Elsevier

Neuropeptides

Volume 83, October 2020, 102073
Neuropeptides

Erythropoietin shows gender dependent positive effects on social deficits, learning/memory impairments, neuronal loss and neuroinflammation in the lipopolysaccharide induced rat model of autism

https://doi.org/10.1016/j.npep.2020.102073Get rights and content

Abstract

We aimed to evaluate the effects of EPO in the lipopolysaccharide (LPS) induced rat model of autism in terms of social deficits, learning and memory impairments, as well as their neurochemical correlates.

Sixteen female Sprague Dawley rats randomly distributed into two equel groups, then were caged with fertile males for mating. At the 10th day of pregnancy, 0.5 ml %0,9 NaCl saline was given to first group, 100 μg/kg LPS was given to second group to induce autism. On postnatal 21th day, forty-eight littermates were divided into four groups as; 8 male, 8 female controls, 16 male and 16 female LPS-exposed. Then, LPS groups were also divided in to two groups as saline (1 mg/kg/day) and EPO 600 U/kg/day groups, and animals were treated 45 days. At 50th day, after behavioral evaluations, brain levels of TNF-α, nerve growth factor (NGF) were measured. Histologically, hippocampal neuronal density and GFAP expression were assessed.

Three-chamber sociability and social novelty test, passive avoidance learning test were revealed significant differences among the EPO and control groups. Histologically, hippocampal CA1 & CA3 regions displayed significant alterations regarding gliosis (GFAP-positive cells) and regarding frontal cortical thickness in EPO groups compare to controls. Biochemical measurements of the brain levels of TNF-α and NGF levels showed significant differences between controls and EPO groups.

According to our findings EPO treatment has beneficial effects on ASD-like symptoms, learning and memory processes, neuronal loss and neuroinflammation in the LPS induced rat model of autism, with some gender differences through inflammatory and neurotrophic pathways.

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with early onset symptoms characterized by deficits in social and communicative skills, repetitive behaviors and/or restricted areas of interest (Vahia 2013). With a drastic increase in its prevalence over the few decades, ASD is now seen one in every 100 individuals and affects males more than females (Fombonne 2009). The etiology of ASD is poorly understood and tend to be complex and heterogenous with considerable amount of variation from one individual to another (Huguet et al. 2016; Hallmayer et al. 2011). In a study, it is reported that while genetic alterations may explain %35–40 of the cases; environmental factors during the different periods of brain development may cover the remaining cases of ASD. Neuroimmune alterations and inflammatory processes during brain development may contribute to the etiology of ASD (Hallmayer et al. 2011). In lipopolysaccharide induced rat model of autism, a well-known maternal immune activation model of ASD, it is shown that maternal immune activation during pregnancy may alter the expression of different pro- and anti-inflammatory cytokines in the developing brain and associated with abnormalities of neuronal proliferation, differentiation, maturation and neurodegeneration in different areas of cerebral cortex and hippocampus which eventually lead to an ASD-like phenotype (Boksa 2010; Ornoy et al. 2019). In animal studies, LPS administration to the pregnant rodents at the 10th gestational day is known to yield autism-like behavior in the offspring, with males being affected more severely. LPS exposed rats tend to display deficits in communicative and social skills, memory impairments and repetitive/restrictive behaviors (Kirsten et al. 2010).

Erythropoietin (EPO) is a glycoprotein hormone and has an important role in neurogenesis, along with its well-known role for erythropoiesis (Dhir 2010). Both EPO and its receptors are expressed in various regions of the fetal brain including hippocampus, internal capsule, cerebral cortex and midbrain (Frymoyer et al. 2017; Dhir 2010). Administration of human recombinant EPO is shown to have neuroprotective and neurotrophic effects in various clinical and non-clinical studies of different neuropsychiatric disorders including Alzheimer's disease, traumatic brain injury, epilepsy, neuropathies and multiple sclerosis (Sargin et al. 2010; Othman et al. 2018). In animal studies, it is shown that EPO exert its neuroprotective and neurotrophic effects by different mechanisms of action. Along with its anti-inflammatory, anti-excitotoxic and anti-oxidant properties, it also has modulatory roles on the processes of neurogenesis, angiogenesis and programmed cell death (Maiese 2016). It is also associated with improved performance on cognitive tasks of memory and learning, as well as increased expression of long term potentiation in hippocampus(Kamal et al. 2011).

