots) and global features (sinusoidal-like curves). Experiments were designed to reveal whether global features changed their haptic roughness estimation. Furthermore, the present study tested whether the exploration method (direct, indirect, and static) changed haptic roughness estimations and examined the contribution of global features to roughness estimations. The results showed that sinusoidal-like curved surfaces with small periods were perceived to be rougher than those with large periods, while the direction of finger movement and indirect exploration did not change this phenomenon. Furthermore, the influence of global features on roughness was modulated by local features, regardless of whether raised-dot surfaces or smooth surfaces were used. Taken together, these findings suggested that an object's global features contribute to haptic roughness perceptions, while local features change the weight of the contribution that global features make to haptic roughness perceptions.

ß-Glucan ameliorates anxiety-like behavior in mice chronically infected with the Toxoplasma gondii Wh6 strain.

Chronic Toxoplasma gondii (T. gondii) infection has been revealed to be a risk factor for neuropsychiatric diseases, including anxiety. However, there is no intervention strategy. The present study aimed to investigate the protective effect of ß-glucan on T. gondii Wh6 strain-induced anxiety-like behavior in mice. The anxiety mouse model was established by infection with 10 cysts of the T. gondii Wh6 strain. ß-Glucan was intraperitoneally administered 2 weeks before infection. Open field and elevated plus maze tests were performed to assess anxiety-like behavior. In the open field test, Wh6-infected mice spent less time in the central zone and had fewer entries into the central zone. In the elevated plus maze test, the infection reduced the frequency and time of head entries in the open arms. These results showed that Wh6 causes anxiety-like behavior in mice. Interestingly, the administration of ß-glucan significantly ameliorated anxiety-like behavioral performance. The present study shows that ß-glucan can alleviate the anxiety-like behavior induced by chronic T. gondii infection in mice, which indicates that ß-glucan may be a potential drug candidate for treating T. gondii-related mental disorders, including anxiety.

Different activation signatures in the primary sensorimotor and higher-level regions for haptic three-dimensional curved surface exploration.

Haptic object perception begins with continuous exploratory contact, and the human brain needs to accumulate sensory information continuously over time. However, it is still unclear how the primary sensorimotor cortex (PSC) interacts with these higher-level regions during haptic exploration over time. This functional magnetic resonance imaging (fMRI) study investigates time-dependent haptic object processing by examining brain activity during haptic 3D curve and roughness estimations. For this experiment, we designed sixteen haptic stimuli (4 kinds of curves × 4 varieties of roughness) for the haptic curve and roughness estimation tasks. Twenty participants were asked to move their right index and middle fingers along the surface twice and to estimate one of the two features-roughness or curvature-depending on the task instruction. We found that the brain activity in several higher-level regions (e.g., the bilateral posterior parietal cortex) linearly increased as the number of curves increased during the haptic exploration phase. Surprisingly, we found that the contralateral PSC was parametrically modulated by the number of curves only during the late exploration phase but not during the early exploration phase. In contrast, we found no similar parametric modulation activity patterns during the haptic roughness estimation task in either the contralateral PSC or in higher-level regions. Thus, our findings suggest that haptic 3D object perception is processed across the cortical hierarchy, whereas the contralateral PSC interacts with other higher-level regions across time in a manner that is dependent upon the features of the object.

ß-Glucan from Lentinula edodes prevents cognitive impairments in high-fat diet-induced obese mice: involvement of colon-brain axis.

