Effect of experimental autoimmune encephalomyelitis and opioid growth factor treatment on proteomic profiles of lumbar spinal cord

Open Access
Author:
Dumpala, Pradeep kumar Reddy
Graduate Program:
Laboratory Animal Medicine
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 18, 2012
Committee Members:
  • Ian Stuart Zagon, Thesis Advisor
Keywords:
  • Multiple sclerosis
  • Experimental autoimmune encephalomyelitis
  • Opioid growth factor
  • Proteomics
  • 2-D DIGE
  • Pathway analysis
  • mouse
  • lumbar spinal cord
Abstract:
Multiple sclerosis (MS) is a chronic, progressive, demyelinating autoimmune disease of the human central nervous system and is a common condition affecting western countries. The pathophysiology of this disease is very complex and needs further research to elucidate the exact mechanisms of pathogenesis at the molecular level. There are several animal models available, of which experimental autoimmune encephalomyelitis (EAE) is popular and closely resembles several crucial aspects of the pathogenesis of MS including the autoimmune component. Research has shown that opioids regulate immune system function, but their role in MS has not been elucidated. Previous research revealed the immunomodulatory role of the endogenous opioid [Met5]-enkephalin (also known as opioid growth factor (OGF)) in EAE models. Very few studies have been conducted analyzing proteomic aspects of MS. Hence, the overall objective of this study is to analyze and annotate the differential protein expression profiles of the lumbar spinal cord of EAE compared to normal mice. Secondly, to evaluate protein expression in EAE mice receiving OGF treatment or phosphate buffer saline (PBS). High-throughput proteomic profile analysis was conducted using two-dimensional difference gel electrophoresis coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (2-D DIGE MALDI TOF/TOF). Ingenuity Pathways Analysis (IPA) was used to gain insight into various biological functions, pathways, and networks that are significantly represented by differentially expressed protein datasets. A total of 12 unique proteins were identified that were up-regulated in the lumbar spinal cord of mice with EAE at Day 20 compared to normal mice. Some of these proteins have previously identified in the pathogenesis of EAE such as GFAP, neurofilament medium polypeptide, moesin, and lamin B1. Eleven canonical pathways and 1 network (score 36) were significantly represented by these differentially expressed proteomic dataset. Protein expression profile analysis of lumbar spinal cord of EAE mice at Day 20 in response to daily OGF treatment resulted in identification of 8 down-regulated and 1 up-regulated proteins. Further functional analysis of these 9 differentially expressed proteins resulted in significant representation of 1 network (score 23) and 15 canonical pathways. Pathway analysis of the differentially expressed in both studies determined 18 canonical pathways and 2 networks. The present study identified several differentially expressed proteins that were previously shown to play a role in the pathogenesis of EAE/MS. These proteins may be used as targets for further functional analysis which may aid in elucidating the exact mechanism of pathogenesis of EAE/MS at the molecular level.