Trial of Prasinezumab in Early-Stage Parkinson's Disease.

BACKGROUND: Aggregated α-synuclein plays an important role in the pathogenesis of Parkinson's disease. The monoclonal antibody prasinezumab, directed at aggregated α-synuclein, is being studied for its effect on Parkinson's disease. METHODS: In this phase 2 trial, we randomly assigned participants with early-stage Parkinson's disease in a 1:1:1 ratio to receive intravenous placebo or prasinezumab at a dose of 1500 mg or 4500 mg every 4 weeks for 52 weeks. The primary end point was the change from baseline to week 52 in the sum of scores on parts I, II, and III of the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS; range, 0 to 236, with higher scores indicating greater impairment). Secondary end points included the dopamine transporter levels in the putamen of the hemisphere ipsilateral to the clinically more affected side of the body, as measured by 123I-ioflupane single-photon-emission computed tomography (SPECT). RESULTS: A total of 316 participants were enrolled; 105 were assigned to receive placebo, 105 to receive 1500 mg of prasinezumab, and 106 to receive 4500 mg of prasinezumab. The baseline mean MDS-UPDRS scores were 32.0 in the placebo group, 31.5 in the 1500-mg group, and 30.8 in the 4500-mg group, and mean (±SE) changes from baseline to 52 weeks were 9.4±1.2 in the placebo group, 7.4±1.2 in the 1500-mg group (difference vs. placebo, -2.0; 80% confidence interval [CI], -4.2 to 0.2; P = 0.24), and 8.8±1.2 in the 4500-mg group (difference vs. placebo, -0.6; 80% CI, -2.8 to 1.6; P = 0.72). There was no substantial difference between the active-treatment groups and the placebo group in dopamine transporter levels on SPECT. The results for most clinical secondary end points were similar in the active-treatment groups and the placebo group. Serious adverse events occurred in 6.7% of the participants in the 1500-mg group and in 7.5% of those in the 4500-mg group; infusion reactions occurred in 19.0% and 34.0%, respectively. CONCLUSIONS: Prasinezumab therapy had no meaningful effect on global or imaging measures of Parkinson's disease progression as compared with placebo and was associated with infusion reactions. (Funded by F. Hoffmann-La Roche and Prothena Biosciences; PASADENA ClinicalTrials.gov number, NCT03100149.).

Two novel DEG/ENaC channel subunits expressed in glia are needed for nose-touch sensitivity in Caenorhabditis elegans.

Neuronal DEG/ENaC (degenerin and epithelial Na(+) channel) Na(+) channels have been implicated in touch sensation. For example, MEC-4 is expressed in touch neurons in Caenorhabditis elegans and mediates gentle-touch response. Similarly, homologous mammalian ASIC2 and ASIC3 are expressed in sensory neurons and produce touch phenotypes when knocked out in mice. Here, we show that novel DEG/ENaC subunits DELM-1 and DELM-2 (degenerin-like channel mechanosensory linked-1 and degenerin-like channel mechanosensory linked-2) are expressed in glia associated with touch neurons in C. elegans and that their knock-out causes defects in mechanosensory behaviors related to nose touch and foraging, which are mediated by OLQ and IL1 sensory neurons. Cell-specific rescue supports that DELM-1 and DELM-2 are required cell-autonomously in glia to orchestrate mechanosensory behaviors. Electron microscopy reveals that in delm-1 knock-outs, OLQ and IL1 sensory neurons and associated glia are structurally normal. Furthermore, we show that knock-out of DELM-1 and DELM-2 does not disrupt the expression or cellular localization of TRPA-1, a TRP channel needed in OLQ and IL1 neurons for touch behaviors. Rather, rescue of the delm-1 nose-touch-insensitive phenotype by expression of a K(+) channel in socket glia and of a cationic channel in OLQ neurons suggests that DELM channels set basal neuronal excitability. Together, our data show that DELM-1 and DELM-2 are expressed in glia associated with touch neurons where they are not needed for neuronal structural integrity or cellular distribution of neuronal sensory channels, but rather for their function.

Knockout of glial channel ACD-1 exacerbates sensory deficits in a C. elegans mutant by regulating calcium levels of sensory neurons.

Degenerin/epithelial Na(+) channels (DEG/ENaCs) are voltage-independent Na(+) or Na(+)/Ca(2+) channels expressed in many tissues and are needed for a wide range of physiological functions, including sensory perception and transepithelial Na(+) transport. In the nervous system, DEG/ENaCs are expressed in both neurons and glia. However, the role of glial vs. neuronal DEG/ENaCs remains unclear. We recently reported the characterization of a novel DEG/ENaC in Caenorhabditis elegans that we named ACD-1. ACD-1 is expressed in glial amphid sheath cells. The glial ACD-1, together with the neuronal DEG/ENaC DEG-1, is necessary for acid avoidance and attraction to lysine. We report presently that knockout of acd-1 in glia exacerbates sensory deficits caused by another mutant: the hypomorphic allele of the cGMP-gated channel subunit tax-2. Furthermore, sensory deficits caused by mutations in G(i) protein odr-3 and guanylate cyclase daf-11, which regulate the activity of TAX-2/TAX-4 channels, are worsened by knockout of acd-1. We also show that sensory neurons of acd-1 tax-2(p694) double mutants fail to undergo changes in intracellular Ca(2+) when animals are exposed to low concentrations of attractant. Finally, we show that exogenous expression of TRPV1 in sensory neurons and exposure to capsaicin rescue sensory deficits of acd-1 tax-2(p694) mutants, suggesting that sensory deficits of these mutants are bypassed by increasing neuronal excitability. Our data suggest a role of glial DEG/ENaC channel ACD-1 in supporting neuronal activity.

An inhibitory gate for state transition in cortex.

Large scale transitions between active (up) and silent (down) states during quiet wakefulness or NREM sleep regulate fundamental cortical functions and are known to involve both excitatory and inhibitory cells. However, if and how inhibition regulates these activity transitions is unclear. Using fluorescence-targeted electrophysiological recording and cell-specific optogenetic manipulation in both anesthetized and non-anesthetized mice, we found that two major classes of interneurons, the parvalbumin and the somatostatin positive cells, tightly control both up-to-down and down-to-up state transitions. Inhibitory regulation of state transition was observed under both natural and optogenetically-evoked conditions. Moreover, perturbative optogenetic experiments revealed that the inhibitory control of state transition was interneuron-type specific. Finally, local manipulation of small ensembles of interneurons affected cortical populations millimetres away from the modulated region. Together, these results demonstrate that inhibition potently gates transitions between cortical activity states, and reveal the cellular mechanisms by which local inhibitory microcircuits regulate state transitions at the mesoscale.

Layer-specific excitatory circuits differentially control recurrent network dynamics in the neocortex.

In the absence of external stimuli, the mammalian neocortex shows intrinsic network oscillations. These dynamics are characterized by translaminar assemblies of neurons whose activity synchronizes rhythmically in space and time. How different cortical layers influence the formation of these spontaneous cellular assemblies is poorly understood. We found that excitatory neurons in supragranular and infragranular layers have distinct roles in the regulation of intrinsic low-frequency oscillations in mice in vivo. Optogenetic activation of infragranular neurons generated network activity that resembled spontaneous events, whereas photoinhibition of these same neurons substantially attenuated slow ongoing dynamics. In contrast, light activation and inhibition of supragranular cells had modest effects on spontaneous slow activity. This study represents, to the best of our knowledge, the first causal demonstration that excitatory circuits located in distinct cortical layers differentially control spontaneous low-frequency dynamics.