ERR2 and ERR3 promote the development of gamma motor neuron functional properties required for proprioceptive movement control.

The ability of terrestrial vertebrates to effectively move on land is integrally linked to the diversification of motor neurons into types that generate muscle force (alpha motor neurons) and types that modulate muscle proprioception, a task that in mammals is chiefly mediated by gamma motor neurons. The diversification of motor neurons into alpha and gamma types and their respective contributions to movement control have been firmly established in the past 7 decades, while recent studies identified gene expression signatures linked to both motor neuron types. However, the mechanisms that promote the specification of gamma motor neurons and/or their unique properties remained unaddressed. Here, we found that upon selective loss of the orphan nuclear receptors ERR2 and ERR3 (also known as ERRß, ERRγ or NR3B2, NR3B3, respectively) in motor neurons in mice, morphologically distinguishable gamma motor neurons are generated but do not acquire characteristic functional properties necessary for regulating muscle proprioception, thus disrupting gait and precision movements. Complementary gain-of-function experiments in chick suggest that ERR2 and ERR3 could operate via transcriptional activation of neural activity modulators to promote a gamma motor neuron biophysical signature of low firing thresholds and high firing rates. Our work identifies a mechanism specifying gamma motor neuron functional properties essential for the regulation of proprioceptive movement control.

Prediction of Belimumab Pharmacokinetics in Chinese Pediatric Patients with Systemic Lupus Erythematosus.

BACKGROUND AND OBJECTIVE: Intravenous (IV) belimumab is the first treatment approved for children ≥5 years of age with active autoantibody-positive systemic lupus erythematosus (SLE) in the USA, Europe, and Japan. Pharmacokinetic data for belimumab were collected from several clinical trials in Chinese and non-Chinese adults and non-Chinese pediatric patients with SLE. This study aimed to predict the belimumab dose-exposure relationship to Chinese pediatric patients with SLE, as part of the belimumab registration process for this population in China, using a population PK modeling approach. METHODS: An initial linear two-compartment population pharmacokinetic model was built using data from adults only, and considering and adjusting for the covariates age, body weight, body mass index, fat-free mass, race, baseline albumin and immunoglobulin G levels. The model was used to study possible ethnic differences between Chinese and non-Chinese adults and to predict pediatric pharmacokinetic data in a study of non-Chinese pediatric patients (PLUTO study; NCT01649765). The predicted data were compared with the observed data from PLUTO. The model was then updated with pediatric data from PLUTO to predict steady-state belimumab exposure in Chinese pediatric patients with SLE receiving belimumab 10 mg/kg IV every 4 weeks. RESULTS: The dataset comprised 9650 sampled concentration values from 1783 patients. The pharmacokinetics of belimumab were adequately described by the final model using all adult and pediatric data with the estimated typical clearance of 238 ml/day in adult and pediatric patients and steady-state volume of distribution of 4915 ml in adults. Between-patient variability was modest (coefficients of variation: 26.1% for clearance; 8.9% and 28.5%, respectively, for volumes of distribution of the central and peripheral compartments). Six covariates were identified that influenced pharmacokinetics: age, fat-free mass, an indicator of North East Asian race, baseline albumin, immunoglobulin G, and an early study indicator (two early phase I and phase II belimumab studies: LBSL01 and LBSL02). The analysis showed no apparent difference in steady-state exposure between Chinese and non-Chinese populations and between pediatric and adult populations receiving belimumab 10 mg/kg IV. CONCLUSIONS: In Chinese pediatric patients with SLE, belimumab 10 mg/kg IV every 4 weeks is expected to have exposure similar to that in Chinese adults and non-Chinese pediatric patients with SLE, supporting the use of this regimen in Chinese pediatric patients with SLE. CLINICAL TRIAL REGISTRATION NUMBERS: NCT01649765, NCT00657007, NCT00071487, NCT01345253, NCT01516450, NCT00410384, NCT00424476, NCT02880852, NCT01583530.

Role of ciliary neurotrophic factor in microglial phagocytosis.

