Project description:The incidence of infectious diseases affecting the central nervous system (CNS) has been increasing over the last several years. Among the reasons for the expansion of these diseases and the appearance of new neuropathogens are globalization, global warming, and the increased proximity between humans and wild animals due to human activities such as deforestation. Neurotropism affecting normal brain function is shared by organisms such as viruses, bacteria, fungi, and parasites. Neuroinfections caused by these agents activate immune responses, inducing neuroinflammation, excitotoxicity, and neurodegeneration. Purinergic signaling is an evolutionarily conserved signaling pathway associated with these neuropathologies. During neuroinfections, host cells release ATP as an extracellular danger signal with pro-inflammatory activities. ATP is metabolized to its derivatives by ectonucleotidases such as CD39 and CD73; ATP and its metabolites modulate neuronal and immune mechanisms through P1 and P2 purinergic receptors that are involved in pathophysiological mechanisms of neuroinfections. In this review we discuss the beneficial or deleterious effects of various components of the purinergic signaling pathway in infectious diseases that affect the CNS, including human immunodeficiency virus (HIV-1) infection, herpes simplex virus type 1 (HSV-1) infection, bacterial meningitis, sepsis, cryptococcosis, toxoplasmosis, and malaria. We also provide a description of this signaling pathway in emerging viral infections with neurological implications such as Zika and SARS-CoV-2.
Project description:B cells have emerged as a critical player in autoimmune disorders of the central nervous system (CNS), such as multiple sclerosis (MS). While locally educated B cells with a CNS non-self-reactive immune repertoire are observed at the brain borders, the specific function of these CNS-compartmentalized B cells in the neuroinflammation pathogenesis remains unclear. Here we demonstrated that autoreactive B cells promoted neuroinflammation through local cognate interaction with pathogenic T cells in the meninges. By selectively perturbing B cell compositions in the CNS through intra-cisterna magna injection, we found that CNS-compartmentalized autoreactive T-B interactions drove the influx of pro-inflammatory phagocytes and initiated vascular inflammation responses, which were dependent on the expression of class II major histocompatibility complex molecules. Selective targeting of B cells in the CNS effectively alleviated relapses of neurological inflammation. These findings elucidate the pathogenic functions of CNS-compartmentalized B cells, highlighting their potential as therapeutic targets for relapsing MS.
Project description:While there were early papers about the extracellular actions of purines, the role of ATP as a purinergic neurotransmitter in nonadrenergic, noncholinergic nerves in the gut and bladder in 1972 was a landmark discovery, although it met considerable resistance for the next 20 years. In the early 1990s, receptors for purines were cloned: four P1 receptor subtypes and seven P2X ionotropic and eight P2Y metabotropic receptor subtypes are currently recognized and characterized. The mechanisms underlying ATP release and breakdown are discussed. Purines and pyrimidines have major roles in the activities of non-neuronal cells as well as neurons. This includes fast signalling roles in exocrine and endocrine secretion, platelet aggregation, vascular endothelial cell-mediated vasodilation and nociceptive mechanosensory transduction, as well as acting as a cotransmitter and neuromodulator in most, if not all, nerve types in the peripheral and central nervous systems. More recently, slow (trophic) purinergic signalling has been implicated in cell proliferation, migration, differentiation and death in embryological development, wound healing, restenosis, atherosclerosis, ischaemia, cell turnover of epithelial cells in skin and visceral organs, inflammation, neuroprotection and cancer.
Project description:In a recent study of the pathophysiology of mild, blast-induced traumatic brain injury (bTBI) the exposure of dissociated, central nervous system (CNS) cells to simulated blast resulted in propagating waves of elevated intracellular Ca(2+). Here we show, in dissociated human CNS cultures, that these calcium waves primarily propagate through astrocyte-dependent, purinergic signaling pathways that are blocked by P2 antagonists. Human, compared to rat, astrocytes had an increased calcium response and prolonged calcium wave propagation kinetics, suggesting that in our model system rat CNS cells are less responsive to simulated blast. Furthermore, in response to simulated blast, human CNS cells have increased expressions of a reactive astrocyte marker, glial fibrillary acidic protein (GFAP) and a protease, matrix metallopeptidase 9 (MMP-9). The conjoint increased expression of GFAP and MMP-9 and a purinergic ATP (P2) receptor antagonist reduction in calcium response identifies both potential mechanisms for sustained changes in brain function following primary bTBI and therapeutic strategies targeting abnormal astrocyte activity.
Project description:The coordination of tissue function is mediated by gap junctions (GJs) that enable direct cell-cell transfer of metabolic and electric signals. GJs are formed by connexins of which Cx43 is most widespread in the human body. In the brain, Cx43 GJs are mostly found in astroglia where they coordinate the propagation of Ca(2+) waves, spatial K(+) buffering, and distribution of glucose. Beyond its role in direct intercellular communication, Cx43 also forms unapposed, non-junctional hemichannels in the plasma membrane of glial cells. These allow the passage of several neuro- and gliotransmitters that may, combined with downstream paracrine signaling, complement direct GJ communication among glial cells and sustain glial-neuronal signaling. Mutations in the GJA1 gene encoding Cx43 have been identified in a rare, mostly autosomal dominant syndrome called oculodentodigital dysplasia (ODDD). ODDD patients display a pleiotropic phenotype reflected by eye, hand, teeth, and foot abnormalities, as well as craniofacial and bone malformations. Remarkably, neurological symptoms such as dysarthria, neurogenic bladder (manifested as urinary incontinence), spasticity or muscle weakness, ataxia, and epilepsy are other prominent features observed in ODDD patients. Over 10 mutations detected in patients diagnosed with neurological disorders are associated with altered functionality of Cx43 GJs/hemichannels, but the link between ODDD-related abnormal channel activities and neurologic phenotype is still elusive. Here, we present an overview on the nature of the mutants conveying structural and functional changes of Cx43 channels and discuss available evidence for aberrant Cx43 GJ and hemichannel function. In a final step, we examine the possibilities of how channel dysfunction may lead to some of the neurological manifestations of ODDD.