BACKGROUND: Long-term high fat (HF) diet intake can cause neuroinflammation and cognitive decline through the gut-brain axis. (1, 3)/(1, 6)-ß-glucan, an edible polysaccharide isolated from medical mushroom, Lentinula edodes (L. edodes), has the potential to remodel gut microbiota. However, the effects of L. edodes derived ß-glucan against HF diet-induced neuroinflammation and cognitive decline remain unknown. This study aimed to evaluate the neuroprotective effect and mechanism of dietary L edodes ß-glucan supplementation against the obesity-associated cognitive decline in mice fed by a HF diet. METHODS: C57BL/6J male mice were fed with either a lab chow (LC), HF or HF with L. edodes ß-glucan supplementation diets for 7 days (short-term) or 15 weeks (long-term). Cognitive behavior was examined; blood, cecum content, colon and brain were collected to evaluate metabolic parameters, endotoxin, gut microbiota, colon, and brain pathology. RESULTS: We reported that short-term and long-term L. edodes ß-glucan supplementation prevented the gut microbial composition shift induced by the HF diet. Long-term L. edodes ß-glucan supplementation prevented the HF diet-induced recognition memory impairment assessed by behavioral tests (the temporal order memory, novel object recognition and Y-maze tests). In the prefrontal cortex and hippocampus, the ß-glucan supplementation ameliorated the alteration of synaptic ultrastructure, neuroinflammation and brain-derived neurotrophic factor (BDNF) deficits induced by HF diet. Furthermore, the ß-glucan supplementation increased the mucosal thickness, upregulated the expression of tight junction protein occludin, decreased the plasma LPS level, and inhibited the proinflammatory macrophage accumulation in the colon of mice fed by HF diet. CONCLUSIONS: This study revealed that L. edodes ß-glucan prevents cognitive impairments induced by the HF diet, which may occur via colon-brain axis improvement. The finding suggested that dietary L. edodes ß-glucan supplementation may be an effective nutritional strategy to prevent obesity-associated cognitive decline.

Supplement of microbiota-accessible carbohydrates prevents neuroinflammation and cognitive decline by improving the gut microbiota-brain axis in diet-induced obese mice.

BACKGROUND: Western pattern diets induce neuroinflammation and impair cognitive behavior in humans and animals. Neuroinflammation and cognitive impairment have been associated with microbiota dysbiosis, through the gut-brain axis. Furthermore, microbiota-accessible carbohydrates (MACs) found in dietary fiber are important in shaping the microbial ecosystem and have the potential to improve the gut-brain-axis. However, the effects of MACs on neuroinflammation and cognition in an obese condition have not yet been investigated. The present study aimed to evaluate the effect of MACs on the microbiota-gut-brain axis and cognitive function in obese mice induced by a high-fat and fiber deficient (HF-FD) diet. METHODS: C57Bl/6 J male mice were fed with either a control HF-FD or a HF-MAC diet for 15 weeks. Moreover, an additional group was fed with the HF-MAC diet in combination with an antibiotic cocktail (HF-MAC + AB). Following the 15-week treatment, cognitive behavior was investigated; blood, cecum content, colon, and brain samples were collected to determine metabolic parameters, endotoxin, gut microbiota, colon, and brain pathology. RESULTS: We report MACs supplementation prevented HF-FD-induced cognitive impairment in nesting building and temporal order memory tests. MACs prevented gut microbiota dysbiosis, including increasing richness, α-diversity and composition shift, especially in Bacteroidetes and its lower taxa. Furthermore, MACs increased colonic mucus thickness, tight junction protein expression, reduced endotoxemia, and decreased colonic and systemic inflammation. In the hippocampus, MACs suppressed HF-FD-induced neuroglia activation and inflammation, improved insulin IRS-pAKT-pGSK3ß-pTau synapse signaling, in addition to the synaptic ultrastructure and associated proteins. Furthermore, MACs' effects on improving colon-cognitive parameters were eliminated by wide spectrum antibiotic microbiota ablation. CONCLUSIONS: These results suggest that MACs improve cognitive impairments via the gut microbiota-brain axis induced by the consumption of an HF-FD. Supplemental MACs to combat obesity-related gut and brain dysfunction offer a promising approach to prevent neurodegenerative diseases associated with Westernized dietary patterns and obesity.

Facile access to 2,2-diaryl 2H-chromenes through a palladium-catalyzed cascade reaction of ortho-vinyl bromobenzenes with N-tosylhydrazones.

A palladium-catalyzed cascade reaction of ortho-vinyl bromobenzenes with N-tosylhydrazones has been developed, which provides a facile approach to 2,2-disubstituted 2H-chromenes. The migration of palladium from the aryl to vinyl position is crucial, as the in situ produced vinyl palladium intermediate could further react with diazo compounds to generate the reactive species for the sequential annulation.

