Human oligodendroglial cells express low levels of C1 inhibitor and membrane cofactor protein mRNAs

The validity of animal models to explore the pathogenic role of the complement system in multiple sclerosis: A review

Animal models of multiple sclerosis (MS) have been extensively used to characterize the disease mechanisms in MS, as well as to identify potential pharmacologic targets for this condition. In recent years, the immune complement system has gained increased attention as an important effector in the pathogenesis of MS. Evidence from histological, serum, and CSF studies of patients supports an involvement of complement in both relapsing-remitting and progressive MS. In this review, we discuss the history and advances made on the use of MS animal models to profile the effects of the complement system in this condition. The first studies that explored the complement system in the context of MS used cobra venom factor (CVF) as a complement depleting agent in experimental autoimmune encephalomyelitis (EAE) Lewis rats. Since then, multiple mice and rat models of MS have revealed a role of C3 and the alternative complement cascade in the opsonization and phagocytosis of myelin by microglia and myeloid cells. Studies using viral vectors, genetic knockouts and pharmacologic complement inhibitors have also shown an effect of complement in synaptic loss. Antibody-mediated EAE models have revealed an involvement of the C1 complex and the classical complement as an effector of the humoral response in this disease. C1q itself may also be involved in modulating microglia activation and oligodendrocyte differentiation in these animals. In addition, animal and in vitro models have revealed that multiple complement factors may act as modulators of both the innate and adaptive immune responses. Finally, evidence gathered from mice models suggests that the membrane attack complex (MAC) may even exert protective roles in the chronic stages of EAE. Overall, this review summarizes the importance of MS animal models to better characterize the role of the complement system and guide future therapeutic approaches in this condition.

Species differences in immune-mediated CNS tissue injury and repair: A (neuro)inflammatory topic

Cells of the adaptive and innate immune systems in the brain parenchyma and in the meningeal spaces contribute to physiologic functions and disease states in the central nervous system (CNS). Animal studies have demonstrated the involvement of immune constituents, along with major histocompatibility complex (MHC) molecules, in neural development and rare genetic disorders (e.g., colony stimulating factor 1 receptor [CSF1R] deficiency). Genome wide association studies suggest a comparable role of the immune system in humans. Although the CNS can be the target of primary autoimmune disorders, no current experimental model captures all of the features of the most common human disorder placed in this category, multiple sclerosis (MS). Such features include spontaneous onset, environmental contributions, and a recurrent/progressive disease course in a genetically predisposed host. Numerous therapeutic interventions related to antigen and cytokine specific therapies have demonstrated effectiveness in experimental autoimmune encephalomyelitis (EAE), the animal model used to define principles underlying immune-mediated mechanisms in MS. Despite the similarities in the two diseases, most treatments used to ameliorate EAE have failed to translate to the human disease. As directly demonstrated in animal models and implicated by correlative studies in humans, adaptive and innate immune constituents within the systemic compartment and resident in the CNS contribute to the disease course of neurodegenerative and neurobehavioral disorders. The expanding knowledge of the molecular properties of glial cells provides increasing insights into species related variables. These variables affect glial bidirectional interactions with the immune system as well as their own production of "immune molecules" that mediate tissue injury and repair.

Inflammation in Alzheimer disease-a brief review of the basic science and clinical literature

Biochemical and neuropathological studies of brains from individuals with Alzheimer disease (AD) provide clear evidence for an activation of inflammatory pathways, and long-term use of anti-inflammatory drugs is linked with reduced risk to develop the disease. As cause and effect relationships between inflammation and AD are being worked out, there is a realization that some components of this complex molecular and cellular machinery are most likely promoting pathological processes leading to AD, whereas other components serve to do the opposite. The challenge will be to find ways of fine tuning inflammation to delay, prevent, or treat AD.

