Original Article
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 14, 2014; 20(38): 13911-13919
Published online Oct 14, 2014. doi: 10.3748/wjg.v20.i38.13911
Distribution of the P2X2 receptor and chemical coding in ileal enteric neurons of obese male mice (ob/ob)
Márcia Sanae Mizuno, Amanda Rabello Crisma, Primavera Borelli, Bárbara Tavares Schäfer, Mariana Póvoa Silveira, Patricia Castelucci
Márcia Sanae Mizuno, Patricia Castelucci, Department of Anatomy/Biomedical Science Institute, University of São Paulo, São Paulo 05508-900, Brazil
Amanda Rabello Crisma, Primavera Borelli, Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo 05508-900, Brazil
Bárbara Tavares Schäfer, Mariana Póvoa Silveira, Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-900, Brazil
Author contributions: Mizuno MS performed all of the experiments and analyzed the results for this work; Crisma AR and Borelli P collected and analyzed the blood samples; Schäfer BT and Silveira MP helped write and edit the manuscript; Castelucci P planned the study and wrote the manuscript.
Supported by São Paulo Research Foundation (FAPESP/São Paulo Research Foundation/Proc: 05/04752-0) and CAPES Fellowship
Correspondence to: Patricia Castelucci, PhD, Department of Anatomy/Biomedical Science Institute, University of São Paulo, R. Dr. Lineu Prestes 2415, São Paulo 05508-900, Brazil. pcastel@usp.br
Telephone: +55-11-30918463 Fax: +55-11-30917366
Received: February 10, 2014
Revised: April 29, 2014
Accepted: June 13, 2014
Published online: October 14, 2014
Processing time: 247 Days and 16.4 Hours
Abstract

AIM: To investigate the colocalization, density and profile of neuronal areas of enteric neurons in the ileum of male obese mice.

METHODS: The small intestinal samples of male mice in an obese group (OG) (C57BL/6J ob/ob) and a control group (CG) (+/+) were used. The tissues were analyzed using a double immunostaining technique for immunoreactivity (ir) of the P2X2 receptor, nitric oxide synthase (NOS), choline acetyl transferase (ChAT) and calretinin (Calr). Also, we investigated the density and profile of neuronal areas of the NOS-, ChAT- and Calr-ir neurons in the myenteric plexus. Myenteric neurons were labeled using an NADH-diaphorase histochemical staining method.

RESULTS: The analysis demonstrated that the P2X2 receptor was expressed in the cytoplasm and in the nuclear and cytoplasmic membranes only in the CG. Neuronal density values (neuron/cm2) decreased 31% (CG: 6579 ± 837; OG: 4556 ± 407) and 16.5% (CG: 7796 ± 528; OG: 6513 ± 610) in the NOS-ir and calretinin-ir neurons in the OG, respectively (P < 0.05). Density of ChAT-ir (CG: 6200 ± 310; OG: 8125 ± 749) neurons significantly increased 31% in the OG (P < 0.05). Neuron size studies demonstrated that NOS, ChAT, and Calr-ir neurons did not differ significantly between the CG and OG groups. The examination of NADH-diaphorase-positive myenteric neurons revealed an overall similarity between the OG and CG.

CONCLUSION: Obesity may exert its effects by promoting a decrease in P2X2 receptor expression and modifications in the density of the NOS-ir, ChAT-ir and CalR-ir myenteric neurons.

Keywords: Obesity, P2X2 receptor, Myenteric neurons, Chemical coding

Core tip: The neuronal density (neuron/cm2) of nitric oxide synthase- and calretinin-ir neurons are decreased and the density of choline acetyl transferase-ir neurons is significantly increased in male ob/ob mice. In addition, the P2X2 receptor is only expressed in the enteric neurons of healthy mice. These findings have clinical relevance for understanding alterations in gastrointestinal motility in obesity.