Cognitive Function and Heat Shock Protein 70 in Children With Temporal Lobe Epilepsy

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1 Original Article Cognitive Function and Heat Shock Protein 70 in Children With Temporal Lobe Epilepsy Journal of Child Neurology 2017, Vol. 32(1) ª The Author(s) 2016 Reprints and permission: sagepub.com/journalspermissions.nav DOI: / journals.sagepub.com/home/jcn Azza M. Oraby, MD 1, Ehab R. Abdol Raouf, MD 2, Mostafa M. El-Saied, MSc 2, Maha K. Abou-Khadra, MD 1, Suzette I. Helal, MD 2, and Adel F. Hashish, PhD 2 Abstract We conducted the present study to examine cognitive function and serum heat shock protein 70 levels among children with temporal lobe epilepsy. The Stanford-Binet Intelligence Test was carried out to examine cognitive function in 30 children with temporal lobe epilepsy and 30 controls. Serum heat shock protein 70 levels were determined with an enzyme-linked immunosorbent assay. The epilepsy group had significantly lower cognitive function testing scores and significantly higher serum heat shock protein 70 levels than the control group; there were significant negative correlations between serum heat shock protein 70 levels and short-term memory and composite scores. Children with uncontrolled seizures had significantly lower verbal reasoning scores and significantly higher serum heat shock protein 70 levels than children with controlled seizures. Children with temporal lobe epilepsy have cognitive dysfunction and elevated levels of serum heat shock protein 70, which may be considered a stress biomarker. Keywords children, cognitive function, heat shock protein 70, stress biomarker, temporal lobe epilepsy Received February 28, Received revised June 13, Accepted for publication August 8, Introduction Epilepsy is a common neurologic disorder that can be complicated by neurobehavioral comorbidities, including cognitive impairment, psychiatric disorders, and social problems. 1 These comorbid conditions not only have a significant impact on the child but are also a burden and a source of increased stress for families. 2 Cognitive function is more frequently impaired in people with epilepsy than in the general population, and the degree of cognitive impairment varies according to the epilepsy syndrome. 3 The cognitive and behavioral effects of temporal lobe seizure foci range from subtle problems with memory and psychomotor speed to severe impairments in intellectual function and psychiatric disorders. 4 Because of the localization of neuropathology in memory-related brain structures, problems with episodic memory represent the major cognitive comorbidity of temporal lobe epilepsy. 5 A recent review of cognitive outcomes in patients with chronic temporal lobe epilepsy showed that approximately 70% of patients with temporal lobe epilepsy have problems with declarative memory function, and low levels of intelligence (intelligence quotients <85) are reported in approximately 30% of patients. 6 According to Wilson et al, 7 childhood-onset temporal lobe epilepsy can disrupt the achievement of normative developmental tasks, which is independently predicted by medical, biologic, and cognitive factors. They concluded that early testing of cognition in children with epilepsy is important for identifying and proactively treating children who are at risk for altered or delayed developmental outcomes. As reported by Turturici and colleagues, 8 heat shock proteins are induced in response to many injuries, including stroke, neurodegenerative disease, epilepsy, and trauma, and heat shock protein 70 is a stress marker in temporal lobe epilepsy. Yang et al 9 reported that heat shock protein 70 was a useful indicator of neuronal stress in the acute phase of epilepsy. Chang and colleagues 10 found that adult patients with temporal lobe epilepsy had higher serum levels of heat shock protein 70 than controls and that serum levels of heat shock protein 70 were positively correlated with hippocampal atrophy and memory dysfunction, in addition to being elevated in patients with higher seizure frequencies. Therefore, they 1 Department of Pediatrics, Faculty of Medicine, Cairo University, Giza, Egypt 2 Department of Research on Children with Special Needs, National Research Centre, Centre of Excellence of Medical Research, Cairo, Egypt Corresponding Author: Maha K. Abou-Khadra, MD, Department of Pediatrics, Faculty of Medicine, Cairo University, 2 Yousef Fahmy Street, El-Areech Street, Al-Ahram Street, Giza 12151, Egypt. maha_korany71@yahoo.com

