Neuromagnetic evidence of abnormal movement-related beta desynchronization in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder associated with debilitating motor, posture, and gait abnormalities. Human studies recording local field potentials within the subthalamic nucleus and scalp-based electroencephalography have shown pathological beta synchronization throughout the cortical-basal ganglia motor network in PD. Suppression of such pathological beta synchronization has been associated with improved motor function, which may explain the effectiveness of deep-brain stimulation. We used magnetoencephalography (MEG) to investigate neural population-level beta responses, and other oscillatory activity, during a motor task in unmedicated patients with PD and a matched group of healthy adults. MEG is a noninvasive neurophysiological technique that permits the recording of oscillatory activity during movement planning, execution, and termination phases. Each of these phases was independently examined using beamforming to distinguish the brain areas and movement phases, where pathological oscillations exist during motor control. Patients with PD exhibited significantly diminished beta desynchronization compared with controls prior to and during movement, which paralleled reduced alpha desynchronization. This study is the first to systematically investigate neural oscillatory responses in PD during distinct stages of motor control (e.g. planning, execution, and termination) and indicates that these patients have significant difficulty suppressing cortical beta synchronization during movement planning, which may contribute to their diminished movement capacities.

Immune Checkpoint Function of CD85j in CD8 T Cell Differentiation and Aging.

Aging is associated with an increased susceptibility to infection and a failure to control latent viruses thought to be driven, at least in part, by alterations in CD8 T cell function. The aging T cell repertoire is characterized by an accumulation of effector CD8 T cells, many of which express the negative regulatory receptor CD85j. To define the biological significance of CD85j expression on CD8 T cells and to address the question whether presence of CD85j in older individuals is beneficial or detrimental for immune function, we examined the specific attributes of CD8 T cells expressing CD85j as well as the functional role of CD85j in antigen-specific CD8 T cell responses during immune aging. Here, we show that CD85j is mainly expressed by terminally differentiated effector (TEMRAs) CD8 T cells, which increase with age, in cytomegalovirus (CMV) infection and in males. CD85j+ CMV-specific cells demonstrate clonal expansion. However, TCR diversity is similar between CD85j+ and CD85j- compartments, suggesting that CD85j does not directly impact the repertoire of antigen-specific cells. Further phenotypic and functional analyses revealed that CD85j identifies a specific subset of CMV-responsive CD8 T cells that coexpress a marker of senescence (CD57) but retain polyfunctional cytokine production and expression of cytotoxic mediators. Blocking CD85j binding enhanced proliferation of CMV-specific CD8 T cells upon antigen stimulation but did not alter polyfunctional cytokine production. Taken together, these data demonstrate that CD85j characterizes a population of "senescent," but not exhausted antigen-specific effector CD8 T cells and indicates that CD85j is an important checkpoint regulator controlling expansion of virus-specific T cells during aging. Inhibition of CD85j activity may be a mechanism to promote stronger CD8 T cell effector responses during immune aging.

Expression of CD39 on Activated T Cells Impairs their Survival in Older Individuals.

In an immune response, CD4(+) T cells expand into effector T cells and then contract to survive as long-lived memory cells. To identify age-associated defects in memory cell formation, we profiled activated CD4(+) T cells and found an increased induction of the ATPase CD39 with age. CD39(+) CD4(+) T cells resembled effector T cells with signs of metabolic stress and high susceptibility to undergo apoptosis. Pharmacological inhibition of ATPase activity dampened effector cell differentiation and improved survival, suggesting that CD39 activity influences T cell fate. Individuals carrying a low-expressing CD39 variant responded better to vaccination with an increase in vaccine-specific memory T cells. Increased inducibility of CD39 after activation may contribute to the impaired vaccine response with age.

Murine motor and behavior functional evaluations for acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication.

Acute intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces nigrostriatal neurodegeneration that reflects Parkinson's disease (PD) pathobiology. The model is commonly used for rodent studies of PD pathogenesis and diagnostics and for developmental therapeutics. However, tests of motor function in MPTP-intoxicated mice have yielded mixed results. This unmet need reflects, in part, lesion severity, animal variability, and the overall test sensitivity and specificity. In attempts to standardize rodent motor function and behavioral tests, mice were trained on the rotarod or habituated in an open field test chamber, and baseline performance measurements were collected prior to MPTP intoxication. One week following MPTP intoxication, motor function and behavior were assessed and baseline measurements applied to post-MPTP measurements with normalization to PBS controls. Rotarod and open field tests assessed in this manner demonstrated significant differences between MPTP- and saline-treated mice, while tests of neuromuscular strength and endurance did not. We conclude that the rotarod and open field tests provide reliable measures of motor function for MPTP-intoxicated mice.

Inflammation and adaptive immunity in Parkinson's disease.

The immune system is designed to protect the host from infection and injury. However, when an adaptive immune response continues unchecked in the brain, the proinflammatory innate microglial response leads to the accumulation of neurotoxins and eventual neurodegeneration. What drives such responses are misfolded and nitrated proteins. Indeed, the antigen in Parkinson's disease (PD) is an aberrant self-protein, although the adaptive immune responses are remarkably similar in a range of diseases. Ingress of lymphocytes and chronic activation of glial cells directly affect neurodegeneration. With this understanding, new therapies aimed at modulating the immune system's response during PD could lead to decreased neuronal loss and improved clinical outcomes for disease.

Pathways towards an effective immunotherapy for Parkinson's disease.

Immunizations that target specific types of immune responses are used commonly to prevent microbial infections. However, a range of immune responses may prove necessary to combat the ravages of neurodegenerative diseases. The goal is to eliminate the 'root' cause of neurodegenerative disorders, misfolded aggregated proteins, while harnessing adaptive immune responses to promote neural repair. However, immunization strategies used to elicit humoral immune responses against aberrant brain proteins have yielded mixed success. While specific proteins can be cleared, the failures in halting disease progression revolve, in measure, around adaptive immune responses that promote autoreactive T cells and, as such, induce a meningoencephalitis, accelerating neurodegeneration. Thus, alternative approaches for protein clearance and neural repair are desired. To this end, our laboratories have sought to transform autoreactive adaptive immune responses into regulatory neuroprotective cells in Parkinson's disease. In this context, induction of immune responses against modified brain proteins serves to break immunological tolerance, while eliciting adaptive immunity to facilitate neuronal repair. How to harness the immune response in the setting of Parkinson's disease requires a thorough understanding of the role of immunity in human disease and the ways to modify such immune responses to elicit therapeutic gain. These are discussed in this review.