Project description:Long-term neurological and neurodevelopmental sequelae are a concerning issue for people with Enterovirus A71 (EV-A71) central nervous system (CNS) infection. Unfortunately, no longitudinal prospective clinical study has systematically investigated the consequences of EV-A71 CNS infection during early life on the later development of other psychiatric disorders. In this naturalistic longitudinal follow-up design, we followed forty-three youth, who got EV-A71 CNS involvement 6-18 years ago and were enrolled in other EV-A71 clinical studies then. Their psychiatric presentation, emotional/behavioral problems, and cognitive issues were examined using a psychiatrist-conducted diagnostic interview, parent- and self-rated questionnaires, and neuropsychological tests, respectively. We compared the prevalence of psychiatric disorders in youth with EV-A71 CNS involvement to a nationally representative cohort. Emotion/behavior and cognition in EV-A71-CNS-infected youth were compared to those in a matched community-based sample of healthy controls and youth with attention-deficit/hyperactivity disorder (ADHD). Compared to a national sample (absolute ADHD prevalence 10.1%), youth with EV-A71 CNS involvement had three times the odds of receiving an ADHD diagnosis (standardized prevalence ratio, 95% CI = 1.8, 4.2; absolute ADHD prevalence 34.9%). No other psychiatric diagnoses were more common in EV-A71-CNS-infected youth. Compared to community-based ADHD youth, EV-A71-CNS-infected youth with psychiatric disorders showed comparable core ADHD symptoms, opposition/defiance, autistic features, and suboptimal sustained attention performance (based on the Conners' Continuous Performance Test), all of which were more severe than healthy controls. EV-A71-CNS-infected youth without psychiatric disorders showed comparable autistic features to EV-A71-CNS-infected youth with psychiatric disorders and ADHD youth. EV-A71 CNS involvement may cause long-term, adverse psychiatric outcomes that develop into an ADHD diagnosis alongside social/communication/emotion problems and autistic features. We recommend earlier identification and intervention of these problems among these children.
Project description:Due to the extremely wide-spread expression of purinergic receptors, purinergic signalling has been implicated in numerous physiological and pathophysiological areas. To better understand the involvement of purinergic receptors in such areas, the researcher's requirement for diverse and varied purinergic receptor ligands has greatly increased. This has generated increased commercial opportunities for life science suppliers, and ultimately, has led to a rapid expansion in the number of commercially available purinergic receptor ligands. The wide-spread availability of ligands to researchers has greatly benefited the scientific community, nurturing the rapid and continued expansion of the purinergic signalling field.
Project description:1. P2 purinoreceptors are present in hypothalamic and brainstem nuclei that are involved in the regulation of body temperature (T(b)). The role of ATP acting on these P2 receptors in thermoregulation was investigated by studying the effects of the stable ATP analogue alpha,beta-methyleneATP (alpha,beta-meATP) and P2 receptor antagonists suramin and pyridoxal-5'-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on T(b) when injected intracerebroventricularly (i.c.v.) via a pre-implanted cannula in conscious rats at various ambient temperatures and during lipopolysaccharide (LPS)-induced fever. 2. Depending on ambient temperature, alpha,beta-meATP (0.2 micromol, i.c.v.) induced a fall in T(b) (-3.3 degrees C, P<0.05), no changes in T(b) when compared to pre-injection levels, or an increase in T(b) ( approximately 1.0 degrees C, P<0.05) in rats maintained at 10 degrees C, 25 degrees C and 30 degrees C ambient temperature, respectively. 3. Suramin (7 nmol, i.c.v.) induced a lasting (up to 6 h) increase in T(b) (on average 1.2 degrees C, P<0.05) in rats kept at 25 degrees C or 30 degrees C, but failed to induce any rise in T(b) in rats at 10 degrees C ambient temperature. An increase in T(b) was also observed in rats (25 degrees C ambient temperature) treated with PPADS (0.2 micromol, i.c.v.). 4. alpha,beta-meATP (0.2 micromol) injected i.c.v. or directly into the anterior hypothalamus caused a profound fall in T(b) (by 0.9 degrees C and 1.0 degrees C, respectively; P<0.05) during LPS (E.coli; 50 microg kg(-1))-induced fever in rats at 25 degrees C ambient temperature. Fever was initiated more rapidly in rats treated with suramin (7 nmol) or PPADS (70 nmol), however its late phase was unaffected. Suramin (7 nmol) and PPADS (70 nmol) injected at the time when fever was already developed (2.5 h after LPS injections) did not alter febrile T(b). 5. These data indicate that purinergic signalling may play a significant role in central mechanisms of T(b) regulation at various ambient temperatures and during fever.