2 42 Journal of Child Neurology 32(1) suggested that it may be a stress marker in temporal lobe epilepsy. Childhood-onset epilepsy has an adverse impact on brain development and cognition. 11,12 To our knowledge, no previous study has examined the relationship between heat shock protein 70 and cognitive function in children with temporal lobe epilepsy. The aims of this study were to assess cognitive function and serum heat shock protein 70 levels among a group of Egyptian children with temporal lobe epilepsy and to investigate the relationship between this possible stress biomarker and both cognitive function and epilepsy severity. Methods Participants Thirty children with temporal lobeepilepsyagedbetween4and 12 years were recruited from the pediatric neurology clinic at Cairo University Pediatric Hospital and the Department of Research on Children with Special Needs, National Research Centre, Centre of Excellence of Medical Research. Temporal lobe epilepsy was diagnosed according to the Commission on the Classification and Terminology of the International League Against Epilepsy criteria. 13 Children with temporal lobe epilepsy underwent extensive clinical, electroencephalographic, and neuroimaging assessments. All the children had semiology and interictal electroencephalography findings that were consistent with temporal lobe epilepsy. Children with symptomatic epilepsy, a history of central nervous system infection, a history of perinatal insults, dysmorphic features, or medical disorders were not recruited. Thirty healthy control children without temporal lobe epilepsy were selected from a group of children presenting for preoperative checkups for tonsillectomy and from among relatives of the children with temporal lobe epilepsy. The study was approved by the research committee of the Department of Pediatrics, Faculty of Medicine, Cairo University. Ethical approval was obtained from the Institutional Review Board for Human Subject Research at the National Research Centre, Cairo, Egypt. Written informed consent was obtained from the parents of the children participating in the study. Cognitive Function The Stanford-Binet Intelligence Scale, Fourth Edition, 14 was used to provide an estimate of general intellectual ability. The subscales of abstract/visual reasoning, quantitative reasoning, short-term memory, and verbal reasoning are summed to produce a composite intelligence quotient score. Serum Heat Shock Protein 70 Levels Serum heat shock protein 70 concentrations were measured using an ab heat shock protein 70 enzyme-linked immunosorbent assay kit (Abcam, Cambridge, MA). The enzyme-linked immunosorbent assay procedure followed the manufacturer s protocol. Statistical Analysis Data were analyzed using IBM Statistical Package for the Social Sciences (SPSS), version 22 (IBM Corp, Armonk, NY). Numerical data were expressed as means and standard deviations. Categorical data were expressed as frequencies and percentages. Significant differences between groups were tested using a chi-square test for Table 1. Composite Intelligence Quotient and Subscale Scores of the Patients and Controls. Controls (Mean + SD) (n ¼ 30) Patients (Mean + SD) (n ¼ 30) P Verbal reasoning Abstract/visual reasoning Quantitative reasoning Short-term memory Composite Abbreviation: SD, standard deviation. categorical variables. Comparisons of parametric data between 2 independent groups were performed using Student t test. Comparisons of nonparametric data between 2 independent groups were performed using the Wilcoxon rank-sum test. Spearman correlation was used to study the possible associations between 2 nonparametric variables in each group. A P value <.05 was considered significant. Results Sample Characteristics Of the 30 children, 22 (73.3%) were boys and 8 (26.7%) were girls. Their ages ranged from 4 to 12 years, with a mean age of 8.30 years (standard deviation ¼ 2.86). The mean age of epilepsy onset was years. Five patients (16.6%) were newly diagnosed, and they did not receive medication until their intelligence quotient assessments. The mean duration of illness was years. Seizure activity was controlled (less than 1 seizure per month or sporadic) in 8 patients and uncontrolled in 17 patients. On epilepsy onset, focal seizures were noted in 22 patients, and generalized seizures were noted in 8 patients. The control group consisted of 30 healthy children. The mean age of the control group was ; 18 (60.0%) of the children were boys. There were no significant differences between the temporal lobe epilepsy and control groups with respect to age (Z ¼ 0.957, P ¼.338) or sex (w 2 ¼ 1.014, P ¼.314). Comparisons of Composite Intelligence Quotient and Subscale Scores As shown in Table 1, there were significant differences between the temporal lobe epilepsy and control groups with respect to quantitative reasoning (P ¼.024), short-term memory (P ¼.001), and composite intelligence quotient (P ¼.006). The mean + standard deviation verbal reasoning score of the children with controlled seizures was The mean + standard deviation verbal reasoning score of the children with uncontrolled seizures was There was a significant difference between the children with controlled and uncontrolled seizures with respect to verbal reasoning (t ¼ 2.219, P ¼.044). There were no significant differences between the children with controlled and uncontrolled seizures