Microglia, CNS-resident macrophages, serve as scavengers to remove cellular debris and facilitate tissue remodeling in the developing and injured CNS. Little is known as what and how microenvironmental factors mediate the phagocytotic ability of microglia. Our previous study has indicated that treatment with glial cell line-derived neurotrophic factor (GDNF) increased the phagocytotic activity of primary rat microglia possibly through the upregulation of alpha5 integrin. In the present study, ciliary neurotrophic factor (CNTF), which has been reported to be produced by glia, was shown to have stimulatory effect on the phagocytosis of primary rat microglia and mouse microglial cell line BV2. Ca2+ imaging analysis and the application of intracellular calcium chelator BAPTA-AM revealed that CNTF-induced increase in microglial phagocytosis was mediated by a calcium signaling pathway. Furthermore, treatment with CNTF led to an increase in the expression of alphav integrin, which has been reported to be involved in the phagocytosis of the apoptotic cells. In summary, we have provided evidence that CNTF can increase microglial phagocytosis through a calcium-mediated pathway. Our results also suggest that the upregulation of alphav integrin by CNTF could be involved in the increased phagocytotic activity of microglia.

Regulation of microglial activities by glial cell line derived neurotrophic factor.

Much attention has been paid to the ability of glial cell line-derived neurotrophic factor (GDNF) to protect neurons from neurotoxic insults in the central nervous system (CNS). However, little is known about GDNF action on CNS glia that also can express GDNF receptor systems. In this study, we examined the effects of GDNF on primary rat microglia that function as resident macrophages in the CNS and as the source of proinflammatory mediators upon activation. We found that treatment of primary rat microglia with GDNF had no effect on the secretion of the proinflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), but it increased the nitric oxide (NO) production to some extent. In addition, GDNF increased the enzymatic activity of superoxide dismutase (SOD), the gene expression of surface antigen intercellular adhesion molecule-1 (ICAM-1), the production of the integrin alpha5 subunit, and the phagocytotic capability in primary rat microglia. Furthermore, inhibition of mitogen-activated protein kinase (Erk-MAPK) in the mouse microglial cell line BV2 by U0126 indicated that the MAP kinase signaling pathway may be involved in the regulation of NO and integrin alpha5 production by GDNF. In vivo evidence also showed that amoeboid cells with integrin alpha5 or with ED1 immunoreactivity appeared in GDNF-treated spinal cord tissues at the lesion site 1 week post spinal cord injury (SCI). Furthermore, inhibition of Erk-MAPK in the mouse microglial cell line BV2 by U0126 indicated that the MAP kinase signaling pathway may be involved in the regulation of NO and integrin alpha5 production by GDNF. Taken together, our results indicate that GDNF has a positive regulatory effect on microglial activities, such as phagocytosis and the upregulation of adhesion molecules.

Inhibition of lipopolysaccharide-induced microglial activation by preexposure to neurotrophin-3.

Microglia activated by neural injuries produce proinflammatory mediators, but activated microglia also appear in developing neural tissue to phagocytose cell debris resulting from programmed cell death without inducing tissue damage. Thus, factors associated with the developing CNS may modulate microglial activities. Previously we reported that pretreatment with neurotrophin-3 (NT-3), a factor known to regulate neural development, inhibits the production of proinflammatory mediators, nitric oxide (NO), tumor necrosis factor-alpha, and interleukin-1beta, in BV2 activated by inflammagen lipopolysaccharide (LPS). In this study, the inhibition of proinflammatory mediators by NT-3 pretreatment (preNT-3) in primary microglia with LPS stimulation was corroborated. Moreover, pretreatment of LPS-activated microglia with NT-3 induced a trend of reduction in phagocytotic ability. By using LPS-activated BV2 cells, we further found that reduced expression of inducible NO synthetase by preNT-3 was mediated by MAP kinase and PI3 kinase signaling pathways. Moreover, pretreatment of BV2 cells with NT-3 led to reduced levels of the p65 subunit of nucleus factor-kappaB (NFkappaB) and its DNA binding activity. Accordingly, our results indicate that preexposure of microglia to NT-3 leads to a reduced production of proinflammatory mediators in activated microglia by the induction of MAP kinase and PI3 kinase signaling, which in turn may reduce NFkappaB DNA binding activity. This suggests that an NT-enriched microenvironment may be favorable for preventing the inflammatory reaction of microglia.