Targeted deletion of PAC1 receptors in retinal neurons enhances neuron loss and axonopathy in a model of multiple sclerosis and optic neuritis.

Chronic inflammation drives synaptic loss in multiple sclerosis (MS) and is also commonly observed in other neurodegenerative diseases. Clinically approved treatments for MS provide symptomatic relief but fail to halt neurodegeneration and neurological decline. Studies in animal disease models have demonstrated that the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP, ADCYAP1) exhibits anti-inflammatory, neuroprotective and regenerative properties. Anti-inflammatory actions appear to be mediated primarily by two receptors, VPAC1 and VPAC2, which also bind vasoactive intestinal peptide (VIP). Pharmacological experiments indicate that another receptor, PAC1 (ADCYAP1R1), which is highly selective for PACAP, provides protection to neurons, although genetic evidence and other mechanistic information is lacking. To determine if PAC1 receptors protect neurons in a cell-autonomous manner, we used adeno-associated virus (AAV2) to deliver Cre recombinase to the retina of mice harboring floxed PAC1 alleles. Mice were then subjected to chronic experimental autoimmune encephalomyelitis (EAE), a disease model that recapitulates major clinical and pathological features of MS and associated optic neuritis. Unexpectedly, deletion of PAC1 in naïve mice resulted in a deficit of retinal ganglionic neurons (RGNs) and their dendrites, suggesting a homeostatic role of PAC1. Moreover, deletion of PAC1 resulted in increased EAE-induced loss of a subpopulation of RGNs purported to be vulnerable in animal models of glaucoma. Increased axonal pathology and increased secondary presence of microglia/macrophages was also prominently seen in the optic nerve. These findings demonstrate that neuronal PAC1 receptors play a homeostatic role in protecting RGNs and directly protects neurons and their axons against neuroinflammatory challenge. SIGNIFICANCE STATEMENT: Chronic inflammation is a major component of neurodegenerative diseases and plays a central role in multiple sclerosis (MS). Current treatments for MS do not prevent neurodegeneration and/or neurological decline. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to have anti-inflammatory, neuroprotective and regenerative properties but the cell type- and receptor-specific mechanisms are not clear. To test whether the protective effects of PACAP are direct on the PAC1 receptor subtype on neurons, we delete PAC1 receptors from neurons and investigate neuropathologigical changes in an animal model of MS. The findings demonstrate that PAC1 receptors on neurons play a homeostatic role in maintaining neuron health and can directly protect neurons and their axons during neuroinflammatory disease.

Sample size considerations for matched-pair cluster randomization design with incomplete observations of binary outcomes.

Multiple public health and medical research studies have applied matched-pair cluster randomization design to the evaluation of the intervention and/or prevention effects. One of the most common and severe problems faced by researchers when conducting cluster randomized trials (CRTs) is incomplete observations, which are associated with various reasons causing the individuals to discontinue participating in the trials. Although statistical methods to remedy the problems of missing data have already been proposed, there are still methodological gaps in research concerning the determination of sample size in matched-pair CRTs with incomplete binary outcomes. One conventional method for adjusting for missing data in the sample size determination is to divide the sample size under complete data by the expected follow-up rate. However, such crude adjustment ignores the impact of the structure and strength of correlations regarding both outcome data and missing data mechanism. This article provides a closed-form sample size formula for matched-pair CRTs with incomplete binary outcomes, which appropriately accounts for different missing patterns and magnitudes as well as the effects of matching and clustering on the outcome and missing data. The generalized estimating equation (GEE) approach treats incomplete observations as missing data in a marginal logistic regression model, which flexibly accommodates various types of intraclass correlation, missing patterns, and missing proportions. In the presence of missing data, the proposed GEE sample size method provides higher accuracy as compared with the conventional method. The performance of the proposed method is assessed by simulation studies. This article also illustrates how the proposed method can be used to design a real-world matched-pair CRT to examine the effect of a team-based approach on controlling blood pressure (BP).

Ethnic Disparities in Early-Onset Gastric Cancer: A Population-Based Study in Texas and California.

BACKGROUND: Incidence rates of gastric cancer are increasing in young adults (age <50 years), particularly among Hispanic persons. We estimated incidence rates of early-onset gastric cancer (EOGC) among Hispanic and non-Hispanic White persons by census tract poverty level and county-level metro/nonmetro residence. METHODS: We used population-based data from the California and Texas Cancer Registries from 1995 to 2016 to estimate age-adjusted incidence rates of EOGC among Hispanic and non-Hispanic White persons by year, sex, tumor stage, census tract poverty level, metro versus nonmetro county, and state. We used logistic regression models to identify factors associated with distant stage diagnosis. RESULTS: Of 3,047 persons diagnosed with EOGC, 73.2% were Hispanic White. Incidence rates were 1.29 [95% confidence interval (CI), 1.24-1.35] and 0.31 (95% CI, 0.29-0.33) per 100,000 Hispanic White and non-Hispanic White persons, respectively, with consistently higher incidence rates among Hispanic persons at all levels of poverty. There were no statistically significant associations between ethnicity and distant stage diagnosis in adjusted analysis. CONCLUSIONS: There are ethnic disparities in EOGC incidence rates that persist across poverty levels. IMPACT: EOGC incidence rates vary by ethnicity and poverty; these factors should be considered when assessing disease risk and targeting prevention efforts.

PACAP/PAC1 Regulation of Inflammation via Catecholaminergic Neurons in a Model of Multiple Sclerosis.

The sympathetic nervous system (SNS) serves to maintain homeostasis of vital organ systems throughout the body, and its dysfunction plays a major role in human disease. The SNS also links the central nervous system to the immune system during different types of stress via innervation of the lymph nodes, spleen, thymus, and bone marrow. Previous studies have shown that pituitary adenylate cyclase-activating polypeptide (PACAP, gene name adcyap1) exhibits anti-inflammatory properties in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Because PACAP is known to regulate SNS function, we hypothesized that part of the immunoprotective action of PACAP is due to its neuromodulatory effects on sympathetic neurons. To examine this, we used an inducible, targeted approach to conditionally disrupt not only the PACAP-preferring PAC1 receptor gene (adcyap1r1) in dopamine ß-hydroxylase-expressing cells, which includes postganglionic sympathetic neurons, but also catecholaminergic neurons in the brain and adrenomedullary chromaffin cells. In contrast to our previous EAE studies using PACAP global knockout mice which developed severe and prolonged EAE, we found that mice with conditional loss of PAC1 receptors in catecholaminergic cells developed a delayed time course of EAE with reduced helper T cell type 1 (Th1) and Th17 and enhanced Th2 cell polarization. At later time points, similar to mice with global PACAP loss, mice with conditional loss of PAC1 exhibited more severe clinical disease than controls. The latter was associated with a reduction in the abundance of thymic regulatory T cells (Tregs). These studies indicate that PAC1 receptor signaling acts in catecholaminergic cells in a time-dependent manner. At early stages of disease development, it enhances the ability of the SNS to polarize the Th response towards a more inflammatory state. Then, after disease is established, it enhances the ability of the SNS to dampen the inflammatory response via Tregs. The lack of concordance in results between global PACAP KO mice and mice with the PAC1 deletion targeted to catecholaminergic cells during early EAE may be explained by the fact that PACAP acts to regulate inflammation via multiple receptor subtypes and multiple targets, including inflammatory cells.

Correction to: PACAP/PAC1 Regulation of Inflammation via Catecholaminergic Neurons in a Model of Multiple Sclerosis.

The original version of this article unfortunately contained mistakes. The captured article title and corresponding author were incorrect.