3 Oraby et al 43 Table 2. Correlation between Duration of Epilepsy and Intelligence Quotient Scores. r P Verbal reasoning Abstract/visual reasoning Quantitative reasoning Short-term memory Composite Table 3. Comparison of Serum Heat Shock Protein 70 Levels between the Temporal Lobe Epilepsy and Control Groups. Controls (mean +SD) (n ¼ 30) Patients (mean + SD) (n ¼ 30) Z P Serum heat shock protein 70 (ng/ml) Abbreviation: SD, standard deviation <.001 with respect to composite intelligence quotient or other subscale scores (P >.05). Correlations between Duration of Epilepsy, Patient Age, and Age of Seizure Onset and Intelligence Quotient Scores As shown in Table 2, there were significant negative correlations between duration of illness and short-term memory (P ¼.037) and composite intelligence quotient scores (P ¼.021). There were no significant correlations between patient age or age of seizure onset and intelligence quotient composite scores or subscale scores (p>0.05). Comparison of Serum Heat Shock Protein 70 Levels Between the Temporal Lobe Epilepsy and Control Groups As shown in Table 3 and Figure 1, there was a significant difference between the groups with respect to serum heat shock protein 70 levels (P <.001). Comparison of Serum Heat Shock Protein 70 Levels Between the Children With Controlled and Uncontrolled Seizures The mean + standard deviation serum heat shock protein 70 level in children with uncontrolled seizures was The mean + standard deviation serum heat shock protein 70 level in children with controlled seizures was There was a significant difference between the children with uncontrolled and controlled seizures (Z ¼ 2.359, P ¼.018). Figure 1. Comparison of serum heat shock protein 70 levels between the temporal lobe epilepsy and control groups. Table 4. Correlations between Serum Heat Shock Protein 70 Levels and Intelligence Quotient Scores. Verbal reasoning Abstract/visual reasoning Quantitative reasoning Short-term memory Composite Correlations Between Intelligence Quotient Scores, Patient Age, Age of Illness Onset, and Duration of Illness and Serum Levels of Heat Shock Protein 70 As shown in Table 4, there were significant negative correlations between serum heat shock protein 70 levels and shortterm memory (P ¼.008) and composite intelligence quotient scores (P ¼.014). There were no significant correlations between serum heat shock protein 70 levels and intelligence quotient scores among the controls (P >.05). There were no significant correlations between patient age, age of illness onset, or duration of illness and serum heat shock protein 70 levels (P >.05). Discussion The present study was conducted to assess cognitive function and serum heat shock protein 70 levels among Egyptian children with temporal lobe epilepsy and to investigate the relationship between this possible stress biomarker and both cognitive function and epilepsy severity. Our results showed significantly lower quantitative reasoning, short-term memory, and composite intelligence quotient scores in the children with temporal lobe epilepsy than in the r P

4 44 Journal of Child Neurology 32(1) controls and significant negative correlations between duration of epilepsy and cognitive test scores. Children with uncontrolled seizures had significantly lower verbal reasoning scores and significantly higher serum heat shock protein 70 levels. Our results are in agreement with those of previous studies that reported a high prevalence of cognitive impairment in children with temporal lobe epilepsy. Rzezak et al 15 demonstrated that some aspects of memory and executive function are impaired in children and adolescents with temporal lobe epilepsy. In a study that compared neuropsychological testing in children with temporal lobe epilepsy and healthy controls, Guimãraes et al found that children with temporal lobe epilepsy had neuropsychological disturbances and that an earlier onset of epilepsy was associated with worse verbal stimuli storage. 