LRRK2 expression in normal and pathologic human brain and in human cell lines

Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) have been recently identified in families with autosomal-dominant late-onset Parkinson disease. We report that by reverse transcriptase-polymerase chain reaction, the mRNA of LRRK2 is expressed in soluble extracts of human brain, liver, and heart and in cultured human astrocytes, microglia, and oligodendroglia as well as in human neuroblastoma cell lines. We find by Western blotting using a polyclonal antibody of the leucine-rich repeat kinase 2 protein (Lrrk2) specific for C-terminal residues 2,511-2,527 that an apparent full-length protein and several of its fractions are expressed in soluble extracts of normal human brain. By immunocytochemistry, the antibody recognizes neurons, and more weakly astrocytes and microglia, in normal brain tissue. It intensely labels Lewy bodies in Parkinson disease and related neurodegenerative disorders. It also labels a subset of neurofibrillary tangles in Alzheimer disease and the Parkinsonism dementia complex of Guam (PDCG). It labels thorn-shaped astrocytes and oligodendroglial coiled bodies in PDCG; oligodendroglial inclusions in multiple system atrophy; Pick bodies in Pick disease; nuclear and cytoplasmic inclusions in Huntington disease; and intraneuronal and glial inclusions in amyotrophic lateral sclerosis. In summary, LRRK2 is constitutively expressed in neurons and also in glial cells of human brain. It strongly associates with pathological inclusions in several neurodegenerative disorders.

Alpha-synuclein and its disease-causing mutants induce ICAM-1 and IL-6 in human astrocytes and astrocytoma cells

Autosomal dominant Parkinson disease (PD) is caused by duplication or triplication of the alpha-synuclein gene as well as by the A30P, E46K, and A53T mutations. The mechanisms are unknown. Reactive astrocytes in the substantia nigra of PD and MPTP-treated monkeys display high levels of the inflammatory mediator intercellular adhesion molecule-1 (ICAM-1), indicating that chronic inflammation contributes to the degeneration. Here we report that alpha-synuclein strongly stimulates human astrocytes as well as human U-373 MG astrocytoma cells to up-regulate both interleukin (IL)-6 and ICAM-1 (ED50=5 microg ml(-1)). The mutated forms are more potent stimulators than wild-type (WT) alpha-synuclein in these assays. We demonstrate by immunoblotting analysis that this up-regulation is associated with activation of the major mitogen-activated protein kinase (MAPK) pathways. It is also attenuated by PD 98059, an inhibitor of the MAPK/extracellular-regulated kinase kinase MEK1/2, SP 600125, an inhibitor of c-Jun N-terminal kinase (JNK), and SB 202190, an inhibitor of p38 MAPK. The inhibitory effects on human astrocytes have IC50 values of 2, 5, and 1.5 microM respectively. We hypothesize that the neuroinflammation stimulated by release of an excess of normal alpha-synuclein or by release of its mutated forms can be involved in the pathobiology of PD.

Thrombin and prothrombin are expressed by neurons and glial cells and accumulate in neurofibrillary tangles in Alzheimer disease brain

Thrombin is a serine protease that is generated by proteolytic cleavage of its precursor, prothrombin. We previously showed that thrombin proteolyses the microtubule-associated protein tau and that phosphorylation of tau inhibits this process. To characterize further the role of thrombin in the brain, we investigated prothrombin and thrombin expression in cultured brain cells and in brains of control, Alzheimer disease (AD) and parkinsonism-dementia complex of Guam (PDCG). We show by reverse transcriptase-polymerase chain reaction that prothrombin mRNA is expressed in brain tissues, neuroblastoma cells, and cultured human astrocytes, oligodendrocytes, and microglial cells. We also show by immunohistochemistry that the proteins prothrombin and thrombin are present in brain using specific monoclonal and polyclonal antibodies for both proteins. All antibodies stained residual serum in blood vessels, as well as normal pyramidal neurons and their processes, and some astrocytes. Additionally, in AD and PDCG cases, all antibodies stained extra- and intracellular neurofibrillary tangles (NFTs), senile plaques, and reactive microglial cells. The ubiquitous expression of prothrombin and thrombin in brain cells suggests that thrombin plays an important physiological role in normal brain. The accumulation of thrombin and prothrombin in NFTs supports the hypothesis that thrombin may be involved in tau proteolysis and that failure to metabolize tau may lead to its aggregation in neurodegenerative diseases.