A Modular Approach to Dibenzo-fused ϵ-Lactams: Palladium-Catalyzed Bridging-C-H Activation.

Tricyclic ring systems possessing a dibenzo structure joined to a seven-membered heterocyclic ring frequently show important biological activities. However, a modular approach to these molecules based on efficient intermolecular reaction of readily available chemicals is lacking. Herein, an unprecedented palladium-catalyzed formal [4+3] annulation for modular construction of these tricyclic systems is described. This reaction features easily accessible reactants (o-haloarylaldehydes and N-tosylhydrazones), broad substrate scope, and excellent functional group compatibility. The synthetic potential is demonstrated by the easy scale-up reactions, late-stage modification of complex molecules, and collective synthesis of bioactive molecules and approved drugs.

Tactile angle discriminability improvement: roles of training time intervals and different types of training tasks.

Perceptual learning, which is not limited to sensory modalities such as vision and touch, emerges within a training session and between training sessions and is accompanied by the remodeling of neural connections in the cortex. However, limited knowledge exists regarding perceptual learning between training sessions. Although tactile studies have paid attention to between-session learning effects, there have been few studies asking fundamental questions regarding whether the time interval between training sessions affects tactile perceptual learning and generalization across tactile tasks. We investigated the effects of different training time intervals on the consecutive performance of a tactile angle discrimination (AD) task and a tactile orientation discrimination (OD) task training on tactile angle discriminability. The results indicated that in the short-interval training group, AD task performance significantly improved in the early stage of learning and nearly plateaued in the later stage, whereas in the long-interval training group, significant improvement was delayed and then also nearly plateaued in the later stage; additionally, improved OD task performance resulted in improved AD task performance. These findings suggest that training time interval affects the early stage of learning but not the later stage and that generalization occurs between different types of tactile tasks.NEW & NOTEWORTHY Perceptual learning, which constitutes important foundations of complicated cognitive processes, is learning better perception skills. We demonstrate that training time interval can affect the early stage of learning but not the later stage. Moreover, a tactile orientation discrimination training task can also improve tactile angle discrimination performance. These findings may expand the characteristics of between-session learning and help understand the mechanism of the generalization across tactile tasks.

HIV-1 Tat enhances purinergic P2Y4 receptor signaling to mediate inflammatory cytokine production and neuronal damage via PI3K/Akt and ERK MAPK pathways.

BACKGROUND: HIV-associated neurocognitive disorders (HANDs) afflict more than half of HIV-1-positive individuals. The transactivator of transcription (Tat) produced by HIV virus elicits inflammatory process and is a major neurotoxic mediator that induce neuron damage during HAND pathogenesis. Activated astrocytes are important cells involved in neuroinflammation and neuronal damage. Purinergic receptors expressed in astrocytes participate in a positive feedback loop in virus-induced neurotoxicity. Here, we investigated that whether P2Y4R, a P2Y receptor subtype, that expressed in astrocyte participates in Tat-induced neuronal death in vitro and in vivo. METHODS: Soluble Tat protein was performed to determine the expression of P2Y4R and proinflammatory cytokines in astrocytes using siRNA technique via real-time PCR, Western blot, and immunofluorescence assays. Cytometric bead array was used to measure proinflammatory cytokine release. The TUNEL staining and MTT cell viability assay were analyzed for HT22 cell apoptosis and viability, and the ApopTag® peroxidase in situ apoptosis detection kit and cresyl violet staining for apoptosis and death of hippocampal neuron in vivo. RESULTS: We found that Tat challenge increased the expression of P2Y4R in astrocytes. P2Y4R signaling in astrocytes was involved in Tat-induced inflammatory cytokine production via PI3K/Akt- and ERK1/2-dependent pathways. Knockdown of P2Y4R expression significantly reduced inflammatory cytokine production and relieved Tat-mediated neuronal apoptosis in vitro. Furthermore, in vivo challenged with Tat, P2Y4R knockdown mice showed decreased inflammation and neuronal damage, especially in hippocampal CA1 region. CONCLUSIONS: Our data provide novel insights into astrocyte-mediated neuron damage during HIV-1 infection and suggest a potential therapeutic target for HANDs.