16 As reported by Rzezak and colleagues, 17 epilepsy duration rather than chronological age or age at epilepsy onset is now recognized as a major determining factor with respect to interindividual intelligence quotient variability in adult patients with temporal lobe epilepsy. Similarly, we found significant negative correlations between epilepsy duration and short-term memory subscale scores and composite intelligence quotient scores. However, these findings contrast with those of Baxendale et al, 18 who reported that epilepsy duration was not related to intelligence quotient, memory, or language scores and suggested that the profile of cognitive deficits is already established as children with temporal lobe epilepsy enter adulthood. Hamiwka and Wirrell 2 reported that younger age at seizure onset and intractability are biological factors that are associated with a greater risk of comorbidity in epilepsy. In the present study, we found that children with uncontrolled seizures had significantly lower verbal reasoning scores, but there was no significant correlation between age of epilepsy onset and cognitive test scores. Our findings highlight the importance of screening for cognitive deficits in children with temporal lobe epilepsy, in addition to achieving seizure control. Detailed knowledge regarding the patterns of molecular alterations that occur during epileptogenesis is a presupposition for identifying targets for preventive or disease-modifying treatment approaches, as well as for identifying biomarkers of the disease. 19 As reported by Stetler and colleagues, 20 heat shock proteins are involved in processes such as synaptic transmission, autophagy, the endoplasmic reticulum stress response, and protein kinase and cell death signaling and also function as protein chaperones, which ensure proper protein folding. Seizure activity has been linked to heat shock protein induction, which appears to be a stress response rather than a protective mechanism as their expression occurs in both surviving cells and cells destined for death. A recent study suggested that increased heat shock protein expression in key hippocampal subfields in patients with mesial temporal lobe epilepsy reflects increased epileptogenicity and is predictive of poorer outcomes in epilepsy surgery. 21 In the present study, children with temporal lobe epilepsy had significantly higher serum heat shock protein 70 levels than healthy controls; there were significant negative correlations between serum heat shock protein 70 levels and short-term memory and composite intelligence quotient scores. In addition, we found that children with uncontrolled seizures had significantly higher serum heat shock protein 70 levels than children with controlled seizures. To our knowledge, no previous study has examined the relationship between heat shock protein 70 and cognitive function in children with temporal lobe epilepsy. However, our findings are similar to those of Chang et al, 10 who reported higher serum heat shock protein 70 levels in adult patients with temporal lobe epilepsy compared with controls, as well as an inverse relationship between memory test scores and elevation of heat shock protein 70 levels in patients with higher seizure frequencies. These findings may indicate that heat shock protein 70 is a stress marker in children with temporal lobe epilepsy. However, further research is needed to support this idea as the relationship between heat shock protein 70 levels and epilepsy is correlational rather than causal. The limitations of this study include a small sample size and the recruitment of children from a neurology clinic at a tertiary facility that attracts cases of severe temporal lobe epilepsy; thus, these results may not be generalizable to other patients with childhood temporal lobe epilepsy. Additionally, most of the children were receiving antiepileptic medications, which are believed to affect cognitive function 22,23 and may have an impact on serum biomarker levels. 10 In conclusion, children with temporal lobe epilepsy exhibit cognitive dysfunction with respect to quantitative reasoning and short-term memory and elevated levels of serum heat shock protein 70, which may be considered a stress biomarker. Acknowledgments We would like to thank the parents and children who participated in this study for their cooperation. Author Contributions AMO and ERA designed the study. MME-S and SIH collected the data. AFH performed the laboratory analysis. MKA-K analyzed the data and wrote the first draft and final manuscript. All the authors approved the final manuscript. Declaration of Conflicting Interests The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The authors received no financial support for the research, authorship, and/or publication of this article. Ethical Approval The study was approved by the Institutional Review Board (13072) for Human Subject Research at the National Research Centre, Cairo, Egypt. Written informed consent was obtained from the parents of the children participating in the study.