While different agents with neuroprotective properties such as Vitamin D and fingolimod (Vuillermot et al. 2017; Wu et al. 2017) were studied on animal models of ASD and shown to be ameliorating the symptoms of ASD, to the best of authors knowledge, there is no study evaluated the effects of EPO on the social deficits, learning and memory impairments, neuronal loss and neuroinflammation in the lipopolysaccharide induced rat model of autism. In this study, we aimed to evaluate the effects of EPO in the lipopolysaccharide induced rat model of autism in terms of social deficits, learning and memory impairments, as well as, their neurochemical and histopathological correlates.

Section snippets

Animals

Sixteen female and 6 male Sprague Dawley adult rats (238 ± 10 g) were included in the study. The rats were housed in plastic cages and maintained under standard conditions with 12-h light/dark cycles at room temperature (22 ± 2 °C). All animal studies strictly adhered to the animal experiment guidelines as designated by the Institutional Animal Care and Ethics Committee.

Study design

Female rats were randomly distributed into two groups: Group A (control, n = 8) and Group B (LPS induced group n = 8) group.

Statistical analysis

Statistical evaluation was performed using SPSS version 15.0 for Windows (SPSS Inc., Chicago, IL, USA). Shapiro-Wilk's W and Levene's tests were used to check the normality and the homogeneity of variance, respectively. The results are presented as mean ± standard error of the mean (SEM). The value of p < .05 was accepted as statistically significant.

Results

A total of 48 rats exposed to % 0.9 NaCl saline or LPS were included in this study (8 male and 8 female rats exposed to % 0.9 NaCl saline as the control group; 16 male and 16 female rats exposed to LPS as the study group). Rats in the study arm were further divided into four groups and treated with saline or EPO (Group 1: 8 male rats LPS-exposed and saline treated; Group 2: 8 female rats LPS-exposed and saline treated; Group 3: 8 male rats LPS-exposed and EPO treated; Group 4: 8 male rats

Discussion

In this study, we found some beneficial effects of EPO, especially in male rats, on ASD-like symptoms, learning and memory processes at the levels of behavior and neurochemistry in a lipopolysaccharide induced rat model of autism. Anti-inflammatory effects of EPO, as evidenced by the findings of our study (lower level of TNF-α and lower number of GFAP-positive neurons in the hippocampus and increased frontal cortical thickness), may be helpful in explaining the beneficial effects of this

Declaration of competing interest

all the authors declares that there is no conflict of interests.

Author Contribution Statement.

VS: conceived and designed research, wrote the manuscript, Conceptualization. MAE and AA: Data curation, conducted experiments, wrote the manuscript AM and OE: Formal analysis, conducted experiments, edited the text. All authors read and approved the manuscript.

References (46)

  • Y. Yang et al.

    Developmental maturation of astrocytes and pathogenesis of neurodevelopmental disorders

    J. Neurodev. Disord.

    (2013)
  • Gussenhoven R, Westerlaken RJJ, Ophelders DRMG, Jobe AH, Kemp MW, Kallapur SG, Zimmermann LJ, Sangild PT, Pankratova S,...
  • L.S. Abdelli et al.

    Propionic acid induces gliosis and Neuro-inflammation through modulation of PTEN/AKT pathway in autism Spectrum disorder

    Sci. Rep.

    (2019)
  • M. Brines et al.

    The receptor that tames the innate immune response

    Mol. Med.

    (2012)
  • Castillo-Melendez M, Yan E, Walker DW. 2005. 'Expression of erythropoietin and its receptor in the brain of...
  • A. Dhir

    Novel discoveries in understanding the complexities of epilepsy and major depression

    Expert Opin. Ther. Targets

    (2010)
  • E. DiCicco-Bloom et al.

    The developmental neurobiology of autism spectrum disorder

    J. Neurosci.

    (2006)
  • Erbas O, Erdogan M. A, Khalilnezhad A, Gürkan F.T, Yiğittürk G, Meral A, Taskiran D. 2018. 'Neurobehavioral effects of...
  • E. Fombonne

    Epidemiology of pervasive developmental disorders

    Pediatr. Res.

    (2009)
  • A. Frymoyer et al.

    High-dose erythropoietin population pharmacokinetics in neonates with hypoxic-ischemic encephalopathy receiving hypothermia

    Pediatr. Res.

    (2017)
  • T. Goyagi

    Erythropoietin reduces Neurodegeneration and long-term memory deficits following Sevoflurane exposure in neonatal rats

    Neurotox. Res.

    (2019)
  • J. Hallmayer et al.

    Genetic heritability and shared environmental factors among twin pairs with autism

    Arch. Gen. Psychiatry

    (2011)
  • Huguet, G., M. Benabou, and T. Bourgeron. 2016. 'The Genetics of Autism Spectrum Disorders.' in P. Sassone-Corsi and Y....
  • Cited by (0)

    View full text