5 Oraby et al 45 References 1. Hermann B, Seidenberg M, Jones J. The neurobehavioural comorbidities of epilepsy: can a natural history be developed? Lancet Neurol. 2008;7: Hamiwka LD, Wirrell EC. Comorbidities in pediatric epilepsy: beyond just treating the seizures. J Child Neurol. 2009;24: Cornaggia CM, Beghi M, Provenzi M, Beghi E. Correlation between cognition and behavior in epilepsy. Epilepsia. 2006;47: Kenney D, Wirrell E. Patient considerations in the management of focal seizures in children and adolescents. Adolesc Health Med Ther. 2014;5: Helmstaedter C, Elger CE. Chronic temporal lobe epilepsy: a neurodevelopmental or progressively dementing disease? Brain. 2009:132; Helmstaedter C, Kockelmann E. Cognitive outcomes in patients with chronic temporal lobe epilepsy. Epilepsia. 2006;47: Wilson SJ, Micallef S, Henderson A, et al. Developmental outcomes of childhood-onset temporal lobe epilepsy: A communitybased study. Epilepsia. 2012:53: Turturici G, Sconzo G, Geraci F. Hsp70 and its molecular role in nervous system diseases. Biochem Res Int. 2011;2011: Yang T1, Hsu C, Liao W, Chuang JS. Heat shock protein 70 expression in epilepsy suggests stress rather than protection. Acta Neuropathol. 2008;115: Chang CC, Lui CC, Lee CC, et al. Clinical significance of serological biomarkers and neuropsychological performances in patients with temporal lobe epilepsy. BMC Neurol. 2012; 12: Kaaden S, Helmstaedter C. Age at onset of epilepsy as a determinant of intellectual impairment in temporal lobe epilepsy. Epilepsy Behav. 2009;15: Kaaden S, Quesada CM, Urbach H, et al. Neurodevelopmental disruption in early-onset temporal lobe epilepsy: evidence from a voxel-based morphometry study. Epilepsy Behav. 2011;20: Engel J. A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology. Epilepsia. 2001;42: Thorndike RL, Hagen EP, Sattler JM. The Stanford-Binet Intelligence Scale: 4th ed. Technical Manual. Chicago: Riverside Publishing; Rzezak P1, Guimarães CA, Fuentes D, et al. Memory in children with temporal lobe epilepsy is at least partially explained by executive dysfunction. Epilepsy Behav. 2012;25: Guimãraes CA, Rzezak P, Fuentes D, et al. Memory in children with symptomatic temporal lobe epilepsy. Arq Neuropsiquiatr. 2014;72: Rzezak P, Valente KD, Duchowny MS. Temporal lobe epilepsy in children: executive and mnestic impairments. Epilepsy Behav. 2014;31: Baxendale S, Heaney D, Thompson PJ, Duncan JS. Cognitive consequences of childhood-onset temporal lobe epilepsy across the adult lifespan. Neurology. 2010;75: Walker A, Russmann V, Deeg CA, et al. Proteomic profiling of epileptogenesis in a rat model: focus on inflammation. Brain Behav Immun. 2016;53: Stetler RA, Gan Y, Zhang W, et al. Heat shock proteins: cellular and molecular mechanisms in the central nervous system. Prog Neurobiol. 2010;92: Kandratavicius L, Hallak JE, Carlotti CG Jr, et al. Hippocampal expression of heat shock proteins in mesial temporal lobe epilepsy with psychiatric comorbidities and their relation to seizure outcome. Epilepsia. 2014;55: Mula M, Trimble MR. Antiepileptic drug-induced cognitive adverse effects: potential mechanisms and contributing factors. CNS Drugs. 2009;23: Eddy CM, Rickards HE, Cavanna AE. The cognitive impact of antiepileptic drugs. Ther Adv Neurol Disord. 2011;4: